US 6,494,694 B2 · Disposable infusion cassette with low air bubble retention and improved valves

Abstract

A disposable cassette for use with a medical infusion pump. An elastomeric membrane is captured between a facing member and a base of the cassette and is displaced into a pumping chamber. The elastomeric membrane includes a generally T-shaped lip, and corresponding grooves are provided on the facing member and base. As the cassette is assembled, an interference fit between the lip and the grooves causes the membrane to stretch taut and to be securely anchored, eliminating a break-in period when the cassette is initially used. “Lobes” of increased thickness provided on the undersurface of a portion of the elastomeric membrane overlying the pumping chamber reduce the residual volume of the pumping chamber, thereby reducing the volume of air retained within the chamber and increasing the accuracy of the cassette. The lobes also sweep air bubbles from the sides of the pumping chamber during operation, further reducing air bubbles retained in the pumping chamber. A distal tube support retains a distal fluid line between air or pressure sensors included on a pump drive mechanism, thus reducing the likelihood of sensing errors. Inlet and outlet valve flaps and corresponding seating surfaces included in the base are configured to provide quieter operation, further reduce the residual volume of the pumping chamber, increase fluid velocity through the outlet valve to sweep air bubbles from the pumping chamber, and protect against a “blown” inlet valve.

Claims38

Dependent claims

A cassette that is adapted to engage a drive mechanism, for use in infusing a fluid into a patient, comprising:

(a) a housing having a base on which is mounted a facing member, a fluid path being defined at least in part by the base and extending through the cassette between an inlet port and an outlet port, said fluid path including:
(i) an inlet passage coupled in fluid communication with the inlet port;
(ii) an outlet passage coupled in fluid communication with the outlet port;
and
(iii) a pumping chamber disposed between the inlet passage and the outlet passage;
and
(b) an elastomeric membrane that extends over the fluid path and when displaced into the pumping chamber, is adapted to force a fluid from the pumping chamber, said elastomeric membrane including a substantially T-shaped lip extending around and proximate its peripheral edge, said T-shaped lip being captured in an interference fit within a groove formed in opposed surfaces of the facing member and the base so that the elastomeric membrane is stretched taut as the facing member is joined to the base, said groove including inclined surfaces that are in interference with corresponding inclined surfaces on said T-shaped lip when the facing member is seated onto and joined to the base with the lip of the elastomeric membrane captured in the groove, a tension in the elastomeric membrane produced by said interference fit due to an interaction of the inclined surfaces of the groove and the T-shaped lip compensating for any inelastic stretching of the elastomeric membrane occurring when the elastomeric membrane is displaced into the pumping chamber, to thereby reduce errors in achieving a desired volume of a fluid infused by the cassette.

4 more elements

A method for mounting an elastomeric membrane in a cassette used for infusing a fluid into a patient, so as to pre-load the elastomeric membrane under an outwardly directed tension, comprising the steps of:

(a) providing a generally T-shaped lip extending around and proximate to a peripheral edge of the elastomeric membrane, said T-shaped lip having inclined surfaces extending from where the T-shaped lip extends from a generally planar surface of the elastomeric membrane toward distal tips of the T-shaped lip;
(b) providing a base and a facing member for the cassette that each include a groove with inclined surfaces shaped and sized to receive a different distal tip of the T-shaped lip in an interference fit;
(c) positioning a distal tip of the T-shaped lip of the elastomeric membrane in the groove formed in one of the base and the facing member;
(d) seating the groove formed in the other of the base and the facing member onto an opposite:distal tip of the T-shaped lip;
(e) pressing the base and the facing member toward each other until the T-shaped lip seats within the grooves formed in the base and the facing member, the interference fit between ;the inclined surfaces of the grooves and the T-shaped lip drawing the elastomeric membrane taut under a pre-load tension;
and
(f) joining the base and the facing members together in a state achieved by step (e) so that the elastomeric membrane is captured under the pre-load tension between the facing member and the base.

