Solid-body heating unit

#1. Field of the Invention

#The present invention relates to a solid-body heating unit, and more particularly, to a solid-body heating unit for preserving warmth, heating, melting, and heat treating, and which is suitable for use with plate or pattern capable of controlling surface temperature therein.

#2. Description of the Prior Art

#Other and further objects of the invention will become apparent to those skilled in the art from the following description with reference to the annexed sheet of the drawings, in which:

#FIG. 1 is a sectional elevation view of the heating unit of the present invention taken on line 1--1 of FIG. 2;

#FIG. 2 is a plan view of the heat unit of the present invention; and

#The solid-body heating unit of the present invention comprises a solid-body structure having a 15 to 1,000.mu. thick electroconductive layer closely adhered thereon. If necessary, the thickness of the electroconductive layer is varied locally to control the electrical resistance of the layer, thereby to achieve a desired temperature distribution.

#When wood or plastic is used for the solid-body structure, the surface of the solid-body structure is provided with a refractory heat-insulating ceramic layer which is in turn covered with an electroconductive material such as an alloy or a compound or a reformed carbonaceous material having characteristics similar to such an alloy or a compound. The thickness of the electroconductive layer is suitably 15 to 1,000.mu., with the regions requiring higher resistivity being given greater thickness.

#Generally speaking, a material that has a large positive temperature coefficient of resistivity gives rise to little biased or concentrated current so that a stable distribution of temperature can easily be obtained. In other words, in the present invention, an electroconductive layer material which increases in resistivity with rising temperature is most preferred. A layer material having a resistivity of 30-30,000 .mu..OMEGA.cm is used.