Abstract:
A bicycle frame, comprising at least two members, capable of improving upon at least several aspects of existing bicycle frames, including cost, weight, and reliability, while accommodating a wide range of rear tire widths. Various embodiments accomplish these improvements through the employment of structurally efficient cross sections, few supporting members, a cantilever rear wheel support, and few locations where members are adjoined and susceptible to certain failure modes.

Description:
BACKGROUND 
     The present application relates to a bicycle frame; specifically, it relates to a frame design that improves upon limitations of existing bicycle frame designs, including weight, reliability, and cost. Early bicycle frames were constructed of tubular sections joined together with lugs. Over time, innovations in the fields of materials and manufacturing methods drove improvements in bicycle frame design, including the elimination of lugs and tubing, reductions in weight, lower construction costs and improvements in strength and rigidity. Presently, diamond-type bicycle frames are common given an economic combination of strength, stiffness, and manufacturability. Such designs are constructed by joining a head tube, a top tube, a down tube, a seat tube, a pair of seat stays, and a pair of chain stays. To improve strength and rigidity, such frames utilize duplicate seat stays and chain stays, resulting in higher weight and cost. These members often reflect cross sections which do not offer a high stiffness relative to cross-sectional area when compared to more structurally efficient cross sections. Consequently, achieving overall frame stiffness in such designs requires additional material, further contributing to higher overall weight and cost. More recent bicycle frame innovations, such as monocoque designs, successfully reduce weight but are more difficult and expensive to manufacture, thereby limiting accessibility to many consumers. Although manufactured relatively inexpensively and thus accessible to many consumers, diamond-type bicycle frames feature many locations where members are adjoined by methods such as brazing and welding; such joining methods add to the total cost of frame construction and introduce the possibility of failure modes at those locations. Some relevant failure modes include fatigue fracture, brittle fracture, and impact fracture at the location where members are adjoined. Separately, the distance between the seat stays of diamond-type bicycle frames limits the wheel and tire combinations which may be mounted to the frame. For example, a frame designed to accommodate a standard 26 inch×2.1 inch rear tire may not be able to accommodate a 26 inch×3.8 inch rear tire. Thus, there is a continuing need for improvements in bicycle frame design. As a result of the shortcomings of the prior art described above, a bicycle frame design which features a lower weight and lower susceptibility to certain failure modes while reducing cost and enabling the use of a wide range of tire sizes is needed. 
     SUMMARY 
     It is therefore an object of one embodiment of the lightweight cantilever bicycle frame to provide an improved bicycle frame capable of being manufactured with a lower overall cost. Another object of one embodiment is to provide an improved bicycle frame with reduced weight. Still another object of one embodiment is to provide an improved bicycle frame with lower susceptibility to failure modes associated with joining methods. Still another object of one embodiment is to provide an improved bicycle frame capable of supporting a wide range of rear tire sizes. 
     According to one embodiment of the lightweight cantilever bicycle frame, there is provided a bicycle frame comprising: a primary member of continuous length of material with at least three bends and a rear hub supporting means, wherein the cross section of at least a portion of the primary member reflects a structural shape; a secondary member attached to the primary member, whereby the primary member and the secondary member are together operable to support bicycle components and a rider with fewer members, less material, and fewer locations where members are adjoined, and to support a wider range of rear tire sizes when compared to the prior art. 
     ADVANTAGES 
     Thus one advantage of one or more aspects is its reduced weight when compared to diamond-type bicycle frames of comparable size. This advantage follows because the present embodiment is constructed from as few as two members, supports the rear wheel assembly in a cantilever manner, and utilizes a structurally efficient cross section in the primary member to reduce materials usage. 
     Thus another advantage of one or more aspects is that it has fewer locations where joining methods are suggested, resulting in lower cost and fewer locations susceptible to failure of such joining methods. 
     Thus another advantage of one or more aspects is that it can be constructed less expensively due to reduced materials usage and fewer locations where joining methods are suggested, and also due to the correspondingly lower labor requirements for assembly. Additionally, the primary and secondary members can be constructed from commonly available materials, resulting in reduced cost when compared to certain other materials. 
     Thus another advantage of one or more aspects is that it can accommodate a wide range of rear tire widths, thereby enabling the rider to reconfigure the bicycle for different terrains. 
    
    
     
       DRAWINGS-FIGURES 
         FIGS. 1A to 1C  show one embodiment of the primary member. 
         FIG. 2  shows the rear hub supporting means. 
         FIGS. 3A and 3B  show one embodiment of the secondary member. 
         FIGS. 4A and 4B  show one embodiment of the lightweight cantilever bicycle frame as it would appear as part of a complete bicycle assembly. 
     
    
    
     DRAWINGS-REFERENCE NUMERALS 
     
         
           10  primary member 
           11  forward end 
           12  first length 
           13  rearward end 
           14  first bend 
           16  second bend 
           18  third bend 
           20  rear hub supporting means 
           21  rear hub aperture 
           22  cross section 
           23  rear hub 
           30  secondary member 
           31  upper end 
           32  second length 
           33  lower end 
           34  secondary member aperture 
           36  drive feature supporting means 
           38  bicycle seat supporting means 
           39  bicycle seat assembly 
           40  front assembly 
           41  front wheel assembly 
           42  rear wheel assembly 
           44  drive feature assembly 
       
