Magnetic detent and position detector for fluid pump motor

• US 5,482,438 A
• Filed: 03/09/1994
• Issued: 01/09/1996
• Est. Priority Date: 03/09/1994
• Status: Expired due to Fees

• Current Assignee: Baxter International Inc.
• Original Assignee: Baxter International Inc.
• Inventors: Anderson, Robert L., Stracener, Steve W., Castleberry, Jeffrey P.
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): Korytnyk, Peter G.
• Application Number:
  US08/208,343
• Time in Patent Office: 671 Days
• Field of Search: 417/63.1, 417/42, 417/412, 417/44.1, 417/474, 604/153, 178/DIG. 12
• US Class Current: 417/44.1
• CPC Class Codes: A61M 2005/1404 Keep vein-open rate [KVO], i.e. low flow rate
• CPC Class Codes: A61M 39/281 Automatic tube cut-off devices, e.g. squeezing tube on detection of air
• CPC Class Codes: A61M 5/142 Pressure infusion, e.g. using pumps
• CPC Class Codes: A61M 5/16854 by monitoring line pressure

Abstract

A medical infusion pump (10) including an improved electric motor assembly (256). The medical infusion pump (10) includes a pumping mechanism (250) and a pump chamber (132) in an operative position with respect to the pumping mechanism (250), the pumping mechanism (250) manipulating the pump chamber (132) to pump liquid through the pump chamber. An electric motor (256) having a rotatable drive shaft (316) is operably linked to the pump driving mechanism (250) and the pump driving mechanism (250) pumps a select amount of liquid through the pump chamber (132) on each rotation of the electric motor drive shaft (316). The improved electric motor assembly (256) includes a motor having a portion of a drive shaft (388) extending therefrom. A magnet (392) is attached to the extending portion of the drive shaft for rotation with the drive shaft. A flux gatherer (396) is spaced from and magnetically coupled to the magnet (392) for biasing the poles of the magnet in a select orientation relative to the flux gatherer (396) so as to stop the pump driving mechanism (250) in a select position. A magnetic position detector (400) is spaced from and magnetically coupled to the magnet (392) for emitting an electrical signal each rotation of the drive shaft (388).

Claims

1. In a medical infusion pump including a pump driving mechanism and a pump chamber in an operative position with respect to the pump driving mechanism, the pump driving mechanism manipulating the pump chamber to pump liquid through the pump chamber, an electric motor having a rotatable drive shaft operatively linked to the pump driving mechanism and means for driving the electric motor, the pump driving mechanism pumping a select amount of liquid through the pump chamber on each rotation of the electric motor, an improved electric motor assembly comprising:

a motor having a portion of a motor shaft extending therefrom, the motor shall being linked to the electric motor to turn with each revolution of the electric motor;

a magnet, the magnet being attached to the extending portion of the motor shaft for rotation with the motor shaft;

a flux gathering means spaced radially from and magnetically coupled to the magnet for biasing the poles of the magnet in a select orientation relative to the flux gathering means so as to stop the pump driving mechanism in a select position; and

a magnetic position detector means spaced from and magnetically coupled to the magnet for emitting an electric signal each rotation of the motor shaft.

2. The improved electric motor assembly of claim 1 further comprising:

a. ferromagnetic collar encircling the magnet; and

means mounting the magnetic position detector means between an inner surface of the ferromagnetic collar and the magnet.

3. The improved electric motor assembly of claim 2 wherein the flux gathering means comprises an integral protrusion extending inwardly from the inner surface of the ferromagnetic collar.

4. The improved electric motor assembly of claim 2 wherein the mounting means comprises a pair of spaced bosses extending inwardly from the inner surface of the collar, the bosses being spaced to receive the magnetic position detector therebetween.

5. The improved electric motor assembly of claim 1 wherein the magnetic position detector means is a Hall sensor.

6. The improved electric motor assembly of claim 5 wherein the Hall sensor has a planar surface and the flux gathering means is spaced from the planar surface with the magnet between the planar surface and the flux gathering means.

7. The improved electric motor assembly of claim 1 wherein the magnet is cylindrical Neodynium-Yag magnet.

8. A pump driving mechanism for a medical infusion pump, the pump driving mechanism comprising:

a pump chamber;

plunger means operatively associated with the pump chamber for compressing the pump chamber to expel liquid from the pump chamber;

a motor having a rotating drive shaft extending therefrom and a motor shaft extending therefrom, the motor shall rotating with each rotation of the motor;

linking means between the plunger means and the drive shaft for translating rotation of the drive shaft to compression of the pump chamber by the plunger means;

a magnet attached to a portion of the motor shaft extending from the motor for rotation with the motor shaft; and

flux gathering means spaced radially from and magnetically coupled to the magnet for biasing the poles of the magnet in a select orientation relative to the flux gathering means with a select stopping torque to stop the plunger means in a select position, whereby the magnetic couple between the magnet and the flux gathering means prevents movement of the plunger in the absence of a torque on the motor shaft in excess of the select stopping torque.

9. The pump driving mechanism of claim 8 further including a magnetic position detector means spaced from and magnetically coupled to the magnet for emitting an electric signal each rotation of the drive shaft.

10. The pump driving mechanism of claim 9 further comprising:

a ferromagnetic collar encircling the magnet; and

means mounting the magnetic position detector means between an inner surface of the ferromagnetic collar and the magnet.

11. The pump driving mechanism of claim 10 wherein the mounting means comprises a pair of spaced bosses extending inwardly from the inner surface of the collar, the bosses being spaced to receive the magnetic position detector therebetween.

12. The pump driving mechanism of claim 9 wherein the magnetic position detector is a Hall sensor.

13. The pump driving mechanism of claim 8 further comprising a ferromagnetic collar encircling the magnet and the flux gathering means comprises an integral protrusion extending inwardly from the inner surface of the ferromagnetic collar.

14. The pump driving mechanism of claim 8 wherein the Hall sensor has a planar surface and the flux gathering means is spaced from the planar surface of the magnet between the planar surface and the flux gathering means.