Abstract:
A stretching bicycle comprises a front frame section having a hollow front bar as a portion of crossbar, a rear frame section having a hollow rear bar for slidably receiving the front bar, the front and rear bars being disposed in a straight line not aligned with the front and rear wheels, and fastening means for securing the front and rear bars together at a front opening and a rear opening of the rear bar respectively. The bicycle has the advantages of adjusting length for accommodating users of different body heights in use, saving storage space after disassembly, and being structurally strong and lightweight.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to bicycles and more particularly to a stretching bicycle with a length adjustment mechanism so as to have the advantages of accommodating users of different body heights in use, saving storage space after disassembly, and being structurally strong and lightweight. 
   2. Description of the Prior Art 
   Stretching bicycles have the advantages of permitting users to adjust the length of the bicycle for accommodating his/her body height and saving storage space after disassembly. Thus, stretching bicycles as a continuous development of foldable bicycles are gaining popularity. 
   Referring to  FIG. 10 , a well-known stretching bicycle (“Document I”) is shown. It discloses a separable crossbar consisting of a front bar  90  and a rear bar  91  releasably secured to the front bar  90  by a bolt  94 . Document I has the following drawbacks. Only a small length reduction of the crossbar (i.e., the front bar  90 ) is achievable because the rear bar  91  is fixedly coupled to the seat tube  92  (i.e., seat tube  92  being a stop). Moreover, the fastening of the crossbar by the bolt  94  is weak, resulting in a potential of the crossbar being broken apart while driving. This is dangerous. 
   Referring to  FIGS. 11 and 12 , U.S. patent application Ser. No. 10/346,128, filed by the inventor of the present invention on Jan. 17, 2003 now U.S. Pat No. 6,712,375 B2 is shown. It discloses a stretching bicycle capable of eliminating the above drawbacks. As shown, two parallel main seat tube  71  and auxiliary seat tube  74  are extended upwardly from the bottom bracket  70  in a slightly inclined direction. Also, the main seat tube  71  is laterally displaced a predetermined distance from a lengthwise direction of the bicycle (i.e., not aligned with the crossbar). A seat stay is extended rearward from both the main seat tube  71  and the auxiliary seat tube  74  to the rear wheel  73 . A seat post  75  is slidably inserted into the main seat tube  71 . A laterally extended bar  76  is interconnected the seat post  75  and a saddle  77  so that the saddle  77  is adapted to align with the lengthwise direction of the bicycle again (i.e., aligned with the crossbar). The lower portion of the auxiliary seat tube  74  is coupled to a reinforcement tube  86  and a top thereof is coupled to a crossbar  78  having both ends open. Two T-shaped gaps  79  are formed adjacent a front end and a rear end of the crossbar  78  respectively so as to provide flexibility thereto. A sliding tube  81  has a front end fixedly coupled to head tube  80  and a rear end adapted to insert through the crossbar  78 . Also, a lengthwise first groove  84  and a lengthwise mated second groove  85  are formed on the crossbar  78  and the sliding tube  81  respectively for facilitating a correct coupling of the crossbar  78  and the sliding tube  81  and preventing both from turning each other. Two quick releases  82  and  83  are adapted to clamp around the gaps  79  for securing the sliding tube  81  to the crossbar  78 . Document II has advantages of being structurally strong and a maximum length reduction of the bicycle is achievable. However, Document II still has the disadvantage of having a relatively heavy frame due to the provision of the main seat tube  71 , the auxiliary seat tube  74 , and the laterally extended bar  76 . Moreover, as stated above, the saddle  77  and the seat post  75  are not aligned in the vertical direction. Hence, the weight of the driver may not totally transmit to other components of the frame via the saddle  77 , the laterally extended bar  76 , and seat post  75 . In other words, the joining portion of the laterally extended bar  76  and the seat post  75  bears a great portion of the weight of the driver. This in turn has the potential of breaking the joining portion while driving. This is dangerous. In brief, the bicycle can only support a driver having a small body weight. Thus, the need for improvement of the stretching bicycle still exists. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a stretching bicycle having the advantages of 1) being capable of decreasing the length of the bicycle to a minimum for greatly reducing storage space, increasing portability, and being adapted to mount in the trunk of a car for carrying; 2) being capable of preventing the crossbar and the sliding tube from turning each other so as to ride the bicycle as a typical fixed frame bicycle and eliminate the problem of hardly controlling the balance in riding as experienced in the prior stretching bicycle; 3) eliminating the provision of a seat tube composed of a plurality of components so as to be lightweight, easy in carrying, and simple in manufacture, and eliminate the need of aligning the center line of a saddle again; and 4) without providing an offset arrangement in the seat tube such that the seat tube, the seat post, and the saddle are adapted to align and dispose on the same vertical plane as the front and rear wheels, the structural strength of the bicycle is further enhanced, and the load borne on the saddle is without any adverse affection. 
