Abstract: A hydraulic system, in particular a hydraulic transmission controller, includes a first pump, which provides a large volumetric flow for a cooling and/or lubricating device at an outlet, and a second pump, which provides a high pressure for at least one hydraulic load at an outlet. The hydraulic system also includes an additional active valve, which is connected upstream of the cooling and/or lubricating device, is connected to a system pressure valve and to at least one hydraulic load to be boosted in such a manner that in a boost state, the outlets of the two pumps are connected to the hydraulic load to be boosted via a boost line.

Abstract: Provided is a construction machine in which travel operability is not impaired when a combined operation is performed in which a single-rod hydraulic cylinder is driven during a travel operation. A hydraulic excavator includes a controller that controls the delivery direction and delivery flow rate of a closed-circuit pump, opens and closes a travel switching valve and an assist switching valve, and controls the delivery flow rate of the open-circuit pump, according to a travel operation lever and a work operation lever. The controller holds the assist switching valve in a closed position irrespective of whether or not the work operation lever is operated in a case where the travel operation lever is operated.

Abstract: A power unit includes at least one drive source that outputs rotational power to a drive target other than pumps; a first pump rotationally driven by the rotational power of the drive source; a second pump rotationally driven by the rotational power of the drive source, the second pump being different form the first pump; and a power transmission structure that transmits the rotational power of the drive source to the first and second pumps. The power transmission structure includes transmission components and transmits the rotational power to the first pump through one of the transmission components and to the second pump through another of the transmission components.

Abstract: A system for controlling an operation of a hydrostatic circuit of a work machine includes a flush control valve. The flush control valve is configured to be fluidly coupled to the hydrostatic circuit. The hydrostatic circuit is configured to operate in at least two operating modes to supply fluid power to selectively run a plurality of sub-systems of the work machine. In at least one operating mode of the at least two operating modes of the hydrostatic circuit, the flush control valve is configured to move and regulate a flushing flow rate of the fluid to equalize the flushing flow rate with a desired flushing flow rate based on a signal indicative of the at least one operating mode.

Abstract: A hydraulic pressurizing medium supply assembly has an adjustable axial piston machine. An actuating cylinder is controlled by way of a pilot valve. The pilot valve is actuated by a control installation. The control installation, as input variables, has an actual pressure and/or an actual swivel angle of the adjustable axial piston machine. One or a plurality of the input variables are compared with a matching nominal value and a control value is emitted, or in each case a control value is emitted. The controlling of the input variables is part of a first closed-loop control circuit. An underlying second closed-loop control circuit has an input variable which is based on the control variable or the control variables and serves as a nominal variable. A further input variable of the second closed-loop control circuit is an actual delivery-volume adjustment rate of the axial piston machine.

Abstract: A hydraulic drive system includes a swing directional control valve 81 and a third boom directional control valve 82 that are connected to a third hydraulic pump 33. Furthermore, the hydraulic drive system includes: a second auxiliary directional control valve 84 that is connected to the third hydraulic pump 33, and is connectable with a second special hydraulic actuator 64 for driving special attachments; and a first selector valve 96 that is connected to the third hydraulic pump 33 upstream of the second auxiliary directional control valve 84, and is connectable with an additional hydraulic pump 97. The first selector valve 96 switches the hydraulic fluid source of the second special hydraulic actuator 64 connected to the second auxiliary directional control valve 84 at least between the third hydraulic pump 33 and the additional hydraulic pump 97.

Abstract: A hydraulic system for an aircraft. The hydraulic system can include a hydraulic actuator that is operatively coupled to a flight control member. Hydraulic fluid is moved through the hydraulic system by an engine driven pump that delivers hydraulic fluid to the actuator at a first pressure, and a boost pump that delivers hydraulic fluid to the actuator at a second pressure that is higher than the first pressure. The hydraulic system is configured such that the hydraulic fluid returning from the actuator to the engine driven pump can be delivered to the boost pump prior to reaching the engine driven pump.

