Methods and systems are disclosed for an integrated voltage regulator with open loop digital control for power stepping. In one aspect, a method for regulating an output voltage includes receiving data indicative of a power setting associated with an identified state of an electrical circuit, the power setting based on a load current demand of the electrical circuit in the identified state, enabling one or more parallel driver segments based on the received data indicative of the power setting. The method further includes sourcing by the enabled one or more parallel driver segments sufficient current to meet the load current demand of the electrical circuit in the identified state while maintaining the output voltage at a predetermined voltage level, and providing the output voltage to the electrical circuit at the predetermined voltage level.

In general, voltage regulators are designed to automatically maintain a constant regulated voltage level. A voltage regulator can include both analog and digital electronic components. The voltage regulator can control one or more alternating current (AC) or direct current (DC) voltages. The voltage regulator provides a regulated, stabilized output voltage level to components included in an electrical circuit independent of changes in the load current demand of the electrical circuit and the input voltage to the voltage regulator.
A voltage regulator can use a voltage-controlled current source to force a desired fixed voltage to appear at the output of the voltage regulator. Control circuitry included in the voltage regulator can monitor or sense the output voltage of the voltage regulator and adjust the voltage-controlled current source dependent on the load of the electrical circuit in order to hold the output voltage of the voltage regulator at the desired fixed voltage. A design limitation of the voltage-controlled current source can define the maximum load current the voltage regulator can source while still maintaining a regulated output voltage. Exceeding this design limitation may result in an unstable or out of regulation output voltage.

Fully integrated voltage regulator using open loop digital control for optimum power stepping and slew rate


A piezoelectric buzzer driving circuit (200) for driving a piezoelectric buzzer (211) with two terminals includes a reverser (216). The reverser includes an output terminal and an input terminal (24) configured for receiving a controlling signal to control an output of the reverser. The two terminals of the piezoelectric buzzer respectively connected to the input terminal and the output terminal such that a D-value of the voltage across the piezoelectric buzzer is twice as large as the voltage of the controlling signal.

1. Field of the Invention
The present invention relates to sound control units, particularly to piezoelectric buzzer driving circuits.
2. Description of Related Art
General consumer electronic products, such as personal computers, automobiles, communication terminals etc. can produce sounds, such as warning or ringing sounds. This is done by using internal sound producers, such as buzzers.
One type of buzzer is a piezoelectric buzzer. Referring to FIG. 5, a typical piezoelectric buzzer driving circuit is shown. The piezoelectric buzzer driving circuit includes a driving circuit 10 for driving a piezoelectric buzzer 111. The driving circuit 10 includes a transistor Q10, and two resistors R1 and R2.
The base of the transistor Q10 is connected to a controlling terminal 12, which provides a controlling signal to the piezoelectric buzzer 111 via the resistor R2. The collector of the transistor Q10 is connected to a power supply terminal 11 via the resistor R1. The emitter of the transistor Q10 is grounded.
Two terminals of the resistor R1 are set respectively as a first output terminal 14 and a second output terminal 16 of the driving circuit 10. The piezoelectric buzzer 111 is connected to the first output terminal 14 and the second output terminal 16.
The power supply terminal 11 provides a direct-current power supply with a voltage U11. The controlling signal provided from the controlling terminal 12 is a periodic impulse signal with a constant frequency for controlling the input voltage at the power supply 11. The transistor Q10 may be turned on or off according to the controlling signal.
A voltage across the piezoelectric buzzer 111 is ΔU1, a voltage at the first output terminal 14 is U14, and a voltage at the second output terminal 16 is U16. Therefore, ΔU1 is expressed as: ΔU1=U14−U16.
When the transistor Q10 is turned on, the voltage U14 of the first output terminal 14 is approximately equal to the voltage U11, and the voltage U16 of the second output terminal 16 is approximately equal to zero. Therefore, the voltageΔU1=U14−U16=U11.
When the transistor is turned off, the voltage U14 of the first output terminal 14 and the voltage U16 of the second output terminal 16 are both approximately equal to the voltage U11. Therefore, the voltageΔU1=U14−U16=0.
With the above description, during each on-off period of the transistor Q10, a varied voltage ΔU12 across the piezoelectric buzzer 111 is expressed as ΔU12=U110=U11. That is to say, maximum varied voltage ΔU12 across the piezoelectric buzzer 111 during each on-off period of the transistor Q10 is approximately equal to the voltage U11. On the other hand, a sound efficiency (i.e., electrical energy input against sound energy output) of the piezoelectric buzzer 111 is dependent on the voltage from the power supply terminal 11. The higher the voltage from the power supply terminal 11 is, the better the sound efficiency of the piezoelectric buzzer 111 is. However, high voltage electricity may cause damage in some consumer electronic products.
What is needed, therefore, is to provide a piezoelectric buzzer driving circuit with satisfactory sound efficiency even under low voltage.


In transmitting a packet string having variable packet intervals by converting the packet string into that having even packet intervals with each of the packets being attached with a time stamp as information for reproducing original packet string, when the value of the time stamp, which is decided by adding a specified offset time to the synchronization time, is not smaller than the value of the time stamp attached to the previous packet, the time stamp is attached to the packet and the packet is transmitted. If the value of the time stamp becomes not more than the value of the time stamp attached to the previous packet as a result of providing shortened offset time due to increased bit rate of the original packet string, the packet is discarded so as to protect the transmission from being stopped.

The present invention relates to a method and an apparatus for transmitting a packet string having variable packet intervals by converting the packet string to a packet string having even packet intervals with information for reproducing the original packet intervals being attached, more particularly to a method of continuing communications without stopping even when a bit rate becomes higher, that is, when packet intervals become shorter.
When an attempt is made to transmit a packet string in which packets are arranged at variable intervals, that is, a packet string whose bit rate changes, it is indispensable to prepare a data bus provided with a capacity corresponding to the maximum bit rate. Compared with a capacity necessary for transmission at an average bit rate, this makes the bus capacity redundant.
To avoid such a redundancy, a method is proposed in which packets are stored in a buffer (hereinafter referred to as a smoothing buffer) once, then the packets are read out at a fixed rate (hereinafter referred to as a leak rate) and transmitted at a fixed leak rate so as not to require a redundant transmission bus. At this time, however, if packets are transmitted via a smoothing buffer, original packet intervals become unknown. As a result, the original packet intervals cannot be reproduced on the receiving side. To avoid this, interval information is added to each packet so that the original packet intervals can be reproduced in the receiver.
Packet intervals are reproduced as described below. At first, synchronized clocks are started on both transmitting side and receiving side. Then on the transmitting side, the time when the leading edge of a packet is detected at the inlet of the smoothing buffer is stored and a time stamp of a value T decided by adding a specified offset time D to the detected time is attached to the packet before the packet is transmitted. On the receiving side, each received packet is stored in a receiving buffer once and the value T of the time stamp is fetched from the packet. The packet is read out from the receiving buffer when the clock value becomes equal to T to reproduce the original packet interval. FIG. 1A shows a discrete packet string whose average bit rate is A, FIG. 1B shows a discrete packet string to each packet of which a time stamp is attached at the inlet of the smoothing buffer, FIG. C shows a periodical packet string read out from the smoothing buffer and having a leak rate B, and FIG. 1D shows a packet string read out from the receiving buffer and for which the original packet intervals are reproduced.
In the above described method, no problem arises as long as the average bit rate A remained constant. However, when an average bit rate becomes higher, arises the following problems.
If, when the smoothing buffer size is fixed, the bit rate A becomes higher, then the leak rate must be set higher in order to prevent the buffer from overflowing. Thus, the transmission rate must also be raised, and accordingly the total time required for transmitting packets is shortened. Consequently, the above described offset time D must also be set smaller.
If a smaller offset time D is set, however, there is a possibility that the time stamp value calculated by using the smaller offset value becomes less than the value of the time stamp attached to the previous packet. If such an inversion occurs in the time stamp value, the communication is stopped. This is because the time for reproducing the packet attached with the time stamp having the smaller offset value has already lapsed on the receiving side when the previous packet is reproduced.
It is an object of the present invention to solve such problems by providing each packet string having variable packet intervals with information for reproducing original packet intervals so that the packet string can be transmitted continuously, which is converted to a packet string having even packet intervals, even when the bit rate becomes higher.

Method and apparatus for packet transmission


An apparatus and method for automatically electrically stimulating poultry carcasses in poultry processing plants in order to tenderize the poultry meat are disclosed. Carcasses suspended by shackles from a moving processing line are transported between two preferably curved electrical conductive bars, which are positioned to apply the electrical stimulation across the breast of the suspended carcass. The carcasses may otherwise be dragged through a charged saline or water solution, or across a charged metal mesh or grill. The carcasses are subjected to almost constant electrical stimulation for 8 to 13 seconds by the application of an intermediate level, 100 percent duty cycle, AC voltage for the period of stimulation.

