US1633967A - Electric furnace - Google Patents

Description

Patented June 28, 1927.

UNITED STATES PATENT OFFICE.

JAMES C. WOODSON, 0F EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTING- HOUSE ELECTRIC MANUFACTURING OOMPANY, A CORPORATION OF PENNSYL- VAN IA.

ELECTRIC FURNACE.

Application led October My invention relates to electric furnaces and particularly vto furnaces of the resistor t e.

yIAn object of my invention is to provide supporting and spacing means for resistors in electric furnaces whereby an even distribution of heat may be effected. u

Another object of my invention is to provide supporting and spacing means for electric furnaces which lend themselves to siniple series, parallel or series-parallel arrangements whereby an even distribution of heat may be obtained.

Another object of my invention is to provide refractory supporting and spacing means which lend themselves to uniform distribution and to such arrangements of the resistors that the power input may be controlled, thereby effecting uniform temperatures within the furnace chamber.

In the accompanying drawings,

Figure 1 is a view in vertical cross section of an electric furnace embodying my invention,

Fig. 2 is a view of a modified form of my invention whereby three groups of resistors may be supported.

Fig. 3 is a view in section of a portion of a furnace showing the supporting and spacing means illustrated in Fig. 2.

Referring more particularly to Fig.. 1, an electric furnace structure 11 comprises a plurality of Walls 12 of refractory heat-1nsulating materials enclosing a furnace chamber 13. Supporting members 14 extend laterally from the Walls of the furnace structure llinto the furnace chamber 13 and form two rows of supports 15 and 16 respectively in the upper and lower part of' the furnace chamber 13. The supporting members 14 of the lower row are identical with those of the upper row 15 with the exception that they are in reverse relation thereto.

The supporting and spacing members 14 have a rear portion 17 which extends into the refractory walls of the furnace 11. A plurality of lugs 18 and 19 extend inwardly into the furnace chamber 13 and are inte\ gral with the rear portion 17. The extremities of the inwardly extending lu s 18 and 19 are semi-circular at the top and ave 1, i925. serial No. 59,761.

straight sides extending downwardly and are larger in section than the'intermediate portion 21 thereby forming the flange 22 at the ends thereof.

Resistors 23 fit over the rounded top of the portion 21 and are therefore securely held in place by reason of the flange 22. One group of the resistors 23 is looped over two of the upper extending lugs 19 in the upper row 15 of the supporting members 14 and underneath the single lug 18 in the lower row 2O of supports 14 as indicated 'in Fig. 1. The second group of resistors 23 is looped over one of the extending lugs 18 in the upper row 15 of supporting members 14 and underneath two of the extending lugs 1.9 in the lower row 16. From the symmetry of the foregoing arrangements of the resistors, it is evident that the lengths of all the resistor groups will be equal and since the resistors are substantially equal in crosssection the resistance of each of the groups will also be substantially equal.

By means of the foregoing arrangement of resistors, a uniform distribution of heat may be obtained as can readily be seen from the symmetry of the spacing of the resistors along the refractory walls 12 of the furnace chamber 13. The resistors 19 may be of either rod or ribbon shape and obviously forms of resistors other than those illustrated in the drawing may be used.

By the symmetrical arrangement of resistors as shown in Fig. 1, it is possible to have the two groups of resistors of equal length and cross-section, hence equal in ohmic resistance, connected in parallel across the supply circuit in order that the furnace may be brought up to the desired tempera.- ture in a comparatively short time, depending upon the size of the furnace chamber 13, the thickness of the walls 12 and the amount of power disposed of by the resistors. After the furnace has attained the required temperature, the resistor groups may be either connected in series, or one of them may be disconnected from the supply circuit whereby only the required amount of power is supplied to take care of the radiation losses of the furnace. Obviously, from the symmetry of the location of the resistors, the heat distribution with the `furnace chamber 13 will be substantially identical whether the several groups of resistors are electrically connected either in parallelseries, or series-parallel with the source of power supply.

In Fig. 2, I have illustrated another form of the supports 14 illustrated in the furnace structure 11. There are four parallel rows of laterally extending lugs attached to a rear portion 17 as illustrated by the rows 24, 25, 26 and 27 in Fig. 3. As illustrated in Figs. 1 and 2, the extending lugs in each of the rows 15 and 16 are staggered vertically in order to permit three independent groups of resistors to be supported and arranged as indicated in the drawings.

