Patent Grant
11136984
1. Field of the Invention
The present invention relates generally to molten metal pump systems, and in particular, to a molten metal pump assembly and associated system for controlled delivery of molten metal to molds.
2. Description of Related Art
Various applications exist where liquid or molten metal needs to be moved. Molten metal pumps are an effective way of accomplishing this task. For instance, centrifugal pumps (sometimes referred to as circulation pumps) have been used to circulate molten metal within a container, and to transfer molten metal from one location to another, among other uses. Centrifugal pumps utilize an impeller (or rotor) to direct the flow of molten metal in such applications. However, when it comes to applications such as casting (i.e., filling molds with molten metal) or molten metal dosing, centrifugal pumps have not been used as a means for filling molds.
Instead, the task of filling a mold in casting or dosing applications has traditionally been left to ladeling, pressurized furnaces, and electromagnetic pumps (EMPs). However, these solutions suffer from drawbacks which make them insufficient for filling molds to required fill metrics. For instance,
Alternatively, EMPs have been utilized to pump molten metal into molds. However, EMPs are expensive relative to centrifugal pumps or similar equipment capable of accomplishing the same task. Additionally, EMPs, like pressurized furnaces, are also difficult to control with respect to accurate delivery of the molten metal.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Accordingly, disclosed herein is a pump assembly and associated system for controlled delivery of molten metal to molds. Embodiments disclosed herein find particular application in casting molten metal (i.e., filling molds with molten metal) as well as molten metal dosing, and will be described with particular reference thereto. However, it is to be appreciated that the disclosed embodiments may also be utilized in other similar applications.
In some embodiments, a system to deliver molten metal to one or more molds comprises a holding furnace including at least one pump assembly therein to deliver the molten metal to at least one mold associated with the pump assembly. The pump assembly comprises a shaft, an impeller coupled to the shaft, and a controller to control a rotational speed of the impeller according to a programmable fill profile while delivering the molten metal to the at least one mold. Additionally, the holding furnace may be of an open configuration and configured to receive the molten metal from a melting furnace, the open configuration allowing for uninterrupted flow of the molten metal from the melting furnace and to the one or more molds. The pump assembly may further comprise a throttle to manipulate a flow rate or pressure of the molten metal relative to the rotational speed of the impeller.
In some embodiments, a process of filling a mold with molten metal comprises transferring the molten metal to a holding furnace, rotating an impeller within the holding furnace to direct a flow of the molten metal to the mold, delivering the molten metal to the mold, and adjusting a rotational speed of the impeller according to a programmable fill while delivering the molten metal to the mold.
In embodiments disclosed herein, a rotational speed of the impeller may be finely controlled via a programmable control profile which is utilized to adjust the electrical voltage applied to a motor of the pump assembly. Importantly, the disclosed pump assembly's ability to fine-tune the flow of molten metal allows for precise fill profiles to be achieved in scenarios such as filling molds for casting applications, and molten metal dosing applications. This is especially important in the context of filling complex molds with molten metal where complete filling of the molds without casting defects (e.g., chemical defects, voids, mechanical defects, etc.) is often required. Furthermore, the embodiments disclosed herein allow for a system to include an open-furnace architecture where a melting furnace may continuously supply molten metal to holding furnaces without the need to interrupt operations in order to refill the furnaces. Thus, the embodiments disclosed herein provide a revolutionary technique for controlled delivery of molten metal to molds which will transform an industry currently reliant on techniques that are insufficient and impractical for filling molds to precise fill metrics.
Other features and advantages of the present invention will become apparent from the following description of the invention, which refers to the accompanying drawings.
The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same reference numbers in different figures indicate similar or identical items.
Referring to
The pump assembly 200 is shown from a side view submerged in a bath of molten metal 202 which is contained in an open holding furnace 204, or tank (shown from a cross sectional view). As used herein, the term “molten metal” will be understood to mean any metal, such as aluminum, copper, iron, and alloys thereof, which are amendable for casting, dosing or similar applications. The molten metal 202 may be maintained in its molten or liquid state by heating elements 206 disposed in any suitable location around the holding furnace 204. For example, the heating elements 206 may be disposed along the side of the holding furnace 204, or underneath the holding furnace 204 in what is sometimes referred to herein as an “under-heater design” for the open holding furnace 204. In such a configuration, the molten metal 202 is heated from below at an appropriate temperature to maintain the molten metal 202 in liquid form. The heating elements 206 may electrical, gas, oil, or any suitable heating element.
