Planar heating unit

Details Planar heating unit Planar heating unit

1984-02-22

1986-05-06

Albritton, C. L.

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

219345, 338308, F24H 900

Patent

active

045874026

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a heating unit which generates Joule heat upon energization, and more particularly to a planar heating unit wherein an assembly including a heating conductor, a base plate supporting the same, etc. is constructed in the form of a plate whose surface radiates infrared rays.


BACKGROUND ART

Planar heating units are used as a heat source for heating equipment, cooking appliances, and driers and are attracting attention because they meet such requirements as the reduction of apparatus thickness and uniform heating.
Requirements which planar heating units should meet are as follows. of energy utilization. dielectric breakdown strength).
Most of the conventional planar heating units are in the form of a mica or other insulation base plate having a heater wound thereon and are poor in transmission of heat to heating loads, and since their electric heating material is not sealed, there has been a problem in their moisture resistance.
There is another form of planar heating unit wherein a nonsintered sheet, such as alumina, is formed with an electrically conductive pattern using a conductor paste, such as tungsten, with a sheet stuck thereto, and the assembly is sintered. This heating unit is suitable for applications requiring high heat value, but presents such problems as high heat capacity which results in a long heat-up time, and high sintering temperature which makes it difficult to lead out the electrodes because of the melting of contact material.
There are other forms of heating units including one in which an electrically conductive pattern formed between silicone resin, polyimide or other organic films and the heating unit is constructed as by lamination, but these heating units are limited in heat resistance temperature to 250.degree. C. and their service life is also limited.


DISCLOSURE OF INVENTION

A planar heating unit according to the present invention comprises a base plate having an electrical insulation surface, a Joule heat generating conductor disposed on said electrical insulation surface, and a cover layer formed of an enamel layer for fixing said conductor to said base and covering said conductor.
This arrangement makes it possible to provide a planar heating unit which is superior in heat resistance and moisture resistance and whose heat capacity is low. Further, the function of the enamel layer ensures a high infrared radiation coefficient and high efficiency of energy utilization.


BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a fragmentary sectional view showing an embodiment of the arrangement of the planar heating unit of the present invention;
FIGS. 2(a) and 2(b) are plan views showing heating conductors in the planar heating unit of the invention;
FIGS. 3 and 4 are fragmentary sectional views showing other examples of the arrangement of the planar heating unit of the invention;
FIG. 5 is an enlarged sectional view of the principal portion of FIG. 3;
FIG. 6 is a graph showing changes in the volume resistivity of various planar heating units due to temperature; and
FIGS. 7 and 8 are sectional views of planar heating units according to embodiments of the invention.


BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows an example of the basic arrangement of the planar heating unit of the present invention. In this figure, 1 denotes an enameling metal base plate whose surfaces are covered with insulation enamel layers 2a and 2b in advance. The numeral 3 denotes a planar heating conductor disposed above one enamel layer 2a and covered with a cover enamel layer 4 formed by spraying an enamel layer-forming slip onto the enamel layer 2a and firing the same, said conductor being integral with the base plate.
The planar shape of the heating conductor 3 may be for example as shown in FIG. 2(a) or FIG. 2(b).
The planar heating unit of FIG. 1 can be produced by the following process.
First, a steel plate forming the base plate 1 is subjected to degreasing, boiling wash, pickling, and boiling wash, and then to nickel plating, boiling wash, and dr

REFERENCES:
patent: 3737624 (1973-06-01), Ellenberger
patent: 3805024 (1974-04-01), Joeckel et al.

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