An instrument for the testing for accuracy of weighbridges and other weighing instruments of high capacity

摘要

695,362. Testing weighing apparatus. BURTON, P. Nov. 29, 1950 [Nov. 30, 1949]. No. 30714/49. Class 143. An instrument for testing the accuracy of weighing instruments of high capacity, e.g., weighbridges, comprises a fulcrummed lever, one end of which is coupled, during testing, to the long arm of a steelyard under test or, if a self indicating scale is under test, to a subsidiary lever thereof, and a weight carrier which is supported by said lever between said one end and the lever fulcrum; and is characterized in that the carrier is movable along the lever so that the movement of a unit weight supported thereby can be adjusted to balance a heavier unit weight supported by the weighing instrument whereafter, when additional unit weights are placed on the carrier, the movements of the load counterbalancing means of the weighing instrument necessary to return the weighing instrument to equilibrium should correspond with unit increments of load indicated by said weighing instrument. The instrument shown in the Figure operates as follows: With the lever A coupled to the long arm of a steelyard M by link O, carrier I in its extreme position of adjustment on the left hand end of the lever and a detachable weight G exactly counterbalancing said carrier, a heavy load, e.g. a lorry, is moved onto the weighbridge and the steelyard counterpoise is adjusted to return the system to equilibrium. Since the lever is itself in equilibrium it plays no part in counterbalancing the load. The detachable weight G is now removed, an additional load of one ton is applied to the weighbridge and the carrier I is moved by a screw K to a new position on the lever in which it again restores equilibrium in the system, thus the additional load is exactly counterbalanced by the carrier assembly and subsequent, incremental additions of weights-each of the same weight as the carrier assembly-can then be counterbalanced by incremental subtractions, in one ton steps, of the counterbalancing force exerted by the steelyard counterpoise to check its accuracy. In a modification described in the Provisional Specification only the detachable weight G is replaced by a weight equal to the carrier assembly and mounted on a reverse threaded screwed extension of screw K so that the carrier is counterbalanced in all positions of adjustment. With this arrangement assuming the parts to be in equilibrium with the heavy load on the weighbridge, a one ton weight is applied to the weighbridge, a one unit weight is applied to the carrier and the system is again brought into equilibrium by movement of the carrier; the testing operation is then carried out as before. The use of both these instruments is also described in connection with the testing of self indicating scales.