Abstract: A monitoring device including a microcomputer of a detector that calculates a first time derivative value by differentiating a first pressure value with respect to time, and/or calculates a second time derivative value by differentiating a second pressure value with respect to time. In addition, based on at least one from among the first time derivative value and the second time derivative value, the microcomputer determines whether or not the piston has arrived at one end or another end inside the cylinder main body.

Abstract: Systems and methods for controlling valve assemblies associated with an actuator in an electro-hydraulic system are disclosed. In one method, a controller monitors hydraulic fluid flow for an actuator to identify one valve assembly connected to the actuator as a meter-in valve and another valve assembly connected to the actuator as a meter-out valve. In one aspect, the valve assembly most recently identified as the meter-in valve is controlled to maintain a pressure setpoint and the valve assembly most recently identified as the meter-out valve is controlled to maintain a hydraulic fluid flow rate. The method can also include determining whether the actuator is in a passive state or an overrunning state and controlling the valve most recently identified as the meter-in valve to maintain a first pressure setpoint when the actuator is in a passive state and to maintain a second pressure setpoint when the actuator is in an overrunning state.

Abstract: A relief pressure control system is provided with a controller for outputting, responsive to an adjustment signal output from a dial switch, a control signal to control a relief pressure of a variable solenoid relief valve, a display unit for displaying, responsive to display signals outputted from the controller, a relationship between a circuit pressure output from a pressure sensor and a pressure required by a hydraulic cylinder, and a control device constituting a start instruction unit for instructing a start of control of the variable solenoid relief valve. Stop valves are arranged in sections of main lines, which communicate a directional control valve and the hydraulic cylinder with each other, to open or close the section. The sections are located between positions on the main lines, where the variable solenoid relief valves are connected to the main lines, respectively, and the hydraulic cylinder.

Abstract: A hydraulic control, for example of a hydraulically operable working tool, includes a hydroconsumer that can be acted upon against a permanent force via a pressure source, and a switching valve with working power/pressure control function reacting against a spring force depending on a pressure and/or through flow volume. The switching valve connects the hydroconsumer with a tank for a return stroke of the hydroconsumer when the pressure source is switched off. The hydroconsumer can be hydraulically stopped with the return stroke via the pressure source by a pressure pulse and/or through flow volume pulse. In a hydraulically operable working tool, the hydroconsumer can be hydraulically stopped in the return stroke even before a predetermined end position is reached by switching on the pressure source.

Abstract: A cold start valve for a hydraulic circuit has a valve slide with two counteracting control faces. It is possible to load a first control face with a control pressure and to load a second control face with a feed pressure. In addition, the first control face is loaded with the spring force of a valve spring. A damping space is configured to damp a stroke movement of the valve slide. The damping space is delimited by a damping face formed on the valve slide and oriented in accordance with the first control face. The damping face is configured to be loaded via the damping space with a damping pressure to damp the stroke movement. The damping space is connected in a throttled manner to a pressure space. The second control face of the valve slide is configured to be loaded with the feed pressure via the pressure space.

Abstract: A hydraulic control system is disclosed for use with a machine. The hydraulic control system may have a pump, a tank, and an actuator. The hydraulic control system may also have at least a first valve configured to control fluid flow between the pump, the tank, a first chamber of the actuator, and a second chamber of the actuator; a second valve fluidly disposed between the second chamber and the tank; and a third valve fluidly disposed between the first and second chambers. The hydraulic control system may further have a controller configured to selectively cause the second valve to block fluid flow from the second chamber of the actuator to the tank, and to selectively cause the third valve to fluidly communicate the first and second chambers of the actuator when the second valve blocks fluid flow from the second chamber of the actuator to the tank.

Abstract: A hydraulic system is disclosed. The hydraulic system may have an over-center, variable-displacement pump, an actuator, and first and second passages that create a closed-loop circuit. The hydraulic system may also have first and second check valves disposed in the first and second passages, respectively, to allow flow only from the pump to the actuator. The hydraulic system may further have a first bypass line connecting the first passage at a location between the actuator and the first check valve to the first passage at a location between the first check valve and the pump, and a second bypass line connecting the second passage at a location between the actuator and the second check valve to the second passage at a location between the second check valve and the pump. The hydraulic system may additionally have a valve configured to control flow through the first and second bypass lines.

