Abstract:
A flanged coupling unit having a radial flange with an axial boss and a concave exterior corner surface approximating the external surface of a quadrant of an ellipse. Optionally, a similar internal surface is provided. In either case, the resulting unit exhibits substantially enhanced strength and structural integrity and a significant reduction in weight.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Flanged coupling units having radial annular flanges and integral axial bosses have been used for perhaps a century or more in the interconnection of elongated tubular conduits and elongated structural members and the like. However, despite the long life of these couplings, little or no improvement has been realized in their design and construction. 
         [0002]    Conventional coupling units tend to have their weakest and fracture prone areas at the junction or corner between their radial flanges and integral axial bosses. In an attempt to overcome this problem, couplings with frusto-conical bosses have been designed using considerably more material and with a consequent substantial increase in weight. However, weak and fracture prone areas are still encountered at small fillets occurring at relatively thin cross sectional areas at the ends of the frusto-conical surface area. 
         [0003]    It is the general object of the present invention to redesign flanged coupling units of the type under consideration and thus provide improved units both lighter in weight and of greater strength and structural integrity. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the present invention and in fulfillment of the foregoing object, a flanged coupling unit is provided for primary use individually or with a similar unit in interconnected mating relationship for the endwise connection of axially aligned elongated members. The unit has a radial annular flange with at least a partial generally planar surface on one side. Means are provided for rigidly connecting the flange individually with a foundation or other surface or with the mating flange of a similar coupling unit, the planar surfaces of the two flanges being interengaged in face-to-face relationship. A boss formed integrally with the flange forms an external corner surface area therewith on the side thereof opposite its planar surface and projects axially therefrom for connection with an end portion of a first elongated member, the mating flange of a second coupling having a similar boss for connecting a second elongated member in endwise relationship with the first member. 
         [0005]    An important feature of the invention resides in the contour of the corner area and the external surfaces adjacent and on opposite sides thereof. The adjacent area extending along the neck of the boss to the corner area, the corner area, and the adjacent area on the opposite side thereof along the inner portion of the flange are arcuate-concave viewed in a radial direction and are bounded by two points, or, more accurately, two imaginary annular lines, the first being spaced substantially outwardly along the axial surface on the neck of the boss. A second imaginary annular line on the flange is spaced outwardly along the radial length of the flange. The boundary line on the boss is substantially farther from the corner area than the similar line on the flange and the external surface curves gradually adjacent the former and substantially more rapidly adjacent the latter. Stated differently, the surface adjacent the line on the boss has a shallow slope relative to the axis of the boss and the arcuate surface adjacent the line on the flange has a substantially sharper slope relative to the axis. Still another way to view the contour of the external surface is the definition of the same by reference to the radii of curvature involved. The arcuate-concave surface is defined by at least three discrete radii of curvature, the smallest radius appearing adjacent the flange. Preferably there are an infinite number of radii of curvature employed in establishing the desired contour of the surface. In any event the radii blend smoothly so as to present a continuously varying gradually curved surface closely similar to that of a quadrant of an ellipse. 
         [0006]    In addition to the foregoing it should be noted that where the flange and boss have an axially extending through opening or bore, the internal corner and adjacent areas may be arcuate-convex in a manner similar to that of the external corner and adjacent areas. With regard to both external and internal corner and adjacent areas, it should also be noted that in preferred form an external quadrant surface of an ellipse is approximated by each of the surfaces. 
         [0007]    Another feature of the invention resides in the provision of the coupling unit having a radial flange and axial boss with an axial bore as aforesaid, wherein the wall thickness of the boss increases from the free end of the boss inwardly along its neck and substantially throughout its length, through the junction or corner area between the boss and the flange and thereafter remains substantially constant in progression radially outwardly along the flange. This feature may occur alone but is inherent with and of particular importance in combination with the aforesaid feature relating to the curvature of inner and or outer external corner and oppositely adjacent areas. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  of the drawings is a side elevational section of a PRIOR ART flanged coupling unit, 
           [0009]      FIG. 2  is a side elevation in section of a second PRIOR ART flanged coupling unit, 
           [0010]      FIG. 3  is a side elevation in section of an improved flanged coupling unit in accordance with the present invention, 
           [0011]      FIG. 4  is a side elevation in section of a second embodiment of an improved flanged coupling unit in accordance with the present invention, 
           [0012]      FIG. 5  is a side elevation of a third embodiment of an improved flanged coupling unit in accordance with the present invention, 
           [0013]      FIG. 6  is a schematic view of a tower employing a number of improved flange coupling units interconnecting elongated tubular structural members, 
           [0014]      FIG. 7  is an enlarged sectional view of an assembled coupling employing a pair of similar units with flanges bolted together to interconnect hollow tubular structural units as in  FIG. 6 , 
           [0015]      FIG. 8  is a view similar to  FIG. 7 , but employing an alternative means in the form of a clamp connecting the flanged coupling units, 
           [0016]      FIG. 9  is an enlarged elevational view in section showing an improved coupling unit used individually in mounting an elongated generally vertical support member for a wind tower or the like. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    Referring particularly to  FIG. 1 , a PRIOR ART coupling unit is indicated generally at  10  and comprises a radial flange  12  and an axial boss  14  formed integrally with the flange. A junction or corner area between the boss and flange is indicated at A and is conventionally defined by a curve on a relatively small radius. In either event, the corner region A is the weakest area in the flanged unit and the area most likely to fracture under heavy load. 
