Abstract:
A method of forming a shaft for transferring force from a driving element to a driven element makes use of a tube. The tube is deformed to define distal ends of said shaft. At least one of the distal ends of the tube is trimmed to define a yoke for engaging one of the driving element or the driven element, with the yoke being integrally formed with the shaft.

Description:
PRIOR APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/611,977 filed Mar. 16, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally toward a driveshaft for transferring force from a driving element to a driven element. More specifically, the present invention is directed toward an integrated yoke-driveshaft formed from a tube. 
       BACKGROUND 
       [0003]    Shafts have been used for transferring torque from a driving element to a driven element for many years. One example of this type of shaft is a driveshaft of an automotive vehicle that transfers driving force from a motor to wheels for driving the automobile. 
         [0004]    These shafts have been formed from tubes and have a yoke or universal joint welded onto a distal ends of the shaft to pivotally engage a drive train or driving element on one end and a differential or a driven element on an opposing end. These yokes are formed from a casting that require a machine or grinding operation to form required apertures for receiving a cruciform or pin to engage the driving element and driven element as explained above. 
         [0005]    Once the casting has been machined to its desired configuration, it is welded onto the tube to form the driveshaft. Due to the inherent design and manufacturing flaws associated with a cast yoke, the drive shaft must be balanced to reduce the vibration by affixing weights to various locations of the driveshaft. This process of balancing and welding has proven to be cost prohibitive and inefficient while reducing performance due to the increase in weight resulting from the attempt to balance the shaft. 
         [0006]    Therefore, it would be desirable to reduce the necessary operations of affixing a cast yoke to a tube to form a driveshaft, which would improve vehicle performance while reducing manufacturing cost. 
       SUMMARY 
       [0007]    The method of forming a shaft for transferring forces from a driving element to a driven element makes use of a tube. The tube is deformed to define distal ends of the shaft. At least one of the distal ends of the shaft is trimmed to define a yoke from engaging one of the driving element or the driven element. The yoke or universal joint is integrally formed with the shaft by way of roll forming or cold forming. 
         [0008]    Integrally forming a yoke from a tube to compose a driveshaft significantly reduces the cost and mass from present driveshaft designs. Specifically, the elimination of a cast yoke provides a substantial weight reduction. The elimination of a welding process required to affix the cast yoke to a tube additionally reduces manufacturing costs and mass associated with the weld material. Furthermore, by forming a yoke integral with a tube to derive a fully functional driveshaft, the requirement of balancing a welded, cast driveshaft is eliminated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0010]      FIG. 1  shows a tube formed into a shaft of the present invention; 
           [0011]      FIG. 2  shows a method of forming a tube into the shaft of the present invention; 
           [0012]      FIG. 3  shows a perspective view yoke formed onto a distal end of the shaft of the present invention; 
           [0013]      FIG. 4  shows a side view of the yoke having a shaft seal; 
           [0014]      FIG. 5  shows plan view of the yoke and shaft seal; 
           [0015]      FIG. 6  shows a side view of both ears of the yoke; 
           [0016]      FIG. 7  shows a distal end of a tube prior to forming a flange; 
           [0017]      FIG. 8  shows the distal end of the shaft having a formed flange onto an exterior surface; 
           [0018]      FIG. 9  shows a yoke formed into the flange disposed upon the distal end of the shaft; 
           [0019]      FIG. 10  shows distal end of the shaft having a formed flange onto an interior surface; 
           [0020]      FIG. 11  shows a yoke formed into the flange disposed upon the distal end of the shaft; 
           [0021]      FIG. 12  shows a perspective view an alternative embodiment of the shaft of the present invention; 
           [0022]      FIGS. 13 and 16  show end views of the alternative embodiment of the shaft of the present invention; 
           [0023]      FIG. 14  shows a perspective view of an alternative embodiment of the present invention having a collapsible shaft; and 
           [0024]      FIG. 15  shows an end view of the alternative embodiment of the present invention having a collapsible shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    A tube is generally shown at  10  of  FIG. 1 . The tube includes a shaft  14  disposed between opposing distal ends  12 . 
         [0026]    Referring also to  FIG. 2 , the shaft  14  defines a shaft diameter  16  and the opposing distal ends  12  define a yoke diameter  18  as will be explained further herein below. The shaft  14  defines the shaft diameter  16  that is narrower than the yoke diameter  18  by way of roll or cold forming elements  19  and  20 . The roll forming elements  19 ,  20  forcibly engage the shaft  14  to reduce the shaft diameter  16  from the yoke diameter  18 , which is substantially identical to the original tube diameter (not shown) prior to roll forming the shaft  14 . 
