Patent Grant
6889747
The present invention relates to a new and improved method and apparatus for casting a metal article. More specifically, the invention relates to the use of a baffle in association with a fluidized bed into which a mold is moved.
An apparatus for use in casting a metal article is disclosed in U.S. Pat. No. 4,573,516. This apparatus includes a furnace assembly and a mold which is filled with molten metal. The apparatus also includes a fluidized bed which is disposed below the furnace assembly. The mold is lowered from the furnace assembly into the fluidized bed to effect solidification of the molten metal in the mold.
Another apparatus for use in casting metal articles and utilizing a fluidized bed is disclosed in U.S. Pat. No. 6,035,924. This apparatus includes a furnace assembly from which a mold containing molten metal is lowered into a fluidized bed. A layer of hollow spherical bodies is disposed on an upper end portion of the fluidized bed.
Another apparatus and method for use in casting a metal article is disclosed in U.S. Pat. No. 6,443,213. This patent discloses a furnace assembly from which a mold is lowered into a fluidized bed. Still another apparatus for use in casting a metal article is disclosed in Japanese Laid-Open Patent Application No. 54-106031. This publication discloses a mold which is lowered from a furnace assembly into a fluidized bed.
The present invention relates to a new and improved method and apparatus for use in casting a metal article. During casting of the metal article, a mold is moved into a fluidized bed. A baffle is provided to retard heat transfer from the furnace assembly to a fluidized bed during heating of a mold in the furnace assembly. In addition, the baffle retards transfer of heat from a portion of the mold disposed outside of the fluidized bed to the fluidized bed during movement of the mold into the fluidized bed.
The baffle may be connected with the furnace assembly. Alternatively, the baffle may be connected with a container which holds the fluidized bed. As another alternative, the baffle may float on the fluidized bed. Regardless of how the baffle is supported, the baffle may be provided with flexible segments which engage the mold during movement of the mold through a central opening in the baffle to at least partially block movement of particulate through the central opening in the baffle and to block radiation of heat through the central opening in the baffle.
The baffle may have a central opening and a plurality of secondary openings. The secondary openings enable particulate to move from an upper side of the baffle into the fluidized bed. This tends to minimize accumulation of particulate on the upper side of the baffle. If desired, the secondary openings may be omitted.
It should be understood that any one of the features mentioned above and/or additional features may be utilized by itself or in combination with other features of the invention. It should also be understood that the invention is not to be limited to any one of the specific embodiments disclosed herein. This is because there are many different ways in which the various features of the invention may be used together or separately and in which they may be changed from the specific embodiments disclosed herein.
The foregoing and other features of the invention will become more apparent upon consideration of the following description taken in connection with the accompanying drawings wherein:
FIG. 1. is a schematic sectional view of one embodiment of an apparatus for use in casting a metal article and depicting the relationship between a furnace assembly, a mold, and a fluidized bed during movement of the mold into the fluidized bed;
FIG. 2. is a schematic plan view, taken generally along the line 2—2 of
FIG. 3. is an enlarged schematic fragmentary sectional view, taken generally along the line 3—3 of
FIG. 4. is a schematic fragmentary sectional view, generally similar to
FIG. 5. is a fragmentary schematic sectional view, generally similar to a portion of the apparatus of
FIG. 6. is a schematic fragmentary sectional view, generally similar to
FIG. 7. is a schematic fragmentary sectional view, generally similar to
General Description
A casting apparatus 10, which is constructed and operated in accordance with one or more of the features of the present invention, is illustrated schematically in FIG. 1. The casting apparatus 10 includes a furnace assembly 12 which is of the known induction type and includes an induction coil 14. The coil 14 is located in a surrounding relationship with a cylindrical refractory wall 16 of the furnace assembly 12. A cylindrical radiation liner 18 is provided within the refractory wall 16. A cover (not shown) may be provided over an upper end portion of the furnace assembly 12.
A suitable mold 22 is disposed on a movable support 24. A shaft 26 is connected with the mold support 24. The shaft 26 is movable along an axis 28 to raise and lower the mold support 24 relative to the furnace assembly 12 and a container 32 in which a fluidized bed 34 is disposed.
A drive assembly 36 is connected with the shaft 26 and is operable to move the shaft along its central axis 28. The central axis 28 of the shaft 26 is coincident with a central axis of the cylindrical furnace assembly 12 and the cylindrical container 32.
