Patent Document

BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention relates to metallurgical processes and apparatus, and more particularly to metallurgical processes and apparatus in which metal chips are melted in a molten metal vortex which is fed by an inert gas bubble-actuated molten metal pump.  
           [0003]    2. Technical Background  
           [0004]    My following U.S. patents disclose various apparatus and processes related to the introduction of metal chips into the charge-well of a metal melting furnace and the conveyance of molten metal from one place to another within or out of a metal melting furnace.  
           [0005]    U.S. Pat. No. 4,710,126 discloses a process for producing dry metal chips. This process includes the steps of entraining fluid-containing metal chips in a gas, introducing the gas into a cyclone separator having an internal wall heated to fluid-vaporizing temperature by combustion in a surrounding chamber, purging and vaporizing fluid from said chips, exhausting hot gases and exiting dried metal chips from said separator, conducting hot gaseous products of combustion from the combustion chamber to a continuous centrifuge, extracting extractable fluid from starting metal chips in the centrifuge, entraining the chips in the hot gaseous products of combustion introduced into the centrifuge, and conducting the gaseous products with entrained chips from the continuous centrifuge to the cyclone separator, thereby providing an essentially closed system. The combustion chamber may be a part of an afterburner furnace and hot gases entraining vaporized oil exhausted from the cyclone separator may be recycled and employed as fuel for the combustion chamber.  
           [0006]    U.S. Pat. No. 4,721,457 discloses a process for producing dried and cleaned metal chips by entraining metal chips in a gas, introducing the gas into a cyclone separator having a wall heated to fluid-vaporizing temperature by combustion effected in a surrounding chamber, purging fluid from said chips, exhausting hot gases and exiting dried metal chips from said separator, conducting hot gaseous products of combustion from the combustion chamber to a continuous centrifuge, extracting extractable fluid from starting metal chips, which may be previously uncleaned and/or unwashed, in the centrifuge, entraining the chips in the hot gaseous products of combustion introduced into the centrifuge, and conducting the gaseous products with entrained chips from the continuous centrifuge to the cyclone separator, thereby providing an essentially closed system. The combustion chamber may be a part of an afterburner furnace and hot gases entraining vaporized oil exhausted from the cyclone separator may be recycled and employed as fuel for the combustion chamber. Provision is made in the system for hot water and/or steam from either an external source of from a water jacket around the cyclone separator, preferably together with solvent and/or detergent, and a final chip drying step wherein the drying is effected using products of combustion which are en route back to the continuous centrifuge.  
           [0007]    U.S. Pat. No. 4,872,907 discloses an apparatus and method for charging metal chips into a molten bath of the metal from which the chips are formed, comprising a compacting extruded and a delivery conduit which is resistant to the mass of molten metal and which is pivotable to dip into the molten metal bath when chips are being charged thereinto and out of contact with the bath when charging is to be discontinued, are disclosed. The chips are forced through the delivery conduit in the form of a compacted or densified mass preferably having a density between about 30 and 60 percent of the density of the solid metal and preferably between about 55 and 80 pounds per cubic foot. Feed is continued while the delivery conduit is in the molten metal bath and until it is removed therefrom to prevent entry of molten metal into the delivery conduit. The method is preferably conducted on a continuous basis and various sensors with appropriate wiring may be employed for safety and for making the method substantially automatic in operation.  
           [0008]    U.S. Pat. No. 5,203,910 discloses a method for the conveyance of molten metal from one place to another, in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool, employing an at least partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit and thereby inducing a flow of molten metal in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material.  
           [0009]    U.S. Pat. No. 5,211,744 discloses a process for utilization of metal chips, especially scrap metal chips, particularly brass and aluminum, by introduction of the metal chips into a pool of molten metal of which they are formed or an alloy thereof. The process allows for minimization of fuel cost, heat loss, and minimal conversion of the metal at the surface of the molten metal pool to metal oxide, as well as an increase in the yield of utilizable metal from the remelting or recycling operation, by maintaining a non-oxidizing atmosphere at the surface of the molten metal pool and optionally utilizing vaporized residual impurities from chips being recycled such as oil, lacquer, or similar vaporizable impurity to assist in maintaining the non-oxidizing atmosphere. Elimination of impurity-removal steps previously required for preparation of the chips for recycling by introduction into such a molten metal pool is eliminated. Environmental pollution is also conveniently and simultaneously substantially reduced from vaporizable contaminants, fumes, and decomposition products of combustion thereof.  
