Abstract:
A rear wheel is axially removable from a bicycle frame after a support arm is pivoted away from an initial position overlying the rear wheel. A bicycle drive mechanism is not removed together with the rear wheel, but instead, is left mounted on another support arm. Both support arms straddle the rear wheel during bicycle use and are pivotable to fold the bicycle for compact storage.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to bicycles and, more particularly, to bicycle frames which are foldable to occupy less storage space, and which enable quick and easy removal of rear bicycle wheels for replacement or repair. 
   2. Description of the Related Art 
   Folding bicycles, whether driven by foot pedaling and/or whether assisted by a motor drive, are well known to conserve storage space when the bicycles are not being ridden. Although generally satisfactory for their intended purpose, the known bicycles are foldable about an axis other than the pedal axis and, hence, occupy more storage space than necessary. 
   Another problem with bicycles, whether foldable or not, is wheel maintenance, especially the rear wheel on which a drive mechanism is conventionally mounted. It is often laborious to change a flat rear wheel tire due to the presence of the drive mechanism which conventionally includes a gear changer and a braking assembly. 
   SUMMARY OF THE INVENTION 
   Objects of the Invention 
   One object of this invention is to enable rapid removal of, and easy access to, a rear wheel of a bicycle to effect repairs or replacement. 
   Another object of this invention is to enable removal of the rear wheel without also removing the drive mechanism. 
   Still another object of this invention is to fold the bicycle for minimum storage space about the pedal axis. 
   Yet another object of this invention is to enable the front and rear wheels to be identical for easier replacement and maintenance. 
   FEATURES OF THE INVENTION 
   In keeping with these objects and others which will become apparent hereinafter, one feature of this invention resides, briefly stated, in a frame for a bicycle in which a front wheel is mounted on a main frame support, and a rear wheel is mounted by at least one frame support arm, or by a pair of frame support arms, on the main frame support. The arms straddle and support the rear wheel in a use position for rotation about a rear wheel axis during bicycle motion. 
   In accordance with one aspect of this invention, at least one of the arms is movable to enable movement of the rear wheel away from the use position when the bicycle is not in motion. Preferably, the movable arm is pivotably mounted on the main frame support about a pivot axis parallel to the rear wheel axis. In the preferred embodiment, the pivot axis is coincident with a pedal axis about which a foot pedal drive assembly is rotated when the bicycle is in motion. 
   Upon pivoting the movable arm out of its initial straddling position at one side of the rear wheel, the rear wheel is removed in a direction axially of the rear wheel axis in a manner not unlike the axial removal of an automobile tire from an automobile. This axial removal has heretofore not been achieved for bicycle wheel maintenance. 
   Another aspect of this invention relates to the mounting of a bicycle drive mechanism on the other of the arms. The drive mechanism typically includes a gear changer and a brake assembly, and these components are conventionally mounted on the rear wheel for joint movement therewith, thereby complicating rear wheel maintenance. In accordance with this invention, the drive mechanism is not jointly mounted on the rear wheel, and hence, the rear wheel can be removed from the bicycle while leaving the drive mechanism in place on the other arm. 
   Each arm may be independently pivotably mounted on the main frame support, and both arms may be simultaneously pivotable to reposition the rear wheel from its initial use position in which the rear wheel is directly behind the front wheel, to a folded-up position in which the rear wheel is elevated relative to the front wheel to achieve compact storage. By pivoting both arms about the foot pedal axis, a particularly compact storage space is obtained. 
   The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of a bicycle having a frame in accordance with this invention; 
       FIG. 2  is a broken-away, enlarged, sectional view taken on line  2 — 2  of  FIG. 1 ; 
       FIG. 3  is a broken-away view taken on line  3 — 3  of  FIG. 1 ; 
       FIG. 4  is a sectional view taken on line  4 — 4  of  FIG. 1 ; 
       FIG. 5  is a view similar to  FIG. 4 , but during rear wheel movement; 
       FIG. 6  is a view of the rear of the bicycle of  FIG. 1  during rear wheel movement; 
       FIG. 7  is a sectional view taken on line  7 — 7  of  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a bicycle  10  includes a frame  12 , a front wheel  14 , a rear wheel  16 , handlebars  18 , a seat  20 , and a foot pedal assembly  22 . The frame includes a main frame support  24  and a pair of frame support arms  26 ,  28  mounted on the main support  24  and straddling the rear wheel  16 , as best seen in  FIG. 2 . 
   The main support  24  includes a front tube  30  through which a steering post  40  is inserted. The handlebars  18  are mounted at one end of the post  40 , and the opposite end of the post  40  is connected to a hub  42  of the front wheel. The post  40  is mounted for rotation in the front tube  30  and, hence, steering is achieved by turning the handlebars  18 . 
   The main support  24  also includes a rear tube  32  through which a seat post  38  is inserted. The seat  20  is mounted at an upper end of the post  38  and is slid lengthwise thereof until a desired seat height is achieved. The main support  24  further includes upper tube  34  extending between upper regions of the front  30  and rear  32  tubes, and a lower tube  36  extending between lower regions of the front  30  and rear  32  tubes. In some bicycles, the upper tube  24  can be eliminated. 
