Abstract:
A sizable reduced weight bicycle frame and method for making such incorporating tubes of a composite material, the method providing for flexibility and full customization of the bicycle frame with a minimum amount of tooling, which tooling securely holds lugs of the bicycle frame at selected customized positions relative to the tooling during the molding process.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This patent application is a divisional application of U.S. patent application Ser. No. 10/881,910, entitled “Sizable Composite Tube Bicycle Frame and Method of Making”, and filed Jun. 30, 2004, the contents of which are incorporated herein by reference, in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention generally relates to a sizable bicycle frame including composite tubes and method for making same, and more specifically to a bicycle frame having tubes that may be fabricated from a pre-impregnated composite material that may be sized as desired to form a bicycle frame of a desired size.  
       BACKGROUND OF THE INVENTION  
       [0003]     The manufacturing and fabrication of customizable, strong and reduced weight bicycle frames provides many benefits to both the competitive and the recreational bicycler. In use, a reduced weight bicycle requires less energy to propel which can be significant during long bicycle races or on inclines.  
         [0004]     To reduce the weight of bicycle frames composite materials have been utilized for bicycle frames in numerous different ways with limited success. For instance, U.S. Pat. Nos. 4,850,607 and 4,889,355 describe the manufacture of unitary construction bicycle frames that comprise a resin having a fibrous material provided therein such as, fiber glass, carbon fiber or Kevlar.  
         [0005]     The interconnecting bars are first fabricated from the resin and fibrous material. Once formed to the desired length, the interconnecting bars are then placed in a common fixture that maintains their relative orientations while they are connected to each other by lugs or joints formed of additional resin and fibrous material. However, the lugs are stress points for the bicycle frame and as they comprise the resin and fibrous material, they are not strong enough to withstand the forces often encountered during aggressive or competitive cycling. In addition, customization of the bicycle frame requires the mold to be retooled and adjusted for each use according to the dimensions of the user.  
         [0006]     Other systems have sought to provide a strong reduced weight bicycle frame including U.S. Pat. Nos. 5,803,476 and 5,876,054. Both of these patents disclose unitary composite bicycle frames comprising a single section of woven fabric, such as glass fiber, Kevlar, or carbon fiber which is impregnated with a heat curable epoxy resin. However, both of these references teach that the entire bicycle frame is molded as a unitary or composite structure with the top tube, down tube and seat tube each being connected to each other through the lugs. This process is highly undesirable because adjustability and customization of the bicycle frame is extremely difficult, time consuming and expensive because many different molds and tooling must be stocked and used to manufacture different sized bicycle frames adding to the total cost involved in the manufacturing process. In addition, the epoxy resin continuously extends as a unitary structure completely through each of the lugs which may undesirably add to the total weight of the bicycle frame.  
         [0007]     Another approach has been to utilize bladder molds to mold carbon fiber into titanium tubes and then weld them into a frame. This process however necessitates making the tubes before they are needed and inventorying them and further limits the composite section because the tube must be fabricated first and then mitered.  
         [0008]     Still another approach is disclosed in U.S. Pat. No. 5,158,733. In this reference a bicycle frame is disclosed in which fibers are impregnated with a heat curable synthetic resin for use with a unitary bicycle frame. In this system, a metallic unitary bicycle frame is provided with a regular pattern of holes or pieces of the metal frame removed into which holes a resin impregnated fabric is compressed, which results in a reduced weight bicycle frame being a unitary metal frame with a larger percentage (i.e. the holes) filled with a composite material. However, this is still a unitary metal bicycle frame and while the regular pattern of holes provided in the metal frame does reduce the overall weight (i.e. the metal from the holes has been removed), the frame is still too heavy because the tubes mostly comprise structural metal. In addition, as this is a unitary frame assembly, customization for a particular user requires inventorying many differing molds and tooling according to the desired dimensions of the bicycle frame based upon the size and height of the user.  
         [0009]     What is desired then is a reduced weight bicycle frame that having lugs that will withstand the forces often encountered during aggressive or competitive cycling.  
