A fluid end for use with a power end. The fluid end comprises a plurality of fluid end sections positioned adjacent one another. Each section includes a single horizontally positioned bore. A plunger is installed within the bore and includes a fluid passageway. Low-pressure fluid enters the bore through the plunger and high-pressure fluid exits the fluid end through an outlet valve installed within the bore. The intake of low-pressure fluid within the fluid end section is regulated by an inlet valve installed within the plunger. Low-pressure fluid enters the plunger through an inlet component attached to both the plunger and an inlet manifold.

Various industrial applications may require the delivery of high volumes of highly pressurized fluids. For example, hydraulic fracturing (commonly referred to as "fracking") is a well stimulation technique used in oil and gas production, in which highly pressurized fluid is injected into a cased wellbore. As shown for example in FIG. 1, the pressured fluid flows through perforations 10 in a casing 12 and creates fractures 14 in deep rock formations 16. Pressurized fluid is delivered to the casing 12 through a wellhead 18 supported on the ground surface 20. Sand or other small particles (commonly referred to as "proppants") are normally delivered with the fluid into the rock formations 16. The proppants help hold the fractures 14 open after the fluid is withdrawn. The resulting fractures 14 facilitate the extraction of oil, gas, brine, or other fluid trapped within the rock formations 16.
Fluid ends are devices used in conjunction with a power source to pressurize the fluid used during hydraulic fracturing operations. A single fracking operation may require the use of two or more fluid ends at one time. For example, six fluid ends 22 are shown operating at a wellsite 24 in FIG. 2. Each of the fluid ends 22 is attached to a power end 26 in a one-to-one relationship. The power end 26 serves as an engine or motor for the fluid end 22. Together, the fluid end 22 and power end 26 function as a hydraulic pump.
Continuing with FIG. 2, a single fluid end 22 and its corresponding power end 26 are typically positioned on a truck bed 28 at the wellsite 24 so that they may be easily moved, as needed. The fluid and proppant mixture to be pressurized is normally held in large tanks 30 at the wellsite 24. An intake piping system 32 delivers the fluid and proppant mixture from the tanks 30 to each fluid end 22. A discharge piping system 33 transfers the pressurized fluid from each fluid end 22 to the wellhead 18, where it is delivered into the casing 12 shown in FIG. 1.
Fluid ends operate under notoriously extreme conditions, enduring the same pressures, vibrations, and abrasives that are needed to fracture the deep rock formations shown in FIG. 1. Fluid ends may operate at pressures of 5,000-15,000 pounds per square inch (psi) or greater. Fluid used in hydraulic fracturing operations is typically pumped through the fluid end at a pressure of at least 8,000 psi, and more typically between 10,000 and 15,000 psi. However, the pressure may reach up to 22,500 psi. The power end used with the fluid end typically has a power output of at least 2,250 horsepower during hydraulic fracturing operations.
High operational pressures may cause a fluid end to expand or crack. Such a structural failure may lead to fluid leakage, which leaves the fluid end unable to produce and maintain adequate fluid pressures. Moreover, if proppants are included in the pressurized fluid, those proppants may cause erosion at weak points within the fluid end, resulting in additional failures.
It is not uncommon for conventional fluid ends to experience failure after only several hundred operating hours. Yet, a single fracking operation may require as many as fifty (50) hours of fluid end operation. Thus, a traditional fluid end may require replacement after use on as few as two fracking jobs.
During operation of a hydraulic pump, the power end is not exposed to the same corrosive and abrasive fluids that move through the fluid end. Thus, power ends typically have much longer lifespans than fluid ends. A typical power end may service five or more different fluid ends during its lifespan.
With reference to FIGS. 3 and 4, a traditional power end 34 is shown. The power end 34 comprises a housing 36 having a mounting plate 38 formed on its front end 40. A plurality of stay rods 42 are attached to and project from the mounting plate 38. A plurality of pony rods 44 are disposed at least partially within the power end 34 and project from openings formed in the mounting plate 38. Each of the pony rods 44 is attached to a crank shaft installed within the housing 36. Rotation of the crank shaft powers reciprocal motion of the pony rods 44 relative to the mounting plate 38.
A fluid end 46 shown in FIGS. 3 and 4 is attached to the power end 34. The fluid end 46 comprises a fluid end body 48 having a flange 50 machined therein. The flange 50 provides a connection point for the plurality of stay rods 42. The stay rods 42 rigidly interconnect the power end 34 and the fluid end 46. When connected, the fluid end 46 is suspended in offset relationship to the power end 34.
A plurality of plungers 52 are disposed within the fluid end 46 and project from openings formed in the flange 50. The plungers 52 and pony rods 44 are arranged in a one-to-one relationship, with each plunger 52 aligned with and connected to a corresponding one of the pony rods 44. Reciprocation of each pony rod 44 causes its connected plunger 52 to reciprocate within the fluid end 46. In operation, reciprocation of the plungers 52 pressurizes fluid within the fluid end 46. The reciprocation cycle of each plunger 52 is differently phased from that of each adjacent plunger 52.
With reference to FIG. 6, the interior of the fluid end 46 includes a plurality of longitudinally spaced bore pairs. Each bore pair includes a vertical bore 56 and an intersecting horizontal bore 58. The zone of intersection between the paired bores defines an internal chamber 60. Each plunger 52 extends through a horizontal bore 58 and into its associated internal chamber 60. The plungers 52 and horizontal bores 58 are arranged in a one-to-one relationship.
Each horizontal bore 58 is sized to receive a plurality of packing seals 64. The seals 64 are configured to surround the installed plunger 52 and prevent high-pressure fluid from passing around the plunger 52 during operation. The packing seals 64 are maintained within the bore 58 by a retainer 65. The retainer 65 has external threads 63 that mate with internal threads 67 formed in the walls surrounding the bore 58. In some traditional fluid ends, the packing seals 64 are installed within a removable stuffing box sleeve that is installed within the horizontal bore.
Each vertical bore 56 interconnects opposing top and bottom surfaces 66 and 68 of the fluid end 46. Each horizontal bore 58 interconnects opposing front and rear surfaces 70 and 72 of the fluid end 46. A discharge plug 74 seals each opening of each vertical bore 56 on the top surface 66 of the fluid end 46. Likewise, a suction plug 76 seals each opening of each horizontal bore 58 on the front surface 70 of the fluid end 46.
The discharge and suction plugs 74 and 76 are retained within their corresponding bores 56 and 58 by a retainer 78, shown in FIGS. 3, 5, and 6. The retainer 78 has a cylindrical body having external threads 79 formed in its outer surface. The external threads 79 mate with internal threads 81 formed in the walls surrounding the bore 56 or 58 above the installed plug 74 or 76.
As shown in FIGS. 3 and 4, a manifold 80 is attached to the fluid end 46. The manifold 80 is also connected to an intake piping system, of the type shown in FIG. 2. Fluid to be pressurized is drawn from the intake piping system into the manifold 80, which directs the fluid into each of the vertical bores 56, by way of openings (not shown) in the bottom surface 68.
When a plunger 52 is retracted, fluid is drawn into each internal chamber 60 from the manifold 80. When a plunger 52 is extended, fluid within each internal chamber 60 is pressurized and forced towards a discharge conduit 82. Pressurized fluid exits the fluid end 46 through one or more discharge openings 84, shown in FIGS. 3-5. The discharge openings 84 are in fluid communication with the discharge conduit 82. The discharge openings 84 are attached to a discharge piping system, of the type shown in FIG. 2.
A pair of valves 86 and 88 are installed within each vertical bore 56, on opposite sides of the internal chamber 60. The valve 86 prevents backflow in the direction of the manifold 80, while the valve 88 prevents backflow in the direction of the internal chamber 60. The valves 86 and 88 each comprise a valve body 87 that seals against a valve seat 89.
Traditional fluid ends are normally machined from high strength alloy steel. Such material can corrode quickly, leading to fatigue cracks. Fatigue cracks occur because corrosion of the metal decreases the metal's fatigue strength—the amount of loading cycles that can be applied to a metal before it fails. Such cracking can allow leakage that prevents a fluid end from achieving and maintaining adequate pressures. Once such leakage occurs, fluid end repair or replacement becomes necessary.
Fatigue cracks in fluid ends are commonly found in areas that experience high stress. For example, with reference to the fluid end 46 shown in FIG. 6, fatigue cracks are common at a corner 90 formed in the interior of the fluid end 46 by the intersection of the walls surrounding the horizontal bore 58 with the walls surrounding the vertical bore 56. A plurality of the corners 90 surround each internal chamber 60. Because fluid is pressurized within each internal chamber 60, the corners 90 typically experience the highest amount of stress during operation, leading to fatigue cracks. Fatigue cracks are also common at the neck that connects the flange 50 and the fluid end body 48. Specifically, fatigue cracks tend to form at an area 92 where the neck joins the body 48, as shown for example in FIGS. 4-6.
For the above reasons, there is a need in the industry for a fluid end configured to avoid or significantly delay the structures or conditions that cause wear or failures within a fluid end.


A thin and flexible wrist watch that includes a segmented e-paper display screen for displaying time. The watch is programmable and rechargeable by interaction with a base station.