           [0010]    U.S. Pat. No. 5,395,424 discloses a method for the conveyance of molten metal from one place to another, in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool employing at least a partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit is employed. A flow of molten metal in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material. According to the present invention, an intermittent or pulsating inert gas feed is employed to produce essentially spherical or cylindrical bubbles within the conveying conduit, thereby resulting in greater efficiency and economy because of the possibility of reducing the quantity of inert gas employed to induce the flow of an identical amount of molten metal.  
           [0011]    U.S. Pat. No. 5,407,462 discloses a mass flow gravity feed furnace charger comprises a vertically-oriented elongated hollow conduit which is associated with an apertured heat-resistant charge-well cover adapted to lie essentially in contact with the upper surface of a molten metal pool in the charge well of a metal-melting furnace. Presized scrap metal charged into the conduit collects atop the surface of the molten metal pool, since the bottom opening of the conduit communicates with the charge-well cover aperture and permits the metal scrap to fall by gravity directly into the molten metal in the charge well. When the weight of the metal scrap column is sufficient to offset the resistance of the upper surface of the molten metal pool, the weight of the collected metal scrap gravitationally forces it into the molten metal mass it melts and is assimilated. Employment of the method and charge of the invention enables the controlled introduction of metal scrap by mass flow and gravity feed directly into and beneath the surface of the pool of molten metal and obviates numerous disadvantages and inconveniences of past practices.  
           [0012]    U.S. Pat. No. 5,468,280 discloses a method for the conveyance of molten metal from one place to another in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool. At least partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit is employed. A flow of molten metal is thereby inducted in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material. The inert gas is fed into the conveying conduit at a supersonic velocity, thereby simultaneously effecting a degassing of the molten metal while it is being conveyed.  
           [0013]    U.S. Pat. No. 5,735,935 discloses an inert gas bubble-actuated molten metal pump which is located in a metal-melting furnace to effect circulation of molten metal throughout the furnace. The inert gas employed to actuate the molten metal pump is captured beneath a heat-resistant and flame-resistant cover located above the exit port of the pump and over a substantial portion of the molten metal to thereby to prevent splashing, spattering and disruption of a thin protective layer or skin of oxidized metal at the surface of the molten metal as well as to provide a non-oxidizing atmosphere at the surface of the molten metal beneath said cover. In this manner the inert gas is employed efficiently and economically.  
           [0014]    U.S. Pat. No. 5,853,454 discloses a mass flow gravity feed furnace charger apparatus includes a charge-well cover having an aperture and an essentially vertical conduit for forming a substantially vertically-oriented column of metal chips or scrap within and above the aperture, and structure for bringing both the cover and conduit into position above a charge-well. The conduit is rapidly movable up and down to force the metal chips or scrap into molten metal in the charge-well even when the dross level at the surface of the molten metal is considerable, so that the apparatus and corresponding methods permit charging when gravity feed alone is not sufficient or sufficiently rapid. In a preferred embodiment, the conduit has an interior surface provided with gripping means to assist with the downward movement of metal chips or scrap into the molten metal in the charge well when the up and down motion of the conduit is in effect.  
           [0015]    U.S. Pat. No. 5,919,283 discloses an inert gas bubble-actuated molten metal pump is located between one section of a metal-melting furnace and a second section to pump molten metal form the one section, wherein the molten metal is at a higher temperature, into the second section, wherein the molten metal is at a lower temperature, and its effluent is directed into contact with metal chips being charged into the second section, thereby assisting in the more rapid melting of the chips into the molten metal mass in the second section. The inert gas employed to acturate the molten metal pump is captured beneath a heat-resistant and flame-resistant cover located above the exit port of the pump and over a substantial portion of the molten metal mass in the second section, thereby providing a non-oxidizing atmosphere at the surface of the molten metal mass or pool beneath said cover. In this manner the inert gas is employed not only to actuate the inert gas bubble-actuated molten metal pump, but also to assist in the rapid melting of metal chips being charged, as well as to provide a non-oxidizing atmosphere at the surface of the molten metal.  
