Abstract:
A frame and method of forming a frame. The frame includes a first part formed of wood; a second part formed of wood. The first part and the second part are bonded together forming a space between first part and the second part, and providing structural support for the frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) from U.S. Provisional Application Ser. No. 60/980,401 filed Oct. 16, 2007, titled WOODEN TUBULAR FRAMES, the contents of which are herein incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to tubular frames and, in particular, to wooden tubular frames. 
         [0003]    Bicycle frames are predominantly made from materials such as steel, aluminum and carbon fiber. Though traditional and relatively easy to manufacture, frames made of these materials have several weaknesses. 
         [0004]    Many metal frames are made of butted tubing which has a very thin wall for most of the tube length to make the tube lightweight, and a much thicker wall at the ends for strength and to facilitate welding at the joints. The thinner sections of these tubes can be easily dented. Even a minor dent can render the frame unsuitable to ride, as stated in a leading manufacturer&#39;s owner&#39;s manual, ‘Do not ride a bicycle or component with any crack, bulge or dent, even a small one.’ Furthermore, metal frames are subject to corrosion, and in the case of aluminum specifically, galvanic corrosion in the presence of carbon fiber or aluminum components. Both steel and aluminum frames are subject to stress cracking and even the smallest dent can result in stress cracks. Such cracks can quickly propagate, and do so more quickly if corrosion is present. Finally, the ride qualities of these frame materials can be undesirably harsh or sharp when the frames are made stiff enough for many bicycling activities, due to the proportionality of strength and stiffness in these materials. 
         [0005]    The use of carbon fiber has produced frames that are generally lighter than aluminum or steel. Carbon fiber also cracks due to stress. However, carbon fiber is also very susceptible to cracks propagating from scratches or chips, which, as a leading manufacturer of both aluminum and carbon fiber bicycles states in the owner&#39;s manual, “Significant scratches, gouges, dents or scoring create starting points for cracks,’ ‘If you find a crack, replace the part’, and ‘Riding a cracked frame, fork or component could lead to complete failure, with risk of injury or death.’ In addition to cracking, hidden delamination of carbon fiber parts is a serious problem. The largest of the manufacturers cautions ‘Damaged carbon fiber can fail suddenly. Carbon fiber can conceal damage from an impact or crash.’ They provide a separate web page, and an online movie entitled Composite Part Inspection which shows bicycle owners how to inspect their bikes for damage and how to test for hidden delamination. With steel, aluminum and carbon fiber frames, a typical carbon fiber and aluminum bicycle manufacturer&#39;s caution is ‘Once a crack starts, it can grow, and grow fast. If you find a crack, replace the part.’ 
         [0006]    The problems with these materials could be eliminated by simply making the frames of thicker walled tubing, but such a bicycle would be unacceptably heavy. 
         [0007]    Wood as a frame material has characteristics which can avoid the problems stated above, and solid wood frames have been built, but they also are too heavy. So wood has been generally ignored and even discouraged as a bicycle frame material: 
         [0008]    ‘Indeed, whenever an I-beam or tube construction is selected to carry tension and bending only, wood is a fine choice. Unfortunately, the tubes that make up bicycle frames are also subjected to torsion, and with no helical fibers, a wood rod or tube would be absolutely unacceptable as regards strength or stiffness.’ 
         [0009]    Bicycling Science, 3 rd  Ed. p. 378, (ISBN 0-262-73154-1). 
         [0010]    Accordingly, there remains a need for an improved bicycle frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an illustration of the formation of a wooden tube according to an embodiment. 
           [0012]      FIG. 2  is an illustration of a bicycle frame using wooden tubes of  FIG. 1 . 
           [0013]      FIG. 3  illustrates a plank with wooden blanks before the wooden blanks are cut from the plank according to an embodiment. 
           [0014]      FIG. 4  illustrates a plan view and side view of the wooden blanks of  FIG. 3  assembled into a frame blank. 
           [0015]      FIG. 5  is a cross-sectional view of the frame blank of  FIG. 4  at various stages of machining. 
           [0016]      FIG. 6  illustrates an internal webbing in a frame half according to an embodiment. 
           [0017]      FIG. 7  illustrates a side view of a frame half according to an embodiment. 
           [0018]      FIG. 8  illustrates two frame halves prior to assembly according to an embodiment. 
           [0019]      FIG. 9  illustrates an assembled frame and inserts according to an embodiment. 
           [0020]      FIG. 10  illustrates an example of wooden blanks of  FIG. 3  according to an embodiment. 