         [0018]    The PRIOR ART flanged unit of  FIG. 2  indicated generally at  16  includes a radial flange  18  and a boss  20  which projects axially therefrom. The boss  20  is frusto-conical in configuration and obviously provides a much thicker wall and increased strength at the junction or corner area between the boss and the flange. It should be noted, however, that there is substantially more material used resulting in a substantially heavier and more expensive unit. Further, the unit remains subject to fracture at the small fillets  24 ,  26  at inner and outer ends of the frusto-conical section of the boss. 
         [0019]    In  FIG. 3 , a first embodiment of the present invention is indicated generally at  28  and has a radial flange  30  and an axial boss  32  projecting axially therefrom. A corner area at the junction of the flange and boss is indicated generally at C with adjacent area B extending from the corner region along the neck and toward the free end of the boss. A second and substantially smaller area D adjacent the corner area C on its opposite side extends along the flange  30  toward its free end. A through opening or axial bore  35  extends from the free end of the boss to a planar surface  36  on the flange which resides in a radial plane. The corner or junction E between the planar surface  36  and internal annular surface  35  of the boss  32  is defined by a convex curve E also on a relatively small radius. 
         [0020]    As mentioned above, the external surfaces of the unit at B, C, and D are bounded by two points or imaginary annular lines  33 , 34  respectively on the axial surface of the boss and the radial surface of the flange. The former line is substantially farther from the corner than the latter as indicated by the dimensions F, G. As will be apparent on inspection, the external surface  35  curves gradually adjacent the boundary line  33  and substantially more rapidly adjacent the boundary line  34  on the flange. At each end, however, the arcuate surface blends smoothly in transition to a linear surface on the opposite side of the boundary line. As stated above the curve may also be regarded as having a gently changing slope adjacent the boss and a more sharply changing slope adjacent the flange. Still further, the external surface  35  may be viewed as defined by at least three, and preferably an infinite number of discrete radii. In any event, the portions of the surface blend together to form a continuously varying smooth arcuate surface with the surface of the smallest radius on the flange  30 . Preferably the surfaces B, C, D, taken in the aggregate, at least approximately follow the contour of the external surface of a quadrant of an ellipse, shown in broken line at  40 . 
         [0021]    As mentioned above, the enhanced thickness of the wall of the coupling unit is a second important feature of the present invention. As will be obvious from inspection of the drawings, the wall thickness of the unit proceeds along the neck of the boss toward the flange increasing through the regions B and C and remaining substantially constant in outward progression along the flange from C to the outer end of the flange. 
         [0022]      FIG. 4  shows a second embodiment of the invention in the form of a coupling unit  42  having a flange  44  and an axial boss  46 . The external surface of the unit at its corner region and adjacent areas may be identical with those of the coupling of  FIG. 3 . The internal surface of the unit, however, varies substantially from that of the  FIG. 3  coupling and instead may be substantially identical with the external surface. As will be obvious, this results in a slight reduction of the thickness of the coupling wall but the unit is nevertheless found to have excellent strength characteristics and is obviously of exceptionally lightweight construction. 
         [0023]    A third embodiment of the coupling unit of the present invention is indicated generally at  48  in  FIG. 5 . The unit has a flange  50  and a boss  52  with an external corner area C with a relatively small radius of curvature similar to that of convention coupling units. The internal surface of the unit at  54 , however, is substantially identical with the external surface B, C, and D in  FIG. 3  and with the internal and external surfaces in  FIG. 4 . This entails a substantial radial inward bulge of the inner surface, which will be acceptable in certain applications. Wall thickness is superior in this embodiment to both the  FIG. 3  and  FIG. 4  embodiments. 
         [0024]      FIG. 6  illustrates a structural use of the improved coupling of the present invention in a wind turbine tower or the like having a plurality of elongated tubular structural members  56 ,  56  interconnected by coupling units  28 ,  28  shown in enlarged fragmentary section in  FIG. 7 . As illustrated in  FIG. 7 , each of the flanges  30 ,  30  of mating coupling units  28 ,  28  is provided with an annular series of axial openings  58 ,  58  which receive bolts  60 ,  60  connecting the units together. 
         [0025]    In  FIG. 8  an alternative means of connection is provided in the form of a clamp member  62  which surrounds the flanges  30 ,  30  and is in turn interconnected by bolts  64 ,  64  whereby to clamp and firmly hold the flanges in engagement. 
         [0026]      FIG. 9  illustrates the use of a single coupling unit  66  as a mounting support for a large generally vertical elongated base member  68  of a wind turbine tower or the like. The unit  66  may have a configuration substantially identical with the  FIG. 3  unit and may be attached to a foundation  70  by a plurality of bolts  72 , 72  as illustrated. 
         [0027]    From the foregoing it will be apparent that design improvements have been made which may initially seem to be minor in nature, but which in the aggregate are nevertheless found to substantially enhance the strength and integrity of the units while simultaneously reducing the weight and the amount of material consumed in manufacture of the improved coupling units.