Abstract:
The present invention provides polygonal connections for connecting a shaft with a flange. In a preferred embodiment, the polygon connection includes a polygon shaped recess in the flange, a polygon shaped terminus on the shaft, an outward projection on the terminus, and a groove on the flange. The cross sections of the recess of the flange and the terminus of the shaft are preferably complimentary polygon shapes so that the recess fittingly receives the terminus. An inward projection and ridge cooperatively define the groove of the flange. The groove axially retains the flange on the terminus.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates generally to a polygon connection between a shaft and a flange.  
         BACKGROUND OF THE INVENTION  
         [0002]    Rotary energy can be transferred from a shaft to another device by fitting the device onto a terminal end of the shaft. Flanges of various types are frequently used as the device that receives rotary energy from a shaft. In these assemblies, the connection between the flange and the shaft is critical because a poor connection can result in inefficient transfer of rotary energy, slippage of the flange on the shaft, or even complete disconnection of the flange from the shaft.  
           [0003]    To avoid these potential problems, a unitary shaft/flange apparatus can be manufactured that eliminates the need for a connection between the two elements. While these constructs may have benefits, they are often large and cumbersome structures making them difficult to manufacture and transport. Furthermore, for large parts such as vehicle axles and drive shafts, a unitary shaft/flange apparatus requires elaborate and expensive forging equipment  
           [0004]    Various other types of connections between a shaft and a flange have been proposed and produced. The simplest connection between a shaft and a flange is one in which the shaft has a circular cross section that fits into a slightly larger circular recess in the flange. In these assemblies, there is no interface between the surfaces of the peripheral surface of the shaft with the recess of the flange. Consequently, these connections rely on secondary connectors to transfer the rotary energy from the shaft to the flange. For example, the flange and shaft can both have openings through which bolts or other fasteners can pass, securing one element to the other. The need for extra connectors in these connections increases the expense and weight of constructs employing them.  
           [0005]    Another approach to a connection between a shaft and flange involves a forced fit connection. In this arrangement, a shaft having a cross section that is slightly larger in size than the recess of a flange is force fit into the recess. Secondary connectors may also be used in this arrangement. Due to the need for the forced fit, these connections are often difficult to assemble. Some force fit connections utilize temperature induced size changes to allow the flange to be retained on the shaft. While this approach does eliminate the need for some of the forcing during assembly, it still requires precise control of manufacturing conditions to ensure that appropriate temperatures are achieved.  
           [0006]    Additionally, some connections rely simply on weld joints between a flange and a shaft, either alone or in combination with bolts and/or other fasteners. As with the simple circular connections mentioned above, the need for weld joints and/or fasteners in this arrangement increases the expense of manufacturing and assembling the connection and also increases the overall weight of the apparatus.  
           [0007]    Thus, there is a need for a connection design between a shaft and a flange that allows for a precise fit, efficient transfer of energy between the shaft and the flange, and simple and cost effective manufacturing and assembly of an apparatus utilizing the connection.  
         SUMMARY OF THE INVENTION  
         [0008]    In a preferred embodiment, the connection relates to a two-piece axle shaft utilizing a polygon connection. This embodiment utilizes a connection between a shaft and a flange comprising a terminus on the shaft having a polygon-shaped cross section, a complimentary shaped recess in the flange, and a groove in the flange that receives and retains an outward projection defined by the terminus of the shaft. In a second embodiment, the connection comprises a yoke attachment that utilizes a polygon spline pilot to improve the interface between the vehicle axle and drive shaft. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a plan view of a polygon connection between and shaft and a flange in accordance with a first preferred embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is a plan view of a shaft having a polygon-shaped terminus at one end for use in a connection according to the present invention;  
         [0011]    [0011]FIG. 3 is a plan view of a flange for receiving and retaining a shaft to form a connection in accordance with the present invention;  
         [0012]    [0012]FIG. 4 is an exploded view of a driveshaft and flange connection in accordance with a second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    The present invention provides a polygon connection between a shaft and flange. FIG. 1 illustrates one embodiment of a polygon connection  10  according to the present invention. The polygon connection  10  comprises a shaft  12  and flange  14 . The shaft  12  is preferably an elongated member having two ends. At least one end of the shaft  12  defines a terminus  16  having a cross section that defines a polygon shape  18 . Alternatively, the shaft  14  can be any body having the polygon shape  18 , such as a flange in a connection with a yoke.  