Abstract: A construction machine is provided which includes a hydraulic closed circuit in which a single rod hydraulic cylinder is driven directly by a bidirectionally tiltable variable displacement pump and can stably speed up the contraction action of the single rod hydraulic cylinder. In the case where a contraction action of a hydraulic cylinder 10 is instructed through an operation lever 30, when a differential pressure obtained by subtracting the pressure of a cap chamber 10a from the pressure of a rod chamber 10b is equal to or lower than a first threshold value a set to a level equal to or higher than a selection setting pressure of a flushing valve 14, a controller 20 closes a rod side selector valve 12b to disable rod assist action for supplying hydraulic fluid from a second hydraulic pump 8 to the rod chamber, and when the differential pressure is higher than the first threshold value, the controller 20 opens the rod side selector valve to enable the rod assist action.

Abstract: A drive control method of a hydraulic actuator of a construction machine includes: determining whether a rotation operation lever and a working device operation lever are operated; calculating the required pressure of a hydraulic cylinder fix a working device according to the operation amount of the rotation operation lever; calculating the required flow rates of a swing motor and the hydraulic cylinder for the working device, the required flow rates corresponding to the operation amounts of the working device operation lever and the rotation operation lever; calculating the opening areas of the first and second proportional solenoid valves of an inlet side and an outlet side by using the calculated required pressure and required flow rates of the hydraulic cylinder for the working device and the swing motor; and calculating current values to be inputted into the first and second proportional solenoid valves of the inlet side and the outlet side according to preset data values or a table in comparison with th

Abstract: A pump attenuator bypass valve (40/100/200) is located at an outlet of a pump (30) in a vehicle braking system (10) between the pump (30) and an attenuator (34). The attenuator bypass valve (40/100/200) includes a bypass valve housing (41), a first fluid flow path (74, 57/179/220, 208), and a second fluid flow path (80/183). The first fluid flow path (74, 57/179/220, 208) is defined in the housing (41) and is configured to allow continuous flow of fluid when the pump (30) operates at a first pump flow rate. The second fluid flow path (80/183) is defined in the housing (41) and is configured to bypass the first fluid flow path (74, 57/179/220, 208) and to allow continuous flow of fluid when the pump (30) operates at a second pump flow rate higher than the first pump flow rate.

Abstract: In a hydraulic driving system, a plurality of loading-line driving devices adjust a flow rate of an operating liquid flowing from a loading-line pump to a loading-line actuator, and a steering-line driving device adjusts a flow rate of the operating liquid flowing from the steering-line pump to the steering actuator. When one of a plurality of loading-line actuators is driving, a switching valve device connects a loading-side passage and a steering-side passage. When any of the plurality of loading-line actuators is not driving, the switching valve device disconnects the loading-side passage and the steering-side passage.

Abstract: In a hydraulic control device, a first valve device is brought into an open state when a first value obtained by subtracting a value of a pressure in the first output side oil passage from a value of a pressure in the second output side oil passage is equal to or larger than a first threshold value. A second valve device is brought into an open state when an oil pressure in a third connection oil passage is equal to or larger than a second threshold value, and is brought into a closed state when the oil pressure in the third connection oil passage is smaller than the second threshold value. The first value is equal to or larger than the first threshold value and the first valve device is in the open state when the second valve device is in the closed state.

Abstract: A hydraulic jack capable of quickly lifting a load includes a frame (1) mounted with a lifting arm (2), a long connecting rod, a tray (4), a bracket and a hydraulic oil pump (3) for driving the lifting arm (2), and further includes a large pump (11) and a small pump (12) for supplying high pressure oil to the hydraulic oil pump (3). An inner cavity of the large pump (1) and a small pump core are axially connected to a hand press (8) respectively. The inner cavity of the large pump (11) is in communication with a first pressure regulation mechanism (9), and the inner cavity of the small pump (12) is in communication with a second pressure regulation mechanism (10).

