Hydraulically driven diaphragm pump

Abstract

A diaphragm pump for pumping a fluid, such as paint, includes a diaphragm separating a first chamber for accommodating and dispensing the paint from a second chamber for accommodating a drive fluid, and a piston that reciprocates to drive the drive fluid within the second chamber in order to flex the diaphragm to provide the pumping action within the first chamber. The diaphragm pump also includes a backing ring mounted adjacent the diaphragm that is configured to distribute the drive fluid across the diaphragm to cause a flexible region of the diaphragm to flex toward the first chamber from the outer perimeter inward toward a central pumping surface in a rolling manner. This diaphragm movement results in substantially all of the paint adjacent the diaphragm within the first chamber to move out of the first chamber when the diaphragm reaches its travel limit, and thus improves the efficiency of the diaphragm pump. Additionally, the diaphragm pump includes a drive fluid inlet formed within the piston, such that reciprocating movement of the piston results in an inflow of drive fluid into the second chamber. An input port in the piston is continuously submerged in the drive fluid when open, thereby substantially eliminating the introduction of air into the drive fluid system and thus reducing drive fluid priming problems.