US1084466A - Electric furnace. - Google Patents

Description

G. METTLER.

ELEGTRIG FURNACE.

APPLICATION FILED NOV. 28, 1911.

Patented Jan. 13, 1914.

4 SHEETB SHEET 1.

wh-NEssEs .F k RH m e M w NO. m o c m G ATTO KNEYS G. MBTTLER.

ELECTRIC FURNACE.

APPLICATION rum) NOV. 23, 1911.

- Patented Jan. 13, 1914.

4 SHEETS-SHEET 2.

INVENTOR- -Giacomo MH'ler' ATTORNEYS G. METTLER.

ELECTRIC FURNACE.

APPLICATION FILED NOV. 28, 1911.

Patented Jan. 13, 1914.

4 SHEETS-SHEET 3.

JNVENTOK Giacomo Me'H-Ier- WITNESSES ATTORNEYS G. ME/TTLBR.

ELECTRIC FURNACE.

APPLICATION FILED NOV. 28, 1911.

4 SHEETS-SHEET 4.

1,084,466, Q Patented Jan. 13, 1914.

WITNESSES INVENTOR- gciiag Me'H/erf m4 6 9 Q ATTORNEYS by way of ex mple; Fi

cracoiao names, or niiaiim, oiinmNY.

' I y L: .r. ELECTRIC FURNACE.

Specification of iiettersiiitent.

Patented Jan. 13,1914.

Application m Novemb'er mm. Serial No. 662,953.

To all whom it concern a v y Be it known that I, Giacomo Mirrrnnn, a citizen of'the Swiss Republic, residi n at Berlin, in the Kingdom'of Prussia and erman mpire, have invented a new and useful Improved Electric Furnace, of which the flillowing is a specification.

The invention relates to an electric resistance furnace which can be continuously charged and uniformly re' ulated up to temperatures of about'-2 10()" a ,All parts of the furnace are easily accessile and exchangeable, and the contraction or warping of the parts cannotun favorably influence t ieoperation of the furnace.

In the rawings illustrating the invent on are 1 is a vertical section pf the urnace, F1g. 2 a partsection of another construction of the smelting shaft, Fig. 3, a plan ofthe late over which the ,material to be melte falls into the smelting shaft Fig. 4, a section through the insulating cone surroundipg the electric, resistance cone, showing a Joint til, and Fig. 5, a part sectionof another construction of the smelting sha t. I p v A circular iron mantle 1 (Fig. 1), which is provided with four or, more hinges, about which it can be opened, surrounds a fireproof mantle 2 of unslaked lime, which possesses a number of horizontahrecesses or 0 rings 3 to admit electric conductors. Insi c this lining 2, and in the upper part o the iurnace, are provided fouror more supporting blocks 5, of fire proofmaterial which have a segmental form in pan, and, underneath these blocks, there are four or more similar segmental blocks 6, which support segmental plates 6' of magnesia. The blocks 5 carry asbestos disks 7, on which the under surface 9. of the upper electric resistance carbon cone 8 bears, to the outer thickened end 10 of which the electric current issupplied by the copper poles 11. The thickness of the cone 8 decreases toward its lower end, and this cone forms the shaft into which the material to be melted falls, he lower thin end 1 10f this cone 8 fits into a carbon cone 15, which forms the smelting zone. This cone 15 must there ore be a'ble to ex-- pand without the contact between it and the upper cone 8 bein disturbed andwithout one or the other 0 said cones being broken by unequal contraction. The lower pne 15 is provided with a horizontal extens on 67 to which the other electric pole is connected,

andhas further a vertical rib 18, which pro- JeQts into the magnesia filling' 19 which surrounds the pper carbon cone.

