US2948524A - Pump for molten metal - Google Patents

Description

Aug. 9, 1960 v. D. swEENEY ETAL 2,948,524

PUMP FOR MOLTEN METAL Filed Feb. 18, 1957 2 Sheets-Sheet 1 asA r7.1 BY Zi:

ATTORN EYS AU8 9 1960 v. D. swEENr-:Y ETAL 2,948,524

Y PUMP FOR MOLTEN METAL Filed Feb. 18, 1957 2 Sheets-Sheet 2 F1 7. 71 mvENTRs Vctor D. Sw'eeney l Walter U. Ka

ATTORNEYS United States Patent fO PUMP FOR MOLTEN METAL Victor D. Sweeney, Merion Station, and Walter U. Kaji,

Philadelphia, Pa., assignors to Metal Pumping Services, Inc., Cleveland, Ohio, a corporation of Ohio Filed Feb. 18, 1957, Ser. No. 640,686

7 Claims. (Cl. 266-38) The present invention relates to pumps, and in particular to pumps for lifting and conveying molten metal.

It has long been an object of the art to develop satisfactory means for pumping molten metal to locations where work is to be done with the metal or to the metal. However, the great difculty has been to provide a pump in Which the parts exposed to contact with the molten metal will resist the deleterious attack thereof. In the case of molten aluminum, metal pump parts are unsatisfactory since relatively high melting point metals, such as iron, are dissolved when in contact with molten aluminum, in spite of the fact that the molten aluminum may be at a Itemperature of approximately one-half of that at which iron melts. In this situation, iron is introduced into the aluminum, and it is well-known that for most purposes any substantial quantity of iron constitutes an undesirable impurity in aluminum or its alloys. In the same way, many molten metals attack other metals and refractory materials to varying extents.

lIt is, therefore, an object of the present invention to provide a pump for conveying molten metal in which the parts of the pump exposed to contact with the molten metal comrise a material which will resist the deleterious attack of such molten metal.

Pumps of the general type to which the present invention pertains have been heretofore provided, but such pumps have been costly and eloborate in construction, particularly in view of the fact that the large hollow casings of such pumps were formed of refractory material which, in the relatively bulky mass, had to be gradually cooled and cured over a period of many weeks in order to form casings which would have a reasonable commercial life. The expense of using these pumps was high because of their initial cost. This expense was further compounded by the necessity for frequently replacing the pumps, which had a short service life when operating under the service yconditions for which they were intended.

` For the above reasons, the pumps of the prior art which were of the general type to which the present invention pertains, although representing a distinct advance in the art, were nevertheless limited in commercial application because of the several disadvantages mentioned above, and they have never come into widespread use.

. Accordingly, an object of the present invention is to overcome the above mentioned disadvantages of the prior art and to provide a pump for molten metal which is far less expensive to fabricate and far less expensive to replace than the pumps of lthe prior art.

Another object of the invention is to provide a pump for molten metal in which the pump impeller is connected by a long Vertical shaft to the pump drive, the pump shaft being surrounded by a plurality of openly spaced columns which support the pump drive, one of the columns providing an outlet conduit for the pump. Y Another object of the invention is to provide a pump for molten metal in which the pump shaft is exposed and 2,948,524 Patentedv Aug. 9, 1960 ice the path of inflow of the molten metal is downwardly in surrounding relationship with the pump shaft at the intake of the pump, the shaft being surrounded by a plurality of columns which support the pump drive.

Another object of the invention is to provide a novel shrouded impeller structure for metal pumps.

These and other objects and advantages of the invention will become apparent from the following description and accompanying drawings of a specic example of the invention. In the drawings:

Figure 1 is an elevational View, with parts broken away, of a pump embodying the present invention in operative association with a molten metal bath from which metal is to be pumped.

Figure 2 is a sectional View taken on line 2-2 in Figure l, with parts broken away.

Figure 3 is a fragmentary view taken from line 3--3 in Figure 1. f Figure 4 is a sectional view taken on line 4-4 in Figure 1. Y f

Figure 5 is a fragmentary sectional view, on anV fen-- larged scale, taken on line 5-5 in Figure 1.