           [0016]    U.S. Pat. No. 5,984,999 discloses an arrangement in which the vortex well of a metal melting furnace is provided with an internal cavity having a circular cross section when viewed from the top, preferably a cavity of cylindrical or conical configuration, and with a peripheral exit port located tangentially with respect to said cavity at a lower level thereof for exit of molten metal into the main chamber of the furnace. An inert gas bubble-actuated molten metal pump brings molten metal from a hotter section of the furnace, advantageously directly form the main chamber, and has its exit port located tangentially to the periphery of the cavity at an upper level thereof, thereby creating vortical flow of molten metal therein and for circulation of hotter molten metal throughout the furnace. A head of molten metal can be created in the vortex well, which advantageously has an exit port of restricted internal cross-sectional area, to assist with attainment of these objective. A heat and flame-resistant cover may be located above the cavity and advantageously has an aperture therein for the loading of metal chips or scrap thereinto. A gravity-feed chip charger may surmount the aperture for the discharge of new metal chips or scrap into the cavity through the said aperture.  
           [0017]    U.S. Pat. No. 6,068,812 discloses an inert gas bubble-actuated molten metal pump, for the movement of molten metal in a molten-metal bath, which obviates the necessity of a heat proof and flameproof cover to counteract splashing and spattering at the surface of the molten metal bath above the pump, comprising an inert gas diffusion means at an upper end thereof, the diffusion means having an upper surface containing a multiplicity of small upwardly-opening apertures for the breaking up of large bubbles and the diffusion of small bubbles of inert gas upwardly therethrough. The pump includes a refractory block which comprises a conveying conduit which is preferably elongated in width and a spreader cavity in communication with both a passageway in the block for providing a source of inert gas and a lower end of the conveying conduit.  
           [0018]    My above referenced patents are incorporated herein by reference.  
           [0019]    The purpose for creating a vortex in the vortex well is to rapidly submerge the small particles of metal whose mass would otherwise prevent the particles from penetrating the surface tension of the molten metal bath, thus causing a substantial increase in the percentage of metal loss due to oxidation. It has, however, has been determined that further steps must be taken to reduce oxidation, particularly when relatively more expensive metals such as aluminum are being used.  
         SUMMARY OF THE INVENTION  
         [0020]    It is an object of the present invention to provide a means for further reducing metal losses due to oxidation in the vortex molten bath.  
           [0021]    It is another object of the present invention to provide a way of integrating the functions of circulating molten metal and submerging metal chips in molten metal vortex to allow for rapid recovery of any temperature drop which may result from the introduction of the cold scrap.  
           [0022]    It is still another object of the present invention to provide a means for efficiently burning off volatile hydrocarbons which may be present with metal chips that are being melted.  
           [0023]    These and other objects are attained by the present invention which is a metal melting closed furnace which includes a main chamber, a circulation well connected to the main chamber by a communications passageway and a vortex well having an exit outlet for molten metal into the main chamber. A cover or other suitable containment means is emplaced above the vortex well. An inert gas bubble activated molten metal pump is provided in which there is an entry port in the circulation well and exit port tangentially arranged with respect to the periphery of the cavity. This exit port will typically be at or near the top of the vortex well. In order to reduce oxidation, inert gas bubbles are captured from the discharge of the molten metal pump, creating an inert gas atmosphere or blanket above the molten metal vortex so that this inert gas atmosphere is continuously or intermittently replenished.  
           [0024]    Also encompassed by the present invention is a process for melting metal in a furnace in which molten metal is heated in a main chamber and then circulated to a circulation well. The molten metal is then moved from the circulation well by an inert gas bubble actuated pump to the vortex well. An inert gas atmosphere is formed below the cover and is continuously or intermittently replenished by inert gas from the bubbles in the pump.  
           [0025]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a vortex well having periphery, a top and an exit outlet for recovering molten metal therefrom, and a cover is emplaced over the vortex well. On occasion, the vortex well is the circulation well. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well, wherein the exit port is positioned at a vertical position which is higher than the entry port. There is also an inert gas atmosphere positioned in the vortex well above the surface of molten metal.  
