US3221379A

US3221379A - Furnaces

Info

Publication number: US3221379A
Application number: US173293A
Authority: US
Inventors: Wilbur E Shearman
Original assignee: Ajax Magnethermic Corp
Current assignee: Park Ohio Holdings Inc
Priority date: 1962-02-14
Filing date: 1962-02-14
Publication date: 1965-12-07
Anticipated expiration: 1982-12-07
Also published as: GB1029622A

Description

Dec. 7, 1965 w. E. SHEARMAN 3,221,379

FURNACES Filed Feb. 14, 1962 5 Sheets-Sheet 1 I NVENTOR.

m I! Ni} BY Dec. 7, 1965 w. E. SHEARMAN FURNACES 3 Sheets-Sheet 2 5O POURS INVENTOR.

Filed Feb. 14, 1962 United States Patent 3,221,379 FURNACES Wilbur E. Shear-man, Yardley, Pa., assignor to Ajax Magnethermic Corporation, Youngstown, Ohio, a corporation of Ghio Filed Feb. 14, 1962, Ser. No. 173,293 Claims. (CI. 22-69) My invention relates to pressure pouring furnaces for molten metal and relates more particularly to refill means adapted to permit the furnace to be replenished with mol ten metal without interruption of the pour cycle.

Among the objects of my invention is to provide refill means of the type described which will permit uninterrupted accurate pouring of molten metal;

A further object is to control the rate at which the furnace is recharged;

A further object of my invention is to provide means for refilling a pressure pouring furnace with molten metal while maintaining predetermined pressures or pressure cycles for the molten metal in the container during refill;

Another object of my invention is to provide a refill chamber wherein the use of a door seal at the refill or charging opening may be eliminated;

A further object of my invention is to provide refill means for molten metal so disposed with respect to the discharge or pouring tube that, in the event the minimum metal level in the hearth be exceeded for any reason, pressure will escape through the said refill means rather than through the pour means, to avoid danger to the casting machine operator;

Still further object is to provide refill means for molten metal which will not overflow, a maximum refill level being provided therein;

Another object of my invention is to provide in a pres sure pouring furnace of the character described, means whereby, upon the application of pressure to the molten metal in the hearth, the level of molten metal in both the pouring tube and refill chamber will rise, but wherein level fluctuations within the refill chamber are minimized;

Another object of my invention is to provide refill means adapted for use in furnaces where relatively high pressures are exerted on the molten metal to effect the pour;

Still a further object of my invention is to increase the output of a pressure pouring furnace for a given time by eliminating a loss of time for replenishing the molten metal in the hearth, maintaining thermal balance in the mold and avoiding faults in the castings;

A further object of my invention is to provide in a furnace of the type described a relatively rapid refill or replenishing of molten metal within the hearth;

A further object of my invention is to provide refill means of minimum height to facilitate the refilling of the hearth;

A still further object of my invention is to provide refill means for a pressure pouring furnace which is relatively simple in manufacture and which eliminates the necessity of additional holding furnaces, heaters therefor, etc., in conjunction with such pouring furnace, effecting savings in space, cost, and which is highly efficient in use achieving a relatively high production rate.

These and other objects of the invention will become more readily apparent by reference to the accompanying drawing, and appended description, in which drawing;

FIG. 1 is a sectional view of the furnace taken on line 1--1 of FIG. 3;

FIG. 2 is an end elevational view of the furnace of FIG. 1 showing in dotted lines the hearth, refill means, etc., positioned with relation to the pour tube thereof;

FIG. 3 is a top plan view of the furnace of FIG. 1,

3,221,379 Patented Dec. 7, 1965 portions being shown in dotted lines to clarify the showing thereof;

FIG. 4 is a graph illustrating the relation of metal levels in the furnace hearth and refill chamber during operation, the same having as the abscissa the pours and as the ordinate the metal levels in inches, the refill tube 18 being shown in vertical relation to the levels illustrated; and

FIG. 5 is a transverse sectional view of a tilting furnace, showing a further embodiment of my invention.

