Abstract:
A vertical member, which is preferably a support post used in a molten metal pump, includes a ceramic tube and tensioning structures to add a compressive load to the tube along its longitudinal axis. This makes the tube less prone to breakage. A device, such as a pump, used in a molten metal bath includes one or more of such vertical members.

Description:
CROSS-REFERENCE TO 
       [0001]    This application claims the benefit of provisional application Ser. No. 62/278,314, filed Jan. 13, 2016, and entitled “Tensioned Support Shaft and Other Molten Metal Devices,” the contents of which are incorporated herein by reference, to the extent such contents do not conflict with the present disclosure. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to tensioned support shafts that may be used in various devices, particularly pumps for pumping molten metal. 
       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, which 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 of any suitable configuration, 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 shaft is typically an impeller shaft connected to one end of a motor shaft, the other end of the drive shaft being connected to an impeller. Often, the impeller (or rotor) shaft is comprised of graphite and/or ceramic, 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. Other molten metal pumps do not include a base or support posts and are sized to fit into a structure by which molten metal is pumped. Most pumps have a metal platform, or super structure, that is either supported by a plurality of support posts attached to the pump base, or unsupported if there is no base. The motor is positioned on the superstructure, if a superstructure is used. 
         [0005]    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. 6,124,523, 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. 
         [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. Circulation pumps may be used in any vessel, such as in a reverbatory furnace having an external well. The well is usually an extension of the charging well, in which scrap metal is charged (i.e., added). 
         [0007]    Standard transfer pumps are generally used to transfer molten metal from one structure to another structure such as a ladle or another furnace. A standard transfer pump has a riser tube connected to a pump discharge and supported by the superstructure. As molten metal is pumped it is pushed up the riser tube (sometimes called a metal-transfer conduit) and out of the riser tube, which generally has an elbow at its upper end, so molten metal is released into a different vessel from which the pump is positioned. 
         [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 both 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. The gas may also be released into any suitable location in a molten metal bath. 
         [0010]    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. 
         [0011]    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 impeller. 
         [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. 
         [0013]    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, or other ceramic material 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. 
         [0014]    Ceramic, however, is more resistant to corrosion by molten aluminum than graphite. It would therefore be advantageous to develop vertical members used in a molten metal device that are comprised of ceramic, but less costly than solid ceramic members, and less prone to breakage than normal ceramic. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention relates to a vertical member used in a molten metal device. The member is comprised of a hollow ceramic outer shell that has tension applied along a longitudinal axis of a rod therein. When such tension is applied to the rod, the ceramic outer shell is much less prone to breakage. One type of vertical member that may employ the invention is a support post. The disclosure also relates to pump including such support posts and to other molten metal devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a pump for pumping molten metal, which may include rotor shaft and plurality of support posts, in accordance with various embodiments. 
           [0017]      FIG. 2A  is a profile view of a support post, in accordance with various embodiments. 
           [0018]      FIG. 2B  is an exploded view of a support post, in accordance with various embodiments. 
           [0019]      FIG. 3A  is a cross sectional view of a support post, in accordance with various embodiments. 
           [0020]      FIG. 3B  is a cross sectional view of a bottom portion of a support post, in accordance with various embodiments. 
           [0021]      FIG. 3C  is a cross sectional view of a top portion of a support post, in accordance with various embodiments. 
           [0022]      FIGS. 3D-3Z  illustrate various components of exemplary support posts in accordance with various embodiments of the disclosure. 
           [0023]      FIGS. 4A-4C  illustrate a rotor plug in accordance with exemplary embodiments of the disclosure. 
           [0024]      FIGS. 5A-1, 5A-2  and  FIGS. 5B-5R  illustrate a support post and various components thereof in accordance with additional exemplary embodiments of the disclosure. 
           [0025]      FIGS. 6A-6J  illustrate a rotor shaft and various components thereof in accordance with additional exemplary embodiments of the disclosure. 
           [0026]      FIGS. 7A-7P  illustrate a coupling and various components thereof in accordance with additional exemplary embodiments of the disclosure. 
           [0027]      FIGS. 8A-8T  illustrate a pump and various components thereof in accordance with exemplary embodiments of the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    For any device described herein, any of the components that contact the molten metal are preferably formed by a material that can withstand the molten metal environment. Preferred materials are oxidation-resistant graphite and ceramics, such as silicon carbide. 
