Patent GB-498303-A (GB)
Title: Improvements in or relating to graphical stress-strain recording apparatus and strain indicating and measuring apparatus
IPC: G01N3/06
Filed: 1937-07-05
Abstract: 498,303. Testing physical qualities of materials. HUMMERSTON, J. July 5, 1937, No. 18580. [Class 106 (ii)] In a graphical stress-strain recording or strain indicating apparatus, the movement due to strain of a test piece and the movement from an independently operated strain recording or indicating mechanism are simultaneously communicated to different parts of a pivoted indicating member which is provided with optical means for magnifying the resultant movement. The test piece 1 is suspended from the holder 2. The chart holder 7 is flat and attached to a slide 8 operated by a screw 10 which may be moved from a motor 11 through worm, belt and bevel gearing, 12, 15, 17, 18. An " intermediate " lever 19 works on pivots 20, 21 carried by an " adjusting lever 22 working on pivots 23, 24 engaging holes in a bracket 25 fixed to the recorder bracket 6. A screw 26 serves to adjust the lever 22. The right-hand end of lever 19 rests by means of a hardened ball 28 on a projection 29 fixed to the slide 8. An " indicating " lever 30 shaped as in Fig. 8, with its breadth much greater than the length, is supported upon pivots 31, 32 carried by a bracket 33 attached to the lever 19, and is connected at a definite distance from the pivot line of the lever by a rod 34 to a lever system 39, 40 engaging the test piece 1. The upper lever 39 is supported through bearing pins 41, 42 from the suspension plates 43, 44 while the lower lever 40 is suspended from the upper by an articulated linkage 45. The left-hand end of lever 40 engages the lower end of the rod 34 which passes through a hole in the upper lever. A weight 47 balances the system. A stop 48 may be moved up to locate the lower lever when not connected to the test piece, a pin being inserted in the hole 49. The suspension plates 43, 44 are connected to a rotatable socket 50 by studs 51, 52 so that the levers 39, 40 may be swung out of the way when inserting a test piece. A latch piece 53 serves to position the levers 39, 40 while connecting to the test piece. The " indicating " lever 30 is provided with a mirror 38 which reflects a beam from a source 55 to a screen 56, a lens 57 serving for focusing. The screen is marked with two parallel lines between which the image of the lamp filament is caused to lie by adjusting screw 26. When testing, a constant movement is given to the chart holder 7 by the motor 11, and if the operator watches the image and so regulates the application of strain to the test piece that the image is stationary, the movement of the chart must be proportional to the strain. The members may be designed to give the required ratio. Alternatively, the strain may be applied at a constant rate and the movement of the chart regulated. The horizontal movement of the pen 65 is derived from the loading mechanism by any suitable means. The lever 30 may carry a pointer instead of a mirror. To provide a larger velocity ratio between chart holder and pointer, multiplying mechanism may be used and one form of this construction is described. In another form the pen is given a vertical movement proportional to stress and the chart holder is moved horizontally proportional to strain. A form in which a recording drum is used is also described.