Abstract:
A variable vane actuation system with a plurality of vanes which may be rotated to change an approach angle of associated airfoils. A cylinder drives a piston rod to in turn cause a linkage system to vary the approach angle of the airfoils. The cylinder has a tailstock at an end remote from the piston rod. A spherical bearing mounts the tailstock. A bearing retainer provides a stop to prevent undue rotation of the tailstock relative to the bearing. A compressor and a gas turbine engine are also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a bearing retainer that prevents undesired rotation of the actuator for a variable vane system. 
         [0002]    Gas turbine engines are known, and typically include a fan delivering air into a compressor section. The air is compressed in the compressor section, and delivered downstream into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. 
         [0003]    The compressor section typically includes a plurality of compressor stages having rotors carrying a plurality of rotating blades. Intermediate the compressor stages are static vanes, which serve to redirect the airflow between the compressor stages. 
         [0004]    A desired approach angle for the air may vary during operation of the gas turbine engine, and dependent upon operational conditions. Thus, it is known to provide so-called variable vanes which are pivotably mounted such that their angle can be changed. Typically, a single actuator drives a ring to rotate, and this rotation causes the orientation of a plurality of vanes to be changed. 
         [0005]    One known actuator includes a piston rod of a cylinder to cause the rotation of a bell crank. The cylinder is mounted at a rear end on a spherical bearing, and the piston is also mounted on a spherical bearing within a clevis. 
         [0006]    The use of the spherical bearings allows some misalignment such as may be due to manufacturing tolerances or thermal displacement. 
         [0007]    However, when stresses and force are placed on the actuator, and in particular the piston rod, the cylinder may rotate about its own axis. When this occurs, the cylinder or its mount structure may strike a mount structure associated with a housing. This is undesirable. 
       SUMMARY OF THE INVENTION 
       [0008]    In a featured embodiment, a variable vane actuator has a plurality of vanes which may be rotated to change an approach angle of associated airfoils. A cylinder is mounted to drive a piston rod to in turn cause a linkage system to vary the approach angle of the airfoils. The cylinder has a tailstock at an end remote from the piston rod. The tailstock is pivotably mounted within a clevis, and on a bolt. A spherical bearing is between the bolt and tailstock, and includes an inner member riding on the bolt and having a spherical outer surface, and an outer member which moves with the tailstock, and a spherical inner surface moveable on the spherical outer surface of the inner member. The clevis includes two spaced ledges. A bearing retainer is between one of the ledges and the spherical bearing. The bearing retainer is formed of a material that is softer than a material forming the tailstock such that the bearing retainer provides a stop to prevent undue rotation of the tailstock and the outer member relative to the inner member. 
         [0009]    In another embodiment according to the previous embodiment, the bearing retainer has a shape of a top hat, with an extension extending from a planer section. The planer section abuts the spherical bearing. The extension fits within an opening in one of the ledges. The bolt extends through the extension, through the planer portion, through the inner member, and then through a second of the ledges. 
         [0010]    In another embodiment according to any of the previous embodiments, the bearing retainer is generally cylindrical. 
         [0011]    In another embodiment according to any of the previous embodiments, the bearing retainer has a truncated portion associated with a limited circumferential extent of the bearing retainer. The truncated portion is positioned adjacent an under surface of the cylinder from which the tailstock extends. 
         [0012]    In another embodiment according to any of the previous embodiments, the bearing retainer is formed of one of a composite or metal. 
         [0013]    In another embodiment according to any of the previous embodiments, a first gap is defined between the bearing retainer and tailstock, and a second gap is defined between a second of the ledges and tailstock. The first gap is smaller than the second gap. 
         [0014]    In another embodiment according to any of the previous embodiments, one of the ledges receives a head of the bolt. 
         [0015]    In another featured embodiment, a compressor section has a plurality of compressor stages spaced for rotation about a central axis. A plurality of vanes is positioned between adjacent ones of the plurality of compressor stages, with the plurality of vanes provided with an airfoil for directing air to a downstream compressor stage. An approach angle of the plurality of airfoils is changeable by an actuator. The actuator includes a cylinder mounted to drive a piston rod to in turn cause a linkage system to vary the approach angle of the airfoils. The cylinder has a tailstock at an end remote from the piston rod, with the tailstock being pivotably mounted within a clevis, and on a bolt. A spherical bearing is between the bolt and tailstock, with the spherical bearing including an inner member riding on the bolt and having a spherical outer surface. An outer bearing member moves with the tailstock, and has a spherical inner surface moveable on the spherical outer surface of the inner member. The clevis includes two spaced ledges. A bearing retainer is between one of the ledges and the spherical bearing and tailstock. The bearing retainer is formed of a material that is softer than a material forming the tailstock such that the bearing retainer provides a stop to prevent undue rotation of the tailstock and the outer member relative to the inner member. 