Abstract: A control device for a continuously variable transmission includes: a line pressure generating-section configured to generate a line pressure; a pilot valve configured to supply a pilot pressure regulated so as not to exceed a first predetermined pressure when the line pressure exceeds the first predetermined pressure; a control section configured to generate the clamping forces by controlling the pilot pressure; a line pressure increase section configured to increase the line pressure to be greater than the first predetermined pressure when the control to increase the line pressure is performed when the line pressure is lower than the first predetermined pressure.

Abstract: The invention is a combined motor that combines or integrates electric and hydraulic power producing technologies into a single compact motor by means of common or shared rotor and stator elements. The invention allows optimized power, torque, performance and energy usage in electric and electric-hybrid vehicles and offers reduced weight and lower production costs due the use of common or shared components. The combined motor's electric and hydraulic power producing elements are preferably coaxial and coplanar, permitting axial compactness and enabling efficient space utilization in the vehicle. In typical electric vehicle drive cycles disproportionately large energy losses occur during the launch acceleration and brake energy recovery modes of vehicle torque demand. The combined motor increases overall efficiency by substituting high-efficiency hydraulic torque for low-efficiency electric torque during these modes.

Abstract: Disclosed are a control device for confluence flow rate of a working device and a control method therefor, the control device being capable of minutely operating a working device when a flow rate supplied to the working device is merged or blocked.

Abstract: A hydraulic system adapted to recover inertial energy is disclosed. The hydraulic system includes a pump, a variable displacement pump/motor having an input/output shaft, an accumulator, and a valve arrangement. The valve arrangement is operable in: a) a first mode where the variable displacement pump/motor is driven by the pump to rotate the input/output shaft and the load; b) a second mode where the variable displacement pump/motor uses inertial energy from a deceleration of the load to charge the accumulator; and c) a third mode where the variable displacement pump/motor is driven by the accumulator to rotate the input/output shaft and the load. The hydraulic system also includes a controller for controlling operation of the pump, the variable displacement pump/motor and the valve arrangement.

Abstract: A hydraulic pressure supply system of an automatic transmission may include a mechanical oil pump driven by an engine to supply the oil stored in the oil pan to a first supply path fluidly-connected to the mechanical oil pump, a switch valve fluidly-connected to the first supply path and selectively supplying oil supplied from the first supply path to the transmission unit through a second supply path fluidly-connected to the switch valve and the transmission unit, a solenoid valve actuator engaged to the switch valve, and an electrical oil pump fluidly connected to the oil pan to pump the oil stored in the oil pan as a second high-pressure hydraulic pressure and supply the oil in the pan to a third supply path fluidly-connected with the second supply path, wherein the first and second hydraulic pressures may be applied to the transmission unit through three operation modes.

Abstract: A pump device includes a first pump that includes a first discharge portion and a second discharge portion, a first flow path that connects the first discharge portion and a first chamber of a cylinder, a second flow path that connects the second discharge portion and a second chamber of the cylinder, a second pump that includes a third discharge portion and a fourth discharge portion, a third flow path that connects the third discharge portion and the first chamber, a fourth flow path that connects the fourth discharge portion and the second chamber, a branch path that branches from the third flow path and reaches the tank, and an opening valve that opens the branch path, the opening valve being disposed in the branch path so as to open the branch path when a pressure in the second chamber is higher than a predetermined pressure.

Abstract: A method for controlling torque transfer of a force-fitting shift element includes controlling a closing pressure at least temporarily upon presence of a closing request for the force-fitting shift element and when a prevailing system pressure of the hydraulic circuit is above a threshold value for the system pressure. The closing pressure is controlled in a manner that is different than upon the presence of the closing request for the force-fitting shift element and when the prevailing system pressure is below the threshold value for the system pressure.

