GB754672A - A centrifugal electric switch - Google Patents

Abstract

754,672. Centrifugal switches; magneticswitches. DUURKOOP, H. J. April 22, 1954 [April 24, 1953], No. 11700/54. Class 38(5) A centrifugal electric switch comprises a permanent magnet 18 which forms part of two parallel magnetic paths, there being an armature and an air gap in each path, the width of the air gap in one path being dependent on the centrifugal forces acting on the armature in that path. When the rotational speed of a motor shaft 15 is low the armatures 19 in a first magnetic path are positioned towards the shaft 15, thus the air gap between the armatures 19 and the members 16, 17 is large and most of the flux emanating from the permanent magnet 18 takes a second magnetic path formed by the members 16, 17 and an armature 13 which is secured to a plate 8. The armature is thereby attracted towards the members 16, 17 and in moving causes a contact 11 to close on a fixed contact 12 by means of a rivet 7 connecting the plate 8 and a member 6 carrying the moving contact 11. When the rotational speed of the shaft 15 increases the air gap between the armatures 19 and the members 16, 17 disappears so that now the majority of the flux from the permanent magnet 18 takes this path. The weakened flux flowing in the second magnetic path is now no longer sufficient to attract the armature 13, thus the armature moves away from the members 16, 17 under the influence of a spring 10 thereby opening the contacts 11, 12. The movement of the armatures 19 is controlled by a screw 23 and a spring 22. The arrangement of the switch is such that the transfer of flux from one magnetic path to the other occurs suddenly thus the movement of the armature 13 is very rapid. In a further embodiment the armature 13 is arranged to move radially.