Abstract:
The present invention is a method for casting a part having a complex shape or having a complex shape thereon. The method includes providing a pattern and securing at least one core to the pattern. A conformable material is located about the pattern and the core to create a complementary shape to the pattern and core in the conformable material. The pattern is removed and the core is left behind in the conformable material. The core leaves space, or an empty form, for a negative draw that cannot be formed in known casting methods. A mold is located adjacent the shaped, conformable material. A hardenable material is located between the mold and the shaped, conformable material and into the core. The hardenable material is allowed to harden and then it is removed. A cast part having a complex shape, or having a complex shape integrally formed with the part, results.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method for casting an article.  
       BACKGROUND OF THE INVENTION  
       [0002]     Methods for casting articles are well known to those skilled in the art. Current attempts to cast an article having a complex shape, however, are not practical. For example, one such known method is described in U.S. Pat. No. 4,694,879. In U.S. Pat. No. 4,694,879, a casting process that uses gasifiable parts located on a reusable part is described. The gasifiable parts are alleged to enable parts to be cast with contours that would otherwise be difficult to produce by known casting methods. The reusable part, with the gasifiable part initially located thereon, is located in a packed sand mold and then removed. The sand takes on the shape of the reusable part and the gasifiable part remains behind in the sand mold. As liquid material is added to the sand mold, it destroys the gasifiable part and fills the void it left behind. The liquid material hardens in a desired shape of the part.  
         [0003]     The method described above may be adequate to produce a part with a limited number of non-standard contours, however, the high cost and low efficiency associated with using gasifiable parts is likely prohibitive for large scale production. Furthermore, the above-described process may be limited in shapes and the types of parts that can be produced.  
         [0004]     Other than the method described above, the known casting methods are disadvantageous since they are limited to relatively simple shapes and designs for the parts. This is primarily because those skilled in the art know that, in a parting line system, the mold impression of a complex shape having a negative draw will crumble when it is unsupported. The crumbled mold impression cannot be used later in the process.  
         [0005]     In light of the disadvantages in the prior art, it would be advantageous to have a method for casting complexly shaped parts having a negative draw, or parts having a complex shape associated with them, in a cost effective and efficient manner.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is directed toward an article casting process where at least one pattern is provided having at least one core secured to the pattern. Preferably, the core is a negative draw design, as known to those skilled in the art. A conformable material is located about the core and the pattern to form the material into a complementary shape to the core and pattern. The pattern is then removed from the conformable material and the core is retained as part of the mold impression. A hardenable material is located within the core to form at least a portion of a complex shape for a part.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:  
         [0008]      FIG. 1  is a schematic side view of one embodiment of a first pattern of the present invention;  
         [0009]      FIG. 2  is a schematic side view of the invention depicted in  FIG. 1  with one embodiment of a core on the first pattern;  
         [0010]      FIG. 3  is a schematic side view of the core and first pattern within a first flask;  
         [0011]      FIG. 4  is a schematic side view of one embodiment of a second pattern within a second flask;  
         [0012]      FIG. 5  is a schematic side view of the first flask filled with a conformable material;  
         [0013]      FIG. 6  is a schematic side view of the second flask filled with a conformable material;  
         [0014]      FIG. 7  schematically depicts a side view of a compressing means located over the first flask;  
         [0015]      FIG. 8  schematically depicts a side view of a compressing means located over the second flask;  
         [0016]      FIG. 9  schematically depicts a side view of the compressing means in contact with the first flask;  
         [0017]      FIG. 10  schematically depicts a side view of the compressing means in contact with the second flask;  
         [0018]      FIG. 11  schematically depicts a side view of the first flask with the compressing means removed;  
         [0019]      FIG. 12  schematically depicts a side view of the second flask with the compressing means removed;  
         [0020]      FIG. 13  schematically depicts a side view of the first flask removed from the first pattern;  
         [0021]      FIG. 14  schematically depicts a side view of the second flask removed from the second pattern;  
         [0022]      FIG. 15  schematically depicts a side view of a mold positioned above the second flask;  
         [0023]      FIG. 16  schematically depicts a side view of the mold located in the second flask;  
         [0024]      FIG. 17  schematically depicts a side view of the first flask located above the second flask;  
         [0025]      FIG. 18  schematically depicts a side view of the first flask adjacent the second flask;  
         [0026]      FIG. 19  schematically depicts a side view of hardenable material being located into the first and second flasks;  
         [0027]      FIG. 20  schematically depicts a side view of the hardenable material within the first and second flasks;  
         [0028]      FIG. 21  schematically depicts a side view of at least one sand core being removed from the first and second flasks;  
         [0029]      FIG. 22  schematically depicts a side view of one embodiment of a cast part with a pouring system attached and showing a complex shape attached to the part; and  
         [0030]      FIG. 23  schematically depicts a side view of the cast part. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.  
