Abstract: A fluid control valve system for controlling the flow of hydraulic fluid supplied to and discharged out of an actuator having first and second actuator ports, comprising: a valve housing having a pressure sensing chamber for sensing the pressure of the hydraulic fluid introduced therein and a pressure port for introducing a hydraulic fluid; a valve spool axially movably received in the valve housing; valve spool operating means having the valve spool axially moved and including a force motor, a piston rod having the valve spool slidably received thereon and driven by the force motor, and a fixed piston firmly connected with the piston rod; and resiliently urging means for resiliently urging the valve spool along the center axis of the valve housing, the valve spool being urged by the hydraulic pressure of the hydraulic fluid in the pressure sensing chamber and the resiliently urging means to assume operation positions consisting of normal operation positions where the hydraulic pressure of the hydraulic fluid

Abstract: The invention relates to a method for supplying a device or system with a pulsating or cyclic flow of power or energy that alternates in the manner of a noise, with the noise having a spectral amplitude or intensity distribution that is essentially the inverse of the amplitude frequency pattern of a noise parameter of the device or system so that low-noise transmission of power or energy is made possible.

Abstract: A controlled float circuit is provided for controlling a load free of requiring flow from the source of pressurized fluid even when the float mode is activated with the load above the ground. The subject invention includes having a load lowering check valve arrangement disposed adjacent an actuator having first and second inlet ports with a pilot operated check valve disposed between the second inlet port and a location downstream of the load lowering valve. A first normally open electrically controlled valve is disposed in the pilot conduit leading to one end of a directional control valve and a second normally closed electrically controlled valve disposed between a source of pressurized pilot fluid and the pilot stage of the pilot operated check valve. Engagement of the float mode of operation blocks pilot flow to one end of the directional valve and opens the pilot operated check valve.

Abstract: A hydraulic pressure-control valve for controlling a pressure to be supplied to a frictional engaging element such as a start clutch in an automatic vehicle transmission, including a first pressure-regulating valve connected to a hydraulic pressure source and connected to the frictional engaging element through a second passage, and a solenoid for displacing the first-pressure-regulating valve.

Abstract: An apparatus for the damped positioning of a piston running in a cylinder at one fixed abutment at least and more particularly for setting in a terminal position. The apparatus includes sensor means connected with an electronic regulating means for detecting the piston position as an actual value signal. A valve means adapted to be regulated by the regulating means serves for regulated braking of the piston prior to reaching the respective desired position by influencing opposing pressure in the cylinder outlet side. For forming the setting quantity for the proportional valve a position regulating means is provided which is modified by a value dependent on the respective speed and/or acceleration of the piston. This apparatus ensures an extremely accurate regulation of position simply by detecting of the position of the piston as an actual value signal. It is more particularly possible to brake the piston in the terminal positions with a damping action that an additional damping system is no longer necessary.

Abstract: The proposal is for a control for the scoop flap (1) of a construction machine, especially an excavator, with at least one distributing regulator (9) acting with at least one hydraulic cylinder (4) to which hydraulic control pressure can be applied via at least one electrically actuated valve of at least one control device. When an actuating component (17) is triggered, the control device acting electrically therewith, the valve (10, 11) and via it the distributing regulator (9) and the hydraulic cylinder (4) are actuated according to a predeterminably timed current ramp (22).

Abstract: The present invention relates generally to agricultural machinery and, more particularly, to a device for controlling a double-acting steering cylinder of a steering system, having two working connections of the steering cylinder, wherein the working connections are each connected by means of an input pipe or an output pipe to a valve unit, which comprises two switching valves that can be moved alternately into a first switching position and into a second switching position and the steering cylinder in the first switching position of the first switching valve admits a fluid at the first working connection and the steering cylinder in the second switching position of the second switching valve admits the fluid at the second working connection.

Abstract: An electro-pneumatic control system pneumatically connected to a pressure source and electrically connected to an electrical signal source includes a selector switch having an electrical input connected to the electrical signal source, and having a first electrical output and a second electrical output. The system further includes a body having a movable member positioned therein, wherein the body has a first port and a second port; a first regulator valve having a bidirectional port connected to the first port of the body, having an input port connected to the pressure source, having an exhaust port, and having an electrical actuator connected to the first electrical output of the selector switch; and a second regulator valve having a bidirectional port connected to the second port of the body, having an input port connected to the pressure source, having an exhaust port, and having an electrical actuator connected to the second electrical output of the selector switch.