         [0029]    Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings.  FIG. 1  depicts a molten metal pump  100  according to exemplary embodiments of the disclosure. When in operation, pump  100  is typically positioned in a molten metal bath in a pump well, which is typically part of the open well of a reverbatory furnace. Pump  100  includes motor  120 , superstructure  130 , support shafts  140 , drive shaft  122 , rotor  110 , base  160 , and a gas transfer system  170 . The gas transfer system  170  may comprise gas-transfer foot  172  and gas-transfer tube  174 . 
         [0030]    The components of pump  100  or portions thereof that are exposed to the molten metal (such as support shafts  140 , drive shaft  122 , rotor  110 , base  160 , gas-transfer foot  172  and gas-transfer tube  174 ) are preferably formed of structural refractory materials, which are resistant to degradation in the molten metal. 
         [0031]    Pump  100  need not be limited to the structure depicted in  FIG. 1 , but 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. Preferred pump  100  includes a base  160  (e.g., a pump base) for being submersed in a molten metal bath. Pump base  160  preferably includes a generally nonvolute pump chamber  210 , such as a cylindrical pump chamber or what has been called a “cut” volute, although pump base  160  may have any shape pump chamber suitable of being used, including a volute-shaped chamber. Pump chamber  210  may be constructed to have only one opening, either in its top or bottom, if a tangential discharge is used, since only one opening is required to introduce molten metal into pump chamber  210 . Generally, pump chamber  210  has two coaxial openings of the same diameter and usually one is blocked by a flow blocking plate mounted on, or formed as part of, rotor  110 . Base  160  further includes a tangential discharge  220  (although another type of discharge, such as an axial discharge may be used) in fluid communication with pump chamber  210 . 
         [0032]    In this embodiment, one or more support posts  140  connect base  160  to a superstructure  130  of pump  100  thus supporting superstructure  130 . Pump  100  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 the pump base. 
         [0033]    Motor  120 , which can be any structure, system or device suitable for driving pump  100 , but is preferably an electric or pneumatic motor, is positioned on superstructure  130  and is connected to an end of a drive shaft  122 . A drive shaft  122  can be any structure suitable for rotating an impeller, and preferably comprises a motor shaft (not shown) coupled to a rotor shaft. The motor shaft has a first end and a second end, wherein the first end of the motor shaft connects to motor  120  and the second end of the motor shaft connects to the coupling. Rotor shaft  124  has a first end and a second end, wherein the first end is connected to the coupling and the second end is connected to rotor (or impeller)  110 . 
         [0034]    Rotor  110  can be any rotor suitable for use in a molten metal pump and the term “rotor,” as used in connection with this disclosure, means any device or rotor used in a molten metal device to displace molten metal. 
         [0035]    As described herein, support post (also referred to herein as support shaft)  140  may be a structure that is configured to support a motor and/or superstructure of a molten metal pump. In various embodiments and with reference to  FIG. 2A  and  FIG. 2B , a support post  240 , suitable for use as support post  140 , comprises a tube  250 , a tension rod  242 , a bottom cap  246 , and a top cap  244 . Tension rod  242  may be disposed within a cavity  251  defined by the inner wall  149  of tube  250 . Tension rod  242  may be attached at one and to bottom cap  246  and at its other end to top cap  244 . In this embodiment, tension rod  242  is placed in tension by bottom cap  246  and top cap  244 , creating a compressive load on tube  250 . 
         [0036]    Tube  250 , illustrated in more detail in  FIGS. 3L-3N , preferably comprises a first end  250 A and a second end  250 B. Bottom cap  246  is configured to receive, engage, retain, and/or otherwise mate to the first end  250 A of tube  250 . Bottom cap  246  may also be operatively coupled to the first end  242 A of tension rod  242 . Top cap  244  may be configured to receive, engage, mate with, couple to, and/or otherwise receive the second end  250 B of tube  250 . Similarly, top cap  244  may be configured to operatively couple to, engage, and/or otherwise mate with the second end  242 B of tension rod  242  and/or a portion of tension rod  242  adjacent to the second end  242 B of tension rod  242 . 