         [0032]      FIG. 1  depicts a pattern, or cope  100 , located on a cope base  102 .  FIG. 1  only illustrates one embodiment of the cope  100 . Those skilled in the art will appreciate that copes of various sizes and shapes other than that depicted in  FIG. 1  may be used with the present invention. The cope  100  shown in  FIG. 1  is designed to have a complementary shape to at least a portion of the part that will be cast. A sprue  104  is depicted as extending from the cope  100 . The sprue  104  may be of any shape or size and may extend from the cope  100  at other locations than that depicted in  FIG. 1 .  
         [0033]      FIG. 2  depicts a core  106  attached to one portion of the cope  100 . The core  106  may be of any shape or size and may be located on any portion of the cope  100 . In this embodiment, the core  106  is attached to a side portion  108  of the cope  100 . Preferably, at least a portion  110  of the core  106  is hollow to accept a hardenable material in a negative draw process, as known to those skilled in the art. The hollow portion  110  of the core  106  has a complementary shape to a shape that is desired to be included with the cast part.  
         [0034]     The hollow portion  110  may be comprised of one or more curvilinear shapes, such as convex, concave and/or compound curves, although any design is within the scope of the present invention. The curvilinear shapes of the core  106  are used to integrally form complementary shaped structures with the part that cannot be created during a typical casting process, hereinafter inclusively called complex shapes, because of the negative draw design.  
         [0035]     Although only one core  106  is depicted as attached to one portion  108  of the cope  100 , those skilled in the art will appreciate that additional cores of the same, or differing shapes and sizes, may be attached. Those skilled in the art will also appreciate that one or more cores may be attached to a drag. A drag is described in more detail below.  
         [0036]     The core  106 , or cores  106  as the case may be, may be constructed of a variety of materials. In a preferred embodiment, the core is constructed of one or more a resinous materials. By way of example only, a phenolic resin and a polyisocianate resin are combined to form a material for the core. The mixed resins may be hardened with a catalyst, such as an amine. Those skilled in the art will appreciate that there are other ways to create core, such as shell molding, hot box processes and carbon dioxide processes, that are well within the scope of the present invention.  
         [0037]     Referring back to  FIG. 1 , the core  106  is preferably attached to the cope  100  with one or more pins  112 . The pins  112  extend from the cope  100  and fit within complementary shaped recesses  114  in the core  106 . The pins  112  are designed and positioned to allow the core  106  to slide off the cope  100  in only a single direction. In the preferred embodiment depicted in the figures, the pins  112  are designed and positioned to allow the core  106  to slide off the cope  100  in a generally vertical direction only as shown by the arrow  116 . The pins  112  resist, or prevent, movement of the core  106  with respect to the cope  100  in any other direction.  
         [0038]     Those skilled in the art will appreciate that other devices and processes other than the pins  112  described above may be used to selectively secure the core  106  to the cope  100  for any parting line. The core  106  may also be secured to the cope  100  by one or more mechanical fasteners, mechanical or fluid driven clamps, pins that expand and contract either mechanically or via fluid means, vacuum, magnets and/or any other structure known by those skilled in the art.  
         [0039]     It is also well within the scope of the present invention to not use any devices to secure the core  106  to the cope  100 . In this embodiment, the core  106  is designed with a fit that precisely complements the shape of the cope  100 , or drag, as the case may be. The precise complementary shape only allows the core  106  to be removed from the cope  100  in a particular direction, such as vertically, to ensure that it will not be inadvertently removed. The structures and/or processes used to secure the core  106  to the cope  100  will depend on the design of the piece to be cast.  