By having several independent groups of resistors 23 supported as shown in Fig. 2, it is possible to have the same heat distribution in the bottom of the furnace as in the top, by reason of the symmetrical arrangement of the extending lugs located in rows 24, 25, 26 and 27. When the furnace has attained the required temperature, partof the resistor groups may be taken out of the circuit entirely and one or two groups only, as may be required to compensate for the radiation losses of the furnace, may be left in the circuit in order to maintain a predetermined constant temperature. It is also possible by means of this arrangement to have a constant power circuit which is energized at all times during normal operation of the furnace and is designed to take care of substantially the radiation losses only, whereas the other resistor groups may be in a temperature-controlled circuit whereby the difference between the on and olf temperatures may be decreased to desirable limits without materially affecting the heat distribution of the resistors.

rIhe device embodying my invention provides a relatively simple means for uniformly spacing independent groups of resistors of equal lengths within the furnace chamber of electric furnaces. |The supports may be designed with two, three or four, or a plurality of rows of inwardly projecting lugs which are integral with an outwardly extending portion that is adapted lo lit into the walls of the furnace proper. Each of the inwardly projecting lugs are staggered vertically with respect to the horizontal parallel rows formed by the above inwardly projecting lugs whereby the individual groups of resistors will have alternately similar recurring groups of return-bent loop portions formed by' the resistors as they are bent to fit or to conform with the arrangement of the supports. This arrangement permits of connecting the groups in series, parallel or series-parallel arrangement and ensures equalized heat distribution irrespective of the connections employed.

`Various other modifications of my invention may be made without departing from the spirit and the scope thereof. I, therefore, desire that only such limitations shall be placed thereon as shall be imposed by the prior art.

I claim as my invention:

1. In an electric furnace, the combination with a furnace chamber, of a plurality of refractory wall members and a plurality of resistors supported by said refractory wall members in such manner that the depending loop portions along each of the walls are alternately similar.

2. In an electric furnace, the combination with a wall, a plurality of independent members extending laterally from said wall in rows one above the other, and resistors so disposed in groups along each of the walls on said laterally extending members that they are equally spaced in alternately recurring symmetrical arrangement.

3. In an electric furnace, the combination with a furnace chamber enclosed by a plurality of refractory walls, a plurality of independent resistor groups having similar alternately recurring depending loop portions, and a plurality of refractory supporting members secured to said walls, a plurality of refractory spacing members, extending laterally into the furnace chamber from said refractory walls in rows one above the other, whereby the resistor groups are so supported and equally spaced that the top and bottom return-bent loop portions occur alternately in similar group relation.

4. In an electric furnace, the combination with a plurality of refractory walls enclosing a furnace chamber, a plurality of refractory supporting members extending therefrom in rows one above the other adjacent to the upper part of said walls, a plurality of refractory spacing members extending laterally from the walls in rows one above the other adjacent to the lower part of the walls, and a plurality of independent resistors, having top and bottom return-bent loop portions, supported from the refractory members adjacent to the top of said walls and uniformly spaced apart by said refractory members adjacent the bottom of said walls, whereby the top and the bottom loop portions occur alternately in similar grouped relation. A

5. In an electric furnace, the combination with a plurality of refractory walls enclosing a furnace chamber, a plurality of refractory members extending laterally therefrom in two pairs of parallel rows spaced one above the other, one pair of parallel rows being located adjacent to the top and the other pairof rows located adjacent to the bottom of said walls, and a pair of independent resistors, having a plurality of depending loops portions supported from the said refractory members of the upper pair of rows by the upper return-bent loops and spaced apart by the refractory members of the lower pair of rows.

6. In an electric furnace, in combination with a plurality of refractory walls inolosing a furnace chamber, aplurality of refractory members staggered vertically and extending laterally into the furnace chamber therefrom in a plurality of parallel rows adjacent to the top and the bottom of said walls, and a plurality of independent resistors, having return-bent top and bottom loop portions with substantially straight parts therebetween, supported from the loopkof the top return-bent loop portions and spaced uniformly apart at the lower loop portions, whereby the said top and bottom returnben-t loop portions occur alternately in similar grouped relation. p

In testimony whereof, I have hereunto Subscribed my name this 17th day of September, 1925.

JAMES C. WOODSON.

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