GB1415843A - Electric immersion heater assemblies - Google Patents

Abstract

1415843 Mounting immersion heaters OTTER CONTROLS Ltd and J C TAYLOR 1 Jan 1973 [14 Jan 1972] 1924/72 Addition to 1316436 Heading H5H [Also in Division H1] The immersion heater of the parent Specification 1,316,436 is modified to enable it to be fitted into the opening in the container wall from the inside without the need to dis-assemble electrically interconnected components thereof. This is achieved by arranging that the imaginary envelope enclosing the components mounted externally of the container lies within the projected area of the radially projecting mounting flange 8 of the mounting head 2 of the unit. The head is secured in the opening by a screw threaded collar which is screwed on to the threaded extension 7 of the head. The immersion heater comprises a "boil-dry" termal switch 3, serially connected to a steam sensitive switch 4 and a steam tube 5 passing through the head 2 and switch 3 to the switch 4, the steam tube 5 having a steam trap 6 surrounding its inlet and as in copending application 4067/71. The boildry switch 3, is mounted in the head 2 so that a conductive sleeve in an aperture 12 makes contact with a cold lead of element 1. A cantilever contact blade 19 is connected to the sleeve and co-operates with a fixed contact on the underside of a projection 21 which electrically connected to a fixed contact 17 (Fig. 1) projecting from the boil-dray switch 3. A brass plate 23 riveted to the moulding of the boil-dry switch: so as to be in thermal contact with mounting head 2 carries a trifurcated retractive snapacting bimetallic spring blade 25 which actuates cantilever blade 19 via a push rod 22. The backwall of the mounting head 2 is curved to conform with the bimetal 25 so that normally the bimetal 25 makes good thermal contact with the head. A screw threaded terminal pin 16 (Fig. 1) projecting from boil-dry switch -is electrically connected to the other heating element cold lead. The steam switch 4 comprises a complex moulding which has a horizontal shelf 32 (Fig. 4D) which separates the contacts 17, 64 of the switch from the steam sensitive trifurcated bimetallic element 71 and the end of the steam pipe 5. The fixed contact 17 of the steam switch 4 is provided on the moulding of boil-dry switch 3. The moving contact 64 is provided on a cantiliver blade secured to a U-shaped metal contact carrier, and is biased by a snap acting bow spring 65. Movement of bimetal 71 is transmitted through shelf 32 by a push rod 36 to blade contact 64 and to a pivotal operating button via a push rod 69. Button 40 projects when the switch is opened to give a visual indication and has to be depressed to reset the switch 4. A cable may be connected to the immersion heater directly or by a plug connector. The steam sensitive switch 4 may be automatically reset and may be in the form of a solid state switching circuit.