Patent GB-1424952-A (GB)
Title: Time switch
IPC: G04C23/30
Filed: 1974-02-27
Abstract: 1424952 Time switches; partly magnetic switches AMF Inc 27 Feb 1974 [4 April 1973] 8954/74 Heading H1N A timer for providing a timing cycle at a selected time for a selected period comprises first and second timing dials synchronously driven at predetermined relative speeds, the first dial 14 having actuator means 24 selectively positioned thereon for preparing the timer for initiation of said timing cycle at a selected time, and the second dial 12 having two actuator means 48A and 42A thereon spaced according to the selected period of the timing cycle, a pivoted lever 16 with follower surfaces 16A, 16E and 16D thereon being disposed for engagement by the actuator means of the dials in a predetermined sequence such that the lever is moved to actuate switch means 20 for initiating and for terminating said timing cycle. As shown dials 12 and 14 are driven respectively at one revolution in two hours and one revolution in twenty-four hours. A lever 16, pivoted at 16F, is normally urged by an over-centre C-spring 18 to a position somewhat more anti-clockwise than that shown, and when snapped clockwise (Fig. 2, not shown) an end portion 16B depresses the buttons 20A of two microswitches 20. An actuator 24 can be positioned in a selected slot 14A on dial 14 to engage portion 16A at the selected time of day and move lever 16 to the "prepared" or "ready" position shown, bringing a surface 16E into the path of a pin 48A (on dial 12) which can then urge lever 16 over-centre to actuate switches 20. A surface 16D now lies in the path of a pin 42A on an arm 42 which is adjustable around a ring of grooves 44 spaced at one-minute intervals. After the preselected period (as shown, about one hour) the pin 42A restors lever 16 to its anti-clockwise position and switches 20 are opened. A solenoid 22 may be energized to cancel operation of switches 20 by rotating lever 16 anti-clockwise. To avoid interference by pin 48A if solenoid 22 is energized soon after 48A has engaged surface 16E, the pin 48A is carried on a spring-urged arm 48 pivoted on dial 12 such that, after acting on lever 16, it snaps clear of surface 16E. The solenoid is in series with one of the switches 20 so that it is automatically de-energized when it restores lever 16. The timer is mounted as a module on a frame including three rods 40A, 40B and 40C. It is pivotable about rod 40C and is releasably latched in position by a spring-urged lever 28. Dials 14 are synchronized with the actual time of day by aligning a scale (14D, Figs. 4 and 7, not shown) with a reference mark (not shown) on plate 26. Drive shaft 34 has a slot 34B at one end and a corresponding stub (34A) at the other end so that several timer modules may be assembled (Fig. 7, not shown) for conjoint drive by a common synchronous motor (52). An auxiliary motor (53) is provided for simultaneous energization with motor (52) or upon failure thereof. The slots 14A in the respective dials 14 are relatively staggered to prevent more than one timer switching on at any given time; this is particularly useful when the assembly is used to turn on defrost heaters in a bank of freezers, for example, since it avoids a possible power failure due to overload.