GB842752A - Improvements in electric watches - Google Patents

Abstract

842,752. Watches. HAMILTON WATCH CO. Oct. 23, 1957 [Jan. 28, 1957], No. 33066/57. Class 139 In a watch having an electro-magnetically maintained balance, the balance carries a coil so wound as to have two portions spaced along the balance rim and extending parallel to the balance axis. In the first example, Figs. 2 and 3, the balance rim is located in a recess 38 in the plate 12. Attached to the balance is a plastic ring 72 in which is encased a zig-zag coil 70 which extends between concentric rings 50, 80 of magnetic material. Equiangularly spaced round the ring 50 are four inwardly projecting cylindrical magnets 60, 62, 64, 66 which cooperate with the vertical sections 78 of the coil to impulse the balance when the coil is periodically energised as the switch 31, 33, Fig. 2, is closed. The zig-zag coil may have a plurality of complete waves in which case an equal number of cylindrical magnets are provided. The small spaces between the inner ends of the magnets the coil and the ring 80 allow shocks to be taken up by mechanical abutment of such parts. In a modification the rings 50 and 80 rest on a flat ring located in the recess 38. In another example, Fig. 8, the rings 50, 80 are omitted, the four magnets 110 each being carried by one limb of a U-shaped keeper the other limb of. which carries a shunt member 118. The coil need not extend completely round the balance rim but may, as shown in Fig. 9, be of curved rectangular form and be clamped to the balance rim. The magnets again being carried by U- shaped keepers. In this instance the balance must be counter-balanced opposite the coil. Part of the coil may extend radially of the balance and be encased in a sheet of synthetic resin, Fig. 12 (not shown). Specifications 764,450 and 837,842 are referred to.