Abstract:
In the absence of centrifugal force produced during rotation of helicopter blades, damage may result if a blade is rotated upward by wind or other forces. Lock units removably appended between the rotor assembly and each blade pitch housing attached to a helicopter blade are usable to restrict upward rotation. A base portion of a lock unit may be configured to be held in position by a removable pin device. An extendible device extending from the base portion to a surface of a blade pitch housing can be adjusted to press the base portion back against a surface of the rotor assembly. The lock unit thereby restricts these surfaces of the blade pitch housing and rotor assembly from moving closer to each other and thereby restricts upward rotation of the blade pitch housing and its attached helicopter blade. The lock units are readily removable in preparation for returning a helicopter to active use.

Description:
RELATED APPLICATIONS 
   (Not Applicable) 
   FEDERALLY SPONSORED RESEARCH 
   (Not Applicable) 
   BACKGROUND OF THE INVENTION 
   The invention relates to helicopter storage and shipment and, more particularly, to prevention of undesired upward rotation of helicopter blade pitch housings and attached blades during out-of-use periods. 
   Helicopter blades, during operation, are rotated basically in a plane of rotation which is nominally a horizontal plane. A helicopter blade is typically attached to a blade pitch housing (enabling controlled adjustment of blade pitch) which is attached to the rotor assembly, rotation of which produces blade rotation. While rotating, displacement or rotation of the blades upward from the plane of rotation is limited by the effects of centrifugal force. When out-of-use (e.g., parked, stored, in shipment) no centrifugal forces act on the blades and the blades and pitch housings are permitted to flap downward (called “droop”) a small amount under the influence of gravity. Their weight is supported by a droop stop mechanism. When out-of-use the blades are typically unrestrained from a range of upward rotation (e.g., rotation in a vertical plane, about the connection point to the rotor assembly). Such upward rotation may be caused by wind forces while parked or stored, or by sudden altitude or attitude changes or other forces experienced during shipment of a helicopter in a transport aircraft or while being towed on the ground, for example. 
   During shipment or storage the blades of a helicopter may be folded (i.e., some or all blades positioned toward the tail or nose of the helicopter) while each blade still remains attached to its respective blade pitch housing which remains attached to the rotor assembly (blade folding is further described in U.S. Pat. No. 6,783,327, having a common assignee). Whether or not the blades are folded, upward rotation of a blade pitch housing, during shipment for example, is undesirable and may result in damage to the blade, the blade pitch housing or other components of the rotor blade mechanism, or to the interior area of a transport aircraft immediately above the stowed helicopter. For present purposes, uncontrolled upward rotation of a blade pitch housing (i.e., with its attached blade) of a helicopter which is not in use will be termed “flap”. Correspondingly, undesired upward rotation of a blade may be termed “blade flap”. Prior mechanisms and techniques have not provided effective limitation of blade flap or have been subject to limitations regarding cost, complexity, reliability, durability or other disadvantages. 
   Objects of the present invention are to provide new and improved lock units and methods, which may provide advantages such as the following: 
   ease of installation; 
   reliable operation; 
   absence of required aircraft modification; 
   cost effectiveness; 
   low complexity of construction; 
   durability; and 
   ease of removal. 
   SUMMARY OF THE INVENTION 
   In accordance with an embodiment of the invention, a lock unit usable to restrict upward rotation of a blade pitch housing attached between a rotor assembly and a helicopter blade, includes a base portion having, on a first side, a contact surface to contact the rotor assembly and, on a second side opposed to the first side, a first opening. The base portion is configured to enable the control unit to be removably positioned adjacent appended to the rotor assembly. An extendible device positioned in the first opening is extendible to an extended position to contact the blade pitch housing. The extendible device is configured to releasably retain that extended position to restrict upward rotation of the blade pitch housing. 
   More particularly, the extendible device may include a threaded shaft having a near end inserted into the first opening in the base portion and also having a far end. A first nut device is rotatable on the threaded shaft to adjustably extend the threaded shaft out of the first opening to position the far end adjacent to the blade pitch housing. In this embodiment the extendable device is configured to apply a thrust force between the rotor assembly and the blade pitch housing when the first nut device is tightened to extend the extendible device forward into contact with the blade pitch housing and to press the base portion contact surface back against the rotor assembly. 
