Variable capacity reciprocating pump

Abstract

A variable reciprocating pump assembly including a driven crank wheel, a crank arm coupled to and driven by the crank wheel the crank arm terminating at a wrist pin, a pump housing, and a piston is disclosed. The assembly may be adjustable to provide varied stroke length and pump capacity without affecting performance or drive properties.

1 . A reciprocating piston pump assembly comprising:
 a driven crank wheel;   a crank arm coupled to and driven by the crank wheel, the crank arm terminating at a wrist pin;   a pump housing defining a pump chamber;   a piston including a plunger provided within the pump chamber and configured to reciprocate along a pumping axis with respect to the pump chamber;   a drive slot formed in one of the piston and the pump housing and configured to guide reciprocal movement of the wrist pin, the drive slot receiving the wrist pin such that the one of the piston and the pump housing having the drive slot is configured to be driven relative to the other one of the piston and the pump housing to drive the reciprocation of the plunger with respect to the pump chamber;   an adjustment member defining a rearward stop engageable by the wrist pin, the adjustment member adjustable to change a rearward limit of the wrist pin within the drive slot,   wherein the drive slot is provided as a variable-length drive slot so that lost motion can be selectively incurred, in accordance with a length of the drive slot, between a motion of the crank arm and a retraction of the plunger with respect to the pump chamber, and wherein variation of the length of the drive slot is configured to change both a stroke length of the plunger reciprocation and the volume of the pump chamber through which the plunger reciprocates so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate at which the crank wheel is driven.   
     
     
         2 . The reciprocating piston pump assembly of  claim 1 , wherein a tail portion of the piston extends rearwardly from the plunger, and wherein the adjustment member is coupled to a rear end of the tail portion of the piston, and has a surface arranged to form a rear end of the drive slot. 
     
     
         3 . The reciprocating piston pump assembly of  claim 2 , wherein the adjustment member is a screw that threads into the rear end of the piston tail portion. 
     
     
         4 . The reciprocating piston pump assembly of  claim 2 , wherein the adjustment member forms a locking interface with the piston tail portion to fix the adjustment member and the piston tail portion to a single, predetermined relative axial positioning. 
     
     
         5 . The reciprocating piston pump assembly according to  claim 1 , further comprising a valving arrangement configured to provide two-stage pumping action between the pump chamber and a secondary pump chamber such that the reciprocating piston pump assembly is configured to discharge fluid in both directions of the plunger reciprocation. 
     
     
         6 . The reciprocating piston pump assembly of  claim 5 , wherein the valving arrangement includes a one-way interstage valve member that is separate from a peripheral seal on the plunger and positioned between the pump chamber and the secondary pump chamber. 
     
     
         7 . The reciprocating piston pump assembly of  claim 5 , wherein the valving arrangement includes a one-way interstage valve member that also acts as a peripheral seal on the plunger, the one-way interstage valve member opening by elastic deflection in the presence of a pressure in the pump chamber that exceeds a pressure in the secondary pump chamber. 
     
     
         8 . The reciprocating piston pump assembly according to  claim 5 , wherein the valving arrangement includes a one-way interstage valve member that also acts as a peripheral seal on the plunger, the one-way interstage valve member provided as a floating peripheral seal that is slidable on the plunger to selectively expose a fluid passage between the pump chamber and the secondary pump chamber in the presence of a pressure in the pump chamber that exceeds a pressure in the secondary pump chamber. 
     
     
         9 . The reciprocating piston pump assembly according to  claim 1 , wherein the pump housing is formed in two separate pieces that cooperate to form the drive slot, a first one of the pump housing pieces forming the pump chamber receiving the plunger and a second one of the pump housing pieces forming a pump chamber receiving a second plunger of the piston, and wherein the reciprocating piston pump assembly further comprises an adjustment member operable to change a spacing distance between the two pump housing pieces. 
     
