Abstract:
A flexible drive shaft extension for hand tools comprises serially nested, socket-ended Shaft components of polygonal cross-section which have freedom of universal motion from axial alignment limited to about five degrees of arc and which are forcibly retained in coupled connection within a sleeve by spring biasing.

Description:
FIELD OF THE INVENTION  
         [0001]    A drive shaft imparts torque from a power source to machinery.  
         BACKGROUND OF THE INVENTION  
         [0002]    Flexible drive shafts are provided for utilizion with portable tools in spacially restricted locations which do not allow for use of one&#39;s hands or placement of a power source in a manner required for conventional operation of the tool.  
         SUMMARY OF THE INVENTION  
         [0003]    Universal joints in serially connected assembly are known for use as articulated drive shafts for portable tools. Such assemblies are limited in utility by the strength of an enveloping sleeve to restrict articulation of the joints to a degree less than that which causes the sleeve to crimp or twist into helical contortion in response to torque applied to the the shaft.  
           [0004]    The drive shaft of this invention provides a flexible elongated sleeve housing containing spring loaded, unconnected, abutting torque transmission elements. The configuration of each element provides for limited freedom of universal movement from axial alignment to occur between between conjoined elements. Preferably, such movement is limited to about five degrees of diviation from axial alignment, not to exceed about ten degrees. Such construction improves torque transmitting capacity of a drive shaft with lesser complexity than prior art means utilizing pinned or or interlocking connection between elements.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a cross-sectional elevation of a preferred embodiment of a flexsible drive shaft this invention shown in axially straight disposition.  
         [0006]    [0006]FIG. 2 is a cross-sectional elevation of the apparatus of FIG. 1 shown in curvilinear axial disposition.  
         [0007]    [0007]FIG. 3 is an enlarged view of one end portion of the drive shaft of FIGS. 1 and 2.  
         [0008]    [0008]FIG. 4 is an isolated view of element  40  of FIG. 1. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0009]    [0009]FIG. 1 depicts drive shaft  10  for use with, for example, hand tools such as manually operated ratchet drivers or compressed air driven impact tools. The drive shaft is usable with a wide range of other tools and machinery.  
         [0010]    Driven element  11  at a first end of drive shaft  10  is operably connectable to a prime mover, not shown, by square distal end socket portion  12  of element  11  being, preferably, of standard face width dimension for such use, e.g. in the English system of measurement, ¼ inch, ⅜ inch, ½ inch, etc. for operably receiving a square shaft end of complementary size.  
         [0011]    The remainder of driven element  11  comprises proximal end socket portion  18 . The inner cross-sectional socket configuration may be any suitable polygonal cross-section, but preferably is hexagonal. The outer surface cross-sectional configuration is preferably round. Proximal end socket portion  18  is configured with inner and outer peripheral diameters reduced in size from those of distal end socket portion  12 .  
         [0012]    End cap  17  extends axially beyond distal end socket portion  12  with flange portion  19  thereof projecting radially inward to provide a bearing surface for slidable rotational contact with the face of distal end socket portion  12 . Central opening  15  in end cap  17  enables endmost accessibilty into drive shaft  10  to be made by a shaft end of a prime mover or other power source.  
         [0013]    At the opposite end of drive shaft  10 , driver end element  13  is configured with cross-sectionally square distal end stud portion  14 , which is complementary in size to distal end socket portion  12  of element  11 . Any other operable configuration of end elements  11  and  13  may be utlized to accomodate other connecting means.  
         [0014]    Proximal end portion  21  of driver end element  13  is preferably cross-sectionally round. In FIGS. 1 and 3, shoulder portion  24  of element  13  provides a stepped increase in the outer diameter of element  13  from which the surface assumes a truncated ellipsoidal form which decreases in diameter approximately ellipsoidally toward the proximal end face of element  13  with a tangent angle between the outer surface of element  13  at the proximal end to the longitudinal axis of element  13  being preferably about five degrees and not more than about ten degrees. Socket  31 , which may be of any suitable polygonal cross-section, but preferably is hexagonal, opens to the proximal end of element  13 , extending axially longitudinal in element  13 .  
         [0015]    End cap  27  is configured with radially inward extending, distal end face flange portion  28  disposed in sliding contact with the peripheral face of distal end portion  21  of element  13 . End caps  17  and  27  retain assembly of drive shaft  10  intact.  
         [0016]    Helical compression spring  30  is disposed peripherally around proximal end portion  21  of driver element  13  between shoulder  24  of element  13  and flange portion  28  of end cap  27 .  
