METHOD OF INHIBITING CASTING PROBLEMS

Abstract

The teachings provide a fill tube assembly for a casting mold and methods of using the assembly. The fill tube assembly includes a fill tube having a tubular member with a receiving end, a mold-engaging end and an intermediate portion. The mold-engaging end has a tapered flange radially extending therefrom, the remainder of the tubular member has a substantially, uniform cross-section. A clamping assembly is structured to maintain a substantially leakproof seal at the fill tube, casting mold interface while accommodating dimensional variations. The clamping assembly includes a gasket, a load ring, a clamping plate and a pre-load gap between the clamping plate and the casting mold and optionally includes a dimensional compensating ring. When tightened, the clamping plate biases the load ring against the flange thereby distributing a uniform load against the casting mold, compressing the gasket therebetween while narrowing the pre-load gap to accommodate dimensional variations.

Claims

1. A method of inhibiting casting problems, the method comprising: installing an assembly for transferring a molten metal through a joint, the assembly accommodating dimensional variations that occur in the transfer of a molten metal and comprising: a casting mold operably connected to a fill tube through a joint used in the transfer of a molten metal; and, a non-rigid, pre-loaded clamping mechanism operably connecting the casting mold to the fill tube to form the joint, the non-rigid, pre-loaded clamping mechanism having a pre-load gap that facilitates application of a substantially uniform compressive load against a flange irrespective of the temperature of the clamping assembly to avoid leakage at the joint; wherein the installing at least inhibits a casting problem.

2. The method of claim 1, further comprising configuring the clamping mechanism to include the pre-load gap for assembly in a bottom pressure, reverse casting process to substantially reduce leaking in the reverse casting process, wherein the pre-load gap is equal to or greater than the dimensional variation.

3. The method of claim 1, further comprising configuring the pre-load gap size to exceed an expected aggregate dimensional variation and accommodate for an additional and unforeseen dimensional variation occurring during operation of the casting process.

4. The method of claim 1, further comprising configuring the preload gap for a variation selected from the group consisting of thermal expansions, tolerance variations, fabrication defects, assembly errors, and combinations thereof.

5. The method of claim 1, further comprising configuring the operable connection between the casting mold and the fill tube is an engaging of a surface of the casting mold to a surface of the fill tube, and either the casting mold or the fill tube has a tapered non-engaging surface that is configured to mate with the non-rigid, pre-loaded clamping mechanism, the taper configured in an amount ranging from about 15 degrees to about 85 degrees from a horizontal plane to minimize stress concentrations from the non-rigid, pre-loaded clamping mechanism.

6. The method of claim 5, wherein the configuring includes tapering the tapered non-engaging surface in an amount of about 45 degrees from the engaging surface.

7. The method of claim 1, further comprising disposing a gasket material between the engaging surfaces of the first component and the second component, the gasket material comprising a component selected from the group consisting of a high-temperature silicon, a high-temperature polymer, a graphite sheet material.

8. The method of claim 1, wherein the configuring includes configuring the joint to include an airtight connection between the first component and the second component.

9. The method of claim 5, further comprising configuring the joint with a clamping plate with a threaded aperture, the force from the non-rigid, clamping mechanism includes the clamping plate with the threaded aperture.

10. The method of claim 1, further comprising pulling a vacuum to evacuate air within the casting mold.

11. The method of claim 1, further comprising forcing a molten metal having an excess upward through the fill tube into the casting mold.

12. The method of claim 1, further comprising filling the casting mold with the molten metal.

13. The method of claim 1, further comprising draining the excess downward through the fill tube.

14. The method of claim 1, further comprising: pulling a vacuum to evacuate air within the casting mold; forcing a molten metal having an excess upward through the fill tube into the casting mold; filling the casting mold with the molten metal; and, draining the excess downward through the fill tube.

15. The method of claim 1, further comprising: estimating the dimensional variations that could occur during operation of the accommodating assembly; sealably connecting the casting mold to the fill tube to form the joint, wherein the sealably connecting includes applying a force from the clamping mechanism having the pre-load gap sized to accommodate a variation at least equal to the estimated dimensional variations; and, maintaining a substantially uniform compressive load against the interface irrespective of the temperature of the clamping assembly through the use of the pre-load gap.