   To achieve the above and other objects, the present invention provides a stretching bicycle in which both the sliding front bar and the rear bar for receiving the front bar are disposed in a straight line not aligned with a straight line from the front wheel to the rear wheel while that the seat tube, the seat post, and the saddle are disposed on the same vertical plane as the front and rear wheel such that a sliding movement of the front bar through both openings of the rear bar is not interfered by the seat tube in the center of the bicycle for achieving a maximum length reduction of the bicycle. 
   In one embodiment of the present invention, the rear bar and the seat tube are fixedly coupled together by a reinforcement member having a flat base portion secured to the side surface of the seat tube and two extended portions secured to the rear bar. The lower portion of the auxiliary seat tube is coupled to a reinforcement tube which has one end secured to a bottom bracket by soldering. The reinforcement tube is oblique with respect to the vertical plane formed by the front and rear wheels. The rear bar is thus disposed in a straight line not aligned with the straight line from the front wheel to the rear wheel. The front bar is extended rearward from the head tube in an oblique angle the same as that of the rear bar such that the front bar is free to slide through the front and rear openings of the rear bar having the same oblique angle with being interfered by the seat tube in the center of the bicycle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings disclose an illustrative embodiment of the present invention which serves to exemplify the various advantages and objects hereof, and are as follow: 
       FIG. 1  is an exploded perspective view of a first preferred embodiment of stretching bicycle according to the invention; 
       FIG. 2  is a perspective view of the assembled bicycle of  FIG. 1 ; 
       FIG. 3  is a side plan view of the bicycle shown in  FIG. 2 ; 
       FIGS. 4 and 5  are cross-sectional views taken along line  4 — 4  and line  5 — 5  of  FIG. 3  respectively; 
       FIG. 6  is a partial rear view in part section of the bicycle of  FIG. 3 ; 
       FIG. 7  is a view similar to  FIG. 2 , where the length of the bicycle has been adjusted to a position ready to ride; 
       FIG. 8  is a view similar to  FIG. 7 , where the length of the bicycle has been adjusted to a minimum and the saddle and the seat post are removed to be inserted into the horizontal tube for storage; 
       FIG. 9  is a perspective view of a second preferred embodiment of stretching bicycle according to the invention; 
       FIG. 10  is a side plan view of a conventional stretching bicycle; 
       FIG. 11  is a perspective view of another conventional stretching bicycle; and 
       FIG. 12  is a schematic front view in part section of the bicycle of  FIG. 11 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1 to 8 , there is shown a stretching bicycle constructed in accordance with a first preferred embodiment of the invention. The bicycle comprises a front frame section  10  and a rear frame section  20 . A fastening and length adjustment mechanism is provided to secure the frame sections  10  and  20  together as detailed later. The front frame section comprises a head tube  12 , a fork  14 , handlebars  13 , a handle tube  16  interconnected the handlebars  13  and the head tube  12 , a front wheel  15  releasably coupled to the fork  14  by mean of a well known quick release, two bearings (not shown) provided between the fork  14  and the head tube  12  so that the handlebars  13  are adapted to turn a predetermined angle, and a hinge  17  provided at the joining portion of the head tube  12  and the handle tube  16  so that the handle tube  16  is adapted to fold downwardly from the hinge  17 . 
   The rear frame section  20  comprises a bottom bracket  35 , a pair of pedals  27  coupled to the bottom bracket  35 , a sprocket wheel  21  coupled to the bottom bracket  35 , a rear wheel  25 , a chain stay  29  extended rearward from the bottom bracket  35  to an axle of the rear wheel  25 , a seat tube  24  extended upwardly from the bottom bracket  35 , a seat stay  28  having a rear end coupled to the axle of the rear wheel  25 , a seat post  23  slidably inserted into the seat tube  24 , the seat post  23  having a top saddle  55 , and a quick release (not numbered) at a top opening of the seat tube  24 , the quick release being adapted to secure the seat post  23  and the seat tube  24  together. 
   A crossbar comprises a hollow front bar  11  having a front end fixedly coupled to an outer surface of the head tube  12  (i.e., the front bar  11  is not aligned with the head tube  12 ) by a first reinforcement member  18  having a section of substantially U in which the flat base portion of the first reinforcement member  18  is secured to the outer surface of the head tube  12  and two extended portions thereof are secured to the front bar  11  so that the coupling strength between the front bar  11  and the head tube  12  can be increased significantly. A first cap  52  is adapted to matingly couple to a front opening of the front bar  11  so that articles such as umbrella, air pump, etc. stored in the front bar  11  can be prevented from leaving accidentally. Moreover, in a case of the bicycle implemented as an electric bicycle and powered by rechargeable battery assembly, the battery assembly can be stored in the front bar  11 . 
   The crossbar further comprises a hollow rear bar  22  having a portion proximate a rear opening  34  fixedly coupled to a side surface of the seat tube  24  by soldering (i.e., the rear bar  22  is not aligned with the seat tube  24 ). A second cap  53  is adapted to matingly couple to the rear opening of the front bar  11  for enclosing. The front bar  11  is adapted to slide through a front opening  33  and the rear opening  34  of the rear bar  22  because an outer diameter of the front bar  11  is substantially conformed to an inner diameter of the rear bar  22 . As shown in  FIG. 5 , a lengthwise first groove  37  and a lengthwise mated second groove  36  are formed on the rear bar  22  and the front bar  11  respectively for facilitating a correct coupling of the rear bar  22  and the front bar  11  and preventing both from turning each other. Two T-shaped gaps  38  and  39  are formed adjacent the front opening  33  and the rear opening  34  respectively so as to provide flexibility thereto. 
