Abstract:
An insert and system for removing molten metal from a vessel is disclosed. The insert defines an enclosed cavity, and includes a first opening in its side through which molten metal can enter the cavity, and a second opening at its top through which molten metal can exit the cavity. A trough at the top of the insert directs molten metal exiting the second opening out of the vessel. The system includes the insert and a molten metal pump that forces molten metal through the first opening and into the cavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and incorporates by reference the disclosure of U.S. Provisional Patent Application No. 61/334,146 entitled Launder Transfer Pump Insert, filed on May 12, 2010, the disclosure of which that is not inconsistent with this document is incorporated herein by reference. This Application also claims priority to and is a continuation-in-part of U.S. application Ser. No. 12/853,253, entitled System and Method for Degassing Molten Metal, filed on Aug. 9, 2010, and U.S. application Ser. No. 11/766,617 entitled Transferring Molten Metal from One Structure to Another, filed on Jun. 21, 2007 the disclosures of which that are not inconsistent with this document are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to an insert for placing in a vessel to assist in transferring molten metal out of the vessel, and to a system utilizing the insert in combination with a molten metal pump. 
       BACKGROUND OF THE INVENTION 
       [0003]    As used herein, the term “molten metal” means any metal or combination of metals in liquid form, such as aluminum, copper, iron, zinc and alloys thereof. The term “gas” means any gas or combination of gases, including argon, nitrogen, chlorine, fluorine, freon, and helium, that are released into molten metal. 
         [0004]    Known molten-metal pumps include a pump base (also called a housing or casing), one or more inlets (an inlet being an opening in the housing to allow molten metal to enter a pump chamber), a pump chamber, which is an open area formed within the housing, and a discharge, which is a channel or conduit of any structure or type communicating with the pump chamber (in an axial pump the chamber and discharge may be the same structure or different areas of the same structure) leading from the pump chamber to an outlet, which is an opening formed in the exterior of the housing through which molten metal exits the casing. An impeller, also called a rotor, is mounted in the pump chamber and is connected to a drive system. The drive system is typically an impeller shaft connected to one end of a drive shaft, the other end of the drive shaft being connected to a motor. Often, the impeller shaft is comprised of graphite, the motor shaft is comprised of steel, and the two are connected by a coupling. As the motor turns the drive shaft, the drive shaft turns the impeller and the impeller pushes molten metal out of the pump chamber, through the discharge, out of the outlet and into the molten metal bath. Most molten metal pumps are gravity fed, wherein gravity forces molten metal through the inlet and into the pump chamber as the impeller pushes molten metal out of the pump chamber. 
         [0005]    A number of submersible pumps used to pump molten metal (referred to herein as molten metal pumps) are known in the art. For example, U.S. Pat. No. 2,948,524 to Sweeney et al., U.S. Pat. No. 4,169,584 to Mangalick, U.S. Pat. No. 5,203,681 to Cooper, U.S. Pat. No. 6,093,000 to Cooper and U.S. Pat. No. 6,123,523 to Cooper, and U.S. Pat. No. 6,303,074 to Cooper, all disclose molten metal pumps. The disclosures of the patents to Cooper noted above are incorporated herein by reference. The term submersible means that when the pump is in use, its base is at least partially submerged in a bath of molten metal. 
         [0006]    Three basic types of pumps for pumping molten metal, such as molten aluminum, are utilized: circulation pumps, transfer pumps and gas-release pumps. Circulation pumps are used to circulate the molten metal within a bath, thereby generally equalizing the temperature of the molten metal. Most often, circulation pumps are used in a reverbatory furnace having an external well. The well is usually an extension of the charging well where scrap metal is charged (i.e., added). 
         [0007]    Transfer pumps are generally used to transfer molten metal from the external well of a reverbatory furnace to a different location such as a ladle or another furnace. 
         [0008]    Gas-release pumps, such as gas-injection pumps, circulate molten metal while introducing a gas into the molten metal. In the purification of molten metals, particularly aluminum, it is frequently desired to remove dissolved gases such as hydrogen, or dissolved metals, such as magnesium. As is known by those skilled in the art, the removing of dissolved gas is known as “degassing” while the removal of magnesium is known as “demagging.” Gas-release pumps may be used for either of these purposes or for any other application for which it is desirable to introduce gas into molten metal. 