           [0021]      FIG. 11  illustrates an example of a frame blank formed from wooden blanks of  FIG. 10  with an outline of a desired frame half. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Wood can be formed into hollow tubes or monocoque frames which can be made into, for example, the frames of bicycles or wheelchairs. Wood has several advantages over metal or carbon fiber composite frames. Wood is approximately one quarter the density of aluminum which can result in a lighter frame. Wood has superior vibration damping, which, in a bicycle for example, results in a smoother ride. Wood is extremely impact tolerant, enabling it to withstand impacts which would ruin frames of other materials. Wood has the property of stopping crack propagation, as observed in wooden posts and beams in old buildings, and it will not propagate a crack from a scratch or dent like aluminum, carbon fiber and titanium. Wood is highly resistant to stress concentration, so that inserting fasteners has little effect on mechanical properties. The work of fracture for wood is as high as ductile steel. 
         [0023]      FIG. 1  is an illustration of the formation of a wooden tube according to an embodiment. Wooden strips  12  and  14  are wrapped around mandrel  10 . Strips  12  and  14  are aligned at angles relative to each other. In one embodiment, strips  12  and  14  are aligned to be at about 90 degrees relative to each other. In addition, each strip  12  and  14  can be aligned to be about 45 degrees off from axis  20  of the mandrel  10 . In an embodiment, strips  12  and  14  can be at +45 degrees and −45 degrees off of axis  20 , respectively. 
         [0024]    Wooden strips  12  and  14  can be successively laid over the mandrel  10 . For example, wooden strip  12  can be wound over the mandrel in a counter-clockwise direction. In an embodiment, the wooden strip  12  can be wound around the mandrel  10  such that edges of the wooden strip  12  abut one another. That is, the edges of the wooden strip  12  do not overlap. Region  18  indicates a location where edges of the wooden strip  12  abut one another. Similarly, wooden strip  14  can be wound around the mandrel  10  such that the edges of the wooden strip  14  abut one another as shown in region  16 . In this example, wooden strip  14  is wound clockwise around mandrel  10 . 
         [0025]    When winding the wooden strips  12  and  14  around the mandrel  10 , tension can be applied to the strips. Accordingly, the wooden strips  12  and  14  form tight contact with any previously wound strips. 
         [0026]    In addition to wooden strips  12  and  14 , additional wooden strips (not shown) can be placed longitudinally along the mandrel  10 . For example, strips of wood can be placed following the axis  20  of the mandrel  10 . Accordingly, wooden strips can be wound around the mandrel  10  offset from the axis  20  by any angle. 
         [0027]    An adhesive can be used to hold the wooden strips  12  and  14  in place. Examples of such adhesive can include epoxy, PVA, or the like. The adhesive is cured. Accordingly, the wooden strips formed over the mandrel  10  retain their shape after the mandrel  10  is removed. As a result, the laminated wooden strips form a hollow wooden tube. 
         [0028]    In an embodiment, the grain of the wood selected for the strips can run substantially in the same direction as the strip. For example, arrows  22  and  24  indicate the directions of the grain for wooden strips  12  and  14 , respectively. In addition, the grain of a longitudinal wooden strip can be substantially parallel to the axis  20 . Accordingly, once the wooden tube is formed, the grains of the various wooden strips are aligned to resist forces that are placed on the tube. For example, wooden strips with grain aligned to along the axis  20  can resist bending. Wooden strips  12  and  14 , for example, can resist torsion on the tube. In one example, wooden strip  12  can resist torsion in a first direction about axis  20  and wooden strip  14  can resist torsion in a second direction about axis  20 . 
         [0029]    Furthermore, as grains that are aligned in different directions provide resistance to various forces, the number and directions of the wooden strips used to form the wooden tube can be selected as desired to achieve the desired physical properties of the application of the wooden tube. For example, if a greater resistance to torsion is desired, additional wooden strips such as wooden strips  12  and  14  can be used. 
         [0030]    The wooden strips can have a variety of thicknesses. In an embodiment, the wooden strips can be from about 0.005″ to about 0.020″. A finished wooden tube can have a thickness of about 0.190″. Accordingly, multiple strips can be overlaid to form the finished wooden tube. Although particular ranges of thicknesses for the strips and the finished tube have been given, the dimensions can be changed as desired. For example, thicker strips can be used when making a thicker finished tube. Thinner strips can be used when using a mandrel with a complex shape. Furthermore, the thickness of strips can vary within a given wooden tube. 
