Patent Publication Number: US-11046460-B2

Title: Machine holding fixture for machining composite laminates on a rotor blade

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. patent application Ser. No. 15/282,239 filed Sep. 30, 2016, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Exemplary embodiments of the invention relate to rotary-wing aircraft and, more particularly, to a bond fixture for use during the manufacture or repair of a rotor blade of a rotary-wing aircraft. 
     Rotary wing aircraft include a plurality of main rotor blades coupled to a central hub. The rotor blades include aerodynamic surfaces that, when rotated, create lift. The configuration of the main rotor blades, particularly the leading edge thereof, is selected to enhance rotor blade performance, for example to increase the hover and lift capabilities of the rotary-wing aircraft. Rotor blades are subjected to high stresses and strains resulting from aerodynamic forces developed during operation. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one embodiment of the invention, a holding fixture includes a first blade support assembly and a second blade support assembly. The second blade support assembly is spaced at a distance from the first blade support assembly and includes a base plate removably mounted to a milling machine, an adjustable conic support connectable to the base plate via a spacer block, and a blade adjustment assembly movable to control a pressure applied by the blade adjustment assembly. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the conic support includes at least one pin receivable within a hollow interior of a blade spar of a rotor blade. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the conic support includes two pins receivable within the hollow interior of the blade spar. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the position of the pins may be adjusted to control a pressure applied by the pins to the blade spar to couple the conic support to the blade spar. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the holding fixture further comprises a contour support having a first support plate and a second support plate. The second support plate is movable between a closed position and an open position. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments an interior surface of both the first support plate and the second support plate is complementary to a rotor blade such that when the second support plate is in the closed position, the first support plate and the second support plate are operable to apply a pressure to the rotor blade to restrict movement of the rotor blade relative to the first blade support assembly. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the second support plate is pivotally coupled to the first support plate. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the second support plate is detachably coupled to the first support plate. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the first blade support assembly includes a table and the contour support is mounted to an upper surface of the table. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the contour support is connected to an upper surface of the base plate. 
     According to another embodiment, a method of machining a laminate attached to a surface of a rotor blade includes providing a first assembly for supporting a first portion of the rotor blade and providing a second assembly for supporting a second portion of the rotor blade. The second assembly is spaced apart from the first assembly and includes a base plate. The base plate is coupled to a milling machine. A conic support is attached to a root end of the rotor blade. The conic support is mounted to the base plate. The rotor blade is positioned relative to the first assembly and the second assembly such that movement of the rotor blade is restricted and a first surface of the rotor blade including a first laminate is facing upwardly. The blade adjustment assembly is operated such that a block of the blade adjustment assembly is nested against an underside of the rotor blade. The first laminate is machined to remove a desired portion. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments positioning the rotor blade relative to the first assembly and the second assembly includes enclosing the rotor blade within a first contour support associated with the first assembly and a second contour support associated with the second assembly. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments attaching the conic support to the root end of the rotor blade includes inserting a plurality of support pins extending from the conic support into a blade spar of the rotor blade and adjusting the plurality of support pins to apply a pressure to opposite sides of the blade spar. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments mounting the conic support to the base plate includes fastening the conic support to a spacer block extending from an upper surface of the base plate. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments including removing the rotor blade from the holding fixture, repositioning the rotor blade relative to the first assembly and the second assembly such that movement of the rotor blade is restricted and a second surface of the rotor blade including a second laminate is facing upwardly, operating the blade adjustment assembly such that a block of the blade adjustment assembly is nested against an underside of the rotor blade, and machining the second laminate to remove a desired portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an example of a rotary wing aircraft; 
         FIG. 2  is a perspective view of an example of a rotor blade of a rotary wing aircraft; 
         FIG. 3  is a perspective view of a holding fixture for supporting a rotor blade during a machining operation according to an embodiment; 
         FIG. 4  is a side view of the holding fixture of  FIG. 3  according to an embodiment; 
         FIG. 5  is a top view of the second assembly of the holding fixture according to an embodiment; 
         FIG. 6  is a side view of the second assembly of the holding fixture according to an embodiment; 
         FIG. 7  is a perspective view of the root end of the rotor blade engaged with the second assembly of the holding fixture according to an embodiment; 
         FIG. 8  is an end view of the root end of the rotor blade engaged with the second assembly of the holding fixture of  FIG. 7  according to an embodiment; 
         FIG. 9  is an exploded perspective view of the second contour support according to an embodiment; 
         FIG. 10  is an end view of the second contour support according to an embodiment; and 
         FIG. 11  is a method of machining a composite laminate of a rotor blade according to an embodiment. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically illustrates a rotary-wing aircraft  10  having a main rotor system  12 . The aircraft  10  includes an airframe  14  having an extending tail  16  which mounts a tail rotor system  18 , such as an anti-torque system for example. The main rotor assembly  12  is driven about an axis of rotation A through a main gearbox (illustrated schematically at T) by one or more engines E. The main rotor system  12  includes a plurality of rotor blade assemblies  20  mounted to a rotor hub assembly H. Although a particular helicopter configuration is illustrated and described in the disclosed non-limiting embodiment, other configurations and/or machines, such as high speed compound rotary-wing aircraft with supplemental translational thrust systems, dual contra-rotating, coaxial rotor system aircraft, turbo-props, tilt-rotors, and tilt-wing aircraft are also within the scope of the invention. 
