GB981014A - Improvements in or relating to electromagnetically actuated timepieces - Google Patents

Abstract

981,014. Clocks and watches. BULOVA WATCH CO. Inc. May 7,1963, No. 18088/63. Heading G3T. [Also in Divisions H2 and H3] An electromagnetic transducer arrangement for an electromagnetically actuated timepiece having a tuning-fork oscillator 10, comprises first and second transducers T 1 , T 2 for actuating the fork, each transducer including a magnetic element 21, 25 attached to a tine of the fork, a pick-up coil coacting with one of the magnetic elements, and a drive coil 22, 26 coacting with both of the magnetic elements, the pick-up coil being constituted by two serially connected portions 23a, 23b wound in opposing directions to minimize the effect of unwanted coupling between the drive and pick-up coils. The pick-up coil is associated with the cup shaped magnetic element 21 carried by the tine 15, the coils being wound on a stationary carrier 24 whereon the inner, pick-up coil portions 23a, 23b are separated axially by a ridge 24a and surrounded by the outer, drive coil portion 22. The other part 26 of the drive coil coacts with a similar magnetic element on the other tine 16 which drives the watch train 12 through a pawl and ratchet 13,14. Transistor 28 may be of Germanium junction P-N-P type, the base being connected through a biasing R-C network 30, 31 to one end of the pick-up coil 23a, 23b the other end of which is connected through drive coils 22, 26 to the collector C,the emitter being connected through battery 29 to the junction of the pick-up and drive coils. This circuit operates in known manner to maintain the tuning fork. The voltages induced in the sensing coil portions 23a, 23b owing to coupling with the drive coil 22 will be of equal amplitude and in phase opposition and will tend to cancel out. On the other hand the voltages induced in portions 23a, 23b by movement of the magnetic element are not of equal amplitude, since the flux density in the air gap region 21c in which portion 23b lies is greater than that for portion 23a. This produces a resultant output voltage sufficient to control the transistor. In an alternative circuit, Fig. 5, a silicon high beta transistor 32 of grounded collector type is used. In order that the embodiment utilizing this circuit may be constituted as a stop watch, two silicon diodes 33, 34 are interposed in series as shown between the -v of battery 29 and drive coil 26, these diodes being shunted by an on-off switch 35. In stop position, switch 35 being open, the voltage applied to the transistor is reduced such that the amplitude of the tuning fork is insufficient to drive the ratchet wheel 14, and on closing switch 35 normal running of the watch is resumed. Specifications 840,086 and 854,196 are referred to.