         [0010]     It is further desired to provide a bicycle frame that comprises a light weight composite material that is fully customizable to the individual without the need to retool for each customized frame fabricated.  
         [0011]     It is still further desired to provide a method for fabricating a bicycle frame that utilizes the same mold for fabricating many differing sized bicycle frames.  
         [0012]     It is yet further desired to provide a method for fabricating a bicycle frame that utilizes standard sized forms that are fully customizable without the need to stock many differing sized forms.  
         [0013]     It is still further desired to provide a bicycle frame that comprises a light weight composite material and provides robust lugs that will not fail during use.  
         [0014]     It is yet further desired to provide a bicycle frame utilizing a bond between the bicycle frame members and the lugs.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     These and other objectives are achieved by the provision of the bicycle frame that utilizes a structural fiber and resin composite for the bicycle frame members or tubes including the top tube, the down tube and the seat tube, and further utilizes robust lugs or joints for joining the tubes together. The lugs may comprise for instance, a light weight durable metal or metal alloy capable of withstanding the increased stresses encountered during use.  
         [0016]     The structural fiber and resin composite material is provided as pre-impregnated material having a standard length. This pre-impregnated material may be trimmed or cut to substantially any length desired and are positioned between the lugs. In this manner, the lugs may be positioned substantially any distance relative to each other such that many differing sized bicycle frames may be fabricated with a single mold.  
         [0017]     The structural fiber and resin composite tubes may also be bonded with the lugs to provide a secure connection. In one advantageous embodiment the tubes are further mechanically interlocked with the lugs.  
         [0018]     In one aspect of the invention bladder molding is utilized in the fabrication of the bicycle frame. Bladder molding also allows for a wide variety of customization of the tubing since the wall thickness of the tubes can be varied on the inner diameter, allowing both radial and circumferential butting.  
         [0019]     In this method composite tubes are molded into lugs. Short tube sections may be welded onto the top tube and seat tube to create lugged joints. Alternatively, main tube sections may be cut out of a complete welded frame to create the lugs. The “lugs” are then arranged then arranged or positioned so that they are in the same orientation they were before the tube sections were cut apart. A pre-impregnated material of the composite material is then inserted in the lugs, being exposed in the center section of the tube and internal to the lug at the junctions. A film adhesive may be used between the pre-impregnated material and the lug to facilitate bonding. Individual molds with an internal cavity matching the lugs at the ends and the finished shape of the exposed composite tube are placed over the exposed pre-impregnated material and the composite parts are bladder molded in place. This will create a composite tubed frame without secondary bonding operations and allow flexible sizing, excellent control over tube optimization and an aesthetically pleasing design with seamless joints. While a film adhesive may be used to facilitate bonding, holes may further be cut or machined into the tubes in the overlap region of the lug and composite material such that when the composite material is heated it flows into the holes to provide a mechanical interlock between the composite and lug.  
         [0020]     Additionally, the molds can have features for cable guides and the like, which would be nearly impossible for a conventionally manufactured tube.  
         [0021]     A major benefit of this approach is that it allows the manufacture of small, equal length lugs for all sizes and easy varying of the composite pre-impregnated material lengths of the frame members before molding to make different frame sizes. In addition, tooling pins that hold the bicycle frame to the mold provides greater flexibility in the use of the tooling. This approach then provides a relatively lightweight composite frame with variable sizing options without requiring a relatively large tooling inventory.  
         [0022]     In one advantageous embodiment a bicycle frame is provided comprising a first portion, a second portion, and a composite material extending between the first and second portions, the composite material sized to provide a preferred distance between the first and second portions and to size the bicycle frame. The bicycle frame further comprises an adhesive layer between an inner surface of at least the first portion and the composite material to adhere the composite material to at least the first portion.  
         [0023]     In another advantageous embodiment a system for fabricating a bicycle frame is provided comprising a mold body having an inner molding surface, a first portion at least partially in contact with the inner molding surface, and a second portion at least partially in contact with the inner molding surface. The system further comprises an attachment device for connecting at least one of the first and second portions to one of multiple positions in the mold body to size the bicycle frame, and a composite material placed within the mold body between and within at least a part of the first and second portions.  
