GB824899A - Improvements in and relating to control valve assemblies for fluid pressure operated braking apparatus - Google Patents

Abstract

824,899. Fluid-pressure brakes. COMPAGNIE DES FREINS ET SIGNAUX WESTINGHOUSE. Feb. 17, 1958 [Feb. 19, 1957], No. 5044/58. Class 103 (1). In a control valve assembly for fluid pressure operated braking apparatus in which the braking effort is proportional to the load, a pivotally mounted lever has two arms, one of which is adapted to limit the degree of opening of the valve controlling flow of fluid under pressure to the brake cylinder and another arm which is connected to an equalizing piston subjected on one side to the fluid pressure in the brake cylinder and on the other side to atmospheric pressure, the pivot point of the lever being manually displaceable along an axis substantially coincident with that connecting the free ends of the two arms of the lever. In the control valve assembly for a tractor-trailer assembly illustrated, a tractor valve T and a trailer valve R are both actuated by a double arm rocker bar 3 and connecting-rod 2. The valves R and T each have a separate lever handle 15 and 151 respectively to control the load and braking pressure according to the load on the respective vehicle. Fig. 2 shows a section through II-II of Fig. 1 through trailer valve assembly R; the tractor valve being of similar construction as may be seen in Fig. 3 apart from the inclusion of a spring which ensures a certain delay in the operation of the tractor braking valve in comparison with the operation of the trailer braking valve R upon actuation of the rod 2. Under normal running conditions no pressure is applied to the plungers in the valves T and R such that the passage 11 leading to the trailer brake cylinders (Fig. 2) is open to atmosphere via aperture 12. Similar conditions hold good for the tractor brake cylinders associated with the valve T. For the braking condition, the control levers 15, 15<SP>1</SP> are preset to the loading conditions prevailing to displace sleeve 17 carrying lever 13 along an axis substantially coincident with that connecting the free ends of the arms of the lever 13, and the driver actuates the control rod 2 by means of a brake pedal (not shown) to force the plungers 4a of each valve downwards against a valve 9 thus breaking the connection between the braking cylinders and atmosphere and then continuing its downward movement ensures opening of valve 9 to admit compressed air to the braking cylinders and urge equalizing piston 18 downwards such that its action on lever 13 of the empty-load device limits the downward movement of plunger 4a and hence the degree of opening of valve 9 to restrict to a predetermined value the fluid pressure exerted on the brake cylinders to a function of the vehicle load as preset.