Patent Application
20240198416
The present exemplary embodiment relates to a molten metal pumping system. Pumps for pumping molten metal are used in furnaces for the production of metal articles. Common functions of pumps are circulation of molten metal in the furnace or transfer of molten metal to remote locations. The present description is focused on molten metal pumps for transferring metal from one location to another. It finds particular relevance to systems where molten metal is elevated from a furnace bath into a launder system.
Currently, many metal die casting facilities employ a main hearth containing the majority of the molten metal. Solid bars of metal may be periodically melted in the main hearth. A transfer pump can be located in a well adjacent the main hearth. The transfer pump draws molten metal from the well and transfers it into a conduit, and from there, to a die casting machine that forms metal articles. The present disclosure relates to pumps used to transfer molten metal from a furnace to a die casting machine, ingot mold, or the like. The present disclosure can employ, for example, the style of pumping systems described in U.S. Pat. Nos. 10,415,884; 10,072,891; 9,909,808; 9,982,945; and 10,352,620, the disclosures of which are herein incorporated by reference.
Typically, a launder is used to transfer the molten from the pumping system to a casting location. The launder is essentially a trough, channel or conduit outside of the reverbatory furnace. A launder may be used to pass molten metal from the furnace and into a ladle and/or into molds. The launder may be of any dimension or shape. For example, it may be one to four feet in length, or as long as 100 feet in length. The launder is usually sloped gently, for example, it may be sloped downward or gently upward at a slope. In use, a typical launder includes molten aluminum at a depth of approximately 1-10″.
When feeding a ladle, launder or other structure or device utilizing a transfer pump, the pump is turned off/on and accelerated according to when more molten metal is needed. This can be done automatically. If done automatically, the pump may turn on and/or accelerate when the molten metal in the ladle or launder is below a certain amount.
The present invention relates to an apparatus for degassing, submerging, agitating and pumping molten metal. Particularly, the present invention relates to a mechanical apparatus for moving or pumping molten metal such as aluminum, zinc or magnesium. More particularly, the present invention is related to a drive for such an apparatus in which a motor is positioned above a molten metal bath and rotates a vertical shaft. The lower end of the shaft drives an impeller or a rotor to impart motion to the molten metal. The middle portion of the assembly is supported by a steel shaft, which is reinforced by a ceramic post. The invention finds similar application in the construction of the post which supports the motor.
In the processing of molten metals, it is often necessary to pump molten metal from one place to another. When it is desired to remove metal from a vessel, a so-called transfer pump is used. When it is desired to circulate molten metal within a vessel, a so-called circulation pump is used. When it is desired to purify molten metal disposed within a vessel, a so-called gas injection pump is used. In each of these pumps, a rotatable impeller is submerged, typically within a pumping chamber, in the molten metal bath contained in the vessel. Additionally, the motor is suspended on a superstructure over the bath by posts connected to the base. In another embodiment of these pumps, a rotatable impeller can be submerged in the molten metal bath by a shaft affixed to a suspended motor, where the motor is not supported over the bath by any posts. Rotation of the impeller within the pumping chamber forces the molten metal as desired in a direction permitted by the pumping chamber design.
Mechanical pumps for moving molten metal in a bath historically have a relatively short life because of the destructive effects of the molten metal environment on the material used to construct the pump. Moreover, most materials capable of long term operation in a molten metal bath have relatively poor strength which can result in mechanical failure. In this regard, the industry has typically relied on graphite, a material with adequate strength, temperature resistance and chemical resistance, to function for an acceptable period of time in the harsh molten metal environment.
While graphite is currently the most commonly used material, it presents certain difficulties to pump manufacturers. Particularly, mechanical pumps usually require a graphite pump housing submerged in the molten metal. However, the housing is somewhat buoyant in the metal bath because the graphite has a lower density than the metal. In order to prevent the pump housing from rising in the metal and to prevent unwanted lateral movement of the base, a series of vertical legs are positioned between the pump housing and an overhead structure which acts simultaneously to support the drive motor and locate the base. In addition to functioning as the intermediate member in the above roles, the legs, or posts as they are also called, must be strong enough to withstand the tensile stress created during installation and removal of the pump in the molten metal bath.
Similarly, the shaft connecting the impeller and the motor is constructed of graphite. Often, this shaft component experiences significant stress when occluding matter in the metal bath is encountered and sometimes trapped against the housing. Since graphite does not possess as high a strength as would be desired, it would be helpful to reinforce the leg and shaft components of the pump.
A shaft or post assembly made entirely of ceramic would be brittle and subject to an unexpected failure. Furthermore, exposed metal components residing in the molten metal bath can dissolve.
In addition, graphite can be difficult to work with because graphite has different thermal expansion rates in its two grain orientations. This may result in a post and base having divergent and conflicting thermal expansion rates in the molten metal environment. This problem is compounded by the fact that pump construction has historically required cementing the graphite post into a hole in the graphite base. This design provides no tolerance between the components to accommodate this divergent thermal expansion. Unfortunately, this can lead to cracking of the base or the post. Accordingly, it would be desirable to have a molten metal pump wherein the mating of a post and a base is achieved in a manner which accommodates divergent thermal expansion tendencies.