Figure 6 is a plan view of anelement of the pump shown in Figure 1. f

Figure 7 is a sectional view taken on line 7-7 in Figure 6.

Figure 8 is a plan view of the impeller of the pump shown in Figure 1.

Figure 9 is a side elevation of the structure shown in Figure 8.

vThe numeral 10 in Figure 1 illustrates a bath of molten metal disposed in a suitable container, such as a holding furnace or the like, having a iloor `1l and side walls 12. lined With a material having refractory properties and resistive to attack by the molten metal.

One embodiment of a pump made according to the present invention is shown Vin partially submerged position in the molten metal bath, and it may be seen'that the form illustrated comprises a pump foot body 13 which rests on the floor 11 of the container for the moltenmetal bath. The body 13 is in the form of a slab and has a` major bore 1'4 which comprises the pumpv chamber. Axially aligned with the bore 14 is a reduced bore 15. An offset bore 16 extends partially downwardly through the body 13 and may communicate through a short slot 16a with the reduced bore 15. A volute member 17 is positioned in the upper portion of the major bore `14 and is supported in such position by a spacer ring 18 which is cemented in position within the bore 14, as indicated in Figure 1. It will be understood that the volute is definitely preferred but that advantages of the invention can be realized without the employment of the volute.v

In its stead there may be employed a projection on the trailing side of the intersection between the bore 14 and the bore 16 (the term trailing being used with respect to the direction of rotation of the impeller, described below).

The pump impeller 19 is a circular body having a bore 20 formed therein and having radially extending passages 21 communicating with the bore 2@ and with the periphery of the impeller. The passages 21 are preferably of constant cross-section and slant backwardly with respect to the direction of rotation of the impeller. The impeller is threadedly engaged on the bottom end of a' pump shaft Z2. The space between the impeller 1'9 and the spacer ring 18 is such as to establish a running t suitable for the metal being pumped. The portion of the impeller apposite the m'ng 18 is essentially below the passages 21 and may be termed the skirt of the impeller.

Column members 23 and 24 are provided which are engaged with the pump foot body 13, as indicated in the drawings. The columns 23 may be threadedly engaged with the body 13, and the column 24, which comprises a hollow conduit, is received within the offset bore 16 so aS to extend down partially past the top of the bore 14. The lower end of the conduit 24 is partially cut away to accommodate the impeller 19 and to provide an unobstructed path for the flow of molten metal from the pump chamber to the conduit 24, the cut away being indicated in Figures 1, 4 and 5. i

At their upper ends, the columns 23 may be provided with suitable metal studs and may be bolted to a horizontal strap 25, which in turn is connected by the vertical straps 26 to an upper plate 27. Mounted on the upper plate 27 is a frame assembly 28 which supports an air motor 29. A source of air pressure (not shown) cornmunicates through the air line 30 and the air control valve 31 with the air motor 29. The shaft 32 of the air motor passes through a pedestal bearing 33 and is coupled through a bayonet connection generally indicated at 34 and a universal joint generally indicated at 35 to a metal cap -36 which is fixed on the upper end of the pump shaft 22. The bayonet connection 34- makes possible convenient changing of pump shafts (or more accurately convenient exchange of pump rotor assemblies, each of which comprises an impeller and an associated pump shaft 22).

Each bolted connection between a column 23 and the strap 2S may be supplemented by the provision of a sleeve 42 in which is packed a suitable ceramic cement or furnace cement 43. This prevents vibration between the bolt threads and the tapped column member which causes relatively rapid erosion of the bolt threads. Once the direct cemented connection is established it matters little or none if the bolts fail or fall out.

The upper end of the hollow column or conduit 24 is received in a hollow spout body 37. The hollow spout body is supported beneath the upper plate 27 by a pair of bolts 38 and the transverse strap 39'. The outlet end of the spout body 37 leads to or toward the point at which it is desired to discharge the molten metal. A sheet 40 of asbestos fibers or other insulating material may be positioned between the spout body 37 and the plate 27.

