Improvements relating to electric heaters, particularly immersion heaters for liquids

摘要

419,847. Heating by electricity. JACKSON, R. A. F., 4, Melrose Gardens, Glasgow, and WILSON, A. V., 39, Merry Street, Motherwell, Lanarkshire. Jan. 29, 1934, No. 2927. [Class 39 (iii).] In an immersion heater comprising a sheathed straight wire element coiled to form a hollow tube which contacts directly with the fluid to be heated, the tube is mounted on a terminal block and for the greater part of its length is deformable, the part adjacent the block being stiffened by a fore-shortened perforated central tube. The sheathed element 17 may be coiled into two concentric tubes 18, 18a which, together with the perforated central tube 24 are fitted to the terminal block 20 by screw-threading the base of the heater into the wall 23 of the vessel to be heated. Stiffening ribs 19 or a wire mesh core may extend throughout the length of the tubes. In modifications, the coiled sheathed element may itself be wound helically to form the tube ; the coil may be wound on a screwshaped former to form an undulating tube ; or the sheathed element may be coiled longitudinally, the windings 17, Fig. 7, being mounted on a pair of formers 27 which permit circulation of the liquid through the heater. The coiled tube may be divergent from inlet to outlet. In use, the part of the heater 28, Fig. 8, extending clear of the central tube 24, is bent to any desired configuration. The heating element may comprise nickel-chrome wire with successive coverings of asbestos yarn, paper, braided asbestos and a protective sheath of tinned copper. In a modification, the wire is insulated from a jacket of asbestos 16, Fig. 10, by glass beads 34, the whole being enclosed in a copper sheath 17.