GB636689A - Improvements in and relating to electromagnets - Google Patents

Abstract

636,689. Electromagnets. BRITISH THOMSON-HOUSTON CO., Ltd. June 12, 1947, No. 15533. Convention date, June 13, 1946. [Class 35] [Also in Group XXXVII] An electromagnet with which is associated an armature, comprises a magnetic core member carrying a winding and having a shim arm pivoted between one of its ends and a magnetic pole member, which shim arm has part of a surface covered by a non-magnetic material, the uncovered part of the surface co-operating with a surface of the. core or pole members to an extent varied by rotating the shim arm. In a D.C. time delay relay of the kind described in Specification 591,480, [Group XXXVII], the rotation of the shim arm 14, part of a surface of which is covered by a brass or other non- magnetic layer 18, brings more or less of the uncovered part 19 into contact with the upper surface of a pole member 15. The reluctance of the magnetic circuit through U-shaped cover member 1, shim arm 14, pole member 13, and a centrally pivoted armature 5 carrying contact arms 21, 22, and therefore the time delay of the relay, is thereby varied. Energization of coil 16 causes rotation of armature 5 against a spring 8 until its ends abut against the left-hand end of core member 1 and the upper surface of pole member 13 respectively, so that contact is broken at 21, 23 and made at 22, 24. Core member 1 consists of an iron core encased in a copper sheath. Shim arm 14 may be chromiumplated all over. Specification 483,100 is also referred to.