Multi-chamber molten metal pump

In accordance with one aspect of the present exemplary embodiment, a molten metal pump comprising a refractory material body defining an elongated chamber is provided. The chamber is configured to receive a shaft and impeller assembly. The chamber includes an open top through which the shaft passes and a bottom inlet. The impeller is located in or adjacent the inlet. The body further defines an elongated passage adjacent to the chamber. An opening provides fluid communication between the elongated passage and the elongated chamber. The elongated passage is in fluid communication with a discharge channel configured to direct molten metal at least substantially perpendicular to an elongated axis of the elongated chamber.

BACKGROUND

The present exemplary embodiment relates to a molten metal pump. It finds particular application in conjunction with lifting molten metal from a vessel, and will be described with reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.

A reverbatory furnace is used to melt metal and retain the molten metal while the metal is in a molten state. 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. Reverbatory furnaces usually include a chamber containing a molten metal pump, sometimes referred to as a pump well. The pump is utilized for numerous purposes including circulation of the molten metal bath in the furnace, for introduction of metal treatment agents such as chlorine gas, and for removal of the molten metal from the furnace.

Pumps for pumping molten metal typically include a base. Such pumps also include one or more inlets in the pump base which allow molten metal to enter the pump chamber. An impeller is mounted in the pump chamber and is connected to a drive shaft. The drive shaft is typically coupled to a motor. As the motor turns the shaft, the shaft turns the impeller and the impeller pushes molten metal out of the pump chamber.

Molten metal pump casings and impellers usually employ a bearing system comprising ceramic rings wherein one or more rings on the impeller align with one or more rings in the pump base. The purpose of the bearing system is to reduce damage to the components, particularly the rotor and pump chamber wall, during pump operation.

The materials forming the molten metal pump components that contact the molten metal bath should remain relatively stable in the bath. Structural refractory materials, such as graphite or ceramic, that are resistant to disintegration by corrosive attack from the molten metal may be used.

Molten metal transfer pumps have been used, among other things, to transfer molten aluminum from a furnace well to a ladle or launder from where it is cast in molds into solid, pieces such as ingots. A ladle is a large vessel into which molten metal is poured from the furnace. After molten metal is placed into the ladle, the ladle is transported from the furnace area to another part of the facility where the molten metal inside the ladle is poured into molds. The launder is essentially a trough, channel or conduit outside of the reverbatory furnace.

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 the main hearth. The transfer pump draws molten metal from the well in which it resides and transfers it into a ladle or launder and from there to die casters that form the metal articles. The present disclosure relates to pumps used to transfer molten metal by lifting it from a furnace for transport to a die casting machine, ingot mold, DC caster or the like.

One type of transfer pump is described in U.S. Published Application 2008/0314548, the disclosure of which is herein incorporated by reference. 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 H1and 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 H2that is lower than height H1and the second chamber is juxtaposed another structure, such as a ladle or launder, into which it is desired to transfer molten metal from the vessel. The pump (either a transfer, circulation or gas-injection pump) is submerged in the first chamber 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.

An alternative transfer style pump is disclosed in U.S. Published Application 2013/0101424, the disclosure of which is herein incorporated by reference. The pump comprises an elongated pumping chamber tube with a base end and an open top end. A shaft extends into the tube and rotates an impeller proximate the base end. The pumping chamber tube preferably has a length at least three times the height of the impeller. The base end includes an inlet and the top end includes a tangential outlet. Rotation of the impeller draws molten metal into the pumping chamber and creates a rotating equilibrium vortex that rises up the walls of the pumping chamber. The rotating vortex adjacent the top end exits the device via the tangential outlet.

BRIEF DESCRIPTION

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 intended neither to identify certain elements of the disclosure, nor to delineate the 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.

In accord with one aspect of the present exemplary embodiment, a molten metal pump comprising a refractory material body defining an elongated chamber is provided. The chamber is configured to receive a shaft and impeller assembly. The chamber includes an open top through which the shaft passes. The chamber further includes a bottom inlet. The impeller is located in or adjacent the inlet. The body further defines an elongated passage adjacent to the chamber. An opening provides fluid communication between the elongated passage and the elongated chamber. The elongated passage is in fluid communication at its top end with a discharge channel configured to direct molten metal at least substantially perpendicular to an elongated axis of the elongated chamber.