         [0037]    In various embodiments, tube  250  may comprise inner or interior surface  149  that defines a hollow channel or cavity  251  within tube  250 . As discussed herein, tension rod  242  may be installable within and/or housed by tube  250  within its hollow channel. Moreover, tension rod  242  may be separated from the interior surface of tube  250 . In this regard, there may be a gap defined between tension rod  242  and the interior surface  149  of tube  250 . 
         [0038]    In various embodiments, tube  250  may be a homogeneous ceramic material. For example, tube  250  may be formed of a ceramic material such as, for example, silicon carbide. 
         [0039]      FIGS. 3O-3Q  illustrate tension rod  242  in greater detail. Tension rod  242  can be formed of, for example, steel. Exemplary tension rods have a length of about 38.75 to about 45.75 inches and can have a diameter of about one inch. First end  242 A can include a flat face  242 D, while second end  242 B can include a tip that includes a first portion  242 E, which is cylindrical in shape and which has a smaller diameter than a middle section  242 G, and a second section  242 F that is frusto-conical in shape. 
         [0040]    Top cap  244  and bottom cap  246  are preferably made of graphite. In various embodiments, and with reference to  FIG. 2B , bottom cap  246  is in the form of an assembly. Bottom cap  246  comprises a housing  247  and a cover  248 . Cover  248 , may be operatively coupled to and/or may be installable within housing  247 . For example, cover  248  may comprise a threaded portion  272  that is configured to thread into or otherwise engage with a receivable channel or cylinder within housing  247 . Moreover, bottom cap  246  may comprise a fastener  254 - 1  and a washer  252 - 1 . Fastener  254 - 1  and/or washer  252 - 1  is configured to engage the first end  242 A of tension rod  242 . 
         [0041]    Bottom cap  246  and portions thereof are illustrated in greater detail in  FIGS. 3D-3K . Housing  247  includes a top portion  260  including a top surface  261  having a recess  262  formed therein for receiving tube  250 , a channel  264  for receiving tension rod  242 , and an opening  266  for receiving cover  248  through a bottom portion  268  of housing  247 . Recess  262 , and channel  264  and opening  266  can be coaxial. As illustrated in  FIG. 3E . a portion of opening  266  can be threaded, so as to enable engagement with threaded portion  272  of cover  248 . Housing  247  can also include a cavity  270 . 
         [0042]    In various embodiments, top cap  244  is an assembly comprising housing  243  and spring  256  (illustrated in more detail in  FIGS. 3U-3W ). Spring  256  is installable within housing  243  of top cap  244 . Second end  242 B of tension rod  242  is configured to pass through and protrude from housing  243  of top cap  244 . Spring  256  is installable over second end  242 B of tension rod  242 . In this regard, spring  256  is preferably configured to add tension to rod  242 . Top cap  244  may further comprise a spring cover  257  (illustrated in more detail in  FIGS. 3X-3Z ), one or more washers including, for example, washer  252 - 2  and washer  252 - 3 , and a fastener  254 - 2 . Spring cover  257  as shown is installable over spring  256 . One or more washers such as, for example, washer  252 - 2  and washer  252 - 3  may be installable on either side of spring cover  257 . In this regard, washer  252 - 2  and/or washer  252 - 3  are configured to retain spring  256  within spring cover  257 . Moreover, fastener  254 - 2  may be configured to engage and/or may be installable on the second end  242 B of tension rod  242 . Second end  242 B of tension rod  242  may comprise a threaded portion  242 C. Fastener  254 - 2  may be configured to engage and/or may be installable on the threaded portion  242 C. Fastener  254 - 2  may also be configured to seat against and/or retain one or more of washer  252 - 2 , washer  252 - 3 , spring  256 , and/or spring cover  257 . In this regard, the assembly within top cap  244  is preferably configured to create a load on tension rod  242  thus creating a compressive load on tube  250 . 
         [0043]      FIGS. 3R-3T  illustrate housing  243  in greater detail. Housing  243  includes a first opening  274 , a passage  276 , and a second opening  278 , all of which can be coaxial. Recess  243  can be configured to receive a portion of tube  250 , passage  276  can be configured to receive tension rod  242  therethrough, and recess  274  can be configured to receive washer  252 - 2 , spring  256 , spring cover  257 , washer  252 - 3 , and fastener  254 - 2 . 
