Syringe pumps

• US 6,551,277 B1
• Filed: 06/29/2000
• Issued: 04/22/2003
• Est. Priority Date: 07/03/1999
• Status: Expired due to Term

• Current Assignee: Smiths Group plc (Smiths Group International Holdings Ltd.)
• Original Assignee: Smiths Group plc (Smiths Group International Holdings Ltd.)
• Inventors: Ford, Andrew John
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): Trieu, Theresa
• Application Number:
  US09/605,870
• Time in Patent Office: 1,027 Days
• Field of Search: 604/131, 604/151, 604/154, 604/155, 604/152, 604/153, 128/218, 340/540, 606/154, 600/561
• US Class Current: 604/131
• 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
• CPC Class Codes: A61M 5/16854 by monitoring line pressure

Abstract

A syringe pump has a plunger head retainer with two retainer arms mounted on shafts extending parallel to the syringe axis. Each shaft carries a gear, which is engaged by common gear wheel mounted on a threaded shaft. Initially, the shaft is rotated to displaces the gear and hence the retainer arms axially forwardly, and thereafter swing the retainer arms outwardly to an open position. After the syringe has been loaded in the pump, the plunger head retainer is driven forwards until a pad coupled with a force sensor detects contact with the head. This causes the retainer arms to be swung in across the forward side of the plunger head and to be pulled rearwardly against the plunger head. The pump then reduces the force applied by the retainer arms to ensure that the force sensor can respond to force on the plunger during expulsion of liquid from the syringe.

Claims

1. A syringe pump adapted to receive a syringe of the kind having a plunger movable along a barrel, the pump comprising:

a location for said syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism, said retainer mechanism including a pad member and a force sensor, said force sensor coupling said pad member with said retainer mechanism, wherein said pad member is adapted to engage a rear surface of a head of the plunger such that a forwardly-directed force is applied to the plunger via the pad member and such that said force sensor is responsive to force exerted on the plunger head by the retainer mechanism during displacement of the plunger.

2. A syringe pump adapted to receive a syringe of the kind having a plunger movable along a barrel, the pump comprising;

a location for said syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism,

said retainer mechanism including a forwardly-facing surface adapted to engage a rear surface of a head of the plunger and to apply a forwardly-directed force to the plunger,

wherein the plunger head retainer mechanism includes a force sensor responsive to force exerted on the plunger head by the retainer mechanism during displacement of the plunger,

wherein the retainer mechanism is arranged to pull the plunger head initially rearwardly relative to the retainer mechanism, thereby increasing force on said sensor, and is arranged subsequently to relieve the force on said sensor.

3. A syringe pump adapted to receive a syringe of the kind having a plunger movable along a barrel, the pump comprising:

a location for the syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism,

said retainer mechanism having a forwardly-facing surface adapted to engage a rear surface of a head of the plunger and apply a forwardly-directed force to the plunger, a force sensor coupled with said forwardly-facing surface, and at least one retainer member that is movable both laterally and axially so as to be displaceable laterally across a front surface of the plunger head and displaceable by the drive mechanism axially rearwardly relative to the retainer mechanism against a front surface of the plunger head.

4. A syringe pump according to claim 3, wherein the force sensor is provided by a strain beam supporting a pad exposed on said forwardly-facing surface.

5. A syringe pump according to claim 4, wherein the retainer mechanism includes a spring arranged to urge the pad forwardly.

6. A syringe pump according to claim 3, wherein said retainer mechanism is operable such that the retainer member is initially displaced axially rearwardly relative to the retainer mechanism to apply force between a rear surface of said plunger head and said forwardly-facing surface, and wherein the retainer mechanism is subsequently displaced axially forwardly a small distance to reduce said force.

7. A syringe pump according to claim 3, wherein said retainer mechanism includes two said retainer members located on laterally opposite sides of said plunger.

8. A syringe pump according to claim 3, wherein said retainer mechanism includes an electric motor coupled with said retainer member.

9. A syringe pump according to claim 3 including a position sensor arranged to detect a limit of movement of said retainer member.