1. Field of the Invention.
The present invention relates generally to processing poultry for human consumption, and, in particular, to a method and apparatus for automatically electrically stimulating poultry carcasses in poultry plants to tenderize the poultry meat.
2. Discussion of Related Art.
The consumer demand for poultry in recent years has shifted from fresh, whole carcasses to fresh, cut-up poultry and other processed poultry products. Due to the muscle tensioning associated with rigor mortis, poultry carcasses need to be aged for four to six hours to obtain poultry breast meat which is sufficiently tender for human tastes. Because deboning non-aged poultry carcasses produces meat that is unacceptably tough to the consumer, because storing poultry carcasses for a lengthy aging period to obtain tender poultry meat is expensive, and because storing increases the risk of microbial growth and decomposition of the meat, numerous studies have been conducted in an effort to find a way to accelerate the aging process.
One line of investigation has been directed toward the electrical stimulation of poultry carcasses promptly after their slaughter as a result of some degree of acceptance of electrical stimulation of beef carcasses in the meat-packaging industry to accelerate the aging process. Wide disagreement, however, continues to exist within the beef industry over the best specific type of electrical stimulation.
Broadly speaking, three general types of electrical stimulation have received some acceptance in the meat-packing industry. In one approach, pulses in excess of 1000 volts are applied to a carcass rubbing against an electrified rail. In a second approach, high voltage pulses are applied across the hind legs of the beef carcass. In both of these approaches, electrical stimulation occurs for a period in excess of 90 seconds and in some instances for several minutes. In a third approach, a series of low voltage pulses on the order of 20 volts are applied through a rectal probe for at least 90 seconds. In each of these methods, the periods of high current flow are minimized in comparison to the spacing between the pulses to minimize or avoid burning the meat. However, due to the differences in size and meat composition, and biochemical and physiological differences in the nerve and muscle systems of beef and poultry, such approaches provide little guidance for the poultry processing industry.
As discussed in "Electrical Stimulation in Poultry, A Review and Evaluation," by Yanblin Li, T. J. Siebenmorgen, and C. L. Griffis, 1993 Poultry Science, numerous laboratory studies of electrical stimulation of poultry meat have been conducted since 1960, with most of the activity involving chickens conducted since 1986. Although numerous different voltages, currents, and stimulation times have been used in such studies, most have been directed to the use of high voltage pulses above 440 volts separated by periods of no stimulation, as exemplified by "Fragmentation, Tenderness and Post-Mortem Metabolism of Early-Harvested Boiler Breast Fillets from Carcasses Treated with Electrical Stimulation and Muscle Tension," by S. G. Birkhold and A. R. Sams, 1993 Poultry Science, March 1993.
The studies to date relating to the electrical stimulation of poultry have been inconclusive because the optimum electrical parameters, the electrical properties of poultry meat, and the biochemical and physiological responses of poultry nerve and muscle systems to electrical stimulation have not been known. Further, there has yet to be developed a practical method of automatically electrically stimulating poultry meat in poultry processing plants in order to effectively tenderize poultry breast meat without additional aging of the poultry carcasses in storage areas at the plant site.
Additionally, it has been found that skin weakness of the poultry causes skin tears which are undesirable but sometimes unavoidable in the electrical stimulation process. A need exists to minimize skin tears, or to have the skin tears occur in parts of the poultry carcass not to be utilized for human consumption, or in the less expensive portions of the carcass.

Post kill tenderization of poultry meat through constant electrical stimulation


A photoresist mask for use in a photolithographic process for fabricating semiconductor devices. The photo mask including a transparent substrate, and at least two light blocking regions. The at least two light blocking regions are separated by a first opening and arranged at a first pitch P.sub.1 satisfying the following relationship on a main surface of the transparent substrate in a first direction: EQU P.sub.1 >2.lambda./NA (1+.sigma.). where .lambda. represents a wavelength of exposure light in an exposure system, NA represents a numerical aperture of the exposure system and C represents coherency of the exposure light. The at least two light blocking regions are formed with second openings at second pitches smaller than the first pitch in the first direction and the second openings have the exposure light transmitting therethrough, which has a weaker intensity than the exposure light transmitting through the first opening.