           [0026]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a vortex well having a periphery, a top and bottom exit outlet for recovering molten metal therefrom, and a cover or other containment means is emplaced over the vortex well. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well. There is also an inert gas atmosphere positioned in the vortex well beneath the cover.  
           [0027]    Also encompassed by the present invention is a metal melting furnace which includes a main chamber and a circulation well containing molten metal having a surface level connected to the main chamber by a communication passageway. There is a vortex well having a periphery, a top and an exit outlet for recovering molten metal therefrom, and a cover is emplaced over the vortex well. The furnace also includes a sensor for measuring the surface level of the molten metal in the circulation well and a means for stopping feed to the vortex well to prevent over filling of the furnace.  
           [0028]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a well block having, a vortex well, said vortex well having a periphery, top and an exit outlet for recovering molten metal therefrom. A cover is emplaced over the vortex well, wherein said cover has a periphery positioned in inward spaced relation to the well block to form a peripheral gas release space between said cover and the well block. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well. An inert gas and volatile hydrocarbon gas atmosphere is positioned in the charge well beneath the cover, and this atmosphere is releasable through said peripheral gas release space.  
           [0029]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a vortex well, which may sit in or be the circulation well, containing a molten metal vortex and having a periphery, a top and an exit outlet for recovering molten metal therefrom and a cover is emplaced over the vortex well adjacent the surface of the molten metal vortex. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well. An inert gas atmosphere is also positioned in the vortex well beneath the cover or above the surface of molten metal.  
           [0030]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a vortex well having a periphery, a top and an exit outlet for recovering molten metal therefrom and a cover emplaced over the vortex well. A feed tube extends through said cover to enable metal chips to be added to the vortex well adjacent the periphery of said vortex well. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well. An inert gas atmosphere is also positioned in the vortex well beneath the cover.  
           [0031]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. The furnace also includes a vortex well having a periphery, a top and an exit outlet for recovering molten metal therefrom and said vortex well is positioned in a vortex well block. A cover is also emplaced over the vortex well. There is also an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port tangentially arranged with respect to the periphery of said vortex well at or near the top of the vortex well. An inert gas atmosphere is positioned in the vortex well beneath the cover. An end block is also positioned in adjoining relation to the vortex well block. These blocks are connected by a projection extruding from one block which engages a recess in the other block. The circulation well is contained in said adjoining blocks.  
           [0032]    Also encompassed by the present invention is a metal-melting furnace which includes a main chamber and a circulation well connected to the main chamber by a communication passageway. There is also a vortex well having a periphery, a top and an exit outlet for recovering molten metal therefrom and may include a cover emplaced over the vortex well. A feed tube extends through said cover to enable metal chips to be added to the vortex well. The vortex well is adapted to hold molten metal up to a maximum level from the bottom of the vortex well. The furnace also includes an inert gas bubble actuated molten metal pump having an entry port in the circulation well and an exit port to the vortex well. The exit port is positioned so that it is adapted to lie at least partially above the maximum level of molten metal held in the vortex well. Preferably, the exit port lies at least 50% or entirely above the maximum level of molten metal in the vortex well. An inert gas atmosphere is also positioned in the vortex well beneath the cover or containment means. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]    The present invention is further described by means of the accompanying drawing in which:  
         [0034]    [0034]FIG. 1 is a vertical cross-sectional view of a molten metal pump and furnace for use therewith which comprises a first preferred embodiment of the present invention;  
         [0035]    [0035]FIG. 2 is a cut away perspective view of the main molten metal chamber, circulation wall, vortex well and adjacent chamber of the molten metal pump and furnace in FIG. 1;  
         [0036]    [0036]FIG. 3 is a cross-sectional through  3 - 3  in FIG. 2;  
         [0037]    [0037]FIG. 4 is a partial end view of the molten metal pump and furnace shown in FIG. 1 from  4 - 4 ;  