Referring more particularly to the drawings, in all of which like parts are designated by like reference characters, and referring more particularly to the form of my invention illustrated in FIGS. 1 to 3 inclusive, at 10 I show a pressure pouring furnace capable of maintaining a bath of molten metal 11 at the proper temperature. The normal maximum level of the molten metal is indicated at A and the normal minimum level is indicated at A. The furnace is provided with means for heating the molten metal, for instance, with an induction coil 12 that induces heat in the

melting channels

13, 14 and 15. The furnace is further preferably provided with automatic temperature control equipment and level sensing devices (not shown in the drawings).

The induction furnace 10 illustrated herein is of the single chamber stationary type having a cover 16 secured thereto, said cover having in the form shown a generally funnel-shaped opening 17 therein in which a charging chamber or refill tube 18 is seated, as hereinafter described.

The location of the refill tube may be varied, being disposed at any point within the furnace convenient for the refilling operation. The furnace is further provided with discharge means generally indicated at 20, and best Shown in FIG. 1. The furnace has a lateral recess or pocket 21 in one of its side walls adjacent the lowermost hearth bottom and the recess 21 is open toward its exterior at an opening 22. A cover 23 is removably mounted to said side to cover the opening 22. Said cover is provided with a metallic shell or closure 25 having on its interior a refractory lining 26, apertured axially and having seated in said aperture a discharge conduit 27.

The conduit 27 shown in FIG. 1 is disposed for the pouring or discharge of molten metal from the furnace at an incline to said furnace and communicates with the molten metal in said hearth adjacent the bottom thereof; the conduit -is preferably cylindrical in form and formed of high heat conductivity, such as silicon nitride bonded silicon carbide material, and is provided preferably with a tubular body portion of substantially uniform crosssectional diameter throughout having a restricted orifice or constriction 32 at the entrance thereof. The orifice 32 disposed in said discharge conduit is located below the minimum molten metal level in the furnace, as described in US. Letters Patent No. 2,646,740, for the purpose of throttling the molten metal forced into the conduit by pressure means, such as air or gas, exerted on the molten metal contained in the hearth. An electric heater coil 29 is preferably provided to prevent freezing of the molten metal while flowing through tube 27.

Mounted, in the form herein shown in FIGS. 1 to 3 inclusively, centrally of the furnace and depending from the upper cover 16 thereof, as related hereinbefore, is a preferably cylindrical refill chamber or tube 18 preferably provided with a funnel-shaped open upper portion 28 at its upper end, said upper portion 28 being in secure engagement within the funnel-shaped opening 17 in the cover 16, thereby forming an airtight seal therewith. The tube 18 is provided with a restricted orifice '40 adjacent its lowermost end which acts as a control for the rise and fall of metal in said tube. The said refill means is of such length and so disposed as to extend into the hearth sufliciently to have its orifice opening disposed below the determined minimum level A of the molten metal in the hearth. In the form shown in FIGS. 1 to 3, the said opening is disposed above the level of the restricted orifice 32 of the discharge conduit 27, the tube 18 adapted to be of such height as to extend sufficiently above the maximum level A of the said molten metal in the furnace to permit refilling of the furnace or molten metal container with molten metal at a desired rate while maintaining the predetermined pressure or pressure cycle for the molten metal therein whereby over-flow may be prevented. It should be noted that a maximum refill level of the molten metal in the refill tube 18 is indicated at D in FIGS. 1 and 4. In FIG. 4, which illustrates a specific operating condition, I have designated at B and B the pressure head levels in the refill tube 18 above the levels A and A, respectively, in the hearth, which are equivalent to the pouring pressures without consideration to other control criteria such as, e.g., the dimensions of the refill tube, the size of the discharge orifice, etc. The level C indicates the actual level of molten metal in the refill tube 18 when the level of molten metal in the hearth is at the minimum level -A' and pressure is applied thereto. The level C indicates the level of the molten metal in the refill tube when the level of molten metal in the hearth is at A and the same pressure is applied thereto. It will be understood that as the molten metal level in the hearth fluctuates between A and A the molten metal level in the refill tube '18 will fluctuate between C and C and the pattern of said fluctuations will be determined by the pressure, ratio of pressure time to cycle time, and the size of the orifice opening 40 in said refill tube. In the form shown, the control criteria are such that the actual level C-C of molten metal in the refill tube, never closely approaches the pressure head levels "B-B. FIG. 4 illustrates a pattern of fluctuation in the refill tube level at C-C under certain conditions but it will be obvious that the pattern will vary under different operating conditions.

