Tapered impeller

Abstract

An impeller is tapered. The degree of tapering may be in a range of about 1° to about 15°, including from about 2° to about 10°, from about 3° to about 9°, from about 4° to about 8°, from about 5° to about 7°, about 5.5° to about 6.5°, about 5.75° to about 6.25°, about 5.9° to about 6.1°, or about 6°. An impeller shaft assembly includes the impeller and a rotatable shaft connected to the impeller. A molten metal pump includes the impeller and a shaft rotatably connecting the impeller to a motor.

Description

Aty. Dkt. No. MLCZ 200288W001TAPERED IMPELLER

[0001] The present application claims the benefit of U.S. Provisional Application Serial Number 63 / 740,404, filed December 31, 2024, the disclosure of which is herein incorporated by reference.BACKGROUND

[0002] The present exemplary embodiment relates to a tapered impeller and a molten metal pump including the impeller. The tapered impeller finds particular application in conjunction with a drain-out pump and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amendable to other like applications.

[0003] Molten metals such as aluminum, tin, lead, and zinc are commonly used. Of course, to be placed in a molten state, the metal must be exposed to elevated temperatures. A variety of types of furnaces and other devices are used for this purpose, including smelting furnaces for aluminum production, induction furnaces for metal processing, and refractory furnaces for metal recycling. The following paragraphs describe several varied systems in which a molten metal exists.

[0004] Exemplary aluminum smelting pots consist of a rectangular steel box insulated with fire bricks along the bottom and the sides. Carbon blocks containing conductor rods are attached to the bottom brick lining, with the rods protruding from the cell structure. The sides of the cell are lined with carbon on top of the firebricks. Square anode blocks constructed form compressed petroleum, coke and coal tar are fixed to rods and suspended from two beam-like bus-bars attached to the cell structure, which as well as supplying electric current can lower or raise the anode blocks. Alumina is provided to the cell through an ore bin located above the cell and a portable fume extraction hood covers the cell. Aluminum is derived from the added aluminum within the melting pots via an electrolytic process.

[0005] As another example, induction furnaces employ electromagnetic energy to induce electrical currents within a charge of metal or metal alloy. The electrical resistance of the metal produces heat as a natural consequence of the induced currents flowing in the metal. The combination of applied electrical power and frequency can be chosen toinduce sufficient heat within the metal to cause it to melt, providing a molten liquid which can be poured into molds or otherwise used to produce a wide variety of metal products. The basic elements of an induction furnace include an electromagnetic induction coil, a vessel having a lining of refractory material, and a support structure for the coil and vessel.

[0006] As a further example, metals may be melted in a reverberatory furnace. In a reverberatory furnace direct flame and radiation from hot refractory linings heat the metal. At its simplest, such a furnace is a steel box lined with alumina or other refractory brick having a flue at one end and a generally vertically lifting door at the other end closing a main entrance for the furnace through which a metal is directly charged into the furnace. The charge of molten metal may be introduced through the main entrance and lies in a shallow hearth having a relatively low roof so that flame passes across the surface of the charge. Conventional oil or gas burners are usually placed on either side of the furnace to heat the refractory lining and to melt the metal. The resulting molten metal is then transferred to a casting machine to produce metal ingot.

[0007] In the hot-dip galvanizing of an object, for example of iron, steel etc., the object is immersed in a bath of molten zinc, the iron and zinc forming alloys with one another. The molten zinc is typically housed in a refractory container during this process.

[0008] T ransfer pumps are generally used to transfer molten metal from a vessel, such as the external well of a reverberatory furnace, to a different location such as a launder, ladle, or another furnace. Examples of transfer pumps are disclosed in U.S. Pat. No.6,345,964, U.S. Pat. No. 9,506,346, and WO 2023 / 200834 A1, each of which is herein incorporated by reference in its entirety except for any inconsistent definitions, disclaimers, or disavowals with the present application.

