GB1236791A - Improvements in or relating to apportioning valves for braking systems - Google Patents

Abstract

1,236,791. Fluid pressure brakes. CLAYTON DEWANDRE CO. Ltd. 29 Jan., 1969 [29 Jan., 1968; 16May,1968], Nos. 4489/68 and 23374/68. Heading F2F. In an apportioning valve for use in an air pressure braking system for motor vehicles, concentric inner and outer pistons 3 and 4 are adapted to be displaceable by signal pressure supplied through conduit 9 connected to the brake control line and arranged to actuate directly valve means 13 controlling flow of air pressure to the brake actuator via port 19 and a pressure-sensitive reaction piston 24 is also responsive to the active braking pressure via passage 26 and acts in a direction at right angles to the axes of the pistons 3 and 4 to force a roller member 35 along an inclined plane 36, the angle of which is variable according to the vehicle load. Fig. 2 shows the arrangement for varying the inclined plane 36 wherein a torsion spring arm 40 is clamped at one end to the member 37. In operation, under normal running conditions, the hollow spring-loaded poppet valve 13 engages a seating 14 whilst a seating 15 is spaced from the valve so that the brake actuators are connected to exhaust through a passage 18, the bore of the valve 13 and the chamber 21. When the brakes are applied, a signal input from the brake valve is introduced through the port 9 to displace the piston assembly 3, 4 downwardly to close of the exhaust connection at valve seating 15 and then displace the poppet valve 13 from its seating 14 to connect the brake actuators with the compressed air brake supply via passage 17. The downward movement of the input piston assembly is transmitted through the interconnected piston and push rods 27, 31 to the reaction piston 24, but the pressure created in the passage 18 is also transmitted through passages 26 to the outer face of the reaction piston opposing movement thereof. The degree of reaction and thus the brake in pressure created for the given braking effort is dependent upon the inclination of the yoke member and therefore upon the vehicle load. An alternative embodiment is disclosed in Figs. 6 and 7 (not shown), wherein the apportioning valve is adapted for use in a dual-line tractor-trailing braking system and wherein a relay emergency valve unit for the trailer braking section is superimposed on the apportioning valve to provide relay and emergency actuation of the trailer brakes through the apportioning valve.