Abstract: A rotary hydraulic machine which includes a housing having a shaft mounted for rotation within the housing about a shaft axis. A cylinder block is coupled to the shaft for corotation with the shaft within the housing and includes a plurality of cylinders disposed in a circumferential array parallel to and surrounding the shaft axis. A piston is disposed to reciprocate within each of the cylinders and is coupled to a yoke for determining displacement of the pistons within the cylinders. A valve plate is affixed within the housing and includes arcuate slots at a radius from the axis of rotation corresponding to that of the cylinders. The slots respectively connect cylinders to the machine inlet and outlet ports as the cylinders register with the slots.

Abstract: An electrohydraulic system includes a plurality of electrohydraulic devices individually controlled by on-board microprocessor-based control electronics. Each individual device controller is connected to and addressable by a master controller for coordinating operation of the various devices. An electrohydraulic servo valve assembly includes a hydraulic manifold having a valve spool variably positionable therein under control of a torque motor. A microprocessor-based controller is connected to the torque motor and is mounted on the manifold by a cover which encloses and protects both the controller and the torque motor. A watchdog timer in the microprocessor-based controller monitors pulsewidth modulated signals to the torque motor for terminating operation in the event of signal loss. In a preferred embodiment of the invention, the servo valve assembly is coupled to a linear actuator which has its position monitored by an electroacoustic transducer.

Abstract: An electrohydraulic servo system which includes an actuator having a cylinder and a piston variably positioned therewithin, a servo valve responsive to valve control signals for coupling the actuator to a source of hydraulic fluid, and control electronics responsive to piston position for generating the valve control signals. A variable frequency rf generator is coupled through associated directional couplers to a pair of antennas which are positioned within the actuator cylinder and physically spaced from each other in the direction of piston motion by an odd multiple of quarter-wavelengths at a nominal generator output frequency.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions and a variable displacement pump with loading sensing control for supplying fluid to said actuator. A pilot operated spool type meter-in valve is provided to which the fluid from the pump is supplied and a pilot controller alternately supplies fluid at pilot pressure to the meter-in valve for controlling the direction and displacement of movement of the meter-in valve and the direction and velocity of the actuator. A pair of lines extends from the meter-in valve to the respective openings of the actuator and a pilot operated meter-out valve is associated with each line of the actuator for controlling the flow out of the actuator when that line to the actuator does not have pressure fluid from the pump applied thereto.

Abstract: An electrohydraulic servo system which includes a linear actuator having a cylinder and a piston variably positioned therewithin, a servo valve responsive to valve control signals for coupling the actuator to a source of hydraulic fluid, and control electronics responsive to piston position for generating the valve control signals. A coaxial transmission line is formed within the linear actuator to include a center conductor coaxial with the actuator and an outer conductor. A bead of ferrite or other suitable magnetically permeable material is coupled to the piston and surrounds the center conductor of the transmission line for altering impedance characteristics of the transmission line as a function of position of the piston within the cylinder.

Abstract: An electrohydraulic system which includes a plurality of electrohydraulic devices individually controlled by microprocessor-based control electronics. A central controller for coordinating operation among the various devices includes a host controller for providing low speed serial and/or parallel output of control signals, and a master controller having a low speed serial and parallel I/O port for connection to the host controller, and a high speed serial I/O port connected by a full duplex bidirectional data bus in common to all of the device controllers.

Abstract: An electrohydraulic servo system which includes a plurality of pressure compensated flow control servo valves for feeding hydraulic fluid from a variable displacement pump to associated actuators and loads. A closed-loop velocity-control servo system is coupled to each servo valve, and is responsive to velocity command inputs from an operator and to feedback signals from the respective loads for providing flow control signals to the respective servo valves. A pump controller receives the valve flow control signals, derives associated valve flow rates from predetermined functional characteristics of the pressure compensated valves, and obtains a total flow demand as a function of the sum of the indicated individual valve flow rates. A pump displacement command is derived as a combined function of total flow demand and pump speed to accommodate volumetric inefficiencies which vary with speed, and the displacement command signal is fed to a pump displacement servo control loop for controlling pump output.

Abstract: A hydraulic system comprised of a pump, a first valve in the inlet to the pump, and a second valve which activates or deactivates a third valve which permits the loading and unloading of the pump discharge. A motor is provided to operate the first valve for opening or closing the pump inlet. This motor also actuates the second valve in concert with the operation of the first valve to open or close a vent port to the third valve which opens or closes the passage from the pump discharge to tank, located away from the pump inlet. This permits unloading the pump discharge during the restriction of the pump inlet and allows the loading of the pump discharge after the opening of the pump inlet. With the pump inlet restricted, the system provides a low restrictive passage for circulating the prescribed small volume of flow used to lubricate and cool the pump.

Abstract: An electric motor driven inline hydraulic apparatus comprises a common housing, a stationary shaft mounted in said housing and spaced pump cylinder block subassemblies that rotate around and are mounted on said shaft. Each subassembly includes a cylinder block and a plurality of circumferentially spaced pistons. The cylinder block subassemblies are positioned such that the pistons of one subassembly extend toward the other subassembly. A common yoke plate is mounted between the two cylinder blocks and bears the two groups of piston shoes, one on each of its two bearing surfaces. Each cylinder block is driven independent of and in direction opposite to the other by an electric motor integrally mounted such that its hollow rotor houses the block and drives it. All components described above are contained in one housing and operate submerged in hydraulic fluid.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions and a pump system with load sensing control for supplying fluid to said actuator. A meter-in valve is provided to which the fluid from the pump is supplied and a manual or electrohydraulic controller alternately supplies fluid at pilot pressure to the meter-in valve for controlling the flow therefrom to the actuator to control direction and displacement of movement of the meter-in valve and the direction and velocity of the actuator. A pair of lines extends from the meter-in valve to the respective openings of the actuator. A meter-out valve is associated with each line to the actuator for controlling flow out of the actuator. Each meter-out valve is operated by the pilot pressure from the controller.

