Patent GB-746215-A (GB)
Title: Improvements in hydraulic braking systems for vehicles
IPC: B60T8/26
Filed: 1954-05-26
Abstract: 746,215. Hydraulic brakes. SVENSKA BROMSBANDSFABRIKEN AKTIEBOLAG. May 26, 1954 [May 27, 1953], No. 15540/54. Class 103 (1). In an arrangement for hydraulic braking systems, provided with a common operating member to apply the brakes both on the front and rear wheels of a vehicle, a weight or the like is actuated by the retardation and movable in the longitudinal direction of the vehicle, and adapted when moving to control the supply of pressure to the rear wheel brakes. In the diagrammatic view illustrated in Fig. 1, locking of the rear wheels of the vehicle on retardation, due to load transference to the front axle, is prevented by means of a weight 13 carried by a yoke 12 and adapted to swing substantially about the pivot of the link 14, leading from the braking pedal 11, at the yoke in the direction of the curved arrow when the retardation of the vehicle reaches some predetermined figure. This tendency of the weight 13 thus results in the braking force on the front wheels 1 to be increased due to the increased penetration of the piston 9 of the hydraulic master cylinder 7 supplying the front wheel brake cylinders 3 via conduit 5, whereas the braking power on the rear wheels 2 decreases due to the fact that the piston 10 of the hydraulic master cylinder 8 supplying the rear wheel brake cylinders 4 tends to withdraw from the cylinder. Depending on the mechanical construction, it is possible to alter the linkage to obtain a varying degree of braking on the front and rear wheels of the vehicle. In the embodiment illustrated in Fig. 2, a valve arrangement is shown which is intended to be used in systems where there is only one master cylinder and from which conduits 5 and 6 lead to the wheel brake cylinders of the front and rear wheels respectively. This arrangement comprises a cylindrical chamber 16 within which slides a piston 17, which corresponds to the weight 13 in Fig. 1. The piston 17 is provided with a bore 18 connecting both sides of the piston to one another and stem 19, the free end of which forms an abutment which is adapted to co-operate, against the action of a spring 21, with a spring-biased valve 23 which co-operates with an outlet opening 20 in one end wall of the chamber 16 which has its axial extension in the longitudinal direction of the vehicle. In operation, when the brake pedal is depressed, hydraulic pressure is supplied via conduit 15 to the chamber 16 and thence to the front and rear wheel brake cylinders 3 and 4 via conduits 5 and 6 respectively. At a certain retardation, the piston 17 is forced to the left to close the conduit 6 to the rear wheel brakes and continued depression of the foot brake pedal will not increase the pressure supplied to the rear wheel brakes, which are thus braked with constant power, whereas the front wheel brakes are braked more powerfully. A differential piston device 26 is also fitted in conjunction with the valve arrangement to assist in further reducing the braking pressure supplied to the rear wheel brakes when a certain retardation has been reached. By adjusting the tension of the spring 21 or by inclining the chamber 16 slightly rearwardly or forwardly, the arrangement will be made to operate at a higher or a lower retardation respectively.