10. A syringe pump adapted to receive a syringe of the kind having a plunger movable along a barrel, the pump comprising:

a location for the syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism,

said retainer mechanism having a forwardly-facing surface adapted to engage a rear surface of a head of the plunger and apply a forwardly-directed force to the plunger, and at least one retainer member that is movable both laterally and axially so that it can be displaced laterally across the front surface of the plunger head and can be displaced axially rearwardly relative to the retainer mechanism against a front surface of the plunger head,

wherein the retainer member includes an arm extending from a shaft, and wherein said shaft extends parallel with an axis of the syringe, such that the arm can be displaced laterally by rotating it about the shaft.

11. A syringe pump according to claim 10, wherein the arm is displaced axially by moving the shaft along its axis.

12. A syringe pump according to claim 10, wherein the retainer mechanism includes a gear assembly coupled with said shaft, said gear assembly including a rotatable, threaded shaft and a gear wheel threaded on said threaded shaft such that rotation of said threaded shaft initially moves the gear wheel along said threaded shaft to its end and thereafter continued rotation of said threaded shaft rotates the gear wheel.

13. A syringe pump according to claim 12, wherein the said shaft of said retainer member carries a gear, and wherein said gear assembly and the said gear on said shaft have cooperating flange and channel formations.

14. A syringe pump adapted to receive a syringe of the kind having a plunger movable along a barrel, the pump comprising:

a location for said syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism, said retainer mechanism including two arms, a motor coupled with said arms and operable to swing the arms across a rear surface of a head of the plunger and to pull the arms rearwardly relative to the mechanism, a pad member and a force sensor, said force sensor coupling said pad member with said retainer mechanism, wherein said pad member is located to engage a rear surface of a head of the plunger when said arms are pulled rearwardly, and wherein said force sensor is responsive to force exerted on the plunger head by the retainer mechanism during displacement of the plunger such that the force sensor is responsive to any obstruction to displacement of the plunger.

15. A method of loading a syringe in a syringe pump comprising:

locating a syringe on the pump with a plunger head retainer in a rear position and with a retainer member on the plunger head retainer in an open position;

displacing the plunger head retainer forwardly until it contacts a rear surface of a plunger head of the syringe;

in response to an output from a force sensor in contact with the plunger head, displacing the retainer member initially to a closed position forwardly of a forward surface of the plunger head; and

thereafter, displacing the retainer member to a rear position in contact with the forward surface of the plunger head.

16. A method of loading a syringe in a syringe pump comprising the steps of:

displacing a plunger head retainer to a rear position;

operating a motor in the plunger head retainer in one sense to locate a retainer member radially outwardly and axially forwardly;

locating a syringe on the pump;

displacing the plunger head retainer forwardly until it contacts a rear surface of a head of a plunger of the syringe;

rotating said motor in an opposite sense such that the retainer member moves initially to a closed position forwardly of a forward surface of the plunger head and thereafter to a rear position in contact with the forward surface of the forward surface of the plunger head.

17. A method of operating a syringe pump, comprising:

locating a syringe on the pump with a plunger head retainer in a rear position;

displacing the plunger head retainer forwardly until it contacts a rear surface of a plunger head of the syringe;

retaining a head of a plunger of the syringe with the plunger head retainer to prevent forward displacement of the plunger head relative to the retainer but allowing continued monitoring of force applied between the plunger head and the retainer;

advancing the retainer to move the plunger forward and dispense contents of the syringe; and

monitoring the force applied between the plunger head retainer and the plunger head while advancing the retainer to move the plunger forward and dispense contents of the syringe.

18. A syringe pump adapted to receive a syringe of the kind having a plunger movable long a barrel, the pump comprising:

a location for said syringe;

a syringe drive mechanism; and

a plunger head retainer mechanism,

said retainer mechanism including a pad member and a force sensor,

said force sensor coupling said pad member with said retainer mechanism,

wherein said pad member is adapted to engage a rear surface of ahead of the plunger such that a forwardly-directed force is applied to the plunger via the pad member and such that said force sensor is responsive to force exerted on the plunger head by the retainer mechanism during displacement of the plunger,

wherein the retainer mechanism is arranged to pull the plunger head initially rearwardly relative to the retainer mechanism, thereby increasing force on said sensor, and is arranged subsequently to relieve the force on said sensor.