The portions of the pump which are exposed to contact with the molten metal or which are immersed in the molten metal bath, such as the pump foot body 13, the volute 17, the ring 18, the impeller 19, the shaft Z2, the columns 23 and 24, and the spout body 37, are all formed of a suitable material which will resist corrosive attack of the molten metal. t

The above mentioned parts may be fabricated from a structural refractory material, that is, a material subject to structural fabrication and having high resistance to disintegration by either corrosive or erosive attack from a bath of molten metal and having a capacity to remain relatively stable and not introduce contaminants into the molten metal. Structural carbonaceous refractory materials, such as carbon of a dense or structural type, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite, silicon carbide, or the like, have been found to be highly resistant to attack by molten aluminum. Such materials may be coated or uncoated and glazed or unglazed. Pump parts composed of suitable materials may be made by mixing ground graphite or silicon carbide with a fine clay binder, forming the part and baking. Such parts may also be made by mixing ground -silicon carbide with a binder such as pitch, tar, etc., molding or otherwise forming the article to the desired shape, and baking it at a sucient temperature to cause any temporary bonding material to substantially disappear.

The several parts fabricated from structural refractory material may be subjected to simple machining operations, such as the boring of the small holes and the like. The holes in the pump foot body 13 which threadedly receive the columns 23 may be formed in the article by molding. The threads are preferably rather large and gross, whether they are molded or whether they are later machined within the holes. The holes may be drilled through the body 13 after it is formed. In general, the larger openings or spaces, such as the major bore 14 of the pump body 13, are not formed by machining but are formed in the molding of the part.

It will be seen that of all the parts submerged in the molten metal 10, only the relatively slender shaft and columns 22, 23, and 24 extend upwardly from the surface of the molten metal 10. Pumps for pumping molten metal which have previously been provided have generally comprised a massive body or housing extending upwardly from the surface of the metal bath. To the extent that molten metal may be forced upwardly or splashed upwardly into the upper portions of the housings to locations where it may freeze and interfere with the operation of working parts of the pump,` the trouble-free operation of the pumps is impaired. However, in the present invention the possibility of such impairment is eliminated since the pump chamber is submerged well below the surface of the molten metal, and the relatively slender members 22, 23, and 24 extend upwardly out of the Surfaec of the molten metal in open relationship.

The flow of the molten metal through the pump occurs downwardly through the bores 15 and 2d; thence radially outwardly through the passages 21, and then upwardly through the conduit 24, and nally outwardly along the interior of the spout body. It will be apparent that when, the pump is used to convey molten metal from the molten metal bath to a point outside the bath, the molten metal is withdrawn from a point well beneath the surface of the molten metal bath and will, therefore, be relatively free from slag or other contaminants which are generally lighter than the molten metal and rise to the surface of the molten metal bath. Any pieces of slag or other material which are drawn toward the impeller do not snag and break the impelling members of the impeller, the passages 21 amounting in effect to shrouded impeller teeth. Further, despite the deeply immersed location of the pump chamber, withdrawing of the molten material directly from the bottom of the bath is avoided, and pumping of any sedimentary materials as there may be at the bottom of the bath does not occur. In this respect, the structural arrangement whereby the path of inow of the molten metal is downwardly in surrounding relationship with the pump shaft at the intake of the pump is highly advantageous, although it will be appreciated that many of the other advantages of the invention may be realized without this feature.

This application is a continuation-in-part of our prior application Serial No. 603,578, filed August 13, 1956 (now abandoned).

It will be understood that the foregoing description of a preferred embodiment of the invention is not intended to limit the scope of the invention as particularly pointed out and claimed in the following claims.