Molten metal is discharged from the furnace upwardly through the discharge conduit 27 by means of a pressure source (not shown), the pressurized gas entering through tube '50, solenoid valve 52,, chamber 54 and opening 56 in an end wall of the furnace into the hearth above the level of the molten metal therein. Solenoid valve 52 controls the flow of pressurized gas in a conventional manner, whereby the pressurized gas is admitted to or withheld from the hearth of the furnace. The amount of gas pressure applied or the time period during which the pressure is applied varies according to the amount desired in each pour, the level of the molten metal in the hearth, etc., and various well known control mechanisms could be employed to accurately regulate the application of pressure to the hearth above the level of the molten metal. One well known method for compensating for the resulting decrease in the level of molten metal is to employ a level sensing mechanism, e.g., a float, which in turn regulates a timer to increase the time during which the pressure is applied. Another method of compensating for a decrease in molten metal level is to employ a level sensing float which functions to actuate a control mechanism for increasing the pressure applied to the hearth to discharge the molten metal. The specific manner in which the application of pressure is controlled does not form part of this invention, and therefore a detailed description thereof is deemed unnecessary.

As pressure is applied to the hearth above the level of the molten metal, the level of molten metal in both the refill tube *18 and the discharge conduit 27 will rise due to the fact that both of said tubes are open to atmosphere at their upper ends and the otherwise complete sealing of the hearth. The discharge end of the pour tube in the FIG. 1 embodiment is at a lower level relative to the level of the upper end of the refill tube whereby the molten metal will flow upwardly through and outwardly from the discharge conduit to make the desired pour. During the application of pressure, the level of the molten metal in the refill chamber will rise, and if the time during which the pressure is applied is sufficiently long, the level could attain the pressure head, e.g., at or between the illustrated levels B or B, depending on the level of molten metal in the hearth. However, in the form shown, the pour time is relatively short, e.g., between one and five seconds, and during such relatively short time the level in the refill tube will not closely approach the maximum level of the pressure head.

The restricted orifice 40 of the refill tube, formed in the bottom wall 41 thereof assists in limiting or controlling the rate at which the molten metal can rise in the refill tube. The restricted orifice 40 acts to minimize the fluctuations in the level of metal in the refill tube and permits the use of refill tubes of practical dimensions and avoids the necessity of having the refill tube excessively high and positioned above the furnace. The size of such orifice is adapted to be of varied dimensions, being of substantially lesser cross-sectional area than the crosssectional area of the refill tube, and its dimensions are determined by the type of metal, size of castings, fre quency of pour, pressure exerted, etc. The restriction achieved by the orifice 40 could also be achieved by the provision of a plurality of orifices in said tube (not shown) which however have a total cross-sectional area substantially less than the average cross-sectional area of the tube or conduit 18.

When the pouring pressure is removed, thus stopping the pour, the level of molten metal in the refill tube 18 will recede, and if the time period between pours is sufficiently long, the level will eventually assume the level of the molten metal in the hearth, e.g. at or between A and A. Generally, however, the time interval between pours is relatively short, e.g. from five to ten seconds, and the level of the molten metal in the refill tube 18 Will never in such cases recede to the level of the molten metal in the hearth, primarily due to the restricted flow rate caused by the restricted orifice 40.

Referring now to the manner in which the furnace is refilled through the refill tube 18, the refill tube 18 can be filled at any time during the pouring cycle, i.e. whether or not pouring pressure is being applied at the time of refill. To obtain an adequate refill rate, -a sufficient height of the refill tube must be provided to prevent the overflow of the molten metal from the top of the refill tube. Thus, if the refill tube 18 is filled during the time interval between pours, the maximum refill level must be a sutficient distance from the top of the refill tube to accommodate a rise of molten metal in the refill tube resulting from the subsequent application of pouring pressure.

