GB400277A - Improvements in or relating to inductance coils and methods of manufacture thereof - Google Patents

Abstract

400,277. Inductances. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, and ROBINSON, F. E., Old Heath House, Colchester, Essex. April 23, 1932, No. 11735. [Class 37.] An inductance coil having a negligible external magnetic field is made by filling a wound coil with a mixture of latex and dust of magnetic material and then solidifying the latex. A coil 1 is wound on a straight former 2, Fig. 1, in a number of layers, each layer being brushed over with latex. The coil is then dipped in latex and wholly or partly vulcanized. The former 2 is then removed and the coil again dipped in latex to give a coating inside the coil. The coil 1 is then bent round into toroidal shape but with a space left between the ends, as shown in Fig. 2, and is placed in a deep glass container in which a mixture of latex and iron dust is poured. The iron dust gradually settles and fills up the coil, a current being passed through the coil so that the particles of iron take up their correct magnetic positions. Surplus latex is then poured off and the container and coil are placed in an oven to vulcanize the coil. In an example a mixture of 80 parts by weight of iron dust to 20 parts of latex is employed. In an alternative method the coil is filled with a paste of iron dust and latex before being bent into toroidal form. An ordinary flat wave wound coil may be employed instead of a toroidal coil. According to the Provisional Specification, binding material other than latex may be employed.