Method and device for detecting blocked condition in a tube of a liquid infusion pump

• US 4,976,151 A
• Filed: 03/15/1990
• Issued: 12/11/1990
• Est. Priority Date: 02/17/1987
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Morishita, Masakazu
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US07/494,838
• Time in Patent Office: 271 Days
• Field of Search: 73/730, 73/728, 336/30
• US Class Current: 73/730
• CPC Class Codes: A61M 5/16854 by monitoring line pressure
• CPC Class Codes: G01L 9/0004 using variations in inductance G01L9/007 takes precedence

Abstract

A detector for a blocked condition in a tube of a liquid infusion pump includes a moveable shaft which is kept in contact with the outer wall of a flexible tube for transporting a liquid therethrough and moves according to the changes in the outer diameter of the tube corresponding to changes in the internal pressure of the liquid. A magnet core is affixed to this shaft and affects the inductance of a solenoid coil which is affixed at a fixed position. A blocked condition in the tube is detected by monitoring the change in the inductance of this coil.

Claims

1. A detector for a blocked condition in a tube of a liquid infusion pump comprising

a tubular member, having a center flange and a back flange,

a shaft having one end in contact with the outer wall of a flexible tube for transporting a liquid therethrough by a liquid infusion pump, said shaft having a front flange and being slidably movable through said tubular member, said tubular member being secured so as to remain stationary independently of the motion of said shaft,

a magnet core affixed to said shaft,

a solenoid coil disposed around said tubular member and secured to and extending between said center flange and said back flange, said magnet core being sufficiently near said coil such that the inductance of said coil is affected by said magnet core, the inductance of said coil changing by a movement of said magnet core,

a coil spring disposed around said shaft and secured to and compressed between said center flange of said tubular member and said front flange of said shaft, and

a cover piece attached to said back flange of said tubular member and substantially entirely enclosing said tubular member, said cover piece having an inwardly protruding flange serving as a stopper for said flexible tube,

said detector being capable of detecting a blocked condition in said flexible tube by detecting a change in the inductance of said coil.

2. The detector of claim 1 wherein said shaft and said solenoid coil are coaxial with respect to each other.

3. A method of detecting a blocked condition in a tube of a liquid infusion pump, said tube having an outer wall which moves according to a change in pressure inside said tube, said method comprising the steps of

providing a tubular member affixed to remain stationary independently of movements of said outer wall of said tube, said tubular member having a center flange and a back flange, a solenoid coil being disposed around said tubular member and being secured to and between said center flange and said back flange,

attached a magnet core to a shaft which is in contact with said outer wall of said tube so as to be movable and to cause said magnet core to move with said outer wall longitudinally along said solenoid coil while remaining near said solenoid coil such that the inductance of said solenoid coil is affected by said magnet core, and

detecting a blocked condition in said tube by detecting a change in the inductance of said solenoid coil.

4. The method of claim 3 wherein said shaft is kept in contact with said outer wall of said tube by means of biasing means.

5. The method of claim 4 wherein said biasing means comprises a spring.

6. The method of claim 5 wherein said shaft has a front flange formed thereon and said spring is compressed between said front flange of said shaft and said center flange of said tubular member.

7. The method of claim 3 wherein said shaft and said solenoid coil are coaxial with respect to each other.

8. The method of claim 3 further comprising the step of providing a tubular cover piece which is attached to said back flange of said tubular member and substantially entirely encloses said tubular member and said shaft.