1. Field of the Invention
The present invention relates to a photo mask used in a photolithographic process for fabricating semiconductor devices, in particular a photo mask wherein light blocking regions of a mask pattern with a large pitch can be formed with a small opening to improve the depth of focus of the mask pattern.
2. Discussion of Background
As semiconductor devices are required to operate faster and to be formed in high integration, there has arisen a demand for provision of micro geometry to patterns. The micro geometry is required to be provided on a plane with steep steps in high relief with good precision, which requires not only good resolution but also great depth of focus. In general, a photo mask which is used in a photolithographic process has large and small patterns mingled on a single plane. The patterns vary in size from fine geometry of patterns with a small pitch such as wiring to patterns with a large pitch such as peripheral circuits. With regard to such fine geometry of patterns, there have been proposed various high resolution techniques which can improve depth of focus and resolution as stated later. However, such techniques can't give a desired effect to patterns with a large pitch, creating a problem in that it is impossible to obtain depth of focus to cope with steep steps in high relief.
Now, a photolithographic process using a conventional photo mask will be explained.
First, a transferring step for a mask pattern by a projection exposure system using a conventional circular light source method will be described.
In FIG. 15, there is shown a schematic view of the structure of a reduction-type projection exposure system according to a conventional circular light source method, which is used in a photolithographic process. Now, a step to transfer a mask pattern onto a wafer by the reduction-type projection exposure system will be explained.
Referring to FIG. 15, light which has been emitted from a circular light source 6 (the optical path of the light is indicated by solid lines) irradiates the entire plane of a photo mask 1 at an angle perpendicular thereto after the light has been condensed by a condenser lens 7. The light which has irradiated the photo mask 1 goes out in a direction depending on a pitch of a mask pattern 3 formed on the photo mask 1 after the light has been diffracted by the mask pattern. The outgoing diffracted light is converged by a projection lens 7'. The diffracted light is reduced by the projection lens 7' after the light has passed through a pupil plane 8 in the projection lens. The reduced light forms an optical image of the mask pattern 3 at a best focused position on the wafer 4. The wafer 4 has had e.g. a resist coated thereon. A patterned resist 5 is obtained so as to correspond to the mask pattern by subjecting the resist on the wafer to an ordinary photolithographic process.
Next, the relationship between the light diffracted by the photo mask and the pitch in the mask pattern will be described in detail.
In FIGS. 16 and 17, there are shown enlarged plan views of mask patterns which are arranged on the photo mask. The respective views show a pattern which has a large pitch in an x direction and a pattern which has a small pitch near to a resolution limit in the x direction. In FIGS. 18 and 19, there are shown cross-sectional views taken along the line III--III of FIG. 16 and taken along the line IV--IV of FIG. 17. In these Figures, reference numeral 1 designates the photo mask, reference numeral 2 designates a transparent substrate, reference numeral 3 designates light blocking regions which are formed by a thin film made of metal such as chromium, and reference numeral 9 designates an opening which is arranged between the light blocking regions 3.
In the mask pattern shown in FIG. 16, a plurality of rectangular light blocking regions 3a are periodically arranged at a large pitch P.sub.xL in the x direction and at a pitch P.sub.yL in a y direction. In the mask pattern shown in FIG. 17, a plurality of line arrays of light blocking regions 3b are periodically arranged in a line and space pattern with a small pitch P.sub.xs in the x direction.
In FIGS. 20 and 21, there are shown schematic diagrams wherein the optical paths of the light diffracted by the mask patterns of the photo mask shown in FIGS. 16 and 17 are indicated. In FIGS. 20 and 21, reference numeral 1 designates the photo mask, reference numeral 3 designates the mask patterns, reference numeral 4 designates the wafer, reference numeral 7' designates the projection lens, and reference numeral 8 designates the pupil plane. Reference numeral 50 designates zero order diffraction light, reference numerals 51 and 52 designates -first order diffraction light and +first order diffraction light, respectively, and reference numerals 53 and 54 designates -second order diffraction light and +second order diffraction light, respectively.
The light (irradiated light) which is incident on the photo mask is diffracted by the mask patterns, and an outgoing angle of each diffraction light with respect to the optical axis is determined by the pitches of the mask patterns and the order of the diffraction light. In general, when the outgoing angle of a first order diffraction light with respect to the optical axis is defined as .theta., the wavelength of the light is defined as .lambda. and the pitch of the mask patterns is defined as P, there is a relationship of Sin.theta.=.lambda./P. The outgoing angle becomes greater as the order becomes higher.
Referring to FIG. 20, when the pattern pitch is large, the outgoing angle of the -first order diffraction light 51a and the outgoing angle .theta. of the +first order diffraction light 52a symmetrical thereto with respect to the optical axis become smaller, and the outgoing angles of higher order diffraction light such as the -second order diffraction light 53a and the +second order diffraction light 54a symmetrical thereto with respect to the optical axis become also smaller, so that higher order diffraction light can pass through the pupil plane 8 of the projection lens 7'. Each diffraction light which has passed through the pupil plane 8 causes interference to form an optical image at a best focused position on the wafer 4.
Referring now to FIG. 21, when the pattern-pitch is small and near to a resolution limit, the outgoing angle of each diffraction light becomes larger, causing higher order diffraction light such as the second order diffraction light 53a and 54a to deviate outside of the pupil plane 8, and allowing only the zero order diffraction light 50 and the first order diffraction light 51 and 52 to pass through the pupil plane 8.
As explained, the outgoing angle of each diffraction light varies depending on the size of a pattern pitch. As the pitch becomes larger, the optical image can be formed by multiple order diffraction light.
In FIGS. 22(a) and (b), there are shown schematic views wherein the diffraction light shown in FIGS. 20 and 21 is viewed as light source images on the pupil plane. In FIGS. 22(a) and (b), reference numeral 60 designates the light source image by the zero order diffraction light, reference numerals 61 and 62 designates the light source image by the -first order diffraction light and the light source image by the +first order diffraction light, respectively, and reference numerals 63 and 64 designates the light source image by the -second order diffraction light and the light source image by the +second order diffraction light. Reference numeral 8 designates the pupil plane.
As shown in FIGS. 22(a) and (b), the center distance between the light source image 60 by the zero order diffraction light and the light source images 61 and 62 by each first order diffraction light is equal to .lambda./P, and the radius of the pupil plane 8 is equal to the numerical aperture NA of the projection lens. The center of the respective light source images aligns with the optical axis of each diffraction light shown in FIGS. 20 and 21.
Referring to FIG. 22(a), when the pattern pitch is large, the light source images 61-64 by each diffraction light gather towards the center of pupil plane 8 so as to overlap one another as the outgoing angle of each diffraction light becomes smaller as explained with respect to FIG. 20. In the case of FIG. 22(b), since the pattern pitch is small, the outgoing angle of each diffraction light becomes larger, causing the respective light source images to be apart from the center of the pupil plane 8, and thereby completely deviating the light source images 63 and 64 by each second order diffraction light from the pupil plane 8.
Now, the size of a pattern pitch will be explained.
FIGS. 23(a)-(c) are schematic diagrams showing how a light source image by each diffraction light is obtained depending on a change in a pattern pitch. In FIG. 23(a), there are shown the light source images which are obtained when the pattern pitch is set just to he resolution limit, wherein the center of the light source images 61 and 62 by each first order diffraction light is located on an outer circumference of the pupil plane 8 and the light source images 63 and 64 by each second order diffraction light are completely deviated from the pupil plane 8. If the pattern pitch becomes smaller, each first order diffraction light 61 and 62 is also gradually deviated from the pupil plane 8, making formation of an optical image difficult. This means that at least interference between the zero order diffraction light and either one of the .+-.first order diffraction light is required to form an optical image with contrast in brightness. When the pattern pitch which is set to the resolution limit is defined as P, the numerical aperture of a projection exposure system is defined as NA and coherency is defined as .sigma., the following relationship is found: EQU P=.lambda./NA (1)
In FIG. 23(b), it is shown how the light source images are obtained when the pattern pitch becomes larger than that in FIG. 23(a) and be near to the resolution limit, wherein the light source images by each first order diffraction light gather near to the center of the pupil plane 8 while the light source images 63 and 64 by each second order diffraction light are still deviated from the pupil plane 8. In this case, the light source images 63 and 64 by each second diffraction light are circumscribed with the outer circumference of the pupil plane 8, which shows the minimum pitch at which each second diffraction light is completely deviated from the pupil plane. When the pitch in this case is defined as P, the following relationship is found: EQU P=2.lambda./NA(1+.sigma.) (2)
In FIG. 23(c), it is shown that the pattern pitch becomes larger than that in FIG. 23(b), and the light source images 63 and 64 by each second order diffraction light enter the pupil plane 8 to make a little contribution to formation of the optical image. When the pattern pitch in this case is defined as P, the following relationship is found: EQU P>2.lambda./NA(1+.sigma.) (3)
Accordingly, a small pattern pitch which is near to the resolution limit can be defined as a pitch satisfying the following formula based on the formulas (1)-(3), i.e. a pitch which prevents at least the light source images by each second diffraction light from entering the pupil plane and which can form an optical image: EQU .lambda./NA.ltoreq.P<2.lambda./NA(1+.sigma.) (4)
A large pitch can be defined as a pitch satisfying the formula (3), i.e. a pitch which allows the second order diffraction light or more to enter the pupil plane even a little to contribute to formation of an optical image.
Now, the relationship between diffraction light and depth of focus will be described.
In general, the depth of focus shows what contrast in brightness a reproduced optical image has at defocused positions under and above a best focused position on a wafer as a reference.
For example, when the pattern pitch is small and only the zero order diffraction light 50 and the .+-.first order diffraction light 51 and 52 pass through the pupil plane 8 as shown in FIG. 21, such three kinds of diffraction light travel along different optical paths as zero order diffraction light 50b, and first order diffraction light 51b and 52b, and form an optical image on the best focus position on the wafer 4 by interference among three kinds of diffraction light (it is called 3 beams interference). At positions which are defocused upward and downward from the best focus position, the contrast in the optical image is gradually lowered depending on defocusing since the zero order diffraction light 50b and each first order diffraction light 51b and 52b are out of phase (the -first order diffraction light 51b and the +first order diffraction light 52b are in phase because they are symmetrical to each other with respect to the optical axis).
When the pattern pitch is large and the -second diffraction light 53 and the +second diffraction light 54 together with the zero order diffraction light 50 and the .+-.first order diffraction light 51 and 52 pass through the pupil plane 8 as shown in FIG. 20, the second diffraction light having a different optical path contributes to formation of the optical image to further lower the contrast in the optical image. When the pattern pitch becomes much larger, third order diffraction light, fourth order diffraction light or more are added to furthermore lower the contrast though not shown.
As explained, in a pattern with a large pitch, the depth of focus is lowered. Simulation results of the depth of focus obtained by the shown mask patterns will be indicated.
In FIGS. 24 and 25, there are shown the results which were obtained by simulating a light intensity distribution of an optical image formed by the mask pattern with a large pitch shown in FIG. 16 on best focusing and on defocusing.
The mask pattern which was used in this simulation was the same as the mask pattern shown in FIG. 16, wherein the pitch P.sub.xL was 1.5 .mu.m and the opening between the light blocking regions had a spacing D.sub.x of 0.3 .mu.m. The optical conditions were that the wavelength of exposure light was 248 nm(KrF excimer laser), the numerical aperture NA was 0.55 and the coherency .sigma. was 0.8. When the best focused position in FIG. 24 was zero .mu.m, the defocused value in FIG. 25 was 0.4 .mu.m. The ordinates in both Figures represent standardized light intensity wherein 1 represents the maximum intensity and degrees of intensity are classified with tones.
When the light intensity distribution in the x direction is viewed referring to FIGS. 24 and 16, there is a gentle gradient from the weakest light intensity portion corresponding to a central portion of the light blocking region 3a having of an intensity of 0-0.1 to the strongest light intensity portion corresponding to an opening around the light blocking region. A spacing d.sub.1 in the x direction between the central portion regions having the weakest intensity is about 0.5 .mu.m. Referring now to FIGS. 25 and 16, the light intensity distribution on defocusing was characterized in that the intensity gradually become stronger from a central portion to a peripheral portion of a light blocking region as on best focusing, and that a spacing t.sub.2 in the x direction between the central portion regions having the weakest intensity of 0-0.1 was about 0.8 .mu.m, which showed that the spacing was extended in comparison with the spacing on best focusing. This means that the gradient of the intensity distribution in the x direction become gentler to make the contrast lower.
As explained, the depth of focus is extremely lowered in a mask pattern with a large pitch because an optical image is formed by a plurality of kinds of diffraction light having different optical paths (it is called multiple flux interference).
With respect to a mask pattern with a smaller pitch, there have been proposed techniques which further improve the depth of focus.
For example, "Illumination Modification of an Optical Aligner" KTI Microelectronics Seminar, pp. 217-230 (1989) has proposed a modified illumination method which is illustrated in FIG. 26 showing a schematic view of light paths of light diffracted by a photo mask. The modified illumination method is a technique which controls diffraction light caused by a pattern having a small pitch near to resolution limit to improve the depth of focus.
In this Figure, the photo mask 1 is the same as the conventional photo mask shown in FIG. 17, and has a line and space pattern 3b arranged thereon at a pitch P.sub.xs near to resolution limit. The other reference numerals indicate parts identical or corresponding to those indicated by the reference numerals in FIG. 21.
Referring to FIG. 26, according to the modified illumination method, the zero order diffraction light 50 from the photo mask 1 and only one of the .+-.first order diffraction light 51 or 52 (e.g. first order diffraction light 52) enters the pupil plane 8 of the projection lens 7, and the incident angle .alpha. of incident light is selected so as to symmetrically pass the zero order diffraction light and the first order diffraction light through the pupil plane 8 in the 3 beams interference of a pattern having a small pitch P.sub.xs near to the resolution limit (formation of an optical image by interference among the zero order diffraction light and the .+-. first order diffraction light). By this method, the number of interfering diffraction light is decreased to have so-called two luminous flux interference, and two kinds of diffraction light which form an optical image have symmetrical light paths, allowing the depth of focus to be improved without lowering the contrast in brightness of the optical image even at a defocused position.
For example, "Improving Resolution in Photolithography with a Phase Shifting Mask", IEEE Trans. Electron Devices, ED-29, pp. 1828-1836 (1982) has proposed a Attenuated phase shifting technique which is illustrated in FIGS. 27(a), (b) and (c) showing a cross-section view of a photo mask and schematic views of the intensity of the light transmitted through the mask.
In the Attenuated phase shifting technique, diffraction light caused by a pattern having a small pitch near to resolution limit is controlled to improve resolution and depth of focus as in the modified illumination method. As in the modified illumination method, the photo mask shown in FIG. 27(a) is the same as the conventional photo mask shown in FIG. 16, and the photo mask has a line and space pattern arranged thereon at a small pitch P.sub.xs near to the resolution limit.
In the Attenuated phase shifting technique, either one of openings adjacent to a mask pattern 3b with a small pitch on the photo mask 1 is formed with a thin transparent film 90 (see FIG. 27(a)) to shift the phase of transmission light 56 with respect to transmission light 55 adjacent thereto by 180.degree., thereby cancelling the amplitude of light at an overlapped portion of light amplitude 70 and light amplitude 71 of each transmission light (see FIG. 27(b)) to obtain light intensity 80 with good resolution (see FIG. 27(c)). By the 180.degree. of shift, the zero order diffraction light from an opening and the zero order diffraction light from an adjacent opening are cancelled together to establish the two luminous flux interference due to only the .+-.first order diffraction light having symmetrical optical paths for formation of an optical image, and simultaneously improving depth of focus.
As another conventional measure, there has been a technique in JP-A-736174 wherein a rectangular pattern has openings formed in a stripe-like shape to improve resolution of fine geometry.
The conventional techniques as stated earlier improve the depth of focus and the resolution by controlling diffraction light caused from a mask pattern having a small pitch near to the resolution limit. However, with regard to a mask pattern having a greater pitch beyond the resolution limit, the modified illumination method can't decrease diffraction light because the optical image is formed by multiple order diffraction light, and the phase shifting method is difficult to apply because the presence of a large distance between adjoining openings prevents light from interfering.

