US 3724831 A
A shaped strainer for the inlet of a molten metal pump to be immersed in the molten metal reservoir of a metal furnace. The end of the strainer adjacent the pump inlet is spaced by bosses from the pump inlet to define a plurality of openings for the flow of molten metal from the reservoir to the pump. Additional apertures are provided in the main body of the strainer and function to militate against the passage of foreign matter, such as for example, dross, from entering the pump upon initial insertion of the pump into the furnace and during operation thereof.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 1 Apr. 3, 1973 Huffman  MOLTEN METAL STRAINER  Inventor: Richard D. Huffman, Toledo, Ohio  Assignee: Gerity-Schultz Corporation, Toledo,
Ohio  Filed: Nov. 24, 1971  Appl. No.: 201,793
 U.S. Cl ..266/38, 415/121 G  Int. Cl. ..C21b 7/14  Field of Search ..266/34 A, 38,222/D1G. 6;
 References Cited UNITED STATES PATENTS 3,172,850 3/1965 Englesberg et al. ..415/121 G Primary Examiner-Gerald A. Dost Attorney-Wilson & Fraser  ABSTRACT A shaped strainer for the inlet of a molten metal pump to be immersed in the molten metal reservoir of a metal furnace. The end of the strainer adjacent the pump inlet is spaced by bosses from the pump inlet to define a plurality of openings for the flow of molten metal from the reservoir to the pump. Additional apertures are provided in the main body of the strainer and function to militate against the passage of foreign matter, such as for example, dross, from entering the pump upon initial insertion of the pump into the furnace and during operation thereof.
' 14 Claims, 4 Drawing Figures PATENTEUAPR3 I975 3,724,831
m1; \"I'OR. RICHARD Dv HUFFM N BY dmwwiwb A TTUR \E V MOLTEN METAL STRAINER BACKGROUND OF THE INVENTION In fields where pumps are employed to transfer molten metals, it has long been a problem to obtain a long life span for the pump and maintain the pump in continuous service. The problem has been aggravated by the presence of dross which forms on the upper surface of molten metal together with the residual materials which sink to the bottom, both of which can plug or permanently jam the pump mechanism.
Previous attempts to eliminate the above problem by utilizing strainer means gave rise to still other problems particularly a restriction in flow of the required metal to the pump when the dross and residuals were held outside the strainer. Oftentimes the dross on the surface of the molten metal would jam the pump as the pump was initially inserted into the body of molten metal.
Molten zinc has presented particular problems also. Due to the highly corrosive effect of molten zinc on other materials, the strainer must be designed to resist erosion by the flow of zinc through it.
The present invention overcomes the above problems by providing a strainer structure containing a combination of openings therein which allow free flow of metal while the shape of the strainer prevents clogging of the pump by dross upon insertion into the molten metal. Further, the structure is designed to maintain circulation in the fluid body while allowing only molten metal to enter the pump during operation.
SUMMARY OF THE INVENTION The present invention relates to strainers and more particularly to molten metal strainers for use on the inlet of molten metal pumps. The strainer is affixed to the pump and includes a body portion which may be a frustrum in the form of a cone in one embodiment, having a larger end thereof and a base closing ofi the smaller end of the frustrum portion. A flange is located adjacent the larger end and extends outwardly from the frustrum portion. Means located between the strainer and the pump, such as bosses are spaced apart and extend from the body portion and are disposed generally parallel to the axis of the body portion to engage the pump and define a plurality of openings each of which is defined by a pair of adjacent spaced apart bosses, the flange and the pump inlet housing. Typically, fastener means, such as screws may be associated with the bosses to attach the strainer to the pump housing. The frustrum portion of the strainer body includes a plurality of spaced openings to provide for flow of molten metal from the associated molten metal reservoir through an opening in the larger end of the body portion to the pump inlet without an accompanying flow of foreign matter. Further, the strainer is capable of parting and penetrating the dross formed on the surface of the molten metal without allowing the dross to enter the pump.
The strainer in combination with the pump results in increased pump life in the magnitude of 1,000 percent and reduces maintenance on the pump while being rugged, removable and serving to enhance circulation of the molten metal.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a top view of the strainer illustrated in FIG.
FIG. 4 is a sectional view of the strainer illustrated in FIG. 3 taken along line 4-4 thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates an immersible molten metal pump 10 having a housing 12 and discharge outlet 14. The housing 12 encloses an impellar (not illustrated) which is operative to convey the molten metal of the molten metal reservoir into which the pump is immersed through the outlet 14 and thence to the die cavity of a die casting machine, for example. The impellar is coupled to a drive shaft 16 which extends upwardly to a drive motor (not illustrated) for imparting rotation to the shaft 16. A series of screws 18 serve as means for attaching a strainer 20 in a secure removable manner to the base of the pump 10. The strainer 20 is adapted to fit over the inlet of the pump 10. An example of a suitable pump 10 would be a model D-l 3 manufactured by Metal Pumping Services, Division of Carbonrundum Company, Solon, Ohio. Clearly, other pumps could be used and one skilled in the art will be aware of various modifications which can be made to the strainer 20 to adapt it for use with other types of molten metal pumps. In order to reach the inlet of the pump 10, the molten metal in which it is immersed must pass through the strainer 20 and enter the inlet of the pump 10.