         [0038]    [0038]FIG. 5 is a cross-sectional view through  5 - 5  in FIG. 1;  
         [0039]    [0039]FIG. 6 is an end view from  6 - 6  of the molten metal pump and furnace shown in FIG. 1;  
         [0040]    [0040]FIG. 7 is a detailed view of area  7  in FIG. 1;  
         [0041]    [0041]FIG. 8 is a cross sectional view through  8 - 8  in FIG. 7;  
         [0042]    [0042]FIG. 9 is a partial top view of the well block and end block from  9 - 9  in FIG. 7;  
         [0043]    [0043]FIG. 10 is a vertical cross-sectional view similar to FIG. 1 in which the feed tube and vortex well cover are in their elevated positions;  
         [0044]    [0044]FIG. 11 is a detailed view similar to FIG. 7 in which the feed tube and vortex well cover are in intermediate elevated position still covering the vortex well;  
         [0045]    [0045]FIG. 12 is a top plan view of the vortex well lock and part of the end block from  12 - 12  in FIG. 11 in which an alternate vortex well cover is shown;  
         [0046]    [0046]FIG. 13 is a detailed cross-sectional view of a second embodiment of a molten metal pump and furnace for use therewith in accordance with the present invention, in which the outlet of the molten metal pump is positioned at least partially above the uppermost level of molten metal in the vortex well; and  
         [0047]    [0047]FIG. 14 is a detailed cross-sectional view of a third embodiment of a molten metal pump and furnace for use therewith in accordance with the present invention, in which the outlet of the molten metal pump is positioned totally above the level of molten metal in the vortex well. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0048]    Referring to FIGS.  1 - 9 , the furnace is shown generally at  10  has a bottom wall  12 , side walls  14  and  16 , front wall  18  and a rear wall  19 . Furnace  10  also has an intermediate transverse wall  20  which defines along with the other wall a main chamber  22 . Conventional fossil fuel burners (not shown) are used to maintain a molten metal bath  24  in this main chamber. Main chamber  22  also has a cover, shown in fragment, at numeral  26 . Adjacent main chamber  22  is a circulation chamber  28  also having a molten metal bath  30  which is connected to main chamber  22  by means of communicating passageway  32 . The molten metal may be aluminum, magnesium, zinc, copper, brass or steel. Adjacent the circulation chamber  28  there is a molten metal pump shown generally at  34  which includes an end block  36 . Adjacent end block  36  there is well block  38 . Preferably well block  38  is a separate and replaceable block of refractory material. It would alternately be possible to integrate end block  36  and well block  38  into a single unit. In the end block  36  there is end block projection  40  which engages recess  42  on well block  38 . Between end block  36  and well block  38  there is also a vertical space  44 . As may be seen in FIG. 7, in end block  36  there is a vertical passageway  46  which has a lower opening  48  and a medial outlet  50 . An inert gas line  52  extends from a tank  54  containing nitrogen, argon or other inert gas, to controls  56  and then to inert gas outlet  58  into passageway  46 . Adjacent medial outlet  50  of vertical passageway  46  there is a seal  60  at the point vertical passageway  46  connects to horizontal passageway  64  in well block  38 . Horizontal passageway  64  has an opening  66  and an outlet  68  and may be adjacent a plate  70  with a plurality of apertures as at aperture  72 . As is conventional in molten metal pumps, such as in molten metal pump  34 , there are a plurality of inert gas bubbles  74 ,  76 , and  78  in vertical passageway  46  and horizontal passageway  64 . Bubbles  74 ,  76  and  78  rise through passageways  46 ,  64  to move molten metal masses as at  80  and  82  from circulation chamber  28  to vortex well (shown generally at  84 ). Above plate  70  there is an inert gas collection recess  86  in well block  38 . Vortex well  84  has an upper region  88 , medial region  90  and a lower region  92  with a surrounding liner  94 . At the bottom of the lower region  92  there is a lower outlet  96  which communicates with a bottom recess  98  in well block  38 . A horizontal passageway  100  extends through to an intermediate well  102 . In this intermediate well  102  there is another molten metal bath  104  which re-circulates back to main chamber  22  by means of communicating passageway  106 . Above vortex well  84  there is a refractory cover  108 . Other suitable vortex well containment means such as an upward extension of the vortex well shown generally as numeral  109  in FIG. 7 may be substituted for cover  108 . Cover  108  will be equipped with a sensor  110  which overlies a molten metal vortex  112  in vortex well  84 . Sensor  110  senses the surface level  400  of molten metal vortex  112  to prevent overfilling of furnace  10 . Between cover  108  and molten metal vortex  112  there is an inert gas atmosphere or blanket  114  which is continuously or intermittently replenished with inert gas from inert gas bubbles in molten metal pump  34 . These bubbles