WO2025217358A1 - Molten metal overflow transfer weir system - Google Patents

Abstract

A molten metal pump comprising an elongated tube having a base end, a top end, and a longitudinal axis. The tube defines a pumping chamber. A shaft is disposed within the tube and a centrifugal impeller is rotatable by the shaft. The impeller is disposed in the pumping chamber proximate the base end. The base end includes an inlet and the top end includes an outlet. The top end includes a chamber directing a flow of molten metal radially to the outlet. The outlet is in fluid communication with a trough. The trough includes a first end, a second end, and at least one flow modifying block disposed there between.

Description

MOLTEN METAL OVERFLOW TRANSFER WEIR SYSTEM

BACKGROUND

[0001] Pumps for pumping molten metal are used in furnaces in 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 along transfer conduits or risers that extend from a base of the pump to the remote location, for example a mold.

[0002] 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 is located in a separate well adjacent and connected to the main hearth. The transfer pump draws molten metal from the well in which it resides and transfers it into a ladle or conduit and from there to die casters that form the metal articles. The present invention relates to pumps used to transfer molten metal from a furnace to a die casting machine, ingot mold, DC caster or the like.

[0003] A traditional molten metal transfer pump is described in U.S. Pat. No. 6,286,163, the disclosure of which is herein incorporated by reference. Referring to FIG. 1 , the molten metal pump is indicated generally by the reference numeral 10. The pump 10 is adapted to be immersed in molten metal contained within a vessel 12. The vessel 12 can be any container containing molten metal, although the vessel 12 as illustrated is an external well of a reverberatory furnace 13. The pump 10 has a base member 14 within which an impeller (not shown) is disposed. The impeller includes an opening along its bottom or top surface that defines a fluid inlet for the pump 10. The impeller is supported for rotation within the base member 14 by means of an elongate, rotatable shaft 18. The upper end of the shaft 18 is connected to a motor 20. The base member 14 includes an outlet passageway connected to a riser 24. A flanged pipe 26 is connected to the upper end of the riser 24 for discharging molten metal into a spout or other conduit (not shown). The pump 10 thus described is so-called transfer pump, that is, it transfers molten metal from the vessel 12 to a location outside of the vessel 12.

[0004] Another exemplary transfer pump is described in CA 2284985. The pump consists of two main parts, an upper tube portion which is suspended above the molten metal bath during operation and lower tube portion which is immersed in the bath. A motor is positioned at the top of the upper portion. A coupling attaches an auger shaft to the motor. The coupling holds the weight of the auger shaft and positions it in place inside the tube. The auger shaft is centered within the internal diameter of the two portions, running the length of both, and is held in position by a set of guide bearings. The lower portion is comprised of a cylindrical casing in which the auger is located and aligned. Several inlet holes are located in the walls of the cylindrical casing. A second set of inlet holes in the cylindrical casing are located near the base of the pump. These inlet holes permit the surrounding molten metal to enter the pump.

[0005] The auger comprises a shaft, upon which are welded flutes. The pitch of the flutes preferably varies between 2 to 4 inches. The auger acts like a positive displacement pump. The rotation of the auger shaft by the motor supplies a steady force to the molten magnesium, forcing the molten liquid to the bottom of the pump and out of an elbow shaped connector located at the outlet end of the cylindrical casing at the base of the pump. The molten magnesium displaced to the bottom of the pump is downwardly forced out through the connector by means of the rotation of the auger. The connector is attached to a heated transfer tube which will convey the molten magnesium from the holding furnace to the die of a casting machine.

[0006] A further alternative transfer pump is described in U.S. Published Application 2008/0314548. The system comprises at least (1) a vessel for retaining molten metal, (2) a dividing wall (or overflow wall) within the vessel, the dividing wall having a height H1 and dividing the vessel into a least a first chamber and a second chamber, and (3) a molten metal pump in the vessel, preferably in the first chamber. The second chamber has a wall or opening with a height H2 that is lower than height H1 and the second chamber is juxtaposed another structure, such as a ladle or lauder, into which it is desired to transfer molten metal from the vessel. The pump (either a transfer, circulation or gas-release pump) is submerged in the first chamber (preferably) and pumps molten metal from the first chamber past the dividing wall and into the second chamber causing the level of molten metal in the second chamber to rise. When the level of molten metal in the second chamber exceeds height H2, molten metal flows out of the second chamber and into another structure. If a circulation pump, which is most preferred, or a gas-release pump were utilized, the molten metal would be pumped through the pump discharge and through an opening in the dividing wall wherein the opening is preferably completely below the surface of the molten metal in the first chamber.

