US 3836280 A
A pump having a pumping chamber, an impeller shaft enclosed in a shaft bore communicating with the chamber, and an impeller carried on a shaft in the chamber is partially immersed in liquid so that the shaft bore extends down to the chamber from a location above the liquid, and the shaft bore is pressurized with an inert gas to counteract the pressure of the liquid head and the pumping pressure and thereby prevent the liquid from rising in the bore around the shaft.
Description (OCR text may contain errors)
United States atent [191 Koch [ MOLTIEN METAL PUMPS lFenton C. Koch, Chesterland, Ohio  Assignee: High Temperature Systems, 1nc., Newbury, Ohio  Filed: Oct. 17, 1972  App]. No.: 298,415
 11.5. C1 415/175, 415/200, 415/214  1nt. C1. F04d 7/00, F04d 7/02, F04d 29/10  Field of Search 415/200, 175, 214
 References Cited UNITED STATES PATENTS 2,528,210 10/1950 Stewart 415/214 3,048,384 8/1962 Sweeney et a1. 415/214 FOREIGN PATENTS OR APPLICATIONS 788,831 1/1958 Great Britain 415/175 Sept. 17, 1974 s 7/1929 Germany ..415/214 11/1955 Netherlands ..415/175 Primary Examiner-Henry F. Raduazo Attorney, Agent, or Fir'm-Watts, Hoffmann, Fisher & Heinke Co.
[5 7 ABSTRACT A pump having a pumping chamber, an impeller shaft enclosed in a shaft bore communicating with the chamber, and an impeller carried on ashaft in the chamber is partially immersed in liquid so that the shaft bore extends down to the chamber from a location above the liquid, and the shaft bore is pressurized with an inert gas to counteract the pressure of the liquid head and the pumping pressure and thereby prevent the liquid from rising in the bore around the shaft.
1 im 6 Wavin lis te MENIEDSEP 1 719m SHEU @1331 OF 3 1 I 3 1 ///fi Y 4 5 fin //p Q/ o o o o f MOLTEN METAL lP'UMlPS BACKGROUND OF THE INVENTION This invention relates generally to the pumping art, and more specifically to apparatus and method for lifting, conveying or circulating high temperature and/or corrosive materials such as molten aluminum, zinc and the like.
The present state of the art makes the handling of molten metals with a centrifugal pump very expensive and somewhat impractical. Presently used molten metal pumps are assembled from many different parts of several different refractory materials. These different parts are commonly cemented together or fitted together with threaded connections. The various parts of these presently used pumps are not subjected to the same degree of abrasive wear, mechanical strain, corrosive attack by the molten metal at elevated temperatures, oxidation from exposure to the high temperature air in the metal container at the interface of the molten metal and the atmosphere or thermal shock during immersion of the pump and during its operation.
The drive shaft of a molten metal pump in a typical molten metal container connects the impeller located below the molten metal surface to the drive motor located above the molten metal surface. For this reason the pump drive shaft rotates at the interface between the molten metal and the high temperature air in the molten metal container. The shaft, rotating at this point, constantly stirs a mixture of high temperature metal and high temperature air forming large amounts of the oxide on the metal commonly called skim or dross. This dross itself constitutes a serious loss, but in addition not only wears away the shaft at the metal air interface during rotation because of its abrasive character but presents a substantial disposal problem.
The support members and the discharge tube in pumps of present art are subjected to severe but different rates of deterioration. Neither of these parts rotate but are subjected to oxidation, corrosion, thermal shock and mechanical abuse.
For these explained reasons, the useful lives of the various parts of the pumps presently used are not of equal length. Failure ofa part cannot be predicted, and when it occurs in service it is almost always during pump operation. Because of the basic structural weakness of cemented and threaded joints in a refractory pump, any part breakage usually results in a multiple part failure that requires a complete pump overhaul.
A large stock of many different refractory pump parts as well as spare complete pumps are required to assure even intermittent operation. This fact is a severe detriment to a more universal use of molten metal pumps.
The deficiencies of the present state of the art are well known and have been well known for a long period of time. In spite of this, the present pumps available do not fill the need for a simple, reliable and practical method for pumping molten metal and high temperature molten material.
SUMMARY OF THE INVENTION An object of the present invention is to provide pumping apparatus and methods for handling molten, high temperature and/or corrosive materials.