Photo mask and method for fabricating semiconductor devices using the photo mask


A flow distributor provided within an exhaust system for a combustion engine configured to generate an exhaust fluid stream. The flow distributor comprising an inlet, and a plate. The plate having at least one perforation defining an outlet, a first peak and a second peak spaced from the first peak.

In an attempt to reduce the quantity of NOx and particulate matter emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment devices have been developed. Typical aftertreatment systems for diesel engine exhaust may include a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst, a reductant injector and/or a hydrocarbon injector. A mixer or flow distributor is typically provided for mixing the injected reductant or hydrocarbon with the exhaust gas upstream of a catalyst or filter. Flow distributors may also spread the flow of an exhaust airstream over more surface area of the catalyst or filter to maximize the effectiveness of the catalyst or filter. Without such exhaust flow distributors, a percentage of catalyst or filter surface area may be unused or underutilized.
Flow distributors can include a front face with a plurality of perforations. The front face can be formed as a planar or dome-shaped front face. These configurations, however, do not provide an exhaust air flow that covers the entire catalyst or filer and they are susceptible to failure or warping from high or prolonged thermal loads.

Exhaust system for a combustion engine including a flow distributor

Tenneco Automotive Operating Company Inc.


The invention relates to aqueous dispersions containing aminooxy crosslinking agents, of copolymers containing carbonyl groups, to processes for the preparation thereof and to the use thereof as a crosslinking system in binders, adhesives and coating agents.

1) Field of the Invention
The invention relates to aqueous dispersions, containing aminooxy crosslinking agents, of copolymers containing carbonyl groups, to processes for the preparation thereof and to the use thereof as a crosslinking system in binders, adhesives and coating agents.
2) Description of the Related Art
Aqueous dispersions based on copolymers which contain carbonyl groups and contain polyhydrazides or polyhydrazones, lead to the formation of highly crosslinked films during the film formation as a result of the chemical reaction between the carbonyl groups of the cohydrazides or polyhydrazones. Such crosslinking systems have been disclosed, for example, by DE-A 1,495,706 (U.S. Pat. No. 3,345,336) or EP-A 15,644 (U.S. Pat. No. 4,256,809).
Due to the good adhesion properties, such copolymer dispersions which crosslink on film formation are used as binders (DE-A 3,319,239=EP-A 130,336), adhesives (EP-B 148,386 =U.S. Pat. No. 4,609,420, DE-A 3,319,240=U.S. Pat. No. 4,529,772), sealing compounds (DE-A 3,537,099) and coating agents (DE-A 3,724,369 U.S. Pat. No. 4,8941261). A disadvantage is, however, the unsatisfactory strength of the adhesive bonds on storage in water.
A further disadvantage of these crosslinking systems is the release of highly toxic and carcinogenic hydrazines during the storage and use of such systems. In EP-B 3,516 (U.S. Pat. No. 4,250,070), DE-A 2,819,092 (U.S. Pat. No. 4,267,091) and DE-A 3,216,967, it is therefore proposed to add water-soluble transition metal salts to the polyhydrazine-containing copolymer dispersions, in order to reduce the content of free hydrazine.
DE-A 3,241,829 (U.S. Pat. No. 4,546,078) has disclosed a process for the immobilization of microorganisms, the microorganisms being suspended in an aqueous solution of an acrolein/vinylpyrrolidone copolymer. After the addition of an aqueous solution of an alkylenedioxydiamine compound, the microorganisms are enclosed in the immediately forming, gel-like polymer mass.
It is an object of the present invention to provide aqueous dispersions which are based on dispersions, containing carbonyl groups, with crosslinking agents and which crosslink on film formation, but with which no release of hydrazine or at least a lower release of hydrazine than in the case of the polyhydrazine crosslinking agents mentioned in the state of the art. Moreover, the crosslinking should proceed only at temperatures of.gtoreq.about 10.degree. C., preferably.gtoreq.room temperature. Additionally, the systems should also have a high storage stability coupled with a high degree of crosslinking during the film formation. The adhesive bonds produced with the dispersions should be resistant to water or organic solvents.

Aqueous dispersions, containing aminooxy crosslinking agents, of copolymers containing carbonyl groups


An acetabular cup inserting instrument includes a first handle and a second handle rotatable about and extending from the first handle. The second handle is ratchetable about the first handle and selectively lockable in a desired position with respect to the first handle. The ratchet mechanism of the second handle includes a biased pawl that engages radially spaced notches on the first handle.

The present invention relates to an acetabular cup inserting instrument which is used by a surgeon to insert and properly position an acetabular cup implant into its proper anatomical location.
A number of instruments are known in the art for inserting acetabular cup implants into position in the acetabulum. An example of one such instrument is shown in U.S. Pat. No. 4,716,894 assigned to the assignee of the present invention and incorporated herein by reference. That patent shows a cup inserting instrument with a main gripping handle and second handle which is rotatable about the first handle.
Both the main and second handles of the instrument, shown in U.S. Pat. No. 4,716,894, include grooved, radial disks that intermesh and interlock when a locking sleeve forces the two handles together. The rotatable locking sleeve locks the second handle to the main handle.
Although this instrument enables the second handle to be locked in selectable positions, when the locking sleeve is unlocked thereby disengaging the grooved disks, the second handle can fall unimpeded if it slips out of the surgeon's grasp. Therefore it is important that the surgeon maintain a good grasp on the second handle when in its released position. Free rotatability of the second handle can be prevented to a degree by backing off the locking sleeve to the point where the grooved disks are only partially disengaged. As the second handle is rotated, the teeth on the disks "jump" over each other in much the same fashion as gears that are only partially engaged. However, this jumping movement is very erratic and rough and does not provide the controlled movement that is desirable in order to accurately position the second handle when placing an acetabular cup during a hip replacement procedure.


A ferroelectric layer is deposited or in close proximity to a ferromagnetic ferrite layer to make a microwave substrate on which conductors can be deposited or placed to make devices. The permittivity of the ferroelectric layer can be changed by applying a voltage and the permeability of the ferromagnetic layer can be changed with a magnetic field. This makes it possible to tune the device characteristics with two different effects taking best advantage of the capabilities of each. A material example is ferromagnetic yttrium-iron-garnet on which is deposited a thin film of ferroelectric barium strontium titanate. To minimize losses, the ferroelectric film should be high quality, but practical yttrium-iron-garnet substrates are polycrystalline so that the use of buffer layers is desirable. At least two methods can be used to deposit the ferroelectric film, pulsed laser deposition and metal-organic chemical liquid deposition. A variety of dual tunable microwave devices can be made with this substrate, including by way of example only, phase shifters, frequency filters, and resonators.

