US2846740A - Furnace ladling apparatus - Google Patents

Description

United States Patent O 2,846,740 FURNACE LADLING APPARATUS Elmer Edstrand, Berkley, Ill., assignor to Lindberg Engineering Company, Chicago, Ill., a corporation of Illinois Application September 17, 1956, Serial No. 610,077

7 Claims. (Cl. 22--79) This invention relates to furnace ladling apparatus, and more particularly to apparatus for discharging controlled amounts of molten metal from a furnace.

Heretofore it has been proposed to discharge or ladle molten metal from a furnace by applying gas or air pressure to the surface of the metal in the furnace chamber or in a Crucible in the furnace chamber to force the metal through an upwardly extending discharge tube projecting out through the upper portion of the furnace chamber. When a separate crucible is used, or when the furnace is ofthe multiple chamber type, the gas pressure tends to force the metal from the Crucible or ladling chamber of the furnace back into the furnace. The use of valving to prevent such ow is difficult and is not satisfactory, and the presence of backow tends to vary the quantity of metal discharged through the discharge passage.

Furthermore, all such apparatus is subject to a varying rate of discharge responsive to changes in the level of molten metal in the furnace. Attempts to overcome this difficulty heretofore have resulted in complex systems which are expensive lto build and diicult to maintain in proper operation.

It is accordingly one of the objects of the present invention to provide furnace ladling apparatus which discharges accurately measured quantities of molten metal at each operation without the use of valves or other moving parts.

Another object is to provide furnace lladling apparatus in which the quantity of molten metal discharged at each operation is uniform regardless of variations in the level of rnolten metal in the furnace.

Still another object is to provide furnace ladling apparatus in which the metal is discharged from a separate c'rucible in the furnace chamber, and backflow of metal from the Crucible to the furnace Achamber Ais prevented without the use of valves or other moving parts.

According to one feature of the invention, a vertical passage extends downwardly from the inlet opening to the Crucible to trap metal in the crucible which is forced out through the discharge tube whose inlet end is below the inlet opening. The .passage is of such length, or may be provided with a dovvnward'extension,` to produce sufcient head 'topreverit backflow of pressure to the furnace chamberduring the discharge operation.

According to another feature, the inlet opening to the crucibl'e is of smaller diameter than the tube to limit bubbling or violent agitation of the metal asit flows into the crucible.

vA further object is to provide a furnace ladlin'g apparatus in `which vthe supply of -fluid pressure to the Crucible is controlled automatically in a cycle by which the chamber yis first vented to permit metal to flow into it, second, yis vsubjected `to a low pressure suicient to -reduce the metal level -to the top ofthe filling tube, and

third,gis subjected to a high pressure to force out the desired quantity of moltenmetal.

The above and other objects and features of-the invenice tion will be more readily apparent fiom the following description when read in connection with the 'accomf panying drawing, 'in which:

Figure 1 is a partial sectional view of a furnace equipped `with ladling apparatus embodying the inven# tion; u

Figure 2 is apartial sectionsimilar to Figure-..1 showing the apparatus during a discharge operation; i

Figure 3 Ais a disassembled perspective view ofthe crucible; and f Figure 4 is a diagrammatic view of the control circuit.

While Ythe ladling apparatus of the present vinvention can be used with any desired type of melting orholdin'g furnace, it is illustrated in Figures l and `2 as applied to a furnace of vthe type more particularly vdisclosed -in the patent to Lillienberg, No. 2,648,715. This furnace is a double chamber induction furnace having a ceramic body l10 formed with a charging chamber 11 and a pouring-or ladling chamber 12. The chambers are connected by two or more submerged channels'13 which are threaded by a primary core 14 carrying a winding 15 which is energized by alternating current to induce a secondary melting current in the metal in the chambers and channels. In normal operation of a furnace of this type the metal to be melted or heldvis charged in the chamber 11 and molten metal is-discharged from the chamber 12.

