US3663730A

US3663730A - Molten metal dispensing equipment

Info

Publication number: US3663730A
Application number: US125499A
Authority: US
Inventors: Wilbur C Gates
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-03-18
Filing date: 1971-03-18
Publication date: 1972-05-16
Anticipated expiration: 1989-05-16
Also published as: NL7203259A; DE2212652A1; FR2130356A1; BE780857A; JPS5037023B1

Abstract

An apparatus is disclosed which automatically dispenses a metered quantity of molten metal from a reservoir of the particular metal and which is particularly suitable for automated casting operations such as ferrous die casting. The apparatus employs an induction heating coil to raise the level of molten metal in the reservoir whereupon the molten metal is poured into a dispensing chamber and thereafter discharged to a mold or other forming equipment.

Description

United States Patent [151 3,663,730

Gates [451 May16 1972 [541 MOLTEN METAL DISPENSING 3,581,040 5/1971 Halley ..219/7.5

EQUIPMENT Primary Examiner-Bemard A. Gilheany [72] Inventor: Wilbur C. Gates, Mentor, Ohio Assistant Examiner-R. N. Envall, Jr.

Attorney-John F. McDevitt, Henry P. Truesdell, Frank L.

[73] Assignee: General Electric Company Neuhauser, Oscar B. Waddell and Joseph B. Fonnan 22 Filed: Mar. 18, 1971 21 Appl.No.: 125,499 [57] ABSTRACT An apparatus is disclosed which automatically dispenses a me- [52] US. Cl ..13/33, 13/27, 219/7.5, tered quantity f molten meta] f a rv ir of the particu- 222/ 1, 222/25] lar metal and which is particularly suitable for automated cast- [51] Int. Cl. ..H05b 9/02, F27d 3/ 12 i operations h as f rrous die casting. The apparatus em- Field Of ar 1 3/27, 33; 219/75; 222/146 R, ploys an induction heating coil to raise the level of molten 2 2/1 1 v 1 metal in the reservoir whereupon the molten metal is poured into a dispensing chamber and thereafter discharged to a mold [56] References Cited or other forming equipment.

UNITED STATES PATENTS 8 Claims, 2 Drawing Figures 3,534,886 10/1970 Von Starck ..13/33 X Patented May 16, 1972 3,663,730

2 Sheets-Sheet 1 lnven tor: LbUT C. Gates Q (Q a-Q -"His At torneg BACKGROUND OF THE INVENTION Induction heating has been used to melt electrically conductive metals which aregenerally confined in a crucible or other container means located within the turns of an induction heating coil. The container material will generally be a refractory oxide or some other ceramic material which does not react deleteriously with the molten metal in order to avoid contamination of the finished product. It is also known to melt conductive metals by induction heating means wherein a plurality of induction coils is employed aligned along a vertical axis and having a space therebetween in which a mass of the conductive metal is suspended during melting and the use of a container to confine the metal is avoided. The strength of a magnetic field needed to suspend the conductive metal in the latter summarized method has so far been found to advise against its widespread commercial acceptance.

The present day method of die casting metals, such as aluminum, magnesium, copper and iron, and alloys thereof dispenses molten metal to a die casting machine by manual means from a ladle and results in frequent spillage as well as lack of uniform pours. The frequency of dispensing cycles to a die casting machine also varies with hand ladling which can adversely affect quality of the finished product. It would also be in the interest of safety to avoid human handling of molten metal in favor of automatically dispensing the metal to the forming equipment.

SUMMARY OF THE INVENTION The present invention provides an apparatus which automatically dispenses metered quantities of a molten metal from a reservoir heated by induction furnace means and which can include means to recharge the raw material to the reservoir while the furnace is in operation. The reservoir islocated within the turns of an induction heating coil so that a magnetic field from said coil raises the level of molten metal from the nominal operating level when additional electrical power is applied to the induction coil in order to pour the molten metal into a dispensing chamber which is in communication with the reservoir. Discharge means are provided to dispense the molten metal from the apparatus when the dispensing chamber has been filled with molten metal. Conventional induction heating means are employed in the apparatus having enough excess power capacity above that needed to melt the quantity of conductive metal in the reservoir in order to generate the magnetic field employed in pouring the molten metal into the dispensing chamber.