         [0044]    In various embodiments, and with reference to  FIG. 3A ,  FIG. 3B , and  FIG. 3C , a support post  340 , which may be the same or similar to support post  240 , may comprise portions that are self-contained. For example, bottom cap  346  may create a self-contained assembly when tube  350  is installed with and/or engages bottom cap  346 . In this regard, bottom cap  346  may be configured to isolate a tension rod  342  from a molten metal environment when support post  340  is installed on a molten metal pump. In operation, portions of support post  340  would be submerged within a molten metal bath. In order to prevent corrosion of tension rod  342  (which can be the same as or similar t tension rod  242 ), tube  350  (which can be the same as or similar to tube  250 ) and bottom cap  346  may be configured to form a liquid tight assembly that prevents molten metal (e.g., molten aluminum) from reaching tension rod  342 . 
         [0045]    In various embodiments, and as discussed herein, bottom cap  346  may comprise various parts including washers such as, for example, washer  352 - 1  and fasteners such as, for example, fastener  354 - 1 . These washers and fasteners may be separately removable components or they may be integrally formed within one or more components of bottom cap  346 . For example, washer  352 - 1  may be integrally formed within housing  347 . In this regard, a first end  342 A of tension rod  342  may be configured to pass through housing  347  and/or washer  352 - 1 . Moreover, the first end  342 A of tension rod  342  may comprise a threaded portion  342 C that threads into and/or threads through housing  347  and/or washer  352 - 1 . Housing  347  and/or cover  348  may also comprise and/or may be configured with an integrally formed fastener  354 - 1 . In this regard, first end  342 A of tension rod  342  may be configured to thread through the integral fastener  354 - 1  and/or may be capable of having the integral fastener threaded on the threaded portion  342 C of the first end  342 A of tension rod  342 . 
         [0046]    In various embodiments, top cap  344  may be an assembly that is configured to receive a threaded portion  342 D of a second end  342 B of tension rod  342 . Top cap  344  may comprise various components including, for example, washers  352 - 2  and  352 - 3 , fastener  354 - 2 , spring  356 , and/or spring cover  357 . One or more of these elements may be integrally formed within top cap  344 . For example, washer  352 - 2  may be integrally formed within or as part of top cap  344 . Moreover, top cap  344  may be a multi-piece assembly that allows for installation of various components including, for example, spring  356  and/or spring cover  357 . Top cap  344  may be, for example, a clamshell assembly having two halves that thread together. A first portion  344 A of the clamshell assembly of top cap  344  may comprise a washer  352 - 2  that is configured to provide a seat or loading surface for spring  356  and a seating surface for spring cover  357 . Moreover, a second portion  344 B of a clamshell assembly of top cap  344  may comprise an integrally formed fastener  354 - 2  and washer  352 - 3 . In this regard, the first portion  344 A and second portion  344 B of the clamshell assembly of top cap  344  may be operatively coupled to one another with various fasteners, threading and/or the like. 
         [0047]    In various embodiments, the second end  342 B of tension rod  342  may comprise a threaded portion  342 D that is configured to thread through and/or pass through one or more components of top cap  344 , including, for example, spring  356 , washers  352 - 2  and  352 - 3 , spring cover  357 , fastener  354 - 2 , housing  343 , and/or the like. In this regard, the second end  342 B of tension rod  342  may comprise a threaded portion  342 D and a guide portion  342 E having a tip with a reduced diameter and/or a chamfered edge. 
         [0048]    In various embodiments, the second end  342 B of tension rod  342  may pass through top cap  344  allowing engagement with a base or superstructure of a molten metal pump. 
         [0049]      FIGS. 5A-5C  illustrate a support post  540 , also suitable as support post  140 , in accordance with additional exemplary embodiments. Support post  540  includes a tube  550 , a tension rod  542 , a bottom cap  546 , and a top cap  544 . Tension rod  542  can be disposed within a cavity  551 , which is defined by an inner wall  549  or tube  550 . 
         [0050]      FIG. 5D  and  FIGS. 5F-5H  illustrate bottom cap  546  in greater detail. Bottom cap  546  includes a housing  548  to receive a first end  542 A of tension rod  542 . In the illustrated example, housing  548  includes a recess  551  to threadedly or otherwise engage with first end  542 A of tension rod  542 . As illustrated in  FIG. 5H , recess  551  can include a substantially cylindrical section  560  and a conical section  562  that comes to a point. Housing  548  also includes a recess  553  to receive a first end  550 A of tube  550 . Recesses  552  and  551  can be coaxial. As illustrated in  FIG. 5G , recess  553  includes a tapered section  564  and a cylindrical section  566 . Recess  553  includes a flat surface  555 , having a hole therethrough to receive first end  542 A of tension rod  542 . 