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 first inlet port extends radially through a valve sleeve into an internal bore. A first outlet port extends radially outwardly through an outer periphery of the valve sleeve. A second inlet port on an opposed side of the first outlet port from the first inlet port, extends radially through a wall of the valve sleeve. A valve spool is received in the internal bore and has a first channel at an outer peripheral surface selectively communicating the first inlet port to the first outlet port. The valve spool has a second channel at the outer peripheral surface that communicates the second inlet port to an axial vent formed in an internal surface of the valve sleeve. The axial vent extends axially to communicate the second channel to the first outlet port. A pumping system is also disclosed.

Abstract: Disclosed herein are an apparatus and a method for supplying a fuel to an engine of a ship. The apparatus for supplying a fuel to an engine of a ship includes: a high pressure pump pressurizing a liquefied natural gas (LNG) and supplying the pressurized LNG to the engine; a hydraulic motor driving the high pressure pump; and a lubricating pump supplying lubricating oil to the high pressure pump.

Abstract: In a hydraulic closed circuit system with hydraulic pumps which maintains a well-balanced flow rate by automatically controlling the flow rate, a first hydraulic pump is connected to a hydraulic cylinder device such that the hydraulic closed circuit is made, a second hydraulic pump is connected at one of paired delivery ports to a bottom side of the hydraulic cylinder device and at the other of the ports to a tank, and a prime mover drives the first and second hydraulic pumps and recovers motive power from these pumps. A pump capacity control unit detects a moving direction of the hydraulic cylinder device, and a pressure in a lower-thrust side of the device, and controls a capacity of the second hydraulic pump so that the flow rate during the extension/retraction of the hydraulic cylinder device becomes balanced between the first and second hydraulic pumps and the hydraulic cylinder device.

Abstract: In some implementations, bending or other shape changes of a device are actuated by inflating or deflating a bladder in the device. Then, once the desired new shape is achieved by this actuation, another bladder in the device is layer-jammed, to make the device rigid in the new shape. In some cases, sheets in the layer-jamming bladder are coated with abrasive particles. In some cases, layer jamming bladders are interwoven to form a woven device. The rigidity of the woven device can be anisotropically controlled. Layer jamming some, but not all, of the bladders in the woven device causes the woven device to have a rigidity that varies by direction. In some cases, a layer-jamming bladder includes a solid layer with a crease in it. As a result, the bladder can easily bend at the crease.

Abstract: A method of controlling a pump for a hybrid transmission includes commanding a first line pressure of the transmission and deriving a first torque value—an open-loop torque value—from the first line pressure command, and commanding the pump to operate at the first torque value. The method monitors actual speed of the pump and derives a second torque value—a closed-loop torque value—therefrom. A third torque value is derived from the first and second torque values, and the pump commanded to operate at the third torque value. A first speed value may be derived from the first line pressure command, and the second torque value derived from the difference between the monitored and the first speed values. Deriving the third torque value may include a substantially-linear combination of the first and second torque values.

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

Abstract: A power transmission device that transmits power from a motor to a wheel via a hydraulically driven friction engagement element and that includes a mechanical pump driven by the motor to produce a hydraulic pressure that is regulated by a pressure regulating valve; an electric pump that produces a hydraulic pressure; a switching mechanism that either switches an output pressure of the regulating valve or an output pressure of the electric pump to a servo of the engagement element based upon a signal pressure, and a drain valve that opens to drain oil when a hydraulic pressure of a preset pressure or more is applied, and the switching mechanism connects to the drain valve to allow communication between the electric pump and the drain valve in the first state, and shut off communication between the electric pump and the drain valve.

Abstract: A fluid delivery system includes a first hydraulic circuit, and a second hydraulic circuit. The first hydraulic circuit includes a first hydraulic pump, and a first hydraulic motor. The first hydraulic motor is fluidly connected to the first hydraulic pump and is configured to be driven by the first hydraulic pump. The second hydraulic circuit includes a second hydraulic pump, and a second hydraulic motor. The second hydraulic pump is mechanically coupled to the first hydraulic motor and configured to be driven by the first hydraulic motor. The second hydraulic motor is disposed in loop with the second hydraulic pump and configured to be driven by the second hydraulic pump. The fluid delivery system further includes a delivery pump mechanically coupled to the second hydraulic motor and fluidly connected to a fluid source. The delivery pump is configured to deliver a pressurized fluid.