In apreferred embodiment of the invention, the apparatus comprises a cast zirconia container disposed within the turns of an induction coil helix which is aligned in a substantially vertical direction with said refractory container having disposed therein a zirconia dispensing tube aligned along the central vertical axis of the heating coil and thereby concentrically oriented with respect to the container member. The length of the dispensing tube is selected so that its upper end is above the normal operating level of molten metal in the container and said tube has an orifice opening at its lower end which is fitted with a retractable plug-rod of refractory material in order to discharge the molten metal after the tube has been filled.

' In a different preferred embodiment of the invention, the apparatus can include automatic level measurement of molten metal in the reservoir means as well as means to withdraw the dispensing chamber from the apparatus as a means of emptying the reservoir when it is desired to interrupt furnace operation. More particularly, it is beneficial to have automatic sensing means in the apparatus for determining the normal level of molten metal in the reservoir means and thereby be certain at all times that enough metal is available to entirely fill the dispensing chamber and discharge a metered quantity of metal. While such a determination could be made visually by locating an observation window which leads to the molten metal reservoir, it is still preferable to do so automatically in keeping with fully automated operation of the apparatus. And while it is also recognized that fully automatic operation can be obtained by simply sizing the reservoir capacity to handle a given number of discharges followed by refilling the reservoir and repeating the discharge cycle, it is still considered preferable to have automatic level sensing means in the apparatus for greater reliability of operation. The additionally provided means of removing the dispensing chamber prior to solidification of molten metal in the reservoir permits reuse of the components during subsequent operation.

DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Thepresent invention. provides an apparatus from which molten metal can be dispensed to a variety of forming equipment, including molds, a die casting machine, or forming rolls such that a metered quantity of the molten metal is discharged with each release of molten metal from the apparatus. In so doing the various forms of unreliability associated with manual pouring of metal from a ladle are avoided and it becomes further possible to control the pouring operation by automatic process control techniques. The present apparatus is particularly suitable for die casting of ferrous metals which, by reason of the extremely elevated temperatures at which such metals are poured, encounter a number of serious difficulties due to corrosive and thermal attack upon the-materials which are used for transfer of liquid metal from the melting furnace to the die. In order to minimize the above-mentioned problems and still others associated with casting molten metal, especially ferrous metals, an apparatus has been discovered which does not depend upon the efficiency or dexterity of a human operator to pour the metal by hand.

In FIG. 1 there is a vertical section of the apparatus which includes induction heated furnace means to melt a reservoir quantity of metal confined in a crucible-shaped container having means to discharge the molten metal therefrom to remotely located forming equipment. The dispensing chamber means from which molten metal is discharged is centrally located in the crucible member so that when molten metal is raised in said container under the influence of an increased magnetic field produced with the heating coil there will be a uniform overflow of metal to said dispensing means. Central location of the dispensing means with respect to the reservoir further provides a uniform temperature in the'molten metal contents throughout the pouring operation. Accordingly, the molten metal dispensing apparatus 10 depicted in the preferred embodiment is constructed with an external housing 12 which is in the form of a closed vertical cylinder having a removable top section 14 and a bottom section 16 which includes a centrally disposed exit aperture 18 from the apparatus. Top sec tion 14 is removably attached to the external housing to facilitate an access to the reservoir cavity in the apparatus for repair or replacement of the component parts located therein. The external housing is fabricated from a non-metallic refractory material such as asbestos by reason of being in close proximity to the induction coil which produces undesirable coupling if a metal or other receptive material is employed. On the other hand, it will be appreciated that a metal housing can be employed if located at a greater distance from the coil or else shielded by a barrier to the induction field. A cast zirconia crucible member 20 is disposed concentrically within said external housing and is aligned along the central vertical axis of the apparatus so that an annular space 22 exists between the inner wall of the external housing and the exterior wall of the crucible member. The annular space can be occupied by an inert gas which precludes contamination of the molten metal by the surrounding atmosphere. A conventional water-cooled induction heating coil 24 is embedded in the outer wall 5 of crucible member 20 to provide optimum heating efficiency of the furnace contents and with said coil being aligned concentrically with the central vertical axis. Electrical power leads 26 and 27 are connected to the heating coil from a high-frequency generator 28 having a sufficient electrical capacity to raise the normal level of the metal charge in the crucible member to a height which overflows metal into the dispensing means of the apparatus in accordance with practice of the present invention. Power control means are operatively associated with the high-frequency generator 28 to vary the electrical power applied to the heating coil and said control means can consist of conventional resistance circuit means 29 such as a rheostat-type control shown simply in block diagram form in FIG. 1.

