GB581964A - Improvements in or relating to magnetic means for the hardness testing of metals - Google Patents

Abstract

581,964. Photo - electric apparatus. STANDARD TELEPHONES & CABLES, Ltd., and STOCKS, H. R. April 30, 1940, No. 7800. [Class 40 (iii)] [Also in Group XXXVI] A machine for the continuous sorting of magnetizable objects such as rifle and machinegun bullets in accordance with hardness, includes means for comparing the remanence of of each object in turn with that of a standard, and means operated by the comparing means for directing the object during discharge. On one arm of a balance BAL is a mirror TM forming part of an optical system which includes . a light source, a fixed mirror FM, and a photoelectric cell of the split type. The coils TC are in series and are supplied with current through one of the contact sets CS for a fraction of each cycle. They are so connected that they have polarities similar to the lower ends of the two bullets, so that if the flux densities of the bullets are equal the two coils are repelled by equal forces and no deflection of the balance takes place. If the bullet under test has a greater flux density than the standard bullet, the balance BAL is forced against a stop AS, which prevents motion of the balance. If the tested bullet is weaker, the balance BAL is deflected in a clockwise direction and causes the image of the light source to deflect from its position at the junction of the photo-electric cell on to one half of the cell and the resulting' output of the cell operates an electromagnet controlling the bullet-deflecting member, which is operated after a delay corresponding to the time taken for the bullet to travel from the rotating drum to the shoot.