Abstract:
A magnetic pump in a pump well in a molten metal furnace with a long, relatively thin side wall that wraps around a significant fraction of the circumference of the pump, which facilitates creation of an eddy current based flow field in the molten material with better magnetic coupling, thereby enhancing the effectiveness of the pump. Breach of the well wall will not result in spillage of metal outside the furnace, and the well can be monitored for any such breach or other change so that the pump can be lifted out of the well to protect it from contact with the molten metal in the event of such a breach, or other appropriate action can be taken.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/202,123, filed Mar. 10, 2014, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/776,316 filed Mar. 11, 2013, the entire contents of each which are incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to pumps used to circulate material in non-ferrous molten metal furnaces and, more specifically, to the location and operation of electromagnetic or permanent magnet-based molten metal pumps. 
       BACKGROUND 
       [0003]    It is desirable for a number of reasons to cause material to flow in non-ferrous molten metal furnaces. Magnetic pumps are sometimes used to induce eddy currents in the metal in order to induce such flow or agitation. Electromagnetic devices are used in some known pumps, and permanent magnets are used in other such pumps. Such pumps are typically attached to the outside of a side wall of a furnace, and the molten metal may be piped into and around the pump structure (as in published U.S. patent application publication numbers 2011/0248432 and 2010/0244338, which are both incorporated herein by reference). This means that molten metal is moved outside the furnace, elevating the likelihood of an uncontained leak from such pumps and associated structures. Moreover, some existing devices project magnetic flux through furnace external walls, which need to be thick for safety reasons. 
         [0004]    Each of these approaches can be inefficient in agitating molten metal and create a significant risk of leakage of molten metal through the side wall of the furnace or within the structures outside the furnace and through which the metal flows. Such a leak or breach may result in significant risk of leakage outside the pump structure, not to mention the risk of damage to the pump structure. 
       SUMMARY 
       [0005]    The terms “invention,” “the invention,” “this invention” and “the present invention” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim. 
         [0006]    The present invention solves the problems described above, and provides other benefits by positioning a magnetic pump, which may be an electromagnetic or permanent magnet based pump, at the entrance to a side well of the furnace and in a pump well with a long, relatively thin side wall that wraps around a significant fraction of the circumference of the pump. The long, thin side wall of the pump well and significant wrap angle around the pump well facilitates creation of a strong eddy current based flow field in the molten material with better magnetic coupling, thereby enhancing the effectiveness of the pump. The risk of breach of the relatively thin pump well wall is acceptable because breach of the well wall and flow of molten metal into the well will not result in spillage of metal outside the furnace. Moreover, the well can be monitored for any such breach so that the pump can be lifted out of the well to protect it from contact with the molten metal in the event of such a breach. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0007]      FIG. 1  is a perspective view of a pump of this invention in a well in a metal furnace. 
           [0008]      FIG. 2  is an elevation view, in section of the installed pump shown in  FIG. 1 . 
           [0009]      FIG. 3  is a schematic plan view of a furnace and pump of this invention. 
           [0010]      FIG. 4  is a schematicized side view, partially in section, of another embodiment of the pump of this invention in a well in a metal furnace. 
           [0011]      FIG. 5  is a schematic plan view of a furnace and pump according to another embodiment. 
           [0012]      FIGS. 6-7  are isometric views of a lift system according to an embodiment. 
           [0013]      FIG. 8  is a schematic plan view of a furnace and pump according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
         [0015]    The present invention solves the problems described above by positioning a magnetic pump  10 , which may be an electromagnetic or permanent magnet based pump, in a well  12  located entirely inside the exterior wall  14  of a metal melting furnace  16  and near the entrance  22  to a side well  18  of furnace  16 . Certain kinds of scrap may be added in the side well  18 , and the extra turbulence in the molten metal generated by the pump  10  quickly submerges and melts the scrap. Agitation in side well  18  also agitates the metal in the main hearth area  20  of furnace  16 . 
         [0016]    While other pump configurations may be used, the pump  10  illustrated in  FIGS. 1-2  is a permanent pump that is driven by a motor  24  coupled to a gear box  26 . The motor  24  may be electrically powered with alternating current or direct current, hydraulically powered or otherwise operated to provide rotational force. The gear box  26 , which may be interposed between the motor  24  and a vertical shaft (not visible in  FIGS. 1-3 ), reduces the relatively high rotational speed of the motor  24 . This provides a lower rotational speed for rotating an arrangement of one or more permanent magnets (also not visible in  FIGS. 1-2 ) that rotate just inside the inner wall  28  of the cooling jacket  30  through which air, nitrogen or other suitable cooling medium is circulated through inlet  34 . 
         [0017]    Cooling jacket  30  is adjacent to a relatively thin refractory wall  32  of the furnace  16  well  12 . This cooling maintains a thermal freeze plane. This reduces the likelihood that the aluminum or other molten metal will dissolve holes in the wall  32  of the well  12 . If such holes nevertheless form, because the metal is still retained within the furnace, the consequences typically will be less severe than those potentially associated with breach of an exterior wall of a furnace. 
         [0018]    As mentioned, other pump arrangements, such as an electromagnetic pump, may be used instead of a permanent rotatable pump. For example, an induction motor such as the one described in U.S. Pat. No. 3,824,414, which issued Jul. 16, 1974 and is incorporated herein by reference, may be incorporated into a side well of a furnace.  FIG. 8  illustrates a linear induction motor  200  that may be positioned in a well  212  located entirely inside a metal melting furnace  216  and near a side well  218  of furnace  116 . In some embodiments, the surface that is normally flat in a linear induction motor is convex as illustrated in  FIG. 8 . Agitation in side well  212  also agitates the metal in other areas of the furnace and circulates the metal between the main hearth area  220  and the side well  218  of the furnace  216  in the direction of arrows  215 . In some embodiments, submerged ports  222  allow metal to flow between side well  218  and hearth area  220 . A submerging pump  224  may be used to submerge and melt any scrap (such as, without limitation, light gauge, clips, chips, or post-consumer based bale scrap) added to the side well  218 . 
