US1690678A - Electric resistance furnace - Google Patents

Description

A a 9 1 6 v 0 N ELECTRIC RESISTANCE FURNACE Original Filed Jan. 23 1924 Patented Nov. 6 192 8. A A

UNITED STATES- PATENT OFFICE.

ALBERT J. HANSON, OF ARLINGTON, MASSACHUSETTS, ASSIGNOR TO AMERICAN METALLURGICAL CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

ELECTRIC RESISTANCE FURNACE.

Application filed January 23, 1924, Serial No. 687,913. Renewed May 7, 1927.-

This invention relates to an electric resisb bends by gravity on their supports, there is ance furnace. no opportunity for the weight of a resistor' One object of the invention is to provide an when at high ten'iperature to cause its attenuelectric resistance furnace of novel and imation with consequent decrease of effective 5 proved construction, particularly with recross section with its result-ant danger of spect to the supporting of the resistor Within overheating and burning out, a condition the furnace, to produce a furnace which is which it is found in practice is liable to occur 55 simple, durable and capable of maximum When the resistor is suspended at its upper efliciency in operation, and also one in which bends; the weight of the resistor then sub- 0 the liability of short-circuiting the resistor jecting it to tension stresses which in its softand burningout the same are reduced to a ened condition" at high temperature it is not minimum. able to withstand. The projecting portion on Another object of the invention is to proof one resistor support is preferably arvi'de afurnace of the character specified ranged to cooperate with the upper bends of whichniay be constructed in a simple and ina resistor section arranged beneath the same expensive manner, and particularly one in and retain the. upper end of such lower resiswhich the resistor sections may be installed tor section in operative position, with the up 35 and removedata minimum expense and in a per bends maintained in spaced relation.

simple and convenient manner. Provision is also preferably made for remov- A still further object of the invention is-to ably retaining the lower bends of each resisprovide a novel and improved construction tor section in their proper positions upon the of resistor support for electric resistance furresistor support, as will be described. The 7 naces. resistor support may, and preferably will, To these ends, the resistor of the electric comprise a unitary structure adapted to be resistance furnace comprises preferably the laid up between the brick of thefurnace wall usual ribbon bent into a general sinuous in a manner such that a plurality of the reshape, having a plurality of bends at opposite sistor supports cooperate to form a projectsides thereof, and the resistor support coming shelf for supporting the resistor sections. prises a body of electrical insulating mate- These and other features will be herein- 30 rial, preferably having high thermal transafter described, and particularly pointed out mitting and radiating properties, and which in the claims at the end of the specification. is preferably embedded in and arranged to In the drawings illustrating the preferred 30 project from a wall of theheating chamber of embodiment of the invention, the furnace to support the resistor thereon. Figure 1 is a perspective of. the improved In the preferred embodiment of the inven- .resistor support. tion, the resistor support comprises a pre- Figure 2 is a section on line 22 of F ig formed tile adapted to be laid up between the ure 1. brick in'a wall of the heating chamber of the Figure 3 is a perspective of one of the defurnace and to project from the wall to form, vices for retaining the resistor upon the re- 40 in effect, a supporting shelf. Each resistor sistor support.

section is preferably arranged to be sup- Figured is a vertical section of a portion ported upon and to rest directly upon the proof the wall of the heating chamber, illustrat-- jccting portion of the resistor support-wand ing the resistors and their manner of supthe latter preferably has provision for mainport.

45 taining the bends of the resistor in spaced re- Figure 5 is a front View of a portion of the lation to one another and in spaced relation face of the Wall illustrated in Figure 4c; and to the wall of the heating chamber. By sup- Figure 6 is a perspective of one of the auxilporting the resistors by resting their lower iary supports to be referred to.

