Abstract:
A method for aligning a component including at least a first and a second datum for inspection. The method includes providing a tool including a fixture having at least a first and a second datum locator, aligning the first datum with the first datum locator, and rotating the component about the first datum to align the second datum with the second datum locator.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to inspection techniques, and more specifically to methods and apparatus for aligning components for inspection. 
   Accurately measuring a surface of a component may be a significant factor in determining a manufacturing time of the component, as well in determining subsequent maintenance and repair costs and activities. Specifically, when the component is a gas turbine engine blade, accurately measuring the contour of the blade may be one of the most significant factors affecting an overall cost of fabrication of the gas turbine engine, as well as subsequent modifications, repairs, and inspections of the blade. For example, at least some known gas turbine engine blades include a tip shroud that for performance reasons requires an accurately machined radius along the tip and center section of the blade. At least some known fabrication systems establish the radius using a system of datums referenced about the profile of the blade. 
   At least some known inspection processes use coordinate measuring machines (CMMs) to obtain dimensional information for a component. Within at least some CMMS, the component is held within a three-coordinate measurement space such that one or more datums are exposed to the CMM. A CMM probe is also positioned within the three-coordinate measurement space and contacts one or more of the datums, at which time a position of the probe tip is measured. The process must be repeated many times to determine a surface contour of the component, and as such, using a CMM may be time-intensive, and result in high cycle times and costs. Furthermore, it may be difficult to align the components in a position that facilitates accurate inspection of the component without distorting the profile and/or features of the component. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method is provided for aligning a component including at least a first and a second datum for inspection. The method includes providing a tool including a fixture having at least a first and a second datum locator, aligning the first datum with the first datum locator, and rotating the component about the first datum to align the second datum with the second datum locator. 
   In another aspect, a tool is provided including a fixture, a first datum locator coupled to the fixture, and a first biasing mechanism fixedly coupled to the fixture for biasing a component such that the component is aligned with respect to the first datum locator. 
   In yet another aspect, an apparatus is provided for aligning a gas turbine engine blade. The apparatus includes a fixture, a first datum locator coupled to the fixture, a second datum locator coupled to the fixture, and a first biasing mechanism fixedly coupled to the fixture. The first biasing mechanism biases the gas turbine engine blade such that the gas turbine engine blade rotates about the first datum locator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an exemplary gas turbine engine blade; 
       FIG. 2  is a perspective view of a fixture assembly for aligning a component, such as the gas turbine engine blade shown in  FIG. 1 , in position during inspection; 
       FIG. 3  is a side view of the fixture assembly shown in FIG.  2  and showing a dovetail alignment mechanism; 
       FIG. 4  is a perspective view of a portion of the dovetail alignment mechanism shown in  FIGS. 2 and 3 , and an integrator; and 
       FIG. 5  is a cross-sectional view of the fixture assembly shown in  FIG. 2  taken alone line  5 — 5  and illustrating a tip shroud alignment mechanism. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As used herein, the terms “inspection” and “inspecting” may include any inspection process. For example, inspection processes may include measurement by a machine, measurement by humans, visual inspection by a machine, and/or visual inspection by a human. 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 “inspection” and “inspecting”. In addition, as used herein the term “component” may include any object to which an inspection 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 inspection process. Accordingly, practice of the present invention is not limited to the inspection of turbine blades or other components of gas turbine engines. 
     FIG. 1  is a perspective view of a turbine blade  10  that may be used with a gas turbine engine (not shown). In one embodiment, a plurality of turbine blades  10  form a high-pressure turbine rotor blade stage (not shown) of the gas turbine engine. Each blade  10  includes a hollow airfoil  12  and an integral dovetail  14  that is used for mounting airfoil  12  to a rotor disk (not shown) in a known manner. Alternatively, blades  10  may extend radially outwardly from a disk (not shown), such that a plurality of blades  10  form a blisk (not shown). 
   Each airfoil  12  includes a first contoured sidewall  16  and a second contoured sidewall  18 . First sidewall  16  is convex and defines a suction side of airfoil  12 , and second sidewall  18  is concave and defines a pressure side of airfoil  12 . Sidewalls  16  and  18  are joined at a leading edge  20  and at an axially-spaced trailing edge  22  of airfoil  12 . More specifically, airfoil trailing edge  22  is spaced chordwise and downstream from airfoil leading edge  20 . First and second sidewalls  16  and  18 , respectively, extend longitudinally or radially outward in span from a blade root  24  positioned adjacent dovetail  14 , to an airfoil tip  26 . In one embodiment, airfoil tip  26  includes a tip shroud (not shown) extending radially outward therefrom in a direction away from airfoil  12 . 
