Spring-biased valve for use in a positive displacement volumetic pump

• US 5,078,362 A
• Filed: 06/04/1991
• Issued: 01/07/1992
• Est. Priority Date: 03/15/1990
• Status: Expired due to Fees

• Current Assignee: Abbott Laboratories Incorporated
• Original Assignee: Abbott Laboratories Incorporated
• Inventors: Lawless, Michael W., Natwick, Vernon R.
• Primary Examiner(s): Fox, John C.
• Application Number:
  US07/711,117
• Time in Patent Office: 217 Days
• Field of Search: 251/4, 251/7, 251/9, 137/844
• US Class Current: 251/9
• CPC Class Codes: A61M 5/14228 with linear peristaltic action, i.e. comprising at least three pressurising members or a helical member
• CPC Class Codes: F04B 43/082 the tubular flexible member being pressed against a wall by a number of elements, each having an alternating movement in a direction perpendicular to the axes of the tubular member and each having its own driving mechanism

Abstract

A "cracking valve" for use in a volumetric pump. A volumetric pump (30) includes a plunger (48) for compressing a pumping portion (34b) of a flexible tubing that extends through the pump. An inlet cracking valve (46) and an outlet cracking valve (52) are disposed so that they compress the flexible tubing to control fluid flow therethrough. The inlet cracking valve operates in three modes, including a fully open mode, a closed mode that stops fluid flow through the flexible tubing, and a cracking mode. The outlet cracking valve only operates in the closed mode and the cracking mode. As the plunger compresses the flexible tubing, fluid pressure within the pumping portion of the flexible tubing initially builds until it exceeds a predefined cracking pressure, forcing open the inlet cracking valve, which is in its cracking mode, so that excess fluid is forced back to a container (32). After the pumping portion of the flexible tubing is compressed to a predefined volume, fluid at the cracking pressure is forced through the outlet cracking valve, which is then in its cracking mode. To compensate for changes in the elasticity or stiffness of the flexible tubing, balance blocks (42, 58) cooperate with the inlet cracking valve and the outlet cracking valve, respectively. The balance force developed by the balance block as a function of the stiffness of the flexible tubing is added to the force of a cracking flexure to produce the desired predefined cracking force at the inlet cracking valve and the outlet cracking valve. A "T-shaped" formation comprising a transverse ridge (166) and a longitudinal ridge (168) comprises valve faces (106a, 106b) at both cracking valves. The transverse ridge controls fluid flow, whereas the longitudinal ridge has a surface area over which the fluid pressure within the pumping portion of the flexible tubing acts to overcome the cracking force.

Claims

1. A valve for controlling fluid flow through a passage defined by an elastomeric member, comprising:

a. a frame, said frame including backing means for supporting the elastomeric member;

b. a valve member that is pivotally mounted to the frame to rotate about a pivot axis and is generally positioned on an opposite side of the passage from the backing means, said valve member including;

(1) flow control means for;

(a) closing the passage by compressing the elastomeric member against the backing means with a cracking force that is independent of any external load applied to the valve member,

(b) blocking fluid flow through the passage until the pressure of a fluid within the passage exceeds a predetermined cracking pressure sufficient to force open the passage, and

(c) regulating the pressure of fluid thus flowing through the passage to the cracking pressure;

(2) force balance means, disposed generally on an opposite side of the pivot axis from the flow control means and in contact with the elastomeric member but incapable of blocking flow through the passage, for;

(a) developing a force as a result of contact with the elastomeric member that adds to the cracking force by an amount that depends on an elasticity of the elastomeric member, and

(b) compensating for any variations in the elasticity that would otherwise vary the cracking pressure; and

c. a spring mounted between the frame and the valve member, said spring contributing to the cracking force exerted against the elastomeric member by the flow control means.

2. The valve of claim 1, wherein the elastomeric member comprises flexible tubing.

3. The valve of claim 1, further comprising closure means for pivoting the valve member so that the flow control means compresses the elastomeric member, closing the passage with a relatively greater force than the cracking force, preventing fluid flow through the passage even though the pressure of fluid within the passage substantially exceeds the cracking pressure.