enter recess  86  through apertures, as at aperture  72 , in plate  70 . Between cover  108  and well block  38  there is a peripheral space  116  which allows for the formation of a combustion zone  118  for allowing oils, paints, lacquers as well as other volatile hydrocarbons to exit from below cover  108  and be burned off. It will be appreciated that this peripheral space  116  will also allow the escape of inert gas from the inert gas atmosphere or blanket  114  as additional inert gases are added to this space. Well cover  108  will have sufficient space around its periphery to allow oil, paints, lacquer or nitrogen, as well as any other volatile hydrocarbons which have been carried into the molten metal stream or the scrap charge material, to exit from below cover  108 . Heat resistant cover  108  may be adjustable in height, but normally provides several inches of clearance above surface level  400  of molten metal bath for the containment of the replenishing supply of inert gas. As seen in FIG. 1, above combustion zone  118  there is a smoke collection hood  120  with air intakes  124  and  126  having respective closure doors  128  and  130 . From smoke collection hood  120  there is a line  132  to a stack or particle collection equipment (not shown). Extending downwardly through smoke collection hood  120  there is a scrap feed tube  134  in which scrap as in metal chips  136  are fed into molten metal vortex  112  in vortex well  84 . It will be appreciated that metal scrap may be substituted for metal chips and, for the purposes of this disclosure, the term “metal chips” should be understood to include both metal chips and metal scrap. Metal chips  136  are preferably fed tangentially into molten metal vortex  112  adjacent the periphery of vortex well  84 . Feed tube  134  is attached to cover  108  by means of a flange  138 . At its upper end, feed tube  134  receives metal chips from a hopper  140  which is in turn fed by a screw conveyor  142  which receives metal chips  136  from a feed opening  144 .  
         [0049]    Referring to FIG. 10, it will be seen that feed tube  134  and cover  108  may be withdrawn upwardly from vortex well  84  by well known conventional means.  
         [0050]    Referring to FIG. 11, it will be seen that feed tube  134  may also be adjusted in height so that cover  108  lies proximate the top of vortex well  84 . The height of inert gas blanket  114  is thereby adjusted.  
         [0051]    Referring to FIG. 12, an alternate embodiment of the cover is shown. In this embodiment a well block  146  is shown as well as a fragmented portion of end block  148 . A vertical space  150  is interposed between the well block  146  and end block  148 . An alternate cover  152  is positioned on the top of the well block  146  by means of radial peripheral supports  154 ,  156 ,  158  and  160 . Between cover  152  and well block  148  there are peripheral spaces  162 ,  164 ,  166  and  168  and positioned above these peripheral spaces there are respectively combustion zones  170 ,  172 ,  174  and  176 . A feed tube  180 , that is connected to cover  152  by means of a bracket  182 , allows metal chips to be fed into molten metal vortex  184 .  
         [0052]    Referring to FIG. 13, there is a shown a second embodiment of a molten metal pump and furnace in accordance with the present invention. The basic structure and function of the furnace is the same as previously described. However, the structure of the molten metal pump is different in that the outlet of the pump into the vortex well is at least partially elevated above the molten metal in vortex  112 . A molten metal pump, generally shown at  234  lies adjacent the circulation chamber  28 . Molten metal pump  234  includes an end block  236  and a well block  238 . Preferably well block  238  is a separate and replaceable block of refractory material. It would alternately be possible to integrate end block  236  and well block  238  into a single unit. In end block  236  there is end block projection  240  which engages recess  242  on well block  238 . End block  236  has a vertical passageway  246  which has a lower opening  248  and a medial outlet  250 . An inert gas line  252  extends from a tank (not shown)containing nitrogen, argon or other inert gas in the same manner as previously described. Gas line  52  terminates in outlet  58  into passageway  246 . Adjacent medial outlet  250  of vertical passageway  246  there is a seal  260  at the point vertical passageway  246  connects to horizontal passageway  264  in well block  238 . Horizontal passageway  264  has an opening  266  and an outlet  268 . Vortex well  84  is adapted to hold molten metal therein. When the maximum amount of molten metal is held within vortex well  84 , the molten metal will rise to a maximum specific level signified by a distance D from the bottom wall  12  of the furnace  10 . As will be understood by those skilled in the art, different size furnaces will be adapted to hold different maximum amounts of molten metal in the vortex well of that particular size furnace. Those different maximum amounts of molten metal will each rise to a different specific level for each size of furnace.  
