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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
It is yet further desired to provide a bicycle frame utilizing a bond between the bicycle frame members and the lugs.
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.
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.
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.
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.
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.
Additionally, the molds can have features for cable guides and the like, which would be nearly impossible for a conventionally manufactured tube.
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.
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.
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.
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.
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.
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.
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.
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.
The invention and its particular features and advantages will become more apparent form the following detailed description considered with reference to the accompanying drawings.
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views.
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.
Referring now to
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.
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.
Referring now to the additional features of bicycle frame 100 shown in
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
Referring now to
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.
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.
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
As can be seen from
As illustrated in
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
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.
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.
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.
Number | Date | Country | |
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Parent | 10881910 | Jun 2004 | US |
Child | 11609633 | Dec 2006 | US |