         [0016]    In another embodiment according to the previous embodiment, the bearing retainer has a shape of a top hat, with an extension extending from a planer section. The planer section abuts the spherical bearing. The extension fits within an opening in one of the ledges, with the bolt extending through the extension, through the planer portion, through the inner member, and then through a second of the ledges. 
         [0017]    In another embodiment according to any of the previous embodiments, the bearing retainer is generally cylindrical. 
         [0018]    In another embodiment according to any of the previous embodiments, the bearing retainer has a truncated portion associated with a limited circumferential extent of the bearing retainer, with the truncated portion positioned adjacent an under surface of the cylinder from which the tailstock extends. 
         [0019]    In another embodiment according to any of the previous embodiments, the bearing retainer is formed of one of a composite or metal. 
         [0020]    In another embodiment according to any of the previous embodiments, a first gap is defined between the bearing retainer and tailstock, and a second gap is defined between a second of the ledges and tailstock. The first gap is smaller than the second gap. 
         [0021]    In another embodiment according to any of the previous embodiments, one of the ledges receives a head of the bolt. 
         [0022]    In another featured embodiment, a gas turbine engine has a compressor section, a combustor, and a turbine section. The compressor section includes a plurality of compressor stages spaced for rotation about a central axis. A plurality of vanes is positioned between adjacent ones of the plurality of compressor stages, with the plurality of vanes being provided with an airfoil for directing air to a downstream compressor stage. An approach angle of the plurality of airfoils is changeable by an actuator. The actuator includes a cylinder mounted to drive a piston rod to in turn cause an actuator to vary the approach angle of the airfoils. The cylinder has a tailstock at an end remote from the piston rod. The tailstock is pivotably mounted within a clevis, and on a bolt. A spherical bearing is between the bolt and tailstock, and includes an inner member riding on the bolt and having a spherical outer surface, and an outer bearing member which moves with the tailstock. A spherical inner surface is moveable on the spherical outer surface of the inner member. The clevis includes two spaced ledges. A bearing retainer is between one of the ledges and the spherical bearing and tailstock. The bearing retainer is formed of a material that is softer than a material forming the tailstock such that the bearing retainer provides a stop to prevent undue rotation of the tailstock and the outer member relative to the inner member and the bolt. 
         [0023]    In another embodiment according to any of the previous embodiments, the bearing retainer has a shape of a top hat, with an extension extending from a planer section. The planer section abuts the spherical bearing. The extension fits within an opening in one of the ledges, with the bolt extending through the extension through the planer portion, through the inner member, and then through a second of the ledges. 
         [0024]    In another embodiment according to any of the previous embodiments, the bearing retainer is generally cylindrical. 
         [0025]    In another embodiment according to any of the previous embodiments, the bearing retainer has a truncated portion associated with a limited circumferential extent of the bearing retainer. The truncated portion is positioned adjacent an under surface of the cylinder from which the tailstock extends. 
         [0026]    In another embodiment according to any of the previous embodiments, a first gap is defined between the bearing retainer and tailstock, and a second gap is defined between a second of the ledges and the tailstock. The first gap is smaller than the second gap. 
         [0027]    In another embodiment according to any of the previous embodiments, one of the ledges receives a head of the bolt. 
         [0028]    These and other features of this application will be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1A  schematically shows a gas turbine engine. 
           [0030]      FIG. 1B  shows an alternative engine. 
           [0031]      FIG. 2  shows an actuator structure for use in the  FIG. 1  engine. 
           [0032]      FIG. 3  is a cross-sectional view through a mount incorporated into the present invention. 
           [0033]      FIG. 4  shows a detail of a top hat bearing retainer. 
           [0034]      FIG. 5  is a perspective view of the bearing retainer. 
           [0035]      FIG. 6  is a section along axis  6 - 6  of  FIG. 3  showing rotation. 
           [0036]      FIG. 7  shows rotation in a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      FIG. 1A  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath B while the compressor section  24  drives air along a core flowpath C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. Also, industrial gas turbines will come within the scope of this application. 