         [0031]    Although the mandrel  10  has been illustrated as cylindrical, the mandrel  10  can take a variety of shapes. In an embodiment, the mandrel can have any shape such that the wooden strips can conform to the mandrel. In an embodiment, the mandrel can have a polygonal cross-section. The edges of the mandrel corresponding to the corners of the polygon can be selected to have radii such that wooden strips applied to the mandrel can conform to the mandrel without tearing. 
         [0032]      FIG. 2  is an illustration of a bicycle frame using wooden tubes of  FIG. 1 . The bicycle frame  30  includes top tube  32 , down tube  34 , and seat tube  36 . Top tube  32  and seat tube  36  are joined by a connector  40 . Top tube  32  and down tube  34  are joined by connector  42 . Down tube  34  and seat tube  36  are joined by connector  38 . 
         [0033]    The connectors  38 ,  40 , and  42  can be formed from a variety of materials. For example, the connectors  38 ,  40 , and  42  can be formed from machined wood, molded metal, or the like. Any technique of capturing the ends of the respective tubes can be used for the connectors  38 ,  40 , and  42 . 
         [0034]    The bicycle frame  30  gives an example of tubes with different physical requirements. For example, seat tube  36  may encounter increased bending forces, but relatively reduced torsion. Accordingly, seat tube  36  can have additional longitudinal strips. In contrast, down tube  34  may encounter more torsion than seat tube  36 . Accordingly, down tube  34  can be formed with additional crossed strips such as wooden strips  12  and  14  of  FIG. 1 . 
         [0035]      FIG. 3  illustrates a plank with wooden blanks before the wooden blanks are cut from the plank according to an embodiment. In an embodiment, a monocoque wooden frame can be formed from wooden blanks. The plank  60  can be any size and/or shape of wood. The plank can be a solid piece of wood. In another embodiment, the plank  60  can be a laminate formed of multiple layers of wood. In an embodiment, the grains of the wood are all substantially aligned in one direction. For example, the grain of the wood can be aligned in substantially the same direction of arrow  88 . In another embodiment, the wood can be a laminate formed with the grains of the component sheets in a variety of directions. 
         [0036]    In the embodiment illustrated in  FIG. 3 , wooden blanks  62 ,  64 ,  66 , and  68  are arranged in a line on the plank. The plank  60  can, but need not have dimensions such that the wooden blanks  62 ,  64 ,  66 , and  68  can only be laid out in a line. For example, the plank  60  can have different dimensions such that the wooden blanks  62 ,  64 ,  66 , and  68  can be laid out in more than one direction. 
         [0037]    In an embodiment, the wooden blanks  62 ,  64 ,  66 , and  68  correspond to different portions of a bicycle frame. Wooden blank  62  corresponds to the down tube, wooden blank  64  corresponds to the top tube, wooden blank  66  corresponds to the seat tube, and wooden blank  68  corresponds to the HT. If the grain of the wood is aligned with arrow  88 , then the grain of the wood is aligned accordingly in the wooden blanks  62 ,  64 ,  66 , and  68 . 
         [0038]    Each of the wooden blanks  62 ,  64 ,  66 , and  68  can be finger jointed where the wooden blank will be joined with other wooden blanks. For example, wooden blank  62  has finger joints at regions  70  and  72  corresponding to where the wooden blank  62  can be joined to wooden blanks  68  and  66 , respectively. Wooden blank  64  has finger joints at regions  74  and  76  corresponding to where the wooden blank  64  can be joined to wooden blanks  66  and  68 , respectively. Wooden blank  66  has finger joints at regions  78  and  80  corresponding to where the wooden blank  66  can be joined to wooden blanks  62  and  64 , respectively. Wooden blank  68  has finger joints at regions  82  and  84  corresponding to where the wooden blank  68  can be joined to wooden blanks  64  and  62 , respectively. In an embodiment, finger joints can be formed such that when the wooden blanks are assembled into a frame, the individual fingers are aligned in the direction of a force expected to be applied to the joint. 
         [0039]    Although finger joints have been described, other joints can be used. For example, a biscuit joint, a dovetail joint, a mortise and tenon joint, a tongue and groove joint, a dowel joint, or the like can be used. 
         [0040]    The wooden blanks  62 ,  64 ,  66 , and  68  can be cut from the plank  60 . Any technique of cutting can be used. Although not illustrated, the wooden blanks  62 ,  64 ,  66 , and  68  can remain attached to the plank  60  through breakable tabs. Accordingly, the wooden blanks  62 ,  64 ,  66 , and  68  can remain in the remainder of the plank  60  for ease of manufacturing. Once cut from the plank  60 , the wooden blanks  62 ,  64 ,  66 , and  68  can be routed, notched, slotted, or the like to form the desired joint in the desired location. 