   Also in accordance with the invention, a method for restricting upward rotation of a blade pitch housing attached between a rotor assembly and a helicopter blade may include the steps of: 
   (a) positioning, between the rotor assembly and the blade pitch housing, a lock unit having an extendible device; 
   (b) removably appending the lock unit to the rotor assembly with a contact surface of the lock unit adjacent a surface of the rotor assembly; 
   (c) extending the extendible device to an extended position to contact the blade pitch housing; and 
   (d) releasably retaining the extendible device at the extended position to restrict upward rotation of the blade pitch housing and attached helicopter blade. 
   For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings and the scope of the invention will be pointed out in the accompanying claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a helicopter rotor assembly with one blade pitch housing and blade attached and a lock unit installed. 
       FIG. 2  is an enlarged view of a portion of  FIG. 1 . 
       FIG. 3  is a view corresponding to  FIG. 2 , with the lock unit removed. 
       FIG. 4  is a view of a lock unit from above. 
       FIG. 5  is a view of the  FIG. 4  lock unit from below. 
       FIG. 6  is a partially exploded view of the  FIG. 4  lock unit. 
       FIG. 7  is a second partially exploded view of a lock unit. 
       FIG. 8  is a view of a second embodiment of a lock unit from above. 
       FIG. 9  is a partially exploded view of the  FIG. 8  lock unit. 
   

   DESCRIPTION OF THE INVENTION 
     FIG. 1  provides an overview showing blade pitch housing  10  attached between rotor assembly  12  and helicopter blade  14 , with lock unit  20  removably appended to the rotor assembly. It will be understood that for a typical helicopter there would be attached to the rotor assembly  12  two or more identical blade pitch housing/blade combinations at positions spaced equally around the rotor assembly. Pursuant to the invention, a blade lock unit may be similarly installed at each such position. 
     FIG. 2  provides a more detailed view of lock unit  20  of  FIG. 1 .  FIG. 3  is a view of blade pitch housing  10  and rotor assembly  12  as in  FIG. 2 , but with lock unit  20  removed. Other included reference numerals will be referred to below. Thus,  FIG. 3  represents these components of a helicopter in operational relationship and  FIG. 2  shows the removable inclusion of lock unit  20  to restrict upward rotation of the blade pitch housing and attached helicopter blade during a period in which the helicopter is not in use (e.g., during storage or shipment). 
     FIG. 4  is a front/top form of three-dimensional view of lock unit  20  alone and  FIG. 5  is a corresponding back/bottom view.  FIG. 6  provides an exploded view of a portion of the lock unit  20  as shown in  FIG. 4 . As illustrated, lock unit  20  includes a base portion  22  having, on a first side, a contact surface  24  (which may be covered by a thin contact pad of rubber or other suitable material) and, on a second side opposed to the first side, a first opening  26  (visible in  FIG. 6 ). In the configuration shown, the main part of base portion  22  may be machined from steel stock or other suitable material, with a side part  22   a  of steel plate or other suitable material bolted to the main part. In other embodiments, base portion  22  may be cast or otherwise formed in one piece or multiple pieces in the same configuration as illustrated or in other suitable configurations as may be determined by skilled persons for use in particular applications. 
   In the embodiment shown, base portion  22  is configured to enable the lock unit  20  to be removably appended to the rotor assembly  12  (e.g., as illustrated in  FIG. 2 ). For this purpose, the lock unit includes an insertion pin device  30  which is insertable through a second opening  32  in the lower area of side part  22   a  and into an opening in the rotor assembly. As shown in  FIG. 4 , pin device  30  is inserted through this opening, so that the opening  32  itself is not fully visible. The opening is visible in  FIG. 6 . The opening in the rotor assembly  12 , through which pin device  30  is inserted, is visible at  12   a  in  FIG. 3 . Thus, insertion of the pin device  30  through opening  32  of the base portion  22  and into opening  12   a  of the rotor assembly  12 , enables the lock unit to be removably appended to the rotor assembly. 
