Abstract: In the magnetic chuck control disclosed herein, the chuck winding is selectively energized in one direction or the other through respective triggerable semiconductor current switching devices. Successively reducing current levels are applied in successive phases of operation, the polarity of the current being reversed in successive phases. During a first portion of each phase the device is triggered to apply a corresponding preselectable voltage. During a second portion of each phase the switching devices are triggered quite late to provide an average voltage which opposes the current flow which was induced during the first portion thereby to quickly reduce the level of current flowing in the winding.

Abstract: The flow matching valve disclosed herein incorporates a fill port in addition to the source, load and respective drain ports employed in previous load matching valves. The inclusion of the fill port allows reconfiguration of hydraulic systems to reduce leakage and improve reliability and to eliminate auxiliary check valves in certain configurations.

Abstract: The pumping apparatus disclosed herein recovers pumping energy required in feeding solution to a reverse osmosis unit. The reverse osmosis unit generates a purified product but also a concentrate stream which is discharged at a pressure only slightly lower than the feed pressure. The discharge flow is utilized to displace hydraulic fluid in a work exchange vessel and this displaced fluid is then boosted in pressure and supplemented by an additional flow of hydraulic fluid, the combined hydraulic fluid flow being then utilized to pressurize, through another work exchange vessel, the solution feed flow to the reverse osmosis unit.

Abstract: A caching system for a shared bus multiprocessor which includes several processors each having its own private cache memory. Each private cache is connected to a first bus to which a second, higher level cache memory is also connected. The second, higher level cache in turn is connected either to another bus and higher level cache memory or to main system memory through a global bus. Each higher level cache includes enough memory space so as to enable the higher level cache to have a copy of every memory location in the caches on the level immediately below it. In turn, main memory includes enough space for a copy of each memory location of the highest level of cache memories. The caching can be used with either write-through or write-deferred cache coherency management schemes.

Abstract: The apparatus disclosed herein provides controlled operation of a pneumatic actuator by effecting charging and discharging of the actuator through an intermediate step volume, the pressure in the step volume being regulated as a respective function of the existing pressure in the actuator during charging and discharging.

Abstract: In the ion nitriding power supply disclosed herein, power to the discharge chamber is normally current-regulated by a pulse-width modulated current switching device effectively in series with a switching inverter which energizes the chamber, instantaneous current variations being smoothed by a series inductance which, together with the chamber, is shunted by a freewheeling diode. Incipient arcing is quickly extinguished by semiconductor switching devices incorporated in the inverter which, when energized simultaneously, shunt the chamber, instantaneous current limiting being provided by the series inductance. The shunt switching devices are triggered when the voltage across the discharge drops below a level indicative of the formation of an arc.

Abstract: The fan speed controller disclosed herein is particularly useful in the cooling of electronic equipment and provides a feedback control characteristic from an exhaust air temperature sensor such that the change in outlet temperature over the range of air flow rates is substantially equal to the change in temperature rise of typical heat generating devices in electronic equipment over that same range. Accordingly, device temperature is maintained substantially constant over a range of varying input air temperatures. Preferably, the controlled fan includes a d.c. motor which is energized in a pulsed d.c. mode to prevent stalling or instability at low flow rates.

Abstract: The fan speed controller disclosed herein mounts directly on a fan whose speed is to be controlled and provides electronic speed control circuitry mounted in a disk-like enclosure aligned with the fan hub. The enclosure is compartmented and apertured to provide a representative air flow past a temperature sensitive element employed by the circuitry. Fan speed is controlled as a function of air temperature above a sharply defined minimum to provide effective cooling with minimal noise generation.

Abstract: A dot matrix line printer comprised of a main frame assembly and a shuttle frame assembly hinged thereto for limited pivotal movement around a horizontal hinge axis. The main frame assembly carries a paper drive subassembly and an adjustable platen subassembly. The shuttle frame assembly carries one or more hammer banks and a shuttle drive motor for shuttling each bank to move the hammers thereof along a print row extending across the width of the paper parallel to the front face of the platen. By pivoting the shuttle frame assembly up and away from the main assembly, ready access is afforded to the paper path for loading and to the hammer banks for servicing. Each hammer includes a hammer element mounted on the free ends of first and second spaced parallel leaf springs for linear movement toward and away from a paper to be printed upon. The parallel leaf springs are anchored at one end and biased to impact the hammer element against the paper.

Abstract: In the microlithographic system disclosed herein, the spaces between elements in a projection lens are filled with flowing helium gas which substantially reduces the refraction errors caused by barometric changes in the atmosphere, even though the portions of the optical path outside the lens are exposed to the atmosphere.

