Abstract:
A gas turbine engine includes a synchronizing ring. A cradle includes an integrally formed anti-rotation feature. The cradle is secured to the synchronizing ring and located relative thereto with the anti-rotation feature. A bumper is slidably supported within the cradle. In one example, a bushing is provided within a hole in the bumper. A fastener is inserted into the hole and a bushing to secure the bumper to the synchronizing ring.

Description:
[0001]    This invention was made with government support under Contract No. N00019-02-C-3003 awarded by the United States Navy. The Government has certain rights in this invention. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to a gas turbine engine synchronizing assembly. More particularly, the disclosure relates to bumpers used between a synchronizing ring and a compressor case. 
         [0003]    Some gas turbine engines utilize variable stator vanes that are actuated about their rotational axes to improve the overall compressor characteristics. A synchronizing assembly is used to manipulate the vanes. One type of synchronizing assembly includes a synchronizing ring that is slid relative to a compressor case by actuators. Multiple bumpers are circumferentially arranged between the synchronizing ring and the compressor case to facilitate movement of the synchronizing ring throughout the changing clearances during engine operation. 
         [0004]    In one example, the bumper is constructed from a composite polymer material. The bumper is secured to the synchronizing ring by fasteners. Typically, the composite polymer material is arranged between a head of the fastener and the synchronizing ring such that the composite polymer material is loaded under a clamping force. Over time, the composite polymer material fatigues and cracks, which requires service to the synchronizing assembly. 
         [0005]    One example bumper assembly includes a box-like structure machined out of titanium block. The box is secured to the synchronizing ring using a discrete locating pin to prevent rotation of the box during installation of a fastener that is used to secure the bumper assembly to the synchronizing ring. The locating pin must be very precisely machined. The bumper is secured within the box using an adhesive. 
       SUMMARY 
       [0006]    A synchronizing assembly for a gas turbine engine includes a synchronizing ring. A cradle includes an integrally formed anti-rotation feature. The cradle is secured to the synchronizing ring and located relative thereto by the anti-rotation feature. A bumper is supported within the cradle. 
         [0007]    In one example, the bumper includes a composite polymer block having a base and a projection integral with and extending from the base to a sliding surface. The base provides mounting flanges on opposing sides of the projection. A hole extends a depth through the base and the projection. The projection has a perimeter shape. A bushing is received in the hole and interference fit at an end opposite the mounting surface and includes a height less than the depth. 
         [0008]    A method of assembling the synchronizing assembly includes sliding the bumper into the cradle. The cradle is positioned onto the synchronizing ring with a locating feature arranged exteriorly of the synchronizing ring. A fastener is inserted through holes in the bumper and the cradle. The bumper is fastened to the synchronizing ring without clamping the bumper, for example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0010]      FIG. 1  is a highly schematic view of an example gas turbine engine with a synchronizing assembly. 
           [0011]      FIG. 2  is an exploded view of a portion of a synchronizing assembly and its corresponding compressor case. 
           [0012]      FIG. 3  is a side perspective view of another example synchronizing assembly. 
           [0013]      FIG. 4  is a bottom perspective view of the synchronizing assembly illustrated in  FIG. 3 . 
           [0014]      FIG. 5  is a cross-sectional view of the synchronizing assembly illustrated in  FIG. 3 . 
           [0015]      FIG. 6  is a perspective view of a bumper and a cradle illustrated in  FIGS. 3-5 . 
           [0016]      FIG. 7A  is a perspective view of another example cradle. 
           [0017]      FIG. 7B  is an end view of the cradle illustrated in  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A gas turbine engine  10  is schematically illustrated in  FIG. 1 . The engine  10  includes a core  12  having compressor, combustor and turbine sections  14 ,  16 ,  18 , which are housed within a core nacelle  20 . The core  12  is supported relative to a fan case by circumferentially arranged flow exit guide vanes  24 . A fan duct  26  is provided between the fan case  22  and the core nacelle  20  and receives airflow from a fan  28 . 
         [0019]    In the example engine  10 , the compressor section  14  includes at least one stage of variable stator vanes  30  that are actuated by a synchronizing assembly  31  to rotate the vanes  30  about their respective axes to improve the overall efficiency of the compressor section  14 . 
