US3181845A - Crucible furnace - Google Patents

Description

May 4, 1965 A. E- MALM ETAL 3,181,845

CRUCIBLE FURNACE Filed April 2, 1962 3 Sheets-Sheet 2 A. E. MALM ETAL May 4, 1965 CRUCIBLE FURNACE Filed April 2, 1962 3 Sheets-Sheet 3 W/A. X 92% Fig.4

United States Patent Office 3,181,845 Patented May 4, 1965 3,181,845 CRUCHBLE FURNACE Anders Ewert Malm and Rolf Birger Thorselius, Hallstahamrnar, Sweden, assignors to Aktiebolaget Kanthal, Hallstahammar, Sweden, a corporation of Sweden Filed Apr. 2, 1962, Ser. No. 184,215 Claims priority, application Sweden, Apr. 21, 1961, 4,199/ 61 6 Claims. (Cl. 263-12) The present invention relates to a crucible furnace and generally has for its object to provide a simple and reliable crucible furnace. Particularly, it is the object of the invention to provide a crucible furnace which is easily operated at the emptying of the crucible and in which the loss of heat unavoidably inherent with the emptying of the crucible is limited to the lowest possible value.

For the said purposes, the crucible furnace according to the invention is substantially characterized in that a portion of its side wall and a portion of the bottom of the furnace integral therewith and carrying the crucible are movable and pivotally journalled around a horizontal axis in such a way that for emptying the crucible they may be swung outwardly in relation to the remaining walls of the furnace and to the furnace vault. In view of the space requirements, inter alia. it is particularly suitable that the pivot axis is located below the bottom of the furnace, it being preferred with a view to obtain a satisfactory seal between the different parts of the furnace as well as for constructional reasons that the pivot axis intersects an imaginary extension of the vertical axis of the crucible which is disposed substantially centrally in the furnace.

Although the crucible in the furnace according to the invention lies very well protected and is subjected neither to such shock-like chillings as occur in crucible furnaces when the crucible is lifted out of the furnace or to the mechanical stresses which are unavoidably inherent with lifting out the crucible by means ofso-called crucible grippers and similar lifting means, as was the prior custom, failures of the crucible cannot always be avoided. For this reason, the invention proposes an embodiment, which is substantially characterized in that the pivotal portion of the furnace bottom is provided with ribs, on which the crucible normally stands, and between the ribs said bottom has a surface sloping in the direction to the corner between the pivotal wall portion of the furnace and the bottom portion in question, and in that a channel extends from said corner to the underside of the furnace, said channel being normally closed by means of a closing means, applied from below. It is suitable that the closing means consists of a wedge-shaped plug disposed on one arm of a pivoted double-armed lever carrying a counter-weight on its opposite arm.

It will be appreciated that the above is generally applicable in crucible furnaces irrespective of how they are heated. However, the principle proposed according to the invention is particularly valuable in connection with electrically heated crucible furnaces. According to a further aspect it is then especially suitable that the charging opening in the furnace vault has a considerably smaller diameter than the substantially cylindrical furnace chamher so that an annular shoulder is formed around the charging opening. Through this annular shoulder the elements, which are U-shaped and at least for the main part consist of molybdenum disilicide, Mosi are removably inserted from above with their two connecting ends disposed at the top side of the furnace vault and their glow zone portion depending freely along the inside of the furnace walls. Contrary to the previous crucible furnaces,

which are tipped in their entirety, the greater part of the electrically heated crucible furnace according to the invention will remain stationary so that the elements depend in an unchanged position. It will be easily realized that this is of extreme importance, as the elements, which are in a slightly plastic state when the furnace is in operation, are thereby permitted to depend freely without any special grooved bricks or the like being required to support the elements. To protect the elements against mechanical stresses, for instance from metal pieces falling beside the crucible in charging and striking the elements, it is preferred according to the invention that the elements are arranged with their glow zone portions depending between vertically extending protective ribs protruding radially inwards from the inside of the furnace Walls.

Further features of the crucible furnace according to the invention and advantages achieved thereby will be pointed out hereinafter in connection with the description of an electrically heated crucible furnace chosen as an example and illustrated in the accompanying drawings.

FIGURE 1 shows, in vertical section, an embodiment of an electrical crucible furnace according to the invention;

FIGURE 2 shows the same crucible furnace in horizontal sectional planes, the upper part of the figure showing the crucible furnace in horizontal section along the line 11-11 of FIG. 1 and the lower part of the figure illustrating a horizontal section in a plane slightly below the said sectional plane IlII;

FIGURES 3 and 4 show the different mountings of the elements.

The electrically heated crucible furnace shown as an example has a cylindrical wall 113, a bottom 11 and a vault 12 with a shutter 13 for the charging opening 14. The shutter 13 is suspended in a bar 13A and adapted to be lifted by means of e.g. a hydraulic jack 13B. As shown especially clearly in FIG. 2, a portion 16A of the furnace wall and a portion 11A of the bottom of the furnace, integral with said wall portion and carrying the crucible 15 are movable in relation to the remainder of the furnace wall and the furnace vault. The said portions are supported in a horizontal frame 16, as shown in the figure, said frame being pivotally journaled around a horizontal shaft 17. The frame 16 and thus the said portions 10A and 11A of the furnace wall and the furnace bottom, respectively, may be pivoted by means of a hydraulic jack 19 below the furnace, the piston rod 20 of said jack being hinged to the frame 16.

