US1271093A - Electric-furnace contact. - Google Patents

Description

F. T. SNYDER.

ELECTRIC FURNACE CONTACT. APPLlc/Tlon FILED MAR. l. 19H.

1,271,093. mmmmywm n n l l Il:y

By W. Aff@ I FREDERICK T. SNYDEB, 0F OAK PARK, ILLINOIS.

l:ELEGTRI()-IEUBN'ACE CONTACT.

` Specification of Letters Patent.

Patented July 2, 1918.

Application filed Hatch 1, 1917. Serial No. 151,718.

To all rwhom it may concern:

Be it known that I, FREDERICK'T. SNYDER, a citizen of the United States, residing at Oak Park, in the county of Cook and State of Illinois, have invented a` certain new and useful Improvementin Electric-Furnace Contacts, of which the following .is a full, clear, concise, and exact description.

The present invention relates to improvements in electric furnaces and more particularly to electric furnace contacts.

As heretofore constructed, electric fur-K nace contacts have been provided with an elongated solid cylindrical portion adapted to extend through the bottom vof the furf nace and into the melting chamber thereof,

the lower end of said contact being enlarged and provided with a cooling chamber terminating below the shell of said furnace. As is well known in the art, a small amount of molten metal remains in the melting chamber of the furnace after the pouring operation. This metal, when it hardens, be-

comesan integral part of the contact forming what is commonly termed a mushroom on the inner end thereof. This formationrenders diflicult the removal of the contact from thefurnace in a downward direction, while the enlargement on the lower 'end of the contact within which is formed the cooling chamber, prevents the removal of the contact from the furnace in an upward direction. Furthermore, in the use of contacts as now constructed, molten metal.

sometimes leaks out through the bottom of the -furnace around the contact durin the melting operation, owing to the ina ility of the cooling chamber, which terminates below the bottom of said furnace, to cool the metal enough as it nears the lower end of said contact, to canse the same to con- O'eal and thus close any opening which has been formed between the said contact and the adjacent walls of the opening in which it is mounted. Another disadvantage in the use of thisjformer form of contact, resides inwhat may be termed piping of the contact when it is made of a casting, or in other words, in the formation of a small opening through the contact from the cooling chamber thereof to the melting chamber of the furnace, due to shrinkage of the casting,- This casting shrinkage pipe does not extend entirely through the contact when cast, but is sometimes opened up by the partial melting down of-the upper end of said contact when in use in the furnace. This pipe or passage thus formed, may permit water to pass from the cooling chamber into the molten metal, where the water is decomposed by the intense heat and the nascent oxygen thus liberated, oxidizes the lnetal and thereby modifies unfavorabl its physical characteristics. A further o jection to the use of contacts', as now commonly constructed, resides in the excess heat conductivity which they afford by reason of their large cross-sectional area. It is well known, that the passage of an electric current through a conductor produces rings of magnetic force, not only around the outside of the conductor, but also within the same, the rings cf magnetic force being formed within said con uctor around each thread of current passing therethrough. Where the current ra idly alternates in direction, these rings o magnetic force move in and out and reacting with the threads of electric current cause the threads of cur- 'rent to be forced outward from the center axis of the conductor, toward the outer surface thereof. In other words, most of the current, when alternating flows through the lconductor adjacent to the outer surface thereof, little current flowing through the central area. This is commonly termed the electric"skin effect and is more marked in conductors made of magnetic material,

such as steel. It will be seen therefore,'that the central portion of thev contact conducts very little current, while on the other hand, it acts to increase vthe objectionable conductivity of -heat from the furnace.

The present-invention therefore aims to overcome these various disadvantages, and has for one of its objects, the provision of a contact which shall be provided with means whereby a maximum electrical conextend into the shell of the furnace to-there.- by prevent the leakage of molten metal through the bottom off said urnace around said contact.

Other objects and advantages will be apparent from the following description, 'taken in connection with the accompanying drawings, wherein the preferred embodiment of the invention is illustrated.

Figure l is a transverse sectional view taken through an electric furnace showing the contact in position.

Fig. 2 is an enlarged vertical sectional view of the contact.

Figu 3 is a cross sectional view of the contact taken on the line 3 3 of Fig. 2.

Fig. l is a section taken on the line 4 4 of Fig. i.

Fig. 5 is a section taken on the line 5--5 of rig a Referring more in detail to the drawings, the electric furnace is shown at l and is provided With the usual refractory lining 2, a heat insulating lining 3 and an outer metallic shell 1i. rlhe melting chamber of the furnace is indicated at 5. Extending through the bottom of the furnace and terminating in the melting chamber 5 thereof, is provided an opening` (i, which is adapted to receive the electric contact 'Z'.