In some embodiments, the pump assembly 200 comprises a motor 208 coupled to a rotatable elongated shaft 210. The motor 208 is configured to be run at variable speeds with a programmable controller (not shown). The programmable controller may be suitably programmed or otherwise configured to execute computer-executable instructions according to a programmable control profile stored in computer-readable memory which causes a rotational speed of an impeller 212 to vary according to the control profile, as will be explained in more detail below with reference to
Additionally, or alternatively, the controller may be part of a feedback control system, or closed-loop control system to monitor the fill status of a mold via sensors which may be situated in the mold and configured to monitor the fill status of the mold. These sensors, may be probes, or any similar monitoring mechanism capable of monitoring a property associated with filling the mold and sending feedback signals to the controller. In this scenario, a desired system output for filling a mold may be specified and may vary over time according to the programmable fill profile. At a particular point in one or more sensors within the mold can measure the actual system output and feed this measured system output to the controller. In some embodiments, the controller is a proportional-integral-derivative (PID) controller, suitable for feedback control systems. The controller takes the error (i.e., difference) between the desired system output and the measured system output and adjusts the command voltage to the motor 208 in order to operate the impeller at a desired rotational speed for maintaining the desired system output.
Accordingly, a computing device may be associated with the pump assembly 200 and equipped with one or more processors, such as the programmable controller, and one or more forms of computer-readable memory. In some embodiments, the computing device may include a computer program product including a non-transitory machine-readable storage medium having stored thereon instructions (in compressed or uncompressed form) that may be used to program a computer (or other electronic device) to perform processes or methods described herein. The machine-readable storage medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, compact disc read-only memories (CD-ROMs), digital video discs (DVDs), read-only memories (ROMs), random access memories (RAMs), erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), flash memory, magnetic or optical cards, solid-state memory devices, or other types of media/machine-readable medium suitable for storing electronic instructions.
The computer-readable memory may be used to store any number of functional, or executable, components, such as programs and program modules that are executable on the processor(s) to be run as software. Each component stored in the computer-readable memory may comprise computer-executable instructions that, when executed, cause the one or more processors to perform acts and to implement techniques described herein. Each component may be in the form of data structures, program modules, or other data. The components included in the computer-readable memory may include the aforementioned programmable control profile.
With continuing reference to
In some embodiments, the elongated shaft 210 comprises a cylindrically shaped, elongated orientation having a rotational axis that is generally perpendicular to the base member 214. The elongated shaft 210 also comprises a proximal end that is configured to couple to the motor 208, and a distal end that is configured to couple to the impeller 212. The elongated shaft 210 is configured to be rotated by the motor 208 and extends from the motor 208 and into the chamber of the base member 214 such that the impeller 212 is rotated by the elongated shaft 210 and within the chamber of the base member 214. Rotation of the impeller 212 therein causes a directed flow of the molten metal 202 by drawing the molten metal 202 into the chamber via an inlet of the base member 214, and forcing the molten metal 202 out of the chamber via an outlet of the base member 214. The outlet of the base member 214 may be disposed in any suitable location on the base member 214, and is typically adjacent a side wall or top wall of the base member 214. The outlet of the base member 214 may be coupled to a riser 220 for transfer of the molten metal 202 to an associated transfer system, and subsequently to a mold. The associated transfer system typically comprises a system of pipes adapted for fluid communication that also maintain the molten metal 202 at a desired temperature while it is transferred through the transfer system. The riser 220 may be surrounded by a refractory sheath or otherwise suited for submergence in the bath of molten metal 202.
It is to be appreciated that the specific dimensions, proportions, shapes and configurations of each of the component parts of the pump assembly 200 are not specific to the present invention. For example, impeller 212 may be shaped or contoured in various ways to provide a suitable impeller for moving the molten metal 202, and the base member 214 may be of various sizes, or heights, for a particular configuration.