         [0051]    Top cap  544 , illustrated in greater detail in  FIGS. 5E and 5O-5R , includes a housing  570  to receive a second end  542 B of tension rod  542 . In the illustrated example, housing  570  includes a recess  571  to threadedly or otherwise engage with second end  542 B of tension rod  542 . Recess  571  can include a first substantially cylindrical section  572 , a second substantially cylindrical portion  573 , and a conical section  574  that comes to a point  575 . Housing  570  or top cap  544  also include a recess  576  that includes a (e.g., flat) surface  577  that engages with and can contact second send  550 B of tube  550 . Top cap  544  can also include a notch on at least a portion of housing  570 . Top cap  544  can also include a hole  580  extending partially or entirely through housing  570 . 
         [0052]    Top cap  544  and bottom cap  546  can be attached (e.g., threadedly) to second end  542 B and first end  542 A, respectively, of tension rod  542  to apply a compressive load to tube  550 . 
         [0053]      FIGS. 5I-5K  illustrate tube  550  in greater detail. Tube  550  includes a first cylindrical portion  582 , a tapered portion  586 , and optionally a second cylindrical portion  588 . As illustrated in  FIG. 5J , cavity  551  extends through portions  582 ,  586 , and  588 . Cavity  551  can be tapered, such that an opening at first end  550 A is smaller than the opening of cavity  551  at second end  550 B. For example, the opening at second end  550 B can have a diameter of about 1.6 inches and the opening at first end can have a diameter of about 1.4 inches, when a length L of tube  550  ranges from about 27.9 to about 38.5 inches. 
         [0054]    First end  550 A of tube  550  includes tapered portion  586  and optional cylindrical portion  588 . As illustrated in  FIG. 5C , portions  586  and  588  can be received by housing  548  of bottom cap  546 . First end  550 A also include a face  590 , which can be flat or substantially flat, so as to engage (e.g., contact) surface  555  of bottom cap  546 . Similarly, second end  550 B includes a face  592  that can be flat and configured to engage with and/or contact surface  577  of top cap  544 . A portion of first cylindrical portion  582  can be received within recess  576 , so that face  592  contacts surface  577 . Recess  576  can be, for example, about ¾ inches thick with a diameter of about 5.05 inches. 
         [0055]      FIGS. 5L-5N  illustrate tension rod  542  in greater detail. As previously noted, tension rod includes first end  542 A, which includes an engagement mechanism  594 , such as threads. Similarly, second end  542 B includes an engagement mechanism  596 , such as threads. Engagement mechanisms  594  and  596  allow top cap  544  and bottom cap  546  to attach to tension rod  542 , so as to allow a compressive force to be applied to tube  550 . As illustrated, ends  542 C and  542 D or tension rod  542  can include a flat face that is perpendicular to the axis of tension rod  542 . 
         [0056]      FIGS. 6A-6J  illustrate a rotor shaft in accordance with various embodiments of the disclosure. Rotor shaft  600  includes an outer tube  602 , an inner rod  604 , a cap  606 , and a structure  618 . Rotor shaft  600  is attached to a rotor  608 . 
         [0057]    Outer tube  602  includes a first end  610 , a second end  612 , and an outer surface  612 . Outer tube  602  includes a cavity  614  spanning therethrough to receive inner rod  604 . Outer tube  602  can be formed of, for example, a ceramic, such as silicon carbide. 
         [0058]    Inner rod  604  can include a rod (e.g., steel) that is partially threaded—e.g., including first (e.g., threaded) portion  615  and second (e.g., threaded) portion  616 . Structure  618 , such as a nut, can be threadedly attached to second threaded portion  616  to retain rotor  608  proximate or adjacent second end  612 . First portion  615  can be used to engage with cap  606  to retain cap  606  proximate or adjacent first end  610 . Rotor shaft  600  can also include a washer  620 —e.g., between rotor  608  and nut  618 . 
