Patent Document

BACKGROUND 
       [0001]    This application relates to a method of molding a platform for an airfoil, wherein lost core elements are utilized. 
         [0002]    Airfoils are known and are utilized in a number of applications. In one common application, airfoils are utilized in turbine and compressor sections for gas turbine engines. The airfoils have a platform which may be mounted to a rotor structure. In particular, static vanes associated with the turbine or compressor sections include airfoils and platforms. 
         [0003]    The airfoils can be exposed to high temperatures, and thus it is known to circulate cooling air within passages inside the airfoils and platforms. Thus, the combined airfoil and platform must have openings to receive the cooling air, and to communicate the cooling air into internal passages. 
         [0004]    To form passages in airfoils and their platforms, so-called “lost core” molding techniques have been utilized. In a lost core molding technique, an element is made of a material which can be leached or otherwise dissolved, and which bears the shape of desired openings and spaces in the airfoil and platform. 
         [0005]    In the prior art, there has been a main body core, which has been placed in a mold, and then utilized as a lost core component to form openings in a final platform. Molten metal is moved into the mold, and solidifies around the cores. Then the cores are dissolved or leached, leaving cavities within the final part. 
         [0006]    Typically, a large opening is formed at a top of the platform to receive cooling air delivered toward the airfoil. From this large opening, side openings extend into cooling chambers within the platform. 
         [0007]    Typically, a portion of one of the cores has extended upwardly beyond the top surface of the platform to form an opening in the top surface once the core has been leached away. This opening then provides an access point such that a machine, such as an electro-discharge machine (EDM) is able to move in, and machine the rest of the large opening away. 
         [0008]    At that point, the side openings must be formed such as by cutting into an intermediate part. 
       SUMMARY 
       [0009]    A method of molding a platform opening includes the steps of providing a main body core and a platform core, with the main body core having a portion that forms a portion of the platform. The platform core has at least one side portion that will form a side opening. Molten metal is directed around the cores within a mold and solidifies. The cores are removed, leaving cavities where the cores were within the molten metal, and includes an opening in a side face formed by the side portion of the platform body core. 
         [0010]    Lost core components are also disclosed and claimed. 
         [0011]    These and other features of the present invention can be best understood from the following specification and drawings, of which the following is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  shows a vane for use in a gas turbine engine. 
           [0013]      FIG. 1B  shows another detail of the vane. 
           [0014]      FIG. 1C  shows a portion of a final platform. 
           [0015]      FIG. 2  schematically shows a molding operation. 
           [0016]      FIG. 3A  shows the initial lost core structures assembled together. 
           [0017]      FIG. 3B  shows one of the two lost core structures. 
           [0018]      FIG. 4A  shows the initial molded structure. 
           [0019]      FIG. 4B  shows a further detail of the  FIG. 4A  intermediate part. 
           [0020]      FIG. 5A  shows the  FIG. 4  structure after the cores have been dissolved away. 
           [0021]      FIG. 5B  shows another detail of the  FIG. 5A  intermediate part. 
           [0022]      FIG. 6  schematically shows electro-discharge machining to the  FIG. 5  product. 
           [0023]      FIG. 7A  shows an alternative platform mold. 
           [0024]      FIG. 7B  shows yet another alternative platform core. 
           [0025]      FIG. 7C  shows yet another alternative platform core. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    A vane  10  is illustrated in  FIG. 1A , and would typically be utilized in a turbine section of a gas turbine engine. While this application specifically discloses a method for forming a portion of a vane, other components, such as turbine blades, may benefit from the teachings of this application. 
         [0027]    As shown, an airfoil  12  extends between an inner platform  14  and an outer platform  16 . It is known in the art that the airfoil  12 , and platforms  14  and  16  include any number of flow passages for circulating cooling air. Thus, as shown in  FIG. 1A , an opening  26 , and a side opening  22  are formed to bring cooling air through the platform  14 , and to the airfoil  12 , and platform  16 . As shown, a boss  20  forms the opening  26 , and extends inwardly from a nominal face  19  of the platform  14 . 
         [0028]    For purposes of this application, the boss  20  and the nominal end face  19 , together form outer inner end face of the platform  14 . 
         [0029]      FIG. 1B  shows the vane  10  having a portion of the nominal face  19  cut away, and a portion of the boss  20  cut away. One can see there is a lower wall  13  on an opposed side of the nominal face  19 , and a cooling chamber  15  is defined between the two faces  19  and  13 . A side opening  11  is formed within the boss  20 , and delivers air into the cooling chamber  15 . Side opening  22  also delivers air into chamber  15 . 
         [0030]      FIG. 1C  shows a boss  20  having an opening  26  surrounded by a lip  28 . As show, a platform side opening  22  extends through a side wall  30  of the boss, and allows cooling air flow in to the platform, and also within the interior of the airfoil. 
         [0031]    As can be appreciated, the enlarged opening  26  provides a relatively large cross-section for air flow. Also, as can be seen, the opening  22  has a frame  24 , which extends inwardly from the nominal inner wall  30  of the boss  20 . The lip  28  also extends inwardly of inner wall  30 . 
