Apparatus for converting a pump to a controller

Abstract

Apparatus controls the maximum pressure of the fluid which can flow through a pump. The apparatus includes a disposable unit with an inlet for receiving fluid from a source, an outlet for transferring the fluid to a patient and a chamber communicating between the inlet and the outlet. A diaphragm across the chamber is constrained in accordance with the pressure of the fluid in the chamber. The diaphragm transmits the constraint to a stiffener. The disposable unit is removably attached to the pump casing. A knob is externally disposed on the pump casing and is adjustable to control the maximum force of the fluid in the disposable unit. The knob controls the force exerted on biasing means in a first direction. A force is also exerted against the biasing means in a second direction opposite to the first direction. This force is dependent upon the force on the stiffener. The biasing means may include a spring. The force on the biasing means in the first direction is provided by a back-up member which is pivotable at one end and is disposed against the spring at an intermediate position and is provided with an adjustable lever arm dependent upon the adjustment of the knob. The force in the opposite direction is transmitted by the stiffener to a diaphragm in the pump casing. This diaphragm in turn transmits the force to a vane which is pivotable at one end and is disposed against the spring at an intermediate position. Sensor means are coupled to the vane to provide an output indication after the vane has overcome the bias provided on the spring in the first direction.