This is a method and an apparatus that provides string bearings (32) and constant inter string pitch correction and pitch trajectory control tremolo device (64 or 80) for a stringed musical instrument (12). The string bearings (32) allow the strings (18) of the instrument to move freely in the axial direction and to be guided with high stiffness in the radial direction. The string bearings contain low axial friction and high radial stiffness bearing inserts (40) whose surface supports the strings to provide the witness points of nuts, bridges, frets, and finger boards. The material of preference for the string bearing inserts (40) is one of the highest energy resiliency and stiffness and the lowest friction. The string bearings and their inserts are adjustable (32, 56, 42, 58) or fixed position. Adjustments are in the horizontal, vertical, and axial (46, 50, 48) directions or any combination thereof. The constant inter string pitch correction and pitch trajectory control tremolo device (64 or 80 in FIG. 5 or 6) provides the simultaneous correction of string pitch to maintain a constant open tuning ratio relationship throughout all tremolo bar input angles and the control of the strings' pitch trajectories to provide a chromatic (FIG. 8), linear (FIG. 9), natural (FIG. 10), or combination pitch trajectory. Non linear string tension devices from the group of substantially non circular pulleys (66), cams (82), and electrically activated solenoids and motors (96) whose axial displacement table (FIGS. 8A, 9A, 10A) has been designed to provide the constant inter string pitch correction and pitch trajectory control multiplicand of the tremolo bar input (76) angle.