         [0009]    Gas-release pumps generally include a gas-transfer conduit having a first end that is connected to a gas source and a second end submerged in the molten metal bath. Gas is introduced into the first end and is released from the second end into the molten metal. The gas may be released downstream of the pump chamber into either the pump discharge or a metal-transfer conduit extending from the discharge, or into a stream of molten metal exiting either the discharge or the metal-transfer conduit. Alternatively, gas may be released into the pump chamber or upstream of the pump chamber at a position where molten metal enters the pump chamber. 
         [0010]    Generally, a degasser (also called a rotary degasser) includes (1) an impeller shaft having a first end, a second end and a passage for transferring gas, (2) an impeller, and (3) a drive source for rotating the impeller shaft and the impeller. The first end of the impeller shaft is connected to the drive source and to a gas source and the second end is connected to the connector of the impeller. Examples of rotary degassers are disclosed in U.S. Pat. No. 4,898,367 entitled “Dispersing Gas Into Molten Metal,” U.S. Pat. No. 5,678,807 entitled “Rotary Degassers,” and U.S. Pat. No. 6,689,310 to Cooper entitled “Molten Metal Degassing Device and Impellers Therefore,” filed May 12, 2000, the respective disclosures of which are incorporated herein by reference. 
         [0011]    The materials forming the components that contact the molten metal bath should remain relatively stable in the bath. Structural refractory materials, such as graphite or ceramics, that are resistant to disintegration by corrosive attack from the molten metal may be used. As used herein “ceramics” or “ceramic” refers to any oxidized metal (including silicon) or carbon-based material, excluding graphite, capable of being used in the environment of a molten metal bath. “Graphite” means any type of graphite, whether or not chemically treated. Graphite is particularly suitable for being formed into pump components because it is (a) soft and relatively easy to machine, (b) not as brittle as ceramics and less prone to breakage, and (c) less expensive than ceramics. 
         [0012]    Generally a scrap melter includes an impeller affixed to an end of a drive shaft, and a drive source attached to the other end of the drive shaft for rotating the shaft and the impeller. The movement of the impeller draws molten metal and scrap metal downward into the molten metal bath in order to melt the scrap. A circulation pump is preferably used in conjunction with the scrap melter to circulate the molten metal in order to maintain a relatively constant temperature within the molten metal. Scrap melters are disclosed in U.S. Pat. No. 4,598,899 to Cooper, U.S. patent application Ser. No. 09/649,190 to Cooper, filed Aug. 28, 2000, and U.S. Pat. No. 4,930,986 to Cooper, the respective disclosures of which are incorporated herein by reference. 
       SUMMARY OF THE INVENTION 
       [0013]    The invention is an insert that is positioned in a vessel in order to assist in the transfer of molten metal out of the vessel. In one embodiment, the insert is an enclosed structure defining a cavity and having a first opening in the bottom half of its side and a second opening at the top. The insert further includes a launder structure (or trough) positioned at its top. Molten metal is forced into the first opening and raises the level of molten metal in the cavity until the molten metal passes through the second opening and into the launder structure, where it passes out of the vessel. 
         [0014]    The insert can also be created by attaching or forming a secondary wall to a wall of the vessel, thus creating a cavity between the two walls. A first opening is formed in the secondary wall and a launder structure is positioned, or formed, at the top of the secondary wall and the wall of the vessel, so that a second opening is formed at the top. Molten metal is forced into the first opening and raises the level of molten metal in the cavity until the molten metal passes through the second opening and into the launder structure, where it passes out of the vessel. 
         [0015]    A system according to the invention utilizes an insert and a molten metal pump, which is preferably a circulation pump, but could be a gas-injection (or gas-release) pump, to force (or move) molten metal through the first opening and into the cavity of the insert. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a top, perspective view of a system according to the invention, wherein the system is installed in a vessel designed to contain molten metal. 
           [0017]      FIG. 1A  is another top, perspective view of a system according to  FIG. 1 . 
           [0018]      FIG. 2  is a side, perspective view of an insert used with the system of the present invention. 
           [0019]      FIG. 3  is a side, perspective view of the insert of  FIG. 2  with an extension attached thereto. 
           [0020]      FIG. 4  is a top, perspective view of an alternate system according to the invention. 
           [0021]      FIG. 5  is a top view of the system of  FIG. 4 . 