         [0027]    The roll forming elements  19  and  20  provide force in the direction of F 3  and F 4  substantially, narrowing the diameter of the tube to achieve a predetermined shaft diameter  16 . Two, and possibly three roll forming elements  19 ,  20  can be used to form the shaft  14  to the predetermined shaft diameter  16 . During the forming process, the tube is elongated in a direction of force arrows F 1  and F 2  as represented in  FIG. 2 . The elongation of the tube  10  aligns the material grain of the tube  10  in the directions of arrows F 1  and F 2 . Alignment of the material grain provides an increase in tube strength in addition to the cold working increase in material strength. It should be understood by those of ordinary skill in the art that various materials may be used including steel, aluminum, copper, and variations thereof. It is also contemplated by the inventor that certain polymeric materials may also be used to form the integrated drive shaft of the present invention. Furthermore, the shaft  14  may be formed from extrusion dies, and flow forming. 
         [0028]    The opposing distal end  12  includes a yoke wall  21  having a yoke wall thickness  22  as will be explained further herein below. The shaft  14  includes a shaft wall  23  having a shaft wall thickness  24  that is less than the yoke wall thickness  22 . While roll forming, the shaft wall thickness  22  is decreased from the yoke wall thickness  24 , which is substantially the same thickness as the original tube thickness prior to forming. 
         [0029]    Referring now to  FIG. 3 , the distal end  12  of the shaft  14  has been formed into a yoke  27 . It should be understood by those of skill in the art that this embodiment includes both opposing distal ends  12  being formed into a yoke  26 . One yoke  18  engages in driving element such as, for example, an axial driven transmission element (not shown) and the other yoke  18  engages in a driven element such as, for example, a differential (not shown). Each yoke  27  includes opposing ears  28 , each defining an aperture  30 . Each aperture  30  receives a pin or cruciform to engage an opposing yoke to establish a universal joint as is known to those of skill in the art. It is further possible to form a cardon joint (not shown). 
         [0030]    Therefore, an integrated shaft providing connecting features is established where increased wall thickness is provided at the yoke  26  and where a substantial portion of the forces known to cause failure, in such as, for example, drive shafts of automobiles is known to occur. Furthermore, the reduced wall thickness of the shaft  14 , relative to the yoke  26 , provides a means for reducing the overall weight of a typical driveshaft of an automotive vehicle by providing wall thickness only where necessary. The integrated shaft  10  of the present invention may also be used for steering columns and other devices where driving elements transfer rotational force to driven elements. 
         [0031]    Referring to  FIGS. 4 ,  5 , and  6 , a seal is provided to prevent contamination from entering the shaft  14  through the yoke  27  in the instance of the integrated shaft  14  being used in an exterior environment. The seal  32  is affixed to the shaft  14  by way of welding, or interference fit, or equivalent. 
         [0032]    An alternative embodiment is shown in  FIGS. 7 through 11 . In this embodiment, it is contemplated that a thinner yoke wall thickness may be used. As best represented in  FIG. 8 , a flange  34  is formed at the opposing distal ends  12  of the shaft  14 . The flange  34  affectively doubles the thickness of the distal ends  12  of the shaft  14 . As represented in  FIG. 9 , the flange distal end  12  is machined or otherwise cut by laser, water jet, or mechanical device to form an alternative yoke  36 . Similar to that stated above, alternative ears  38  are formed defining apertures  40  so that the alternative yoke  36  functions as set forth above. While  FIG. 8  represents the flange being formed onto an exterior surface  42  of the shaft  14  it should be understood by those skilled in the art that the flange  34  may also be formed into an inner surface  44  of the shaft  14 . It should also be understood by those skilled in the art that the seal  32  described above is also included in this alternative embodiment, when necessary. 
         [0033]    A still further embodiment is shown in  FIGS. 12 ,  13  and  16 . In this embodiment, an alternative shaft  46  is formed having ribs  48  extending lengthwise on the alternative shaft  46  to provide additional strength to the alternative shaft  46 . It should be understood to those skilled in the art that the ribs  48  may be formed on an inner surface, outer surface, or both inner and outer surface of the alternative shaft  46 . The ribs  48  may be formed by the roll forming elements  19 ,  20  set forth above, or by way of an alternative or subsequent forming operation. 
         [0034]    A still further embodiment is shown in  FIGS. 14 and 15 . In this embodiment, an integrated shaft  50  includes a yoke  26  on only a single distal end. The integrated shaft  50  is received by a second integrated shaft  52  having a larger diameter so that the shaft provides axial movement to collapse upon impact of the vehicle. As shown in  FIG. 15 , the alternative shaft ribs  51  engage alternative shaft ribs  53  disposed upon the second integrated shaft  52  for locking engagement providing rotational movement between the first integrated shaft  50  and the second integrated shaft  52 . 
         [0035]    While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation while material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention but that the invention will include all embodiments falling within the scope of the appended claims.