         [0041]      FIG. 4  illustrates a plan view and side view of the wooden blanks  62 ,  64 ,  66 , and  68  assembled into a frame blank. The wooden blanks  62 ,  64 ,  66 , and  68  can be joined together by the joints described above to form frame blank  94 . Although the wooden blanks  62 ,  64 ,  66 , and  68  have been defined by the joints between tubes in a frame, the actual joint can be placed in different locations. As illustrated, wooden blank  62  and  64  extend into wooden blank  68  to a plane  92 . However, in another embodiment, wooden blanks  62  and  64  can extend into wooden blank  68  to plane  90 . Any position along the frame blank can have a location for a joint. 
         [0042]    In an embodiment, once assembled, the frame blank  94  may be coplanar. Accordingly, the frame blank  94  can be planarized to a plane  96 . For example, the frame blank  94  can be sanded down to plane  96 . In another example, a plane can be used to form the surface of plane  96 . For example, a thickness of the plank  60  can be selected such that the frame blank  94  is greater than about 0.050″ in excess of the desired thickness of the finished frame half. Although a particular range has been given as an example, an amount of the additional material can be selected as desired. For example, the additional material can be a thickness sufficient to accommodate an expected variation in heights due to the placement of the joints. Accordingly, a substantially uniform surface at surface  96  can be formed on the frame blank  94 . As will be described below, the substantially uniform surface can aid in bonding two frame blanks together. 
         [0043]      FIG. 5  is a cross-sectional view of the frame blank of  FIG. 4  at various stages of machining. In an embodiment, at this point, the frame blank  94  is in a rough shape of one half of a finished frame. Cross-section  100  illustrates the frame blank  94  at plane I of  FIG. 4 . Dashed lines  108  and  110  represent the desired surfaces of the finished frame half. The frame blank  94  can be machined to form the desired shape. For example, the frame blank  94  can be loaded on to a computer-numerical-controlled (CNC) machine. Region  106  can be machined away to result in cross-section  102 . Similarly, region  112  can be machined away to result in cross-section  104 . As a result, the desired shape of the frame half can be machined from the frame blank. In an embodiment, the planarization to surface  96  of  FIG. 4  can be performed by the machining described above. 
         [0044]    In an embodiment, regions on the frame blank  94  similar to region  106  of  FIG. 5  can be machined away in the same process. Once finished, the frame blank  94  can be flipped so that the opposite surface can be machined. 
         [0045]    In an embodiment, during machining, the frame blank  94  can be secured to the CNC machine using vacuum. Once the material similar to region  106  has been removed, the frame blank  94  can be flipped and secured again with a vacuum. In an embodiment, the edge including surface  109  may be continuous around the removed region  106 . Accordingly, when flipped, a vacuum can still be formed within the frame blank  94  to secure it to the CNC machine. Holes, openings, cutouts, slots, or the like can be formed in the before and after machining. To maintain the vacuum, such openings can be plugged for subsequent machining. In another embodiment the frame blank  94  can be secured to the CNC machine using a jig. 
         [0046]    Although the term frame half has been used to describe portions of a frame, a frame half is not limited to half of a frame. For example, a frame half can be one of multiple parts that are machined and combined into a completed frame. 
         [0047]      FIG. 6  illustrates an internal webbing in a frame half according to an embodiment. Frame half  120  has webbing  122  remaining in a machined region  126 . The webbing  122  can be placed as desired throughout the frame half  120 . A hole  124  can be formed in the webbing  122 . Such a hole  124  can be used for a variety of purposes. For example, the hole  124  can be used for drainage, cable routing, or the like. Although the internal webbing has been illustrated in the frame half  120 , in an embodiment, the frame half  120  need not have any webbing. 
         [0048]      FIG. 7  illustrates a side view of a frame half according to an embodiment. Cables can be routed through the frame blank  130 . In this embodiment, the frame blank  94  has been machined to remove material to form surface  140 . Surface  142  has not yet been formed through machining. Before forming surface  142 , a hole  134  can be formed in the frame blank  130 . A tube  132  can be inserted into the hole  134 . Although not illustrated, the tube  132  can also extend through another hole in the frame blank  130 . The tube  132  is secured in the hole  134  with an adhesive, epoxy, filler, or the like. 
