Method of pouring molten metal from a molten metal holding and pouring box with dual pouring nozzles

Abstract

A method of pouring molten metal from a molten metal holding and pouring box with a rectangular-shaped upper section and a pyramidal-shaped lower section provides a relatively constant flow of molten metal being poured from the box through each of two bottom nozzles into two separate foundry molds at the same time.

Claims

1. A method of pouring a molten metal from a volume of the molten metal in a molten metal holding and pouring box into one or more pair of molds, the molten metal holding and pouring box having an upper rectangular-shaped section and a lower pyramidal-shaped section comprising a downward sloped region extending from the upper rectangular-shaped section to a bottom region, the molten metal holding and pouring box having a unitary dual nozzle assembly located in the bottom of the lower pyramidal-shaped section, the unitary dual nozzle assembly having a pair of nozzles, the method comprising: pouring the volume of the molten metal into the molten metal holding and pouring box through a closeable opening in the upper rectangular-shaped section; transporting one of the one or more pair of molds into a molten metal receiving relationship with the molten metal holding and pouring box; holding the unitary dual nozzle assembly at the same temperature as the volume of the molten metal in the molten metal holding and pouring box by constant contact of the unitary dual nozzle assembly with the molten metal; and pouring the molten metal from the molten metal holding and pouring box through each of the pair of nozzles in the unitary dual nozzle assembly so that 75 percent of the volume of the molten metal poured into the molten metal holding and pouring box is poured into the one of the one or more pair of molds with no more than a 30 percent decrease in the rate of flow of the molten metal.

2. The method according to claim 1 further comprising forming the closeable opening from a box cover extending across an upper portion of the upper rectangular-shaped section of the molten metal holding and pouring box.

3. The method according to claim 1 further comprising: forming the pair of nozzles from a low thermal resistance refractory metal; thermally insulating the unitary dual nozzle assembly from contact with the lower pyramidal-shaped section with a thermal insulating material; and providing a pair of stopper rods to engage the pair of nozzles for controlling the pouring of the molten metal through each of the pair of nozzles.

4. The method according to claim 3 further comprising providing an outer structural supporting layer and at least one inner thermal insulating material layer for the molten metal holding and pouring box to maintain the temperature of the molten metal within the molten metal holding and pouring box.

5. The method according to claim 3 further comprising forming the unitary dual nozzle assembly from a material selected from the group consisting of alumina and silica.

6. The method according to claim 3 further comprising forming each of the pair of nozzles with a conical funnel-shaped inlet and arranging a nozzle insertion end of each of the pair of stopper rods so that when the nozzle insertion ends of the pair of stopper rods are inserted in the conical funnel-shaped inlet of the pair of nozzles to stop the flow of the molten metal through the pair of nozzles a portion of the conical funnel-shaped inlet in each of the pair of nozzles is in contact with the molten metal in the molten metal holding and pouring box.

7. The method according to claim 3 further comprising removably fastening a unitary dual nozzle retention plate to the bottom region of the lower pyramidal-shaped section of the molten metal holding and pouring box around an outlet of each one of the pair of nozzles in the unitary dual nozzle assembly.

8. The method according to claim 7 further comprising providing a pair of retaining posts fastened to the bottom region of the lower pyramidal-shaped section and a retention fitting passing through each one of the pair of retaining posts below the unitary dual nozzle retention plate for removably fastening the unitary dual nozzle retention plate to the bottom region of the lower pyramidal-shaped section of the molten metal holding and pouring box.

9. The method according to claim 8 further comprising thermally insulating the unitary dual nozzle assembly from contact with the lower pyramidal-shaped section by a combination of a thermal insulating material surrounding the unitary dual nozzle assembly and a thermal insulating standoff installed around the outlet of each one of the pair of nozzles with the thermal insulating standoff disposed between a bottom of the unitary dual nozzle assembly and an upper side of the unitary dual nozzle retention plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangement and instrumentality shown.

(2) FIG. 1 is a simplified cross sectional view through line A-A in FIG. 3 of one example of a molten metal pouring and holding box of the present invention illustrating an installed unitary dual nozzle assembly in the pyramidal-shaped lower section of the box.

(3) FIG. 2 is the cross sectional view of FIG. 1 with the unitary dual nozzle assembly removed from the molten metal pouring and holding box.

(4) FIG. 3 is a top perspective view of one example of a molten metal pouring and holding box of the present invention with a unitary dual bottom pour nozzle assembly in the pyramidal-shaped lower section of the box.

(5) FIG. 4 is a bottom perspective view of the molten metal pouring and holding box shown in FIG. 3.

