GB558671A - Improvements in or relating to permanent magnet structures - Google Patents

Abstract

558,671. Permanent magnets ; motors. HITCHCOCK, S. I. July 14, 1942, No. 9793. [Class 35] A permanent magnet 2, Fig. 1, is provided with a flux leakage path 6, 7 and an armature 12, 13 both of similar form and relatively movable and comprising soft iron portions 6, 12 separated by non-magnetic portions 7, 13. When the soft iron portions are staggered, as shown, the flux from pole-pieces 3 threads its way alternatively between them in a zig-zag manner, and the force between the magnet and the armature is great ; whereas when they are opposite the force is small. In its application to a permanent magnet motor the cylindrical permanent magnet 2, with four poles 3 and associated flux leakage paths, is mounted on shaft 1 between four pole-pieces 10 each carrying an armature. The axial movement of the armatures is effected against springs 16 by cam 21, followers 22, and levers 23, and is timed so that the force between the rotor and stator poles is a maximum when they are approaching each other and a minimum when they are receding, thus facilitating the continued movement of the rotor. Timing is adjusted by moving the cam-follower mechanism about the axis. In a modification, the stator also carries permanent magnets 27, Fig. 5, which oppose the magnet 2 and still further reduce the attractive force in the minimum position. In a work-holder, the armature 28, 29, Fig. 6, forms the work table and co-operates with permanent magnet 33 and flux leakage path 30, 31. When the handle 34 moves the table from the position shown to the position when the soft iron portions are opposite, the force on the top of the table rises from a minimum to a maximum. Specifications 429,199 and 552,558 are referred to.