         [0024]     In still another advantageous embodiment a method for manufacturing a bicycle frame is provided comprising the steps of providing a first portion, providing a second portion, and extending a composite material between the first and second portions, the composite material sized to provide a preferred distance between the first and second portions and to size the bicycle frame. The method further comprises the step of positioning an adhesive layer between an inner surface of at least the first portion and the composite material to adhere the composite material to at least the first portion.  
         [0025]     In yet another advantageous embodiment a bicycle frame is provided comprising a first portion, a composite material at least partially inserted into the first portion, and an adhesive layer between an inner surface of the first portion and the composite material to adhere the composite material to the first portion. The bicycle frame is provided such that the composite material may be trimmed to provide a preferred length.  
         [0026]     In still another advantageous embodiment a method for fabricating a bicycle frame is provided comprising the steps of cutting a composite material to a desired length, and inserting the composite material into an end of a first portion. The method further comprises the steps of positioning an adhesive layer between an inner surface of the first portion and the composite material, and adhering the composite material to the first portion such that the adhesive layer is sandwiched between the composite material and the inner surface of the first portion.  
         [0027]     In yet another advantageous embodiment a system for fabricating a bicycle frame is provided comprising a mold body having an inner molding surface, a composite material placed within the mold body and at least partly within a frame portion, with the inner molding surface encasing both the composite material and at least a part of the frame portion. The system further comprises an attachment device for connecting the frame portion to one of multiple positions in the mold body to size the bicycle frame.  
         [0028]     In still another advantageous embodiment a bicycle frame having a first portion and a second portion with a composite material extending between the first and second portions, the composite material sized to provide a preferred distance between the first and second portions and to size the bicycle frame, and having an adhesive layer between an inner surface of at least the first portion and the composite material to adhere the composite material to at least the first portion is provided. The bicycle frame is fabricated by a system comprising a mold body having an inner molding surface, where the first portion is at least partially in contact with said inner molding surface, and the second portion is at least partially in contact with said inner molding surface. The system further comprises an attachment device for connecting at least one of the first and second frame portions to one of multiple positions in the mold body to size the bicycle frame, and a composite material placed within the mold body between and within at least a part of the first and second portions.  
         [0029]     The invention and its particular features and advantages will become more apparent form the following detailed description considered with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0030]      FIG. 1  is an illustration of a side view of a bicycle frame according to one advantageous embodiment of the present invention;  
         [0031]      FIG. 2  is a side view of a frame used according to one method of the present invention to fabricate the bicycle frame according to  FIG. 1 ;  
         [0032]      FIG. 3  is a side view of the frame of  FIG. 2  illustrating the lugs;  
         [0033]      FIG. 4  is a side view of the frame of  FIG. 3  with pre-impregnated material, film adhesive and bladders inserted;  
         [0034]      FIG. 5  is a partial exploded side view of the bicycle frame according to  FIG. 1  with a mold illustrated thereabout with the tooling pins;  
         [0035]      FIG. 6A  is a side view of the frame according to  FIG. 5  with the mold thereabout prior to removal;  
         [0036]      FIG. 6B  is a side view of the frame according to  FIG. 5  with the mold thereabout prior to removal;  
         [0037]      FIG. 7  is a partial enlarged view according to  FIG. 4  showing an end of a pre-impregnated material in a lug and a mold;  
         [0038]      FIG. 7A  is an enlarged view according to  FIG. 4  showing an end of a pre-impregnated material in a lug and a mold;  
         [0039]      FIG. 8  is a view according to  FIG. 7  showing the pre-impregnated material expanded in the mold and the lug;  
         [0040]      FIG. 8A  is a view according to  FIG. 7A  showing the pre-impregnated material expanded in the mold and the lug;  
         [0041]      FIG. 9  is a view according to  FIG. 8  with the mold removed therefrom;  
         [0042]      FIG. 9A  is a view according to  FIG. 8A  with the mold removed therefrom; and  
         [0043]      FIG. 10  is a side view of the molds according to one advantageous embodiment for molding the bicycle frame according to  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0044]     Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views.  
