GB663999A - Improvements in or relating to electrical resistance and heater elements - Google Patents

Abstract

663,999. Metal grid resistances. EXPANDED METAL CO., Ltd. Aug. 30, 1949 [June 2, 1949], No. 22546/49. Class 37. [Also in Group XI] A meshwork, especially an expanded metal diamond-shaped mesh resistance heater has one or more insulated stiffening members engaging the meshwork along a length lying alongside of or outside the zig-zag current path or paths through the meshwork. The strip is a complete mesh or more wide and is cut so as to leave at the lateral edges projections 19, 20, 21 through which current does not pass, and these projections are engaged by the stiffening members which comprise U-shaped metal strips 24 with insulating liners 25, e.g. asbestos tape or mica. The ends of the metal strips may be unexpanded and carry terminals. When the strip has a greater width than one mesh, two or more zig-zag current paths are provided as shown by arrows 16, and between them are strips 18 through which current does not flow. The resistance may alternatively be supported by the engagement of the intermediate strips 18 in a medial line with a stiffening member comprising a notched rod of insulating material. The resistance metal may be steel 0.015 inches thick with meshes 0.015 inches wide. When the edges of the resistance are supported they may be covered with insulating porcelain enamel or cement and the stiffening member 24 may be of insulating material, e.g. moulded resin. A long resistance strip may be engaged at spaced intervals by the stiffening members leaving intermediate parts flexible so that the strip may be bent into zig-zag shape.