Abstract:
A lock link for locking variable stage stator vanes in a compressor includes a substantially planar body portion having a slot formed on one edge and a narrow neck portion extending away from an opposite edge, the narrow neck portion adapted to seat in a corresponding slot in an adjacent lock link attached to an adjacent vane; and a profiled opening in the substantially planar body portion adapted to receive a key provided on a vane stem to prevent relative rotation between the vane and the lock link.

Description:
BACKGROUND 
       [0001]    This invention relates to turbine and/or compressor vanes and particularly to a mechanism by which all of the variable stator vanes in an annular row of such vanes can be locked in a desired angular orientation. 
         [0002]    Variable stage vanes in multi-stage turbine compressors are used to address surge/stall conditions in the compressor. Typically, each vane is provided with a vane arm for rotating the vane, and the vane arms in the stage are connected to a sync or unison ring, bolted to the compressor case, that enables simultaneous rotation of all of the vanes in the stage. There are occasions, however, when testing establishes that the variable feature is not required for a particular stage of the multi-stage compressor. Converting a tested variable vane or airfoil arrangement in a selected stage to a fixed vane or airfoil arrangement in the same stage require another complete compressor test. This can be avoided, however, by locking the variable stage vanes from rotation in the respective stage, and several techniques have been utilized to effect the change from variable to fixed vanes. 
         [0003]    For example, it has been proposed to use rigid links to lock the sync or unison ring but this approach is undesirable in that the heavy and cumbersome unison ring hardware is retained, thus also adding to the overall cost. 
         [0004]    In order to save weight and eliminate some of the complexity of sync or unison rings, there have been attempts to eliminate the vane arm and sync or unison ring in favor of vane locks that join adjacent vanes and lock them in the selected position. See, for example U.S. Pat. No. 5,211,537. This approach is problematic in that the vanes have to be removed in order to install the vane locks, and to remove the vanes in the lower half of the turbine case, the rotor must be pulled from the case. 
         [0005]    While there are many ways to lock a variable vane arrangement in place, there remains a need for a locking arrangement that does not alter the loaded condition of the vane during operation. In other words, the locking arrangement should load the vane in substantially the same manner as an unlocked vane during turbine operation. In addition, it would be advantageous to provide a single lock-link design for use with all vanes in the selected row of vanes. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    In one exemplary but nonlimiting embodiment, the invention provides a lock link for locking variable stage stator vanes in a compressor stator comprising a substantially planar body portion having a slot formed on one edge and a narrow neck portion extending away from an opposite edge, the narrow neck portion adapted to seat in a corresponding one of the slots in an adjacent lock link; a profiled opening in the substantially planar body portion; and at least one inwardly projecting load tab. 
         [0007]    In another exemplary but nonlimiting embodiment, the invention provides a turbine system comprising a compressor; a turbine operatively connected to the compressor via a rotor; wherein the compressor comprises multiple stages, at least some of which comprise respective rows of variable stator vanes attached to a compressor case and further wherein at least one of the respective rows of variable stator vanes is provided with link locks for locking all of the variable stator varies against rotation, each lock link comprising a substantially planar body portion having a slot formed on one edge and a narrow neck portion extending away from an opposite edge, the narrow neck portion seated in a corresponding one of the slots in an adjacent lock link; and a profiled opening in the substantially planar body portion received over a complementary-shaped stem of a respective stator vane. 