Abstract: A fail-safe second stage valve for controlling actuator movement upon power loss in a multiplexed fluid power control system. The second stage valve is interposed between a corresponding actuator and a fluid multiplexer to operate generally as integrating or amplifying device which regulates flow to the actuator. The second stage valve is provided with a dampening mechanism in the form of a bleed port to reduce fluid flow to the actuator. The bleed port bleeds off accumulated fluid received by the second stage valve over a predetermined range of valve positions. This changes the position of the valve and thereby reduces flow rate to the actuator. The multiplexed fluid power control system using the fail-safe second stage valve controls the flow to the corresponding actuator upon electrical power loss. The actuator may be used to open and close variable stator vanes in an aircraft gas turbine engine.

Abstract: A system and method for controlling an independent metering valve operating in a hydraulic circuit determines a displacement command for one or more metering valves to provide desired flows through the metering valves and desired pressure drops across the metering valves. The system determines the displacement command based on a mode of operation of the hydraulic circuit and a velocity for a hydraulic device controlled by the hydraulic circuit. The system determines the displacement command further based on an amount of flow available to the hydraulic circuit. The system allows the hydraulic circuit to be electronically controlled thereby providing flexibility not found in conventional hydraulic control systems.

Abstract: A system and method for controlling an independent metering valve operating in a hydraulic circuit determines a displacement command for one or more metering valves to provide desired flows through the metering valves and desired pressure drops across the metering valves. The system determines the displacement command based on a mode of operation of the hydraulic circuit and a velocity for a hydraulic device controlled by the hydraulic circuit. The system determines the displacement command further based on an amount of flow available to the hydraulic circuit. The system allows the hydraulic circuit to be electronically controlled thereby providing flexibility not found in conventional hydraulic control systems.

Abstract: A butterfly water valve for a heater core has a vacuum motor attached to the water valve body with the vacuum motor connected to the butterfly valve crank. The vacuum motor housing has a well formed therein and a solenoid operated valve is quick connected in the well and is ported directly to the vacuum motor pressure chamber. The solenoid valve well communicates with a vacuum connector formed integrally with the vacuum motor housing. The vacuum motor housing is preferably formed of two shells welded together and sealing about the rim of a pressure responsive diaphragm.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal. Boom and bucket angle sensors sense the position of the work implement and responsively produces an boom angle signal and a bucket angle signal respectively. A microprocessor based controller receives the boom angle, bucket angle, and operator command signals, modifies the operator command signal, and produces an electrical valve signal in response to the modified operator command signal. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical valve signal.

Abstract: An electrohydraulic displacement controlled valve module is disposed in a bore of a valve body for controlling fluid flow between first and second ports. A main valve element slideably disposed in the bore is biased to a closed position blocking communications between an annular groove of the valve element and the second port. An actuating chamber defined at one end of the valve element receives pressurized pilot fluid for urging the main valve element toward an open position communicating the first and second ports through the annular groove. A passage communicates the actuating chamber with a control chamber disposed at the other end of the valve element through an orifice. A poppet is disposed within the control chamber and is biased into sealing engagement with an annular valve seat of an outlet port by a feedback spring disposed between the valve element and the poppet.

Abstract: A hydraulic circuit in a monoblock structure for lifting and lowering a load has at least two electromagnetically actuatable proportional distributing valve elements, a check valve, a pressure balance for load-independent lifting of the load as an input element, a housing accommodating at least some of the elements and having at least one pump connection, at least one consumer connection, and at least one return connection, the proportional distributing valve elements being disposed parallel to one another, electromagnetic drives seated side-by-side on a same side and at a same height, the pressure balance having a piston which is disposed coaxially next to a longitudinal slide of a first one of the proportional distributing valve elements in a bore that guides and supports both the valve elements, the longitudinal slide of the first proportional distributing valve elements being spring-loaded, and at least one component for adjusting a prestressing and bracing of a spring on the housing of a control penetrat

Abstract: A positioning system uses a position feedback signal to position and damp a platform. The position feedback signal is input to an electronic controller that provides a plurality of control signal that are used to position the platform and dampen the platform motion.

Abstract: A valve assembly senses the cumulative volume of hydraulic fluid that has passed to an actuator and senses and subtracts from that cumulative volume the volume of return fluid that has passed from the actuator. When the difference between the volumes exceeds a preset value, the system shuts off the flow to the actuator to prevent further loss of fluid from a leak. The assembly may employ separate sensors in separate pressure and return lines or a common line with a common sensor which reverses signal polarity when flow reverses. Target flowmeters with signal adding and subtracting circuits may provide the differential volume information.