[0009] Additional molten metal pumps have been described in U.S. Pat. Nos.5,947,705; 6,354,796; 6,254,340; 6,451,247; 6,464,458; 9,951,777; 11,131,309; 11,136,984; and 11 ,193,492; and U.S. Patent Publication No. US2022 / 0403846, each of which is herein incorporated by reference in its entirety except for any inconsistent definitions, disclaimers, or disavowals with the present application.

[0010] There are issues associated with contaminants and impurities preventing the proper functioning of rotating components in molten metal pumps. For example, dirtycasting sand and grit in heated crucibles can lock up and freeze impellers in molten metal pumps.BRIEF DESCRIPTION

[0011] Disclosed, in some embodiments, is molten metal pump including: an elongated tube having a base end and a top end; a shaft disposed within the tube; and an impeller having a lower end and an upper end. The upper end is connected to the shaft. The impeller is rotatable by the shaft. The lower end of the impeller is disposed proximate the base end. The base end of the elongated tube includes a molten metal inlet. The top end of the elongated tube includes a molten metal outlet. The impeller is tapered by from about 1° to about 15° from the lower end to the upper end. The degree of the taper may be from about 2° to about 10°, from about 3° to about 9°, from about 4° to about 8°, from about 5° to about 7°, from about 5.5° to about 6.5° from the lower end to the upper end, from about 5.75° to about 6.25° from the lower end to the upper end, from about 5.9° to about 6.1 °, or about 6° from the lower end to the upper end. The molten metal pump may further include a motor connected to the shaft. In some embodiments, the impeller includes a bearing ring at the lower end. The impeller may include a plurality of helical protrusions extending from an outer surface thereof.

[0012] Disclosed, in other embodiments, is an impeller for a molten metal pump. The impeller includes an inlet for receiving a shaft; and a plurality of helical protrusions extending from an outer surface of the impeller. The impeller is tapered by from about 10to about 15° from a lower end to an upper end of the impeller. The degree of the taper may be from about 2° to about 10°, from about 3° to about 9°, from about 4° to about 8°, from about 5° to about 7°, from about 5.5° to about 6.5° from the lower end to the upper end, from about 5.75° to about 6.25° from the lower end to the upper end, from about 5.9° to about 6.1°, or about 6° from the lower end to the upper end. In some embodiments, the impeller includes a bearing ring at the lower end.

[0013] Disclosed, in further embodiments, is an impeller shaft assembly for a molten metal pump. The assembly includes a shaft having a top end and a bottom end; and an impeller. The impeller includes an inlet at an upper end for receiving the bottom end of the shaft; and a plurality of helical protrusions extending from an outer surface of theimpeller. The impeller is tapered by from about 1° to about 15° from the lower end to the upper end of the impeller. The degree of the taper may be from about 2° to about 10°, from about 3° to about 9°, from about 4° to about 8°, from about 5° to about 7°, from about 5.5° to about 6.5° from the lower end to the upper end, from about 5.75° to about 6.25° from the lower end to the upper end, from about 5.9° to about 6.1°, or about 6° from the lower end to the upper end. In some embodiments, the impeller includes a bearing ring at the lower end.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

[0015] FIG. 1 is a perspective view of a molten metal pump in accordance with some embodiments of the present disclosure.

[0016] FIG. 2 is a perspective view showing a molten metal transfer system including the pump disposed in a furnace bay.

[0017] FIG. 3 is a perspective view of a pumping chamber.

[0018] FIG. 4 is a top view of the pumping chamber.

[0019] FIG. 5 is a view along the line A-A of FIG. 4.

[0020] FIG. 6 is a perspective view of a prior art embodiment of an impeller shaft assembly with an untampered impeller.

[0021] FIG. 7 is a perspective view of an impeller shaft assembly in accordance with some embodiments of the present disclosure.

[0022] FIG. 8 is a first view of an impeller accordance with some embodiments of the present disclosure.

[0023] FIG. 9 is a second view of an impeller accordance with some embodiments of the present disclosure.

