GB859911A - Improvements in master cylinders for hydraulic systems - Google Patents

Abstract

859,911. Hydraulic brakes. GIRLING Ltd. June 3, 1957 [June 2, 1956], No. 17120/56. Class 103(1). In a master cylinder of the kind in which a port in the end of the cylinder remote from the working piston is connected to a reservoir and is adapted to be closed by a valve when the system is under pressure, a frictional sliding coupling is provided between the working piston and a rod attached to the valve controlling communication between the cylinder and the reservoir when the piston is advanced to apply pressure to the system the valve is moved forwardly, as a result of the frictional coupling, into engagement with its seating to close the valve independently of the fluid pressure in the cylinder without reliance on spring-loading of the valve. In the embodiment illustrated, a master cylinder 10 has formed integrally therewith a fluid reservoir 11 which is in communication with the cylinder bore 12 of the master cylinder by way of axial opening 13; the opening and closing of said axial opening being controlled by a valve member 31 provided on the end of an axiallyextending split rod 26 which slides into an axially-extending recess 24 in the master cylinder piston 18. The length of the rod 26 in relation to the other dimensions of the assembly is such that when the piston is fully retracted and the valve 31 is open in engagement with a cage 35 abutting against the end of the cylinder, the head 25 on the rod is in frictional engagement, with the wall of the recess 24 and is in engagement with the flange or lug 28 on a thimble 29 surrounding inwardly-extending spigot 22 of piston 18, the parts being in the position shown in Fig. 1. In operation, when piston 18 is moved to the left to pressurize the brake cylinders via connection 17, the frictional coupling between rod 26 and piston 18 causes the valve to move with the piston until the valve engages its seating and cuts off the reservoir from the cylinder. The rod 26 can then telescope into the piston as the piston advances. On the return movement of the piston the valve opens as soon as the piston starts to move and the pressure in the cylinder falls, but if the valve should stick and fail to open it will be positively opened by the engagement of the flange or lug 28 with the head 25 on the rod 26 when the piston returns to its fully retracted position.