4. The valve of claim 3, wherein the closure means comprises a second spring mounted between the housing and the valve member, which is selectively controlled to increase the force applied by the valve member to compress the elastomeric member sufficiently to block fluid through the passage.

5. The valve of claim 1, wherein the valve member further includes a spring link connecting a first portion of the valve member on which the flow control means is disposed to a second portion of the valve member on which the force balance means is disposed.

6. The valve of claim 5, wherein the spring link comprises a thin metal flexure that bends with sufficient elasticity to enable the first portion of the valve member to assume a position in which the passage between the first portion of the valve member and the backing means is open, independent of fluid pressure, said first portion of the valve member pivoting further away from the elastomeric member than the second portion, leaving the passage substantially open and the elastomeric member substantially uncompressed both between the flow control means and the backing means and between the force balance means and the backing means.

7. The valve of claim 6, further comprising means for pivoting the flow control means away from the elastomeric member, in opposition to the cracking force, to open the passage.

8. A cracking valve for use in a pump that positively displaces fluid by compressing a pumping portion of flexible tubing against a backing member until the pressure of the fluid within the compressed pumping portion exceeds a predetermined cracking pressure, said cracking pressure being defined as a fluid pressure of sufficient magnitude to force the cracking valve to open, permitting the fluid to flow from the pump, comprising:

valve member means, mounted to the pump adjacent the flexible tubing so as to pivot about a pivot axis, for regulating the pressure of fluid flowing past the valve member means to the cracking pressure, independent of any externally applied load, said valve member means including;

flow control means disposed proximal to the pumping portion of the flexible tubing that is compressed, for compressing the flexible tubing against the backing member with a cracking force, and

force balance means disposed distal to the pumping portion of the flexible tubing that is compressed and continuously in contact with the flexible tubing but substantially incapable of limiting fluid flow through it, for compensating the cracking force for variations in an elasticity of the flexible tubing, the flow control means and the force balance means tending to pivot the valve member means in opposite directions in reaction to the elasticity of the flexible tubing; and

spring means for biasing the valve member means to pivot about the pivot axis so that the flow control means compress the flexible tubing against the backing member with the cracking force, the force balance means and the spring means thus determining the cracking force so that its magnitude is independent of any load applied to the valve member means.

9. The cracking valve of claim 8, wherein the valve member means is generally "Y" shaped, having first, second, and third legs joined together, and wherein the flow control means and force balance means are disposed on the first and second legs, respectively.

10. The cracking valve of claim 9, wherein a vertex of the valve member at which the first, second, and third legs are joined is connected to pivot arms that extend laterally from opposite surfaces of the "Y-shaped" section, said pivot axis being disposed within the pivot arms.

11. The cracking valve of claim 8, wherein the third leg is actuated by a profiled rotating cam surface, the rotating cam surface selectively changing the compression force exerted by the flow control means against the flexible tubing during a pumping cycle so that the cracking force is not applied.

12. The cracking valve of claim 8, wherein the spring means comprise a flexure that is mounted so as to apply a spring bias against the valve member means, causing it to compress the flexible tubing with the flow control means.

13. The cracking valve of claim 8, wherein the spring means comprise a plurality of springs that each contribute to a force biasing the valve member means to pivot about the pivot axis so as to move the flow control means toward the flexible tubing, one of the springs providing a closure force that substantially exceeds that required to determine the cracking pressure, said one spring causing the flow control means to completely block fluid flow through the flexible tubing, independently of the cracking pressure.

14. The cracking valve of claim 8, further comprising means for moving the flow control means away from the backing member so as to open a passage through the flexible tubing.

15. The cracking valve of claim 14, further comprising a flexure connecting the force balance means to the flow control means, said flexure enabling the valve member means to pivot the flow control means away from the backing member to open the flexible tubing without causing the force balance means to compress the flexible tubing sufficiently to significantly block fluid flow therethrough.

16. The cracking valve of claim 15, wherein the valve member means is disposed on an inlet side of said pumping portion of the flexible tubing in respect to a source of the fluid and serves as an inlet valve for the pump.

17. The cracking valve of claim 8, wherein the valve member means is disposed on an outlet side of said pumping portion of the flexible tubing with respect to a source of the fluid and serves as an outlet valve for the pump.