[0007] An additional alternative transfer pump is described in WO 2021/076743 A1 , the disclosure of which is herein incorporated by reference. This system includes a sensor arranged to monitor molten metal flow in a launder. With regards to these sensors, an important operational parameter of the sensor is the height of metal in the launder which relates to poor rate. An issue arises when sensing low levels of molten metal due to turbulence and reflections. This problem is solved by inserting a removable insert particularly for use when the molten metal level in the launder is anticipated to be low. The removeable insert functions to narrow the cross-section of the launder, causing an upstream increase in molten metal depth in the region in which the sensor is directed.

[0008] In certain environments, there is a discernible necessity to provide an pump of the above style with a less turbulent flow profile. This necessity for an overflow molten metal pump with a smooth outflow is not adequately addressed by existing designs. The lack of a calming zone within molten metal pumps has downsides such as increased turbulence and air injection. Calming helps minimize turbulence in the flow of molten metal which in turn promotes smoother and more consistent metal transfer.

[0009] The present disclosure provides a system for a molten metal overflow transfer weir system that minimizes the previously mentioned drawbacks of the prior art by adding flow modifying blocks that act as a calming zone for the molten metal.

SUMMARY OF THE INVENTION

[0010] 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.

[0011] According to one embodiment of this disclosure, a molten metal pump comprising an elongated tube having a base end and a top end is provided. A shaft extends into the tube and rotates an impeller proximate the base end. The tube has a length at least three times the height of the impeller. The base end includes an inlet and the top end includes an outlet. The outlet comprises a first end, a second end, and a flow modifying block.

[0012] According to an alternative embodiment, a molten metal pump comprising an inlet, an outlet, and a flow modifying block is provided.

BRIEF DESCRIPTION OF THE FIGURES

[0013] 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.

[0014] FIG. 1 is a schematic view of a prior art system including a furnace, a melting bay and an adjacent bay containing a transfer pump;

[0015] FIG. 2 is a perspective view showing a molten metal transfer system including the pump disposed in a furnace bay;

[0016] FIG. 3 is a perspective partially in cross-section view of the system of FIG.

2;

[0017] FIG. 4 is a side cross-sectional view of the system shown in FIGS. 2 and 3;

[0018] FIG. 5 is a perspective view of the pumping chamber;

[0019] FIG. 6 is a top view of the pumping chamber;

[0020] FIG. 7 is a view along the line A-A of FIG. 6;

[0021] FIG. 8 is a perspective view of the impeller top section;

[0022] FIG. 9 is a perspective view of the assembled impeller;

[0023] FIG. 10 is an alternative impeller design;

[0024] FIG. 11 is an exploded view of the impeller of FIG. 10;

[0025] FIG. 12 is an alternative embodiment with an electric motor;

[0026] FIG. 13 is a further alternative embodiment with an air motor.

[0027] FIG. 14 is a cross-sectional view of the trough along the line 14-14 of FIG.

6;

[0028] FIG. 15 is a view from the inlet end to the outlet end of the trough;

[0029] FIG. 16 is a view from the outlet end to the inlet end of the trough; and [0030] FIG. 17 is a schematic illustration of an exemplary flow pattern.

DETAILED DESCRIPTION OF THE INVENTION

[0031] 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.

[0032] 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.

[0033] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0034] As used herein, the terms about, generally and substantially are intended to encompass structural or numerical modifications which do not significantly affect purpose of the element or number modified by such term.

[0035] As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1,1.5, 2, 2.75, 3, 3.6, 4 and 5 and the like). Similarly, where multiple ranges are set forth with respect ot an item, it is intended that the ranges reflect the various combinations thereof (e.g. 1 to 5 or 2 to 3 also includes the ranges 1 to 3 and 2 to 5, and the like).

[0036] 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, orwords 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 or process 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.

