Rebuildable cassette assembly for displacement pump

Abstract

A radial pump has a housing with a cylinder ring pivotally mounted therein. The cylinder ring has a circular aperture within which a cam surface is formed. A cylinder block rotates within the cylinder ring aperture and has a plurality of radially extending cylinders each having port which selectively communicates with a fluid inlet and a fluid outlet as the cylinder block rotates. A plurality of pistons is slideably received within the cylinders and engages the cam surface. The movement of the pistons within the cylinders is directly related to the magnitude of fluid flow delivered by the pump and moving the cylinder ring thereby controls the fluid flow.

What is claimed is: 
     
         1 . A variable displacement pump comprising: a removable cassette assembly, fitted to a fitting hole within a pump casing so as to be movable and displaceable, forming a pump chamber with respect to an outer peripheral portion of the rotor: said cassette brought into slidable contact with one side of the casing: a high pressure chamber formed at a position facing to a discharge region of the pump chamber between a back surface of the pump casing; a low pressure chamber formed at a position facing a suction region of the pump chamber, and communicating with the suction region of the pump chamber; and at least two annular seal members, wherein the cassette is provided with a tapered head at a first end and a check valve at a second end. 
     
     
         2 . A variable displacement pump as claimed in  claim 1 , wherein the high pressure chamber and the low pressure chamber are provided in a tapered manner in the pump housing of the pump casing. 
     
     
         3 . A variable displacement pump as claimed in  claim 1 , wherein the low pressure chamber is communicated with the suction region of the pump chamber via a communication surface of the tapered head of the cassette, pierced in the pump housing, and a lubricating fluid return path returning a fluid from a portion around the bearing of the pump shaft to the suction passage. 
     
     
         4 . A variable displacement pump as claimed in  claim 2 , wherein the annular seal member is constituted by an O-ring.