As will be described in more detail below, in some embodiments, a throttle for manipulating a flow rate or pressure of the molten metal 202 is associated with the pump assembly 200. The throttle may be a static throttle or a dynamic throttle. A static throttle, as used herein, means a throttle that does not change in characteristic while the pump assembly 200 is operating. In other words, a static throttle may be thought of as a fixed tolerance throttle. A dynamic throttle, by contrast may be dynamically changed with regard to characteristics such as size, shape or output of the throttle to dynamically adjust the flow rate or pressure of the molten metal 202 via control of the throttle. The throttle, whether static or dynamic, operates to lessen a magnitude of a change in flow rate or pressure of the molten metal 202 relative to a rotational speed of the impeller 212.
In some embodiments, the throttle may be fixed tolerance leakage path (e.g., a “bypass,” or “bypass gap”). This leakage path may be finely tuned to a designed tolerance and is operative to enable control of a flow rate and/or a pressure of the molten metal 202 by allowing the molten metal 202 to leak from the chamber 402 to an environment outside of the base member 214 (i.e., an exterior atmosphere) at a predetermined rate. In this scenario, the leakage path is a static throttle.
In yet other embodiments, the throttle may be a dynamic throttle. For example, the tolerance of a leakage path may be dynamically adjusted, via a controllable bearing assembly or similar mechanism that can increase or decrease the amount of molten metal that is leaked to an exterior atmosphere. In yet other embodiments, the throttle may be adjustable/controllable heating elements to tune the heat directed to the holding furnace containing the molten metal 202. This is due to the fact that controllability of the flow rate or pressure may be dependent, at least in part, on a viscosity of the molten metal 202 such that optimal control of the delivery of the molten metal 202 may be manipulated by adjusting the temperature of the molten metal 202 to indirectly change the viscosity of the molten metal. This is an example of a dynamic throttle.
By utilizing a throttle to manipulate the flow rate or pressure of the molten metal 202 relative to the rotational speed of the impeller 212, an associated user is able to finely tune the volumetric amount and/or pressure of the molten metal 202 provided to an associated mold. Accordingly, a throttle further improves the controllability of the delivery of the molten metal 202. It is to be appreciated that controllability may be dependent, at least in part, on a viscosity coefficient of the molten metal 202. Namely, in one embodiment, as the viscosity of the molten metal 202 decreases, a parameter of the throttle (e.g., the size of the impeller 212, or size of the leakage path, temperature of the molten metal, etc.) would need to be adjusted to get the optimal control for the delivery of the molten metal 202. Furthermore, different applications (e.g., dosing, casting, etc.) may call for different sensitivity in response due to a change in the rotational speed of the impeller 212.
Referring now to
The pump well 304 includes a transfer pump 306 configured to pump the molten metal 202 into a launder transfer system 308, which may optionally be heated to maintain the molten metal 202 at an appropriate temperature while it is being transferred via the launder transfer system 308. In some embodiments, the transfer pump 306 may be replaced with an overflow transfer (OFT) system that includes a metal level sensor, such as a laser leveling sensor, which accomplishes the same task of transferring the molten metal 202 from the pump well 304 via the launder transfer system 308. The launder transfer system 308 may comprise a system of troughs, conduits, channels, pipes, etc., adapted for fluid communication. Furthermore, as shown in
The molten metal 202 is transferred via the launder system 308, or in some embodiments, via the transfer ladle 312, to one or more holding furnaces 320(1)-(N). The one or more holding furnaces 320(1)-(N) are of an open configuration such that each holding furnace 320(1)-(N) is accessible from the top. Accordingly, continuous, or uninterrupted, flow of the molten metal 202 may be provided to the open-holding furnace architecture from the melting furnace 302 such that the requirement to delay or altogether halt operations in the plant for refilling the molds is eliminated. That is, uninterrupted supply of molten metal to the one or more holding furnaces 320(1)-(N) is enabled by virtue of the pump assembly 200 and the open-holding furnace configuration. Each holding furnace 320(1)-(N) is further configured with an under-metal heater design such that the molten metal 202 is heated from below at an appropriate temperature to maintain the molten metal 202 in liquid form. Additionally, or alternatively, heating elements, such as the heating elements 206, may be disposed on one or more sides of the holding furnaces 320(1)-(N). The heating elements may be electrical, gas, oil, or any suitable heating element. In some embodiments, the heating elements are tubular heaters of the “Tonnetsu style,” known to a person having ordinary skill in the art. The holding furnaces 320(1)-(N) may optionally comprise lids on the top that at least partially cover the tops of the holding furnaces 320(1)-(N).
