Patent Publication Number: US-6901821-B2

Title: Stator damper anti-rotation assembly

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for preventing tangential rotation of a damper used in a stator. 
     Anti-rotation devices are placed on stators to prevent the tangential rotation of spring damper assemblies used therein. Typically, these anti-rotation devices consist of pins or lugs welded into machined/EDM milled holes or slots on an edge of the stator inner air seal. The welds inherently crack during engine operation creating a risk of domestic object damage. 
     There is a need for an improved anti-rotation device for such stator spring damper assemblies which eliminates the risk of such domestic object damage. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved stator damper anti-rotation assembly. 
     It is a further object of the present invention to provide an assembly as above which significantly decreases the risk of domestic object damage. 
     It is yet a further object of the present invention to provide an assembly as above which has increased durability and which is easy to produce. 
     The foregoing objects are attained by the stator damper anti-rotation assembly of the present invention. 
     In accordance with the present invention, an assembly for preventing rotation of a damper used in a stator system of an engine is provided. The assembly broadly comprises a block which engages a slot in the damper to prevent rotation of the damper. The block is positioned within a groove milled in an inner air seal which forms part of the stator system. In a preferred embodiment of the present invention, side portions of the block are brazed to side edges of the groove to effectively eliminate any risk of domestic object damage. 
     Other details of the stator damper anti-rotation assembly of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a stator system having an inner air seal, a damper, and a damper anti-rotation device in accordance with the present invention; 
         FIG. 2  is a perspective view of the inner air seal used in the stator system of  FIG. 1  with the anti-rotation device of the present invention; 
         FIG. 3  is a sectional view of the anti-rotation device of the present invention taken along lines  3 — 3  of  FIG. 2 ; and 
         FIG. 4  is a perspective view of the damper and the slot for receiving the anti-rotation device of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring now to the drawings,  FIG. 1  illustrates a stator system  10 . The system  10  includes a stator  12 , an inner air seal  14  which mates with a lower portion  18  of the stator  12 , and a damper  16  positioned between the lower portion  18  of the stator and a surface  20  of the inner air seal  14 . The damper  16  may comprise any suitable damper known in the art, such as the spring type, metallic sheet damper shown in FIG.  4 . During operation of the engine of which the stator system  10  is part, tangential vibrations will cause rotation of the damper  16  unless the damper  16  is restrained from such movement. 
     In the instant invention, rotation of the damper  16  is prevented by the presence of a block  22  which fits within a slot  24  in the damper  16 . As can be seen from  FIG. 4 , damper  16  has a longitudinal axis and slot  24  is oriented perpendicular to the longitudinal axis. When assembled, the damper slot  24  engages the block  22  and thereafter traps the block  22  in place during engine operation. The engagement between the block  22  and the walls  36  of the damper slot  24  prevents rotation of the damper  22 . 
     As shown in  FIG. 2 , the block  22  is seated within a groove  26  machined in the inner air seal  14 . The block  22  is preferably located at a mid-span portion of the inner air seal  14 . This allows the damper  16  to be symmetric so it can fit on the inner air seal  14  in either direction. The groove  26  may be machined using any suitable technique known in the art. Preferably, the groove  26  is machined to a depth which is approximately fifty to sixty-five percent of the height h of the block  22 . The width of the groove  26  is determined by the width of the block  22 . If desired, the groove  26  may have rounded or arcuately shaped edges  28  joining substantially planar side edges  38 . The arcuately shaped edges  28  help properly seat the block  22 . 
     The block  22  may be formed from any suitable metallic or non-metallic material known in the art. As shown in  FIG. 3 , the block  22  has a substantially rectangular cross-section with chamfered edges  30  and  32 . The edges  30  and  32  are chamfered to assist in the positioning of the block  22  in the groove  26 . The chamfer depends on how much of the block  22  is to be fitted down into the groove  26 . The chamfer has to be sufficient to clear the radius in the groove  26 . 
     After the block  22  has been placed in the groove  26 , a line of brazing material  49  is applied to each side portion  34  of the block  22  and the corresponding side edge  38  of the groove  26  to secure the block  22  in place. The brazing material  49  may comprise any suitable brazing material known in the art and may be applied using any suitable brazing technique known in the art. The block  22  can be brazed to the inner air seal  14  during normal braze operations, thus eliminating the need for additional operations. The braze joint which is thus formed is a more robust means for attaching the block. If the braze joint fails during engine operation, the block  22  will be trapped in the groove  26 , thereby significantly decreasing, and effectively eliminating, any risk of domestic object damage. 
     As previously discussed, during engine operation, vibrations will tend to cause rotation of the damper  16 . This rotation is prevented by the interaction between the block  22  and the slot  24  in the damper  16 . 
     The anti-rotation device and damper assembly of the present invention has increased durability. Further, the anti-rotation device and damper assembly is easily reproducible and lends itself to use in a wide variety of stator assemblies. For example, the size of the block  22  and the damper slot  24  may be varied for different stator assemblies, thereby assuring that the correct damper assembles to the correct inner air seal and eliminating assembly mistakes. Producibility is improved due to the location and the shape of the block  22 . 
     It is apparent that there has been provided in accordance with the present invention a stator damper anti-rotation assembly which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Therefore, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.