Referring to the drawing, represents a portion of one wall of the heating chamber of an electric resistance furnace, which may be of the usual construction, and 12 a resistor of any usual or preferred construction. Preferably as illustrated in Figure 5, it comprises the usual nickel chromium ribbon of a general sinuous shape having a plurality of bends 13, 14 at the opposite sides thereof. The resistor 12 is preferably built in sections, which are installed in the furnace and electrically connected in any well known manner. In accordance with the present invention, the sections of the resistor 12 are supported upon the wall 10 of the heating chamber of the furnace by preformed insulating supporting members 15 embedded in the wall and having portions 16 projecting from the face of the wall and upon which the resistor sections are supported. As herein shown, the

. resistor supports which comprise preformed tiles of electrical insulating material, such as carborundum, crystolon, or similar material having high electrical insulating properties at high temperatures, and, in addition,

good thermal transmitting and radiating.

properties, are laid up between adjacent brick in the construction of the wall of the heating chamber, as illustrated in Figure 4.

Provision is made for removably mounting the resistor sections in operative substantially upright position upon the projecting portions 16 in a novel manner to permit the sections to be installed and removed in a simple and convenient manner, and for this purpose as herein shown, the resistor supports 15 are arranged to project from the face of the wall to form a series of transversely extending shelves arranged one above the other and spaced from one another slightly more than the height ofthe resistor section 12 which it is desired to employ. A resistor section is arranged to rest upon the upper surfaces of the resistor supports 15 forming each shelf,

and the under portions of the resistor supports of the next higher shelf are constructed to cooperate withthe upper ends of the resistor section to retain it in operative position while supported on the next lower shelf.

Provision is also made for spacing the individual bends 13, 14 or parts of each resistorsection from one another, and also'from the wall of the. furnace, and as illustrated in the drawing, both the upper and lower surfaces of the projecting portions 16 of the resistor supports 15 are provided with grooves 25, 26 of a size. sufficient to receive the upper and lower bends 13, 14 of the resistor. The grooves 25 and 26 are spaced apart in staggered or ofiset relation to pro vide intervening bodies 28, 29 of insulating material, and the walls of the grooves also serve to restrain the sections from transverse movement. The forward ends of the grooves 25 in the under surface of the resistor supports 'are closed by retaining members 30 preferably comprising a part of the front wall 31 of each support, as illustrated in Figure 1, and which cooperate with the upper bends 13 ofthe resistor to prevent forward displacement thereof. By reference to Figures 4 and 5, it will be seen that each resistor section is supported upon a resistor support with the lower bends 14 thereof resting in the grooves 26 in the upper surface of the resistor support, and that each section is retained at its upper end with the upper bends 13 loosely received in the grooves 25 in the under surface of the next higher resistor support, by the members 30 closing the forward ends of the grooves. In order to prevent displacement of the lower bends 14 of each resistor section, a series of lips 34 are'preferably provided at the forward ends of the insulating portions 29 between the grooves 26 in the upper surface of the resistor support, as illustrated in Figures 1 and 2, and one or more transversely extending retaining members 36, preferably of lava, or other refractory material havin electrical insulating properties and pref transmitting and radiating properties, rests upon the upper surface of the resistor support immediately in front of the resistor section and between it and the lips 34. The retaining members 36 are held in place by gravity, and are prevented from forward displacement by the lips 34. i

In order to insulate the resistor sections from the face of the wall of the heating chamber, the-resistor supports 15 are preferably laid up in the wall in a manner such as to cause the rear ends 38 of the grooves 25, 26, and consequently the rear of each resistor section, to be spaced a short distance from the face of the wall, as'illustrated in Figure 4.

In practice, the resistor supports 15 are, as has been stated, composed of carborundum or other similar material, having high electrical insulating properties at high temperatures, and good thermal transmitting and radiating properties, and the resistor supports are preferably cast in the form illustrated in Figure 1, having the grooves 25, 26 in the upper and lower surfaces thereof offset to permit the resistor supports to be laid up one above the other and to have the grooves 25,26 in the correct position to receive the upper and lower bends 13, 14 of the usual sinuous shaped resistor, such as is illustrated in Figure 5. This construction of resistor supporting member 15 possesses strength, and there is therefore little liability ofits fracture during the normal use of the furnace.