According to a second embodiment, a method for transferring molten metal from a vessel is provided. The method comprises disposing a molten metal pump having an elongated chamber in a bath of molten metal. The chamber is configured to receive a shaft and impeller assembly through an open top. The impeller is located in or adjacent to an inlet to the chamber. The body further includes an elongated passage adjacent to the chamber. An opening provides fluid communication between the elongated passage and the elongated chamber. The elongated passage is in fluid communication with a discharge channel configured to direct molten metal at least substantially perpendicular to the elongated axis of the elongated chamber. Rotation of the impeller elevates molten metal within the elongated chamber and the elongated passage such that molten metal is selectively discharged from the pump via the discharge channel.

According to a further embodiment, a molten metal pump including a body comprised of a refractory material defining an elongated chamber and configured to receive a shaft and impeller assembly is provided. The chamber includes an open top through which the shaft passes and a bottom inlet. The impeller is located in or adjacent the inlet. The chamber is in fluid communication with a discharge channel located at a top end of the body and configured to direct molten metal at least substantially perpendicular to an elongated axis of the elongated chamber. The body also includes a plurality of rods having a first anchor end disposed in the body and a second attachment end secured to a pump support assembly. The rods also receive a compressible element configured for establishing a compressive force on the body. The tension supplying rods advantageously allow the pumping chamber to be formed and attached to the pump support assembly without use of a metal cladding. Elimination of a metal cladding allows the full length of the body to be immersible in a molten metal bath. In addition, the use of the tension supplying rods allows the pump body to be optionally constructed with a relatively small footprint. Accordingly, installation in space constrained regions of a furnace is a viable option.

DETAILED DESCRIPTION

The following description and drawings set forth certain illustrative implementations of the disclosure in detail. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other advantages and alternative features of the invention will be apparent to the skilled artisan when considered in conjunction with the drawings.

Referring now toFIG. 1, a molten metal reverbatory furnace100is depicted. A pump well102extends from the reverbatory furnace and receives transfer pump104of the present disclosure. Pump104is suspended by a super structure including two beams106. Pump104hangs into cavity108of the pump well102. Cavity108receives molten metal from a main portion of reverbatory furnace100via a passage.

Beams106receive a motor mount110which supports motor112(air or electric). Pump104is suspended such that an inlet end (seeFIGS. 2-5) can be disposed in molten metal contained in cavity108with a discharge channel114positioned adjacent or slightly above notch116formed in the wall of pump well102. As a skilled artisan will discern, a tube or other launder assembly can be affixed to the discharge channel114and extend through the notch116to facilitate transport of molten metal out of the reverbatory furnace for delivery as desired. Of course, the assembly can also be positioned such that discharge channel114extends through the notch116and mates with a launder system externally to the pump wall. Advantageously this system does require lifting of the molten metal above the height of the exterior walls of the pump well.

Turning now toFIGS. 2-4, pump200includes a refractory body201constructed of ceramic or graphite, for example. Body201defines a first pumping chamber202which receives a shaft204and impeller206. Impeller206can be disposed in (or adjacent) an inlet208formed in a lower portion of the pump body201.

The inlet208can include a bearing surface (such as a bearing ring) receiving the impeller206. The impeller206may include a corresponding bearing ring. The bearing surface can be an inward face of the inlet and the impeller bearing surface can be a radially external surface of the impeller snout, for example. The impeller can be a bottom inlet, side outlet type.

The impeller can also include a top plate. Moreover, it is believed that a top plate can provide a more gradual upward flow of molten metal within the pumping chamber. This more gradual upward flow can be demonstrated by a relatively minimal (or substantially zero) vortex (see line306inFIG. 5) being formed in the pumping chamber.

The impeller is advantageously controllable with respect to the quantity of molten metal it transfers per RPM. In this regard, the impeller can have a flow rate per RPM that is relatively slow but provides the head necessary to lift the molten metal within the pumping chamber. For example, the impeller can provide an increase of molten metal throughput of between about 1 and 2 pounds per minute for a single unit increase in RPM.

Shaft204and impeller206can be inserted into pumping chamber202via open top209. While the shaft/impeller assembly is depicted as centrally located within the chamber it is envisioned that an off center location may also function adequately.

An opening210is formed in a side wall212of the pumping chamber202. The opening210is in fluid communication with an elongated passage216running adjacent and generally parallel to the pumping chamber202. The largest cross-section of the elongated passage216can be less than a largest cross-section of the pump chamber202. The pumping chamber202and the elongated passage216can each be at least substantially cylindrical and a diameter of the elongated passage216can be less than a diameter of the pumping chamber202.

Elongated passage216is in fluid communication with a discharge channel220oriented to direct flowing molten metal perpendicularly away from an elongated axis of the pumping chamber202.