     FIG. 2  is a perspective view of a fixture assembly  50  for aligning turbine blade  10  in position during inspection. Fixture assembly  50  includes a fixture  52  used for inspection processes, a dovetail alignment mechanism  54  coupled to fixture  52 , a tip shroud alignment mechanism  56  coupled to fixture  52 , a measuring assembly  58  coupled to fixture  52 , and a support assembly  59 . Dovetail alignment mechanism  54 , tip shroud alignment mechanism  56 , measuring assembly  58 , and support assembly  59  are coupled to fixture  52  using any suitable coupling means. For example, in one embodiment, at least one of dovetail alignment mechanism  54 , tip shroud alignment mechanism  56 , measuring assembly  58 , and support assembly  59  is coupled to fixture  52  using threaded bolts and threaded nuts. In another embodiment, at least one of dovetail alignment mechanism  54 , tip shroud alignment mechanism  56 , measuring assembly  58 , and support assembly  59  is coupled to fixture  52  using threaded bolts and threaded openings in fixture  52 . Prior to undergoing an inspection process, a turbine blade  10  is positioned in fixture assembly  50 . 
   In the exemplary embodiment, measuring assembly  58  includes a fixed retainer  62  fixedly coupled to fixture  52  and a linear variable differential transformer device (LVDT)  64 . Fixed retainer  62  is fixedly coupled to fixture  52  using any suitable means. For example, in the exemplary embodiment fixed retainer  62  is coupled to fixture  52  using threaded bolts and threaded nuts  63 . In another embodiment, fixed retainer  62  is coupled to fixture  52  using threaded bolts and threaded openings in fixture  52 . LVDT  64  is slidably coupled to fixed retainer  62  along a measuring axis  66  using any suitable means such that LVDT  64  moves within, and with respect to, fixed retainer  62  along measuring axis  66 . 
   Support assembly  59  includes an integrator  68 , a support plate  70 , and a plurality of support members  72 . Support members  72  are coupled to fixture  52 , integrator  68 , and support plate  70 . Support members  72  extend outwardly from fixture  52  to integrator  68 , thereby supporting integrator  68 . As discussed above, with respect to support assembly  59 , support members  72  are coupled to fixture  52 , integrator  68 , and support plate  70  using any suitable means. In the exemplary embodiment, support members  72  are coupled to fixture  52 , integrator  68 , and support plate  70  using threaded bolts and threaded openings in at least one of fixture  52  and support members  72 . Integrator  68  includes a stop  74 , discussed in more detail below. 
   Dovetail alignment mechanism  54  includes a biasing mechanism mount  75  used for mounting a biasing mechanism (shown in  FIG. 3 ) thereto. Using the biasing mechanism, dovetail alignment mechanism  54  aligns blade dovetail  14  such that dovetail  14  is maintained in position with respect to fixture  52  to facilitate an accurate inspection of blade  10 . Tip shroud alignment mechanism  56  aligns blade tip shroud  27  such that tip shroud  27  is maintained in position with respect to fixture  52  to facilitate an accurate inspection of blade  10 . Accordingly, the combination of dovetail alignment mechanism  54  and tip shroud alignment mechanism  56  facilitates aligning blade  10  in a position with respect to fixture  52  to facilitate an accurate inspection of blade  10 . When blade  10  is loaded into fixture assembly  50 , LVDT  64  contacts at least one target datum point located on blade tip shroud  27 . More specifically, at least a portion of LVDT  64  is displaced along axis  66  by each respective target datum point. The displacement of LVDT  64  is then measured to determine the locations of the target datums. 