(6) FIG. 5 is a side elevational view of the molten metal pouring and holding box shown in FIG. 3.

(7) FIG. 6 is a bottom plan view of the molten metal pouring and holding box shown in FIG. 3.

(8) FIG. 7 is a perspective view of a single nozzle.

(9) FIG. 8 is a perspective view of one example of a unitary dual nozzle retaining plate used in the present invention to retain the unitary dual nozzle assembly in a molten metal pouring and holding box of the present invention.

(10) FIG. 9(a) is a perspective view of one example of a retaining post used in the present invention to mount the unitary dual nozzle retaining plate shown in FIG. 8 in place on the molten metal holding and pouring box.

(11) FIG. 9(b) is a perspective view of one example of a fitting used to retain the retaining plate shown in FIG. 8 against the molten metal holding and pouring box when it is mounted on the retaining posts shown in FIG. 9(a).

(12) FIG. 10(a) is an isometric view of one example of a unitary dual nozzle assembly used in one example of the molten metal holding and pouring box having a pyramidal-shaped lower section of the present invention; FIG. 10(b) is at top plan view of the unitary dual nozzle assembly shown in FIG. 10(a); FIG. 10(c) is a cross sectional elevation view of the unitary dual nozzle assembly through line C-C in FIG. 10(b); and FIG. 10(d) is a cross sectional elevation view of the unitary dual nozzle assembly through line D-D in FIG. 10(a).

(13) FIG. 11 is a partial cross sectional elevation view of a molten metal pouring and holding box having a pyramidal-shaped lower section of the present invention with a unitary dual pour bottom nozzle assembly of the present invention being used with two stopper rod positioning and control apparatus.

DETAILED DESCRIPTION OF THE INVENTION

(14) Referring now to the drawings, wherein like numerals indicate like elements, there is shown in the figures one example of a molten metal pouring and holding box 10 having a pyramidal-shaped lower section with a unitary dual nozzle assembly 12 that can be used in automated molding systems found in casting foundries. A typical automated molding system comprises a conventional conveyor line that transports a plurality of adjacent molds to a casting station where two adjacent molds that are to be cast are filled with molten metal from box 10 via nozzles 12b and 12c in the unitary dual nozzle assembly. Typically when two molds are filed at the same time, the mold conveyor line advances molds two at a time, either in-line or side-by-side, and at a constant speed. Molten metal holding and pouring box 10 provides the source of molten metal to be used for the casting of the molds.

(15) The molten metal holding and pouring box 10 has positioned in its pyramidal-shaped bottom region at least one unitary dual nozzle assembly 12. Molten metal holding and pouring box 10 can be positioned directly above a pair of casting molds 80, as shown, for example, in FIG. 11. If required for a particular installation, a pair of orthogonally disposed X-directional and Y-directional trolley assemblies as disclosed, for example in UK Patent Application Publication No. GB 2,229,384 A to allow for adjustment of the positions of the two nozzles relative to the sprue cups 80a in molds 80 into which the molten metal is poured.

(16) Molten metal holding and pouring box 10 comprises an upper rectangular-shaped section 10a and a lower pyramidal-shaped section 10b. An outer structural shell 14 contains at least a refractory material layer 16 that forms the inner molten metal holding rectangular and pyramidal shaped volumes. As in the prior art, box 10 can have a box cover that extends across the upper portion of the rectangular-shaped section 10a. Molten metal can be fed into box 10 through a closeable opening in the box cover. Box 10 can have a discharge port 92 formed into section 10a for pouring of molten metal from the box when the box is tilted as disclosed, for example, in U.K. Patent Application Publication No. GB 2,229,384 A.

(17) As in the prior art box 10 can be optionally divided by a vertical baffle of heat refractory material, into a pouring section and a refilling section as further disclosed, for example, in U.K. Patent Application Publication No. GB 2,229,384 A.

(18) The box cover can have a single, or a pair of separate openings that provides a passageway for the insertion of two stopper rods 94 into box 10. The stopper rods and associated positioning and control apparatus may be as disclosed in U.S. Pat. No. 4,953,761 or U.S. Patent Application Publication No. 2010/0282784 A1, both of which are incorporated herein by reference in their entireties. Stopper rods 94 can be independently positioned with stopper rod tips 94a seated (engaged) on the inlets 12b and 12c of nozzles 12b and 12c to block flow of molten metal, or independently raised by the associated positioning and control apparatus to allow flow of molten metal through one or both nozzles.

