GB955402A - Thermally responsive switch device - Google Patents

Abstract

955,402. Thermal switches. RANCO Inc. May 1, 1962 [May 5, 1961], No. 16602/62. Heading H2B. A thermostat for use in refrigerators, airconditioners and the like has a housing comprising three walls 11c, 11a and 11b of a channelshaped sheet metal member 11 closed at one end by an insulating member 12 retained by bosses 12e extending through openings in member 11, and closed at the other end by a plate 44 held by lugs 11e. An insulating cover 14 slides between walls 11a and 11b and is held by their inturned edges. The insulating member 12 carries a fixed contact 20 on a terminal bracket 19, and a moving contact 18 on a resilient arm 17, while at the other end of the housing the plate 44 carries thermally-responsive bellows 40 coupled to the moving contact via a snap-action mechanism comprising bell-crank members 22 and 23 interconnected by a C- spring 24. Member 22 is of insulating material shaped for engaging the free end of arm 17 as shown, and also comprises a metal plate 22b formed with knife edges 25 pivoted in notches 26 in member 12. The member 23 is a sheet metal stamping pivoted on a triangular section pin 29 extending between walls 11a and 11b and carries an adjustable screw 41 abutting a post 40a on temperature-responsive bellows 40 under action of a spring 48 connected to a lug 49 bent up from member 23. Spring 48 is connected at its other end to an adjusting lever 52 by means of screw 50 and nut member 51 lodged in the convolutions of spring 48. Lever 52 has spaced bearing portions 52a pivoted in slots 53 in wall 11a and an upstanding lug 52b which passes through a slot in wall 11b to engage a cam 55 manually rotatable by a shaft 56 journalled in wall 11b. A screw 34 and a bendable lug 38 on terminal bracket 19 form stops for member 22 to preset the switch differential, while screws 41 and 50 are preset to provide the required range of control by cam 55. An over-riding " OFF " position is provided by a high rise 55a on cam 55 which may be brought to bear on follower 52b such that a hook member 59 on lever 52 is moved into engagement with a hook-like extension 58 on member 23 and thereby maintains contacts 18, 20 open regardless of temperature changes. The modified embodiment of Fig. 8 has a preset " cut-in" " temperature since the cam 55<SP>1</SP> does not move follower 52b except for the OFF condition, and the " cut-out " temperature is controlled by a further cam 65 on shaft 56 but inside the housing and acting on an extension arm 67 of member 22. In this embodiment lug 38 is replaced by an adjustable fixed. contact 68.