   Pin device  30  may be of a known type of construction in which depression of a central button  30   a  controls depressibility of a metallic protrusion  30   b  (e.g., a hemispherical steel protrusion) or of other suitable construction. In the form illustrated, pressure on button  30   a  permits the shaft of pin device  30  to be inserted into opening  12   a  in the rotor assembly and, with the release of pressure on button  30   a  after insertion, the non-depressibility of protrusion  30   b  makes pin device  30  resistant to removal from the opening  12   a  in the rotor assembly. 
   The lock unit of  FIGS. 4 ,  5  and  6  further includes an extendible device  40 , shown in an exploded view in  FIG. 6 . The extendible device  40  is positioned in the first opening  26  (visible in  FIG. 6 ) and is extendible to an extended position to contact the blade pitch housing (as shown in  FIG. 2 ). In this embodiment, extendible device  40  includes: 
   (i) A threaded shaft  42  having a near end  41  inserted into the first opening  26  and a far end  43 . 
   (ii) A first nut device  44  rotatable on threaded shaft  42  to adjustably extend the threaded shaft out of the first opening. Thus, if nut device  44  is kept in contact with the base portion surface adjacent opening  26  (as it will be in use as described) rotation clockwise will advance threaded shaft  42  to the right, to contact blade pitch housing  10  as in  FIG. 2 . Then, when use of the lock unit is no longer desired, counterclockwise rotation of nut device  44  will draw threaded shaft further back into opening  26  and away from the blade pitch housing. 
   (iii) An end piece  46  extending beyond the far end  43  of threaded shaft  42 . As will be further described, end piece  46  is adjustable for alignment with a surface of blade pitch housing  10 . 
   (iv) A second nut device  48  rotatable on threaded shaft  42  to releasably secure an adjustment of end piece  46  (e.g., to lock the end piece in place in a desired alignment). 
   (v) A ball and socket configuration including socket fitting  52  (which may be fixed to end piece  46  by set screws  45 ), a ball fitting  54 , a flat washer  55 , a concave spherical washer  56  and a convex spherical washer  57 . The ball and socket configuration may be configured to provide a known type of swivel capability by use of these components or as may otherwise be provided by skilled persons for particular applications. The end piece  46  is thus coupled to far end  43  via the ball and socket configuration. 
   (vi) A contact pad  47 , of rubber or other suitable material to provide a surface for contact with the blade pitch housing, may be adhered to the end piece  46 . 
   (vii) A threaded stud  58  which passes through and is slidable within a slot  58   a  in base portion  22  and is screwed into a hole in the near end  41  of threaded shaft  42 , as represented in  FIG. 6 . In other embodiments a roll pin may be frictionally positioned in substitution for threaded stud  58 , for example. As shown in  FIG. 6 , the first opening  26  may include a circumference having at least one substantially flat portion which is configured to cooperate with a flattened portion (i.e., material removed to form a flat) of the near end  41  of the threaded shaft  42  as shown in  FIG. 6 . With this configuration, the presence of the flat on the threaded shaft extending within the opening  26  limits rotation of threaded shaft  42  and threaded stud  58  functions as a shaft retention pin. The combination of these elements thus retains the threaded shaft within opening  26 , while still permitting it to be adjustably extended outward and retracted inward, and also prevents any significant rotation of the threaded shaft  42 . As a result, nut device  44  is enabled to function as a lock nut when it is rotated so as to press end piece  46  outward against a surface of blade pitch housing  10 , which also results in contact surface  22  of the base portion being pressed back against a surface of rotor assembly  12 . 
