US1969478A - Electric furnace - Google Patents

Description

Aug. 7, 1934. v. H. SANDERS ELECTRIC FURNACE 2 Sheets-Sheet 1 Filed Feb. 23, 1933 INVENTOR Wrnon H. Sanders mm m,

ATTORNEYS 1934. v. H. SANDERS 1,969,478

ELECTRIC FURNACE 2 Sheets-Sheet 2 Filed Feb. 25, 1933 I IIIIIIIII' 4 'IIIIIIIIII INVENTOR Viv-non II. Sanders ATTORNEYS Patented Aug. 7, 1934 UNITED STATES PATENT OFFICE ELECTRIC FURNACE Application February 23, 1933, Serial No. 657,976 In Canada November 9, 1932 Claims.

This invention relates to electric furnaces designed for heating articles as they are fed through a tubular passageway, the tube being a resistance element composed mainly of a material such as carbon which has a relatively high electrical resistance and which is intensely heated by the passage of a current of high amperage therethrough.

An object of the present invention is to provide 10 a construction in which the heating tube is effectually insulated to retain the heat generated therein and effectually protected from contact with air to prevent deterioration of highly heated portions of the tube by oxidation.

A further object of the invention is to provide a furnace of the character described in which the heat losses are small and in which there is an efiective interchange of heat between incoming and outgoing material passing through the tube.

A further object is to provide a furnace structure in which the outer casing is formed of metal and is substantially air-tight and in which means is provided for conducting current through a portion of the carbon tube with a minimum loss. A further object is to provide electrodes in the form of suspension members which serve" to support the heated tube intermediate its ends.

A further object is to provide means permitting escape of gases from the interior of the tube,'to-

. gether with means for controlling the discharge of gases.

With the above and other objects in view, the

invention may be said to comprise the furnace as Figure 1 is a top plani view of a furnace.em-

4 bodying the invention;

central longitudinal section;

' at 4 -4"in 'Fig'; 2'; A

through one end of "the carbon tube and the 'cas ing forming an extension of the tube;

, Fig. 2 is,,aside elevation of the'furnace with:

a portion thereof"bmken"a'way.and ls'hownim the top of the'furnace. The vertical end'porl Fig-l4 isa section taken 'onthe line' indica'ted" Fig. 6 is a section taken on the line indicated at 6-6 in Fig. 5.

Referring to the accompanying drawings, the outer shell of the furnace is in the form of a box-like metal casing constructed of sheet metal plates and having riveted or welded joints. This casing has a bottom 1, side walls 2, and end walls 3. Extending longitudinally through the casing centrally thereof there is a tube 4 formed-of high resistance material such as carbon which has a central longitudinally extending partition 5 which divides the interior of the tube into two passages 6 and '7. The tube 4 is preferably rectangular in cross section and the partition 5 extends upwardly from the bottom of the tube centrally thereof.

Articles to be heated indicated at 8 in Fig. 6 are fed through the passages 6 and '7, the articles on one side of the partition 5 being advanced in one direction and the articles on the opposite 5 side of the partition being advanced in the opposite direction.

The opposite ends of the carbon tube 4 are disposed in openings 10 in the end walls 3 and are seated in collars 11 secured to the outer sides of so the walls at the margins of the openings 10. At each end thereof the casing has tubular extensions in the form of castings 12 which are secured to the collars 11 and form continuations of the carbon tube 4. The extensions 12 serve to lengthen the passages for the material so that a more complete interchange of heat between the previously heated articles and the cold articles is effected. Each of. the tubular extensions 12 is closed at its outer end by a door '13 which is carried by a hinged bar 14 which swings about a pivot 15 and which is provided with a latch 16 near its free end which engages with a suitable keeper on the casting.

Each door 13 has a loose connection with its supporting bar 14 and is adapted to be pressed tightly against the end of the extension 12 toseal the end thereof by means of a screw 17 which is threaded in the bar and engages; the door 13.

.Intermediate the ends, of the furnace two cross bars lfl which are bent to U-shape extend across Fig- 3 is a section taken on the line indicated a t1ons of these cross ba ale secured at their lower endsfto longitudinal bars 19 attachedto the upper edges rifthefs'ide walls 2 of the casing. The cross baifslS are 'spac'edfap'artlongitudinally of the 3 s f furnace. each) cross bar serving as a support for an Fig. v5 is: ax fragmentary lOngitudinal QsectiOn" electrode connected to thecarb'on tube 4 so that of the electrodes is suspended from central por tions of a cross bar 18 by means of suspension rods 20 which are attached to water cooling heads 21, each of which is clamped to a pair of electrode bars 22, which may be composed of carbon, by means of a cross bolt 23. The electrode bars 22 which are composed of electrically conductive material are spaced apart a distance correspond ing to the width of the carbon tube 5 and engage with opposite side walls of the tube. The electrode bars 22 extend below the carbon tube 4 and between their ends there is secured a spacer block 24.