Abstract: A pump for use in pumping hydraulic well control fluid expelled from a control device of a well, comprises means for accumulating such hydraulic well control fluid and means for using the pressure of hydraulic fluid supplied to the well to pump accumulated hydraulic well control fluid into a production flowline of the well.

Abstract: An energy recovery system is disclosed for use with a hydraulic machine. The energy recovery system may have a tank, a pump configured to draw fluid from the tank and pressurize the fluid, an actuator, and an actuator control valve movable to direct pressurized fluid from the pump to the actuator and from the actuator to the tank to move the actuator. The energy recovery system may also have a motor mechanically connected to a rotary device and configured to selectively receive fluid discharged from the actuator, and at least one valve movable to selectively redirect fluid exiting the motor back to the actuator.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system has a source of pressurized fluid, a fluid actuator, and a tank. The hydraulic system utilizes a directional control valve to direct flow between the source, the actuator, and the tank. The hydraulic further utilizes a variable backpressure control valve to control the system backpressure.

Abstract: An articulated dump truck is provided with an electro-hydraulic bin control system including a proportional control valve for the bin lift cylinders and including a solenoid-operated regenerative valve assembly mounted adjacent the lift cylinders and being actuated, during lifting the bin for dumping a load of material from the bin, to cause a regenerative flow to occur when the force required by the bin lift cylinders to continue lifting the bin falls to a predetermined force. The force required for tilting the bin is continuously calculated by an electronic control unit taking into account a sensed bin load, a sensed bin tip amount and a sensed side-to-side inclination of the bin. In a simplified second embodiment, the proportional control valve controls the regenerative flow.

Abstract: A method is provided for, when necessary, automatically limiting a pressure in a hydraulic system during operation. A system is arranged to deliver pressurized hydraulic fluid to at least one fluid actuated device arranged to perform a work function, where the procedure includes sensing a pressure in at least one position of the system, comparing the detected pressure value, or an associated value, with a first predefined pressure limit, and opening a communication of fluid between the fluid actuated device and a reservoir through a first conduit if the sensed pressure value, or an associated value, exceeds the predefined limit.

Abstract: An actuating device for a shift element of a transmission which is acted upon by a hydraulic actuating pressure (p_B1) and comprises a valve device. To vary the actuating pressure (p_B1), the valve device is acted upon by a control pressure (p_EDS) in an area of active surfaces (A18, A19) of at least a first and a second valve slides. An active surface (A38) of the first valve slide (A8) is acted upon by a hydraulic pressure (p_B2) which is equivalent to the actuating pressure (p_B1), acts in opposition to the control pressure (p_EDS) and can be adjusted as a function of the control pressure (p_EDS) applied, such that a smaller variation of the actuating pressure (p_B1) results from a change of the control pressure (p_EDS) within a first pressure range of the control pressure (p_EDS) than within a second pressure range of the control pressure (p_EDS).

Abstract: Methods and systems for operating a cylinder lock valve to control fluid flow to a hydraulic cylinder operating a drilling rig sub-system. The lock valve 1) allows fluid flow through the valve if pressure on a main and pilot area overcomes a closing spring force on the valve, or 2) blocks flow through the valve if a loss in charge pressure in the main and pilot area falls below the closing spring force on the valve.

Abstract: An ultrasound diagnosis system and a centesis support controlling method by which positions and directions of a centesis needle traveling to a target region can accurately and easily be determined, including an MPR image data generating unit which generates target image data by setting a prescribed target MPR plane on volume data acquired through 3D scan over a 3D volume including a target region; a centesis needle MPR plane setting unit which generates centesis needle data indicating position and directions of the centesis needle, based on the acquired volume data; a crossing angle detection unit which detects a crossing angle between the target MPR plane and the centesis needle MPR plane including the centesis needle data; and a needling support data generating unit which generates needling support data by composing the target image data and the centesis needle data overlapped with centesis needle image data based on the detected crossing angle.

