Dual piston pump assembly with anti-rotation guide rails

Abstract

A dual piston-pump apparatus is provided having a pump chassis that includes a pair of spaced-apart, elongated piston bores, and a lead screw shaft. This shaft includes a motor driven end, and another portion thereof rotatably mounted to the chassis for rotation about a screw rotational axis. A piston drive member threadably cooperates with the lead screw shaft for selective reciprocating movement longitudinally along the screw rotational axis thereof between a first position and a second position. The drive member includes a pair of spaced-apart piston shafts, each piston shaft of which includes a respective piston head slideably received in a respective piston bore of the chassis. As the drive member is driven along the screw shaft between the first position and the second position, each piston head is simultaneously reciprocated between a dispensing condition and an aspiration condition. An anti-rotation device cooperates between the pump chassis and the drive member to substantially prevent rotational displacement of the drive member relative to the pump chassis and about the screw rotational axis during rotational motion of the screw shaft.

1 . A dual piston-pump apparatus comprising:
 a pump chassis assembly having a pair of spaced-apart, elongated piston bores;   a lead screw shaft having a motor driven end, and another portion thereof rotatably mounted to said chassis assembly for rotation about a screw rotational axis;   a piston drive member threadably cooperating with said lead screw shaft for selective reciprocating movement longitudinally along the screw rotational axis thereof between a first position and a second position, said drive member having a pair of spaced-apart piston shafts, each piston shaft having a respective piston head portion slideably received in a respective piston bore of the chassis assembly between a dispensing condition and an aspiration condition as the drive member is driven along the lead screw shaft between the first position and the second position, respectively; and   an anti-rotation device cooperating between the pump chassis assembly and the drive member to substantially prevent rotational displacement of the drive member relative to the pump chassis assembly and about the screw rotational axis during rotational motion of the lead screw shaft.   
   
   
       2 . The dual piston-pump apparatus according to  claim 1 , wherein
 said anti-rotation device includes a rail member coupled to said chassis assembly, and having an elongated contact surface formed and dimensioned for relative sliding contact against an sliding support surface of said drive member during reciprocating movement thereof between the first position and the second position.   
   
   
       3 . The dual piston-pump apparatus according to  claim 2 , wherein
 said rail member includes an upper rail portion upstanding from a floor portion of said chassis assembly, and having opposed sidewalls collectively converging to an apex portion, defining said elongated contact surface.   
   
   
       4 . The dual piston-pump apparatus according to  claim 3 , wherein
 a transverse cross-sectional dimension of said upper rail portion is substantially in the shape of an inverted “U”.   
   
   
       5 . The dual piston-pump apparatus according to  claim 3 , wherein
 said contact surface is substantially linear, and is directionally aligned along the chassis floor portion substantially parallel to the rotational axis of said lead screw shaft.   
   
   
       6 . The dual piston-pump apparatus according to  claim 5 , wherein
 said sliding support surface of said drive member defines an alignment groove configured to slideably receive said upper rail portion during said relative reciprocating movement between the first position and said second position.   
   
   
       7 . The dual piston-pump apparatus according to  claim 5 , wherein
 said rail member including a lower rail portion formed and dimensioned to removably mount to the chassis floor portion.   
   
   
       8 . The dual piston-pump apparatus according to  claim 1 , wherein
 one of the elongated piston bores is oriented on one side of the lead screw shaft, and the other of the elongated piston bore is oriented on the other side of the lead screw shaft, and wherein   one of the piston shafts of the drive member is also oriented on one side of the lead screw shaft, and the other of the piston shafts is oriented on the other side of the lead screw shaft.   
   
   
       9 . The dual piston-pump apparatus according to  claim 8 , wherein
 said piston bores are substantially linear, and are directionally aligned substantially parallel to the rotational axis of said lead screw shaft.   
   
