This application claims the benefit of U.S. Provisional Application No. 63/358,384 filed July 5, 2022, the disclosure of which is herein incorporated by reference.

BACKGROUND

[0001] The present exemplary embodiment relates to molten metal impeller with a rock guard. It finds particular application in conjunction with gas injection pumps, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.

[0002] As used herein, the term "molten metal" means any metal or combination of metals in liquid form, such as aluminum, copper, iron, zinc, magnesium 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.

[0003] Known molten-metal pumps include a pump base (also called a housing), 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 housing. An impeller 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. As the motor turns the drive shaft, the drive shaft turns the impeller shaft which turns the impeller. The impeller pushes molten metal out of the pump chamber, through the discharge, out of the outlet and into the molten metal bath or a riser.

[0004] 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, U.S. Pat. No. 4,169,584, U.S. Pat. No. 5,203,681 , U.S. Pat. No. 5,947,705 and U.S. Pat. No. 5,993,728 all disclose molten metal pumps. The disclosures of the patents noted above are incorporated herein by reference.

[0005] Three basic types of pumps for pumping molten metal, such as molten aluminum, are utilized: circulation pumps, transfer pumps and gas-injection pumps.

[0006] 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 reverberatory 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 reverberatory furnace to a different location such as a ladle or another furnace. [0008] Gas-injection pumps circulate molten metal while releasing 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, from the molten metal. 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 injection pumps may be used for either of these purposes or for any other application where it is desirable to introduce gas into molten metal. Gas injection pumps generally include a gas-transfer conduit having a first end that is connected to a gas source and a second 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 metaltransfer conduit extending from the discharge, or into a stream of molten metal exiting either the discharge or the metal-transfer conduit. The present impeller design may have particular benefit for use in gas injection pumps because furnaces that use chlorine injection typically accumulate more debris (e.g. magnesium chloride refractory pieces).

[0009] When a conventional molten metal pump is operated, the impeller rotates within the pump housing. The pump housing remains stationary relative to the impeller. A problem with such molten metal pumps is that the molten metal in which it operates includes solid particles, such as dross and refractory debris.

[0010] As the impeller rotates molten metal including the solid particles enters the pump chamber through the inlet. A solid particle may lodge between the moving impeller and the stationary inlet, potentially jamming the impeller and potentially damaging one or more of the pump components.

[0011] Many attempts have been made to solve this problem, including the use of filters or disks to prevent solid particles from entering the inlet solutions reduce solid injection but simultaneously degrade pump performance. Similarly, impellers have been designed with hardened surfaces to resist cracking. Unfortunately, while the hardened impeller surface is protected, the pump base is still exposed to damage.

[0012] The present disclosure relates to impellers used for pumping molten metal wherein the impeller has a protective top to alleviate damage to the impeller caused by dross or other hard particles striking the impeller. The present rock guard is advantageous because it expels solid particles before the molten metal enters the chamber of a molten metal pump in which the impeller is retained but does not degrade pump performance.

BRIEF DESCRIPTION

[0013] 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.

[0014] According to one embodiment, an impeller for use in a molten metal pump is provided. The impeller comprises (a) a body including a plurality of blades or passages and (b) a top portion having an inverted cup-shape. A top wall of the cup includes a bore configured to receive a shaft. A sidewall includes a plurality of openings. A rim of the cup is mated to the body.

[0015] According to another embodiment, a molten metal pump including a superstructure on which a motor is supported and a pump base including a pump chamber is provided. A plurality of support posts connecting the superstructure to the pump base. The impeller of paragraph [0014] is received in the pump chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] FIG. 1 shows a perspective view of an impeller body according to the present disclosure.

[0018] FIG. 2 shows a perspective view of a first protective cap design according to the present disclosure.

[0019] FIG. 3 shows a perspective view of a second protective cap configuration of the present disclosure.

[0020] FIG. 4 shows a perspective view of an impeller according to the present disclosure disposed in a pump base.

DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0024] 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. [0025] 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.

[0026] FIG. 1 shows an impeller body according to aspects of the present disclosure. Impeller body 100 as shown has six identical impeller blades (also called "vanes") 102 forming intermediate channels 104. The impeller has a body (or body portion) 103. The impeller body 100 can be constructed of graphite. "Graphite" means any type of graphite, whether or not chemically treated. Graphite is particularly suitable for being formed into pump components because it is soft and relatively easy to machine and less expensive than ceramics.

[0027] Impeller body 100 may have a bearing plate or ring (not shown) at the bottom edge 105. The bearing plate or ring can be comprised of a hard, wear-resistant material, such as ceramic. 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.

[0028] Impeller body 100 further includes a connection portion 107 which can be a bore or any structure capable of engaging a drive shaft. A radial edge of each blade 102 includes a recess 109 configured to receive a rock guard cap.

[0029] The rock guard cap (see Figs. 2 and 3) can be secured to the impeller body 100 by cementing into the recesses 109. Additional spaces 111 may provide openings receiving dowel pins (not shown) or a mechanical cement locking interface that mate with complementary spaces in the rock guard assembly to help secure the rock guard assembly to the impeller body 100.

