Abstract: A working machine includes a prime mover, a rotation-speed operation actuator, a rotation detector, a hydraulic pump, a hydraulic unit, an operation valve capable of changing a pilot pressure of a pilot fluid supplied from the hydraulic pump to the hydraulic unit in accordance with an operation of an operation member, an actuation valve operating in accordance with a control signal and capable of changing a primary pressure as the pilot pressure of the pilot fluid supplied from the hydraulic pump to the operation valve, and a controller that outputs the control signal based on a difference between target and actual rotation speeds to the actuation valve to control an opening thereof. The controller has a mode including calculating the control signal based on the difference, correcting the calculated control signal, and increasing or decreasing a target primary pressure value set in accordance with the control signal.

Abstract: A hydraulic arrangement for distributing a fluid in pressure coming from a source among multiple hydraulic units of a work vehicle. At least one of the hydraulic units provides an electronic load sensing signal and of the hydraulic units provides a hydraulic load sensing signal. The hydraulic arrangement includes a priority valve configured to divide the flow of fluid between the hydraulic units. The priority valve and source are hydraulically controlled by a first hydraulic load sensing signal resulting as the greatest of a plurality of hydraulic load pressure signals taken from the hydraulic unit. The hydraulic arrangement also includes a conversion unit configured to transform an electronic load sensing signal of at least one of the hydraulic units in an equivalent hydraulic load sensing signal so as to define the first hydraulic load sensing signal.

Abstract: A mobile hydraulic system includes a hydraulic actuator coupled to a load, and a control unit coupled to the load and/or to the hydraulic actuator. The control unit is adapted to anticipate an over-center transition of the load relative to a gravity vector prior to the over-center transition through the use of sensors configured with accelerometers, gyroscopes and magnetometers. In some examples, the over-center transition is from an overrunning driving of the load to a passive driving of the load. In some examples, the over-center transition is from a passive driving of the load to an overrunning driving of the load. In some examples, the control unit is adapted to control change in a metered flow through one or more ports of the associated actuator to minimize and/or prevent one or more hydraulic effects of the anticipated over-center transition. In some examples, the control unit controls the metered flow by causing one or more actuators (e.g.

Abstract: The press machine includes: a hydraulic cylinder configured to drive a slide; a plurality of hydraulic pumps/motors; a first port of each of which is connected to a first pressurizing chamber of the hydraulic cylinder; a plurality of servomotors axially connected to rotating shafts of the respective hydraulic pumps/motors respectively; a low-pressure accumulator to which second ports of the hydraulic pumps/motors are each connected; a high-pressure accumulator connected to a second pressurizing chamber of the hydraulic cylinder; and a slide position controller configured to control the servomotors so that a position of the slide matches a position corresponding to a slide position command signal based on the slide position command signal from a slide position commander and a slide position signal from a slide position detector.

Abstract: Provided is a wheel loader capable of moving up a lift arm in a short time during excavation work. A wheel loader comprises a controller configured to control maximum traction force of the wheel loader and input torque of a working device hydraulic pump, and include a specific condition determination section configured to determine whether a specific condition for specifying excavation work is satisfied, an elapsed time measurement section configured to measure an elapsed time from start of the excavation work, and an input torque control section configured to limit the input torque to a first input torque value when the specific condition is satisfied and increase the input torque from the first input torque value when a second set time elapses from the elapse of a first set time.

Abstract: A monitoring device for determining a position of a displacement piston (1) guided longitudinally movably in a housing (7) and, in the housing (7) and delimits a fluid chamber (3, 5) with a variable volume and connected via a pressure supply connector (9, 11) to a pressure fluid control device (13). A volumetric flow regulating device (45) and a pressure determining device (47) are connected between the pressure fluid control device (13) and the measuring connector (15, 17) of the fluid chamber (5, 3). The pressure determining device (47) outputs a measuring signal when the displacement piston (1) reaches an end position.

