US792022A - Electric furnace. - Google Patents

Description

No. 792,022. PATENTED JUNE 13, 1905. E. HAAGN.

ELEGTRIC FURNACE.

APPLICATION FILED IAB. 8, 1905.

UNITED STATES Patented June 13, 1905.

PATENT OFFICE.

ERNST 'HAAGN, OF HANAU, GERMANY, ASSIGNOR TO THE FIRM OF C. HERAEUS, OF HANAU, GERMANY.

ELECTRIC FURNACE.

SPECIFICATION forming part of Letters Patent No. 792,022, dated June 13, 1905.

Application filed March 8, 1905. Serial No. 248,970.

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Be it known that I, ERNST HAAGN, a subject of the German Emperor, and a resident of Hanan, (Jrermany, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

My invention relates to a simple device for indicating the proper current strength at varying temperatures for electric furnaces, which device may be arranged as an automatic cut-out to prevent the current strength from exceeding a certain limit.

1 will proceed to describe my invention, with re feren cc to the accompanying d rawing, which represents a vertical cross-section through an electric nm'fiie-furnace and shows the device.

The electric conductors leading to and from electric furnaces with heating resistances, such as mufiles or the like, are very liable to melting the moment the furnace attains a high temperature. Evidently the temperature of the conductor is determined, on the one hand, by the electric energy conducted by it, and, on the other hand, by the temperature of the surrounding parts of the furnace. The higher the temperature of the furnace is of course the smaller is the current strength which the conductor will be able to withstand without melting.

For insuring a quick heating of the electric furnace usually a high strength of the current is employed at the beginning, and afterward this current strength is gradually reduced as the temperature of the furnace increases. In order to effect this preliminary heating of the furnace in a safe manner, it was hitherto necessary to watch the ten'iperature of the furnace and to employ an ampere-meter.

The electric furnace l), illustrated in the drawing, is made of any suitable material and. shown as placed on a convenient support It comprises a heating or melting chamber 0, into which a charge to be heated or melted (as the case may be) can be introduced in any known manner. Two binding-posts 7t and are shown as disposed beneath the furnacet and connected with the two conductors v, and Z, whose ends terminate in the heating or melting chamber 0, as usual. A recess (Z is provided in the wall of the furnace I) and made to extend to near 5 may be a wire or a strip of sheet metal of the required strength and can be easily watched from without. The two binding-posts g and 71. are connected by the two conductors m. and a with the respective source of electricity.

The simple device t. 6., the wire or strip 0 5 is connected in series with the heating resistance.

The device operates as follows: On sending the current of a certain strength through the circuit the furnace will be gradually heated, 7

so that the wire or strip a is not only heated by the electric current, but also by the heat of the furnace I), so that it will soon become red. As it is made of a certain metal or alloy and the red heat can be easily recognized, it

is possible to know the temperature of the furnace and to determine the proper strength of the current. The latter should be so regulated by reducing it from time to time that the wire or strip a. maintains its color of a commencing red. Then the conductors '2' and Z; will be able to conduct the current in a safe manner without melting no matter what temperature the furnace b may have.

W here so preferred, the device (1 may be ar- 5 ranged as an automatic cut-out, as it is only necessary to make it of a metal (for example, silver) or an alloy the melting-point of which is a little above the temperature at which it commences to become red. the device will serve as a safety means, it melting under an overcharge, the strength of the current being in all cases the lower the higher the temperature of the furnace is.

The simple device maybe varied without deviating from the spirit of my invention.

This 55 Then 9 What I claim as my invention, and desire to secure by Letters Patent, is-

1. In an electric furnace, the combination With a recess in the Wall of the furnace and reaching to near its heating or melting chamber, of a conductor-piece leading to said heating or melting chamber and engaging in said recess near its end face, a conductor engaging in said recess, and a metal indicator connecting the ends of said conductor-piece and said conductor in said recess and being so disposed, that it can be Watched from Without and indicate by its commencing red heat the correct strength of the current. r

2. In an electric furnace, the combination with a recess in the Wall of the furnace and reaching to near its heating or melting chamber, of a conductor-piece leading to said heating or melting chamber and being bent Without, so that its other end engages in said recess and reaches to the end face of the latter, a conductor engaging in said recess, and a metal indicator connecting the ends of said conductor-piece and said conductor in said recess and being so disposed, that it can be Watched from Without and indicate by its commencing red heat the correct strength of the current.

3. In an electric furnace, the combination With a recess in the Wall of the furnace and reaching to near its heating or melting chamber, of a conductor-piece leading to said heating or melting chamber and being bent Without, so that its other end engages in said recess and reaches to the end face of the latter, a conductor engaging in said recess, and a metal rod connecting the ends of said conductor-piece and said conductor in said recess and adapted to be Watched from Without, so that it can indicate by its commencing red heat the correct strength of the current.

4. In an electric furnace, the combination with a recess in the Wall of the furnace and reaching to near its heating or melting chamber, of a conductor-piece leading to said heating or melting chamber and being bent without, so that its other end engages in said recess and reaches to the end face of the latter,

a conductor engaging in said recess, a metal rod connecting the ends of said conductorpiece and said conductor in said recess and adapted to be Watched from Without, a second conductor leading to said heating or melting chamber, a source of electricity connecting the other ends of said two conductors, and means for regulating the strength of the current, said metal rod indicating by its commencing red heat the correct strength of the current.

5. In an electric furnace, the combination With a recess in' the Wall of the furnace and reaching to near its heating or melting chamber, of a conductor-piece leading to said heating or melting chamber and being bent Without, so that its other end engages in said recess and reaches to the end face of the latter, a conductor engaging in said recess, a rod connecting the ends of said conductor-piece and said conductor in said recess and adapted to be Watched from Without, a second conductor leading to said heating or melting chamber, a source of electricity connecting the other ends of said two conductors, and means for regulating the strength of the current, said rod being made of a metal Whose melting-point is a little above the red heat and this rod indicating by its commencing red heat the correct strength of the current.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

ERNST HAAGN.

W'itnesses:

JEAN GRUND, CARL GRUND.

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