Fluid pump

Abstract

A pump for fluid, comprising a pump body defining a bore, a pumping plunger having an end region which is slidably received within the bore, a spill port defined by the pump body in a wall of the bore which port is coverable by the end region of the pumping plunger as the plunger is driven on a pumping stroke, in use, so as to initiate fluid pressurization within a pumping chamber; and a spill feature defined by the pumping plunger being arranged to uncover the spill port during a pumping stroke so as to cause depressurization of the pumping chamber. The pumping plunger further defines a speed sensitive feature configured to permit a controlled leak of fluid from the pumping chamber to the spill port towards the end of a pumping stoke. The invention also encompasses a pumping plunger particularly suited for use in the above described pump.

1 . A pump for fluid, comprising:
 a pump body defining a bore, and a pumping plunger having an end region which is slidably received within the bore;   a spill port defined by the pump body in a wall of the bore which port is coverable by the end region of the pumping plunger as the plunger is driven on a pumping stroke, in use, so as to initiate fluid pressurization within a pumping chamber; and   a spill groove defined by the pumping plunger being arranged to uncover the spill port during a pumping stroke so as to cause depressurization of the pumping chamber;   wherein the pumping plunger further defines a speed sensitive feature configured to permit a controlled leak of fluid from the pumping chamber to the spill port towards the end of a pumping stoke, the leak rate being dependent on the speed of operation of the pump.   
   
   
       2 . The pump of  claim 1 , wherein the spill groove extends around a portion of the outer surface of the pumping plunger at an angle to the longitudinal axis of the pumping plunger. 
   
   
       3 . The pump of  claim 1 , wherein the speed sensitive feature is adapted to be effective during a rated load operating condition of the pump. 
   
   
       4 . The pump of  claim 1 , wherein the pumping plunger has a range of angular movement and the speed sensitive feature is effective in approximately the last 20 percent of the range of angular movement. 
   
   
       5 . The pump of  claim 1 , wherein the speed sensitive feature is a groove disposed in the surface of the pumping plunger in advance of the spill groove and in communication therewith and extends away from the spill groove in a direction to define an angle to the longitudinal axis of the pumping plunger. 
   
   
       6 . The pump of  claim 5 , wherein the speed sensitive groove has a depth in the range of 30 to 60 micrometres. 
   
   
       7 . The pump of  claim 5 , wherein the speed sensitive groove has a width in the range of 0.3 to 1.0 millimetres. 
   
   
       8 . A pumping plunger for a fluid pump, comprising an elongate rod defining an end face and a side surface, the pumping plunger including a spill groove provided in the side surface of the plunger which defines an angle with a longitudinal axis of the plunger, and a speed sensitive feature in communication with the spill groove and configured to permit a controlled flow of fluid therethrough, in use, at an end of a pumping stroke of the plunger, the leak rate being dependent on the speed of operation of the fluid pump. 
   
   
       9 . The pumping plunger of  claim 8 , wherein the spill groove extends around a portion of the outer surface of the pumping plunger at an angle to the longitudinal axis of the pumping plunger. 
   
   
       10 . The pumping plunger of  claim 8 , wherein the speed sensitive feature is adapted to be effective during a rated load operating condition of the pump. 
   
   
       11 . The pumping plunger of  claim 8 , wherein the pumping plunger has a range of angular movement and the speed sensitive feature is adapted to be effective in approximately the last 20 percent of the range of rotation. 
   
   
       12 . The pumping plunger  claim 8 , wherein the speed sensitive feature is a groove that is disposed in the surface of the pumping plunger in advance of the spill groove and in communication therewith and extends away from the spill groove in a direction to define an angle to the longitudinal axis of the pumping plunger. 
   
   
       13 . The pumping plunger of  claim 12 , wherein the angle is between approximately 70 and 110 degrees. 
   
   
       14 . The pumping plunger of  claim 12 , wherein the speed sensitive groove extends away from the spill groove in a direction substantially perpendicular to the longitudinal axis of the pumping plunger. 
   
   
       15 . The pumping plunger of  claim 10 , wherein the speed sensitive groove has a depth in the range of 30 to 60 micrometres. 
   
   
       16 . The pumping plunger of  claim 10 , wherein the speed sensitive groove has a width in the range of 0.3 to 1.0 millimetres. 
   
   
       17 . A pump for fluid, comprising:
 a pump body defining a bore, and a pumping plunger having an end region which is slidably received within the bore;   a spill port defined by the pump body in a wall of the bore which port is coverable by the end region of the pumping plunger as the plunger is driven on a pumping stroke, in use, so as to initiate fluid pressurization within a pumping chamber; and   a spill groove defined by the pumping plunger, the spill groove extending around a portion of the outer surface of the pumping plunger at an angle to the longitudinal axis of the pumping plunger and being arranged to uncover the spill port during a pumping stroke so as to cause depressurization of the pumping chamber;   wherein the pumping plunger further defines a speed sensitive feature that is configured to permit a controlled leak of fluid from the pumping chamber to the spill port towards the end of a pumping stoke, wherein the speed sensitive feature is adapted to be effective during a rated load operating condition of the pump and such that the leak rate is dependent on the speed of operation of the pump.   
   
   
       18 . The pump of  claim 17 , wherein the pumping plunger has a range of angular movement and the speed sensitive feature is effective in approximately the last 20 percent of the range of angular movement. 
   
   
       19 . The pump of  claim 17 , wherein the speed sensitive feature is a groove disposed in the surface of the pumping plunger in advance of the spill groove and in communication therewith and extends away from the spill groove in a direction to define an angle to the longitudinal axis of the pumping plunger.