Upon entering the holding furnaces 320(1)-(N), the molten metal 202 may optionally be degassed via a degasser 322. The degasser 322 is configured to disperse gas, such as nitrogen, argon, or similar substances, throughout the molten metal 202 in order to precipitate undesirable constituents, such as hydrogen gas. The holding furnaces 320(1)-(N) may further include a filter 324 to filter undesirable constituents that are either precipitated via the degasser 322, or that exist in the molten metal 202 from the scrap that is melted in the melting furnace 302. The holding furnaces 320(1)-(N) may further include a metal level sensor 326, such as a laser level sensor, to ensure that the molten metal 202 within the holding furnaces 320(1)-(N) stays at an optimal level within the holding furnaces 320(1)-(N).
One or more centrifugal molten metal pump assemblies 328(1)-(M) are provided within the holding furnaces 320(1)-(N). The pump assemblies 328(1)-(M) may be the same or similar pump assemblies as the pump assembly 200 of
It is to be appreciated that the illustrated number of components in the system 300, as well as the illustrated configurations of each of the component parts of the system 300 are not specific to the present invention. For example, any number of holding furnaces 320(1)-(N), pump assemblies 328(1)-(M), or molds 330(1)-(P) may be utilized in the system in any combination or configuration of elements as is deemed suitable for a particular application.
Referring now to
In some embodiments, the impeller 212 comprises a first radial edge 406a that is axially spaced from a second radial edge 406b such that the first radial edge 406a is adjacent the elongated shaft 210. The first and second radial edges 406a/b are located peripherally about a circumference of the impeller 212. In some embodiments, the chamber 402 houses a bearing assembly 408 which comprises a first bearing ring 410 that is axially spaced from a second bearing ring 412. The first radial edge 406a is facially aligned with the first bearing ring 410, and the second radial edge 406b is facially aligned with the second bearing ring 412 such that the bearing assembly 408 surrounds the impeller 212 within the chamber 402. The first and second bearing rings 410, 412 are made of a material, such as silicon carbide, having frictional bearing properties at high temperatures to prevent cyclic failure due to high frictional forces. The first and second bearing rings 410, 412 are further adapted to support the rotation of the impeller 212 within the chamber 402 of the base member 214 such that the pump assembly 200 of
In some embodiments, the impeller 212 comprises a first peripheral circumference 414a which is axially spaced from a second peripheral circumference 414b. The elongated shaft 210 is coupled to the impeller 212 at the first peripheral circumference 414a. The second peripheral circumference 414b is spaced opposite from the first peripheral circumference 414a and is aligned with a bottom portion 416 of the base member 214. The first radial edge 406a is adjacent the first peripheral circumference 414a, and the second radial edge 406b is adjacent the second peripheral circumference 414b.
In some embodiments, a bottom inlet 418 is provided in the second peripheral circumference 414b. More specifically, the bottom inlet 418 comprises the annulus of a bird cage style of impeller 212. It is to be appreciated that the bottom inlet 418 may be formed of vanes, bores, annulus (“bird cage”), or other assemblies known to a person having ordinary skill in the art. The rotation of the impeller 212 draws the molten metal 202 into the bottom inlet 418 and into the chamber 402 such that continued rotation of the impeller 212 causes the molten metal 202 to be forced out of the chamber 402 at an outlet 420 of the base member 214.
In some embodiments, the bearing assembly 408 comprises a base ring bearing adapter 422 that is configured to couple the second bearing ring 412 to the bottom portion 416 of the base member 214. The base ring bearing adapter 422 comprises a radial flange portion 424 that is securely coupled to a disk body 426 and is operative to support bearing rings of various sizes along the bottom portion 416 of the base member 214. The radial flange portion 424 is adjacent the chamber 402 and is generally perpendicular to the disk body 426. The base ring bearing adapter 422 is generally circular and is configured to receive the second bearing ring 412.
