Abstract: A hydraulic cylinder includes a piston that defines a driving pressure chamber and a cushion pressure chamber within a cylinder tube, an air chamber defined inside a hollow piston rod, an orifice that leads a working fluid in the cushion pressure chamber into the air chamber when the cushion pressure chamber contracts during an extension operation, a check valve that returns a working fluid in the air chamber to the driving pressure chamber when a differential pressure between the air chamber and the driving pressure chamber rises to or above a predetermined value, and a valve housing that houses the check valve. A throttle gap is defined between an outer peripheral surface of the valve housing and an inner peripheral surface of the piston rod, and a working fluid ejected from the orifice during the extension operation flows into the air chamber through the throttle gap.

Abstract: A hydraulic cylinder includes a piston that defines a driving pressure chamber and a cushion pressure chamber within a cylinder tube, an air chamber defined inside a hollow piston rod, an orifice that leads a working fluid in the cushion pressure chamber into the air chamber when the cushion pressure chamber contracts during an extension operation, a check valve that returns a working fluid in the air chamber to the driving pressure chamber when a differential pressure between the air chamber and the driving pressure chamber rises to or above a predetermined value, and a valve housing that houses the check valve. A throttle gap is defined between an outer peripheral surface of the valve housing and an inner peripheral surface of the piston rod, and a working fluid ejected from the orifice during the extension operation flows into the air chamber through the throttle gap.

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.