[0037] With reference to FIGS. 2-4, the molten metal pump 30 of the present invention 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. Bearing rings can be provided to facilitate even wear and rotation of the impeller 38 therein. In operation, molten metal is drawn into the impeller through the inlet (arrows) and forced upwardly within tube 41 in the shape of a forced (“equilibrium”) vortex. At a top of the tube 41 a volute shaped chamber 42 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. [0038] 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.

[0039] 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.

[0040] Turning now to FIGS. 5-7, the tube 41 is shown in greater detail. FIG. 5 shows a perspective view of the refractory body. FIG. 6 shows a top view of the volute design. FIG. 7 shows 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. 7.

[0041] FIGS. 5 and 6 show a first flow modifying block 300 and a second flow modifying block 302. The purpose of the flow modifying blocks is to create a calming flow of the molten metal after being discharged from the volute chamber 42. Moreover, although other configurations are considered effective, flow modifying block 300 forms a restricted passage adjacent the inlet to trough 44 and flow modifying block 302 lifts the molten metal in the trough 44. This weir system creates a serpentine flow path that has been found to suppress turbulence both upstream (i.e. in the volute chamber) and downstream.

[0042] It is noted that the figures depict block 300 and 302 as inserts. The flow modifying shapes, however, can be integrally formed from the ceramic/refractory material forming the trough.

[0043] FIGS. 8 and 9 depict the impeller 38 which includes top section 46 having vanes 48 supplying the induced molten metal flow and a hub 50 for mating with the shaft 36. In its assembled condition, impeller 38 is mated via a pinned cement joint or a threaded connection to an inlet guide section 52 having a hollow central portion 54 and bearing rings 56. The impeller can be constructed of graphite or other suitable refractory material. It is envisioned that any traditional molten metal impeller design would be functional in the present overflow vortex transfer system.

[0044] Referring now to FIGS. 10 and 11 , an alternative impeller design is depicted. In this embodiment, the impeller top section 62 includes bores 64 in the vanes 65 which receive posts 66 to facilitate proper registration of the components and increase the mating strength. In addition, the inlet guide section 68 has been extended relative to the prior design to include bearing rings 56 and added alignment element 70. Particularly, alignment element 70 is received within a the cooperatively shaped inlet 43.

[0045] Referring now to FIG. 12, the pump assembly has a metal frame 101 surrounding the top portion (outlet chamber) of the refractory tube 41, and includes a motor mount 102 which is secured to the pump assembly 100. The motor mount assembly 102 is secured to together via hex bolts 103, flat washers 104, lock washers 105 and hex nut 106. Motor adaptor assembly 107 joins electric motor 108 to the motor mount 102. Particularly, hex bolts 109, lock washers 110, hex nuts 111 provide the mating between electric motor adaptor assembly 107 and electric motor 108. A hanger 112 is provided to facilitate the lifting of the assembly. Hanger 112 is secured to the motor via hex bolts 113 and flat washers 114. Heat break coupling assembly 115 mates the motor drive shaft to the shaft and impeller assembly 116.

[0046] A mounting support assembly 117 can be provided to secure the assembly to the furnace. A strainer 123 and a filter cap 122 are provided to protect against ingress of unwanted debris into the pump. In this embodiment, a compressible fiber blank can be disposed between the steel frame and the refractory bowl to accommodate variations in thermal expansion rates. Furthermore, in this embodiment the outlet chamber is provided with an overflow notch 123 to safely return molten metal to the furnace in the event of a downstream obstruction which blocks primary outlet trough 124. Overflow notch 123 has a shallower depth than primary outlet trough 124.

[0047] Referring now to FIG. 13, an overflow pump with an air motor option is depicted. Particularly, a metal frame 201 surrounds tube 41 and is mated to a motor mount assembly 202 via hex bolts 203, flat washers 204, lockwashers 205 and hex nuts 206. Motor adapter assembly 207 facilitates mounting of the air motor 208 thereto. Air motor 208 includes a muffler 209 and is secured to the air motor adapter assembly 207 via hex bolts 210, and lock washers 211. A heat break coupling 212 mates the drive shaft of the air motor 208 to shaft and impeller assembly 213. Mounting support assembly 214 is provided to secure the unit to the refractory furnace. In addition, strainer 218 and filter cap 219 are provided.

