Patent Publication Number: US-2020277085-A1

Title: Main rotor blade cuff bond fixture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional application of U.S. Ser. No. 15/232,235, filed on Aug. 9, 2016, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Exemplary embodiments of the invention relate to a 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 bond fixture including a plurality of supports mounted about a surface. At least one of the plurality of supports includes a vertical member and a hand crank operable to adjust a position of the vertical member. A first fixture is disposed at an end of the bond fixture and is movable relative to the surface. The first fixture includes a base and a support extending from the base. A second fixture includes a first member and a second member movably coupled. A fastener extending between the first member and the second member controls relative movement of the first member and the second member to define an opening there between. Each of the first member and the second member includes a plate having a heater formed therein. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments a portion of a component is receivable in the opening between the first member and the second member. Each plate includes a plurality of openings substantially identical to a plurality of openings formed in the component. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the first member and the second member are pivotally coupled together to form a clamping mechanism. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments at least one of the plurality of supports has a contour complementary to a portion of a component received therein. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments operation of the hand crank is used to align an opening formed in a component with a corresponding opening in the first fixture. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the heat generated by the heater is uniform across the heater. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the heat generated by the heater varies across the heater. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments comprising an expandable support including an actuating mechanism and a plurality of movable members, wherein operation of the actuating mechanism causes the movable members to move radially. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the expandable support is positionable within a hollow interior of a first end of a component, the expandable support and the second fixture cooperate to apply a pressure to one or more walls of the component. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the bond fixture is configured for use with a rotor blade. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the second fixture is configured to bond a blade cuff to a root end of the rotor blade. 
     According to another embodiment, a method of bonding a blade cuff to a rotor blade includes installing the blade cuff to a root end of the rotor blade, mounting the rotor blade within a plurality of supports, coupling the blade cuff to a first fixture, installing a second fixture about the blade cuff, and applying localized and constant heat and pressure to the blade cuff via the second fixture. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments coupling the blade cuff to the first fixture includes adjusting a position of the rotor blade to align a blade cuff lug hole with a corresponding opening in the first fixture. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments coupling the blade cuff to the first fixture includes installing at least one fastener through the opening in the first fixture and the blade cuff lug hole. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments installing a second fixture about the blade cuff includes positioning a portion of the blade cuff downstream from the first fixture within an opening defined between a first member and a second member of the second fixture. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments installing a second fixture about the blade cuff includes aligning the first member and the second member with the portion of the blade cuff such that a plurality of openings formed in the first member and the second member are concentric with a plurality of blade cuff alignment openings formed in the blade cuff. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments comprising connecting a power source to the second fixture to apply heat to the blade cuff. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments comprising installing an expandable support within a hollow interior of the blade cuff. 
    
    
     
