Abstract: A rotary fluid pressure device (11) having a housing (13,31), inlet and outlet ports (21,23), a gerotor gear set (15), a valve member (51) and an input-output shaft (49). A seal assembly (73) is disposed radially between the shaft (49) and the housing (31). The seal assembly comprises, in the order of leakage flow from a case drain region (63), a high pressure shaft seal (77), an annular chamber (71) in which is disposed a rigid back-up member (79;91) for the seal (77), a drain passage (81) communicating from the annular chamber (71) to a case drain port (47), and a low pressure shaft seal (83). The back-up member (79;91) may cooperate with either the housing (31) or the seal (77) or the input-output shaft (49) to define fluid passage means (87,89;93,95), so that any leakage flow past the high pressure shaft seal (77) flows through the drain passage (81) to the case drain port (47).

Abstract: A rotary fluid pressure device (11) having a housing (13,31), inlet and outlet ports (21,23), a gerotor gear set (15), a valve member (51) and an input-output shaft (49). A seal assembly (73) is disposed radially between the shaft (49) and the housing (31). The seal assembly comprises, in the order of leakage flow from a case drain region (63), a high pressure shaft seal (77), an annular chamber (71) in which is disposed a rigid back-up member (79) for the seal (77), a drain passage (81) communicating from the annular chamber (71) to a case drain port (47), and a low pressure shaft seal (83). The back-up member (79) may cooperate with either the housing (31) or the seal (77) to define radial fluid passage means (87,89), so that any leakage flow past the high pressure shaft seal (77) flow to the case drain port (47).