Stroke adjustment mechanism for reciprocating pumps

Abstract

A stroke adjustment mechanism having fewer parts that are easier to manufacture. In order to translate stroke adjustment into an eccentric offset of a rotating shaft to act as a rotating cam surface, the present invention utilizes two separate and identical plungers. The plungers are easier to manufacture as they do not require complex machining in mating parts. The present invention is also easier to assemble than prior designs. The present invention allows the drive gear to be produced with a simple round ID bore and also uses a one-piece, easy to machine round shaft. This provides for a simple and strong design.

1 . A stroke adjustment mechanism for a reciprocating pump, the stroke adjustment mechanism, comprising:
 a first plunger;   a cam operatively associated with the plunger, the cam having a central opening surrounded by inside walls;   a shaft disposed through the opening in the cam, the shaft having a cavity and having a pair of openings disposed in communication with the cavity, the shaft rotating about a fixed axis;   a sliding member disposed in the cavity and capable of movement relative to the shaft, the sliding member having a pair of angled surfaces;   a pair of second plungers disposed through the openings in the shaft and extending between the inside wall of the cam and the angled surface on the sliding member; and,   an adjustment shaft connected to an end of the sliding member, the adjustment shaft connected to the sliding member such that the sliding member is capable of rotating with respect to the adjustment shaft, the adjustment shaft capable of being moved in an axial direction to adjust the position of the sliding member.   
   
   
       2 . The stroke adjustment mechanism of  claim 1 , wherein each of the second plungers has an angled surface. 
   
   
       3 . The stroke adjustment mechanism of  claim 1 , further comprising a knob connected to the adjustment shaft. 
   
   
       4 . The stroke adjustment mechanism of  claim 3 , wherein the adjustment shaft has threads capable of engaging with threads on a housing such that rotation of the cap produces adjustable axial motion of the adjustment shaft. 
   
   
       5 . The stroke adjustment mechanism of  claim 1 , wherein the angled surfaces on the sliding member are disposed on opposite sides. 
   
   
       6 . The stroke adjustment mechanism of  claim 1 , wherein the first plunger is spring biased into engagement with the cam. 
   
   
       7 . The stroke adjustment mechanism of  claim 1 , wherein the cam rotates eccentrically about the shaft. 
   
   
       8 . The stroke adjustment mechanism of  claim 1 , wherein each of the pair of second plungers is substantially identical. 
   
   
       9 . A stroke adjustment mechanism for a reciprocating pump having a diaphragm, the stroke adjustment mechanism, comprising:
 a first plunger connected to the diaphragm;   a cam spring biased into engagement with the plunger, the cam having a central opening surrounded by inside walls;   a shaft disposed through the opening in the cam, the shaft having a cavity and having a pair of openings disposed in communication with the cavity, the shaft rotating about a fixed axis;   a sliding member disposed in the cavity and capable of movement relative to the shaft, the sliding member having a pair of angled surfaces;   a pair of second plungers with each having a first end with a substantially flat surface and having a second end with an angled surface, the plungers disposed through the openings in the shaft and extending between the inside wall of the cam and the angled surface on the sliding member; and,   an adjustment shaft connected to an end of the sliding member, the adjustment shaft connected to the sliding member such that the sliding member is capable of rotating with respect to the adjustment shaft, the adjustment shaft capable of being moved in an axial direction to adjust the position of the sliding member; and,   wherein movement of the adjustment shaft in the axial direction causes the sliding member to move in the axial direction, the axial movement of the sliding member causing the second plungers to move in equal and opposite directions substantially perpendicular to the axial direction such that the position of the cam relative to the shaft is adjusted for eccentric rotation.   
   
   
       10 . The stroke adjustment mechanism of  claim 9 , further comprising a knob connected to the adjustment shaft. 
   
   
       11 . The stroke adjustment mechanism of  claim 10 , wherein the adjustment shaft has threads capable of engaging with threads on a housing such that rotation of the cap produces adjustable axial motion of the adjustment shaft. 
   
   
       12 . The stroke adjustment mechanism of  claim 9 , wherein the angled surfaces on the sliding member are disposed on opposite sides. 
   
   
       13 . The stroke adjustment mechanism of  claim 9 , wherein each of the pair of second plungers is substantially identical. 
   
   
       14 . A shaft assembly for a stroke adjustment mechanism, the shaft assembly comprising:
 a unitary body having a first end, a second end, a cavity, and a pair of openings in communication with the cavity;   a sliding member having a first end and a second end, the sliding member disposed in the body and capable of moving axially relative thereto, the sliding member having a pair of angled surfaces;   a pair of plungers having a first end and a second end with an angled surface opposite the first end, the plungers disposed through the openings in the body such that the angled surface on the second ends of the plungers engages with the angled surfaces on the sliding member; and,   an adjustment shaft connected to the first end of the sliding member such that the sliding member is capable of rotating with respect to the adjustment shaft, the adjustment shaft capable of being moved in an axial direction to adjust the position of the sliding member.   
   
   
       15 . The shaft assembly of  claim 14 , further comprising a knob connected to the adjustment shaft. 
   
   
       16 . The shaft assembly of  claim 14 , wherein the adjustment shaft has threads capable of engaging with threads on a housing such that rotation of the cap produces adjustable axial motion of the adjustment shaft. 
   
   
       17 . The shaft assembly of  claim 14 , wherein the angled surfaces on the sliding member are disposed on opposite sides. 
   
   
       18 . The shaft assembly of  claim 14 , wherein each of the pair of plungers is substantially identical. 
   
   
       19 . The shaft assembly of  claim 14  further comprising a cam having a central opening for receiving the shaft assembly therethrough. 
   
   
       20 . The shaft assembly of  claim 19 , wherein the shaft rotates in a set of bearings about a fixed axis and movement of the sliding member causes the plungers to adjust the position of the cam in a direction substantially perpendicular to the fixed axis. 
   
   
       21 . The stroke adjustment mechanism of  claim 1 , wherein the shaft has a cylindrical end.