Abstract: A variable displacement pump including a control mechanism shiftable between first and second states, when the control mechanism is in the first state, the spool is in an initial position in which fluid communication between an introduction port and the remaining ports is restrained, fluid communication between a first control port and a drain port is allowed, and fluid communication between a second control port and the drain port is restrained, and when the control mechanism is shifted to the second state in accordance with increase in fluid pressure discharged, the spool is in an operating position in which the fluid communication between the introduction port and the first control port is allowed, the fluid communication between the first control port and the drain port is restrained, and the fluid communication between the second control port and the drain port is allowed.

Abstract: Described herein is a device comprising: a chamber wall comprising outer and inner surfaces, wherein the inner surface encloses a lobed chamber with a plurality of lobes and the inner surface comprises segments of arcuate surfaces, each of the segments of arcuate surfaces being tangent with its immediate neighboring segments, and wherein the chamber wall further comprises channels connecting the outer surface and the inner surface of the chamber wall and/or channels through an end surface of the chamber wall; a lobed piston configured to translate along a circular path relative to the chamber wall, the outer surface of the piston and the inner surface of the chamber wall engaged during translation; and holes fluidly connected to the lobed chamber and configured to allow fluid discharge from the lobed chamber through the holes and to prevent fluid flow into the lobed chamber through the holes.

Abstract: An improved fluid pump having two or more cylindrical eccentric or elliptical rotors drive connected to revolve together at identical angular velocities, and positioned in cylindrical chambers for compressing fluids therein. The pump includes separate intake ports and discharge ports to and from the chambers allowing the pump to be used as a single stage pump or by connecting the discharge port of one chamber with the intake port of the other chamber the pump can be used as a two stage pump for increased pressure with less volume.

Abstract: An apparatus having at least one alternately expanding and contracting chamber comprises a plurality of cylindrical rollers each having an exterior surface in continuous rolling engagement with two adjacent rollers, the rollers being rotatable along parallel axes, with at least one of the rollers rotating about an eccentric and/or reciprocating axis. The rollers are preferably of equal length with adjacent rollers being in contact substantially along their entire respective lengths, the chamber being defined between the rollers and enclosed at its ends by end plates.