GB1102929A - Improvements in and relating to hydraulic master cylinders - Google Patents

Abstract

1,102,929. Hydraulic brakes. H. A. L. VENNER (Renak-Werke VEB). 23 Aug., 1965, No. 36094/65. Heading F2F. In a dual circuit master cylinder for hydraulic braking systems, a primary piston 3 and a secondary piston 2 are arranged one behind the other, a connecting rod 28 and a compression spring 27 being arranged between the primary and secondary pistons, the connecting rod being displaced by a spring 32 in the direction of the primary piston and being arrested axially in the same direction in the secondary piston by means of a pin member 29 which engages a disc 30 and a spring ring provided in the rearmost end of the secondary piston 2 so that a resilient seal 31 on the end of the connecting rod 28 facing the primary piston 3 opens, in the position of rest, an equalizing bore 33 for communication with an equalizing chamber C communicating with a replenishment reservoir via a bore 35. The secondary piston 2 is also provided with an equalizing bore 19 for communication with an equalizing chamber D communicated with a replenishment reservoir via bore 20. The equalizing bore 19 in the secondary piston is adapted to be closed by means of a valve 15, 16 in any position of the secondary piston other than the position of rest. In operation, when the primary piston 3 is moved by a pressure rod (not shown) connected to the brake pedal, the sealing face of the piston 3 approaches the resilient seal 31 on the connecting rod 28 and the chamber A is closed from communication with chamber C. At the same time the secondary piston 2 is moved by the compression springs 27 and 32 and also by the slight pressure building up in the chamber A to close the bore 19 by the packing 16 of the valve 15 so that a further rise in pressure proceeds uniformly in both the pressure chambers A and B leading to respective braking circuits connected to closure screws 7 and 43. When the braking action is terminated the compression springs 4 and 11 and 27 and 32 press the pistons 2 and 3 back into their initial positions, the push-rod 14 and connecting-rod 28 reaching the position of rest sooner than the two pistons due to stop members being provided on the push-rod 14 and the connecting-rod 28 to effect an opening of the equalizing bores 19 and 33 to allow communication between equalizing chamber C and the primary pressure chamber A and between equalizing chamber D and the secondary pressure chamber B. Valve members 41 and 8 ensure a degree of pre-pressure in each of the braking circuits.