Abstract: A hydraulic linear actuator system known as the “Dynaco Stepper Pump Hydraulics System” is which is an electrically driven hydraulic pump system made of durable materials for use in an electronically controllable hydraulic system comprised of: (a) an electrically driven stepper motor; (b) a hydraulic pump to pressurize a hydraulic fluid; (c) a means to connect the stepper motor to the hydraulic pump; (d) a pressurized reservoir for a quantity of hydraulic fluid; (e) a means to supply pressurized fluid to a hydraulic actuator; (f) the hydraulic actuator with a means to provide linear motion to an object; (g) the means to provide linear motion to an object; (h) a means to return lowered pressurized fluid to the reservoir. An alternative embodiment is further comprised of a controller with a series of feedback signals.

Abstract: A boom driving device comprises a boom control valve causing a boom cylinder to elongate and contract. The boom control valve returns a hydraulic fluid discharged from an working chamber of the boom cylinder to a tank in a boom descending position A part of the discharged hydraulic fluid is branched in the upstream of the boom control valve and is supplied to a generator through a regenerative passage for power generation. The regenerative passage is provided with a regenerative control spool valve. The regenerative control spool valve is opened when a flow cross-sectional area of the hydraulic fluid flowing from the working chamber to the tank reaches a predetermined area while the boom control valve is in the descending position. According to this construction, it is possible to alleviate a shock that may be generated at the start of power generation by the generator.

Abstract: A hydrostatic variable displacement pump (2) has a displacement volume set by an electro-hydraulic control device (10) provided with a safety function. In a fault scenario, the variable displacement pump (2) is set to a neutral position. The electro-hydraulic control device (10) has a single electro-hydraulic setpoint encoder (30) to specify the setpoint of the displacement volume of the variable displacement pump (2) and an electrically actuatable valve device (35) connected in series downstream of the setpoint encoder (30), by which the direction of displacement of the variable displacement pump (2) is controlled and which is provided with the safety function.

Abstract: First and second mechanical hydraulic valves are disposed between a pump and the cap side chamber of an actuator and the pump and the rod chamber of the pump. The first and second valves are actuated as a result of respective pressure differentials applied across the valves. A controller controls flow from a pump in response to a commanded motion to control movement of the actuator, and cause the valves to open. The valves are disposed in their no-flow positions when the pump is not operative, and when the hydraulic system of off or locked out to hold a load.

Abstract: The invention provides a rotation control device capable of reducing a loss of a power of a hydraulic pump in a backward direction operation and also provides a construction machine including the same. The controller controls a capacity of the hydraulic pump such that, in a forward direction operation in which an operating direction detected by the operation sensor and a rotating direction detected by a rotation sensor coincide with each other, the capacity of the hydraulic pump is increased in accordance with an increase in the operation amount detected by an operation sensor, on the other hand, restricts the capacity of the hydraulic pump more in a backward direction operation, in which the operating direction detected by the operation sensor and the rotating direction detected by the rotation sensor are reverse to each other, than in the forward direction operation.

Abstract: A system and method for controlling the movement of an implement of an earthmoving machine. The system includes a hydraulic actuator adapted to move the implement. A variable displacement pump is coupled to the actuator for delivering a pressurized fluid to and receiving pressurized fluid from chambers within the actuator. A sensor generates an output based on the position of the actuator's piston or piston rod, and a controller controls the displacement of the variable displacement pump in response to the output of the sensor by executing an algorithm to reduce the flow rate of the fluid to and from the actuator's chambers and thereby reduce the velocity of the piston as it approaches an end of a piston stroke thereof and prevent the piston from impacting the actuator at the end of the piston stroke.

Abstract: A power generating apparatus includes a rotating shaft, a hydraulic pump driven by the rotating shaft, a hydraulic motor driven by pressurized oil supplied from the hydraulic pump, and a generator coupled to the hydraulic motor. Each of the hydraulic pump and motor includes working chambers each defined by a cylinder and a piston, a high pressure manifold and a low pressure manifold. Each of the high and low pressure manifolds includes branch channels connected to the working chambers and a merging channel connected to a high or low pressure oil line. The branch channels are equipped with high or low pressures valves, joined together and merged into the merging channel.

