Coating apparatus – Projection or spray type
Reexamination Certificate
1999-03-02
2001-02-13
Beck, Shrive (Department: 1762)
Coating apparatus
Projection or spray type
C118S307000, C118S419000, C239S591000, C417S423150, C417S424100
Reexamination Certificate
active
06187096
ABSTRACT:
TECHNICAL FIELD
This invention relates to pumps for pumping molten metal. More particularly, this invention relates to a spray assembly for spraying molten metal onto a substrate.
BACKGROUND OF THE INVENTION
A transfer pump generally transfers molten metal out of one furnace to another furnace, into a ladle, or the like. Transfer pumps typically include a motor carried by a motor mount, a shaft connected to the motor at one end, and an impeller connected to the other end of the shaft. Such pumps also include a base with an impeller chamber, the impeller being rotatable in the impeller chamber. Transfer pumps may either be top feed pumps or bottom feed pumps depending, among other things, on the configuration of the base and orientation of the impeller relative to the direction of shaft rotation. Support members extend between the motor mount and the base. The pump may include a shaft sleeve surrounding the shaft, support posts, and a tubular riser. The tubular riser is usually attached to a molten metal outlet opening in the base.
Transfer pumps may be designed with pump shaft bearings, impeller bearings and with bearings in the base that surround the impeller to avoid damage of the shaft and impeller due to contact with the base. The shaft, impeller, and support members for such pumps are immersed in molten metals such as aluminum, magnesium, zinc, lead, copper, iron and alloys thereof. The pump components that contact the molten metal are composed of a refractory material such as graphite or ceramic.
In a transfer pump, the tubular riser extends vertically upward from the molten metal outlet opening of the base and provides a passageway for molten metal. The riser typically extends vertically up to the motor mount from which a conduit in communication with the riser may direct molten metal to a remote location. The end of the tubular riser or pipe may be open for pouring molten metal unidirectionally onto substrates. In a coating operation, molten metal is poured in a stream, like water from a faucet, out of the riser opening towards the substrate. Coating substrates with such transfer pumps is typically slow and difficult due to the time required for the molten metal to drip around to all sides of a substrate or the time required for multiple passes of an object so that all sides are sufficiently coated. Moreover, the coating quality and uniformity of molten metal discharged in this manner onto a substrate are generally poor, the underside coating of the substrate being different than on other sides.
SUMMARY OF THE INVENTION
The present invention overcomes the prior art problems of directly coating molten metal onto a workpiece or substrate with a molten metal pump. The present invention simultaneously coats all of the exterior surfaces of the workpiece. The delays associated with having to wait for the molten metal to drip to the underside or for multiple coating passes to occur, are eliminated. Moreover, multidirectional coating of molten metal onto substrates improves coating uniformity and increases productivity.
The present invention is directed to a pump for pumping molten metal onto a workpiece or substrate to be coated. In particular, the pump includes a motor fastened to a motor support, a base having an impeller chamber, at least one molten metal inlet opening to the base, a molten metal outlet opening from the base, a shaft connected to the motor at one end, an impeller connected to the other end of the shaft and rotatable in the impeller chamber, an apertured conduit in communication with molten metal discharged from the base outlet opening and an insulating region located between the conduit and the motor support. The base, shaft, impeller and riser, and preferably all components that are in contact with molten metal, are formed of a refractory material such as graphite.
More specifically, the conduit is formed of a refractory material, preferably graphite, and includes an arcuate shaped portion in which a plurality of molten metal outlet openings are disposed. The conduit is shaped with the outlet openings arranged to enable molten metal to travel toward an interior of the conduit in upward and downward directions. Preferably, the conduit is in the shape of a ring with the conduit openings configured and arranged to discharge molten metal through the conduit outlet openings toward an interior of the ring in upward and downward directions. Thus, the exterior surfaces of a workpiece passed through the ring is simultaneously coated on all sides. The conduit may include a section that is connected to the base.
Alternatively, the conduit as described is in communication with a tubular riser. One end of the tubular riser is attached and in fluid communication with the base outlet opening. The other end of the tubular riser is attached and in fluid communication with the conduit. Molten metal discharged from the base outlet flows though the tubular riser and into the conduit. The conduit discharges the molten metal though the conduit outlet openings. The conduit openings are configured such that all surfaces of a workpiece passed therein may be coated in one pass. This is a significant advantage for continuous galvanizing operations wherein high levels of productivity and coating quality are required.
The insulating region may be a gap such that there is no contact between the conduit and the motor support (e.g., the motor mount). The insulating region preferably comprises an insulating member of a nonmetallic material, such as ceramic or other refractory. The insulating region advantageously inhibits the conduit outlet openings from clogging with hardened molten metal during operation.
Another embodiment is directed to a spray assembly for a pump for pumping molten metal. The spray assembly includes an apertured conduit adapted to be fastened near the outlet opening in the base. The conduit is constructed of dimensions and of a configuration that enable it to extend beneath the motor support so as to leave an insulating region between the conduit and the motor support. The insulating region is comprised of air or an insulating member. The insulating member is connected to the conduit and to the motor support. The conduit may be integrally formed with the insulating member that extends in the insulating region, the insulating member being preferably comprised of nonmetallic insulating material, such as ceramic or other refractory.
Another embodiment is directed to a method of coating molten metal onto workpieces, such as angle iron, and comprises flowing molten metal into the interior of the base of the transfer pump. The impeller is rotated in the interior of the base to cause molten metal to move toward the base outlet opening. The molten metal is directed from the base outlet opening to the conduit, through the outlet openings of the conduit and onto the workpiece. The conduit openings are configured so that the exterior surfaces of the workpiece are coated. The method includes inhibiting the openings of the conduit from being clogged with hardened molten metal during operation. The step of inhibiting clogging is carried out by minimizing heat transfer from the conduit to the motor support. The conduit is insulated with air or with the insulating member located in the insulating region between the conduit and the motor support. The conduit may be integrated with the insulating member and extend to the motor support. Molten metal is discharged from the conduit outlet openings in upward and downward directions so that the exterior surfaces of the workpiece are coated.
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26 page article: HTS Pump Equation fo
Beck Shrive
Calcagni Jennifer
Watts, Hoffmann, Fisher & Heinke Co. LPA
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