In the construction of the electric resistance furnace, the precast resistor-supporting members 15 are shipped to the job and laid up between the fire brick comprising the face of the wall of the heating chamber to form an erably good thermal the two inch integral part of the wall. In practice, the resistor supports are preferably cast substantially one inch in thickness, so that using the usual two inch brick, the mason by laying up the resistor supports with a double course of rick intervening, provides a distance between the resistor supports of substantially five inches, this being slightly greater than the height of the resistor sec tion commonly employed. In order to install the resistor sections, the workman bends the resistor ribbon into the desired shape,

preferably the sinuous shape illustrated in Figure 5, and thereafter inserts the upper bends 13 of each section in the grooves 26 on the under side of the upper resistor support. It is possible to do this by inclining the resistor section and slipping the upper bends beneath the members 30, closing the forward ends of the grooves 25. When the upper bends 13 of the resistor section have been thus placed in the ooves 25, the lower bends '14 are slid into t e grooves 26 upon the upper surface of the lower resistor support, the grooves 26 being open at their forward ends readily permittlng this to be done. Thereafter the operator simply drops the retaining members 36 in position, in front of the resistor section, the members being retained by gravity in their operative position and prevented from forward displacement by the retaining lips 34: projecting from the surface of the resistor support. It will therefore be apparentthat the resistor sections may be installed in an exceeding simple and practical manner, in-a-minimum of time, and at a relativelysmallexpense. In a similar manner,

they may be easily and conveniently removed,

all that is required being for the operator to remove the retaining members 36, to slide out the lower ends of the resistor sections, and then drop the sections down until the upper' I bends 13 clear the members 30 which close the front of the grooves 26.

In order to insure against the possibility of saggingof the upstanding loops of the re sistor sections when the furnace is operatedthe grooves 25 upon the uppersurface of the resistor support. 'The auxiliar supporting members 40*comprise preforme members of insulating material, preferably carborundum orsimilar material having high electrical in sulating properties and good thermal transmitting and radiating properties, and are preferably of a tapered shape, as illustrated in Figure 6. The members 40 are removably' retained in anoperative position by the upstanding lip 34 and by the members 30 closing the forward ends of the grooves 26 on the lower surfaces of each resistor support, as illustrated in Figure 4. While during the By reference toFigure 4, it will be seen that the resistor supports project forwardly from the wall of the heating chamber beyond the resistor sections, and the projecting portions together with the upstanding lips 34 serve to protect the resistor sections against mechanical damage or breakage from impact with anything which may tip over within the furnace. observed that the upper and lower bends 13, 14 of each section of the...resistor are spaced from each other'by bodies 28, 29 of electrical insulating material, and furthermore in the preferred construction of resistor support, the lower bends 14 of one section of the resistor are separated from the, upper bends 13 of the next lower resistor section by an intervening body of electrical insu lating material comprising the body portion of the resistor support itself, and as a result, the liability of short-circuiting of the resistors is reduced to a minimum.

The present construction of electric re sistance furnace is designed to reduce to a'minimum, the liability of burning out the resistor. The manner of supporting the resistors, it will be observed, is such as to expose them for direct radiation into the heating chamber of the furnace, so that when the furnace is operated at high tem perature the heat is radiated directly into the heating chamber'where it is utilized and the accumulation of heat and the building up of excessive temperatures in the immediate vicinity of the resistor is avoided. This construction therefore is conducive to the long life of the resistors.

It is also to be observed that in the present construction of furnace, the resistor sections 'are supported in a manner such that a maximum amount of wall space may be utilized for the resistors, producing a furnace having a maximum electrical capacity per square foot of wall space.

The term sinuous as usedthroughout the specification and claims, is to be understood is including shapes of resistors having closed bends of,various shapes at the opposite sides thereof.

WVhile the referred embodiment of the invention has een illustrated and described, it is to be understood that the different features of the invention may be embodied in other forms within the scope of the following claims.