Abstract: A pressure control valve for controlling a travel primary side pressure that is a pressure of a primary side of a travel operation device is controlled by a control unit, thus the travel primary side pressure is controlled, and thereby a traveling speed is intended to be increased, preventing an engine stall.

Abstract: The present invention relates to a device for controlling a hydraulic pump of construction machinery.

Abstract: To perform updating of maximum values and minimum values of measurement data with a simple procedure without incurring an increase in the computational load of an arithmetic processing element such as a microcomputer. When processing is started, a most recent maximum value stored in a nonvolatile storage element is written to a maximum value-use variable Xmax and a positive maximum value is written to a minimum value-use variable Xmin. Each time temperature data is acquired, a value of acquired data Xk and a most recent minimum value Xmin are compared and the smaller value is set as a new minimum value Xmin. Each time updating of this minimum value is repeated a predetermined number of times of processing Ns, the minimum value Xmin at that point in time and the maximum value Xmax are compared and the larger value is set as a new maximum value Xmax.

Abstract: A shock absorption device and a control method thereof for a small swing radius (SSR) excavator are provided, which can relieve shock generated on a boom cylinder by controlling only the discharge flow rate of hydraulic pumps, being supplied to the boom cylinder, even without controlling a main control valve when a boom of the excavator ascends at its maximum height through manipulation of a control level.

Abstract: Actuator piston (100) formed by an injection-molded piece (120) consisting of a cylindrical body (121) and a collar (122) to receive the hydraulic actuator (110) and the travel detector (160). The piece (120) comprises a shell (150) covering its front face and receiving the return spring (250) and the thrust rod (130). The actuator piston (110) includes lugs (115) engaged behind the lugs (125) of the body (121), by a pivoting movement about the axis. The rotational position is blocked by a locking and guiding sleeve (180).

Abstract: An electro-hydraulic actuation system (901) includes an unbalanced hydraulic actuator (902) capable of motion in retraction and extension directions during movement of a load (904). A pump (204) provides a flow of fluid to the actuator. A displacement of the pump controls a velocity of the actuator during motion in the retraction and extension directions. An electric motor (202) drives the pump. Speed and direction of the electric motor affects the displacement of the pump. A controller (802) controls the speed and direction of the electric motor. A feedback device (228,248) is operable for sensing a system condition and for providing a feedback signal indicative of the sensed system condition to the controller. The controller is responsive to the feedback signal for determining an occurrence of an over-center load condition and for modifying the speed of the electric motor in response to the occurrence in an attempt to maintain the velocity of the actuator.

Abstract: A by-pass control system for a meat injection system has a variable speed pump that transports fluid to a meat injection machine. Excess fluid is transported to a by-pass control valve. The valve has a moveable piston disposed therein that separates the valve into a fluid chamber and an air chamber. The piston moves back and forth based on the relationship between fluid pressure and air pressure. Sensors are disposed within or through the lid or the valve to sense the position of the piston. A controller is connected to the sensors and the variable speed pump and adjusts the speed of the pump based on the position of the piston.

Abstract: A hydraulic motor unit according to the present invention includes an electric motor having an electric motor main body that is electrically controlled, an electric motor case that accommodates the electric motor main body and an electric motor main body output shaft that is rotated around an axis line thereof by the electric motor main body, the electric motor case being detachably mounted to the motor housing, wherein mounting of the electric motor to the motor housing causes the electric motor main body output shaft to be operatively connected to the first end of the control shaft so that the control shaft is rotated around the axis line in accordance with rotation of the electric motor main body output shaft.

Abstract: A method of controlling a machine having a hydraulically actuated linkage includes lowering a load suspended by the leakage at least in part by leaking hydraulic fluid from a portion of a hydraulic actuation system, and generating a drift compensation control signal responsive to leaking hydraulic fluid. A machine includes an electronic controller in control communication with a valve, the electronic controller being configured to compensate for leakage induced drift of at least one hydraulic actuator of a machine hydraulic system by selectively commanding adjusting of the valve if drift criteria for the hydraulic system are satisfied.

