GB820969A - Vehicle weight responsive means - Google Patents

Abstract

820,969. Electrical weighing apparatus. WESTINGHOUSE AIR BRAKE CO. Dec. 6, 1956 [Dec. 9, 1955], No. 37331/56. Class 40 (1). In apparatus for measuring the weight per wheel of a railway vehicle, a plurality of carbon resistors, located within a slot in a rail so as to be responsive to deflection of the upper part of the rail into the slot under the weight of a load, are connected in a Wheatstone bridge arrangement, the unbalance current of which is fed to relays differentially biased to operate at discrete load values. As shown, Fig. 1, in a slot 5 in a rail 1 is located a device 9 comprising a base 10 which is bolted to the rail, four rectangular compartments 14, Fig. 3 (two only shown), defined by insulating walls 13, and a pile of carbon discs 15 in each compartment. Deflection of the top of the rail 1 by a wheel 5a depresses, down to a limit imposed by stops 6, a rail contactor 27 to compress, via a member 20, two of the carbon piles, which are connected to form opposite arms of a Wheatstone bridge energized by a battery (not shown), the other two carbon piles comprising the remaining arms of the bridge and providing temperature compensation. The bridge output is fed to the parallel-connected first coils of three two-coil relays (not shown), a second coil on each of which is supplied from a D.C. source with a biasing current the value of which is adjusted by a variable resistor in each second coil circuit to secure that the relays operate separately at predetermined discrete values of unbalance current. In a modification (Fig. 5) two mutually insulated carbon piles are coaxially located in each of two compartments so that depression of a rail contactor 61 mounted on a lever 57 pivotally supported on a bridge member 55, against the action of a coil spring 66, compresses the two piles CP1, CP4, which form two opposite arms of the bridge and reduces the pressure on the piles CP2, CP3, which complete the bridge. The three relays in the output circuit (not shown) comprise two-coil polarized stick relays, the biasing coil of each of which is connected between the mid-point of a D.C. source and the adjustable contact of one of three potentiometers connected across the source, to supply a biasing current to aid or oppose the bridge output current in the second coil and thus to select the relay operation point in each direction.