GB846310A - Process of manufacturing electrically heated devices - Google Patents

Abstract

846,310. Making electrically heated devices; stamping; working at specified temperatures. SUNBEAM CORPORATION. Aug. 19, 1957 [Nov. 19, 1956], No. 26154/57. Classes 83 (2) and 83 (4). [Also in Group XI] In a method of making an electrically heated device a pattern of weld-preventing material is placed between a pair of superimposed metallic sheets, the sheets are welded together and the areas covered by weld-preventing material are expanded by fluid pressure to form a passageway in the composite welded sheet, a flexible electric heating element being inserted in the passageway. Sheets 21a and 21b of two different aluminium alloys are degreased, deoxidized and secured together by welding or crimping the edges, a pattern of stop-weld consisting of graphite and waterglass having been included between. The stop-weld may be applied by using a masking die or a stencil or may be squeezed through a silk screen. The sheets are then first hot-rolled in a reducing atmosphere at a temperature of approximately 1000‹ F., e.g. 925‹-950‹ F. to pressure weld them and form a unitary sheet, then cold-rolled to gauge and annealed at 660‹ F. The unbonded areas are then inflated by water under pressure the passageways 33a, 33b, 33c, 33d being formed by expansion of the sheet 21b only into the die 32, the die 31 having a plane face. After steamcleaning the passageways the branch 33d is closed by rolling. Several unitary blanks may be simultaneously made by bonding and inflating two large sheets having a number of separate stop weld patterns between. Heating elements 36 consisting of a resistor wound on a glass fibre core and covered by glass fibre insulation are mounted in the passageways 33a and 33b prior to or after the deep-drawing of the unitary sheet to form the container 21 of an electric frying pan 20. If the elements are in the passageways during the deep-drawing the metal is pressed into contact with the elements. One of the projecting ends of the heating elements which are in series is connected to a conductor 51 mounted in the handle 22 which is attached to a watertight housing 40 welded to the body of the pan. The handle 22 is adapted to receive a power lead in its remote end to which the conductor 51 and a slidable rod 45 operated by a control knob are attached. The other end of the heating element is attached through a switch 42 operated by a bi-metal thermostat 46 to the rod 45. In a modification the housing may be detachably secured by screws which engage tapped lugs welded to the container. The invention may also apply to a coffee maker, egg cooker, saucepan or deep-fat fryer. Specification 810,728 is referred to.