Reciprocating antirotation pump

Abstract

A pump for pumping discrete liquid volumes is provided with an anti-rotation construction to prevent a nut mated to a rotating head screw from rotating when the lead screw is rotated. The anti-rotation construction comprises a set of rails that slideably fit within a mating set of tracks. The pump also can include a variable homing position for a pump piston having at least two different homing positions.

1 . A pump adapted to deliver a plurality of discrete liquid samples comprising a motor adapted to rotate a shaft including a lead screw clockwise or counter clockwise, a nut mated to said lead screw adapted to reciprocate when said lead screw is rotated, a first housing for said nut having an outside surface provided with either a first set of rails or a first set of tracks, a second set of tracks positioned on a stationary housing positioned to mate with said first set of rails or a second set of rails positioned on said stationary housing to mate with said first set of tracks, a pump piston mounted on said first housing, said first set of tracks or said second set of tracks having a length sufficient to permit said piston to travel a desired distance when said motor is rotated. 
   
   
       2 . The pump of  claim 1  wherein said first housing includes said first set of rails. 
   
   
       3 . The pump of  claim 1  wherein said first housing includes said first set of tracks. 
   
   
       4 . The pump of  claim 3  wherein said second set of tracks are positioned on removable inserts that are attachable to said stationary housing. 
   
   
       5 . The pump of  claim 2  wherein said second set of tracks is positioned on an inner surface of said stationary housing. 
   
   
       6 . A pump adapted to deliver a plurality of discrete liquid samples and having a variable homing position for accepting a visible homing flag in one of at least two positions. 
   
   
       7 . The pump of  claim 6  having two of said positions for said homing flag. 
   
   
       8 . The pump in  claim 2  having an anti-backlash nut feature integrated into the ferrule. 
   
   
       9 . The pump in  claim 2  having two heads actuated by a dual shaft motor with shafts protruding from both sides of the motor.