1. Field of the Invention
This invention relates to the nut and bridge nodal points called witness points, as well as frets, and finger boards and the tremolo bridge assembly as used on guitars, basses, pedal/lap steel, piano, and other instruments in the stringed family.
2. Description of the Prior Art
Guitarists want to provide a tremolo action to their playing style. Many tremolos have been devised over the past 50 years. They range in design from tremolos that functionally allow only changes in pitch downward to modern tremolos that allow pitch changes in both directions. A few books that discuss modern electric guitar and bass design, for example, are "Electric Guitar" and "Introduction to Scientific Guitar Design" by Donald Brosnac and "Constructing a Solid Body Guitar" by Roger H. Siminoff.
Many design problems exist in the tremolos over the last 15 years. The most important problem is one of staying in tune. The problem is experienced by the user as strings changing pitch during play due to string metal creep and plasticity. Also standard tuning machines have a tendency to rotate, backlash, and experience beam flex at the stem, providing a further causation of a changing string tension and thus pitch.
To date these issues have been addressed in a number of ways. The first basic method was to provide a nut system witness point that locked the string but allowed the tremolo to move freely. Tuning in this system can only be performed by microtuners or by unlocking the string at the nut, with a wrench. The second type of nut system allows the string to move freely across it. Tuning in this system would be either by standard machine tuners or tremolo microtuners.
Tremolos have had several basic designs, which include a bridge witness point that is a hard knife edge that structurally flexes to allow axial string motion, a roller under each string which provides an upward radial force allowing free axial string motion, and a fixed portion of the tremolo movable assembly so that the combined strings can move axially but have radial fixation.
String dynamics are what provides for various degrees of sustain, harmonics & tone, tuning stability, and tremolo action and reaction. The problems with both of the nut witness point systems is that they do not fully provide an environment that supports the string/neck/body unitary structural combination with the proper support to optimize each of the aforementioned attributes. A major contributor to the diminishment of each of these attributes is the stick/slip action of a standard brass and bone type nut witness point. With this traditional design a V or U shaped grove is supplied to fit the individual diameter of each string, as well as that of it's relative vertical and horizontal position. However, the nature of the brass or bone material is that the string always presses its way into the material by it's axial movement and radial pressure. This is often desired by the usual thinking, and provides not only a solid radial force but, in the negative a large axial frictional force of the stick/slip kind. This force is easily overcome by the change in string tension due to tuning machine adjustment, but NOT by the micro-movements in the axial displacement component of the string motion during vibration. The nature of this type of frictional motion is highly non-linear and stochastic in nature. In addition, the nature of this type of force in combination with tuning peg problematic movement, versus intentional tuning adjustments, and knife edged and/or hook return spring based tremolo bridges, constitutes a serious departure from the structural support requirements of the ideal string dynamics as discussed herein.
Typical tremolo designs all have a large disadvantage in that the pitches of the individual strings alter significantly from the inter string pitch ratios of open string tuning. Very quickly the strings each take a different pitch trajectory from the ideal. A secondary result is the lower pitch strings reach slackness well before the higher pitch strings. In addition the pitch trajectories follow an uncontrolled path where each string has its unique and un-orchestrated pitch trajectory. Therefore even the best musician cannot control their music in a fully chromatic or even linear way. This problem precludes a fundamentally basic need in musicology of retaining chromatic order. The ability to produce inter string (note) and chromatically correct music during pitch changes is something almost any synthesizer keyboard can provide.
Secondly tremolo design has been nearly exclusively based upon variations in the knife edge pivot point and roller or edge or rotational witness point type tremolo bridge assemblies. As discussed in the previous section these bridge witness point designs have disadvantages in their approach to string support and produce an adverse effect on string dynamics.
Thirdly in addition to these disadvantages, there exists those intrinsic to knife edge and post pivot designs and hook spring return support blocks. The typical knife edge and post pivot design provides the tremolo with a cost effective way to locate the tremolo axially as well as horizontally and vertically. Usually one post has a semi-circular groove on the tremolo body while the other has a straight edge, the later to allow for location without misalignment. The tremolo body is forced into the post groove by the opposing tensions of the six strings and the two or three hook tension springs. Therefore the static and dynamic axial and radial forces of the six strings are opposed by the two slender posts and the tremolo body hook springs. The knife edge and post groove interface as well as the hook tension springs provide a series of extra resonances, energy storage mechanisms, and highly non-linear forces. Moreover as the tremolo is used and the relative angle of the tremolo body is changed so also the attack face of the knife edge and post groove interface changes, adding further to the stick/slip friction. All these actions take away from the optimum string support and thus diminish the string dynamics comprised of the sustain, harmonics and tone, tuning stability, and tremolo action and reaction.
It could be argued that these non-linear effects add to the "sound"; they may add a type of character to the sound but only detract from user control and the rest of the string dynamics.
Applicant's therefore feel the value of a complete solution to these problems lies in the user's experience of longer sustain, greater tone, more stable tone and phase decay, better feel, stable tuning, improved intonation accuracy, smoother tremolo action/reaction, and force feedback.
Appliant's shall first examine the notable prior art of guitar nut witness points in as regards to the invention, described herein, of String Bearings. The range of interesting prior art includes patents from as early as Faas U.S. Pat. No. 118,353; Hafer U.S. Pat. No. 550,268; and Eurich U.S. Pat. No. 3,695,137; to the contemporary U.S. Pat. No. 4,171,661 Rose; U.S. Pat. No. 4,475,432 Stroh; to most recently U.S. Pat. No. 4,517,874 Fender. In applicant's opinion the landmark patent of this series is that of Rose U.S. Pat. No. 4,171,661. Rose developed a good knife edge/post pivot based tremolo bridge and provided locking mechanism on both ends of the scale length of the strings; the nut and bridge witness points. This was acclaimed by Rose and the industry at the time as the way to insure maintenance of the tuning of the strings while under the strain of the tremolo operation. Many licences of the Rose system continue today producing variations of the lock nut or knife edge bridge. The main theoretical advantage of locking the strings at the Nut Witness point is the maintenance of proper tuning. However this is largely abated by the the need for bridge mounted tuners, lock nut wrenches, and the warped or deformed strings that result from their use. These disadvantages are mechanical, however the dynamic disadvantages also include less tone, instable tone and phase decay, and less smooth tremolo action/reaction, and force feedback for the user. Nevertheless at the time of the Rose patent only the mechanical disadvantages where evident and prompted Edwards U.S. Pat. No. 4,579,033 to develop and patent the Finger Operated Lock Nut. This design obviated the need for wrenches to loosen and re-tighten the clamping action on the strings. The mechanical disadvantages remain albeit less so. With this design the user must still lift the nut's locking handles and then tune/re-tune and re-tighten the handles before continuing. However this design has done nothing to improve string dynamics. It's disadvantages include less tone, instable tone and phase decay, and less smooth tremolo action/reaction, and lower force feedback. Also it is apparent from the use of the locking nut that once the instrument has been tuned that the very clamping action of the lock nut may rechange the tuning parameter once again away from the tuning where the user had previously adjusted it.
Applicant's strong opinion, and the basis for part of the Sting Bearing invention, is that in order to optimize the string dynamics as previously discussed one must allow the string to move axially over the Witness Point with only radial force present. A highly linear and high stiffness structure must provide near zero axial force due to resistance or friction. This must occur for the micro-displacement movements caused by the combinatorial motion of the string and guitar neck/body movements. These motions are on the order of acoustic and flexural displacement axial motions present in a vibrating structure such as a guitar or other stringed instrument.
Applicant's should further point out that standard bone or brass type nuts with fixed cut string groove, require adequate down pressure of the strings into the nut grooves. These grooves are intentionally cut to provide very high grabbing friction from the sides of the nut's grooves to the strings. This friction can be overcome by tuning adjustments. These structures therefore impose a large axial friction force on the strings due to the micro-displacement movements of the strings during play, thus producing an additional undesirable and adverse affect on the string dynamics. Additionally such typical nuts provide low radial stiffness whose characteristics are not linear. Moreover, when a tremolo type bridge is used the normal axial forces imposed by the tremolo action on the strings cause a stick-slip friction response by the V groove and nut interface. This type of force dynamic has an additional adverse effect on the string dynamics.
With these issues in mind it is applicant's opinion that the second landmark patent, in regards to prior art nut witness point technologies, lies in Wilkinson U.S. Pat. No. 4,709,612. Wilkinson also cites U.S. Pat. No. 2,191,776 Schrieber and U.S. Pat. No. 2,905,402 Hoyer. The Nut for Stringed Instruments amounts to a block with individual rollers supporting each string and guidance shapes such as a V shape to guide the entrance and exit of each string in their path to the tuners (this function is normally performed by a string tree guide). It should also be noted that Witness Point technology for the Bridge end can be found in various roller forms such as Storey U.S. Pat. Nos. 4,457,201 and 4,487,100. These rollers however are in a pulley form with a true bearing while Wilkinson's are of the wide cylindrical type riding on their circumferential area. The problems with the Roller Nut are manifold. Practice has shown that the strings do not actually cause the rollers to rotate because of the opposing friction force generated between the rough body's interior and the small diameter roller. In fact the string slides and deforms while crossing the small diameter rollers. The resulting string deformation is plastic, not elastic, and causes many problems in the string dynamics, as previously discussed. Even true pulley rollers, as in Storey's design, have this mechanical behavior in response to the aforementioned micro-displacement movements present in real vibrating systems. It should be pointed out that the Roller Nut does provide the benefit of Tuning adjustments that can be performed without the aforementioned drawback of wrench operated or lever operated Lock Nut designs. These adjustments however comprise relatively gross axial motions in comparison to the aforementioned micro-displacement movements present during string vibration. A final disadvantage of the Wilkinson Roller Nut is that the friction due to the aforementioned micro-displacement movements is exacerbated by the string's rubbing on the sides of the V shape entrance and exit areas.
Applicant's have not discovered any prior art that covers the issues of vertically, horizontally, axial, or any other combination thereof, adjustable nut witness points.
These nut systems, as well as standard bone or brass fixed cut groove style nuts often require a string tree guide for several of the strings. String trees help to maintain an adequate down pressure of those strings into the nut grooves. These structures also impose a friction force, or even plastic deformation force due to the micro-displacement movements of the strings, thus producing additional undesirable results.
The value of solving the problem of the nut witness point lies in improving the string dynamics which in turn allows the user to experience longer sustain, greater tone, more stable tone and phase decay, better feel, stable tuning, improved intonation accuracy, smoother tremolo action/reaction, and force feedback. Operational and mechanical improvements should include: no nut wrench or handle adjustments required, strings do not become plastically deformed (kinked), tuning adjustments are single step only, intonation adjustments are easier, no string tree guides should be required, and strings should not cut themselves deeper into the nut grooves with time. These improvements reduce maintenance cost as well.
The requirements for a novel solution to these problems should provide a basis that allow the dynamics of the strings and instrument structure combination to truly move freely in the axial direction while simultaneously transmitting the vibratory forces of the strings into the instrument without loss or distortion in the radial direction.
Applicant's shall demonstrate that the string bearing invention described herein meets or exceeds these requirements.
Applicant's shall secondly examine the notable prior art in as regards as to Tremolo Bridges. From the early patents such as Faas U.S. Pat. No. 118,353; Van Dusen U.S. Pat. No. 462, 519; Weber U.S. Pat. No. 509,414 and Farigenele U.S. Pat. No. 2,214,957 to the early Fender patent U.S. Pat. No. 2,741,146; and followed by Burns U.S. Pat. No. 3,196,729. Many patents on fixed and tremolo bridges exist.
However the landmark patent in applicant's opinion is that of Rose U.S. Pat. No. 4,171,661. Rose developed a good knife edge/post pivot based tremolo bridge and provided locking mechanism on both ends of the scale length of the strings; the nut and bridge end. Licensing of the Rose system as enforced by his patent continues today. The main issue that appears to be both unique as well as enforceable is the knife edge and post pivot claim.
Some of the most notable tremolo patents are: Storey U.S. Pat. No. 4,457,201 & U.S. Pat. No. 4,487,100 and Wilkinson U.S. Pat. No. 4,709,612. Some tremolo and fixed bridge patents are:
______________________________________ U.S. patents 118353 3563126 4464970 4843941 D269440 462519 3695137 4475432 4856404 D290017 509414 4171661 4487100 4867031 D302563 550268 4206679 4538498 4913024 RE32863 2191776 4230014 4574678 4928564 2214957 4334454 4579033 D244051 2741146 4430919 4677891 D260271 2905402 4464970 4709612 D268272 3196729 4517874 4724737 D269438 3453920 4457201 4811646 D269439 Foreign Patents 620858 3996 72716 ______________________________________
The Rose patent is a landmark primarily because of the knife edge and post pivot design. The Storey patents are interesting because of the micro-tuner and height adjustments as well as mono-cam style rotation of the bridge end string terminations. Important is the "autolatch" device which allows the user to lock the tremolo into neutral center position by use of the tremolo bar rotation. The Wilkinson patent shows an elegant string termination method. Practically however the pivot design is a variation on the Rose patent.
These patents have no bearing on the invention herein described.
Additional prior art of significance is from the Steinburger company. They have developed and are now selling a tremolo with a form of pitch correction. No patents appear at the time of this writing to be issued. The units sold have been marked with the phrase "Patent Pending" and are called the `TransTrem`. The tremolo has been designed to provide for locking the device at specifically calibrated positions in order to allow the user to put the tuning up or down specific steps in pitch. This function is called transposition and has been performed using a typical Capo which is applied on the finger board near the top (nut end) frets. After examination of the production tremolo device applicant's have observed that it has a rotatable assembly with six saddles, one per string. The strings terminate in the saddle whose relative circumferential adjustment allows that each string will have a unique fixed effective radii from the assemblies effective center of rotation. Applicant's have, in applicants work with the invention described herein, proved that such a structure can only provide an effective inter string pitch correction if the set of effective radii that are produced during the assembly's rotation are exact. Applicant's have determined that the Steinburger design could only provide inter string pitch correction within a narrow range or rotation. It is therefore inadequate and inexact for this first task. Furthermore the Steinburger has no facility to provide chromatically correct, or any other, pitch trajectory control. Its ability to provide a transpositional function is derived from calibrated steps provided for the user to leave the tremolo in a particular position to achieve say a step or half-step down. This function is NOT an intrinsic aspect of their design but is no doubt the result of a trial and error effort which resulted in the development of tremolo angle position indentations that provide only specific settings. The use of theoretically constant radii CANNOT provide any continuously chromatic functioning. Furthermore the design that applicant's have inspected is not capable of accurate inter string pitch correction and may not provide true pitch coherence as well.
Most of these tremolo designs have several major drawbacks in their design from a string dynamic, as well as a guitar neck & body dynamics, point of view. Primarily they are the vibratory and acoustic dynamic characteristics of the knife edge and post pivot and those of the hook return springs. Secondly their use of rotating, flexing, or V groove Bridge Witness points is also a large drawback.
The drawbacks of the knife edge and post pivot design lay in three areas. The first is in the rotational micro-angular changes in the interface between the groove on the tremolo support base plate and the post knife edge type head. This changing interface is highly non-linear and contributes mechanical noise to the subtle displacements due to the string/instrument dynamics. Secondly, the interface itself between the knife edge post head and the base plate screw along with the contribution of the changing interface attack surface, is one whose mechanical acoustic wave signal impedance characteristics are dubious. The impinging stress wave due to the normal string dynamic cannot easily pass through this pivot structure without large distortion and reflection. Thirdly, the post itself is a resonant structure of fairly high resonant frequency which should on first examination be in the upper frequency range of musically useful interest. On further examination one can see a highly unusual acoustic/mechanical impedance mismatch between the various guitar components such as the neck, body, even the tuning pegs and the two small pivot posts on the typical tremolo. The various guitar components such as the neck, body, and the tuning pegs (1 per string) have a much higher stiffness and certainly more stable acoustic/mechanical impedances than do the two small posts that must carry the entire reactive force component into the body of the guitar in both radial as well as axial directions.
The drawbacks of using hook springs to provide return action in opposition to the strain of the strings in these tremolo designs lies in a similar way to the drawbacks inherent in the knife edge post, namely they are insuffcient nonlinear mechanical elements with regards to stress wave mechanical signal impedance. Unlike posts, hook type return springs have fundamental resonant frequencies within the frequency bands of interest. They contribute both resonant and anti-resonant peaks to the response spectra of the structure. This effect is most often to the detriment of the dynamics, and playability, of the instrument.
The drawbacks of rotating, flexing, V groove, and pulley Bridge Witness points lies in several areas. For rotating cam like witness points as found on many tremolo bridges such as Storey and Wilkinson, they lack a true witness point. Namely the string flexes around the surface of the cam and does not actually have a radial witness point per se. Only friction and the final anchor point provide a radial reactive force component. In addition most designs actually move the witness point axially while rotating. For flexing type witness points the drawbacks include that the witness point moves axially as well as the string must drag the witness point structure along with itself by only the friction between them. For typical rigid V groove witness point bridges the strings have a large friction force axially as well as a stick-slip friction response action. Lastly for pulley type witness points, they provide low axial friction but add an undesirable dynamic due to the mechanical clearance of the elements. Moreover usually this pulley type witness point has been made to move its effective axial position with the tremolo rotation causing the overall string length to change with operation. All these aforementioned actions provide undesirable results by combining both string tension and length based pitch changes simultaneously, and add a frictional element that is highly non-linear and damping on the vibratory string dynamics. All these actions are clearly undesirable from the point of view of string dynamics, intonation, tonality, and playability.
The final major drawback of all these prior art tremolo designs is they lack the ability to maintain a relative and accurate tune between the six strings. This is true because when all the strings have a relatively fixed relation among them the high strings will provide a different pitch change factor than the lower strings for an equal change in string length. This is because the typical tremolo designs such as Storey and Rose change the displacement of all the six strings equally.
Such equal displacement change CANNOT provide for constant inter string tuning nor for any type of pitch trajectory control.
Mechanically, the ideal for a witness point and tremolo bridge is:
First to maintain a constant string length by not moving the positions of the nut or bridge witness points.
Secondly, provide for the strings to be elastically strained to provide the pitch change.
Third, the strings must remain in relative open tuning pitch ratios to one another while the overall tremolo pitch change occurs during tremolo operation.
Fourth, the trajectories of the pitches of the strings must be controlled to provide continuous and accurate, chromatically correct music.
Fifth, the ideal in an acoustic wave sense for a witness point and tremolo bridge is to allow the acoustic mechanical stress waves to pass through the tremolo structure without gross mechanical impedance changes and without resonant structures with resonant frequencies either in the band of interest or with transient responses much less than those of the neck and strings and the other major mechanical guitar components.
No prior art patented or not patented, known to these writers provides these five criteria in total or in majority.

