US3009974A - Electric furnace - Google Patents

Description

Nov. 21, 1961 E B. SEKKELSTEN ETAL ELECTRIC FURNACE Filed April 14, 1959 INVENTORS Erfir Bjb'm Sekke/sten Hans Er/ana' Sundf I /MM, all ix/ M A TTORNEYS United States Patent Ofiice 3,099,974 Patented Nov. 21, 1961 3,009,974 EEJECTRIC FURNACE Erik Bjorn Sekkelsten, Oslo, and Hans Erland Sundt,

Baerum, Norway, ,assignors to Ingenior Gunnar Schjelderup Industriovner, Oslo, Norway Filed Apr. 14, 1959, Ser. No. 806,261 Claims priority, application Norway Apr. 26, 1958 2 Claims. (Cl. 13-25) The present invention relates to furnaces of the type in which the heating element consists of a refractory receptacle composed of sections and containing an electric resistance material, through which an electric current is passed to generate heat, said receptacle extending rectilinearly between two oppositely situated furnace walls.

Such furnaces are for instance utilized in heat treatment of cast blocks of steel or iron which are to be rolled. During operation the trough attains a very high temperature exceeding 1000 C. Occasionally it is, however, necessary to put the furnace out of service, during which time the furnace cools down to room temperature. As a result of alternating heating and cooling, cracks occur in the refractory receptacle, especially at the joints between the separate sections. Such cracks or fractures are for several reasons very unfavourable. Air may for instance penetrate through the cracks causing combustion of the undermost layer of coke in the receptacle. This combustion process usually cannot be observed from up above the trough, therefore considerable time may lapse before the burned coke can be replaced.

The purpose of the present invention is to eliminate or reduce the tendency of crack formation in the trough material. According to the invention this is accomplished by providing an electric furnace comprising a receptacle composed of sections of refractory material and adapted to contain electrical resistance material, said receptacle extending between two oppositely situated furnace walls, means for passing an electric current through said resistance material, an element slideably arranged in an opening in one of said furnace walls, said element abutting at its inner end against one end of said receptacle and means for providing a resilient compression force against said element. Since in many instances it is of vital importance to prevent the air from leaking into the furnace at electrode insertions, said pressure transmitting element preferably should be constructed as a bushing confining the electrical supply electrade and establishing an air-tight connection with the furnace wall in such a way that the movement of the refractory receptacle is not impeded.

For further illustration the invention shall be described .with reference to the drawing, the single figure of which schematically shows a sectional view of an embodiment of the device according to the invention.

In the drawing 1 indicates the furnace lining, 2 is an outside casing. 3 is an opening in the furnace wall and 4 is one in the opening arranged conductor box. 5 is a trough-shaped receptacle extending from the furnace wall 1 to the oppositely positioned furnace wall. Several such trough-shaped receptacles may be arranged in one furnace. The trough is composed of sections. 6a is the section situated closest to the furnace wall 1 and 6b is the adjacent trough section. 7 is a current supply electrode which extends through the furnace 'wall and which not shown in the drawing.

inner end 7a is situated in the trough in contact with the resistance material which for sake of simplicity is 8 is a tubular bushing of refractory material arranged in the contact box 4 and encircling the electrode 7. At its inner end the bushing 8 is abutting the outer end of the trough section 6a. At its outer end the bushing 8 is subjected to a compression force from a spring 10 through a gasket 9. The spring 10 is at the embodiment shown composed of three disc springs 10a, 10b and 10c, which are abutting each other at the inner end at the outer edges alternatively. Between the abutting surfaces of the springs is at least one annular air-tight gasket 15. The springs may be maintained in compressed state by means of a gland 11, the inner face of which is furnished with a gasket and bearing against the outermost disc spring. The spring tension may be provided and adjusted by placing bolts in the bolt holes 12, said bolts being threaded into the housing 13, which is sealinlgly fixed to the furnace casing2.

In virtue of the present invention it is possible to maintain the entire receptacle in a state of compression by an outside spring arrangement and yet provide air-tight imposters and electrode connections. It shall be understood that the invention is notlimited to the example illustrated in the drawing where the resistance element consists of an open trough-shaped receptacle containing coke since the resistance elements of course may be given any desirable form or design. Further, any suitable means for providing said resilient comprmsion force may be employed, instead of springs.

We claim:

I. An electric furnace comprising two spaced opposed walls, a receptacle comprised of a plurality of sections of refractory material for containing coke which acts as a resistance material, said receptacle extending between said two walls, one of said walls having an opening therein, a tubular element slidably mounted in said opening in said one of said walls, one end of said tubular element abutting one end of said receptacle, resilient compression force providing means on the outside of said one of said walls abutting the other end of said tubular element for exerting a force thereon, and a current supply electrode extending through said tubular element with the inner end thereof extending into said receptacle for contacting the resistance material therein.

2. An electric furnace as claimed in claim 1 in which said resilient compression force providing means comprises a cylindrical housing on the outside of the said References Cited in the file of thispatent UNITED STATES PATENTS 1,572,893 Little Feb. 16, 1926 1,671,337 Baily May 29, 1928 2,179,153 Jones Nov. 7, 1939 2,904,609 Schjelderup et al. Sept. 15, 1959

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