         [0032]      FIG. 2  schematically shows a molding system  130  for forming the boss  20 . As can be appreciated,  FIGS. 2-6  focus on the molding of only the boss  20 , openings  11 ,  22  and  26 , and their associated structure. In fact, the entire molding system  130  would include a good deal of other cores and components to form the entire vane  10 . As shown, a first lost core element  36  is combined with a second lost core element  34 . The lost core element  36  is placed within the mold  130 , and there is space  42 ,  44 , and  46  about this core  36 . As is known, when molten metal is injected into the mold  130 , the spaces  42 ,  44 , and  46  will form the boss as shown in  FIG. 1A . As can be appreciated, portions  38  and  35  extend outwardly beyond the end of the mold. Thus, those core portions will be found in an intermediate molded part, and will ensure that cavities extend outwardly to the end of the intermediate part, as will be explained below. 
         [0033]    The core portion  34  is spaced at  32  from the portions  38 . The molten metal will move into the spaces  32  such that the walls  132  (see  FIGS. 4A and 5A ) will also be formed in the intermediate part. Also, as shown, a space  333  between portions  34  and  36  also receives metal. 
         [0034]      FIG. 3A  shows further detail of the cores  34  and  36 . As shown, the core  36  extends to the upper portions  38  upwardly beyond shoulders  42 . The core portion  34  has an element or side portion  46  extending outwardly, and which will form the opening  11  in the final molded part. 
         [0035]    As shown, edges  33  of the mold core  34  are spaced from the portions  38  such that there are spaces  32  when the two cores are assembled together. Some way of positioning the two relative to each other within the mold is preferably utilized. 
         [0036]    As shown in  FIG. 3B , the core  34  has another portion  17  which extends from an opposed side of the top portion  35 , and forms the opening  22 . 
         [0037]      FIG. 4A  shows a first intermediate product  121  which would come out of the mold  130  after the molding process of  FIG. 2 . As can be seen, walls  132  are formed between the uppermost portion  35  of the core  34 , and the uppermost portions  38  of core  36 . The product will have solid portions  144  beyond each of the extreme ends of the portions  38 . Similarly, there are portions  110  along each side of the portions  35  and  38 . 
         [0038]      FIG. 4B  shows a detail of the formation of the side walls in the intermediate part  121 . As shown, the portion  17  extends through the side wall of the boss, and will eventually form the opening  22 . On the other side, the portion  46  extends through the side wall of the boss, and will form the opening  11 . It should be understood that  17  and  46  can be extended to form the platform cooling chamber  15  which is to the bottom of the face  19  and the top of the face  30  in  FIG. 4B . However, those extensions have been omitted for simplicity in this Figure. Also,  FIG. 4B  (and  5 B) are somewhat simplified in that portions  17  and  46  are illustrated on the same vertical plane. As can be appreciated from  FIG. 3B , the portion  46  is actually beneath portion  17 . 
         [0039]    The provision of the portions on the platform core which form the side openings eliminates the need for machining of the side openings after the initial molding. As such, the provision of the combined cores greatly simplifies the manufacture of the final product. 
         [0040]      FIG. 5A  shows a second intermediate part  120  after the core portions have been removed. A worker of ordinary skill in the art would know that the cores are formed of some material which can be dissolved, leached, etc., leaving cavities  134  and  138  as shown in  FIG. 5A and 5B . After the procedure as shown in  FIG. 5A , the intermediate part end face would include the material  144 , the material  110 , and the walls  132 . 
         [0041]      FIG. 5B  shows the  FIG. 4B  after the core  34  has leached away. As shown, the openings  22 ,  11 , and  134  remain. As shown, opening  22  communicates with a portion of the cooling chamber  15  extending into and out of the plane of the Figure (and also in  FIG. 4B ). 
         [0042]    Also seen in  FIGS. 4A and 5A , is boss  20 . 
         [0043]    As shown schematically in  FIG. 6 , intermediate part  120  will receive electro-discharge machining such as by tool  201  (shown schematically) to remove the material  144 , walls  132 , and material  110 . What remains is the boss  20  of  FIGS. 1A ,  1 B and  1 C, having an opening  26  with a lip  200  extending inwardly from the inner wall  30 , and the frame  24  ( FIGS. 5A and 5B ) around the opening  22 . Alternatively, a milling process may be used. 
         [0044]    By providing the open spaces  134  and  138  as shown in  FIG. 5A , the surface area required for electro-discharge machining to get to the structure of  FIGS. 1A ,  1 B and  1 C is dramatically reduced. 
         [0045]    Alternative platform cores are illustrated in  FIGS. 7A-7C . This shows the power of forming the side openings of any shape and location that is provided by the use of the platform cores. 
         [0046]    As shown in  FIG. 7A , a core  180  has the upper surface  182 , and side extensions  184  which will form the side openings in the final product. A portion  188  would be positioned on the opposed side of the portion  38  of the main body core. 
         [0047]      FIG. 7B  shows an alternative  190 , wherein two portions  194  and  198  will form side openings. A portion  200  can be positioned on the opposed side of the portion  38  of the body core. 
         [0048]      FIG. 7C  shows a core  210  having a portion  212 , and portions  214  and  216  that will form side openings. 
         [0049]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Technology Category: 2