High pressure hydraulic seal for sliding shaft - has pressure on seal controlled to suit operating pressure

摘要

The shaft (20) slides in the housing (21) and the high pressure (PH) is sealed by two U-section seals (22, 23). These seals are separated by an annular chamber which is divided into two regions (26, 27) by the piston (24). The region (27) is vented to low pressure by the hole (28). Any leakage from the high pressure (PH) past the seal (30) creates an intermediate pressure (PR) in the region (26). If the leakage increases, the pressure (PR) increases and pushes the piston (24) against the seal (30) increasing the sealing pressure and so reducing the leakage. The pressure on the seal (30) is thus kept to the minimum necessary for effective sealing which minimises friction between shaft (20) and seal (30).