(19) If required for a particular application, the molten metal holding and pouring box 10 can include means for tilting itself as disclosed, for example, in UK Patent Application Publication No. GB 2,229,384 A, so that unused molten metal can be removed from the box through discharge port 92.

(20) Unitary dual nozzle assembly 12 is constructed of a thermally conductive material and extends upward within box 10 so that its upper peripheral inlet surfaces 12a and 12a constantly remain in contact with the molten metal (M) held within box 10 whether or not a stopper rod is in engagement with one or both of the nozzles within assembly 12. Unitary dual nozzle assembly 12 is preferably constructed of an alumina/silica material or other suitable low thermal resistance refractory metal, and the nozzles used therein preferably have circular inner dimensions with conical funnel-shaped inlets 12b and 12c and cylindrical-shaped outlets 12b and 12c. The construction of unitary dual nozzle assembly 12 provides for its constant contact with the molten metal within the interior of box 10, particularly in the central region 12a of the assembly between the nozzles. This constant contact causes the two nozzles within assembly 12 to always remain in a heat exchange relationship with the molten metal. This heat exchange relationship retards any clogging of the two nozzles that might otherwise occur during any cooling conditions to which the nozzles may be subjected.

(21) Further the construction of the unitary dual nozzle assembly 12 eliminates the heat sink problem where the metallic structure (shell 14 and a reinforcing plate that is used to support a pouring nozzle as disclosed in U.K. Patent Application Publication No. GB 2,229,384 A) of the box 10 itself draws heat energy away from the pouring nozzles. In the present invention the unitary dual nozzle assembly 12 is surround by an insulating material 18 (as shown in FIG. 1) which insulates the dual nozzle assembly from heat sinks, along with insulation standoffs 70a on dual nozzle assembly retaining plate 70 as further described below.

(22) Unitary dual nozzle assembly 12 is shown, for example, in FIG. 11 as installed in a molten metal pouring and holding box having a pyramidal-shaped lower section. Details of one example of a unitary dual nozzle assembly 22 that can be used in the present invention are illustrated in FIG. 10(a) through FIG. 10(d). The unitary dual nozzle assembly 22 can also be used in a flat bottom launder as described in U.S. Patent Application Publication No. 2010/0282784 A1. In FIG. 10(a), the overall dimensions of a particular unitary dual nozzle assembly 22 are selected based on the maximum spacing between sprue cups on the pair of molds into which molten metal is to be poured through the nozzles in the unitary dual nozzle assembly. In FIG. 10(a) the maximum spacing between nozzle centers is defined as x.sub.1 between nozzles 24a and 24b as cast, or otherwise formed, within the unitary dual nozzle assembly. Subsequent to installation and use of unitary dual nozzle assembly 22 as shown in FIG. 10(a), a requirement for closer spaced nozzles, such as nozzle pair 24a and 24b in FIG. 10(b) with a spacing of x.sub.2 between nozzle centers can be cast, or otherwise formed in a unitary dual nozzle assembly having the same overall dimensions of the unitary dual nozzle assembly shown in FIG. 10(a) to accommodate a distance between sprue cup centers that is less than the maximum spacing.

(23) Although a nozzle assembly is formed from heat resistant materials, the nozzle assembly will wear over a period of use with exposure to the flow of molten metals and have to be replaced. Typically replacement is accomplished without allowing the pour box structure surrounding the nozzle assembly to cool down, and therefore it is preferable to accomplish nozzle assembly replacement as quickly and efficiently as possible. In a double pour application, the single dual nozzle assembly, such as dual nozzle assembly 12 or 22 in FIG. 10(a) through FIG. 10(d) accomplishes this requirement. Further a single dual nozzle assembly of the present invention allows the distance between the openings of each nozzle in the dual nozzle assembly to be changed when the replacement dual nozzle assembly is originally cast or otherwise formed. For example as shown in FIG. 10(b) the distance x.sub.1 between centers of nozzle openings for nozzle pair 24a and 24b (shown in solid lines) as cast in a first dual nozzle assembly, can be changed to distance x.sub.2 between centers of nozzle openings for nozzle pair 24a and 24b (shown in dashed lines) as cast in a second dual nozzle assembly having the same overall dimensions as the first dual nozzle assembly. Thus a significant change in the distance between, and relative positions of each nozzle in a single dual nozzle assembly having the same overall dimensions can be achieved. Comparatively if two single replacement nozzle assemblies are used, the distance between centers of the nozzle openings must be accomplished during the actual fitting of the two single replacement nozzle assemblies in the bottom of a hot pour box. The ability to change the length between centers of the two separate nozzle openings is related to the length (or location) between sprue cups 80a in adjacent molds in a dual pour automated mold line as shown, for example, in FIG. 11. That is, in a dual pour process utilizing a single molten metal holding and pouring box with a pyramidal-shaped lower section, if the relative locations of sprue cups in adjacent molds in an automated line of molds changes, then the relative locations of the dual nozzles will also need to be changed by changing out the nozzle assemblies. The stopper rod positioning features of the stopper rod positioning and control apparatus 10 as disclosed in U.S. Patent Application Publication No. 2010/0282784 A1 can be used to quickly adjust the stopper rod position of each apparatus to changes in positions of the nozzles in a newly installed unitary dual nozzle assembly.