         [0008]    In still another exemplary but nonlimiting embodiment, the invention provides a compressor stator comprising at least one row of variable stator vanes attached to a compressor case, the stator vanes having radially outward stems projecting outside the compressor case, the stems provided with link locks for locking all of the variable stator vanes against rotation, each lock link provided with a substantially planar body portion having a slot formed on one edge and a narrow neck portion extending away from an opposite edge, the narrow neck portion seated in a corresponding one of the slots in an adjacent lock link; a profiled opening in the substantially planar body portion received over a respective one of the stems, the profiled opening and the stem shaped to prevent relative rotation therebetween; and a load tab on the lock link adapted to pry its respective stator vane or an adjacent stator vane in a radially outward direction toward the compressor case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a partial and simplified cross section of a conventional multi-stage, variable stator vane compressor; 
           [0010]      FIG. 2  is a partial end view of compressor vanes incorporating lock links in accordance with a first exemplary but nonlimiting embodiment of the invention, with the compressor case removed for the sake of clarity; 
           [0011]      FIG. 3  is a plan view of the compressor vanes as shown in  FIG. 2  but also illustrating the compressor case; 
           [0012]      FIG. 4  is a partial end view of a lock link load tab in accordance with the first exemplary embodiment; 
           [0013]      FIG. 5  is a partial end view of a lock link load tab in accordance with the second exemplary embodiment; 
           [0014]      FIG. 6  is a partial end view of a lock link load tab in accordance with the third exemplary embodiment; 
           [0015]      FIG. 7  is a partial perspective view of lock links in accordance with the first exemplary embodiment, with vane stem fasteners removed to show details of the lock links; 
           [0016]      FIG. 8  is a partial end view of two of the vanes/lock links taken from  FIG. 7  from outside the compressor case; 
           [0017]      FIG. 9  is a partial perspective view of lock links in accordance with a second exemplary but nonlimiting embodiment, applied to a row of stator vanes; 
           [0018]      FIG. 10  is a partial perspective view of lock links in accordance with a third exemplary but nonlimiting embodiment, applied to a row of stator vanes; 
           [0019]      FIG. 11  is a partial perspective view of lock links in accordance with a fourth exemplary but nonlimiting embodiment, applied to a row of stator vanes; 
           [0020]      FIG. 12  is a partial plan view of lock links in accordance with a fifth exemplary but nonlimiting embodiment of the invention; and 
           [0021]      FIG. 13  is a partial end elevation of the lock links of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]      FIG. 1  illustrates a multi-stage, variable vane compressor  10  including a rotor (represented by rotor axis  12 ) mounting plural wheels  14 , each supporting a circumferential row of buckets  16 . Between the wheels  14  are rows of fixed stator vanes  18  supported on the compressor case. In the compressor embodiment shown, each vane in the rows where the vanes are of the variable type, is provided with a vane arm  20  that attaches to a sync or unison ring assembly  22  that rotates relative to the compressor case  24  to simultaneously rotate each vane about its longitudinal axis to thereby uniformly change the vane angle throughout the entire row. 
         [0023]    This invention, relates to a unique locking mechanism for locking otherwise variable vans in a selected angular position, using identical lock links about the periphery of the row. 
         [0024]    Turning to  FIGS. 2 and 3 , a row  26  of otherwise variable vanes  28  is supported from the compressor case  24  ( FIG. 3 ), with threaded stems  30  projecting through the case and secured by fasteners (e.g., nuts)  32 . It will be understood in the context of this invention that for a row of variable stator vanes supported in conventional fashion, the vane arms (see arms  20  in  FIG. 1 ) and associated sync or unison ring have been removed). In accordance with a first exemplary but nonlimiting embodiment of the invention, self-locking links  34  are attached to the vane stems  30  of adjacent vanes, with one end of each link engaging the opposite end of the next successive link (as viewed, for example, in a right-to-left direction in  FIG. 3 ). Each lock link  34  is formed to include a main body portion  36  and an extended, narrow neck portion  38  provided with a load tab  40  at its distal end. In this first exemplary embodiment, the load tab  40  projects radially inwardly as seen, for example, in  FIG. 2 .  FIGS. 4 ,  5  and  6  show different possible load tab configurations including a presently preferred rivet  42  with flattened underside  44  ( FIG. 4 ); load tab  46  welded to the narrow neck portion  48  ( FIG. 7 ); and integral load tab  50  formed on the end of narrow neck portion  52 . 
         [0025]      FIG. 7  shows the lock links  34  in more detail in that the fasteners  32  have been removed to reveal the manner in which a center pedestal portion  54  of the of the lock link  34  engages the vane stem  52 . Specifically, in the exemplary embodiment, the vane stem is formed with an eccentric D-shaped key  56  which, in the exemplary embodiment, is generally rectangular in shape, with one rounded side  58  and an opposite flat side  60 . The round pedestal portion  54  of the lock link  34  is provided with a cut-out  62  that mates with the key  56  thereby preventing any relative rotation between the lock link  34  and the vane stem  30  (and hence the vane  26 ). An undercut  64  is formed at the base of the stem  30  where it is joined to the key  56 , and the undercut lies above the pedestal portion  54  of the lock link when the lock link is located over the key, as best seen in  FIG. 8 . The undercut provides a required amount of clearance or “play” to facilitate assembly and alignment of the vanes. 
