Precision liquid dispenser

Abstract

A precision liquid dispenser embodying the present invention includes a displacement diaphragm pump and a hydraulic system for selectively deforming the diaphragm. The diaphragm pump includes a pump body, a pump cavity, a pump diaphragm, and an input/output port. A solenoid operated valve assembly selectively connects the port to a source of liquid to be dispensed. The hydraulic system for selectively deforming the diaphragm includes a body with a cavity, a piston, a sealing ring, and hydraulic fluid in the space between the piston and diaphragm. The position of the piston is controlled by a stepping motor, a mechanical threaded coupling, which converts rotary motion of the motor output shaft to linear motion of the piston. The volume of fluid dispensed is determined by the number of pulses applied to the stepping motor. The output flow rate as a function of time is controlled by the rate of pulses applied to motor as determined by the control logic. A solenoid valve assembly, under the control of signals from the dispenser control logic, selectively connects a valve input port to the valve input/output port, or connects the input/output port to a valve output port. Valve control signals from control logic are coordinated in time with control signals from the reversible motor.