The orifice 40 limits the rate at which the furnace can be refilled, and to obtain faster refill flow and greater refill rates a larger orifice or higher refill tube, or both, could be employed. In this connection, reference should be made to FIG. 4 wherein the level in the refill tube is ghciswn at C-C' and lies between the level A-A' and The specific size of the refill tube 18 can be varied, within limitations, such limitations being necessary to avoid solidification and excessive level variations in the main hearth. The refill tube in FIG. 1 is shown spaced from the walls of the furnace and a refill tube of relatively large cross-sectional area is employed. This is one method of accomplishing the desired results and is preferred from the standpoint of temperature stability, the molten metal into which the tube is disposed and the heat conducting material of the tube 18 contributing to such stability.

It should be noted that in the FIG. 1 embodiment, the lower end of the refill tube 18 is preferably positioned above the lower end of the pour tube 27 for safety purposes. If the level of the molten metal in the hearth recedes to a level below the minimum operating level A for any reason, pressure in such case will be caused to escape through the higher opening, or the restricted opening 40 in the refill tube. This escape of pressure carries molten metal with it whereby the molten metal is directed upward, rather than outward, as would be the case if orifice 32 of discharge conduit were located above the restricted orifice 40. Thus, there is much less danger to the casting machine operator.

Referring now to FIG. 4, as hereinbefore described, there is therein graphically illustrated the changing refill tube level under certain specific conditions during the pouring cycle, beginning with an idle, filled hearth. The ordinate of the graph indicates the metal level in inches, the zero or central point on the ordinate axis being equal to the level of the molten metal in the hearth, when said hearth is in a filled condition. The abscissa indicates the number of pours made during the operation of the furnace. As used in FIG. 1, the letters A, A, and B, B' are used in FIG. 4 to represent the minimum and maximum equivalent pressure head levels. The jagged line CC' in FIG. 4 represents the actual refill tube level during operation. The tube 18 is shown in dotted lines at E.

It will be seen that when the furnace is idle and the hearth is filled with molten metal to level A, prior to the pouring operation, the refill tube level is also at level A. As the pouring cycle begins, the level of molten metal in the refill tube gradually builds up over the first few pours and gradually levels off at a level between the hearth level A and the pressure head level B. The levelling off will occur when the reflow rate and time balance the rate at which metal is forced into the refill tube during the pour cycle. As the pours continue, and assuming a constant production rate, the actual level in the refill tube will oscillate, as shown by the jagged line C-C, the level decreasing as the hearth level decreases.

When the molten metal in the hearth reaches the minimum operating level A, reached in the graphic representation in FIG. 4 after the twenty-fourth pour, the hearth is preferably refilled through the refill tube at a predetermined rate. Since the furnace is discharging continually during the refilling, the maximum refill level D will not be reached until a time period equal to several pours has passed. When the maximum refill level A of molten metal in the furnace is again attained, refilling is caused to cease thereupon, as shown, the refill tube level gradually levels off and assumes an oscillating level wherein the flow of molten metal to the hearth is balanced by the rate at which the molten metal is forced into the chamber during the pour cycle, said level varying as the hearth level varies.

It should be noted that the FIG. 4 graph shoWs the level of the molten metal in the refill tube as oscillating only a relatively slight amount between the pressure head level B and the hearth level A, a condition indicative of a relatively short period and a relatively short interval between pours. As pointed out above, where the pour period is increased, the refill tube level will more closely approach the level B, and where the time interval between pours is increased, the refill tube level will more closely approach level A.

It should be further noted that although FIG. 4 shows the refilling process subsequent to the molten metal in the hearth reaching level A, it will be understood, as pointed out above, that the refilling can be performed at any time regardless of level of molten metal in the hearth.

