Patent Publication Number: US-2022213895-A1

Title: Rotor and rotor shaft for molten metal

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 15/916,089 entitled Rotor and Rotor Shaft for Molten Metal, filed Mar. 8, 2018, which is a continuation of and claims priority to U.S. patent application Ser. No. 14/791,166 entitled Rotor and Rotor Shaft for Molten Metal, filed Jul. 2, 2015 (Now U.S. Pat. No. 10,138,892, which is a non-provisional of and claims priority to U.S. Provisional Application Ser. No. 62/020,332 entitled “Coupling and Rotor Shaft for Molten Metal Devices, filed on Jul. 2, 2014, the contents of each of the aforementioned applications are incorporated herein in their entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The inventions herein relate to devices used in molten metal environments and include (1) a rotor, and (2) a rotor shaft to be connected to the rotor. 
     BACKGROUND OF THE INVENTION 
     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. 
     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. 
     This application incorporates by reference the portions of the following publications that are not inconsistent with this disclosure: U.S. Pat. No. 4,598,899, issued Jul. 8, 1986, to Paul V. Cooper, U.S. Pat. No. 5,203,681, issued Apr. 20, 1993, to Paul V. Cooper, U.S. Pat. No. 5,308,045, issued May 3, 1994, by Paul V. Cooper, U.S. Pat. No. 5,662,725, issued Sep. 2, 1997, by Paul V. Cooper, U.S. Pat. No. 5,678,807, issued Oct. 21, 1997, by Paul V. Cooper, U.S. Pat. No. 6,027,685, issued Feb. 22, 2000, by Paul V. Cooper, U.S. Pat. No. 6,123,523, issued Sep. 26, 2000, by Paul V. Cooper, U.S. Pat. No. 6,303,074, issued Oct. 16, 2001, by Paul V. Cooper, U.S. Pat. No. 6,689,310, issued Feb. 10, 2004, by Paul V. Cooper, U.S. Pat. No. 6,723,276, issued Apr. 20, 2004, by Paul V. Cooper, U.S. Pat. No. 7,402,276, issued Jul. 22, 2008, by Paul V. Cooper, U.S. Pat. No. 7,507,367, issued Mar. 24, 2009, by Paul V. Cooper, U.S. Pat. No. 7,906,068, issued Mar. 15, 2011, by Paul V. Cooper, U.S. Pat. No. 8,075,837, issued Dec. 13, 2011, by Paul V. 
     Cooper, U.S. Pat. No. 8,110,141, issued Feb. 7, 2012, by Paul V. Cooper, U.S. Pat. No. 8,178,037, issued May 15, 2012, by Paul V. Cooper, U.S. Pat. No. 8,361,379, issued Jan. 29, 2013, by Paul V. Cooper, U.S. Pat. No. 8,366,993, issued Feb. 5, 2013, by Paul V. Cooper, U.S. Pat. No. 8,409,495, issued Apr. 2, 2013, by Paul V. Cooper, U.S. Pat. No. 8,440,135, issued May 15, 2013, by Paul V. Cooper, U.S. Pat. No. 8,444,911, issued May 21, 2013, by Paul V. Cooper, U.S. Pat. No. 8,475,708, issued Jul. 2, 2013, by Paul V. Cooper, U.S. patent application Ser. No. 12/895,796, filed Sep. 30, 2010, by Paul V. Cooper, U.S. patent application Ser No. 12/877,988, filed Sep. 8, 2010, by Paul V. Cooper, U.S. patent application Ser. No. 12/853,238, filed Aug. 9, 2010, by Paul V. Cooper, U.S. patent application Ser. No. 12/880,027, filed Sep. 10, 2010, by Paul V. Cooper, U.S. patent application Ser. No. 13/752,312, filed Jan. 28, 2013, by Paul V. Cooper, U.S. patent application Ser. No. 13/756,468, filed Jan. 31, 2013, by Paul V. Cooper, U.S. patent application Ser. No. 13/791,889, filed Mar. 8, 2013, by Paul V. Cooper, U.S. patent Application Ser. No. 13/791,952, filed Mar. 9, 2013, by Paul V. Cooper, U.S. patent application Ser. No. 13/841,594, filed Mar. 15, 2013, by Paul V. Cooper, and U.S. patent application Ser. No. 14/027,237, filed Sep. 15, 2013, by Paul V. Cooper. 
     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). 
     Transfer pumps are generally used to transfer molten metal from the one structure to another structure such as a ladle or another furnace. 
     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. 
     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. 
     Molten metal pump casings and rotors often employ a bearing system comprising ceramic rings wherein there are one or more rings on the rotor that align with rings in the pump chamber (such as rings at the inlet and outlet) when the rotor is placed in the pump chamber. The purpose of the bearing system is to reduce damage to the soft, graphite components, particularly the rotor and pump base, during pump operation. 
     Numerous rotor shaft to motor shaft couplings are known. A problem with the couplings, however, is that by applying driving force to the rotor shaft the rotor shaft tends to break at the location where the force is being applied. This is typically at the location where the coupling and rotor shaft are in contact, and the broken end of the rotor shaft must often be chiseled out of an opening in the coupling in which it is retained. 