Another object of the present invention is to provide a pump characterized by a rotating impeller shaft enclosed in a shaft bore extending down into a liquid bath and means for pressurizing the shaft bore with an inert gas in order to prevent the liquid from rising in the bore around the shaft.
A more specific object of the present invention is to provide a pump having structure defining a pump chamber, a shaft bore and a discharge bore communicating with the chamber, a shaft extending through the shaft bore, an impeller carried on the shaft in the chamber for pumping liquid through the discharge bore, and means for supplying an inert gas under pressure to the shaft bore around the shaft so that liquid in the pump chamber is prevented from rising in the shaft bore around the shaft.
Still another object of the invention is to provide a pump as described in any of the preceding paragraphs which is further characterized by an inlet opening extending through the wall of the shaft bore into its inte- A further object of the present invention is to provide a pump including structure extending down into liquid in a reservoir and defining a pump chamber having an inlet opening below the liquid level, a shaft bore and a discharge bore communicating with the chamber, a shaft enclosed in the shaft bore and extending down to the pump chamber from a location above the liquid, an impeller on the shaft in the pump chamber, and means for supplying an inert gas to the shaft bore at a pressure sufficient to counteract the pumping pressure and the pressure of the liquid head so that liquid is prevented from rising in the shaft bore around the shaft.
A further object of the present invention is to provide a method of pumping liquid using a pump as described in any of the preceding paragraphs and comprising the steps of immersing part of the pump including the pump chamber in a liquid so that the shaft bore extends from a location above the liquid and pressurizing the shaft bore with an inert gas at a pressure sufficient to counteract the pumping pressure and the pressure of the liquid head so that the liquid is prevented from rising in the shaft bore around the shaft.
Still another object of the present invention is to provide a pump as described in any of the preceding paragraphs which is further characterized by a construction requiring no structural supports or discharge tube, thus eliminating cemented or threaded structural joints.
Still another objective of this invention is a pump having the shaft bore and discharge bore located to equalize their lives in spite of their exposure to different degrees of deterioration, resulting in longer useful pump life and reducing the possibility of massive pump damage by sudden individual part failure.
Other objects and a fuller understanding of the invention will be apparent from the following detailed description and the accompanying drawings.
DESCRIPTION or THE DRAWINGS FIG. I is an elevation view of a pump resulting from the present invention with parts sectionally broken away below the molten material line.
FIG. 2 is a bottom view of the pump resulting from this invention showing the pump body, bottom plate and impeller in position.
FIG. 3 is a sectional view showing the pump body, impeller, discharge bore and connecting chamber in position.
FIG. 4 is a sectional view showing the pump body, shaft bore and discharge bore in position.
FIG. 5 is a sectional of a pump resulting from this invention providing a discharge for the molten material below the surface of the molten material in the pot or container.
FIG. 6 is a sectional view of a pump resulting from this invention providing an inlet for the molten material above the bottom of the pump.
DETAILED DESCRIPTION OF INVENTION FIG. 1 shows a molten metal bath 1 containing one embodiment ofa pump according to the present invention. It can be readily understood that the specific details of the container or pot would be dependent on the character of the molten material and the specific work being done on or by the molten material and the pump .that is the subject of this invention. Because of this,
there is no reason or need to describe the container in detail.
The pump body 2 is held in a partially submerged position in the molten material by the superstructure 4. The superstructure 4 may be an assembly of metal or like material that fits the upper surface of the pump body 2, that has a drive motor mount as a part and has holes bored, machined or made in some like manner to suit the bores provided in the pump body 2 for the shaft 13 and discharge 9. The superstructure 4 also may have holes provided to attach a pillow block assembly 16 and a discharge tube 17 using bolts 15 or other means.
If the density of the molten material is less than the effective density of the pump, the pump can be held by a suitable hook, chain or cable attached to the superstructure 4 and is usually held somewhat above the bottom of the molten material container. If the molten material bath is more dense and the pump tends to float, the pump must be held in position by suitable brackets attached to the superstructure 4 and the molten material bath container.
The pump body 2 as shown is circular in cross section. It should be easily understood, however, that the pump body 2 could as easily be another shape in cross section such as a square, octagon or ellipse.
