GB301784A - Improvements in or relating to magnet cores - Google Patents

Abstract

301,784. Automatic Telephone Manufacturing Co., Ltd., and Roseby, P. N. Sept. 5, 1927. Electromagnets. - Magnet cores for loading- coils &c. are formed of powdered iron, or an iron alloy containing from 2 to 8 per cent of silicon, which is annealed in air-tight pots at about 660‹ C. and is then treated with synthetic resin varnish and air-dried while kept in a state of agitation. The synthetic resin preferably comprises a phenol-aldehyde condensation product. The resulting mass is then stoved at about 250‹ C. to polymerize the synthetic resin and render it insoluble in the solvent used. A second coating of the varnish is then applied, and the powder is air-dried and subjected to a pressure of from 20 to 40 tons per square inch in a mould heated to 120‹ C., producing a solid ring or body of other desired form and having a specific gravity of about 6.2. The pressed rings are baked at 150‹ C. to stabilize the resin and drive off volatile matter. Four to eight such rings are bound together with tape and are wound with two windings on opposite halves of the core followed by a further two windings on top of those previously wound. One inner winding is connected with the opposite outer winding, and the two coils so produced form the windings of the loading coil. The coil is then dried and embedded in resin. Before treatment, the powdered alloy may be passed through a magnetic separator to separate out the non-magnetic particles. According to the Provisional Specification, the first stoving takes place at from 100‹ to 200‹ C., and the compression at from 10 to 50 tons per square inch.