US2836865A - Crucible pour mechanism - Google Patents

Description

June 3, 1958 R. F. BRAVARD ETAL 2,836,865

CRUCIBLE POUR MECHANISM Filed Feb. 9, 1956 '2 Sheets-Sheet 1 Fig -1 Eifer/zeg R. F. BRAVARD ETAL 2,836,865

. CRUCIBLE POUR MECHANISM June 3, 1958 2 Sheets-Sheet 2 Filed Feb. 9, 1956 f l INVENToRs Foy f' la Z/afd BY Jaunes //Uahaffey McDo/laid 5./Vel5o/z Biwd 4MM lUnited States CRUCIBLE POUR MECHANISM This invention relates to a crucible bottom pour mechanism. More specifically, it relates to a refractory bottom pour mechanism for use in vacuum melting furnaces and the like and constitutes an improvement over the mechanism disclosed in patent application Serial No. 324,021, led December 4, 1952, on behalf of Adam Becker and Alfred W. Wolzer now Patent No. 2,770,856.

Satisfactory operation of vacuum melting furnaces and the like depend upon some mechanism for retaining the metal in the crucible until desired conditions for proper flow are attained. Various methods of accomplishing this purpose are in use, some of which are: (l) A plug made of the same metal which is being melted; (2) A refractory plug which is to be sheared at time of pour; (3) Slide mechanisms. Each of the present methods possesses inherent objectional features. When using the plug of the same metal as being melted the operator maintains no control over the time of the pour, this being governed by the moment of the melting of the plug. If the refractory plug is not sheared cleanly and completely the molten metal seeps around the shearing mechanism and clogs the passageway and usually results in al damaged crucible which must be discarded. The slide mechanisms are mechanical devices which easily freeze due to an accumulation of metal.

An object of this invention, therefore, is to provide a pour mechanism by the use of which an operator may select the exact moment of pour. Another object is to provide a mechanism which, if the shear is not clean and complete, does not restrict the flow of molten metal to the mold. Still another object is to provide a mechanism which does not damage the crucible in the case of an incomplete shear of the plug so that the crucible may be reused.

These and other objects will become apparent from the following more complete description of the invention and the annexed drawings wherein:

Fig. l is a verticalsectional view of a crucible provided with a stopper and slide;

Fig. 2 is a horizontal view partially in section taken on the line 2 2 of Fig. 1;

Fig'. 3 is a fragmentary vertical sectional View taken along the line 3-3 of Fig. 1; and

Fig. 4 is a fragmentary vertical sectional view similar to Fig. l, but with the crucible stopper broken so as to constitute a nozzle through which molten metal may pour from the crucible.

A crucible is generally indicated at 1 in Fig. l. lt is preferably a cylindrical container composed of a refractory material such as graphite. The bottom of the crucible has a centrally disposed tap hole 2.

This hole is adapted to receive a stopper 3 which is composed of a frangible refractory material such as graphite and has a blind bore 4 which extends from the top surface of the stopper to a point spaced from the bottom surface. The lower end of the stopper is formed as a cap 5 which is joined to a nozzle portion 6 through a neck which is at the closed end of the bore 4. The exteriors of the nozzle portion and the hole 2 in the atent O M 2,335,865 Patented June 3, 1958 crucible are shaped like a truncated cone with the diameter increasing in a downward direction so that the stopper 3 may be applied vto the crucible from below and the nozzle portion 6 may be lirmly cemented in place in the hole 2.

The crucible has a notch 7 (see Fig. 2) of substantial depth extending diametrically across the base thereof into which the tap hole 2 opens. AA slide 8, formed of graphite or other suitable material, is adapted to be contained in and moved along the upper part of this notch. The slide has an inner end 9 which is engageable with a bolt 16 which may be made of titanium and an outer end 1l.. The slide is provided with two apertures 12 and 13 connected by a slot 14 which extends completely through the slide. This slot is of less diameter than the cap 5. The aperture 12 is disposed nearer the inner end 9 of the slide than is the aperture 13 and is provided with an annular shoulder 15 which separates a lower portion 16 of small diameter from an upper portion 17 of larger diameter. The height of the upper portion 17 of the aperture 12 is greater than the height of cap 5. The upper portion of the aperture 12 is larger in diameter than the cap 5 and loosely receives it in the position of Fig. l, and the lower portion of the aperture 12 is smaller in diameter than the cap 5. The aperture 13 is larger in diameter than the tap hole 2.