           [0022]      FIG. 6  is a partial, sectional view of the system shown in  FIG. 5  taken along line C-C. 
           [0023]      FIG. 6  is a top, perspective view of the system shown in  FIG. 4 . 
           [0024]      FIG. 7  is a side view of the insert shown in  FIG. 2 . 
           [0025]      FIG. 8  is a top view of an alternate embodiment of the invention. 
           [0026]      FIG. 9  is a partial sectional view of the system of  FIG. 8  taken along line A-A. 
           [0027]      FIG. 10  is a partial sectional view of the system of  FIG. 8  taken along line B-B. 
           [0028]      FIG. 11  is a close-up view of Section E of  FIG. 10 . 
           [0029]      FIG. 12  is a partial sectional view of the system of  FIG. 8  taken along line C-C. 
           [0030]      FIG. 13  is an exploded view of the system of  FIG. 8  showing an optional bracketing system. 
           [0031]      FIG. 14  is a top, perspective view of the system of  FIG. 13  positioned in a vessel. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    Turning now to the drawings, where the purpose is to describe a preferred embodiment of the invention and not to limit same, a system and insert according to the invention will be described.  FIGS. 1-3  and  7  show a system  10  according to an aspect of the invention, and a vessel  1 . Vessel  1  has a well  2 , a top surface  3 , a side surface  4 , a floor  5 , and a vessel well  6 . 
         [0033]    System  10  comprises a molten metal pump  20  and an insert  100 . Pump  20  is preferably a circulation pump and can be any type of circulation pump satisfactory to move molten metal into the insert as described herein. The structure of circulator pumps is know to those skilled in the art and one preferred pump for use with the invention is called “The Mini,” manufactured by Molten Metal Equipment Innovations, Inc. of Middlefield, Ohio 44062, although any suitable pump may be used. The pump  20  preferably has a superstructure  22 , a drive source  24  (which is most preferably a pneumatic motor) mounted on the superstructure  22 , support posts  26 , a drive shaft  28 , and a pump base  30 . The support posts  26  connect the superstructure  22  to the base  30  in order to support the superstructure  22 . 
         [0034]    Drive shaft  28  preferably includes a motor drive shaft (not shown) that extends downward from the motor and that is preferably comprised of steel, a rotor drive shaft  32 , that is preferably comprised of graphite, or graphite coated with a ceramic, and a coupling (not shown) that connects the motor drive shaft to end  32 B of rotor drive shaft  32 . 
         [0035]    The pump base  30  includes an inlet (not shown) at the top and/or bottom of the pump base, wherein the inlet is an opening that leads to a pump chamber (not shown), which is a cavity formed in the pump base. The pump chamber is connected to a tangential discharge, which is known in art, that leads to an outlet, which is an opening in the side wall  33  of the pump base. In the preferred embodiment, the side wall  33  of the pump base including the outlet has an extension  34  formed therein and the outlet is at the end of the extension. This configuration is shown in  FIGS. 5 ,  9  and  10 . 
         [0036]    A rotor (not shown) is positioned in the pump chamber and is connected to an end of the rotor shaft  32 A that is opposite the end of the rotor shaft  32 B, which is connected to the coupling. 
         [0037]    In operation, the motor rotates the drive shaft, which rotates the rotor. As the rotor (also called an impeller) rotates, it moves molten metal out of the pump chamber, through the discharge and through the outlet. 
         [0038]    An insert  100  according to this aspect of the invention includes (a) an enclosed device  102  that can be placed into vessel well  2 , and (b) a trough (or launder section)  200  positioned on top of device  102 . Device  102  as shown (and best seen in  FIGS. 2-3  and  5 ) is a generally rectangular structure, but can be of any suitable shape or size, wherein the size depends on the height and volume of the vessel well  3  into which device  102  is positioned. The device  102  and trough  200  are each preferably comprised of material capable of withstanding the heat and corrosive environment when exposed to molten metal (particularly molten aluminum). Most preferably the heat resistant material is a high temperature, castable cement, with a high silicon carbide content, such as ones manufactured by AP Green or Harbison Walker, each of which are part of ANH Refractory, based at 400 Fairway Drive, Moon Township, Pa. 15108, or Allied Materials. The cement is of a type know by those skilled in the art, and is cast in a conventional manner known to those skilled in the art. 
