Recuperation in master cylinders.

摘要

A master cylinder in which a piston (20) can be withdrawn from the cylinder bore (14) at least to the extent of providing past the seal (16) between the piston and the bore, a recuperation flowpath communicating between the cylinder bore and a reservoir for hydraulic fluid. The seal which is normally piston mounted, comprises a ring of sealing material having a stiffness sufficient to resist extrusion and a reinforcing girdle (23) to prevent radial expansion of the seal and axial crushing of the seal against its back sealing face. By mounting the seal with limited radial and axial clearance between axially opposed faces on the piston, for example a bearing ring (30) at the leading side and a shoulder (22) at the a trailing side, recuperation can be provided also during the return stroke via a gap (31) in the bearing ring, the radial clearance and the axial gap between the trailing side of the seal and shoulder on the piston.