Abstract:
A coating system includes a coating source and a planetary manipulator assembly that includes a first driveshaft capable of receiving rotational input, a sun gear rotationally fixed to the first driveshaft, a planetary gear engaged with the sun gear, a second driveshaft rotationally fixed to the planetary gear such that torque is transmitted from the sun gear to the planetary gear, a support shaft operatively engaged with the second driveshaft, a carrier body supporting the planetary gear relative to the sun gear, a third driveshaft capable of receiving rotational input, and a drive gear rotationally fixed to the third driveshaft. The support shaft is arranged substantially perpendicular to the second driveshaft. The carrier body is rotatable by the drive gear about a common axis with the sun gear, and rotation of the carrier body rotates the planetary gear and the second driveshaft about the sun gear.

Description:
BACKGROUND 
     The present invention relates to coating systems for applying coatings to workpieces, and more particularly to coating systems that include a manipulator having planetary gearing. 
     In order to apply coatings to workpieces with desirable coating distribution, manipulators can be used to move the workpiece within a stream, plume or cloud of coating material. Such manipulators allow more even coating thickness distribution on various surfaces of workpieces, especially workpieces with relatively complex geometries and hard-to-reach (e.g., non-line-of-sight) areas. Gear-driven manipulators exist, including those with gear-driven arms that rotate and move upward and downward at up to +/−45° in a “butterfly” movement to provide one complete axis of rotation and one partial axis of rotation. 
     Gas turbine engines include numerous components with a variety of coatings. For example, gas turbine engines often include vane segments, such as “doublets” with a pair of airfoils extending between inner and outer platforms. Such doublets can include thermal barrier coatings (TBCs) made of ceramics or other materials, as well as environmental or other coatings. The configuration of typical vane doublets with highly contoured end walls can make coating uniform coating distribution difficult, including in the throat area between the airfoils. 
     Therefore, it is desired to provide an alternative coating system having an alternative workpiece manipulator. 
     SUMMARY 
     A coating system according to the present invention includes a coating source and a planetary manipulator assembly that includes a first driveshaft capable of receiving rotational input, a sun gear rotationally fixed to the first driveshaft, a planetary gear engaged with the sun gear, a second driveshaft rotationally fixed to the planetary gear such that torque is transmitted from the sun gear to the planetary gear, a support shaft operatively engaged with the second driveshaft, a carrier body supporting the planetary gear relative to the sun gear, a third driveshaft capable of receiving rotational input, and a drive gear rotationally fixed to the third driveshaft. The support shaft is arranged substantially perpendicular to the second driveshaft. The carrier body is rotatable by the drive gear about a common axis with the sun gear, and rotation of the carrier body rotates the planetary gear and the second driveshaft about the sun gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an embodiment of a coating application system according to the present invention. 
         FIG. 2  is a perspective view of a portion of the coating application system of  FIG. 1 . 
     
    
    
     While the above-identified drawing figures set forth an embodiment of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale. 
     DETAILED DESCRIPTION 
     It is desired to provide a workpiece manipulator for a coating application system that allows for workpiece movement that approaches random movement. More random workpiece movement facilitates more even coating application and resultant thickness distribution. According to the present invention, a workpiece manipulator assembly is provided that utilizes planetary movement to provide pseudo- or near-random part movement to provide desirable coating distribution. The system of the present invention can be utilized to provide electron beam physical vapor deposition (EB-PVD) application of thermal barrier coatings (TBCs) to gas turbine engine components, as well as to provide a variety of other types of coating materials with a variety of different coating application methods to desired workpieces. 
     It has been discovered that movement of coating delivery mechanisms (e.g., coating sprayers for use with large workpieces) can produce undesirable flow effects in material supply conduits. Therefore, improved part manipulation according to the present invention without reliance on coating delivery mechanism manipulation allows for consistent coating application without dependence upon particular coating delivery mechanisms. Various features and benefits of the present invention will be appreciated by those of ordinary skill in the art in view of the figures and the description that follows. 
