A servohydraulic drive includes a hydrostatic displacement machine, an electric machine that is mechanically speed-coupled with the displacement machine, a hydraulic cylinder that is fluidically connected to the displacement machine via first and second working lines, a hydraulic accumulator, and a supply unit. The displacement machine has a stroke that is adjustable via a hydraulic adjustment device. The cylinder is configured to be activated by reversal of the fluid flow through the displacement machine in opposite directions. The accumulator is preset to a low pressure and is fluidically connected via a valve assembly in each case to the lower pressure working line. The supply unit is configured to supply the adjustment device with pressurized fluid under the necessary pressure for the adjustment regardless of the present pressure in the working lines such that the displacement machine is configured for an active and load pressure-independent adjustment of its stroke volume.

The invention relates to a hydraulic drive (1) comprising a working cylinder (2) and a travel cylinder (3) which is mechanically connected to the working cylinder (2). The working cylinder (2) and the travel cylinder (3) each comprise an upper and a lower cylinder chamber (21, 22, 31, 32), and all four cylinder chambers (21, 22, 31, 32) of the working and travel cylinder (2, 3) are connected to one another in a suitable manner in a closed pressure circuit (4) which is filled and prestressed with a hydraulic fluid (F). A rotational speed-variable hydraulic machine (5) with a first and second pressure connection (51, 52) is arranged in the pressure circuit (4) in order to conduct the hydraulic fluid (F) between the individual cylinder chambers (21, 22, 31, 32) of the working and travel cylinder (2, 3) during the operation (B) of the hydraulic drive (1). At least one first and second distributing valve (6, 7) are arranged in the pressure circuit (4) such that the respective valve switch positions (61, 62, 71, 72, 73) which are suitable for the different operating phases of the hydraulic drive (1) together with the suitably driven hydraulic machine (5) allow a common movement of the work and travel cylinder (2, 3) in one or the other piston movement direction (R1, R2). For this purpose, preferably only the first and the second distributing valve (6, 7) are arranged in the pressure circuit (4). The hydraulic drive (1) requires a minimum number of components, maintains a low installation complexity, improves the energy efficiency, can be constructed in a compact manner, and can be operated in a sufficiently variable manner.

A pressure measuring system, including a tube system having at least one first device for measuring pressure in a fluid. The at least one first device includes a coupling element, at least one pressure transducer and at least one measuring chamber, which can be filled with a fluid. Between the first device and the feed of the fluid, the tube system has a second device for regulating a fluid flow, the second device having a tube section through which fluid can flow and at least one tube clamp, which can be set in the regulation positions open, closed and perfused.

A cylinder acceleration mechanism includes a buffer tank that supplies and discharges oil to and from a bottom-side line that is connected to a bottom-side chamber of an actuating cylinder, and an inversion lever having an intermediate fulcrum as a rotation axis. The buffer tank includes a buffer chamber with a variable capacity achieved by a seal lid moving back and forth inside of a case, and extends and reduces a length of a coupling rod provided to the seal lid and projects from the case. A bottom-side branching line branched from the bottom-side line is connected to the buffer chamber. The actuating rod of the actuating cylinder and the coupling rod of the buffer tank are coupled to respective ends of the inversion lever. The actuating rod and the coupling rod extend and retract alternately with respect to each other as the inversion lever turns.

A fluid pressure driving device includes a first air-fluid converter and a second air-fluid converter each configured to convert air pressure supplied from an air pressure source to fluid pressure, a fluid pressure actuator having a first pressure chamber and a second pressure chamber, an operation state acquisition unit configured to acquire an operation state of the fluid pressure actuator, and first and second air pressure valves respectively provided on first and second air supply paths, the first and second air supply paths being configured to supply air from the air pressure source to the first and second air-fluid converters respectively, wherein the control device is configured to control the first air pressure valve and the second air pressure valve on the basis of an acquired result from the operation state acquisition unit.

An actuator comprising: a piezo actuator; a drive having a drive chamber and a drive piston element driven by the piezo actuator; a first output having an output chamber and a piston element; and a second output having an output chamber and a piston element. At least part of the hydraulic fluid is conveyed out of the drive chamber by movement of the drive piston element and into the first output chamber. At least part of the hydraulic fluid is conveyed out of the drive chamber and into the second output chamber. The second output piston element has a hydraulically active second output face which is different in size from the first output face. There may be a coupling device mechanically coupling the first output piston element to the second output piston element.

A valve device (200) includes a tank pressure port (218), a first pressure port (212), a second pressure port (214), and a pressure shut-off valve (224). The valve is switched between the individual ports (212, 214, 218), and has two valve components (226, 228). Upon reaching a predefinable pressure cut-off value, the first pressure port (212) can be connected to the tank pressure port (218) by the first valve component (226). In the event of the fluid pressure being higher at the second pressure port (214) than at the first pressure port (212), the second pressure port (214) can be separated from the first pressure port (212) by the second valve component (228). Both valve components (226, 228) are combined to form a tradable structural unit and are integrated in a common valve housing (230), preferably making direct contact. A hydraulic system has this valve device.

A piston body (11) of an advancing-retracting first piston (10) and a force-multiplying second piston (15) are arranged in series in a vertical direction in a housing (1). Force acting on the second piston (15) due to pressurized oil in a lock chamber (16) is multiplied and converted into multiplied upward force via engaging balls (32) of a force multiplier (30). Then, the multiplied upward force is transmitted to an output rod (12) of the first piston (10). At an intermediate part of a first air detection passage (38) for use in detection formed in the housing (1), a first detection valve (40) is provided. When the engaging balls (32) move inward in a radial direction, the first detection valve (40) is closed.

A modular electrohydraulic actuator including an electric motor, a hydraulic pump driven by the electric motor, and a hydraulic actuator in fluid communication with the hydraulic pump. The hydraulic actuator includes a hydraulic cylinder supporting a pressure sleeve in which a piston and rod is adapted for reciprocating motion in response to a supply of pressurized fluid to a first side or a second side of the piston, wherein at least one of the electric motor, hydraulic pump, hydraulic cylinder, piston, piston rod or the pressure sleeve supported in the hydraulic cylinder is selectively removable and replaceable with a different component to vary at least one performance characteristic of the electrohydraulic actuator.

A hydraulic cylinder comprising a cylinder, a piston element movably guided in the cylinder in a working direction and comprising an active surface, and a first opening for feeding a fluid into a cylinder chamber by the active surface. A working pressure of the fluid acting on the active surface drives the piston element in the working direction. The active surface includes a first partial surface and at least one second partial surface, the cylinder chamber being divided into a first sub chamber with the first opening by the first active surface and a second partial surface with a second opening by the second partial surface, and the partial surfaces are hydraulically separated from each other at least in a selectable operating mode.