Abstract: A hydraulic excavator includes: an oil-pressure cut valve for suspending pressure oil supply to a PPC valve; a lock switch for operating the oil-pressure cut valve; and a control device for controlling a switching of the oil-pressure cut valve. The control device includes: a lock-state determining unit that determines a lock state of working equipment by considering the status of the lock switch; a traveling-state determining unit that determines a traveling state of the hydraulic excavator; an alert-issuing controlling unit that issues an alert urging locking of the working equipment; and a relay control unit that actuates the oil-pressure cut valve to suspend the flow of pressure oil. The alert-issuing controlling unit issues the alert and the relay control unit actuates the oil pressure cut valve when the hydraulic excavator is determined to be traveling and the working equipment is determined not to be in the lock state.

Abstract: A system and method for controlling the movement of an implement of an earthmoving machine. The system includes a hydraulic actuator adapted to move the implement. A variable displacement pump is coupled to the actuator for delivering a pressurized fluid to and receiving pressurized fluid from chambers within the actuator. A sensor generates an output based on the position of the actuator's piston or piston rod, and a controller controls the displacement of the variable displacement pump in response to the output of the sensor by executing an algorithm to reduce the flow rate of the fluid to and from the actuator's chambers and thereby reduce the velocity of the piston as it approaches an end of a piston stroke thereof and prevent the piston from impacting the actuator at the end of the piston stroke.

Abstract: A hydraulic pump displacement control apparatus for a working vehicle capable of reliably detecting the working vehicle under excavating operation and reducing loss in power is provided. For this purpose, the control apparatus includes a bottom pressure detector (45) for detecting a hydraulic pressure in a bottom side (13A) of a cylinder (60) for operating a working machine (10), a displacement control device (41) for controlling a displacement of a variable displacement hydraulic pump (26), and a controller (50) which determines that an excavating operation starts when a predetermined time elapses with a detection value from the bottom pressure detector at a predetermined value or less and thereafter, the detection value exceeds the predetermined value, and outputs a displacement control signal to reduce the displacement of the hydraulic pump to a predetermined displacement that is smaller than the maximum displacement to the displacement control device.

Abstract: A method for reducing a torque load associated with an implement includes determining a speed associated with a power source, wherein the power source is configured to provide power to a hydraulic pump, determining a position associated with an implement system, and limiting a flow associated with the hydraulic pump based on the speed associated with the power source and the position associated with the implement system.

Abstract: A drive system of a working vehicle including a main engine drivingly connected to a hydraulic pump. The hydraulic pump is connected to first and second hydraulic motors. When an undesirable operating condition is detected, a control device shifts an actuator associated with at least one of the wheels, to reduce the displacement volume of the hydraulic motors driving that wheel. In addition, shifts are made in the actuator of the respective other hydraulic motor and/or in the actuator of the hydraulic pump, in order to maintain a constant speed of travel. The control device shifts the actuator of the hydraulic motor of the other wheel toward greater displacement, and if that shift is insufficient to compensate for the undesirable operating condition, the control device will shift the actuator of the hydraulic pump in the direction of reduced displacement volume.

Abstract: The present disclosure is directed to a control system for a power machine that provides selected resolution of the adjusted speed control and other controls, such as attachment controls, to provide more options to the operator for fine positioning. The present disclosure includes a control system for a power machine. The power machine has a full speed. The control system has an adjustable propulsion controller that an operator can position along a range of movement. Examples of the adjustable propulsion controller include a joystick or an accelerator. The position of the propulsion controller along the range of movement selects the speed of the power machine between a first speed and a second speed, where the first speed is greater than the second speed. The first speed is selectable from a plurality of percentages of the full speed.