Abstract: The invention relates to a hydraulic control arrangement and to a method for controlling a hydraulic consumer that comprises a pressure chamber on the input side and on the return side, said pressure chamber being connected to an adjusting pump or a tank via a valve device. The valve device is controlled by means of a control unit via which it can be adjusted in a regeneration mode, in which both pressure chambers are connected to the adjusting pump. According to the invention, the adjusting pump is pressure controlled, whereby in the regeneration mode, it is automatically switched to the normal operation in which the supply side of the pressure chamber is connected to the adjusting pump and the return side of the pressure chamber is connected to the tank when the pumping rate falls below the demand for the pressure medium.

Abstract: An articulated dump truck is provided with an electro-hydraulic bin control system including a proportional control valve for the bin lift cylinders and including a solenoid-operated regenerative valve assembly mounted adjacent the lift cylinders and being actuated, during lifting the bin for dumping a load of material from the bin, to cause a regenerative flow to occur when the force required by the bin lift cylinders to continue lifting the bin falls to a predetermined force. The force required for tilting the bin is continuously calculated by an electronic control unit taking into account a sensed bin load, a sensed bin tip amount and a sensed side-to-side inclination of the bin.

Abstract: A machine, such as a backhoe, has a series of components connected in series and moved by separate hydraulic actuators. A position estimator determines the present position of each component from the load acting on the associated hydraulic actuator and a velocity command for the component. For each component, a function parameter estimator uses the present positions of the components to derive a set of parameters that include a static structure load that the components exert on the associated hydraulic actuator, acceleration and deceleration limits for both directions of component motion, and a control bandwidth for the associated hydraulic actuator. The set of parameters for a given component is used to control the associated hydraulic actuator.

Abstract: An actuator using a fluid cylinder in which rigidity may be attained with a simple configuration, includes a fluid cylinder, a first choke valve device, and a second choke valve device. The first choke valve device is disposed between a fluid pressure source and a first chamber, and the second choke valve device is disposed between the fluid pressure source and a second chamber. An opening of a valve of a discharge valve mechanism included in each of the choke valve devices is set so as to be in inverse proportion to a target pressure in the chamber in which the fluid pressure is adjusted by the choke valve device.

Abstract: A cogeneration process and system which provides for the reclamation of a grease fuel from a concentrated grease trap pumping waste stream and the use of said grease fuel in a compression ignition reciprocating engine for the production of electric power. The concentrated grease trap pumpings are heated and mixed in the first stage of the process to ensure all grease is liquefied. This warm mixed stream is then separated by centrifuge into a heavy stream consisting of water and sediments and an oil-rich stream consisting of oil, grease/water emulsion and residual water. This oil-rich mixture is heated sufficiently to evaporate the residual water as well as the water of emulsion yielding a water free grease fuel suitable for use in the compression ignition engine. Heat energy for grease liquefaction and emulsion breaking is supplied by an engine jacket water cooling circuit and an exhaust heat recovery, respectively.

Abstract: A back-pressure valve comprises a case having first and second oil chambers through which oil passes. A piston is slidably accommodated within the case to partition the first oil chamber and the second oil chamber. A spring urges the piston in a sliding direction. A projecting member and a check valve allow the first oil chamber to communicate with the second oil chamber when the pressure of the oil in the first fluid chamber reaches a predetermined pressure. An area of the piston on which oil pressure is received in the first oil chamber is made lager than an area on which oil pressure is received in the second oil chamber. A part of the piston located at an end thereof opposite to the end thereof which faces the first oil chamber communicates with the outside of the case.

