Abstract:
A low-cost, lightweight telescoping torque tube assembly is reliable, safe, and easy to operate. The assembly has no loose fasteners, and no tools are required to operate the telescoping assembly. The telescoping torque tube assembly has only two parts, namely an end fitting and a torque tube. A resiliently deflectable locking tab is provided on one of the parts, and the locking tab is received by a corresponding locking slot formed in the other part. The locking tab has an abutment edge, and the locking slot has a limit edge facing the abutment edge for engaging the abutment edge when the locking tab is undeflected to prevent axially directed adjustment of the end fitting relative to the torque tube from an extended position toward a retracted position. A user deflects the locking tab to enable adjustment of the end fitting from the extended position to the retracted position.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to torque tubes (sometimes referred to as torque shafts) used on an aircraft utility or flight control drive line, or on any drive line that requires a telescoping torque tube. 
       BACKGROUND OF THE INVENTION 
       [0002]    A telescoping torque tube is a type of shaft used in drive lines that can be temporarily shortened in length by moving an end fitting on the torque tube from an extended position to a retracted position to facilitate installation or removal of the torque tube. In order for the torque tube to function properly, the telescoping end fitting must be locked in the extended position. Torque is commonly transmitted between the torque tube and end fitting by meshed splines on the torque tube and end fitting. 
         [0003]    There are several known ways of releasably locking an end fitting at an extended position on a torque tube. One technique simply uses a cross bolt to lock the end fitting to the torque tube. The installer inserts the cross bolt transversely through aligned holes in axially overlapping end portions of the end fitting and the torque tube and uses the required tools to tighten the bolt. Typically, the cross bolt only restrains axial motion of the end fitting, and torque is transmitted by meshed splines, unless the torque carried by the torque tube is very low. The cross bolt must be removed to shorten the telescoping assembly. 
         [0004]    Another technique uses an axially arranged internal spring acting between the torque tube and the end fitting to bias the end fitting toward the extended position. The end fitting and torque tube may be configured such that the end fitting can be locked in the extended and retracted positions by relative rotation between the end fitting and the torque tube about a longitudinal axis of the torque tube, and can be unlocked by relative counter-rotation. To shorten the telescoping torque tube assembly, the installer may rotate the end fitting to unlock it from the extended position, and then push the end fitting to the retracted position. 
         [0005]    Another known technique employs a spring-loaded radially extending detent pin arranged to lock the end fitting of a telescoping torque tube assembly from axial movement. The installer presses the spring detent pin to stop the interference between the pin and the end fitting and allows axial movement of the end fitting. 
         [0006]    These state of the art approaches for coupling an end fitting to a torque tube in a telescoping torque tube assembly require additional parts beyond the torque tube and end fitting, thereby adding weight and cost to the assembly while diminishing its reliability. The procedure to retract the end fitting may be time consuming, may require tools, and may involve loose fasteners. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a low-cost, lightweight telescoping torque tube assembly that is reliable, safe, and easy to operate. The assembly has no loose fasteners, such as nuts, bolts, cotter pins, snap rings, etc., that can be dropped or lost. No tools are required to operate the telescoping assembly. The telescoping torque tube assembly of the invention has only two parts, namely an end fitting and a torque tube. 
         [0008]    In a first embodiment of the invention, a resiliently deflectable locking tab is provided on the torque tube, and the end fitting includes a locking slot arranged for receiving the locking tab when the end fitting is in an extended position. The locking tab has an abutment edge, and the locking slot has a limit edge facing the abutment edge of the locking tab for engaging the abutment edge when the locking tab is in an undeflected state to prevent axially directed adjustment of the end fitting relative to the torque tube from the extended position toward a refracted position. The locking tab is deflectable by a user such that the abutment edge of the locking tab is not faced by the limit edge of the locking slot, thereby permitting axially directed adjustment of the end fitting relative to the torque tube from the extended position to the retracted position. 
         [0009]    In a second embodiment of the invention, the location of the locking tabs and locking slots is reversed (i.e. the locking tabs are on the end fitting and the locking slots are formed in the torque tube). 