String bearing and tremolo device method and apparatus for stringed musical instrument


In a vehicle seat, in particular a motor vehicle seat, having a seat substructure (3) and a backrest (6) which is to be fastened to the seat substructure (3), the backrest (6) can be fastened to the seat substructure (3) by means of a quick-fitting connection (10, 13).

The invention relates to a vehicle seat, in particular a motor-vehicle seat, having a backrest fastened to a seat substructure.
During production of known vehicle seats of this type, the metal structures of the seat substructure and of the backrest are first of all screwed together and then the upholstery is fitted. Variations in width and distortion of the seat substructure may result in the backrest adjuster becoming deformed and therefore in loss of comfort.
In accordance with one aspect of the invention, a vehicle seat has a backrest fastened to a seat substructure by means of a quick-fitting connection. The structures can first of all be upholstered separately and then assembled in a simple manner. If required, the seat substructure and backrest can be transported to the vehicle manufacturer""s facility prior to being assembled and assembled only once there. This has the advantage of a smaller volume for transportation and an optimum packing density. This also enables different equipment versions of the seat substructure and backrest to be more easily combinable, either at the vehicle-seat manufacturer""s facility or at the vehicle manufacturer""s facility. The compensating of tolerances which is generally required can be shifted into this intersecting point between the seat substructure and backrest. The quick-fitting connection is preferably such that the seat substructure and backrest can be connected to one another without requiring the use of any tools, so that the assembly can be brought about in a simple manner. Screw connections, which in the prior art lead to deformation when there are variations in tolerance, are avoided by means of the screw-less and rivet-less quick-fitting connection of the present invention. Assembly generally takes place once during the production of the vehicle seat. However, the quick-fitting connection may, if appropriate, also be released in a controlled manner by the seat user and re-made if the seat user wants, for example, to create further storage space in his vehicle.
In a preferred embodiment, sockets into which feet of the backrest can be introduced are provided on the seat substructure. Sockets and feet may be provided the other way round on the other part in each case. The forces which act on the backrest, in particular in the event of a crash, are passed on via the feet and the sockets into the seat substructure. The sockets preferably have bolts which can be introduced into curved slots in the feet. Bolts and curved slots may be provided the other way around on the other part in each case. The quick-fitting connection is first latched in place by means of the bolts and curved slots, this latching being simple to produce and therefore being cost effective. As regards safety in a crash, curved slots have the advantage that it is not possible for a movement in a single direction to cause the bolts to leave the curved slots and that there is a positive lock in the respective other directions which, if the parts are dimensioned appropriately, absorbs very large crash forces. A respective socket and a foot having two bolts and curved slots in each case are preferably provided on each side of the vehicle seat. However, a different number of these latching elements may also be provided.
For further latching in place, a spring-loaded locking eccentric is provided which, in an assembled state of the vehicle seat, acts as a blocking element holding at least one of the available bolts in the associated curved slot. The eccentric shape produces a clamping action, i.e. securing by means of a force fit. A release catch is preferably provided in order to hold the blocking eccentric in an unlocked manner in a dismantled state of the vehicle seat. So that it is possible for this release latch to be released easily, in a dismantled state of the vehicle seat it is arranged in such a manner that it preferably traverses one of the curved slots, i.e. lies in the path to be covered by the bolt. In order to secure the blocking eccentric in the assembled state of the vehicle seat, a spring-loaded blocking pawl is preferably provided which prevents an unintentional opening movement of the blocking eccentric.

Vehicle seat with a joint for rapid assembly


A partially overmolded integrated circuit package (10) comprises a substrate (14) having circuit traces (11) and a semiconductor die receiving area (15) for attachment of a semiconductor die to the semiconductor die receiving area. Conductive bumps (18) are then applied to a plurality of contact pads on the semiconductor die. Then overmolding compound (16) is applied over the semiconductor die and a portion of the conductive bumps, leaving a portion of the conductive bumps partially exposed (19). Finally, interconnections (13) between the exposed portion of the conductive bumps and the circuit traces of the substrate are formed.

Wirebonding in integrated circuit packages is one of the sources of intensive labor and of yield defects. Furthermore, conventional chip-on-board packages and overmolded pad array carriers (OMPAC) have a profile or thickness that could be reduced. The cost of manufacturing flip chip and chip-on-board packages could be reduced if fine pitched lines and spaces were not required on a printed circuit board. Both flip chip and chip-on-board packages require fine pitched printed circuit boards or substrates. Further expense is found in the requirement of gold plating for wirebonding on chip-on-board packages.
Flip-chip and chip-on-board packages also have mechanical and electrical disadvantages. For instance, with flip-chip packages there are tiny solder joints and heat dissipation problems. With chip-on-board packages and other packages requiring wirebonding, electrical characteristics may vary due to the flexibility of conductor widths and materials and the inconsistency of wire lengths. Finally, many packages require the extra step of passivating die pad surface. Therefore, a need exists for a smaller profiled IC package that does not require fine pitched printed circuit boards or gold plating for wirebonding. Furthermore, a need exists for an IC package that has excellent mechanical and electrical characteristics that does not require passivation for die pads and overcomes the problems described above.

Method and apparatus for partially overmolded integrated circuit package


After subjected to a developing process, a rinsing process and a replacing process in this order in a developing unit 10A, 10B, a substrate W wet with an anti-drying solution is wet-transported to a supercritical drying unit 20 by a primary transport robot 30. The supercritical drying unit 20 performs a high-pressure drying process (supercritical drying process) in a dedicated manner. Accordingly, by virtue of the presence of the anti-drying solution, the substrate W is effectively prevented from becoming air-dry during the transportation of the substrate W.