     FIG. 3  is a side view of fixture assembly  50  showing dovetail alignment mechanism  54 .  FIG. 4  is a perspective view of a portion of dovetail alignment mechanism  54  and integrator  68 . Dovetail alignment mechanism  54  includes a datum locator base  76  that is coupled to fixture  52 , and a biasing mechanism base  78  that is coupled to biasing mechanism mount  75  (shown in FIG.  2 ). Biasing mechanism base  78  is coupled to biasing mechanism mount  75  using any suitable means, for example threaded bolts and threaded openings. As discussed above with respect to dovetail alignment mechanism  54 , datum locator base  76  and biasing mechanism mount  75  are coupled to fixture  52  using any suitable means. In the exemplary embodiment, datum locator base  76  and biasing mechanism mount  75  are coupled to fixture  52  using threaded bolts and threaded openings in at least one of fixture  52 , datum locator base  76 , and biasing mechanism mount  75 . Biasing mechanism base  78  includes a biasing mechanism  80 . In the exemplary embodiment, biasing mechanism  80  is integrally formed with biasing mechanism base  78 . However, in an alternative embodiment, biasing mechanism  80  is a separate component coupled to biasing mechanism base  78  using any suitable means. Furthermore, and in one embodiment, biasing mechanism  80  is a spring such as, but not limited to a helical spring, a plate spring, or a leaf spring. In the exemplary embodiment, at least a portion of biasing mechanism  80  is received within at least portion of dovetail  14 . In an alternative embodiment (not shown), at least a portion of dovetail  14  is received within at least a portion of biasing mechanism  80 . 
   Datum locator base  76  includes an upper surface  82  that at least partially defines a first datum locator  84  used to facilitate locating a first datum on blade  10 , and more specifically dovetail  14 . In one embodiment, first datum locator  84  is substantially planar. In addition, integrator  68  includes a second datum locator  86  used to facilitate locating a second datum on blade  10 , and more specifically dovetail  14 . Second datum locator  86  enables blade  10  to rotate about second datum locator  86 , and more specifically second datum rotational axis  88 , while the second datum is aligned with respect to second datum locator  86 . In the exemplary embodiment, second datum locator  86  is at least partially a convex surface and is integrally formed with integrator  68 . In an alternative embodiment, second datum locator  86  is a separate component that is coupled to integrator  68  in any suitable manner. Furthermore, in another alternative embodiment, second datum locator  86  is integrally formed with, or coupled to, a portion of dovetail alignment mechanism  54  or fixture  52 , rather than integrator  68 . 
     FIG. 5  is a cross-sectional view of fixture assembly  50  taken along line  5 — 5  of FIG.  2  and illustrating tip shroud alignment mechanism  56 . Tip shroud alignment mechanism  56  includes a datum locator base  90  that is coupled to fixture  52 , and a biasing mechanism base  92  that is coupled to fixture  52 . As discussed above with respect to tip shroud alignment mechanism  56 , datum locator base  90  and biasing mechanism base  92  are coupled to fixture  52  using any suitable means. In the exemplary embodiment, datum locator base  90  and biasing mechanism base  92  are coupled to fixture  52  using threaded bolts and threaded openings in at least one of fixture  52 , datum locator base  90 , and biasing mechanism base  92 . 
   Biasing mechanism base  92  includes a first biasing mechanism  94  and a second biasing mechanism  96 . In the exemplary embodiment, at least a portion of a second biasing mechanism  96  is received within at least a portion of blade tip shroud  27 . In an alternative embodiment, at least a portion of blade tip shroud  27  is received within at least a portion of second biasing mechanism  96 . Furthermore, and in one embodiment, a portion of first biasing mechanism  94  is received within at least a portion of blade tip shroud  27 . In an alternative embodiment, at least a portion of blade tip shroud  27  is received within at least a portion of first biasing mechanism  94 . In the exemplary embodiment, first biasing mechanism  94  and second biasing mechanism  96  are integrally-formed with biasing mechanism base  92 , however, it should be understood that first biasing mechanism  94  and second biasing mechanism  96  may be coupled to, or formed with, biasing mechanism base  92  in any suitable manner. In an alternative embodiment, first biasing mechanism  94  is coupled to, or integrally-formed with, a different biasing mechanism base than second biasing mechanism  96 . In addition, and in another alternative embodiment, tip shroud alignment mechanism  56  includes only one biasing mechanism. Furthermore, and in one embodiment, at least one of the biasing mechanisms  94  or  96  is a spring, such as but not limited to a helical spring, a plate spring, or a leaf spring. 
   Datum locator base  90  includes a third datum locator  98  used to facilitate locating a third datum on blade  10 , and more specifically blade tip shroud  27 . In addition, datum locator base  90  includes a fourth datum locator  100  used to facilitate locating a fourth datum on blade  10 , and more specifically blade tip shroud  27 . In one embodiment, at least one of datum locator  98  or  100  is substantially planar. In the exemplary embodiment, third datum locator  98  and fourth datum locator  100  are both integrally-formed with datum locator base  90 . However, in an alternative embodiment at least one of third datum locator  98  and fourth datum locator  100  is a separate component coupled to datum locator base  90  in any suitable manner. 
