GB967218A - Master cylinder for hydraulic fluid pressure systems - Google Patents

Abstract

967,218. Hydraulic brakes. GIRLING Ltd. Oct. 4, 1962 [Oct. 12, 1961], No. 36606/61. Heading F2F. A master cylinder 1 for hydraulic fluid pressure systems includes within the working space 5 of the cylinder a channel 21 which is in alignment with the outlet 7 of the cylinder and which is in communication with the outlet and with the main part of the working space into which a piston 2 moves to displace fluid from the cylinder, the channel being positioned so that air or any other gases trapped in the working space will be collected in the passage and will, during bleeding of a system to which the cylinder is connected, be carried along the passage to the outlet. The channel 21 is annular and is defined by a neck 20 formed in a liner 18 located in the space 5 so that the outlet 7 communicates with the channel 21 and not directly with the main part of the space 5, whereby, when the piston 2 is advanced (to the right as shown in the Figure) to displace fluid from the space 5 through the system and, with it, any bubbles of air present (a nipple or cock being opened at a suitable point in the hydraulic system during the bleeding operation) the fluid, instead of passing straight out through the outlet 7 and so leaving air bubbles trapped in the space 5, flows at least part of the way round the annular channel 21 and through an opening 22 at the top of the neck 20, so producing effective scavenging and removing any trapped bubbles of air. A tandem master cylinder is shown in Fig. 1, the outlet 7 from the cylinder space 5 being connected to the front (or rear) brakes of a vehicle and an outlet 8 from a cylinder space 6 being connected to the rear (or front) brakes. The piston 4 in the cylinder space 6 is floating, i.e. it is connected with, but not firmly attached to, an extension from the piston 2 into its hollow rear end. Valves 15, 16 lead to an hydraulic fluid reservoir. On application of the brake the main piston 2 is advanced (to the right) by a pedal-operated push-rod which enters a recess 3 in the piston and the floating piston 4 also advances, assisted by a spring 17, and a flange 13 thereon moves away from the stem of the spring-loaded valve 15 and allows the valve to close, causing pressure to build up in the space 5. This causes the floating piston 4 to advance further and allow the valve 16 to close, so building up pressure in the space 6.