The contact 7 is shown in the drawings as provided at its lower end with a suitable cooling dome 8, and a pluralityof thin Hat conducting ribs 9, extending-up from said dome 8. llhese fiat conducting ribs 9 arespaced apart and terminate at their inner ends at a point short of the central axis of the contact 7, as shown in Fig. 3. The upper inner edges of the conducting ribs 9 merge into a substantially tubular extension l0, said extension being shown protecting beyond the upper ends of the conducting ribs 9, into the melting chamber 5 of the furnace l. This is to facilitate the 'initial formation o the arc betweenthe contact 7 and the electrode (not shown), when Erst starting with a new contact. Shortly after the melting operation has been started, however, this projecting portion of' the tube l0 melts oli" ush with the upper ends of said conducting ribs 9. lt will be noted from this construction that the contact 7 is provided'with a central opening extending from the upper surface of the cooling dome 8, up through the entire length of said contact, thereby eliminating the possibility' of an excessive heat conductivity, and at the same time providing means whereby a maximum electrical. conductivity is obtained. The inner wall of the cooling dome 8 is preferably provided with a plurality of heat radiating ns il.

The structure thus far described is pref-' erably cast integral, and of the same material that is being melted within the furnaceD .nat/noce A suitable hollow plug l2, which may be of cast iron, is shown extending upwardly into the cooling dome 8 and is so positioned with relation thereto as to form a chamber i3, the plug 12 being provided at its lower end with a screw-threaded portion lll, which is adapted to engage the lower end of the contact 7, to thereby retain said plug in position, A suitable cooling medium such as water, is circulated through the chamber i3, the same being forced into said chamber through. the intake pipe 15 and -out through the outlet pipe 16. lt will vbe noted that the outlet pipe leaves the cooling vchamber i3 at substantially the uppermost portion thereof., This construction acts to edectively remove any air which may be trapped in the chamber i3, and also removes 'the hottest water rs as it rises within the same. lt will be noted that the plug 12 is of substantial size and extends into the cooling dome 8 in such manner that the walls thereof lie in close proximity to the inner Wall and radiating ns 1l of the dome 8. This permits of an increased velocity in the water circulation through the chamber i3, by reducing the cross section of the water ilow, which increases the heat transfer capacity of the Water jacket Contact area.

lt will be noted from Fig. i ci? the drawings, that the cooling chamber i3 of the contact entends past the outer metallic shell e: of the furnace and into the refractory ulining 2- thereof?. rEllis structure provides means whereby that portion of the contact adjacent said cooling chamber and, within the shell of the furnace is e'ectively cooled during the melting operation. lhecooling chamber also acts to cool that portion of the refractory lining 2 of the furnace which lies adjacent thereto. From this it will be noted that should any of the molten metal from the chamber 5 leak down around the contact'- 7, the same will be congealed around said contact when it reaches the lower portion thereof, by the action of the cooling medium thereon. ilhe metal thus congealed, will act as a barrier and prevent any further leakage. This cooling can be conveniently accomplished by extending the bottom of the furnace downwardly in the shape of a cone, the contact being inserted in the tip of the cone. Heretofore, electric steel furnaces of this type have been built with a dat bottom through which the contacts projected,

lt will be noted from the construction of the contact as hereinbeore set forth, thatthe same is of substantially the same diameter throughout. -This permits of the contact being drawn upward through the melting chamber 5, when it is desired to remove the same, for the purpose of replacing it with a new one. lt will be noted that in the formation of the contact as herein described, no

fact that the conducting ribs 9l are so thin as to prevent the formation of openings therein. It will thus be seen that the possibility of oxidation of the metal, heretofore caused bythe piping of the contact, has

been eliminated, as no large masses of castings are permitted by the present design of contact within which casting pipes can form.

The current is conducted to the contact 7 by means of a suitable straprl?, which 1s clamped about the lower end of the contact, by means of the bolts 18. A support 19 cooperates with the bolts 1S to hold the strap in place. The iiexible conductors 20 are preferably clamped between the ends of the strap 17 as shown, and are supported by means of a suitable supporting member 21. A plate 22, preferably asbestos board, is

v shown mounted over the strap 17 and the conductors 20 to protect the same against -injury from molten metal, which may drop from the furnace.

lt is obvious thatvarious changes and modifications may be made in the structure herein illustrated, and the right is therefore reserved to make such changes and modifications as may fall within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A contact for electric furnaces, comprising a member having a small cross sectional area in proportion to its cross sectional perimeter, whereby said contact has high conductivity for alternating electric current and a low conductivity for heat.

