GB1288618A - - Google Patents

Abstract

1288618 Thermal switches SMITHS INDUSTRIES Ltd 13 Nov 1970 [28 Nov 1969] 58268/69 Heading H1N A temperature responsive switch comprises a bimetal element 10, a reference element 11 and a switch unit 14 arranged to be operated at a predetermined separation of the elements 10, 11, the position of the reference element being adjustable, to set the operating temperature, by two members 17, 18 acting separately to provide coarse and fine adjustment respectively. The microswitch 14 is clamped by a bracket to the free end of the bimetal 10 whereby at the set operating temperature the operating button 15 is brought into engagement with the unclamped end of element 11 which end carries a set screw 21 and a cam follower 11A. The two slidable adjusting members 17, 18 carry respectively a number of corrugations 17C of increasing height and a ramp (not shown co-operating respectively with the follower 11A and set screw 21. Each step of member 17 produces a 10 degree change in setting while the total travel of members 18 provides a 10 degree variation. Each member. 17, 18 carries an appropriate scale and can be replaced by others giving a different range. A second microswitch 22 is pivotally mounted on a fixed bracket 24 and arranged to be operated by the bracket carrying the first microswitch 14. The position and operating temperature is determined by a follower 23 and a third adjusting member 25 which is aligned with member 17 such that it cannot be set to a higher temperature. The first and second microswitches control respectively the daytime and night time temperatures of a domestic central heating system the appropriate one being selected by a timeswitch (not shown).