The ladliug apparatus vof the present invention comprises a Crucible 16, made of refractory material and supported in the upper part of the pouringchamber 12 to project downwardly into the molten met-al therein. The top'of the cr-ucible is 'closed by a cover 17 to which an air or gas connection 18 extends to supplyair or vgas under pressure to the upper part of the crucible. In'its lower part the crucible is formed with a relatively ire'- stricted opening 19 and a discharge opening 2-1 extend.- ing through one side thereof. Metal in the Crucible, is` adapted to be forced out the discharge opening by gas or air pressure and `to flow through a discharge tube 22 which communicates with the discharge opening 21 and extends-upwardly to project through the `side wall of the furnace `chamber 1-2. vat a level above the normal level of molten metal in the-chamber. Molten metal liiowin'g throughthe discharge tube 22 may ow into a trough23 o rmay be forced directly into a mold which is placed incommunication with the outer end of the discharge tube'.

Toecontrolrthe amount of metal forced through the dis.-v charge tube and to prevent backflow of 'pressure/to the chamber 12 from the cruciblefa vertical passage shown asa tube 24 communicating with'the opening 19extends upwardly into the crucible to a level below the normal level of molten metalin the chamber 12 and terminates in an inlet opening 24a in the crucibleabove the level "of the discharge opening'21. The tube'2`4 ispreferably'of larger Vdiameterthan the opening 19 tovminimize boiling oragitationoflthe molten metal as it ows through the opening 19 and tube into the -crucible. In some cases4 Where the crucible is relatively shallow, a second tube 25 may be provided communicating -with the opening 19 and extending downwardtherefrom intofthe chamber'IZ toi-a pointnear thebottornthereof. The tube 25 provides "a substantial vhead of molten metal between the level rof metal inrthecharnber 1-2and the upper part ofthe crucible, so that pressure inthe Crucible cannot lblow -back throughthe tubes into the chamber lI2.

In operation of the apparatus with molten metal inthe chambers l11 and 12 substantially to the level shown, and with no pressure present in the upper part of the crucible, metal will iiow byl gravity from the chamber 12 4through the tubes 24 and 2S'and the opening'19`into thecru'cibl'e n to the same level as the metal inthe chamberflZ. .'Prcf erably, the length of the tube 24 is selected to be slightly below the normal metal level and about 3 inches below the metal level in the embodiment shown and described. The furnace is normally so operated that its level will never fall below the inlet opening 24a and will normally be approximately 4 inches below the upper end of the discharge tube 22.

After the crucible is filled, a relatively low air or gas pressure is supplied thereto through the conduit 18 to depress the level of metal in the crucible to or slightly below the inlet opening 24a. This condition is illustrated in Figure l wherein the level in the crucible is shown at the inlet opening 24a and below the level in chamber 12, while the level in the discharge tube 22 is above the level in the chamber 12 but below the upper end of the discharge tube.

In a practical operating furnace it has been found that this low pressure may satisfactorily be 6 ounces of pressure which with aluminum will produce a variation in head of 3% inches. Thus when the 6 ounce pressure is applied, the difference in level between the inside of the crucible and the discharge tube 22 will be 3% inches, and the dierence in level between the metal inside the tube 24 and in the chamber 12 will be 3% inches. It will be seen that even though there are fluctuations in the level in the chamber 12, the crucible 16 will always be filled to exactly the same level, and the metal will stand in the discharge tube 22 at exactly the same level, even though the level within the ltube 24 and in the chamber 12 may fluctuate.

The apparatus is now ready for a discharge operation and a higher discharge pressure on the order of 20 ounces is applied to the crucible through the conduit 18. This pressure will force the metal trapped within the crucible by the tube 24 out through the discharge tube 22, and since there is no blow-back of pressure, as explained hereinafter, and there is precisely the same quantity of metal in the crucible and discharge tube at precisely the same level during each operation, a very accurate quantity of metal may be discharged by controlling the value of the discharge pressure and the time it is effective.

