GB1505250A - Control devices incorporating electric switches - Google Patents

Abstract

1505250 Time switches SMITHS INDUSTRIES Ltd 14 March 1975 [26 March 1974] 13376/74 Heading H1N A switch control arrangement particularly applicable to a time switch wherein tappets 14 on a dial 13 actuate a switch unit 15 by causing engagement and disengagement of a member 39 with a latch 41 operatively associated with contacts 43, 48, has a selector means 21 which can be retained in a plurality of positions in one of which it engages the latch 41 to prevent its latching with member 39 and thus inhibits actuation of contacts 43, 48 by the tappets, and in another position is disengaged from the latch 41 and allows contact operation by the tappets. As shown the selector 21 has four positions selected and retained by sliding a knob 23 to a respective position A, B, C or D. In position C (Fig. 11) an "off" tappet can depress spring-loaded member 39 to engage under latch 41 and thence lift the latter such that a nose 64 lifts contact 48 off contact 43; the top of latch 41 then lying in the path of an "on" tappet which disengages it from member 39 to allow contacts 48, 43 to close. In position A (Fig. 9, not shown) the tip 89 of member 21 engages part 71 of latch 41 under action of spring 90 and holds the latch clear of member 39, thus rendering it ineffective, and contacts 43, 48 are continuously closed. An additional position D is provided wherein the end 89 of lever 21 depresses the nose 63 to pivot the latch about 60 so that nose 64 holds contacts 48 permanently off contact 43 as in (Fig. 12, not shown). Additional position B causes the latch 41 to be held at a lower level such that member 39 has to be depressed a distance (w, Fig. 10, not shown) greater than distance z in order to engage latch 41, and this enables differentiation between tappets (14alpha, 14c) of differing length, thus providing one cycle per 24 hours whereas position C would provide two. A fixed contact may be provided above contact 48 to provide a change-over facility or to interchange the ON and OFF states.