Patent GB-447487-A (GB)
Title: Improvements in or relating to graphical stress and strain recording apparatus
IPC: G01N3/06
Filed: 1934-11-19
Abstract: 447,487. Testing physical qualities of materials. HUMMERSTON, J., 5, Midland Road, Hyde Park, Leeds. Nov. 19, 1934, No. 33241. [Classes 106 (ii) and 106 (iv)] Comprises a stress-strain recording apparatus including on the one hand test piece engaging levers and on the other hand a pen or chart, one or other of which is carried by a swinging frame, the connection between the two being located coaxially with the pivot of the frame. The hinged frame 8 is supported on brackets 6, 7 on the rear pedestal 5 and passes behind the body 1 so that the test piece engaging mechanism carried by the frame can be disengaged by a backward movement of the latter. The test piece engaging mechanism comprises two horizontal equal and parallel levers 15, 16 extending forwards to engage the test piece 2 by means of their front bifurcated ends provided with centre points tightened by rotation of screwed sockets. Each lever is built up of light metal pieces connected by steel plates. The upper lever 15 which carries a balance weight is connected to the frame 8 by gimbals 32, 33 carried by a bracket 29 adjustable on the bar 14 by means of a screw 31 passing through a bracket 30 fixed to the bar. The levers 15, 16 are connected by means of an adjustable strut 40 provided with pointed ends engaging coned bearings in the levers and held up by springs connecting the levers. The free end of the lower lever 16 carries a bearing block for the lower end of an adjustable strut 52 passing upwards through the hollow gimbal joint to a bearing piece on the end of an intermediate lever 54. When not connected to. the test piece 2, the free end of the lower lever 16 is supported by pins 151 in a spring-pressed bracket 146 slidable vertically in a socket depending downwards from the bracket 29, the upper lever being supported by springs extending from the bracket to engage the outer gimbal ring of the universal joint. These supports are withdrawn when the levers are secured to the specimen by mechanism operated from a central control. The intermediate lever 54 is supported on the frame 8 by means of a knife-edge bearing 55. The other end of the lever is provided with a bearing block 57 engaged by a rod 58 passed vertically through the hollow upper bearing for the hinged frame 8 and engaging the pen operating lever 77 at its other end. The rods 52, 58 are retained in their bearings by springs in the same manner as the strut 40. The pen operating lever 77 is supported on a knife-edge bearing 78 and at its front end carries a light arm 79 and pen 80. The latter, moved vertically proportional to strain, engages a chart held by a holder 85 moved horizontally proportional to stress. The holder 85 is supported by a carriage 88 moved on guides 90 by a screw 91 driven through gears 95, 96, shaft 97 and gears 100, 101, 102 from the wheel 4 controlling the loading mechanism. With long levers, a flat chart holder as shown may be used, but with short levers a cylindrical form of holder with the axes of the surface coincident with the pen axes may be used. The flat chart holder 85 has in front of it a plate 110 drawn against the rear plate by springs acting on studs 113 passing through holes in the plate 85. The holder is attached to a spindle 114 slidable without rotating in bearings 115, 116 so as to engage or withdraw the chart from the pen 80. The front and rear plates may be separated for insertion of a chart by withdrawing the spindle 114 to its extreme position when studs 113 engage stops 120 just prior to this position, the parts separating on the last part of the movement. The spindle 114 is withdrawn by a lever 121 operated from a central control against the influence of a spring. The apparatus may be fitted with a centrifugal control mechanism similar to that described in Specification 397,596 providing for a control lever which through cam and Bowden wire mechanism accomplishes in proper sequence the withdrawal of stops for the hinged frame 8, the strain transmission levers 15, 16, the engagement and disengagement of pen and chart, and the fastening and release of the chart. In a modification, an intermediate lever of bellcrank form is used.