US1431825A - Electric resistance heater - Google Patents

Description

H. G. LEMOINE.

. 21. 1,431,825, Patented Oct. 10, 1922.

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H. G. LEMOINE.

ELECTRlC RESISTANCE HEATER.

APPLICATION FILED .IULYIB, I92I.

Patented Oct. 10, 1922.

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Patented Oct. 10, 1922.

UNITED STATES HENRI GUIDO LEMOINE, F PARIS, FRANCE.

ELECTRIC RESISTANCE HEATER.

Application led July 18,

To all whom t may con-cem:

Be it known that I, HENRI GUIDO LE- MOINE, citizen of the Republic of France, residing at Paris, France, and whose ostoffice address is 4 Rue Taltbout, aris, France, have invented certain new and 'useful Improvements in Electric Resistance Heaters, of which the following is a speelfication. I

This invention relates to electrlc resistance heaters and has for its object an improved high temperature resistance heater, and particularly the application of such heating resistances to electric furnaces.

According to this invention I provide an electric' heating element which comprises essentially a filament, strip or helix or the like of tungsten or other suitable metal, sbstance or alloy suitably folded upon itself in order to offer a large surface and embedded in a mixture of zirconium oxide, or other oxide of a metal of the same group as the latter metal such as yttrium or thorium oxide, and magnesia. The elements which are constituted in this manner allow of the attainment of temperatures susceptible to attain 3000o C. when the current is passing in the said filament, stri helix or the like, without deterioration o the said element, which is protected by the refractory matrix from the action of oxidizing or other detrimental agents. In order to avoid overheating at the bends the internal metallic filament or strip or the like of the resistance is 36 preferably reinforced at these oints.

Heating elements of this kin may be used for the heating of electric furnaces, being put in circuit by means of carbon external contact pieces. The use of such elements for 40 the heating of furnaces has also the advantage that it allows of the simultaneous production of pressure in the furnace chamber, together with the attainment of an elevated temperature.

Referring to the drawing filed herewith, which illustrates diagrammatically as examples several methods of practical construction of some particular forms of heating elements:

Figs. 1 and 2 are two diagrammatic views in vertical and transverse section respectively of a heating plate constructed accordin to this invention.

ig. 3 is a diagrammatic vertical 'section 1921. Serial N0. 485,518.

of another method of construction of the heating plate.

Figs. 4 and 5 illustrate in vertical and horizontal section respectively an alternative construction in which the heating element has a cylindrical shape.

Fig. 6 is a view showing, diagrammatically in vertical section, a heating element having the shape of a cone.

The heating element shown in Figs. 1 and 2 of the drawing is constituted by a tungsten strip a folded back upon itself and embedded in a mass b constituted by a mixture of zirconium oxide and magnesia. As shown in the drawing the bends a* of the strip a are reinforced in order to avoid fusion of these points which are particularly delicate.

The manufacture of such -an element is performed in arranging the tungsten strip, previously folded to a suitable shape, in a. mould and maintaining it slightly above the bottom of the said mould, and in subsequently pouring in the latter the mixture of zirconium oxide and magnesia; the whole is then compressed, and a current is passed in the metallic resistance to solidify and harden the matrix of zirconium oxide and magnesia. When the whole has cooled it possesses all thehardness and rigidity required for practical use in industrial furnaces. It will be understood that the pressure and the intensity of the current used for the manufacture depend upon the use to which the element is to be put ultimately.

Electric contact with the heating elements is obtained by means of two carbon contact pieces c passin through the Wall d of the furnace. Simi ar elements can of course be used in any suitable number in the same furnace.

In the example shown Fig. 3 the resistance is constituted by a tungsten filament a coiled in a helix and the whole of which is disposed in a suitable manner similar to that used for the strip of Fig. l, the whole being also embedded in a mixture of zirconium oxide and of magnesia b.

In the alternative construction shown Figs. 4 and 5 the heating element is constituted by a tungsten strip a folded back upon itself and reinforced at the bends as shown in al, said strip being embedded in a mass of zirconium oxide and of magnesia b having the shape of a solid cylinder; the strip a splitting.

being given a suitable outline for this purose.

p In the construction shown in Fig. 6 the heatin element has the shape of a hollow cone, the strip being coiled in spiral round this cone and embedded in the mass b of zirconium oxide and magnesia. 'One could in a similar manner construct a hollow cylindrical element.

It will be understood that it would be possible to construct heating elements of any suitable shape, adapted either to any particular operation to be carried out or to any special configuration of the furnace itself, by embedding the tungsten resistance in any suitably moulded mass of zirconium oxide and magnesia. Similarly 'the strip, filament, helix or the like of tungsten within the matrix can affect all possible and suitable shapes.

Although zirconium oxide seems to be the substance which gives the best result for the purpose in view, one could nevertheless replace it by yttrium oxide or thorium oxide or any other oxide of a metal of the same group.

' Similarly the tungsten used for the resistance could be replaced, although with different results. by a chrome-nickel alloy or any other substance, metal or suitable alloy, even by carbon.

The coefficient of expansion of the matrix of the above described heating elements being inferior to that of crystal, these elements can be exposed without damage to large variations of temperature and therefore to sudden cooling without any risk of crack-ing or Besides` these elements being, as has been explained above, compressed at a high temperature during the course of their manufacture the resistance, strip, filament, helix or the like which they completely enclose, itself impresses, at that time in the matrix the space required for its dilatation, the production of which gives rise, when the element- 1s cooling, to a theoretical absolute vacuum round the resistance.

Claims:

Improved electric heating element com.- prislng a electric resistance constituted by a metal of the tungsten group, and a refractory mass enclosing this resistance and having a lower coefficient of expansion than the metal of the resistance.A

2. Improved electric heating element comprising a electric resistance constituted by a metal of the tungsten group, and a refractory mass enclosing this resistance and cony sisting of a mixture of an oxide of the zirconium group and magnesia.

3. Improved electric heating elementcomprising a electric resistance constituted by a tungsten member, and a refractory mass enclosing this resistance and constituted by a mixture of zirconium oxide and magnesia.

4. Improved electric heating element comprising a bended tungsten filament, reinforced parts at the bends of this filament, and a mixture of zirconium oxide and magnesia enclosing the said tungsten filament.

In the manufacture of a improved electric heating element, embedding a tungsten resistance into a refractory mixture of zirconium oxide and magnesia, compressing the whole, closing the electric current through the tungsten resistance, and cooling the element to obtain an absolute vacuum between the resistance and the refractory mixture.

In testimony whereof I affix my signature.

HENRI GUIDO LEMOINE.

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