In the form of my invention disclosed in FIG. 5, I have shown a tilting furnace preferably of the type generally shown and specifically described in US. application Serial No. 138,802, filed September 18, 1961, the inventor of the instant application being a co-inventor of the application referred to. The tilting furnace comprises a single chamber induction furnace 60 open at the top 61 and having a cover 62 to close the top reasonably airtight. Pressure is applied to the hearth through pipe in a conventional manner. The furnace 60 is provided with a discharge device generally indicated at 63 generally shown at one side of the furnace termed the for- Ward side and a charging chamber or refill tube 64 at an opposite side of the furnace termed the fill side. It will be understood that in this form of my invention the refill tube is not located at or near the axis of tilt, although this is sometimes preferred, as where runners are employed from a molten metal supply to the fill tube. It will be further noted that in the furnace shown in FIG. 5 the fill tube 64, similarly to the fill tube 18 in the FIG. 1 embodiment is provided with a generally funnel-shaped upper portion 65 and with a restricted orifice 66. It will be further noted that the discharge tube 67 of the FIG. 5 embodiment is inclined in the manner similar to discharge tube 27 of the FIG. 1 embodiment and is preferably provided with a restriction 68. However, in this form of my invention the lower end of the refill tube is positioned below the orifice 68 or inlet opening of the discharge tube and is angled with respect to the chamber. It is preferably disposed in the container at a point of minimum motion. In a manner more fully described in the above application, the furnace 60 is adapted to be tilted about a horizontal tilt axis (not shown) whereby the discharge orifice of discharge device 63 can be maintained at a predetermined spaced relation With molds movable therebelow. It will thus be understood that the minimum level line A shown as an inclined line in FIG. 5 will in reality be horizontal when the furnace is in a tilted position.

The improved fill tube of my invention, although described in connection with a stationary furnace, also could be employed in an oscillating furnace or other type furnace, and when so employed, it would be desirable to locate the same at its center of oscillation.

The graph representation of FIG. 4 with respect to maximum and minimum levels in the hearth and in the refill tube applies in principle to the form of my invention illustrated in FIG. 5, it being understood that the hearth level showing applies to the level of the molten metal in the vicinity of the refill tube.

The operation of the illustrated furnaces employing my novel refill tube or chamber should be apparent from the above description but will be briefly redescribed for purposes of clarity.

The hearth of the furnace is filled through the refill tube 18 or tube 64 in the FIG. 5 embodiment, to the maximum level A. Upon initiation of the pouring operation, molten metal is discharged through the discharge conduit 30 or tube 67, FIG. 5, upon the application of pressure to the area in the hearth above the level of the molten metal, said pressure simultaneously causing the molten metal to rise in the refill tube to a level not exceeding D. The cessation of pressure will cause molten metal to return to the hearth from the refill tube.

As the level of molten metal in the hearth recedes during the pouring operation, said hearth can be refilled at any time and in any amount through the

refill tubes

18 or 64, FIG. 5.

It will be apparent to those skilled in the art that various changes might be made in the disclosed invention without departing from the spirit thereof.

What I claim as my invention is:

1. A single chamber apparatus for holding and intermittently and pneumatically dispensing molten metal comprising in combination an essentially pneumatically sealed single chamber container, a molten metal discharging conduit communicating with the exterior and interior of said container in gas tight sealed relationship with said container, an inlet opening of said discharge conduit communicating with the interior of said chamber at a level below the minimum surface level of molten metal in said container, an outlet opening in said discharge conduit disposed exteriorally of said container and at a level above the maximum surface level of molten metal within said container, a refill tube disposed substantially Within said container for supplying molten metal thereto, said refill tube having a restricted orifice therein communicating with the interior of said chamber at a level below the minimum surface level of molten metal in said container, said restricted orifice being of substantially lesser cross-sectional area than the cross-sectional area of the refill tube and sufiiciently small to substantially limit and control the rate at which molten metal can pass therethrough, said refill tube passing through said chamber in airtight sealed relationship with said chamber and having a second opening communicating with the exterior of said chamber for receiving molten metal to charge and refill said apparatus, said second opening being disposed at a level above the outlet opening in said discharge conduit and above the maximum surface level of molten metal in said container, pressure means for intermittently applying pressure on said molten metal in the container; Whereby the container may be refilled without interrupting the maintaining of a predetermined pressure cycle in said container.

