US1372676A - Crucible-furnace - Google Patents

Description

J. H L. DE BATS;

- CRUCIBLE EURNACE. APPLICATION FILED MAR. 3. 1917.

RENEWED AUQ. 5| 1920.

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WITNESSES J. H. L. DE BATS.

- CRUCIBLE FURNACE. APPLICATION FILED MAR. 3.1911. RENEWED AUG. 5,4920,

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I 1 9 I I y I 1 I WITNESSES INVENTOR nnirsn JEAN HUBERT LOUIS DE BATS, 0F ZELIENOPLE, PENNSYLVANIA, ASSTGNOB, BY IVTESNE ASSIGNMENTS, TO LAVA CRUCIBLE COMPANY 01 PITTSBURGH, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

CRUGIBLE-FUBNACE.

Specification of Letters Patent.

Patented liliar. 29, 1921.

Application filed March 3, 1917, Serial No. 152,430. Renewed August 5, 1320. Serial No. 401,565.

[a all to ham it may concern Be it known that T, JEAN T-lUnEn'r LOUIS Dn Bars, a resident of Zelienople, in the county of Butler and State of Pennsylvania, have invented a new and useful Improvement in Crucible-Furnaces, of which the following is a specification.

This invention relates to so-called crucible furnaces in which metals are melted, refined or otherwise treated in pots or crucibles placed within the furnace. The object of the invention is to provide a furnace of this kind which will conserve and extend the life of the crucible or pot; prevent oxidation and contamination of the metals being melted and treated, by the gases produced by the combustion of the fuel in the furnace; facilitate the removal of the crucible or. pot and the replacement thereof in the furnace; lessen the labor of supplying metals to the crucible or pot; and, when solid fuel is used, prevent waste of fuel, conservethe heat and lessen the labor necessary for cleaning and replenishing the fire.

In the accompanying drawings Figure 1 is a vertical section through the improved furnace, taken on line 1-1 Fig. 3; Fig. 2 is a plan view of the furnace; Fig. 3 is a horizontal section taken on line 3-3 Fig. 1; and Fig. 1 is a sectional View of the grate bars on the line k t, Fig. 3.

The furnace comprises an outer chamber for containing the fire or fuel and a secondary chamber within the outer chamber for containing the pot or crucible so that it is out of direct contact with the fire or flame.

As shown the funace comprises an outer wall 1 built up of brick or other refractory material and inclosing the furnace chamber 2, and within said chamber is a wall 3 some distance inwardly from the wall 1 to provide a space a for the fuel or fire, said wall 3 inclosing a crucible chamber 5 in which the crucible or pot 6 rests. The bottom of the chamber 2 is formed by a plate 7 upon which wall 3 is erected and which plate 7, around the wall 3, is formed as a grate 8 for receiving coal, coke or other solid fuel. If desired, gas or liquid fuel burners may be applied in the space 4. The outlet from the chamber 2 is through a side flue 9, through which the products'of combustion are carried and conducted to a suitable stack or disposal medium, not shown. The top of the furnace is provided with an opening or openings 10 through which the crucible is inserted and removed, and through which fuel is supplied to the furnace chamber 2.

The wall 3 will be built up of suitable heat conducting and refractory material, and I have found that carbid of silica is suitable for this purpose, as it is not only strong and refractory but also a good conplementary wall 3, the bottom plate 7 is so mounted that it can be raised and lowered. To this end the furnace is supported on 001- umns 14. resting on the foundation 15, four such columns being shown, and at their upper ends supporting an annular plate 16 on which the furnace walls 1 are erected, thus leaving an open space underneath the furnace. The bottom plate 7 is provided with guide lugs 17 on two diametrically opposite points, which engage two of the columns 1 1, to guide the plate 7 when being raised and lowered. Said bottom plate 7 is carried on the upper end of a lifting bar 18 which extends downwardly into a well 19 in the foundation 15. This lifting bar will be adapted for a suitable ack, either hydraulic, pneumatic or mechanical, and as shown is a ratchet bar adapted for actuation by an ordinary ratchet jack, indicated generally at 20, and which operates like any drawn out through the fine 9.

and waste pipes. The opening or openings 10 through the top of the furnace will of course be closed by a cover or covers as is usual in crucible furnaces.

