GB687948A - Improvements in or relating to electromagnetic secondary clocks - Google Patents

Abstract

687,948. Clocks. TELEFONBAU UND NORMALZEIT GES. April 5, 1950 [Dec. 2, 1948; Dec. 2, 1948], No. 8559/50; Class 139 An electromagnetic secondary clock comprises an electromagnetic system having a stator and a co-operating substantially cylindrical rotor for driving a hand of the clock, the rotor being permanent magnet magnetized exclusively along its rim so as to have at least four poles of alternate polarities on its rim. The stator 14, Fig. 1, has two pole pieces 15, 16 which co-operate with the four poles of the armature 11 which is magnetized along its circumference and is mounted on an arbor 12. Current impulses pass in alternating directions through the winding 17 of the stator 14 to impart alternate north and south magnetism to the pole pieces 15, 16. The armature may be shaped as shown in Fig. 2 and have embossed poles 19. The rotor may be pressed from comminuted magnetizable material held together by a binder. The limbs of the stator may each have two pole pieces and the associated armature six poles, Fig. 6 (not shown). Two of the pole pieces of the stator may extend in the direction of the next succeeding pole of the armature, Fig. 5, to determine the direction of rotation of the rotor. When the clock is assembled. Fig. 9, the armature is enclosed in a .casing formed by caps 57, 58 and the limbs of the stator. The cap 58 has two extensions 60, 61, Fig. 8, which extend between the stator limbs 52, 53, having pole pieces 55 and 56 respectively.