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.

Abstract: A flow detector for use in a volumetric pump to determine if fluid is being displaced by the pump. The volumetric pump (30) includes an inlet cracking valve (46) and an outlet cracking valve (52) disposed on opposite sides of a plunger (48) used to displace fluid by compressing flexible tubing (34). During a pumping segment of a pumping cycle for the volumetric pump, the outlet cracking valve is closed with a cracking force that compresses the flexible tubing until the pressure of the fluid displaced by the plunger exceeds a cracking pressure, at which time the outlet cracking valve opens to enable fluid flow from the volumetric pump. A cracking flexure (182) provides the cracking force.

Abstract: Apparatus and method for determining leakage, particularly of valves, in a pumping cassette. A cassette (70) includes a primary valve (34) and a secondary valve (36), which may be selectively activated to control the source of fluid input to the cassette. The cassette also includes an inlet valve (48) and an outlet valve (56) disposed on each side of a pumping chamber (52). Downstream of the outlet valve is disposed a pressure sensor (60) which produces a signal indicative of the pressure of fluid within the cassette at that point. The cassette also includes an air-in-line sensor (40), disposed between a manifold line (38) that connects the primary and secondary valve in fluid communication with an air trap reservoir (44). Leakage in the inlet or outlet valves is detected by closing both valves, pressurizing fluid in the pumping chamber for a predetermined period of time, and then opening the outlet valve.