         [0014]    The polygon shape  18  can take on any polygon configuration, such as a triangle, a square, a pentagon, a hexagon, heptagon, and octagon. Due to ease of manufacturing, a polygon shape  18  having a generally hexagonal shape is preferred. The sides of the polygon shape  18  can be flat, convex, or concave. Without convex or concave sides, the corners of the polygon shape  18  transmit the majority of the torque of the shaft  12  to the flange  14 , making them brittle and susceptible to damage. The rounded appearance created by the use of convex or concave sides distributes the load around the perimeter of the polygon shape  18 , making the connection  10  stronger. A polygon shape  18  and recess having concave sides are preferred because the shape is able to carry more torque than a convex design.  
         [0015]    As illustrated in FIGS. 2 and 3, the terminus  16  of the shaft  12  can also define further structural elements that interact with corresponding structural elements on the flange  14  to ensure retention of the shaft  12  on the flange  14 . For example, a terminus can define an outward projection  20  that extends away from the central axis of the terminus  16 . The outward projection  20  is preferably circumferential around the terminus  16 , i.e. the outward projection  20  can extend around the entire perimeter of the terminus  16 . Alternatively, the outward projection  20  may be intermittent, effectively defining a plurality of projections around the perimeter of the terminus  16  separated by gaps. When the outward projection  20  is circumferential, it essentially confers a nail head configuration onto the shaft. Also preferable, the outward projection  20  as will be developed more fully below, structurally cooperates with the flange  14  to ensure a stable connection between the shaft  12  and flange  14 .  
         [0016]    Preferably, the shaft  12  has a constant diameter along its entire length, excluding the polygon shape  18  of the terminus  16 . This allows for relatively easy fabrication of the shaft  12 . Also preferable, the shaft  12  has a circular cross-sectional shape, except for the polygon shape  18  of the terminus  16 . Alternatively, if necessary for interaction with the flange  14 , the shaft  12  may define a taper  22  or a plurality of tapers  22  that effectively widen or narrow the diameter of the shaft  12 . FIG. 1 illustrates an example of a shaft  12  in which the diameter is gradually widened by a series of tapers  22  until the terminus  16  of the shaft  12  has a diameter comparable to the diameter of the flange  14 . Also alternatively, the shaft  12  can have any suitable cross-sectional shape. Indeed, the shaft  12  can have a cross-sectional shape that is the same in size and form as that of the polygon shape  18  of the terminus  16 .  
         [0017]    The terminus  16  of the shaft  12  may also define a cavity if appropriate for the type of shaft  12  being utilized. A cavity may be desired if a reduced overall weight of the assembly is appropriate. A cavity may also provide a point at which a shaft  12  or an assembly of a shaft  12  and a flange  14  can be manipulated by machinery or an individual. Alternatively, the shaft  12  can be a solid body without a cavity, effectively forming a plug structure.  
         [0018]    The shaft  12  is preferably made of steel. Readily available steel, such as  1050  modified steel, that is easily machined is particularly preferred. Alternatively, aluminum, or any other metal, alloy, or other material suitable for the application for which the shaft will be utilized can be used. The shaft  12  is preferably fabricated by methods known in the art, such as forging or machining. Alternatively, the shaft  12  can be fabricated by any suitable method.  
         [0019]    Preferably, the flange  14  is a circular member as illustrated in FIG. 3. However, the flange can take on any shape appropriate for the ultimate use to which the assembly between the shaft  12  and flange  14  is being utilized.  
         [0020]    The flange  14  is a separate member that defines a recess  24  for receiving the terminus  16  of the shaft  12 . The recess  24  defines a void having a shape that is generally a polygon The shape of the recess  24  is preferably complimentary to the polygon shape  18  defined by the terminus  16  of the shaft  12 . Thus, when the terminus  16  defines a square projection, the recess  24  of the flange  14  defines a void in the shape of a square. When the polygon has convex or concave sides, the recess  24  preferably forms an appropriate shape. FIG. 4 shows a flange  14  having a recess  24  that is complimentary in shape to a terminus  16  that defines a polygon shape  18  with concave sides.  
         [0021]    The recess  24  is preferably slightly larger in volume than the terminus  16  of the shaft  12 . This configuration allows the recess  24  to readily receive the terminus  16  of the shaft  12 . Also preferable, the recess  24  is not too large to prevent sufficient contact between the terminus  16  and the outer walls of the recess  24 , which would lead to an unstable connection  10 . Alternatively, if a force fit or temperature sensitive connection is desired, the recess  24  should be slightly smaller in volume than the terminus  16 .  
         [0022]    The recess  24  may define stepped polygon shapes  26 , which comprise a series of polygon shapes arranged in a step-wise manner. FIG. 3 illustrates this configuration. A flange  14  having a recess  24  defining stepped polygon shapes  26  is able to receive a variety of shafts  12 , each having a differently sized terminus  16  appropriate for one of the stepped polygons  26  of the recess  24 . This configuration allows the flange  14  to have a reduced overall weight due to the additional material removed from the flange  14 . The depth between the stepped polygon shapes  26  can be uniform or varied, depending on the desired interaction with the terminus  16  of the shaft  12 . Furthermore, the terminus  16  can define a reciprocal series of polygon projections, if desired.  