A container drive assembly 42 is connected with the container 32 and is operable to raise and lower the container and fluidized bed 34 relative to the furnace assembly 12. A porous layer 46 is provided in a lower end portion of the container 32 and cooperates with the container to form a plenum chamber 48. The plenum chamber 48 is connected with a source of gas (argon) under pressure through a conduit 50.
Pressurized gas flows from the plenum chamber 48 through the porous layer 46 to fluidized granular material and form the fluidized bed 34. A water cooling passage or jacket 52 extends around the container 32 and is effective to cool the fluidized bed 34. A stirrer assembly 54 may be provided in the lower portion of the fluidized bed 34 to promote an even distribution of particulate in the fluidized bed. However, if desired, the stirrer assembly 54 may be omitted.
The fluidized bed 34 is formed of particles suspended in a flow of gas. The gas may be argon. The particles may be alumina particles of 325 to 90 mesh size. Although the particles may be formed of alumina, it is believed that it may be preferred to use zircon particles which have a more rounded configuration than alumina particles. For example, it may be preferred to form the fluidized bed 34 by conducting gas through 200 mesh zircon particles. It should be understood that a gas and/or particulate other than the specific gas and/or particulate set forth herein may be used to form the fluidized bed 34.
Prior to fluidization of the bed 34, the particulate in the container 32 is supported by the cylindrical porous layer 46. When the bed 34 is to be fluidized, gas under pressure is conducted into the plenum chamber 48 through the conduit 50. When a predetermined minimum pressure, which is a function of the height fluidized bed 34, is obtained in the plenum chamber 48, a flow of gas is conducted from the plenum chamber through the porous layer 46 into the particulate. The flow of gas is effective to form the fluidized bed 34.
When the particulate in the container 32 becomes fluidized, the bed 34 shimmers and particles of particulate are suspended in the flow of gas through the bed. The smooth shimmering effect of the fluidized bed 34 is maintained as the fluid pressure in the plenum chamber 48 is increased to a predetermined maximum pressure.
The casting apparatus 10 may include a housing assembly having an upper housing and a lower housing. The furnace assembly 12 may be disposed in the upper housing. The lower housing has a loading chamber in which the container 32 and mold 22 may be lowered by operation of the drive assemblies 42 and 36. It is believed that the housing assembly and furnace assembly 12 may be constructed in the same manner as is disclosed in U.S. Pat. No. 3,841,384.
When the mold 22 is to be utilized to form one or more cast metal articles, a door to the lower housing is opened with the container 32 and mold support 24 in their lowered positions. The mold is placed on the mold support 24 while the empty mold support is disposed slightly above the container 32.
Particulate within the container 32 is then fluidized to enable the mold support 24 to be lowered into the container. Once the particulate in the container 32 has been fluidized, the mold support drive assembly 36 is operated to lower the mold support 24 into the fluldized bed in the container 32.
The door of the lower housing is then closed and the upper and lower housings are connected in fluid communication with a source of vacuum. This results in a cylindrical heating chamber 60 in the furnace assembly 12 being evacuated. The mold support drive assembly 36 is then operated to move the mold 22 upward into the furnace assembly 12.
After the mold 22 has been moved into the furnace assembly 12, the container 32 is moved to the raised position shown in
In the foregoing description of movement of the mold 22 into the furnace assembly 12, the mold has first been moved into the fluidized bed! 34. The mold 22 is then withdrawn from the fluidized bed 34 and moved into the furnace assembly 12, while the container 32 holding the fluidized bed 34 is stationary. The stationary container 32 and fluidized bed 34 are subsequently moved upward to the position illustrated in
It should be understood that the mold 22 and container 32 can be moved relative to the furnace assembly 12 in a different manner if desired. For example, the mold 22 may be moved into the furnace assembly 12 before gas is conducted into the container 32 to fluidized the particulate in the container. If this is done, the container 32 may be moved to the raised position illustrated in
Alternatively, the bed 34 may be fluidized and the mold 22 moved into the bed while the container 32 is in the lowered position. The container 32 and mold 22 may be then moved together to the raised position with the mold in the fluidized bed 34, by effecting simultaneous operation of the mold support drive assembly 36 and the container drive assembly 42. The mold support drive assembly 36 would then be operated to move the mold 22 out of the raised container 32 into the furnace assembly 12.
While the mold 22 is disposed in the furnace assembly, the mold is heated to a temperature between 2,500 degrees Fahrenheit and 3,000 degrees Fahrenheit. At this time, the fluid pressure in the heating chamber 60 of the furnace assembly 12 is between 6×10−4 atmospheres and 1.0 atmosphere. It should be understood that the specific temperatures and pressures in the furnace assembly 12 may vary depending upon the characteristics of the molten metal to be poured into the mold. It is contemplated that other temperatures and pressures may be utilized.