It has been found, for example, in a practical operation that by utilizing 20 ounces of pressure and controlling the time of its application, accurately measured quantities of molten metal can be discharged at each operation varying in quantity from on the order of l pound to 30 pounds or more. During the discharge operation the metal level within the vertical passage formed by the tubes 24 and 25 will be depressed, as illustrated in Figure 2, but the vertical length of this passage is made great enough so that the pressure cannot force the metal completely out of the passage due to the head between the bottom of the passage and the level of metal in the chamber 12. There is thus no escape of pressure, and the interior of the crucible is always subjected to precisely the same discharge pressure during a ladling operation.

It will be understood that the crucible is never emptied to the point that the level therein will fall below the discharge opening 21 so that the air or gas can never blow out the discharge tube. As long as the discharge pressure in the crucible is less than the head between the level in the chamber and the lower or inlet end of the passage defined by the tubes 24 and 25, the pressure cannot blow back through the inlet passage and into the chamber. The pressure must, of course, be high enough to force the metal from the crucible out the discharge tube 22 and may be high enough to produce a relatively rapid ow as long as it is not high enough to blow back through the inlet passage. Thus for many furnaces the tube 25 may be omitted entirely, its use being desirable only when a high discharge pressure is used to produce a rapid discharge of metal.

Figure 4 illustrates diagrammatically a control circuit for eiecting automatically the cycle of operations as described above. As shown in this gure, the conduit 18 is connected to a source of air or gas under pressure indicated at 26 and which may be regulated to the discharge pressure of 20 ounces. The source is connected to the conduit 18 through a three-way valve 27 which is operated by a solenoid 28 to connect the conduit 18 either to the source 26 or to a by-pass conduit 29. The by-pass conduit is connected through a three-way valve 31 and a reducing valve 32 to the source 26. The three-way valve 31 is operated by a solenoid 33 to connect the pipe 29 either to an atmospheric vent 34 or to the reducing valve 32.

The solenoids 28 and 33 are controlled in an automatic cycle by a cycle switch which may be of any desired conventional construction, but which is shown as including a disc 35 driven counter-clockwise at constant speed and having conductive segments 36 and 37 thereon. The disc is connected to a source shown as a battery 38, although the source would normally be a transformer or the like, one side of which is connected to the solenoids 28 and 33. The other sides of the solenoids are connected to brushes which contact the strips 36 and 37 respectively. As the disc turns, a circuit will first be completed through the solenoid 33 to move the three-way valve 31 90 from the illustrated position to connect the reducing valve 32 through the three-way valve 27 to the crucible.

The reducing valve 32 may be adjusted to produce the desired low pressure such as 6 ounces to accomplish the rst portion of the cycle as described above. As the disc continues to turn, the solenoid 33 will be de-energized to return the valve 31 to the position shown, and substantially simultaneously the solenoid 28 will be energized to turn the valve 27 to a position in which it connects the source 26 directly to the crucible. At this time full discharge pressure is applied to the crucible, and the metal therein will be discharged as described above. Upon further turning of the disc, the solenoid 28 will be de-energized and the crucible will be vented through the three- way valves 27 and 31 to allow metal to flow from the chamber 12 into the crucible. At this time the apparatus is in condition for a second cycle.

While one embodiment of the invention has been shown and described in detail, it will be understood that this is lllustrative only and is not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

l. Furnace ladling apparatus comprising a hollow chamber to contain molten metal, a crucible in the chamber, means defining a vertically extending passage projecting at its lower end into the molten metal and terminating at its upper end in an inlet opening in the crucible above the bottom thereof, means defining an outlet opening in the crucible below the inlet opening, a discharge tube communicating with the outlet opening and extendlng upward .therefrom to a level above the normal level `of molten metal in the chamber, and means to apply tluid pressure to the upper part of the crucible to force metal in the crucible beneath the inlet opening through the outlet opening and discharge tube, said passage being of suflicient vertical height that lluid under the lapplied pressure will not blow past the molten metal therein.

