Abstract:
A device and method for measuring the spacing between adjacent airfoils. A notched member engages a trailing edge of one of the adjacent airfoils with the notched member being rotatable about the one airfoil trailing edge. A wheel is rollable across the surface of the other airfoils while moving in a first direction toward and away from the notched member, and biased away from the notched member. A gauge secured to the notched member measures the distance of the guide from the notched member in the first direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       FIELD OF THE INVENTION 
       [0002]    The present application relates to measuring devices and more particularly devices for measuring spacing between airfoils. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gas turbines typically include components which operate at high speeds and are subjected to high mechanical loads at elevated temperatures. Proper and efficient operation of such turbines require precision in placement and relative orientation of the components, particularly the turbine airfoils. 
         [0004]    Typically, in the industrial gas turbine (IGT) industry, this requires checking the measurement of the minimum distance (“throat”) between two adjacent airfoils to ensure that proper airfoil positions are maintained. Such measurements are typically made at three radial positions, perpendicular to the trailing edge of an airfoil, with each turbine typically having a large number of such spaced airfoils. 
         [0005]    Heretofore, such measurements have typically been taken by first wedging either adjustable parallels or telescoping gauges into the expected throat position, and then maintaining those parallels/gauges in that position for subsequent measurement with Vernier calipers or micrometers. 
         [0006]    This technique can be time consuming, requiring not only positioning the parallels/gauges properly, but then separately measuring the parallels/gauges, with the results of such technique often being user dependent. Further, if the position of the parallels/gauges is not adequately maintained prior to measurement (by, e.g., a micrometer), added time can be required to reposition the parallels/gauges for each such measurement. Of course, if it is not noticed that the position is not properly maintained prior to measuring, this can also yield incorrect measurements. In fact, dimensional repeatability errors of 15-25% of the applicable tolerance have been found to occur even between skilled operators, 
         [0007]    The present invention is directed toward improving upon the efficiency and reliability of measuring between turbine airfoils. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect of the present invention, a device for measuring the spacing between adjacent airfoils is provided, including a notched member adapted to engage a trailing edge of one of the adjacent airfoils with the notched member being rotatable about the one airfoil trailing edge. A guide is movable across the surface of the other of the adjacent airfoils, the guide being secured for movement in a first direction toward and away from the notched member, the guide being biased away from the notched member. A gauge secured to the notched member measures the distance of the guide from the notched member in the first direction, 
         [0009]    In one form of this aspect of the invention, the guide is a wheel rotatable about an axis substantially parallel to the axis of rotation of the notched member about the one airfoil trailing edge, and the wheel rolls on the other airfoil when the notched member is rotated about the one airfoil. 
         [0010]    In another form of this aspect of the invention, the gauge includes a resettable indicator of the minimum spacing of the guide relative to the notch since the indicator was last reset. 
         [0011]    In still another form of this aspect of the present invention, the spacing between adjacent airfoils is measured by (a) positioning the measuring device with the trailing edge of the one adjacent airfoil in the notch member, (b) rotating the measuring device around the one airfoil trailing edge while maintaining the trailing edge in contact with the notch member, (c) maintaining the guide in contact with the other of the adjacent airfoils during the rotating step, and (d) determining from the measuring device gauge the minimum distance between the notch member and the guide during the rotating step. 
         [0012]    In another aspect of the present invention, a device for measuring the spacing between adjacent airfoils is provided, including a device frame having a longitudinal direction and a lateral direction, with a notched member on the frame adapted to engage a trailing edge of one of the adjacent airfoils, the notched member being rotatable about the one airfoil trailing edge. A wheel is secured to the frame for movement in the longitudinal direction, the wheel being aligned in the longitudinal direction with the notched member and biased away from the notched member. A gauge is secured to the frame and measures the position of the wheel relative to the notched member in the longitudinal direction. 
         [0013]    In one form of this aspect of the present invention, the gauge includes a resettable indicator of the minimum spacing of the wheel relative to the notch since the indicator was last reset. 
