GB714411A - Improvements in or relating to hydraulic brake systems - Google Patents

Abstract

714,411. Hydraulic brakes. AUTO UNION AKT.-GES. April 20, 1950 [April 20, 1949], No. 9751/50. Class 103(1) In a hydraulic brake system, especially for motor vehicles, in which the master cylinder assembly includes a main piston 8 and a spring-loaded precompression piston 10 for maintaining pressure in the brake circuit when the brakes are inoperative, the pistons are of the same diameter and the stroke of piston 10 is such that its swept volume exceeds normal operating requirements, whereby on the braking stroke the pistons normally advance together, the force in the compression spring 13 remaining constant, and displacement of liquid past piston 10 being avoided, while in addition provision,.such as a groove 21 in the wall 20 of the master cylinder, is made to permit liquid to flow past piston 10, with piston 8 in the " off " position, if the pressure in the brake circuit should rise and move piston 10 back beyond its normal " off " position. Instead of the groove 21, a projection may be provided in the cylinder wall to deform the lip of the piston washer 18. In the event of piston 10 engaging an abutment 16 at the end of the master cylinder, due 'for example to excessive leakage, forward movement of piston 8 forces liquid past the washer 18 into the brake circuit, and the pistons are thus returned to their normal distance apart on the return stroke. Specification 539,821 is referred to.