1. Field of the Invention
The present invention relates to a substrate processing method of performing sequential processes from a predetermined wet process to a drying process on a variety of substrates such as semiconductor wafers, glass substrates for photomask, glass substrates for liquid crystal display, glass substrates for plasma display, optical disk substrates (hereinafter, simply referred to as "substrate"), as well as to a substrate processing apparatus and a substrate processing system suited for such a method.
2. Description of the Related Art
In recent years, the semiconductor devices have been speeding toward fine structure which has raised new problems in the substrate processing field. In a case where a fine pattern is formed by patterning a resist applied on a substrate, for example, a wet developing process and a drying process are performed in this order. In the wet developing process for developing the resist applied on the substrate, an alkaline developing process and a rinsing process are carried out, for example. Specifically, the alkaline developing process uses an aqueous alkaline solution for removal of unwanted resist, whereas the rinsing process uses a rinse liquid such as pure water for removal of the aqueous alkaline solution (for terminating the developing process). In the drying process, on the other hand, the substrate is rotated thereby subjecting the rinse liquid remaining on the substrate to centrifugal force for removing the rinse liquid. Thus is dried the substrate (spin drying). In the drying process, the substrate encounters the appearance of interface between the rinse liquid on the substrate and gas as the drying process proceeds. When such an interface appears in a gap between fine pattern portions of a semiconductor device, the fine pattern portions are drawn toward each other by the surface tension of the rinse liquid so that the fine pattern portions are collapsed.
In addition, fluid resistance produced in the spin drainage of the rinse liquid, pressure acting to discharge the rinse liquid from the fine pattern portions, and the air resistance and centrifugal force associated with the high-speed rotation in excess of 3000 rpm are thought to be involved in the collapse of the fine pattern portions.
As a solution to this problem, there has been proposed a supercritical drying process wherein the substrate is retained in a pressure container while a supercritical fluid having properties of low viscosity, high diffusivity and no surface tension (hereinafter, referred to as "SCF") is introduced into the pressure container for accomplishing the supercritical drying of the substrate.
For instance, an apparatus described in Japanese Unexamined Patent Publication No. 2000-223467 (hereinafter, referred to as "Patent Document 1") is adapted to retain, in a reaction chamber, a substrate subjected to the developing process (alkaline developing process and rinsing process). With the substrate retained in the reaction chamber, the apparatus activates a pump unit to pump a given amount of liquefied carbon dioxide from a cylinder into the reaction chamber. In the meantime, the pressure of carbon dioxide in the reaction chamber is automatically controlled by way of a pressure control valve so as to be maintained in the range of 7.38 to 8 MPa whereby the carbon dioxide in the reaction chamber is transformed to the supercritical fluid. Subsequently, the supercritical fluid is released from the reaction chamber to reduce the pressure in the reaction chamber, whereby the substrate is allowed to dry.
The supercritical drying apparatus is dedicated solely to the drying process and hence, the developing process (alkaline developing process and rinsing process) is carried out in a developing apparatus separate from the drying apparatus. In order to subject the substrate to the sequential substrate processes from the developing process to the drying process, the conventional practice requires the substrate wet with the rinse liquid to be transported to the supercritical drying apparatus after the performance of the alkaline developing process and rinsing process in the developing apparatus. This is because if the substrate becomes air-dry during the transportation from the developing apparatus to the supercritical drying apparatus, the fine pattern portions are drawn toward each other by the surface tension of the rinse liquid so as to be collapsed. As a consequence, the performance of the supercritical drying means nothing.
As a solution, it may be contemplated to provide a developing unit functioning as the developing apparatus and a high-pressure processing unit functioning as the supercritical drying apparatus in the same apparatus, which is further provided with a transport robot as a transport unit which may wet-transport the substrate developed by the developing unit to the high-pressure processing unit.
Unfortunately, the aforesaid substrate processing apparatus including the developing unit, the high-pressure processing unit and the transport robot takes only the alkaline developing process into consideration, thus suffering poor versatility. The developing process taken in the fabrication process for fabricating electronic components such as used in semiconductor apparatuses and liquid crystal display units is not limited to the aforesaid alkaline developing process but includes a plurality of developing processes. In cases, for example, in place of the alkaline developing solution, an organic developing solution such as butyl acetate may be used according to a film material for forming a resist film. The developing process using the organic developing solution may be followed by the rinsing process using isopropyl alcohol (IPA) as the rinse liquid.
In order to enhance the versatility of the substrate processing apparatus, it may be contemplated to provide the processing apparatus not only with the alkaline developing unit, an alkaline-development transport robot for transporting an alkaline developed substrate and a high-pressure processing unit which carry out the alkaline developing process, but also with an organic developing unit for performing an organic developing process, an organic-development transport robot for transporting an organically developed substrate and a high-pressure processing unit which carry out the organic developing process. However, such a substrate processing apparatus provided with the special transport units (the alkaline-development transport robot and the organic-development transport robot) corresponding to the individual developing contents is detrimentally increased in size and costs.
On the other hand, a substrate processing apparatus has been proposed which is designed to perform a wet process such as the developing process and a high-pressure drying process using the SCF in the same reactor. According to an apparatus disclosed in Japanese Unexamined Patent Publication No. 11-87306 (hereinafter, referred to as "Patent Document 2"), for example, when a processing fluid, such as a rinse liquid, an etching solution or a developing solution, is introduced from a liquid tank into the reactor with a substrate set at place therein, the processing fluid in the reactor is stirred by a rotating mechanism so that a smooth and consistent wet process is effected. Subsequently, a rinse liquid in place of the processing solution is introduced from a liquid tank into the reactor for carrying out the rinsing process. Thereafter, the rinse liquid is discharged from the reactor while the SCF from a gas cylinder is introduced into the reactor. Thus, the rinse liquid is replaced with the SCF. Then, the SCF is slowly discharged for carrying out the supercritical drying process or the high-pressure drying process. That is, this substrate processing apparatus negates the need for transporting the substrate from the developing apparatus to the supercritical drying apparatus. Therefore, there occurs no problem that the substrate becomes air-dry during the transportation so that the fine pattern portions are collapsed as drawn toward each other by the surface tension of the rinse liquid.
However, the following problem is encountered by the conventional apparatus wherein the wet process and the high-pressure drying process are sequentially performed in a single reactor. Specifically, the substrate processing apparatus designed to perform the high-pressure drying process has more limiting conditions than the conventional substrate processing apparatus widely used in the art or the substrate processing apparatus carrying out surface treatment under normal pressures. The most crucial one of the limiting conditions is that the range of selection of the processing fluid is limited. The reason is as follows. This substrate processing apparatus must employ a pressure container as the reactor. Where a corrosive processing fluid of strong acid or strong alkali is used for carrying out the surface treatment, the processing fluid corrodes a liquid contacting surface of the pressure container. On this account, a corrosive chemical agent of strong acid or alkali cannot be introduced in the pressure container for carrying out the surface treatment. As a result, the range of selection of the processing fluid is notably reduced.
It may naturally be contemplated to apply an anti-corrosive coating such as of a fluorine resin to an inside surface of the pressure container for the purpose of eliminating the above limitation. However, it is actually impossible to ensure that the anti-corrosive coating continues to exhibit its function over an extended period of time under the high pressure condition. Even if the inside surface of the pressure container is coated with the anti-corrosive coating, it is impracticable to apply the anti-corrosive coating on the inside surfaces of all the associated components including thin piping extended to the pressure container, joints, high-pressure valves and the like.

Substrate processing method, substrate processing apparatus and substrate processing system


The present invention relates to novel methods for the prevention, treatment and diagnosis of Alzheimer's disease. In addition, the invention relates to methods for assessing an individual's susceptibility or pre-disposition to Alzheimer's disease. The methods of the present invention involve the use of therapeutic targets and diagnostic and/or predictive markers within the mTOR signalling pathway. The methods also involve screening subjects for genetic polymorphisms associated with rapamycin-sensitive genes.

Alzheimer's disease is the most common form of dementia in older people. As a result of population aging worldwide, the prevalence of this disease is set to increase significantly in coming years. As such, there is an urgent need to develop better prognostic and diagnostic tools and new treatments for people identified as having this disease.
Alzheimer's disease is a chronic neurodegenerative disorder characterised by selective loss of cortical neurons within the hippocampus and the temporal and frontal lobes of the brain. The neurodegenerative process occurring in Alzheimer's disease is accompanied by progressive cognitive impairment leading ultimately to dementia in affected individuals.
There is currently no accepted "gold standard" diagnostic test for Alzheimer's disease in the live patient. This reflects the difficulties associated with identifying patients who would go on to be classified as having this disease at post mortem examination. Clinical diagnosis of Alzheimer's disease is typically based on evaluation of clinical criteria, such as the NINCDS/ADRDA criteria (McKhann, G. et al., (1984) Neurology 34: 939-944).
The problem with the diagnostic methods used to date lies in the fact that patients are typically diagnosed once clinical dementia has started to develop. It follows therefore, that existing treatment strategies are limited to agents used primarily to manage the symptoms of disease. For example, cholinesterase inhibitors are administered to patients so as to block the degradation of the neurotransmitter acetylcholine and thereby enhance neurotransmission in the brain. Use of such agents can help to preserve cognitive function, but does not improve the underlying pathology and is therefore not a curative approach.
Although the etiology of Alzheimer's disease is poorly understood, the neuropathology associated with the development of this disease has been relatively well characterised. The classical hallmarks of this disease consist of amyloid-β plaques, which accumulate in the brain, and neurofibrillary tangles (NFT) consisting of hyperphosphorylated tau protein present in affected neurons. Additional changes occurring at the cellular level, which are now thought to precede the deposition of plaques and NFTs, include damage to cells caused by oxidative stress, mitochondrial malfunction and aberrant re-entry of neurons into the cell division cycle.
In addition to difficulties associated with diagnosing Alzheimer's disease, there are also problems associated with identifying individuals in the population who are at increased and/or decreased risk of developing Alzheimer's disease during their lifetime, as compared with the average level of risk associated with the general population. The only known genetic risk factor for late onset sporadic form of Alzheimer's disease is the polymorphism on the ApoE gene. Other discovered polymorphisms appear to be restricted to relatively small patient subgroups. Thus risk prediction or assessment of susceptibility, before the development of clinical Alzheimer's disease, is difficult as well.
There is now good evidence to suggest that the neuropathology underlying Alzheimer's disease begins years, maybe even a decade, prior to the diagnosis of clinical dementia (Forlenza et al., (2010) BMC Medicine 8:89). Based on these observations, the continuum of Alzheimer's disease progression has been classified into three phases:    (i) asymptomatic Alzheimer's disease (preclinical stage);    (ii) mild cognitive impairment (MCI) due to Alzheimer's disease (pre-dementia stage); and    (iii) clinically-defined Alzheimer's disease (dementia).
In light of the above, there now exist several opportunities for improved management of Alzheimer's disease. In particular, it may be possible to identify individuals at increased risk of developing Alzheimer's disease, and/or diagnose individuals at a much earlier stage of disease, for example, individuals with asymptomatic disease or those patients with MCI that will go on to develop clinically-defined Alzheimer's disease. If susceptible individuals can be identified and/or diagnosed at an earlier stage of disease, it will be possible to develop, test and use new preventative and/or curative treatments intended to stabilize and/or reverse the neurodegenerative process and thereby prevent cognitive decline.
Researchers are already using the improved knowledge of Alzheimer's disease pathogenesis to develop more effective methods of diagnosis and treatment. In this regard, diagnostic biomarkers have been identified that can be measured in humoral fluids, mainly cerebrospinal fluids, and biomarkers that may be detected using advanced neuroimaging methods (Gustaw-Rothenberg et al., (2010) Biomark. Med. 4(1):15-26).
Furthermore, new "disease-modifying" treatments are being developed that tackle the deposition of β-amyloid plaques and NFTs (Bonda et al., (2010) Curr. Opin. Drug Discov Devel. 13(2): 235-246)
There remains however, an ongoing need to improve methods for the diagnosis and treatment of Alzheimer's disease, particularly early-stages of disease. The present invention seeks to address these issues.

Therapeutic targets for Alzheimer's disease


An NPN bipolar transistor and a PNP bipolar transistor are formed in a semiconductor substrate. The NPN bipolar transistor has a p type emitter region, a p type collector region and an n type base region and is formed in an NPN forming region. The PNP bipolar transistor has an n type emitter region, an n type collector region and a p type base region and is formed in a PNP forming region. Only one conductive type burying region is formed in at least one of the NPN forming region and the PNP forming region. A current that flows from the p type emitter region to the n type base region flows in the n type base region in a direction perpendicular to the substrate.