16. The method of claim 1, wherein the casting problem includes a broken fill tube.

17. The method of claim 1, wherein the casting problem includes creating scrap castings.

18. The method of claim 1, wherein the casting problem includes extending casting operation downtime.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

[0033] FIG. 1 is a cross-sectional elevational view of a fill tube assembly.

[0034] FIG. 2 is an exploded isometric view of a fill tube assembly in accordance with the present invention.

[0035] FIG. 3 is a cross-sectional elevational view of the fill tube assembly of FIG. 2 with the clamping plate shown in the tightened position in phantom-line drawing.

[0036] FIG. 4 is a cross-sectional elevational view of a fill tube assembly in accordance with another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Accordingly, the present invention provides a fill tube assembly and fill tube therefor having a tapered flange at one end and a relatively constant cross section along the remainder of its length and an adjustable clamping assembly adaptable to compensate for departures from manufacturing or fabrication dimensional tolerances; assembly errors, such as, for example, bolt tightening sequencing, overloading of assembly components, and alignment of assembly components; dimensional changes resulting from, for example, thermal changes; and component degradation from, for example, recurrent use.

[0038] As employed herein, the term dimensional variations, refers to changes or misalignment of fill tube assembly components caused by such things as, for example, assembly errors, fabricated component tolerance ranges, thermal expansion and contraction and fill tube assembly component degradation. As discussed herein, variations in each of these dimensional parameters has an effect on the ability to maintain a substantially leak-proof seal at the fill tube to casting mold interface.

[0039] Until the compliant fill tube assembly of the present invention was discovered, such dimensional variations resulted in undesirable and costly casting problems, such as, broken fill tubes, scrap castings and extended casting operation downtimes. The fill tube assembly of the present invention can accommodate, among other things, the foregoing dimensional variations while maintaining a sufficient fill tube to casting mold seal.

[0040] FIG. 1 illustrates a traditional fill tube assembly for transferring molten metal, such as, for example, molten aluminum, from a melting furnace (not shown) or other source of molten metal, through a fill tube 2 into a casting mold 4. The fill tube assembly shown in FIG. 1, is exemplary of known prior art fill tube assemblies employed for reverse casting operations such as, for example, vacuum-riserless or pressure-riserless casting. However, it will be appreciated that the fill tube, fill tube assembly and method of use thereof, of the present invention can be readily employed in a wide array of casting systems, expressly including, but not limited to, conventional low pressure casting processes not requiring a vacuum. The fill tube 2 is made from a material, such as the exemplary ceramic material, which is substantially impermeable to moisture penetration. It is well known in the casting art that ceramics are capable of withstanding compressive stresses, but react quite poorly to tensile stresses.

[0041] Continuing to refer to FIG. 1, the fill tube 2 is attached to the casting mold 4 by an attachment ring 8 tightened using a plurality of fasteners, such as the exemplary threaded bolts 10, shown. A gasket 6 made from any known or suitable material is disposed between the end of the fill tube 2 and the casting mold 4, in an attempt to create an air-tight seal therebetween. As shown, the fill tube 2 has a variable cross-section forming a flange 12. This abrupt variation in cross-section at the formation of the flange 12 with relatively sharp transition corners 14 and 16, creates an undesirable stress-riser in the ceramic fill tube 2. As is well known in the art, such areas of stress concentration are susceptible to failure. For example, the flange 12 is susceptible to failure upon over-tightening of the attachment ring 8. Additionally, as shown, the fill tube assembly has very tight tolerances between components. For example, there is substantially no space between corners 16 of flange 12 and the casting mold 4. Accordingly, the fill tube assembly cannot accommodate or compensate for dimensional variations in, for example, the fill tube 2, the gasket 6 or the casting mold 4. Furthermore, the fill tube assembly cannot accommodate assembly errors, such as, for example, bolt 10 tightening sequence errors or over-tightening. Moreover, the rigid nature of the fill tube assembly and the tight tolerances thereof, cannot accommodate dimensional variations caused, for example, by thermal expansion and contraction. Each of these dimensional variations effect the sufficiency of the load on the seal at the fill tube, casting mold interface. If the seal permits infiltration of air into the casting mold 4, damage to the cast product will likely occur.

