Abstract:
A gasket assembly includes a closed periphery core of compressible sealing material, the core having top and bottom surfaces and inner and outer edges; a first cover component enclosing at least the outer edge of the closed periphery core; and a second cover component enclosing the inner edge of the closed periphery core and extending into overlapping relationship with the first cover component.

Description:
[0001]    This invention relates generally to rotary machine technology, and more specifically, to a new gasket construction for a turbine combustor end cover or casing. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gaskets are typically employed in turbine combustor systems to seal the interface between various combustor components, e.g., combustor end covers and combustor casings, in order to prevent leakage of combustion gases. Currently, such gaskets are composed of graphite serviceable in a range of about 850° F. to 1050° F. in normal environments. However, the graphite gasket material has been known to degrade at temperatures as low as 450° F., apparently due to exposure to combustion gases. There remains a need, therefore, for a gasket construction for use in gas turbine combustion systems that is not subject to the leaking issues currently experienced on a regular basis with graphite gaskets. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    In one exemplary but nonlimiting aspect, the present invention relates to a gasket assembly comprising: a core of compressible sealing material, the core having top and bottom surfaces and inner and outer edges; a first cover component enclosing at least the outer edge of the core; and a second cover component enclosing the inner edge of the core and extending into overlapping relationship with the first cover component. 
         [0004]    In another aspect, the invention relates to a gasket assembly comprising: a closed periphery core of compressible sealing material, the core having upper and lower planar surfaces and radially inner and outer edges; a first cover component enclosing the radially outer edge and a relatively minor portion of the upper and lower planar surfaces; a second cover component enclosing the radially inner edge and a relatively major portion of the upper and lower planar surfaces, wherein upper and lower sides of the second cover component overlap upper and lower sides of the first cover component; and further wherein free edge portions of the second cover component are formed to include hollow, continuous annular ribs, respectively, projecting away from the closed periphery core. 
         [0005]    In still another exemplary but nonlimiting aspect, the invention relates to a method of sealing adjacent, annular bolt flanges on respective machine components comprising: forming an annular gasket groove in one of the bolt flanges; providing an inner core of compressible sealing material; enclosing the inner core with a pair of cover components, one having a radially outer edge and first upper and lower sides, and the other having a radially inner edge and second upper and lower sides that overlap the first upper and lower sides, free end portions of the second upper and lower sides formed to include respective continuous, hollow ribs projecting away from the inner core, the free end portions engageable with the first upper and lower sides; inserting the gasket assembly in the groove; and securing the bolt flanges. 
         [0006]    The invention will now be described in connection with the drawings identified below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a partial perspective view, partially cut away, illustrating a combustor casing flange formed with a groove for receiving a gasket in accordance with an exemplary embodiment of the invention; 
           [0008]      FIG. 2  is an enlarged partial perspective view of a gasket assembly in accordance with an exemplary embodiment of the invention; and 
           [0009]      FIG. 3  is a cross section taken through the gasket assembly shown in  FIG. 3 , and seated in the casing groove shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    With reference initially to  FIG. 1 , a combustor casing  10  is formed with, or provided with, a bolt flange  12  at one end thereof, the bolt flange formed with a circular array of bolt holes  14  used to secure the casing  10  to another machine component. The forward or mounting surface  16  of the bolt flange  12  is also formed with a gasket groove  18  radially inwardly of the array of bolt holes  14 . The gasket groove  18  is in the form of an open channel, and includes a base surface  20 , an inside groove wall  22  and an outside wall  24 . The groove is sized to receive a gasket  26  assembly described in further detail below. 
         [0011]    Turning to  FIGS. 2 and 3 , the gasket assembly  26  is formed with an inner closed periphery core  28  of relatively soft sealing material, preferably graphite, the surface properties of which are similar to graphite gaskets currently in use. The core  28  has inner and outer edges  30 ,  32  and top and bottom surfaces  34 ,  36 , respectively. A substantially backwards C-shaped platen ring (or first inner cover component)  38  having an outer edge  40  and upper and lower sides  42 ,  44  is applied over the radially outer edge  32  of the graphite core  28  and minor portions of the top and bottom surfaces  34 ,  36 , terminating at edges  46 ,  48 . The platen ring  38  is preferably constructed of a relatively heavy stainless steel material that is precompressed, and thus not easily deformed from the shape illustrated in the drawings. 
         [0012]    A substantially C-shaped second outer cover component  50  having an inner edge  52  and upper and lower sides  54 ,  56  encloses the inner edge  30  of the core  28 , extending over the remaining major portions of the top and bottom surfaces  34 ,  36  of the core and overlapping the upper and lower sides  42 ,  44  of the platen ring  38 . 
         [0013]    The outer cover component  50  is preferably constructed of a softer metal such as copper, and the upper and lower sides  54 ,  56  thereof are formed with embossments  58 ,  60  adjacent free edges  62 ,  64  thereof. The embossments  58 ,  60  comprise continuous hollow ribs that extend about the entire closed periphery of the gasket. Note that the free edges  62 ,  64  terminate short of, but adjacent the outer edge  40  of the platen ring  38 . Thus, the inner and outer components  38 ,  50  may be assembled about the core  28  by pushing the inner and outer components  38 ,  50  over the core  28  from opposite directions such that the upper and lower sides  54 ,  56  of the outer component  50  overlap the upper and lower sides  42 ,  44  of the inner component  38 . 
         [0014]    When installed, the inner edge  52  of the outer cover component  50  and the inner edge  40  of the platen ring  38  will engage the inner and outer walls  22 ,  24  of the groove  18 . When a matching bolt flange of another component (not shown) is applied to the bolt flange  12  and tightened, the gasket assembly  26  will be fully seated in the groove  18 , and embossments  42 ,  44  will be compressed and deformed as needed to conform with surface irregularities on the opposed bolt flanges. At the same time, the graphite core  28  remains fully enclosed and thus protected from harmful combustion gases. Note that the heavier first, inner cover component or platen ring  38  allows the embossments  42 ,  44  to be compressed onto a solid backing (I.e., the platen ring) as the gasket is installed, preventing damage to the core  28 . In addition, by terminating the free edges  62 ,  64  of the second cover component  50  short of the inner edge  40  of the platen ring  38 , space is provided for some radial expansion of the embossed edges under compression, uninhibited by the outer groove wall  24 , best appreciated from  FIG. 3 . 
         [0015]    The ability of the gasket assembly  26  to conform to surface irregularities and to also protect the inner graphite core  28  from exposure to harsh conditions, substantially eliminates leakage issues experienced with unprotected graphite gaskets. 
         [0016]    It will be appreciated that the gasket construction need not be of a closed periphery design, but may also be used where other machine components are joined, with gaskets required only in certain areas thereof. 
         [0017]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.