The furnace has two or more electric circu ts (1 & -A and B- -l 3), in which, for example, 1n the case of a furnace requiring a current of H. P., the strength of the current can'lbe transformed up to 1200 amperes,

while the electromotive force of the alternat ng current is reduced to 25-10 volts. I

All other hollow spaces in the furnace are preferably filled out with, or stamped full of, melted magnesla which can'be subsequently filled upas occasion requires. Immediately underneath the smelting cone 15 there is a rectification chamber 20 consisting of, a cylinder 21 of; highly burnt zirconium oxid, a top plate22 preferably of the same material aihoming thej smelting cone, and a bottom p ate 23 earn d by the head 27 of a vertical cylindrical wall 24 The rectification chambet- 2Q 1s closed by a valve 26 made if zircomum ox d or ther. refractory material, which ts in a bot om opening in said chamber an also bears against thehea 27 servas a valve seat. The valve26 can be a usted from below bymeans of a pipe 28 and rod 29 both of fireproof material, Said valye 26 can however also be pressed upwar by gases. If the pressure of the rod 29 and pipe 28, or oft e gases, is reduced, the valve 26 will fall an the melted material can flow out. Through a channel consisting pretenably of an inner pipe 30 an outer pipe 31 made of fire proof material such as zirconium oxild or for lower temperatures chamotte, t e contact surf ces of which are coated with graphite. he rectification chamber is also surrounded by an electric resistance 8', madie of carbon or other suitahle maftierial an having a .tubular shape w th a ange at to and bottom, switched into the circuit v Thewall 21 of the refining chamber 20 is oiil 4 made of zirconium oxid when chemical y re silicates in small quantities are to be kep liquid. in said chamber. At the back of the wall 21 a space. is provided to perm t contraction and .expanslon of said well and this space is filled with suitable metal carbide, such as carbid of tun sten or titanium, Thisspace is necessary ecause the ectric res stance 8 surrounding it need notex'pai d cont ct under the changes e samedegree as" the wall 21. Said electric resistance'heats of temperature in eziactly th air, and constituent which is all the parts it incloses and is itself surrounded by any suitable heat-insulating material, such as magnesia, etc.

The furnace is charged by the worm 32 which is gastight. The air necessary for the preliminary heating enters through the hole 33, while the gases are drawn oil through the openings 34. The Worm 32 rotates 1n the casing 36, the top flange 37 of rovided with grooves 38 serving as a race or porcelain or steel balls 39. The horizontal disk44 is integral with the worm 32 and is connected by screws 41 with the pulley 40 driven by the belt 43, asbestos disk 42 being interposed, in order to prevent the pulley 40 from becoming hot.

In operation the furnace is preliminarily heated by the burner 45, which is adapted to be raised and lowered in the pipe 46 and can also be adapted to be rotated by being connected by the plate 46' with the pulley 40, as shown in dotted lines. The pipe 46 is extended into a disk 47 which repels the heat rising from the smelting shaft. The pipe 45 is provided with a shoulder which leaves a space 48 for the admission of water for cooling. At the top of this pipe, which is preferably made of porcelain containing chromium oxid (according to the process of Prof. Marquardt) there is a rounded screwthread 49, so that a gas-tight metal pipe, or a jointcoupling, can be attached. By means of the pulley 40, or a spur-wheel, the-:xgorm 32 is rotated, which takes up the material to be treated through the opening 50 and presses it down through the groove 52, whereupon it falls on the cone 8, which, toward its lower end, becomes more slanting facilitates the feed of the material toward the smelting zone. Through the pipe 45 hydrogen, oxyhydrogen, or some other suitable, gas is supplied (which, according to the character of the material to be melted, must form an oxidizing or reducing flame 53), so that a vertical downwardly directed flame is formed, which centrally heats the material. Because the point of the flame, or of several flames, communicates its temperature about 1700 C. to the quartz or metal to be melted, the material soon becomes red hot, free from striae, water etc., and becomes a better conductor. The electric current passes therefore into the smelting zone through the carbon shaft lining of zirconium oxid or thorium oxid, without considerable resistance, and the melted material flows in the form of a thread or tube through the narrowest opening of the shaft. The current is conducted from the carbon cone to the lining 54 and through this into the melted material, because the lining 54 which preferably consists of zirconium oxid fritted with sesquioxid of boron at the high temperature of the smelting zone becomes a good conductor of electricity. Between the resistance cone and the lining may be provided a cement consistin of a mixture of sesquioxid of boron with zirconium oxid and silicate of potash and sulfid of ammonium. The ammonium sulfid renders the silicate of potash less viscous so that only quite small quantities are necessary for binding the sesquioxid of boron. Sesqui-oxid of boron and zirconium oxid are used in a finely pulverized condition. The cement made by melting together these substances is a good conductor of electricity and is very hard, remaining fire-proof at high temperatures. The carbon cone, at its narrowest point, also has the minimum thickness, and, accordingly, becomes hotter there than at any other point. At 2000 C. the lining 54 becomes a good conductor. It can also be fritted with sesuioxid or boron and some form of tungsten i or instance tungsten oxid, in which case it becomes a still better conductor.