[0042] Referring now to FIG. 2, a compliant fill tube assembly 50 in accordance with the present invention, is shown. As shown, the exemplary fill tube assembly 50 includes a fill tube, such as the exemplary ceramic fill tube 58, having a tubular member 60 with a receiving end 62, for receiving molten metal (not shown), a mold engaging end 64 and an intermediate portion 66 extending there between. As shown, the intermediate portion 66 of the exemplary fill tube 58 has a generally annular cross-section in plain view. The mold-engaging end 64 includes a flange 68 radially extending therefrom. The flange 68 includes a mold-engaging face 70 and a non-engaging face 72. The exemplary non-engaging face 72 is tapered, as shown. The tapered non-engaging face 72 provides a gradual transition from the intermediate portion 66 to the flange 68, thus minimizing the creation of undesirable stress-risers occurring in many known prior art fill tubes (see, for example, the abrupt transition of corners 14, 16 of flange 12 in FIG. 1). For example, the taper of the tapered non-engaging face 72 is preferably at an angle of about 15-85 degrees relative to the horizontal plane of the engaging face 70, and more preferably at an angle of about 45 degrees. The remainder of the tubular member 60 has a substantially uniform cross-section.

[0043] In addition to reducing undesirable stress concentrations, the exemplary fill tube design 58 is lighter in weight than, for example, the fill tube 2 of FIG. 1, which is representative of known prior art fill tube designs. While the exemplary fill tube 58 is made from ceramic material, it will be appreciated that it could alternatively be made from any material which will maintain its stability, structure and other properties when in contact with molten metal.

[0044] Continuing to refer to, the exemplary fill tube assembly 50 further includes a gasket 76 disposed between the mold-engaging face 70 of the fill tube flange 68 and the fill tube socket 54 of the casting mold 52. The gasket 76 is generally annular in shape and may be made from any known or suitable material having durability at high temperatures, such as, for example, above about 800 F. Such materials expressly include, but are not limited to, for example, high-temperature silicon, high-temperature polymers, graphite sheet material commonly known in the art as grafoil, mica and any other known or suitable gasket material.

[0045] As shown, a clamping assembly 74 is employed to seal the fill tube 58 against the casting mold 52 while compressing the gasket 76 therebetween, in order to create an air-tight seal. The clamping assembly 74 includes a load ring 78. As shown, the exemplary load ring 78 includes a flange-engaging face 80 and a non-engaging face 82 and has a generally annular cross-section in plain view. The exemplary flange-engaging face 80 is tapered corresponding to the taper of the flange non-engaging face 72. The load ring 78 is disposed over the fill tube 58, in order to uniformly engage the flange 68 thereof (best shown in FIG. 3).

[0046] The clamping assembly 74 further includes a clamping plate 84 disposed over the fill tube 58 onto the load ring 78. The clamping plate 84 is structured to bias the load ring 78 against the flange 68, thereby distributing a uniform compression load against the casting mold 52 while uniformly compressing the gasket 76 therebetween. As shown, the exemplary clamping plate 84 has a generally annular cross-section in plain view. The clamping plate 84 includes at least one fastener, such as the exemplary plurality of fasteners 88, structured to fasten the clamping plate 84 to the casting mold 52. As shown, the exemplary clamping plate 84 includes a plurality of fastener-receiving openings 86 (four fastener-receiving openings 86 are shown in FIG. 2), which are structured to receive a plurality of fasteners, such as the exemplary bolts 88, shown, in order to tighten the clamping plate 84 against the casting mold 52. The exemplary fasteners are a plurality of threaded bolts 88 (two threaded bolts 88 are shown in FIG. 2) inserted through the fastener-receiving openings 86 and threaded into the fastener-receiving apertures 56 in the casting mold 52.

