Patent GB-1376736-A (GB)
Title: Timing mechanisms for the automatic operation of apparatus
IPC: G04F3/06
Filed: 1971-08-24
Abstract: 1376736 Time switches SATCHWELL CONTROLS Ltd 18 Aug 1972 [24 Aug 1971] 39623/71 Heading H1N [Also in Division F2] In order to avoid the necessity of any special control action before an apparatus, such as a domestic cooker, for example, can be used without automatic delay following its use with such delay, a timing mechanism which is separately settable to maintain the apparatus in an operative condition for a desired period and to terminate the said desired period at a desired time after setting, is arranged such that, at the end of each said operative period, the period setting is automatically restored to zero and the finishing time setting is automatically set so as to allow any further desired period which is then manually set to occur immediately, without delay and without manually setting the finishing time. As shown, the contacts 40 of an oven thermostat are held open by a lever 41 only during automatic delay of start time and allowed to close at the computerized start time, i.e. at the finish time, less the set operative period ; and upon expiry of the operative period the contacts are opened by motor drive of the thermostat setting control back to its "OFF" position. Thus subsequent manual setting of the thermostat causes an immediate start of a further cooking period without any adjustment of the timing mechanism, and the cooking may be terminated by restoring the thermostat to "OFF", either manually or by the motor drive if an operative period has been set on the timing mechanism, such setting having no effect on the lever 41. A synchronous motor M drives clock hands 1b, 2b (Fig. 1), an eccentric 12 (Fig. 4), which oscillates a pawl 23, and is also coupled to drive the thermostat setting control (33, Fig. 3, not shown), via a differential clutch (28, 29, 30), when the planet pinion carrier (29) thereof is held stationary. A cooking period is set by axial depression and rotation of knob 22 (Fig. 2a), which rotates a gear 17 and also rotates cams 38, 39 and ratchet wheel 27 which are coupled by gears not shown. The gear 17 has an arcuate slot extending over approximately 180 degrees such that the pin 16a does not interfere with its rotation which is limited to six hours. The cams 38, 39 have edge markings of minutes and hours respectively to form a visible indication. A finish time hand 3b is carried on the hub 3 of a gear 3a meshing with a contrate gear 5 of a differential whose other contrate gear 6 is  coupled for reverse rotation to hour hand 2b and whose planet pinion 7 is carried on the hub 8 of a gear 9 arranged to drive shaft 10. Since shaft 10 is normally held stationary by engagement of pin 160 in a recess 15a in frame 15, the pinion 7 is held stationary and hand 3b rotates in alignment and synchronism with hour hand 2b. To set a finish time knob 20 is depressed to engage gears 20a and 3a, at the same time acting on a lever 20b to move shaft 10 axially, thereby releasing pin 16a from frame 15 and causing lever 41 to open contacts 40. Rotation of knob 20 now sets hand 3b, and, since contrate gear 6 is relatively stationary, rotates pinion 7, gear 9 and shaft 10 to the desired finish time. On release of knob 20 the pin 16a rides on the surface of gear 17 and contacts 40 remain held open. Contrate gear 5 is now stationary and the time drive to contrate gear 6 drives pinion 7 and hence shaft 10 until pin 16a reaches the end (17b. Fig. 6b, not shown), of the arcuate slot in gear 17. This position corresponds to the finish time less the cooking period and shaft 10 now moves axially to close contacts 40, and also moves a lever 25 (Fig. 4), to allow pawl 23 to engage ratchet wheel 27 so that the cams 38, 39 are time-driven back to their zero position (where lever 14 disengages pawl 23 to uncouple the drive). About ten minutes before cams 38 and 39 reach their zero position recesses therein (38b, 39b, Fig. 5, not shown), allow a pawl (35) to restrain planet pinion carrier (29) so that motor M drives the thermostat control (33, Fig. 3, not shown), back to its "OFF" position where it opens contacts 40, and a lug (33a) on control (33) lifts the pawl (35) to uncouple the thermostat drive. The pin 16a has meanwhile returned to its start position and relocates in the recess 15a in frame 15. The mechanism is now not only ready for a further automatic delayed operation but requires no special adjustment for manual operation of contacts 40 (by mere thermostat setting), or for an immediate timed cooking period by setting knob 22. Since the latter action merely moves gear 17 within the limits set by its arcuate slot and pin 16a it does not open contacts 40, but the concurrent setting of cams 38, 39 allows pawl 23 to become effective (by depression of lever 14), and produces their timed-drive back to zero where the thermostat is motor restored to "OFF' as described above. To permit pin 16a to be positioned for a finish time between 6 and 18 hours from zero without prematurely re-engaging the slot in gear 17 a part-annular ramp 18 is positioned to engage the end 16b of arm 16 and prevent pin 16a dropping on to gear 17 until about six hours before finish time. A lost-motion disc 43 between gears 2a and 3a prevents anti-clockwise driving of hand 36 by knob 20 without similar driving of the clock train and also prevents hand 3b being advanced more than one and a half revolutions (18 hours), beyond hand 2b.