Pump and method of driving same

USRE29055E · kind E · reissue

Inventor

• Josef Wagner · Augsburg, DE

Key dates

• Filing date: Dec 19, 1974
• Grant date: Nov 30, 1976
• Expiry date: Dec 19, 1994

Classification

• Technology area (CPC —): General

Abstract

A fluid transfer device such as a reciprocating pump, preferably of the diaphragm type suitable for use with an airless spray-gun for painting and the like, having a pumping side for the fluid to be pumped and a driving side driven through a piston through a solution or mixture of liquid and gas, such as oil and air. Under throttled or standby operation conditions, reduced diaphragm movement is accommodated without changing the piston stroke by reducing the volume of the driving liquid and by releasing gas from the reduced volume of liquid to prevent vaporization and condensation of the driving fluid itself. A dead space is provided on the pumping side allowing some diaphragm movement into the pumping side even when completely closed so that only a small proportion of driving liquid is released and only a small amount of gas is freed from the driving liquid to accommodate the reduced diaphragm movement during the full piston stroke. The loading and unloading of the driving fluid on the power and suction strokes of the piston is controlled so that the driving fluid is always above its vapor pressure. The gas is released from the driving liquid according to Henry's Law.