Devices for measuring time have become an integral part of human life. Devices used to measure time have evolved from sundials to mechanical and digital wrist watches, pendulum wall clocks, and other devices. When the wrist watch was first introduced, it was analog in design that included many gear and springs arrangements with the springs requiring periodic manual rotation by a knob for the watch to operate for a period of time. However, due to regular use, the process of rotating the knob commonly led to a reduction in the accuracy of the timekeeping function of the watch. Also, the analog watches were prone to shocks an individual when carried.
Subsequent to analog mechanical watches, digital timepieces were developed. These watches utilized internal circuitry to display time via a Liquid Crystal Display. Although, digital watches were successful in providing an accurate time, they required a battery cell that must be regularly replaced after a period of use to provide energy for operation of the internal circuits and the displaying of time. Also, the digital display face can become difficult to view under bright light (e.g., sunlight). Moreover, digital watches are typically bulky due to the depth of their face as a result, in large part, to the required circuitry, Liquid Crystal Display, battery cell, and operational buttons.
Known mechanical and digital wristwatches include various components that operate in unison to keep time that are contained in a housing and a band that is fastened to the housing and releasably connectable to a user's wrist by a gripping means. Generally, a gripping means includes a clasp and a buckle. However, not only is it challenging in many situations to fasten and unfasten the clasp and buckle of a watch, but they can become worn out and break or cause irritation to the skin of the user and as a result, the user can develop an allergic reaction.

Flexible wristwatch with segmented e-paper display


The present invention relates to a trocar for laparoscopic surgery for performing the laparoscopic surgery through a surgical instrument by making a puncture in the abdomen of a patient, the trocar including: a head unit 10 including an upper case 11 and a lower cover 12; a base unit 20 including a lower case 24 having a trocar sleeve fixing protrusion 21 in a lower part thereof and a coupling member 25 installed at an upper surface thereof; a trocar sleeve 17 installed at the trocar sleeve fixing protrusion 21; a lip valve 60 installed within the head unit 10 and having a tapered lower part; an insertion unit 30 installed at the upper part of the lip valve 60; a button unit 40 including a button 41 elastically installed at an elastic bush 43; and a trocar needle 50 introduced into the trocar sleeve 17 through the lip valve 60 or the insertion unit 30.

1. Field of the Invention
The present invention relates to a trocar for laparoscopic surgery, and more particularly, to a trocar for performing laparoscopic surgery by making a small hole instead of opening the abdomen of a patient for surgery.
Specifically, when making a puncture in the abdomen, internal organs can be protected by installing a sliding rod within a support pipe of a trocar needle that is inserted into a trocar sleeve and makes a puncture in the patient's skin.
Further, since a head unit of the trocar includes a packing to which elastic fibers are attached, a flexible tube, and a sleeve, even though any on of other surgical instruments having smaller diameter than that of the trocar sleeve installed at the abdomen is inserted into the head unit, external air and inner carbon dioxide can be prevented from being injected and discharged through the packing when performing laparoscopic surgery.
Further, the present invention relates to a trocar for laparoscopic surgery for easily taking out gauzes and extracted materials of internal organs generated when performing the surgery.
2. Description of the Related Art
A trocar is generally used when laparoscopic surgery is performed.
In a conventional trocar, after a sleeve pipe that accommodates a trocar needle and that is installed within a head unit is fixed and installed corresponding to a trocar sleeve coupled to the lower end thereof, a separate movable piece corresponding to an end portion of the sleeve pipe is suppressed by elasticity of a spring, thereby maintaining airtightness.
When the trocar needle is inserted into an injection port of the sleeve pipe, a needle rod is inserted into a trocar sleeve while pushing the movable piece corresponding to the end portion of the sleeve pipe, and thus an end portion of the trocar needle is protruded.
The trocar may cause damage to internal organs of the abdomen by a perforating force while making a puncture in the abdomen of a patient, and therefore making a puncture in the abdomen should be carefully performed, and if the internal organs are erroneously damaged, recovery may be delayed due to the damaged internal organs.
Further, in order to perform laparoscopic surgery, a plurality of trocars are inserted into the abdomen of a patient and in this case, a single needle rod is inserted into any one of the plurality of trocars already inserted into the abdomen.
When performing surgery in the abdomen using an endoscope, in order to secure a visual field for surgery, the space therefor is maintained by injecting carbon dioxide through a valve and the movable piece corresponding to the end portion of the sleeve pipe closely contacts by elasticity of a spring interposed at one side of a shaft.
Therefore, when an elastic force of the spring is not uniformly distributed in a close contact surface of the movable piece, carbon dioxide may be leaked.
Further, after surgery has been performed, carbon dioxide is discharged through a separate means instead of being discharged through a head unit of the trocar and thus a discharge time of carbon dioxide may be delayed.
Particularly, because the conventional trocar is an expensive product, the trocar is reused after washing and disinfecting instead of disposing after using and thus an inanitary problem may occur.
When using several kinds of surgical instruments having different diameters, separate head units corresponding to diameters of each of the surgical instruments should be provided and exchanged and thus it may be inconvenient and take long time.


An exposed top end of a vertical oxide spacer is removed, and a nitride layer is deposited in an amount sufficient to replace the removed portion prior to exposing a memory device to a self align contact etch process. The nitride layer may be used to prevent a short circuit through the oxide spacer. The present invention also provides memory devices that have a gate stack, a vertical spacer adjacent to the gate stack, in which the vertical spacer has a lower portion comprising an oxide and an upper portion comprising a nitride, and a continuous nitride layer overlaying the vertical spacer and the gate stack. The present invention further provides methods of fabricating the above devices, and processor systems which include the devices.

The semiconductor industry requires processes for achieving higher device density within a given die area. This is particularly true in memory circuit fabrication, in which the number and density of memory cells on a given chip have dramatically increased. The increase in density is a result of downsizing of the individual semiconductor devices, due partly to advances in photolithography and directional (anisotropic) plasma etching. As the horizontal device feature sizes continue to decrease to submicron dimensions, it is necessary to use self-alignment techniques to relax the alignment requirements and improve critical dimension (CD) control. One such technique is called a self-align contact (SAC) etch, in which a pair of adjacent gate stacks are utilized to align an etched opening in an insulating layer.
A conventional SAC process includes first providing a substrate on which there are at least two memory cells (such as MOS devices or flash memory cells), then forming an insulating layer, such as silicon oxide, on the substrate. Each of the two or more memory cells includes a polysilicon gate and spacers on the sidewalls of the gate. The two cells have a common source/drain region located between the gates of the cells. The insulating layer is patterned to form a self-align contact opening which exposes the common source/drain region. A conductive layer is deposited in the self align contact opening to form a contact. SAC etch processes primarily involve dry or plasma etches, typically utilizing a CxFy (x>1)-type plasma chemistry, such as, for example C4F8, C5F8, or C4F6 in combination with other diluent gases.
The increase in packing density also places increased demands on many aspects of the fabrication process. Alignment of features from one level to the next is critically important, particularly the alignment of contact holes with underlying structures. The miniaturization of the devices makes the formation of interconnect structures difficult. To maintain sufficient electrical communication, the interconnect structure must be formed in precise alignment with the underlying active region. At the same time, the area of the interconnect structure interfacing with the active area must be maximized. Thus, as device sizes decrease, there is less room for misalignment errors of the interconnect structure.
Moreover, misalignment during an etch process can create problems resulting from the unintended etching or removal of an oxide seam (or spacer) along a gate stack, which forms between the gate stack and nitride spacers when spacer process formation includes the deposition of an oxide liner. In a flash cell, for example, if the misaligned SAC etch removes the oxide seam, metal will be deposited during subsequent plug fill metallization steps into the space where the seam previously was located, thereby causing the control to become shorted to both the floating gate and the substrate. FIGS. 1-3 illustrate this problem.
FIG. 1 depicts a pair of typical flash cell gate stacks 1 positioned adjacent to each other on a substrate 2 at an intermediate stage prior to SAC etching. Each stack includes a tunnel oxide layer 3 positioned on top of the substrate 2. A polysilicon floating gate 4 is positioned on top of the tunnel oxide layer 3 and an oxide/nitride/oxide (ONO) layer 5 is positioned on top of floating gate 4. A polysilicon control gate 6 is typically formed on top of the ONO layer 5 with a tungsten silicide layer 7 formed on top of the control gate 6. A cap 8, which is typically either nitride or TEOS is positioned on the tungsten silicide layer 7. Between the gate stacks is the area 9 in which the contact will be etched into the substrate.
FIGS. 2A-2D illustrate processing steps that may be performed subsequent to the intermediate stage illustrated in FIG. 1. First, an oxide layer 10, preferably a TEOS layer with a thickness of between about 50 Å and about 300 Å, more preferably, 100 and 200 Angstroms, is deposited over the surface of the device (FIG. 2A), to include sidewall S/D oxidation. Next, dry etching is used to remove horizontal TEOS surfaces, leaving vertical surfaces to form oxide spacers (also referred to herein as seams) 11, along the gate stack edge (FIG. 2B). To form a nitride spacer, a nitride layer 12 is deposited over the surface of the device, as shown in FIG. 2C. To complete nitride spacer formation, a dry etch is used, resulting in gate stacks having oxide seams (spacers) 11 separating nitride spacers 13 from gate stack 1 (FIG. 2D). The oxide seams 11 are exposed at the top 14, which can present a problem during the subsequent SAC etch process.
Following a first dielectric layer deposition, a self-align contact etch is used to remove the dielectric from the common region between the gate stacks to prepare the contact region 15 for metal deposition. FIG. 3 illustrates a problem that occurs when the self-align contact etch 17 is misaligned so as to hit a gate stack, rather than merely the contact region between adjacent gate stacks. Because the first level dielectric 16 and the exposed oxide seam 11 are composed of the same material, the etch plasma chemistry, which is selective to this material, etches out the oxide seam as well as the intended dielectric, leaving a void where the seam was. Once the seam is etched out, the resulting void would then be filled with metal. Because the metal deposited in the vertical space where the oxide seam had been is conductive, the control gate would be shorted to the floating gate and to the substrate (in a flash memory cell for example), or the gate would be shorted to the substrate (in a device other than a flash cell, such as, for example, a standard MOS transistor). This shorting results in a non-functional device.
There is thus a need for a method which mitigates or eliminates the above disadvantages. In particular, there is a need for a method which prevents problems, such as shorting between gate stack components, that occur when a misaligned self-align contact etch unintentionally removes an oxide seam or spacer.