Abstract: The wafer chuck disclosed herein is adapted to hold a semiconductor wafer during high energy treatment in a vacuum environment. The wafer is clamped by its rim to a circular domed plate so as to distort the wafer into close proximity with the domed face of the plate. Ports are provided in the face of the plate for introducing a mobile gas under controlled pressure to the interstitial space between the wafer and the domed face of the plate. An annular groove is provided around the periphery of the domed face and this groove is connected to a vacuum pumping means thereby to minimize leakage of the mobile gas into the vacuum environment.

Abstract: In the lifting magnet system disclosed herein, demagnetization and releasing of a load are accomplished without switching inductively loaded d.c. power by employing a.c. energization, through respective bridge rectifiers, of entirely separate lifting and drop coils.

Abstract: The high speed print pin actuator disclosed herein is constructed as two sub-assemblies, a U-shaped fixed magnet structure and an armature sub-assembly. One leg of the U-shaped structure constitutes a coil core and the other includes a permanent magnet and a keeper plate, the ends of the keeper and the core being finished to a common plane. The armature assembly includes a flux return bridge structure which extends from the keeper to a region adjacent the end of the coil core and which is bifurcated to receive an armature which is selectively attracted to the coil core. The armature is carried on a spring which is, in turn, mounted on the bridge structure. With the spring in a deflected position, the armature is finished to a common surface with the portion of the bridge which mates with the magnet structure. Accordingly, assembly of the armature sub-assembly with the U-shaped fixed magnet structure is facilitated and accurate parallelism of the armature and pole piece is provided.

Abstract: The slaved ramp voltage generator disclosed herein facilitates the writing of characters by a servo controlled stylus carried on a moving carriage. The carriage is driven at a selectable speed and the drive system generates pulse signals at a rate which is proportional to carriage speed. A digital counter is advanced by these pulse signals and the digital value held by the counter is converted to an analog voltage which varies in proportion to displacement of the carriage. This carriage displacement voltage is summed with a vector-defining position voltage to obtain a control voltage which drives the stylus servo mechanism to effect writing with respect to a moving frame of reference.

Abstract: In the dot matrix printer disclosed herein, a multicolor ribbon is shifted to bring different colored stripes in alignment with the nosepiece of a dot matrix printhead by means of cup-like ribbon guide members journaled on either side of the nosepiece. Each guide member provides, in its periphery, an arcuate slot through which the ribbon can freely slide as the printhead traverses. A stepping motor is coupled to the guide members for rotating them so as to selectively bring a stripe of desired color into operative position.

Abstract: In the reticle bar code scheme disclosed herein, the peculiar characteristics and requirements of a microlithographic reticle are utilized in a bar code scheme which provides multiple levels of error checking while permitting an extensive repertoire of reticle identifying characters. In reading the bar code, the reticle is moved passed a photoelectric sensor and, by counting a clock signal, the width of each bar is measured. A synchronization character at the start of the data character string provides a nominal bar width value and each character comprises three bars of each polarity, the bars being integral multiples of the nominal value with the width of the character being ten times the nominal value.

Abstract: In the temperature measuring apparatus disposed herein, a first intermediate output signal is obtained which is a function of the ratio of the brightness of a target at two different wavelengths and a second intermediate output signal is generated which is a function of the brightness of the target at a single wavelength. The two intermediate output signals are combined in preselectable proportion to yield a temperature output signal which is relatively insensitive to target surface characteristics.

Abstract: The valve disclosed herein functions, in one sense, as a flow matching device and, in another sense, as a reciprocative check valve. By employing the valve, a hydraulic system may be implemented in which filling and emptying of a variable volume load, such as a hydraulic piston may be accomplished through a single check valve structure at controlled flow rates.

Abstract: In the heat treating apparatus disclosed herein, semiconductor wafers are baked on the circular hot plate while being sheathed with a uniform vapor flow. The preferred vapor is a mixture of a relatively large volume of nitrogen carrying a relatively small volume of HMDS. After passing over the wafer, the vapor sheath is drawn, through an annular gap, into an exhaust chamber which surrounds and underlies the hot plate thereby avoiding heat and vapor loss into the other portions of the semiconductor fabrication line within which the baking apparatus is typically incorporated.

Abstract: A recording or printing device which will print bidirectionally in both the left to right and right to left directions by use of an ink jet head travelling horizontally with respect to a printing medium. A carriage carries the ink jet head and an image is formed by ink droplets from the ink jet head. To compensate for relative horizontal displacement of the ink droplets caused by the horizontal travel of the head and carriage, tilting compensating structure is provided for parallel electrostatic deflection plates. The deflection plates are mounted on a pivotable structure upon the traverse carriage and because of the bias effect of a pair of springs and a slide block will tilt in the correct direction to provide the needed compensation of the ink droplets. Mechanical limit stops on a slide bar determine the amount of tilt for more than one speed of carriage traverse, and changeable limit stop structure permits the limit stops to be changed for a second, a third or more speed of carriage movement.