Abstract: Cushion chambers (8) disposed in the vicinity of both ends of a hydraulic cylinder (1) to throttle inflow or outflow of an operating oil caused by a piston (5) moving close to a piston stroke end, pressure sensors (16, 17) to detect pressures in the cushion chambers (8), and a control valve (13) disposed in a passage to supply/drain the operating oil to and from oil chambers (6, 7) of the hydraulic cylinder (1) for varying a flow amount of the operating oil are provided. A controller (9) varies an opening degree of the control valve (13) within a piston stroke end range based upon outputs of the pressure sensors (16, 17), adjusts a cushion pressure and controls a moving speed of the piston (5). Thereby deceleration degrees of the piston (5) can be freely adjusted within the piston stroke end range based upon a change of the operating conditions of the hydraulic cylinder (1).

Abstract: A hydraulic circuit is disclosed that can include a flow control element, a pressure compensator connected via a pair of load sense lines to an inlet line and an outlet line, respectively, of a flow control element to provide a constant pressure drop across the flow control element, and a load sense line control valve installed in a load sense line to provide controllable resistance in a flow passage in opposite flow directions, the resistance in each flow direction being different. The load sense line control valve can include a restrictive orifice followed by a spring-loaded check valve in a first flow direction and at least one other restrictive orifice and a check valve in a second flow direction, the second flow direction opposing the first flow direction.

Abstract: A hydraulic control system has an actuator with first and second chambers, first and second valves having elements movable to fill and drain the first and second chambers, and at least one sensor configured to generate a load signal indicative of a load on the fluid actuator. The system has an interface device movable to generate a desired velocity signal of the actuator. The system has a controller in communication with the first and second valves, the at least one sensor, and the interface device. The controller is configured to move the element of the first valve to a position based on the desired velocity signal and to move the element of the second valve to a position based on the load signal and a desired pressure within the second chamber.

Abstract: A poppet valve assembly with a control chamber that can be fluidly connected to a number of different hydraulic ports via a pilot valve assembly. The poppet valve assembly includes a poppet valve member whose movement is controlled by filling or draining the control chamber, and which can be hydraulically locked into a given position by fluidly isolating the control chamber from any other hydraulic connections. The poppet valve member includes a control hydraulic surface exposed to fluid pressure in the control chamber. The poppet valve assembly may be part of a valve assembly that includes a plurality of poppet valve assemblies that operably control a hydraulic cylinder connected to an implement of a work machine.

Abstract: The present disclosure is directed to a valve system including a controller and a valve including a valve element and a valve bore. The valve element is selectively movable relative to the valve bore at least partially in response to a signal communicated from a controller. The communicated signal is at least partially based on a load on the actuator and a determined pressured drop. The determined pressure drop is at least partially based on a hysteretic filter.

Abstract: A hydraulic system for raising and lowering aircraft landing gear (11, 12) includes an actuator (18) which is extendible and retractable to operate the landing gear, the actuator (18) including a movable member (19) in a casing (20), the movable member (19) being moved relative to the casing (20) in a first direction to extend the actuator (18) when fluid under pressure is supplied to a first side (22) of the movable member (19) while fluid is exhausted from a second side (23) of the movable member (19), and the movable member (19) being moved in a second direction to retract the actuator (18) when fluid under pressure is supplied to the second side (23) of the movable member (19) while fluid is exhausted from the first side (22) of the movable member (19), and there being selector valve (25) selectively to supply pressurized fluid to the first (22) or second (23) side of the movable member (19), and a check valve (40) to permit exhausted fluid from at least one of the first (22) and second (23) sides of the

Abstract: A system and method for controlling an electro-hydraulic valve arrangement to perform a pump check function are provided. The system includes an electro-hydraulic valve arrangement disposed between a source of pressurized fluid and a hydraulic actuator. Pressure sensors are provided to sense a source pressure representative of the fluid pressure between the source of pressurized fluid and the electro-hydraulic valve arrangement and an actuator pressure representative of the fluid pressure between the electro-hydraulic valve arrangement and the actuator. A control device receives a signal to open the electro-hydraulic valve arrangement to provide a requested flow rate to the hydraulic actuator. The received signal is modified to prevent fluid flow through the electro-hydraulic valve arrangement when the source pressure is less than the actuator pressure.

