GB1274126A - Driving circuits for driving moveable elements particularly for motors or timepieces - Google Patents

Abstract

1,274,126. Transistor oscillators. HATTORI TOKEITEN K.K. 24 Feb., 1970 [28 March, 1969], No. 8880/70. Heading -H3T. [Also in Division G3] A self-starting oscillator circuit for driving a moving element of a timepiece-e.g. a balance wheel 1 (Figs. 1 and 2) or a vibratory arm (Fig. 4, not shown) or a ferrite disc rotor of a motor (Fig. 5, not shown)-comprises an astable multivibrator having a coil L as a load and which functions both as a drive and pick up coil. To effect starting the width of a drive pulse is greater than when steady state conditions are reached. As shown, Fig. 2, a ring coil L is coupled electromagnetically to a balance wheel disc 3 on a shaft 2 and carrying a permanent magnet 4 and counterbalance mass 5. In operation, with wheel 1 (Fig. 1) stationary and a switch S closed, a capacitor C is charged to a voltage Al (Fig. 3a) from a source E via coil L, R 1 and S. When C is charged Tr 1 turns ON. C then begins -to discharge through a loop comprising the base/emitter of Tr 2 , Tr 1 , C and Tr 2 turns ON so that C also discharges through a loop-Tr 2 , R 1 and C. As long as Tr 2 is ON a current pulse e 0 (Fig. 3c) flows in coil L and drives-wheel 1. When C is discharged Tr 1 , Tr 2 turn OFF. C thus begins to charge again and the cycle is repeated .Movement of wheel 1 magnet induces a voltage [in L. Thus a waveform b 1 (Fig. 3b) is applied to the base/emitter circuit of Tr 1 , i.e. a waveform as b 0 with the induced voltage superimposed. At this time C is charged with waveform a 2 to a voltage A 3 and Tr 1 is turned ON. Tr 2 -is switched ON by the discharge of C and a drive pulse e 2 is applied to coil L. The amplitude of oscillation of wheel 1 gradually increases and the induced voltage also rises and is applied to Tr 1 -base/emitter thus increasing the frequency at which Tr1 is turned ON. The charge and discharge periods of C are shortened also the drive pulse widths are steadily narrowed until a steady state vibration of the balance wheel 1 is reached. The drive pulse widths and frequency stabilize and synchronize with the natural frequency of the balance wheel 1. Modified oscillator circuits 4, 5, 6 (not shown) operate similarly. Their operation is not described. In the Fig. 4 embodiment a thermistor is provided for temperature compensation.