Patent GB-721800-A (GB)
Title: Brake torque limiter for hydraulic brakes
IPC: B64C25/46
Filed: 1953-01-05
Abstract: 721,800. Brake torque limiter for hydraulic brakes. WINGFOOT CORPORATION. Jan. 5, 1953 [Aug. 26, 1952], No. 263/53. Class 103 (1) In a brake assembly combination including an axle, a wheel journalled on the axle, a brake actuator support axially movable on the axle, a hydraulic chamber between the axle and the brake actuator support and brake actuation means for retarding the rotation of the wheel and for moving the brake actuator support axially on the axle, pressure actuated means is provided for reducing the actuation of the brake actuation means when a predetermined pressure is set up in the hydraulic chamber. When conventional spot-type disc brake means 12, operatively associated with brake actuation support flange 4, are applied, the support flange 4 is provided with a slight axial and radial movement on the axle 1 due to the inclined splines 2, 3 on the axle and support flange 4 respectively (Fig. 1). This action results in fluid in hydraulic chamber 11 being compressed to operate piston 17 which is slidable in the hydraulic control cylinder 14. The piston 17 is provided with a head 18 adjacent the opposite end of the cylinder 14 from that which fitting 15 engages and is connected thereto by a piston rod 19. Hydraulic pressure is transmitted by head 18 through fitting 20 to a pressure-actuated electrical switch 21 which is provided with a pressure-controlled diaphragm 24; a predetermined pressure on which results in switch 21 being closed. Fig. 3 shows how the brake application means can be controlled through the electric switch 21; power being supplied from source 26 which is connected in series to a control solenoid 27 so that when switch 21 is closed, the solenoid operates to control a two-position valve 31. The normal position of the valve 31, when the switch 21 is not made, is illustrated in which hydraulic fluid is supplied by a suitably driven pump 32 through a brake pedal-controlled valve 33 and conduit 34 to the conventional spot-type disc brake actuating means 12 when the brake pedal is actuated. However, when switch 21 is closed, the solenoid 27 is energized to draw valve 31 to a second position in which the fluid in the brake actuating means 12 flows back through a bore 35 in the valve 31, through conduit 36 to a fluid storage chamber 37. In the embodiment shown, a plurality of independent brake discs and brake actuators are shown mounted on axle 1. A second brake actuator support flange 39 acts in a similar manner to support flange 4 but moves in an oppositely axial direction on axially-directed splines 44, 45 as braking forces are applied to the brake actuation means 55. Fluid in the hydraulic chamber 46 is thus pressurized and fluid flows through conduit 48 to the hydraulic control cylinder 14 and fluid pressure acts on the underside of piston 18 and operates the piston in the manner previously described to release pressure on brake actuation means 55 when the pressure reaches the predetermined level. Accordingly, the apparatus of the invention functions to limit the total braking torque where the brake actuator flanges 4 and 39 have equal or totally different braking forces applied thereto. The rotational direction of the wheel is such with relation to splines 2 and 3, 44 and 45 that the brake actuator support flanges are urged outwardly apart as braking forces are applied to the brake discs. This creates the torque measuring and control pressures in chambers 11 and 46, as aforesaid, to control the operation of the switch 21 and the relief of the braking pressure if the total braking torque exceeds a safe limit.