         [0020]    The synchronizing assembly  31  includes a synchronizing ring  34  interconnected to the vanes  30  by arms  33 . The synchronizing ring  34  is slidably mounted to a compressor case  32 . An actuator  36  moves the synchronizing ring  34  in a generally axial direction along an arcuate path to rotate the vanes  30 . Bumper assemblies  38  are arranged circumferentially between the synchronizing ring  34  and the compressor case  32 . As illustrated in  FIG. 2 , the bumper assemblies  38  are supported on pads  40  circumferentially arranged on the exterior of the compressor case  32 . The synchronizing ring  34  includes holes  100  that provide attachments for a clevis (not shown) that cooperates with the actuator  36  as is known. 
         [0021]    The synchronizing assembly  31  includes a synchronizing ring  34  that is connected to the vanes  30  ( FIG. 1 ) by arms  33 , as illustrated in  FIGS. 1 and 3 . Vane arm bushings  76  are received within and supported by the synchronizing ring  34  and are operatively coupled to the arms  33 . 
         [0022]    An example bumper arrangement is illustrated in  FIGS. 3-6 , which only utilizes a single fastener. A cradle  78  is constructed from a stamped piece of sheet metal, which may be constructed from nickel, for example. The cradle  78  includes a base  98  having an integral tab  82 , which is bent at generally a 90° angle relative to the base  98  in the example shown. The tab  82  abuts a lateral wall  44  of the synchronizing ring  34 , which prevents rotation of the cradle  78  during installation and operation of the synchronizing assembly  31 . The bumper  80  slides into the cradle  78  during assembly. In one example, the bumpers  80  are constructed from a composite polymer material, such as chopped fiber reinforced polyimide resin. In one example, the bumper is constructed from a DuPont VESPEL SCP-5050. 
         [0023]    The bumper  80  includes a projection  60  that is integral with and extends from a base  61  to a sliding surface  62 . The base  61  provides mounting flanges  88  on opposing sides of the projection  60 . The hole  90  extends a depth  66  through the base  61  and the projection  60 . The projection  60  has a perimeter shape, which is a quadrilateral, and in the example, a square. The sliding surface  62  is generally flat and engages the pads  40  when the synchronizing assembly  31  is installed on the engine  10 . 
         [0024]    The cradle  78  includes retaining walls  79  bent generally parallel to the base  98  to provide spaced apart channels  84 , which receive opposing flanges  88  extending from opposite sides of the bumper  80 . A hole  90 , which is central within the projection  60 , extends axially through the bumper  80 . A bushing  48  is press fit into the hole  90  with the bushing  48  near the synchronizing ring  34  opposite the sliding surface  62 . The bushing  48  includes a height  68  that is less than the depth  66 . In one example, the bushing  48  is constructed from a stainless steel material. A fastener  92  is received within the hole  90  and bushing  48  to secure the bumper  90  and cradle  78  to the synchronizing ring  34  using a retainer  94  or nut. The fastener  92  includes a head  96  that is generally the same diameter as the hole  90  to retain the bumper  80  within the cradle  78  without applying any clamping load to the composite bumper. The head  96  does not extend beyond the sliding surface  62 . In the example, the head  96  engages the bushing  48  such that that bumper  80  is not provided between the head  96  so that the bumper  80  is not loaded. 
         [0025]    The cradle  78  includes notches  86  in the area of the channels  84 , which provide clearance for the vane arm bushing  76 , as best shown in  FIG. 4 . A shim can be used between the cradle  78  and synchronizing ring  34 , if desired. A shim may be provided between the bumper assembly  38  and the wall  42  to provide the desired clearance between the circumferentially arranged bumper assemblies  38  and the compressor case  32 . Thus, any shim, the bushing  48  and the cradle  78  comprise the loaded structure in the synchronizing assembly  31 . 
         [0026]    Another example cradle  178  is illustrated in  FIGS. 7A and 7B . The cradle  178  includes a pair of tabs that are spaced from one another and extend from the base  198 . The tab  182  of the cradle  178  is bent relative to the base  98  in a first direction to provide a face  81  that is generally 90° from the base  98 . In the example shown in  FIGS. 7A and 7B , the tabs  182  are bent in a different direction and provide edges  181 , which abut the synchronizing ring  34  when assembled. 
         [0027]    Although example embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.