Patent GB-313957-A (GB)
Title: Improvements in brake system for automotive vehicles
IPC: B60T13/46
Filed: 1929-06-06
Abstract: 313,957. Bragg, C. S., and Kliesrath, V. W. June 20, 1928, [Convention date]. Fluid-pressure. - In vehicle brake mechanism of the kind in which the ,cylinder chambers on both sides of the operating piston are normally connected to the suction pipe of the vehicle engine, and one chamber is connected to a source of higher fluidpresure, for example the atmosphere, to apply the brakes, a pressure regulating valve is interposed between the source of higher pressure and the cylinder chamber, to limit the maximum pressure difference on the piston. This maximum may be adjusted by the operator according to the conditions of load and road surface. Fig. 1 shows an arrangement for a tractor and a trailer vehicle comprising cylinders 1, 101 on the tractor and trailer respectively operating rock shafts 76, 76<a> connected to the brakes C, D. The forward chambers of the cylinders 1, 101 are constantly connected by pipes 26, 26<a> to the engine suction pipe 62. The rear cylinder chambers are respectively connected by pipes 16, 16<a>, and pressure regulating valves R, R<1>, and pipe 15 to the operator's control valve V. This valve comprises a casing 6, Fig. 5, connected by a rod 82 to the pedal 80 and a valve member 10 secured to a rod 20, 79 connected to the rock shaft 76. A diaphragm 8 attached to the rod 20 and to the casing is normally seated on the valve 10. An annular chamber 12 is connected by the pipe 14 to the suction pipe 62. The pressure regulating valves R, R<1> each comprise a pair of diaphragms 34, 35, Fig. 2, attached to a casing 30 and to a rod 38. The diaphragm 35 divides a chamber 31 permanently connected to the suction pipe 62, by pipe 27, from a chamber 32 which is open to the chamber 33 through apertures 34a in the diaphragm 34. The chamber 33 is connected to the valve V by pipe 15 and the diaphragm 34 constitutes a valve which seats on an annular member 36 to control the connection of the chambers 32, 33 with the rear piston chamber through the pipe 16. The rod 38 is urged to the right by a spring 39, the tension of which is adjustable by turning a disc 41 having a. cam face in contact with a corresponding face on the casing. Normally, the operator's valve is as shown in Fig. 5, whereby the rear piston chambers are open to suction by way of the pipes 16, 16<a>, the valves R, R', pipe 15, chamber 13 of valve V and pipe 14. When the pedal is depressed to apply the brakes, the diaphragm 8, Fig. 5, seats on the member 11 and is withdrawn from the member 10, whereby air is admitted to the rear piston chambers through apertures 18, 19 in the rod 20, Fig. 5, pipe 15, valves R, R<1> and pipes 16, 16<a>. When the pressure in the rear piston chamber of each cylinder and in the chambers 32, 33 of the corresponding valve R, R<1> has risen to a value sufficient to overcome, the spring 39, the diaphragm valve 34 is seated to prevent further admission of air. By turning the disc 41 by a handle 42 this maximum pressure may be regulated according to the loading of the vehicle or the road conditions. The operator may apply a direct effort to the tractor brakes when desired by the engagement of the casing of the valve V with the member 10. In an alternate arrangement a single pressure regulating valve is provided for both vehicles and is connected by a pipe to the aperture 18 of the valve V so that it controls the supply of air to the rear piston chambers before this air passes through the valve V.