GB678756A - Improvements in or relating to demagnetising devices - Google Patents

Abstract

678,756. Demagnetizing. IGRANIC ELECTRIC CO., Ltd., and TAYLOR, J. R. April 25, 1951 [May 3, 1950], No. 10915/50. Class 35. A magnetic chuck is demagnetized by feeding its exciting coil with current which is automatically and repeatedly reversed and reduced in value. In the normal working connection, Fig. 1, the exciting coil W is fed directly from the lines L+, L-, the current flowing through the coil from a to b. In the first demagnetizing step, Fig. 2, the coil is fed through resistances r<SP>1</SP>, r2 connected to its terminals while L - is connected to a, the coil current, which is less than before, then flowing from b to a. In the next step, Fig. 3, the terminal b of the coil is connected to L - through a resistance r3 so that a further reduced current flows from a to b, while in a still further step, which again reduces and reverses the current in the coil, is provided by connecting terminal a to L - through a resistance r4 as shown in Fig. 4. In further steps, which again reverse and reduce the current, resistances r3 and r4 are partly short-circuited in turn. A time delay relay circuit for carrying out these operations is described and resistance values are given.