A fluid pressure actuator including a fluid pressure cylinder having a first position detector and a second position detector, a piston body having a piston head and a rod, the piston head mounted on the rod and slidably accommodated in the fluid pressure cylinder, the rod including a first scale and a second scale, the first scale facing the first position detector and the first position detector configured to detect a position in a sliding direction of the piston body, the second scale facing the second position detector and the second position detector configured to detect a position of the rod in a rotation direction of the piston body, and a controller configured to perform a first positioning control of a position of the rod in the sliding direction and a second positioning control of the rod in the rotation direction may be provided.

A hydraulic rotary feed-through with a neck which is accommodated in a housing via a bearing arrangement and through a pressurized fluid line extends to a pressure space with a seal arrangement provided axially between the pressure space and the bearing arrangement, the bearing arrangement and the seal arrangement are disposed in frames which are accommodated in the housing axially engaged with one another under pressure.

A hydraulic cylinder enclosing a cavity, the cylinder containing a thru hole, an inner cylinder surface, and a longitudinal axis, and a piston within the cavity and movable relative to the cylinder in parallel to the longitudinal axis between a first and second positions. The piston includes a rod extending through the thru hole, the piston attached to the rod and in sealed engagement with the inner cylinder surface, and dividing the cavity into low and high pressure cavities, and each of the low and high pressure cavities containing a hydraulic fluid. The hydraulic cylinder further including a flexible bladder within the high pressure cavity containing a gas and preventing the gas from mixing with hydraulic fluid in the high pressure cavity. The flexible bladder is attached to an end of the cylinder, and is expandable within the high pressure cavity so that when the piston is in the first position, the flexible bladder and the gas are compressed, and as the piston moves toward the second position, the flexible bladder and the gas fill at least a portion of the high pressure cavity.

A sealing device is disposed within a circumferential groove of an inner member that reciprocates relative to an outer member. An inner seal ring of the sealing device is made of a resin and includes an outer peripheral surface having a circumferential groove. An outer seal ring of the sealing device has a high elasticity and is fitted into the circumferential groove of the inner seal ring. The outer seal ring is brought into slidable contact with the inner peripheral surface of the hole of the outer member. A back ring of the sealing device has a high elasticity, is disposed radially inside the inner seal ring, and is compressed between the inner peripheral surface of the inner seal ring and the bottom wall surface of the circumferential groove of the inner member. Inclined surfaces are formed at both ends of the outer peripheral surface of the inner seal ring in the axial direction of the inner seal ring, each of the inclined surfaces having a diameter that decreases as a distance from a center of the outer peripheral surface of the inner seal ring in the axial direction increases. Protruding annular portions are formed at both ends of the inner peripheral surface of the inner seal ring in the axial direction, the protruding annular portions protruding radially inward to restrict movement of the back ring in the axial direction.

A fluid pressure cylinder is provided with a cylinder tube having a sliding hole internally; a piston unit disposed along the sliding hole so as to be capable of moving back and forth, and a piston rod projected in the axial direction from the piston unit. The piston unit can shorten the axial dimension of a piston body by mounting a wear ring to an outer circumferential section of a ring-shaped magnet attached to an outer circumferential section of the piston body.

An actuator assembly comprises a housing having a piston at least partially disposed therein. The actuator assembly includes at least one biasing mechanism disposed within the housing to selectively position the piston between a first position, a second position, and a third position located between the first and second positions.

Disclosed are seal arrangements in a hydraulic device. The seal arrangement includes a seal channel defining a loop. A seal is seated within the seal channel. A coolant flow passage has a first part intersecting with the seal channel at a first point and a second part intersecting with the seal channel at a second point. The first part of the coolant flow passage is configured to provide hydraulic fluid to the seal channel such that, at the first point, a first portion of the hydraulic fluid flows in a first direction around the loop and a second portion of the hydraulic fluid flows in a second direction opposite to the first direction around the loop. At the second point, the first portion of hydraulic fluid and the second portion of hydraulic fluid are configured to flow into the second part of the coolant flow passage.

A clutch piston includes a piston that reciprocates in a piston chamber into which an oil flows, and a sealing member configured to seal the oil in the piston chamber. The sealing member includes a proximal portion mounted to an end of the piston and a seal lip that slides on a wall surface of the piston chamber when the piston reciprocates. The end of the piston extends in a direction intersecting the wall surface. The end includes a far-side face disposed on a far side of the piston chamber and a near-side face disposed on a near side of the piston chamber. The near-side face includes a recessed surface to which the proximal portion of the sealing member is mounted, a projecting surface disposed on a nearer side of the piston chamber than the recessed surface, and an inclined surface inclined relative to the recessed surface and the projecting surface and connecting the recessed surface and the projecting surface.

A piston unit is provided with a piston body; a packing mounted on an outer circumferential portion of the piston body; a holding member having a plurality of magnet holding portions that are arranged along a circumferential direction; a plurality of magnets which are held at intervals in the circumferential direction; a first annular yoke disposed on one side in an axial direction of the plurality of magnets; and a second annular yoke disposed on the other side in the axial direction of the plurality of magnets.

Disclosed is a method for repairing a piston-cylinder unit within a working machine or within an attachment, wherein a connection of the piston rod with the machine or implement structure is released and the piston rod, the piston and at least one bearing head is jointly removed from the cylinder housing as an assembly and replaced by a premounted substitute assembly consisting of piston rod, piston and at least one bearing head.