In the use of the furnace, the crucible with gases from the fire are drawn upwardly to the outlet flue 9, the material or metal in the crucibleor pot will not be contaminated by these gases and will not be oxidized on its surface by any excess oxygen in these gases. To supply fuel to the chamber l a metal cover will be lowered down through the opening in the top of the furnace, to cover the chamber 5-*"and thus allow fuel to be dumpedin to fill the chamber l. The crucible or'pot will be placed in the chamber 5 and removed therefrom by means of suitable tongs in the usual manner, and because of the open space around the crucible or pot, the tongs can be made to engage the crucible or pot with ease and without danger of injuring the crucible.

When the fire is to be cleaned the jack 20 will be operated to lower the bottom plate 7 a few inches, thus allowing cl inkcrs and ash to drop from the grate 8, after which the bottom plate '7 is again lifted. This cleaning therefore can be ,efiected very quickly and easily and without the necessity of poking,

etc, as is necessary in ordinary crucible furnaces. Also, to make repairs or alterations to the walls 8 the plate 7 will be lowered so that the entire wall construction 3 is below the normal grate level and as the furnace is entirely open underneath ready access is thereby had.

The furnace construction described has numerous advantages over crucible furnaces asordinarily constructed, in which the crucible or pot rests within the furnace chamber proper and is surrounded or packed in the burning coal. or coke. Under ordinary prac ,tice the life of the crucible or pot is quite short, due to several causes or destructive agencies:

,First: The crucible is sub ected to excessive oxidation under a high heat, and'as these crucibles are formed of a mixture of graphite and clay the oxygen and heat have the effect of oxidizing the graphite on the outer surface of the crucible and producing a vitreous or glazed condition. of the clay, so

that the outer surface has a different 00- efficient of expansion and contraction than the body or inner portion of the walls, The depth of the glazed or vitreous portion increases with each heating, and because of the difference of expansion and contraction said glazed portion will spall or chip off, thus reducing the thickness of the crucible walls and soon leading to its entire destruction. With the improved furnace above described the crucible is entirely protected from the oxygen and consequently there will be no oxidation or withdrawal of the graphite, the crucible walls tending to remain of the same composition or texture throughout, giving a longer life.

Second: In the old practice the crucible is subjected to uneven temperatures on various parts thereof, no matter whether solid, gaseous or liquid fuel is employed, which is liable to cause the crucible to crack andthus destroy the same. By having a crucible 1n the secondary chamber, as described, the heat.

is evenly diffused over the entire surface of the crucible, thus reducing its liability to crack. v

Third: Under the old practice the crucible is liable to mechanical injury due to being in direct contact with the solid fuel, which has hard sharp edges which may injure the outer surface of the crucible, and particles of which are frequently crushed into the walls of the crucible by means of the tongs used to remove the pot, thus forming indentations in the crucible walls which soon burn entirely through and thus destroy the crucible. 7 Fur thermore, to remove the crucible from the old style furnace it is necessary by means of a suitable instrument to poke downwardly along the side of the pot at two opposite points to provide spaces for the insertion of the tongs. The action of such tool fre-' quently breaks or at least injures the crucible walls. All of these difliculties are overcome by the furnace construction above described, as no fuel. is in direct contact with the pot and sufhcient space is left on the sides of the pot for theinsertion of the tongs.

Fourth: Under present crucible use it is necessary to work over an open flame furnace when tamping down the fire to provide openings for the insertion of tongs and for this reason the workmen cannot guide the tools and frequently hit the crucible or pet and injure it, which is entirely avoided by the furnace construction described because the adjustment of the tongs to the crucible can be done so quickly that the workmen can do the same carefully.

Fifth: With the old furnace practice there is a tendency ofthe solid fuel to fusebetween the cruciblef and the block upon which it rests so that frequently the crucible is destroyed in an efl'ort to remove it from the furnace. This is entirely avoided by the furnace construction described above in that the pot rests upon a refractory block, out of contact with the fuel so that it IS always perfectly free to be lifted when the charge iscompleted.

For these reasons the furnace construction above described very greatly increases the life of the crucible or pots.

There is also a great saving in the fuel, particularly when solid fuel is used. Vith the old furnace construction, inasmuch as the crucible or pot is practically embedded in the fuel, whenever it is removed the fuel falls down in the space occupied by the crucible or pot, and before a new pot can be inserted a large part of this fuel must be poked down into the ash pit, so as to provide sufficient space for the new crucible or pet, after which a new supply of fuel must be added to replace that which was poked down. This not only results in a waste of fuel, but the new fuel cools the furnace so that it requires considerable time to bring the furnace up to its heat and thus lengthens the period of treating a crucible or pot of metal. With the new construction there is no waste of fuel whatsoever when one pot is removed and a new one put in, because the fuel is never in contact with the pot, and furthermore, the temperature of the fur nace is conserved and thereby the length of time of an individual heat is very greatly reduced.

