Patent GB-201704-A (GB)
Title: Improvements in and relating to appliances for the testing of materials
IPC: G01N3/32
Filed: 1922-06-10
Abstract: 201,704. Dalby, W. E. June 10, 1922. Testing physical qualities of materials; linear-dimension gauges.-Relates to machines of the type in which a test piece is rigidly coupled coaxially with a standard torque bar, and consists in converting the twists in the test piece and in. the standard bar respectively into a longitudinal movement parallel to the axis of the test piece and a movement at right angles to the axis of the torque bar for the purpose of actuating indicating means. The preferred form of test bar shown in Fig. 2<a> comprises a cylindrical part b with flanges a marking the gauge length and provided with large flat end parts c. Fig. 3 shows the torque-bar the thin part f of which takes the angular twist, and the bar is so designed that the specimen b' breaks well before the torque bar reaches its limit of elasticity on shear. One end of the torque-bar is bolted at k, Fig. 4, to a part l of the framing, the other end being clamped by the screws h to one. end of the specimen. The other end of the latter is received into a similar jaw q provided with a square shank which fits into a socket in the end of a part r which passes through the boss of a worm whee! and can be adjusted lengthways along the axis of the wheel but cannot rotate relatively to it. A worm m and handle t serve to turn the wheel and place the system under torsion. The torquebar is extended at o beyond the flange j and carries a casing for the optical apparatus. This comprises two mirrors formed by two double reflecting prisms with a focussing lens between them, the axes of the mirrors being at rightangles to one another. The angular twist of the specimen is transmitted to the upper prism by means of a triangular table or plate u having three legs. One leg d engages a hole in one flange, the second leg v<1> engages a groove in the other flange which groove is parallel to the axis of the specimen, while the third leg v<2> engages a groove w<1> in a lever w supported on a knifeedge X. A screw H passing through the end of the lever engages a pivoted rod Z which transmits motion to the upper prism y'. The movement of the torque bar is transmitted to the lower prism U by a rod A connected to the thick part B and carrying an arm C which moves a vertical rod E which tilts the lower mirror. The reflected rays from a small lamp source O<3> are received on a screen or photographic plate G. Means are described to eliminate any effects due to 'bending of the torque-rod. The machine is calibrated by placing a lever on the jaw g of the torque-bar, and hanging known weights on the lever. This moves the lower prism and the upper one is moved by hand to trace a line on the photographic plate. To calibrate for twist, a specimen is prepared consisting of two parts which can be moved relatively to one another, one part being provided with a collar having a scale of degrees engraved thereon. The part held in the sliding sleeve r can be turned through a known number of degrees relatively to, the other part, and the lower mirror is tilted by hand so that a line is traced on the plate corrres. ponding to a definite angle of twist. Specification 113,008 is referred to.