Once the mold 22 has been heated to a desired temperature in the furnace assembly 12, the mold is filled with molten metal. In the specific embodiment of
Shortly after the mold 22 has been filled with molten metal, the mold is lowered into the fluidized bed 34. To lower the mold 22 into the raised fluidized bed 34, the mold support drive assembly 36 is operated to lower the mold support 24 while the container 32 is held stationary relative to the furnace assembly 12 by the container drive assembly 42.
If desired, the mold 22 may be lowered into the fluidized bed 34 only far enough to completely immerse in the fluidized bed the portion of the mold in which article mold cavities 66 are disposed. A gating system 70 which extends between the article mold cavities 66 does not have to be completely immersed into the fluidized bed. However, it is believed that it will probably be desired to lower the mold 22 at least far enough into the fluidized bed 34 so as to immerse the lower end portion of the gating system 70 in the fluidized bed.
Once the mold 22 has been lowered into the fluidized bed 34, the mold support drive assembly 36 and container drive assembly 42 are operated to simultaneously lower the mold and the container 32. When the container ˜32 has been moved to a lowered position, the mold 22 will still be immersed in the fluidized bed 34. The fluid pressure, that is, argon gas pressure, in a housing assembly enclosing the furnace assembly 12 and container 32 is then vented to atmosphere.
Once the housing enclosing the furnace assembly 12 and container 32 has been vented to atmosphere, the mold 22 is removed from the housing assembly with solidified molten metal in the mold. The next succeeding mold may then be positioned on the mold support 24. Molten metal is then cast in the next succeeding mold in the manner previously described in conjunction with the mold 22.
The construction and method of operation of the casting apparatus 10 is the same as is disclosed in U.S. Pat. No. 6,443,213. The disclosure from the aforementioned U.S. Pat. No. 6,443,213 is hereby incorporated herein in its entirety by this reference thereto. It should be understood that the casting apparatus 10 may have any of the constructions and/or modes of operation disclosed in U.S. Pat. No. 6,443,213.
If desired, the container 32 may have an annular cross-sectional configuration as viewed in a plane perpendicular to the axis 28. This would result in the fluidized bed 34 having an annular configuration. The annular container and fluidized bed may be part of an apparatus 10 having the same construction and mode of operation as is disclosed in U.S. patent application Ser. No. 10/189,656 filed Jul. 3, 2002 by Lawrence D. Graham, et al. and entitled System for Casting a Metal Article (Publication No. US-2002-0170698A1, published Nov. 21, 2002). The disclosure in the aforementioned application Ser. No. 10/189,656 is hereby incorporated herein in Its entirety by this reference thereto.
Baffle
In accordance with a feature of the present invention, a baffle 80 is provided between the fluidized bed 34 and at least a portion of the furnace assembly 12. The baffle 80 has a central opening 82 (F1 g. 2). At least a portion of the mold 22 moves through the opening 82 during movement of the mold from the heating chamber 60 of the furnace assembly 12 into the fluidized bed 34.
The baffle 80 is effective to retard transfer of heat from the mold structure 22 and furnace assembly 12 to the fluidized bed 34 during heating of the mold structure in the furnace assembly. In addition, the baffle 80 is effective to retard transfer of heat from the heating chamber 60 of the furnace assembly 12 and the portion of the mold in the heating chamber to the fluidized bed 34 during withdrawal of the mold 22 from the heating chamber. In addition, the baffle 80 is effective to retard movement of particulate from the fluidized bed 34.
The illustrated baffle 80 has an annular construction with a circular central opening 82 (FIG. 2). However, it is contemplated that the baffle 80 may have a construction which is not annular. The baffle 80 may be constructed with either a circular or a noncircular central opening 82. When a plurality of articles are to be cast or when the mold 22 has projecting portions, the baffle 80 may be constructed with a noncircular central opening 82. The noncircular central opening 82 may have lobes in which article mold portions of a mold are received. The diametrically outer peripheral edge portion of the illustrated baffle 80 is circular. However, the outer peripheral edge portion of the baffle 80 may have a noncircular configuration if desired.
The baffle 80 facilitates the establishment of a relatively large temperature differential between the heating chamber 60 of the furnace assembly 12 and the fluidized bed 34 in the container 32 (FIG. 1). This is because the baffle 80 is effective to at least partially block radiant heat transmission between the heating chamber 60 of the furnace assembly 12 and the fluidized bed 34.