Crucible member 20 in the apparatus includes a removable top section 30 and a central body portion 30 which rests upon bottom section 16 of external housing 12. A central opening 32 in the base of member 30' accommodates a bushing 33 which is fabricated of refractory material and forms a support for the dispensing means employed to discharge molten metal from the apparatus. Said bushing further includes a valve-type seating feature to be more fully described presently in connection with the dispensing means of the apparatus. Refractory tube member 34 is mounted upon upper shoulder 31 of bushing 33 to form a seal precluding flow of molten metal from the crucible member except upon actuation of a refractory plugrod 36 which interfaces with the seat element provided in the refractory bushing. The means for dispensing molten metal from the apparatus includes a refractory tube 34 having an upper end 38 for entry of molten metal from the crucible member 20 and a lower end 40 which terminates with an orifice opening 42. The tip of refractory plug-rod 36 closes the orifice opening by engagement with a mating seat in bushing 33 until the rod has been withdrawn upwardly. Annular space 44 existing between the outer surface of the refractory plugrod and the inner diameter of refractory tube 34 defines the metered volume of molten metal which is discharged from the apparatus when the tip 46 of said rod is unseated from the mating surface 48in the bushing. The movable plug-rod is withdrawn vertically by means of an operatively associated air cylinder assembly 50 connected at the upper end of said rod by conventional lifting means 52 and which further includes weight member 54 to exert a downward mechanical force upon the plug-rod that precludes inadvertent discharge of molten metal from the apparatus. Weight member 54 slidably engages sleeve 56 which is secured in top cover 14 of the external housing. Top section 30 of the crucible member is urged in physical contact with the upper lip of the crucible body 30 by tightening of thread screw elements 58 which act upon an O-ring seal 60. Also located in the top cover 14 of the apparatus is a charging port 62 for adding the solid metal to be melted directly to the crucible cavity while the furnace is in operation and which port is kept closed when raw material is not being added by means of a port cover 64 having a sight glass opening 66 therethrough for visual observation of the liquid level in the crucible cavity. As was earlier pointed out, the sealing of the crucible cavity from any admission of the ambient atmosphere precludes contamination of the molten metal from oxidation effects which could have an adverse impact upon purity of the final metal product. The charging port component can be secured by conventional means to top cover 14 or be fastened to an opening therein to top section 30 in the crucible member. A further penetration is made through top cover 14 and top section 30 of the crucible member in the form of inert gas means 68 which can consist of an inlet pipe 70 leading to the crucible cavity from a source of the particular gas employed (not shown). The gas is admitted under positive pressure in excess of ambient pressure and operates as a seal against entry of the atmosphere through other openings in the apparatus.

In operation, a charge of the solid metal to be melted is placed in the crucible cavity 72 and heated by application of electrical power to the induction coil which is located at the outer wall of said member. To provide a better grasp of the operation for this apparatus with an actual ferrous metal, it has been possible to charge a zirconia crucible member having an inside diameter of 10% inches and a depth of 12 inches with a 100 pound charge of steel particles which were rapidly and uniformly melted in approximately 30 minutes by application of approximately 25-30 kw to the induction coil supplied from a 100 kw high-frequency generator. Upon melting of the ferrous metal charge, the electrical power supplied to the induction coil was raised to the approximately 100 kw level whereupon a mixing action took place in the molten metal and the height of the liquid level raised to a point at which liquid level overflowed the entrance end of the zirconia dispensing tube 34. By having the central longitudinal axis of said dispensing tube aligned along the central vertical axis of the apparatus, it was possible to quickly fill the entire available annular free space 44 in said dispensing tube with molten metal as well as maintain the temperature in the metered quantity of metal in said tube at the same temperature as the molten metal in the crucible cavity until discharged from the apparatus. The electrical power supply to the induction coil is lowered after the dispensing tube is filled to a level sufiicient for maintaining the main bath of metal in the crucible in a molten condition. By selecting zirconia material for construction of the crucible container as well as the dispensing chamber means in the above-described apparatus, there can be obtained an operational advantage due to non-wetting of said ceramic material by the molten steel. More particularly, the surface tension forces existing at the interface of molten metal with the orifice opening in the dispensing means will be sufficient so long as wetting does not take place to help preclude leakage of molten metal from the apparatus. Additional surface tension forces existing at the interface between the upper end of the refractory dispensing tube and the operating level of molten metal in the crucible cavity also help preclude inadvertent overflow of metal into said tube except at the selected time periods when it is desired to discharge molten metal from the apparatus. Said forces also can permit a lesser elevational difference between the upper end of the dispensing tube and the normal operating level of molten metal in the crucible cavity for greater reliability of carrying out the invention.