[0024] FIG. 10 is a third view of an impeller accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0025] The present disclosure may be understood more readily by reference to the following detailed description of desired embodiments included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent can be used in practice or testing of the present disclosure. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and articles disclosed herein are illustrative only and not intended to be limiting.

[0027] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0028] 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 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, mixtures, 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.

[0029] With reference to FIGS. 1 and 2, the molten metal pump 30 is depicted in association with a furnace 28. Pump 30 is suspended via metallic framing 32 which rests on the walls of the furnace bay 34. A motor 35 rotates a shaft 36 and the appended impeller 38. A refractory body 40 forms an elongated generally cylindrical pump chamber or tube 41. The refractory body can be formed, for example, from fused silica, silicon carbide or combinations thereof. Body 40 includes an inlet 43 which receives impeller 38. Preferably, bearing rings are provided at the bottom of the impellerto facilitate even wear and rotation of the impeller 38 therein. In operation, molten metal is drawn upwardly within tube 41 in the shape of a forced (“equilibrium”) vortex. At a top of the tube 41 a volute shaped chamber 43 is provided to direct the molten metal vortex created by rotation of the impeller outwardly into trough 44. Trough 44 can be joined / mated with additional trough members or tubing to direct the molten metal to its desired location such as a casting apparatus, a ladle or other mechanism as known to those skilled in the art.

[0030] Although depicted as a volute cavity, an alternative mechanism could be utilized to divert the rotating molten metal vortex into the trough. In fact, a tangential outlet extending from even a cylindrical cavity will achieve molten metal flow. However, a diverter such as a wing extending into the flow pattern or other element which directs the molten metal into the trough may be preferred.

[0031] In addition, in certain environments, it may be desirable to form the base of the tube into a general bell shape, rather than flat. This design may produce a deeper vortex and allow the device to have improved function as a scrap submergence unit.

[0032] Turning now to FIGS.3-5, the tube 41 is shown in greater detail. FIG.3 shows a perspective view of the refractory body. FIG. 4 shows a top view of the volute design and FIG. 5 a cross-sectional view of the elongated generally cylindrical pumping chamber. These views show the general design parameters where the tube 41 is at least 1.1 times greater in diameter, preferably at least about 1.5 times, and most preferably, at least about 2.0 times greater than the impeller diameter. However, for higher density metals, such as zinc, it may be desirable that the impeller diameter relative to pumping chamber diameter be at the lower range of 1.1 to 1.3. In addition, it can be seen that the tube 41 is significantly greater in length than the impeller is in height. Preferably, the tube length (height) is at least three times, more preferably at least 10 times, greater than a height of the impeller. Without being bound by theory, it is believed that these dimensions facilitate formation of a desirable forced (“equilibrium”) vortex of molten metal as shown by line 47 in FIG. 5.

[0033] FIG. 6 illustrates an example of an impeller shaft assembly 100 including a straight (i.e., untapered) impeller 138. The impeller 138 includes a plurality of helical protrusions 199 and a bearing ring 145. A line drawn from the lower end 145 to the upperend 146 of the impeller along an outermost edge of the helical protrusions 199 is perpendicular to the bottom of the impeller 138. The upper end 146 of the impeller 138 is connected to the bottom end 152 of the shaft 136. The shaft 136 also includes a top end 151 for connection to a motor (not shown) which provides the power necessary to rotate the shaft 136 and impeller 138. The straight impeller is prone to locking up when there are impurities or contaminants in the molten metal such as dirty casting sand, grit, etc.