Abstract: A pneumatic actuating arrangement with a plurality of consumers (1) having working areas (7,8), a plurality of feed air/signal distributors (13) connected to a common pressure source and a common control unit (19), a plurality of electrically-actuated switching devices respectively arranged directly at the consumers (1) forming separate consumer units (9), and a combination line (12) extending between each consumer unit (9) and a feed air/signal distributor (13), each combination line including a supply pressure line for supplying air to the working areas of a respective consumer and electrical signal lines for connecting the electrically-actuated switching devices of a respective consumer unit to said common control unit.

Abstract: A refrigerant powered actuated ball valve for use in the fluid circuit of a refrigeration or air conditioning system which can be remotely controlled by a low amperage control signal is disclosed. The actuated ball valve harnesses the pressurized refrigerant from the fluid circuit in which it is installed as the primary power medium to actuate the valve. The valve includes actuation means with a manifold having an inlet port which is in constant fluid communication with a high-pressure side of the fluid circuit. Pressurized refrigerant supplied to the manifold is branched to a series of fluid channels running through the manifold. Exhaust port operators are mounted in conjunction with the manifold to connect the actuation means to the low-pressure side of the fluid circuit and to direct the flow of pressurized refrigerant to either an exhaust port or the manifold.

Abstract: The main control servo valve responsive to electrical input signals modulates a power piston to position a throttle valve that varies the flow of fluid during normal operation. A transfer servo valve responsive to the pressure in the servo system moves hard over upon sensing a low pressure signal that is normally lower than the system's pressure to cause the power piston to position the throttle valve closed. In the preferred embodiment the system throttles compressor air of a gas turbine engine to provide an anti-icing function and activates the transfer servo valve upon a hard over malfunction.

Abstract: A control method and a device to control construction equipment attachments include during manual operation, the pilot pressure discharged from a pilot pump is fed from a manual operation valve through an electromagnetic change valve to a main control valve. During automatic operation, the pilot pressure from an automatic-mode selecting valve is fed through an electromagnetic proportional control valve as well as the electromagnetic change valve, all of which are controlled by a controller, to a main control valve. When the operation range is restrictively set during manual operation, the pilot pressure output from the manual operation valve is fed through the electromagnetic proportional control valve as well as the electromagnetic change valve to the main control valve. Both the main control valve and the electromagnetic proportional control valve are controlled by control signals from the controller.

Abstract: The invention is an apparatus for determining a valve transform curve in a fluid system. The fluid system has a valve and a fluid actuator arranged to initiate movement of a load. The invention includes a desired velocity manager, a load responsive device, and a valve transform curve manager. The desired velocity manager determines a desired velocity of the load. The load responsive device determines a characteristic of the load, such as weight or position. The valve transform curve manager receives responsively determine a valve transform curve based on the desired velocity and load characteristic.

Abstract: A control and safety system for coordinating movement of multiple hydraulic cylinders to reciprocally rotate a truck-mounted refuse compacting arm. The system includes a logic board controller in communication with a cam and switch arrangement mechanically linked to the rotating arm. Signals from the switches indicate the position of the arm to the logic board which responds by operating directional control valves to regulate movement of the cylinders. A pressure switch is activated to rotate the arm in the opposite direction if the arm is prevented from reaching a limit switch.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal, which is indicative of a desired velocity. A velocity sensor senses the velocity of the lift cylinder and tilt cylinders and responsively producing respective cylinder velocity signals. A microprocessor receives the cylinder velocity and operator command signals, determines the difference between the actual and desired cylinder velocity, and responsively produces an electrical valve signal in response to the velocity difference. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical value signal.

Abstract: Method for controlling a pressurized fluid-actuated double acting cylinder in an assembly such as a hydraulic tightening spanner (1) with a control unit therefor, wherein a piston (5) may be reciprocated repeatedly, firstly with an active stroke providing a desired maximum force, and then with an opposed passive stroke returning the piston (5) to its starting point to enable repetition, and wherein said method comprises selecting a set fluid pressure corresponding to the desired maximum force (Fr) and measuring the time elapsed (Te) between the beginning and the end of the passive return stroke to determine that the force has been achieved. A device for implementing the force is also disclosed.