No mold is necessarily used in connection with this furnace. In the case of silicates the valve 26 with which the lower end of the molten thread comes into contact and which normally closes the refining chamber, can be moved downward and when so moved slowly pulls the molten thread downward and in any case the refining chamber can only be used to collect a small quantity of the molten material when silicates are being treated. The top of the valve pulls the molten thread at the same speed as it issues from the shaft. As soon as a certain length of the thread is reached the electric current can be caused to pass through said thread, the heated valve being a conductor of electricity at the high temperature in question. If the furnace is used for melting metals the tubes 30, 31 (as indicated by the arrows) and the plate 23 and valve 26 can be removed so that the molten material can descend in the form of a thread into the mold or into any vessel arranged underneath the furnace in any suitable manner.

In the construction shown in Fig. 2 an inner cone 57 of zirconium bears against an intermediate layer 58 of tungsten, which can also be cemented with oxid of titanium or metallic titantium or made of suitable metal carbide (such as carbids of tungsten or titanium or other rare metals, for example yttrium) and serves to distribute the current better and to prevent undue heating at the narrowest point of the furnace and acts as an electric resistance. Outside the cone 57 there is an inner cone 57 of zirconium oxid or other suitable material which is backed by metal carbids 60, such as carbids of tungsten or titanium or other rare metals, for example yttrium, which take up the current uniformly from the carbon cone 15. The inner coating of tungsten mentioned by way of example can also be cemented with sesquioxid of boron alone instead of titanium, a

mechanically tight connection with the zirconillln cone being formed without the various coeflicients of expansion being disturbed, and without the tungsten absorbing oxygen, or the distribution of the heat and the dilatation of the cone being prevented. This tungsten can be better protected from contact. with carbomiceous gases by the zirconium cone 5? being fritted with sesquioxids of boron. The carbon cone is moreover insulated at the back by a cone 61 of zirconium oxid. This cone consists of several parts as shown in part sectional plan in Fig. 4 and is provided with strenghtening ribs (32 which also serve to better support the carbon. The top late 22 of the rectification chamber is beve ed off and allows free play for the interior zirconium cone 57 (Fig, 2). The colder zone of the carbon cone is covered 'with a layer 63 (Figs. 1 and 2) of melted magnesia, which overlaps and bears against. the zirconium cone 57. When using the furnace for finer metallurgical purposes the outer cones of the smelting zone must have larger dimensions and be formed as shown in Fig. 5.

In this furnacean inner cone of any suitable fireproof material covers a carbon resistance 8, the lower end of which is beveled off and is in contact with a similar surface of the carbon cone 15, which forms the heating zone proper. This bottom cone 1.) is curved round at the bottom and ends in a horizontal flange 15. This flange is covered with kryptol material which is a granular graphite and carbon mixture, universally used for making electric resistances. The back cone supporting the resistance cone has long ribs (52 so that this cone, as seen from the top, has a star shape. The space between the ri s is partially filed up with magnesia or the like, which falls in the direction of the arrows 1t) and behind the plate (52' the kryptol material is provided. The plate (32 only serves to separate these two materials. The electric current is then caused to take the direction shown by tliedotted arrows,

being collected by the plate 81 and led off at 82. The inclined plate 80, preferably made in sections connected together by flanges 80" amLbolts 80', is designed to enable the magnesia 19 or the like to be inserted without becoming mixed with the kryptol material (36. The space between the concentric cones 57 and 57 may be filled wit-h a layer consisting of metals or metal oxids of the chromium group, tungsten, titanium or their carbids alone or together.

In Fig. l C-U is a line along which the entire parts serving for the preliminary heatin of the melting shaft can be mechanically ifted off. 68 designates insulating material such as quartz sand etc. The rec-- tan ular frame 69 supports, by means of the ang e iron 70 the flange 37 and can be raised or lowered with the assistance of the counter weight 72 suspended by a chain passing over the roller 71. This construction permits not only the, casing 36 and all parts secured thereto, but also the burner 45, and the part 47, with ribs 47, to be raised. 34' are lids adapted to close the suction openings 34. 73 and 7+ are insulating layers of magnesia. .\t the bottom of the furnace there is an iron plate 75 carried by rails 76 which can be moved horizontally on beams 77.

