Hydraulically powered diaphragm pump with pretensioned diaphragm
A hydraulically driven diaphragm pump with a diaphragm clamped at its edge between a pump body and a pump cover separating a delivery chamber from a hydraulic chamber and pretensioned in the direction of its intake stroke by spring force. A hydraulic diaphragm drive in the form of an oscillating displacement piston is displaceable in the pump body between a reservoir chamber for the hydraulic fluid and the hydraulic chamber. The diaphragm is so strongly pretensioned by spring force that it exerts a substantial compressive force on the hydraulic fluid in the hydraulic chamber. Therefore a substantial hydrostatic pressure is built up in the hydraulic chamber relative to the delivery chamber.
1. 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.
2. Diaphragm pump according to claim 1 , wherein the spring force is so dimensioned that vacuum pressure is avoided in the hydraulic chamber at any time during the intake stroke.
3. Diaphragm pump according to claim 1 , wherein a total of a pressure differential at the diaphragm and a differential holding pressure of a leakage compensating valve generated by the spring force is always at least 1 bar.
4. Diaphragm pump according to claim 3 , wherein the pressure differential on the diaphragm is at least 0.8 bar and the differential holding pressure of the leakage compensating valve is at least approximately 0.3 bar.
5. Diaphragm pump according to claim 1 , wherein the spring force pretensioning the diaphragm in the direction of the intake stroke is generated by the diaphragm.
6. Diaphragm pump according to claim 1 , wherein the spring force pretensioning the diaphragm in the direction of the intake stroke is generated by at least one spring element incorporated into the diaphragm.
7. Diaphragm pump according to claim 1 , wherein the spring force pretensioning the diaphragm in the direction of the intake stroke is generated by a compression spring arranged in the hydraulic chamber, supported by a central guide rod connected to the diaphragm, the compression spring having two ends with one end of the compression spring supported at the pump body and the other end of the compression spring supported at an end of the guide rod, said spring force corresponding to an effective diaphragm area.
8. Diaphragm pump according to claim 1 , wherein the diaphragm is a molded diaphragm.
9. Diaphragm pump according to claim 8 , wherein the molded diaphragm has a peripheral bead on a concave side face of the diaphragm facing towards the hydraulic chamber.