Abstract: The invention relates to a hydraulic drive system used for the covers of vehicle openings, in particular for vehicle roofs with a construction that can be opened. In said system, the actuator that is designed to displace the cover is supplied with a bulk current, whose target value is determined in accordance with the control path of the actuator, which is in correlation with the controlled displacement of the cover and whose actual value is detected when supplied to the actuator by means of a bulk current sensor. The bulk current is adjusted to compensate for differences between the actual and target values.

Abstract: The apparatus is an automatic velocity control system for an agricultural machine. Three feedback circuits are used to increase reliability and repeatability of the apparatus despite variations in load and ground conditions and non-linear responses of control components. A solenoid current sensor supplies a feedback signal to control a current controller for solenoids controlling a hydraulic valve, a hydraulic cylinder position sensor provides a feedback signal to counteract the non-linearity of the hydraulic valve controlling the hydraulic cylinder, and wheel speed sensors supply vehicle speed signals to be compared to the signal from the operator's speed control. A microprocessor processes the sensor signals to maintain the desired velocity.

Abstract: A method and an apparatus for monitoring the operation of a percussion device, which percussion device comprises a percussion piston and a pressure channel for supplying pressure medium to the percussion device for moving the percussion piston. The method and the apparatus measure pressure pulsation of the pressure medium acting in the pressure channel, which pressure pulsation is depicted as a pressure curve. From pressure pulsation are determined parameters depicting the operating state of the percussion device and the operating state of the percussion device is determined on the basis of the parameters. In addition, an arrangement for controlling the operation of the percussion device on the basis of the operating state of the percussion device.

Abstract: If an instruction to move a ram (5U) is issued, a ram instructed speed is instructed to be suppressed to a certain warming-up speed not higher than a target speed until a release speed determination section (75) determines that a moving speed of the ram (5U) calculated by a ram moving speed calculation section (51) reaches a predetermined warming-up release speed; if the release speed determination section determines that the moving speed of the ram (5U) reaches the predetermined warming-up release speed, the warming-up speed is released to accelerate the ram (5U) to the target speed.

Abstract: An electronic transmission control system that can achieve a transmission ratio based on the operator inputs and the current vehicle operating conditions. The transmission constantly connects the engine to the load, and the transmission ratio is only varied by a change in command from the present invention. The transmission's mechanical function is solely to vary the ratio between its input and output. In using the present invention, an operator must select an operating mode, either automatic or manual, using a two-position switch. While in the automatic mode, the present invention determines the vehicle speed by considering the position of the throttle and the operator's use of brakes. In the manual mode, the present invention further considers the operator's selection of a gear condition.

Abstract: A pump displacement control arrangement uses the inherent swivel torques of a fluid translating device in cooperation with a proportional force feedback to more consistently and precisely control the displacement of the fluid translating device. The subject invention uses a variable displacement control arrangement having an actuator mechanism coupled to a swash plate of the fluid translating device and controlled by a proportional valve arrangement to control the displacement of the fluid translating device. A force feedback mechanism is disposed between the actuator mechanism and the proportional valve arrangement and provides a more precise and repeatable displacement control.

Abstract: An electronic transmission control system that can achieve a transmission ratio based on the operator inputs and the current vehicle operating conditions. The transmission constantly connects the engine to the load, and the transmission ratio is only varied by a change in command from the present invention. The transmission's mechanical function is solely to vary the ratio between its input and output. In using the present invention, an operator must select an operating mode, either automatic or manual, using a two-position switch. While in the automatic mode, the present invention determines the vehicle speed by considering the position of the throttle and the operator's use of brakes. In the manual mode, the present invention further considers the operator's selection of a gear condition.

Abstract: A control arrangement to supply-pressure medium to at least two hydraulic consumers having a variable-displacement pump controlled according to required flow and the setting of which can be changed by a, pump controller as a function of highest load pressure of the actuated hydraulic consumers; two adjustable meter-in variable restrictors, a first of which is arranged between a feed line, which leads from the variable-displacement pump, and a first hydraulic consumer, and the second of which is arranged between the feed line and a second hydraulic consumer; and two pressure compensators, a first of which is connected downstream of the first meter-in variable restrictor and the second of which is connected downstream of the second meter-in variable restrictor, and the control piston of which can be acted on in opening direction by the pressure downstream of the associated meter-in variable restrictor.

