Controlled pumping system

• US 4,089,624 A
• Filed: 06/04/1976
• Issued: 05/16/1978
• Est. Priority Date: 06/04/1976
• Status: Expired due to Term

• Current Assignee: Becton, Dickinson & Co
• Original Assignee: Becton, Dickinson & Co
• Inventors: Watts, Paul Jene, Nichols, Philip Thorbus
• Primary Examiner(s): Husar, C. J.
• Application Number:
  US05/692,897
• Time in Patent Office: 711 Days
• Field of Search: 417/419, 417/417, 417/415, 417/362, 74/22 A, 74/89.15, 74/424.8 R, 128/218 A, 128/218 P, 128/236, 128/214 F, 128/DIG. 1
• US Class Current: 417/362
• CPC Class Codes: B01L 3/0206 of the plunger pump type
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 53/164 Stoffing boxes
• CPC Class Codes: F04B 7/0007 and having a rotating movement
• CPC Class Codes: F04B 9/02 the means being mechanical
• CPC Class Codes: Y10T 74/18616 Single input, plural outputs
• CPC Class Codes: Y10T 74/18688 Limit stop

Abstract

A pumping system for dispensing controlled and variable amounts of fluids in predetermined quantities includes a pump piston which moves axially in a pump chamber. The piston is reciprocated by a drive lead nut cooperating with a non-rotatable lead screw attached to the piston. The piston is sealed to the pump chamber by a seal element whose distance from the lead nut is fixed regardless of the position of the piston, thus protecting the seal. The rotatably driven lead nut includes a hollow driven shaft, containing lubricant, so that the lead screw is lubricated as it travels into the shaft of the lead nut. The motor for the system is a pulse operated reversible stepping motor enabling accurate output from the pump, for example, between .01 ml/min to 9.99 ml/min as controlled by the stepping motor. One motor may drive two pumps for a continuous controlled pumping system. If desired a flush mechanism may be used to rinse the piston of any pumped material which adheres to the surface.

Claims

1. A pumping system for dispensing controlled variable amounts of pumpable material comprising:

means forming a support housing,

a pump cylinder assembly mounted on said housing and including pump cylinder means forming a pump chamber, said pump cylinder assembly including inlet and outlet means for the material being pumped,

a pump piston and lead screw assembly mounted on said support housing for generally axial movement of the pump piston into and out of said pump chamber,

driven nut means rotatably mounted in said support housing and receiving said lead screw,

stationary seal means positioned at one end of said pump cylinder assembly and forming a fluid tight seal between said piston and pump cylinder means preventing leakage between said piston and pump chamber,

said seal means being a distance from said drive nut which remains fixed during movement of said pump piston whereby the geometry between the seal means and said pump piston is maintained the same during movement of said pump piston relative to said seal means,

said pump piston including an outer peripheral surface spaced from the opposing surface of said pump chamber and movable in sealing contact relative to said stationary seal means,

means mounted on said pump piston and lead screw assembly to prevent rotation thereof, and

motor means connected to effect rotation of said driven nut means whereby said pump piston is reciprocated relative to said pump cylinder assembly for pumping and filling said pump chamber.

2. A pumping system as set forth in claim 1 wherein said driven nut includes a hollow shaft,

said pump cylinder assembly being spaced from said driven nut,

said lead screw being moved in axial reciprocating manner into and out of said hollow shaft by said driven nut, and

lubricant contained within said hollow shaft for lubricating said lead screw.

3. A pumping system as set forth in claim 1 further including valve means mounted for fluid communication with said inlet and outlet means for controlling flow of fluid into and out of said pump chamber.

4. A pumping system as set forth in claim 1 wherein said motor is a pulse operated reversible stepping motor.

5. A pump system as set forth in claim 1 wherein said seal means includes a pair of seals spaced axially,

means forming a flushing chamber between said seals and surrounding said pump piston, and

means to circulate flushing fluid into said flushing chamber.

6. A pump system as set forth in claim 1 wherein said pump piston is a floating piston supported by said drive nut and by said seal means.

7. A pump system as set forth in claim 4 including means to effect reversal of motor rotation as said piston reaches a predetermined position within said chamber.

8. A pump for dispensing controlled variable amounts of a pumpable material comprising:

a generally cylindrical pump housing having a pump base affixed at one end thereof and a cylinder assembly at the other end thereof,

said cylinder assembly including a pump chamber and means forming an inlet and an outlet for said chamber,

rotatable and axially fixed drive shaft means positioned within said pump base and including one end extending out of said pump base,

bearing means mounted in said pump base to support said drive shaft in rotating relation relative to said housing,

axially fixed drive nut means mounted on said drive shaft for rotation therewith,

lead screw means mounted for axial movement by said drive nut,

cylindrical pump piston means mounted for axial movement with said lead screw and movable axially into and out of said chamber to fill and discharge fluid therein,

stationary seal means mounted in said cylinder assembly and in sealing relation with said piston to prevent leakage between said piston and said pump chamber,

said piston being cylindrical and having an outer peripheral surface spaced from the opposing surface of said chamber and movable in sealing relation to said stationary seal means,

said seal means being a distance from said drive nut which remains fixed during movement of said piston whereby the geometry between said seal means and said piston is maintained the same during movement of said piston relative to said seal means, and

means to prevent rotation of said lead screw and said piston.

9. A pump as set forth in claim 8 wherein said drive shaft is hollow,

said lead nut being mounted over the open end thereof,

lubricant positioned within the hollow shaft and operative to lubricate said lead screw as the latter is driven into and out of said hollow shaft by said driven nut.

10. A pump as set forth in claim 8 wherein said seal means includes axially spaced seals each in sealing relation with said pump piston.

means forming a rinse chamber surrounding said piston and between said seals, and

means to circulate rinsing fluid into and out of said rinse chamber to remove material on the center surface of said piston as the latter passes through said rinse chamber.