[0034] FIG. 7, in contrast, illustrates a non-limiting embodiment of an impeller shaft assembly 200 in accordance with the present disclosure. This assembly 200 may be used, for example, in the molten metal pump 30 of FIGS. 1 and 2. This assembly 200 includes a tapered impeller 238. The term “tapered” refers to the size of the impeller decreasing from its lower end 245 to its upper end 246. A line drawn from the bottom to the top of the impeller along an outermost edge of the helical protrusions 299 is not perpendicular to the bottom of the impeller. Instead, such a line is offset from perpendicular such that the upper end 246 of the impeller is smaller than the lower end 245 of the impeller. The extent of the tapering is the degree of offset, from perpendicular to the lower end of the impeller, of the line drawn from the bottom to the top of the impeller along the outermost edge / protrusions 299 of the impeller 238. The degree of the taper may be from about 1° to about 15 °, from about 2° to about 10°, from about 3° to about 9°, from about 4° to about 8°, from about 5° to about 7°, from about 5.5° to about 6.5° from the lower end to the upper end, from about 5.75° to about 6.25° from the lower end to the upper end, from about 5.9° to about 6.1 °, or about 6°. Advantageously, the tapering of the impeller 238 reduces or eliminates the likelihood of impeller function degradation due to contaminants / impurities. The upper end 246 of the impeller 238 is connected to a bottom end 252 of the shaft 236. The shaft 236 also includes a top end 251 for connection to a motor (not shown) which provides the power necessary to rotate the shaft 236 and impeller 238.

[0035] FIG. 8 is a first view of an impeller accordance with some embodiments of the present disclosure.

[0036] FIG. 9 is a second view of an impeller accordance with some embodiments of the present disclosure.

[0037] FIG. 10 is a third view of an impeller accordance with some embodiments of the present disclosure.

[0038] 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 within the scope of the appended claims or the equivalents thereof.

Claims

CLAIMS:

1. A molten metal pump comprising:an elongated tube having a base end and a top end;a shaft disposed within the tube; andan impeller having a lower end and an upper end;wherein the upper end is connected to the shaft;wherein the impeller is rotatable by the shaft;wherein the lower end disposed proximate the base end;wherein the base end includes a molten metal inlet;wherein the top end includes a molten metal outlet;wherein the impeller is tapered from the lower end to the upper end.

2. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 1° to about 15° from the lower end to the upper end.

3. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 2° to about 10° from the lower end to the upper end.

4. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 3° to about 9° from the lower end to the upper end.

5. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 4° to about 8° from the lower end to the upper end.

6. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 5° to about 7° from the lower end to the upper end.

7. The molten metal pump of claim 1 , wherein the impeller is tapered by from about 5.5° to about 6.5° from the lower end to the upper end.

8. The molten metal pump of claim 1, wherein the impeller further comprises:a plurality of helical protrusions extending from an outer surface thereof.

9. The molten metal pump of claim 1 , wherein the impeller impeller further comprises:a bearing ring at the lower end.

10. The molten metal pump of claim 1 , further comprising a motor connected to the shaft.

11. An impeller for a molten metal pump, the impeller comprising:an inlet for receiving a shaft; anda plurality of helical protrusions extending from an outer surface of the impeller; wherein the impeller is tapered from a lower end to an upper end of the impeller.

12. The impeller of claim 11 , wherein the impeller is tapered by from about 1° to about 15° from the lower end to the upper end.

13. The impeller of claim 11 , wherein the impeller is tapered by from about 2° to about 10° from the lower end to the upper end.

14. The impeller of claim 11 , wherein the impeller is tapered by from about 3° to about 9° from the lower end to the upper end.

15. The impeller of claim 11 , wherein the impeller further comprises:a bearing ring at the lower end.

16. An impeller shaft assembly for a molten metal pump, the assembly comprising:a shaft having a top end and a bottom end; andan impeller comprising:an inlet at an upper end for receiving the bottom end of the shaft; a plurality of helical protrusions extending from an outer surface of the impeller;wherein the impeller is tapered from the lower end to the upper end of the impeller.

17. The assembly of claim 16, wherein the impeller is tapered by from about 1 ° to about 15° from the lower end to the upper end.

18. The assembly of claim 16, wherein the impeller is tapered by from about 2° to about 10° from the lower end to the upper end.

19. The assembly of claim 16, wherein the impeller is tapered by from about 3° to about 9° from the lower end to the upper end.

20. The assembly of claim 16, wherein the impeller further comprises: a bearing ring at the lower end.

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