The temperature differential between the heating chamber 60 and the fluidized bed 34 is sufficient to maintain a solidification front between liquid metal in the article mold cavity 66 and solidified metal at a location adjacent to the baffle 80 during movement of mold 22 into the fluidized bed 34. Thus, the solidification front between the molten and solidified metal in the article mold cavity 66 is maintained horizontal and in general alignment with the upper surface of the fluidized bed 34 as the mold 22 is withdrawn from the furnace assembly 12.
If the mold 22 is moved at a relatively rapid rate from the heating chamber 60 of the furnace assembly 12 into the fluidized bed 34, the molten metal in the article mold cavity 66 may solidify with an equiaxed crystallographic structure. However, if the mold 22 is withdrawn at a slower rate from the heating chamber 60, the molten metal in the article mold cavity 66 may solidify with a columnar grain crystallographic structure. If the article mold cavity 66 in the mold 22 is associated with a single crystal starter, such as is disclosed in U.S. Pat. No. 5,062,468, and the mold is withdrawn slowly from the heating chamber 60, the molten metal may solidify with a single crystal crystallographic structure.
The baffle 80 has sufficient rigidity to maintain its original shape during withdrawal of the mold 22 from the heating chamber 60. Although the mold 22 may engage a portion of the baffle 80, there is no significant deformation of the baffle during withdrawal of the mold from the heating chamber 60 and movement of the mold into the fluidized bed 34. Thus, during withdrawal of the mold 22 from the furnace assembly 12, the baffle 80 maintains its original configuration.
The baffle 80 may have a layered construction composed of one or more layers of graphite felt and/or graphite foil. The graphite felt may be enclosed by the layers of graphite foil. However, it should be understood that the baffle 80 could be formed of a different material and in a different manner if desired. For example, the baffle 80 may be formed of a suitable ceramic or a suitable refractory metal. Rather than having a multi-layered construction, the baffle 80 may be formed by a single piece of graphite felt or other material. It should be understood that the baffle 80 must be capable of withstanding relatively high temperatures. This is because the temperature in the heating chamber 60 of the furnace assembly 12 is approximately 3,000 degrees Fahrenheit during preheating of the mold 22.
The baffle 80 may be formed as a single piece. Alternatively, the baffle 80 may be formed of a plurality of pieces. If the baffle 80 is formed by a plurality of pieces, each of the pieces may be interconnected with suitable fasteners, such as staples, or with a suitable adhesive.
In accordance with one of the features of the present invention, the baffle 80 may advantageously be provided with a plurality of secondary openings 88 (FIGS. 2 and 3). The secondary openings 88 are formed in the baffle 80 at a location spaced from the central opening 82 in the baffle. The secondary openings 88 extend between an upper major side surface 90 and a lower major side surface 92 (
The upper and lower major side surfaces 90 and 92 of the baffle 80 extend parallel to each other. The annular upper and lower major side surfaces 90 and 92 of the baffle 80 are interconnected by a cylindrical inner minor side surface 94 and a cylindrical outer minor side surface 96 (Flg. 2). The inner and outer minor side surfaces 94 and 96 are disposed in a coaxial relationship with each other. It should be understood that the baffle 80 may have a configuration different than the configuration illustrated in
In the embodiment of the baffle 80 illustrated in
Although the illustrated secondary openings 88 are formed as slots, it is contemplated that the secondary openings may have a different configuration if desired. For example, the secondary openings 88 may be formed as circular holes disposed in an array about the central opening 82 in the baffle 80.
Although only inner and outer arrays 102 and 104 of secondary openings 88 have been illustrated in
The secondary openings 88 in the baffle 80 enable particulate to move from the upper side 90 of the baffle 80 through the openings to the fluidized bed 34. During use of the casting apparatus 10, particulate may move onto the upper side of the baffle 80. This movement may result from boiling of the fluidized bed 34 or other causes. For example, when the mold 22 is raised from the fluidized bed 34 into the heating chamber 60, particulate may cling to the mold 22 and/or mold support 24 and subsequently be deposited on the baffle 80. As another example, if the fluid pressure conducted through the conduit 50 to the plenum chamber 48 is relatively high, there may be some boiling of the fluidized bed. This boiling of the fluidized bed may result in particulate being projected upwardly from the fluidized bed 34 through the central opening 82 in the baffle 80 onto the upper major side surface 90 of the baffle 80.