         [0040]     As seen in  FIG. 3 , the cope  100  with the core  106  located thereon is placed in a first flask, or cope flask,  118 . The cope  100  and core  106  can be located in the first flask  118  by manual or automated means as known to those skilled in the art. Preferably, the core  106  has been secured to the cope  100  before they are located in the first flask  118 , however, the core  106  can be secured to the cope  100  in the first flask  118 .  
         [0041]      FIG. 4  depicts a pattern, or drag  120 , located on a drag base  122  within a second flask, or a drag flask,  124 .  FIG. 4  only illustrates one embodiment of the drag  120 . Those skilled in the art will appreciate that drags of various sizes and shapes other than that depicted in  FIG. 4  may be used with the present invention. The drag  120  depicted in  FIG. 4  is designed to have a complementary shape to at least a portion of the part that will be cast.  
         [0042]     Those skilled in the art will also appreciate that although the preferred embodiment described herein refers to a cope  100  and a drag  120  and a first flask  118  and a second flask  124 , the concept of the present invention can be practiced with a single pattern and flask without departing from the scope of the invention.  
         [0043]      FIGS. 5 and 6  depict a conformable, heat-resistant material, such as sand  126 , located in the first flask  118  and second flask  124 . The sand  126  may be located in the flasks  118 ,  124  by manual or automated means as known by those skilled in the art. One or more binder materials (not shown) may be added to cause the sand  126  to stick together.  
         [0044]     A first compacting structure  128  is positioned over the first flask  118  and a second compacting structure  130  is positioned over the second flask  124 , as best seen in  FIGS. 7 and 8 , respectively. Preferably, the first compacting structure  128  has a portion  132  for creating a hollow portion within the sand  126 . The portion  132  can be of any shape or size, but preferably it is designed to provide a passageway  134  from an upper surface  136  of the first flask  118  to the riser  104 .  
         [0045]     The first and second compacting structures  128 ,  130  compress the sand  126  within the first and second flasks  118 ,  124 , as shown in  FIGS. 9 and 10 . The compression creates a mold impression of the cope  100  in the sand  126  and a mold impression of the drag  120  in the sand  126 . More specifically, the compression conforms the sand  126  into a first complementary shape  138  with the cope  100  and core  106  and a second complementary shape  140  with the drag  120 . The first and second compacting structures  138 ,  140  are then removed from the first and second flasks  118 ,  124  by manual or automated means, as best seen in  FIGS. 11 and 12 . The passageway  134  from the upper surface  136  of the first flask  118  to the sprue  104  is now apparent.  
         [0046]     Those skilled in the art will appreciate that other means to compress and/or harden the sand  126  within the first and second flasks  118 ,  124  are well within the scope of the present invention. By way of example only, such means to compress and/or harden may include, but are not limited to, using one or more hardening chemicals, baking the sand, not baking the sand, hot box processes, metallic mold processes, and/or ceramic mold processes.  
         [0047]      FIG. 13  depicts the cope  100 , base  102  and sprue  104  being removed from the first flask  118 . Preferably, the cope  100 , base  102  and sprue  104  are moved in a downward, vertical direction away from the first flask  118  so as to allow the core  106  to slide off the pins  112  on the cope  100 . Those skilled in the art will appreciate that the cope  100 , base  102  and sprue  104  can be removed from the first flask  118  in other directions depending on the orientation of the pins  112  on the cope  100  and the position of the core  106  on the cope  100 . Those skilled in the art will also appreciate that if other structures or processes, such as mechanical fasteners, mechanical or fluid driven clamps, magnets and/or vacuum are used with, or instead of the pins  112 , that they must release the core  106  from the cope  100 .  
         [0048]     The drag  120  is also removed from the second flask  124 , as shown in  FIG. 14 . In the preferred embodiment, the drag  120  is moved in a vertical downward direction away from the second flask  124 , however, depending on the orientation of the second flask  124 , those skilled in the art will appreciate that the drag  120  may be moved away from the second flask  124  in other directions.  
         [0049]     The second flask  124  is then rotated 180 degrees by manual or automated means. As shown in  FIG. 15 , a mold  142  is positioned over the second complementary shape  140  of the rotated second flask  124 . The mold  142  is then located at least partially within the second complementary shape  140  by automated or manual means, as known to those skilled in the art. The mold  142  preferably has a similar shape to at least part of the second complementary shape  140 . In the preferred embodiment, a space  144  exists between the mold  142  and the second complementary shape  140 , as best seen in  FIG. 16 .  