2. An apparatus as claimed in claim 1, the said refill tube extending to such determinate height above the surface of the molten metal as to prevent overflow of molten metal therefrom during simultaneous filling of the container and pressure application.

3. An apparatus as claimed in claim 1, said fill tube being of substantially greater length than the diameter thereof.

4. An apparatus as claimed in claim 1, the container being tiltable.

5. An apparatus as claimed in claim 1, the container being tiltable and the refill tube being disposed at an acute angle to the vertical axis of the container.

References Cited by the Examiner UNITED STATES PATENTS 1,972,684 9/1934 Jacobson 2279 XR 1,972,710 9/ 1934 Jacobson 2279 XR 2,674,640 4/1954 Tarna 2279 XR 2,756,988 7/1956 Tama 2279 XR 2,816,334 12/1957 Edstrand 22--79 2,821,378 1/1958 Tarna 2279 XR 2,846,740 8/ 1958 Edstrand 2269 XR 2,936,326 5/1960 Tarna 2269 XR FOREIGN PATENTS 803,343 10/1958 Great Britain. 837,867 6/1960 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, MICHAEL V. BRINDISI,

Examiners.

Claims

1. A SINGLE CHAMBER APPARATUS FOR HOLDING AND INTERMITTENTLY AND PNEUMATICALLY DISPENSING MOLTEN METAL COMPRISING IN COMBINATION AN ESSENTIALLY PNEUMATICALLY SEALED SINGLE CHAMBER CONTAINER, A MOLTEN METAL DISCHARGING CONDUIT COMMUNICATING WITH THE EXTERIOR AND EXTERIOR OF SAID CONTAINER IN GAS TIGHT SEALED RELATIONSHIP WITH SAID CONTAINER, AN INLET OPENING OF SAID DISCHARGE CONDUIT COMMUNICATING WITH THE INTERIOR OF SAID CHAMBER AT A LEVEL BELOW THE MINIMUM SURFACE LEVEL OF MOLTEN METAL IN SAID CONTAINER, AN OUTLET OPENING IN SAID DISCHARGE CONDUIT DISPOSED EXTERIORALLY OF SAID CONTAINER AND AT A LEVEL ABOVE THE MAXIMUM SURFACE LEVEL OF MOLTEN METAL WITHIN SAID CONTAINER, A REFILL TUBE DISPOSED SUBSTANTIALLY WITHIN SAID CONTAINER FOR SUPPLYING MOLTEN METAL THERETO, SAID REFILL TUBE HAVING A RESTRICTED ORIFICE THEREIN COMMUNICATING WITH THE INTERIOR OF SAID CHAMBER AT A LEVEL BELOW THE MINIMUM SURFACE LEVEL OF MOLTEN METAL IN SAID CONTAINER, SAID RESTRICTED ORIFICE BEING OF SUBSTANTIALLY LESSER CROSS-SECTIONAL AREA THAN THE CROSS-SECTIONAL AREA OF THE REFILL TUBE AND SUFFICIENTLY SMALL TO SUBSTANTIALLY LIMIT AND CONTROL THE RATE AT WHICH MOLTEN METAL CAN PASS THERETHROUGH, SAID REFILL TUBE PASSING THROUGH SAID CHAMBER IN AIRTIGHT SEALED RELATIONSHIP WITH SAID CHAMBER AND HAVING A SECOND OPENING COMMUNICATING WITH THE EXTERIOR OF SAID CHAMBER FOR RECEIVING MOLTEN METAL TO CHARGE AND REFILL SAID APPARATUS, SAID SECOND OPENING BEING DISPOSED AT A LEVEL ABOVE THE OUTLET OPENING IN SAID DISCHARGE CONDUIT AND ABOVE THE MAXIMUM SURFACE LEVEL OF MOLTEN METAL IN SAID CONTAINER, PRESSURE MEANS FOR INTERMITTENTLY APPLYING PRESSURE ON SAID MOLTEN METAL IN THE CONTAINER; WHEREBY THE CONTAINER MAY BE REFILLED WITHOUT INTERRUPTING THE MAINTAINING OF A PREDETERMINED PRESSURE CYCLE IN SAID CONTAINER.