The particulate can move downward from the upper side 90 of the baffle 80 through the secondary openings 88 to the fluidized bed 34. This results in particulate which moves onto the baffle 80 being returned to the fluldized bed 34 rather than accumulating on the upper side 90 of the baffle. The secondary openings 88 are effective to impart a self cleaning action to the baffle during operation of the casting apparatus 10.
It is believed that it will be preferred to form the baffle 80 with the secondary openings 88. However. If desired, the secondary openings 88 may be omitted from the baffle 80. Of course, eliminating the secondary openings 88 may, under some circumstances at least, result in accumulation of particulate on the upper side 90 of the baffle 80. This particulate may be transferred to the upper side of the baffle 80 from the fluidized bed during operation of the casting apparatus 10.
Baffle-Secondary Openings
In the embodiment of the invention illustration in
A baffle 80a (
Although the secondary openings 88a may have many different configurations, the illustrated secondary openings 88a have the same configuration as the secondary openings of
The relatively large cross sectional configuration, of the upper end portions 110 of the secondary openings 88a, facilitates movement of particulate from the upper side surface 90a of the baffle 80a into the openings 88a. The relatively small lower end portions 112 of the openings 88a tends to minimize upward flow of particulate from the fluidized bed through the secondary openings 88a (
In the embodiment of baffle 80a illustrated in
The slots forming the secondary openings 88a in the baffle 80a have the same arcuate configuration as the slots 88 of FIG. 2. However, there are three circular arrays of secondary openings 88a in the baffle 80a rather than two arrays as illustrated in
Between the upper end portions 110 of adjacent secondary openings 88a, rounded peaks 116 are formed in the baffle 80a. The rounded peaks 116 promote movement of particulate from the upper major side surface 90a of the baffle 80a into the secondary openings 88a. Therefore, there is little or no accumulation of particulate on the upper side surface 90a of the baffle 80a.
Although rounded peaks 116 are provided between secondary openings 88a in the baffle 80a, sharply defined peaks may be provided if desired. The sharply defined or rounded peaks 116 are tangent to a plane containing the upper side surface 90a of the baffle 80a. The sharply defined or rounded peaks 116 may be disposed above and/or below the upper side surface 90a of the baffle 80a. Of course, the secondary openings 88a may be spaced further from each other than is illustrated in
During use of the casting apparatus 10 in the manner previously explained in conjunction with
Although the secondary openings 88a of
Although the baffles 80 and 80a of
Container Mounted
Baffle
In the embodiment of the invention illustrated in
A casting apparatus 10b includes a furnace assembly 12b (FIG. 5). The furnace assembly 12b includes an induction coil 14b, a refractory wall 16b and a liner 18b. An annular ring 122 is provided at the lower end portion of the furnace assembly 12b. A mold 22b is disposed on a mold support, corresponding to the mold support 24 of FIG. 1.
The mold support and mold 22b are movable in an upward direction, as viewed in
The manner in which the mold 22b is moved into and out of the furnace assembly 12b during casting of an article and the manner in which the mold 22b and molten metal in the mold are cooled during use of the casting apparatus 10b is the same as was previously described in conjunction with the casting apparatus 10 of FIG. 1. As was previously mentioned, the casting apparatus 10b may have any one of the constructions disclosed in U.S. Pat. No. 6,443,213 and/or in U.S. patent application Ser. No. 10/189,656 filed Jul. 3, 2002 by Lawrence D. Graham (Publication No. 20020170698-A1). The aforementioned U.S. Pat. No. 6,443,213 and patent application Ser. No. 10/189,656 are hereby incorporated herein in their entirety.
In accordance with a feature of the embodiment of the invention illustrated in
The annular baffle 80b has a circular central opening 82b corresponding the circular central opening 82 in the baffle 80 of FIG. 2. Although the baffle 80b has an annular configuration, it is contemplated that the baffle could have a different configuration if desired. For example, the central opening 82b may have a noncircular configuration.
The baffle 80b does not have secondary openings corresponding to the secondary openings 88 in the baffle 80 of
During operation of the casting apparatus 10b, the mold 22b is moved into the furnace assembly 12b. The container 32b and baffle 80b are simultaneously raised to the position shown in FIG. 5. Molten metal is poured into the mold 22b. The mold 22b is then withdrawn from the furnace assembly 12b and moved into the fluidized bed 34b. As the mold 22b moves into the fluidized bed, the molten metal in the mold 22b solidifies with a desired crystallographic structure.
As the mold 22b is withdrawn from the furnace assembly 12b, the mold moves downward through the central opening 82b in the stationary baffle 80b. There is no significant deformation of the baffle 80b as the mold 22b moves through the central opening 82b in the baffle.