         [0045]      FIG. 1  is a side view of one advantageous embodiment of the present invention showing bicycle frame  100 . Bicycle frame  100  generally comprises front and rear triangular sections. The front triangular section includes head lug  102 , seat lug  104  and lower lug  106 , which define the corners of the front triangular section. As the lugs are major stress points for bicycle frame  100 , advantageously they comprise a robust material such as for instance, a metal or metal alloy.  
         [0046]     Connecting the lugs together are tube sections. Top tube  108  connects head lug  102  to seat lug  104 . Seat tube  112  connects seat lug  104  to lower lug  106 . Finally, down tube  110  connects head lug  102  to lower lug  106 .  
         [0047]     Referring now to  FIG. 1  and  FIG. 9  which is a cross-sectional of  FIG. 1 , a description of the interaction between a first portion top tube  108 , and a second portion head lug  102  is provided. Head lug  102  comprises a sleeve  114  having an opening  116  into which top tube  108  is at least partially inserted with an inside diameter of sleeve  114  is defined by a perimeter wall  118 .  
         [0048]     Top tube  108  comprises two different diameters, one for the portion of top tube  108  located inside sleeve  114  and a larger diameter for the portion of top tube  108  not located inside sleeve  114 . The diameter of top tube  108  outside sleeve  114  may advantageously be approximately the same as the outer diameter of sleeve  114 , while the diameter of top tube  108  inside sleeve  114  is essentially the same as the inner diameter of sleeve  114 .  
         [0049]     Also provided in wall  118  is hole  120  into which protrusion  122  is positioned. The engagement of protrusion  122  with hole  120  provides a mechanical interlock between the first portion top tube  108 , and the second portion head lug  102 . This type of connection is highly secure as opposed to simply bonding top tube  108  to head lug  102  with for instance, an epoxy or cement which can fracture or break with the high stresses placed upon the joint.  
         [0050]     Referring now to the additional features of bicycle frame  100  shown in  FIG. 1 , head lug  102  further comprises sleeve  124  and opening  126 , which receives down tube  110  in a similar manner as described above. Still further, lower lug  106  comprises sleeves  128 ,  130  for receiving down tube  110  and seat tube  112  respectively. Lower lug further comprises holes  132 ,  134  for creating a mechanical interlock between lower lug  106  and down tube  110  and seat tube  112  respectively. Seat lug  104  is also illustrated in  FIG. 1  comprising sleeves  136 ,  138  for receiving seat tube  112  and top tube  108  respectively. In addition, sleeves  136 ,  138  are provided with holes  140 ,  142  for mechanically interlocking seat tube  112  and top tube  108  to seat lug  104  respectively.  
         [0051]     While the lugs may advantageously comprise a rugged material such as a metal or a metal alloy in order to withstand the stresses encountered at the stress points, top tube  108 , down tube  110  and seat tube  112  may advantageously comprise a composite material, illustrated with diagonal cross-hatching in  FIG. 1 , for reducing the overall weight of the bicycle frame  100 . The composite material may comprise for instance, but is not limited to a structural fiber impregnated with a heat curable resin wherein the structural fiber may comprise carbon fibers, glass fibers, polyethylene fibers, or combinations thereof. As an alternative, it is contemplated that thermoplastic composites may be utilized as desired. In any event, it is contemplated that many differing compositions may be utilized as the composite material for use in fabricating the tube sections.  
         [0052]     Referring now to  FIG. 2 a  standard welded bicycle frame  10  is shown. The bicycle frame  10  comprises lugs as described in connection with  FIG. 1 , however the tubes comprise a metal or a metal alloy rendering bicycle frame  10  heavier than bicycle frame  100 .  
         [0053]      FIG. 3  shows the bicycle frame  10  according to  FIG. 2  but with the tubes removed leaving only head lug  102 , seat lug  104  and lower lug  106  in spatial relation to each other. These lugs may then be positioned relative to each other for full customization of the bicycle frame. In one advantageous embodiment the bicycle frame is divided up into multiple portions where for instance, a first portion may comprise head lug  102 , a second portion may comprise seat lug  104  and a third portion may comprise lower lug  106 .  