The pivotal portion 11A of the furnacebottom is provided with a nose-like projection 21 at its inner end, said projection normally protruding into a groove 22 in the stationary portion of the furnace bottom. Thereby a labyrinth-like seal is formed which prevents losses of heat. The shoulder or projection 23 above the groove 22 prevents particles falling down from the elements and the furnace walis to enter the seals 21, 22, to obstruct or render impossible the complete closing of the furnace. It is apparent from FIG. 2 that the pivotal portions are larger next to the outside of the furnace to form vertically extending, step- like shoulders 24, 25, which are likewise intended to reduce the loss of heat through the joints between the movable and stationary portions of the furnace. In order to effect the said seals in the simple way described, it' has been found desirable to arrange the pivot shaft 17 under the furnace bottom 11 and in such a way that it intersects an imagined extension of the vertical axis of the crucible 15.

Of course, when possible and necessary sand seal or fluid seals are used, as exemplified by the seals 26 and 27.

The pivotal portion 11A of the furnace bottom is provided with ribs 28 on which, normally, the crucible 15 rests. Between the ribs 23 there is a bottom 29 sloping in the direction to the corner between the wall portion WA and the bottom portion MA; A vertical channel 30 extends from said cor'n'er to the underside of the furnace,'s aid channel being normally closed by means of e Wedge-shaped plug 3 1 put in from below. The plug 31 pivotally secured to one arm of a double-armed, pivotal lever 32*the opposite arm of which carries a counterweight 33 that holds the plug 31 in closing position. In =case of "afa-ilure of the crucible, the charge flows into the channel 3i and the plug 31 is automatically opened to let (hit the charge. Further, the pivotal bottom por- -tion 11A is provided with a vertical rib 34 extending aro rnd three sides. It will be seen that the arrangements -;described above eliminate any risk of short circuiting of 1 the elements by outflow of charge.

Inside the pivotal portion 16A of the furnace wall there are provided supporting ribs 35 on which the crucible 15 rests when being emptied. Then, the smelted charge flows through a channel 35 in the upper end of the pivotal wall portion 10A.

Above the pivotal Wall portion lilA the furnace is provided with a raisable inspection shutter 37 which renders possible an inspection of the charging and the surface of the charge. Before the pivotal portions of the furnace are swung about the pivot 17, the shutter 37 is elevated out of the way of these movable parts.

it is apparent from FIG. 1 that the charging opening 14 of the furnace vault has a considerably smaller diameter than the substantially cylindrical furnace chamber. Thus, an annular shoulder 38 is formed around the charging opening, of course with an interruption where the pivotal portion 10A of the furnace wall is located. Through said annular shoulder the U-shaped elements 39, substantially consisting of molybdenum desilicide, MoSi are removably inserted from above with their connecting ends 35% disposed at the upper side of the furnace vault and their glOW zone portion 3% depending freely along the inside of the furnace Wall. FIG. 2

shows that the elements 39 are arranged with their glow zone portions depending between vertically extending protective ribs 4t protruding radially inwards from the inside of the furnace wall. in the interest of simplicity, said protective ribs have been omitted in the other figures. As shown in FIGS. 3 and 4, the connecting ends 39A (of the elements 39 are located in refractory plugs 41, inserted from above through holes 4-2 in the furnace vault. The plugs 41 are adapted to rest against the lining 43 of Lthe furnace roof. According to FIG. 3, the hole 44 in ithe lining is sligh' tly smaller than the hole 42,, for the pur- ,jpose mentioned, and thereby a shoulder 45 is formed on which the plug 41 is supported. According to FIG. 4, the lower and 41A of the plug 41 consists of the same ma i dhe furnace lining or of a similar material, and 33111 5 case the plug extends as far as the inside of the ff frace vault. Of course, the advantage of this arrangement is that when the plug 41 is pulled out there opens a larger hole in the furnace vault so that also deformed glow zone portions can easily be removed. In both cases the plugs are provided with a lifting handle td so that for inserting or replacing the elements they can be easily han dled from the top of the furnace vault.

An approximately annular casing 47 has been provided over the connecting ends of the elements, and of course said casing can be put under some super-pressure to prevent leakage through the furnace vault. In the case shown the casing 47 is provided with vents so that the electrical connections are slightly cooled.

"It will be appreciated that a plurality of modifications and alterations of details may be made within the scope of the inventive idea.