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1A-1C , a primary member  10  is constructed of a first length  12  of material characterized by a forward end  11 , a first bend  14 , a second bend  16 , a third bend  18 , and by a rearward end  13  coupled slidably and affixed to a rear hub supporting means  20 . In this embodiment, a cross section  22  of first length  12  reflects an I-beam. It is envisioned that first length  12  could be manufactured by imparting bends  14 ,  16 , and  18  upon a commonly available length of structural material. 
     Again with reference to  FIGS. 1A-1C , primary member  10  supports a front wheel assembly  41  via a front assembly  40 , it supports a secondary member  30  via a secondary member aperture  34 , and it supports a rear wheel assembly  42  via rear hub supporting means  20 . Primary member  10  also acts as a deflecting beam to absorb impacts, such as those received through forward end  11  from riding over a drop off. Cross section  22  of primary member  10  reflects an I-beam in order to take advantage such shape&#39;s high second moment of area relative to the cross sectional area, thereby controlling deflection and materials usage. First bend  14 , second bend  16 , and third bend  18  enable primary member  10  to support rear wheel assembly  42  in a cantilever manner via rear hub supporting means  20 , thereby further reducing materials usage and cost. 
     With reference to  FIG. 2 , rear hub supporting means  20  is a component of primary member  10  affixed to rearward end  13 . A rear hub aperture  21  extends through the width of rear hub supporting means  20 . It is envisioned that rear hub supporting means  20 -could be manufactured from a polymer, such as through a combination of injection molding and material removal processes. Alternatively, rear hub supporting means  20  may be manufactured from metal or other materials. 
     Again with reference to  FIG. 2 , rear hub supporting means  20  supports rear wheel assembly  42  in a cantilever manner. To accomplish this, rear hub supporting means  20  couples with and is affixed to rearward end  13 . Rear hub aperture  21  receives a rear hub  23 , which is a component of rear wheel assembly  42 . 
     In the embodiment shown in  FIGS. 3A-3B , secondary member  30  comprises a second length  32  oriented in a near-vertical manner with an upper end  31  and a lower end  33 . Secondary member aperture  34  extends through second length  32  at a point proximal upper end  31 , and may reflect cross section  22  of primary member  10 . At a point proximal lower end  33 , any joining method may be employed to affix a drive feature supporting means  36  to second length  32 . In this embodiment, drive feature supporting means  36  reflects a cylindrical housing with an interior profile suitable to contain components of a drive feature assembly  44 . At a point proximal upper end  31 , a bicycle seat supporting means  38  is incorporated. 
     Again with reference to  FIGS. 3A-3B , secondary member aperture  34  receives primary member  10 , thereby affixing the position of secondary member  30  relative to primary member  10  along two orthogonal axes. To fix the position of secondary member  30  relative to primary member  10  along a third axis, any joining method may be employed. 
     In the illustrated embodiment, secondary member  30  supports drive feature assembly  44  via drive feature supporting means  36  and supports a rider via bicycle seat supporting means  38  and a bicycle seat assembly  39 . Furthermore, bicycle seat supporting means  38  permits the rider to adjust the distance of bicycle seat assembly  39  relative to drive feature supporting means  36 . Secondary functions of secondary member  30  may include maintaining tension in drive feature assembly  44  and transferring energy from the rider to drive feature assembly  44 . 
     One embodiment of the lightweight cantilever bicycle frame is illustrated in  FIGS. 4A and 4B . The frame comprises primary member  10  affixed to secondary member  30  by way of secondary aperture  34 . Forward end  11  is affixed to front assembly  40 , which supports front wheel assembly  41 . Rear hub aperture  21  receives rear hub  23 , which is a component of rear wheel assembly  42 . In this embodiment, drive feature assembly  44  is connected at opposing ends to drive feature supporting means  36  and rear wheel assembly  42 . 
     The manner of using the lightweight cantilever bicycle frame is similar to existing bicycle frames. Namely, the frame supports front assembly  40 , front wheel assembly  41 , rear wheel assembly  42 , drive feature assembly  44 , and bicycle seat assembly  39 , thus enabling a rider to achieve self-propelled forward motion. 
     By utilizing primary member  10  and secondary member  30  to perform the functions of a bicycle frame, utilizing structurally efficient cross section  22  in primary member  10 , and by supporting rear wheel assembly  42  in a cantilever manner, it is possible to construct a bicycle frame from less material, enabling lower construction costs and reduced weight when compared to existing designs while accommodating the use of a wide range of rear wheel assembly  42  widths. Additionally, there are fewer locations where joining methods are susceptible to failure when compared to certain existing bicycle frame designs. Furthermore, because primary member  10  will support secondary member  30  even if the joining method employed at that junction fails, the likelihood of rider injury resulting from such a failure is reduced. 
     Thus the reader will see that at least one embodiment of the lightweight cantilever bicycle frame is capable of providing a lighter, less expensive, more reliable bicycle frame that can accommodate a wide variety of rear tire widths. Consequently, consumers may acquire a bicycle built upon the lightweight cantilever bicycle frame to economically meet their transportation and recreation needs. While the above description contains many specificities, these should not be construed as limitations on the scope, but rather as an exemplification of one embodiment thereof. Many other variations are possible. For example, secondary member  30  may take the form of a beam, leaf spring, or other shape, depending on the application. Additionally, rear hub supporting means  20  may reflect different geometries and materials, so long as it operates in conjunction with primary member  10  to support rear wheel assembly  42  in a cantilever manner. Additionally, bicycle seat supporting means  38  may be altered, so long as it enables the adjustment of distance of bicycle seat assembly  39  from drive feature supporting means  36 . Accordingly, the scope should be determined by the appended claims and the legal equivalents thereof, not by the illustrated embodiment.