         [0038]    The engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0039]    The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
         [0040]    The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes airfoils  59  which are in the core airflow path. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
         [0041]    As is clear,  FIG. 1A  is a highly schematic view. Among the components of the compressor section  24 , are a plurality of compressor stages  300  in both the high pressure and low pressure compressors. The compressor stages  300  are each defined by a plurality of rotating blades. Intermediate the stages are a plurality of static vanes  301 . The static vanes may be fixed, or may be variable vanes. The variable vanes have an airfoil that may be rotated to adjust an approach angle of the air from one compressor stage approaching the next downstream compressor stage. 
         [0042]      FIG. 1B  shows an alternative engine  420  that would also have a compressor with variable vanes. Engine  420  is shown to schematically include a compressor section  422  delivering compressed air into a combustor section  424 . A turbine section  426  is downstream of the combustor section  424 , and serves to drive the compressor  422 . In addition, a generator  427  is shown schematically for generating electricity. 
         [0043]    Additional turbine stages  428  may be driven by products of the combustion to in turn drive a generator  430 . Engine  420  is an industrial gas turbine, such as may be utilized in land-based applications to generate electricity. The features of this application would apply to this type engine as well. 
         [0044]      FIG. 2  shows an actuator drive  75  which includes a cylinder  80  that drives a piston rod  88  outwardly or inwardly. The cylinder driver may be fluid, or may be electrical, mechanical, etc. The piston is pivotally connected at  94  to a clevis  90 . Clevis  90  drives a sync ring rod  92 . As is known, the rod  92  causes a ring to rotate, and this then adjusts the angle of a plurality of vanes, such as the vanes  301  shown in  FIG. 1 . The actuation of the vanes, and the reason for changing the approach angle of the vanes are as known in the art. 
         [0045]    This application relates to improvements in a tailstock mount, which mounts a tailstock  82  associated with the cylinder  80  in a clevis  84  on a static housing. As shown, a bolt  86  mounts the tailstock  82  in the clevis  84 . 
         [0046]      FIG. 3  is a cross-sectional view through this connection, and shows a nut  106  locking the bolt  86  in the clevis, and locking the tailstock  82  of the cylinder  80 . As shown, the clevis  84  includes two side ledges  100 , and the bolt  86  extends through openings in those two ledges  100 . The tailstock  82  is mounted on the bolt  86  through a spherical bearing  102 / 104 . The spherical bearing includes an inner spherical portion  104  which is fixed with the bolt  86 , and an outer portion  102  which is fixed to the tailstock  82 . As shown, a bearing retainer  110  forces the bearing against an opposed ledge  100 . The bearing retainer  110  has the shape of a top hat, and includes an extending portion  111  received within an opening in one ledge  100 , and a planer portion  112  which abuts the bearing. An edge  121  of the bearing retainer  110  faces the tailstock. The bolt  86  clamps the bearing retainer  110  and bearing inner spherical portion  104  against one side ledge. 
         [0047]    As shown in  FIG. 4 , the retainer  110  has a flat edge  113  which is truncated compared to an otherwise cylindrical shape  115 . The truncated portion  113  provides clearance adjacent to a lower surface  302  of the cylinder  80 . 
         [0048]      FIG. 5  shows details of the retainer  110 . 
         [0049]    As shown in  FIG. 6 , the tailstock  82 , and the outer bearing portion  102  have rotated on the inner spherical bearing portion  104 . In the past, this could allow the tailstock  82  to contact one of the ledges  100 , which could cause damage to the ledge or the tailstock. However, as shown at  130 , with this rotation, the tailstock is abutting a portion of the retainer  110  as shown at  130 . This prevents further rotation. 
         [0050]    The  FIG. 7  discloses a distinct assembly  500  wherein the bearing retainer  210  is positioned adjacent the opposed ledge from the ledge that receives a head  300  of bolt  86 . Again, with rotation, there is contact between retainer  210  and the tailstock as shown at  131 . It should be understood the bearing retainer could be at either side. 
         [0051]    Returning to  FIG. 3 , a first gap  113  between the edge  121  of the bearing retainer  110  and the tailstock  82  is less than a second gap  109  between the tailstock  82  and the opposed ledge  100 . This results in the gap  315  also being greater than the gap  113 . Thus, when misalignment, as illustrated in  FIG. 6 , occurs, the contact will occur between edge  121  and tailstock  82 , rather than at the opposed side  215 . The same gaps are found in the  FIG. 7  assembly. 
         [0052]    The retainer  110  is formed of a composite or metal such as aluminium or steel. Generally, the retainer  110  should be formed of a softer material than the material used for the actuator tailstock, or the bearing outer surface  102 . Thus should there be damage due to the rotation, it will be the less expensive retainer  110  which is damaged. 
         [0053]    While 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.