Above each of the spacer blocks 24 there is an insert 25 of electrically conductive material which engages the bottom wall of the tube and between each pair of electrode bars above the tube there is an insert 26 of electrically conductive material which engages the top wall of the tube.

Seated at its ends on the spacer blocks 24 there is a longitudinal beam 27 upon which the tube 4 rests from one electrodeto the other. The upper ends of the electrodes are preferably cooled by water supplied to the heads 21 through pipes 28. Suitable electrical connections are provided at the upper end of each electrode for supplying current thereto.

Midway between the two electrodes a pair of arched cross bars 29 extends across the top of the casing and directly over the tube 5 the cross bars 29 support a water cooling head 30 through which extends a stack 31 which communicates at its lower end with the interior of the carbon tube 4 and provides a passage for the escape of gases from the interior of the tube. Suspension rods 32 extend downwardly from the head 30 and beneath the beam 2'7 to provide an additional support for the tube intermediate the electrodes.

At its upper end the stack 31 is provided with a hinged closure member 33' which is adapted to be opened or closed by actuation of a connecting rod 34 which is attached at its lower end to the hinged closure member 33 and its upper end to a. crank 35 which is positioned midway between the ends of a shaft 36 which is journaled in studs 37 extending upwardly from opposite ends of the casing. At each end the shaft 36 is provided with a hand crank 38 so that an operator standing at either end of the furnace can actuate the closure member 33 to open or close the stack 31. It is desirable to close the stack to prevent an inrush of air when the door at either end of the furnace is opened to remove articles which have passed through the furnace and to insert articles which are to be passed through the furnace. The central portion of the heating tube is raised to a very high temperature and opening of the end of the tube would cause an inrush ofair through the stack and a blast of heated gases through the open end of the tube 4 if the stack 31 were left opened. After the carbon tube has been assembled in the casing with the electrodes and central stack, the entire box-like casing is filled with a suitable insulating material such as lamp black, and the top of the casing is closed by means of a sheet metal roof 40 composed of arched plates and the Joints sealed with high temperature cement. Openings 41 are preferably provided immediately adjacent the electrodes so that additional lamp block can be delivered into the interior of the casing to replace any lamp black which may be consumed during operation of the furnace.

Since an alternating current of very high amperage is passed through the electrodes, it is denimble that there be no magnetic material in the casing structure surrounding the electrodes. For this reason the cross bars 18 are made of U- shape with their vertical end portions adjacent the side walls and with the central portions from which the electrodes are separated spaced above the tops of the electrodes. The sheet metal of the roof is preferably composed of a. non-magnetio metal, such as copper or brass.

In the operation of the furnace the articles to be heated are inserted one after another into one end of one of the longitudinal passageways through the tube 4, and into the opposite end of the other longitudinal passageway, so that as the operation progresses the articles will travel in one direction through one of the passageways and in the opposite direction in the adJoining passageway.

As before explained, the electric current passing through the central portion of the carbon tube 4 generates a very intense heat which is transmitted to the articles in the passageways as the articles pass through this central heating zone. In the outer end portions of the tube 4 the articles in one passageway which have been intensely heated during their passage through the heating zone transfer a considerable portion of their heat to articles in the adjoining passageway which are being moved toward the heating zone.

In order to avoid the necessity of opening the ends of the carbon tube 4 each time an article is introduced into or taken out of the tube, push rods 42 may be provided in the doors 13. These rods are slidably mounted in the doors extending through packed openings in the doors, the rod in one door being centrally disposed with respect to the passage 6 and the rod in the other door being centrally disposed with respect to the passage 7, so that articles in the two passages may be advanced by pushing the rods through the doors, therebymaking it possible to remove several of the articles which have been heated and insert several articles to be heated each time the doors 13 are opened.

The location of the hand cranks 38 convenient to an operator standing at either end of the furnace enables the operator to quickly close the stack as either door 13 is being opened so as to avoid an outrush of heated gases.

