Hydraulic locking device for vehicle brake - uses second piston in main actuating piston to lock main piston in activated position by friction coupling

摘要

A hydraulically actuated piston is displaced to operate the mechanism and a second piston can be displaced to lock or release the main piston. The second piston is tightly fitted inside the first, and the two pistons are locked by friction when the hydraulic pressure is released. To release the locking between the two pistons hydraulic fluid is injected between them. The main piston slides in a cylinder. An annular chamber is incorporated between the main piston and its cylinder wall, and dual hydraulic inlets are used, one for normal operation, the other for activating the locking piston. The annular sealing joints are provided between the contact surfaces of the two pistons. The volume between these two joints defines a chamber from which a fluid supply conduit is led out.