[0048] Referring now to FIG. 14, a cross-sectional view of the trough 44 is provided. The trough contains a first flow modifying block 300 and a second flow modifying block 302. This figure shows two flow modifying blocks, however it should be noted that in a typical embodiment, the number of flow modifying blocks can vary from one to many (e.g. 10). The flow of molten metal through the trough 44 is shown by arrow 304. Moreover, molten metal flows through passage 306 below block 300 and then through passage 308 above block 302, both as contained by the floor and sidewalls of the trough.

[0049] Referring now to FIG. 15, a view of the trough 44 at its inlet is provided. This figure shows a typical embodiment of the flow modifying blocks in the channel. Flow modifying block 300 in this instance directs molten metal downward whereas the second flow modifying block 302 prevents molten metal flow along the trough floor 310, directing the flow of molten metal upwards.

[0050] Referring now to FIG. 16, a view from the outlet of the trough 44 is provided. This figure shows the flow modifying blocks in the same arrangement as FIG. 15. In this depiction the first modifying block 300 still directs flow downward and the second flow modifying block 302 directs the flow of molten metal upwards through passage 308.

[0051] The arrangement in FIG. 15 and FIG. 16 is only exemplary and other arrangements are possible. For example, the first flow modifying block could direct flow upwards and the second flow modifying block direct the flow of molten metal downwards. Generally speaking, an exemplary embodiment staggers the blocks to allow each consecutive flow modifying block to direct flow inverse to its adjacent flow block(s).

[0052] FIG. 17 shows a cross-section of a launder 400 with which a first block 402 and a second block 404 reside. Molten metal (M) enters launder 400 at inlet end (I) from the vortexing pump described previously. Block 402 keeps the flow of molten metal contained to a height Hi. The speed of the pump can be used to provide molten metal height Hi, or block 402 can impart a downward flow to the molten metal upstream of the block. Molten metal travels downstream below block 402 to channel 406 between blocks 402 and 404. The molten metal flows upward over block 404 and spills gently into the launder 400 at space 408 where a smoother flow pattern is achieved.

[0053] The flow modifying blocks can be of various sizes. Moreover, there is no particular requirement for block height, thickness or width and their size and/or shape can vary depending on flow requirements. Accordingly, the blocks may allow some level of flow between a passage that could be formed between one or both sides of the block and the sidewalls of the trough.

[0054] Furthermore, there is no required height of the block such that a specified passage (see 306 and 308) dimension is achieved. In that regard, the passage dimensions may be different for different blocks.

[0055] Similarly, the blocks can be placed various distances apart. The distance between the blocks could be between % inches and 12 inches apart. Flow can be controlled by the number of blocks within the channel. The flow modifying blocks could run anywhere from only a portion of the channel to the full width of the channel. Typically, the passage that exists between the modifying block and the trough top or bottom is between greater than 1% or 10% and less than 100% of the flow modifying block height. The blocks can vary in individual width. For example, one block can range anywhere from 50% to 100% percent of the trough width.

[0056] The flow modifying block can be made of various materials including but not limited to heat resistant materials such as unitary, ceramic or graphite construction.

[0057] The flow modifying blocks can be placed variable distances from one another.

[0058] The use of flow modifying blocks offers numerous advantages that are not currently present in the existing product landscape. Flow modifying blocks provide a beneficial calming zone which reduces turbulence and disturbances in the molten metal as it flows through the pump. By minimizing turbulence, calming zones help ensure a smoother and more consistent flow of metal, which can improve the efficiency of the casting process and reduce defects in the final product. Additionally, calming zones can also help prevent splashing and spattering of molten metal which enhances worker safety.

[0059] The invention has many advantages in that its design creates an equilibrium vortex at a low impeller RPM, creating a smooth surface with little to no air intake. Accordingly, the vortex is non-violent and creates little or no dross. Moreover, the present pump creates a forced vortex having a constant angular velocity such that the column of rotating molten metal rotates as a solid body having very little turbulence.

[0060] The pump has excellent flow tunability, its open design structure provides for simple and easily cleaning access. Advantageously, only shaft and impeller replacement parts will generally be required. In fact is generally self-cleaning wherein dross formation in the riser is eliminated because the metal level is high. Generally, a lower torque motor, such as an air motor, will be sufficient because of the low torque experienced.