Method to remove an oxide seam along gate stack edge, when nitride space formation begins with an oxide liner surrounding gate stack


A semiconductor laser device includes: a first light emitting device, the first light emitting device including a first first-conductive-type cladding layer, a first active layer having a first window region in the vicinity of a light emitting edge surface and a first second-conductive-type cladding layer stacked in this order on a substrate; and a second light emitting device, the second light emitting device including a second first-conductive-type cladding layer, a second active layer having a second window region in the vicinity of a light emitting edge surface and a second second-conductive-type cladding layer stacked in this order on the substrate. In the semiconductor laser device, respective lattice constants of the first second-conductive-type and second second-conductive-type cladding layers are adjusted to compensate for a difference in diffusion rate of an impurity between the first window region in the first active layer and the second window region in the second active layer.

The present invention relates to semiconductor laser devices, and more particularly relates to a semiconductor laser device used for an optical disc device such as a DVD-RAM, a DVD-R, a DVD-RW, a DVD+R, a DVD+RW, a CD-R, a CD-RW, a DVD-ROM, a CD-ROM, a DVD-Video, a CD-DA, a VCD or the like, optical information processing, optical communication, optical measurement or the like, and a method for fabricating such a device.
Semiconductor laser devices have been used for pickup light sources of optical disc devices and other light sources for optical information processing, optical communication and optical measurement. For example, an AlGaInP based red laser having a wavelength of 650 nm is used as a pickup light source for performing a read/write operation from/onto a DVD-RAM. As another example, an AlGaAs based infrared laser having a wavelength of 780 nm is used as a pickup light source for performing a read/write operation from/onto a CD-R.
To support both of DVD-RAM and CD-R, it is necessary to provide both of a red laser and an infrared laser in a single drive. Therefore, in general, drives including both of an optical integrated unit for DVD and an optical integrated unit for CD have been widely used. In recent years, however, because reduction in the size and cost of drives, simplification of assembling process steps for optical systems and the like are required, there are strong demands for development of drives which can support both of DVD-RAM and CD-R and include a single optical integrated unit.
For this reason, in recent years, double wavelength laser devices in which an AlGaInP based red laser having a wavelength of 650 nm and an AlGaAs based infrared laser having a wavelength of 780 nm are integrated are becoming put into practical use (see, for example, Japanese Laid-Open Publication No. 2001-57462). With use of a double wavelength laser device as a pickup light source, an optical disc device including a laser for both DVD and CD on a single optical integrated unit can be realized.
To perform a data write operation on a DVD-RAM, a CD-R or the like, increase in output power of a semiconductor laser device is required.
However, in a semiconductor laser device, an interface state is formed in part of an active layer located in the vicinity of a light emitting edge surface (this vicinity area will be hereafter referred to be as a "light emitting edge surface vicinity region"), so that non-radiative recombination of carriers is facilitated. Accordingly, in the part of the active layer located in the light emitting edge surface vicinity region, laser light generated in the semiconductor laser device is absorbed to generate heat, thus resulting in increase in temperature.
As an optical output density is increased, a larger amount of laser light is absorbed in the part of the active layer located in the light emitting edge surface vicinity region, so that increase in temperature due to heat generation is accelerated. As a result, finally, the temperature in the part of the active layer located in the light emitting edge surface vicinity region is increased to reach a melting point of a crystal constituting each semiconductor layer. Thus, part of each semiconductor layer located in the light emitting edge surface vicinity region is melted and a laser emission operation is terminated.
As described above, in the semiconductor laser device, the part of each semiconductor layer located in the light emitting edge surface vicinity region is damaged when the semiconductor laser device is in a high power density operation (hereafter, this will be referred to as "optical damage").
As a solution for the above-described problem, semiconductor laser devices having a window structure have been put into practical use.
Hereafter, a method for fabricating a semiconductor laser device having a window structure will be simply described (see, for example, IEEE journal of Quantum Electronics, Vol. 29, No. 6, pp. 1874-1879 (1993)).
First, a plurality of semiconductor layers including an active layer having a multiple quantum well structure are formed on a substrate. Subsequently, a ZnO film is selectively formed over parts of the semiconductor layers located in the light emitting edge surface vicinity region by sputtering. Then, Zn contained in the ZnO film is diffused by annealing so as to reach lower part of the ZnO film in the active layer.
Thus, in part of the active layer in which Zn is diffused, a bandgap can be expanded by disordering the part of the active layer, so that a window region having a larger bandgap than a bandgap of an inner region in the active layer can be formed in the part of the active layer located in the light emitting edge surface vicinity region.
As described above, in the semiconductor laser device having a window structure, a window region having a larger bandgap than the bandgap of the inner region of the active layer is provided in the part of the active layer located in the light emitting edge surface vicinity region.
Thus, in the semiconductor laser device having a window structure, laser light generated in the semiconductor laser device is not absorbed in the part of the active layer located in the light emitting edge surface vicinity region, so that termination of a laser emission operation can be prevented.
As has been described, in a double wavelength laser device, to achieve an infrared laser and a red laser which allow high power operation, a window region has to be formed in each of part of an infrared laser active layer located in a light emitting edge surface vicinity region and part of a red laser active layer located in a light emitting edge surface vicinity region.
However, in a method for fabricating a double wavelength laser device, when Zn diffusion for forming a window region in an infrared laser and Zn diffusion for forming a window region in a red laser are performed in a single step, that is, a infrared laser window region and a red laser window region are formed by a single Zn diffusion step, the following problems arise.
As has been described, in a double wavelength laser device including an infrared laser and a red laser, AlGaAs mixed crystal is used as an infrared laser active layer and AlGaInP mixed crystal is used as a red laser active layer.
In this case, a Zn diffusion rate in AlGaAs mixed crystal is smaller than a Zn diffusion rate in AlGaInP mixed crystal.
Thus, when conditions for the Zn diffusion process step are adjusted so that a necessary amount of Zn for achieving the function of a window structure is diffused in the infrared laser active layer of AlGaAs mixed crystal, an excessive amount of Zn is diffused in the red laser active layer of AlGaInP mixed crystal.
Thus, crystal quality in part of the red laser semiconductor layer located in the light emitting edge surface vicinity region is drastically deteriorated. Furthermore, excessively diffused Zn in the part of the red laser semiconductor layer located in the light emitting edge surface vicinity region reaches even the substrate, thus resulting in electrical short circuit in the semiconductor laser device.
In contrary, when conditions for the Zn diffusion process step are adjusted so that a necessary amount of Zn for achieving the function of a window structure is diffused in the red laser active layer of AlGaInP mixed crystal, a sufficient amount of Zn for achieving the function of a window structure can not be diffused in the infrared laser active layer of AlGaAs mixed crystal.
Accordingly, a preferable window region can not be formed in the part of the infrared laser active layer located in the light emitting edge surface vicinity region, so that laser light generated in the semiconductor laser device is absorbed in the part of the infrared laser active layer located in the light emitting edge surface vicinity region. Thus, the part of the infrared laser semiconductor layer located in the light emitting edge surface vicinity region is melted, so that infrared laser emission operation is terminated.
As described above, in the method for fabricating a double wavelength laser device, a preferable window region can be formed in one of the infrared laser and the red laser but not in the other one by a single Zn diffusion step.
Therefore, in the method for fabricating a double wavelength laser device, when a Zn diffusion step of forming a window region in an infrared laser and a Zn diffusion step of forming a window region in a red laser are separately performed, that is, an infrared laser window region and a red laser window region are formed by separate two Zn diffusion steps, respectively, the following problems arise.
Since the method for fabricating a double wavelength laser device requires two separate Zn diffusion steps, the number of fabrication process steps is increased and thus fabrication cost is increased. Furthermore, in the double wavelength laser device, two separate Zn diffusion steps are performed, so that Zn diffusion step is performed twice to one of an infrared laser and a red laser. Therefore, a yield of the double wavelength laser device is reduced.

Semiconductor laser device and method for fabricating the same

Matsushita Electric Industrial Co., Ltd.


Described herein is a modular outlet system that provides flexibility in locating switches, outlets, and sensors. A base can be recessed into a surface, such as a wall, floor, or ceiling and can be connected to a power source. The base can accept multiple types of inserts. The inserts can include switches, outlets, sensors, and blank plates. The inserts can lock into place with the base and unlock based on manipulation of a recessed button. Inserts can engage the base with staged gate opening to minimize chances of electrical shock.

Electrical fixtures, such as switches and outlets, are typically installed by an electrician and directly connected to a building's power supply. However, this limits the changes that can be made to outlets and fixtures after the fact since a user must pay an electrician or risk electric shock. Replacement can also require the assistance of at least one other person to (among other things) hold the fixture itself while the installer strips, twists together, and safely connects multiple pairs of bare wire ends, and finally mechanically attaches the fixture to the structure.
The burdens of the conventional method fall on both residential and commercial users. Residential users typically install or change fixtures infrequently, partially due to the complexity and difficulty of the conventional process. Commercial users face the repeated cost of unwiring and rewiring fixtures. This burden may be particularly felt in industries where fixtures are often updated to match changing decor, such as in the hospitality or restaurant industries.
Users often want to customize their home to their own personal tastes. Builders waste a lot of money outfitting a home with standard outlets and switches only to have a user replace the outlets and switches with more stylish varieties later. Additionally, users are limited regarding changing the type of fixture that exists at a particular location. If they could do so more easily, they would likely customize the placement and types of electrical fixtures.
In view of at least the above shortcomings, a need exists for a modular consumer-configurable electrical outlet system.

