US2234476A

US2234476A - Electrode

Info

Publication number: US2234476A
Application number: US150016A
Authority: US
Inventors: Jessop Louis
Original assignee: BELLIS HEAT TREATING CO
Current assignee: BELLIS HEAT TREATING CO
Priority date: 1937-06-24
Filing date: 1937-06-24
Publication date: 1941-03-11
Anticipated expiration: 1958-03-11

Description

March 11, 1941.

L JESSOP ELEGTRODE Flld June 24, 1937 2 Sheets-Sheet l INVENTOR.

Louis Sesso? L. JESSOP :Lac'rnoDE March 1l, 1941.

Y 2 ShoetsSheet 2 Filed June 24, 1937 f P4 ,31 A90 INVENTOR Lous'SOP W m ATT E Patented Mar. ll, 1941 PATENTv OFFICE ELEcTRoDE Louis Jessop, Bradford,

Bellis Heat Treating Co.,

England, assignor to The Branford, Conn., a

corporation of Connecticut Application June 24, 1937, Serial No. 150,016

1 Claim.

This invention relates to electrodes for electric furnaces of the salt bath type, and has for its object to provide means for cooling such electrodes.

In electrodes of the kind referred to it has been found that since a part thereof is exposed to the atmosphere, relative cooling by radiation is permitted, whereas the parts which pass through the 1 furnace walls and which it is not possible to cool by radiation, become hot and thereby the current flow is affected. This change which occurs in the current flow has necessitated considerabler research in an endeavor to ascertain its cause. As a result of this research work I-propose to subject that part of the electrode which passes through the furnace wall, to a cooling action, preferably a water-cooling and thereby neutralize any actions in the electrodes as the result of variations in the current flow. 2 For this purpose, my invention consists in an electrode having two legs, one for entrance into the bath and the other for the electric conductor, and my improved electrode has a cooling means disposed in the intermediate portion between said legs as a result of which'the heat of the furnace wall passing through said intermediate section, is neutralized.

The invention will be more fully described hereinafter, embodiments shown in the drawings, and finally pointed out in the subjoined claim.

In the accompanying drawings- Figure 1 is a partial plan view of a furnace bath;

' Figure 2 is a. sectional view taken on the line 85 2 2 of Fig. 1:

Figure 3 is a side view of a section of an electrode;

Figure 4 is a section taken on line 4 4 of Figure 3;

Figure 5 is an enlarged sectional view of the labyrinth portion shown in Figure 3; and taken on the line 5 5 thereof; and

Figure 6 is a sectional view of a of the structure shown in Figure 3.

Similar characters of reference indicate corresponding parts throughout the several views.

Referring to the drawings, the wall of the electric bath furnace which receives the salt bath material, is indicated by I0. Exterior to the wall 50 I0, which is usually made of metal, is built awall of refractory brick or like material, indicated by reference numeral II, and through this wall .II

electrodes are passed. These electrodes are provided with means at one end thereof by which 55 they are electrically connected with a transformer to receive electric current. g

In Figure 1, electrode I2 is shown secured to electric conductor I3, the latter being secured to a transformer (not shown). The electrode I2 passes through said wall II and bends downward modified form entering the bath material, asv shown by the downwardly extending leg I in Fig. 2. The portion I5 of the electrode I2 extends into the bath material the level of which is shown at I'I, and it will be noted that that part I 5 ofthe electrode I2 above the level of the bath material and to the wall II including that part extending beyond the wall II, is exposed to the atmosphere. These exposed portions permit radiation of heat and there'- byA remain at a very low temperature. However, when a part of the electrode is enclosed within a wall such as II, as shown in Figs. 1 and 2, there is no possibility of radiation of the heat in the electrode, to the atmosphere. In consequence, that portion of the electrode becomes needlessly high in temperature and deviation in the current results. This heavy current also heats the metal to such degree as to cause deterioration of the electrode with a resultant decrease in its efficiency,

These defects are obviated by passing cooling water through a labyrinth for keeping the metal of the electrode cool, since the cooler the metal is the better does it conduct electricity and deterioration from oxidation is prevented. By this arrangement it is possible to insulate the furnace completely instead of having ventilation around the electrode for air cooling.

Referring particularly to Figures 3` and 4, it will be seen that the water-cooling structure device consists of a series of barriers 20 which are arranged on the lower part of the electrode forming spaces 2i therebetween and into these spaces there project barriers 22 projecting from the upper portion of the electrode downwardly. In consequence any water entering the inlet 24 passes over the barrier 20 and below the barriers 22 and proceeds above the barrier 2B, and so on until it reaches the -outlet 2'5. 'I'his undulating flow through the labyrinth thereby causes the heat in the electrode to be abstracted therefrom and carried away by the cooling water through the outlet 25, 4the flow being indicated by the arrows 2B.

In the structure shown in Figs. 1 to 5 inclusive, this labyrinth is shown as extending along only a part of the length of the electrode, it having been shown that this was a satisfactory arrangement.

In Figure 6, there is shown a modified form in which the labyrinth extends between the two parts of the electrode which are proximate to the ends of the walls I I. The inlet end of the labyrinth is at the side IIa of the wall' II and the outletend of the labyrinth is at the side IIb of the wall II. 'I'his embodiment permits the connecting of the inlet supply and outlet discharge pipes/21 and 28 respectively, at either side of the wallll, so that in the event any repairs are required a very simple connection of such pipes with: the labyrinth can be effected.

