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: Provision is made for an air control valve to bypass the ice forming exhaust of a reciprocating pressure activation chamber in a reciprocating double diaphragm pump utilizing the supply pressure to close a check valve in line between the valve and the chamber which is then opened to exhaust by exhaust fluid flow from the chamber.

Abstract: The piston of a pile driving hammer is raised by hydraulic (water) pressure. As the hammer is permitted to fall, the water pressure is diverted from the cylinder, until the cycle begins again. Pressure surges, upon switching to and from pressure diversion, are turned to advantage by providing large pressure vessels with bag accumulators upstream and downstream of the hydraulic pressure supply pump. The water pressure is selectively throttled to control the frequency and amplitude of the stroke. The pressure vessel may be a pressure tank containing an air cushion. In this way, much of the pressure accumulated or reduced while the pump is working against an isolated pressure vessel acts in concert with the pump to advance the water when the respective pressure vessel is reconnected.