       FIG. 1  is a schematic illustration of an embodiment of a coating application system  10 , and  FIG. 2  is a perspective view of a portion of the coating application system  10 . In the illustrated embodiment, the system  10  includes a manipulator assembly  11  that includes a driveshaft  12 , a sun gear  14 , a planetary gear  16 , a driveshaft  18 , bevel gears  20  and  22 , a support shaft (or spindle)  24 , a fixture  26 , a driveshaft  28 , a drive gear  30 , a carrier gear  32 , a carrier body  34 , and a housing  36 . The manipulator assembly  11  can be used to hold and manipulate a workpiece  38  (e.g., a gas turbine engine vane doublet) for application of a coating delivered by a coating source  40 . Portions or all of the manipulator assembly  11 , workpiece  38  and the coating source  40  can be positioned within an enclosure  42 . 
     In one embodiment, a geartrain defined by the manipulator assembly  11  can be configured as follows. The driveshaft  12  is rotationally fixed to the sun gear  14  for common rotation about an axis A. The sun gear  14  is engaged with the planetary gear  16 , such that rotation of the sun gear  14  rotates the planetary gear  16 . In one embodiment a gear ratio of approximately 2.5:1 can be used between the planetary gear  16  and the sun gear  14 , though any desired gear ratio can be used in alternative embodiments. The driveshaft  18  is rotationally fixed to the planetary gear  16  and rotates with the planetary gear  16 . The driveshaft  18  is arranged parallel to the driveshaft  12 . The bevel gear  20  is fixed to the driveshaft  18 , and the bevel gear  22  is fixed to the support shaft  24 . The bevel gears  20  and  22  engage each other to transmit torque between the driveshaft  18  and the support shaft  24 . The fixture  26  is supported at a distal end of the support shaft  24 , opposite the bevel gear  22 . The shaft  28  is arranged parallel and adjacent to the shaft  12 . The drive gear  30  is rotationally fixed to the shaft  28  for common rotation. The carrier gear  32  can be rotatably supported on the shaft  12  about the axis A, with the carrier gear  32  configured to allow rotation independent of the shaft  12 . Drive gear  30  and the carrier gear  32  engage each other to transmit torque. The carrier gear  32  is rotationally fixed to the carrier body  34 . The driveshaft  12  can pass through the carrier body  34 , but the carrier body  34  is rotationally independent from the driveshaft  12 . The planetary gear  16  is supported and carried by the carrier body  34 , though the planetary gear  16  can rotate relative to the carrier body  34 . Rotation of the carrier body  34  about the axis A causes the planetary gear  16  to travel about a circumference of the sun gear  14  (about the axis A). The housing  36  can enclose components of the manipulator assembly  11  to shield them from coating materials and help prevent coating material accumulation on sensitive gears, etc. of the assembly  11 . 
     The fixture  26  can engage and retain at least one workpiece  38 , and can have any suitable configuration to secure one or more desired workpieces. In  FIG. 2 , the workpiece  38  is shown exploded relative to the support shaft  24 , and the fixture  26  is omitted for simplicity. As shown in the embodiment of  FIG. 2 , the workpiece  38  is a gas turbine engine vane segment “doublet” having a pair of airfoils  38 - 1  and  38 - 2  extending between an inner platform  38 - 3  and an outer platform  38 - 4 . The fixture  26  supports the vane segment workpiece  38  with the support shaft  24  positioned at a midpoint located in between the airfoils  38 - 1  and  38 - 2  and in between the inner and outer platforms  38 - 3  and  38 - 4 . In general, the workpiece  38  can be positioned relative to the support shaft  24  to provide optimal line-of-sight positioning relative to one or more axes of movement and a coating source  40 . 
