Fluid pump assembly

Abstract

A fluid pump assembly comprising a driven cam and a reciprocating member reciprocal within a bore provided in a pump housing as the cam is driven, in use, to cause pressurisation of fluid within a pump chamber. The pump assembly further comprises an interface between the cam and the reciprocating member, for example in the form of bevelled surfaces of the cam and the reciprocating member, which serve to drive the reciprocating member (i) to translate in a first, axial direction within the bore and (ii) to rotate within the bore in a second, rotational direction. An optional feature of the fluid pump assembly is that the pump housing defines a bearing for the cam which is provided with a recess to define a region of weakness to allow the bearing to deflect, in use, thereby to provide an increased lubrication volume between the cam and the bearing. The reciprocating member may take the form of a tappet which cooperates with a pumping plunger to pressurise fluid within the pump chamber.

1 . A fluid pump assembly comprising:
 a driven cam;   a reciprocating member reciprocal within a bore provided in a pump housing as the cam is driven, in use, to cause pressurisation of fluid within a pump chamber; and   an interface between the cam and the reciprocating member which cause the reciprocating member (i) to translate in a first, axial direction within the bore and (ii) to rotate within the bore in a second, rotational direction, as the cam is driven.   
     
     
         2 . A fluid pump assembly as claimed in  claim 1 , wherein the reciprocating member is caused to rotate about its own axis. 
     
     
         3 . A fluid pump assembly as claimed in  claim 1 , wherein the reciprocating member is an intermediate drive member which is cooperable with a pumping plunger to cause pressurisation of fluid within the pump chamber as the pumping plunger is driven by the intermediate drive member. 
     
     
         4 . A fluid pump assembly as claimed in  claim 1 , wherein the reciprocating member is a pumping plunger which interfaces directly with the cam. 
     
     
         5 . A fluid pump assembly as claimed in  claim 1 , wherein the reciprocating member rotates at substantially the same angular velocity as the cam. 
     
     
         6 . A fluid pump assembly as claimed in  claim 1 , wherein the interface includes a bevelled face of the reciprocating member and a correspondingly bevelled face of the cam which cooperate so as to impart axial and rotational motion to the reciprocating member as the cam rotates. 
     
     
         7 . A fluid pump assembly as claimed in  claim 1 , further comprising (i) an axial bearing for the cam defined by an axially-facing internal surface of the pump housing and/or (ii) a radial bearing for the cam defined by a radially-facing internal surface of the pump housing. 
     
     
         8 . A fluid pump assembly as claimed in  claim 7 , further comprising a coating applied to the surface of the cam which deforms, in use, to the profile of the radial bearing. 
     
     
         9 . A fluid pump assembly as claimed in  claim 7 , wherein the axial bearing is provided with at least one recess to provide a volume for receiving lubricating fluid. 
     
     
         10 . A fluid pump assembly as claimed in  claim 7 , wherein the axial bearing includes an un-recessed area which defines a load bearing surface for the cam. 
     
     
         11 . A fluid pump assembly as claimed in  claim 7 , wherein the axial bearing is provided with a region of weakness to allow the axial bearing to deflect, in use, thereby to encourage lubricating fluid to be drawn between the axial bearing and the cam as it rotates. 
     
     
         12 . A fluid pump assembly as claimed in  claim 11 , wherein the region of weakness is defined by a recess formed in the axial bearing. 
     
     
         13 . A fluid pump assembly as claimed in  claim 7 , wherein the axial bearing is provided with a cut-away section to define a lead-in edge for lubricant drawn between the axial bearing and the cam as it rotates. 
     
     
         14 . A fluid pump assembly as claimed in  claim 1 , wherein either the pump chambers are defined within the pump housing and are closed by a plate mounted to the pump housing, or wherein the pump chambers are defined entirely within the pump housing. 
     
     
         15 . A fluid pump assembly as claimed in  claim 1 , wherein an output end of the drive shaft extends rearward of the cam and acts against a bearing defined by the pump housing so as to counter side loads applied to an input end of the drive shaft. 
     
     
         16 . A fluid pump assembly comprising:
 a driven cam; and   a reciprocating member reciprocal within a bore provided in a pump housing as the cam is driven, in use, to cause pressurisation of fluid within a pump chamber;   wherein the reciprocating member includes a bevelled face which cooperates with a correspondingly bevelled face of the cam so as to impart drive to the reciprocating member as the cam rotates.   
     
     
         17 . A fluid pump assembly as claimed in  claim 16 , wherein the reciprocating member is a tappet which is cooperable with a pumping plunger. 
     
     
         18 . A fluid pump assembly as claimed in  claim 16 , wherein the reciprocating member is a pumping plunger which interfaces directly with the cam. 
     
     
         19 . A fluid pump assembly comprising:
 a driven cam; and   a reciprocating member reciprocal within a bore provided in a pump housing as the cam is driven, in use, to cause pressurisation of fluid within a pump chamber;   wherein the pump housing defines a bearing for the cam which is provided with a region of weakness to allow the bearing to deflect, in use, thereby to provide an increased lubrication volume between the cam and the bearing.   
     
     
         20 . A fluid pump assembly as claimed in  claim 19 , wherein the bearing is provided with a recess to define the region of weakness.