   When blade  10  is loaded into fixture assembly  50 , and more specifically when dovetail  14  is loaded into dovetail alignment mechanism  54 , biasing mechanism  80  deforms such that a portion of biasing mechanism  80  is received within a portion of dovetail  14 . More specifically, biasing mechanism  80  biases dovetail  14  against first datum locator  84  and second datum locator  86  causing the first datum of blade  10  to contact first datum locator  84  and the second datum of blade  10  to contact second datum locator  86 , which facilitates aligning the first and second datums with first datum locator  84  and second datum locator  86 , respectively. Dovetail  14  then contacts first datum locator  84  and is positioned against second datum locator  86 . 
   When blade tip shroud  27  is loaded into tip shroud alignment mechanism  56 , second biasing mechanism  96  deforms such that a portion of second biasing mechanism  96  is received within a portion of blade tip shroud  27 . First biasing mechanism  94  and second biasing mechanism  96  bias blade tip shroud  27  to rotate blade  10  about second datum locator  86 , and more specifically second datum rotational axis  88 , from an ‘unaligned’ position (not shown) to an ‘aligned’ position (shown in FIGS.  2  and  5 ). More specifically, first biasing mechanism  94  biases blade tip shroud  27  against stop  74 , and second biasing mechanism  96  biases blade tip shroud  27  against third datum locator  98  and fourth datum locator  100 . In one embodiment, second biasing mechanism  96  facilitates biasing blade tip shroud  27  against stop  74 . In another embodiment, a pneumatic system (not shown) facilitates biasing blade tip shroud  27  against stop  74  and applies pressure to blade tip shroud  27  to bias blade tip shroud  27  against stop  74  during inspection of blade  10 . 
   In one embodiment, only one of first biasing mechanism  94  and second biasing mechanism  96  bias tip shroud  27  of blade  10  to rotate blade  10  from the ‘unaligned’ position to the ‘aligned’ position. In the ‘unaligned’ position, the first and second datums contact, and are aligned with, first datum locator  84  and second datum locator  86 , respectively, and the third and fourth datums of blade  10  do not contact, and are not aligned with, third datum locator  98  and fourth datum locator  100 , respectively. In the ‘aligned’ position, the first and second datums contact, and are aligned with, first datum locator  84  and second datum locator  86 , respectively, and the third and fourth datums contact, and are aligned with, third datum locator  98  and fourth datum locator  100 , respectively. When in the ‘aligned’ position dovetail  14  is positioned against first datum locator  84  and against second datum locator  86 , and tip shroud  27  of blade  10  is positioned against third datum locator  98  and fourth datum locator  100 . Support plate stop  74  prevents blade  10  from rotating about second datum locator  86  and axis  88  past the ‘aligned’ position. Once in the ‘aligned’ position, biasing mechanisms  80 ,  94 , and  96  facilitate maintaining blade  10  in the ‘aligned’ position without distorting the profile and/or features of blade  10 . In one embodiment, at least a portion of LVDT  64  is slidably engageable with a portion of tip shroud  27  of blade  10  such that LVDT  64  facilitates aligning the third and fourth datums with third datum locator  98  and fourth datum locator  100 , respectively, during rotation of blade  10  from the ‘unaligned’ position to the ‘aligned’ position. 
   When blade  10  is in the ‘aligned’ position, dovetail  14  and tip shroud  27  of blade  10  are aligned in a position with respect to fixture assembly  50  that facilitates accurate inspection of blade  10  without distortion of the profile and/or features of blade  10 . More specifically, when blade  10  is in the ‘aligned’ position, at least a portion of LVDT  64  contacts a target datum on tip shroud  27  of blade  10  different from the third and fourth datums. The target datums displace at least a portion of LVDT  64  along axis  66 . Using the displacement of LVDT  64 , the locations of the target datums can then be determined and compared to desired locations for the respective target datums. 
   The above-described tool is cost-effective, highly reliable, and highly accurate for aligning a component during inspection. The tool permits a blade dovetail and a tip shroud to be accurately aligned during inspection. More specifically, the tool aligns the blade dovetail and tip shroud in a position facilitating accurate inspection of blade  10  without distorting the profile and/or features of the blade. Because the blade may be self-aligned once coupled to the tool, the tool requires minimal input from an operator and the cycle time is greatly reduced. As a result, the tool facilitates reducing inspection costs in a cost-effective and reliable manner. 
   Exemplary embodiments of tool assemblies are described above in detail. The systems are not limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. Each tool assembly component can also be used in combination with other tool assembly components. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.