Patent ID: 6884045

Claim:
Hydraulically driven diaphragm pump comprising: a pump body, a pump cover, an edge of a diaphragm clamped between the pump body and the pump cover, the diaphragm separating a delivery chamber from a hydraulic chamber, a spring force pretensioning the diaphragm in a direction of an intake stroke, and a hydraulic diaphragm drive including an oscillating displacement piston, said oscillating displacement piston being displaceable in the pump body between a reservoir chamber for hydraulic fluid and the hydraulic chamber, the diaphragm being pretensioned by the spring force so that only the spring force controls a position of the diaphragm and the diaphragm follows an intake stroke of the piston even when a vacuum is present in the delivery chamber, and, when the pump is static, the diaphragm does not move in a direction of a compression stroke due to internal leakage even when the vacuum is present in the delivery chamber while the diaphragm remains in a rear dead center position, the diaphragm being only supported by a surface that is formed by part of the pump body and by a diaphragm coupling disk, the spring force being so dimensioned that a pressure in the hydraulic chamber is always at least 1 bar greater than a positive pressure in the delivery chamber.