   As best seen in  FIG. 3 , the front pedal assembly  22  includes a pair of foot pedals  44 ,  46  mounted on crank arms  48 ,  50  to turn a pedal gear  52  about a pedal axis  54 . A gear changer  60  comprised of multiple gears is, as described below, operatively connected with the rear wheel  16 . An endless drive chain  58  is trained about the pedal gear  52  and a selected gear  62  of the gear changer  60 . A rider rotatably pushing the foot pedals about the pedal axis  54  causes the rear wheel  16  to rotate about a rear wheel axis  64  through the chain  58  at a rate determined by the gear ratio between the pedal gear  52  and the selected gear  62 . 
   As previously mentioned, the support arms  26 ,  28  are mounted on the main frame support  24  and extend rearwardly thereof in straddling relation to the rear wheel  16 . The support arms  26 ,  28  mount the rear wheel on the bicycle frame for rotation about the rear wheel axis  64  during use when the bicycle is in motion. As described below, by movement of at least one of the support arms, the rear wheel is removable from the bicycle frame for repair or replacement. Also, by movement of both support arms, the bicycle is folded up for compact storage. 
   As shown in  FIG. 1 , each support arm  26 ,  28  is generally shaped as an isosceles triangle having three bars  66 ,  68 ,  70  bounding an open triangular space  72  to reduce weight. Each comer between bars  66 ,  68  is pivotably connected for movement about the pedal axis  54  at a lower region of the rear tube  32 . Each comer between bars  66 ,  70  is connected to the rear wheel  16  at rear wheel axis  64 . Each corner between bars  68 ,  70  is connected to the rear tube  32  at an upper region above the pivotable connection at the pedal axis  54 . 
   As shown in  FIG. 3 , the rear wheel  16  includes a tire  80  mounted on a rim  78  having a central hub  74  which is connected by a plurality of fasteners  76  to a circular flange  82  of a tubular housing  84  extending along the rear wheel axis  64 . An axle  86  extends through the housing  84  and is connected at its opposite axial ends to the support arms  26 ,  28 . Bearings  88 ,  90  assist in journaling the axle  86 . The gear changer  60  is exteriorly mounted on the housing  84 . A disk brake  92  is likewise exteriorly mounted on the housing  84 . As described so far, the brake  92 , changer  60 , housing  84 , bearings  88 ,  90 , together with the illustrated nuts and washers, constitute a drive mechanism. 
   A quick-release fastener  94 , as best seen in  FIGS. 4–5 , is employed to detachably connect the arm  26  to the axle  86 . Another quick-release fastener  96 , as best seen in  FIG. 2 , is employed to detachably connect the arm  26  to the rear tube  32 . Upon release by the fasteners  94 ,  96 , the arm  26  is free to be pivoted in the counterclockwise direction depicted by arrow A in  FIG. 6  about the pedal axis  54  until the arm  26  no longer overlaps the rear wheel. Thereupon, the fasteners  76  are removed to release the rear wheel from the drive mechanism. The rear wheel can now be axially removed from the axle  86  along the axis  64 , as depicted in  FIG. 7 . The drive mechanism remains in place and is not removed together with the rear wheel. The rear wheel can now be repaired and/or replaced. 
   Mounting the repaired or a new rear wheel is achieved by reversing the above procedure. The rear wheel is axially returned to the axle  86 , the fasteners  76  reconnect the hub  74  to the flange  82 , the arm  26  is pivoted clockwise opposite to the arrow A, and the fasteners  94 ,  96  are reengaged. 
   In order to stow the bicycle in a folded configuration, both arms  26 ,  28  are pivoted about the pedal axis  54  in the direction of arrow A, as shown by dashed lines in  FIG. 1 . Before this is done, however, the fasteners  96  on both sides of the rear tube  32  are operated to release the arms  26 ,  28 . As the arms are pivoted, the rear wheel  16  jointly moves with them. Thus, the bicycle has been folded from its initial state in which the front and rear wheels are aligned, one directly behind the other, to a folded state in which the rear wheel is elevated and closer to the front wheel. 
   It will be understood that each of the elements described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above. 
   For example, each support arm need not be directly connected to the main frame support at the rear tube  32 . Each support arm could be connected through a suspension to the main frame support. The suspension could be a shock absorber connected to another location on the main frame support, for example, the lower tube  36 . 
   The invention herein need not be limited to the use of two support arms as described above, and could also be implemented as a single support arm  28  on which the drive mechanism is mounted. In other words, in some applications, the support arm  26  can be eliminated. The single support arm  28  need not be movable and, in some cases, may be rigid with the frame. The rear wheel is axially removable from the single support arm  28  whether movable or rigid. 
   Another advantageous feature of this invention resides in the feature that the front wheel and the rear wheel can be identical, and that a single spare can be used to replace either the front or rear wheels. In a conventional bicycle, the front and rear wheels are different and cannot be interchanged. 
   While the invention has been illustrated and described as embodied in a foldable bicycle frame with axial rear wheel removal, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.