         [0023]    Preferably, the sides of the recess  24  are perpendicular to the central axis of the flange  14 . Alternatively, the sides may have a slight inward taper, slanting toward the center of the recess  24 . In this configuration, the inward taper provides an additional mechanism for guiding the terminus  16  of the shaft  12  into the recess  24  of the flange  14 .  
         [0024]    As best illustrated in FIG. 3, the flange  14  may define several additional structural elements that cooperate with the outward projection  20  of the shaft  12 . In a preferred embodiment, the flange defines an inward projection  28 , and a ridge  30 . These additional elements allow the flange  14  to be retained on the terminus  16  of the shaft  12 .  
         [0025]    The flange  14  defines an inward projection  28  that extends toward the central axis of the flange  14 . FIG. 3 illustrates the inward projection  28  as an upstanding lip, which is the form this element has prior to the preferred method of assembling the polygon connection  10  of the present invention, which will be developed more fully below. The inward projection  28  is preferably a circumferential projection around the perimeter of the flange  14 . Alternatively, the inward projection  28  may be intermittent, effectively defining a plurality of inward projections  28  separated by gaps. Opposite the inward projection  28 , the flange  14  may also define a ridge  30 . The ridge  30  is a shoulder formed in the sidewall of the recess  24  of the flange  14 . Similar to the inward projection  28 , the ridge  30  is also preferably circumferential in nature. Alternatively, however, the ridge  30  may be intermittent. The inward projection  28  and the ridge  30  are opposing structural elements of the flange  14 . As such, the inward projection  28  and the ridge  30  cooperatively define a groove  32 , as best illustrated in FIG. 1. The groove  32  is also preferably circumferential in nature, extending around the perimeter of the recess  24 . Alternatively, the groove  32  may be intermittent in nature. A series of intermittent inward projections  28 , ridges  30 , and grooves  32  can be used to create a locking relationship with an intermittent outward projection  20  of the shaft  12 .  
         [0026]    Preferably, the dimensions of the groove  32  are such that the outward projection  20  of the terminus  16  of the shaft  12  can be positioned within the groove  32 . Also preferable, the inward projection  28  defines a particular angle, Preferably, the angle is complimentary to the particular angle defined by outward projection  20  such that no gap exists between the groove  32  and the outward projection  20 . This embodiment is illustrated in FIG. 1. Alternatively, the angles may not be complimentary, effectively creating a gap between the outward  20  and inward  28  projections.  
         [0027]    Like the shaft  12 , the flange  14  is preferably made of steel. Alternatively, the flange  14  may be fabricated from aluminum, any other metal, an alloy, or any other material suitable for the application. The flange  14  is preferably fabricated by techniques known in the art, such as forging and machining. Alternatively, the flange  14  can be fabricated by any suitable method. If present, the inward projection  28  is preferably formed by a roll-forming process, in which a tooling is rotated at a constant angle in a circular travel pattern over the flange and pressing down on the flange lip, an upwardly extending projection. The tooling elastically deforms the lip, creating the inward projection  28 . This formation of the inward projection  28  is preferably conducted after the polygon shape  18  of the terminus  16  is fit into the recess  24  of the flange  14 , effectively locking the components together and creating the polygon connection  10 .  
         [0028]    The periphery  34  of the flange  14  may further define elements that allow the flange  14  to take on certain functional characteristics appropriate for the end use of the assembly of the flange  14  and shaft  12 . For example, the periphery  34  of the flange  14  may define a single or a plurality of through openings  36 . These through openings  36  can serve as passageways for connectors such as bolts, allowing the flange  14  to be secured to another device. This arrangement allows the flange  14  to further transfer a rotary energy from the shaft  12  to the attached device.  
         [0029]    As shown in FIG. 4, the polygon shape  18  defined by the terminus  16  of the shaft  12  can have sides that are either convex or concave in nature, effectively giving the polygon  18  a rounded appearance. These convex or concave sides provide an additional degree of alignment when the terminus  16  is being positioned within the recess  24  of the flange  14 . Further, the use of concave or convex sides on the polygon  16  provides additional surface contact between the polygon  16  and the recess  24 , thereby allowing a more efficient transfer or rotary energy from the shaft  12  to the flange  14 .  
         [0030]    The foregoing disclosure is the best mode devised by the inventors for practicing the invention. It is apparent, however, that polygon connections incorporating various modifications and variations may be conceivable by one skilled in the art of joining a shaft and flange. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but rather should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.