Patent Publication Number: US-2019186184-A1

Title: Replaceable actuator tip

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 15/549,038, filed Aug. 4, 2017, which is a National Stage application of PCT/US2015/065160, filed Dec. 11, 2015, which claims the benefit of U.S. Provisional Application No.: 62/116,024, filed Feb. 13, 2015, all of which are incorporated by reference in their entirety herein. 
    
    
     FEDERAL RESEARCH STATEMENT 
     This invention was made with Government support under Contract No. N00019-06-C-0081 with the United States Navy. The Government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     Exemplary embodiments of the invention relate to a blade fold assembly for a rotary wing aircraft, and more particularly, to an actuator pin movable between an extended and a retracted position during operation of a blade fold system. 
     The flight capabilities of rotary-wing aircrafts make them effective for a wide variety of missions; however, operation of rotary-wing aircraft in certain environments may be limited by the overall structural envelopes thereof. The radial dimensions of a rotary-wing aircraft main rotor assembly results in a rotary-wing aircraft having relatively large structural envelopes which may impact its utility in some environments. For example, space on a ship or vessel is generally at a premium and the structural envelope of a rotary wing aircraft may require a significant allocation of such limited space. Furthermore, strategic and tactical considerations in the military utilization of rotary-wing aircrafts has led to a requirement for rotary-wing aircrafts having main rotor assemblies that may be readily reconfigured for rapid deployment, routine transport, and/or stowage by reducing the structural envelope. 
     One way to reduce the structural envelope of rotary-wing aircraft to facilitate rapid deployment, routine transport, stowage, and reduce the vulnerability thereof to environmental conditions is to design the main rotor assembly so that the main rotor blades fold relative to the main rotor hub. Typically a portion of the rotor blade is pivotally mounted to an adjacent rotor hub with one or more pins for example. The high contact loads applied to the pin when the pin retains the rotor blade in an extended position may cause damage during use. For example, offsets between the bushings through which the pin extends cause high frictional loads that wear the material as well as gall and gouge the pin. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one embodiment of the invention, a pin of a hinge system movable between a first position and a second position is provided, wherein in the first position, the pin is received within a first component and a second component. The pin includes a cylindrical body coupled to an actuator for movement along an axis between the first position and the second position. A tip is removably attached to an end of the cylindrical body. The tip is configured to contact at least one of the first component and the second component when the pin is in the first position. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the actuator is a linear actuator having a piston arranged coaxially with the pin. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the actuator is a rotary actuator. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the first end of the cylindrical body is connected to the actuator. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is formed from a sacrificial metallic material. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is threadably attached to the cylindrical body. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is configured to receive and couple to a post extending from the end of the cylindrical body. 
     According to one embodiment of the invention, a hinge assembly is provided including a first component and a second component. The second component is coupled to and movable relative to the first component about a hinge axis between a first position and a second position. A hinge system is configured to selectively couple and decouple the first component and the second component. The hinge system includes an actuator and a pin having a cylindrical body coupled to the actuator for movement along an axis between an extended position and a retracted position. When the pin is in the extended position, the first and second component are coupled, and when the pin is in the retracted position, the second component is decoupled from the first component. A tip is removably attached to an end of the cylindrical body. The tip is configured to contact at least one of the first component and the second component when the pin is in the extended position. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the actuator is a linear actuator having a piston arranged coaxially with the pin 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the actuator is a rotary actuator. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is formed from a sacrificial metallic material. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is threadably attached to the cylindrical body. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the tip is configured to receive and couple to a post extending from the end of the cylindrical body. 
     In addition to one or more of the features described above, or as an alternative, in further embodiments the hinge assembly includes a blade fold system such that the first component is a sleeve and the second component is a 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. 2A  is a top view of the main rotor system of the rotary wing aircraft of  FIG. 1 ; 
         FIG. 2B  is a top view of a main rotor blade assembly of a rotary wing aircraft including a blade fold system; 
         FIG. 3  is a perspective view of an example of a rotary win aircraft having a plurality of main rotor blade assemblies arranged in a folded configuration; 
         FIG. 4  is a side view of a portion of a blade fold system of a rotary wing aircraft according to an embodiment of the invention; 
         FIG. 5  is a perspective view of a pin of the blade fold system according to an embodiment of the invention; 
         FIG. 6  is a perspective view of the pin of the blade fold system in an extended position according to an embodiment of the invention; and 
         FIG. 7  is a side view of the pin of the blade fold system in a retracted position according to an embodiment of the invention. 
     
    
    