         [0039]    Device  102  as shown has four sides  102 A,  102 B,  102 C and  102 D, a bottom surface  102 E, and an inner cavity  104 . Bottom surface  102 E may be substantially flat, as shown in  FIG. 2 , or have one or more supports  102 F, as shown in  FIGS. 3 and 7 . 
         [0040]    Side  102 B has a first opening  106  formed in its lower half, and preferably no more than 24″, or no more than 12″, and most preferably no more than 6″, from bottom surface  102 E. First opening  106  can be of any suitable size and shape, and as shown has rounded sides  106 A and  106 B. First opening  106  functions to allow molten metal to pass through it and into cavity  104 . Most preferably, opening  104  is configured to receive an extension  34  of base  30  of pump  10 , as best seen in  FIGS. 5 ,  9  and  10 . In these embodiments, the outlet is formed at the end of the extension  34 . 
         [0041]    Device  102  has a second opening  108  formed in its top. Second opening  108  can be of any suitable size and shape to permit molten metal that enters the cavity  104  to move through the second opening  108  once the level of molten metal in cavity  104  becomes high enough. 
         [0042]    Trough  200  is positioned at the top of device  102 . Trough  200  has a back wall  202 , side walls  204  and  206 , and a bottom surface  208 . Trough  200  defines a passage  210  through which molten metal can flow once it escapes through second opening  108  in device  102 . The bottom surface  208  of trough  200  is preferably angled backwards towards second opening  108 , at a preferred angle of 2°-5°, even though any suitable angle could be used. In this manner, any molten metal left in trough  200 , once the motor  20  is shut off, will flow backward into opening  108 . The bottom surface  208  could, alternatively, be level or be angled forwards away from opening  108 . Trough  200  may also have a top cover, which is not shown in this embodiment. 
         [0043]    In the embodiment shown in  FIGS. 1-3  and  7 , the trough  200  at the top of insert  100  is integrally formed with device  102 . In a preferred method, after insert  100  is formed, the shape of the launder portion is machined into the top of device  102 . Further, part of the front wall  102 A is machined away so that trough  200  extends outward from wall  102 A, as shown. Trough  200 , however, in any embodiment according to the invention, can be formed or created in any suitable manner and could be a separately cast piece attached to device  102 . 
         [0044]    If trough  200  is a piece separate from device  102 , it could be attached to device  102  by metal angle iron and/or brackets (which would preferably made of steel), although any suitable attachment mechanism may be used. Alternatively, or additionally, a separate trough  200  could be cemented to device  200 . 
         [0045]    An extension  250  is preferably attached to the end of trough  200 . Extension  250  preferably has an outer, steel frame  252  about ¼″-⅜″ thick and the same refractory cement of which insert  100  is comprised is cast into frame  252  and cured, at a thickness of preferably ¾″-2½″. Brackets  260  are preferably welded onto frame  252  and these align with bracket  254  on trough  200 . When the holes in brackets  260  align with the holes in bracket  254 , bolts or other fasteners can be used to connect the extension  250  to the trough  200 . Any suitable fasteners or fastening method, however, may be used. In one embodiment the bracket  254  is formed of ¼″ to ⅜″ thick angle iron, and brackets  260  are also ¼″ to ⅜″ thick iron or steel. Preferably, the surfaces of the refractory cement that from the trough and extension that come into contact with the molten metal are coated with boron nitride. 
         [0046]    It is preferred that if brackets or metal structures of any type are attached to a piece of refractory material used in any embodiment of the invention, that bosses be placed at the proper positions in the refractory when the refractory piece is cast. Fasteners, such as bolts, are then received in the bosses. 
         [0047]    An upper bracket  256  is attached to trough  200 . Eyelets  258 , which have threaded shafts that are received through upper bracket  256  and into bosses in the refractory (not shown), are used to lift the insert  100  into and out of vessel  1 . 
         [0048]    Positioning brackets  270  position insert  100  against an inner wall of vessel  1 . The size, shape and type of positioning brackets, or other positioning devices, depend on the size and shape of the vessel, and several types of positioning structures could be used for each vessel/insert configuration. The various ones shown here are exemplary only. The positioning structures are usually formed of ⅜″ thick steel. 