         [0049]    The frame blank  130  is then machined to remove material in region  138 . During the machining, a portion of the tube  132  and the adhesive  136  within region  138  are machined. As a result, the opening of the tube is substantially coplanar with the surface  142 . In this embodiment, since the tube passed through the hole  134  at an angle offset from perpendicular to the surface  142 , any cable entering or exiting the hole can also be at such an angle relative to the surface  142 . 
         [0050]    In an embodiment, the adhesive  136  and the tube  132  seal the hole  134 . Accordingly, any vacuum applied to the frame blank  130  can still secure the frame blank for machining. 
         [0051]    In an embodiment, surfaces of the frame half can be coated with a waterproofing layer. All surfaces of the frame half can, but need not be coated with waterproofing. For example, only the inner surface can be coated with waterproofing. 
         [0052]      FIG. 8  illustrates two frame halves prior to assembly according to an embodiment. First frame half  150  and second frame half  152  can be joined together to for a frame. First frame half  150  has a surface  154 . Second frame half has a surface  156 . An adhesive can be applied to one or both of the surface  154  and surface  156 . The adhesive can, but need not be continuous on the surface to which it is applied. Although a surface  154  around the perimeter of the first frame half  150  has been illustrated, the surface  154  can include surfaces of other structures of the first frame half  150 . For example, as described above, webbing may be within a frame half. Accordingly, the adhesive can be applied to a surface of the webbing. Adhesive can be applied to any surface of a frame half that will contact a corresponding surface of the another frame half. 
         [0053]    The first frame half  150  and the second frame half  152  can be brought together so that the adhesive joins the two halves together. Although not illustrated, a frame half can have alignment structures to aid in aligning the first frame half  150  to the second frame half  152 . For example, the first frame half  150  can have dowels places around the first frame half  150 . The second frame half  152  can have corresponding holes for the dowels. In another example, a groove, notch, slot, or the like can be machined into the surface  154 . A corresponding mating structure can be machined in surface  156 . In an embodiment, the alignment structures can be formed in the webbing described above. 
         [0054]      FIG. 9  illustrates an assembled frame and inserts according to an embodiment. In an embodiment, frame  160  is a bicycle frame. Inserts  162 ,  164 , and  166  can be inserted into the frame  160 . For example, insert  162  can be a stem tube insert. Insert  164  can be a crank insert. Insert  166  can be a seat tube insert. An insert can be used in any location where something is mounted or in contact with the frame  160 . The inserts  162 ,  164 , and  166  can be secured in a variety of ways. For example, the inserts can be secured by friction, adhesive, mechanical detents, fasteners, or any other mechanical capturing technique. 
         [0055]    Although the inserts  162 ,  164 , and  166  have been described as being inserted into the frame  160 , the inserts can be assembled with the frame halves as described above, For example, the inserts  162 ,  164 , and  166  can be assembled with the first frame half  150 . During assembly with the second frame half  152 , the inserts  162 ,  164 , and  166  can be secured between the first and second frame halves  150  and  152 . 
         [0056]    Once assembled, the frame  160  can be used as would any other bicycle frame. For example, a crank can be inserted through insert  164 , a stem can be inserted through insert  162 , and a seat can be inserted through insert  166 . In addition, a rear triangle can be attached to the frame  160 . Since the frame  160  can be used as any other frame, any type of rear triangle can be used. For example, rear triangles formed from steel, aluminum, carbon composite, or the like can be used. Furthermore, a rear triangle can be formed from wood as described above. 
         [0057]    By using wood in such structures, the quality of the ride can be tailored to the rider. For example, a 200 lb. rider may need a stiffer quality than a 95 lb. rider. Accordingly, wood species, grain orientation, wood strip orientation, or the like can be modified separately, or in combination to achieve desired characteristics. 
         [0058]    Any variety of wood can be used as desired. Wood species can be selected based on a variety of characteristics. For example, wood can be selected based on its machinability, grain density, straightness, impact resistance, or the like. Furthermore, the same wood species can, but need not be used throughout a single frame. For example, wood species selected for strength can be used in internal portions of the frame, while wood species selected for aesthetics can be used as an outer lamination or veneer. 
         [0059]      FIG. 10  illustrates an example of wooden blanks of  FIG. 3  according to an embodiment. Numbers  1 - 4  illustrate the corresponding surfaces.  FIG. 11  illustrates an example of a frame blank formed from wooden blanks of  FIG. 10  with an outline of a desired frame half. 
         [0060]    Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. Accordingly, all modifications and variations coming within the spirit and scope of the above disclosure are included.