Hydraulic syringe drive

• US 4,437,859 A
• Filed: 08/03/1981
• Issued: 03/20/1984
• Est. Priority Date: 08/03/1981
• Status: Expired due to Fees

• Current Assignee: DRS Infusion Systems Incorporated
• Original Assignee: DRS Infusion Systems Incorporated
• Inventors: Burt, Allan G., Cox, Nigel, Whitehouse, Craig M., Snyder, Daniel R.
• Primary Examiner(s): Yasko, John D.
• Application Number:
  US06/287,861
• Time in Patent Office: 960 Days
• Field of Search: 604/131, 604/93, 604/141, 604/142, 604/143, 604/150, 604/149, 604/218, 604/236, 604/237, 604/152
• US Class Current: 604/131
• CPC Class Codes: A61M 2005/14264 with means for compensating influence from the environment
• CPC Class Codes: A61M 2005/14506 mechanically driven, e.g. spring or clockwork
• CPC Class Codes: A61M 2005/14513 with secondary fluid driving or regulating the infusion
• CPC Class Codes: A61M 5/14526 the piston being actuated by fluid pressure
• CPC Class Codes: A61M 5/1456 with a replaceable reservoir comprising a piston rod to be moved into the reservoir, e.g. the piston rod is part of the removable reservoir

Abstract

A syringe driving unit comprising free pistons in interconnected cylindrical chambers, one of the pistons carrying a syringe plunger driver and being biased, directly or indirectly, in the driving direction, and one piston being movable to force both pistons into primed or loaded position, the connections between the chambers including a pressure regulator, flow regulator and a needle valve to regulate adjustably the return flow or hydraulic fluid corresponding to the movement of the driving piston. The priming piston may be moved mechanically or pneumatically, and fail-safe mechanism may be provided, if needed, to become effective in case of leakage. Bolus delivery, to augment optionally the adjusted flow, is also provided for.

Claims

1. An automatic drive for a hypodermic syringe having a barrel for containing a fluid medicament and a plunger adapted to eject said medicament, the drive comprising a housing, means in said housing for supporting a syringe in operative position, first and second variable volume chambers each having a movable wall element, a conduit interconnecting said chambers to constitute a constant voluem capacity, a substantially incompressible fluid filling said capacity, means associated with the first chamber for forcing fluid contained therein into the second chamber, a syringe driver associated with one of the movable wall elements and operatively engageable with the syringe plunger, means biasing the movable wall element of the second chamber in a fluid-expelling direction, adjustable means associated with the conduit for accurate metering of the fluid flow from the second chamber to the first chamber, said adjustable means automatically operative to adjust the fluid flow during the operation of said automatic drive to maintain said fluid flow constant responsive to ambient pressure and to pressure changes upstream and downstream of said adjustable means.

2. An automatic syringe drive according to claim 1 which includes a one-way check valve between the first and second chambers.

3. An automatic syringe drive according to claim 1 or 2 wherein the flow metering means includes an adjustable needle valve.

4. An automatic syringe drive according to claim 3 wherein the flow metering means includes an adjustable constant pressure regulator.

5. An automatic syringe drive according to claim 1 or 2 wherein the flow metering means includes an adjustable flow regulator.

6. An automatic syringe drive according to claim 3 which includes manually actuated means for controllably bypassing at least a portion of the flow metering means.

7. An automatic syringe drive according to claim 1 which includes a fail-safe device adapted to arrest the movement of the syringe driver upon the occurrence of leakage of fluid from the constant volume capacity.

8. An automatic syringe drive according to claim 7 wherein the fail-safe device comprises a rack fixed to the housing, a latch element movable with the syringe driver along a path adjacent the rack and shielding means operable to prevent engagement of the latch element with the rack during normal operation and permit such engagement upon the occurrence of a movement of the second chamber wall element without movement of the first chamber wall element.

9. An automatic syringe drive according to claim 1 wherein the syringe driver is associated with the movable wall element of the second chamber.

21. An automatic syringe drive according to claim 1 or 10 wherein the second chamber biasing means is at least one spring.

22. An automatic syringe drive according to claim 1 or 10 wherein the second chamber biasing means is compressed air.

10. An automatic drive for a hypodermic syringe having a barrel for containing a fluid medicament and a plunger adapted to eject said medicament, the drive comprising a housing, means in said housing for supporting a syringe in operative position, first and second cylindrical chambers, each chamber being provided with a movable piston defining a variable volume, a conduit interconnecting said variable volumes to constitute a constant volume capacity, a constant volume of a substantially incompressible fluid filling said capacity, means associated with the first chamber piston for moving said piston to force fluid through the conduit into the second chamber, a syringe drive associated with one of the pistons and operatively engageable with the syringe plunger, means biasing said second chamber piston in a fluid-expelling direction, means associated with the conduit for metering the flow of fluid from the second chamber to the first chamber, said flow metering means automatically operative to adjust the fluid flow during the operation of said automatic drive to control said fluid flow responsive to ambient pressure changes and to pressure changes upstream and downstream of said flow metering means.

11. An automatic syringe drive according to claim 10 which includes a one-way check valve between the first and second chambers.

12. An automatic syringe drive according to claim 10 wherein the flow metering means includes an adjustable needle valve.

13. An automatic syringe drive according to claim 12 wherein the flow metering means includes an adjustable constant pressure regulator.

14. An automatic syringe drive according to claim 12 or 13 wherein the flow metering means includes an adjustable flow regulator.

15. An automatic syringe drive according to claim 12 which includes manually actuated means for optionally bypassing at least a portion of the flow metering means.

16. An automatic syringe drive according to claim 10 wherein the syringe drive is associated with the piston in the first chamber.

17. An automatic syringe drive according to claim 10 wherein the means for moving the first chamber piston to force fluid into the second chamber is a screw.

18. An automatic syringe drive according to claim 10 wherein the means for moving the first chamber piston to force fluid into the second chamber is pneumatic.

19. An automatic syringe drive according to claim 10 wherein cup-shaped diaphragms are associated with each piston.

20. An automatic syringe drive according to claim 10 wherein each piston has a fluid-tight fit in its respective cylinder.

23. An automatic syringe drive according to claim 4 or 13 wherein the regulating pathway is adapted to function independently of ambient pressure and ambient medium.