The strainer 20 is more clearly illustrated in FIGS. 2 and 3 and is particularly adapted for use with molten zinc which is highly corrosive on most materials it contacts. The strainer 20could likewise by used with other molten metals as well.
A body portion of the strainer 20 having side walls inclined to and encompassing the longitudinal axis thereof such as a frustrum 22 is in the form of a cone having a base 24 closing off one end thereof to form the main body of the strainer 20. Other frustrum configurations could be used though possibly not being as effective, for example, a pyramid. At the other end of the frustrum portion 22 is a flange 26 extending outwardly therefrom in a plane perpendicular. to an axis passing longitudinally through the frustrom portion. Preferrably, the base 24 is parallel with the flange 26. The flange 26 forms an annulus whose inside diameter corresponds to that of the large end of the frustrum portion 22. Positioned adjacent the outer diameter of the flange 26 and equally spaced apart from each other are a plurality of bosses 28 extending from the flange in a direction generally parallel to the axis of the frustrum portion 22. Alternate bosses 28 have apertures passing longitudinally therethrough and through the flange 26 to allow passage of the screws 18, illustrated in FIG. 1, for securing the strainer 20 to the base of the pump housing 12, asclearly illustrated in FIGS. 3 and 4.
FIG. 4 illustrates the opening at the large end of the frustrum portion 22 of the strainer 20 together with the plurality of openings 30 in the surface thereof. It will be noted that the frustrum portion 22 diverges in the direction of flow of the molten metal entering openings therein to accommodate an accumulation of flow. The openings 30 in the frustrum portion 22 are cast, drilled, or otherwise formed and have theirlongitudinal axes perpendicular to and intersecting with the axis of the frustrum portion 22. The openings 30 in the illustrated embodiment, are spaced over the entire periphery of the frustrum portion 22 in an alternating pattern of pairs aligned one above the other and single openings 30 located in a plane midway between each of the pairs of openings 30. The radial dispersion of the openings 30 is best illustrated in FIG. 3. The arrayof openings 30 is maintained a predetermined distance from the base 24 to elevate them above a level in a body of molten metal below which a combination of residual material or residue and loose pieces tend to settle and collect. It is to be understood that the size of the strainer 20. is a function of the size of the pump and the desired maximum flow of molten metal flowing therethrough.
In the particular example illustrated, the strainer 20 has an overall height of 4 inches of which the frustrum'portion 22 is 3 inches and the flange is threeeighths of an inch. The walls of the frustrum portion 22 and base 24 are three-eighths of an inch thick and the openings 30 in the frustrum portion 22 are five-sixteenths of an inch 'in diameter spaced on 30 increments over the periphery thereof with seven-sixteenths of an inch vertical spacing between each layer of openings 30. The inclination to the axis of the frustrom portion 22 is 10 and the opening at the large end is 2 l/l6 inches in diameter. At the intersection of the flange 26 and the frustrum portion 22, the outer diameter of the frustrum portion 22 is 5 inches, while the outside diameter of the flange 26 is 5 inches. Eight bosses 28 of substantially rectangular cross-section, as illustrated in FIG. 3, are equally spaced on 45" increments on the face of the flange 26. The bosses are 1 inch with a cross-sectional configuration of threefourths inch by five-eighths inch.
The strainer 20 is preferably formed as a casting, but may also be fabricated by other manners. Examplesof materials which are acceptable for manufacture of the strainer 20 include meehanite forcastings and stainless steel for other types of fabrications.
The strainer 20 has a dual function, serving as both a separator and a penetrating shield. As a separator it functions to maintain the pump free of foreign matter such as residue and particulate material during the pumps operation, and as a shield it functions to guard the pump 10 inlet as the pump 10 is plunged through the dross on the surface of a body of molten metal to prevent the dross from entering the pump 10. The shielding function differs from the separating function in that the frustrum portion 22 with its inclined or tapered sides andflat base effectively parts the dross on the surface of the body of molten metal to allow the pump to be submerged without contacting the dross. In
separating the residue and particulate material in the molten metal, the strainer 20serves as a point of demarcation between the foreign matter and the metal passing through the openings 30 in the frustrum portion 22.
Referring to FIG. 1, the majority of flow of molten metal to the pump 10 is caused to pass through the passageways defined by the flange 26, the bosses. 28, and the base of the pump 10. It was found necessary to supplement the openings 30 in the frustrum portion 22 with the passageways between the bosses to maintain the required flow of molten metal by the pump 10 To assure that the efiec'tiveness of the strainer 20 was not adversely altered by the introduction of the passageways between the bosses 28, the openings 30 are disposed at a level above the residue and particulate material which has settled to the bottom zone of the reservoir of molten metal. The above design involves locating the openings a predetermined distance above the base of the strainer 20 for a given application to place the openings 30 above the foreign matter when the base 24 is embedded in the foreign matter and in contact with the bottom of the receptacle containing the molten metal. v
Ina manner similar to the above design, the openings 30 are located at an elevation above the base 24 sufficient to clear the heaviest deposit of foreign matter, the residue, and permit the flow of molten metal immediately thereabove to enhance circulation of molten metal within the receptacle. Theopenings 30 are of a size to prevent undesired particles from passing therethrough. Further, the disposition of the openings 30 is such that the frustrum portion 22between the openings 30 will not be eroded by the passage of molten metal prior to termination of the life of the remainder of the strainer 20 and pump 10.