         [0017]    Flexible sleeve  20  is fixedly secured to the inner peripheral surfaces of end caps  17  and  27 . It is kept tautly drawn by tensioning action of spring  30  acting through tightly coupled nesting components of drive shaft  10  disposed intermediate the two ends of the shaft. Spring  30  forcibly bears on shoulder  24  of element  13  and flange portion.  28  of end cap  27 , and resiliently adjusts by operably expanding or contracting in response to curvilinear flexing of drive shaft  10  during use.  
         [0018]    In the embodiment of invention of FIG. 2, driver end element  13 ′ differs from similar element  13  of FIGS. 1 and 3 by comprising two components, i.e. core piece  13 ″ and socket piece  31 ′. The two latter components are unitarily affixed to provide the same configuration as element  13  of FIGS. 1 and 3, but allows for alternative ways of manufacturing components, whether by forging, casting, machining, press fitting or other known processes. In FIG. 2 shoulder  24 ′ is configured as an integral band configured portion which increases the outer diameter of core piece  13 ″ for a short axial distance rather than providing a step in the configuration of the whole outer diameter as in the case of shoulder  24  of FIGS. 1 and 3. Correspondingly, socket piece  30 ′ of FIG. 2 while being a separate part is unitarily affixed to core piece  13 ″ to provide a resuting structure similar to element  13  of FIGS. 1 and 3.  
         [0019]    Seven identical core elements  40  together with one non-identical core element  40 ′ comprise the remainer of components of drive shaft  10  shown in the FIGS. 1, 2, and  3 . They are shown each to be of two-piece construction, and in all material ways are subject to similar choice of construction practice as shown for elements  13  and  13 ′ so as to be constructed either from one piece or from two pieces which are subsequently unitarily connected. Each core element  40  comprises unitary shank portion  41  and socket portion  42 . Shank portion  41  (FIG. 4) is disposed with jacketed end portion  41 ′ encased unitarily in the base end of socket portion  42  and can either be of polygonal or circular cross-sectional interface configuration, or of other operable mating configuration as desired. Nesting end portion  41 ″ of shank portion  41 , integral with end portion  41 ′, is configured with a polygonal cross-section, which may be of any operable shape, but preferably is regular hexagonal. From approximately the longitudinal axial mid-point of nesting end portion  41 ″ toward each axial end extremity of portion  41 ″ the planar faces of the peripheral polygonal surface of end portion  41 ′ each make an angle of preferably about five degrees with the longitudinal axis of core element  40  whereby end portion  41 ″ is of lesser diameter at each end than at the middle. In addition, it is preferred as shown in the drawings, but not required, that the end face of end portion  41 ″ be configured with planar segments disposed at an angle of approximately one hundred degrees to associated planar peripheral faces of portion  41 ″. The resulting configuration is one of providing a faceted protruding conical end to end portion  41 ″.  
         [0020]    Socket portion  42  of core element  40  is in all material respects similar to socket piece  31 ′ of FIG. 2 with the exception that the inner peripheral face portion  42 ′ encasing peripheral portion  41 ″ is of uniform diameter rather than being of stepped diameter as it is for socket piece  31 ′. Instead of being affixed to core piece  13 ′ as in FIG. 2, socket portion  42 ′ is affixed to base portion  41 ′ of shank portion  41  to provide unitary core element  40 . The outer peripheral surface of socket portion  42  is of circular cross-section and of ellipsoidal axially longitudinal section. The inner peripheral surface is of annular socket portion  42 ″ is of polygonal cross-section with regular hexagonal cross-sectional configuration being preferred. Socket portion  42 ″ inner diameter is such as to be complementary for operable receiving nesting end portion  41 ″ of shank portion  41  of a next adjacent core element  40 . The depth of socket portion  42  is such that nesting end portion  41 ″ disposed within a socket will contact the bottom of the socket, i.e. the end face of base portion  41 ′ of element  40  with which it is nested, while the endmost extremities of socket portions  41 ′ of next adjacent core elements  40  are spacially separated when drive shaft  10  is disposed in straight as it is shown in FIG. 1. This configuration insures that core elements  40  are fully nested by action of compression spring  30  thereby insuring that axial deviation between next adjacent core elements  40  does not exceed intended design limitation, such as a preferred limitation of about five degrees herein suggested when drove shaft  10  is flexed as shown in FIG. 2.  
         [0021]    Core element  40 ′ differs from core elements  40  in the particular that the base portion  42 ′ of shank portion  41  is sized to be received in end socket portion  18  of driven element  11 .  
         [0022]    The provision of spring loading elements in nested joinder at all times during use serves to prevent excessive angular deviation between elements from occurring and resulting in failure of the drive shaft to perform satisfactorly for its intended use.