Abstract:
A torque limiting adapter readily usable with rotary drivers and tool holders customarily received in a chuck of rotary drivers. The torque limiting adapter is installed in the rotary driver, and in turn, receives the tool holder which holds a fastener or other item to be rotatably driven into the substrate. The torque limiting adapter includes an input shaft received by the rotary driver, a separate output shaft, and an internal spring clutch adjustable to transmit only a desired torque value from the input shaft to the output shaft. A rotatable adjuster adjusts a spring of the spring clutch to vary maximum transmissible torque. The rotatable adjuster includes a locking mechanism to maintain a selected maximum torque value.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Utility Application Ser. No. 62/239,151, filed Oct. 8, 2015. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to torque transmitting implements, and more particularly, to a self-limiting torque transmitting implement to be installed between a powered rotary driver and a tool to be rotated by the powered rotary driver. The self-limiting torque transmitting implement limits torque which can be imposed on the tool to be rotated. 
       BACKGROUND 
       [0003]    Tools have been developed to drive rotary fasteners and other items into supporting substrates. If no provision is made to limit torque imposed on the rotary fasteners, they may be overtightened and destroy threading that would otherwise retain them in place. In particular, rotary drivers such as powered drills, and rotatable tool holders which are typically secured within chucks of the rotary drivers are frequently made with no provision for torque limitation. There exists a need for a device which may be readily assembled with rotary drivers and associated tool holders to limit torques applied to the fasteners and other driven items. Beyond this, there exists a need for a torque limiting device having provision for adjusting the amount of torque which may be transmitted to the fastener and other driven items. 
       SUMMARY 
       [0004]    The disclosed concepts address the above stated situation by providing a torque limiting adapter readily usable with rotary drivers and tool holders customarily received in a chuck of rotary drivers. The torque limiting adapter is installed in the rotary driver, and in turn, receives the tool holder which holds a fastener or other item to be rotatably driven into the substrate. The torque limiting adapter includes an input shaft received by the rotary driver, a separate output shaft, and an internal spring clutch adjustable to transmit only a desired torque value from the input shaft to the output shaft. 
         [0005]    A rotatable adjuster adjusts a spring of the spring clutch to vary maximum transmissible torque. The rotatable adjuster includes a locking mechanism to maintain a selected maximum torque value. 
         [0006]    It is an object to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Various objects, features, and attendant advantages of the disclosed concepts will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
           [0008]      FIG. 1  is a longitudinal cross sectional view of a torque limiting adapter, taken along line A-A of  FIG. 3 , according to at least one aspect of the disclosure; 
           [0009]      FIG. 2  is a redundant view of  FIG. 1 , taken along line B-B of  FIG. 1 , provided to avoid unnecessary clutter of reference numerals and their leader lines; 
           [0010]      FIG. 3  is an environmental side view of the torque limiting adapter of  FIG. 1 ; 
           [0011]      FIG. 4  is a cross sectional view of the torque limiting adapter of  FIG. 1 , taken along line C-C in  FIG. 1 ; 
           [0012]      FIG. 5  is a top view of the torque limiting adapter of  FIG. 1 ; and 
           [0013]      FIG. 6  is a cross sectional view of the torque limiting adapter of  FIG. 1 , taken along line D-D in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring first to  FIGS. 2 and 3 , according to at least one aspect of the disclosure, there is shown a torque limiting adapter  100  for interfacing between a powered rotary driver (represented by its chuck  102  in  FIG. 3 ) and a driven tool  104  ( FIG. 3 ). Torque limiting adapter  100  may comprise an outer housing  22  comprising a top wall  210  including an inlet opening  30 , an opposed bottom wall  31  including an outlet opening  32 , and a lateral wall  33  spanning top wall  210  and bottom wall  31 . A chamber  34  is surrounded by top wall  210 , bottom wall  31 , and lateral wall  33 . 
         [0015]    An input shaft  13  extends through inlet opening  30  of top wall  210 . Input shaft  13  terminates in a flange  16  of transverse dimension greater than a transverse dimension of input shaft  13 . Flange  16  is contained within outer housing  22 . 
         [0016]    An output shaft  35  is axially aligned with input shaft  13 . Output shaft  35  extends through outlet opening  32  of outer housing  22 . 
         [0017]    A spring clutch  14  is adjustable to transmit torques imposed on input shaft  13  to output shaft  35 , and to establish disengagement of input shaft  13  from output shaft  35 . Spring clutch  14  may further comprise an upper member  36 , an axially aligned lower member  18 , a clutch spring  15  clamping upper member  36  against lower member  18 , and an adjuster  37  adjustable to vary clamping pressure exerted by clutch spring  15 . 
         [0018]    Adjuster  37  may comprise a threaded adjuster member  1  threadedly engaging a threaded interior surface  38  of outer housing  22  and arranged to travel axially along output shaft  35  and to bear against clutch spring  15  when rotated. A locking mechanism  2  is configured to maintain threaded adjuster member  1  in a selected adjustment position along output shaft  35  relative to clutch spring  15 . 
         [0019]    A receiver  20  including a socket  310  is configured to receive and rotate driven tool  104  responsive to rotation of output shaft  35 . Receiver  20  may comprise a drive tool lock  40  configured to releasably retain driven tool  104  in socket  310 . 
