GB670628A - Improvements in or relating to electric generators - Google Patents

Abstract

670,628. Machines with permanent magnets. BIRMINGHAM SMALL ARMS CO., Ltd., and GOLDSCHMIDT, R. Nov. 4, 1949 [Nov. 4, 1948], No. 28620/48. Class 35. In an inductor type generator having a permanent magnet or magnets to provide the magnetic field a copper ring 25 gripping the outer periphery of the permanent magnet 22 is provided in order to oppose flux variations of the permanent magnet. Fig. 1 shows the generator incorporated in the hub of a cycle wheel on a spindle 1. On a wall 13 of the mounting member fixed to the spindle 1 through a core 2 and nut 10, are mounted a permanent magnet ring 22 magnetized in an axial direction, a dished flux conveyer ring 23 in magnetic contact with one side of the magnet 22, and two polar rings 15, 17 having interdigitated teeth 16, 18 embracing an armature winding 21. A spacer iron ring 19 is concentrically mounted on the wall 13 between the polar rings 15, 17. The rotating member of the generation is a keeper ring 31 of magnetic material and is secured to the cylindrical wall 30 of a sheet 28 fixed to a boss 27 of the hub 4. The keeper ring 31 has fourteen teeth 33 arranged to co-operate magnetically with the fixed polar ring teeth 16, 18 lying in a cylindrical surface and the relative widths of the polar teeth and keeper teeth are such that a keeper tooth is at all times opposite a tooth 16 or 18 or opposite a part of a tooth 16 and a part of tooth 18. When the keeper teeth 33 are opposite the teeth 18 the magnetic circuit is completed with the exclusion of the winding 21 and when the keeper teeth 33 are opposite the teeth 16 the winding 21 is linked with the magnetic circuit thus formed. The mounting of the copper ring 25 on the permanent magnet 22 is so positioned as to oppose by Lenz's law the variations of the flux emanating from the permanent magnet ring 22. Specifications 120,897, 136,705, [both in Class 35], 627,014, 636,465 and 670,627 are referred to.