         [0054]      FIG. 4  illustrates the insertion of composite material that may on one advantageous embodiment comprise a pre-impregnated material, which will serve as top tube  108 , down tube  110  and seat tube  112 . In one advantageous embodiment, bladder molding carbon fiber/epoxy pre-impregnated material may be provided with unidirectional and bias plies formed from pre-impregnated fabric. These pieces of pre-impregnated carbon fiber may be rolled onto for instance, a bladder  144 , assembled into the lugs, and then molded, which may involve raising the temperature of the pre-impregnated material. In practice, the composite pre-impregnated material may advantageously comprise only a few standard lengths thereby reducing the need to stock many differing sized pre-impregnated material units. Full customization of bicycle frame  100  is achieved by the pre-impregnated material being inserted into the sleeves of the respective lugs to a desired depth depending upon the customized size of bicycle frame  100  for the user. For instance, once a custom size is determined, a mold ( FIGS. 5 &amp; 6 ) is positioned about and attached to the lugs. Once so positioned, the pre-impregnated material may then be cut or trimmed to the desired length relative to the mold and the lugs. In this manner a standard length pre-impregnated material may be utilized to manufacture a fully customizable bicycle frame.  
         [0055]     A bladder  144  illustrated as a dashed line inside of the pre-impregnated material connecting head lug  102  to seat lug  104  is positioned inside of the composite pre-impregnated material for later expansion of the pre-impregnated material. The bladder can be sealed and inflated in a number of different ways such as is disclosed in U.S. Pat. Nos. 4,889,355; 4,900,050, and 5,803,476 which are incorporated herein by reference. A neck  146  extends from the end of bladder  144  through opening  116  and exits from head lug  102  for later attachment to a source of pressurized air for expansion of bladder  144 , which will cause the pre-impregnated material to expand.  
         [0056]     Still further, an adhesive  148  may in one advantageous embodiment, be used to affix the composite material to the lug in a fixed desired position until the composite material is expanded into a permanent position relative to the lug. The adhesive  148  may comprise a thin epoxy film adhesive that is cut and adhered to the inside of the lugs before the composite material is inserted and then co-molded.  
         [0057]      FIG. 5  is a side view of bicycle frame  100  and the attachment of molds  150 ,  152  for molding of the composite material that will become top tube  108 . The molds are designed to enclose the various composite material prior to application of heat and expansion of the bladders. While the following description references top tube  108 , head lug  102  and molds  150 ,  152 , the description equally applies to each of the tubes, lugs and molds. Referring to molds  150 ,  152  for the molding of top tube  108 , molds  150 ,  152  are provided with an inner surface  162  formed to shape top tube  108 . In one advantageous embodiment inner surface  162  is partially cylindrical and partially oblong shaped toward head lug  102 . However it is contemplated that many differing tube shapes may be desired depending upon the application and use.  
         [0058]     The molds comprise any suitable material that may withstand the relatively high temperatures applied to the composite material such that they become pliable for expansion such that they may take on the shape of inner surface  162 . In addition, molds  150 ,  152  are provided such that they may be secured to each other so as to be securely held to bicycle frame  100  during the molding process. In addition, attachment devices  164 ,  166  (in this case insertable tooling pins) associated with for instance, molds  150 ,  152  respectively are also provided to firmly affix molds  150 ,  152  to head lug  102  during the molding process. Attachment devices  164 ,  166  allow great versatility in the placement of the molds relative to the lugs because mounting holes  165 ,  167  respectively may be cut into the lug at virtually any location along the length of sleeve  114  as desired. In addition, once molds  150 ,  152  are positioned on sleeve  144 , the composite material may be cut to the desired length. While  FIG. 5  depicts hole  120  located in sleeve  114 , this illustrates only one advantageous embodiment.  
