Patent GB-414790-A (GB)
Title: A machine for testing extensible material
IPC: G01N3/16
Filed: 1933-02-22
Abstract: 414,790. Testing physical qualities of materials. DUNLOP RUBBER CO., Ltd., 32, Osnaburgh Street, London, WILLSHAW, H., and BRENTNALL, G. C., Fort Dunlop, Birmingham. Feb. 22, 1933, No. 5398. [Class 106 (ii).] A power driven machine for testing extensible material is so arranged that the stretching movement is adapted to be automatically stopped at any two or all three of the following points (a) when the test piece breaks, (b) at a given elongation, and (c) at a given load. The rubber ring to be tested is placed around bollards 2, 3 of which the support for the first is connected by a steel band 98 to the shaft of a pendulum weight 4 the other being mounted on a nut 5 on a screw 6 driven through a clutch 8 and belt and pulley mechanism from a motor 7. Parallel to the screw is a scale 9 attached to the support for the bollard 2 on which slides a cursor 10. The latter carries a trip mechanism 11 which can be set to coact with a trip mechanism 12 carried by the nut 5. The weight 4 hangs on a shaft 14 and its movement is transmitted to a pointer 15 movable over a load scale 16. The pointer can be secured to the scale and control a load trip. Elongation and breaking test. The cursor 10 and pointer 15 in this case are free on their scales. A push button 18 is pressed to rock a bell crank 19 which displaces a rod 20 to tilt a mercury starting and stopping switch 22 and through an extension 23 to tilt a second switch 24. In the latter, the mercury moves from contacts 25-26 to contacts 26-27 and a solenoid 28 is energized which through levers 29, 21 moves the central member 34 of the friction clutch, which is keyed on the shaft 6, to engage a pulley 35 continuously rotated from the motor 7 through belt gearing. The screw 6 is thus driven and moves the pulley 3 away from the bollard 2. As the ring extends, the nut 5 pushes the cursor 10 and the pointer 15 moves over its scale. At breakage the trip 12 comes into play. The nut is made in two parts 39, 40 of which the former engages the threads while the latter, slidable on the part 39 is separated by a spring 41, which during a test is held compressed by the ring 1. The part 40 carries a bracket 42 having a leg 44 adapted to coact with a peg 45 on the part 39, and a leg to coact with a detent 46 on a pivoted part 47 which coacts with a detent 48 on a pivoted part 49 to which is fixed the cursor switch 24. The parts 47, 49 are pivoted to the member 39. Breakage causes the part 40 to move relatively to the part 39 and the detent 46 to tilt the part 47, disengage detent 48 and allow the switch 24 to rock, the mercury moving from contacts 27-26 to 26-25 which de-energizes the solenoid 28 and energizes a solenoid 52 to move the clutch member to engage a pulley driven by a crossed belt and reverse the screw. At the end of the backward travel the nut 5 engages a trip on the support for bollard 2 and stops the motor. The nut 5 also comes on to a plane part 63 of the shaft 6 and is spring loaded at 64 to facilitate re-engagement. Load test for a given elongation. The pointer 15 is free and the cursor 10 is fixed to the scale 9 at the desired elongation. On the cursor is a lever 65 having a leg provided with a lip 68 adapted to engage any of a series of notches 69 in the edge of the scale 9. Setting the lever 65 also sets a cursor trip comprising a leg 71 and stop 72. As the nut 5 approaches the cursor the peg 73 engages the trip and the switch 24 is tilted. Elongation at given load. The cursor is free, its knob being moved to the other side. The pointer 15 is pushed by hand to indicate the given load and is fixed by a nut 74. This causes a cam 75 on the nut to be turned and clamped in position 77. The shaft 14 pivots with the test and rotates through a gear a spindle to which is fixed an arm 80 carrying a cradle for switch 82. Pivoted at 83 is a small lever 84 forked to engage a pin 86 on the switch 82. When the lever 84 contacts with the cam 75 the switch is tilted to break contacts 87-88 and make contacts 88-89 which reverses the drive. Meanwhile, the cursor has been pushed to indicate the elongation. When the pointer 15 is loose it is pushed by the arm 80 engaging a peg 91 fast with the pointer. During the test the specimen is rotated by a gear on the pulley 3 engaging a fixed rack. Cushioning return of pendulum weight. The shaft 14 carries a worm wheel in one with a ratchet wheel with which engage pawls on the support, the wheel being driven from shaft 37 through gearing 100 and shaft 101 in the opposite direction to which the shaft 14 pivots when the weight 4 is lifted. During lifting the pawls click idly round the ratchet, but when the specimen breaks the weight tends to fall in the same direction as the worm wheel is driven and is thus lowered gently.