GB147987A - Improvements in or relating to measuring or gauging instruments - Google Patents

Abstract

147,987. Landon, J. W., and Barker, A. W. April 23, 1919. Indicating.-Extensometers, micrometer screw gauges, and other instruments required to measure under conditions of uniform pressure, are provided with a yielding means, employed to obtain uniformity of resistance in the touch or to give a magnified indication of a departure therefrom. Fig. 1 shows the application to an extensometer whereof two levers B, B<1> are attached by centre points to a test piece A, and are separated by a strut F providing at each end a fulcrum for one of the levers. The distance apart of the outer ends of the levers is measured by means of a system of guide rods L, with micrometer screw adjustment M, P, graduated for the effective length of the test-bar, which acts against the attractive force of a spring S, and a part of this system consists in the yielding-means referred to. In the form shown they consist of two long narrow strips of metal G, mounted at their ends in blocks G', G<2> which bear the lever-contracting members H, M', and when the micrometer screw is adjusted for normal tension of the spring S they are very slightly bowed, fiduciary marks upon two blocks G<3> attached to the midpoints of the strips being very slightly displaced. The strips, or equivalent members, must be such that small relative movements of their ends in the direction of their length produce large movements of the blocks. A cover R with inspection opening R' is provided. By suitable connexions the movement may be still more magnified by use of two such sets of strip in series. Scales carried by the mid-point blocks may give a direct indication of the movement of the ends, or these may be indicative by optical means.