         [0010]    The locking tabs may be configured to have a pair of abutment edges and the locking slot may have a pair of limit edges to provide locking in both axial directions so that the end fitting is locked from adjustment toward the retracted position and is also retained on the torque tube. Alternatively, separate retainer tabs and retainer slots may be provided to restrict movement of the end fitting in a direction tending to separate the end fitting from the torque tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0012]      FIG. 1  is a perspective view showing a telescoping torque tube assembly formed in accordance with a first embodiment of the present invention; 
           [0013]      FIG. 2  is a cross-sectional view of one end of the telescoping torque tube assembly, wherein an end fitting of the torque tube assembly is locked in an extended position; 
           [0014]      FIG. 3  is a cross-sectional view similar to that of  FIG. 2 , illustrating deflection of a pair of locking tabs to unlock the end fitting for telescoping adjustment; 
           [0015]      FIG. 4  is a cross-sectional view similar to that of  FIG. 2 , wherein the end fitting is shown in its retracted position; 
           [0016]      FIG. 5  is a plan view of one of the locking tabs and its associated locking slot; 
           [0017]      FIG. 6  is a view similar to that of  FIG. 5 , showing a locking tab having an alternative configuration; 
           [0018]      FIG. 7  is a cross-sectional view of the same end of the telescoping torque tube assembly shown in  FIG. 2 , wherein the sectioning plane is orthogonal to the sectioning plane of  FIG. 2  to illustrate a pair of retainer tabs of the assembly for preventing separation of the end fitting from the torque tube when the end fitting is in the extended position; 
           [0019]      FIG. 8  is a cross-sectional view of one end of a telescoping torque tube assembly formed in accordance with a second embodiment of the present invention, wherein an end fitting of the torque tube assembly is locked in an extended position; 
           [0020]      FIG. 9  is a cross-sectional view similar to that of  FIG. 8 , illustrating deflection of a pair of locking tabs to unlock the end fitting for telescoping adjustment; 
           [0021]      FIG. 10  is a cross-sectional view similar to that of  FIG. 8 , wherein the end fitting is shown in its retracted position; 
           [0022]      FIG. 11  is a plan view of one of the locking tabs of the torque tube assembly of  FIGS. 8-10 ; 
           [0023]      FIG. 12  is a view similar to that of  FIG. 11 , showing a locking tab having an alternative configuration; and 
           [0024]      FIG. 13  is an elevational view of the locking table shown in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIGS. 1 and 2  show a telescoping torque tube assembly  10  incorporating an apparatus for telescopically coupling end fittings  12  of the assembly to a torque tube  14  of the assembly in accordance with a first embodiment of the present invention.  FIG. 1  shows the entire assembly  10  having an end fitting  12  at each opposite end region of torque tube  14 . Assembly  10  has a longitudinal adjustment axis  11  along which end fittings  12  are telescopically adjustable relative to torque tube  14 . The overlapping end regions of end fittings  12  and torque tube  14  include meshed splines  16  and  18  for transmitting torque between end fittings  12  and torque tube  14 . In the description that follows, the apparatus for coupling one of the end fittings  12  to a mating end region of torque tube  14  is described in detail, it being understood that the end fitting at the opposite end of torque tube  14  may be coupled in mirror image fashion. 
         [0026]    In  FIG. 2 , end fitting  12  is locked in its extended position, which is the position end fitting  12  is in during normal operation of torque tube assembly  10 . In the illustrated embodiment, a pair of resiliently deflectable locking tabs  20  are provided on torque tube  14 . Each locking tab  20  extends in an axial direction of torque tube  14  and is bent slightly outward in a radial direction of the torque tube. Each locking tab  20  has an abutment edge  20 A. End fitting  12  includes a pair of locking slots  22  arranged for respectively receiving the pair of locking tabs  20 . Each locking slot  22  has a limit edge  22 A facing the abutment edge  20 A of the corresponding locking tab  20  for engaging the abutment edge when the locking tab is in an undeflected state. Consequently, axially directed retraction of end fitting  12  relative to torque tube  14  is prevented. As shown in  FIG. 2 , locking tabs  20  and spline  18  of torque tube  14  may be formed on a separate sleeve  15  that is fixed to an end region of the torque tube  14 , for example by welding, to become part of the torque tube  14 . Alternatively, locking tabs  20  and spline  18  may be formed integrally with torque tube  14 . Spline  16  of end fitting  12  may be bottled bored into the inner wall of the end fitting. 
         [0027]      FIGS. 3 and 4  illustrate how end fitting  12  may be unlocked and telescopically adjusted from the extended position to a retracted position suitable for installing or removing assembly  10  from a drive line. As indicated in  FIG. 3 , the pair of locking tabs  20  are simultaneously deflectable radially inward by a user, for example by manually pressing both locking tabs at the same time. This displaces the abutment edges  20 A of the locking tabs  20  such that the abutment edges are not faced by limit edges  22 A of locking slots  22 , thereby enabling axially directed adjustment of end fitting  12  relative to torque tube  14  to the retracted position shown in  FIG. 4 . To facilitate simultaneous deflection of locking tabs  20 , the locking tabs may be arranged diametrically opposite one another about axis  11 . 
         [0028]    End fitting  12  may be returned from the retracted position to the extended position. When end fitting arrives at the extended position, the resilient locking tabs  20  will once again be received by locking slots  22  as shown in  FIG. 2 . 
         [0029]      FIG. 5  shows one of the locking tabs  20  in plan view. Locking tab  20  in  FIG. 5  has the shape of a rectangular finger. 
         [0030]      FIG. 6  shows an alternative configuration of locking tab  20  wherein the locking tab loops around to have a “U” shape. The configuration shown in  FIG. 6  is designed to prevent movement of end fitting  12  from the extended position to the retracted position, and to also limit movement of end fitting  12  in an opposite direction to prevent separation of end fitting  12  from torque tube  14 . The U-shaped locking tab  20  has a first abutment edge  20 A facing a first limit edge  22 A of locking slot  22 , and has a second abutment edge  20 B facing a second limit edge  22 B of locking slot  22 . When end fitting  12  is in the extended position, further extending movement of end fitting  12  relative to torque tube  14  is blocked by engagement of second limit edge  22 B with second abutment edge  20 B, thereby preventing separation of end fitting  12  from torque tube  14 . 