2. The construction of claim 1 in which the passage includes a portion of reduced cross-sectional area below the inlet opening.

3. Furnace ladling apparatus comprising a furnace body defining a chamber to hold molten metal, a crucible fitting into the chamber to be partially immersed in the molten metal therein, the crucible having an inlet opening above its bottom, and a discharge opening below the inlet opening, a discharge tube communicating with the discharge opening and extending upwardly therefrom to a level above the normal level of molten metal in the chamber and discharging outside of the chamber, 'a tube communicating with the inlet opening yand extending downward within the Crucible through the lower :part thereof, and means to apply Huid under pressure to the upper part of the Crucible to force molten metal therein out the discharge tube, the last named tube being of such a vertical height that the head of molten metal above its lower end will be greater than the applied uid pressure.

4. Furnace ladling apparatus comprising a furnace body defining a chamber to hold molten metal, a Crucible extending down into the chamber to be partially immersed in the molten metal therein, the `Crucible having `an inlet opening above the bottom of lthe Crucible and a discharge opening below the inlet opening, a discharge tube communicating with the discharge opening and extending upward therefrom at an angle to horizontal to `a level above the level of molten metal in the chamber and discharging outside of the chamber, means defining a passage -communicating with the inlet opening and extending downward therefrom to a level below the level of the discharge openin-g, a cover for the Crucible, and means to supply gas under pressure to the upper part of the `Crucible to force molten metal therein out the discharge tube.

5. The construction of Claim 4 in which the passage includes a portion of restricted cross sectional area below the inlet opening.

6. Furnace ladling apparatus comprising a furnace body defining a chamber to hold molten metal, a `Crucible extending down into the chamber to be partially imrnersed in the molten metal therein, the Crucible having `an inlet opening above its bottom and a discharge opening below the inlet opening, a discharge tube communi- Icating with the discharge opening and extending upward therefrom to a level above the level of lmolten metal in the chamber `and discharging outside of the chamber, means deiining a passage communicating with the inlet opening and extending downward therefrom into the molten metal in the chamber, connections from the upper part of the Crucible to sources of two different fluid pressures, one pressure being `suii'icient to reduce the level of molten metal in the Crucible to substantially the level of the inlet opening `and the other being sufficient to force molten metal out the discharge tube Without being suicient to force the metal level below the bottom of said passage, and control means to `vent the Crucible or to connect it selectively to said sources.

7. Furnace ladling apparatus comprising a furnace body dening a chamber to hold molten metal, Ia Crucible extending down into the chamber to be partially immersed in the molten metal therein, the Crucible having an opening in its bottom Iand a discharge opening near its bottom, a discharge tube Communicating with the discharge opening and extending upward therefrom to `a level above the level of molten metal in the chamber and discharging outside of the chamber, a tube communicating `with the inlet opening and extending upward therefrom in the Crucible and terminating in an inlet opening -at a level below `the normal level of lmolten metal in the chamber, a second tube communicating with the inlet opening and projecting downward therefrom into the chamber, connections from the upper part of the Crucible to sources of two different iiuid pressures, one pressure being suf- `iicient to reduce the level of molten metal in the Crucible to substantially the level of the inlet opening and the other being sufficient to force molten metal out the dis charge tube without being sufiicient to force the metal level below the bottom of the last named tube, valves for venting the Crucible and for Connecting it selectively to said sources, and a cyclic Controller for the valves operating through `a cycle in which the valves iirst vent the Crucible, second connect the Crucible to the source of said one pressure, and third connect the Crucible to the source of said other pressure.

References Cited in the file of this patent UNITED STATES PATENTS 328,570 Damm Oct. 20, 1885 1,634,482 Youtsey July 5, 1927 1,672,728 Otis June 5, 1928 2,774,122 Hodler Dec. 18, 1956 FOREIGN PATENTS 430,373 Germany .lune l5, 1926 571,806 Germany IMar. 6, 1933 583,338 Germany Sept. 1, 1933 687,011 Germany Ian. 20, 1940

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