     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. 
     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. 
     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 may be used in conjunction with the scrap melter to circulate the molten metal in order to maintain a relatively constant temperature within the molten metal. 
     Rotors are used in molten metal processing for a variety of purposes, such as in a pumping device to circulate molten metal, in a rotary degasser to circulate molten metal and mix gas therewith, and in scrap melters to help create a downward draw to pull scrap into the molten metal where the scrap is melted. The most common type of connection between a rotor shaft and a rotor is to: (1) thread an end of the rotor shaft, (2) bore a threaded opening into the rotor, and (3) then screw the threaded end of the rotor shaft into the threaded opening of the rotor. Problems with this type of connection are that the threads can fail over time, thereby causing the rotor to move erratically and fail, and it is difficult to reverse the threaded end of the shaft to remove the rotor. Thus, if the rotor or rotor shaft fail, often both components must be replaced. 
     SUMMARY OF THE INVENTION 
     The present invention alleviates these problems by providing a rotor that includes a section for connecting to a rotor shaft. The connecting section of the rotor has a cavity, an upper surface, and an opening in the upper surface, the opening leading to the cavity. The opening has at least one elongated section. The rotor shaft has an outer surface and a second end with at least one projection extending therefrom, the second end configured to fit through the opening in the upper surface of the rotor (with the at least one projection passing through the at least one elongated section). Once the second end of the rotor shaft is received in the cavity of the rotor, the rotor and/or rotor shaft are rotated so the at least one projection is retained in a position under the top surface and next to an abutment. As the rotor shaft turns the projection presses against the abutment to transmit driving force to the rotor. 
     In one preferred embodiment the rotor shaft has three or four projections, the opening in the upper surface has the same number of elongated sections that respectively align with each of the projections. The second end of the rotor shaft passes through the opening and into the cavity and is then rotated so each projection is positioned against a respective abutment and under the upper surface of the rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a perspective view of a pump for pumping molten metal, which includes a rotor and rotor shaft according to aspects of the invention. 
         FIG. 2  is a perspective view of a rotary degasser that may include a rotor shaft and rotor according to aspects of the invention. 
         FIG. 3  is a perspective view of a scrap melter that may include a rotor shaft and rotor according to aspects of the invention. 
         FIG. 4  is a side view of a rotor shaft according to aspects of the invention. 
         FIG. 5  is a view of the rotor shaft of  FIG. 4 . 
         FIG. 6  is a top view of a rotor according to aspects of the invention. 
         FIG. 7  is a side, cross-sectional view of the rotor of  FIG. 6  taken along lines A-A. 
         FIG. 8  is a top view of the rotor of  FIG. 6  with the top surface removed. 
         FIG. 9  is a side, perspective view of a rotor according to aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring now to the drawing where the purpose is to illustrate and describe embodiments of the invention, and not to limit same,  FIG. 1  shows a molten metal pump  20  that includes a rotor shaft  44  and rotor  100  in accordance with aspects of the present invention. During use, pump  20  is usually positioned in a molten metal bath B in a pump well, which may be part of the open well of a reverbatory furnace. 
       FIG. 2  shows an example of a rotary degasser that could potentially use a rotor shaft/rotor connection in accordance with aspects of the invention and  FIG. 3  shows an example of a scrap melter that could potentially use a rotor shaft/rotor connection in accordance with aspects of the invention. Rotor shaft  44 ′ of rotary degasser  200  is in all respects the same as rotor shaft  44  described below with respect to the way in which it couples to rotor  300 . 
     The components of pump  20 , including rotor  100 , that are exposed to the molten metal are preferably formed of structural refractory materials, which are resistant to degradation in the molten metal. Carbonaceous refractory materials, such as carbon of a dense or structural type, including graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite, or the like have all been found to be most suitable because of cost and ease of machining. Such components may be made by mixing ground graphite with a fine clay binder, forming the non-coated component and baking, and may be glazed or unglazed. In addition, components made of carbonaceous refractory materials may be treated with one or more chemicals to make the components more resistant to oxidation. Oxidation and erosion treatments for graphite parts are practiced commercially, and graphite so treated can be obtained from sources known to those skilled in the art. 
     Pump  20  can be any structure or device for pumping or otherwise conveying molten metal, such as the pump disclosed in U.S. Pat. No. 5,203,681 to Cooper, or an axial pump having an axial, rather than tangential, discharge. One preferred pump  20  has a pump base  24  for being submersed in a molten metal bath. In this embodiment, pump base  24  preferably includes a generally nonvolute pump chamber  26 , such as a cylindrical pump chamber or what has been called a “cut” volute, although pump base  24  may have any shape pump chamber suitable of being used, including a volute-shaped chamber. Chamber  26  may have only one opening, either in its top or bottom, since only one opening is required to introduce molten metal into pump chamber  26 , although chamber  26  may have an opening in both its top and bottom. Generally, pump chamber  24  has two coaxial openings of the same diameter and usually one is blocked by a flow blocking plate mounted on the bottom of, or formed as part of, rotor  100 . Base  24  further includes a tangential discharge  30  (although another type of discharge, such as an axial discharge may be used) in fluid communication with chamber  26 . 