         [0014]    In another form of this aspect of the present inventon, the wheel is rotatable about an axis substantially parallel to the axis of rotation of the notched member about the one airfoil trailing edge, and the wheel rolls on the other airfoil when the notched member is rotated about the one airfoil. 
         [0015]    In still another form of this aspect of the present invention, the spacing between adjacent airfoils is measured by (a) positioning the measuring device with the trailing edge of the one adjacent airfoil in the notch member, (b) rotating the device frame around the one airfoil trailing edge while maintaining the trailing edge in contact with the notch member, (c) maintaining the wheel in contact with the other of the adjacent airfoils during the rotating step, and (d) determining from the measuring device gauge the minimum distance between the notch member and the wheel during the rotating step. 
         [0016]    In still another aspect of the present invention, a device for measuring the spacing between adjacent airfoils is provided, including a device frame having a longitudinal direction and a lateral direction and including a base having substantially flat first and second surfaces lying in first and second planes, respectively, with the frame being rotatable about a trailing edge of one of the adjacent airfoils with both the first and second surfaces engaging the one airfoil. A wheel is secured to the frame for movement in the longitudinal direction, with the wheel being aligned in the longitudinal direction with the frame base and biased away from the frame base. A gauge is secured to the frame, with the gauge measuring the position of the wheel relative to the frame base in the longitudinal direction. 
         [0017]    In one form of this aspect of the invention, the wheel rotates about an axis, and the first and second planes intersect along a line substantially parallel to the axis. 
         [0018]    In another form of this aspect of the invention, the base first surface extends in the lateral direction and the base second surface extends in the longitudinal direction, and the guide measures the distance in the longitudinal direction of the wheel from the base first surface. 
         [0019]    In yet another form of this aspect of the invention, the gauge includes a resettable indicator of the minimum spacing of the wheel relative to the notch since the indicator was last reset. 
         [0020]    In still another form of this aspect of the present invention, the spacing between adjacent airfoils is measured by (a) positioning the measuring device with the trailing edge of the one adjacent airfoil engaging the base first and second surfaces, (b) rotating the measuring device around the one airfoil trailing edge while maintaining the trailing edge in contact with the base first and second surfaces, (c) maintaining the wheel in contact with the other of the adjacent airfoils during the rotating step, and (d) determining from the measuring device gauge the minimum distance between the base and the wheel during the rotating step. 
         [0021]    Other objects, features, and advantages of the invention will become apparent from a review of the entire specification, including the appended claims and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a side cross-sectional view of one embodiment of the measuring device of the present invention; and 
           [0023]      FIG. 2  is a view of the measuring device in use measuring the spacing between two air foils. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The measuring device  10  of the present invention is illustrated in  FIG. 1 . The measuring device  10  includes a frame  14  with a longitudinal direction  16  and lateral direction  18 . 
         [0025]    A notched upper arm or base  20  is secured on one side of the frame  14  and includes a longitudinally extending flat surface  22  perpendicular to a laterally extending flat surface  24 , with the two surfaces  22 ,  24  together defining the notch  26 . The flat base surfaces  22 ,  24  lie in planes which intersect along a line perpendicular to both the longitudinal and lateral directions. The width of the flat surfaces  22 ,  24  (in the direction of the line of intersection) is sufficient to allow the device  10  to be rotated reliably about an airfoil trailing edge as described below without the device  10  wobbling out of the plane of the longitudinal and lateral directions. 
         [0026]    A gauge  30  which measures the spacing of airfoils (as further described hereinafter) is also secured to the frame  14 . 
         [0027]    A carriage or guide structure  40  is secured to the frame  14  so as to be longitudinally movable relative to the notched base  20 . In the illustrated embodiment, the guide structure  40  includes a longitudinally extending rail or guide rod  42  having a laterally extending guide arm  46  secured to its bottom. The guide rod  42  is reciprocal in the longitudinal direction relative to the frame  14 , with the gauge  30  measuring the longitudinal position of the guide rod  42 . 
