GB1271784A - Improvements relating to electric timepieces - Google Patents

Abstract

1,271,784. Electric timepieces; controlling vibration amplitude. SUWA SEIKOSHA K.K. March 13, 1970 [March 14, 1969], No.12299/70. Headings G3R and G3T. The amplitude of vibrations of a tuning fork vibrator for a timepiece and driven by an electrostrictive element 13, Fig.2, from a circuit controlled by an electrostrictive pick-up element 11, are maintained at a predetermined value by a further control circuit which changes the impedance of the drive circuit to control the amplitude. Fig. 2 includes a known oscillator arrangement (as illustrated in Fig. 1 (not shown)) wherein the pick-up element 11 detects the fork vibrations and controls a driving transistor 17 connected to a step up auto-transformer 15 and source 18 thereby energizing the driving element 13 to maintain the fork oscillation. However, to control the vibration amplitude a further electrostrictive pick-up element 24 is provided whereby if the said amplitude increases, the potential at a point 23 will change. If the negative peak voltage at this point exceeds a predetermined value, as set by a diode 20, current flows through the diode and charges the capacitance of the electrostrictive element 24. The average value of the voltage at 25 thereby increases. This voltage is divided by R25 and R26. The divided voltage is proportional to the amplitude of vibration and when it exceeds a predetermined value a transistor 23 conducts turning off transistor 17 so that the vibration amplitude will no longer increase. As the amplitude decreases Tr23 cuts off and Tr17 conducts to increase the amplitude of vibrations. In an alternative embodiment Fig. 3 (not shown) a single element (48) fulfils the functions of the elements 11 and 23 in Fig.2 The location of the above circuit components in a watch is illustrated in Fig.4 (not shown), a gear train being driven directly by the vibrator fork.