     The invention is not limited to any particular type or configuration of base, or of even having a base. A pump used with the invention could be of any size, design or configuration suitable for utilizing a rotor shaft and rotor according to the invention. 
     In the preferred embodiment, post clamps  35  secure posts  34  to superstructure  36 . In the embodiment shown, one or more support posts  34  connect base  24  to a superstructure  36  of pump  20  thus supporting superstructure  36 , although any structure or structures capable of supporting superstructure  36  may be used. Additionally, pump  20  could be constructed so there is no physical connection between the base and the superstructure, wherein the superstructure is independently supported. The motor, drive shaft and rotor could be suspended without a superstructure, wherein they are supported, directly or indirectly, to a structure independent of a pump base. 
     A motor  40 , which can be any structure, system or device suitable for powering pump  20 , but is preferably an electric or pneumatic motor, as shown is positioned on superstructure  36  and is connected to an end of a drive shaft  42 . Drive shaft  42  can be any structure suitable for rotating a rotor (also called an impeller), and preferably comprises a motor shaft (not shown) coupled to rotor shaft  44 . The motor shaft has a first end and a second end, wherein the first end of the motor shaft connects to motor  40  and the second end of the motor shaft connects to a coupling. 
     Rotor shaft  44  is shown in  FIGS. 1, 4 and 5  and has a first end  44 A that connects to the coupling and a second end  44 B that connects to rotor  100 , best seen in  FIGS. 6-9 . End  44 A can connect to a coupling in any suitable manner. 
     End  44 B of rotor shaft  44  has at least one outwardly-extending projection  50 , and as shown has four outwardly-extending projections  50  equally radially spaced about the outer surface  52  (which as shown is cylindrical or annular) of rotor shaft  44 , although any suitable number of projections may be used. Each projection  50  can be of any suitable size or shape, and at any suitable location on end  44 B of rotor shaft  44 . In one embodiment each projection  50  is generally rectangular, between ⅜″ and 1½″ wide, between ¾″ and 3″ in length (as measured along the longitudinal axis of rotor shaft  44 ) and extends outward from rotor shaft  44  by ¼″ to 2½″. Each projection  50  can be integrally formed with or attached to rotor shaft  44 . For example, a slot (not shown) may be formed in rotor shaft  44  and a projection  50  could be cemented or otherwise affixed into the slot. Each slot (if used) is preferably about 1/32″ to ¼″ wider and longer than the width and length of the projection  50  that fits therein, and each slot and could be between 3/16″ to 1″ deep in rotor shaft  44 . Second end  44 B also may include a chamfered portion  54  that assists in positioning the second end  44 B into a connective portion  110  in rotor  100 . If rotor shaft  44  is used in a rotary degasser, it would preferably have an internal passage (not shown) for the transfer of gas from first end  44 A to second end  44 B. 
     One preferred rotor  100 , shown in  FIGS. 6-9 , could be of any shape or size suitable to be used in a molten metal pump, a rotary degasser or scrap melter, respectively, with the present invention being directed to the connection between the rotor shaft and the rotor and the respective structures of the rotor shaft end  44 B and rotor connective portion. Rotor  100  is preferably circular in plain view (although it can be of any suitable shape for its intended use) and includes a displacement structure  102 , an inlet structure  104 , a top surface  106 , a bottom surface  108 , and a connective portion  110 . Rotor  100  could be comprised of a single material, such as graphite or ceramic, or could be comprised of different materials. For example, inlet structure  104  may be comprised of ceramic and the displacement structure  102  may be comprised of graphite, or vice versa. Any part or all of rotor  100  may also include a protective ceramic coating. 
     Connective portion  110  connects to end  44 B of rotor shaft  44 . Connective portion  110  preferably includes (1) an upper surface  300 , (2) an opening  302  in upper surface  300 , the opening  302  as shown in this embodiment being generally circular and having at least one elongated section  304 , and as shown, four elongated sections  304 , (3) a cavity  306  beneath upper surface  300  and in communication with each elongated portion  304 , and (4) at least one abutment  308  within each cavity  306 . 
     The at least one abutment  308  is adjacent to the at least one elongated section  304  and on the rotational downstream side of elongated section  304 . In this manner, when shaft  44  is rotated during operation, rotational driving force is transmitted to rotor  100  by the at least one projection  50  pushing against and transmitting force to the at least one abutment  308 . Further, the rotation of shaft  44  during operation would not move a projection  50  back into alignment with a corresponding elongated portion  304 , which could lead to the rotor  100  and shaft second end  44 B separating. 
     To connect the rotor shaft  44  to rotor  100 , end  44 B of rotor shaft  44  is moved through opening  302 . The rotor shaft  44  and/or rotor  100  are rotated until at least one projection  50  is under upper surface  300  and pressed against an abutment  308 . In this manner the rotor shaft  44  is connected to rotor  100  and can provide rotational driving force thereto. 
     Having thus described different 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 product.