2. Acontact of the type described, comprisin a cooling dome, a plurality of space -apart conducting ribs, and a tubular extension adapted to project into the melting chamber of a furnace.

c 3. A contact for electric furnaces, comprising a tube having conducting ribs mounted thereon.

@A contact for electric furnaces, comprising a tube having radial ribs mounted thereon, capable of conducting both electricity and heat.

5. A contact for electric furnaces, comprising a hollow portion adapted to contain a cooling medium and ribs mounted thereon, papable of conducting both electricity and eat.

@A contact for electric furnaces, comprislng a hollow portion adapted to contain a cooling medium and ribs projecting therefrom inside and outside said hollow portion.

7. The combination with an electric furnace, containing a molten bath, of a contact contalning a cooling medium and a thin metallic conductor between the bath and the cooled portion of the contact.

8. The combination with an electric furnace, containing a molten bath, of a cooling chamber and a thin metal conductor carrying heat and electricity between the bath and the cooling chamber.

9. The combination with an electric furnace, containing a molten bath of a coollng chamber and a thin metal conductor in electrical and thermal contact with both bath and chamber.

10. A contact for electric furnaces comprising a plurality of s aced-apart radially' arranged conducting ri s, the inner edges of said ribs terminating short of the longitudinal axis of said contact.

11. A contact for electric furnaces comprising a plurality of vertical spaced-apart conducting ribs, said ribs merging into an extension at the u per end of said contact.

l2. contact for electric furnaces, containing hot material, comprising a cooling chamber yprovided with an inlet and an outlet for a cool' medium, a conductor having a small horizontal cross section adapted to transfer electricity and little heat from such hot material to said chamber, said outlet being arranged to remove the cooling medium from that portion of the chamber nearest to said conductor.

13. A contact for electric furnaces, containing hot material, comprising a-cooling chamber below su'ch material, a conductor having a small cross sectional area in pro- Iportion to its cross sectional perimeter arl ranged between said material and said chamber, and an outlet arranged to remove the cooling medium and any liberated gas from the top of said chamber.

14:. A contact for electric furnaces, comprising a cooling dome, a plurality of spaced-apart conducting ribs cast integral therewith 'and extending upwardly therefrom and merging into an extension, the inner wall of said cooling dome being provided with a plural-ity of heat radiating fins.

15. A contact for electric furnaces, comj prising a cooling dome, a plurality of spaced-'apart conducting ribs cast integral therewith and extending upwardly therefrom and merging into an extension, the

inner Vwall of said cooling dome being provided with a plurality of heat radiating ins, said cooling dome being adapted to receive a hollow plug, said plug coperating with said dome to form a cooling chamber and means whereby water may be circulated therethrough.

i6. The combination with an electric furnace, of a contact therefor, comprising a cooling chamber and a Jfiller substantially lling the space in said cooling chamber, whereby the amount of cooling medium within said chamber is reduced and the velocity of :Elow of said medium is increased.

17. The combination with an electric furnace, of a contact therefor, adapted to ex-` tend through the bottom thereof, e eonuetor electrieeily eonnected. therewith, and. e. shield adopted to divert from seid conductor material leaving the furnace neer seid contact.

i8. The 'combination 1with en electric furnoce, of e contact therefor edepte to extend through the `loottom thereof, one enci of seid contact extending iceiow seid bottom, e. strep adopted to encircle .seid end9 a supportV for said sti-ap, end moons `for clamping the ends of conductors between the ends of seid strap, thereby eording menus for the conduction of current to Said contact, end means :for protecting said strep and seid conductors ugeinst injury.

19. A contact of the type described, comprising e cooling dome cest integral therewith., a, hollow plug adopted' to be secured within said dome, and means 'for circuietin a. cooling medium between seid dome en seid plug. A

20. The combination with en electric nece o e contact edepted to extend through nemoee the bottoni thereof, the ends of seid. contact extending both above end below seid loottom, one of seid yends being of less diameter' than the body of the contact.

21. The combination with en electric furnece, having a bottom in the forni of e. cone, of a contact adepte-d to extend through the exis of said cone, and means for connecting said cone electrically with said. Contact.

22. The combination with an electric :turn-ece, having a lower nieta-l shell in the form ot o cone, of e nietel Contact entering the furnace through the point of said cone and refractory lining material filling the space 'my name this 23rd dey of February, A. D.

. FREDERICK T. SNYDER.

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