[0030] A first rock guard design 200 is shown in FIG. 2. The rock guard 200 is an inverted cup-shaped body having a top wall 202 and a side wall 204. A rim 206 is configured to mate with the impeller body 100 of Fig. 1 . Side wall 204 includes a plurality of openings 208 generally equally spaced about the periphery of the rock guard 200. Generally speaking, it is desirable that the openings 208 have at least one dimension that is smaller than an inlet to the channels between adjacent blades or an inlet to the passages of the impeller body. Moreover, if the openings to the rock guard are smaller than the passages between vanes in the impeller body, any solids that enter internal chamber 216 will be capable of passing through the impeller body without causing damage.

[0031] The openings 208 can have a forward canted front 210 and trailing 212 walls (see arrow reflecting intended direction of rotation) to encourage inflow of molten metal. [0032] The rock guard 200 further includes a bore 214 which accommodates passage of a shaft for mating with the connection portion 107 of the impeller body 100.

[0033] The rock guard 200 can form an internal chamber 216 where molten metal is drawn in from a molten metal bath and effectively staged for introduction into the channels 104 between vanes 102 of the impeller body 100.

[0034] The rock guard advantageously extends above the pump base and pumping chamber (see Fig. 4) such that solids in the molten metal bath are repelled before entering the mechanical interface between impeller and pump housing. The rock guard can be comprised of a ceramic material to better absorb the impact of solids in the molten metal. [0035] To further improve the ability of the rock guard 200 to absorb impact of solids in the molten metal the interface region 218 between the top wall 202 and the side wall 204 is rounded or beveled.

[0036] Without being bound by theory, it is believed that providing the relatively large volume internal chamber 216 above the inlets to the channels 104 between vanes 102 allows the performance of the impeller to be maintained while providing protection against solids. Moreover, prior attempts to discourage solids from entering the impeller body have typically impeded molten metal flow into the impeller and resulted in a corresponding reduction in performance. It is believed that a sufficient internal chamber volume can be achieved when the side wall of the rock guard has a height at least 50%, or at least 75%, or at least 90% of a height of the impeller body. [0037] FIG. 3 displays an alternative rock guard design 300. Again, the rock guard 300 is an inverted cup-shaped body having a top wall 302 and a side wall 304. In this embodiment, the side wall 304 is inwardly inclined between a rim 306 and the top wall 302. Rim 306 can have a vertical orientation to improve its interface with the surface of the pump base which the rim opposes (see Fig. 4). The bottom surface 307 of the rim can be shaped in any manner to facilitate cementing to the recesses 109 of the impeller body 100.

[0038] Side wall 304 includes a plurality of openings 308 generally equally spaced about the periphery of the rock guard 300.

[0039] In this embodiment, the bore 314 which accommodates the shaft mating with the connection portion 107 of the impeller body 100 includes a pair of keyways 315 configured to accept a key to improve mating to corresponding keyways on the shaft.

[0040] In the present embodiment, the side wall 304 is inwardly inclined between the rim 306 and the top wall 302. It is believed that the inclined side wall can better use the advantages of gravity to encourage molten metal flow into internal chamber 316. To provide the inclined side wall a circumference of the top wall can be less than a circumference of the rim.

[0041] In some embodiments, the incline can be between about 20 and 50 degrees relative to a plane in which the rim 306 resides.

[0042] Referring now to Fig. 4, the submerged components of a molten metal pump 400 including the impeller of the present disclosure is displayed. The molten metal pump 400 includes a base 402 defining a pumping chamber 404 in which the impeller 405 (the assembly of the components of Figs. 1 + 3) is disposed. Pumping chamber 404 is in fluid communication with outlet 406.

[0043] The molten metal pump includes a superstructure (not shown) on which a motor is supported. A plurality of support posts 408 connect the superstructure to the pump base 402. A shaft 410 links the motor and the impeller 405 for rotation thereof.

[0044] As assembled, a majority of the rock guard 300 portion of impeller 405 extends above an upper surface 412 of the base 402. More particularly, the openings 308 are located above upper surface 412 such that large solid pieces are prevented from entering the impeller where it interfaces with the pump base 402, i.e., locations where a moving impeller abuts non-moving components of the pump assembly.

[0045]

[0046] Example:

[0047] J-50SD pump (available from Pyrotek Inc.) with Rock Guard of Fig. 3: .

[0048] The testing demonstrated that 1 ) with the inlets being vertical at the outside diameter of the rockguard, the guard had relatively low flow and 2) by angling the side wall and inlets, the distance for flow to reach the impeller outlet is reduced and the efficiency of the impeller increases. With the vertical inlets at the OD of the guard, the flow has to turn 180 degrees from where it enters the guard until it exits the impeller whereas with angled inlets, the turn is less, and performance is improved.

[0049] The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come withing the scope of the appended claims or equivalents thereof.

[0050] To aid the Patent Office and any readers of this application and any resulting patent in interpreting the claims appended hereto, applicants do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.