GB587099A - Hydraulic brake - Google Patents

Abstract

587,099. Brakes. PAGE, H. E. Jan. 3, 1945, No. 256. Convention date, Jan. 3, 1944. [Class 103 (i)] In a hydraulic brake system, pressure is first applied to a small area of a piston in the brake cylinder and subsequently to a larger area of the same piston. Fig. 6 shows the brake cylinder for an internally expanding brake operated by a pedal-actuated master cylinder. The members 23 are pivoted to the brake shoes and abut against plugs 50 in the ends of pistons 45, 55 each of which has a small inner end 45a, 55a and a larger outer end 45b, 55b. The brake cylinders are correspondingly stepped. The master cylinder is connected to an inlet port 37, so that the pressure fluid flows through passages 65, 66, to act upon the small areas of the pistons 45, 55, the valves 48 remaining closed. When the brake linings contact with the drum, the fluid pressure rises and the valves 48 open to admit the pressure fluid, through ports 95 in the pistons, to the larger piston areas. The spaces behind the larger piston areas are kept filled, during the initial movements of the pistons, by suction from a reservoir R through a passage 76, a ball-valve 79 and a passage 70 connecting the said spaces. When the master cylinder pressure rises a piston valve 60 rises against spring pressure to close the return passage 72 connecting the said spaces in the reservoir R. The shoes are withdrawn from the drum by springs anchored on lugs 82. In a modification, a single two-area piston is provided in a cylinder disposed radially relatively to the brake drum, a piston rod being connected to toggle links pivoted to the ends of the shoes.