GB772299A - Improved method of, and apparatus for, manufacturing strain-gauges - Google Patents

Abstract

772,299. Resistance strain gauges. ARMSTRONG SIDDELEY MOTORS, Ltd. May 25, 1955 [May 27, 1954], No. 15661/54. Class 40 (1). [Also in Group XXII] A method of making a strain-gauge includes engaging, in a series of equally-axially-spaced positions, a lightly-tensioned straight length of wire, drawing the alternate and intermediate engagement points separately, in a desired sequence, in opposite lateral directions for applying a zig-zag configuration to the wire, and adhesively applying a wafer to the wire for maintaining the applied configuration. Wire 95 to form the strain-gauge passes from a bobbin 86 in a loop tensioned by a weight 97 over a guide bar 91, under a guide bar 83, between guide posts 81 and across hooked needles 21, when the latter are intercalated over a horizontal table 30, and the leading end of the wire is clamped in a channel 66 by a block 67. A strip 34 of absorbent paper is nipped under the needles 21 by the table 30 which is raised by a cam 35 on a shaft 39 rocked by a handle 47. The hooked needles are then manually moved apart in succession from the needle 21a to the needle 21j to form the wire into a sinuous grid. An adhesive soluble in acetone is then applied along lines 100, Fig. 7, and allowed to set to secure the grid to the strip 34. The ends of the wire are then severed at 95a, 95b, the needles 21 moved in to release the grid and the table 30 raised to remove grid from the hooks of the needles. Lead wires 101, Fig. 8, are then adhered to the ends of the strip 34 and the ends of the grid welded thereto at 102. The straingauge may then be applied to a test-piece, e.g. a gas-turbine blade which operates at a high temperature. The gauge is applied wire side down to a layer of heat-resistant insulating cement applied to the test piece, the strip 34 removed by a suitable solvent, and the grid and leads coated with the cement which is caused to adhere to the first layer.