         [0049]    It is also preferred that the pump  20  be positioned such that extension  34  of base  30  is received in the first opening  100 . This can be accomplished by simply positioning the pump in the proper position. Further the pump may be head in position by a bracket or clamp that holds the pump against the insert, and any suitable device may be used. For example, a piece of angle iron with holes formed in it may be aligned with a piece of angle iron with holes in it on the insert  100 , and bolts could be placed through the holes to maintain the position of the pump  20  relative the insert  100 . 
         [0050]    In operation, when the motor is activated, molten metal is pumped out of the outlet through first opening  106 , and into cavity  104 . Cavity  104  fills with molten metal until it reaches the second opening  108 , and escapes into the passage  210  of trough  200 , where it passes out of vessel  1 , and preferably into another vessel, such as the pot P shown, or into ingot molds, or other devices for retaining molten metal. Installation of the insert into a furnace that contains molten metal is preferably accomplished by pre-heating the insert to 300°-400° F. in an oven and then slowly lowering unit into the metal over a period of 1.5 to 2 hours. 
         [0051]    In another embodiment of the invention shown in  FIGS. 4-6 , the insert  100  is replaced by a secondary wall  400  positioned in a different vessel,  1 ′, next to vessel wall  6 ′. Secondary wall  400  has a side surface  402  and a back surface  404  and is attached to vessel wall  7  by any suitable means, such as being separately formed and cemented to it, or being cast onto, or as part of, wall  6 ′. A cavity  406  is created between the wall  6 ′ of the vessel and secondary wall  400 , and there is an opening (not shown) in secondary wall  400  leading to cavity  406 . A launder  200 ′ is positioned on top of the cavity  406 , and pump  10  is positioned so that its outlet is in fluid communication with the opening in secondary wall  400  so that molten metal will pass through the opening and into the cavity  406  when the pump is in operation. The trough  200  can be formed as a single piece and positioned on top of cavity  402 , or it could be formed onto wall  7  along with secondary wall  400 . Alternatively, a separate trough wall  408  could be separately formed and attached to the top of wall  6 ′ in such a manner as to seal against with the top surface of wall  6 ′ and the back section  404  of wall  400 . In all other respects the system of this embodiment functions in the same manner as the previously described embodiment. This embodiment also includes extension  250  and can use any suitable attachment or positioning devices to position the insert and pump in a desired location in the vessel  1 ′. 
         [0052]    Another embodiment of the invention is shown in  FIGS. 8-12 . This embodiment is the same as the one shown in  FIGS. 1-3  and  7  except for a modification to the insert and the brackets used. This insert is the same as previously described insert  100  except that side  102 A is not machined away. So, the trough  200  does not extend past side  102 A. 
         [0053]      FIGS. 8-10  show a bracket structure that hold pump  20  off of the floor of vessel  1 ″ (which has a different configuration than the previously described vessels).  FIGS. 8-12 , and particularly  FIG. 11 , show an alternate extension  250 ′. Extension is  250 ′ formed in the same manner as previously described extension  250 , except that it has a layer  270 ′ of insulating concrete between ¼″ and 1″ thick between the steel outer shell  252 ′ and the cast refractory concrete layer  272 ′. This type of insulating cement is known to those skilled in the art. Eyelets are included in this embodiment and are received in bosses positioned in the refractory of the extension  250 ′. 
         [0054]    In this embodiment, trough  200 ′ has a top cover  220 ′ held in place by members  222 ′. Extension  250 ′ has a top cover  290 ′ held in place by members  292 ′. The purpose of each top cover is to prevent heat from escaping and any suitable structure may be utilized. It is preferred that each top cover  220 ′ and  290 ′ be formed of heat-resistant material, such as refractory cement or graphite, and that members  222 ′ and  292 ′ are made of steel. As shown, a clamp  294 ′ holds member  292 ′ in place, although any suitable attachment mechanism may be used. 
         [0055]      FIGS. 12 and 13  show the embodiment of the system represented in  FIGS. 8-12 , with an alternate bracing system to fit the vessel into which the system is being positioned. As previously mentioned, the bracing system is a matter of choice based on the size and shape of the vessel, and different bracing systems could be used for the same application. Another structure for aligning the pump  20  with insert  200 ′ is shown in  FIG. 13  bar  400  is received in holders  420 . 
         [0056]    The support brackets are preferably attached to a steel structure of the furnace to prevent the insert from moving once it is in place. A locating pin on the steel frame allows for alignment of the outlet of the pump with the inlet hole at the bottom. 
         [0057]    Having thus described some embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired result.