     Referring to  FIG. 2 , each rotor blade assembly  20  of the rotor assembly  12  generally includes a root section  22 , an intermediate section  24 , a tip section  26 , and a tip cap  28 . Each rotor blade section  22 ,  24 ,  26 ,  28  may define particular airfoil geometries to tailor the rotor blade aerodynamics to the velocity increase along the rotor blade span. As, illustrated, the rotor blade tip section  26  may include an anhedral form (not shown); however, any angled or non-angled forms such as cathedral, gull, bent, and other non-straight forms are within the scope of the present invention. The anhedral form (not shown) as defined herein may include a rotor blade tip section  26  which extends at least partially out of a plane defined by the intermediate section  24 . 
     The rotor blade sections  22 - 28  define a span R of the main rotor blade assembly  20  between the axis of rotation A and a distal end  30  of the tip cap  28  such that any radial station may be expressed as a percentage in terms of a blade radius x/R. The rotor blade assembly  20  defines a longitudinal feathering axis P between a leading edge  32  and a trailing edge  34 . 
     A holding fixture  40  for holding the rotor blade  20  in position during a milling operation is illustrated in  FIGS. 3-10 . The holding fixture  40  includes a first assembly  44  for supporting a central or outboard portion of the rotor blade  20  and a second assembly  42  for supporting the inboard end  22  of the rotor blade  20 . The first assembly  44  includes a movable table  46  having a generally planar upper surface  48 . A first contour support  50  mounted to the upper surface  48  of the movable table  46  includes a stacked first support plate  52  and a second support plate  54 . In an embodiment, the first support plate  52  and the second support plate  54  are pivotally coupled adjacent a first end such that the second support plate  54  is movable relative to the first support plate  52  between an open position and a closed position. The inner surface of both the first support plate  52  and the second support plate  54  has a contour corresponding to an adjacent surface of the rotor blade  20 . As a result, the rotor blade  20  is receivable within the contour support  50  when the second support plate  54  is in an open configuration. Further, when the second support plate  54  is in the closed position, the first contour support  50  applies a pressure to the surface of the rotor blade  20  to prevent movement thereof relative to both the contour support  50  and the table  46 . 
     The second assembly  42  includes a base plate  60  adapted to mount, such as with one or more fasteners (not shown) to a corresponding surface of a milling machine (not shown). When the base plate  60  is coupled to the milling machine, an upper surface  62  of the base plate  60  may, but need not be substantially flush with the upper surface  48  of the table  46 . The base plate  60  is spaced away from the leading edge of the table  46  by a predetermined distance associated with the rotor blade  20 . 
     A second contour support  64  configured to mount to the upper surface  62  of the base plate  60  similarly includes a stacked first support plate  66  and a second support plate  68 . In an embodiment, the first support plate  66  and the second support plate  68  are pivotally coupled adjacent a first end such that the second support plate  68  is movable relative to the first support plate  66  between an open position and a closed position. Alternatively, the second support plate  68  may detachably couple to the first support plate  66 . The inner surface of the first and second support plates  66 ,  68  is contoured to match an adjacent surface of the rotor blade  20 , near the root or inboard end. As a result, when the second support plate  68  is substantially aligned with the first support plate  66  to define a chamber  70  within which the rotor blade  20  is received (see  FIG. 10 ), the second contour support  64  applies a pressure to the surface of the rotor blade  20  to prevent movement thereof relative to the contour support  64  and the base plate  60 . 