Modular consumer-configurable electrical fixture system


A device can receive parking information for a set of street segments within a geographic region. The parking information can include metadata for a set of parking spaces within the set of street segments. The device can create a set of block-face objects that represent block-faces within the set of street segments. The device can generate a data structure that associates the parking information for the set of street segments with the set of block-face objects. The device can receive, from a user device, a request for parking information associated with a geographic area. The device can obtain the parking information associated with the geographic area by using location information included in the request to search the data structure. The device can provide the parking information associated with the geographic area for display on a user interface of the user device.

Geolocation is the identification or estimation of the real-world geographic location of an object, such as a vehicle, a mobile phone, a person, or the like. A device can identify or estimate a geolocation of an object by determining a set of geographic coordinates associated with a location of the object.

Obtainment and display of real-time information for a set of block-faces


An optical scanner includes a light source modulated based on image data, an optical deflection and scanning part deflecting a light beam emitted from the light source, and a scanning and imaging optical system condensing the deflected light beam toward a scanning surface so as to form a light spot optically scanning the scanning surface. The effective scanning region of the scanning surface is divided into a plurality of regions according to a scanning line curving characteristic. Suitable image data for optically scanning the divided regions are selected from image data of a plurality of image lines every time the light spot optically scans the effective scanning region, so that the image data of each of the image lines is written with scanning line curving being corrected.

1. Field of the Invention
The present invention generally relates to optical scanners and imaging apparatuses, and more particularly to an optical scanner that forms a light spot on a scanning surface by using optical deflection and scanning means and a scanning and imaging optical system and optically scans the scanning surface with the light spot, and an imaging apparatus using such an optical scanner.
2. Description of the Related Art
Optical scanners that deflect a light beam emitted from a light source modulated based on image data in a main (primary) scanning direction using optical deflection and scanning means such as a rotary polygonal mirror, focus the deflected light beam into a light spot on a scanning surface (surface to be scanned) using a scanning and imaging optical system such as an fθ lens, and scan the scanning surface with the light spot formed thereon are widely known in relation to imaging apparatuses such as optical printers, optical plotters, and digital copiers.
In an imaging apparatus using such an optical scanner, generally, an imaging process including a step of writing an image by optical scanning is performed. The quality of the formed image depends on the quality of the optical scanning. The optical scanning quality depends on the scanning characteristics of the optical scanner in the main and sub scanning directions.
The scanning characteristics in the main scanning direction include the constant velocity characteristic of optical scanning.
In the case of using a rotary polygonal mirror as optical deflection and scanning means, for instance, a light beam is deflected at a constant angular velocity. Therefore, a scanning and imaging optical system having the fθ characteristic is employed in order to realize the constant velocity characteristic of optical scanning. It is not easy, however, to realize a perfect constant velocity characteristic of optical scanning due to other characteristics required of the scanning and imaging optical system. Therefore, in actual optical scanning, optical scanning is not performed at a perfect constant velocity, so that the constant velocity characteristic as a scanning characteristic is accompanied by "deviation or difference from ideal constant velocity scanning."
The scanning characteristics in the main scanning direction are generated not only by the above-described insufficient correction of the fθ characteristic, but also by: a decrease in the accuracy of optical components or the accuracy of attachment to the housing of the optical scanning system; changes in the optical component properties caused by environmental changes such as changes in temperature and humidity inside the optical scanner; and the shift of a photosensitive body or an intermediate transfer body, which substantially forms the scanning surface, in the direction of its rotation axis.
The scanning characteristics in the sub scanning direction include "scanning line curving" and "scanning line tilting." A scanning line is the trace of movement of a light spot on a scanning surface, and ideally, is a straight line. The optical scanner is designed so as to have a straight scanning line. As it is, however, it is common that the scanning line is curved due to processing or assembly error. This curving of the scanning line is referred to as "scanning line curving," and the degree of curving is referred to as the "scanning line curving characteristic."
In the case of using an "imaging mirror" as a scanning and imaging optical system so as to form an angle in the sub scanning direction between the direction in which the deflected light beam is made incident on the imaging mirror and the direction in which the deflected light beam is reflected therefrom, scanning line curving occurs in principle. In the case of forming the scanning and imaging optical system as a lens system, scanning line curving is unavoidable in multi-beam scanning where the scanning surface is optically scanned by a plurality of light spots separated in the sub scanning direction.
The "scanning line tilting," which is a phenomenon where the scanning line does not cross the sub scanning direction correctly at right angles, is a type of scanning line curving. Accordingly, in the following description, "scanning line tilting" is included in "scanning line curving" unless otherwise indicated.
Imperfection of the constant velocity characteristic of optical scanning distorts a formed image in the main scanning direction, and scanning line curving distorts a formed image in the sub scanning direction. When a single optical scanner writes and forms a monochrome image, the formed image includes no "visually recognizable distortion" if scanning line curving and imperfection of the constant velocity characteristic (or the deviation or difference from the ideal constant velocity scanning) are suppressed to a sufficient extent. However, the image is better with less distortion even if the distortion is visually unrecognizable.
Even in a monochrome image, however, scanning line curving becomes an unignorable problem if image linearity is considered important as in the case of a CAD (computer-aided design) output because even a slight curve of the scanning line significantly degrades the quality of the output image.
Conventionally, in color copiers, images of three colors of magenta, cyan, and yellow or four colors of those three colors plus black are formed as color component images, and a composite color image is formed by superimposing those color component images.
In forming such a color image, a so-called "tandem-type" imaging method is employable. In this imaging method, color component images are formed on different photosensitive bodies by different optical scanners (or different optical scanner parts), respectively. According to this imaging method, however, if the degree of scanning line curving or tilting differs between the optical scanners, an abnormality called "color misregistration" where colors are superimposed inappropriately on top of each other is caused to appear in the formed color image by a slight misalignment of the scanning lines of the optical scanners, thereby degrading the quality of the color image, even if the scanning line curving or tilting is corrected to an acceptable level in each optical scanner.
Further, the "color misregistration" may appear as a phenomenon where a desired tone cannot be obtained in the color image.
In recent years, a special surface, typically, an aspheric surface, has been commonly employed in the imaging optical system of the optical scanners in a bid to improve the scanning characteristics. Accordingly, a low-cost imaging optical system of a resin material, with which such a special surface can be formed easily, is widely used.
When the resin imaging optical system is affected by changes in temperature or humidity, the shape and the refractive index of its element are subject to change. Therefore, the optical properties of the imaging optical system are subject to change. These changes in the optical properties also change the scanning line curving characteristic and the constant velocity characteristic. Then, in the case of successively forming tens of color images, for instance, the imaging apparatus operates continuously to increase its internal temperature, so that the optical properties of the imaging optical system change to gradually change the scanning line curving characteristic and the constant velocity characteristic of each optical scanner. This may cause the phenomenon of color misregistration, thus resulting in a great tone difference between a color image obtained at the beginning and a color image obtained at the end.
Japanese Laid-Open Patent Application No. 2001-215437 discloses a technology of forming an exposure distribution in the sub scanning direction on a scanning surface or in a scanning region. Japanese Laid-Open Patent Application No. 2000-235290 discloses a technology of adjusting a scanning line position in the sub scanning direction by controlling the modulation timing of a light source.
Further, Japanese Laid-Open Patent Application No. 8-313941 discloses a technology relating to a liquid crystal deflection element.

Optical scanner and imaging apparatus using the same


A belt clutch apparatus for an image forming apparatus is is provided and includes a belt that rotates in contact with at least one unit, at least one movable roller for supporting the rotation of the belt, and a variable unit for changing position of the movable roller in order for the belt to have a first running path in contact with the unit and a second running path separated from the unit. Moreover, the belt can be selectively positioned in contact with a predetermined unit or separated therefrom while maintaining belt tension. Therefore, it becomes possible to protect the belt from unnecessary abrasion.

1. Field of the Invention
The present invention relates to a belt apparatus. More specifically, the present invention relates to a belt clutch apparatus, an intermediate transfer belt with the clutch, and an image forming apparatus with the intermediate transfer belt.
2. Description of the Related Art
In general, the operation range of a belt apparatus is determined by a plurality of rollers rotatably installed therein. The belt apparatus serves a wide range of applications such as supplying power to other units that are separated by a predetermined distance or carrying substances during rotation. Generally, in an image forming apparatus for printing color images, the belt is positioned between a developing unit and a printing paper for carrying developer. Particularly, the belt apparatus typically used is called an intermediate transfer belt. FIG. 1 is a schematic view of the color image forming apparatus, which includes a plurality of photosensitive drums for each color, and an intermediate transfer belt for transferring visible images from the photosensitive drums.
As shown in FIG. 1, the color image forming apparatus 1 includes a paper feeding unit 10, a carriage unit 20, a developing unit 30, an intermediate transfer belt 40, a fusing unit 50, and a delivery unit 60.
The paper feeding unit 10 picks up a piece of paper being received, and feeds (or supplies) the paper to the carriage unit 20.
The carriage unit 20 carries the paper to the intermediate transfer belt 40.
The developing unit 30 includes (as shown, e.g., in FIG. 1) four developing cartridges, each having a developing roller and a photosensitive medium, e.g., a photosensitive drum (e.g., 32C, 32M, 32Y, and 32B), so that cyan, magenta, yellow and black developers can be developed individually on the four respectively corresponding photosensitive mediums. When the photosensitive mediums with a visible image formed thereon according to colors are brought in contact with the intermediate transfer belt 40, they rotate and are layered sequentially on the surface of the intermediate transfer belt 40 to form a color image.
The intermediate transfer belt 40 includes a plurality of rollers configured for driving. Usually, the intermediate transfer belt 40 rotates with a backup roller 41, and transfers a color image transmitted from the developing unit 30 onto the printing paper being carried by the carriage unit 20.
The fusing unit 50 applies high temperature and high pressure to the printing paper bearing the visible image in order to fuse the transferred image onto the printing paper.
The delivery unit 60 delivers the printing paper with the color fused image thereon out of the image forming apparatus.
However, because the intermediate transfer belt 40 always rotates in contact with the developing unit 30 and the backup roller 41, it may easily wear out or abrade as the duration of use increases. Therefore, to extend lifespan of the intermediate transfer belt 40, it generally is best to minimize contact time with the developing unit 30 and the backup roller 41 for reducing abrasion as much as possible.
In practice, however, the operation range of the intermediate transfer belt 40 is fixed by a plurality of roller members. Once the operation range is set, it typically cannot be changed. Therefore, even during the cleaning operation, where there is no need for the intermediate transfer belt 40 to be in contact with the developing unit 30 and/or the backup roller 41, the intermediate transfer belt 40 is constantly driven in contact with the developing unit 30 and the backup roller 41.
Accordingly, there is a need for an improved image forming apparatus having which does not unnecessarily abrade the intermediate transfer belt 40.