1. Technical field
This invention is in the general field of microwave devices and, more particularly, devices having at least an electrically tunable ferroelectric layer and at least a magnetically tunable ferromagnetic layer in close proximity.
2. Background
The microwave region of the spectrum ranges very approximately from 1 to 300 GHz with wavelengths of 30 cm to 1 mm, respectively. Most applications use frequencies of less than 50 GHz. In general terms, most microwave devices comprise two or more conductors on, enclosing, or enclosed by non-conductive media. One characteristic of the media is the propagation constant, xcex2, given by:
xcex2=xcfx89(∈oxcexco∈excexce)xc2xdxe2x80x83xe2x80x83Equation (1)
where xcfx89 is the radian frequency and ∈e and xcexce are the effective dielectric constant and permeability of the media, respectively. (For air, ∈e,=xcexce=1). Microwaves traveling along a transmission line experience a delay, usually expressed as a propagation phase difference given by:
xcfx86=xcex2l=xcfx89l(∈oxcexco∈excexce)xc2xd(radians)=360(l/xcex)(∈excexce)xc2xd(degrees)xe2x80x83xe2x80x83Equation (2)
where l is the effective distance between the two points and xcex is the free-space wavelength. Thus, changing or tuning any of l, ∈e or xcexce changes the phase difference. However, in principle, any delay line configuration can also be viewed as a frequency filter structure providing low insertion loss in pass bands and high attenuation in stop bands. Fundamentally, a phase shifter or filter can be viewed as the same device with emphasis on different physical quantities (governed by the propagation constant xcex2). The most useful tunable microwave devices are phase shifters, resonators, and frequency filters.
Conventional microwave tuning is predominantly achieved via changing the physical is dimension with tuning screws, tuning plungers, sliding conductors or sliding walls. Typically, the transmission line is a hollow rectangular waveguide. Mechanical tuning, however, has the major drawbacks of bulkiness, inconvenient operation, and low tuning speed.
Microwave transmission lines can be made on circuit boards. G-10 epoxy (∈e=10, xcexce=1) is useful to 1.5 GHz, where it becomes too lossy, and Teflon(copyright) (∈e=2.3, xcexce=1) at higher frequencies. Typically, the transmission line consists of a ground plane on one side and strip conductors on the other. However, if the dielectric constant is high enough, coplanar conductors on one side only, can be used. This is because the electric fields will be concentrated in the substrate. A mixture of Teflon(copyright) and ceramic powders produce an ∈e=10. Devices are constructed with components including active monolithic microwave integrated circuits (MMICs) connected by such transmission lines. Tuneable oscillators can be constructed with yttrium iron garnet (YIG) spheres or barium titanate (BTO) cylinders placed in close proximity to the transmission line. These produce a resonance in a circuit whose center frequency can be shifted by application of an external magnetic or electric field, respectively. See Handbook of Microwave and Optical Components, Vol. 1, K. Chang, ed., Wiley Interscience (1997), incorporated herein by reference, for background material on traditional microwave devices.
Microwaves are used for both communications and radar. In both, but especially for radar, the beam direction can be steered by using a two dimensional array of phase shifters. For some applications, several thousand are required and there is an incentive to make the shifters as compact as possible. One solution, ca. 1980, uses YIG as the medium in contact with a coplanar transmission line. The permeability, xcexc, of YIG (∈e=15, xcexce=on the order of 1,000) can be varied by the application of an external magnetic field, H, because xcexce is non-linear with H. Therefore, the phase shift of the RF wave can be varied according to Equation 2. Single crystals of YIG are available, but only in small sizes at great cost. However, polycrystalline YIG can be used with low loses even at high power levels. Also, its properties can be varied by changing the chemical composition. It is the preferred technologically important material for many microwave applications.
In the last decade, similar microwave devices based on varying the permittivity, ∈, of a ferroelectric substrate using a voltage between the transmission line conductors have been proposed. The technological material of choice appears to be BaxSr1xe2x88x92x TiO3 (BST) (x=0 to 1) (∈e=on the order of 1000, xcexce=1). The advantages of using BST for tunable microwave applications are its low loss and high tunability, i.e., variation of permittivity with voltage. Tunability is maximized when the material is operated near its Curie temperature. For BST, this can be adjusted by changing the Ba concentration, x. For example, at least for bulk BST, it ranges from 30 K to 400 K for Ba concentrations ranging from x=0 to 1, respectively. The ability to control the dielectric properties of BST in a simple way allows device structures to be easily optimized for maximum tunability and minimum loss at the desired frequency and operating temperature. In addition, for rapid tuning, it is generally easier to provide rapidly changing electric fields than magnetic ones.
Individually, each approach, ferromagnetic or ferroelectric, has limitations. In a phase shifter, ferromagnetic tuning is limited to frequencies less than the ferromagnetic resonance frequency. Ferroelectric tuning is limited by voltage breakdown. For a phase shifter, arbitrarily large phase changes can be obtained by making the transmission line arbitrarily long, but large sizes are generally not desirable. A structure that combined both approaches would have the advantage of producing additional phase shift for the same length. A non phase-shifter example is a multi-element filter where the center frequency, passband, and ripple are determined in a complicated but well known way by conductor geometries and the propagation constant, xcex2. The filter characteristics can be changed by changing xcex2. Providing a separate magnetic field for each element would be inconvenient, but a purely electrical device may not provide enough change in xcex2. Using dual tuning, the magnetic field could provide the broadband tuning of the filter bandpass while electric tuning for each element would allow fine tuning of the filter profile to achieve symmetric and optimum filter characteristics.
One of the problems with electrical or magnetically tunable devices is that the transmission line impedance also changes. Even though initially connected to a matching impedance, changes will introduce unwanted reflections. The impedance is given by:
Zxe2x88x9d(xcexce/∈e)xc2xdxe2x80x83xe2x80x83Equation (3)
with the proportionality being determined by geometrical factors. For most devices, it would be a large advantage to maintain a constant ratio between xcexce and ∈e and therefore a constant Z.
One application where a dual tuning capability would be most advantageous is for phased-array antennas, see U.S. Pat. Nos. 5,309,166 and 5,589,845, incorporated herein by reference, for ferroelectric only versions. Magnetic fields that are difficult to apply to individual elements could be used for overall steering and electric fields for fine tuning each element. In this application, the slower magnetic tuning could be used for gross adjustment and the faster electric tuning for fine adjustment.
Using a material that has the properties of both might seem obvious. Such materials, e.g., europium barium titanate, have been known to exist for a long time. They are, however, not very sensitive to either electric or magnetic fields. Ferroelectric-ferromagnetic composites are also known and have been used to filter out high frequency electromagnetic interference in feed through connectors. The composites are made by sintering fine grain (0.1 um to 1.0 um) oxide powders. However, it is believed that the change in permitivity of the ferroelectric material with an applied electric field would be very low. Thus, no single material having the properties of both has been used for microwave devices. Moreover, no composite material microwave substrate has been produced combining both voltage and magnetic tuning capabilities.
Accordingly the main object of the invention is to provide a dual tunable microwave substrate comprising practical ferroelectric and ferromagnetic material so that those skilled in the art can use the substrate in various geometrical configurations to build phase shifters, delay lines, resonators, oscillators, directional couplers, filters, various antennas, and other microwave and millimeter wave devices that can be controlled or tuned by application of a voltage and/or magnetic field.
A further object of the invention is to provide a dual tunable microwave substrate whose propagation constant can be controlled while maintaining a relatively constant transmission line impedance.
These objectives are realized by depositing a ferroelectric thin film on a ferromagnetic substrate. High quality ferroelectric films are produced by using one or more intermediate layers as buffers for epitaxial growth. One example uses a yttrium iron garnet substrate with a buffer layer of yttrium stabilized zirconia and barium strontium titanate as the ferroelectric thin film. Another example uses buffer layers comprising silicon nitride followed by magnesium oxide. Pulsed laser deposition or a metal-organic chemical liquid deposition process which is novel with respect to the ferroelectric films can be used to deposit them.
An example of a microwave device is a phase shifter constructed by depositing coplanar gold electrodes on the ferroelectric thin film. A two dimensional array of these can be used to construct a phased array antenna. Other examples are frequency filters and resonators. Performance of all devices can be improved by using high temperature superconductors as coplanar electrodes. A microminiature magnetic field generator is useful in some applications.

Dual-tuning microwave devices using ferroelectric/ferrite layers

Corning Applied Technologies Corporation


A swivel connector is provided for use in either an intravenous liquid supply line or an oxygen supply line to allow the line to rotate to prevent kinking. A body portion is provided having a cylindrical cavity formed in one end thereof, and a hollow, cylindrical male member slides into the cylindrical cavity and has sufficient clearance to allow free rotation of the male member within the cylindrical cavity. A locking flange is carried by the male member which engages an annular groove formed in the body portion to prevent the male member from inadvertently disengaging from the body portion. A seal is also provided between the male member and the body.

This invention relates generally to a swivel connector for use in either an intravenous liquid supply line or an oxygen supply line to allow the line to rotate and to prevent kinking of the line.
The prior art includes U.S. Pat. No. 4,875,718 dated Oct. 24, 1989 to Marken, which teaches a ball and socket swivel connector for oxygen lines. However, the ball and socket joint of Marken relies on a fairly close fit between the ball and socket to prevent leakage of oxygen. The tighter the fit between the ball and socket, the more difficult it is for the mechanism to swivel. Furthermore, both ends of the ball and socket connector may rotate if the friction between the ball and socket is sufficiently great. The present invention provides a swivel connector in which oxygen leakage is held to a minimum but wherein the swivel is allowed to rotate freely, because a relatively small surface area is involved in the sealing mechanism of the present invention. Furthermore, the present invention provides a clip attached to the user's clothing which prevents rotation of the body portion of the connector.
The prior art also includes U.S. Pat. No. 4,915,104 dated Apr. 10, 1990 to Marcy. This patent teaches a nasal oxygen tube support which includes a clip used to help support a part of the oxygen tubing. However, this patent does not teach a swivel connector.
The prior art also includes U.S. Pat. No. 5,054,482 dated Oct. 8, 1991 to Bales. This patent teaches a rotatable tracheostomy tube which does include a rotatable connector. However, this connector is extremely cumbersome in design, particularly as applied in an oxygen line.
The prior art also includes U.S. Pat. No. 4,588,402 dated May 13, 1986 to Igari et al. This patent teaches a quick connector for medical fluid lines which is impervious to bacteria. The Igari device is primarily a quick connecting device rather than a freely rotating swivel mechanism.


The present invention is a Distally Assembled Steerable Cannula (DASC), a robotically-manipulated device that can be deployed and extended within a patient's body by growing from its distal end, or can be used in non-medical applications. In some embodiments, growth occurs by sequentially assembling segments that interlock to form a rigid tube with a complex 3-D shape. The segments are individually transported through the growing cannula, and then assembled at the distal end. A segment can be wedge-shaped in profile, allowing adjustment of the local radius and plane of curvature of the cannula to be controlled by relative segment orientation.

This application relates in part to medical procedures, which comprise entering the patient's body with an instrument to remove, ablate, extract, aspirate, modify, or repair tissue and fluids; to perform diagnostic procedures; or to deliver therapeutic agents or devices. The application also relates to implanted devices and to non-medical devices.
Some medical procedures are minimally invasive; such procedures can improve outcomes, speed recovery, limit trauma, and allow earlier intervention. Cannulas and related, often hollow, tubular devices such as needles, catheters, tubes, and endoscopes, are commonly used in such procedures, allowing surgical tools (including powered tools such as microdebriders driven by rotating flexible shafts), diagnostic and therapeutic instruments, implants, and drugs to be introduced into the body and excised tissue and fluid to be removed. Yet due to obstructions such as bone or sensitive organs, current devices may be unable to access a target region, or only do so sub-optimally. A more invasive method, a riskier approach, or a worse outcome is thus sometimes unavoidable. Moreover, in a number of procedures for which multiple targeted regions within the body need to be accessed, it can be time-consuming and involve multiple punctures or incisions, even if access to a single region would be straightforward. These issues arise from the fact that many instruments are substantially rigid and straight and follow substantially straight paths within the body, whether within a hollow (i.e., gas- or liquid-filled) organ or lumen, or in solid tissue. Moreover, even instruments known to the art that are not rigid and/or not straight can also have difficulty in accessing certain regions of the body, as the following examples will illustrate.
There has been extensive research into steerable needles, cannulas, catheters, and endoscopes; snake-like robots; and other devices. To date such devices have been problematic and many remain experimental. Spinning steerable needles with asymmetric tips [1,2,3,4] offer small gauge sizes but have very large curvature/outer diameter (O.D.) ratios (e.g., 70:1 [5]), can only be deployed within solid tissue, and are difficult to control accurately due to varying tissue properties [6], etc. Concentric multi-tube superelastic nickel-titanium (Nitinol) needles [7,8,9,10,11] intended mostly for hollow regions offer relatively few shapes due to the small number of tubes; relatively large curvature/O.D. ratios [12]; limited stiffness; and small lumen/outside diameter ratios. Steerable catheters [13] and jointed, shape locking devices [14] have few degrees of freedom and sometimes large diameters. Snake-like robots [15,16,17] capable of following 3-D paths are typically 0.4-0.8″ diameter and use costly components; their lumen or inner diameter (I.D)/O.D. ratios also tend to be small. Finally, everting endoscopes [18] grow distally and are flexible but not steerable.
Given the limitations of instruments known to the art, there is a need for new, more capable and dexterous instruments capable of curved motion along desirable paths within the body, either within hollow (e.g., gas- or liquid-filled) regions or through solid tissue. Such instruments would preferably be deliverable with minimal difficulty and tissue trauma or damage and have a small outside diameter (e.g., 1-10 mm). They could provide a unique platform technology with the potential to impact a wide variety of medical specialties and procedures, including sinus and skull base surgery (where narrow passages and nearby critical structures make minimally invasive procedures difficult or impossible with current straight or angled instruments, e.g. in the frontal sinus, anterior cranial fossa, cavernous sinus, and brainstem), urology (where, for example, repeated access to specific regions of the kidney can be difficult), and interventional radiology (e.g., for biopsy and drainage while avoiding critical structures, and local regional therapy). Moreover, there is a need (e.g., for cochlear electrodes and annuloplasty rings) for implantable devices that can be delivered in a minimally invasive manner and which have complex 3-D curved shapes; this capability is currently very limited and could be greatly expanded by using the approaches of some embodiments of the invention.