This application is based upon and claims the benefit of Japanese Patent Application No. 2001-123003 filed on Apr. 20, 2001 and No. 2001-203663 filed on Jul. 4, 2001, the contents of which are incorporated herein by reference.
The present invention relates to a semiconductor device having bipolar transistors.
U.S. Pat. No. 5,856,695 discloses a semiconductor device having NPN transistors and PNP transistors. In the semiconductor device, vertical-type transistors having an n+ burying region and p+ burying region are used as the NPN transistors and the PNP transistors in order to coincide both electrical features thereof.
However, both the n+ burying region and the p+ burying region are needed, and masks for forming the n+ burying region and the p+ burying region have to be prepared. Therefore, the manufacturing cost of the semiconductor device is increased.
Alternatively, a lateral-type transistor can be employed as the PNP transistor to avoid above-mentioned limitation. However, use of a lateral-type transistor has other associated limitations.
First, as shown in FIGS. 23A, 23B, a number of carriers are stored in an n+ base region J1 of the PNP transistor because an n+ base region J1 of the PNP transistor is wider than the p+ base region J2. Therefore, a switching speed of the PNP transistor is larger than that of the NPN transistor, thereby generating an unbalance in the switching speeds.
Second, as shown in FIG. 24, a current amplification ratio of the PNP transistor is not fixed in comparison with that of the NPN transistor. Therefore, it is difficult to use the lateral-type transistor in a complementary device.
An SOI (silicon On Insulator) substrate is often used for making a semiconductor device. The SOI substrate has a support layer, an element forming layer and a burying oxide layer that is disposed between the support layer and the element forming layer. In the semiconductor device using the SOI substrate, trenches that reach the oxide layer are provided to isolate respective semiconductor elements.
In a semiconductor device manufactured using an SOI substrate, it is possible to increase a withstanding feature with respect to noise, and to prevent parasitic diodes or transistors in the semiconductor device from activating.
As shown in FIGS. 25A, 25B, a trench 102 is formed in an element forming layer 101 for isolating respective semiconductor elements. A high impurity conductive burying diffusion region 104 is formed on a side of a burying oxide layer 103 of the element forming layer 101. A support layer 105 is disposed on the side of the burying oxide layer 103 that is opposite to the side of the element forming layer 101.
A base region 107 and a V-shaped emitter region 108 are formed in a surface region of the element forming layer 101. A collector region 109 is formed in the surface of the element forming layer 101 separately from the base region 107 and the emitter region 108.
A current flows between an emitter electrode and a collector electrode (not shown) through the burying diffusion region 104. Therefore, resistance between the emitter electrode and the collector electrode decreases, thereby ensuring required current amount.
When the burying diffusion region 104 is formed in the SOI substrate, an ion implantation is conducted from a surface of the element forming layer 101. Also, the burying oxide layer 103 is formed on a surface of the support layer 105. Thereafter, the element forming layer 101 and the support layer 105 are stacked.
Therefore, the element forming layer 101 needs a thickness corresponding to that of the burying diffusion region 104. Accordingly, the formation time of the trench 102 is typically long because the depth of the trench 102 increases depending on the thickness of the element forming layer 101.
Further, because the joint adherence between the burying oxide layer 103 and the burying diffusion region 104 is not very good, the yield ratio of the SOI substrate is low.
On the other hand, the yield ratio of the SOI substrate can be increased and manufacturing time of the SOI substrate can be shortened if the burying diffusion region 104 is removed. Further, the amount of silicon substrate can be reduced.
In this case, however, the resistance between the emitter electrode and the collector electrode will increase. As a result, the required current amount is difficult to secure.
Incidentally, the required current amount can be secured if a total area of the semiconductor device increases. However, the resulting amount of required silicon substrate cannot be reduced.
It is therefore an object of the present invention to provide a semiconductor device having bipolar transistors that is capable of obviating the above problem.
It is another object of the present invention to provide a semiconductor device having a NPN transistor and a PNP transistor having balanced electrical features.
It is a further object of the present invention to provide a semiconductor device having bipolar transistors that is capable of obtaining required current amount without requiring a burying diffusion region.
According to this invention, an NPN bipolar transistor and a PNP bipolar transistor are formed in a semiconductor substrate. The PNP bipolar transistor has a p type emitter region, a p type collector region and an n type base region and is formed in the PNP forming region. The NPN bipolar transistor has an n type emitter region, an n type collector region and a p type base region and is formed in an NPN forming region. Only one conductive type burying region is formed in at least one of the NPN forming region and the PNP forming region. A current that flows from the p type emitter region to the n type base region flows in the n type base region in a direction perpendicular to the substrate.
Accordingly, respective features of the PNP transistor are fixed because the current flows in a longitudinal direction of the substrate. Therefore, it is possible that the semiconductor device can have the NPN transistor and the PNP transistor having balanced electrical features by using the same substrate and only one conductive type burying region.
Further, a p type well region is formed in the PNP forming region. The n type base region is formed on a surface region of the p type well region and the p type emitter region is formed on a surface region of the n type base region. A distance from a bottom portion of the p type emitter region to the p type well region in the direction perpendicular to the substrate is the shortest distance from the p type emitter region to the p type well region. Therefore, a current between the emitter region and the collector region flows in the direction perpendicular to the substrate via the bottom portion of the emitter region.
According to this invention, an n type suction region is further formed in the well region to suck carriers injected from the n type emitter region. Therefore, the holes injected from the emitter region are sucked by the suction region. As a result, the switching speed of the NPN bipolar transistor becomes high.
According to this invention, a p type diffusion region is formed in the PNP forming region for encompassing the p type collector region. Therefore, it is possible to reduce resistance around the bottom portion of the p type collector region at which a current is especially concentrated. Accordingly, it is possible to secure a high current amplification ratio HFE even if a current flowing between the p type emitter region and the collector region is high.
It is preferable that the p type collector region is formed in a center of the PNP bipolar transistor, and that the n type base region and the p type emitter region are formed around the p type collector region.
It is also preferable the p type emitter region is formed in the center of the PNP bipolar transistor, and that the n type base region and the p type collector region are formed around the p type emitter region.
It is furthermore preferable the p type collector, the n type base region and the p type emitter region are arranged in a stripe-like manner.
Further, it is preferable that the n type collector region is formed in a center of the NPN bipolar transistor, and that the p type base region and the n type emitter region are formed around the n type collector region.
It is also preferable that then type emitter region is formed in the center of the NPN bipolar transistor, and that the p type base region and the n type collector region are formed around the n type emitter region.

Semiconductor device having bipolar transistors


The present invention relates to a billing system, method, a service server and end-point terminal respectively which allows the end-point terminal to use billing authentication information of another mobile communication terminal. The billing system comprises: a first mobile communication terminal and at least a second mobile communication terminal with each mobile communication terminal connected in common to a service server through a mobile communication network in which said end-point terminal is connected to said first mobile communication terminal through a first short-range communication network for providing contents to the first end-point terminal that uses the billing authentication information of the second mobile communication terminal and a billing server for performing a billing process if the service server transmits contents to the first end-point terminal upon validation by the service server by comparing the billing authentication information transmitted from the first end-point terminal with billing authentication information received from the second mobile communication terminal to determine if a match exists.

With the advancement of information communication technologies, a variety of end-point terminals capable of playing back documents, images and moving pictures (hereinafter, 'documents, images and moving pictures' will be simply referred to as 'contents' for the convenience of explanation, unless otherwise specified), such as MPeg audio layer-3 (MP3) players, Personal Multimedia Players (PMP) and Ultra Mobile Personal Computers (UMPC), are widely used. A user downloads desired contents from personal computers (PC) and plays back the downloaded contents. However, there is a problem in that the user cannot download desired contents when the user is moving or cannot connect to a PC.
In order to solve the problem, proposed are techniques for adding a communication means connectible to a short-range communication network onto an end-point terminal, such as a Bluetooth or an ultra-wideband (UWB), and connecting the end-point terminal to a mobile communication terminal through the short-range communication network. According to the techniques, a user can be provided with a desired service through an end-point terminal and a mobile communication terminal of the user. That is, the user manipulates the end-point terminal and the mobile communication terminal to communicate with each other in a short-range wireless communication method through the short-range communication network to exchange needed data with each other. The mobile communication terminal is connected to a variety of servers through a mobile communication network (or a wired communication network such as the Internet or the like via the mobile communication network) and relays needed data between the end-point terminal and the servers, and thus the end-point terminal eventually can use a needed data service through the short-range communication network and the mobile communication network owing to the relay of the mobile communication network.
On the other hand, although the end-point terminal used by the user receives contents from a service server via the first mobile communication terminal, a service fee of the end-point terminal needs to be charged on the second mobile communication terminal. For example, if the user is a teenager carrying the first mobile communication terminal and parents of the user have the second mobile communication terminal, the parents may desire a service fee for using contents by the teenage user to be charged on the second mobile communication terminal of the parents, not on the first mobile communication terminal of the child.
Conventionally, techniques for a mobile communication terminal to collect billing information of an end-point terminal for using contents and transmit the billing information to a billing server have been proposed. However, although the conventional techniques are used, the requirements described above cannot be satisfied, and in addition, loads on the mobile communication terminal collecting and transmitting the billing information to the server are intensified furthermore.