In a different preferred embodiment of the apparatus depicted by vertical section in FIG. 2, there is included means to automatically measure the level of molten metal in the reservoir as well as means to remove the component parts of the dispensing tube assembly while molten metal remains in said reservoir. Accordingly, the molten metal dispensing apparatus 72 includes an external non-metallic refractory housing 74 having vertical cylinder section 76 enclosed by top cover 78 and bottom cover 80 with all components being held together by long bolts 82 spaced circumferentially around the cover members. Bottom cover 80 includes central opening 84 which provides an exit path for discharge of molten metal from the apparatus. An induction heating coil 86 is disposed within the external housing in the same manner described for the preceding embodiment. Also disposed within the external housing in the same manner previously described is a refractory crucible member 88 having a central cavity 90 which serves as the reservoir means in the apparatus for a charge of metal. The level of molten metal in the apparatus is shown at 92 for purposes of later explaining operation of the automatic level sensing means in the apparatus. The crucible member 88 is provided with a central base opening 94 which is aligned with exit aperture 84 in the bottom cover of the apparatus. A removable top section 96 for the crucible member permits the replacement or removal of component parts contained in the reservoir cavity. A further entrance means 98 leading to the crucible cavity enables recharging of solid metal or molten metal from an auxiliary reservoir to the apparatus along with admission of a reducing or inert gas to preclude contamination of the molten metal from the ambient atmosphere. Said entrance means can be further equipped with a visual observation window 99 to inspect the furnace contents during operation and with close proximity of the purge gas means being of assistance to keep the window clean. An inlet pipe 100 provided for this purpose leads to a supply source for the reducing gas or inert gas which can be employed. Conventional valve closure means 102 are provided at the entrance means 98 used to recharge the reservoir cavity to block out the observation window when not in use.

Top cover member 78 also provides support means for component 'parts of the dispensing means in the apparatus. More particularly, a housing member 104 is secured to said top cover which includes a diaphragm assembly 106 operated by a vacuum source connected at inlet 108 to vertically withdraw plug-rod 110 in said dispensing means when it is desired to discharge molten metal from the apparatus. The plug-rod interfaces with mating surface 112 which is located in bushing member 114 as previously described. A refractory dispensing tube 116 which forms a principal component of the dispensing means is disposed centrally in the crucible cavity and aligned with the base opening in the crucible member. As can be noted from inspection of FIG. 2 of the drawing, said dispensing tube and the operatively associated bushing 114 are fitted into an extension tube member 118 which permits longitudinal adjustment of the dispensing tube for variation in the volume of molten metal being dispensed. By constructing the metal dispensing means of the apparatus in this manner, it also becomes possible to withdraw the entire assembly of dispensing tube 116, bushing 114 and extension tube 118 before the molten metal solidifies in the reservoir cavity when the furnace is being shut down. More particularly, the aforementioned parts of the dispensing means are permitted to float to the surface by reason of being constructed from refractory materials less dense than the molten metal when the force exerted by spring-loaded refractory retaining rods 120 which physically contact the upper end of dispensing tube 116 is removed. Said retaining rod structure consists of a plurality of the rods being equally spaced about the circumference of the dispensing tube member and with the spring-loaded upper ends of said rods being inserted into said removable housing member 104 which is secured to upper cover member 78 in the external housing. Attachment of said housing member 104 to the top cover of the external housing is accomplished by conventional thumb screw elements 124.