Belt clutch apparatus and image forming apparatus having the same


A press felt for use in the press section of a papermaking machine is provided. The press felt includes a base fabric layer and at least one layer of a staple fiber batt material connected thereto. The press felt has a paper side surface (PS) which when in operation is in contact with a paper web conveyed thereon and a machine side surface (MS) which contacts various press section components. The base fabric layer includes a regenerated cellulosic component in either or both the MD and CD yarns. Regenerated cellulosic fibers may also be provided in the batt and/or scrims located in the batt to improve dewatering when compared to similarly constructed felts which lack this regenerated cellulosic material.

The present invention relates to an improved press felt for use on a papermaking machine. More particularly, the invention relates to press felts having a base fabric layer formed at least partially from multifilament yarns that include regenerated cellulosic fibers in order to improve the dewatering capability of the felt.
Press felts are endless belts which may contain a seam and which are used to convey an embryonic paper web from the forming section, through the press and into the dryer section of a papermaking machine so as to dewater and ultimately dry the paper product so that it is suitable for use. In the press section, at least one press nip is typically provided between either a pair of rotating cylindrical rollers, or a roller and concave shoe. The embryonic paper web passes through the at least one press nip laid either upon a single felt, or sandwiched between at least two press felts. As the web passes through the at least one press nip, water is expressed from it and passes into the at least one press felt.
Papermaker's press felts are well known. See, for example, U.S. Pat. No. 4,199,401 to Liu et al., U.S. Pat. No. 4,356,225 to Dufour, U.S. Pat. No. 4,414,263 to Miller et al., U.S. Pat. No. 4,806,413 to Penven, U.S. Pat. No. 5,360,656 to Rexfelt et al., and U.S. Pat. No. 5,864,931 to Best et al. These felts are usually comprised of a woven base fabric (typically formed of nylon or similar polymeric yarns) to which is attached, generally by needling, at least one layer of a pre-tacked staple fiber web, commonly referred to as a batt. Typical press felt batts will usually include between one and about 5 or more layers of a pre-tacked staple fiber web needled onto a first planar surface of the base fabric (usually the surface which, when in use, will be in contact with the paper sheet, and is hereafter referred to as the "PS") to form a PS batt, and from none to one or more layers needled to the opposite planar surface (which when in use will be in contact with the equipment of the paper machine, and is hereafter referred to as the "MS") to form the MS batt. The staple fibers used to form either or both the MS and PS batt are typically made from one or more nylons, polyesters or other polymeric materials such as are commonly employed in the manufacture of industrial textiles.
The batt provides a smooth surface for the paper web and a void volume into which water, which has been expressed from the paper web at the press nip, can be received. The base fabric provides some additional void volume, as well as a stable structure to which the batt can be attached. The base fabric is typically comprised of interwoven polymeric monofilament or multifilament yarns to which the batt is attached, generally by needling or other entanglement process such as is known in the art.
After the paper web has been pressed in at least one nip in the press section, it will still contain an appreciable amount of water, as much as from 30% to about 60% or more by weight. This remaining water must now be removed in the dryer section of the papermaking machine in order to provide a paper product. The final drying of the paper product is typically carried out by evaporative means, which requires a large amount of energy. This adds substantially to the cost of manufacturing the paper product. Generally, a 1% increase in the dryness of the sheet exiting the press section will translate into about a 4% energy savings in the dryer section. It is also possible that the speed of the paper machine may have to be reduced or at least limited due to the evaporative capacity of the dryer section.
Thus, it would be highly desirable if the water removal characteristics of the press felts could be improved so as to increase the amount of water they are capable of transporting away from the paper product as it passes through the press section.
It has been known to use regenerated cellulosics such as rayon as a component of papermaking fabric batt materials. However, such use has generally been restricted to certain specific circumstances. One known application provided an article of paper machine clothing for a press section of an impulse drying machine having a paper contacting surface layer which included a thermal barrier with sheet release properties, a base structure layer, and at least one intermediate layer. This intermediate layer could include fine denier fibers and/or hydrophilic fibers such as wool, cotton and regenerated cellulosics. Fabrics constructed in this manner and evaluated on a pilot scale impulse drying machine operating at 205° C. were reported to have achieved 4 to 5 percentage points of added dryness in the sheet. However, the intermediate layer was heat shielded, and the improved drying appears to have been mainly due to the high drying temperature of about 205° C. This was a press fabric for use at temperatures well above the normal operating temperature range of press sections, which typically run between about 40° C. and about 80° C., and clearly involved a different application.
Another known felt included a so-called "flow control" layer located between the batt and base to "impede rewetting of the paper web" as it exits the press nip. This flow control layer was reported to be formed of a spunbonded filamentary nylon material which is noncircular in cross-section (such as trilobal). It was also noted that the flow control layer could be formed from various materials, including rayon. However, a hydrophobic treatment was imparted to the flow control layer to prevent water absorption.
Another known press felt has been reported that includes a high proportion of fibrillatable fibers located in at least the PS surface of the batt so as to provide a relatively fine sheet supporting surface for the paper web. The PS surface was indicated as being formed from fibers which are as fine as possible (below 1 denier in size). These fine fibers occur as a result of the fibrillation of relatively larger regenerated cellulosic fibers (e.g. >1 denier in size) due to hydroentanglement or mechanical pressure.
A transfer fabric has also been known that includes a base structure and a fiber batt layer which is impregnated with a polymer matrix. The batt fibers differ from one another with respect to their surface properties so that the PS surface of the belt facing the web has both hydrophilic and hydrophobic areas.
The vast majority of press felts which are manufactured for, and are in use in paper mills today, consist of 100% nylon staple fiber in at least the batt, mainly due to its abrasion resistance, resiliency and tenacity.

Press felt with base fabric layer which includes regenerated cellulosic fibers


An approach is described for securely and automatically handling credentials when used for accessing endpoints, and/or applications and resources on the endpoints, and more particularly accessing web endpoints and/or web applications and resources on the web endpoints. The approach involves selecting and injecting credentials at an endpoint by an accessor and/or protocol agent to log into the endpoint, running applications, or gaining access to resources on the endpoint, without full credential information traversing the accessor's machine.

Traditional means of authenticating access to computer systems and computer applications involve knowing a username and password. This results in a password being an important piece of information that needs to be protected since a password leak could lead to unauthorized access to computer systems or applications resulting in business losses. Remembering a multitude of usernames and passwords can be cumbersome and error-prone for a typical user, which can potentially lead to insecure practices such as using the same passwords across applications and systems which in turn increases the risk when a password is leaked.
Traditional two-factor authentication systems overcome some of these problems by using a physical token and password whereby just the loss of password does not compromise security. However, two-factor authentication can be expensive to install, use, maintain, and administer. In addition, many users are more familiar with single username and password use, and introducing a physical token and/or other means of delivering and using software tokens can result in productivity loss caused by having to adjust to a new security regime. Furthermore, various legacy applications and systems do not support two-factor authentication.
Restricting access to computer systems and applications to a select few individuals, carefully disseminating credential information, frequently changing passwords, monitoring, and auditing access are other traditional means of securing password use. But all of these approaches can be prone to human error resulting in password leakage either by accident, due to malware, phishing or some other cyber-attack.
Additionally, the storing and distributing of information across the internet by means of remote databases, web servers, web clients and web browsers, etc., has introduced another opportunity for insecurity that is not easily controlled due to the anonymous nature of the internet. In some scenarios, if the security of a computer has been compromised unbeknownst to the user, any information such as username and password entered by the user is thereby compromised as well.
When granting internal system access to third-party entities, the challenges of securing credentials multiply as an organization may not have complete control over security, operating, and business practices of a third-party.
Based on the foregoing, there is a need for secure and automated credential handling such that credentials are not revealed except at the point of need and transported to the endpoint or application (such as a web application) using cryptographically sound transport mechanisms.

This patent is subject to a terminal disclaimer.

Systems, methods, and apparatuses for credential handling


Oil is recovered from a mercury containing Hg-containing solids containing abradants by mixing the solids with a sulfidic compound in a molar ratio of sulfur compound to mercury from 5:1 to 5,000:1, and the sulfidic compound when dissolved in water, yields S2-, SH—, Sx2-, or SxH— anions, and optionally a solvent, forming a mixture. The mixture is then separated to recover a first phase containing treated oil in water, and a second phase containing treated abradants having a reduced concentration of mercury. In one embodiment, the treated abradants contain less than 100 ppmw mercury. The abradants are provided by removing at least a portion of a mercury-containing coating from a surface by abradant blasting, laser ablation, laser thermal desorption, and sponge jet blasting.