         [0059]     As can be seen from  FIGS. 6A and 6B , the same molds may be utilized for differing sized bicycle frames due to the versatility of the various attachment devices such as  164 ,  166 . The lugs may be positioned in the molds in a fixed spatial relationship relative to each other such that bicycle frame  100  is easily customizable for the user without the requirement of stocking large quantities of different sized molds and tooling. For instance, attachment devices  164 ,  166  may be inserted substantially anywhere along the sleeve portions of the lugs to adjust the size of the bicycle frame while using the same mold as can be seen in  FIGS. 6A and 6B . The composite material is simply trimmed or cut to any desired length based upon the selected distance between the lugs.  FIG. 6A  is a smaller sized bicycle frame than  FIG. 6B  but uses the same sized molds for fabrication. In one advantageous embodiment, it is determined where the lugs will be positioned relative to each other and holes are cut into the lug for insertion of the associated attachment device relative to the lug. The hole  188  may be cut into the lug by any suitable means such as for instance, laser or mechanical cutting.  
         [0060]     As illustrated in  FIGS. 5, 6A  and  6 B, the molds are paired and affix to each other to fully enclose the composite material and at least a portion of the sleeve protruding from the associated lug. The molds would at least extend over the sleeve to enclose the holes such that the composite material does not escape through the holes during the molding process. The molds are still further affixed to bicycle frame  100  via attachment devices  164 ,  166  such that the molds to not move relative to the composite material that will become the tubes or the lugs during the molding process.  
         [0061]      FIGS. 7 and 7 A are side views of sleeve  114  per  FIG. 6A  with the composite material that will be top tube  108  inserted into opening  116  prior to expansion with molds  150 ,  152  attached around the composite material and sleeve  114 .  FIG. 7  shows the composite material that will become top tube  108  inserted into sleeve  114  with adhesive  115  extending along a portion of the length of the composite material inserted into sleeve  114 . As can be seen in  FIG. 7A , the end of the composite material that will become top tube  108  is inserted past hole  120  so that upon expansion of the composite material, a portion of the composite material will fill into the cavity. While adhesive  115  is shown extending along a length of sleeve  114 , adhesive  115  may extend continuously or may be applied at one or more locations along the length of sleeve  114 . The depth of insertion of the composite material is adjustable inside the sleeve  114  of head lug  102  to increase or decrease the distance of the lugs relative to each other.  
         [0062]      FIGS. 8 &amp; 8A  are side views according to  FIGS. 7 &amp; 7A  showing the composite material expanded to fill the space between the composite material and inner wall  162 , the inner wall of sleeve  114 , and into hole  120  as illustrated in  FIG. 7A . The composite material expands to fill the space in sleeve  114  coming into contact with adhesive  115  forming a bond between the composite material and the lug. In addition, in  FIG. 8A  the composite material also flows into hole  120  and upon cooling, creates a further interlock comprising protrusion  122  co-acting with hole  120 . Once the composite material has cooled and hardened, molds  150 ,  152  may be removed to reveal the top tube  108  and head lug  102  assembly as illustrated in  FIGS. 9 &amp; 9A  respectively.  
         [0063]     As an alternative to the use of the attachment devices to hold the molds in a fixed position relative to the lugs as previously described, another advantageous method may utilized according to  FIG. 10 . Here the molds are held in fixed spatial relationship relative to each other by means of insertable molding pins  170  (shown inserted into to plate  172 ) which attach the molds to plate  172 . While molds  150 ,  152  and molds  154 ,  156  are each illustrated with four molding pins  170  for attachment to plate  172  and molds  158 ,  160  are shown with two molding pins  170  for attachment to plate  172 , it is contemplated that any number of molding pins may effectively be used to hold the molds in fixed spatial relationship relative to each other.  
         [0064]     This system and method of manufacture provides for a quick and inexpensive way to fabricate the bicycle frame  100  according to the invention. In addition, this method of manufacture be even be preferred for fabrication of more common sized bicycle frames as the need to cut holes for the attachment devices is eliminated. In addition, standard sized composite material may still be effectively utilize as once the lugs are positioned in the molds relative to each other, the composite material may then simply be cut to any desired length for connection between the lugs.  
         [0065]     Although the invention has been described with reference to particular ingredients and formulations and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.