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  Method and apparatus for rebuilding gas turbine enginesUSPTO Application #: 20070251924Title: Method and apparatus for rebuilding gas turbine engines Abstract: A method for repairing a component within a SWET box is provided. The method includes providing a SWET box that has a divided interior volume that defines a welding chamber within the interior that is smaller than a total volume of the interior SWET box, positioning a component to be repaired within the welding chamber, introducing protective gas into the SWET box, and controlling the flow of protective gas into the SWET box to facilitate minimizing the consumption of the protective gas within the SWET box. (end of abstract) Agent: John S. Beulick (12729) C/o Armstrong Teasdale LLP - St. Louis, MO, US Inventors: Adeilton Jorge Martins, Adilio Alves Sardinha Filho USPTO Applicaton #: 20070251924 - Class: 219072000 (USPTO) Related Patent Categories: Electric Heating, Metal Heating (e.g., Resistance Heating), Nonatmospheric Environment At Hot Spot (e.g., Resistance Weld Under Oil, Vacuum) The Patent Description & Claims data below is from USPTO Patent Application 20070251924. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] This invention relates generally to gas turbine engines, and more specifically to the repair of turbine blades used in gas turbine engines. [0002] In at least some gas turbine engines, turbine blades used within the engine are cast to an approximate final shape. Portions of the turbine blades, including, but not limited to, a root portion, are then shaped to a final desired form by a shaping technique, such as grinding. The finished turbine blades are assembled into a turbine disk or rotor, such that a "dovetail" formed on each turbine blade engages a complimentarily shaped slot on the turbine disk. [0003] Known turbine blades may be constructed from a high-temperature, high-strength alloy that is adapted to withstand the temperatures and stresses imposed on the parts of a turbine assembly. Because of the high cost of materials, casting operations, and finishing operations, at least some known turbine blades, after being in service, are refurbished to restore the original aerodynamic contours of portions of the blades. At least some known turbine blade repairs, such as those utilized in restoring blade tips, require building up the surface being repaired with a weld bead, and then grinding the surface back to its original contour. [0004] One known technique for building up the blade material by welding is known as superalloy welding at elevated temperatures (SWET) in which tungsten inert gas (TIG) welding is combined with a pre-heating box, referred to as a SWET box. More specifically, in one known method, argon gas is supplied to the SWET box to provide a protective atmosphere for the blades being welded. The argon atmosphere facilitates reducing an amount of contamination within the weld and reducing the amount of cracking within the weld. More specifically, during use a sufficient volume of argon is provided to protect the blade and for good weld quality, and it is not unusual that the argon flow to the SWET box is set excessively high just to facilitate protecting the blades during welding. However, this technique not only unnecessarily increases argon consumption and its associated costs, but also the unnecessarily high gas flow increases the noise level in the area of the SWET box. BRIEF DESCRIPTION OF THE INVENTION [0005] In one aspect, a method for repairing a component within a SWET box is provided. The method includes providing a SWET box that has a divided interior volume that defines a welding chamber within the interior that is smaller than a total volume of the interior SWET box, positioning a component to be repaired within the welding chamber, introducing protective gas into the SWET box, and controlling the flow of protective gas into the SWET box to facilitate minimizing the consumption of the protective gas within the SWET box. [0006] In another aspect, a liner assembly for a SWET box is provided. The liner assembly includes an enclosure configured to be received in a heating chamber of the SWET box. The enclosure includes a rear wall, a front wall opposite the rear wall, a pair of opposed end walls, and a dividing wall defining a welding chamber therein. A gas delivery system is provided for supplying a protective gas into the SWET box and the enclosure. A lid is coupled to the SWET box and extends over the heating chamber and the enclosure, encasing the heating chamber and the enclosure. [0007] In another aspect, a SWET box is provided that includes a heating chamber and an enclosure configured to be received in the heating chamber. The enclosure includes a rear wall, a front wall opposite the rear wall, a pair of opposed end walls, and a dividing wall defining a welding chamber therein. A gas delivery system is provided for supplying a protective gas into the heating chamber and the enclosure. A lid is coupled to the heating chamber and extends over the heating chamber and the enclosure. BRIEF DESCRIPTION OF THE DRAWINGS [0008] FIG. 1 is a schematic cross sectional view of a SWET box; [0009] FIG. 2 is a schematic cross sectional view of a turbine blade being repaired within the SWET box shown in