Electrically controllable hydraulic system for a vehicle transmission and method for controlling the same An electrically controllable hydraulic system (1) for a vehicle transmission comprises a pressure pump system (4a, 4b) and a subsystem (1A) comprising a transmission element (2) and an electrically controlled hydraulic pressure controlling module (1B) including a hydraulic valve element (15) for controlling a hydraulic pressure for actuating the transmission element (2) and an electromagnetically controllable operating element (21) for operating the hydraulic valve element (15). The subsystem (1A) and the pressure controlling module (1B) have a first and a second cut-off frequency (f1, f2) with f2>f1. The hydraulic system includes a driver circuit (32) for driving the pressure controlling module (1B) that comprises a full bridge circuit and a control circuit (42) for simultaneously controlling both switching elements of the driver circuit with a duty cycle according to an input value of the input signal (lset) dithered with a frequency (f.sub.dith) in the range (f1, f2).

A hydraulic servo valve comprising a pair of opposing receiving ports, a piston disposed between the pair of opposing receiving ports and an actuator in contact with the piston. The actuator is configured to provide axial movement of the piston in response to being actuated. The piston comprises a pair of opposed openings that are in operable fluid communication with a respective one of each of the receiving ports, and the axial movement of the piston is configured to vary the amount of a fluid pressure communicated between a respective one of the openings and receiving ports.

A hydraulic valve includes an on/off seat-type main valve with two ports having a displaceable poppet for opening and closing the main flow channel; an on/off seat-type pilot valve with three ports, with a magnetomotive force producing coil, a magnetic circuit, and an anchor movable with the magnetomotive force produced by the coil; and a frame with required channels and spaces for the poppet and for the anchor. Closing the inlet channel displaces the poppet and opens the main flow channel. Opening the inlet channel forces the poppet to close the main channel. The anchor includes a frame with a first sealing element for closing the low-pressure outlet channel of the pilot valve and with a second sealing element for securing the closing of the high-pressure inlet channel of the pilot valve. The sealing surface of the second sealing element is movable in relation to the frame of the anchor.

A construction machine incorporates a hydraulic closed circuit system capable of suppressing, even where a selector valve is stuck in an open state by a failure of the selector valve or a control system therefor, unintended operation of a hydraulic actuator and continuing operation of a machine body. The construction machine includes first sensors that detect open-closed states of a plurality of switching valves, first compulsory valve closing devices that change over the plurality of switching valves to a closed position irrespective of open-close control by a machine body controller, and a valve device controller that controls, when it is detected based on the open-closed states of the plurality of selector values detected by the first sensors that one of the plurality of selector values is stuck in an open state, the first compulsory valve closing device such that other selector valve connected to one of the plurality of closed circuit pumps to which the one selector valve is connected is closed.

An improved servovalve for a seismic vibrator or vibration machine which includes a left additional passageway conducting a portion of sampled pressure from a left cylinder pressure chamber to only a portion of the right end drive surface of the spool, wherein the portion of the right end drive surface is less that of the entirety of the right end drive surface; and a right additional passageway conducting a portion of sampled pressure from a right cylinder pressure chamber to only a portion of the left end drive surface of the spool, wherein the portion of the left end drive surface is less that the entirety of the left end drive surface; thereby providing at least two additional passageways configured to provide linear proportional pressure feedback in spool movement control.

A hydraulic component includes a piston and a cylinder with a piston receiving space in which the piston is displaceably arranged while defining a chamber, via which a pressure may be applied to a first end face of the piston, from a control chamber, via which pressure may be applied to a second end face of the piston which faces away from the first end face. A first hydraulic line and a second hydraulic line open into the chamber and a control line, which branches off from the first hydraulic line, opens into the control chamber. Due to the respective pressure ratio between the pressure in the chamber and the control chamber, the piston is displaceable from a closed position, in which the first and second hydraulic lines are fluidly decoupled, into an open position, in which the first and second hydraulic lines are fluidly connected, and vice versa.

A valve body comprises an inner compartment extending along a longitudinal axis from a second end portion towards a first end portion. First, second, and third fluid ports in to the valve body are perpendicular to the longitudinal axis. The second fluid port is between the third and the first fluid port. A fourth fluid port is parallel to the longitudinal axis. A spool is configured to selectively reciprocate in the inner compartment. The spool comprises a first fluid receptacle configured to block fluid flow to the third fluid port and to fluidly communicate with the second fluid port when the spool adjoins the first end portion. The first fluid receptacle is configured to fluidly communicate with the second fluid port and with the third fluid port when the spool adjoins the second end portion. A second fluid receptacle is configured to receive fluid pressure from the fourth fluid port.

A valve arrangement for hydraulic control of a piston-cylinder of a power switch contains a main stage having a first main valve and a second main valve, and a pilot stage having at least one pilot valve. In order to permit the first main valve to remain securely in the opened state, even in the event of pressure oscillations, the main valve has a total of four control surfaces, of which a second and a third control surface operate in a closing manner and a fourth control surface operates in an opening manner. For this purpose, the second control surface is connected to the high-pressure line, the third control surface is connected to the low-pressure line, and the fourth control surface is connected to the output-side valve connection of the first main valve.

A valve includes an inlet and an outlet, a body including a first seat and a second seat, wherein the first seat and second seat are spaced apart from each other at a predetermined distance, a cavity in the body, a piston positioned in the cavity, wherein the piston rests against the first seat and the second seat when in the closed position, and a pilot ball adjacent the piston.

An example valve includes: (i) a pilot seat member comprising a first channel and a second channel, a pilot seat, and a pilot sleeve portion comprising a pilot chamber and a cross-hole; (ii) a pilot check member disposed in the pilot chamber and subjected to a biasing force of a setting spring, wherein the pilot check member is configured to be subjected to a fluid force of fluid in the second channel; and (iii) a solenoid actuator sleeve slidably accommodated about the pilot sleeve portion, wherein the solenoid actuator sleeve comprises a cross-hole and an annular groove, wherein the cross-hole of the solenoid actuator sleeve is fluidly coupled to a second port of the valve, and the annular groove is configured to selectively fluidly couple the first channel to the second channel based on a position of the solenoid actuator sleeve.