Abstract: A piston bearing structure for a fluid pressure cylinder includes one seal ring which is housed in a housing groove of a piston and is held in sliding contact with a cylinder tube and two backup wear rings which is housed in a housing groove of a piston, is held in sliding contact with a cylinder tube and sandwiches the seal ring. The backup wear ring includes a pressure relief groove which faces the housing groove and extends over the backup ring portion and the wear ring portion, and the pressure relief groove allows opposite sides of the backup wear ring to communicate between the piston and the cylinder tube.

Abstract: A piston bearing structure for a fluid pressure cylinder includes one seal ring which is housed in a housing groove of a piston and is held in sliding contact with a cylinder tube and two backup wear rings which is housed in a housing groove of a piston, is held in sliding contact with a cylinder tube and sandwiches the seal ring. The backup wear ring includes a pressure relief groove which faces the housing groove and extends over the backup ring portion and the wear ring portion, and the pressure relief groove allows opposite sides of the backup wear ring to communicate between the piston and the cylinder tube.

Abstract: There is provided a hydraulic damper including a receiving space formed between a rod guide of a cylinder and an insert metal, for temporarily retaining a working fluid leaked out from an oil chamber through a sliding gap of a rod. The hydraulic damper further includes a communicating path for communicating between a reservoir and the receiving space, and a check valve for allowing a flow of the working fluid only from the receiving space to the reservoir. Either one of a lip part of the check valve or a seat surface provided on the rod guide is formed with a sealing projected part protruding from a mutual contact surface.

Abstract: There is provided a hydraulic dumper including an receiving space 15 formed between the rod guide 4 of the cylinder 1 and the insert metal 5 and for temporarily retaining the working fluid leaked out from the oil chamber R1 through the sliding gap of the rod 3, a communicating path 4d for communicating the reservoir R and the receiving space 15, and a check valve 9 for allowing the flow of the working fluid only from the receiving space 15 to the reservoir R, wherein, either one of the lip part 9a of the check valve or the seat surface 4c provided on the rod guide 4 is formed with a sealing projected part 10, 11 protruding from the mutual contact surface.

Abstract: A U-packing is fitted externally in a seal grove of a piston of a fluid pressure single acting cylinder to maintain fluid tightness between a bottom side and a rod side of the cylinder. The U-packing has an open side facing the bottom side, and a return hole that allows communication between the open side and a non-open side. The U-packing is movable within the seal groove so that when a working fluid pressure on the bottom side is higher than a working fluid pressure on the rod side, the return hole is closed by structure of the seal groove, and when the working fluid pressure on the rod side is higher than the working fluid pressure on the bottom side, the return hole is opened. Working fluid leaked from the bottom side into the rod side can thus be returned to the bottom side of the cylinder.

Abstract: A seal structure for a sliding part including a shaft (11) and a member (10) having a shaft hole (10a) into which the shaft (11) is inserted in a freely and relatively sliding manner, and a first packing (P1) and a second packing (P2) arranged sequentially in series from a direction in which a high pressure is applied between the shaft (11) and the shaft hole (10a). The first packing (P1) includes a sealing member (22) for sealing a space between the shaft (11) and the shaft hole (10), and a backup ring (25) disposed on a part of the side of the sealing member (22) which is in contact with a sliding surface of the shaft (11) or the shaft hole (10a), and the sealing member (22) and backup ring (25) are inseparably integrated.