Fee charging system, fee charging method, service server, service providing method, and storage medium


An audio signal processing system can be configured to provide virtualized audio information in a three-dimensional soundfield using at least a pair of loudspeakers or headphones. The system can include an audio input configured to receive audio program information that includes at least N discrete audio signals, a first virtualization processor circuit configured to generate intermediate virtualized audio information by filtering M of the N audio signals, and a second virtualization processor circuit configured to generate further virtualized audio information by differently filtering K of the N audio signals, wherein K, M, and N are integers. The system can include an audio signal combination circuit to combine the intermediate virtualized audio information with at least one of the N audio signals, other than the M audio signals, to render fewer than N audio signals for transmission to a second virtualization processor circuit.

Audio plays a significant role in providing a content-rich multimedia experience in consumer electronics. The scalability and mobility of consumer electronic devices along with the growth of wireless connectivity provides users with instant access to content. Various audio reproduction systems can be used for playback over headphones or loudspeakers. In some examples, audio program content can include more than a stereo pair of audio signals, such as including surround sound or other multiple-channel configurations.
A conventional audio reproduction system can receive digital or analog audio source signal information from various audio or audio/video sources, such as a CD player, a TV tuner, a handheld media player, or the like. The audio reproduction system can include a home theater receiver or an automotive audio system dedicated to the selection, processing, and routing of broadcast audio and/or video signals. Audio output signals can be processed and output for playback over a speaker system. Such output signals can be two-channel signals sent to headphones or a pair of frontal loudspeakers, or multi-channel signals for surround sound playback. For surround sound playback, the audio reproduction system may include a multichannel decoder.
The audio reproduction system can further include processing equipment such as analog-to-digital converters for connecting analog audio sources, or digital audio input interfaces. The audio reproduction system may include a digital signal processor for processing audio signals, as well as digital-to-analog converters and signal amplifiers for converting the processed output signals to electrical signals sent to the transducers. The loudspeakers can be arranged in a variety of configurations as determined by various applications. Loudspeakers, for example, can be stand-alone units or can be incorporated in a device, such as in the case of consumer electronics such as a television set, laptop computer, hand held stereo, or the like. Due to technical and physical constraints, audio playback can be compromised or limited in such devices. Such limitations can be particularly evident in electronic devices having physical constraints where speakers are narrowly spaced apart, such as in laptops and other compact mobile devices. To address such audio constraints, various audio processing methods are used for reproducing two-channel or multi-channel audio signals over a pair of headphones or a pair of loudspeakers. Such methods include compelling spatial enhancement effects to improve the listener's experience.
Various techniques have been proposed for implementing audio signal processing based on Head-Related Transfer Functions (HRTF), such as for three-dimensional audio reproduction using headphones or loudspeakers. In some examples, the techniques are used for reproducing virtual loudspeakers localized in a horizontal plane with respect to a listener, or located at an elevated position with respect to the listener. To reduce horizontal localization artifacts for listener positions away from a "sweet spot" in a loudspeaker-based system, various filters can be applied to restrict the effect to lower frequencies.

Distributed audio virtualization systems


Embodiments of systems and methods are provided for a tunable laser device. The tunable laser device may include a diffraction grating connected to a pivot arm that pivots the diffraction grating about a pivot point to tune the laser device. In pivoting the diffraction grating about the pivot point, both the wavelength to which the diffraction grating is tuned and the length of the optical cavity may be changed. The length of the pivot arm may be selected to reduce the number of mode hops of the tunable laser device when tuning the laser device over its tuning range.

1. Field of the Invention
The present invention relates generally to lasers, and more particularly, to external cavity lasers.
2. Related Art
The use of an external laser cavity with a spectrally selective element has been used for several decades to create a laser with a narrower spectral linewidth than is available with the non-wavelength selective mirrors in the laser cavity of the typical laser. In addition, the tenability of the spectrally selective element may create a laser with an agile wavelength that may be both narrow in line width and cover a broad tuning range. The spectrally selective element in many non-integrated external cavity lasers may be a diffraction grating. These diffraction gratings may be designed to meet a broad range of laser cavity needs such as size, efficiency, and dispersion. The tuning of the wavelength of the laser may be achieved by adjusting the grating angle of the diffraction grating with respect to the laser beam.
Tuning such a laser by merely adjusting the grating angle may result in the laser occasionally "hopping" from one cavity mode to another cavity mode. A cavity mode (referred to hereafter as a "mode") refers to the integral number of half wavelengths of light at the tuned wavelength that fit within the optical cavity of the laser. Further, these hops from one mode to another are referred to as mode hops. Mode hops may result in the instability of the laser output by the laser system. Thus, it is desirable to reduce the number of mode hops that exist across a tuning range of the laser system.
Accordingly, there is a need for laser systems with improved mode hop performance over the tuning range.


The present invention provides a class of surface-active siloxane compounds each having a single reactive alkoxysilane moiety. The siloxane compounds are linear or cyclic and are reactive to moisture and to compositions having hydroxyl-functionality.

There is an ongoing need to provide surface-active siloxane compounds for use in surface coatings to impart properties such as water repellency, spreadability, low friction coefficient, reduced brittleness, and high gloss to a variety of surfaces such as wood, metal, and concrete. There has correspondingly been a need to control these properties at a molecular level so that undesirable effects, such as excessive surface migration, poor paintablility, and areas of high localized cross-link density do not adversely affect a surface coating in its properties such as consistency, performance, or esthetic surface appearance.
Surprisingly, the present invention provides a class of siloxanes, each having a single reactive alkoxysilane moiety, which siloxanes are reactive to moisture and compositions having hydroxyl-functionality, including polymers of various kinds and inorganic substrates, such as silica fillers, and which siloxanes are stable and have long term storage capabilities.

Surface-active siloxane coating compounds and their use in coatings


The present invention provides a variable valve mechanism, which includes a rocker arm including an input member and an output member; a switching device that switches a drive state of the valve by displacing the switching pin between a coupling position at which the switching pin extends between the first pinhole in the input member and the second pin hole in the output member and a non-coupling position at which the switching pin does not extend; and a lost motion spring. A displacement clearance is formed between an inner peripheral surface of the first or second pin hole and an outer peripheral surface of the switching pin to permit the relative displacement in a range of the displacement clearance at a coupled time so that a tappet clearance is not formed with the input member urged toward the cam by the lost motion spring.

A variable valve mechanism 90 according to the related art illustrated in FIG. 10 is described in Patent Document 1. The variable valve mechanism 90 includes a rocker arm 93 swingably placed on a support member 92 that projects upward. The rocker arm 93 includes an input member 93A driven by cams 91 and 91 (high-lift cams) and an output member 93B that drives a valve 7.
The variable valve mechanism 90 further includes switching pins 96 and 96 and a hydraulic chamber 98 provided inside the rocker arm 93, and an oil passage 97 that extends to the hydraulic chamber 98 by way of the support member 92 and the rocker arm 93. The variable valve mechanism 90 switches the drive state of the valve 7 by displacing the switching pins 96 and 96 between a coupling position at which the switching pins 96 and 96 extend between the input member 93A and the output member 93B and a non-coupling position at which the switching pins 96 and 96 do not extend between the input member 93A and the output member 93B based on variations in hydraulic pressure in the oil passage 97 and the hydraulic chamber 98. The variable valve mechanism 90 further includes lost motion springs 95 and 95 that urge the input member 93A toward the cams 91 and 91 at a non-coupled time.

Variable valve mechanism of internal combustion engine


A novel process for the treatment of wastepaper which provides for enhanced removal of both ink particles and non-ink contaminants is disclosed.

