Low noise high efficiency positive displacement pump

A positive displacement pump comprising:

• a housing;
• in input drive shaft mounted for continuously unidirectional rotary motion about an axis relative to the housing;
• a plurality of pistons each mounted for reciprocating motion on the housing;
• at least one eccentric drive element linked to the input drive shaft and mounted for continuous unidirectional rotary motion in synchronism therewith;
• at least one rigid compression member connected to each of the pistons and reciprocatably moveable with the pistons relative to the housing;
• the plurality of pistons including at least one pair of opposed pistons linked together by one of the at least one compression member;
• and
• at least one tension member connecting each of the pistons in series with the at least one eccentric drive element, the at least one tension member being permanently maintained in tension so as to continuously exert unidirectional force on each of the pistons and on the at least one compression member to permanently maintain the compression member in compression;
• each of the opposed pistons of the pair being moved in the direction of the other piston of the pair by the force exerted by the tension member which in turn moves said other piston through compressive force exerted between the pistons of the pair by the at least one compression member, whereby the pistons of the pair reciprocate in unison with the continuous unidirectional rotary motion of the input drive shaft.

A positive displacement pump comprising:

• a housing;
• a plurality of pistons;
• an eccentric drive element rotatably mounted on an axis to the housing;
• a rigid compression member connected to each of the pistons and reciprocatably moveable with the pistons relative to the housing;
• and
• at least one tension member connecting each of the pistons to the eccentric drive element at a point displaced from the axis, the at least one tension member being 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;
• and
• one and only one bearing between the drive element and the pistons.

A positive displacement pump comprising:

• a housing;
• a piston;
• a drive element continuously unidirectionally rotatable relative to the housing;
• a rigid compression member connected at a first end to the piston with a second end extending to the opposite side of the drive element from the piston, the compression member being reciprocatably moveable with the piston relative to the housing;
• and
• at least one tension member connecting the drive element and first and second ends of the compression member so as to reciprocate the piston in response to the continuous unidirectional rotation of the drive element.