GB719665A - Improvements relating to automatic control valves for variable load braking apparatus for vehicles - Google Patents

Abstract

719,665. Fluid-pressure brakes. WHITE, J. April 24, 1953 [June 25, 1952], No. 15946/52. Class 103(1) In an automatic control valve device for variable load braking apparatus for vehicles, a valve governs communication between a first and second chamber and a measuring piston or diaphragm has its working face subjected to the pressure in the first chamber and acts through a first spring to extend a measuring member against the opposing action of a second spring; a dash pot device is included comprising a pair of axially aligned and rigidly spaced apart movable abutments, the arrangement being such that the valve is opened by the movement of the abutment in one direction and allowed to close by the movement of the abutment in the other direction. In one form, the vehicle is equipped, in addition to the usual brake pipe, triple valve, brake cylinder and auxiliary reservoir, with means for measuring the deflection of the vehicle springs and thus the load carried by the vehicle, a variable volume device and an automatic control valve which forms the subject of the invention and functions in such a manner that when the vehicle is fully loaded, the communication between the brake cylinder and the variable volume device is cut off and when the vehicle is empty or partially loaded and is established, when a brake application is initiated, until a predetermined proportion of the compressed air supplied to the brake cylinder has passed into the variable volume device, thus reducing the brake force exerted by the brake cylinder by an amount determined by the vehicle load. The automatic control valve comprises a cylindrical body having end casings 2, 19 housing the working parts, and mounted on the vehicle underframe. In operation, upon the initiation of a brake application. compressed air is supplied to the brake cylinder (not shown) and passes into the communicating supply chamber 15, the measuring piston 16 thus being forced outwards against the action of the spring 18, the length of its stroke depending upon the deflection of the vehicle springs. This movement is transmitted through the cross member 21 and longitudinal rods 5, 30 to the yoke 1 and through the yoke to the calibrated spring 3 which is compressed accordingly and transmits a corresponding thrust through the oil dashpot device 10 to the diaphragm 12 which controls the opening of the spring loaded valve 13 controlling the flow of air from the supply chamber 15, connected with the brake cylinder, to the second chamber 26 connected with the variable volume device, until the pressure in the latter, acting on diaphragm 12, overcomes the opposing force exerted by the calibrated spring 3 and allows the valve to reclose. Upon release of the brakes, the pressure in the brake cylinder falls below that in the variable volume device and the valve accordingly opens to allow air from the latter to pass back into the brake cylinder and thence to atmosphere. Specifications 602,382 and 719,666, [Group XXXII], are referred to.