         [0053]    In accordance with one of the main features of the present invention, passageway  264  enters vortex well  84  at a point where at least part of the outlet  268  lies above the level D for that size furnace, i.e. at least partially above the level of the maximum amount of molten metal that may be held in the vortex well  84 . Preferably outlet  268  enters vortex well  84  at a point where at least 50% of outlet  268  lies above level D, i.e. at least 50% of the outlet  268  will be elevated above the level of the maximum amount of molten metal that may be held in the vortex well  84 . Horizontal passageway  264  has a longitudinal centerline and preferably that centerline lies at least 50% above level D.  
         [0054]    As is conventional in molten metal pumps, such as in molten metal pump  234 , there are a plurality of inert gas bubbles  274 ,  276 , and  278  in vertical passageway  246  and horizontal passageway  264 . Bubbles  274 ,  276  and  278  rise through passageways  246 ,  264  to move molten metal masses as at  279 ,  280  and  282  from circulation chamber  28  to the vortex well  84 . By assuring that the outlet  268  is positioned at least partially and preferably at least 50% above the maximum level D of the molten metal in vortex well  84 , the back-pressure exerted by molten metal in the vortex well  84  on the material in horizontal passageway  264  and vertical passageway  246  is substantially reduced. The reduction in back-pressure allows the bubbles  274 ,  276  and  278  and therefore the metal masses  279 ,  280  and  282  to move more easily through passageways  246  and  264 . This increases the efficiency of the molten metal pump  234 . As molten metal mass  279  is forced through horizontal passageway  264  and begins to flow into vortex  112 , a gap  281  forms between the interior of passageway  264  and the upper surface  283  of molten metal mass  279 . The inert gas bubble  274  moving through passageway  264  is released into gap  281  as molten metal mass  279  flows into vortex  112  and the gas becomes part of blanket  114 .  
         [0055]    It should also be noted that in the second embodiment of the present invention, the gas bubbles  274 ,  276  and  278  moving through said molten metal pump are directly released into the blanket  114  lying between the surface  209  of the molten metal in vortex  112  and the cover  108 .  
         [0056]    A third embodiment of the invention is shown in FIG. 14. As with the second embodiment of the invention, the furnace&#39;s structure and function are the same as previously described. However, a third embodiment of the molten metal pump, generally referred to as  334 , is provided. The basic structure of molten metal pump  334  is the same as in the second embodiment of the invention, except that the outlet  368  of the horizontal passageway  364  lies entirely above the level of the maximum amount of molten metal that may be held in the vortex well  84 . The maximum level that the molten metal may rise to in vortex well  84  is signified by the distance E from the bottom wall  12  of furnace  10 . As previously set out, it will be understood that different size furnaces will hold different amounts of molten metal and therefore level E will be different for different size furnaces. The bottom  368   a  of outlet  368  preferably is elevated a spaced distance F above the maximum level E of molten metal in vortex well  84 . A gas bubble  374  moving through vertical passageway  346  pushes a metal mass  379  before it. As metal mass  379  begins to drop out of outlet  368  and into vortex  112 , a gap  381  is formed between the interior of horizontal passageway  364  and the upper surface  379   a  of the molten metal mass  379 . As molten metal mass  379  drops into vortex  112 , gas bubble  374  merges with the gases in gap  381  and becomes part of blanket  114 . The structure of molten metal pump  334  reduces the back-pressure that could be exerted by molten metal in the vortex  112  on the material in horizontal passageway  364  and vertical passageway  346 . The reduction of the back-pressure allows bubbles  374 ,  376  and  378  and therefore the molten metal masses  379 ,  380  and  382  to move more easily through horizontal passageway  364  and vertical passageway  346 . By assuring that the outlet  368  is positioned entirely above the maximum level E of the molten metal in vortex well  84 , the back-pressure exerted by molten metal in the vortex well  84  on the material in horizontal passageway  364  and vertical passageway  346  is substantially reduced or eliminated. This again improves the efficiency of the molten metal pump and the furnace.  