As illustrated in
One example technique for varying the tolerance of the bypass gap 428 is to provide bearing rings, such as the first or second bearing rings 410, 412, or base ring bearing adapters 422 of different sizes at the base member 214 which results in a bypass gap 428 of varying sizes. It is to be appreciated that a bored or annulus (“bird cage”) bottom inlet 418 may be advantageous in the embodiment utilizing the bypass gap 428 as the design for the leakage path because the types of impellers 212 with such bottom inlets 418 include a defined radial edge, such as the first and second radial edges 406a/b, allowing a designed tolerance for the bypass gap 428 to be created within the chamber 402.
In some embodiments, the bypass gap 428 is defined by the second bearing ring 412 such that the second bearing ring 412 has a larger diameter than the first bearing ring 410 in the bearing assembly 408. In another embodiment, the bypass gap 428 is defined by the impeller 212 such that the second radial edge 406b of the impeller 212 has a smaller diameter than the first radial edge 406a of the impeller 212. Here, the first radial edge 406a is abuttingly positioned in contact with, and rotatably supported at, the first bearing ring 410.
In yet other embodiments, the bypass gap 428 may be defined by a plurality of removable, segmented teeth or posts that are radially positioned about the perimeter of the impeller 212 such that the plurality of teeth maintain contact with the bearing ring 412 during rotation of the impeller 212 while radial spaces interposed between the plurality of teeth are configured to allow leakage of the molten metal 202 at a predetermined rate.
In some embodiments, a leakage path may be provided by a plurality of apertures located through the first peripheral circumference 414a of the impeller 212 to allow fluid communication with the chamber 402 and an environment outside the base member 214. In this scenario, the first radial edge 406a may be surrounded by the first bearing ring 410 such that the first radial edge 406a is abuttingly positioned with the first bearing ring 410 and rotates while maintaining contact with the first bearing ring 410.
In some embodiments, it is also contemplated that at least one leakage path may also be provided downstream of the impeller 212 within the chamber 402. The leakage path may be located in any suitable position, such as in the riser 220 of
Referring now to
Referring now to
Referring now to
For discussion purposes, the process 800 is described with reference to the pump assembly 200 of
At 802, molten metal is transferred to a holding furnace. In some embodiments, this may be performed via a launder transfer system, such as the launder transfer system 308 of
At 804, the impeller 212 is rotated within the holding furnace to direct a flow of the molten metal toward a mold. The impeller 212 may be positioned within the chamber 402 of the base member 214 to direct, or draw, the molten metal 202 into the chamber 402.
At 806, molten metal 202 is delivered to the mold. At 808, a determination is made as to whether the rotational speed of the impeller 212 needs adjustment (i.e., increasing or decreasing the command RPM). This determination may be made according to a command fill profile, such as those described with reference to
In some embodiments, the process 800 may include dampening a magnitude of a change in flow rate or pressure of the molten metal 202 relative to the rotational speed of the impeller 212. For example, a throttle may manipulate the flow rate or pressure of the molten metal relative to the rotational speed of the impeller. This may allow for fine-tuned controllability when delivering the molten metal 202 to a mold.
Currently, thousands of pressurized furnaces are used for casting, or similar applications for delivering molten metal to molds. The embodiments disclosed herein provide a revolutionary technique for controlled delivery of molten metal to molds which will transform the industry by allowing for a system that utilizes an open-furnace architecture with affordable centrifugal-type pump assemblies. This system enables high performance (e.g., up to 45-50 psi of delivery pressure) and precise control, along with mass production, and continuous operation to deliver molten metal to molds.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. Therefore, the present invention should be limited not by the specific disclosure herein, but only by the appended claims.
This application is a continuation-in-part of, and claims priority to, PCT Application No. PCT/US2012/034048, filed on Apr. 18, 2012, entitled, “MOLD PUMP ASSEMBLY,” which is based on and claims priority to U.S. Provisional Application No. 61/476,433, filed on Apr. 18, 2011, entitled, “MOLD PUMP ASSEMBLY,” the contents of which are herein incorporated by reference.
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| Number | Date | Country | |
|---|---|---|---|
| 20130068412 A1 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61476433 | Apr 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2012/034048 | Apr 2012 | US |
| Child | 13654277 | US |