(24) FIG. 8 illustrates on example of a unitary dual nozzle retaining plate 70 that can be used to provide support for a dual nozzle assembly installed in the molten metal pouring and holding box of the present invention. Retaining posts 72 (in FIG. 9(a)) can be suitably connected to the bottom of box 10 either directly or by intermediate connecting offset brackets 72a. Annular offsets 70a on retaining plate 70 fit up against the bottom of the box with openings 70c around the outlets 12b and 12c of each nozzle and the length of retaining posts 72 passing through openings 70b in the retaining plate. A fitting 74, for example, as shown in FIG. 9(b), is inserted into opening 72 in each retaining post to secure the unitary dual nozzle retaining plate in place. In change out of a dual nozzle assembly, fittings 74 are removed from the retaining posts to release the plate to provide a rapid means of removing an installed unitary dual nozzle assembly. After insulating material 18 is removed, the installed unitary dual nozzle can be removed from box 10, and replaced with a new unitary dual nozzle assembly with new insulating material packed around it and the unitary dual nozzle retaining plate is reinstalled. Thus the prior art heat sink problem is substantially eliminated in the present invention, since unitary dual nozzle assembly 12 is substantially surrounded by insulating material 18 and the insulating annular offsets 70a on the unitary dual nozzle assembly. This arrangement, in combination with regions 12a and 12a of the dual nozzle assembly always being in contact with molten metal in the box, effectively eliminate the previously mentioned clogging problem.

(25) As shown in the figures, box 10 comprises an upper rectangular-shaped section 10a and a lower inverted pyramidal section 10b housing the unitary dual nozzle assembly 12 in its bottom region. The upper rectangular-shaped section 10a may contain a volume V.sub.1 of molten metal which may be expressed as:
V.sub.1=0.5.Math.H.Math.W.Math.L[expression (2)]
wherein W and L respectively represent the width and length dimensions box 10, and H represents the head (H) dimension.

(26) The lower inverted pyramidal-section 10b may contain a volume V.sub.2 of molten metal which may be expressed as:
V.sub.2=.Math.H.Math.W.Math.L[expression (3)].

(27) The total volume V.sub.T of box 10, when full with molten metal, may be expressed as:
V.sub.TV.sub.1+V.sub.2.3.Math.H.Math.W.Math.L[expression (4)].

(28) The shape of box 10, in particular the pyramidal-shaped section 10b, advantageously provides a relatively constant flow (Q) (as previously discussed with reference to expression (1)) of molten metal outward from each nozzle in the dual nozzle assembly to a casting mold. As previously discussed, the relatively constant flow rate (Q) is not only advantageous to the mold casting process itself, but allows for the use of nozzles having small openings which, in turn, ease the task of accurately controlling the outflow of the molten metal from box 10. In particular, the pyramidal-shaped section 10b provides a pouring configuration that makes available approximately 75 percent of the volume (V.sub.T) of the molten contained within box 10, to be poured into a pair of casting molds from the dual nozzles with a corresponding drop of only 50 percent in the pressure head (H), and a drop of only about 30 percent in the flow rate (Q). The flow rate (Q) and the pressure head parameters (H) provided by the present invention forces the molten metal through each of the dual pouring nozzles in a relatively constant manner.

(29) In some examples of the invention the pair of nozzles in the unitary dual nozzle assembly need not have similar dimensions.

(30) Indentations 10c can be provided in the exterior of molten melt holding and pouring box 10 as shown in FIG. 4 for locating imaging apparatus for determination of when molten metal has reached a required level in each of the two sprue cups being filled from the open nozzles in the unitary dual nozzle assembly as disclosed, for example, in U.S. Pat. No. 4,744,407.

(31) The present invention has been described in terms of preferred examples and embodiments. Equivalents, alternatives and modifications, aside from those expressly stated, are possible and within the scope of the invention.