Patent GB-628548-A (GB)
Title: A power braking device for vehicles
IPC: B60T8/18
Filed: 1946-04-05
Abstract: 628,548. Fluid-pressure brakes. SOC. ANON. A. CITROEN. April 5, 1946, No. 10579. Convention date, April 13, 1945. [Class 103 (i)] Hydraulic brake mechanism for tractor and trailer vehicles comprises on the tractor a manually-operated master cylinder supplying wheel brake cylinders through a valve device by which the wheel cylinder pressure is dependent upon the load on the axles and the master cylinder pressure, a power-operated master cylinder becoming operative at a predetermined pressure in the supply line, further to supply the wheel cylinders through the valve device. On the trailer the manual master cylinder on the tractor may control but not supply the valve device. The trailer brakes are applied automatically if the coupling breaks. The power source may be a spring normally stressed by the engine suction. As shown, the valve device 12 comprises a valve V controlled by pistons 1, 2 subject to the pressure in pipes 13, 15 connected to the pedal-operated master cylinders 11 and the wheel cylinders W, the fulcrum 4 of the lever 3 being adjusted in accordance with the load on an axle by the link L. The valve device 12 may also be such as described in Specification 628,317. Pipe 13 is connected through a non- return valve 14 to the supply pipe 7 for the cylinders W. A second master cylinder 17, also connected to pipe 7, is operated by a spring 20 normally tensioned by the engine suction acting in a cylinder 24, through pipes 26, 26<SP>1</SP>, and a valve 28. The valve is held in this position by a spring 29 but when the pressure in pipe 13, acting on piston 30, is sufficient to overcome this spring, the valve moves to connect the pipe 26 to atmosphere at A. The spring 20 is then effective through the lever 25 and master cylinder 17 to increase the pressure in the supply pipe 7 and on further increase of pressure in the pipe 13 by the master cylinder 11, the wheel cylinders Ware supplied by the master cylinder 17. The wheel cylinders W are connected by the valve V, Fig. 1, with an exhaust pipe 6 when the pressure in the pipe 13 is reduced. The trailer is provided with a spring-operated master cylinder assembly 31, Fig. 4, similar to that on the tractor. The piston 1 of the valve device 12a, which otherwise is similar to the device 12, is operated by a lever 9 and cable 8, the cables of the devices for the axles being operated by a spring 35 acting through lever 34, equalizer 33 and springs 32, when the tension in a cable 37 extending between the vehicles is relaxed either by breaking of the coupling or by the pressure in pipe 13, 13a acting in cylinder 39 against the action of a spring 38, by which the cable 37 is tensioned. Breaking of the suction pipe 26a for the power device 31 renders this device effective. In a modification, the piston 1 of the device 12a is operated by a small master cylinder mounted on the trailer and operated by a spring acting in a similar manner to that of spring 35. A torsion bar may be used instead of coil springs, for operating the master cylinder 17 and may act through levers so as to apply a constant pressure throughout the stroke. According to the Specification as open to inspection under Sect. 91, there may be a separate control valve for the power device 31 on the trailer. The application of the trailer brakes may then be caused to precede rather than follow that of the tractor brakes. The power source for operating the master cylinder 17 may comprise a spring stressed by compressed air, electrically or mechanically, or liquid maintained under pressure of a spring or compressed air by a pump, or the pressure may be generated only at the time of brake application as by a vacuum-operated piston acting upon a master cylinder. This subject-matter does not appear in the Specification as accepted.