A non-slip knitted lace fabric has opposed first and second surfaces of yarn and a stretchable tacky layer of cured and foamed, oleophobic and hydrophobic plastisol disposed at least partially on one of the first and second surfaces to provide enhanced frictional engagement of the fabric with a surface adjacent to the tacky layer. Preferably the fabric has a loop-forming yarn knitted therein so as to provide a plurality of loops of the loop-forming yarn as the one surface. The tacky layer extends through the openings of at least some of the loops. Optimally, the loop-forming yarn is elastic and tacky.

The present invention relates to a knitted lace fabric and to a method of manufacturing the same, and more particularly to such a fabric having a non-slip property making it highly suitable for the lacy tops of thigh-high stockings, the lacy bottoms of girdles, and the like.
Elastic material, such as spandex, has been knitted into lace products to provide elasticity. For example, stockings having lace borders commonly contain spandex yarns so that the lace border may stretch to accommodate various sizes and shapes of legs. The spandex yarns create a squeezing effect on the wearer's legs which hopefully keeps the stocking tops up. However, the lace border nevertheless presents a smooth surface, and the presence of the spandex may not prevent the stockings from slipping down the legs. Accordingly, garters or the like are typically used to maintain the stockings on the legs.
In an effort to eliminate the need for garters, rubber yarns have been woven or knitted against the back of a lace band fabric to provide increased friction with the wearer's skin. The rubber yarns were laid flat against the back of the fabric and tied down under full tension. This approach has been eliminated mainly because of the deterioration of the rubber over time, due to exposure to body oils and the like.
Beads of silicone are currently widely used instead of the rubber yarns. The silicone is applied in a pattern to the underside (i.e., skin side) of the finished lace product so as to frictionally engage the user's skin to hold the stocking in place. However, the silicone cannot be dyed and thus, although the silicone is applied to the underside of the lace material, it can be seen therethrough, thereby diminishing the aesthetic appearance of the stocking or other garment. Additionally, the silicone has quite limited elastic properties and tends not to completely stretch with the lace product. Thus when the lace border is periodically stretched as the stocking is put on and worn, the silicone bead may separate and/or crumble from the lace. In addition, upon washing, the silicone rubber also tends to crumble and detach from the lace material. Even further, recent concerns regarding the bio-compatibility of silicone materials and fears that the silicone may leach into the skin have raised concerns among consumers using such products.
Accordingly, it is an object of the present invention to provide a knitted lace fabric which is characterized by a high level of non-slip property--that is, a non-slip fabric.
Another object is to provide such a fabric wherein the non-slip property does not substantially fade away during the time the fabric is being worn.
A further object is to provide such a fabric which resembles ordinary knitted lace fabric not having the non-slip property.
It is also an object of the present invention to provide a method for manufacturing such a non-slip knitted lace fabric.

Non-slip knitted lace fabric and method of manufacturing same


A two part sealant cures rapidly in deep sections when the two parts are mixed together. A first part consists essentially of a hydroxyl endblocked polydiorganosiloxane, non-reinforcing, non-acidic filler, diacetamidosilane chain extender of the general formula ##STR1## and aminoxysilicone compound having from 1 to 100 silicone atoms per molecule and from 3 to 10 aminoxy groups per molecule. A second part consists essentially of a hydroxyl endblocked polydiorganosiloxane, non-reinforcing, non-acidic filler, and water. When mixed together, the two parts cure rapidly in deep sections.

1. Field of the Invention
This invention relates to a two part silicone sealant which cures upon mixing of the two parts to give an ultra low modulus elastomeric sealant.
2. Background Information
British Patent Specification 1,308,985, published Mar. 7, 1983, discloses a method of curing room temperature vulcanizing silicone rubber containing acetoxy-silicon bonds, which method adds sodium alumino silicate having adsorbed water. The water from the aluminosilicate causes the silicone rubber to cure even if the composition is not open to atmospheric moisture.
A silicone composition which cures upon exposure to moisture in the air is described in U.S. Pat. No. 3,817,909, issued Jun. 18, 1974. This composition is obtained by mixing a hydroxyl endblocked polydiorganosiloxane, non-acidic, non-reinforcing filler, a difunctional acetamidosilane, and an aminoxysilicon compound.
An organopolysiloxane composition which rapidly hardens to the elastomeric state is disclosed in U.S. Pat. No. 4,508,888, issued Apr. 2, 1985. The composition comprises a polyhydroxylated polysiloxane, a polyacyloxysilane cross-linking agent, and a hardening accelerator comprising water and an alkali or alkaline earth metal phosphate and/or polyphosphate.

Two-part, ultra low modulus silicone sealant


Microcellular polyurethane elastomer shoe sole components have exceptional physical properties may be prepared from isocyanate-terminated prepolymers derived from polyoxypropylene diols having a molecular weight of from about 2000 Da to 8000 Da, an unsaturation less than about 0.02 meq/g, and a random oxyethylene content of from about 5 to about 15 weight percent. The shoe sole components exhibit high tensile strength, elongation, resilience, and in addition have excellent tear strength, particularly 90.degree. angle tear.

Microcellular shoe soles have become common, particularly for athletic shoes, but increasingly for other shoes as well. In contrast to solid elastomers which were traditionally used before the advent of microcellular elastomers, microcellular shoe sole components offer the opportunity to manufacture shoes with increased cushioning and lighter weight. Although early microcellular components often attained these advantages at the expense of durability and wear resistance, great strides have been made in these areas, and now the use of microcellular components is virtually universal. Microcellular polyurethanes are particularly well suited for these uses.
In the molding of microcellular shoe sole components, prepolymer systems are generally used. Such systems include an isocyanate-terminated prepolymer, prepared by the reaction of 4,4'-methylenediphenylene-diisocyanate (4,4'-MDI, "pure" MDI) or MDI variants with a polyoxypropylene diol, and cured by reaction of the prepolymer with a diol chain extender, e.g. 1,4-butanediol. A minor amount of water, in conjunction with a catalyst which catalyzes the CO.sub.2 -producing water/isocyanate reaction, provides the necessary blowing to produce the small, uniform cells characteristic of microcellular elastomers. The density is generally between about 0.2 g/cm.sup.3 and 0.5 g/cm.sup.3, considerably less than non-cellular polyurethane elastomers, but considerably higher than cellular polyurethanes such as flexible and high resilience flexible foams.
Despite the great improvements which have been made in microcellular polyurethane shoe sole components over the past years, room for considerable improvement still exists. For example, production speed is limited by the time necessary to achieve the requisite "green strength" which allows the molded component to be removed from the mold without tearing and without suffering permanent deformation. Lowering demold time through increased catalyzation is possible, however, the processing window generally suffers as a result. Increased catalyzation can also negatively affect physical properties. Use of high primary hydroxyl polyols, commonly used to increase reactivity of conventional polyurethane foams, is of no help in prepolymer-based microcellular foams, as the polyol component has been prereacted into the prepolymer, and thus the higher reactivity of the primary hydroxy group is irrelevant.
Physical properties of the molded foam product are also important. Improvements in comfort-related properties such as resiliency, support factor, and the like, as well as lowered density, are well known areas where continual efforts toward improvement are being made. Less well known, however, are such factors as tensile strength, elongation, and tear strength. While each of these is to some degree related to desirable end-use physical characteristics, these properties are important in processing as well. For example, a microcellular formulation which produces a product having higher ultimate tensile and tear strength will reach the level of physical properties (green strength) necessary to allow demolding more quickly as compared to a formulation producing microcellular foams having lower ultimate physical properties. The higher tensile and tear strengths will also allow removal from the mold with less frequency of damage, reducing the scrap rate during the molding process. Such characteristics are also required of the demolded, fully cured products, which frequently must be stretched, pulled, or pushed into various shoe cavities, coverings, etc.

Microcellular elastomers with improved processability and properties


An emergency shutdown apparatus for a solid-oxide fuel cell system, including a fuel cell stack, comprises a reservoir containing a reducing fluid, a valve enabling or preventing flow of the reducing fluid from the reservoir to the fuel cell stack, a timing circuit operating and controlling the valve, and a battery powering the timing circuit. The apparatus for an emergency system shutdown is able to operate independently of the main power plant and does not require any active control from the solid-oxide fuel cell system. The disclosed apparatus is entirely a stand-alone component that may be added to any conventional solid-oxide fuel cell system. The apparatus in accordance with the invention can be recharged, allowing the same hardware to be used over and over, however, a disposable unit could be used if found to be desirable.

