Abstract:
A blade processing fixture has first and second jaws. The second jaw is movable relative to the first jaw from a disengaged position for accepting a root of the blade. The blade is accepted in a receiving area between the first and second jaws. The second jaw is movable to an engaged position clamping the blade between the first and second jaws. A gas flow path extends from an inlet port to an outlet port. The outlet port is positioned to introduce gas to a blade inlet port when the blade is installed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional application of Ser. No. 11/326,929, filed Jan. 6, 2006 now abandoned, and entitled Turbine Element Repair Fixture, now abandoned, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to repair of turbine engine components. More particularly, the invention relates to fixtures for repairing turbine engine blades. 
     Turbine engine blades (including fan, compressor, and turbine section blades) are subject to wear and damage (e.g., foreign object damage (FOD)). Repair of such damage may include coating removal, machining of a wear/damage site, and/or the attachment of a scaffold material. The scaffold material may be externally attached, inserted, or in situ formed. The scaffold surface may define an external or internal surface of repair material built-up atop the scaffold. Exemplary build-up may be by welding (including laser cladding), brazing, or deposition. During repair, the blade may be held in a fixture. An exemplary fixture is a vise-like structure having drawers configured to grasp pressure and suction side surfaces of the blade airfoil. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention involves a fixture for processing a blade. The fixture has first and second jaws. The second jaw is movable relative to the first jaw from a disengaged position for accepting a root of the blade. The blade is accepted in a receiving area between the first and second jaws. The second jaw is movable to an engaged position clamping the blade between the first and second jaws. A gas flow path extends from an inlet port to an outlet port. The outlet port is positioned to introduce gas to a blade inlet port when the blade is installed. In various implementations, at least one of the jaws may be removable and replaceable with a structurally different jaw to permit the fixture to accommodate a structurally different blade. The fixture may be used in a build-up repair on the blade. During the repair, a suitably non-reactive gas may be introduced through the fixture to limit or avoid adverse reaction (e.g., oxidation) of a scaffold element, the blade parent material, and/or the deposition material. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a blade processing station. 
         FIG. 2  is a side view of a fixture from the station of  FIG. 1 . 
         FIG. 3  is a front view of the fixture of  FIG. 2 . 
         FIG. 4  is a bottom view of the fixture of  FIG. 2 . 
         FIG. 5  is a top view of the fixture of  FIG. 2 . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a station  20  for processing (e.g., repair) of a turbine element  22  (e.g., a gas turbine engine compressor or turbine section blade). The blade  22  is held by a fixture  24 . 
     An exemplary processing of the blade involves adding material (e.g., a build-up of material in a repair or restoration process). The processing may also or alternatively include removing material (e.g., preparatory or finish machining). An exemplary build-up of material may be by a welding process such as laser cladding. Accordingly, to apply the material, the station  20  may include a welding head  30 . To position the head  30  relative to the blade  22 , one or both of the head  30  and fixture  24  may be movable. For example, the fixture  24  may be mounted to an automatically controlled reference such as a five-axis rotary table  32 . An exemplary head is a laser cladding head having a nozzle  34  and metal powder feed lines  36 . 
       FIG. 2  shows further details of an exemplary blade  22  and fixture  24 . The blade has an airfoil  40 . The airfoil  40  extends from an inboard end  42  at a platform  44  to an outboard tip  46 . In an exemplary repair situation, the tip may have been damaged and the blade is shown having been machined along a surface  48 . A convoluted fir-tree attachment root  50  depends from an underside of the platform  44 . The root  50  has first and second longitudinal ends and first and second circumferential sides  52  and  54 . For reference, “longitudinal”, “circumferential”, and “radial” directions  500 ,  502 , and  504  defined relative to the orientation that the blade assumes when the root  50  is installed in a complementary slot in a disk of a turbine engine. A scaffold element  56  has a first portion extending into a passageway or compartment in the airfoil below the surface  48 . The scaffold  56  has a second portion protruding from the surface  48  for re-forming an end portion of the passageway or compartment when a deposition material is applied atop the surface  48  and scaffold  56 . An exemplary scaffold is a refractory metal-based (e.g., molybdenum) core element. 
