US 5,055,001 A · Volumetric pump with spring-biased cracking valves

Abstract

A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48) for displacing fluid from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump. The pumping portion of the flexible tube fills with liquid when the inlet cracking valve is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (23). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger, roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve applies a cracking force to the flexible tubing, while the plunger compresses the pumping portion of the flexible tubing sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve toward a container (32). After the excess fluid has been forced from the pumping portion of the flexible tubing, a pumping segment of the cycle begins, wherein the inlet cracking valve closes fully and the outlet cracking valve applies a cracking force to compress the flexible tubing. Fluid is then forced by the plunger from the pumping portion of the flexible tubing into a distal portion (34c). The volumetric pump compensates for variations in elasticity of the flexible tubing that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58). A volumetric pump (400) for use with a cassette (300) comprises a second embodiment of the volumetric pump, in which inlet and outlet cracking valves are defined in respect to the forces applied by actuators against a flexible membrane (340) in the cassette, while a plunger (326) displaces fluid from a pumping chamber (360) in the cassette. Volumetric pump (400) applies appropriate forces to an inlet valve actuator (318) and an outlet valve actuator (332) to achieve cracking and closure forces, just as in the first embodiment.

Claims31

Dependent claims

A volumetric pump, adapted to pump a fluid through a passage defined by a flexible member, by elastically deforming different portions of the flexible member in a predefined pumping cycle, said portions of the flexible member defining a chamber, an inlet passage, and an outlet passage, deformation of the portion of the flexible member defining the chamber thereby reducing the volume of the chamber and displacing the fluid from the chamber, said volumetric pump comprising:

a. a chassis;
b. an inlet valve, disposed on the chassis so that it is adjacent the inlet passage, said inlet valve being thus positioned to act on an inlet portion of the flexible member to control fluid flow through the inlet passage, said inlet valve exerting a first and a second sealing force on the inlet portion of the flexible member during the pumping cycle, the first sealing force being substantially less than the second sealing force and allowing fluid to flow through the inlet passage from the chamber as fluid in the chamber is initially pressurized beyond a predefined level, the second sealing force subsequently interrupting fluid flow through the inlet passage from the chamber enabling fluid pressurized in the chamber to be forced through the outlet passage;
c. a plunger disposed on the chassis so that it is adjacent the chamber, and operative to deform a pumping portion of the flexible member to displace fluid from within the chamber;
d. an outlet valve, disposed on the chassis so that it is adjacent the outlet passage, said outlet valve being thus positioned to act on an outlet portion of the flexible member to control fluid flow through the outlet passage, said outlet valve exerting a forward-flow sealing force and a back-flow sealing force on the outlet portion of the flexible member during the pumping cycle, the forward-flow sealing force being substantially less than the back-flow sealing force and allowing the fluid to flow through the outlet passage from the chamber, the back-flow sealing force completely interrupting fluid flow past the outlet valve;
and
e. means for actuating the inlet valve, the outlet valve, and the plunger to deform the portions of the flexible member in the pumping cycle, to force fluid through the outlet passage at a predetermined rate of fluid delivery.

3 more elements

A volumetric pump operating in a pumping cycle for pumping fluid from a source through a passage defined by a flexible member, comprising:

a. inlet valve means, operable at different times during the pumping cycle, for:
(i) compressing an inlet portion of the flexible member with a first sealing force to resist a backward fluid flow therethrough toward the source, until fluid pressure acting on the inlet valve means exceeds a first predefined limit;
(ii) compressing the inlet portion of the flexible member with a second sealing force that is substantially greater than the first sealing force, to interrupt the backward fluid flow therethrough;
and
(iii) opening so as to allow substantially unrestricted forward fluid flow from the source through the inlet portion of the flexible member;
b. pumping means for compressing a pumping portion of the flexible member that is disposed downstream of the inlet valve means, to displace fluid contained within a part of the passage defined by the pumping portion of the flexible member;
c. outlet valve means, disposed downstream of the pumping means and operative at different times during the pumping cycle, for:
(i) compressing an outlet portion of the flexible member with a cracking sealing force to resist fluid flow therethrough, away from the part of the passage defined by the pumping portion of the flexible member until fluid pressure within said part of the passage exceeds a second predefined limit;
and
(ii) compressing the outlet portion of the flexible member with a backward sealing force that is substantially greater than the forward sealing force, to interrupt fluid flow therethrough, away from said part of the passage;
and
d. actuator means, for drivingly actuating the inlet valve means, the outlet valve means, and the pumping means in the pumping cycle.

9 more elements

Dependencies are inferred from the claim text.

Volumetric pump with spring-biased cracking valves

Life of this patent

Volumetric pump with spring-biased cracking valves

Life of this patent

Abstract

Claims31