         [0059]    Cap  606  and portions thereof are illustrated in more detail in  FIGS. 6D-6J . Cap  606  includes a first section  622  having a top section  623  configured to engage with a coupling (an exemplary coupling is described in more detail below) and a bottom section  624  configured to engage with outer tube  602  and inner rod  604 . Top section  622  can be of substantially tubular shape, having one or more L-shaped openings  626  formed therein to connect cap  606  to a coupling. Bottom section  624  includes a cavity  626  to receive inner rod  604 , a first recess  628  to receive a bottom portion of first section  622 , and a third recess  630  to receive a top surface of first end  610  of outer tube  602 . Cap  606  can be formed of, for example, steel. Further, cap  606  can be configures, such that when cap  606  is connected to a coupling and the coupling drives rotor shaft  600 , rotor shaft  600  moves in a direction that tightens the cap against first end  610  of outer tube  602  to apply axial pressure on outer tube  602 . 
         [0060]    Rotor shaft  600  can also include a rotor plug  400 , illustrated in  FIGS. 4A-4C . Rotor plug  400  can be received by (e.g., threadedly) by rotor  608 , as illustrated in  FIG. 6B . Rotor plug  400  includes threads  402  to engage with rotor  608 . Rotor plug  400  can also include recess  404  to facilitate threaded engagement of rotor plug with rotor  608 . 
         [0061]    Rotor  608  connects to second end  612  of rotor shaft  602 . Rotor  608  includes one or more (e.g., a plurality) of spaced-apart blades  632 - 636 , a passageway  638  for receiving second (e.g., threaded) end  616  of inner rod  604 , a cavity for retaining structure  618  and for receiving rotor plug  400 . 
         [0062]      FIGS. 7A-7P  illustrate a coupling  700  suitable for use with a rotor shaft for a molten metal device. Coupling  700  includes a body  702 , one or more securing structures  704 - 708 , and one or more tightening structures  710 ,  712 , and  714 . Coupling  700  can be used to couple rotor shaft  602  to, for example, a motor shaft (also referred to herein as a motor post). Each of the components of coupling  700  can be formed of steel (e.g., hardened steel). 
         [0063]    Body  702  includes an opening  716  to receive a motor shaft from a motor, described in more detail below, and an outer surface  718  to be received by an inner surface  640  of cap  606  of rotor shaft  600 . Body  702  also includes openings  720 ,  722  and  724  to receive (e.g., threadedly) one or more (e.g., manual) tightening structures  710 - 714 . Body  702  also includes opening  726  and  728  to receive a rod  730 , which can be a hardened steel rod having, for example a diameter of about 0.75 inches and a length of about 4.75 inches. Body  702  can further include a notch  732  and/or recessed region  734 . In the illustrated example, opening  716  includes recessed region  734 , a first section  736 , and a second section  738 . A diameter of the opening of recessed region  734  is larger than the diameter of the opening of first region  736 , and the diameter of the opening of first region  736  is larger than a diameter of the opening of second region  738 . Each of the recessed region  734 , the opening in the first region, and the opening in the second region can be cylindrical. 
         [0064]    Securing structures  704 - 708  can be in the form of tubes formed of, for example, schedule  40  pipe, having a one inch diameter (e.g., about 1.049″ ID and about 1.315″ OD) and a length of about 3.5 inches. Securing structures  704 - 708  can be welded to outer surface  718 —e.g., evenly spaced along the same height of outer surface  718 . In the illustrated example, three securing structures  704 - 708  are welded to outer surface  718 . 
         [0065]      FIGS. 8A-8T  illustrate a pump  800  in accordance with various embodiments of the disclosure. Pump  800  can be similar to pump  100 , and similar to pump  100 , pump  800  can be used for circulation or as a degasser or for demagging. Pump  800  includes a base assembly  802 , one or more support posts  806 - 808 , a rotor shaft  810 , an injection button  812 , an injection tube  814 , a pump mount assembly or superstructure  816 , a washer  818  and a lock washer  820 , an injection tube clamp  822 , a motor  824 , a coupling  826 , a motor strap  828 , fasteners (e.g., bolts)  830 - 836  and (e.g., nuts)  838 - 844  and a fastener  846 . Similar to pump  100 , components of pump  800  that are exposed to molten metal can be formed of structural refectory materials, such as ceramic or graphite, that are resistant to degradation in the molten metal. 