Abstract: A slide driving device employs a variable-displacement pump/motor for driving a rotating element of the slide driving device. The displacement volume of the variable-displacement pump/motor, whose output drives the slide, is varied in response to deviation of measured driver parameters from commanded driver parameters. An energy storage device temporarily absorbs excess energy during a portion of a molding cycle, and returns the energy to the system for re-use. In one embodiment, the energy storage device is an accumulator. In a second embodiment, the energy storage device is a flywheel. The combination of variable displacement volume and energy storage maintains the fluid pressure substantially constant during a cycle of the slide driving device.

Abstract: A method for controlling the displacement of a variable displacement hydraulic pump to produce a desired flow of fluid is disclosed. The method includes the steps of: determining that the machine is being operated in a digging cycle; determining a desired displacement of the pump, the desired pump displacement being less than the maximum pump displacement; and controlling the pump displacement to the desired pump displacement to produce a desired flow of fluid.

Abstract: Pressure sensors sense a pilot pressure Pa corresponding to the amount of boom raising operation of a boom operation lever and a pilot pressure Pb corresponding to the amount of arm pulling operation of an arm operation lever. When the condition of Pa>Pb is met during the horizontal pulling operation, the rate of supply of the working fluid to an arm actuating cylinder is reduced to a rate corresponding to the amount of operation of the operation lever. Conversely, when the condition Pa<Pb is met, the rate of supply of the working fluid to the boom actuating cylinder 5 is reduced to a rate corresponding to the amount of operation of the operating lever. Horizontal pulling operation for levelling the ground can be conducted without requiring high level of skill. The horizontal pulling work can be done easily and smoothly, while preventing the bucket from cutting into the ground and from floating above the ground.

Abstract: A Hydraulic Pumping Unit equipped with a flywheel, a high-slip electric motor and a reversible hydraulic pump such that during the downstroke of the Unit, the hydraulic pump operates as a hydraulic motor, accelerating the flywheel and accumulating in this way the energy of the downgoing rodstring in the form of kinetic energy.The interaction between the flywheel, electric motor and weight of the rodstring adjusts automatically the range of speed variation.The upward and downward speeds of the Hydraulic Pumping Unit can be adjusted by hand or automatically by electronically commanded step motors, in such a way that the Hydraulic Pumping Units adjusts itself to the varying conditions of the oilwell.

Abstract: A control and regulation device for a vehicle travel drive, which comprises two hydrostatic transmissions (3, 4) of adjustable transmission ratios, each comprising a hydraulic pump (12, 13) and a hydraulic motor (14, 15), which are in driving connection with two vehicle track arrangements (18, 19) and have each an adjustment device (30, 24; 31, 25) controllable with control signals (v.sub.l, v.sub.r) for adjusting the transmission ratio, with a control section comprising a desired-value setting apparatus (5) and a signal processing means (42, 43), whereby the desired-value setting means sets transmission ratio desired-values of each hydrostatic transmission, employing respective adjustable control levers (36, 37), and outputs desired-value signals (s.sub.l, s.sub.r), and the signal processing apparatus processes desired-value signals to control signals (s.sub.l, s.sub.r) and outputs the latter.

Abstract: Neutralizer valves are useful in hydraulic steering systems to hydraulically stop the steering motion. However the known neutralizer valve arrangements will not work in load sensing hydrostatic steering systems. The subject load sensing hydrostatic steering system has a limit valve disposed in a load pressure signal signal line to normally communicate a load pressure siganl from a steering valve to a displacement controller of a load sensing variable displacement pump so that the displacement of the pump is regulated to meet the demand for pressurized fluid by the steering valve. When a pair of vehicle members reach a preselected position during a steering maneuver, the limit valve is moved to a position interrupting communication of the load pressure signal to the displacement controller causing the pump to destroke to its minimum output thereby stopping the flow of pressurized fluid to the steering valve and to a pair of steering cylinders.