         [0031]      FIGS. 1 and 7  illustrate an alternative approach to keeping end fitting  12  on torque tube  14 . In this approach, a pair of resiliently deflectable retainer tabs  30  are provided on torque tube  14  and end fitting  12  has a corresponding pair of retainer slots  32  arranged for receiving the retainer tabs  30  when end fitting  12  is in the extended position. Each retainer tab  30  has an abutment edge  30 A and each retainer slot has a limit edge  32 A facing the abutment edge  30 A of the retainer tab  30  for engaging the abutment edge when the retainer tab  30  is in an undeflected state. Retainer tabs  30  and retainer slots  32  are arranged to act in an opposite axial direction as compared to locking tabs  20  and locking slots  30 , thus preventing axially directed separation of the end fitting from the torque tube. In the embodiment shown, retainer tabs  30  and retainer slots  32  are offset ninety degrees from locking tabs  20  and locking slots  22  about axis  11 . 
         [0032]      FIGS. 8-10  illustrate a telescoping torque tube assembly  110  formed in accordance with a second embodiment of the present invention. Assembly  110  differs from assembly  10  of the first embodiment in that the locking tabs are provided on the end fitting instead of the torque tube, and the locking slots are provided on the torque tube instead of the end fitting. 
         [0033]    In  FIG. 8 , an end fitting  112  is locked in its extended position, and a pair of resiliently deflectable locking tabs  120  are provided on the end fitting. Each locking tab  120  extends in an axial direction of torque tube  114  and is bent slightly inward in a radial direction of the torque tube. Each locking tab  120  has an abutment edge  120 A. Torque tube  114  includes a pair of locking slots  122  arranged for respectively receiving the pair of locking tabs  120 . Each locking slot  122  has a limit edge  122 A facing the abutment edge  120 A of the corresponding locking tab  120  for engaging the abutment edge when the locking tab is in an undeflected state. Consequently, axially directed retraction of end fitting  12  relative to torque tube  14  is prevented. Torque tube  114  may have a circumferential groove  124  for defining limit edge  122 A and receiving an elbow region of locking tab  120  to ensure locking engagement. 
         [0034]      FIGS. 9 and 10  illustrate how end fitting  112  may be unlocked and telescopically adjusted from the extended position to a retracted position suitable for installing or removing assembly  110  from a drive line. As indicated in  FIG. 9 , the pair of locking tabs  120  are simultaneously deflectable radially outward by a user. For example, locking tabs  120  may have a bent shape defining an outward leg  120 B that can be manipulated by a user to withdraw the locking tab  120  from engagement. This displaces the abutment edges  120 A of the locking tabs  120  such that the abutment edges are not faced by limit edges  122 A of locking slots  122 , thereby enabling axially directed adjustment of end fitting  112  relative to torque tube  114  to the retracted position shown in  FIG. 10 . Similar to the first embodiment, the locking tabs  120  may be arranged diametrically opposite one another to facilitate simultaneous deflection of both locking tabs. 
         [0035]      FIG. 11  shows one of the locking tabs  120  in plan view. Locking tab  120  in  FIG. 11  has the shape of a rectangular finger. 
         [0036]      FIGS. 12 and 13  show an alternative configuration of locking tab  120  intended to allow a user to disengage the locking tab by pressing radially inward. wherein the locking tab loops around to have a “J” shape. A main leg of the “J” shape defines abutment edge  120 A, while a secondary leg of the “J” shape includes a portion  120 C that is curved radially outward. As may be understood, inward pressure applied to curved portion  120 C will provide a camming action against torque tube  114 , thereby lifting abutment edge  120 A away from facing relationship with limit edge  122 A to enable retraction of end fitting  112 . 
         [0037]    End fitting  112  may be retained on torque tube  114  using approaches that are analogous to those described above for the first embodiment. For example, locking tabs  120  may have two abutment edges cooperating with respective limit edges of locking slots  122  to restrict adjustment motion in both axial directions. As another example, at least one retainer tab and retainer slot may be provided separate from the locking tabs  120  and locking slots  122  to prevent separation of end fitting  112  from torque tube  114 . 
         [0038]    With respect to either assembly  10  of the first embodiment or assembly  110  of the second embodiment, those skilled in the art will understand that the number of locking tabs and corresponding locking slots may be varied, and may be as few as one. Those skilled in the art will further understand that the teachings herein may be adapted to a torque tube assembly wherein the end fitting  12 ,  112  is sized to be the male part and the torque tube  14 ,  114  is sized to be the female part. Material for making end fitting  12 ,  112  and torque tube  14 ,  114  may be selected based on strength requirements and weight restrictions. Steel and aluminum are common material choices. 
         [0039]    While the invention has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the invention to the particular forms set forth. The invention is intended to cover such alternatives, modifications and equivalents of the described embodiment as may be included within the scope of the invention.