[0047] As shown in FIG. 3, the exemplary clamping plate 84 is structured to be spaced apart from the casting mold 52 when assembled, in order to form a pre-load gap 90 therebetween. The pre-load gap 90 is structured to compensate or accommodate the forgoing dimensional variations. For example, the pre-load gap 90 is preferably sized to be at least as wide as the aggregate of all of the dimensional variations in the fill tube assembly. More preferably, the pre-load gap 90 is slightly larger than such aggregate to provide additional compensation for any unforeseen, additional dimensional variations, such as, for example, thermal expansion occurring during casting operations. The exemplary pre-load gap 90 permits the clamping assembly 74 to function similar to a spring. For example, when the clamping plate 84 is tightened, it bends toward the casting mold 52 near each tightened, threaded bolt 88 (see, for example, the deflected Belleville washer-shaped clamping plate 84 shown in phantom-line drawing in FIG. 3), thereby narrowing the pre-load gap 90 while applying a constant and uniform compressive load at the fill tube 58, casting mold 52 interface. This uniform load and the somewhat flexible nature of the bent, tightened clamping plate 84, is sufficient to maintain a substantially leak-proof seal at the fill tube 58, casting mold 52 interface, while simultaneously being compliant enough to accommodate dimensional variations in the fill tube assembly 50, such as, for example, thermal expansion, tolerance variations, fabrication defects and assembly errors.

[0048] In comparing the exemplary clamping assembly 74 shown in FIG. 3 to the rigid, tight tolerance assembly indicative of the prior art as represented, for example, in FIG. 1, the exemplary fill tube assembly 50 can accommodate such dimensional variations partly because of the exemplary pre-load gap 90 and partly because of the distinct load ring 78 and fill tube flange 68 and clamping plate 84 interaction. As discussed hereinbefore, when tightened, the edges of the exemplary clamping plate 84 deflect or bend, proximate the fasteners 88, thus narrowing the pre-load gap 90 while the central portion of the clamping plate 84 engages the load ring 78, which distributes a resultant uniform compressive load on the fill tube flange 68 and thus the gasket 76, thereby maintaining a fill tube 58, casting mold 52 interface seal while providing compliance with, and the ability to accommodate any dimensional variations in the fill tube assembly 50.

[0049] Apart from the foregoing, the particular size of the pre-load gap 90 is not a significant limitation. It will be appreciated that a variety of pre-load gaps (not shown) may be necessary for different casting molds (not shown), in order to maintain uniform pressure at the fill tube casting mold interface while accommodating dimensional variations in accordance with the present invention.

[0050] As shown, the exemplary load ring 78 has a tapered flange-engaging face 80 corresponding to the taper of the flange non-engaging face 72. This corresponding tapered relationship permits the exemplary load ring 78 to self-center on the flange 68, thereby ensuring uniform distribution of the compressive load on the flange when the clamping plate 84 is tightened. As discussed hereinbefore, the exemplary tapers of the flange non-engaging face 72 and the flange-engaging face 80 of the load ring 78 are both about 45 degrees. Accordingly, the two tapered surfaces 72,80 will naturally come to rest in a position wherein the exemplary 45-degree tapers will rest fleshly upon one another or self-center as shown. However, it will be appreciated that any suitable load ring 78 to flange 68 arrangement (not shown) may alternatively be employed.

[0051] FIG. 4 illustrates an alternative fill tube assembly embodiment 150 similar to the fill tube assembly 50 of FIG. 3, but additionally including a dimensional compensating ring 200. As shown, the same fill tube 58 is inserted against a gasket 76 within the casting mold 52 fill tube socket 54. Additionally, a load ring 178, substantially similar to load ring 78 of fill tube assembly 50 is disposed over the fill tube 58 and uniformly engages the fill tube flange 68. However, the load ring 178 is compressed against the flange 68 by a dimensional compensating ring 200 disposed over the fill tube 58.

