Abstract:
An architectural unit having an extruded core of wood fiber and a thermoset resin, the extruded core having a central hole coaxial with a major axis of the core and an exterior; a plurality of shaped staves forming a shell, each stave of the plurality of staves disposed about the exterior of the core and parallel to the major axis.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a Continuation of U.S. Utility application Ser. No. 12/328,800, filed Dec. 5, 2008, which claims the benefit of U.S. Provisional Application No. 60/992,350, filed Dec. 5, 2007, both of which are herein incorporated in its entirety by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a structural core or bolt, and more particularly, to an extruded wood fiber core with an applied solid wood exterior shell. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wood fiber cores have been used in applications utilized for winding or spooling industrial products. Extruded wood fiber cores, such as those manufactured by the assignee since the mid 1960&#39;s, have been suitable for applications where low cost is valued, and where durability is not essential. Wood fiber cores have excellent compressive strength in the axial direction, but only moderate or poor tensile strength in the transverse direction. Such fiber cores may be extruded or molded. Wood fiber cores are typically limited to single use as they lack beam strength, and unwinding of materials from the core can produce cracks, fissures or other structural defects rendering them inoperative. 
         [0004]    Solid wood cores are manufactured using labor intensive machining of lumber, gluing, clamping and various steps. While more expensive than extruded core, the solid wood provides improved structural integrity for heavier materials or multiple use applications. Such solid wood cores are of particular value in intracompany uses. Such solid wood cores have improved beam strength. 
         [0005]    Similarly, the steel cores are highly durable, but require expensive fabrication and welding, are heavy, and are expensive to ship. 
         [0006]    What is needed, therefore, are techniques for providing durable, reusable cylinders manufacturable with low labor. 
       SUMMARY OF THE INVENTION 
       [0007]    One embodiment of the present invention provides a method for the production of structural cores with a solid wood exterior, the method comprising: providing a extruded wood core column; providing a plurality of solid wood staves having an interior profile mating an exterior profile of the extruded wood column; applying an adhesive to the interior profile of the staves and the exterior profile of the core; adhering the interior profile of each of the staves to the exterior profile of the core; mechanically securing the staves to the core; allowing the adhesive to cure providing a structural core with a solid wood exterior. 
         [0008]    Another embodiment of the present invention provides such a method further comprising placing at least one steel band about an end of the structural core with the solid wood exterior and embedding the band in the solid wood exterior. 
         [0009]    A further embodiment of the present invention provides such a method further comprising disposing at least one end cap on an end of the structural core with the solid wood exterior and crimping the end cap to secure it to the structural core with the solid wood exterior. 
         [0010]    Yet another embodiment of the present invention provides such a method wherein the step of mechanically securing comprises nailing the staves to the extruded core. 
         [0011]    A yet further embodiment of the present invention provides such a method wherein the step of mechanically securing comprises clamping the staves to the extruded core. 
         [0012]    Still another embodiment of the present invention provides such a method further comprising machining the staves from wood of a variety selected from the group of wood varieties consisting of poplar, oak, ash, maple, mahogany, and walnut. 
         [0013]    A still further embodiment of the present invention provides such a method wherein the wood is an exotic species of wood. 
         [0014]    Even another embodiment of the present invention provides such a method further comprising fluting the staves. 
         [0015]    An even further embodiment of the present invention provides such a method further comprising shaping the staves such that the solid wood exterior is tapered. 
         [0016]    Still yet another embodiment of the present invention provides such a method wherein the solid wood exterior comprises a parabolic frustrum. 
         [0017]    One embodiment of the present invention provides a structural unit; the structural unit comprising: a extruded core comprising wood fiber and a thermoset resin having a central hole coaxial with a major axis of the core and an exterior; a plurality of shaped staves forming a shell, each stave of the plurality of staves disposed about the exterior of the core and parallel to the major axis. 
         [0018]    Another embodiment of the present invention provides such a structural unit further comprising at least one slot disposed in at least one the stave is provided parallel to the axis. 
         [0019]    A further embodiment of the present invention provides such a structural unit wherein the plurality of staves form a cylindrical shell around the core. 
         [0020]    Yet another embodiment of the present invention provides such a structural unit wherein shell has groves where the staves meet. 
         [0021]    A yet further embodiment of the present invention provides such a structural unit wherein the staves are manufactured from a wood, the wood being of a wood species selected from the group of species consisting of poplar, pine, oak, mahogany and walnut. 
         [0022]    Still another embodiment of the present invention provides such a structural unit wherein the staves are tapered, such that the staves form a smooth, longitudinally tapered shell around the core. 
         [0023]    A still further embodiment of the present invention provides such a structural unit, wherein the shell is fluted. 
         [0024]    The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective drawing illustrating an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0026]      FIG. 2A  is a top plan view drawing illustrating a smooth stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0027]      FIG. 2B  is an elevation view drawing illustrating a smooth stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0028]      FIG. 2C  is a bottom plan view drawing illustrating smooth stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0029]      FIG. 3A  is a top plan view drawing illustrating a fluted stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0030]      FIG. 3B  is an elevation view drawing illustrating a fluted stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0031]      FIG. 3C  is a bottom plan view drawing illustrating a fluted stave of an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0032]      FIG. 4  is a cross sectional plan view illustrating an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention and having a spiraled cross section. 
           [0033]      FIG. 5  is a cross sectional plan view illustrating an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention and having retention slots disposed in the solid wood shell. 