Mercury containing ("Hg-containing") solids are commonly encountered in the oil & gas industry. They come from many sources, e.g., pigging wastes, tank bottom sediments, sediments from separators and other processing equipment, desalter fines, etc. Depending on the level of mercury and other hazardous wastes in the solids, there are various disposal options including non-hazardous land fill, encapsulation (e.g., in cement), incineration, hazardous land fill, and pyrolysis (or retorting).
There is a need for improved methods and systems for the treatment of Hg-containing solids, producing a treated solid portion with reduced mercury contents which can be subsequently disposed and optionally, an oil portion with reduced mercury contents.

Process, method, and system for removing heavy metals from oily solids


A method and system, including a computer program product, implementing a color terminology for accurate color grading of gemstones are provided. The method includes generating a reference color to match that of a graded gemstone under the standard viewing environment, processing color data in different color spaces, assigning a color grade to specify the color of the gemstone graded. The reference color can be continuously changed by adjusting the hue, lightness and saturation values. The color grade comprises a color name and one or more corresponding color coordinates and/or one or more corresponding color notations, in the form of Color Name (Color Coordinates). The color name is used for verbal description of the color, and the color coordinate or color notation is for accurate color communication in the jewelry industry.

1. Field of the Invention
The present invention relates in general to color grading of gemstones. More particularly, the present invention relates to a method and system, including a computer program product, for implementing a color terminology in color grading of gemstones.
2. Description of Related Art
Colors of gemstones are usually graded visually against discrete color samples. For example, U.S. Pat. No. 1,617,024 to Munsell describes color chips. U.S. Pat. No. 4,534,644 to Beesley describes simulating color standards. U.S. Pat. No. 4,527,895 to Rubin describes reference color charts. U.S. Pat. No. 5,005,971 to Davis describes resin color chips, and U.S. Pat. No. 5,143,212 to Roberts describes simulated gemstones.
In known gemstone color grading, the color of gemstones can only be approximately graded using the above-referenced patented methods and systems typically using discrete color samples. In practice, each color grade represents a large or very large volume in color space for the discrete color samples. Thus, such methods or systems for color grading of gemstones are not accurate because of the occupation of significantly large volume in color space for each color grade. For example, two gemstones with the same known color grade based upon know methods and systems may actually have a very large color difference. Therefore, the two gemstones may show totally different perceptual colors, such as a dark brown color and a red color.
Several devices were patented for measuring colors ranging from colorless to light yellow for diamonds (D-Z color scale). U.S. Pat. No. 4,056,952 to Okuda describes a colorimeter, and U.S. Pat. No. 4,508,449 to Okazaki describes a spectrophotometer. U.S. Pat. No. 6,473,164 to DeJong et al describes a color device assigned to the Gemological Institute of America (GIA).
Both the Okuda colorimeter and the Okazaki spectrophotometer use an integrating sphere to measure the color, but their accuracies are not high enough for color grading of colors ranging from colorless to light yellow in diamonds. The GIA color device simulates the condition of human visual color grading for colorless to light yellow diamonds, but the detector does not have the basic function of self-focus of the human eye. Further, the fluorescent daylight tube is not stable enough for color measurement. Thus devices such as the GIA color device are not accurate for the purpose of color grading for colorless to light yellow diamonds.
U.S. Pat. No. 5,615,005 to Valente et al describes an imaging device for evaluating gemstones. The evaluation includes color grading of gemstones. The Valente device utilizes a band pass filter and a detector array to obtain spectral photometric data for each individual pixel of a complete color image for evaluating gemstone. However, this device is not well accepted by the jewelry industry since it does not accurately grade the color of the gemstones. The band pass filter may not be very stable in general, and the device may not be well profiled for color processing and color display.
GIA produced a color image device called ColorMaster for color grading of gemstones. The ColorMaster has three primary R, G and B knobs for adjusting the color of a simulated gemstone image. Due to the ColorMaster's original design problems, it is not suitable for color grading of gemstones. For example, it may result in a significantly large color shift for each ColorMaster due to no user calibration, thereby resulting in large color differences among different ColorMasters. In addition, the GIA color description system is not well defined in color space, and is awkward for verbal communication purposes. The ColorMaster has been abandoned.
Recently, GIA has been utilizing a software named Gemewizard to assist students in the teaching of its Colored Stones courses using the GIA color description system for colored gemstones. The software displays each hue page with about 36 separated color images. However, the software can only display discrete color images. Further, each color grade represents a large volume of color space. Thus the true color of a gemstone cannot be graded by the Gemewizard software.
The International Color Consortium promotes standardizing color management by color profile. The color profile defines how color can be rendered accurately. Color profiles can be used to display accurate colors in computer monitors. U.S. Pat. No. 5,619,349 to Ueda et al describes a device for calibrating display color of a CRT to a color standard, and U.S. Pat. No. 6,853,387 to Evanicky et al describes a system for compact flat panel color calibration. Several commercial available devices can be used to calibrate color monitors for accurate color display.
In Kelly et al Color: Universal Language and Dictionary of Names, NBS Special Publication 440, U.S. Government Printing Office, Wash., D.C., (1976), a method of designating colors and defining color names in the Munsell color space is introduced. Color terminologies used for color grading of gemstones are usually concerned with the fineness of level 3 for color designation. The GIA colored diamond grading system (see King et al, Gem & Gemology, 1994) for example, has only nine color grades for each hue, and about half of the grades are concentrated in a very small volume in color space with low saturation and high lightness. Other color grades cover a very large area. Each color grade actually represents a very large range of colors. Thus, known color grading systems cannot accurately represent any individual color such as the color of a diamond.
Therefore, the need arises for a method and system to provide accurate reference color for color grading of gemstones, to process the color data, to designate a color grade comprising of color names for verbal description and color coordinate or color notations for accurate color communication in the jewelry industry.

Method and system for color grading of gemstones


A rotor for a helicopter, the rotor having a drive shaft rotating about a first axis; a hub connected functionally to the drive shaft in angularly fixed manner with respect to the first axis and in rotary manner with respect to a second axis crosswise to the first axis; and two blades connected to the hub in angularly fixed manner with respect to the first and second axis and in rotary manner with respect to respective third axes; the rotor also having supporting means for supporting the blades with respect to the hub in rotary manner about the respective third axes; the supporting means having at least one supporting member made at least partly of elastomeric material and interposed between a first surface and a second surface integral with a respective blade and the hub respectively; and the supporting member deforming, in use, to permit rotation of the blade, with respect to the hub, about the respective third axis.

Helicopters are known comprising a fuselage; a main rotor mounted on top of a central portion of the fuselage; and an antitorque tail rotor for counteracting the torque transmitted by the main rotor to the fuselage.
So-called teetering or see-saw antitorque tail rotors are also known, which substantially comprise a drive shaft rotating about a first axis of rotation crosswise to a second axis of rotation of the main rotor; a hub connected functionally to the drive shaft in angularly integral manner about the first axis, and free to oscillate about the drive shaft about a third axis perpendicular to the first axis; and a number of blades projecting from the hub on opposite sides of the drive shaft.
More specifically, the blades are angularly integral with the hub about the third axis, can rotate about the hub about respective fourth axes crosswise to the first and third axis, and extend longitudinally along the respective fourth axes.
The hub thus rotates the blades about the first axis, and allows the blades to rotate, by external control, about the respective fourth axes to adjust the respective angles of attack with respect to the airflow. The hub also allows the blades to oscillate integrally with one another about the third axis to "flap" the blades.
Known see-saw rotors also comprise supporting means for supporting the blades with respect to the hub, and which, more specifically, allow the blades to rotate about the hub along the respective fourth axes.
See-saw rotors are particularly advantageous for helicopters, by comprising few component parts.
A need is felt within the industry for see-saw antitorque tail rotors designed to minimize wear and so ensure a high degree of dependability.
A need is also felt within the industry to reduce transmission to the hub, and hence to the fuselage, of vibration and noise generated by rotation of the blades, at least over predetermined frequency ranges.


An optical element and a method capable of electromagnetically inducing transparency in a solid. The optical element includes a solid having a number N of sites characterized by at least three energy levels including a first level higher than a second and a third lower than the second, and an excitation device configured to irradiate the solid with a first light having a wavelength corresponding to the energy difference between the first and the second level, and a second light having a wavelength corresponding to the energy difference between the first and the third level. The solid satisfies .sigma..sub.23 .ltoreq..sigma..sub.12 and .sigma..sub.23 .ltoreq..sigma..sub.13 where .sigma..sub.12, .sigma..sub.13 and .sigma..sub.23 are respectively the standard deviations of the energy differences between the first and second level, between the first and third level, and between the second and third level.