   
       10 . The dual piston-pump apparatus according to  claim 9 , wherein
 said drive member includes a central barrel portion positioned between and adjacent to said pair of piston shafts, said central barrel portion defining a central passage extending therethrough, and formed and dimensioned for relative reciprocating receipt of the lead screw shaft therein.   
   
   
       11 . The dual piston-pump apparatus according to  claim 10 , further including:
 a threaded insert fixedly disposed in the central passage of the central barrel in a manner threadably cooperating with a threaded portion of the lead screw shaft.   
   
   
       12 . The dual piston-pump apparatus according to  claim 10 , wherein
 said anti-rotation device includes a pair of spaced-apart rail members each coupled to said chassis assembly, and disposed on opposite sides of lead screw shaft, each said rail member having a respective elongated contact surface formed and dimensioned for relative sliding contact against respective sliding support surfaces of said drive member during reciprocating movement thereof between the first position and the second position.   
   
   
       13 . The dual piston-pump apparatus according to  claim 12 , wherein
 each said rail member includes a respective upper rail portion upstanding from a floor portion of said chassis assembly, and each defined by opposed sidewalls collectively converging to a respective apex portion, each defining the respective elongated contact surface.   
   
   
       14 . The dual piston-pump apparatus according to  claim 13 , wherein
 a transverse cross-sectional dimension of each said upper rail portion is substantially in the shape of an inverted “U”.   
   
   
       15 . The dual piston-pump apparatus according to  claim 13 , wherein
 each said contact surface is substantially linear, and is directionally aligned along the chassis floor portion substantially parallel to the rotational axis of said lead screw shaft.   
   
   
       16 . The dual piston-pump apparatus according to  claim 13 , wherein
 each said sliding support surface of said drive member defines a respective alignment groove configured to slideably receive a respective upper rail portion during said relative reciprocating movement of the drive member between the first position and said second position.   
   
   
       17 . The dual piston-pump apparatus according to  claim 15 , wherein
 each said rail member further includes a respective lower rail portion formed and dimensioned to removably mount to the chassis floor portion.   
   
   
       18 . The dual piston-pump apparatus according to  claim 11 , further including:
 a first sleeve bearing disposed between said chassis assembly and said lead screw shaft for rotating support thereof, and a second sleeve bearing disposed in said central passage of the barrel portion for sliding rotating support between said central barrel and said lead screw shaft.   
   
   
       19 . The dual piston-pump apparatus according to  claim 18 , wherein
 said threaded insert is disposed at a proximal portion of said central passage of said drive member, while said second sleeve bearing is disposed at a distal portion of said central passage.   
   
   
       20 . The dual piston-pump apparatus according to  claim 1 , further including:
 a first piston barrel defining one piston bore extending therethrough, and a second piston barrel defining the other piston barrel extending therethrough, each said piston barrel being removably mounted to said chassis assembly.   
   
   
       21 . The dual piston-pump apparatus according to  claim 20 , wherein
 each said piston barrel defining a distal opening into a respective piston bore, each said distal opening being sized and dimensioned for reciprocating receipt of the respective piston shaft therein.   
   
   
       22 . The dual piston-pump apparatus according to  claim 21 , wherein
 each said piston barrel includes a support flange disposed at a respective proximal portion thereof, each said support flange being formed and dimensioned for friction fit receipt in a respective alignment slot defined by said chassis assembly.   
   
   
       23 . A dual piston-pump apparatus comprising:
 a pump chassis assembly having a pair of spaced-apart piston barrels, each defining a respective piston bore;   a lead screw shaft positioned between said piston barrels, said lead screw shaft having a motor driven end, and mount portion thereof rotatably mounted to said chassis assembly for rotation about a screw rotational axis;   a piston drive member having a central barrel portion threadably cooperating with said lead screw shaft for selective reciprocating movement longitudinally along the screw rotational axis thereof between a first position and a second position, said drive member having a pair of spaced-apart piston shafts on opposed sides of said central barrel portion, each piston shaft having a respective piston head portion slideably received in a respective piston bore of the chassis assembly between a dispensing condition and an aspiration condition as the drive member is driven along the lead screw shaft between the first position and the second position, respectively;   a first sleeve bearing disposed between said chassis assembly and said lead screw shaft for rotating support thereof; and   a second sleeve bearing disposed between said central barrel portion and said lead screw for sliding rotating support thereof during movement of said drive member between said first position and said second position.   
   
