Patent GB-380782-A (GB)
Title: Improvements in apparatus for indicating and/or recording mechanical loads or stresses
IPC: G01N3/06
Filed: 1931-06-08
Abstract: 380,782. Stress indicating and recording apparatus. ROBERTS, A. M., Holly Bank, Irlam Road, Flixton, Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. June 8, 1931, No. 16688. [Class 106 (ii).] A stress-time or stress-strain indicating and/or recording apparatus comprises a diaphragm 1 having a boss 2 in threaded engagement with a link connected to one end of the specimen the other end of which is moved by means of screw-and-nut gear operated through speed reduction mechanism from an electric motor, which reduction mechanism has coupled with it a driving mechanism for photographic paper or films. The diaphragm 1 is integral with the member 4 which is secured to the rigid frame of the apparatus and which has rigidly mounted upon it a member 5 having a diaphragm portion 6 more flexible than the diaphragm 1 and forming with the diaphragm 1 a chamber 7 filled with mercury or other actinically opaque liquid communicating with the restricted passage 8, capillary 9, three jets 11 and recess 16 in the steel member 12 having capillary 17 leading to rectangular tube 13, glass plates 14 forming two sides thereof whilst the steel member 12 forms the other two sides. The tube 13 is closed at its upper end by means of a steel cross member. The diaphragm 6 avoids undesirable effects resulting from fracture of the specimen being then displaced without sensible change of volume of the space 7, the cushioning effect being furthered by the restricted cross section of the communication 9, 11, 17 between the chamber 7 and the tube 13. For zeroizing purposes there is provided a drum-shaped member 18 having a flexible diaphragm 19 and having a finely screwthreaded edge engaging in the member 5 whereby it may be made to variably press upon the diaphragm 6. The photographic paper or film is carried on the drum 20 mounted on the hollow shaft 21 by means of disc members 22, the shaft 21 being secured to a rotating spindle 23 by means of a screw 24 having pinned to it at its upper end a milled head 25 through which the drum 20 and shaft 21 can be readily removed from the spindle 23. The spindle 23 is rotated from a shaft 28 through worm 29 and worm wheel 30, backlash between which is retrieved by a coiled spring 31. The shaft 28 is driven from the reducing mechanism which applies the load to the test piece. The drum 20 may be clock driven. The recording drum is enclosed in a casing 32 having a light-tight removable lid 34 and having a slit 35 arranged against the tube 13, a light shoot 36 being arranged in line with slit 35 and tube 13. A light shutter 37 having a felt or velvet face is provided on the light shoot 36. An electrical contact member 38 having a contact portion 39 is mounted on the partition 33 forming the bottom of the casing 32 and a co-operating movable contact member is carried by the lower supporting member 22 of the drum 20, said contact member comprising a pillar 40 carrying a screw 41, the tip 42 of which engages with the contact portion 39 after one complete revolution of the drum 20 to shortcircuit the no-volt coil on the control gear of the electric motor providing the load. The drum 20 together with its supporting and driving means and the casing 32, 34 and light shoot 36, may be omitted, an indication of load being provided by the liquid in the tube 13.