Abstract Heating apparatus provided with resistance threads lying close to the temperature contact surface thereof and being embedded in grooves which show a cross-sectional area increasing towards and extending to the bottom of the groove, preferably dove-tail shaped, in which grooves the threads are rolled-in leaving clear near to the bottom a space around that thread half that is facing said groove bottom. Said space serves among other things as heat barrier and may be filled under extreme circumstances with a heat insulating material. The heating apparatus can have many applications such as a hot plate, or in calendering or rolling various kinds of material. A special application is stripping off the back-layer of a wide self-adhesive tape for which purpose a crack-back-roll has been developed in which the back-layer of the tape is caused to release from the adhesive layer by crackbuilding created by intensive radiation heat. Temperatures are lying in the reach between 1,000* and 2,000*C requiring special resistance threads. The invention describes how such resistance threads can be embedded into the grooves.
An electric heating device comprising a base metal member having a heating surface provided with at least one continuous groove, the widtH of said groove increasing from its opening toward its bottom, an electrical sheathed heating element positioned in said groove, said heating element having a substantially oval cross section with the longest dimension thereof parallel to said heating surface and greater than the width of the groove opening, and the corss-sectional areas and shapes of said heating element and said groove being respectively so related to each other as to provide a space between the heating element and at least a portion of the groove bottom, said space being substantially filled with a thermally insulating material, whereby said heating element, upon thermal expansion, is confined within said groove, and whereby the major portion of the heat produced by said heating element is effectively transmitted directly toward said heating surface, with only a minor portion of said heat flowing in other directions outwardly from said groove, and a thin metallic layer covering the grooved heating surface.
Claim 2
Dependent Claim
176 words
An electric heating device comprising a base metal member having a heating surface provided with at least one continuous groove, the widtH of said groove increasing from its opening toward its bottom, an electrical sheathed heating element positioned in said groove, said heating element having a substantially oval cross section with the longest dimension thereof parallel to said heating surface and greater than the width of the groove opening, and the corss-sectional areas and shapes of said heating element and said groove being respectively so related to each other as to provide a space between the heating element and at least a portion of the groove bottom, said space being substantially filled with a thermally insulating material, whereby said heating element, upon thermal expansion, is confined within said groove, and whereby the major portion of the heat produced by said heating element is effectively transmitted directly toward said heating surface, with only a minor portion of said heat flowing in other directions outwardly from said groove, and a thin metallic layer covering the grooved heating surface.
Claim 3
Dependent Claim
15 words
A device according to claim 1, in which the groove has a dove-tail cross-sectional area.
Claim 4
Dependent Claim
20 words
A device according to claim 2, in which the groove bottom is convexly curved with reference to the heating element.