Abstract: In a drive train device, in particular a motor vehicle drive train device, with a working fluid pressure system for providing an operating fluid pressure including at least a first and a second operating fluid pressure source connected in at least one operating state directly to the working fluid pressure system, and a lubricating and cooling fluid pressure system with an operating fluid pressure deviating from the operating fluid pressure in the working fluid pressure system, a hydraulic switching unit is provided which in at least one operating state connects the second operating fluid pressure source directly to the lubricating and cooling fluid pressure system for increasing the pressure thereof.

Abstract: Pressure sensors are provided to detect the delivery pressure of a hydraulic pump, the output pressure of an engine revolution speed detecting valve, and the output pressure of a differential pressure reducing valve generating the differential pressure between the delivery pressure of the hydraulic pump and a maximum load pressure. A vehicle controller calculates virtually the displacement of the hydraulic pump by use of the detected pressures and an equation of motion about a swash plate of the hydraulic pump, calculates the power need of the hydraulic pump and the output of the engine using these values, and switches a motor between powering and generation control in accordance with the result of a comparison between the pump power need and the engine output. In this manner, the displacement of the hydraulic pump without using sensors to detect the tilting angle of the swash plate of the hydraulic pump.

Abstract: In order to avoid cavitation in a boom cylinder head end at the beginning of a dig cycle, fluid from an alternate source is supplied to the head end before or in addition to fluid supplied by the main boom-up hydraulic circuit. In one embodiment, an electronic hydraulic valve, related sensors, and control system determines the beginning of a dig operation and uses fluid at an intermediate pressure to rapidly provide fluid to a boom head end cylinder to prevent voiding or cavitation before fluid under high pressure from the main pump can be brought to the cylinder. An on/off fluid switch is activated early in a dig operation to address low pressure at the boom cylinder head end and provide an alternate path for fluid into the cylinder in reaction to the boom being lifted by a motion of the stick and bucket in contact with the work surface.

Abstract: A system for providing pressurized hydraulic fluid includes an engine driven main pump and an electrical motor driven auxiliary pump. The auxiliary pump provides hydraulic fluid at line pressure to shift control subsystems during a vehicle launch while the main pump provides hydraulic fluid to cooler or lubrication subsystems during the vehicle launch. A pressure regulation valve regulates the pressure of the hydraulic fluid from the main pump. Once the main pump reaches a critical speed, the main pump provides hydraulic fluid at line pressure to the hydraulic control system and the auxiliary pump is turned off.

Abstract: A hydraulic closed circuit system using a single rod type hydraulic cylinder prevents hunting of a flushing valve due to a delay in response of the flushing valve and circuit pressure pulsations, thereby preventing a decreasein operability of the hydraulic cylinder. A single rod type hydraulic cylinder is connected to a hydraulic pump via two hydraulic lines. A flushing valve is connected between the hydraulic lines and a tank; and a control unit is configured to add a predetermined control parameter to a pressure in a lower-pressure hydraulic line of the two hydraulic lines. The magnitude of a pressure in the higher-pressure hydraulic line of the two hydraulic lines is compared with the magnitude of a compensation pressure to which the control parameter has been added, and the flushing valve is switched when the compensation pressure and the higher-pressure hydraulic line pressure are found to be reversed in magnitude.

Abstract: A hydrostatic drive system for a machine is provided. The hydrostatic drive system includes a first hydraulic circuit, and a second hydraulic circuit. The first hydraulic circuit includes a first pump and a first hydraulic motor configured to selectively receive a flow of pressurized hydraulic fluid from the first pump at a first pressure. The second hydraulic circuit includes a second pump and a second hydraulic motor configured to selectively receive the flow of the pressurized hydraulic fluid from the second pump at a second pressure. The hydrostatic drive system further includes a controller configured to maintain a pressure balance between the first and the second hydraulic circuits based on a difference between the first pressure and the second pressure.