What is claimed is:

l. Apparatus for raising molten metal from one level to a higher level comprising refractory walls defining the bottom and sides of a reservoir for holding molten metal up to a predetermined maximum level therein, and a rotary submersible pump including a foot body assembly of structural refractory material having a pump chamber formed therein, an impeller of structural refractory material having a solid cylindrical surface, said impeller being positioned in and rotatable within said pump charnber, a pump shaft of structural refractory material attached to said impeller and extending vertically upwardly therefrom to above said predetermined maximum level, a plurality of column members of structural refractory material disposed horizontally outwardly in several directions from said pump shaft and xed to and extending vertically upwardly from said foot body assembly in open relation with each other and with said pump shaft, said column members extending toV above-*said predetermined maximum level, one of said column members comprising a hollow conduit, the interior of which communicates with said pump chamber, outlet means communicating with the hollow interior of. said conduit toward the top thereof, an inlet opening formed inlsaid foot body assembly and extending from the exterior thereof to said pump chamber, and pump drive means structurally associated with said column members above said predetermined maximum level and operatively .connected to said pump shaft, said impeller and pump Vshaft comprising a rotary subassembly which is suspended from said pump drivemeans and all depending portions of which are spaced from all stationary parts of said apparatus, said foot body assembly closely surrounding said solid cylindrical surface of said impeller in radially spaced relationship therewith whereby a molten-metal-lubricated bean'ng is providedv atthe lower end of said rotary subassembly, said structural refractory material comprising a material selected from the group consisting of carbon, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite and silicon carbide.

y 2. Apparatus for raising molten metal from one level to a higher level comprising refractory Walls defining the bottom and sides of a reservoir for holding molten metal up to a predetermined maximum level therein, and a rotary submersible pump including a foot body assembly of structural refractory material having a pump chamber'formed therein, an impeller of structural refractoy material having a solid cylindrical surface, said impeller being positioned in and rotatable within said pump chamber, a pump shaft of structural refractory material attached to said impeller and extending vertically upwardly therefrom to above said predetermined maximum level, a plurality of column members of structural refractory material disposed horizontally outwardly in several directions from said pump shaft and fixed to and extending vertically upwardly from said foot body assembly in open relation with each other and with said pump shaft, said column members extending to above said predetermined maximum level, one of said column members comprising a hollow conduit, the interior of which communicates with said pump chamber, outlet means communicating with the hollow interior of said conduit toward the top thereof, an inlet opening formed in the top of said foot body assembly and extending from the exterior thereof to said pump chamber, said pump shaft extending from said impeller upwardly through said inlet opening, and pump drive means structurally associated with said column members above said predetermined maximum level and operatively connected to said pump shaft, said impeller and pump shaft comprising a rotary subassembly which is suspended from said pump drive means and all depending portions of which are spaced from all stationary parts of said apparatus, said foot body assembly closely surrounding said solid cylindrical surface of said impeller in radially spaced relationship therewith whereby a molten-metallubricated bearing is provided at the lower end of said rotary subassembly, said structural refractory material comprising a material selected from the group consisting of carbon, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite and silicon carbide.

3. Apparatus for raising molten metal from one level to a higher level comprising refractory walls defining the bottom and sides of a reservoir for holding molten metal up to a predetermined maximum level therein, and a rotary submersible pump including a foot body assembly of structural refractory material having a pump chamber formed therein, an impeller of structural refractory material having a solid cylindrical surface, said impeller being positioned in and rotatable within said pump chamber, a pump shaft of structural refractory material attached to said impeller and extending vertically upwardly therefrom to above said predetermined level, aA plurality*k of` columnKmembers of` structural refractory material disposed horizontally outwardly in several directions from said pump shaft and` fixed to and extending vertically upwardly from said foot body assembly in open relation with each other andv with said pump shaft, said column members extending to above said predetermined maximum level, one of said column members comprising a hollow conduit, the'in-.

terior of which communicates with said pump chamber, outlet means communicating with the hollow interior of said conduit toward the topthereof, an inlet opening formed in the top` of said foot body assembly and extending from the exterior thereof to said pump chamber, said pump shaft extending from said impeller upwardly through said inlet opening, said impeller being circular and having an annular slot in its top surface which is in register with said inlet opening and having radially extending openings around its periphery which communicate with said annular slot, and pump drive meansv rotary subassembly, said structural refractory materialv comprising a material selected from the group consisting' of carbon, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite and silicon carbide.