Opening210can be located at a first end of the elongated passage216and the discharge channel220located at an opposed end of the elongated passage216. Opening210can be relatively smaller in cross-section (and/or diameter) than either passage216or pumping chamber202to reduce turbulence within passage216. The opening can be located closer to the bottom inlet than to the open top. The center of the opening can be located above the outlets of the impeller. While opening210can theoretically be located at a location horizontally adjacent the impeller206, locating opening210vertically above impeller206is believed to advantageously reduce turbulence in passage216. Opening210can be located at any height along the length of the pumping chamber. However, it is also noted that spacing the opening too far above the impeller may be undesirable because providing a length to the passage216between opening210and discharge channel220which is at least 50% of the length of the pumping chamber202provides a beneficial calming zone. The opening210can be between approximately 10 and 50%, or between 15 and 30%, of the length of the pumping chamber above a lower most portion of the inlet208.

Turning now toFIG. 5, molten metal flow of the operating pump is depicted. As illustrated, upon rotation of the shaft204and impeller206, molten metal is drawn into an impeller snout300which penetrates inlet208. Molten metal enters the impeller and is radially discharged via impeller outlets302. An upward flow or lifting of molten metal within pumping chamber202is achieved (see arrow304). Depending on the impeller design and speed of rotation such flow may be of an equilibrium vortex style (wherein molten metal rotates and rises at least slightly higher adjacent the walls of the chamber than adjacent the shaft—see line306) or without a vortex wherein the molten metal rises with limited rotation.

Rotation of the shaft204and impeller208and upward lifting of the molten metal within pumping chamber202creates a simultaneously lifting of molten metal in passage216; wherein molten metal accesses passage216through opening210. The molten metal height within the passage216is typically substantially equal to or slightly below the level of molten metal within the pumping chamber202.

When molten metal rises in the passage216to a height reaching a floor310of the discharge channel220, molten metal flows outwardly from the pump to an associated launder or other transfer mechanism for delivery to a ladle, casting apparatus or other desired location. Advantageously, the entire pump assembly below the motor can be immersed in the molten metal.

Turning now toFIG. 6, a further alternative configuration is provided wherein the molten metal pump body400is secured to a super structure402or motor mount404via rods406. Rods406include a first end including mounting anchors408which can be cast into the pump body or secured therein, for example, via side notches or longitudinal insertion with rotation into a locking engagement, etc. A second end409of each rod is secured in a convention manner to the superstructure402or motor mount404. Rods406can include a threaded external surface receiving nuts410which facilitate the application of a compressive force on the pump body via inclusion of intermediate spring assemblies412.

While the anchor assemblies408are depicted relatively close to the top surface of the pump body400, it may be desirable to locate the anchors lower on the pump body (for example at the metal level ML) to provide compressive forces over a greater surface area of the pump body.

Optionally, a launder or other structure for transferring molten metal will be secured to the discharge channel. The launder may be either an open or enclosed channel, trough or conduit and may be of any suitable dimension or length, such as one to four feet long, or as much as 100 feet long or longer. The launder may have one or more taps (not shown), i.e., small openings stopped by removable plugs.

The pump motor is preferably a variable speed motor. The system may be automated by utilizing a float in the ladle, a scale that measures the combined weight of the ladle and the molten metal inside the ladle, or a laser to measure the surface level of molten metal in the launder or other location in the operation, as an example. When the amount of molten metal in one part of the system is determined to be relatively low, the pump can be automatically adjusted to operate at a relatively faster speed to cause molten metal to flow more quickly out of the pump and ultimately into the structure to be filled. When the amount of molten metal in the structure (such as a ladle) reaches a desired level, the pump can be automatically slowed and/or stopped.

The speed of the pump can be reduced to a relatively low speed to keep the level of molten metal statically positioned in the elongated passage at an elevated height but below a height at which molten metal reaches the discharge channel. Advantageously, this maintains the temperature of the pump body at an elevated level and reduces thermal shock on the components when full pump operation is resumed.

A single pump could simultaneously feed molten metal to multiple (i.e., a plurality) of structures, or alternatively be configured to feed one of a plurality of structures depending upon the placement of one or more dams to block the flow of molten metal into the one or more structures.

A control system can be provided. The control system may provide proportional control such that the speed of the molten metal pump is proportional to the amount of molten metal required by a structure. The control system could be customized to provide a smooth, even flow of molten metal to one or more structures such as one or more ladles or ingot molds with minimal turbulence and little chance of overflow.

A control screen may be used with the system. The control screen could include, for example, an “on” button, a “metal depth” indicator allowing an operator to determine the depth of the molten metal as measured by a remote device, an “emergency on/off” button allowing an operator to stop the molten metal pump, an RPM indicator and/or an AMPS indicator to determine an electric current to the motor of molten metal pump.