   
       24 . The dual piston-pump apparatus according to  claim 23 , wherein
 said central barrel portion defining a central passage extending longitudinally therethrough, and formed and dimensioned for relative reciprocating receipt of the lead screw shaft therein.   
   
   
       25 . The dual piston-pump apparatus according to  claim 24 , further including:
 a threaded insert fixedly disposed in the central passage of the central barrel in a manner threadably cooperating with a threaded portion of the lead screw shaft oriented between the motor driven end and mount portion thereof.   
   
   
       26 . The dual piston-pump apparatus according to  claim 25 , wherein
 said threaded insert is disposed at a proximal portion of said central passage of said drive member, while said second sleeve bearing is disposed at a distal portion of said central passage.   
   
   
       27 . The dual piston-pump apparatus according to  claim 26 , wherein
 each said piston barrel being removably mounted to said chassis assembly.   
   
   
       28 . The dual piston-pump apparatus according to  claim 27 , wherein
 each said piston barrel defining a distal opening into a respective piston bore, each said distal opening being sized and dimensioned for reciprocating receipt of the respective piston shaft therein.   
   
   
       29 . The dual piston-pump apparatus according to  claim 28 , wherein
 each said piston barrel includes an annular support flange disposed at a respective proximal portion thereof, each said support flange being formed and dimensioned for friction fit receipt in a respective alignment slot defined by said chassis assembly.   
   
   
       30 . The dual piston-pump apparatus according to  claim 23 , wherein
 said piston bores are substantially linear, and are directionally aligned substantially parallel to the rotational axis of said lead screw shaft.   
   
   
       31 . The dual piston-pump apparatus according to  claim 23 , further including:
 an anti-rotation device cooperating between the pump chassis assembly and the drive member to substantially prevent rotational displacement of the drive member relative to the pump chassis assembly and about the screw rotational axis during rotational motion of the lead screw shaft.   
   
   
       32 . The dual piston-pump apparatus according to  claim 31 , wherein
 said anti-rotation device includes a pair of spaced-apart rail members each coupled to said chassis assembly, and disposed on opposite sides of lead screw shaft, each said rail member having a respective elongated contact surface formed and dimensioned for relative sliding contact against respective sliding support surfaces of said drive member during reciprocating movement thereof between the first position and the second position.   
   
   
       33 . The dual piston-pump apparatus according to  claim 32 , wherein
 each said rail member includes a respective upper rail portion upstanding from a floor portion of said chassis assembly, each said upper rail portion defined by opposed sidewalls collectively converging to a respective apex portion, each defining the respective elongated contact surface.   
   
   
       34 . The dual piston-pump apparatus according to  claim 33 , wherein
 a transverse cross-sectional dimension of each said upper rail portion is substantially in the shape of an inverted “U”.   
   
   
       35 . The dual piston-pump apparatus according to  claim 33 , wherein
 each said contact surface is substantially linear, and is directionally aligned along the chassis floor portion substantially parallel to the rotational axis of said lead screw shaft.   
   
   
       36 . The dual piston-pump apparatus according to  claim 33 , wherein
 each said sliding support surface of said drive member defines a respective alignment groove configured to slideably receive a respective upper rail portion during said relative reciprocating movement of the drive member between the first position and said second position.   
   
   
       37 . The dual piston-pump apparatus according to  claim 36 , wherein
 each said rail member further includes a respective lower rail portion formed and dimensioned to removably mount to the chassis floor portion.