After the mold 22b has been withdrawn from the furnace assembly 12b through the central opening 82b in the baffle 80b, the container 32b, fluidized bed 34b and baffle 80b are moved downward away from the furnace assembly 12b by operation of a container drive assembly, corresponding to the container drive assembly 42 of FIG. 1. At the same time, the mold 22b and mold support are moved downward with the fluidized bed 34b and container 32b by operation of a mold support drive assembly, corresponding to the mold support drive assembly 36 of FIG. 1. Since the baffle 80b is connected with the container 32b, the baffle 80b moves downward away from the furnace assembly 12b with the container 32b and fluidized bed 34b. The mold support drive assembly 36 is operated to move the mold 22b downward with the container 32b, fluldized bed 34b and baffle 80b.
The illustrated baffle 80b (
Floating Baffle
In the embodiment of the invention illustrated in
A casting apparatus 10c includes a furnace assembly 12c. The furnace assembly 12c has an induction coil 14c which extends around a cylindrical refractory wall 16c and a cylindrical liner 18c. The furnace assembly 12c has a cylindrical heating chamber 60c.
A mold 22c is provided to cast metal articles. The mold 22c is provided with a plurality of article mold cavities. However, the mold 22c could be formed with a single article mold cavity.
Although the mold 22c may have any one of many different constructions, the illustrated mold 22c, like the molds 22 and 22b of
The molds 22, 22b, and 22c are integrally formed as one piece by repetitively dipping a wax pattern in a slurry of ceramic mold material in the manner disclosed in U.S. Pat. No. 4,955,423. However, it should be understood that the molds may be formed in many different ways and may be utilized to cast many different articles for use in environments other than in association with turbine engines. It is believed that the present invention will advantageously be used in conjunction with the casting of many types of articles and it is not intended to limit the invention to any specific mold construction, type of mold, article, or type of article.
The mold 22c is raised into the heating chamber 60c by operation of a mold support drive assembly, corresponding to the mold support drive assembly 36 of FIG. 1. When the mold 22c has been heated to a desired temperature, the mold is filled with molten metal. At this time, a container 32c and a fluidized bed 34c will have been moved to the raised position illustrated schematically in FIG. 6. When the container 32c and fluidized bed are disposed in the raised position of
Once the molten metal has been poured into the mold 22c, the mold lis lowered into the fluidized bed 34c In the raised container 32c. This is accomplished by operating the mold support drive assembly, corresponding to the mold support drive assembly 36 of
The solidification front separates the molten metal in the upper portion of the mold 22c from solid metal in the lower portion of the mold. A cellular solidification front may be achieved by slowly lowering the mold 22c into the fluidized bed 34c. If this is done, the resulting cellular solidification front is free of dendrites which commonly project from a solidification front during solidification of molten metal. The absence of dendrites is obtained with a cellular solidification front due to the high rate in which heat is transferred from the mold 22c and the relatively low rate of lowering the mold into the fluidized bed.
It should be understood that the mold 22c may be lowered into the fluidized bed 34c in a manner which results in solidification of the molten metal along a dendritic solidification front. When the solidification front is either a dendritic solidification front or a cellular solidification front, the front has an horizontal configuration and extends across the metal and all of the article mold cavities at a location adjacent to the upper surface of the fluidized bed 34c.
In accordance with a feature of the embodiment of the invention illustrated in
The baffle 80c has an annular configuration, corresponding to the annular configuration of the baffle 80 of FIG. 2. The baffle 80c has a circular central opening 82c. An upper side surface 90c of the baffle 80c is circumscribed by the container 32c. There is no significant deformation of the baffle 80c as the mold 22c moves through the central openings 82c in the baffle. As was previously mentioned, the baffle may have a configuration which is different than the illustrated annular configuration. The baffle 80c is formed of a relatively light material which is capable of floating on the fluidized bed 34c. Although the baffle 80c may be formed of many different materials, it is believed that it may be desired to form the baffle 80c from a low density graphite foam. Of course, the baffle 80c could be formed of other material if desired and have a configuration which is is different than the illustrated configuration.
Since the baffle 80c floats on the upper surface 132 of the fluidized bed 34c, the baffle will move in the fluidized bed with movement of the upper surface of the fluidized bed. For example, if the volume of the fluidized bed 34c in the container 32c is reduced, the baffle 80c will move downward in the container 32c as the upper surface 132 of the fluidized bed moves downward in the container. Similarly, as the upper surface 132 of the fluidized bed 34c moves upward in the container 32c, the baffle 80c will move upward in the container.
