Patent Publication Number: US-2023151845-A1

Title: Adjustable crank arm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     Crank arms are a critical component in many mechanical systems, including systems for folding aircraft blades. In some cases, crank arms can be installed as a final or near final component in a folding mechanism, and such mechanisms can require some degree of rigging or otherwise may need to be provided a specialized length to meet the needs of connecting components of the folding mechanism. Accordingly, conventional crank arms are often customized at the point of installation to bridge a previously inexactly known connection distance and this matching process can involve match drilling a plurality of components to provide a crank arm with the precise length needed for a particular installation. However, utilizing match drilling and other methods of generating crank arms with the needed overall lengths is typically a single use scenario in which the drilled components are good for a single installation and not used thereafter. Accordingly, there remains a need for crank arms that are easily adjustable in overall length and that can be reused and/or adjusted after a successful initial installation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an oblique view of a tiltrotor aircraft configured in a helicopter mode and comprising an embodiment of an adjustable crank arm according to this disclosure. 
         FIG.  2    is an oblique view of the aircraft of  FIG.  1    configured in an airplane mode. 
       Prior Art  FIG.  3    is an oblique view of a portion of a rotor of the aircraft of  FIG.  1    and showing a folding mechanism configured in an extended position, the folding mechanism comprising a prior art crank arm. 
       Prior Art  FIG.  4    is an oblique view of the portion of the rotor of  FIG.  3    and configured in a partially folded position. 
       Prior Art  FIG.  5    is an oblique rear view of a prior art crank arm. 
         FIG.  6    is an oblique view of a portion of a rotor of the aircraft of  FIG.  1    and showing a folding mechanism configured in a partially folded position, the folding mechanism comprising an adjustable crank arm according to an embodiment of this disclosure. 
         FIG.  7    is an oblique view of the adjustable crank arm of  FIG.  6   . 
         FIG.  8    is a partial cross-sectional view of the adjustable crank arm of  FIG.  6   . 
         FIG.  9    is another partial cross-sectional view of the adjustable crank arm of  FIG.  6   . 
         FIG.  10    is an oblique view of another adjustable crank arm according to an embodiment of this disclosure. 
         FIG.  11    is a partial cross-sectional view of the adjustable crank arm of  FIG.  10   . 
         FIG.  12    is another partial cross-sectional view of the adjustable crank arm of  FIG.  10   . 
     
    
    
     DETAILED DESCRIPTION 
     In this disclosure, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of this disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. 
       FIGS.  1  and  2    illustrate a tiltrotor aircraft  100 , which can include a fuselage  102 , landing gear  104 , tail member  106 , wing  108 , propulsion system  110 , and propulsion system  112 . Each propulsion system  110 ,  112  includes a fixed engine and rotatable proprotor  114 ,  116 , respectively. Each rotatable proprotor  114 ,  116  has a plurality of foldable rotor blades  118  and  120 , respectively. The position of proprotors  114 ,  116 , as well as the pitch of blades  118 ,  120 , can be selectively controlled in order to selectively control direction, thrust, and lift of tiltrotor aircraft  100 .  FIG.  1    shows tiltrotor aircraft  100  in a helicopter mode, and  FIG.  2    shows tiltrotor aircraft  100  in an airplane mode. 
     Referring to Prior Art  FIGS.  3  and  4   , to allow for at least some of blades  118 ,  120  to fold, an outboard blade portion  122  is coupled to an inboard portion  124  at hinge  126 , allowing outboard portion  122  to pivot relative to inboard portion  124  via hinge  126  and about pivot axis  128 . 
     A crank arm assembly  130  comprises a prior art crank arm  200  selectively pivotable about a crank axis  134  by operation of a trunnion  135 , trunnion  135  being coupled to an inner end of crank arm  200  with shaft  136 . Crank arm  200  has a bearing pocket  208  located at an outer end of crank arm  200  opposite shaft  136 , pocket  208  being configured for receiving a spherical bearing  140 . An interstitial link  142  couples crank arm  200  to outboard portion  122  of blade  118 , allowing rotation of trunnion  135  about axis  134  to cause rotation of outboard portion  122  about pivot axis  128 . 
     Interstitial link  142  has a crank clevis  144  at an inboard end and configured to be fastened to bearing  140  with fastener  146 , allowing for crank arm  200  and link  142  to pivot relative to each other about pivot axis  148 . A blade clevis  150  is located on the outboard end of link  142  and configured to be fastened with fastener  152  to a spherical bearing  154 , which is carried in pillow block  156  of outboard blade portion  122 . This allows for link  142  and outboard portion  122  to pivot relative to each other about pivot axis  158 . 