Abstract: This invention pertains to a hydrostatic actuation system based on a digitally commutated, piston pump. Typically the pump is a fixed displacement axial piston pump with the hydromechanical commutator (which consists of either check valves or a rotated portplate) replaced by electromagnetically activated switches. The activation of the switches coincides with the extreme position of the pistons. The actual switching events are selected by a digital controller to effect an incremental flow rate to a hydraulic actuator. The flow rate consists of minute volumes of fluid displaced at a frequency and polarity dependent on the magnitude and sign of the rate binary applied to the controller.

Abstract: The actuator for a position-adjusting device, wherein the position-adjusting device has a stationary part, a movable part, and at least one coupling element and wherein the at least one coupling element is hydraulically movable by the actuator for coupling and decoupling the stationary part and the movable part relative to one another, has a housing and at least one valve piston arranged within the housing so as to be movable between two end positions defining an open position and a closed position of the actuator. The housing has a work connector, a pressure-relieved tank connector, and a pressure-loaded tank connector. The pressure-loaded tank connector includes a pressure-limiting valve. The pressure-relieved pressure connector during displacement of the valve piston between the two end positions communicates with the work connector until a respective one of the two end positions is almost reached. In the closed position of the actuator the work connector is connected to the pressure-loaded tank connector.

Abstract: A hydraulic control device for an automatic transmission includes a reverse inhibit valve for inhibiting a reverse gear position to be established when the reverse range is selected by mistake. This reverse inhibit valve is placed in a selected one of a first state in which a first port communicates with a third port, and a second state in which a second port communicates with the third port, depending upon whether a solenoid pressure is applied to one end of a spool of the valve. If the reverse range is selected during forward running of a vehicle, the reverse inhibit valve is placed in the first state in which the first port communicates with the third port, so that an oil pressure of a friction element is drained through the first port.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal. An implement position sensor senses the position of the work implement and responsively produces an implement position signal. A microprocessor based controller receives the implement position and operator command signals, modifies the operator command signal, and produces an electrical valve signal in response to the modified operator command signal. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical valve signal.

Abstract: A control system is typically used for controlling the implements of a machine. The control system includes a lift circuit and a tilt circuit. The control system includes a module which receives a signal from the lift circuit and the tilt circuit and selects a signal for controlling a valve to meter pump-to-cylinder fluid flow.

Abstract: A control system is provided for use in a hydraulic system to provide a simple arrangement with a limited number of elements that bypasses the system flow in the event of an electrical malfunction in the system and further allows other hydraulic circuits to operate even if one or more of the hydraulic circuits have experienced an electrical malfunction. The subject arrangement uses an electro-hydraulic fluid flow control valve mechanism in conjunction with directional valve mechanisms that have at least three functional positions and are controlled by associated electrically controlled displacement control mechanisms in response to receipt of electrical signals from an electrical controller.

Abstract: An apparatus and method for providing a detent function on a hydraulic system. The hydraulic system includes a hydraulic implement movable between first and second implement positions. The apparatus and method receives a control input signal generated by an electronic control handle in response to operator input, monitors the control input signal, and actives a detent function if the control input signal follows a preset pattern. The preset pattern includes moving the handle to a detent area, between first and second positions, and then back to neutral, within a given time period. There is also a force feedback to the handle, opposing operator movement; which is proportional to the distance moved from neutral, and which has different attributes within and outside the detect area.

Abstract: To provide a burglarproof device for a hydraulic machine which has a high degree of security against burglary, ensures high safety, and can be simply installed in a location where the device is hard to find for burglars, a solenoid valve 23 of a burglarproof device 20 is installed in a pilot primary pressure line 3 between a pilot hydraulic pump 1 and a pilot valve device 4. Unless ten numeral keys 21a of a key input device 21 are depressed in the order of the password, an unlocking electronic circuit 22K does not generate an unlock signal and the solenoid valve 23 keeps the pilot primary pressure line 3 cut off. Therefore, a pilot primary pressure from the pilot hydraulic pump 1 is shut off and, even with a manual lever 4c of the pilot valve device 4 operated, no pilot secondary pressure is produced and a main control valve 6 is kept standstill. As a result, a hydraulic cylinder 8 is not operated and the hydraulic machine is unable to move.

Abstract: A control logic for a multiple use hydraulic system includes a selector switch having a first position connecting a battery to a treadle switch operable to energize a solenoid pilot valve for communicating pilot fluid to an end of a first directional control valve. The selector switch has another position connecting the battery to a bi-directional push button switch operable to selectively energize a pair of solenoids of a second pilot valve. Energizing one of the solenoids moves the second pilot valve in one direction to communicate pilot fluid to an end of the first and a second control valve. Energizing the other solenoid moves the second pilot valve in the opposite direction to communicate pilot fluid to the other end of the control valves. The selector switch has a third position connecting the battery to a pair of pressure switches connected to a pair of lines connecting a manually actuated pilot valve to a pair of solenoid blocker valves.

