Patent GB-312350-A (GB)
Title: Improvements in brake system for automotive vehicles
IPC: B60T8/20
Filed: 1929-05-02
Abstract: 312,350. Bragg, C. S., and Kliesrath, v. W. May 25, 1928, [Convention date]. Fluid pressure. - Fluid-pressure brake apparatus for vehicles comprises two or more cylinders or actuators operating brakes on the same or different vehicles and one or more pressure-regulating valves independent of the single-control valve by which the brakes are applied and released, for determining the maximum pressure acting on the pistons according to the load or road-surface conditions. Fig. 1 shows an arrangement for a tractor A and a trailer B wherein the brakes are operated by the suction of the engine. The cylinder 1 on the tractor is secured by arms 77 to the rock shaft 76 whereby it applies the steering-wheel brakes C, the piston being connected to the shaft 76<a> of the rear brakes D. The cylinder 101 actuates the trailer brakes E. The common control valve for both cylinders comprises a casing 6, Fig. 3, connected by the rod 78 to the rock shaft 76<a> of the rear brakes D. A rod 82 extending from the pedal 80 and slidable in the casing is connected to a diaphragm 8 and a disc valve 10. Normally the parts are in the position shown so that the cylinders 1, 101 are connected by the pipes 14<a>, 14<c>, 14, the pressure-regulating valves P, P<1> past the valve 10 and through apertures 19, 18 to the atmosphere. Depression of the pedal 80 seats the valve 10 on the diaphragm 8 and deflects the diaphragm away from the annular seat 11 so as to connect the cylinders 1, 101 through the passage 12 and pipe 32 to the induction pipe 61 of the engine, thus applying the brakes on the two vehicles. The pressure difference acting on the faces of the valves and diaphragm indicates to the operator the pressure applied to the brakes. By the engagement of the collar with the valve casing 6 a direct effort may be applied to the rear brakes D. The pressure-regulating valves P, p<1> that are interposed in the pipe connections 14 from the valve 6 to the cylinders may comprise a casing 30, Fig. 2, to which is secured a diaphragm 36 arranged to seat on an annular seat 34 which forms a chamber 35 connected to the brake cylinder, the chamber 34a being connected to the valve 6. The diaphragm is open on one side by apertures 32 in a fixed cap 31 to the atmosphere and is urged away from its seating by a spring 41 in the form of a spider which bears on a disc 40 rotatable by a hand lever 40<b>. The disc 40 and a fixed disc 43 have interengaging cam surfaces so that the pressure of the spring can be adjusted by the lever 40b. When during the application of the brakes the vacuum in the brake cylinder attains the value sufficient to overcome the spring, the cylinder is cut off from the control valve by the seating of the diaphragm 36. By adjustment of the valves P, P<1> the degree of vacuum attainable in the brake cylinders can be reduced from the maximum suitable for maximum load on a dry track to such as will prevent locking of the wheels with reduced load or wet or muddy conditions. An arrangement is also described in which the pistons of the brake cylinders are normally subject to vacuum on both sides, air being admitted to one side to apply the brakes. In this case the pressure-regulating valves are interposed in the connection between the engine suction pipe and each of the forward chambers of the cylinders in which the vacuum is constantly maintained. An additional pressure-regulating valve may however be interposed between the suction pipe and the control valve, which may comprise a casing 206, Fig. 6, connected by a rod 282 to the pedal and carrying a diaphragm 208 attached to a tubular rod 220 connected to the tractor rear brakes. A cupshaped valve 210 is also secured to the rod 220. With the parts in the normal position shown, the rear chambers of the brake cylinders are connected by the pipe 214<a>, 214<b>, chamber 213 and pipe 232<a> to the engine suction pipe. Left-hand movement of the rod 282 and casing 206 engages the diaphragm 208 with the seating 211 to cut off the suction connection and unseats the valve 210a to permit the supply of air to the brake cylinder chambers by the apertures 218, 218<a> in the rod 220, thus applying the brakes. The forward side of the diaphragm 208 is constantly connected to the suction pipe by apertures 219.