         [0020]    It should be noted at this point that orientational terms such as upper, lower, top, and bottom refer to the subject drawing as viewed by an observer. The drawing figures depict their subject matter in orientations of normal use, which could obviously change with changes in body posture and position. Therefore, orientational terms must be understood to provide semantic basis for purposes of description only, and do not imply that their subject matter can be used only in one position. 
         [0021]    References to an axis, including axial alignment and axial travel as examples, refer to longitudinal axis A shown in  FIG. 1 . 
         [0022]    As will now be explained, outer housing  22  may be complemented by an interior housing  42 . In the absence of interior housing  42 , threaded interior surface  38  would be formed as part of outer housing  22 . Accordingly, outer housing  33  may comprise interior housing  42  including internal threads  44  threadably engaging corresponding threads  21  of the enlarged head  10  of input shaft  13 , and axially extending internal grooves  46  ( FIG. 4 ). Threaded adjuster member  1  engages internal threads  44  of interior housing  42 . 
         [0023]    Locking mechanism  2  may comprise internal adjustment member splines  48  ( FIG. 4 ) on threaded adjuster member  1 , and a locking nut  50  (called out in  FIG. 1 ) including an outwardly projecting locking nut flange  52  ( FIG. 1 ). Locking nut  50  includes external splines  54  ( FIG. 4 ) engageable with internal adjustment member splines  48 (star). This constrains threaded adjuster member  1  from rotation relative to outer housing  22 . Locking nut  50  also includes outwardly projecting tabs  8  on locking nut flange  52  configured to interfit with axially extending internal grooves  46  of interior housing  42 . An adjuster spring  11  urges locking nut  50  into engagement with threaded adjuster member  1 . 
         [0024]    Locking nut  50  has the appearance of an inverted brimmed cylindrical hat, when considering locking nut flange  52 , as seen in the cross section of  FIG. 1 . 
         [0025]    Outer housing  22  may be formed in two mating sections, to facilitate fabrication using methods other than three dimensional printing. To this end, outer housing  22  may further comprise a lower housing section  23  including a floor  56 , a lateral wall  58 , and exterior threads  60  on lateral wall  58 . Outer housing  22  may comprise corresponding outer housing threads  62  enabling lower housing section  23  to thread to corresponding outer housing threads  62  of outer housing  22 , and to close over components contained within chamber  34  of outer housing  22 . 
         [0026]    Drive tool lock  40  may comprise a detent ball  25 . Receiver  20  may comprise an axially slidable sleeve  110  slidably arranged selectively to press detent ball  25  into engagement with driven tool  104  ( FIG. 3 ), and to release detent ball  25  from engagement with driven tool  104 . 
         [0027]    Torque limiting adapter  100  may further comprise seals sealing chamber  34  of outer housing  22  against infiltration by contaminants These seals may comprise an upper O-ring seal  24  at inlet opening  30 , and a lower O-ring seal  6  between outer housing  22  and lower housing section  23 , and a lip seal assembly  5  at outlet opening  32 . 
         [0028]    Output shaft  35  may include a circumferential groove  64  ( FIG. 2 ), and a clip ring  27  engaging circumferential groove  64 . Clip ring  27  has a transverse dimension greater than that of outlet opening  32  of outer housing  22 . Clip ring  27  is further entrapped by a thrust washer  28  between clip ring  27  and lip seal assembly  5 . Output shaft  35  is thus constrained from sliding out of outlet opening  32  and being lost. 
         [0029]    Torque limiting adapter  100  may further comprise a bearing  4  between lower member  18  of spring clutch  14  and floor  68  of interior housing  42 . 
         [0030]    In use, adjuster member  1  is rotated, and due to outer threads  9  engaging the same threads  38  engaged by enlarged head  10  of input shaft  13 , adjuster member  1  travels axially relative to outer housing  22 . This influences spring pressure of spring clutch  14 . After adjuster member  1  has been adjusted as desired, locking mechanism  2  is activated to maintain the selected torque value arising from the above adjustment. 
         [0031]    It will be appreciated that enlarged head  10  of input shaft  13  is tightened to a greater torque (when contacting top wall  29  of outer housing  22 ) than the highest untightening torque anticipated in the use of torque limiting adapter  100 . 
         [0032]    In an exemplary usage, torque limiting adapter  100  is used to install pedicle screws (not shown) in surgery, and may have the following dimensions. Dimension  70  may be forty millimeters; dimension  72  may be about sixty-nine or seventy millimeters; dimension  73  may be about twenty-five or twenty-six millimeters; and dimension  74  may be thirty millimeters. 
         [0033]      FIG. 6  shows details of spring clutch  14 . Notably, upper member  36  is constrained against rotation relative to interior housing  42  by a spline and groove arrangement  76 . Also, it is seen that lower member  18  may have a hexagonal passage  78  to cooperate with hexagonal outer configuration of output shaft  35 . 
         [0034]      FIG. 2  shows that an upper end  17  of output shaft  35  is received within a pilot hole  12  of enlarged head  10  of input shaft  13  to help maintain concentricity of output shaft  35 . This portion of output shaft  35  is rotatable relative to input shaft  13 . That is, it would have a smooth surface, or alternatively, if hexagonal, would be of dimensions smaller than those of pilot hole  12 . 
         [0035]    While the disclosed concepts have been described in connection with what is considered the most practical and preferred implementation, it is to be understood that the disclosed concepts are not to be limited to the disclosed arrangements, but are intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible.