Patent GB-397596-A (GB)
Title: Improvements in or relating to graphical stress and strain recording apparatus
IPC: G01N3/06
Filed: 1932-04-19
Abstract: 397,596. Testing physical qualities; recording-apparatus. HUMMERSTON, J., 11, Acacia Grove, Reddish, near Stockport. April 19, 1932, No. 11145. [Classes 106 (ii) and 106 (iv).] A testing-machine having a flat chart traversed in accordance with applied load and a pen moving in accordance with resultant strain, or vice versa, is provided with centralized control means for withdrawing the chart holder from the pen, releasing the chart from the holder, positioning the levers of the penactuating mechanism when detached from the test piece and positioning the recording apparatus as a whole for attachment to the test piece, and has means for periodically separating the pen from the chart to relieve friction therebetween. The chart holder 10, Figs. 2 and 3, may be given a rectilinear movement by a screw 30 driven through change gearing 36..42 from the hand-wheel 47 by which the loading of the machine is controlled. The frame 1 carrying the recording apparatus swings around the pillar 5. The pen 25 is carried by an arm 84 (or by a slide linked thereto) integral with a lever 82 pivoted between points 83 and resting upon a rod 81 which is actuated by a lever 53 attached to the test piece 6, Fig. 6. An upper lever 52, counterweighted and pivoted on a gimbal ring 64 throngh which the rod 81 passes, forms a datum relatively to which the lever 53 moves about a fulcrum provided by a rod 71. The rod 71 is adjustable in length and the levers are held thereto by a pair of tension springs, the abutments 74, 75 being adjustable in slots 77 by means of bevelled surfaces engaged by tapered set screws 78. The levers 52, 53 are attached to the test piece 6 by pairs of needle points provided with right and left handed screw threads and rotated by pinions 59 from a knob 62. One of the points incorporates a spring plunger so as to follow up any reduction in diameter of the test piece. When the levers are not attached to the test piece they are positioned by means of a support 90 and stems 98, that are lifted into contact with the lower lever 53 and the gimbal ring 64 by a spring 95 when a cable 110 is released by a cam 101 on the spindle 102 of the central control lever 99. A second cam 100, Fig. 3, on the same spindle actuates a cable 109 attached to a lever 27 to withdraw the chart holder 10 from the pen 25. The chart is gripped by a frame 9 carried by studs 24 retracted by springs 23. When the chart holder is withdrawn from the pen, the studs 24 abut against stops 26, and further withdrawal of the rear plate 10 of the holder releases the chart. To prevent damage of the pen by the frame 9 of the chart holder if the range of the test exceeds that of the chart, the holder is withdrawn from the pen by a cam surface 137 engaging a runner 135 mounted on an arm 136 attached to the part 11 of the holder. Periodic withdrawal of the holder to relieve the friction between the pen and chart during the making of the record, is effected by a polygonal cam sliding on the shaft of the screw 30 that moves a lever engaging the member 11. In the case of a fluid-pressure type of testing machine in which the chart holder is traversed by a ram acting against a spring or pendulum, the friction relieving cam may be driven by an electric motor. At the end of its travel the chart holder is stopped automatically by disengagement from the screw 30, by disengagement of the gears 36 .. 42, or by a clutch. In applying the recording apparatus to a test piece, the frame is turned about the post 5 until a cam 119 on the central control spindle 102 engages a stop on the main frame of the machine. When the spindle 102 is turned to bring the chart holder &c. into the operative position, the cam 119 is disengaged from the stop so as to allow slight self-adjustment of the recording apparatus. If a rotary chart holder 149, Fig. 14, is employed it is driven by gearing 143 .. 146 from the shaft 147, the withdrawal of the holder from the pen is effected by a claw 153 engaging a ball race 159, the opening of the chart holder is caused by a plate 152, attached to the studs 151, engaging a boss 139, and the friction relieving cam 167 acts axially, being carried by the rotating holder and engaging a roller 170 mounted on a fixed arm 171. For compressive, transverse, or torsional tests the lever system 52, 53 is modified as described in Specification 216,266.