GB478328A - Improvements in or relating to braking systems for vehicles - Google Patents

Abstract

478,328. Fluid-pressure brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and BROCK, D. T. July 17, 1936, No. 19905. [Class 103 (i)] A vehicle braking system comprising a master cylinder unit having a main piston which is forced along the cylinder to create liquid pressure, an intermediate piston in said cylinder acted upon by said liquid pressure, and mechanical means adapted to connect operatively the main and intermediate pistons should the movement of the main piston fail to create liquid pressure, is characterized in that the liquid pressure normally created by the main piston is communicated to a wheel brake assembly by a pipeline, the intermediate piston being connected by a mechanical rigging with another wheel brake assembly, whereby the ratio between the brake-applying force transmitted through the pipe-line and that applied through the mechanical rigging by the action of the pressure liquid is maintained constant. A master cylinder 10 has a piston 13 defining a space 20 in communication with hydraulic wheel cylinders 22, 23. The piston has a stem 26 connected to a head 27 which has radial projections adapted to slide in slots 34 in a sleeve 30 which slides over the stem 26, carries a piston 31, and is connected at 36.. 39 to mechanically actuated brakes 40, 41. The pedal-actuated member 28 is adapted to act upon the head 27 to which an auxiliary piston 42 is secured. A reservoir 15 feeds liquid through a passage 17 to a space 18 behind the main piston 13, a small breathing aperture 19 being provided just in front of the lip of a packing cup 14 in the inoperative position of the piston. Packing cups are also provided at 32, 33, 43. Between the cups 32, 43 is an auxiliary working space 44 of variable volume in communication through a passage 45 with the main working space 20. In operation, movement of the arm 28 anticlockwise causes the pistons 13, 42 to move forward. This produces mechanical actuation of the brakes 40, 41 and creates pressure in the main cylinder 20 which is transmitted to the space 44. As the pressure builds up the wheel brake cylinders 22, 23 are also actuated, and a time arrives when the pressure in the space 44 is of such value that the piston 31 is moved away from the piston 42 thus applying the hydraulic pressure to the previously mechanically-actuated brakes 40, 41, the sleeve 30 then being separated from the head 27. In the event of a breakage or leakage in the hydraulic system, the arm 28 is still able to press on the head 27 to effect mechanical actuation of the brakes 40, 41.