GB539375A - Improvements in electric heating elements of the sheathed wire type - Google Patents

Abstract

539,375. Electric resistance heaters. BRITISH THOMSON-HOUSTON CO., Ltd. Oct. 11, 1940, No. 15160. Convention date, Oct. 11, 1939. [Class 39 (iii)] In an electric heating element of the sheathed wire type as described in Specifications 144,767, [Class 39 (iii)], 356.586, [Group XXXVI], and 473,876, an insulating support 16 for a helical resistance 11 is formed of two sections 16a, 16b, each with an inwardly extending rib 18 which engages between the turns of the helix. External ribs 17 in contact with the sheath 12 hold the sections in assembled position. The sections are applied to the resistance after the terminals have been secured, as the resistance is being fed into the sheath from left to right. The sheath is marked at points 23a and is then reduced at those points to prevent movement of the supports 16 as the magnesia filling is fed in with the element in a vertical position. A washer 19 closes the sheath at the lower end, and a pin 20 positions the terminal 15 at the upper end, a washer 20 being finally added and secured by deforming the end of the sheath over it. The unit is then elongated and its diameter reduced to compact the insulation, by swaging, rolling, or drawing, to a diameter equal to or less than the parts 23a. In this operation, the supports 16, which may be of lava, are crushed. Lava sleeves 25 for the initial support of the terminals 14, 15 may also be provided. In a modification, Fig. 10, the supports may have part-circumferential flanges 30 instead of longitudinal ribs 17.