GB1530796A - Force transducers - Google Patents

Abstract

1530796 Force transducer: weighing apparatus W & T AVERY Ltd 13 May 1976 [11 March 1975] 10025/75 Headings G1N and G1W This comprises a pair of support members as 10, 12 or 40, 48 constrained to move relative to one another in a predetermined direction and a spaced pair of flexure strips, as 22, 24, or 42, 44, extending alongside one another and face to face, rigidly united together at one end to the support members at the other. Strips 22, 24 are thinner than flexure members 14, 16 and preferably provide 90% of the spring resistance. Connecting piece 26 is displaced to the left or right according to the direction of relative displacement of members 10 and 12 due to the arcuate bending of strips 22, 24 on one or both of the inner faces of which is a strain gauge. These may be a pair of gauges spaced lengthwise on each strip and connected in Wheatstone bridge configuration. The ratio of the flexure length to the spacing between strips is between 1 and 50 and preferably between 1À33 and 20. In the embodiment of Fig. 2 (not shown) support 10 is fixed and force is applied to support 12 and in that of Fig. 3 (not shown) support 12 supports a scale pan. In the embodiment of Fig. 4 (not shown) the force may be applied to strips 22, 24 which extend beyond supports 10, 12. In the embodiment of Fig. 5 the supports comprise a pillar 46 with cantilever 40 and a pillar 48. The embodiment of Fig. 6 (not shown) is similar except that a pair of cantilevers (56) supports a scale pan (50) and the flexure strips (60, 62) are inverted. The flexure strips may be biased in a preloaded state. The change in back pressure of air jets may be used instead of strain gauge signals.