4 more elements

A cassette that is adapted to engage a drive mechanism, for use in infusing a medicinal liquid into a patient, comprising:

(a) a housing having a base on which is mounted a facing member, a fluid path being defined at least in part by the base and extending through the cassette between an inlet port and an outlet port of the cassette, said fluid path including:
(i) an inlet passage coupled in fluid communication with the inlet port;
(ii) an outlet passage coupled in fluid communication with the outlet port;
and
(iii) a pumping chamber disposed between the inlet passage and the outlet passage;
and
(b) an elastomeric membrane that extends over the fluid path and when displaced into the pumping chamber, is adapted to force a fluid from the pumping chamber, said elastomeric membrane having a generally planar undersurface facing toward the base, but including two lobes of increased thickness disposed above the pumping chamber at opposite sides thereof and extending into the pumping chamber, so that when the elastomeric diaphragm is displaced into the pumping chamber by a drive mechanism, the lobes sweep away air bubbles that may be retained on adjacent sides of the pumping chamber, said lobes defining a shallow elongate path through the pumping chamber when the elastomeric membrane is displaced to its full extent into the pumping chamber, so that a substantial portion of any air contained within the pumping chamber is carried out of the pumping chamber with the medicinal liquid being infused.

4 more elements

A cassette that is adapted to engage a drive mechanism, for use in infusing a medicinal liquid into a patient, comprising:

(a) a housing having a base on which is mounted a facing member, a fluid path being defined at least in part by the base and extending through the cassette between an inlet port and an outlet port, said fluid path including:
(i):
an inlet passage coupled in fluid communication with the inlet port;
(ii) an outlet passage coupled in fluid communication with the outlet port;
and
(iii) a pumping chamber disposed between the inlet passage and the outlet passage;
(b) an elastomeric membrane that extends over the fluid path and when displaced into the pumping chamber, is adapted to force a fluid from the pumping chamber, said elastomeric membrane comprising an inlet valve flap and an outlet valve flap, both of which depend from the undersurface of the elastomeric membrane, the inlet valve flap when closed by a fluid pressure within the pumping chamber forming a seal against an inlet valve surface that is formed in the base and is disposed between the inlet passage and the pumping chamber, and the outlet valve flap when closed, forming a seal against an outlet valve surface that is formed in the base and is disposed between the pumping chamber and the outlet passage;
and
(c) means for reducing an audible noise that is otherwise caused by an oscillation of at least one of the inlet valve flap and the outlet valve flap in response to a flow of medicinal liquid through the cassette.

6 more elements

A cassette that is adapted to engage a drive mechanism, for use in infusing a medicinal liquid into a patient, comprising:

(a) a housing having a base on which is mounted a facing member, a fluid path being defined at least in part by the base and extending through the cassette between an inlet port and an outlet port, said fluid path including:
(i) an inlet passage coupled in fluid communication with the inlet port;
(ii) an outlet passage coupled in fluid communication with the outlet port;
and
(iii) a pumping chamber disposed between the inlet passage and the outlet passage;
(b) an elastomeric membrane that extends over the fluid path and when displaced into the pumping chamber, is adapted to force a fluid from the pumping chamber, said elastomeric membrane comprising an inlet valve flap and an outlet valve flap, both of which depend from the undersurface of the elastomeric membrane, the inlet valve flap when closed by a fluid pressure within the pumping chamber forming a seal against an inlet valve surface formed in the base and disposed between the inlet passage and the pumping chamber, and the outlet valve flap when closed, forming a seal against an outlet valve surface formed in the base and disposed between the pumping chamber and the outlet passage;
and
(c) means for achieving a predetermined cracking pressure associated with moving said outlet valve flap away from said outlet valve surface.

5 more elements

Dependencies are inferred from the claim text.

Disposable infusion cassette with low air bubble retention and improved valves

Life of this patent

Disposable infusion cassette with low air bubble retention and improved valves

Life of this patent

Abstract

Claims38