1. Field of the Invention
The present invention relates to an optical element on the basis of electromagnetically induced transparency (EIT) in solid.
2. Description of the Related Art
Recently, concerning optical properties considered to be nature intrinsic to a substance such as absorption and emission spectrum, researches are active about modulating them by employing only quantum mechanical coherence without resort to nonlinear optical process.
For example, intensive researches are made into "EIT" in which light passes through a substance without being absorbed in a wavelength region supposed to show a strong absorption (K. J. Boller et al., Phys. Rev. Lett. 66, 2593, 1991), "lasing without inversion" (LWI) in which it is expected to realize short wavelength laser in ultraviolet ray to X-ray region particularly difficult to form an inversion distribution because laser oscillation is possible without inversion distribution (S. E. Harris, Phys. Rev. Lett. 62, 1033, 1989), "enhancement of index of refraction" in which the refraction index of a substance can be increased very much (M. O. Scully, Phys. Rev. Lett. 67, 1885, 1991, "population trapping" in which an electron is entrapped at a specific level in spite of irradiation of excitation light (E. Arimondo et al., Lett. Nuovo Cimento 17, 333, 1976), and others. Along with these studies, research and development are energetically promoted about various optical elements by applying this kind of quantum coherence, such as light modulation element and LWI laser.
Among the modulation phenomena of optical properties of substance on the basis of quantum coherence, in particular, the EIT is the foundation of all phenomena mentioned above, and in the LWI laser, for example, it is regarded as the indispensable basic technology for realizing it.
Initially, the EIT was a phenomenon discovered when two laser beams were emitted to atom gas, and ever since the first discovery in 1976, similar phenomena were confirmed in various gases. For example, such phenomena were reported by H. R. Gray et al., in Opt. Lett. 3, 218, 1978; M. Kaivola et al., in Opt. Commun. 49, 418, 1984; A. Aspect et al., in Phys. Rev. Lett. 61, 826, 1988; s. Adachi et al., in Opt. Commun. 81, 364, 1991; A. M. Akulsin et al., in Opt. Commun. 84, 139, 1991; Y. Q. Li et al., in Phys. Rev. A51, R1754, 1995; and A. Kasapi et al., in Phys. Rev. Lett. 74, 1447, 1995.
In early days of discovery, meanwhile, it was not called EIT, but was known as population trapping. That is, the EIT is the name when the attention is paid to the spectrum, and the population trapping is the name when attention is paid to the electron distribution, and they refer to the same phenomenon (G. Alzetta et al., Nuovo Cimento B36, 5, 1976).
FIG. 1A to FIG. 1C schematically show the energy level of atom gas and incident light. Referring now to FIG. 1A to FIG. 1C, the basic principle of EIT is described below.
The objective system is basically composed of three levels and two coherent lights (first light, second light). Relating to combinations of levels and lights, there are three types of excitation as shown in FIG. 1A to FIG. 1C.
That is, there are .LAMBDA. type excitation exciting by the first and second light, with the highest level 1 as the common level as shown in FIG. 1A, V type excitation with the basal level 3 as the common level as shown in FIG. 1B, and .XI. type excitation with the middle level 2 as the common level as shown in FIG. 1C.
First, taking note of the case of .LAMBDA. type excitation, in the condition of the light energy .omega..sub.1 of first light (light 1) coinciding with the energy .omega..sub.12 between level 1 and level 2, .DELTA..omega..sub.1 =.omega..sub.1 -.omega..sub.12 =0, the light absorption spectrum is investigated while varying the light energy .omega..sub.2 of second light (light 2).
FIG. 2A shows a light absorption spectrum of second light in this condition. On the axis of abscissas, meanwhile, .DELTA..omega..sub.2 is expressed by the difference of light energy .omega..sub.2 of second light and level 1-3 energy, .DELTA..omega..sub.2 =.omega..sub.2 -.omega..sub.13.
As shown in FIG. 2A, in the spectrum which is supposed to have a single absorption peak, there is a pit of absorption at .DELTA..omega..sub.2 =0 (=.DELTA..omega..sub.1), that is, a transparent region is formed. The width .OMEGA. of the pit at this time is .OMEGA.-(.OMEGA..sub.12.sup.2 +.OMEGA..sub.13.sup.2).sup.1/2, where .OMEGA..sub.12 and .OMEGA..sub.13 are Rabe frequencies of first light and second light.
The Rabe frequency is the quantity expressing the intensity of light, and the Rabe frequencies .OMEGA..sub.12 and .OMEGA..sub.13 are respectively defined as 2.pi..mu..sub.12 E.sub.12 /h and 2.pi..mu..sub.13 E.sub.13 /h, where .mu..sub.12 is the electric dipole moment between level 1 and level 2, .mu..sub.13 is the electric dipole moment between level 1 and level 3, E.sub.12 is the electric field intensity of first light, E.sub.13 is the electric field intensity of second light, and h is Planck's constant.
FIG. 2B shows the light absorption spectrum of second light when the light energy of flight light is fixed in the state of .DELTA..omega..sub.1 .noteq.0. As known from FIG. 2B, there is also a transparent region in which second light is not absorbed in the foot area of absorption where .DELTA..omega..sub.1 =.DELTA..omega..sub.2. In this case, too, the width .OMEGA. of the pit is .OMEGA..about.(.OMEGA..sub.12.sup.2 +.OMEGA..sub.13.sup.2).sup.1/2.
In this way, when first light and second light enter at three levels, in the wavelength satisfying .DELTA..omega..sub.1 =.DELTA..omega..sub.2, light is not absorbed, that is, the EIT occurs even in the region originally showing a strong absorption.
The physical reason why absorption disappears is, intuitively, mutual cancellation by interference effect of optical transition from level 3 to level 1 and transition from level 2 to level 1. A more specific explanation may be made by quantum mechanism, in particular, by analysis of density matrix, and the result of analysis indicates that the absorption is actually eliminated.
So far, all results relate to the .LAMBDA. type excitation, and also the light absorption becomes weak and absorption spectrum is divided into two peaks when the first light (light 1) and second light (light 2) satisfy the relation of .DELTA..omega..sub.1 =.DELTA..omega..sub.2 in the V type excitation, or when satisfying .DELTA..omega..sub.1 =-.DELTA..omega..sub.2 in the .XI. type excitation, as confirmed by both experiment using atom gas and theoretical calculation.
Incidentally, from the result of analysis of density matrix, it is only in the case of .LAMBDA. type excitation that the light absorption strictly becomes zero, but in the V type excitation and .XI. type excitation, by using two lights, it is suggested that the light absorption can decreased nearly to zero.
The principle of LWI on the basis of this EIT is described below.
The LWI also occurs in three schemes, .LAMBDA., V and .XI. types, relating to combinations of level and light, and the .LAMBDA. type excitation is explained below.
FIG. 3A is a schematic expression of energy level of atom gas and incident light.
Herein, the newly added light 3 is incoherent light for pumping electrons from basal state to excitation state incoherently.
Suppose the coherent lights 1, 2 entering the system satisfy the condition of .DELTA..omega..sub.1 =.DELTA..omega..sub.2, and that a transparent region is formed in the absorption spectrum from level 3 to level 1.
If irradiated with incoherent light 3 including transition energy between level 1 and level 3, this light 3 is absorbed in the system. This is, intuitively, because the interference effect by EIT does not work on the incoherent light, and it does not become transparent from level 3 to level 1. The electron excited to level 1 from level 3 by the light 3 falls again at level 3 as coherent light by induction irradiation.
That is, in transition between level 1 and level 3, the incoherent light is absorbed, and the illuminating coherent light is not absorbed, and because of this asymmetry of absorption and illumination, the coherent light 2 is amplified by the incoherent light 3.
Such phenomenon occurs also when the sum of populations of level 1 and level 3 is smaller than the population of level 3 in the basal state, and hence it is noticed as a new principle of laser oscillation.
Thus, to amplify the light 2 without inversion distribution, it requires incoherent pumping means of electrons from level 3 in basal state to level 1 or level 2, or both in excited state.
FIG. 3B shows a scheme of using a new level 4 existing between level 1 and level 2, and pumping electrons to level 2 through this level 4, in which the light 2 can be also amplified without inversion distribution.
As the pumping light, either coherent light or incoherent light may be used. As other pumping means than light, an electron beam may be used as shown in FIG. 3C, and in this case, too, the light 2 can be amplified without inversion distribution.
To compose an LWI laser, as shown in FIG. 4A and FIG. 4B, an EIT medium 101 is held by two mirrors 102 to form a resonator, and only light 1 is emitted as coherent light, and further the electrons are pumped from basal state to excited state incoherently by the light 3.
Herein, supposing the light energy of the light 1 exciting between level 1 and level 2 to be .omega..sub.1, and the level energy between level 2 and level 3 to be .omega..sub.23, a gain of laser oscillation occurs around the center of the light energy (.omega..sub.1 +.omega..sub.23), and hence coherent light occurs. The specific description about the physical reason why laser oscillation occurs without inversion distribution can be shown by analysis of density matrix, same as in the case of EIT.
The above results relate to the .LAMBDA. type excitation, but in the case of V type and .XI. type, too, a gain of laser oscillation occurred in the transparent region having an absorption bit due to EIT, possibility of LWI was suggested from the results of calculation of density matrix.
Hence, when such EIT is applied to the solid, by using one of two lights in the gate and controlling the output intensity of the other light, instead of the light modulation element utilizing the existing nonlinear optics requiring strong light by principle, it leads to realization of light modulation element capable of operating sufficiently even with a feeble light or LWI laser capable of oscillating laser without inversion distribution, and moreover by combination of the modulation phenomenon of optical transition with various properties of solid such as magnetism, electric conductivity, and ferrodielectric property, it is expected to create a functional element of new type different from the conventional electron element.
However, application of EIT into the solid involves the following difficulty. That is, since the EIT interferes the optical transition between specific levels, it is difficult to use levels for forming a band when realizing the EIT in the solid.
Hence, recently, it is intensively studied to realize the EIT by making use of semiconductor superlattice, impurity or defect which are relatively discrete in energy level in the solid (for example, A. Imamoglu et al., Opt. Lett. 19, 1744, 1994; P. J. Harshman et al., IEEE J. Quantum Electronics 30, 2297, 1994; D. Huang et al., J. Opt. Soc. Am. B11, 2297, 1994; and Y. Zhu et al., Phys. Rev. A49, 4019, 1994).
At the present, however, in the solid, such manifest EIT characteristic as noted in the atom gas is not obtained. The causes are large fluctuations in the energy level in the case of the semiconductor superlattice because the superlattice structure cannot be fabricated uniformly by the present element fabrication technology, and also large fluctuations in the energy level in the case of impurity or defect because of distribution in the surrounding crystal field.
Owing to such fluctuations of energy level, there are only few superlattices, impurities or defects that simultaneously satisfy the EIT inducing conditions of .DELTA..omega..sub.1 =.DELTA..omega..sub.2 (in the case of .LAMBDA. type excitation and V type excitation), or .DELTA..omega..sub.1 =-.DELTA..omega..sub.2 (in the case of .XI. type excitation), and hence the EIT characteristic of optical transition is also small as compared with that of atom gas.
That is, in the present element fabricating technology, it is hard to reduce the unevenness of energy level in the solid to a similar level to the level of atom gas, and so far large light modulation characteristic due to EIT indispensable for optical element based on quantum coherence such as light modulating element and LWI laser was not obtained in the solid.
Thus, in the prior art, if the EIT based on the quantum coherence noted in the atom gas is directly applied to the energy level in the solid, a sufficient EIT characteristic cannot be obtained due to random fluctuations of the level in the solid.