A shaft bore 8 and a discharge bore 9 are shown provided vertically through the pump body 2. A pump chamber 11 is defined by an axial bore 10 which opens on the bottom of the pump body 2 and connects with the shaft bore 8 and the discharge bore 9. The pump chamber 11 provides a chamber for impeller rotation. A pump drive shaft 13 and impeller 3 are shown in position connected to a drive motor 14 by a suitable connection 21. The drive motor 14 can be air, hydraulic, electric or driven by other suitable means. A pillow block 16 or some other suitable device provides a top bearing support for the connection 21 between the drive motor 14 and the drive shaft 13. This pillow block may be pressure tight or may permit sufficient passage of gas to cool its bearings. An inert or fluxing gas may be introduced through tubing 18 and a fitting 19 or other suitable means through the pillow block 16 into the shaft bore 8. The pressure of the inert or fluxing gas while maintained in the shaft bore 8 is controlled to provide a dry running shaft down to a bleed hole 20 drilled radially between the outside of the pump body 2 and the shaft bore 8. Prior to or during operation of the pump, the pressure of the inert or fluxing gas is raised from atmospheric until bubbles or gas 22 exit from bleed hole 20 and are observed on the surface of the molten material 1. A bottom plate 12 may be incorporated to provide a running fit bearing for the impeller 3 and to seal the pump chamber 11 around the impeller 3 from the material bath 1. The pump body 2 may be constructed of materials that resist the chemical attack of the molten material bath 1. The shaft bore 8, discharge bore 9 and the bottom axial bore 10 may be cast in place, drilled, machined, bored or formed in some other suitable manner. It should be understood that the pump body 2 can be made in other ways such as by building up cross sectional slabs cemented together within the scope of this invention. The shaft 13 and impeller 3 are constructed of materials resisting the effects of oxidation, abrasion and erosion as well as the chemical attack of the molten material being pumped. It should be understood that a shaft 13 and impeller 3 may be used in one piece or these parts may consist of many parts within the scope of this invention.
The bottom plate 12 may be constructed of material resistant to abrasion at the surface adjacent to the impeller 3 as well as the chemical attack of the molten material being pumped. In many cases all of these parts may be constructed of the same material, simplifing construction. It should be understood, however, that different materials may be substituted for or sections inserted in specific parts to eliminate or reduce localized wear.
The pump body 2 may be attached to the superstructure 4 with bolts 7 threaded into the pump body 2. The pillow block 16 and the discharge tube 17 are shown attached to the pump body by the bolts 15 through the superstructure 4 and through gaskets 5 into the pump body 2. The gaskets 5 of suitable material may be provided to maintain gas pressure in the shaft bore 8 and to prevent leakage of molten material from the connection of the discharge bore 9 and the superstructure 4 and the pump body 2.
During operation of the pump resulting from this invention, the drive motor 14 turns the impeller 3 through the connection 21 supported by pillow block 16 and drive shaft 13. It is to be understood that the construction of the drive shaft 13 and impeller 3 design are dictated by the material being pumped and the requirements of the application and that the illustrated impeller and shaft are only one example of a particular way of constructing the pump of the present invention. Molten material enters the bottom of the-impeller 3 in FIG. 1 and is directed through the pumping chamber 11, up the discharge bore 9 and through the discharge tube 17 or through additional tubing if required by the application. During operation, inert or fluxing gas pressure may be maintained in the shaft bore 8, greatly reducing or eliminating the formation of dross around the drive shaft 13 and thereby greatly reducing or eliminating the abrasive wear presently encountered in similar pumps.
It should be easily understood from FIG. 3 and FIG. 4 that the shaft bore 8 and discharge bore 9 can be located at desirable locations, considering their exposure to wear and their useful lives. The pumping chamber 11 may be provided to connect the discharge bore 9 to the outlet of the impeller 3 and to increase efficiency.
It may be advantageous to provide a pump discharge below the surface of the molten bath by provision of a radial bore 23 into the discharge bore 9 from the outside surface of the pump body 2 as shown in FIG. 5.
It may be advantageous to provide an inlet 24 for the molten material above the bottom of the pump body 2 and above the pump chamber 11 as illustrated in FIG. 6. An impeller 3 of suitable design may be required incorporating a closed bottom and an inlet in its top as shown.
1. Pump apparatus adapted to be immersed in molten material and operated to move the material, said apparatus comprising:
a. a vertically positionable hollow structure of refractory material extendible down into the molten material and defining a submersible pump chamber in the lower end, a shaft bore extending upwardly from said pump chamber in said structure, and a discharge bore in said structure communicating with and extending upwardly from said pump chamber in the direction of said shaft bore,
b. a shaft extending through said shaft bore,
c. motor means operatively connected to said shaft,