Abstract: A hydraulic steering device is provided comprising a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (L, R), direction valve means (2) arranged between said supply port arrangement and said working port arrangement, at least two fluid meters (3, 4), each of said fluid meters (3, 4) having a movable metering element (12, 15),said metering elements (12, 15) being connected by a shaft (5), said shaft (5) having an axis, selector valve means (6) being provided, said selector valve means (6) in a first position arranging said fluid meters (3, 4) hydraulically in parallel and in a second position shutting off one of said fluid meters (3, 4), said selector valve means (6) having a valve element (20) shiftable in an direction parallel to said axis. It is an object to reduce wear in said hydraulic steering device in a simple manner.

Abstract: A control system for a hydraulic system comprises an electronic control module, an electronic system controller, a remote power module, and a solenoid valve. The electronic control module monitors torque output of an internal combustion engine, an electric motor and generator. The electronic system controller monitors torque demand of a first and a second hydraulic circuit. The remote power module is in electrical communication with the electronic system controller. The solenoid valve is in electrical communication with the remote power module. The solenoid valve connects to a combination valve and has a first open position and a closed position. The combination valve is in fluid communication with a first hydraulic circuit and a second hydraulic circuit. The solenoid valve moves to the open position in response to an output signal from the electronic system controller.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may have a hydraulic circuit, and a pump configured to supply pressurized fluid to the hydraulic circuit. The hydraulic control system may also have a first fluid actuator fluidly connected to receive pressurized fluid from the hydraulic circuit, a first valve arrangement movable to control a flow of fluid to the first fluid actuator, a second fluid actuator fluidly connected to receive pressurized fluid from the hydraulic circuit, and a second valve arrangement movable to control a flow of fluid to the second fluid actuator. The hydraulic control system may additionally have a controller in communication with the first and second valve arrangements. the controller may be configured to make a determination of a stall condition of the first fluid actuator, and to selectively change a flow command directed to the second valve arrangement based on the determination.

Abstract: A vehicle using a first MG, a second MG, and an engine as drive sources includes an electric oil pump, a mechanical oil pump driven by power of the engine, and a hydraulic circuit. The hydraulic circuit includes first oil passages for supplying oil to the first MG, a second oil passage for supplying oil to the second MG, a switch-over valve capable of switching over states of communication of the first oil passage, and a switch control valve that outputs pilot hydraulic pressure to the switch-over valve. States of the switch-over valve are switched over in accordance with hydraulic pressure from the switch control valve and hydraulic pressure from the mechanical pump.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system may have a first pump with variable displacement and being load-sense controlled, and a first hydraulic circuit associated with the first pump. The hydraulic system may also have a second pump with variable displacement and being electro-hydraulically controlled, and a second hydraulic circuit associated with the second pump. The hydraulic system may further have a flow-sharing valve arrangement configured to selectively share fluid flow between the first and second hydraulic circuits.

Abstract: A dump truck includes: an oil-cooling center brake; a first hydraulic pump supplying cooling oil to the center brake; a second hydraulic pump supplying cooling oil to the center brake in addition to the cooling oil from the first hydraulic pump; a hydraulic motor driving the second hydraulic pump; a third hydraulic pump supplying hydraulic oil to the hydraulic motor; an open/close valve letting the hydraulic oil bypass the hydraulic motor; and a controller controlling a bypass flow amount at the open/close valve. A capacity of the first hydraulic pump corresponds to a flow amount of the cooling oil required to lubricate a transmission. A capacity of the second hydraulic pump corresponds to a flow amount for compensating the cooling oil from the first hydraulic pump when a brake is off. A capacity of the third hydraulic pump is smaller than the capacity of the second hydraulic pump.