     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, a translational thrust system, a pusher propeller, or a rotor propulsion system for example. Power is transferred from one or more engines ENG to a power transmission gearbox  20 , to drive the main rotor system  12  about a respective axis of rotation R. Although a particular rotary wing aircraft configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as a high speed compound rotary wing aircraft with supplemental translational thrust systems, a dual contra-rotating, coaxial rotor system aircraft, and a turbo-prop, tilt-rotor or tilt-wing aircraft for example, will also benefit from the present invention. 
     Referring now to  FIG. 2A , the main rotor system  12  includes a plurality of rotor blade assemblies  24 , each of which is mounted to a rotor hub  26  for rotation about the axis of rotation R. Although seven rotor blade assemblies  24  are illustrated, it should be understood that the main rotor system  12  may include any number of rotor blade assemblies  24 . Furthermore, since each main rotor blade assembly is generally alike, only one main rotor blade assembly will be described in detail herein with the understanding that the description is generally applicable to each of the rotor blade assemblies  24 . 
     As illustrated in  FIG. 2B , each rotor blade assembly  24  generally includes a main rotor blade  28 , a hinge assembly  30 , an actuator  32 , a sleeve  34 , a yoke  36 , an elastomeric bearing  38 , and a blade lock assembly  40 . The yoke  36  is mounted to the rotor hub  26  through the elastomeric bearing  38  such that the rotor blade assembly  24  may move in pitch, flap, and lead/lag motions as generally understood. The rotor blade assembly  24  may additionally include a damper assembly  42  configured to react against the lead/lag motions of the blade assembly  24  to damper vibration thereof. 
     An example of a rotor blade fold system  44  for a rotor blade assembly  24  is illustrated in more detail. The illustrated, non-limiting blade fold system  44  generally includes the blade lock assembly  42 , the actuator  32 , a retractable blade retaining pin  46 , and a blade fold controller (illustrated schematically at C) to selectively position each rotor blade assembly  24  in a particular folded position to minimize the envelope of the aircraft for stowage ( FIG. 3 ). 
     The blade lock assembly  42  is mounted to the rotor hub  26  and selectively engages the yoke  36 . The blade lock assembly  42  positions each blade assembly  24  in its blade fold position which includes positioning each yoke  36  in a predetermined lead/lag and pitch position and a predetermined rotor blade fold angle. Once the pitch lock assembly  42  engages the yoke  36 , the blade retaining pin  46  is moved to a retracted position and the actuator  32  rotates each rotor blade  28  about the hinge assembly  30  to a predetermined blade fold angle. 
     With reference now to  FIGS. 4-7 , a pin  50  of the blade fold system  44 , such as the retractable blade retaining pin  33  for example, is illustrated in more detail. Although the pin  50  is illustrated and described herein with reference to a main rotor blade assembly  24 , in other embodiments, the pin  50  may be configured as part of a tail rotor blade assembly of a rotary wing aircraft  10 , a pylon fold system, or any lug/clevis hinge or lock joint which is engaged by insertion of the pin  50 . The pin  50  has a generally cylindrical body  52  a portion of which, such as a first end  54  for example, is connected to an actuator  56 . 
     A tip  60  is arranged at a second, opposite end  58  of the cylindrical body  52 . As shown, the tip  60  has a generally frustoconical shape; however, tips  60  having other shapes, such as a conical or semispherical shapes for example, are within the scope of the invention. The tip  60  is generally formed as a sacrificial part of the pin  50 , and therefore may be formed from any number of materials, including, but not limited to, beryllium copper, nickel aluminum bronze, ToughMet®, or other suitable metallic materials. 
     The tip  60  of the pin  50  may be removably attached to the pin body  52 , as shown in  FIG. 5 . For example, in the illustrated, non-limiting embodiment, the tip  60  has an opening (not shown) formed therein generally complementary to and configured to receive a post  62  extending from the second end  58  of the pin body  52 . The post  62  may be slidably inserted, or alternatively, threadably attached to the tip  60 . However, other connection means for removably attaching the tip  60  to the pin body  52 , such as a fastener for example, are within the scope of the invention. In one embodiment, the connection formed between the tip  60  and the pin body  52  is configured to limit unintentional separation of the tip  60  from the body  52  during operation of the blade fold system  44 . For example, the fit formed between the opening in the tip  60  and the post  62  received therein may be designed to prevent separation of the tip  60  from the body  52  during operation of the blade fold system  44 . 
     Because a portion of the pin  50  is connected to an adjacent actuator  56 , the pin  50  is movable between a first, extended position ( FIG. 6 ) and a second, retracted position ( FIG. 7 ). In the illustrated, non-limiting embodiment, the actuator  56  is a linear actuator having a piston or shaft (not shown) arranged coaxially with the pin  50  for movement along an axis A. In another embodiment, the actuator  56  is a rotary actuator wherein rotation of the actuator piston (not shown) may similarly cause the pin  50  to move along an axis A. 
     The pin  50  is movable to selectively couple and decouple two or more adjacent components of the rotor blade assembly  24 . In one embodiment, the pin  50  is configured to couple a blade cuff  39  ( FIG. 2B ) and sleeve  34  of the rotor blade assembly  24  to control movement of the rotor blade  28  about an axis defined by the hinge assembly  30 . When the rotor blade is in a non-folded configuration, a first opening  64  formed in the sleeve  34  and a second opening  66  formed in the blade cuff  39  are generally aligned. In embodiments where the sleeve  34  is a clevis, a third opening  68  formed in an adjacent portion of the sleeve  34  may be aligned with the first and second openings  64 ,  66 . When in the retracted position, the pin  50  does not extend through any of the plurality of openings  64 ,  66 ,  68 , as shown in  FIG. 7 , thereby allowing the blade cuff  39  and rotor blade  28  to freely rotate about a hinge axis. When extended, the pin  50  is received at least partially within each of the plurality of aligned openings  64 ,  66 ,  68 , thereby limiting movement of the blade cuff  39  relative to the sleeve  34 . 
     When the pin  50  is extended, the tip  60  of the pin  50  is at least partially in contact with a surface of one of the plurality of openings, such as the third opening  68  for example. As a result, the tip  60  is configured to experience significant contact pressure. For example, when the openings  64 ,  66 ,  68  of the adjacent components are slightly misaligned, the frictional forces applied to the pin  50  significantly increase. By adequately designing the contour of the tip  60 , the galling and gouging caused by the high friction loads may be directed towards the tip  60 , such that only the tip  60 , and not the pin  50  and actuator  56 , need replacing. 
     Inclusion of a pin  50  having a removable tip  60  in a blade fold system  42  reduces the overall maintenance required for an aircraft  10  by limiting the area where damage occurs to the easily replaceable tip  60  of the pin  50 . In addition, the remainder of the blade fold system have improved durability, by reducing the galling and wear that may occur between the extended pin  50  and the components through which the pin  50  extends. 
     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.