18. A method for compensating a cracking valve for variations in the elasticity of a flexible member that defines a passage through which fluid is pumped due to positive displacement of a pumping portion of the flexible member, said method thereby maintaining a generally constant cracking pressure in the fluid pumped, comprising the steps of:

in response to the elasticity of the flexible member, producing a balancing force; and

adding the balancing force to a flow control force exerted by the cracking valve against the flexible member, producing a cracking force tending to close off the passage, where said cracking force is determinative of a cracking pressure required in the fluid to force open the cracking valve and enable a fluid flow through the passage, thereby preventing any change in the cracking pressure and volume of the fluid displaced from the pumping portion of the flexible member that would otherwise occur due to a variation in the elasticity of the flexible member affecting its resistance to the cracking force.

19. The method of claim 18, further comprising the step of applying a closure force to the cracking valve sufficiently great to block fluid flow through the passage, independently of the cracking pressure.

20. The method of claim 18, further comprising the step of providing a flexure in the cracking valve, said step of producing the balancing force comprising the step of contacting the flexible member with a balance block that is connected to the cracking valve by the flexure, said flexure elastically bending and thus preventing closure of the passage through the flexible member by the balance block as the cracking valve opens to enable fluid to flow into the pumping portion of the flexible member.

21. A cracking valve for controlling the flow of a pressurized fluid through a flexible tubing, comprising:

a pivotally mounted valve member including an elongate surface for applying a compressive force to the flexible tubing, said surface comprising a generally "T" shaped formation that contacts the flexible tubing, said formation being defined by a transverse ridge and a longitudinal ridge, the longitudinal ridge being generally aligned with a longitudinal axis of the flexible tubing and the transverse ridge being generally transverse to said longitudinal axis; and

a spring for biasing the valve member to pivot the surface into contact with the flexible tubing with a flow control force sufficient for the transverse ridge to block fluid flow through the flexible tubing until the pressure of the fluid exceeds a predetermined cracking pressure, said pressure of the fluid within the flexible tubing acting through the flexible tubing over an area of said surface encompassing the longitudinal ridge to achieve a force that exceeds the flow control force, thereby opening a passage in the flexible tubing through which fluid flows past the transverse ridge.

22. The cracking valve of claim 21, wherein the transverse and longitudinal ridges are defined at least in part by curves having radii that do not exceed a conforming curve readily achievable by the flexible tubing.

23. The cracking valve of claim 21, wherein the transverse ridge is disposed on the surface so as to contact the flexible tubing at a point more distal from the pressurized fluid than where the longitudinal ridge contacts the flexible tubing.

24. The cracking valve of claim 21, wherein the longitudinal ridge is at least twice as long as the diameter of the flexible tubing.

25. The cracking valve of claim 21, wherein the longitudinal ridge extends outwardly of said surface of the valve member with an elevation that is greater proximal the transverse ridge than distal thereto.

26. The cracking valve of claim 21, wherein the valve member further comprises means for compensating for variations in the elasticity of the flexible tubing to minimize changes in the cracking pressure.

27. The cracking valve of claim 26, wherein the means for compensating comprise a second surface in contact with the flexible tubing, said second surface being disposed on an opposite side of a pivot axis about which the valve member pivots.

28. The cracking valve of claim 26, wherein the means for compensating comprise a force balance surface that contacts the flexible tubing along a section that is spaced apart from that where the surface of the valve member contacts it and disposed on an opposite side therefrom in respect to a pivot axis of the valve member, said force balance surface transmitting a compensating balance force having a magnitude that is a function of the elasticity of the flexible tubing, through the valve member, said balance force being added to the flow control force provided by the spring to provide a cracking force.

29. The cracking valve of claim 21, where the longitudinal ridge is disposed farther from a pivot axis about which the valve member pivots than the transverse ridge to increase the torque developed by the cracking pressure so that it exceeds the torque developed by the flow control force that acts to compress the flexible tubing with the transverse ridge.

30. The cracking valve of claim 29, wherein the cracking pressure acts on the longitudinal ridge through the flexible tubing to force the transverse ridge away from a backing member against which the transverse ridge is compressing the flexible tubing, thereby enabling fluid to flow through the flexible tubing past the transverse ridge.