In modern times, with the ecological concerns about conservation of raw materials and the rapid decline of available landfill space, it has become increasingly desirable to recover and recycle used raw materials. Thus, recovered wastepaper represents a valuable source of raw material for the paper industry. In order for the wastepaper to be regenerated into a viable starting material and to produce a commercially acceptable paper, the wastepaper must be treated to remove any ink particles and non-ink contaminants.
Many prior art processes are known for deinking wastepaper, many of which are directed to the development of deinking agents. Poppel et al., U.S. Pat. No. 4,586,982 describe a process comprising treating the wastepaper in a pulper at an alkaline pH with alkali silicate, an oxidatively active bleaching agent, an acid selected from the group consisting of fatty acids and resinic acids containing more than 10 carbon atoms and a dispersing agent wherein the acid and dispersing agent are employed together in an oil-in-water emulsion. Other disclosures of deinking agents are set forth in, for example, Wood et al., U.S. Pat. No. 4,618,400 (thiol ethoxylate compounds); Wood et al., U.S. Pat. No. 4,561,933 (a mixture of C.sub.8 to C.sub.16 alkanols and alcohol ethoxylates); DeCeuster et al., U.S. Pat. No. 4,343,679 (compounds capable of liberating ions with a positive charge equal or greater than 2); Bridle, U.S. Pat. No. 4,483,742 (pine oil and a soap-making fatty acid); and Tefft, U.S. Pat. No. 4,786,364 (a hydrolyzed copolymer of dimethyldiallyl ammonium chloride and acrylamide).
Other prior art processes are directed to improvements in either washing or flotation methods of separating ink particles from wastepaper fibers.
Nanda et al., U.S. Pat. No. 4,548,673 describe a deinking flotation method comprising the steps of independently introducing air into a fiber stock slurry, mixing the air bubbles and slurry, and separating the ink-laden air bubbles from the fiber slurry, where each of these steps is independently controlled. Shiori et al., U.S. Pat. No. 4,749,473, describe introducing air bubbles into the wastepaper pulp slurry through a number of orifices formed on a peripheral surface of at least one rotatable horizontal cylinder located in the bottom portion of a flotation vessel. Pfalzer et al., U.S. Pat. No. 4,277,328, describe employing an impeller at the bottom of a flotation apparatus for dispersing air into the wastepaper pulp slurry.
None of these processes however are directed to providing a method which facilitates both removal of ink particles and enhanced removal of non-ink contaminants. The presence of non-ink contaminants is a recurring problem in the recycling of wastepaper. These contaminants have in most cases been added intentionally during the actual manufacture of the paper in order to give the fibrous structures special additional properties, or during processing of the paper. The contaminants may be polymeric and are of various types such as polyvinyl acetates, vinyl acetate/ethylene coplymers, waxes, styrene/butadiene latices, polystyrene, hydrocarbon resins, polyisoprenes, resin esters, butyl rubber or polyamides. They end up in specific products such as sealing tapes, adhesives used for bookbinding, coated cardboard, contact adhesives, envelopes and adhesives for gluing cardboard.
The polymeric contaminants, especially glues or adhesives, are especially troublesome. They form agglomerates which deposit in the installations for regenerating wastepaper and in the machines for manufacturing paper or cardboard. Moreover, these agglomerates detract from the final appearance of the sheet of paper or cardboard and they cause tearing when the paper is used as printing paper, in particular in rotary printing machines.
Maloney et al., U.S. Pat. No. 4,643,800 teaches blending contaminated secondary fiber with water, a substituted oxyethylene glycol surfactant and a dispersant and coincidently heating the blend to a temperature above the melting point of the contaminant to be dispersed and removed. Other disclosures of high temperature decontamination include Maloney et al., U.S. Pat. No. 4,483,741 and Maloney, U.S. Pat. No. 4,599,190.
Hageman et al., U.S. Pat. No. 4,548,674 disclose decontaminating wastepaper fibers by pulping the wastepaper in an acidic aqueous solution (pH=2.5 to 6.5) containing at least one peroxide compound selected from among organic and inorganic peracids.
Clement, U.S. Pat. No. 4,780,179 discloses a decontamination method comprising a cold temperature low mechanical energy pulping step, followed by screening, thickening and high temperature high shear washing steps to aid in removal of non-ink contaminants. The Clement patent however suffers from the need of requiring separate steps of non-ink contaminant removal, ink softening and ink particle detachment, each step requiring a specific set of parameters and thus describing an expensive and difficult to accurately control process.
Thus, there remains a long felt need in the art to provide a simple and easy to control wastepaper treatment process whereby there is obtained enhanced removal of both ink particles and non-ink contaminants.


An improved cleaning step for cleaning interconnects such as tungsten filed vias or contacts. After the tungsten plugs have been formed substantially coplanar with the surrounding dielectric surface (or adhesion or barrier layer surface), the wafers are cleaned in a sequence of chemicals that finishes in a solution that includes hydrogen peroxide. The temperature and concentrations of the active agents are chosen such that etching is minimized until the application of sonic energy. This light etching of the interconnect tungsten and cleaning of the exposed surface has been found to better prepare these surfaces for receiving an overlying metal layer. The electromigration performance of the overlying metal layer shows substantial improvement when this cleaning step is used. The cleaning step is used following an ethylene glycol-HF mixture cleaning step, dependent on the degree of interconnect and dielectric coplanarity after the tungsten etch step. The prior art step of argon sputtering is not needed to obtain the improved electromigration performance. Device yields may be substantially improved depending on the level of wafer cleanliness prior to the application of the clean.

1. Field of the Invention
The invention relates to the field of cleaning associated with metal interlayer connections, particularly plugs used in integrated circuits.
2. Prior Art
Integrated circuits have long used layers of metals for the upper levels of circuitry. These metal layers generally have interlayer connections (interconnects) and sometimes interconnects that allow direct connections to the lower levels of circuitry defined in the silicon substrate or polysilicon levels. Subsequent complexity has added more layers of metalization separated by dielectric layers, and has shrunk the size of the interlayer connections. These interlayer connections are often made with materials different from the primary metal of each layer. The openings in the dielectric layers are typically called contacts or vias, and the fill material is sometimes called a plug. These fill or plug materials are selected for their superior deposition properties in small geometries, in addition to their conductivity. As the physical dimensions of these interlayer connections have shrunk the reliability problems associated with electromigration have increased.
In typical processing for forming an interlayer connection, first an opening is patterned and etched through an interlayer dielectric. The dielectric may be doped glass such as boron-phosphorous glass (BPSG), spun glasses, or deposited or thermally grown oxides commonly referred to as an interlayer dielectric (ILD).
In some processes a thin adhesion layer is next required in preparation for the material used to fill the via or contact. A typical material is titanium nitride (TiN) which may be deposited by physical sputtering or a chemical vapor deposition (CVD) process. This adhesion layer covers the wafer surface and to various degrees the bottom and sidewalls of the contact or via.
The next step is the deposition of the interlayer connection (interconnect) material, which completely fills the openings as well as covering the surface of the dielectric layer or adhesion layer. A typical process deposits tungsten. This material is then partially removed by plasma etching or mechanical polishing until the surface film is removed and the remaining tungsten is somewhat coplanar with the opening in the dielectric. In this manner the interconnect between the layers of circuitry is defined and the wafer is ready for the next layer.
It is necessary to remove substantially all of the interconnect fill material from the surface of the dielectric prior to deposition of the next metal layer. For example, if tungsten is used as an interconnect material, any tungsten residue may create an electrical defect between the metal circuit lines of the overlying layer.
Moreover, the surface of the dielectric layer must typically be cleaned of residues remaining from the etch back or polish process again to prevent pattern disruption in the next metal circuit layer.
Finally, the surface of the interconnect filled via must be prepared for forming a low resistance interface for connection to the next metal layer. This is frequently done in the metal deposition machine using such techniques as argon sputtering. However, this process creates problems of its own as particles from the sputtering apparatus become deposited on the wafer, again creating pattern defects.
In typically processing in preparation for metal deposition of the filled interconnects, combinations of solvents and acids are used to clean the residues and prepare an interface for good conduction. However, this processing typically results in the formation of voids in the metal-interconnect interface as shown in FIG. 5. Additionally, sharp features of the interconnect material can create electric field nonuniformities that are undesirable.
The present invention provides a novel cleaning step for the interlayer connections that addresses these issues and, in fact, can be used to reduce the argon sputtering requirements.

Cleaning step which improves electromigration performance of interlayer connection in integrated circuits


Automatic configuration of devices upon introduction into a networked environment, can be implemented, for example, by having a device randomly generate a series of letters and/or numbers, e.g., generate a PIN (Personal Identification Number) that encodes temporary credentials that, in addition to proving ownership and/or control over the device by virtue of having access to the PIN, also allows creating a temporary secure communication channel based on the PIN over which permanent security credentials may be transferred to the device to facilitate provisioning it to securely communicate in the networked environment. In a wireless scenario, a unique SSID and encryption key (WEP or WPA) may be determined as a function of the PIN, where both the device and its access point utilize the PIN to establish a temporary secure communication channel. Various techniques may be used to establish ownership and/or control over the device to prevent inadvertent association of the device with a wrong networked environment.

Today, if you want to add a device into a networked environment, such as a wireless device to a wireless network, and you are not interested in laying your network open to intruders, it is necessary to delve into the workings of the security systems, such those based on WEP (Wired Equivalent Privacy or sometimes Wired Equivalency Protocol), WPA (Wi-Fi Protected Access), EAP (extensible authentication protocol), IEEE (Institute of Electrical and Electronics Engineers)'s 802.11i, and the like.
Unfortunately, establishing proper credentials in both the wireless device and its associated access point can be difficult and error-prone. And, it typically needs to be done manually to prove ownership and/or control over the device during its introduction into the networked environment. That is, requiring otherwise, e.g., to have the device initially operate in the open (as is done in some consumer products), leaves the device vulnerable to compromise before it can be secured, and one installing the device risks it being erroneously associated with an incorrect networked environment.


A hydraulic oil well pump drive system for driving an oil well sucker rod includes a wellhead hydraulic assembly that is operably connected to the oil well sucker rod to reciprocate the sucker rod. The wellhead hydraulic assembly includes a hydraulic cylinder and a rod that reciprocates linearly within the hydraulic cylinder. The rod has an upper end with a circumferential groove that receives a split cylindrical bearing. The split cylindrical bearing is has two semicircular halves retained within the groove by the inner walls of the cylinder. The halves are retained vertically, relative to the rod, by the groove itself.