Fuel cells, which generate electric current by the electrochemical combination of hydrogen and oxygen, are well known. In one form of such a fuel cell, an anodic layer and a cathodic layer are separated by an electrolyte formed of a ceramic solid oxide. Such a fuel cell is known in the art as a Solid-Oxide Fuel Cell (SOFC). SOFC systems derive electrical power through a high-efficiency conversion process from a variety of fuels including natural gas, liquefied petroleum gas, ethanol, and other hydrocarbon and non-hydrocarbon fuels. Hydrogen, either pure or reformed from hydrocarbons, is flowed along the outer surface of the anode and diffuses into the anode. Oxygen, typically from air, is flowed along the outer surface of the cathode and diffuses into the cathode.
Each O2 molecule is split and reduced to two O−2 anions catalytically by the cathode. The oxygen anions transport through the electrolyte and combine at the anode/electrolyte interface with four hydrogen ions to form two molecules of water. The anode and cathode are connected externally through a load to complete the circuit whereby four electrons are transferred from the anode to the cathode.
When hydrogen as a feed stock for the fuel cell is derived by "reforming" hydrocarbons such as gasoline in the presence of limited oxygen, the reformate gas includes CO which is converted to CO2 at the anode via an oxidation process similar to that performed on the hydrogen. A single fuel cell is capable of generating a relatively small amount of voltage and wattage and, therefore, in practice it is known to stack a plurality of fuel cells together in electrical series.
Reformed gasoline is a commonly used feed stock in automotive fuel cell applications. Reformate gas is typically the effluent from a catalytic liquid or gaseous hydrogen oxidizing reformer and is often referred to as "fuel gas" or "reformate". Reformate typically includes amounts of carbon monoxide (CO) as fuel in addition to molecular hydrogen. The reforming operation and the fuel cell operation may be considered as first and second oxidative steps of the hydrocarbon fuel, resulting ultimately in water and carbon dioxide. Both reactions are preferably carried out at relatively high temperatures, for example, in the range of about 700° C. to about 900° C.
Since optimum fuel consumption and electrical generation, and therefore optimum efficiency of a SOFC stack, are reached at relatively high operating temperatures, a cooling process needs to be performed during normal system shutdowns. The normal system shutdown is a period that occurs, for example, prior to an extended duration of nonuse. Typically, the SOFC stack is cooled with air utilizing the cathode airflow. Due to the relative high operating temperature of the SOFC stack, typically about 750° C. and higher, and the chemical composition of the anodes, purging the entire SOFC stack with cathode air for cooling prior to extended periods of nonuse results in a degrading and fatiguing oxidation of the anodes since oxygen is allowed in the cavities adjacent to the anodes. The anode side of the fuel cell is, in part, nickel. At temperatures above about 400° C., and in the presence of free oxygen, nickel oxide is formed, which may lead to deterioration of the SOFC stack and which over time may cause failure of the SOFC stack. Therefore, it is harmful to the SOFC stack when oxygen is allowed in the cavities adjacent to the plurality of anodes.
The currently accepted method for preventing the oxidation of the anodes in a laboratory environment is a process in which the cavities in the anode side of the SOFC stack are continuously purged with a fluid containing no free oxygen during a normal cooling process. For example, a blend of bottled reducing gas may be flowed through the anode side of the SOFC stack while the system cools from its operating temperature to a temperature below about 400° C. where harmful oxidation of the anodes ceases. Though a purge is required, such continuous purging process requires more pressurized reducing gas than can be stored on an onboard system, such as what might be needed in a non-stationary motor vehicle.
A typical SOFC system requires usually between four to eight hours to cool from its operating temperature to a temperature that will not harm the anode side of the stack. During this time, a continuous purging process will exhaust more reducing gas than a volume of storage bottles, equal to the size of the entire system, can hold. While purging the anode side of the stack during a normal cooling process with a reducing fluid produced by the SOFC system itself, such as utilization of exhaust gas where oxygen has been reduced below ignition concentration, has been proposed, this is not a solution for emergency system shutdowns when an unexpected event requires an immediate shutdown of the entire SOFC system including the use of external power. In such emergency situation, the SOFC system does not have time to execute its normal shutdown process and the anode components of the stack cannot be protected from detrimental oxidation. No protecting mechanisms for the anode side of the stack are currently known for such emergency situation.
What is needed in the art is a cooling apparatus and strategy that prevents detrimental oxidation of the anode side of the stack from occurring in the event that a sudden and complete emergency shutdown of the SOFC system is necessary.
It is a principal object of the present invention to provide an apparatus that enables a SOFC system to safely cool down during an emergency system shutdown, while the anodes of the stack are protected from oxidation by a reducing environment.
It is a further object of the invention to provide an apparatus that requires only a fraction of space required by prior art gas bottles to provide the desired oxygen-free environment.

Apparatus for solid-oxide fuel cell shutdown having a timing circuit and a reservoir


Provided is a printing medium particularly useful for inkjet printing. The printing medium is comprised of a substrate and a coating layer. The coating layer comprises porous particles, a resin binder and colloidal particles, with the colloidal particle being of a size that is greater than the size of the pores of the porous particles, but smaller than the interstitial pores created by the porous particles. The printing medium allows one to realize high optical density and high image resolution, while also offering good mechanical properties, fast drying, good waterfastness and consistent performance in different environments.