     The coating source  40  can be an EB-PVD assembly with a material pool  40 - 1  that can produce a coating vapor plume  40 - 2  directed toward the workpiece  38 . Any conventional EB-PVD assembly can be used. In the illustrated embodiment, the coating plume  40 - 2  can extend toward the workpiece  38  in a direction generally perpendicular to the axis A and aligned with a plane in which the support arm  24  moves, in order to deliver vaporized coating material to the workpiece  38 . Those of ordinary skill in the art should recognize that the EB-PVD system described herein is but one example of a configuration of the coating source  40 , and in alternative embodiment other types of coating delivery techniques and systems can be utilized. 
     The enclosure  42  can be provided to surround at least portions of the manipulator assembly  11 , the workpiece  38  and the coating source  40 . It should be recognized that portions of those components, particularly portions of the manipulator assembly  11  and the coating source  40  can extend outside the enclosure  42 . 
     During operation, torque can be selectively provided to the driveshafts  12  and  28  to provide rotational input to the manipulation assembly  11 . One or more conventional motors or other mechanisms (not shown) can be used to provide torque input to the driveshafts  12  and  28 , which can be rotated independently at the same speed or different speeds. The driveshaft  12  rotates the sun gear  14  about the axis A. The sun gear  14  transmits torque to the planetary gear  16 , which causes the associated driveshaft  18  to rotate. The bevel gears  20  and  22  transmit torque from the shaft  18  to the support shaft  24 , which rotates about an axis B perpendicular to the axis A. In addition, the driveshaft  28  rotates the drive gear  30 , which engages the carrier gear  32  thereby rotating the carrier body  34 . The planetary gear  16  and the driveshaft  18 , as well as the support shaft  24  and the workpiece  38  carried at the end of the support shaft  24 , are moved around the circumference of the sun gear  14  by rotation of the carrier body  34  about the axis A. Coating material can be delivered from the coating source  40  while the workpiece  38  is manipulated by the manipulation assembly  11 . Manipulation of the assembly  11  tends to cause end-to-end rotational movement of the inner and outer platforms  38 - 3  and  38 - 4  of the workpiece  38  about the axis B, with additional rotation (including orbital movement) in relation to the axis A. The movement of the workpiece  38  allows the coating plume  40 - 2  to tend to focus on the airfoils  38 - 1  and  38 - 2  and adjacent surfaces of the platforms  38 - 3  and  38 - 4  while reducing the amount of coating directed to non-flowpath-boundary surfaces of the platforms  38 - 3  and  38 - 4 . It should be noted that the particular orientation of the workpiece  38  relative to the coating plume  40 - 2  shown in  FIG. 2  would only occur momentarily during operation. In general, the movement of the workpiece  38  while the manipulator assembly  11  operates approaches or approximates random movement. It should also be noted that manipulation movement can be adjusted to include dwell times, during which movement of the workpiece  38  is slowed or stopped to increase expose to the coating plume  40 - 2  at a particular orientation. 
     It should be appreciated that exact workpiece orientation on a given support shaft, as well as manipulation angles and dwell times can be adjusted as desired for particular applications to optimize coating thicknesses and coating microstructure (e.g., vertical columns) in difficult to coat areas. Workpiece orientation is driven in large part by workpiece configuration, and the manipulation angles and dwell positions can be prioritized by the amount of coating need in each area on a particular part (e.g., where more thermal protection is needed, more TBC is applied). For instance, in some embodiments, more coating may be applied to an inner platform than an outer platform of a gas turbine engine vane segment because the inner platform runs hotter than the outer platform during engine operation. 
     Any relative terms or terms of degree used herein, such as “substantially”, “approximately”, “essentially”, “generally” and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations and the like. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. For example, a workpiece manipulator according to the present invention can be used in conjunction with coating supply manipulation, and can be utilized with a variety of different types of coatings and coating delivery mechanisms. Moreover, in further embodiments, one or more additional support arms, with additional associated planetary gears, shaft and bevel gears can be engaged with the sun gear to support and manipulate additional workpieces simultaneously. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.