Abstract: Disclosed is a preferably electrohydraulic control for a load-dependently operating variable displacement pump, which is equipped with a differential pressure control device for ensuring a predetermined pressure drop at the control edge of a directional valve integrated into the consumer supply line. The differential pressure control device has a servo valve, the valve spool of which can be brought out of a first position, increasing the output volume of the variable displacement pump, against the compressive force of a spring and of a control pressure led off from the supply pressure upstream of the directional valve, by the pump pressure into a second position, reducing the output volume.

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 secondarily controlled hydrostatic machine with variable volume is connected to a line with impressed system pressure which is fed by a primary unit. By switching over the primary unit the secondary unit is subjected to a displacement amount which results in as large as possible a pivot angle of the secondary unit to obtain the highest possible efficiency. The switching over takes place in dependence upon an upper and lower switching point corresponding to the desired pivot angle range of the secondary unit.

Abstract: An electrohydraulic control system which includes first and second electrically controlled fully variable hydraulic pumps adapted to be driven by the vehicle engine. In the specific embodiment of the invention herein disclosed, the first pump is coupled to the steering and braking control valves, and the second pump is coupled to the bucket and hoist control valves. An electrically controlled poppet valve selectively interconnects the respective pump outputs. Operator-responsive controllers, namely a bucket/hoist joy-stick controller, a vehicle propulsion controller and a steering controller, provide associated electrical signals as respective functions of operator demand. Electrically operated valves control application of hydraulic fluid to the bucket and hoist drive mechanisms, and pressure and position sensors are connected to such valves and actuating mechanisms.

Abstract: A hydrostatic drive in which the ratio of pressure to force is constant is provided having a consumer of hydraulic energy connected to a high pressure system line, a first displacement means interposed between the consumer and the pressure system line, speed regulating means acting on the first displacement means to regulate the speed thereof, a second displacement means connected to the first displacement means by a drive shaft and receiving fluid from the pressure system line, volume output adjusting means acting on one of said first and second displacement means to adjust the volume output per revolution and coupling means connecting the adjustable displacement means with the consumer of hydraulic energy.

Abstract: An improved power steering apparatus includes a variable displacement pump. During a steering operation, a flow control valve effects operation of a motor assembly to vary the displacement of the pump as a function of variations in the demand for power steering fluid. Upon initiation of a steering operation, the displacement of the pump must be quickly increased to enable it to satisfy the impending demand for power steering fluid. Therefore upon initial rotation of a steering wheel, a steering controller restricts a flow of fluid to operate the motor assembly independently of the flow control valve. The displacement of the pump can thus increase before the flow control valve can be actuated during an initial portion of a steering operation.

Abstract: A hydrostatic drive with an automatic adjusting deceleration control device and method for accomplishing the same. The drive includes a prime mover, a variable displacement hydraulic pump, a hydraulic actuator for driving a load through an operating cycle of acceleration, travel, deceleration, and travel, and a control system for regulating drive operation. Sensing devices are used to sense absolute load position at the point the pump reaches minimum displacement following deceleration. This sensed value is then compared by the control system with the theoretical load position within the operating cycle at the point deceleration should be complete, and corrections are made for variations therefrom by advancing or retarding the point at which deceleration is initiated in the operating cycle.

Abstract: A method and apparatus for linear and nonlinear control of a hydraulic press is provided with a feedback loop allowing the operation of a variable displacement pump to be selectively controlled with respect to either hydraulic pressure moving a piston in a cylinder, or the velocity of the piston. During controlled movement of the piston, a directional valve blocks a pump compensator so that the pump operates as a fixed displacement pump to provide fast response to feedback signals. Simultaneously, the directional valve connects a proportional pressure controller to a relief valve. During a period when the piston is maintained in fixed position, the directional valve is switched so that the proportional pressure controller now controls the pump compensator and the relief valve is blocked, so that energy consumption is substantially reduced.