         [0019]    The pump arrangement of this invention provides an open channel flow system to move molten metal due to the eddy current based flow field created by the magnetic pump, thereby agitating the metal and contributing to maintenance of homogeneous temperatures within the metal. The arrangement of the pump within a relatively thin wall of a well within the furnace minimizes the distance between the moving metal and the magnet, thus facilitating creation of strong eddy currents in the molten material, thereby enhancing the effectiveness of the pump. 
         [0020]    In some cases, the magnetic pump is positioned within the furnace such that significant linear vortexes are created within the metal. For instance, the magnet may be positioned and configured to generate eddy current based flow field for the molten metal positioned within approximately half the thickness of the thin wall of the well (closest to the pump) and force a linear flow along this portion of the metal closest to the magnet. The other approximately half of the molten metal within the thin wall flows in a sympathetic, tortuous path that in turn generates a strong linear vortex throughout the depth of the well. 
         [0021]      FIG. 4  depicts another embodiment of a magnetic pump in a well of this invention. Pump  40  is a permanent magnetic based pump and includes a motor/gearbox  42  that drives a shaft  44  that rotates permanent magnets  46  within a well  48  positioned in a molten metal furnace  50  having a main hearth area  52  and a side well  54 . Cooling medium indicated by arrows  56  is blown into the well  48  by a blower  58  and exits through port  60 . A controller  70  controls motor/gearbox  42  and blower  58 . In the event of a breach of well  48  a signal from detector  62  can activate a lift system to lift the pump out of the well. As shown in  FIG. 4 , the lift system includes a hoist (not shown) attached to chain  64  or cable attached to motor/gearbox  42  and capable of lifting pump  40  out of the well  48  to protect it from damage. 
         [0022]      FIGS. 6-7  illustrate another non-limiting embodiment of a lift system  300  configured to hoist a pump (such as pump  400 ) out the well in the event of a breach. The lift system  300  illustrated in  FIGS. 6-7  includes a cart  301  having a plurality of wheels  303 . The cart  301  is configured to traverse along a set of rails  302  to move the pump  400  away from the furnace. 
         [0023]    Detector  62  can be a thermocouple or other temperature detector for detecting the temperature within the well at the location of the detector. In some cases, detector  62  is a duplex type K thermocouple with an open-ended protection tube and ceramic bead insulators, although any suitable thermocouple or other temperature detector may be used. 
         [0024]    Detector  62  could, alternatively, be a detector capable of detecting the presence of molten metal in the well by other means. It can also be any other detector adapted to directly or indirectly detect a condition, such as elevated temperature, cessation of air flow, conductivity which indicates the presence of molten metal, change in moisture content of the air or any other parameter or condition capable of being monitored. 
         [0025]    In some embodiments, more than one detector  62  is used and in some cases, more than one type of detector is used. In one non-limiting embodiment, a thermocouple or other temperature detector is used, as well as a detector capable of detecting the presence of molten metal by another means, such as by measuring conductivity with a conduction probe. In one non-limiting embodiment, one of the detectors may be part of a Warrick® conductivity system circuit that has liquid level sensing capabilities such as, but not limited to, Warrick® Series 16M controls. 
         [0026]    If used, a thermocouple element may detect temperature from any suitable location, for example but not limited to, approximately ½″ from the bottom of the well  48 . If used, a conductivity system, such as but not limited to a Warrick relay reference probe, may be connected directly to the well wall to detect a breach by sensing conductivity associated with any metal infiltration. 
         [0027]    A programmable logic controller or suitable processer can receive and interpret the signal from detector  62  and initiate any suitable action. For example, the PLC can sound or display an alarm so that a furnace operator can determine whether to lift pump  40  out of the well  48 , or take any other appropriate action. Alternatively, the PLC can activate a lift apparatus to lift pump  40  out of well  48 . Signals from detector  62  and/or the PLC could also be used to automatically or through operator action otherwise control the furnace by, for instance, stopping rotation of the magnets  46  or adjusting the speed of rotation by adjusting operation of motor/gearbox  42 , adjust cooling airflow  56  by adjusting operation of blower  58 , or changing heat input to the main hearth  52  or some other portion of the furnace  50 . 
         [0028]      FIG. 5  is another plan view depicting an embodiment of a permanent magnet pump in a well. As shown, a magnetic pump  100  is positioned in a well  112  that is located entirely inside a metal melting furnace  116  and near a side well  118  of furnace  116 . Certain kinds of scrap (such as, without limitation, light gauge, clips, chips, or post-consumer based bale scrap) may be added in the side well  118  and/or side well  122  and the extra turbulence in the molten metal generated by the pump  100  quickly submerges and melts the scrap. Agitation in side well  112  also agitates the metal in other areas of the furnace and circulates the metal between the main hearth area  120 , the side well  118 , and the side well  112  of the furnace  116 . In some embodiments, submerged ports allow metal to flow between side well  112  and hearth area  120  and between side well  112  and side well  118 . 
         [0029]    All patents, publications and abstracts cited above are incorporated herein by reference in their entirety. 
         [0030]    Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and subcombinations are useful and may be employed without reference to other features and subcombinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications can be made without departing from the scope of the claims below.