4. A pump rotor assembly for a pump for pumping molten metal comprising a circular body defined by a circular periphery and upper and lower opposite faces, an annular opening in said upper face and extending into said body, a pump shaft extending into said 'annular opening in spaced relation with the sides thereof and being fixed to said `circular body at the bottom of said annular opening and being otherwise exposed to the interior of said annul-ar opening, and open-ended passages extending predominantly radially outwardly through said body from said annular opening to a plurality of locations around the periphery of Isaid impeller, whereby when said rotor assembly is rotating in a bath of molten metal, metal is drawn downwardly in surrounding and contacting relationship with said shaft and -thence is impelled radially outwardly by shrouded impeller teeth constituted by said open-ended passages, said circular body Iand pump shaft comprising structural refractory material selected from the group consisting of carbon, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite and silicon carbide.

5. A metal pump component of structural refractory material comprising a foot body in the form of a slab of substantially greater length and width than its vertical thickness, a relatively large vertical first bore extending from the lower face of the slab and forming a pump chamber therein, a relatively small vertical second bore coaxial with said relatively large bore and extending from the upper face of the slab to said large bore, and a relatively small vertical third bore odset from the aforesaid first and second bores and extending from the upper face of the slab partially therethrough and downwardly beyond the juncture of said first and second bores, said third bore partially overlapping and intersecting said first bore, said slab comprising structural refractory material selected from the group consisting of carbon, graphite, graphitized carbon, clay-bonded graphite, carbon-bonded graphite and silicon carbide.

6. A metal pump assembly comprising a foot body in the form of a slab of substantially greater length and width than its vertical thickness, a relatively large vertical first bore extending from the lower face of the slab and forming a pump chamber therein, a relatively small vertical second bore coaxial with said relatively large bore and extending from the upper face of the slab to said large bore, a relatively small vertical third bore oiset from the aforesaid first and second bores and extending from the upper face of the slab partially therethrough and downwardly beyond the juncture of said rst and second bores, said third bore partially overlapping and intersecting said first bore, a pump rotor comprising a circular impeller body defined by a circular periphery and upper and lower opposite faces, an annular opening in said upper face and extending into said body, a pump shaft extending into said lannular opening in spaced relation with the lsides thereof and being fixed to said circular body at the bottom of said annular opening, open-ended passages extending predominantly radially outwardly through said body, from said annular opening to a plurality of Ilocations around the periphery of said impeller,

said rotor ybeing mounted for rotation of said circular irnpeller within said first bore with said pump shaft ex tending thereto through said second bore and the periphery of said circular impeller being relatively distantly spaced from the sides of said rst bore, a ring in said rst bore and iixed to said slab, said ring being positioned on a level with the lower portion of said impeller body and essentially below said open-ended passages in said impeller body, the periphery of said circular impeller being relatively closely spaced from said ring to establish a running it therebetween whereby said ring acts as a molten-metal-lubricated bearing for said impeller, and means projecting from the side of said tirst bore toward 7. The :structure raf-claim wherein said last named means comprises evolute in the 4form of ,a tapered ring overlying. said (first Inamedring `and being tapered from one end to the other around -its veircularextent andlhavf ing anouter surface adapted to be tted in said Yfirst bore.,V said tapered ring terminating on either side of the nter-f section between said first and thirdbores.

References Cited in the le ofthis patent UNITED STATES PATENTS 1,196,758 Blair ISept, 5, *11916 1,988,875 Sabonio Jan. 22, '1,935 2,138,814 Bressler Dec.-6, 193'8 '2,173,377 Schultz et al Sept. 19, 1939A 2,300,688 'Nagle NOV. 3, 1942: 2,368,962 Blom Feb. 6, t1945 2,528,210 Stewart 0ct. 31, 1950 2,626,086 Forrest Jan. 20, l1953 2,762,095 Pemetzrieder Sept. 1'1, 1956 2,768,587 Corneil Oct; 30, 1956 FOREIGN PATENTS 30,059 Great Britain of 1913' 261,718 Switzerland Sept. '1, 1949 804,064 Germany Apr. `16, 1951`

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