         [0066]    Pump mount assembly  816  includes a pump mount  846 , pump mount insulation  848 , a motor mount plate  849 , one or more fasteners  850 , such as bolts  852  and washers (e.g., lock washers)  854 . Pump mount insulating  848  can be coupled to pump mount  846  using, for example, bracket  849  and fastener  851 , which can include, for example, a bolt  853  and a washer  855 . Motor mount plate  849  can be attached to pump mount  846  using fasteners  850 . 
         [0067]    Base assembly  802  includes a pump chamber  856  that can include any suitably shaped chamber, such as a generally nonvolute shape—e.g., a cylindrical pump chamber, sometimes referred to as a “cut” volute; alternatively pump chamber  856  can include a volute-shape. Pump chamber  856  can be constructed to have only one opening, either in its top or bottom, if a tangential discharge is used, since only one opening is required to introduce molten metal into pump chamber  856 . Pump chamber  856  can include two coaxial openings of the same diameter, in which case usually one is blocked by a flow blocking plate  803  mounted on, or formed as part of, rotor  801 . Base assembly  802  further includes a tangential discharge  858  (although another type of discharge, such as an axial discharge may be used) in fluid communication with pump chamber  856 . 
         [0068]    The one or more support posts  806 - 808  can be the same or similar to support posts described elsewhere herein. For example, support posts  806 - 810  can be support posts  140 ,  240 ,  340 , or  540 . Similarly, rotor shaft  810  can be the same as or similar to rotor shaft  600 . 
         [0069]    Injection button  812  can be coupled to injection tube  814 . Injection tube  814  can, in turn, can be coupled to pump mount assembly  816  or another portion of pump  800  using, for example, injection tube clamp  822 . Injection button  812  and injection tube  814  can be used to provide gas from a gas source to a molten metal bath, wherein injection button  812  is at least partially within the molten metal bath. The gas can be released downstream of pump chamber  856  into the pump discharge or into a stream of molten metal exiting wither the discharge or a conduit. Alternatively, gas can be released into pump chamber  856  or upstream of pump chamber  856 .  FIGS. 8D-8M and 8T  illustrate various configurations of pump  800 . 
         [0070]    Some specific examples of embodiments of the invention follow:
       1. A support post, comprising:
           a tube defining a hollow channel and having a first tube end and a second tube end;   a tension rod having a first rod end and a second rod end disposed within the hollow channel of the tube;   a bottom cap configured to receive the first tube end and operatively coupled to the first rod end; and   a top cap configured to receive the second tube end and operatively couple to a portion of the tension rod, wherein the tension rod is configured to load the tube in response to be operatively coupled to the bottom cap and the top cap.   
           2. The support post of example 1, wherein the tube is a homogenous ceramic.   3. The support post of example 1, wherein the tube is silicon carbide.   4. The support post of example 1, wherein the tube is comprised of silicon carbide.   5. The support post of any of examples 1-4, wherein the tube comprises an interior surface, and wherein the tension rod is separated from the interior surface defining a gap between the tension rod and the interior surface.   6. The support post of any of examples 1-5, wherein the bottom cap is made of graphite.   7. The support post of any of examples 1-5, wherein the bottom cap and top cap are each comprised of one or more of graphite and silicon carbide.   8. The support post of any of examples 1-7 further comprising a fastener disposed within the bottom cap and configured to engage the tension rod to retain the tension rod within the bottom.   9. The support post of example 8, wherein a portion of the tension rod adjacent the first rod end is threaded and configured to receivably engage the fastener.   10. The support post of example 7 or 8 further comprising a washer installable over the first rod end of the tension rod and engagable by the fastener, wherein the fastener is configured to load the tension rod.   11. The support post of any of examples 1-10, wherein the bottom is a two-piece assembly that is configured to isolate the tension rod from a molten metal environment.   12. The support post of any of examples 1-11, further comprising a spring disposed within the top cap and installable over the second rod end.   13. The support post of example 12, wherein the spring is configured to load the tension rod.   14. The support post of example 12, further comprising a first washer, a second washer, and a fastener, wherein the spring is disposed between the first washer and the second washer and retained by the fastener within the top cap.   15. The support post of example 14, a portion of the tension rod adjacent the second rod end is threaded and is configured to receive the fastener.   16. The support post of any of examples 1-15, wherein the second rod end is configured to protrude through the top cap.   17. A molten metal pump comprising:
           a superstructure;   a motor having a motor post with a first post end connected to the motor and a second post end;   a rotor shaft operatively coupled to the second post end;   a support post comprising,
               a tube defining a hollow channel;   a tension rod having a first rod end and a second rod end disposed within the hollow channel of the tube;   
               a bottom cap operatively coupled to the first rod end; and   a top cap operatively coupled to a portion of the tension rod, wherein the tension rod is configured to load the tube in response to be operatively coupled to the bottom cap and the top cap; and   a base coupled to the superstructure by the support post.   