     
         10 . A reciprocating piston pump assembly comprising:
 a pump housing defining a pump chamber;   a piston including a plunger provided within the pump chamber and configured to reciprocate along a pumping axis with respect to the pump chamber;   a drive slot formed in the piston for receiving a driving input from a drive member extending through the drive slot such that the piston is configured to be driven relative to the pump housing to drive the reciprocation of the plunger with respect to the pump chamber in response to the driving input from the drive member;   a valving arrangement configured to provide two-stage pumping action between the pump chamber and a secondary pump chamber behind the plunger such that the reciprocating piston pump assembly is configured to draw fluid into the pump chamber on a retracting direction of the plunger reciprocation and to discharge fluid from the secondary pump chamber on both the retracting direction and an advancing direction of the plunger reciprocation; and   an adjustment member configured to change both a stroke length of the plunger reciprocation and the volume of the pump chamber through which the plunger reciprocates by altering a length of the drive slot so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate of the driving input.   
     
     
         11 . The reciprocating piston pump assembly of  claim 10 , wherein the valving arrangement includes a one-way interstage valve member that is separate from a peripheral seal on the plunger and positioned between the pump chamber and the secondary pump chamber. 
     
     
         12 . The reciprocating piston pump assembly of  claim 10 , wherein the valving arrangement includes a one-way interstage valve member that also acts as a peripheral seal on the plunger, the one-way interstage valve member opening by elastic deflection in the presence of a pressure in the pump chamber that exceeds a pressure in the secondary pump chamber. 
     
     
         13 . The reciprocating piston pump assembly according to  claim 10 , wherein the valving arrangement includes a one-way interstage valve member that also acts as a peripheral seal on the plunger, the one-way interstage valve member provided as a floating peripheral seal that is slidable on the plunger to selectively expose a fluid passage between the pump chamber and the secondary pump chamber in the presence of a pressure in the pump chamber that exceeds a pressure in the secondary pump chamber. 
     
     
         14 . The reciprocating piston pump assembly according to  claim 10 , wherein the adjustment member provides for lost motion to be incurred in a direction of the retraction of the plunger with respect to the pump chamber, an amount of the lost motion being equal to an amount by which the length of the drive slot, as set by the adjustment member, exceeds a dimension of the drive member providing the driving input. 
     
     
         15 . The reciprocating piston pump assembly according to  claim 10 , wherein the drive member is a wrist pin provided at one end of a crank arm, the reciprocating piston pump assembly further comprising a crank wheel coupled to another end of the crank arm for driving the crank arm in response to rotation of the crank wheel. 
     
     
         16 . The reciprocating piston pump assembly according to  claim 10 , wherein a tail portion of the piston extends rearwardly from the plunger, and the adjustment member is coupled to a rear end of the tail portion of the piston, the adjustment member having a surface arranged to form a rear end of the drive slot. 
     
     
         17 . The reciprocating piston pump assembly of  claim 16 , wherein the adjustment member is a screw that threads into the rear end of the piston tail portion. 
     
     
         18 . The reciprocating piston pump assembly of  claim 16 , wherein the adjustment member forms a locking interface with the piston tail portion to fix the adjustment member and the piston tail portion to a single, predetermined relative axial positioning. 
     
     
         19 . A reciprocating piston pump assembly comprising:
 a first pump housing portion defining a first pump chamber therein, the first pump housing portion configured for reciprocating movement along the pumping axis;   a first plunger positioned along the pumping axis within the first pump chamber to form a first pumping unit with the first pump chamber;   a second pump housing portion defining a second pump chamber therein, the second pump housing portion configured for reciprocating movement with the first pump housing portion along the pumping axis;   a second plunger positioned along the pumping axis within the second pump chamber to form a second pumping unit with the second pump chamber, wherein the second plunger defines an advancing stroke direction in the second pump chamber that is opposite an advancing stroke direction defined by the first plunger in the first pump chamber;   a drive slot formed cooperatively by respective portions of the first and second pump housing portions; and   an adjustment member operable to alter a spacing distance along the pumping axis between the first and second pump chambers to simultaneously alter a plunger stroke distance and a chamber volume for both the first and second pumping units so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate at which the first and second housing portions are reciprocated.   
     
     
         20 . The reciprocating piston pump assembly of  claim 19 , wherein the first and second pumping units have a shared outlet chamber from which fluid is discharged during both of two opposing directions of the reciprocating movement of the first and second pump housing portions.