     Located near the first end  72  of the base plate  60  is a block spacer  74  configured to cooperate with a conic support  76 . When the conic support  76  is coupled to the spacer  74 , the conic support  76  is substantially aligned with the blade spar  36  ( FIG. 7 ) of the adjacent rotor blade  20 . The conic support  76  includes at least one support pin  78  receivable with a hollow interior of the rotor blade spar  36 . In the illustrated, non-limiting embodiment, the conic spar  76  includes two support pins  78 . An adjustment assembly  80  associated with the two support pins  78  is operable to adjust the relative position of the two support pins  78 . For example, the adjustment assembly  80  includes a wheel  82  that when rotated in a first direction moves the support pins  78  towards one another and when rotated in a second direction moves the support pins  78  away from one another. To couple the conic support  76  to the rotor blade  20 , the support pins  78  are adjusted to apply a pressure to the opposing surfaces of the interior of the blade spar  36 . 
     A blade adjustment assembly  84  is coupled to or integrally formed with the base plate  60 . In an embodiment, the blade adjustment assembly  84  is positioned between the block spacer  74  and the second contour support  64 . The blade adjustment assembly  84  is operable to adjust the height of a spacer  86  disposed between the base plate  60  and an adjacent surface of the rotor blade  20 . The spacing provided by the blade adjustment assembly  84  is particularly important after a laminate located on a first side of the rotor blade  20  has been machined. The spacer  86  may be adjusted to compensate for the height of the laminate that was removed when the rotor blade  20  is repositioned within the fixture  40  for machining of a laminate located on a second opposite side of the rotor blade  20 . In the illustrated, non-limiting embodiment, the blade adjustment assembly  84  includes a slidable block  86  engaged with a ramp  88 . A knob  90  connected to the ramp  88  may be manipulated, such as pushed or pulled longitudinally or rotated for example, to adjust the slope of the ramp  88  and control the distance between the upper surface  62  of the base plate  60  and the upper surface of the block  86 . It should be understood that the blade adjustment assembly  84  illustrated and described herein is intended as an example only, and that other assemblies configured to control the position of the rotor blade  20  relative to the upper surface  62  of the base plate  60  are also contemplated herein. 
     With reference now to  FIG. 11 , a method of machining a composite laminate of a rotor blade  20  includes connecting the base plate  60  to the milling machine (not shown) at a desired position relative to the center line of the cutter, as shown in block  102 . The first support plate  66  of the second contour support  64  is coupled to the upper surface  62  of the base plate  60  in block  104 , and the first assembly  44  is positioned at a desired distance from the base plate  60  of the second assembly  42  and is aligned therewith using a laser, block  106 . In block  108 , the first contour support  50  is mounted to the upper surface  48  of the first assembly  44  and is oriented such that the second support plate  54  is in an open position relative to the first support plate  52 . In block  110 , the conic support  76  is installed into the root end  22  of the blade  20  and is tightened to ensure that the conic support  76  remains nested within the root end. 
     The rotor blade  20  is then positioned relative to the first assembly  44  and the second assembly  42  in block  112  such that a first side of the rotor blade  20  having a first laminate is facing upward. Positioning of the rotor blade  20  relative to first assembly  44  includes inserting the rotor blade  20  within the first support plate  52  of the first contour support  50  and rotating the second support plate  54  such that the rotor blade  20  is substantially enclosed by the first contour support. Similarly, positioning of the rotor blade  20  relative to the second assembly  42  includes positioning the conic support  76  onto the spacer block  74  and securing the conic support thereto. In block  114 , the second support plate  68  of the second contour support  64  is coupled to the first support plate  66  and in block  116 , the blade adjustment assembly  84  is operated until the block  86  is nested against the laminate located on the underside of the rotor blade  20 , closest to the upper surface  62  of the base plate  60 . In block  118 , the milling machine (not shown) is then operated to remove a desired portion of the first laminate. The blade  20  may be removed from the holding fixture  40  via a reverse order and may be reinstalled following the same steps with the second side of the rotor blade  20  and the second laminate facing upward. When installing the blade  20  with the second side facing upward, after the first laminate has been machined, the position of the sliding block  86  of the blade adjustment assembly  84  will be in a different location due to the reduced thickness of the first laminate, and there is therefore the need for an increased spacer height. 
     The holding fixture  40  illustrated and described herein allows the rotor blade to be held stationary in a fixed location during both the manufacture of a new rotor blade  20  and the repair of an existing rotor blade  20 . 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.