         [0050]     Those skilled in the art will appreciate that a mold may not even be required depending on the part to be cast and/or the complex shape to be formed.  
         [0051]      FIG. 17  depicts the first flask  118 , with the first complementary shape  138  therein, being positioned above the second flask  124  and the mold  142 . The first flask  118  and the second flask  124  are brought together so that the mold  142  fits within the first complementary shape  138  of the first flask  118 , as shown in  FIG. 18 , to form a single casting.  
         [0052]     In the preferred embodiment depicted in the figures, a space  146  exists between the mold  142  and the first complementary shape  138 . The hollow interior portion  110  of the core  106  is preferably in fluid communication with the space  146 . The sprue  104  is in communication with the space  146  between the first complementary shape  138  and the mold  142  and the second complementary shape  140  and the mold  142 . Those skilled in the art will appreciate that the core  106  can be in fluid communication directly with the sprue  104  or with any space  144 ,  146  in fluid communication with the sprue  104 .  
         [0053]     For the particular depicted embodiment, it is important to locate the first flask  118  and the first complementary shape  138  in a particular location with respect to the second flask  124  and the second complementary shape  140  to align the spaces  144 ,  146  within the first flask  118  and the second flask  124  and to ensure the spaces  144 ,  146  have a uniform thickness, if uniform wall thickness of the cast part is desired. Those skilled in the art will appreciate that other castings may, or may not, require the spaces  144 ,  146 , if any, to be aligned depending on the shape and the design of the part to be cast.  
         [0054]     Referring back to  FIG. 17 , it is preferred that at least two guide pins  148  located on a perimeter portion  150  of the first flask  118  are aligned with, and are inserted into, recesses  152  within a perimeter portion  154  of the second flask  124 . In a more preferred embodiment, one of the recesses  154  has an oval shape. The oval shape allows one of the guide pins  148  to be initially slightly out of alignment with the recess  156 , but still be inserted. Locating at least one of the guide pins  148  within the recess  156  facilitates aligning the other guide pins  148  and recesses  152 .  
         [0055]     The other recess  158  is circular in shape. The guide pin  148  must be precisely aligned with the circular recess  158  to be inserted. Those skilled in the art will appreciate that the guide pins  148  can be located on the second flask  124  and the recesses  152  on the first flask  118  without departing from the scope of the present invention. Other alignment means may also be employed to align the first and second flasks  118 ,  124  without departing from the scope of the present invention.  
         [0056]     Those skilled in the art will appreciate that if a second flask  124  is not required for a particular part, the above step is not required.  
         [0057]     A hardenable material, such as molten metal  160 , is poured into the sprue  104 , as seen in  FIG. 19 . The molten metal  160  flows through, and fills, the space  146  between the first complementary shape  138  and the mold  142 , into the hollow interior portion  110  of the core  106 , and in the space  144  between the second complementary shape  140  and the mold  142 , as depicted in  FIG. 20 . In the preferred embodiment, the core  106  retains its shape, position and design at least during the introduction of the molten metal  160 .  
         [0058]     The first and second complementary shapes  138 ,  140  are then removed from the first and second flasks  118 ,  124  when the molten metal  160  is hardened, as seen in  FIG. 21 . The first and second complementary shapes  138 ,  140  are preferably removed with an automated mechanism which pushes them out of the flasks  118 ,  124 , respectively. The first and second complementary shapes  138 ,  140  are removed from a cast part  162  by means known to those skilled in the art leaving behind the part  162  and the sprue  104 , as depicted in  FIG. 22 . The riser  104  is removed from the part  162  by known means.  
         [0059]     In the preferred embodiment described herein, the core  106  is removed from the cast part  162  to leave behind a complementary shaped part  162 , or portion of the part  162 . Typically, this requires the destruction of the core  106 , although cores that can be removed from the cast part  162  without being destroyed are well within the scope of the present invention. Reusable cores  106  are also within the scope of the present invention.  
         [0060]     The cast part  162  is depicted in  FIG. 23  having the riser  104  removed and a cast on portion  164  from the core  106  integrally formed with the part  162 .  
         [0061]     The embodiment of the invention described above is illustrative of only a single apparatus and process. Those skilled in the art will readily appreciate that the present invention can be used with any parting line apparatus and processes as known to those skilled in the art.  
         [0062]     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.