US Patent 7530646 Master cylinder assembly

Master cylinder assembly (1) for hydraulic control includes a master cylinder body (2) having a longitudinal bore (3). A piston (6) is arranged in the said bore and includes a seal packing (15) separating two chambers (16, 29) adapted to contain a liquid. The piston also includes a recovery conduit (36) connecting the chambers and by-passes the seal packing, and a valve (38). When the piston is in a rest position, an actuator (54) adjusts the position of the valve between an open position opening the recovery conduit and a closed position closing the recovery conduit.