Patent GB-191020369-A (GB)
Title: Improvements in or connected with Testing Machines.
Inventor: DENNISON GEORGE HENRY
IPC: G01N3/06
Filed: 1910-09-01
Granted: 1911-05-18
Abstract: 20,369. Denison, G. H. Sept. 1. Testing physical qualities of materials.-Apparatus for measuring and indicating the extension or ductility of specimens and for indicating the ultimate load is provided with an indicating - scale gripping or releasing device which is controlled by an electro-magnet energized by the current in a circuit of which the specimen forms part. Fig. 1 shows an apparatus for measuring the extension. The specimen is held between jaws a, b, and scales are carried by sliding rods C, D which have fingers A, B in contact with the jaws. The sliding rod D, which carries an index zero-pointer D<4> at its lower end, follows the downward movement of the jaw b so long as a gripping-device is held out of operation by an electro-magnet H<4>. The gripping-device consists of a lever F, carrying a rubber pad F<2>, which is held against the pressure of a spring F<3> by a lever G carrying an armature G<3>, and the current from a battery H passes to the insulated head a, through the specimen S, and through the machine to the electro-magnet H<4>, whence it passes through a switch H<5> to the battery. When the specimen breaks, the current is interrupted, the armature G<3> is released, and the gripping-device is consequently freed to fix the sliding rods. In a modification, clamps a<1>, b<1> are used on the specimen as shown in Fig. 3. The sliding rods may operate a pointer moving over a dial. Fig. 3 shows an apparatus for indicating the total load and the extension. The top straining-jaw a is suspended from a knife-edge on one end of a lever L, which is coupled at its other end to a lever M carrying a quadrant plate M<1>. At a point M<4> on the lever M, a connexion is made with a balance-piece floating in a mercury vessel M<5>. A cord attached to the quadrant M<1> passes round a drum N on an axis N<2> carrying a pointer N<3>, which moves over a dial. A second pointer, loosely carried round in front of the first, shows the maximum position reached. The quadrant plate M' moves between a pair of levers F<10>, F<11>, Fig. 4, which are normally kept apart against the action of a spring by the toe G<14> of a lever G<10> which has an armature normally held up by an electromagnet H'‹ arranged in circuit with the electromagnet H<4>, Fig. 3. When the specimen fractures, the lever G'‹ falls, releasing the gripping- levers F<10>, F", which then hold the plate M'. Fig. 5 shows apparatus for torsion tests. The specimen is held between the heads Q' of a twisting-mandrel, and the number of revolutions given to the specimen is ascertained by means of counting-gear consisting of a worm P<1> and a worm-wheel P<2> fitted with a pointer P<3>. The wheel P<2> is carried by a bell-crank lever P<5> pivoted at P<6>, and is held in engagement with the worm P' against the action of a spring P<8> by an arm R. Current from a battery H passes through the specimen and through an electromagnet R' which holds an armature on the arm R to keep the arm in its normal position, but when the specimen fractures, the armature is released, and the arm R is drawn aside by a spring. The bell-crank lever P<5> then moves so that the wheel P<2> is brought out of engagement with the worm P<1>. Specification 11,012/07, [Class 143, Weighing-apparatus], is referred to.