US1755051A - Electric furnace - Google Patents

Description

ELECTRIC FURNACE 8. Filed March l, 192

April 15, 1930- electrically Patented Apr. 15, 1930 UNITEDA sra'rris.l

OF SCIHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK ROBERT M. CHERRY,

'PATENT' oFFicE .ELECTRIC 4 FURNACE My invention relates to electric furnaces, especially to resistance heating units for electric furnaces, and has for its object the provision of a heating unit which is rugged in construction, efficient in radiating heat, and which may be easily removed from the furnace structure.

For a better understanding of my invention reference may be had to the accompanying drawings in which Fig. l is a side elevation view of a furnace embodying my invention, and Fig. 2 is asectional View taken on the line 2--2 of Fig. 1, looking in the direction of the arrows.

-Referring to the drawing, in carrying out my invention in one form I provide a furnace structure comprising side and roof walls 11 defining an elongated heating chamber 12, the walls being casing 10. These walls are preferably formed by. an inner wall-13 made of heat refractory is spaced from inner wall .13 and the space between the casing and inner wall is filled ywith a suitable powdered refractory heat insulating substance, such as a diatomaceous material. AA heat refractory bottom is also provided. -An opening 12 is provided in one end wall through which the charge may be inserted and removed, or if desired the charge 'may be pushed through the heating chamber and removed through a suitable opening prov-ided in the opposite end.4

The furnaceis heated by. means of one or more electric heating units 15 mounted in the upper part of the heating chamber and also if desired by one or more heating units 16 in the bottom .of the heating chamber. In the elongated furnace shown a plurality of heating units are provided in both the top and the bottom of the furnace. The units at the top are slidably mounted on suitable brackets so that they may be separately inserted and removed from the side of the furnace. As shown, the upper unit 15 adjacent the end ofthe furnace is mounted at one side on a bracket 14 secured to the furnace wall, the opposite side of the 'unit being supported on a bracket formed by a plate 17 which is secured to the lower side of a supporting bar provided with an outer metal insulating bricks. The casing 10 v 18 extending across the heating chamber and y having its ends secured in the side walls as indicated in Fig. 2. This supporting bar 18 may be rigidly secured lto the furnacey walls or`it may be mountedso that it may be readily removed and replaced. The bar 18 is made from a suitable heat'refractory material, such as aluminum oxide. It is shown as supported at the center by means of a metallicl rod 19 extending upward through the roo-f of the furnace. The rod 19 may, however, be dispensed with, or a greater number may be used, depending on the width of the furnace and the weight of the heating units. The plate 17 projects beyond the opposite side of the bar 18 and forms a supporting bracket for one side of the next adjacent heating unit, as indicated in the drawing. A plurality of supporting'bars 18 may be provided depending upon the number of heating units to be supported. heating unit is used, the supporting brackets for both sides may be secured directly to the furnace wall. j

The heating units 16 in the bottom of the furnace are similar in construction to the upper heating units 15 but are mounted in inverted partments 20'in the bottom of the furnace. These compartments are separated by walls 21 which form supports for Ithe abutting edges of hearth plates-23 extending over the lower heating units.v The hearth plates are preferably m'ade of a heat resisting metal, such as 'nickle chromium alloy, as are also In .the event that only a single relation with respectthereto in 'comvarious other metal parts in the interior of the furnace.

Since as Astated above, all of the heating I units are identical, a vdescription of one unit Awill be sufficient. A plurality of L-shaped hanger blocks 24 made of a suitable electri- I cally insulatingV lheat refractory material,

bars 26 are provided for each pair of support- As shown, live cross hook lying in the recess 27. The hook mem` ing bars, one being provided at each end and three intermediate the ends. The elongated supporting bars and the cross bars' 26 held together by'means of the tie rods 25 thus form a grid shaped framework which may be readily-placed upon or'removed from the supporting brackets 14 and 17.

Each hanger block 24 is provided in one side with a triangular recess 27 formed with one of'its sides at one end surfaceof the block i. e., at one end of the L and with its apex toward the center of the block. A hole 28 passes transversely through each block 24 vat l the apex'of the triangular' recess 27. These' holes and recesses inthe blocks are provided to receive metallic hook members 29 made of a suitable heat resisting metal, one hook member being secured to each block and each hook member having a transversely bent end which is inserted in the hole 28, they shank of the bers 29 are inserted in the recesses 27 and 28 in the blocks rwhile the blocks are being assembled and it will be observed that each hook member is free to swing in its slot 27 on the pivot formed by its transversely bent end lying in the hole 28. The hook members are prevented from working out of the holes 28 by the sides of the adjacent blocks 24.

The hook members secured to each framework form supports for a heating resistor 22 which preferably is formed, as shown, from a ribbon of suitable resistance heating mate rial, such as a nickel chromium alloy, the ril bon being bent into a plurality of zig-zag, substantially parallel lengths or convolutions extending back and forth between the parallel refractory bars of each framework. In the upper heating units, for example, it will 'be observed that the bends joining the convollutlons pass around the rshanks of the hook members and lie in the hooks in the lower ends thereof. That is, a hook is provided at each bend of the resistor whereby the resistor is supported. The recesses 27 and holes 28 in the blocks 24 are so placed in the blocks that the hook members are free to swing in a transverse direction with respect to the supporting bars formed by the blocks whereby the hook members are free to swing in the direction of the expansion and contraction of the resistor dueto changes in temperature.