           [0034]      FIG. 6  is an elevation view illustrating an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention having a retention slot. 
           [0035]      FIG. 7  is a perspective view illustrating an extruded core cylinder for sheathing with a solid wood shell configured in accordance with one embodiment of the present invention. 
           [0036]      FIG. 8  is an elevation view illustrating an extruded core cylinder with a solid wood shell configured in accordance with one embodiment of the present invention undergoing clamping. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    As illustrated in  FIG. 1 , a cylinder  12  of extruded wood fiber disposed in a resin matrix is provided by one embodiment of the present invention. The extruded core  12  is covered in a shell  18  of wooden staves  14 . In one embodiment of the present invention, each stave  14  covers one eighth of the circumference of the extruded core  12 . Staves  14 , according to one embodiment of the present invention, are glued to the exterior of the extruded core  12 . Nails may be used to affix the staves  14  to the core  12  while the glue cures, and may add additional strength to the bond between the staves  14  and the core  12 . During manufacture, staves  14  may be clamped to the core  12  to insure proper curing of the adhesive manually, using pipe clamps or other suitable hand clamp with a circular pressure ring, or may be clamped using a automated device whereby pressure is applied to the circumference of the stave shell. In one such embodiment pneumatic pressure may be applied, such as by an air choke. For example, Air Flex® clutch break single and double flange elements, part no. 142197JA sold by Eaton Corporation may be used. A central extruded bore  16  is provided through the core  12  to permit the introduction of shafts or other mounting means as necessary. Staves  14  are illustrated in greater detail in  FIGS. 2A-3C . 
         [0038]    In one embodiment of the present invention, illustrated in  FIG. 6  a slot  22  may be machined in one or more of the staves to allow the introduction of a tongue or anchor into the roll so as to facilitate the anchorage of the material to be wound upon the roller to the roller. Alternative retention means, including a spiraled cross section and a plurality of retention slots are illustrated in  FIGS. 4 and 5 , respectively. 
         [0039]    In one embodiment of the present invention, and end cap may be placed over each of the ends of a completed composite core thereby providing improved radial strength. Such caps are known to those skilled in the art and are used with known solid wood cores. In alternative embodiments where such strength is unimportant, such an endcap is unnecessary. 
         [0040]    In one embodiment of the invention, the staves  14  may be configured with an exterior profile such that when each stave  14  is applied to the core  12  such that the elongate length of the stave  14  is parallel to the axis of the core  12 , the exterior profile of the stave is rounded to form an arc, and the arcs of the eight staves combine to form a circular cross section. In alternative embodiments where the core may be used as structural or aesthetic architectural element, the staves may be machined prior to application to provide a suitable taper to the column, as illustrated in  FIGS. 2A-2C , or in some embodiments fluting as illustrated in  FIGS. 3A-3C . Such a taper may be obtained by applying a “shoe” to the stave during machining. In such esthetic embodiments, the staves may be applied to the core without nails, so as to avoid marring the surface of the lumber; alternatively an additional step may be employed wherein nail holes are filled with wood putty prior to sanding and finishing. One skilled in the art can appreciate that suitable capitals or other ornamental end pieces may be applied. 
         [0041]    The interior profile of each stave  14 , in one embodiment is curved to provide optimum contact with the exterior surface of an extruded core having a circular cross section. As noted above, in one embodiment, staves may comprise eight staves disposed about the circumference of the extruded core, while in alternative embodiments; different numbers of staves may be employed. Similarly, various cross-sectional shapes may be imparted to the extruded cores. In alternative embodiments where extrusions of square, polygonal, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, or decagonal cross section or cross sections of any number of sides, staves with flat interior sides may be provided. In such embodiments same number of staves as of sides may be used. Similarly, in other alternative embodiments, staves may be milled to match the profile of the extruded core. It is noted, however, that polygonal cross sections can reduce the waist rate of the milled staves as the milled stave need only be milled on the exterior. 
         [0042]    Wood used in the construction of staves may, in one embodiment be wood from trees of the genus Populus. Other inexpensive, easily milled, woods may be used. The density of the wood may likewise be selected based upon factors including the desired durability of the unit produced, the weight and strength requirements, and a need for relative flexibility may be considered. Other suitable woods may include softwoods such as pine or hardwoods such as oak or maple. Exotic species, like mahogany, rosewood, and teak may also be used in applications where the esthetics of the finished piece require such woods. 
         [0043]    Glues used in the adhesion of the staves to the core are chemically and structurally compatible with the resins used in the core. Degradation of the core could compromise strength of the system. In one embodiment wood glue, such as that available under the trademarks Elmer&#39;s and Tightbond may be used. Alternatively, resins similar to or identical with that used in the wood fiber extrusion may be used. In one such embodiment both the extrusion and the glue are Urea-Formaldehyde resins. The setting of the Urea-Formaldehyde resin may be accelerated using catalysts. Examples of catalysts used include various metal salts, such as aluminum sulfate. 
         [0044]    In one embodiment of the present invention, first and second bands  20  are disposed about first and second ends of the shell  18 . In one embodiment these bands may be configured from steel or other suitable, high tensile strength material. These bands  20  may be disposed in rabbeted channels disposed in the shell  18 . Alternatively, the tightening of the bands  20  may depress the wood staves sufficiently to keep the steel band  20  from contacting items coiled about the shell  18 . The ends of the bands  20  may be crimped or buckled to ensure a secure and low profile joint. In some embodiments, the crimp or buckle may be recessed in a receiving recess. 
         [0045]    The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.