         [0028]    The laterally extending guide arm  46  on the end opposite the guide rod  42  supports a rotatable wheel  48  which is aligned longitudinally with the notch  26  of the base  20 . The axis of rotation of the wheel  48  is substantially parallel to that line of intersection of the planes of the base surfaces  22 ,  24 . Suitable friction reducing bearings may be provided to facilitate free rotation of the wheel  48  about its axis. 
         [0029]    A biasing leg  50  is parallel to the guide rod  42  and is also suitably secured to the frame  14  so as to be movable linearly in a longitudinal direction relative to the notched base  20 . A suitable biasing mechanism, such as a tension spring  60 , is secured to the proximate (top) end of the leg  50  so as to continuously bias the leg  50  down, with the distal (bottom) end of the leg  50  adapted to push the guide arm  46  down (away from or toward out of the frame  14 ). A suitable stop structure is provided to limit such longitudinal movement to a maximum extension from the frame  14  such as illustrated in  FIG. 1 . 
         [0030]    Use of the measuring device  10  to measure the spacing between two airfoils  70 ,  80  is illustrated in  FIG. 2 . 
         [0031]    The upper arm or base  20  is positioned to cradle or nest with the trailing edge of one of the airfoils  70  so that both base surfaces  22 ,  24  contact the trailing edge. The measuring device  10  is then rotated or swept through an arc  84  about the airfoil trailing edge by maintaining the base surfaces  22 ,  24  in contact with the airfoil trailing edge during such rotation. The biasing of the carriage  40  (by, e.g., the tension spring  60 ) maintains the wheel  48  in contact and rolling across the surface of the other airfoil  80  during such device rotation about the airfoil trailing edge. At some point during that rotation, the carriage  40  will extend a minimum amount (e.g., at the position shown in  FIG. 2 ), such that rotation from that position will cause the carriage  40  to be biased further out from the frame  14 . 
         [0032]    It should be appreciated that measurements may be derived from the device  10  in a variety of manners, where the airfoil spacing measurement is the spacing between the base lateral surface  24  and the wheel  48 . (As used herein, spacing from the wheel  48  refers to spacing from the point on the outer surface of the wheel  48  which is furthest from the base lateral surface  24 , i.e., at the bottom perimeter of the wheel  48  tangential to the lateral direction). 
         [0033]    For example, the gauge  30  may be of the dial type with a dial indicator  90 , with the dial calibrated so that the position of its dial indicator  90  (or other suitable data indicator) reflects in a suitable manner the spacing at any given time of the base lateral surface and the wheel  48 . Thus, the position of the dial indicator  90  in  FIG. 1  would indicate that the surface  24 /wheel  48  spacing is the known maximum with the carriage  40  extended fully. When the device  10  is used as described, the dial indicator  90  will move as the carriage moves, such that the position of the dial  90 ′ as shown in  FIG. 2  indicates a lesser, known calibrated spacing. 
         [0034]    It should be appreciated that the dial may be read by the device user as it is swept through the arc  84 , whereby the person will mentally determine when the minimum spacing is indicated by the dial indicator  90 . A secondary, resectable dial indicator  92  may also be used, which dial indicator  92  is will travel with the primary dial  90  only in the direction indicative of decreasing spacing. With such a dial, the device  10  may be quickly swept through the arc  84  and then the position of the dial indicator  92  read afterwards to determine the minimum spacing. 
         [0035]    Still other gauges may be used while obtaining advantages of the present invention. For example, digital gauges could be used, with digital readouts indicative of spacing and/or transmitters suitable for transmitting the data to a suitable computer for use thereafter. 
         [0036]    It should be appreciated that measuring indicators  10  according to the present invention may be used to quickly and reliable obtain the minimum spacing between adjacent airfoils at numerous points. Moreover, such measurements will be accurate and consistent between different users.