Since the central portion of the carbon tube is heated to a very high temperature it is essential that the tube be effectually. insulated and that air be excluded from this portion of the tube. This is accomplished by providing. an outer casing which is substantially air-tight and an insulating filling closely packed within the casing. It is also highly important that the carbon tube be so supported in the furnace that very little of the heat will be conducted to the walls of the casing, and that the supporting members be ccpable of withstanding the heat without serious distortion. The supporting of the tube by means of suspension members which also serve as electrodes provides a support for the .tube which does not supply a path for the passage of heat to the Furthermore, the construction is relatively 1w 7 time.

Aside from the specific embodiments of the invention herein shown and described, it will be understood that numerous details of construction may be altered and omitted without departing from the spirit and scope of this invention, and it is. not intended to limit the invention to the exact construction set'forth, as it is desired to claim the invention broadly as well as specifically, as indicated in the appended claims.

What I claim is:

1. An electric furnace comprising an outer sheet metal casing, a heating element in the form of a tube of a size suitable for passage of material therethrough extending centrally through the casing from end to end and composed of an electrically conductive material of high resistance, insulating material filling the casing exteriorly of the tube, and means for supporting the central portion of the tube from the top of the furnace including spaced suspension members engaging the tube inwardly of the ends of the casing, said members being in the form of electrodes for connecting the heating tube to a source of current.

2. An electric furnace comprising an outer air excluding casing, a centrally disposed heating element in the form of a carbon tube of a size suitable for the passage of material therethrough and extending centrally through the casing, insulating material filling the casing exteriorly of the tube, supporting members extending across the top of the casing, and means for suspending said tube from said cross'members and for passing a current of electricity through a portion of said tube.

3. An electric furnace comprising an outer air excluding casing, acentrally disposed heating element in the form of a carbon tube of a size suitable for the passage of material therethrough and extending centrally through the casing, insu-' lating material filling the casing exteriorly of the tube, supporting members extending across the top of the casing, means for suspending said tube from said cross members and for passing a current of electricity through a portion of said tube, means for opening and closing the ends of said tube, and a stack communicating with the portion of the tube through which current is passed.

4. An electric furnace comprising an outer air excluding casing, a centrally disposed heating element in the form of a carbon tube of a size suitable for the passage of material therethrough and extending centrally through the casing, insulating material filling the casing exteriorly of the tube, supporting members extending across .the top of the casing, means for suspending said tube from said cross members and for passing a current of electricity through a portion of said tube, means for opening and closing the ends of said tube, a stack communicating with the portion of the tube through which current is passed, and means for opening and closing said stack.

5. An electric furnace comprising an outer air excluding casing, a centrally disposed heating element in the form of a carbon tube of a size suitable for the passage of material therethrough and extending centrally through the casing, insulating material filling the casing exteriorly of the tube, supporting members extending across the top of the casing, means for suspending said tube from said cross members and for passing a current of electricity through a portion of said tube, said means comprising electrodes connected adjacent their upper ends to said supporting members and adjacent their lower ends to said tube to support the same.

6. Anelectric furnace comprising a metal casing having centrally disposed openings in its opposite end walls, a carbon tube through which material may be passed extending longitudinally through the casing and having its ends seated in said openings, tubular members secured to the exterior of said end walls and forming'continuations of the carbon tube, doors for closing the outer ends of said extensions, insulating material filling the casing exteriorly of said carbon tube, spaced electrodes connected to said tube intermediate its ends, and a stack communicating with the interior of said carbon tube intermediate said electrodes and extending through the top of the casing to permit escape of gases.

'1. An electric furnace comprising an outer casing having a top wall composed of non-magnetic metal, a carbon tube forming a passage for material through the casing from end to end centrally thereof, insulating material filling the easing exteriorly of the tube, and electrodes extending through the top wall and connected to the carbon tube at spaced points.

8. An electric furnace comprising a box-like casing, a carbon tube forming a passage for material extending centrally through the casing from end to end, insulating material filling the casing exteriorly of the tube, spaced supporting members extending across the top of the casing transversely of the tube, and electrodes supported by said cross members and supporting the tube at spaced points.

9. An electric furnace comprising a box-like casing, a carbon tube forming a passage for material extending centrally through the casing from end to end, insulating material filling the casing exteriorly of the tube, spaced supporting members extending across the top of the casing transversely of the tube, electrodes supported by said cross members and supporting the tube at spaced points, and a stack communicating with the tube intermediate the electrodes.

10. An electric furnace comprising a box-like casing, a carbon tube extending across the casing centrally thereof, insulating material filling the casing exteriorly of the tube, electrodes connected to the tube at spaced points, a stack communicating with the interior of the tube, means for opening and closing the ends of the tube, a movable closure member for opening and closing the stack, and means accessible to an operator adjacent either end of the tube for actuating said closure member.

VERNON H. SANDERS.

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