Field of the Invention
The present invention relates to a recording medium useful in color printing, particularly for ink jet printing. More specifically, the present invention relates to a recording medium for ink jet printing comprised of a porous coating on a substrate. The present invention also relates to a method of printing using the medium of the present invention.
Ink jet printing is a printing technology in which color dots are formed on a substrate from ink droplets ejected from nozzles in a print head. The inks are generally composed of water, a water-soluble dye or a pigmented dye, one or more water-miscible cosolvents, and one or more surfactants. The substrate (ink jet medium) can be plain paper, coated paper, plastic film, cloth, and any other media which can absorb ink and form a good image. In order to form a high resolution image, the substrate is usually coated with a specially formulated ink jet coating. These coatings can be divided into two major categories, fully dense coatings and porous coatings.
The fully dense coatings are mainly comprised of film-forming polymers, with at least one of the polymers being hydrophilic. This hydrophilic polymer is either water soluble or water swellable. Sometimes a small amount of pigment is incorporated into these coatings, but the amount of pigment is usually far below the critical pigment volume concentration. This type of coating gives a glossy surface and is usually transparent. The fully dense coatings absorb ink and form an image through rapid swelling of the coating itself. The major disadvantages of this type of coating include the long ink dry time, low water resistivity of both the coating and the printed image, sensitivity of the image quality to the environment, and the difficulty in achieving a "universal" medium which would perform on all printers.
A polymeric coating is generally saturated with ink immediately after printing. This ink plasticizes the polymer coating and lowers the glass transition temperature of the coating. The coatings are tacky for a certain amount of time, usually from 30 seconds to 10 minutes, until enough solvent is evaporated from the coating to bring the glass transition temperature of the coating to near or above room temperature. During the time period, the image would smear if touched and it would block to another sheet of paper or film.
A polymeric coating needs to absorb a high amount of water rapidly to obtain a high quality image without bleeding and coalescence. On the other hand, it needs to be waterfast to provide durability. These two requirements frequently conflict with each other. It is very difficult to achieve good waterfastness and high water absorbency at the same time. The coating also needs to anchor the dye molecules in order to achieve image waterfastness. The dye molecules are water-soluble or at least water-dispersible in an aqueous ink and these same molecules need to be completely insolubilized once they are deposited and diffused into the coating. A complete insolubilization of the dye is difficult to achieve.
The polymeric ink jet coating always contains moisture and the amount of moisture depends on the environment. The imaging characteristics and ink dry time is, therefore, a function of temperature and humidity. For example, under cold and dry conditions, the equilibrium moisture in the coating is low, the free volume is also low. The initial diffusion coefficient of ink in the coating is lower than in the same media exposed to a hot and humid atmosphere. Color bleeding and coalescence can occur. In a hot and humid environment, the equilibrium moisture in the coating is high. The free volume of the coating is higher than in dry and cold conditions. Dye molecules in the ink can easily diffuse into the coating. However, the image is likely to be tacky for a long time after printing and blocking resistance of the image is expected to be low. Different environments also affect the dimensional stability of the coating due to the moisture change in the polymer. An anticurl coating is generally needed in order to balance out the dimensional change of the coating with the atmosphere. This anticurl layer adds cost to the production process.
The coating composition needs to be carefully tailored to ensure compatibility between the coating and the dye, the cosolvents in the ink, and the surfactants in the ink. For fully dense polymeric coatings, it is nearly impossible to design a "universal" ink jet medium which performs well on all or most of the commercial ink jet printers.
The second type of coating for ink jet applications is a porous coating. This type of coating is usually composed of inorganic or organic particles bonded together by a binder. The amount of pigment particles in this type of coating is often far above the critical pigment volume concentration, which results in high porosity in the coating. During the ink jet printing process, ink droplets are rapidly absorbed into the coating through capillary action and the image is dry-to-touch right after it comes out of the printer. Therefore, porous coatings allow a fast "drying" of the ink and produces a smear-resistant image. The dye molecules adsorb on the surface of the particles and form an image. High water resistance of both the coating and the image can be achieved with the porous coating. The performance of the porous ink jet coating is less sensitive to the compositions of the ink. Therefore, a universal medium which performs well on all printers can be designed. The performance of a porous coating is also much less sensitive to the temperature and humidity of the environment, so consistent imaging characteristics and dry time can be expected. The disadvantages of this type of coating, however, is the difficulty in achieving high gloss due to the high porosity in the coating.
The pigments used in ink jet coatings are usually clay (U.S. Pat. No. 4,732,786), calcium carbonate (U.S. Pat. No. 4,474,847), magnesium carbonate (U.S. Pat. Nos. 5,338,597, 5,227,962, 5,246,774), silica (UK Patent Nos. GB2129333, 2166063), surface modified silica (U.S. Pat. No. 5,372,884), zeolite, and alumina (U.S. Pat. No. 5,182,175). A combination of two or more of the above mentioned pigments can also be used. Most of these porous coatings are opaque. Therefore, dye molecules should be kept on the top surface layer in order to achieve high optical density. Pigments with high surface area are desirable, in order to keep the dye molecules on the surface layer.
Silica pigments are especially preferred in ink jet applications due to the availability of a variety of silica gels and precipitated silica with high surface area and high internal pore volume. U.S. Pat. No. 4,780,356 describes a coating composed of porous silica bonded by a water-soluble binder such as polyvinyl alcohol. The particles have a pore volume of 0.05-3.00 cc/g, a particle size of 0.1 to 5 .mu.m, and a pore size of 1 to 500 nm. U.S. Pat. No. 5,352,503 describes a coating based on silica gel with polyvinyl alcohol as the binder, polyethylene glycol as a curl-reducing agent, and a polyquaternary amine as a dye mordant.
The porous coatings composed of porous particles such as silica or zeolite possess fast drying characteristics. However, high resolution image and strong mechanical strength are difficult to obtain. The internal pores are between 1 and 50 nm for silica gel, and between 1 and 500 nm for precipitated silica. The interstitial pore size between particles is 0.4 to 3 .mu.m for 2 to 15 .mu.m particles. The nonuniform pore size distribution is a problem in that it results in differential capillary pressures within the coating, causing ink to migrate from large pores to small pores. This ink migration causes nonuniform color density, which lowers the sharpness of color tone.
The binders for these coatings are usually hydrophilic binders such as polyvinyl alcohol. The waterfastness of the coating is a function of the pigment to binder ratio. If the amount of binder is low enough so that all the polymer binder is adsorbed on the particle surface, good waterfastness can be achieved. However, the coating would have very little flexibility. This type of coating can be used with a plain paper substrate, where a thinner coating layer is required since the base paper can absorb some of the ink vehicle. In the case of impermeable substrates such as polyester and polyvinyl chloride, or low permeability substrates such as highly sized glossy paper, a thick coating (10-80 .mu.m) is required to accommodate all the ink since the coating is the sole ink absorbent. This type of coating is not suitable due to its brittleness.
When the pigment to binder ratio decreases, the toughness of the coating increases and the porosity of the coating decreases. After the particle surface is fully covered with adsorbed binder, any additional binder occupies the interstitial space. The binders adsorbed on the particle surface has limited configuration and mobility, and it is water insoluble. The other part of the binder is free polymer and it dissolves in water. As the amount of free polymer increases, the coating loses its waterfastness. The ink jet medium described in U.S. Pat. No. 5,352,503 falls into this category.
U.S. Pat. Nos. 4,879,155, 5,104,730, 5,264,275, 5,275,867 (Asahi) disclose a type of porous coating which is composed of colloidal boehmite particles bonded together by a water-soluble binder such as polyvinyl alcohol. The pore size in these coatings are controlled, so that the radius of the majority of pores lies between 1 and 10 nm. Unlike the porous coating described above, these porous coatings are transparent due to the small particle size and pore size. High optical density can be achieved whether the dye molecules are kept on the surface layer or not. Good waterfastness of both the coating layer and the printed image are achieved in this type of coating, because the polymer binder in the coating and the anionic dye in the inks are adsorbed on the surface of boehmite particles.
A porous coating composed of uniform colloidal particles can provide uniform pore size distribution, which results in high image resolution. The disadvantage of this type of coating is the low mechanical strength of the coating. The porosity only comes from interstitial pores (which are pores created by the particles themselves), i.e., the spaces between the particles, since the colloidal particles themselves are fully dense. As a result, the porosity of this type coating is usually lower than the coating composed of porous particles, which means an even thicker coating is needed to accommodate all the inks. The thicker the coating, the more difficult to overcome the brittleness of this type of coating. It is anticipated that the mechanical properties of this type of medium face severe challenges with the emergence of high ink flux and high resolution printers.
It is therefore an objective of the present invention to provide an ink jet medium which possesses high optical density and high image resolution.
It is another objective of the present invention to provide an ink jet medium which also possesses good mechanical properties, fast drying and good water fastness.
Yet another objective of the present invention is to provide an ink jet medium which provides consistent performance at different environments, as well as high optical density, high image resolution, good water fastness, fast drying and good mechanical properties.
Still another object of the present invention is to provide such an ink jet medium which is universal in that it will perform well with all printers.
These and other objects of the present invention will become apparent to the skilled artisan upon a review of the following specification. The FIGURE of the Drawing, and the claims appended hereto.

Printing medium comprised of porous medium


A system, method and apparatus are provided for secure e-mail message attachment optimization. Content attached to e-mail messages may not be suited to the resource constraints of the destination wireless device. In secure e-mail messages, the message may be signed and/or encrypted. A wireless server can determine resource parameters associated with a destination wireless device, such as display resolution, memory capacity, processor speed, and wireless interface constraints and re-scale the attached content to be optimized for delivery and presentation on the wireless device.

When e-mail messages are sent to wireless devices, or portable electronic devices, they can contain attachments providing content such as images, audio, video or documents. The content may be formatted in a manner that exceeds the capability of the wireless device or an access technology to the wireless device. For example an image may be in a resolution that exceeds the display resolution of the wireless device. Sending the original content, such as the image, to the wireless device may be a waste of resources as the additional size, or resolution may not be of benefit to the wireless device. When secure e-mail messages are sent to the wireless device, either by being signed, encrypted, or signed and encrypted with attached content, the content integrity must be maintained to ensure proper decryption and verification of the secure e-mail message.
Therefore, there is a need for an improved system and method for sending secure e-mail messages containing attached content optimized to a wireless device's capabilities.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

System, method and apparatus for optimizing wireless communications of secure e-mail messages with attachments


An escalator handrail drive system includes a powered drive belt which engages the underneath surface of the handrail along the return path of travel of the latter. A series of pressure rollers engage the outer surface of the handrail to press the latter against the drive belt. The pressure rollers are all biased against the handrail by a single spring. The drive belt is pretensioned by an adjustable pretension spring assembly which can apply a fixed pretensioning force to the drive belt which will not substantially change irrespective of whether the handrail is being driven in the "up" direction or in the "down" direction on the escalator.

Moving handrails on an escalator or moving walkway are typically driven by passing the handrails through a driving pressure nip along the return path of travel of the handrail beneath the balustrades. The nip may be formed by a pair of cooperating rollers, or by a driven belt which cooperates with a plurality of backup rollers. The nip will be powered by chains or the like which are driven by the main drive mechanism of the escalator. Soviet Patent No. SU1286-493A, U.S. Pat. No. 4,134,883, and Austrian Patent No. 247,236 disclose variations of the prior art drive systems described above.
U.S. Pat. No. 5,117,960, granted Jun. 2, 1992 to H. W. Ahls, et al. discloses a handrail drive system which uses a powered drive belt and a pressure belt to drive the handrail along its path of travel. The drive belt is entrained on a powered drive roller, and a free wheeling idler roller. The idler roller is biased by a spring to provide an adjustable tension to the drive belt. A series of adjustable but non-biased backup rollers provide a backing force for the drive belt which holds the latter against the handrail between the drive roller and the idler roller. The pressure belt is entrained on a pair of idler rollers, one of which is spring biased to provide pressure belt tension. A plurality of pressure rollers are disposed between the pressure idler rollers and are individually spring biased against the pressure belt so as to press the latter against the handrail.
The handrail drive system described in the aforesaid U.S. Pat. No. 5,117,960 patent is serviceable, but exhibits certain drawbacks. The use of a pressure belt requires additional hardware to mount the pressure belt and does not add any drive power or stability to the system. The use of individual pressure roller springs renders the drive assembly difficult to properly adjust. The individual pressure springs also limit the flexibility of the force imparted to the handrail which presses the handrail against the drive belt. Finally, the tension spring assemblies which are used to impart tension to the drive belt and the pressure belt, and thus reduce or eliminate belt slippage, are vulnerable to forces which emanate from the handrail that tend to vary the belt tension depending on whether the handrail is being moved in the upward or downward direction, i.e., toward, or away from the belts' tension rollers.
When the handrail is moved in the upward direction, there is greater frictional drag imparted to the handrail by the guide rails which must be overcome by the drive assembly, than when the handrail is moved in the downward direction. When the handrail drive assembly is installed on the escalator, the belt power roller will be below the belt tension roller, and that relationship will not change, whether the handrail is being moved in the upward or downward direction. Thus, the handrail will be moved toward the tension roller when the handrail moves in the upward direction and away from the tension roller when the handrail moves in the downward direction. Since the tension roller is always biased away from the drive roller, the direction of movement of the handrail will tend to lessen the degree of compression of the tension spring if the drive belt is moving toward the tension roller; and will tend to increase the degree of compression of the tension spring if the drive belt is moving away from the tension roller. When the tension spring is further compressed, a decrease in drive belt tension ensues with a concurrent lessening of the driving force applied to the handrail and even drive belt slippage. The result of the aforesaid drive belt tension instability is an inability to accurately control the bi-directional drive force imposed on the handrail by the drive belt. Drive belt tension must be adjusted to take into account the desired direction of movement of the handrail. This factor mitigates against the use of escalators that can be directionally reversed to account for passenger traffic flow. The same applies to horizontal moving walkways, which are typically much longer than escalators.