         [0026]    At the opposite end of each lock link  34 , a slot  66  is provided to receive the narrow neck portion  38  of the adjacent lock link (as best seen in  FIGS. 3 and 7 ), when the lock links are assembled on their respective vanes and engaged with each other as shown. It will be appreciated that, once the links are assembled as shown, the vanes  28  in the entire row are locked together against any differential or relative rotation by reason of the inter-engagement of the narrow neck portions  38  and slots  66 . As the fastener  32  is tightened down against the pedestal portion  54  of a respective lock link, the load tab  42  loads against the outer surface of the case  24 , and as the load tab flexes, the stem/vane is pryed in a radially-outward direction against the inner surface of the case  24 , simulating the normal loading condition for a conventional variable vane connected to a vane arm. In other words, the load tab acts as a spring and prys the vane outwardly against the case, taking up the inherent loose tolerances between the various components required for assembly, including the assembly space created by undercut  64 . Thus, the lock link system as described herein loads the vanes in the same way as the conventional vane arm/unison ring configuration, but in a simpler and less costly arrangement which eliminates the need for the vane arm and synch or unison ring. In addition, only a single lock link design is required for all of the lock links in the chosen compressor stage. 
         [0027]      FIG. 9  illustrates another exemplary embodiment where the lock link  68  is formed to include a pair of spaced narrow neck portions  70 ,  72  and associated load tabs (not visible in  FIG. 9  but may be as shown in  FIGS. 4-6 ) that engage within corresponding slots  74 ,  76  in the adjacent lock link. The spaced narrow neck portions and associated load tabs spread the forces on either side of the vane stem but the lock links otherwise function as described in connection with the embodiments illustrated in  FIGS. 2-8 . 
         [0028]      FIG. 10  shows another variant where the lock link  78  is formed with a narrow-neck portion  80  having an oval-shaped distal end received within a correspondingly-shaped slot  82 . Here again, it will be understood that any of the above-described load tab configurations can be provided at the distal end of the narrow-neck portion  80 . 
         [0029]      FIG. 11  shows yet another exemplary embodiment where the lock link  84  is provided with a load tab  86  extending from the main body portion  88  of the lock link rather than at the distal end of the narrow neck portion  89 . Here, the load tab  86  is formed along one of the side edges of the lock link main body portion, extending substantially perpendicular to the row of vanes, and perpendicular to the narrow-neck portion  89 . 
         [0030]    The embodiments described in  FIGS. 1-11  are particularly beneficial in that the individual lock links can be installed without removing the vanes themselves. 
         [0031]    In another exemplary embodiment, the lock links are configured to load the adjacent link and hence the adjacent vane. With reference to  FIGS. 12 and 13 , lock links  90  are shown attached to corresponding vane stems  98  in a manner similar to the embodiment shown in  FIGS. 2-10 . Here, however, it can be seen that the narrow-neck portion  92  of the lock link extends below the main body portion  94  of the adjacent lock link, and is received within a notch  96  formed on the underside of the adjacent lock link. In this embodiment, the notch is not “open” from top to bottom as in the lock link construction in  FIGS. 1-11  but rather, the notch is “closed” on the top side of the lock link for the purpose described below. As in the previously described embodiment, the collective inter-engagement of the lock links and their respective vane stems  98  and engagement of the narrow neck portions  92  within the notches  96  prevents any relative rotation between the lock links and the corresponding vanes. 
         [0032]    In addition, the load tab  100  is now provided on the underside of the lock link, substantially at the interface between the main body portion  94  and the narrow neck portion  92 . The load tab  100  may be welded to the respective lock link, provided in the form of a rivet, or the entire lock link could be machined from a single blank. In this exemplary embodiment, the load tab serves as a fulcrum so that, as the nut  102  is tightened on the threaded stem  98  of the vane and thus pushing the main body  94  of the lock link  90  radially inwardly, the opposite end of the lock link, i.e., the narrow-neck portion  92   a,  pushes the adjacent lock link and its respective vane in a radial outward direction by reason of its engagement within the closed notch  96 , and thus drawing the vane up against the interior surface of the compressor case. Note that the case  104  is removed from  FIG. 13  for ease of understanding. 
         [0033]    As in the first-described embodiment, the narrow-neck portion  92  could be formed with an oval-shaped distal end. Alternatively, the lock link  90  could be provided with a pair of laterally spaced narrow-neck portions (see  FIG. 9 ) and/or a pair of axially-spaced load tabs  100  to spread the loads on the adjacent lock link in a manner somewhat similar to the lock link shown in  FIG. 9 . 
         [0034]    While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.