For the purpose of connecting these inlet and outlet pipes with the labyrinth, the electrode is provided with an inlet opening 2 9 and outlet opening 3B. The undulating conduit 2Ia is 5 formed by the spaced members 22a and 20a.

'Ihe arrows 26a show the iiows.

In the construction shown in Fig. l, each electrode i2 is placed in a sleeve or envelopelike refractory material 3i which, with the electrode, is placed into an open cut-out in the wall il' and bricks 32 or other refractory materials are then lled in the space between the two sleeves 3i. There have been shown two electrodes, but in some installations only one electrode is used and in other installations more than two electrodes are used.

In electrically heated salt bath furnaces where heating is accomplished by passing low voltage current through the salt bath between electrodes immersed therein, when considerable heat input is required the current passed between the electrodes will have a value of several thousand amperes. The electrodes 'are usually hairpin shaped iron bars, one leg of which is immersed in the bath, the horizontal section going through the furnace wall, and the other leg outside of the furnace extending down towards the transformers which are usually set in a pit. Copper bus bars extend from the transformer terminals to the electrodes. Hitherto it was necessary when installing the electrodes -to leave an air space of several inches all around them where they pass through the furnace wall. Otherwise, if they are tightly insulated, the heat which 'is conducted back to them from the bath and the heat caused by the current flowing through them will combine to cause overheating of this horizontal section of the electrode. This overheating is a progressive matter since the resistance of 40 the electrode material increases as it becomes hotter, hence the amount of4 heat produced by the current passing through the electrodes increases correspondingly. Because of this the heat at this point can reach a value considerably higher than the temperature in the bath, and temperatures high enough to fuse the electrodes have been experienced. Even if actual melting of the metal does not result, the high temperatures cause excessive `oxidizing of the metal and may weaken it so that it will bend and cause the section in the bath to move from its proper position.

By constructing the electrodes with an internal labyrinth in the horizontal -section through which a stream of water may be p-assed the foly lowing advantages are found.

The electrode may be installed tightly in the furnace wall eliminating the heat losses through the air space left around -the electrodes in the previous construction. The external vertical leg of the electrode may be eliminated and the copper bus bars run to a pointjust outside the furnace wall. Since copper is a very efiicient conductor of electricity it isthe best practice to carry the current as far as possible through the copper. Unfortunately copper is a very good heat conductor as well as an electrical conductor and with the electrodes heretofore used it was necessary to make the copper connection to the electrode 18" to 24" from where the electrode emerged from the furnace Wall to prevent the carrying back of an excessive amount of heat through the copper bus bars into the electrical equipment. The electrodes are usually of a magnetic material and reducing the length of the current path through the magnetic conducto-r to a minimum results in an improved eiciency, i. e., more watts are delivered to the furnace. While increased electrode life is the result of this construction, permanent electrodes become possible by veneering with heat resistant metal the short portion of the electrode between 10 the bath level and the water cooling labyrinth. The use of the electrodes heretofore used of solid heat resisting metal has been impractical because of the high resistance of most heat resisting metals and the tendency of these metals to l5 lose their strength and break apart when operating for long periods of moderate temperatures. The excessive resistance losses in the overheated vertical leg of the electrodes heretofore usedare eliminated as even when these electrodes were 20 installed with an air space around them, they ran hot enough to cause considerable resistance losses. Radiation losses from the large external leg were also considerable. The use of electrodes installed through the furnace wall now becomes 25 possible for the highen temperature furnaces which have`previous1y been constructed with adjustable electrodes extending through the top of the furnace and with provisions for being fed into the furnace as they wear away. This awk- 30' ward construction made it impossible to make a tight fitting cover and made it difficultl to handle work with a hoist or crane.

While I have illustrated and described the preferred form of carrying my invention into ef- 35 fect, this is-capable of variations'and modifications without departing from thespirit of my invention, and therefore I do not wish to be limited to the precise details as set forth, but desire to avail myself of such variations, modi- 40 fica-tions, and adaptations as come within the scope of the appended claim.

I claim:

In a salt bath furnace having metal walls for holding the salt bath, the combination of a uni- 45 tary metal electrode comprising a bath immersion leg spaced from the walls of the furnace and extending from above the level of the salt bath into the salt bath with its remaining part exposed to the atmosphere above said level, and a furnace 50 wall leg adapted to pass through the wall of the furnace with its remaining part exposed to the atmosphere for connection with the source of electrical supply at the exterior of the furnace, said last named wall leg having within the same a 55 cooling fluid conduit at its portion enclosed by the wall, means at one end of the conduit for supplying cooling fluid to the conduit, means at the other end of the conduit for discharging said fluid, whereby heat in the electrode is neutralized 50 by the cooling fluid ow in the electrode, and a separate refractory member 'of a lengtlr equal to the width of the wall completely surrounding4 the wall leg of the electrode at the cooling conduit portion adapted to completely iill a corre- 65 sponding gap in the top of the furnace wall to complete the wall structure, said refractory member surrounding the electrode forming a unitary connection with said electrode, whereby on the removal of the said refractory member the 70 electrode is removed therewith.

LOUIS JESSOP.