US Patent 7278263 Charge pump for a hydraulic pump

A charge pump design for a hydraulic drive apparatus such as a hydrostatic transmission, integrated hydrostatic transaxle or pump having a rotatable pump cylinder block mounted in a sump and connected to a hydraulic circuit by means of a center section or the like. A fluid gallery for charge fluid is in communication with the hydraulic circuit and the charge pump is mounted adjacent to and is driven by the pump cylinder block to provide hydraulic fluid from the sump to the fluid gallery. The charge pump can be of many different styles such as a gerotor, a centrifugal pump or a flexible impeller style.