The present invention is equally applicable to a variety of other apparatus used in processing molten metal. Moreover, in addition to pumps, molten metal scrap melting (i.e. submergence), degassing, and agitation equipment, typically rely on the rotation of an impeller/rotor submerged by a vertical shaft in a bath of molten metal. More specifically, a submergence device is used to help melt recycle materials. Two major concerns of the secondary metal industry are production rate and recovery or yield. Recovery is lowered by the generation of oxides and gasses which become entrained or dissolved into the molten metal during the melting of scrap metal. In addition to a loss in yield, entrained impurities decrease the quality and value of the scrap metal which is ultimately marketable as end product. Accordingly, a degassing device is often used to remove these impurities. In the degasser, a hollow shaft is typically provided to facilitate the injection of gas down the shaft and out through the bores in an impeller/shaft rotor. Typically, the introduced gasses will chemically release the unwanted materials to form a precipitate or dross that can be separated from the remainder of the molten metal bath.
An example of a submergence device is described in U.S. Pat. Nos. 4,598,899 and 6,071,024 herein incorporated by reference. An exemplary degassing apparatus is described in U.S. Pat. No. 4,898,367, herein incorporated by reference. In both devices, a vertically oriented shaft having an impeller/rotor disposed at one end in the molten metal bath is employed. Similar problems arise in these apparatuses wherein the components are usually constructed of graphite, and would benefit from an increase in strength.
Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure and is neither intended to identify certain elements of the disclosure, nor to delineate scope thereof. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter.
According to a first embodiment, a molten metal pump post is provided. The molten metal pump post includes an elongated rod of a first material that is heat resistant and an inner member at least partially surrounding the elongated rod. The inner member is of a second material. The elongated rod is operable due to a difference in a coefficient of thermal expansion between the elongated rod and the inner member which creates a compressive force.
According to a second embodiment, an assembly for attaching an associated molten metal pump post to a component of a molten metal pump is provided. The assembly includes a rod having a first end that accommodates an elongated refractory element and an opposed end at least partially surrounded by an inner member wherein the assembly uses thermal expansion to create a compressive force.
The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.
A more complete understanding of the components, processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.
The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
As used herein, the terms about, generally and substantially are intended to encompass structural or numerical modifications which do not significantly affect the purpose of the element or number modified by such term.
As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of” and “consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions or processes as “consisting of” and “consisting essentially of” the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.
Referring now to
Rotation of impeller 7 is achieved when motor 17 rotates shaft 19 by turning shaft coupling 21 provided therebetween. The motor 17 is positioned above the base assembly 3 on a platform assembly 22 having an insulation layer 23, a motor mount bracket 25 and a motor mount plate 26.
In an embodiment as depicted in
In one embodiment, the rod will be constructed of an alloy such as MSA 2000 or MSA 2001 available from Pyrotek, Inc. of Spokane, WA. The optional outer sheath 31 includes a ceramic shield for additional protection against oxidation, erosion, corrosion, etc. The lower end of rod 29 includes cap 35. Cap 35 is disposed within a cavity 37 in base assembly 3. A graphite or refractory plug 39 is cemented into the lowermost portion of the cavity 37 to seal the area from molten metal. Plug 39 is such that its diameter is sufficiently large to include the rod 29 and cap 35, while still sealing the connection within the housing. The upper end of the rod 29 extends through the insulation layer 23 and is secured with nut 41 to motor mount plate 26. The inner member 30 is disposed between the motor mount platform 25 and insulation layer 23.
Turning now to
Turning now to
Table 1 below discloses examples of the length/thickness (inches) and expansion coefficients/K for an embodiment of
It is also contemplated by the present disclosure that CTE can be used to provide compression in a preassembled post configuration. Moreover, CTE can be used without reliance on the motor mount or pump base. For example, the CTE assembly can replace the spring element utilized in U.S. Pat. No. 10,641,270, the disclosure of which is herein incorporated by reference.
Turning now to
L
A
+E
A
+L
B
+E
B
>L
C
+E
C
(LA+LB)+EA+EB>LC+EC
L
C
+E
A
+E
B
>L
C
+E
C
E
A
+E
B
>E
C
This alternate material composition ensures that the goal of maintaining material B in compression is achieved.
As shown in
In various embodiments and with reference to
In various embodiments and with reference to
Thus, it is apparent that there has been provided in accordance with the present invention, a molten metal pump that fully satisfies the objects, aims, and advantages as set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art like of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.
This application claims the benefit of U.S. Provisional Application No. 63/179,029 filed Apr. 23, 2021, the disclosure of which is herein incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/026169 | 4/25/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63179029 | Apr 2021 | US |