Abstract: A regenerative adaptive fluid motor position feedback control system integrating a load adaptive fluid motor position feedback control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary constant displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor position feedback control system integrating a load adaptive flujid motor position feedback system having an energy accumulator. the fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having an independent regenerating circuitry containing an energy accumulator.The fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor output feedback control system integrating a load adaptive fluid motor output feedback control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary constant displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having a built-in regenerating circuitry containing an energy accumulator. The fluid motor control system includes a variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A hydraulic system has a pump (1) with at least one load (4, 5) and accompanying bi-directional valves (8, 8a). A first comparator (A) establishes which motor line (6, 7) is carrying the higher load pressure. A second comparator (B) establishes whether the input-side motor line (6, 7) allocated a directional signal identifying the direction of the valve displacement is carrying the higher pressure or whether a load (4, 5) is being operated with negative loading. Depending on the result of the comparison, the load pressure signal (y1, y2) can be processed differently.

Abstract: A control valve feeds pressurized fluid for moving an actuator in first and second directions. A meter-out valve controls return flow of pressurized fluid from the actuator during actuation in the second direction. The meter-out valve is controlled by a pilot pressure controller independently of the actuator in response both to pilot pressures and to engine speed. The meter-out valve includes both a restricted channel and an unrestricted channel. The restricted channel, and the unrestricted channel are selectively connected dependent on the pilot pressures and the engine speed to supply sufficient fluid flow to permit stable operation of the actuator.

Abstract: Described herein is a brake valve which is arranged to prevent low pressure relief actions by relief valves (59A) and (59B) at the time of starting an actuator, for improving the response characteristics and the safety of operation. This brake valve has relief valves (59A) and (59B) and check valves (70A) and (70B) located in coaxial positions, the check valves (70A) and (70B) being arranged to seat on fore end portions of valve seat members (62A) and (62B) when opened, thereby to substantially block the communication of the valve seat members (62A) and (62B) with inlet link passages (56A) and (56B). Therefore, when the check valve (70A) or (70B) is opened at the time of starting the actuator, the valve seat member (62A) or (62B) is supplied with only a throttled flow of hydraulic pressure through the notched portions (73A) or (73B).

Abstract: In the case of a hydraulic control device for an oscillating load moving system comprising a double-acting hydroconsumer (V), which is adapted to be selectively connected to a pressure source (P) or to a reservoir (T) via two separate main lines (9, 10) and a control valve (C), and further comprising a load supporting valve (H), which is arranged in at least one main line (10) between the control valve (C) and the hydroconsumer (V) and which is adapted to be opened from the other main line (9) via a pilot line (16), a damping device (X), which consists of a bypass line (23) and an interference throttle aperture (D2), is connected to the pilot line (16) of the load supporting valve (H). The pilot line (16) has provided therein a throttle aperture (D1) which is smaller than the interference throttle aperture (D2).

Abstract: Hydraulic control of reversible hydraulic motors typically requires several different valves to provide for the various operating parameters. The subject hydraulic control circuit has only a pair of electrohydraulic control valves to provide all the typical operating parameters. Operation of the control valves is controlled by a microprocessor in response to receiving command signals from a manually controlled command signal outputting device which establishes a desired fluid flow rate and direction of flow through the control valves.

Abstract: A hydraulic positioning means is provided which includes means for selectively allowing or prohibiting the flow of the first hydraulic fluid under the operating pressure. It also includes means in the hydraulic positioning means for selectively positioning the workpiece to a plurality of predetermined locations for performing work operations thereon in response to allowing or prohibiting the flow of the first pressurized hydraulic fluid under the operating pressure. Means are also furnished for supplying the first pressurized fluid under the operating pressure to the hydraulic positioning means for such selective positioning of the workpiece. First fluid conduit means transfer the first pressurized fluid at said operating pressure from the pressurized fluid supply means to the hydraulic positioning means. A hydraulic impact load cushioning means is also bifurcatedly provided.