     To move outboard blade portion  122  between the fully extended position shown in Prior Art  FIG.  3    and a folded position, trunnion  135  and crank arm  200  are rotated together about crank axis  134 . From the fully extended position, crank arm  200  is rotated in the direction shown by arrow  160 , and Prior Art  FIG.  4    shows components moved to a partially folded configuration. As crank arm  200  is rotated, interstitial link  142  transfers force from spherical bearing  140  in pocket  208  of crank arm  200  to outboard portion  122  through the spherical bearing  154  in pocket  156 . Moving outboard portion  122  toward the fully extended position is accomplished by rotating trunnion  135  and crank arm  200  together in the opposite direction. 
     Referring now to Prior Art  FIG.  5   , prior art crank arm  200  generally comprises an overall length  202  that is determined by an amount of longitudinal overlap between a rod end  204  and a receiver arm  206 . Rod end  204  comprises the bearing pocket  208  formed substantially as a ringlike structure configured to receive a bearing, such as, but not limited to, a spherical bearing. Rod end  204  further comprises a mounting plate  210  extending from the bearing pocket  208 . Mounting plate  210  carries opposing sidewalls  212  that further stiffen mounting plate  210 . Receiver arm  206  comprises a cylindrical head  214  connected to a receiver bar  216 . In this embodiment, mounting plate  210  and receiving bar  216  are configured to have profiles that face each other and that are complementary to each other, such as, but not limited to, facing flat surfaces. Crank arm  200  is assembled through a match drilling process in which a desired overall length  202  is selected by moving the above-described complementary profiles into contact with each other, holding rod end  204  stationary relative to receiver arm  206 , drilling multiple through holes through mounting plate  210  and adjacent receiving bar  216 , and finally securing rod end  204  relative to receiver arm  206  using fasteners disposed within the through holes. In this embodiment, threaded bolts  218  are passed through the through holes and secured in place using threaded nuts. While this process of fixing an overall length  202  of crank arm  200  is effective, it is not amenable to adjustments after initially fitting or rigging to a particular installation. Instead, while the components may be reused by drilling more holes and using a new set of holes to provide a different overall length  202 , the revision process is time consuming, generates undesirable debris, and can result in undesirable reductions in strength due to the extraneous holes remaining in the mounting plate  210  and the receiving bar  216 . 
     There is a need for crank arms that are structurally sound and adjustable in overall length without generating the undesirable debris and without potentially introducing a weakness into the connective components. Accordingly, at least two embodiments of adjustable length crank arms are disclosed herein. They are both minutely and/or infinitely adjustable in overall lengths so that changes or slight adjustments to the overall lengths can be easily made. Both embodiments allow the crank arm overall lengths to be quickly lengthened or shortened while still being able to react both longitudinal and axial forces as well as bending across the crank arms as a whole, upon final assembly. As will be explained below, pairing of a threaded rod end and a sandwiched jam nut with a set of wedge pieces and a cross-linked bolt (or other fastener) enable the positioning of the two ends of crank arm  300  to be easily brought together or moved away from each other. The embodiments incorporate a turnbuckle approach to linear adjustment through the use of a threaded rod end shank and jam nut which are restrained by structural members (such as wall features and holes). 
     Referring now to  FIG.  6 - 9   , an adjustable crank arm  300  according to an embodiment of this disclosure is shown.  FIG.  6    shows adjustable crank arm  300  utilized in crank arm assembly  130 , which is a portion of tiltrotor aircraft  100 .  FIGS.  7 - 9    show adjustable crank arm  300  in isolation. Adjustable crank arm  300  comprises a rod end  304  and a receiver arm  306 . The receiver arm  306  is configured to selectively receive a portion of the rod end  304  while additional components are utilized to secure the rod end  304  relative to the receiver arm  306 . Most generally, the adjustable crank arm  300  can be configured to have a variety of different overall lengths  302  by adjusting an amount of longitudinal overlap between the rod end  304  and the receiver arm  306 . 
     Adjustable crank arm  300  further comprises wedges  308  each comprising wedge ramp surfaces  310 . Wedge ramp surfaces  310  are configured to complement rod end ramp surfaces  312  of rod end  304  and receiver arm ramp surfaces  314  of receiver arm  306 . Wedges  308  further comprise holes  316  configured to receive a threaded bolt  318  (or other fastener) therethrough. Washers  319  can optionally be utilized. Accordingly, in response to a threaded nut  320  being advanced along bolt  318 , wedges  308  can be driven toward each other and the resultant interaction between wedge ramp surfaces  310  and each of rod end ramp surfaces  312  and receiver arm ramp surfaces  314  can result in increasing a separation force and/or separation distance between rod end  304  and receiver arm  306 . It will be appreciated that in alternative embodiments, instead of or in addition to using nuts  320  for adjusting the location of wedges  308 , holes  316  can be threaded and used together with bolts  318  to move wedges  308  relative to each other. Further, it will be appreciated that while wedges  308  comprise substantially flat ramp surfaces  310 , in alternative embodiments, wedges can comprise differently shaped surfaces, such as, but not limited to, semi-cylindrical profiles and/or a plurality of suitable surfaces. 
