Flow rate sensing device

Abstract

A flow rate sensing device, particularly for use in regulating the rate of flow in a system for parenteral administration of liquids to patients. The liquid emerges from a storage reservoir and is fed into a housing through an upstream flow passage portion and then is made to pass through a narrow throat passage wherein the velocity of the liquid increases while its pressure decreases. The liquid then emerges into a downstream flow through passage and flows through an outlet from the housing. In an intravenous fluid administration system, the housing outlet is connected to a terminal tubing section and an intravenous needle. A pressure transducer, consisting of two chambers separated by a resilient deformable diaphragm, has its upstream chamber in fluid and pressure communication with the upstream flow path portion and its downstream chamber in fluid and pressure communication with the flow emerging from the throat passage. Variations in the flow rate through the throat passage effect changes in the pressure differential between the transducer chambers and thus cause variable degrees of displacement of the transducer diaphragm. The mechanical signals created by the movement of the diaphragm can be transduced to an arrangement for controlling the rate of fluid flow through the system. Alternatively, the mechanical signal created by the diaphragm can be transduced to flow rate monitoring or flow rate coordinating systems.