The molten metal level sensing means 126 in the apparatus comprises a movable contact electrode 128 which is suspended from cover member 78 in the external housing to cooperate with a fixed electrode 130 by interconnection of electrical circuit means 132. Said electrical circuit means consist of electrical conductors 134 and 136 connecting said electrodes to a voltage source 138 such as ordinary battery means and voltage indicating means 140 being connected in series in the circuit. An open circuit is created in this manner until the circuit is completed through the molten metal in the reservoir cavity by contact of electrode 128 with the top surface of the metal. Lowering of said electrode is obtained by means of an air cylinder 142 to some predetermined elevation and failure to complete the electrical circuit as indicated by the voltage indicating means 140 provides notice that an insufficient level of molten metal remains in the reservoir cavity to fill the dispensing tube 1 16 in accordance with practice of the invention. Said air cylinder is mounted to top cover 78 in the external housing by conventional means and openings in said cover as well as through top section 96 of the crucible member enables actuation of the contact electrode. A conventional power supply and control means for the induction heating coil in this embodiment as was previously described permits fully automatic operation of the equipment.

While preference has been indicated in the foregoing description for particular configurations of the apparatus, it will be apparent that other modifications can be made without departing from the true spirit and scope of the invention. For example, the substitution of a different dispensing chamber configuration or utilization of a plurality of dispensing chamber means in the apparatus to supply a metered quantity of molten metal from the apparatus in the manner above described is contemplated. It is intended to limit the invention, therefore, only to the scope of the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A molten metal dispensing apparatus which comprises,

A. induction heated furnace means having container means for the molten metal disposed within the turns of an induction heating coil,

B. dispensing chamber means disposed within said container means having entrance means above the normal level of molten metal and means to discharge the molten metal from the apparatus, and

C. power control means to vary the electrical power to the induction heating coil whereby the level of molten metal is raised sufficiently for metal to flow into the dispensing chamber.

2. A molten metal dispensing apparatus as in claim 1 which further includes means to provide a protective atmosphere in the molten metal container.

3. A molten metal dispensing apparatus as in claim 1 which further includes means to charge the container while the furnace is in operation.

4. A molten metal dispensing apparatus as in claim 1 wherein the container and dispensing chamber are constructed of a refractory material which does not react deleteriously with the molten metal.

5. A molten metal dispensing apparatus as in claim 1 which further includes means to indicate the level of molten metal in the container.

6. A molten metal dispensing apparatus which comprises,

A. induction heated furnace means having an enclosed container for molten metal disposed within the turns of an induction heating coil,

B. a dispensing chamber of tubular shape disposed centrally within said enclosed container having an open end above the normal level of the molten metal and having an orifice opening at the other end of said tube which can be opened to discharge the molten metal, and

C. power control means to vary the electrical power to the induction heating coil whereby the level of molten metal is raised sufficiently for metal to flow into the dispensing tube.

7. A molten metal dispensing apparatus as in claim 6 having I a retractable plug member seated in the orifice opening of the discharge tube.

8. A molten metal dispensing apparatus as in claim 6 which further includes means to withdraw the dispensing chamber from the apparatus.

Claims

1. A molten metal dispensing apparatus which comprises, A. induction heated furnace means having container means for the molten metal disposed within the turns of an induction heating coil, B. dispensing chamber means disposed within said container means having entrance means above the normal level of molten metal and means to discharge the molten metal from the apparatus, and C. power control means to vary the electrical power to the induction heating coil whereby the level of molten metal is raised sufficiently for metal to flow into the dispensing chamber.

6. A molten metal dispensing apparatus which comprises, A. induction heated furnace means having an enclosed container for molten metal disposed within the turns of an induction heating coil, B. a dispensing chamber of tubular shape disposed centrally within said enclosed container having an open end above the normal level of the molten metal and having an orifice opening at the other end of said tube which can be opened to discharge the molten metal, and C. power control means to vary the electrical power to the induction heating coil whereby the level of molten metal is raised sufficiently for metal to flow into the dispensing tube.

7. A molten metal dispensing apparatus as in claim 6 having a retractable plug member seated in the orifice opening of the discharge tube.