Abstract: A fixed/variable hybrid system has modified constant flow open center hydraulic valves (“fixed/variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Abstract: A system and method for operating a two-stage, high-pressure pumping system includes a low-pressure pump having an output configured to deliver a hydraulic fluid under a low-pressure at a high-volume to drive a tool associated with the two-stage, high-pressure, pumping system under low load conditions. The system also includes a high-pressure pump having an output configured to deliver the hydraulic fluid under a high-pressure at a low-volume to drive the tool under high load conditions. A pilot-operated device is included that is configured to selectively drive the tool with pressure from at least one of the output of the low-pressure pump and the output of the high-pressure pump. The pilot-operated device receives pilot pressure from the output of the low-pressure pump to control selectively driving the tool with the output of the two stage pump.

Abstract: A backup system is provided that has a local electric motor and pump for some or all of hydraulic actuators. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

Abstract: A dual pump hydraulic system is provided for a vehicle driven by an internal combustion engine. The system includes a first circuit with a first high pressure pump supplying hydraulic fluid to the first subsystem at a higher pressure. The system also includes a second circuit with a second lower pressure pump supplying hydraulic fluid to the second subsystem at a second pressure. A first valve controls communication between the first pump and the second circuit. A second valve is operable to communicate the second pump with the first circuit when pressure in the first circuit is less than a second threshold pressure or when commanded by a control unit. A check valve prevents fluid flow from the first circuit back into to the second valve.

Abstract: A hydraulic system for actuating a belt-driven conical-pulley transmission having a variably adjustable transmission ratio, of a vehicle, including at least one hydraulic energy source and having a torque sensor that is supplied with working medium by a pump flow of the hydraulic energy source. A disconnection valve is connected between the hydraulic energy source and the torque sensor, which makes it possible to connect or disconnect an additional pump flow of the hydraulic energy source, depending on need.

Abstract: A hydraulic drive system for an actuator uses a pair of pressure compensated hydraulic machines to control flow to and from the drive chambers of the actuator. The capacity of one of the machines is limited in a motoring mode to determine a maximum rate of efflux from one of the chambers. The pressure of fluid supplied to the other of said chambers is maintained at a predetermined level to provide motive force. The machines are mechanically coupled to permit energy recovery and charge an accumulator to store surplus energy.

Abstract: A power transmission device that transmits power from a motor to a wheel via a hydraulically driven friction engagement element and that includes a mechanical pump driven by the motor to produce a hydraulic pressure that is regulated by a pressure regulating valve; an electric pump that produces a hydraulic pressure; a switching mechanism that either switches an output pressure of the regulating valve or an output pressure of the electric pump to a servo of the engagement element based upon a signal pressure; a passage to supply pressure from the mechanical pump to the hydraulic servo; a check valve in the passage that allows supply of the pressure from the mechanical pump to the hydraulic servo and prohibits supply of the pressure from the electric pump to the mechanical pump, and the switching mechanism either shuts off or allows communication through the passage based upon the signal pressure.

Abstract: A hydraulic system for an automatic transmission operatively connected to an internal combustion engine that is operable in a start-stop mode. The hydraulic system includes a hydraulic energy source to supply the hydraulic system with hydraulic energy, the hydraulic energy source including at least one electrically driven hydraulic pump to supply the hydraulic system with hydraulic energy during a stopping phase of the internal combustion engine. To achieve a reduction in fuel consumption and CO2 emissions, provision is included to enable the electrically driven hydraulic pump to be switched on in addition to a mechanically driven hydraulic pump, as needed during an operating phase of the internal combustion engine.

Abstract: A hydraulic system including a multi-flow hydraulic pressure supply unit, especially a dual-flow hydraulic pressure supply unit, such as a pump, by which a volumetric flow of pressurized fluid is supplied to a hydraulic-fluid-operated device. A valve arrangement is provided either for switching between the individual pump flows or for interconnecting the individual pump flows.