In the central portion of the base of the crucible the notch 7 is enlarged by two concentric depressions in the sides of the notch to form a cylindrical recess 18 which has a depth equal to the depth of the notch '7 less the thickness of the slide 8 and the necessary clearance for the slide. A pour block 19, also formed of graphite or similar material, is held within the recess by a threaded engagement therewith. A nozzle 2Q forming an integral part of the pour blo-ck extends below the base of the crucible. The entire pour block has a bore 21 extending therethrough and serves as a nozzle to protect insulator 22 from the molten metal. Pins 23 fix the location of the crucible on the insulator.

When the parts are assembled as described, the slide 8 rests on and is supported by pour block 19 and the crucible rests on and is supported by the insulator.

In operation, the stopper 3 is pressed into the tap hole 2 in the bottom of the crucible 1 and may be held in position by a light coating of suitable cement. The slide 8 is then placed in position so that the upper portion 17 of the aperture 12 encompasses the cap 5 of the stopper. The pour block 19 is then fastened in position and thus supports the slide 8. The material to be cast is placed in the crucible and the unit is placed into a furnace. When the material to be cast has attained the desired conditions, the slide is struck with a hammer or other object. The stopper being of refractory material, along with the other parts of the pour mechanism, shears at a point below its lower face and the cap drops on shoulder 15 and is carried along with the slide from the position of Fig. l to that of Fig. 4 so that the inner end 9 of the slide contacts the bolt 10.

At the instant of the shearing of the stopper, molten metal begins streaming from the bottom of the crucible. This molten metal pours through the slot 14 in the slide while said slide is in motion and when the slide has reached the limit of its travel through the aperture 13 into the mold which is located below the crucible. If for any reason the shear of the stopper is not complete, a route of escape is available to the metal since it may ow through the slot 14 and bore 21 in the pour block into the mold and success of the pour at all times is assured.

Another advantage of the present invention resides in the fact that the slide is supported by the pour block 19. Thus when it is desired to disassemble the apparatus, all

that is necessary is that the pour block be unscrewed from its position and the slide will thereupon drop-out of the notch. This constitutes a very convenient and relatively Ycheap assembly in which there are no elements which would have to be replaced frequently.

Byutilizing remelt equipment having the bottomV pour mechanism as outlined in the present invention, the average lifetime of crucibles is greatly lengthen'ed.V VPrior to `this invention, if the shear was not complete, metal would seep around the slide and cause seizure of the slide tolthe Crucible body. This would necessitate drilling or chiseling;

bottom of a stoppercomposed of a nozzle portion posi? tioned in the hole, a'cap-protruding from the bottom and a frangible'section between the capra'nd thenozzle portion, and a slide mounted at the bottom so as to be shiftable i therealong, said slide having a first aperture into which the cap normally protrudes, and a second aperture spaced from the first aperture in the direction of shifting. said rst and second apertures being joined by a slot extending through the slide, said slot being narrower than the eX- terior diameter of the cap, whereby movement of the lslide breaks-the stopper at the frangible Vsection permitting the molten metal to pour through the second aperture or the slot of said slide.

2. The combination specified in claim l wherein'said slide is movable in a notch extending diametrically across the base of said Crucible and also comprising a pour block threaded into' the base of the crucible'to serve bothas a :i nozzle and as a support for the Slide.

' 3. VThe combination specied in claim 2 wherein the central part ot" the notch is enlarged to form a cylindrical recess of less depth than the notch and into whichthe pour block isV threaded. Y

4. The combination with a Crucible having a hole in its bottom and a notch extending diametrically across the base of the Crucible wherein the central part of the notch is enlarged to form a cylindrical recess of lessdepth than the notch, of a stopper composed of a nozzle portion 'positioned in the'hole, a cap protruding from the bottom extending into the notch and a frangible section betweenthe cap and the nozzle portion, a slide mounted in the upper part of the notch so as to be shiftable therealong for` breaking the stopper at the frangible section, and a pour block threaded into the cylindricalrecess which serves both as a nozzle and as a support for the slide.

References Cited in the le of this patent UNITED STATES PATENTS ecker et al. Nov. 20, 1956

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