Abstract: A positive displacement pump is provided having a housing, a plurality of pistons and an eccentric drive element rotatably mounted about an axis on the housing. A rigid compression member connected to each of the pistons is reciprocatably moveable with the pistons relative to the housing. At least one tension member is provided, connected between each of the pistons and the eccentric drive element at a point displaced from the axis. The tension member is permanently maintained in tension so as to continuously exert force radially inwardly on each of the pistons and to cause each of the pistons to continuously exert radially inward force on the compression member to permanently maintain the compression member in compression. The plurality of pistons preferably includes one or more pairs of pistons with each piston of the pair linked together by the compression element and reciprocates each in synchronism and 180.degree. out of phase with the other.

Abstract: A rapid pressure swing adsorption oxygen concentrator is provided having a plurality of at least three sieve beds cycled in sequence such that each is pressurized during one segment of a cycle and depressurized during a plurality of segments of a cycle while the other sieve beds are being sequentially pressurized. Preferably, approximately six sieves are provided and pressurized in sequence, with each being pressurized for approximately 60.degree. of the cycle and depressurized for from about 270.degree. to 300.degree. of the cycle. Each sieve is thereby pressurized for about one to two seconds and depressurized for about five to ten seconds. By utilizing the ability of the sieve material to adsorb faster than it can desorb gas, high output of up to 96% pure oxygen results with a low sieve volume and low power consumption.

Abstract: A positive displacement centrifugal pump comprises (a) a pressure generating mass rotatable about a first axis and radially movable relative to it upon rotation of the mass, (b) a pumping unit, and (c) a flexible, non-elastic tensioning element operatively connected to the mass and operable in the course of rotation of the mass to cause the mass to move radially inwardly toward the axis so as to effect intake and/or exhaust of fluid within the pump.

Abstract: A positive displacement pump comprises a mass such as a liquid filled pressure chamber or an annular ring which is rotated at high speed about a first axis so that centrifugal force acting on the liquid or ring creates zones of differential pressure within the interior of the pressure chamber or along the wall of the ring. At least one pumping unit having a pressure-responsive member is oscillated or rotated between the zones of differential pressure while the center of gravity of the pressure chamber or ring is maintained at a fixed distance from the first axis. In the course of moving into one zone having one pressure, the pressure-responsive member of the pumping unit is effective to intake a fluid such as air into the pumping unit. Air is discharged from the pumping unit by the pressure-responsive member in the course of moving from such one zone into another zone having a different pressure.

Abstract: A positive displacement pump comprises a mass such as a liquid filled pressure chamber or an annular ring which is rotated at high speed about a first axis so that centrifugal force acting on the liquid or ring creates zones of differential pressure within the interior of the pressure chamber or along the wall of the ring. At least one pumping unit having a pressure-responsive member is oscillated or rotated between the zones of differential pressure while the center of gravity of the pressure chamber or ring is maintained at a fixed distance from the first axis. In the course of moving into one zone having one pressure, the pressure-responsive member of the pumping unit is effective to intake a fluid such as air into the pumping unit. Air is discharged from the pumping unit by the pressure-responsive member in the course of moving from such one zone into another zone having a different pressure.