Cassette chamber for intravenous delivery system

Claim 1

A cassette for use in an intravenous delivery system of the limited positive displacement type having a pump, said cassette operating between an upstream portion and a downstream portion of the intravenous delivery system and comprising, a cassette body having wall means defining an elongated main chamber, said wall means having an inlet port proximate end of said main chamber and an outlet port proximate the opposite end thereof, a first valve at said inlet port allowing unidirectional flow into said main chamber through said inlet port, a second valve at said outlet port for allowing unidirectional flow out of said main chamber through said outlet port, said cassette body having an opening in said wall means, a deformable membrane extending across said opening and affixed at its periphery to said wall means for varying the volume of said main chamber in response to deformation of said membrane, said cassette body having further wall means defining a prechamber positioned above said inlet port, said inlet port being interposed between said prechamber and said main chamber, said prechamber having a volume at least substantially equal to the volume of said main chamber to accumulate air from the upstream portion of the intravenous delivery system in an amount sufficient to maintain said main chamber air free, means for coupling said prechamber to the upstream portion of the intravenous delivery system, and means for mounting said cassette to a pump such that said outlet port is positioned at the uppermost end of said chamber to be in communication with any gas present in said main chamber with said cassette in operating position in the system and such that said inlet port is positioned at the lowermost end of said prechamber.