       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 side view of a bond assembly for bonding a blade cuff to a root end of a rotor blade according to an embodiment; 
         FIG. 4  is a detailed perspective view of a first fixture of a bond assembly for bonding a blade cuff to a root end of a rotor blade according to an embodiment; 
         FIG. 5  is a side view of a portion of the bond assembly for bonding a blade cuff to a root end of a rotor blade according to an embodiment; 
         FIG. 6  is a perspective view of a support of the bond assembly according to an embodiment; 
         FIG. 7  is an end view of a first fixture of the bond assembly according to an embodiment; 
         FIG. 8  is a top view of a first fixture of the bond assembly according to an embodiment; 
         FIG. 9  is a side view of a first fixture of the bond assembly according to an embodiment; 
         FIG. 10  is a perspective view of a second fixture of the bond assembly according to an embodiment; 
         FIGS. 11 a -11 c    are various views of the second fixture of the bond assembly positioned about a blade cuff according to an embodiment; 
         FIG. 12  is a perspective view of an expandable support for use with the bond assembly according to an embodiment; and 
         FIG. 13  is a schematic diagram of a method of bonding a blade cuff to the root end 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, a tip section having any angled or non-angled form such as cathedral, gull, bent, and other non-straight forms are also contemplated herein. 
     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 . The distance between the leading edge  32  and the trailing edge  34  defines a main element chord length Cm. As shown in  FIG. 2 , a blade cuff  36  is attached to the root section  22  to facilitate mounting of the rotor blade assembly  20  to a rotor hub assembly H. The blade cuff  36  is typically a one-piece machined metallic member bonded to the rotor blade assembly  20 ; however other types of blade cuffs are within the scope of the disclosure. In the illustrated, non-limiting embodiment, the blade cuff  36  includes a plurality of cuff lug holes  37  and a plurality of cuff alignment holes  38 . 
     With reference now to  FIGS. 3-12 , an example of a bonding assembly  40  for bonding the blade cuff  36  to the root section  22  of the rotor blade  20  is illustrated. As shown, the bond assembly  40  includes a table  42  having a plurality of feet  44  configured to rest on or couple to a floor with one or more fasteners (not shown). An upper surface  46  of the table  42  is arranged generally level to the floor, such as at an ergonomic height for example. The table  42  has a length generally equal to or greater than the length of the rotor blade  20 . 
     One or more supports  48  for mounting or constraining the rotor blade  20  are disposed along the length of the table  42 . In the illustrated, non-limiting embodiments, the plurality of supports  48  include at least one support  48  arranged at the intermediate section  24  and at least one support  48  located at the tip section  26 . However, other arrangements of the supports are contemplated herein. A contour of the plurality of supports  48  may be generally complementary to the portion of the rotor blade  20  received therein. In an embodiment, at least one of the supports  48  is configured such that when the rotor blade  20  is located therein, the leading edge  32  of the rotor blade  20  is positioned closest to the upper surface  46  of the table  42 . 
     An example of a support  48  arranged at the intermediate section  24  of the rotor blade  20  is illustrated in more detail in  FIG. 6 . As shown, the support  48  includes a connector  47  operably coupled to a hand crank  49 . Rotation of the hand crank  49  is configured to adjust a position of the connector  47  so that a hole  51  formed in the connector  47  may be substantially aligned with a blade tooling hole (not shown) on the rotor blade  20 . A second connector  53  may be connected to both the rotor blade  20  and the support  48  via a fastener extending through the hole  51  and the hole in the rotor blade  20 . 
     With reference now to  FIGS. 7-9 , the bond assembly  40  includes a first fixture  50  for supporting the root section  22  of the rotor blade  20 . In the illustrated, non-limiting embodiment, the first fixture  50  is movably mounted to the table  42 , such that the fixture  50  is slidable along at least one linear track  52  (see  FIG. 4 ) for example. The first fixture  50  includes a base  54  coupled to the track  52  and a generally vertically extending support  56  arranged at an angle relative to the base  54 . The support  56  includes at least one hole  58  configured to align with the cuff lug holes formed in the blade cuff  36 . 
     A second fixture  60  of the bond assembly  40  includes a scissor clamp mechanism having a first member  62  and a corresponding second member  64  pivotally mounted together about a pin  68 . The scissor clamp mechanism  60  is generally shorter in length than the blade cuff  36  such that a portion of the blade cuff  36 , such as downstream from the blade cuff lug holes  37  for example, is receivable within an opening  66  defined between the first member  62  and the second member  64 . 
     The first and second members  62 ,  64  are configured to cooperate in a manner similar to a clamp or vice to grip the blade cuff  36 . An upper end  70  of the first member  62  and the second member  64  is coupled via a fastener  72 . Rotation of a corresponding nut  74  associated with the fastener  74  about an axis defined by the fastener  72  may be used to adjust the position of the first member  62  and the second member  64  relative to one another and therefore to the surface of the blade cuff  36 . In an embodiment, the nut  74  is adjusted until a portion of the first and second member  62 ,  64  is in contact with and/or applying a pressure to the blade cuff  36 . 
     The portion of each of the first member  62  and the second member  64  positioned directly adjacent the blade cuff  36  includes a plate  76  having a plurality of holes  78  formed therein. The holes  78  of the plates  76  are arranged in a pattern substantially identical to the pattern of cuff alignment holes  38  and may have a diameter equal to or greater than the cuff alignment holes  38 . When the second fixture  60  is installed about the blade cuff  36 , the pattern of holes  78  formed in each plate  76  is substantially aligned with the plurality of cuff alignment holes  38 . In an embodiment, each plate  76  is a heater configured to thermally couple to the blade cuff  36  when power is supplied thereto. The heater may generate a substantially uniform or varied heat across its surface. 
     An expandable support  80 , best shown in  FIG. 12 , may be positioned within the hollow interior of the blade cuff  36 . The support  80  includes a plurality of movable members  82  disposed at a first end  84  thereof. An actuating mechanism  86  is mounted at a second end  88  of the support  80 . In the illustrated, non-limiting embodiment, rotation of the actuating mechanism  86  about an axis causes at least one of the plurality of movable members  82  to translate radially relative to the axis. When the expandable support  80  is positioned within the hollow interior of the blade cuff  36 , the movable members  82  can be expanded to apply an outward force on the interior of the blade cuff  36 . As a result, the scissor clamp mechanism  60  and the expandable support  80  cooperate to apply a clamping force to each sidewall of the blade cuff  36 . 
     With reference now to  FIG. 13 , a method  100  of bonding the blade cuff  36  to the rotor blade assembly  20  includes installing the blade cuff  36  about the root end  22  of the rotor blade  20 , as shown in block  102 . In block  104 , the rotor blade  20  is lowered into a position where a leading edge  32  of the rotor blade  20  is positioned within the plurality of supports  48 . In an embodiment, mounting the rotor blade  20  within the plurality of supports  48  includes adjusting a hand crank  49  associated with one of the supports  48  arranged at the intermediate section  24  of the rotor blade to align a hole  47  formed in the support  48  with an adjacent hole formed in the rotor blade  20 . A second connector  53  may be mounted to the rotor blade  20  and the support  48  via hole  51  to apply a clamping force to the rotor blade  20 . 
     The blade cuff of the rotor blade  20  is then mounted within the first fixture  50 , as shown in block  106 , by inserting one or more fasteners through the blade cuff lug holes  37  and the corresponding holes  58  formed in the vertical support  56  of the first fixture  50 . The hand crank  49  associated with one of the plurality of supports  48  may be operated to adjust a height of the rotor blade  20  to align the holes  38 ,  58 . The rotor blade  20  is in proper alignment with the first fixture  50  once a plurality of cuff attachment bolts arranged within the plurality of cuff alignment holes  38  move freely. In block  108 , the second fixture  60  is mounted about the blade cuff  36 . Mounting the second fixture  60  about the blade cuff  36  includes moving the plates  76  into contact with the blade cuff  36  and aligning the pattern of holes  78  with the pattern of cuff alignment holes  38  such that the holes  78 ,  38  are concentric. The expandable support  80  is then installed within the hollow interior of the blade cuff  36 , as shown in block  110 . This installation of the expandable support includes rotating the actuator  86  of the support  80  to expand the movable members  82  inside the cuff while maintaining an orientation of the cuff. In block  112 , at least one cable is connected to the bond assembly and one or more bond cycles are performed. 
     The bond assembly  40  illustrated and described herein provides localized heat and pressure to a desired area of the rotor blade. The small size of the tool allows the bonding process to be performed in a fixed location without requiring movement to a separate location to cure. As a result, the need for a large walk-in oven to cure components of the blade  20  is eliminated. 
     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.