[0052] In this embodiment, the clamping plate 184 includes a dimensional compensating ring adjustment mechanism, such as the exemplary threaded aperture 204. The exemplary dimensional compensating ring 200 is threaded with threads corresponding to the threads of the threaded aperture 204 in the clamping plate 184. As shown, in use, the exemplary dimensional compensating ring 200 is inserted into the threaded aperture 204 and rotated to tighten against the load ring 178 thereby establishing and maintaining the desired compressive load between the load ring 178 and the exemplary tapered flange 68. In this manner, the exemplary dimensional compensating ring 200 may be assembled to accommodate dimensional variations in, for example, the fill tube 58, casting mold 52, gasket 76 or other fill tube assembly component. For example, as shown, the exemplary dimensional compensating ring 200 is spaced sufficiently far apart from the fill tube 58 to accommodate dimensional variations, while maintaining a uniform compressive load sufficient to maintain the seal at the fill tube 58, casting mold 52 interface. It will be appreciated by those skilled in the art that the particular dimensions of this spaced-apart relationship are not limiting as long as a sufficient seal is maintained while having the ability to accommodate dimensional variations.

[0053] Remaining or additional dimensional variations, such as, for example thermal expansion resulting from the introduction of the fill tube assembly 150 to temperatures higher than those at which it was assembled, may be accommodated by the pre-load gap 190 between the clamping plate 184 and the casting mold 52.

[0054] Accordingly, the dimensional compensating ring 200 provides additional dimensional variation compliance. For example, a fill tube assembly, for example 150, could be pre-assembled with the dimensional compensating ring 200 screwed down or tightened to a specific predetermined preload. Then, the clamping plate 184 and the exemplary pre-load gap 190 between the clamping plate 184 and the casting mold 52 can be adjusted or set to compensate for additional dimensional variations caused by, for example, temperature variations or variations other than those which were accommodated by the dimensional compensating ring 200.

[0055] Although it provides additional compliance, it will be appreciated that use of the exemplary dimensional compensating ring 200 is not required. In fact, it has been discovered in the present invention that dimensional variations may be accommodated while maintaining a substantially leak-proof seal at the fill tube casting mold interface, using the exemplary foregoing embodiment of the invention as discussed with reference to FIGS. 2 and 3.

[0056] The self-centering load ring 78, fill tube tapered flange 68 and the exemplary clamping plate 84 and pre-load gap 90 provide a low-cost, easily assembled fill tube assembly 50 that is retro-fittable for use with existing casting molds, and which maintains a substantially leak-proof fill tube 58, casting mold 52 interface seal while compensating for or accommodating dimensional variations. Accordingly, the exemplary fill tube assembly 50 greatly reduces the incidence of manufacturing defects caused by the infiltration of air into the casing mold, fill tube failures and extended casting process downtimes, thereby greatly increasing efficiency of the casting process.

[0057] It will be appreciated that the fill tube assembly components may be made from a variety of materials. For example, the exemplary load ring 78 is made from 4130 steel. However, it will be appreciated that any known or suitable alternative material could be used. The clamping plate 84,184 may be made from any known or suitable material exhibiting high yield strength at elevated temperatures, such as, for example, above about 800 F. For example, without limitation, the exemplary clamping plate 84,184 is made from Inconel. It will also be appreciated that variations in the arrangement of the fill tube assembly (not shown), such as, the use of spacer ring (not shown) between, for example, the casting mold and fill tube flange or between the load ring and the clamping plate, could be employed.

[0058] It will also be appreciated by those skilled in the art that the clamping plate could alternatively have a variable cross-sectional thickness (not shown) and it is not required to be solid. The clamping plate could, for example, include thru slots (not shown). Moreover, the clamping plate need not have a generally annular cross-section. Similarly, alternatives to other components of the fill tube assembly could be developed within the scope of the overall teachings of the present invention.

[0059] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details, in addition to those discussed above, could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only, and not limiting as to the scope of the invention, which is to be given the full breadth of the claims appended and any and all equivalents thereof.