GB1389293A - Oscillating devices - Google Patents

Abstract

1389293 Electronic watches and clocks BERNARD GOLAY SA 20 April 1972 [4 May 1971] 18434/72 Heading G3T Relates to an arrangement for maintaining and stabilizing the amplitude of oscillation of a balance wheel in a time piece and synchronizing it to a reference signal. The balance wheel 1, Fig.1, is coupled to a spiral balance spring 5 in known manner and carries a permanent magnet 4. In the rest position of the balance the magnet 4 lies between poles 6 of a core 7 carrying a drive coil 3 and control coil 14. A drive circuit, Fig.3, receives synchronizing or timing signals 15 from an oscillator (not shown) and produces drive pulses which are applied to drive coil B3 so as to impart a thrust to the balance each time magnet 4 passes between the poles 6. This pulse will be shaped as pulse 16, Fig.5, when the balance is properly synchronized to the timing signal 15 (shown in the upper part of Fig.5). Signal 15 biases T3 alternatively to conductive and blocked states. Voltage induced in control coil B14 by passage of the magnet, biases T14 conductive via a diode D3, so that energy corresponding to voltage level V-Vd is applied to drive coil B3 and hence to the balance 1. On receipt of a negative going pulse of signal 15, T3 conducts and blocks diode D3 so that energy corresponding to full voltage level V is received by the coil 3 and balance Thus the energy applied will depend upon the phase angle between the induced voltage in B14 and the timing signal 15. If the oscillation amplitude is excessive such that a projection on the balance contacts a leafspring 9, the balance wheel frequency will increase due to acceleration imparted by the spring. Thus the induced voltage in B14 will be advanced in phase so that energy imparted to the balance will be reduced, being that due to voltage level V-Vd solely, i.e. as pulse 17, Fig.5. If the balance wheel frequency falls below normal value f, the induced voltage in B 14 will lag the timing signal so that a pulse 18 wholly at voltage level V will be applied to B3. Acceleration of the balance thus occurs. Pulses 17, 18 represent extreme conditions and normal deviations in frequency will merely shift the instant where the voltage levels change and hence alters the mean voltage applied to B3. The leaf-spring 9 may alternatively be on the balance wheel for engagement with a stationary limit stop, Figs.8 and 9 (not shown). Instead of a leaf-spring there may be a spiral spring, Figs.12, 13 (not shown), or a stationary magnet may be arranged to repel the balance wheel magnet, Figs. 10, 11 (not shown). In a modified drive circuit, Fig.7 (not shown), the timing signal is a saw-tooth wave which operates on a uni-junction transistor (T3").