It will beobserved that the bottom heating units 16 are placed in inverted relation with respect to the upper heating units 15, the resistor 22 in this case resting upon the insulating supporting bars formed by the blocks 24 instead of being hung on the hooks 29. The

resistor is positioned laterally and held in serve to close the recess `27 in thel adjacent viffessaasi i block 24. These spacer blocks 30 may also be placed between the hanger blocks 24 at diiferent points in order to lengthen the unit and adapt a certain resistor to diderent sized furnaces. Attached to and projecting from some of the cross bars 26 are spacing insulators 31,-which are rigidly attached to the cross bars 26 centrally thereof and extend between the pair of lengtlis or convolutions of the resistor at this point. Attached to the cross bars 26 centrally thereof are insulating plates 32 containing slots 33, these plates eX- tending in the opposite direction from the insulator 31. The return leads of the resistors 22 are brought through these slots in the insulating plates 32 to one side or the other of the furnace where they are brought` through the walls in proper insulating bu'shings, not shown. rlh'e other leads 34 of the resistors 22 are shown in F ig. 2 as passing through suitable insulating bushings 35 in the furnace wall.

In Fig. 2 the right-handside wall of the furnace is shown, as containing removable it may be desirable to make thesect-ions 36 `integral with the frame structure of the units l5 or 16 so that a unit and a section of the furnace wall may be removed or replaced in one piece. Suitable tile members 38 are built in the furnace wall to act as a support for the wall when the sections 36 are removed.

Several modilications-may be made without departing from the scope of my invention. For instance, ledges 14 and 19 of the supporting brackets may each be provided with an upward llange, and a downward flange may also be provided on each of the refractory bars formed by the hanger blocks 24 so that by this flange fitting over the flange on the cooperating supporting bracket the blocks will be held more securely on the supporting brackets '14 and`17, but will still be easily removable therefrom. Also, return leads of the resistors may pass through bushings at the back side of the furnace and thus the insulating plates 32' might be dispensed with. On the other hand, the return leads of the bottom units 16 may be brought out along the side of the units through the proper insulators.

Itis to be observed that with my arrangement vthe grid frames from the upper walls of said furnace so as to support their resistors 1n horizontal relation with the resistors positioned in the bottom of said furnace, said l suspending means comprising a supporting bracket" extending across' said furnace for supporting the adjacent edges of each pair of said grid shaped frames.

2. In an electric furnace, a heating unit comprising a plurality7 of refractory L-shaped hanger blocks, means for supporting saidblocks in parallel rows, a metallic'member loosely mounted in and projecting from one leg of each L-shaped block, a heating resistor supported by said metallic members, and means attached to the walls of said furnace on which the other legs of said L-shaped blocks are adapted to rest.

3. In a heating unit for electric furnaces, a plurality of refractory hanger blocks, a` grid shaped framework for holding said blocks in two parallel rows, a metallic hook member loosely mounted in and projecting from each hanger block, and a resistance element supportedby said hook members.

4. In a removable heating unit for electric furnaces, a plurality of refractory hanger blocks, a skeleton framework for supporting said blocks in parallel rows, a metallic member projecting from each of said blocks and pivotally mounted therein, and a sinuous resistance element supported by said metallic 5. In a removable heating unit for electric furnaces, a plurality of refractory hanger blocks, a framework including a plurality of cross bars for supporting said blocks in paraln lel rows, metalic members loosely mounted in and projecting from said blocks, a sinuous heating resistor supported by said metallic members, and insulating guide blocks attached to said cross bars and through which pass the terminals of said resistor..

6. In a removable heating unit for electric furnaces, a plurality of refractory hanger blocks, a framework including a plurality of cross bars for supporting said blocks in parallel rows, metalic members loosely mounted in and projecting from said blocks, a sinuous heating resistor supported by said metallic members, insulating guide blocks attached to some of said cross bars and through which pass the terminals of said resistor, and refractory spacing members attached to said cross bars and holding the turns of said sinuous resistor spaced from each other.

' 7. In a removable heating unit for electric furnaces, a plurality of refractory blocks, means for securing said blocks together `to form a pair of elongated refractory bars, metallic members connecting said refractory bars to form a supporting framework, metallic hooks loosely secured to said bars, and a sinuous resistorv shaped into substantially parallel length extending between said'bars, said resistor being sumiorted on said hooks at the junctions of said lengths.

8. In a furnace, an electrical heating resistor, a removable*v framework extending across said furnace, and metallic hook mem bers secured to said framework engaging and supporting said resistor.

9. In an electric furnace, a heating unit comprising a plurality of refractory L- shaped hanger blocks, a grid shaped framework for holding said blocks in parallel rows, metallic hook members mounted in and projecting from each leg of each L-shaped block, a heating resistor supportedby said metallic members and mea-ns attached' to the to form a supporting framework, a plurality of metallic hook members pivotally secured to said refractory members and a heating resistor supported by said hook members'.

l1. A heating unit for electric furnaces comprising a plurality of refractory members, means for securing said refractory members together, a plurality of hook members pivotallysecured to said refractory members and a heating resistor secured to said hook members.

l12. A removable heating unit for electric furnaces comprising a plurality of elongated refractory members, means for securing said members together to form a supporting framework, a plurality of metallic hook members having transverse end supporting portions secured to said refractory members so as to be pivotally movable on said transverse end portions and a heating resistor supported by said hook members, said resistor extending back and forth between said refractory members.

13. In a. furnace, a framework extending across said furnace and slidably removable from a side wall of said furnace, metallic hook members pivotally secured to said framework, anda heating resistor supported by said hook members extending back and forth between said hook members.

In witness whereof, I have hereunto set my hand this'29th day of February, 1928.

, ROBERT M. CHERRY.

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