Vith the furnace above described the fire is much more quickly and economically cleaned than with the old furnaceconstruction,by merely lowering the furnace bottom and grate, as above described.

Another advantage of the new furnace construction is the preservation of the purity of the metal being treated. The chief danger from impurities of any metal being treated in a crucible is due to the gases of combustion, which contain impurities. In the old furnace constructions these pass directly over the open crucible or pot and contaminate the metal contained therein, and in addition they oxidize the metal to a considerable extent, thereby producing a waste of metal and also preventing uniform results by changing the proportions of the mixtures and compositions of the metal. This is entirely overcome by the furnace construction described above, as the wall 3 inclosing the crucible directs the products of combustion upwardly so that the gas and oxygen do not come in contact with the surface of the metal being treated.

The secondary chamber in the furnace can be readily and economically constructed and is formed by a strong but good heat conducting wall. When formed of carbid of silica it is very durable and not liable to fracture. It is built in a series of horizontal rings and even if one ring should crack,

the crack is not liable to extend into adjacent rings, and should such a crack form in a ring the heat which the same is subjected will again fuse the carbid of silica so as to close the crack. The interlocking of the rings one with another, as described, will hold securely in place any cracked ring so that the inner wall will not break down, and requires only infrequent replacings.

What I claim is:

l. A crucible furnace comprising a main furnace chamber, a bottom therefor. arranged to be lowered and lifted, and a crucible containing chamber erected on said bottom, the walls of said crucible chamber being imperforate and formed of refractory dream-conducting material and rising from the furnace bottom and spaced from the walls of the main chamber to provide a space for the fire therebetwecn, said crucible chamber being wider than the crucible to permit the latter being inserted and removed by means of tongs.

2. A crucible furnace comprising a main furnace chamber and a crucible containing chamber within said main chamber, the walls of said crucible chamber being imperforate and formed of carbid of silica and rising from the furnace bottom and spaced from the walls of the main chamber to provide a space for the fire therebetween, said crucible chamber being Wider than the crucible to permit the latter being inserted and removed by means of tongs.

A crucible furnace comprising a main furnace chamber, a bottom therefor arranged to be lowered and lifted, and a crucible containing chamber erected on said bottom, the walls of said crucible chamber being imperforate and formed by horizontal rings of refractory heat-conducting material and rising from the furnace bottom and spaced from the walls of the main chamber to provide a space for the fire therebetween, said crucible chamber being wider than the crucible to permit the latter being inserted and removed by means of tongs.

at. A crucible furnace comprising a main furnace chamber and a crucible containing chamber within said main chamber, the walls of said crucible chamber being imperforate and formed of horizontal interlocking rings of refractory heat-conducting material and rising from the furnace bottom and spaced. from the walls of the main chamber to provide a space for the fire therebetween, said crucible chamber being wider than the crucible to permit the latter being inserted and removed by means of tongs.

5. A crucible furnace comprising a main furnace chamber, a bottom therefor arranged to be lowered and lifted, and a crucible containing chamber formed by refractory heat conducting walls erected on said bottom and rising therefrom and spaced from the walls of the main chamber to provide a space for the fire therebetWeen said crucible chamber being Wider than the crucible to permit the latter to be inserted and removed by means of tongs, and a grate forming the bottom of the space surrounding said crucible containing chamber.

6. A crucible furnace comprising a main furnace chamber, a bottom therefor arranged to be lowered and lifted, and a crucible containing'chamber supported on said bottom and formed by refractory Walls located Within said furnace chamber and spaced from the Walls thereof to provide a space for the fire exteriorly of said crucible containing chamber, and a grate forming the bottom for the space between the Walls ranged to be lowered and lifted and formed as a grate around its peripheral portion, and a crucible containing chamber on the central portlon of sald bottom and formed of refractory good heat conducting Walls and providing a space for the fire therearound. In testimony whereof I have hereunto set my hand.

JEAN HUBERT rows or BATS.

Witnesses PAUL L. BERKEY, M. W. RAY.

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