Abstract: A hydraulic control valve formed as a magnet valve with several connections and switching positions, comprises a housing provided with several connections, a valve slider displaceable in the housing, an electromagnet provided with an extensible plunger for controlling the valve slider, a valve seat provided in the housing, a ball movable between a closing position and an opening position with respect to the valve seat, a closing spring which urges the ball to the closing position. The ball is bringable by the valve slider to the opening position under the action of a force of the electromagnet, a valve body is firmly but exchangeably inserted in the valve housing so that the valve slider is guided in the valve body. The valve body accommodates the valve slider, the ball and a closing spring which presses the ball against the valve seat. A plurality of conduits are provided, including a pressure conduit, a control conduit and a consumer conduit.

Abstract: A gas operated release or ejection system which compensates for changes in pressure applied to a load being ejected. The pressure regulator compensates for decreases in pressure through a pressure regulating valve, and compensates for increases in pressure through a pressure relief valve.

Abstract: An hydraulic lift system has an actuator connected to an hydraulic circuit, having a pump, via a supply line. A balanced seated valve is connected between the supply line and a reservoir, the valve being controlled by a solenoid and an electric drive unit. The drive unit supplies a gradually increasing or decreasing voltage to the solenoid to open or close the valve gradually. The valve has a valve member that is displaceable along its length and has a valve head of frusto-conical shape. A passage along the valve member balances fluid pressure across the valve member. The solenoid has an armature with a pole face that can be displaced towards a fixed pole face to unseat the valve member. The pole faces have complementary frusto-conical surfaces and there is a non-magnetic washer between them.

Abstract: A three position four way directional control valve having a single spool is typically used for controlling fluid flow from a pump to a cylinder and from the motor to a tank. The present invention includes a pair of electrohydraulic control valves with one of the control valves controlling pump-to-cylinder communication between a pump and the rod end and head end chambers of a hydraulic cylinder while the other control valve controls cylinder-to-tank communication between the rod end and head end chambers and the tank. Each of the control valves includes a displacement controlled proportional valve for controlling the position of a pilot operated valve member. Actuation of the hydraulic cylinder requires moving the valve member of one control valve to control pump-to-cylinder communication to one of the chambers while simultaneously moving the valve member of the other control valve for establishing cylinder-to-tank communication between the other chamber and the tank.

Abstract: A cold fluid protection circuit is provided for controlling the rate of fluid flow in a hydraulic system in response to the temperature of the oil in a reservoir. The subject invention includes a temperature sensor operative to sense the temperature of the fluid in the reservoir and deliver an electrical signal representative thereof to a controller. The controller processes the sensed temperature with respect to the rate of flow in the hydraulic system that is returning to the reservoir from an actuator through a fluid conditioning mechanism and proportionally reduces the rate of flow therethrough by controllably reducing the displacement of a directional valve mechanism in response to the sensed temperature.

Abstract: An adjusting device has a pneumatically operating piston-cylinder unit pressurizable in an operating function thereof for actuating adjusting elements in a printing press. The piston-cylinder unit includes a cylinder housing formed with a cylinder chamber, a piston displaceable in the cylinder chamber, and an electromagnet for applying an activated holding force to the piston, the piston being subjectible pneumatically to a prepressurizing force in the cylinder chamber opposite to and less than the activated holding force.

Abstract: The present invention relates to a drive of the fluid or electric type having a device for controlling an element for transmitting a driving force to a reciprocating or otherwise moveable or displaceable element and an arrangement for damping the driving force at at least one end of the element's travel. The driving force element is at least single-acting, and the drive may also include mechanical shock absorbers and sensors arranged in the area of the ends of travel. In order to achieve an especially soft striking or contact at the end of travel position of the driving force element, the control device includes a counter-pulse module which, via a pre-positioning sensor associated with at least one movement direction, causes a chronologically settable changeover from a previously flowed-through or activated first switching element associated with a first end of travel position to a previously unactivated second switching element associated with a second end of travel position.