   The rear bar  22  and the inserted front bar  11  are secured together by fastening first and second quick releases  30  and  31  at the front T-shaped gap  38  and the rear T-shaped gap  39  by flexibly deforming the T-shaped gaps  38  and  39  respectively. In detail, as seen in  FIG. 5 , an upper flexible member  40  and a lower flexible member  41  are formed by the provision of the T-shaped gap  38 . An upper lug  42  and a lower lug  43  are extended laterally from the upper and lower flexible members  40  and  41  respectively. A bolt  44  of the first quick release  30  is inserted through the holes of the lugs  42  and  43  to be threadedly coupled to a nut  45 . A user may counterclockwise turn the arcuate lever  46  of the first quick release  30  to cause the cam  47  to exert force to pull the lugs  42  and  43  toward each other by flexibly deforming the upper and lower flexible members  40  and  41 . As such, the rear bar  22  exerts force to clamp around the front bar  11  for fastening the front bar  11 . To the contrary, a reverse operation of the lever  46  can unfasten the front bar  11  and the rear bar  22 . This is obvious to those skilled in the art. The second quick release  31  will not be described in detail below since it is a mirror image of the first quick release  30 . 
   Note that the quick release as shown in the embodiment of  FIG. 1  can be replaced by a commercially available ring fastener or the like in any other embodiments. In the embodiment the section of the front bar  11  or the rear bar  22  is oval as shown in  FIG. 5 , while it is appreciated by those skilled in the art that the cross-section of the front bar  11  or the rear bar  22  may be any of other shapes such as circle or rectangle without departing from the scope and spirit of the invention. 
   As shown in  FIG. 6 , the rear bar  22  and the seat tube  24  are fixedly coupled together by a second reinforcement member  26  having a section of substantially U in which the flat base portion of the second reinforcement member  26  is secured to the side surface of the seat tube  24  and two extended portions thereof are secured to the rear bar  22  so that the coupling strength between the rear bar  22  and the seat tube  24  can be increased significantly. Moreover, an oblique down tube  32  as a reinforcement is interconnected the rear bar  22  and the bottom bracket  35 . The rear bar  22 , the seat tube  24 , and the down tube  32  form a triangle. Likewise, the seat stay  28 , the chain stay  29 , and the seat tube  24  form another triangle. As a result, the frame strength of the bicycle is increased greatly. 
   It is noted that both the front bar  11  and the rear bar  22  are disposed in a first straight line. The seat tube  24 , the seat post  23 , the saddle  55 , and the front and rear wheels  15  and  25  are disposed in a second straight line. But the first and second straight lines are not aligned. That is, both the front bar  11  and the rear bar  22  are displaced laterally a predetermined distance with respect to the second straight line. For adjusting the length of the bicycle (i.e., the crossbar), a user may unfasten the first and second quick releases  30  and  31 . Next, slide the front bar  11  through the front opening  33  and the rear opening  34  of the rear bar  22  without being stopped by the seat tube  24  until a desired length is obtained. Finally, fasten the first and second quick releases  30  and  31  again. In a maximum length of the crossbar (see  FIG. 2 ) the bicycle is adapted to be ridden by an adult. In a medium length of the crossbar (see  FIG. 7 ) the bicycle is adapted to be ridden by a short person (e.g., child). In a minimum length of the crossbar (see  FIG. 8 ) both the seat post  23  and the saddle  55  are detached and are ready to insert into a horizontal tube  60  extended rearward from the seat tube  24 . A bolt  61  is adapted to drive into the horizontal tube  60  for fastening the seat post  23  in the horizontal tube  60 . Next, fold the handle tube  16  downwardly at the hinge  17 . The bicycle having the reduced size is thus adapted to store, for example, in the trunk of a car prior to going for an outing. 
   Referring to  FIG. 9 , there is shown a stretching bicycle constructed in accordance with a second preferred embodiment of the invention. The second preferred embodiment substantially has same structure as the first preferred embodiment. The differences between the first and the second preferred embodiments, i.e., the characteristics of the second preferred embodiment are detailed below. The front end of the front bar  11 ′ is enclosed by the head tube  12  and the front bar  11 ′ is extended obliquely (i.e., not aligned with the front and rear wheels  15  and  25 ). Also, the rear bar  22 ′ is aligned with the front bar  11 ′ (i.e., the rear bar  22 ′ is still extended in the same oblique angle). Thus, it is possible of sliding the front bar  11 ′ through the front opening  33 ′ and the rear opening  34 ′ of the rear bar  22  without being stopped by the seat tube  24  in the length adjustment operation. 
   Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.