Oil wells vary in depth from a few hundred feet to up to 14,000 feet. Oil is lifted from these depths by a plunger which reciprocates within a pump barrel at the bottom of the well. The plunger is driven by a sucker rod or an interconnected series of sucker rods which extend down from the surface of the oil well to the plunger.
FIG. 1 shows a conventional pump jack 10 for driving the sucker rod of an oil well pump. Pump jack 10 generally comprises a walking beam 12 which is connected through a polished rod 14 to an in-hole sucker rod (not shown). Walking beam 12 is pivotally supported at an intermediate position along its length by a samson post 16, which is in turn mounted to a base frame 18. A drive crank system 20 is also mounted to base frame 18. Base frame 18 is mounted to a concrete base to rigidly locate all components relative to the oil well.
Drive crank system 20 has a rotating eccentric crank arm 24. Crank arm 24 is driven at a constant speed by an electric or gas motor in combination with a gearbox or reducer, generally designated by the reference numeral 26. Eccentric crank arm 24 rotates about a horizontal axis.
Walking beam 12 has a driven end 30 and a working end 32 on either side of its pivotal connection to samson post 16. One or more pitman arms 34 extend from driven end 30 to a crank pin 35 positioned intermediately along outwardly extending eccentric crank arm 24. Rotation of crank arm 24 is translated by pitman arms 34 into vertical oscillation of the walking beam's driven end 30 and corresponding oscillation of working end 32.
Working end 32 of walking beam 12 has an arcuate cable track or horsehead 36. A cable 38 is connected to the top of the cable track 36. Cable 38 extends downwardly along the cable track 36 and is connected at its lower end to polished rod 14. Pivotal oscillation of walking beam 12 thus produces corresponding vertical oscillation of polished rod 14 and of the connected sucker rod. The arcuate shape of cable track 36 ensures that forces between working end 32 and polished rod 14 remain vertically aligned at all positions of walking beam 12.
The sucker rod of an oil well pump performs its work during an upward stroke, when oil is lifted from the well. No pumping is performed during the downward stroke of the sucker rod. Accordingly, a pump jack such as described above supplies force to a sucker rod primarily during its upward stroke. Relatively little force is produced on the downward stroke. To increase efficiency of a drive system counterbalance weights are utilized to store energy during the sucker rod downward stroke and to return that energy to assist in the sucker rod upward stroke.
In pump jack 10, counterbalance weights 40 are positioned at the outermost end of crank arm 24. Such weights could also be positioned on the driven end 30 of walking beam 12. However, a mechanical advantage is obtained by placing the weights outward along the crank arm from the pitman arm connection. During the downstroke of the sucker rod the driving motor must supply energy to raise weights 40 to the top of their stroke. During the sucker rod's upstroke, however, weights 40 assist the motor and gearbox since the outward end of crank arm 24 moves downward while the sucker rod moves upward. The peak energy required by the motor is therefore greatly reduced, allowing a smaller motor to be used with corresponding increases in efficiency.
Mechanical pump jacks such as described above have been used for many years and continue to be used nearly exclusively for driving oil well pumps. Acceptable substitutes have simply been unavailable. One reason for the popularity of such mechanical systems is their extreme simplicity. They do not involve valves, switches, or electronics, and there are a minimum of moving parts. This simplicity results in reliability which is difficult to accomplish with more complex systems. Reliability is of utmost importance since oil well pumps are unattended for long periods, often being located in remote locations.
The very nature of sucker rod displacement created by a reciprocating pump jack is another apparent reason for its success. An oil well sucker rod is often over 14,000 feet long. While reciprocating, it must not only accelerate and decelerate itself, but also a 14,000 foot oil column. In addition, it must accelerate and decelerate oil within an above-surface production line, which can be as long as five miles. Forces caused by sudden acceleration of the sucker rod are therefore very significant. Any such sudden or undue acceleration can stretch and snap the sucker rod.
The pump jack described above minimizes acceleration and deceleration forces on the sucker rod by producing an approximately sinusoidal displacement at the polished rod. The sinusoidal displacement results from translation of rotary crank motion to linear motion at the polished rod. Such sinusoidal motion significantly reduces strain on the driven sucker rod.
However, while the pumping action of a mechanical pump jack is preferable to previously-known alternatives, its physical size creates significant disadvantages. For instance, the great weight of the walking beam, gearbox, and counterbalance weights requires expensive support bases and land site preparation. Rates of reciprocation are often limited by this weight. In addition, pump jacks must be attached permanently above a wellhead and are therefore not easily moved to another site. This results in costly pumping equipment sitting idle during periods of oil well inactivity.
While alternative drive systems have been attempted, none have met with significant commercial success. FIG. 2 illustrates one prior art drive system, comprising a hydraulic pump drive system which is generally designated by the reference numeral 50. Drive system 50 includes a hydraulic cylinder 52 containing a piston assembly 54. Piston assembly 54 is designed for reciprocal vertical motion within cylinder 52. It comprises an elongated center shaft 56 having a pressure piston 58 on its upper end and a working piston 60 at an intermediate position along its length. Center shaft 56 has a lower end which is connected through a coupling 62 to a polished rod 64.
Cylinder 52 has a centrally located annular flange 66 which seals against center shaft 56 between pressure piston 58 and working piston 60 to divide cylinder 52 into an upper pressure chamber 68 and a lower working chamber 70. Pressure piston 58 reciprocates within pressure chamber 68 and working piston 60 reciprocates within working chamber 70.
Piston assembly 54 is driven up and down by hydraulic force applied alternately to the bottom and then the top of working piston 60. A hydraulic pump 72 supplies hydraulic fluid under pressure from a reservoir 74 to a cross-over hydraulic valve 76. Valve 76 is in fluid communication with working chamber 70 through fluid ports both above and below working piston 60. A lower limit switch 78 and an upper limit switch 80 are actuated by a switch actuator 82 which travels up and down with center shaft 56. Actuator 82 actuates lower limit switch 78 at the bottom of desired piston assembly travel, causing cross-over valve 76 to supply pressurized hydraulic fluid to working chamber 70 below working piston 60. This forces piston assembly 54 upward. Actuator 82 actuates upper limit switch 80 at the top of desired piston assembly travel, causing cross-over valve 76 to supply pressurized hydraulic fluid to working chamber 70 above working piston 60. This forces piston assembly 54 back down. Hydraulic fluid displaced by piston 60 from the non-pressurized side of working piston 60 is returned through valve 76 into fluid reservoir 74.
Pressure chamber 68 is filled with hydraulic fluid below pressure piston 58 and is connected for fluid communication with an accumulator cylinder 84. Accumulator cylinder 84 has a free-floating piston 86 which divides accumulator cylinder 84 into a hydraulic fluid chamber 88 and a gas chamber 90. Hydraulic fluid displaced from pressure chamber 68 by the downward movement of pressure piston 58 is forced into hydraulic fluid chamber 88, forcing free-floating piston 86 toward gas chamber 90. Gas chamber 90 contains pressurized gas which opposes such movement.
Hydraulic drive system 50 thus provides a hydraulic mechanism for alternately moving a sucker rod upward and downward. Furthermore, the opposing pressure of the pressurized gas within gas chamber 90 assists in the upward stroke of piston assembly 56 and the connected sucker rod. This allows using a smaller hydraulic pump than would otherwise be necessary. The drive system does not, however, address the problems of sudden sucker rod acceleration and deceleration. In fact, the significant force applied to the sucker rod is subject to sudden and complete reversal at both the top and bottom of each sucker rod stroke. The resulting acceleration and deceleration tends to greatly reduce the life of a sucker rod.
Attempts have been made to reduce the sudden acceleration and deceleration which often occurs at the point of stroke reversal in prior art hydraulic pump drive systems. For instance, U.S. Pat. No. 2,555,426 to W. C. Trautman et al. describes using a gas accumulator connected to a hydraulic pressure line which feeds a hydraulic drive cylinder. The gas accumulator is said to maintain a constant pressure on a polished rod so that the velocity of the polished rod can vary according to the resistance encountered and produced by the polished rod and connected sucker rod. However, such an accumulator produces a great degree of elasticity in the drive system, often resulting in uncontrolled and erratic sucker rod displacement. Such uncontrolled displacement itself is a cause of unacceptable acceleration and deceleration. The elasticity in the Trautman drive system prevents it from producing the constant, sinusoidal motion of a pump jack, which experience has proven to be preferable.
The Trautman patent also describes a rather complex valving system intended to modulate the reversal of hydraulic oil pressure to the drive cylinder. Recognizing the desirability of reducing acceleration extremes, Trautman proposes a mechanism for decelerating the drive piston rapidly but uniformly at the end of its stroke, and then accelerating it as rapidly as possible at the beginning of the next stroke (column 9, lines 26-34). Using this approach, full hydraulic pressure is applied at the beginning of each stroke, causing rapid and uncontrolled acceleration of the polished rod and connected sucker rod.
The Trautman mechanism and similar devices have failed to gain any significant acceptance as replacements for mechanical pump jacks. One of the primary disadvantages of such prior art mechanisms is that they involve complex valving systems. Often, the mechanisms require numerous valves, hydraulic pumps, displacement and velocity sensors, and other electronic equipment. Such complexities greatly diminish reliability.
In contrast to the valved mechanisms described above, some prior art systems have used crank-type mechanical drives to reciprocate a master cylinder assembly. U.S. Pat. No. 2,526,388 to William Otto Miller is an example of an oil well pump drive system which uses a mechanically-driven master piston. While drive systems such as described by Miller are significantly simpler than systems utilizing hydraulic switching, they have not been proven to be reliable enough to replace conventional pump drive systems. One significant disadvantage of the Miller system is the driving apparatus used in its master cylinder, shown in FIG. 2 of the Miller patent. The master cylinder utilizes what is known as a "Scotch Crosshead." While this driving arrangement produces a linear displacement thought by Miller to be an improvement over the prior art, it requires a number of sliding surfaces and results in off-center or angularly-misaligned forces which tend to reduce the life of the master cylinder components. The Miller system, perhaps in part because of these reasons, has not been commercially accepted.
The Miller system also does not address the problem of oil leakage in hydraulic systems. Oil leakage can be a significant problem with pumping systems which are installed for continuous and unattended operation for long periods. An automatic method of monitoring and replenishing oil is needed which will not add undue complexity and cost.
The invention described below eliminates virtually all of the complexities of the prior art devices. This results in a hydraulic drive system which emulates the motion of a mechanical pump jack while requiring no valves or variable restrictions during its normal operation. Furthermore, the unique master cylinder mounting arrangement used in the invention eliminates off-center or angularly-misaligned forces at the master cylinder assembly. While providing simplicity in both construction and operation, the preferred embodiment of the invention includes means for automatically regulating pump stroke and for monitoring and automatically replenishing leaked oil. The further advantages of the invention over both mechanical pumping jacks and over prior art hydraulic pump drives will be apparent from the discussion below.