GB464005A - Improvements in or relating to devices for testing the hardness of metals - Google Patents

Abstract

464,005. Testing hardness of materials. BARBER, J. H., and BRIDGE, J. F. March 25, 1936, No. 8928. [Class 106 (ii)] In hardness-testing apparatus of the kind in which an impression is made by an indentor through the medium of a spring under a load, for example as described in Specification 280,292, [Class 106 (ii)], automatic means are provided to prevent the application of a load beyond the predetermined one, A bowshaped spring. 22 is employed to transmit the load applied by the spindle 11 to the plunger 21 carrying the indentor 20, and the compression of the spring is indicated by a pointer 27. An adjustable pointer 40 on the same dial is first set at the desired load, and the screw spindle is then advanced by gearing actuated by a hand wheel 14 until the pointer 27 contacts with the pointer 40, whereupon an electric circuit is closed to energize a solenoid 38 which moves a pawl 36 into engagement with a ratchet-wheel 35 on the hand wheel spindle so as to prevent the application of further load. The load is then released and the apparatus is swung about a pillar 2 so as to enable a reading of the diameter of the indentation to be made through a microscope 6. The parts 11, 21 are interconnected by a stirrup 23 co-operating with an adjustable ring 24 on the plunger 21 to limit the maximum separation of the parts. The stirrup 23 carries the rack 29, which actuates through toothed gears, the spindle 26 of the pointer 27, backlash being prevented by a spring.