         [0057]    As was the case with the second embodiment of the present invention, the gas bubbles  374 ,  376  and  378  moving through said molten metal pump are directly released into the blanket  114  lying between the surface  309  of the molten metal in vortex  112  and the cover  108 .  
         [0058]    The operation of the furnace will be described with reference to the first embodiment of the invention, but it will be understood by those skilled in the art that all three embodiments of the invention function in essentially the same manner. In the operation of the molten metal pump and furnace of the present invention, metal chips  136  are fed into feed opening  144  of conveyor  142 . Conveyor  142  transports metal chips  136  to hopper  140  from which they descend into feed tube  134  and into vortex well  84 . Chips  136  drop into molten metal vortex  112 . At the same time, nitrogen or another inert gas is drawn from tank  54  through line  52  and controls  56 . The gas forms bubbles, as at bubble  78 , in vertical passage way  46  of molten metal pump  34 . These inert gas bubbles move molten metal masses, as at mass  82 , from molten metal bath  30  in circulation chamber  28  to molten metal vortex  112  in vortex well  84 . When these bubbles, as in bubble  74 , enter horizontal passageway  64  of molten metal pump  34 , they pass through apertures, as at aperture  72 , in plate  70  to enter recess  86 . Thereafter the bubbles enter vortex well  84  between molten metal vortex  112  and cover  108  to form inert gas atmosphere or blanket  114 . Alternatively inert gas blanket  114  may be contained by the upwardly extending walls of vortex well  84 . This inert gas blanket  114  reduces the formation of oxidation on the metal chips entering molten metal vortex  112 . Oil, paints, lacquers and other volatile hydrocarbons which may be present within the metal chips are volitized and passed through peripheral space  116  (FIG. 7) between cover  108  and well block  38  to be burned in combustion zone  118 . Metal chips flow along with the rest of molten metal vortex  112  in a swirling downward path to outlet  96 , through medial region  90 , into lower region  92 , through outlet  96  and into bottom recess  98 . The direction of the molten metal is then changed to a lateral flow path through horizontal passageway  100  into intermediate well  102 . From intermediate well  102 , molten metal in molten metal bath  104  moves through passageway  106  and into main chamber  22 . After heating in main chamber  22 , molten metal passes through passageway  32  into circulation chamber  28 . From molten metal bath  30  in circulation chamber  28 , the molten metal is again pumped through molten metal pump  34  and back to vortex well  84  where additional metal chips are added under inert gas blanket  114  in the manner previously described. It will be understood that it would alternately be possible to remove molten metal from passageway  32  adjacent circulation chamber  28  to vortex well  84 . For the purposes of this disclosure, the removal of molten metal from circulation chamber  28  to vortex well  84  will be considered to also include the embodiment of removing molten metal from adjacent passageway  32 .  
         [0059]    It will be appreciated that a molten metal pump and furnace for use therewith and a method for its operation has been described in which oxidation of metal chips entering molten metal vortex is substantially reduced.  
         [0060]    It will also be appreciated that the present invention allows for the combination of the functions of circulating molten metal in a fossil fuel reverberatory furnace and submerging metal chips in an open sidewell chamber to cause the melted feed stock to be rapidly circulated back into the main chamber of the furnace. Any resulting loss in temperature due to the introduction of the cold scrap, can quickly be recovered in the presence of the combustion burners located in the enclosed main chamber of the furnace.  
         [0061]    It will also be appreciated that the present invention also lends itself to melting materials such as used beverage cans (UBC) with substantially improved melt yield, without requiring the prior step of de-lacquering the UBC in advance of this melting process.  
         [0062]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0063]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.

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