What we claim is:

1. A crucible furnace having a vertical side Wall, a

bottom and a top c ver, said parts defining a furnace 7 chamber, an upwardly-opening crucible disposed in said chamber and containing material to be heated, the side Wall including a stationary upstanding major portion, heating means disposedin the fixed portions of the furnace chamber for heating the crucible, said stationary side wall portion being formed integrally with a fixed portion of the bottom, the side wall having a movable smaller wall portion formed integrally with the rpinainder of the furnace bottom, said movable Wall portion and the part of the bottom carried by it carrying the crucible in an upright position, said qnovable wall portion and the part of the bottom carried by it being swingable together, means carrying said movable wall portion and the part of the bottom to cause said wall portion and the bottom part to be tiltable around a substantially horizontal axis for emptying the crucible, and power means connected to the smallerwall portion and its connected bottom por-- tion for effecting the tilting to empty the crucible while the major stationary wall portion and the part of the bottom formed integrally therewith remains stationary;

2. A crucible furnace according to claim 1 wherein the movable bottom portion is provided with upstanding ribs on which the crucible rests, said bottom portion ineluding a vertical channel passing through it, a pivotally mounted'plug fitting in and normally closing the channel, said plug being disposed on one arm of a pivoted, doublearmed lever, the second arm of which carries a counter weight.

3. A crucible furnace as provided for in claim l, wherein the walls of the furnace define a furnace cham ber of substantially cylindrical formation, said chamber having a charging opening at the top of considerably smaller diameter than the interior of the furnace chamher, the chamber being provided at the top with an annular shoulder overlying the upper end of the furnace chamher and resulting in the formation of said smaller-diameter top opening, and the heating elements being extended to project vertically downwardly into the furnace chamher around the interior of the fixed portion of the side wall thereof. I

4. A crucible furnace as provided for in claim 3, wherein the heating elements are arranged with glow portions disposed within the furnace chamber, and the fixed portion of the side wall of the chamber being provided with spaced ribs located between said glow portions.

5. A crucible furnace as provided for in claim 3, wherein the heating elements have upper ends disposed at the top of the furnace chamber above the annular shoulder, said ends being supported in a plurality of refractory plugs which are separately removable from out of the top wall of the furnace, said plugs being each of a diameter to result in the production when removed, of an opening in the furnace top of a size topermit of the free passage of a deformed glow zone portion of a heating element.

6. A crucible furnace having a body provided with a peripheral vertical wall and a bottom wall, a portion only of the vertical peripheral wall and a part of the bottom wall being joined together and mounted for pivotal movement together, a frame disposed beneath thev bottom wall and supporting the movable portion thereof and also supporting the movable portion of the peripheral wall, the frame being provided with a pivot located substantially at the vertical axis of the furnace body and disposed horrzontally, means coupled to the frame for swlngably moving the same to thereby pivotally move the portion of the peripheral wall and bottom Wall part, the movable bottom wall part having a ribbed top, and a crucible nor mally supported on said top and swingable to e P Y posit-ion on tilting of the movable wall portion and T part of the bottom attached thereto.

(References on following pag 6 :3 References Cited by the Examiner 2,587,727 3/52 Horswell et a1 263-11 UNITED STATES A S 2,978,563 1 Hackman 1322 X 2/02 Essner et a1. 263-13 FOREIGN PATENTS 9/ 12 Holzapfel 26312 5 370,372 10/30 Great Britain. 6/28 Wirz 13--25 838,917 6/60 Great Britain. 10/39 Hall 263-13 7/42 Brooke X CHARLES SUKALO, Pnmary Examiner. 12/51 Upper 26311 X JOHN J. CAMBY, PERCY L. PATRICK, Examiners.

Claims (1)

1. A CRUCIBLE FURNACE HAVING A VERTICAL SIDE WALL, A BOTTOM AND A TOP COVER, SAID PARTS DEFINING A FURNACE CHAMBER, AN UPWARDLY-OPENING CRUCIBLE DISPOSED IN SAID CHAMBER AND CONTAINING MATERIAL TO BE HEATED, THE SIDE WALL INCLUDING A STATIONARY UPSTANDING MAJOR PORTION, HEATING MEANS DISPOSED IN THE FIXED PORTIONS OF THE FURNACE CHAMBER FOR HEATING THE CRUCIBLE, SAID STATIONARY SIDE WALL PORTION BEING FORMED INTEGRALLY WITH A FIXED PORTION OF THE BOTTOM, THE SIDE WALL HAVING A MOVABLE SMALLER WALL PORTION FORMED INTEGRALLY WITH THE REMAINDER OF THE FURNACE BOTTOM, SAID MOVABLE WALL PORTION AND THE PART OF THE BOTTOM CARRIED BY IT CARRYING CRUCIBLE IN AN UPRIGHT POSITION, SAID MOVABLE WALL PORTION AND THE PART OF THE BOTTOM CARRIED BY IT BEING SWINGABLE TOGETHER MEANS CARRYING SAID MOVABLE WALL PORTION AND THE PART OF THE BOTTOM TO CAUSE SAID WALL PORTION AND THE BOTTOM PART TO BE TILTABLE AROUND A SUBSTANTIALLY HORIZONTAL AXIS FOR EMPTYING THE CRUCIBLE, AND POWER MEANS CONNECTED TO THE SMALLER WALL PORTION AND ITS CONNECTED BOTTOM PORTION FOR EFFECTING THE TILTING TO EMPTY THE CRUCIBLE WHILE THE MAJOR STATIONARY WALL PORTION AND THE PART OF THE BOTTOM INTEGRALLY THEREWITH REMAINS STATIONARY.

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