[0061] Optional additions to the design include the location of a filter at the base of the inlet of the pumping chamber. It is further envisioned that the pump would be suitable for use in molten zinc environments where a very long, pull (e.g. 14 ft.) is required. Such a design may preferably include the addition of a bearing mechanism at a location on the rotating shaft intermediate the motor and impeller. Furthermore, in a zinc application, the entire construction could be manufactured from metal, such as steel or stainless steel, including the pumping chamber tube, and optionally the shaft and impeller.

[0062] The apparatus has been described with reference to preferred embodiments. Modifications will occur to those who read the preceding description, along with the references incorporated by reference. It is intended that this disclosure cover all modifications disclosed by the preceding description, the incorporated references and the equivalents thereof.

Claims

What is claimed is:

1. A molten metal pump comprising an elongated tube having a base end, a top end and a longitudinal axis, said tube defining a pumping chamber, a shaft disposed within said tube and a centrifugal impeller rotatable by said shaft, said impeller disposed in said pumping chamber proximate said base end, said base end including an inlet and said top end including an outlet, a distance between said inlet and said outlet being at least three times a height of said impeller and said top end includes a chamber directing a flow of molten metal radially to said outlet, said outlet being in fluid communication with a trough, and wherein said trough includes a first end, a second end, and a flow modifying block disposed there between.

2. The molten metal pump of claim 1 wherein said tube is comprised of graphite or refractory ceramic.

3. The molten metal pump of claim 1 wherein said chamber includes a volute shape.

4. The molten metal pump of claim 1 wherein said outlet is tangential to a sidewall forming said chamber.

5. The molten metal pump of claim 1, wherein said chamber further includes a safety spillway.

6. The molten metal pump of claim 5 wherein said safety spillway comprises a channel having a depth less than a depth of said outlet channel.

7. The molten metal pump of claim 1 wherein said flow modifying block directs molten metal flow towards a floor of the trough.

8. The molten metal pump of claim 1 wherein, in operation, molten metal is drawn into the impeller through the inlet and forced upwardly within the tube in the shape of a forced vortex.

9. The molten metal pump of claim 1 wherein said chamber has a diameter greater than the diameter of the tube intermediate said inlet and said outlet.

10. The molten metal pump of claim 1 wherein said first end of the outlet is located proximate the top end of the chamber.

11. The molten metal pump of claim 1 wherein said flow modifying block lies adjacent the first end of the trough.

12. The molten metal pump of claim 1 wherein said trough contains a first flow modifying block and a second flow modifying block.

13. The molten metal pump of claim 12 wherein said first flow modifying block directs flow in a first direction and the second flow modifying block directs flow in a second direction.

14. The molten metal pump of claim 13 wherein said first flow direction is inverse of the second flow direction.

15. The molten metal pump of claim 13 wherein said first flow direction is flat or downward and said second flow direction is upward.

16. The molten metal pump of claim 13 wherein said first flow direction is flat or downward, said second flow direction is upward, and a third flow direction is downward.

17. The molten metal pump of claim 1 wherein said flow modifying block is comprised of heat resistant material.

18. The molten metal pump of claim 1 wherein said flow modifying block is comprised of a refractory ceramic or graphitee.

19. The molten metal pump of claim 1 wherein the flow modifying block runs the width of the trough.

20. The molten metal pump of claim 1 wherein a space between the flow modifying block and a floor of the trough is at least 1% of the flow modifying blocks length.

21. The molten metal pump of claim 12 wherein the flow modifying blocks are placed 1 -12 inches distance away from each other.

22. The molten metal pump of claim 15, wherein a space between the first flow modifying block and a trough floor is less than a space between the second flow modifying block on a trough upper surface.

23. The molten metal pump of claim 1 wherein the flow modifying blocks are formed internally with the material forming the trough.

24. The molten metal pump of claim 1 wherein the flow modifying blocks are removeable components.

25. The molten metal pump of claim 1 wherein the flow modifying blocks are between 1 and 12 inches in width.

26. A molten metal pump comprising a vortex pumping chamber having an outlet leading to a launder, said launder including a flow modifier.

27. The molten metal pump of claim 26 wherein the flow modifier comprises a weir system.