FIG. 1. [0010] FIG. 3 is a schematic cross sectional view of the SWET box shown in FIG. 1 with a liner assembly; [0011] FIG. 4 is a perspective view of the enclosure of the liner assembly shown in FIG. 3; [0012] FIG. 5 is a perspective view of the SWET box lid shown in FIG. 3; [0013] FIG. 6 is a perspective view of the first gas delivery system shown in FIG. 3; [0014] FIG. 7 is a perspective view of the blade holder shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION [0015] FIG. 1 is a schematic cross sectional view of a conventional SWET box 10 that may be used in superalloy welding at elevated temperatures (SWET). SWET box 10 includes a heating chamber 12 that has a back wall 14, an opposed front wall (not shown), and opposed ends 16 and 18. SWET box 10 also includes a floor 20 and a removable lid 22. Though shown as being substantially rectangular in shape in FIG. 1, SWET box 10 may be non-rectangular. For example, in one embodiment, one or both ends 16 and 18 are curved such that SWET box 10 has an elliptical cross-sectional profile when viewed from the top along sight line A-A. A heat source 26 is mounted in back wall 14. Typically, in SWET welding, heat source 26 includes one or more quartz lamps, however, other known heating methods may be used. Fluid inlets 28 are provided in floor 20 for introducing protective to create a protective atmosphere inside SWET box 10. [0016] FIG. 2 is a schematic view of a turbine blade being repaired in SWET box 10. Blade 30 includes a dove tail 32 and an airfoil 34 that extends radially outward from dove tail 32 to an airfoil tip 36 that is being repaired. Blade 30 is retained in a fixture 40 that is positioned on a platform 42 at the bottom of heating chamber 12. Platform 42 rests on SWET box floor 20 such that fluid inlets 28 remain un-obstructed. During use, blade 30 is heated by heat source 26, and a protective gas, such as argon, is supplied to SWET box 10 through fluid inlets 28. A weld repair is made to blade 30 in the presence of the protective gas. [0017] As used herein, the terms "repair" and "repairing", may include any repair/inspection process. For example, repair processes may include various known repair techniques including welding, grinding, and/or machining. The above examples are intended as exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the terms "repair" and repairing". In addition, as used herein the term "component" may include any object to which a repair process is applied. Furthermore, although the invention is described herein in association with a gas turbine engine, and more specifically for use with a turbine blade for a gas turbine engine, it should be understood that the present invention may be applicable to any component and/or any repair process. Accordingly, practice of the present invention is not limited to the repair of turbine blades or other components of gas turbine engines. [0018] During SWET welding, SWET box 10 is filled with the protective gas to facilitate enhancing the quality of the weld while minimizing contamination and cracks within the weld. More specifically, to ensure the entire volume of SWET box 10 is filled with protective gas during welding, and increased gas flow rate is used to ensure that the volume of gas is maintained. The higher gas flow rate creates a higher noise level in the vicinity of SWET box 10. [0019] FIG. 3 is a schematic cross sectional view of SWET box 10 including a liner assembly 50 for reducing the amount of protective gas supplied to SWET box 10 and the amount of noise generated in the vicinity of SWET box 10. Assembly 50 includes an enclosure 52 and a lid 54. A first gas delivery system 56 is positioned adjacent a floor 58 of enclosure 52, and a second gas delivery system 60 is coupled through lid 54. A blade holder 62 is positioned above first gas delivery system 56, and a layer of a metallic mesh material 66 is packed around first gas delivery system 56 to facilitate diffusing and reducing noise generated as the flow of protective gas enters SWET box 10. In the example embodiment, metallic mesh 66 is a steel, wool-like structure, and may be fabricated from any metallic material capable of withstanding the fabricating temperatures which develop during welding within SWET box 10. In the embodiment, the temperature within SWET box 10 may reach at least about 900 degrees Celsius. [0020] FIG. 4 is a perspective view of enclosure 52. In the exemplary embodiment, enclosure 52 is fabricated from a metallic material, such as steel, and includes a back wall 68, a front wall 70, a first end wall 72, and an arcuate or curved second end wall 74. First end wall 72 includes a cutout 75 at an upper portion thereof, and back wall 68 includes a window 76 extending there through and in open communication with a heat source 26 (see FIG. 1) in back wall 14 of SWET box 10. A dividing wall 78 separates enclosure 52 into a welding chamber 80 and a cavity 82 that is partially bounded by curved end wall 74. Cutout 75 and curved end wall 74 provide an operator access to manipulate a component being repaired in welding chamber 80. A floor 58 in welding chamber 80 includes a hole 84 extending there through to enable the admission of a protective gas into welding chamber 80. Continue reading... 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