Patent GB-1383529-A (GB)
Title: Crystal electronic timepiece
IPC: G04G3/02
Filed: 1972-12-11
Abstract: 1383529 Frequency dividers NAUCHNOISSLEDOVATELSKY INSTITUT CHASOVOI PROMYSHLENNOSTI 11 Dec 1972 [9 Dec 1971] 57085/72 Heading G4A [Also in Divisions G3 and H3] A timepiece, e.g. a watch has an electronic drive circuit which drives an electromechanical actuator, e.g. a vibratory motor or stepping motor coupled to time indicating hands. The circuit (Fig. 1) includes a crystal controlled oscillator 1 followed by a pulse shaping and dividing circuit 2, divided by three multi-vibrator frequency dividing stages 4, 5, 6 respectively, and a respective coincidence circuit 7, 8, 9 connected to the output of each stage and to the output of shaper 2. The output of gate 9 is applied to a drive pulse shaper 10 which applies drive pulses of suitable amplitude, duration and polarity to a winding 12 of the actuator.  Figs. 3a to 3e illustrate the output pulses of the oscillator 1, pulse shaper 2, and divider stages 4, 5, 6 respectively. The output of shaper 2 is a positive pulse train obtained at the collector of a transistor 26. This is applied to the inputs of the dividing stages switching transistors 39, 44, 57 and to the collectors of the coincidence gate transistors 41, 58, 59 so that the leading edges of pulses at the input of stage 6 for example coincides with those at the input of shaper 2. Consequently any phase errors in stages 4, 5 do not affect the stability of pulses at the output of stage 6, which stability will depend upon the oscillator 1 solely.  For a crystal controlled oscillator output of 9720 Hz the actuator 11 will receive pulses at 120 Hz to drive directly the minute hand. In an embodiment, Fig. 2, two frequency divider chains 65, 66 similar to divider 3 of Fig. 1, are connected in parallel to a pulse shaper 2. The division factors of dividers 65, 66 are n 1 , n 2  respectively. The frequency of pulses at the output of coincidence gate 67 is n 1  x n 2  times lower than that of oscillator 1. Frequency divider operation.-The division ratio of the dividing stage depends upon the time constant of the respective RC circuit e.g. R36 and C35 in stage 4. Considering the operation of state 4, initially T33, T34 are conductive and C35 is charged. The first positive pulse from pulse shaper 2 unblocks switching transistor 39 which changes the state of the multivibrator thus blocking T34. C35 then discharges via R36 turning off T33. As C35 is recharged via R36, R38 the blocking of T33 decreases and the output voltage across R38 is maintained at its upper level during period t 2  (Fig. 3c). The second and third pulses from shaper 2 unblock T39, but the multivibrator does not respond since T33, T34 are already blocked. T33, T34 return to the unblocked state between the third and fourth pulses after period t 2  (Fig. 3c) when C35 has been discharged sufficiently to allow T33 to conduct and the voltage across R38 will be at the lower level. C35 is quickly charged via T33, T34. The fourth pulse from shaper 2 again changes the state of the m.v. blocking T33, T34 and unblocking T39. The period of the output of stage 4 is thus three times that of shaper 2. When T33, T34 conduct, a transistor T41 of a coincidence gate 7 is blocked and is unblocked when a positive pulse from shaper 2 is simultaneously applied to the inputs of stages 4 and 5. Stage 5 operates similarly to stage 4 and its switching transistor 44 is unblocked by a positive signal from the output of coincidence gate 7 so that T45, T46 are blocked for a period t 3  (Fig. 3d). T45, T46 are unblocked between the third and fourth pulses at the output of coincidence gate 7, the fourth pulse unblocking T44 thus blocking T45, T46 and so on.