           18. A molten metal pump comprising:
           a superstructure;   a motor having a motor post with a first post end connected to the motor and a second post end;   a rotor shaft operatively coupled to the second post end;   a plurality of support posts, each of the plurality of support posts comprising,
               a tube defining a hollow channel;   a tension rod disposed within the hollow channel of the tube;   
               
           a bottom cap operatively coupled to the tension rod; and
           a top cap operatively coupled to the tension rod, wherein the tension rod is configured to load the tube in response to be operatively coupled to the bottom cap and the top cap; and
               a base coupled to the superstructure by the plurality of support posts.   
               
           19. A molten metal pump containing one of the support posts of examples 1-17.   20. A rotor shaft for use in a molten metal device, the rotor shaft comprising:
           an outer tube having a first end, a second end, and an outer surface;   an inner rod having a first end and a second end;   a cap that threads onto the first end of the inner rod, and that has an upper portion configured to be connected to a coupling that drives the rotor shaft; and   a structure that retains the second end of the outer tube;   wherein when the cap is connected to the coupling and the coupling drives the rotor shaft, the rotor shaft moves in a direction that tightens the cap against the first end of the outer tube to apply axial pressure on the outer tube.   
           21. The rotor shaft of example 20 wherein the outer tube is comprised of ceramic.   22. The rotor shaft of example 21 wherein the ceramic is silicon carbide.   23. The rotor shaft of any of examples 20-22 wherein the structure that retains the second end of the outer tube is a nut threaded onto the second end.   24. The rotor shaft of example 23 that further includes a washer on the second end.   25. The rotor shaft of any of examples 20-23 that further includes a rotor and a rotor plug received in the bottom of the rotor.   26. The rotor shaft of any of examples 20-25 wherein the upper portion of the cap includes one or more L-shaped openings to connect to the coupling.   27. A rotor for being connected to a rotor shaft used in a molten metal device, the rotor comprising a plurality of spaced-apart blades, a passageway for receiving the second end of a rotor shaft according to any of examples 20-24 or 26, and a cavity for retaining a structure that retains the second end of the rotor shaft.   28. The rotor shaft of example 27 wherein the structure is a nut threadingly received on the second end.   29. The rotor shaft of either of examples 27-28 that further includes a rotor cap on a bottom of the rotor, the cap for covering the cavity.   30. A coupling for use with a rotor shaft for a molten metal device, the coupling comprising:
           a body including an opening for receiving a rotor shaft, and
               one or more securing structures to retain the rotor shaft in the opening;   one or more manual tightening structures on the outer surface.   
               
           31. The coupling of example 30 that has two tightening structures.   32. The coupling of any of examples 30-31 wherein the tightening structures are bolts threaded through the body of the coupling.   33. The coupling of any of examples 30-32 wherein the manual tightening structures are tubes welded to the outer surface.   34. The coupling of any of examples 30-33 that is comprised of steel.   35. The coupling of any of examples 30-34 wherein the opening is cylindrical.   36. The coupling of any of examples 30-35 that further includes two openings for receiving a through bolt.   37. The coupling of example 36 that further includes a through bolt.   38. A molten metal pump comprising the coupling of any of examples 30-37.   39. A rotory degasser comprising the coupling of any of examples 1-37.   40. The rotor shaft of example 23 wherein the nut is retained inside of a rotor.   41. The rotor shaft of example 24 wherein the nut and washer are retained inside of a rotor.       
 
         [0142]    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 result. Further, any dimensions provided herein are provided for reference only. Unless otherwise stated, the invention is not limited to components having such dimensions.