Abstract: A system and method for remotely measuring and linearizing flow characteristics, specifically velocity characteristics, of an electrohydraulic servo valve and actuator system. A plurality of raw command signals are generated in sequence, and corresponding motion data at the valve and load (including the actuator) are measured and stored. A linearized characteristic is then generated corresponding to the range of motions measured, and a look-up table is generated which relates raw command signals to command signals necessary to obtain the desired linear motion characteristics.

Abstract: A variable displacement pump system including a pressure compensator for operating a pump adjusting mechanism to vary the displacement by applying hydraulic fluid to the pump adjusting mechanism and a spring biased piston applying a yielding force to the pump adjusting mechanism opposing the pressure compensator. A load sensing valve senses the pressure of the load to which fluid is supplied from the pump through a system valve and applies this load pressure to work in unison with the spring biased piston for purposes of urging the pump towards its maximum displacement.

Abstract: A hydraulic system includes a pilot controlled, pressure operated, spool valve (2) which acts substantially as a by-pass valve when regulating supply of fluid to an actuator (8), and as an in-line valve when regulating the return flow of fluid from the actuator (8) to tank. Both these regulating functions are provided by means of a single main valve spool (31). A flow sensor (20) provides negative feedback to the pilot valve in both by-pass and in-line modes of operation of the main valve, which makes the operation of the system substantially independent of load, temperature, and pump flow. If it is essential that the actuator (8), once it has reached a desired level, remains at that level, the system may additionally incorporate a releasable non-return valve (7) in the service line (71) from the main valve (2) to the actuator (8).

Abstract: A method of making a rotor of a fluid energy translating device wherein the rotor has an annular passage entirely within the rotor, a plurality of radially extending vane slots intersecting the passage and axial openings intersecting the annular passage. The method comprises forming an annular groove in the periphery of a solid body, closing the open side of the groove to provide the annular passage, forming radial vane slots in the body intersecting the annular passage, and forming axial openings in the body intersecting the annular passage.

Abstract: A power servo system which includes an actuator coupled to a load and receives an input command signal indicative of desired motion at the load. A sampled-data control system receives and samples input signals indicative of desired and actual motion at the hydraulic actuator and load, and provides control signals to the actuator necessary to obtain desired motion. The sampled-data control system includes digital processing circuitry with series and feedback compensation, coordinated with the hydraulic system transfer function, to form a complete closed-loop control system operating in the sampled-data or Z-transform domain. Different equation constants in the series and feedback compensation circuitry are recalculated periodically. In one embodiment of the invention, such constants are recalculated as a function of system behavior, so that system control automatically varies with operating conditions.

Abstract: An electrohydraulic servo control system which includes a position feedback loop responsive to actual position at the hydraulic actuator and load, and a position command reference generator responsive to an operator joystick input command and to an operator mode select switch for generating a position command reference signal to the position loop as differing functions of the joystick input in each of the switch-selectable modes. The selectable modes of operation include an absolute position control mode wherein the joystick input is treated as indicating absolute desired position at the actuator and load, an incremental position control mode wherein the joystick input is treated as indicating desired change in position with reference to a base position, and a velocity control mode wherein the joystick input is treated as indicating velocity at the actuator and load desired by the operator.

Abstract: In a hydraulic valve with flow feedback there is provided a position sensor (13) to sense the position of the flow-controlling valve member and provide a position feedback signal. The flow and position feedback signals are compared and a switching circuit (143) selects whichever of the signals indicates the larger flow.

Abstract: A system and method for pulse-width modulation of multiple solenoid-operated valves in an electrohydraulic servo system employing a microprocessor-based digital controller. Solenoid-energization pulse widths are identified by comparison of operator command input signals to feedback signals responsive to actual motion at the actuators and loads. During each modulation period, all solenoids are initially selectively simultaneously energized as a function of binary information stored in an energization control register, and the shortest energization pulse duration is identified. After a delay corresponding to such shortest duration, during which the microprocessor may perform other control functions, the solenoids associated with such shortest duration are selectively de-energized as a function of binary information stored in a de-energization control register.

Abstract: A pilot operated relief valve has a main relief valve (10) and a pilot relief valve (31) connected between a control chamber (23) and drain. A restriction (16) connects the control chamber (23) to the inlet chamber (22) which is separated from the control chamber by a piston (24) integral with the main relief valve closure member (12). Thus opening of the pilot relief valve against the adjustable force of a spring (14) determines the maximum pressure in the inlet chamber (22). The control chamber (23) can also be connected to drain (70) by a pilot valve (19) which is operated by a force motor (52) against pressure in a feedback chamber (56) connected to the inlet passage (22). The energization of the force motor (52) can be adjusted to adjust the relief pressure to a value below that at which the pilot relief valve (31) opens. Alternatively the pressure in the feedback chamber (56) can depend on the pressure at at least one side of a load fed via a directional valve from the inlet passage (22).

Abstract: A fail-safe solenoid operated two-stage hydraulic spool valve has a pilot spool with four raised lands and is constructed in two parts (12, 13) urged away from each other by a spring (14). The pressure ports (16, 17) lie outside the pilot service ports (4, 5), and the tank gallery (15) is located between them. In normal operation, the solenoids (20, 21) hold the two spool portions (12, 13) together against the force of the spring (14). Should the electric supply to the solenoids fail, the spool portions (12, 13) are separated by the spring (14) thereby venting the service ports (4, 5) to tank, and thereby allowing the centring springs (31, 32) of the main stage to return the main spool (25) to its central position in which the load is hydraulically locked against movement.