The baffle 80c is free of secondary openings corresponding to the secondary openings 88 and 88a of
Flexible Baffle Segments
The central openings 82, 82b and 82c formed in the baffles 80, 80b, and 80c of
A casting apparatus 10d has the same general construction and mode of operation as the casting apparatus 10 of FIG. 1. The casting apparatus 10d includes a furnace assembly 12d. The furnace assembly 12d includes a induction coil 14d, a cylindrical refractory wall 16d and a cylindrical wall 18d. The furnace assembly 12d has a cylindrical heating chamber 60d.
A mold 22d is movable into and out of the furnace chamber 60d by operation of a mold support drive assembly, corresponding to the mold support drive assembly 36 of FIG. 1. The mold 22d is moved into the heating chamber 60d and preheated to a desired temperature. Molten metal is then poured into the mold 22d. After the molten metal has been poured into the mold 22d, the mold is withdrawn from the furnace assembly 12d by operation of the mold support drive assembly.
At this time, a container 32d and a fluidized bed 34d will have been moved to a raised position immediately beneath the furnace assembly 12d by a container drive assembly, corresponding to the container drive assembly 42 of FIG. 1. As the mold 22d is lowered from the heating chamber 60d into the fluidized bed 34d by operation of the mold support drive assembly, molten metal will solidify in the mold in the manner previously described herein.
A baffle 80d is connected to the furnace assembly 12d in the same manner as previously described in conjunction with in the embodiment of the invention illustrated in FIG. 1. However, the baffle 80d may be connected with the container 32d in the same manner as previously described in conjunction with the embodiment of the invention illustrated in FIG. 5. Alternatively, the baffle 80d may be floated on the fluidized bed 34d in the same manner as previously described in conjunction with the embodiment of the invention illustrated in FIG. 6.
The baffle 80d is effective to retard the radiant transmission of heat from the heating chamber 60 of the furnace assembly 12 to the fluidized bed 34d. In addition, the baffle 80d is effective to retard the radiant transfer! of heat from a portion of the mold 22d disposed above the baffle to the fluidized bed 34d. The baffle 80d is also effective to retard movement of particulate from the fluidized bed 34d.
The baffle 80d includes an annular base 142 which is secured to the furnace assembly 12d. A plurality of flexible segments 144 are connected to the base 142 and are engagable with the outside of the mold 22d. Ends 148 of the flexible segments 144 cooperate to define a central opening, corresponding to the central opening 82 of
Although the ends 148 of the flexible segments 144 define a circular central opening corresponding to the central opening 82 of
The base 142 of the baffle 80d includes an annular upper layer and an annular lower layer. The annular upper and lower layers may be formed as a plurality of separate segments which are interconnected at expansion joints. If desired, the base 142 may have a noncircular configuration. The annular upper and lower layers of the base 142 may be formed of graphite. In the embodiment of the baffle 80d illustrated in
The flexible segments 144 may be formed from a single circular piece of graphite foil. The flexible segments 144 are formed as separate cantilevered beams or arms which extend radially inward from the annular base 142.
As the mold 22d moves into and out of the heating chamber 60d of the furnace assembly 12d, the flexible segments 144 of the baffle 80d are resiliently flexed by the mold 22d. The extent to which the flexible segments 144 are deflected varies as a function of the configuration of the irregular side portion of the mold 22d.
As the mold 22d is moved upward into the heating chamber 60d, forces are transmitted from the irregular side portion of the mold 22d to flex the segments 144 radially outward and upward in the manner illustrated schematically in FIG. 7. During upward movement of the mold 22d into the heating chamber 60d of the furnace assembly 12d, the flexible segments block upward movement of particulate from the fluidized bed 34d. In addition, the flexible segments tend to wipe down the outer side surface of the mold 22d to dislodge any particulate which may be adhering to the mold. The particulate which is removed from the exterior surface of the mold 22d by the wiping action of the flexible segments 144 flows downward into the fluldized bed 34d. The natural resilience of the material forming flexible segments 144 causes segments to flex radially inward and outward with variations in the irregular outer side surface of the mold 22d.
After preheating the mold 22d and pouring the molten metal into the mold, the mold 22d is lowered by operation of a mold support drive assembly, corresponding to the mold support drive assembly 36 of FIG. 1. As the mold 22d is lowered the container 32d and fluidized bed 34d remain stationary relative to the furnace assembly 12d.