Abstract: A hydraulic circuit suitable for use in a hydraulic operating circuit of a power shovel includes a hydraulic cylinder for driving a working component and a hydraulic change-over valve for selectively supplying the cylinder with a discharge oil pressure of a hydraulic pump driven from an engine. The hydraulic circuit prevents cavitation in an oil chamber of the cylinder and includes a pair of first signal receiving portions provided in the hydraulic change-over valve for moving the spool thereof in the forward and reverse directions away from a netural position, respectively, and a second signal receiving portion for pulling back the spool toward said neutral position.

Abstract: In a hydrostatic transmission comprising a pump and a hydraulic motor arranged in a main line having low pressure and high pressure sections, wherein an oil drain line of the hydraulic motor is connected to the low pressure section of the main line, the housing of the hydraulic motor is freed from excessively high pressures in the main line by arranging a valve having an adjustable passage cross-section which decreases with increasing pressure in the main line before--in the direction of flow--the line connection of the oil drain line.

Abstract: A hydraulic system having multiple actuators is provided with positive pressure flow equalization for both advancing and retracting movements of the system by means of first and second flow divider elements for each actuator. The flow divider elements are cross-coupled between the actuators, a controllable source of pressurized fluid and a reservoir. The flow divider elements are positive-displacement gear or vane pump units that are connected by a common shaft for coordinating fluid flow to the various actuators. Two or more of the actuators can be connected for lifting a load such as an automobile, the system being provided with safety latches at each actuator, the flow dividers not only coordinating the actuator movements during normal raising and lowering operation, but also preventing loss of synchronization of the actuators in case of engagement of a subset only of the latches.

Abstract: A cylinder unit is supplied with pressurized fluid from a hydraulic machine which is variable in speed and/or displacement. The machine may be operated as a pump and as a motor to increase the pressure or, respectively, to decrease the pressure so that the piston of the cylinder unit may be actuated in both directions and, furthermore, the brake energy is recovered by the machine when the piston is driven through an external load. This results in an increased efficiency of the control apparatus for the cylinder unit avoiding any problems arising from heat.

Abstract: The hydraulic control is constructed for time-sharing of the pump which normally controls the turning mechanism, to operate other hydraulic equipment in conjunction with other pumps.

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, a pump for supplying fluid to said actuator, a pilot operated meter-in valve to which the fluid form the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valves associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve is sensed and caused to produce a force opposing the movement of the meter-out valve controlling flow from the actuator.

Abstract: A flushing valve system suitable for use in a closed circuit hydrostatic transmission including a variable displacement hydraulic pump, a hydraulic actuator and two main lines. The flushing valve system includes poppet valves mounted in passages for respectively communicating the main lines with a fluid tank, passages mounting throttles for causing the pressure in the main lines to act on pressure chambers to keep poppets of the poppet valves from moving to an open position, and a change-over valve responsive to the pressure differential between the main lines to communicate the pressure chamber of the poppet valve connected to the main line on the lower pressure side with the fluid tank. The poppet valve connected to the main line on the lower pressure side opens when a predetermined pressure level is exceeded by the pressure in the main line, to thereby allow working fluid in the main line to be drained to the fluid tank.

Abstract: A jacking mechanism for jacking a well casing or other well pipe vertically, and including a hydraulic control system in which a reversible variable displacement pump acts in one condition to deliver pressure fluid in parallel with another pump to the lower end of a jacking cylinder to actuate the piston thereof upwardly, with fluid discharging from the upper end of the cylinder to the variable displacement pump and being metered therethrough to regulate the rate of upward movement of the piston. In a second condition of the apparatus, flow through the variable displacement pump is reversed to lower the piston, and a variable restriction valve regulates discharge of fluid from the lower end of the cylinder to act with the variable displacement pump in regulating downward movement of the piston and supported pipe.

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, a pump for supplying fluid to said actuator, a pilot operated meter-in valve to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valves associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve is sensed and caused to produce a force opposing the movement of the meter-out valve controlling flow from the actuator.

Abstract: The device comprises in a body a pressure limiting stage, a second stage constituting a fluid check and retarding valve and piloting means between these two stages. The second stage comprises regulating means which are easily accessible from outside the body. The device is particularly compact and is of high interest, for example when it is incorporated in a self-contained cylinder structure.