Patent GB-1427115-A (GB)
Title: Load-responsive valve device for a load-dependent braking force controller
IPC: B60T8/30
Filed: 1974-06-13
Abstract: 1427115 Load-responsive devices KNORR-BREMSE GmbH 13 June 1974 [20 June 1973] 26363/74 Heading F2F A load-responsive device for a load-dependent braking force controller for a pressure-mediumoperated brake system, e.g. for rail vehicles, comprises a housing 1, a control pressure chamber 3 in the housing and communicable with the controller, a control valve mechanism 26, 27 and 27, 29 for controlling the pressure in the chamber as a function of vehicle load, and a load-dependent piston 2 in the chamber to transmit a force to the pressure medium in the chamber which is a function of the vehicle load and which is in opposition to the medium pressure controlled by the valve mechanism, the piston being engageable with the valve mechanism to control operation thereof. A lever-type step-down transmission is coupled to the piston to transmit a position of the vehicle load thereto and to control operation of the valve mechanism and comprises levers 9 uniformly distributed about the longitudinal axis of the housing and extending outwardly of the axis, the levers being mounted for pivotal movement in a flexible plate-like member 22. As shown, the chamber 3 is delimited by a diaphragm 2 provided with a pressure member 7 guided in a housing section 6 and bearing, via balls 8, on three levers 9 formed with transverse recesses 14 for pins 15 which bear on an annular plate 16, and recesses 19 for rollers 18 received in an annular groove 20 in an axially displaceable pressure plate 21, the levers, rollers and balls being cast into a flexible plate 22 of plastics material. Bearing on the diaphragm is a spring-loaded pressure plunger 25 which terminates in a valve seat 26 co-operable with a valve seal 27, the latter is also co-operable with a valve seal 29 of the housing 1; the valve seal is retained in a spring-loaded mount 33 guided in the chamber 38 of an insert 34 mounted in a bore 36 of the housing 1 and provided with a venting cap 35. Pipe connections 4 and 31 are connected respectively to the control pressure input of a load-dependent braking force controller and a source of pressure air. In operation, the valves 26, 27 and 29, 27 being closed, the load on the vehicle axle or springing system bears on the pressure plate 21 part of the load being directly transmitted via the rollers 15 and plate 16 to the housing 1 and a smaller portion of the load via the levers 9, which adopt a predetermined equilibrium position, balls 8 and member 7 to the diaphragm 2 which is loaded by the same force by control pressure in the chamber 3. As the vehicle loading is reduced the diaphragm 2 is able to pivot the levers downwardly, as seen in the figure, which movement is followed by the plunger 25 whereby the valve seat 26 is lifted from the valve seal 27 and pressure air flows from chamber 3 via the bore 37 and the venting cap 35 to atmosphere until the pressure in the chamber is reduced to that corresponding to the vehicle loading reduction when the levers 9 then move the diaphragm back to the initial position thereof. If the vehicle loading is increased by a value exceeding a minimum predetermined value the rollers 18 are able to pivot upwardly the levers 9 when the diaphragm is moved into the chamber 3 to entrain the plunger 25 which by its valve seat 26 lifts the valve seal 27 off the valve seat 29 whence pressure air flows through the chamber 30 into the chamber 3 until the pressure level therein is adequate to move the levers 9 back, via the diaphragm 2, into their original position in the housing; the plunger 25 and mount 33 are also moved to re-close the valve 26, 27 to interrupt the pressure air supply to the chamber 3 so that there obtains in the chamber a pressure corresponding to the new vehicle loading. In alternative embodiments the levers 9 are riveted to a solid or annular plate of flexible material, and the levers may be disposed to extend at an angle to the longitudinal axis of the housing. The valve may operate with a gaseous medium other than compressed air or a liquid pressure medium.