As the mold 22d is lowered, the flexible segments 144 of the baffle 80d flex to maintain engagement with the irregular side portion of the mold structure. Thus, as the configuration or contour of the irregular side portion of the mold 22d changes along the length of the mold, the segments 144 flex in and out to maintain engagement with the side portion of the mold 22d. The segments 144 are resiliently flexed outward by force transmitted from! the mold 22d to the segments. The segments 144 are flexed inward by their own natural resilience to either maintain contact with an inwardly curving contour of the irregular side portion of the mold 22d or to assume their initial flat or straight condition. The flexible segments block movement of particulate from the fluidized bed 34d through the baffle 80d as the mold 22d is lowered into the fluidized bed.
As the mold 22d is lowered, the flexible segments 144 of the baffle 80d tend to remain deflected upwardly as shown in FIG. 7. As the mold 22d moves downward, the upturned flexible segments 144 of the baffle 80d wipe along the surfaces of the mold 22d. If the outer end 148 of an upturned flexible segment 144 encounters a discontinuity or protuberance on the mold 22d, the end 148 may catch on the discontinuity or protuberance and be pulled downwardly with the mold 22d. This would result in an upwardly deflected flexible segment 144 being resiliently flexed to a downward extending orientation. Thus, as the mold 22d moves downward through the baffle 80d, at least some of the flexible segments 144 may be pointed upwardly while other flexible segments are pointed downward.
When the mold 22d has been moved downward to through sufficient distance into the fluidized bed 34d, the upper portion of the mold 22d may move out of engagement with the flexible segments 144. Alternatively, when the fluidized bed 34d and container 32d have been moved downward through a sufficient distance, the upper end portion of the mold 22d may move out of engagement with the flexible segments 144. When the mold 22d moves out of engagement with the flexible segments 144, the flexible segments return to their initial straight, that is, flat, condition under the influence of their own natural resilience.
It Is contemplated that the baffle 80d may have many different constructions. However, a specific baffle 80d which has been illustrated schematically in
Although the baffle 80d has been illustrated in
In view of the foregoing description, it is apparent that the present invention provides a new and improved method and apparatus 10 for use in casting a metal article. During casting of the metal article, a mold 22 is moved into a fluidized bed 34. A baffle 80 is provided to retard heat transfer from a furnace assembly 12 to a fluidized bed 34 during heating of a mold 22 in the furnace assembly. In addition, the baffle 80 retards transfer of heat from a portion of the mold 22 disposed outside of the fluidized bed 34 to the fluidized bed during movement of the mold into the fluidized bed.
The baffle 80 may be connected with the furnace assembly 12. Alternatively, the baffle 80b may be connected with a container 32b which holds the fluidized bed 34b. As another alternative, the baffle 80c may float on the fluidized bed 34c. Regardless of how the baffle 80 is supported, the baffle may be provided with flexible segments 144 which engage the mold 22 during movement of the mold through a central opening 82 in the baffle to at least partially block movement of particulate through the central opening in the baffle and to block radiation of heat through the central opening in the baffle.
The baffle 80 may have a central opening 82 and a plurality of secondary openings 88. The secondary openings 88 enable particulate to move from an upper side 90 of the baffle 80 into the fluidized bed 34. This tends to minimize accumulation of particulate on the upper side 90 of the baffle 80. If desired, the secondary openings 88 may be omitted.
It should be understood that any one of the features mentioned above and/or additional features may be utilized by itself or in combination with other features of the invention. It should also be understood that the invention is not to be limited to any one of the specific embodiments disclosed herein. This is because there are many different ways in which the various features of the invention may be used together or separately and in which they may be changed from the specific embodiments disclosed herein. For example, the baffle 80 may be constructed with or without the secondary openings 88. As another example, any one of the baffles 80, 80a, 80b or 80c may be provided with flexible segments 144. As still another example, any one of the baffles 80b, 80c or 80d may be constructed with secondary openings.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3714977 | Terkelsen | Feb 1973 | A |
| 3810504 | Piwonka | May 1974 | A |
| 4108236 | Salkeld | Aug 1978 | A |
| 4573516 | Quested et al. | Mar 1986 | A |
| 4763716 | Graham et al. | Aug 1988 | A |
| 4774992 | George | Oct 1988 | A |
| 4969501 | Brokloff et al. | Nov 1990 | A |
| 6035924 | Graham | Mar 2000 | A |
| 6443213 | Graham et al. | Sep 2002 | B1 |
| 6695034 | Graham | Feb 2004 | B2 |
| Number | Date | Country |
|---|---|---|
| 54-106031 | Aug 1979 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20040173336 A1 | Sep 2004 | US |
