Pump pressure sensor

• US 4,784,577 A
• Filed: 03/13/1987
• Issued: 11/15/1988
• Est. Priority Date: 09/02/1986
• Status: Expired due to Fees

• Current Assignee: Fresenius AG (Fresenius SE & Co. KGaA), Fresenius USA Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Critikon, Inc.
• Inventors: Danby, Hal C., Ritson, Carl
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Kartchner, Gene B.
• Application Number:
  US07/025,300
• Time in Patent Office: 613 Days
• Field of Search: 604/65, 604/118, 604/121, 604/151, 604/152, 604/153, 604/131, 128/DIG. 1, 128/DIG. 12, 128/DIG. 13, 128/722, 128/672, 128/675, 417/413, 417/219, 417/38, 417/63, 417/18, 73/718
• US Class Current: 417/219
• CPC Class Codes: A61M 2205/12 with interchangeable cassettes forming partially or totally the fluid circuit
• CPC Class Codes: A61M 2205/128 with incorporated valves
• CPC Class Codes: A61M 5/14224 Diaphragm type
• CPC Class Codes: A61M 5/16854 by monitoring line pressure
• CPC Class Codes: F16K 15/144 the closure elements being fixed along all or a part of their periphery
• CPC Class Codes: Y10S 128/13 Infusion monitoring
• CPC Class Codes: Y10T 137/7559 Pump type

Abstract

A back pressure sensor comprising a flexible beam having a pivot end with a pivot pin and a drive connector end with a means for engaging a pump drive. A pump actuator is connected to the flexible beam at a position intermediate the ends and connects with a positive displacement pumping member. A sensor beam is attached to the flexible beam at a connecting point spaced from said pivot end. A first capacitor plate is mounted on the flexible beam at a point which is spaced from the connecting point. A second capacitor plate is mounted on the sensor beam in a position facing and spaced apart from the first capacitor plate at a distance therefrom which permits formation of a capacitance coupling therebetween. The back pressure sensor is particularly advantageous for use with positive displacement pumps such as diaphragm pumps, peristaltic pumps and piston pumps used in parenteral solution delivery systems where substantially increases in back pressure present a hazard to the patient to which liquid is being infused.

Claims

1. A back pressure sensor comprising a flexible beam having a pivot end and a drive connector end, the pivot end thereof having a pivot means, a pump actuator means joined to the flexible beam at a position intermediate the pivot end and drive connector end for connecting to a positive displacement member of a pump, a sensor beam attached to the flexible beam at a connecting position spaced from said pivot means, a first capacitor plate mounted on the flexible beam at a plate position which is spaced from the connecting position, a second capacitor plate mounted on the sensor beam in a position facing and spaced apart from the first capacitor plate at a distance which permits formation of a capacitance coupling between the first and second capacitor plates.

2. The back pressure sensor of claim 1 wherein the initial, unstressed positions of the sensor beam and flexible beam are substantially parallel.

3. The back pressure sensor of claim 2 wherein the first capacitor plate is mounted at the pivot end of the flexible beam and the second capacitor plate is mounted at the end of the sensor beam adjacent the pivot end of the flexible beam.

4. The back pressure sensor of claim 1 wherein the sensor beam is connected to the flexible beam at a position adjacent the drive connector end thereof.

5. A pump-pressure sensor combination of a positive displacement pump and the pressure sensor of claim 1 comprising a pumping chamber for containing liquid to pumped, a positive displacement member means for expelling liquid from the pumping chamber, the positive displacement member means connecting with said pump actuator means, whereby increasing pressure in the pumping chamber effects an increasing flexure of the flexible beam and changes the distance between the capacitor plates.

6. The pump-pressure sensor combination of claim 5, wherein the initial unstressed positions of the sensor beam and the flexible beam are substantially parallel.

7. The pump-pressure sensor combination of claim 6 wherein the first capacitor plate is mounted on the pivot end of the flexible beam and the second capacitor plate is mounted on the end of the sensor beam adjacent the pivot end of the flexible beam.

8. The pump-pressure sensor combination of claim 5 wherein the sensor beam is connected to the flexible beam at a position adjacent the drive connector end thereof.

9. The pump-pressure sensor combination of claim 5 wherein the pump is a diaphragm pump comprising a first plate having a pumping chamber surface, a second plate attached to the first plate around the periphery thereof, the second plate comprising a flexible diaphragm member comprising hinged, rigid plates hingingly mounted on the second plate and opposed to the pumping chamber surface to form a pumping chamber, and a check valve means defined by the first and second plates and communicating with the pumping chamber.

10. The pump-pressure sensor combination of claim 9 wherein the flexible diaphragm member comprises at least three inflexible diaphragm plates with edges in a common plane, each diaphragm plate having at least two straight diaphragm plate hinge edges, each diaphragm plate hinge edge being adjacent to and aligned with a second diaphragm plate hinge edge of an adjacent diaphragm plate, the adjacent edges of each diaphragm plate hinge edge and second diaphragm plate hinge edge being attached together by a flexible hinge strip.

11. The pump-pressure sensor combination of claim 10 wherein the first array of plates comprises at least three identical plates having identical edges, the respective identical edges thereof being positioned equal distant from the axial center of symmetry.

12. The pump-pressure sensor combination of claim 11 wherein the flexible member includes a central plate, the axial center of the center plate being at the axial center of symmetry, the center plate having straight plate edges having the same length, and the plates include an array of plates hingingly connected to the straight sides of the center plate, each plate in the array of plates having a straight center plate hinge edge positioned adjacent to and aligned with a center plate edge and hingingly connected at the center plate edge by a flexible hinge strip.

13. The pump-pressure sensor combination of claim 9 wherein the check valve means is a check valve comprising a circular check valve plate attached to the back plate by a flexible hinge means.

14. The pump-pressure sensor combination of claim 13 including an adjustment means threadingly engaging the back plate and having a surface opposing the check valve plate for pressing the check valve plate toward the front plate.

15. The pump-pressure sensor combination of claim 13 wherein the check valve means is an inlet check valve comprising an inlet check valve plate, a valve seat means opposing the check valve plate, and a flexible diaphragm disk with a central flow passageway between the inlet check valve plate and the valve seat means.

16. The pump-pressure sensor combination of claim 15 wherein the flexible inlet diaphragm disk has an inlet side facing the valve seat and communicating with a fluid inlet, and an outlet side facing the inlet check valve plate and communicating with the pumping chamber, the inlet check valve plate being a check valve activation member which by pressing the flexible inlet diaphragm disk against the valve seat means, activates the inlet check valve.

17. The pump-pressure sensor combination of claim 13 wherein the check valve means is an outlet check valve comprising an outlet check value plate including a valve seat means, an outlet check valve chamber opposing the valve seat means, and a flexible outlet diaphragm disk with a central flow passageway between the outlet check valve plate and the outlet check valve chamber.

18. The pump-pressure sensor combination of claim 17 wherein the flexible outlet diaphragm disk has an inlet face facing the valve seat means and communicating with the pumping chamber and an outlet face facing the outlet check value chamber and communicating with a fluid outlet, the outlet check valve plate being a check valve activation member which by pressing the valve seat means against the flexible outlet diaphragm disk, activates the outlet check valve.

19. The pump-pressure sensor combination of claim 18 including an adjustment means threadingly engaging the back plate and having a surface opposing the outlet check valve plate for pressing the outlet check valve plate toward the flexible outlet diaphragm disk for engagement of the valve seat means with the outlet diaphragm disk.