     The exemplary fixture  24  includes a base  60  for mounting the fixture to the table  32 . An exemplary base  60  is formed as a metal plate (e.g., of an aluminum alloy or steel). In the exemplary base  60 , a pair of metal (e.g., steel) dowel pins  62  ( FIG. 3 ) have upper portions press fit into associated apertures  64  in the base and have lower portions protruding below an underside  66  of the base. The pins  62  may be received by complementary holes or slots in the table to register the fixture relative to the table. The fixture may be secured to the table by means such as clamps (not shown). 
     The upper surface  68  of the exemplary base  60  carries a root-engaging clamp structure  70 . The exemplary clamp structure  70  ( FIG. 2 ) includes a fixed jaw  72  and a movable jaw  74 . The fixed and movable jaws  72  and  74  cooperate to define a channel-like receiving area  76  for receiving the blade root  50 . 
     The exemplary fixed jaw  72  includes the unitary combination of a bottom portion  80  along the base  60  and a wall portion  82  opposite the moving jaw  74  and extending away from the base  60 . The exemplary fixed jaw is mounted to the base by means of registering pins  84  and screws  86  ( FIG. 4 ). 
     A screw or other means are provided for tightening the moving jaw  74 . An exemplary screw assembly  90  includes a threaded shaft  92  passing through a bore  93  in the jaw  74  and into threaded engagement with a bore  94  of the fixed jaw  72 . The exemplary screw  90  further includes an actuator  96  (e.g., a knob). The exemplary knob  96  has a bore  98  receiving an outboard portion of the screw. Tightening/loosening of the knob  96  may do one or both of tightening/loosening of the shaft relative to the knob or the shaft relative to the screw fixed jaw to shift the moving jaw  74  toward/away from an engaged condition. 
     The exemplary screw assembly  90  has a central axis of rotation  510  at an angle θ off-parallel to the base underside  66 . Exemplary θ is 5-30°. With the radial direction  504  essentially normal to the underside  66 , the axis  510  is off-normal to the radial direction by θ. The exemplary bottom portion  80  has a front face  120  oriented normal to the axis  510 . The fixed jaw bottom portion  80  has a generally horizontal upper surface  122 . With the blade installed and the jaws in the engaged condition, an underside  124  of the root contacts the bottom portion upper surface  122 . A shoulder  130  of the fixed jaw wall portion  82  engages an associated neck region  132  of the adjacent side of the root. An upper rear edge portion  140  of the moving jaw  74  engages a neck portion  142  of its adjacent side of the root. The off horizontal angle of the axis  510  helps cause the moving jaw  74  to exert a downward force to the blade root, clamping the blade root both against the fixed jaw wall portion  82  and bottom portion  80 . 
     The exemplary fixture includes additional means for precisely registering the blade relative to the fixture. Exemplary registering means include a projection at least partially captured in an aperture of the blade. In the illustrated embodiment, the projection is formed by the upper end of a pin  150  ( FIGS. 3 and 5 ). The exemplary pin  150  (e.g., steel) has a pin upper portion protruding from the fixed jaw bottom portion  80  upper surface  122  and a pin lower portion received in press-fit relation in an associated bore in the fixed jaw bottom portion  80 . 
     A channel  160  ( FIG. 5 ) is formed in the fixed jaw bottom portion upper surface  122 . The exemplary channel  160  extends elongate in the blade longitudinal direction  500  (i.e., transverse also to the axis  510 ). The exemplary channel  160  is obround and may be formed by milling. A bored port  162  extends downward from a base  164  of the channel. The port meets a transverse bore  170  (e.g., extending approximately in the blade circumferential direction  502 ) from an inlet port  172  on the backside  174  of the fixed jaw. The bore  170  may include pipe threads for engaging a fitting (not shown) to couple the fixture to a source  180  ( FIG. 1 ) of inert gas (e.g., argon or other noble gas or a gas essentially non-reactive in the welding process). For example, otherwise desirable materials for scaffold elements may be subject to oxidation or other chemical degradation. These may include refractory metal-based cores for forming/reforming internal passageways. The gas may be effective to limit such degradation to a tolerable amount or essentially eliminate it. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, details of the particular turbine elements to be worked upon and details of the work station may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.