An apparatus and method for providing disturbance-free speed and position references to drive units in a web-fed printing press to minimize or eliminate detrimental effects on printing speed and quality caused by transient mechanical disturbances occurring at one or more of the drive units during printing.

1. Field of the Invention
The present invention relates generally to position regulation in printing systems. More particularly, the present invention relates to a control system for a printing press that regulates relative positions of drive units within the press.
2. State of the Art
Because conventional web-fed printing presses such as those used for printing newspapers, have traditionally not been expected to produce high quality or high resolution print, a relatively high degree of tolerance for print quality degradation has existed in the printing industry. However, increasing desire for enhanced quality and resolution of printed products has generated a need for printing presses capable of providing printed products having a high level of quality and resolution. The production of higher quality printed products typically involves an attendant reduction in printing speed. Despite this, there is an increased desire within the printing industry for printing presses capable of operating at high speeds. Simultaneously satisfying the needs for quality, resolution, and speed has proven to be a very difficult task.
A conventional printing press typically includes a number of printing units. The relative positions of drive shafts of the printing units must be accurately controlled to maintain proper registration of the different printing units. Proper registration of the different printing units prevents errors such as printing registration errors, web tension errors, web-to-web registration errors, and/or signature cutoff errors. Such errors are aggravated as printing speeds increase.
In certain printing presses, each group of printing units has a drive unit including a drive shaft which is connected with, and driven by, an output shaft of an electric motor for that particular group. A speed controller provides a speed control signal to control the rotational speed of the output shaft of the electric motor. Other groups of printing units as well as non-printing stages within the press can also have drive units. Typically, one of the drive units of the press is designated as a "master", and receives a signal indicating a desired speed for a web of paper passing through the printing press. This desired speed signal is provided to the speed controller of the master to control the speed of the master's drive shaft. Signals representing the actual speed and position of the master's drive shaft are transmitted to the other drive units, designated as "slave" units. The speed controller of each slave unit provides a speed control signal to the slave unit's electric motor based on the actual positions of the slave unit's drive shaft and the master's drive shaft, to cause the slave unit's drive shaft to track both the speed and position of the master unit drive shaft. Ideally, the drive shaft of each slave unit has the same position and speed as the master's drive shaft.
Many types of regulators are available for regulating the position of a slave drive shaft relative to the position of a master drive shaft, such as phase-locked loop regulators and synchro regulators. A synchro regulator typically includes a synchro to transform the angular position of the slave drive shaft into an electrical output signal. The position of the slave drive shaft relative to the position of the master drive shaft is then regulated in response to the electrical output signal from the synchro regulator. regulators having open-loop compensation, such as "forcing", "speed reference", and "dp/dt feed-forward ", are also known. In addition, a "type-3" regulator that doubleintegrates a position error signal (i.e., a difference between the slave and master drive shaft positions) can also be used. Such a regulator is described in U.S. Pat. No. 5,049,798, issued Sep. 17, 1991, which is incorporated by reference into this document.
FIG. 1 illustrates a conventional printing press 10 including infeeds 12 and 14, a group 207 of print units 200-206 and a group 23 of print units 16-22, a dryer 24, chill units 25 and 26, and folder units 28 and 30. Each of the print unit groups 207 and 23 and the folder units 28 and 30 has a drive unit. A master reference signal source 32 provides a signal indicating a desired printing press speed to the drive unit of the group 207, i.e., a speed command signal. The drive unit of the group 207 is designated as a master drive unit. The other drive units corresponding to the group 23 and the folder units 28 and 30 are designated as slave print units, and track the position and speed of the master drive unit.
FIG. 2 shows details regarding internal components of the drive units within the groups 207 and 23 and the folder units 28 and 30, and connections among the drive units and the master reference signal source 32. In particular, the speed command signal from the master reference signal source 32 is input to a speed control 210 of the master drive unit in the group 207 to control a speed of the motor 260. The speed command signal can be an analog signal or a digital signal. A position encoder 230 determines an actual position of a drive shaft 240 driven by the master drive unit motor 260. Since position information provided by the position encoder 230 can be used to derive speed information, the position encoder 230 can optionally provide feedback to the speed control 210 to ensure that the actual speed of the master drive unit drive shaft 240 matches the desired speed.
The speeds and positions of the slave drive unit drive shafts 242-246 are controlled to match the speed and position of the master drive unit drive shaft 240 using the speed of the master drive unit drive shaft 240 together with feedback regarding positions of the slave drive unit drive shafts 242-246 relative to the position of the master drive unit drive shaft 240.
As shown in FIG. 2, the slave drive units have motors 262-266 that drive drive shafts 242-246. Position encoders 232-236 determine actual positions of the drive shafts 242-246 and provide corresponding feedback signals to regulators 222-226 that indicate the determined positions. As noted above with respect to the position encoder 230 of the master drive unit, information provided by the position encoders 232-236 can be used to determine both speeds and positions of the corresponding drive shafts 242-246. The output signal from the position encoder 230, which indicates the actual position of the master drive unit drive shaft 240, is provided as a position reference signal to the regulators 222-226 of the slave drive units within the print unit group 23 and the folder units 28 and 30 as shown in FIG. 2. The regulators 222-226 compare the master drive unit position encoder 230 output signal with the outputs of the position encoders 232-236, and based on the comparison provide command signals to the speed controls 212-216 to control the speed of the motors 262-266 so that the slave drive unit drive shafts 242-246 track the speed and position of the master drive unit drive shaft 240.
According to one configuration of the position encoder 230, the position encoder 230 provides a pulse for each angular increment through which the master drive unit drive shaft 240 rotates. Thus, as the drive shaft 240 rotates, the position encoder 230 will output a stream of pulses. A number of pulses output by the position encoder 230 during a time interval indicates how much the drive shaft 240 changes position during the time interval. An average speed during the time interval can be easily determined by dividing the change in position by the duration of the time interval.
The angular increment corresponding to a pulse is specified so that the position encoder 230 will output 2,048 pulses during each complete revolution. The position encoder 230 is monitored and the pulses output by the position encoder 230 are counted by a counter (not shown). The counter typically turns over upon completion of one revolution, i.e., resets to zero after counting up to 2,048. Some implementations use a different number of pulses per revolution, and other implementations reset the counter less frequently than every revolution. The position encoders 232-236 have a configuration similar to the configuration of the position encoder 230. Positions of the encoders 230-236 can be synchronized by simultaneously resetting the corresponding counters to zero, for example when the paper web is moving through the printing press at a slow and steady velocity. Thereafter, any difference in values of the counters indicates a phase or position difference. For example, if at a certain point in time the value of the counter corresponding to the master drive unit position encoder 230 is 1,000 and the value of the counter corresponding to the slave drive unit position encoder 232 is 795, then at that point in time the position of the slave drive unit drive shaft 242 is lagging the position of the master drive unit drive shaft 240 by 205 angular increments, or about 36.degree.. Computer software accurately tracks phase differences as the counters turn over, and can also track phase differences greater than one complete revolution. In the printing press shown in FIG. 2, each of the regulators 222-226 has a counter (not shown) for counting pulses from the master drive unit position encoder 230, and a counter (not shown) for counting pulses from one of the slave drive unit position encoders 232-236. In some configurations the counters are located within or near the corresponding position encoders.
Although the regulators 222-226 are configured to synchronize slave drive unit drive shaft speeds and positions with those of the master drive unit drive shaft 240, they do not address problems that arise when mechanical disturbances or control errors occur at the master drive unit drive shaft 240. These errors are transmitted to the slave units, which try to emulate the errors. Thus, an error at the master drive shaft can "ripple" down to the slave units. If the disturbances are large, regulator performance is disrupted or compromised, and process problems such as misregistration can result.
Events that can cause speed and position disturbances during printing operations include, for example, a "blanket wash". When a blanket wash is performed, accumulated dirt and lint are washed or brushed from a blanket roller in the printing press. When a blanket wash is performed at the master drive unit, disturbances can occur in the speed and position of the master drive unit drive shaft 240. These disturbances are transmitted to the slave units, potentially disrupting smooth operation of the printing press and resulting in paper waste and reduced print quality. Other printing press operations can also cause disturbances. For example, disturbances can occur when a new paper web is spliced onto an existing web, or when the web is cut at the folder stage.
Because errors at a master unit are transmitted to the slave units, a unit of the printing press where errors occur least frequently and with lowest magnitudes is usually chosen to be a master unit. For example, in a printing press that has infeed units, printing units, drying units, chill roll units and folder units, as shown for example in FIG. 1, one of the printing units is typically chosen to be a master unit instead of one of the folder units. This is because the cutting operation at the folder unit produces a much larger transient disturbance than the blanket wash operation at the printing unit.
Although human operators try to run printing presses as smoothly as possible to minimize transient disturbances that arise at the master drive unit, disturbances do occur. When disturbances occur, filtering networks and reference dead bands are used until the disturbances are identified and corrected. Paper waste and reduced print quality resulting from the disturbances are accepted as a matter of course. However, it would be desirable to provide a printing press wherein effects of transient disturbances are reduced or eliminated so that improved print quality and reduced waste can be achieved, even at higher press speeds.

Method and apparatus for establishing an isolated position reference in a printing operation