GB1474021A - Timing apparatus - Google Patents

Abstract

1474021 Electronic timepieces SMITHS INDUSTRIES Ltd 4 July 1974 [13 July 1973] 33480/73 Heading G3T An electronic timepiece for the timed control of an electrical appliance(s) and which may also indicate time of day, is normally energized from and synchronized with an A.C. mains supply, but is provided with means (energized by a battery) for generating a cylically varying timing signal which is used in the event of failure of the mains supply. In Fig. 1, a unit 10 provides a 5À6V D.C. on a line 12 via a rectifier 39 to a battery 13 and a pulsiform signal on a line 18 at the mains frequency of 50HZ. During normal operation a gate circuit 17 (detailed in Fig. 2 (not shown) is biased by the D.C. signal in line 12 to pass the 50HZ pulses to a frequency divider networks 19 which produces pulses in a line 20 at 25HZ and pulses on a line 22 at 0À5HZ. The pulses on lines 20, 22 are converted by a drive unit 21 into two trains of 0À5HZ pulses, having a pulse width of 20 m. sec. and the pulses of one train occurring mid-way between those of the other, which pulse train drive a stepper motor 25. The motor rotates a timing disc 26 once every twenty four hours via gears 27. A tappet 28 thereon operates to close a switch 30 which is in turn opened by a tappet 29. When the switch 30 is closed a relay 32, 33 connects an appliance(s) to the supply mains. Upon mains failure the gate circuit 17 is biased to pass 50HZ pulses from an oscillator circuit 15 to the divider circuit 19 to drive the stepper motor. The motor may also drive time of day indexing mechanism. Alternatively, to save the battery power the motor and indexing mechanism 25-30 may be rendered inoperative and an electrical up/down counter used to count up the oscillator pulses during the whole period of mains failure. When the mains are restored the counter counts down to provide pulses which are added to and interlaced with those produced by power supply unit 10 whereby to update the indexing mechanism.