Abstract: A fluid-driven motor has a manifold with an arcuate seal including first and second valve openings and a sealing surface. A cylinder pivotally mounted on the manifold has a facing surface cooperating with the arcuate seal. The arcuate seal and the facing surface define a position-responsive valve configuration such that, when the cylinder assumes a neutral position, an aperture of the facing surface faces the sealing surface, and when the cylinder is angularly displaced in either direction, the aperture overlaps one or other of the valve openings, thereby connecting to the correspond fluid flow channel in the manifold. A pressure compensation volume underlies the sealing surface and receives fluid pressure from the fluid flow channels through valves, or from the internal volume of the cylinder, so that a pressure within the pressure compensation volume approaches a value no less than a current pressure within the internal volume.

Abstract: A valve assembly for controlling the flow of pressurized fluid supplied to an actuating cylinder having a piston driven by the pressurized fluid along a stroke path therewithin, the pressurized fluid being applied to alternative driving sides of the piston. The valve assembly comprises a first and a second valve pistons, which cooperate to block the supply of pressurized fluid to the current driving side of the piston when the piston reaches the end of its stroke path, thereby limiting the pressure of the pressurized fluid supplied to the driving side to a level reduced compared to a pressure level applied to drive said piston. If a leak occurs within the actuating cylinder at the end of the stroke path of the piston, it will be at the reduced pressurized fluid pressure.

Abstract: A hydraulic power and control system for operating a reciprocating hydraulic mechanism including pump means connected to the hydraulic mechanism, a continuous torque hydraulic motor, a direction control driven by the motor to sequentially direct hydraulic power fluid to separate inlets of the mechanism, an escapement for restraining the motor at 180.degree. intervals of rotation for sequentially holding the direction control at two separate positions, one for supplying one inlet and the other for supplying the other inlet of the mechanism, and hydraulic limit valves for controlling the escapement when a reciprocating member of the mechanism reaches the end of each stroke. One embodiment has two constant volume hydraulic pumps connected with the hydraulic mechanism through a reversing valve assembly operated by a scotch yoke connected with the escapement.