     Referring to  FIG.  8   , it can be seen that bolt  318  passes through a slot  322  formed in rod end  304  so that some amount of longitudinal adjustment between rod end  304  and receiver arm  306  can be made without applying a bending force to bolt  318  from rod end  304 . Adjustable crank arm  300  further comprises a threaded shank  324  extending from rod end  304  for being received by receiver arm  306 . Receiver arm  306  comprises an internal passage  326  configured to receive threaded shank  324 . Further, a pocket  328  is formed in receiver arm  306  and intersects internal passage  326 . In this embodiment, a cylindrical insert  330  is secured within internal passage  326  and is configured to accept threaded shank  324 . Further, a jam nut  332  is disposed within pocket  328  and sandwiched between a shim washer  334  and a jam nut lock washer  336 . Accordingly, a wrench or other tool can be utilized by inserting the tool into pocket  328  to interface jam nut  332 . With sufficient advancement of jam nut  332  along threaded shank  324 , longitudinal adjustment and tension can be applied to threaded shank  324 , thereby increasing a bending stiffness of the adjustable crank arm  300 . 
     Referring now to  FIG.  10 - 12   , an adjustable crank arm  400  according to another embodiment of this disclosure is shown. Adjustable crank arm  400  can replace adjustable crank arm  300  and/or prior art crank arm  200  in crank arm assembly  130 . Adjustable crank arm  400  comprises a rod end  404  and a receiver arm  406 . The receiver arm  406  is configured to selectively receive a portion of the rod end  404  while additional components are utilized to secure the rod end  404  relative to the receiver arm  406 . Most generally, the adjustable crank arm  400  can be configured to have a variety of different overall lengths  402  by adjusting an amount of longitudinal overlap between the rod end  404  and the receiver arm  406 . 
     Adjustable crank arm  400  further comprises wedges  408  each comprising wedge ramp surfaces  410 . Wedge ramp surfaces  410  are configured to complement rod end ramp surfaces  412  of rod end  404  and receiver arm ramp surfaces  414  of receiver arm  406 . Wedges  408  further comprise holes  416  configured to receive a threaded bolt  418  (or other fastener) therethrough. Washers  419  can optionally be utilized. Accordingly, in response to a threaded nut  420  being advanced along bolt  418 , wedges  408  can be driven toward each other and the resultant interaction between wedge ramp surfaces  410  and each of rod end ramp surfaces  412  and receiver arm ramp surfaces  414  can result in increasing a separation force and/or separation distance between rod end  404  and receiver arm  406 . 
     Referring to  FIG.  12   , it can be seen that bolt  418  passes through a slot  422  formed in rod end  404  so that some amount of longitudinal adjustment between rod end  404  and receiver arm  406  can be made without applying a bending force to bolt  418  from rod end  404 . Adjustable crank arm  400  further comprises a threaded shank  424  extending from rod end  404  for being received by receiver arm  406 . Receiver arm  406  comprises an internal passage  426  configured to receive threaded shank  424 . Further, a pocket  428  is formed in receiver arm  406  and intersects internal passage  426 . In this embodiment, a cylindrical insert  430  is secured within internal passage  426  and is configured to accept threaded shank  424 . Further, a jam nut  432  is disposed within pocket  428  and sandwiched between a shim washer  434  and a jam nut lock washer  436 . Accordingly, a wrench or other tool can be utilized by inserting the tool into pocket  428  to interface jam nut  432 . With sufficient advancement of jam nut  432  along threaded shank  424 , longitudinal adjustment and tension can be applied to threaded shank  424 , thereby increasing a bending stiffness of the adjustable crank arm  400 . 
     In operation, crank arms  300 ,  400  can be used by first rotating jam nuts  332 ,  432  to adjust the length  302 ,  402  of the assembly, and subsequently adjust the nuts  320 ,  420  and/or bolts  318 ,  418  to increase a compression applied by the wedges  308 ,  408 . Alternatively, an overall length can first be achieved by rotating the nuts  320 ,  420  and/or bolts  318 ,  418  to adjust the length  302 ,  402  of the assembly, and subsequently rotating the jam nuts  332 ,  432  to further secure the assembly. In other embodiments, a threaded wedge can be utilized rather than a separate nut. Still further, in other alternative embodiments, the ramps of wedges can comprise any other suitable shape for providing a sliding engagement surface, such as, but not limited to, a semi-cylindrical profile. 
     It will be appreciated that the adjustable length crank arms disclosed herein can be utilized for systems other than folding mechanisms and with systems other than aircraft. The systems and methods disclosed here can be utilized in any other system that requires or benefits from the use of an arm or bar with adjustable total length while retaining load bearing and load transfer capabilities in a multitude of directionalities. 
     At least one embodiment is disclosed, and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of this disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of this disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, R EL , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R s +k*(R u −R 1 ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 95 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. 
     Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. Also, the phrases “at least one of A, B, and C” and “A and/or B and/or C” should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.