I am aware, that an electric furnace is known having a tapering heating chamber with walls containing carbon resistances faced with pyro-conductive material, delivering into a hearth having similar resistances in the sides, and that refractory materials having a comparatively high resistance at ordinary temperature but increasing in conductivity when heated may when applied to an electric furnace be heated by means of a blow-pipe or similar source of intense heat.

\Vhat I claim and desire tosecure by Letters latent of the United States is 1. An electric furnace. comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, and a lining in said cone of a material 9 which conducts electricity at a high temperature, substantially as. and for the purpose, set forth.

2. An electric furnace, comprising in combination, an inverted gas burner. an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, a lining in said cone of a material which becomes a conductor of electricity at a high temperature, and a cone of fireproof material outside said electric resistance cone made in several pieces and of fireproof material such as non-conducting zirconium oxid and having strengthening ril. s,substantially as, and for the purpose, set forth.

3. An electric furnace, comprising in combination, an inverted gas burner, a carbon. cone underneath said burner and consisting of several pieces fitting into each other the wall of which cone becomes more slanting toward the middle, substantially as, and for the purpose, set forth.

4. An electric furnace, comprising in combination, an inverted gas burner. a pipe inclosing said burner and extending intoa disk having heat distributing ribs, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, and a lining in said cone of a material which becomes a conductor of electricity at a high temperature, substantially as, and for the purpose, set forth.

5. An electric furnace, comprising in combination, an inverted gas burner, a pipe inclosing said burner and leaving a space be- CIY pieces fitting in each other, and a lining in said cone of a material which becomes a con-.

ductor of electricity at a high temperature, substantially as, and for tie purpose, set forth.

6. An electric furnace, comprising in combination, an inverted gas burner, a pipe inclosing said burner, a worm surrounding said pipe, a casingsurrounding said worm, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, and a lining in said cone of a material which becomes a conductor of electricity at a high temperature, substantially as, and for the purpose, set forth.

7. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several :pieces fitting in each other, a lining in said cone of a material which becomes a conductor of electricity at a high temperature, and a rectifying chamber underneath said cone the top plate of which chamber has a-rounded nozzle form adjoining the lining of the cone, substantially as, and for the purpose, set forth.

8. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone bf carbon below said burner and made of several pieces fitting in each other, a lining in said cone of a material which becomes a conductor of electricity at a high temperature, a rectifying chamber underneath said cone, a cone closing' the bottom end of said chamber, and means to operate said closing cone, substantially as, and for the purpose, set forth.

9. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other and having an extension projecting into granular carbon, and a lining in said cone of a material which becomes a conductor of electricity at a high temperature, substantially as, and for the purpose, set forth.

10. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, a lining in said cone of a ma- 'terial which becomes a conductor of electricitty at a high temperature, a cone of fireproo material outside said electric resistance cone made in several pieces and of fireproof material such as non-conducting zirconium oxid and having strengthenin ribs, a granular electric insulating filling o magnesia between the electric resistance cone and the insulating cone, and a cone supporting said filling, substantially as, and for the purpose, set forth.

11. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, a lining in said cone of a material which becomes a conductor of electricity at a high temperature, and a cement between the abutting surfaces of the electric resistance cone and lining consisting of a mixture of sesqui-oxid of boron silicate of potassium and sulfid of ammonium, substantially as, and for the purpose, set forth.

12. An electric furnace, comprising in combination, an inverted gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, a lining consisting of two concentric cones leaving a space between them, and a layer consisting of. metals or metal oxides of the chromium group, tungsten, titanium, or their carbids, or of other fireproof metals, Which may be fritted with sesquioxid of boron in said space, substantially as, and for the purpose, set forth.

13. An electric furnace, in which all parts subject to stresses are fritted with sesquioXid of boron, substantially as, and for the purpose, set forth.

14. An electric furnace, comprising in combination, a revoluble gas burner, an electric resistance cone of carbon below said burner and made of several pieces fitting in each other, and a lining in said cone of a material which conducts electricity at a high temperature, substantially as, and for the purpose, set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GIACOMO METTLEB.

Witnesses HENRi. Hasrnn, l/VOLDEMAR HAUPT.

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