GB1128402A - Improvements in or relating to time controlled electric switching devices - Google Patents

Abstract

1,128,402. Time switches. SMITHS INDUSTRIES Ltd. 21 March, 1967 [23 March, 1966], No. 12702/66. Heading H1N. A time switch wherein snap-action contacts 4 and 5 (Fig. 3) are alternately opened and closed by "OFF" tappets 22 and "ON" tappets 23 which engage respective sides of a wedge 8 on a member 13 pivoted at 10 (as disclosed in Specification 1,103,101) is provided with means to selectively permit radial sliding of at least one tappet arm such that engagement of its tappet with wedge 8 is ineffective in operating the latter. Tappet arms 12 and 21 have elongated central holes, which allow radial movement of their tappets 23 and 22 respectively inwardly and outwardly from their operative paths, and an adjustable control plate 25 of plastics material is pivoted concentrically with the tappet arms 11, 12, 20, 21. Wedge 8 extends through an aperture having upstanding lips 35 and 36 which respectively prevent radial movement of tappets 22 and 23 on arms 21 and 12 unless a respective recess 33 or 34 is aligned with the wedge 8. In the setting shown (diagrammatically) in Fig. 3, when tappet 22 on arm 21 engages the wedge 8 it is moved radially outwards into recess 33 and the contacts 4 and 5 are not opened. If plate 25 is rotated clockwise to bring recess 34 into alignment with wedge 8 the wall 35 prevents radial sliding of tappet arm 21 and its tappet 22 is effective to open contacts 4 and 5, but when tappet 23 on arm 12 engages the wedge 8 it is moved radially inwards into recess 34 and does not reclose contacts 4 and 5. In a mid-position of plate 25 both arms 12 and 21 are prevented from radial sliding movement and all four tappets are therefore effective. As shown in Fig. 6 a fixed centre post 37 carries a hollow shaft 28 integral with a gearwheel 38 through which it is driven at one revolution in 24 hours. A knob 45 is a friction fit on shaft 28 and has a flange 40 marked to indicate the hour of day and having dependent serrations 47 with which tappet arms 11, 12, 20, 21 are selectively engageable to be driven thereby. This arrangement thus allows arms 12 and 21 to slide radially without interference with their drive. The plate 25 has an arm (50, Figs. 5 and 8, not shown) accessible through a slot (59) in a cover-plate (58) whereby it is adjustable into its three positions which are located by a spring detent 55 engaging one of three slots (51, 52 or 53) moulded in the plate 25.