   As shown in  FIGS. 4 and 5 , the lock unit  20  also includes a spring-loaded positioning plunger  60 , for which further detail is provided in the exploded view of  FIG. 7 . As illustrated in  FIG. 7 , positioning plunger  60  is arranged to extend through third opening  28  in body portion  22 . Positioning plunger  60  is configured to contact a surface  12   b  of the rotor assembly to aid positioning of lock unit  20  when removably appended to the rotor assembly. Positioning plunger  60  may include a shoulder bolt  62 , a combination of washer  63 , spring  64  and washer  65  on the unthreaded shaft portion of bolt  62 , washer  66  and nut  67  on the upper threaded portion of bolt  62 , and cap  68  (e.g., of rubber) covering the lower end of bolt  62 . With this configuration, when lock unit  20  is placed in position appending to the rotor assembly, cap  68  contacts the upper surface of lower flange  12   b  of rotor assembly  12  (see  FIGS. 2 and 3 ) causing partial compression of spring  64  and some upward displacement of bolt  62  to provide a limited force to assist in maintaining lock unit  20  in a desired position relative to upper flange  12   c  of the rotor assembly, with lip  22   b  (see  FIG. 7 ) under upper flange  12   c . This or alternate constructions may be employed by skilled persons for applications in which inclusion of a positioning plunger or other device is desired for the purpose described. 
   Referring now to  FIG. 8 , there is illustrated a lock unit  20  basically as in  FIG. 4 , but with a second embodiment  40   a  of an extendible device substituted for the first embodiment  40  of  FIG. 4 . Extendible device  40   a  of  FIG. 8 , is shown in greater detail in the exploded view of  FIG. 9 . The extendible device  40   a  is positioned in first opening  26  and may be retained by threaded stud  58  and restrained from rotation by suitable flats, as previously described. In this embodiment, extendible device  40   a  includes: 
   (i) A threaded shaft  42   a  having a near end  41   a  inserted into the first opening  26  and a far end  43   a.    
   (ii) A first nut device  44   a  rotatable on threaded shaft  42   a  to adjustably extend the threaded shaft out of the first opening. 
   (iii) An end piece  46   a  extending beyond the far end  43   a  of threaded shaft  42   a.    
   (iv) A second nut device  48   a  rotatable on threaded shaft  42   a  to releasably secure an adjustment of end piece  46   a.    
   The extendible device  40   a  as configured in  FIGS. 8 and 9  enables end piece  46   a  to be adjustable via a pivot arrangement. More particularly, end piece  46   a  is pinned to far end  43   a  via a threaded stud  49 , which permits end piece  46   a  to pivot up and down (about an axis passing through the length of stud  49 ). Threaded stud  49  is inserted through a hole  49   a  in end piece  46   a  which is aligned with the hole in far end  43   a . End piece  46   a  is thus coupled to far end  43   a  in a manner to enable pivoting of the end piece. To accommodate the pivot action, the back of end piece  46   a  and the adjacent surface of second nut device  48   a  may be provided with cooperating surfaces which respectively approximate portions of convex spherical and concave spherical surfaces to accommodate upward and downward pivoting of the end piece  46   a . A rubber pad  47   a  may be positioned on a surface of end piece  46   a  to provide cushioning of a contact with a blade pitch housing. 
   The pivot capability of the extendible device  40   a  enables end piece  46   a  to make suitable contact with a contact surface of a blade pitch housing in many applications. The particular components and design of extendible device  40   a  may be selected and altered by skilled persons as appropriate for particular applications. For example nut devices, such as device  44   a , may be of any form suitable to provide the result described and other elements may be provided or substituted as appropriate. 
   It will thus be appreciated that when a helicopter is beginning a period of time during which it will not be flown, a lock unit as described may be temporarily appended to the rotor assembly at the position of each blade pitch housing with attached blade. For the embodiments described, the base portion of the lock unit is placed adjacent the rotor assembly, with positioning aided by the spring loaded plunger and maintained by insertion of the insertion pin device into an opening in the rotor assembly. The extendible device can then be extended and locked to provide a structural combination effective to maintain a fixed separation between surfaces of the rotor assembly and blade pitch housing which restricts upward rotation of the blade pitch housing and attached helicopter blade. Then, when the helicopter is to resume flight operations, the lock units may readily be removed and stored for future use. 
   While there have been described the currently preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications and implementations may be made without departing from the invention and it is intended to claim all modifications and variations as fall within the scope of the invention. 
   SEQUENCE LISTING 
   (Not Applicable)