Turbine vane prediction and classification gage and gaging method

Claim 1

An instrument for gaging a production turbine vane having an airfoil with convex and concave surfaces and a sharp trailing edge, root and tip buttresses at the ends of said airfoil with inner confronting shoulder surfaces presented longitudinally of said airfoil, and a class surface along one edge of the tip buttress facing in the same direction as said convex airfoil surface, said airfoil having root and tip chord stations adjacent said root and tip buttresses, respectively, and a center chord station adjacent the center of the airfoil, said instrument comprising: a frame; means on said frame for locating said vane in a fixed gaging position relative to said frame wherein said airfoil chord stations are located in fixed spaced parallel planes of said frame; said locating means comprising means for pivotally seating said airfoil trailing edge to pivotally support said vane on a fixed pivot axis of said frame transverse to said planes, a first fixed vane stop at one side of said axis including a vane engaging element fixed against movement relative to said frame and located in the tip chord station plane of the frame a distance from said axis for engaging said convex airfoil surface in said latter plane at a position spaced from the airfoil trailing edge to locate said vane at a fixed angle relative to said frame, and a second fixed vane stop including a vane engaging element fixed against movement relative to said frame and located on a second axis normal to said planes for engaging one buttress shoulder surface of said vane to locate said vane in a fixed position relative to said frame longitudinally of the vane airfoil; first and second vane gages on said frame at said one side of said pivot axis in the center and root chord station planes, respectively, of said frame, each gage including means movable along an axis in the respective gage plane and offset from said pivot axis for engaging said convex airfoil surface in the respective gage plane at a position spaced from the airfoil trailing edge and an electrical transducer for producing an output voltage representing the position of said gage vane engaging means along its axis of movement; a third vane gage on said frame at the opposite side of said pivot axis and directly opposite said first gage including means movable along an axis in said center chord station plane parallel to the axis of movement of the vane engaging means of said first gage and intersecting said pivot axis for engaging the concave airfoil surface along said airfoil trailing edge, and an electrical transducer for producing an output voltage representing the position of said third gage vane engaging means along its axis of moVement; a fourth vane gage on said frame including means movable along said second axis for engaging the other vane buttress shoulder surface, and an electrical transducer for producing an output voltage representing the position of the latter vane engaging means along its axis of movement; a fifth vane gage on said frame including means engagable with said class surface for producing an output voltage representing the angle of said class surface relative to a given plane of said frame normal to said chord station planes; and a computer coupled to the outputs of said gages including mode selection means for conditioning said computer for operation in either a prediction gaging mode or a classification gaging mode, means operable in said prediction mode for combining the output voltages of said first, second, third, and fourth gages according to a selected prediction formula and producing an output representing the combined voltages while said vane remains fixed in said gaging position, and means operable in said classification mode for combining the output voltages of all of the gages according to a selected classification formula and producing an output representing the combined voltages while said vane remains fixed in said gaging position.