I claim:

combination, a chamber Wall, a resistor section having a plurality of bends at two of the opposite sides thereof, insulating members projecting from the wall on opposite 1. In an electric, resistance furnace, in

It will also be 7 wall.

sides of the resistor section and having spaced apart recesses in adjacent surfaces, and means cooperating with said bends for retaining them in'the recesses and the resistor section in place upon the chamber and the section in place upon the chamber wall.

3. In an electric resistancev furnace, 1n

combination, a chamber wall, a resistor sec-.

tion having a plurality of bends upon two of the opposite sidesthereof, insulating members projecting from the wall on opposite sides of the resistor section and havingrecesses in adjacent surfaces, and means cooperating with said bends to retain the section in operative position between said insulating members and having provision for permitting one side of the section to be moved forwardly upon the insulating member to remove the section from between said insulating members.

4. In an electric resistance furnace, in combination, a chamber wall, two insulating members spaced apart and projecting from the wall, a resistor section having bends at two of its opposite sides arranged between said insulating members, and means for retaining the resistor section between said insulating members including recesses in the adjacent surfaces of the insulating members in which the bends are received,

means carried by one of the insulating members for preventing forward displacement of one set of bends from one set of recesses, and removable means for preventing displacement of the second set of bends from the second set of recesses.

5. In an electric resistance furnace, in combination, a chamber -wall, two insulating members spaced apart and projecting from the wall, a resistor section having a plurality of bends at two of its opposite sides, and means for retaining the resistor section in operative position between the insulating members including grooves in theadjacent surfaces of the insulating members in which said bends are received, one set of grooves being closed at their forward ends and the second set being open, and removable means for retaining the bends in the open grooves. v

6. In an electric resistance furnace, in combination, a chamber wall, a resistor section of general sinuous shape having upper and lower bends, and meansfor removablv supporting the resistor section upon the wall ineluding insulating members projecting from the wall above and below said section, relating pockets in the under surface of the upper insulating member in which said upper bends are received and prevented from displacement by the walls, recesses in the upper surface of 8. A resistor support for electric resistance furnaces, comprising a tile of electrical insulating material provided upon its under surface with a plurality of grooves spaced apart and closed at one end, and having upon its upper surface a plurality of grooves open at one end. I

9. A resistor support for electric resistan' e furnaces, comprising atile of electrical insulating material provided with grooves on opposite surfaces thereof spaced apart and with the grooves upon one surface arranged intermediate adjacent grooves upon the other surface,-and provided with members projecting above one surfaceof the tile, for the purpose specified.

10. In anelectric resistance furnace, in combination, a chamber wall, resistors each having a plurality of upper and lower bends, and a resistor support of insulating material embedded in the wall and having a portion projecting therefrom-provided with depressions in its upper surface in which the lower bends of the resistor rest and depressions in its lo\v er surface to receive the upper bends of the resistors below, said depressions being spaced apart to provide intervening bodies of insulating material between said bends.

11. In an electric resistance furnace, in combination, a chamber wall, resistors eachhaving a plurality of upper and lower bends, and a resistor support of insulating material embedded in the wall and having a portion projecting therefrom provided with depres-- sions in its upper surface in which the lower bends of the resistor restanddepressions in I its lower surface to receive the upper bends of the resistors below, said depressions being spaced apart to provide intervening bodies of insulating material between said bends, and said depressions in the upperand lower surfaces being staggered relative to each other.

12. A resistor support having grooves to Inn receiveand support'the lower bends of a sinutween 'said grooves to hold in position a resistor retalmng element.

13. In combination, a furnace having a re- I sistor support projecting from a wall thereof, 5 said support having grooves extending inupwardly between said grooves along its outer edge, and a bar extending along said edge back of said lips and engaging the forward edge of said'resistorto retain said bends in said grooves.

In testimony whereof I have aflixed my signature.

- ALBERT J. HANSON.

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