Abstract: A hydraulic swing motor which is provided so as to assure an improved cushioning effect near the end of its stroke and ultimately to make possible a reduction in the cushion stroke sector or an increase in the effective stroke, with fluid inlet and outlet passages at the casing being connected to chambers partitioned with a first vane fixed to the shaft side and a second vane fixed to the casing side and which are closed by means of the said first vane when the relative motion of the first and the second vanes nears its end, and with throttle valves to control the fluid discharge rate and relief valves to release the discharge fluid when its pressure rises beyond a certain limit in a section which remains open throughout the whole stroke.

Abstract: A hydraulic actuator comprising a pair of pressure oil chambers each of which has a cushioning port, the two cushioning ports being connected to each other through a cushioning means. The cushioning means includes a pair of cracking valves whose closing pressure is lower than its opening pressure and a pair of restricting means for restricting the flow of a pressure oil provided with regard to said cracking valves. This structure permits an output means for the actuator to be stopped smoothly as a result of fully absorbing the inertial energy that accompanies the output means.

Abstract: An extendible and contractible shaft comprises a number of shaft members on a common longitudinal axis, each except the outermost member being telescoped within the one next adjacent. Each telescoped member has a piston slidably sealed to the inner wall of the next adjacent outer member to form a series of tandem arranged sealed pistons. Fluid passageways are provided between adjacent shaft members so that fluid supplied under pressure to an inlet port of the device flows through the passageways to all the piston heads, thereby extending the telescoped shaft members and at the same time driving fluid out from under each piston through fluid passageways to an exit port of the device. When the pressurized fluid flow is reversed to send pressurized fluid to the undersides of the pistons, thereby driving fluid above the piston heads out through the first mentioned port, there would normally be incurred substantial shock as each piston head strikes its stop in the retraction operation.