In the particular example illustrated, the passageway between the bosses 28 are located 3 inches above the bottom of the base 24 of the strainer 20 for an application within a fumace for melting and maintaining Zinc in the molten state. The effective open area of the openings is approximately 1 inch by 1 .inch. The openings 30 are located 1 /2 inches above the base 24 at their lowest point and are spaced seven-sixteenths of an inch apart vertically from row to row and have a minimum wall thickness between adjacent openings 30 of approximately nine-sixteenths-of an .inch. The flow rate of molten metal to the pump 10 is maintained generally at 1,000 pounds per minute on theabove described strainer 20 without serious deterioration of the strainer 20 prior to termination of the life of the pump 10. The slope of the frustrum portion 22 is 10 relative to its axis.-
The flat bottomed base 24 in combination with the taper slope of the frustrum portion 22 is particularly effective in parting the dross upon the surface of a molten metal body by apparently forcing the dross outwardly with sufficient force to prevent any dross from entering or plugging the openings 30 in the frustrum portion 22. Further, the flange-26 in combination with the taper of the frustrum portion 22 accomplishes the same effect in preventing the dross from entering the openings between the bosses 28 on the strainer 20. Enclosing the inlet of the pump 10 with the strainer 20 prevents agitation of the residue and loose particulate material by the pumping action of the pump, but the openings 30 in the frustrum portion 22 permit flow of molten metal from a region immediately adjacent the residue and particulate material.
It has been found that a strainer constructed in accordance with the invention has resulted in increased pump life of a magnitude of 1,000 percent in actual service in addition to reducing pump maintenance and down time. The strainer 20 is of a simple and rugged design, easily installed, removable, and contains a minimum of parts. The combination of flow openings assures sufficient flow to the pump, while enhancing circulation within the body of molten-metal and militating against the entry of foreign matter into the associated pump.
In accordance with the provisions of the patent statutes, the principle and mode of operation of the device have been explained and what is considered to represent its best embodiment has been illustrated and described. It should, however, be understood that the invention may be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
1. In combination with a molten metal pump, a strainer on the inlet thereof comprising: a body portion having an axis passing longitudinally therethrough, and side walls inclined to and encompassing the longitudinal axis to form a larger and a smaller end thereof; a base closing off the smaller end of said body portion;
means between said pump and said body portion defining openings for flow of molten metal to the inlet of the pump from a body of molten metal outside said strainer; and means for attaching said strainer to said pump; said body portion capable of parting dross on the surface of the body of molten metal while preventing dross and foreign matter within the body of molten metal from entering said pump.
2. The combination according to claim 1 wherein said means defining openings includes a flange adjacent the larger end of said body portion extending outwardly therefrom in a plane perpendicular to the axis thereof to effect further parting of dross.
3. The combination according to claim 1 wherein said means defining openings includes a plurality of spaced apart bosses extending outwardly from said body portion parallel to the longitudinal axis of said body portion to engage said pump.
4. The combination according to claim 2 wherein said means defining openings further includes a plurality of spaced apart bosses extending outwardly from said flange parallel to the longitudinal axis of said body portion to engage said pump and form a plurality of openings each formed by a pair of said bosses, said flange and said pump.
5. The combination according to claim 1 wherein said body portion includes a frustrum portion.
6. The combination according to claim 5 wherein said frustrum portion has a conical shape for dispersing the molten metal upon immersion in a uniform pattern.
7. The combination according to claim 1 wherein said base is perpendicular to the axis of said frustrum portion and flat on the outer side thereof.
8. The combination according to claim 4 wherein said base is located a distance from said openings in the direction of the axis of 881d frustrum portion to position said openings above the foreign matter in the body of molten metal when said base is positioned at an elevation corresponding to the elevation of the bottom of the body of molten metal. 7
9. The combination according to claim 1 wherein said means for attaching said strainer is associated with said bosses.
10. The combination according to claim 1 including a second opening at the larger end of said body portion and a plurality of third openings spaced apart on said frustrum portion over the periphery thereof for passing molten metal therethrough.
11. The combination according to claim 10 wherein said third openings are located a distance from said base in the direction of the axis of said frustrum portion to position said third openings above the residue in the body of molten metal when said base is positioned at an elevation corresponding to the elevation of the bottom of the molten metal.
12. The combination according to claim 10 wherein said third openings include round holes oriented at right angles to the axis of the frustrum portion.
13. The combination according to claim 10 wherein said plurality of third openings includes a series of rows of said openings extending over the body portion in the direction of the axis thereof.
14. The combination according to claim 4 wherein said flange is circular in the plane wherein said flange extends outwardly and said bosses are equally spaced over the outer periphery of said flange.