Abstract: A variable assist power steering system for a motor vehicle has an electronically controlled working pressure valve which normally maintains a working pressure at a relief pressure but increases it in response to steering of the vehicle and according to vehicle status, such as vehicle speed. The system also has electronically controlled direction control valves which are actuated to selectively reduce the working pressure to one side or the other of the steering gear piston so as to match a measured handwheel torque with a value which is desired for the vehicle status.

Abstract: A windshield washer control system for a vehicle having an air pressure source includes an electrically actuated control valve for controlling communication between the air pressure source and a bladder pump which squirts windshield washer fluid up to the windshield of the vehicle. A fluid restricting orifice is opened and closed by a solenoid actuator such that the pressure communicated to the bladder pump is limited to be below that of the air pressure reservoir. A second orifice controls communication from the pump to ambient atmosphere.

Abstract: A vehicular brake booster using fluid pressurized by a hydraulic power steering system hydraulic pump. Fluid pressure is controlled by using a pressure regulator in the pump output and by electronically switching fixed orifices in a boost developing valve controlling fluid flow within the power steering system. Additional control is effected by electronically opening and closing apply and relief valves controlling fluid flow respectively to and from a brake power booster for differing periods.

Abstract: A hydraulic cylinder snubbing arrangement includes a pilot operated control valve having a predetermined snubbing position at which flow exhausted from a hydraulic cylinder actuating chamber must pass through a plurality of flow restricting orifices in a valve spool when the hydraulic cylinder is retracted to a predetermined position. The valve spool is shifted to the snubbing position automatically by reducing the fluid pressure in a pilot chamber at the end of the valve spool to a predetermined level so that a snubber spring device resiliently moves the spool from a lower or float position. By forcing the fluid to pass through the restricted flow path created by the orifices, the gravity induced velocity of the hydraulic cylinder is greatly reduced as the hydraulic cylinder approaches its end of stroke position.

Abstract: A double-acting hydraulic cylinder is controlled by a pair of three-way solenoid valves respectively fluid connected to the two ends of the cylinder and energized in parallel with a continuous stream of pulse width modulated (PWM) pulses to create a mean effective fluid pressure balance at the cylinder ends that hold a desired position of a connected load and mean effective fluid pressure imbalances in the cylinder ends that produce variable rate load movement in either of two directions to a desired new position, all determined by the pulse duty cycle.

Abstract: A controller for changing the ratio of a continuously variable hydrostatic transmission, as determined by the angular position of a swashplate, including an actuator having a cylinder slidingly receiving a piston to define a pair of chambers. A pair of solenoid valves, each configured to connect a respective chamber selectively to sump pump pressure or atmospheric pressure, are energized with a stream of pulses to create differential fluid pressures in the chambers, thereby producing movement of the piston; the piston movement being linked to the swashplate to produce a corresponding adjustment of the swashplate angular position. The rate of change of the swashplate angular position is controlled by pulse width modulating the pulse stream.

Abstract: A hydraulic device for operating an actuator in a working machine such as a hydraulic shovel or the like has a solenoid-operated proportional flow regulating valve connected to a pipe between a hydraulic pump and a directional control valve for changing the direction in which the actuator operates, and a discharge pressure control assembly for controlling the discharge pressure from the hydraulic pump to make constant the differential pressure between the inlet and outlet ports of the solenoid-operated proportional flow regulating valve. Flow rate characteristics of oil supplied under pressure to the actuator with respect to the amount of controlling movement of a control lever are established by a flow rate setting unit depending on a load pressure on the actuator and the rotational speed of an engine which operates the hydraulic pump.

Abstract: A method for controllably moving an implement is provided. The implement is connected to a work machine and is movable between first and second implement positions in response to operation of a hydraulic actuator. The method includes a joystick with first and second positions and a neutral position. The joystick is normally biased in a neutral position and is movable between the first and second positions. The method senses the position of the joystick and responsively generates a joystick position signals The joystick maintained at the first and second detent positions in response to manual movement of the joystick to the respective first and second detent positions. The joystick is released from the detent position in response to receiving a release detent signal. The method senses the position of the work implement with respect to the work machine. The method provides hydraulic fluid flow to the hydraulic actuator in response to a magnitude of an electrical valve signal.

Abstract: A fluidic, in particular a hydraulic, servosystem has an input which can be actuated at will and an output which is elastically drivingly connected thereto, with a relative movement made possible by the elastic connection and dependent on the magnitude of the forces or moments transmitted between the input and the output. The relative movement is transmitted, as between the input and the output setting stroke, to a servovalve which can additionally also be controlled externally for controlling a fluidic servomotor which is drivingly coupled to the output.