Abstract:
A foldable frame for bicycle is provided in the present invention. The foldable frame can be folded up in three simple steps because of the application of two releasable locking systems: (1) release a front locking system; (2) release a rear locking system;(3) fold up a pair of rear forks hinge joint with a crossbar towards the front wheel. Other parts such as seat tube and pedal bar which are hinge joint with the crossbar can be folded up towards the crossbar. To reduce weight of the frame, a single-tube suspension system is also employed at the front of the foldable frame. The foldable frame of the present invention is easy to fold, non-bulky, lightweight and affordable to strong force as compared to any conventional foldable bicycles. The present invention can be applied to bicycle or any two-wheel vehicles such as electricity-driven or petroleum-driven motorcycle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from US provisional patent application 61/762,340 filed Feb. 8, 2013, and the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material, which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     FIELD OF THE INVENTION 
     The present invention relates to a foldable frame for two-wheel vehicle, in particular, a foldable frame for bicycle which is configured to be folded in few simple steps and reduced in weight. 
     TECHNICAL BACKGROUND 
     Most of the conventional bicycles are configured to be foldable for easy transportation. However, many of these conventional foldable bicycles require complicated folding system to transform the bicycle from unfolded state to folded state. For example, in U.S. Pat. No. 6,196,566, the foldable bicycle is needed to form three quadrilaterals first in order to be folded up. The folded state of the bicycle in that patent is relatively bulky because only the four bars forming the two triangles of the bicycle frame can be folded up but not the front/rear forks or the handle bars. Some other conventional foldable bicycles may have a folding system at the middle of the crossbar in order to reduce the length of the bicycle into half when it is folded up, for example, in U.S. Pat. No. 3,865,403. However, that kind of folding system at the middle of the crossbar is unable to withstand strong force against the bicycle frame when the bicycle is in use. A quick, easy to fold, non-bulky and lightweight frame which can withstand strong force in a bicycle is therefore desired. 
     SUMMARY OF THE INVENTION 
     The first aspect of the present invention relates to a foldable frame for any two-wheel vehicle including bicycle. The foldable frame of the present invention can be folded up in three simple steps because of the application of two releasable locking systems to the foldable frame of the present invention: (1) release a front locking system which is configured to releasably connect the handle bars with the head tube which passes through a ring structure at the front end of the crossbar of the foldable frame; (2) release a rear locking system which is configured to releasably connect the crossbar with a pair of rear forks; (3) fold the pair of rear forks about a hinge joint with the crossbar towards the direction of the front wheel after the rear locking system is released such that the rear forks and the head tube can be held in parallel with each other and almost at a right angle to the crossbar. The seat tube which is hinge joint with the crossbar, and the pedal bar which is also hinge joint with the pair of the rear forks, can be further folded towards the crossbar such that the foldable frame is completely transformed from its unfolded state into folded state. 
     In order to reduce the weight of the foldable two-wheel vehicle which requires a suspension system, the second aspect of the present invention relates to a single-tube suspension system which is at the front end of a foldable bicycle. The single-tube suspension system of the present invention is incorporated into the head tube of the foldable bicycle of the present invention as mentioned in the first aspect of the present invention. By incorporating the concept of a single-tube suspension system into the present invention, it avoids the bulkiness and relatively large volume of the conventional dual-tube suspension system. The single-tube suspension system of the present invention is made of lightweight material, e.g. stainless steel, lightweight metal alloy and/or plastic. The single-tube suspension system of the present invention includes three cylindrical members with different circumferences and lengths but they are aligned along the same vertical axis centrically. The top end of a first cylindrical member (the longest cylindrical member) has two arc-shaped structures (or notches) at its periphery to serve as a female member for interlocking with a male member in a cavity at the bottom side of the front locking system in order to secure the handle bar on the head tube. A third cylindrical member (the shortest cylindrical member) situated between the first cylindrical member and a second cylindrical member (the second longest cylindrical member) for enhancing the stability during the movement of the first cylindrical member inside the second cylindrical member. The second cylindrical member further includes a suspension spring situated inside the interior space thereof such that when the first cylindrical member is pressed down towards the bottom of the second cylindrical member, the suspension spring can absorb the downward force from the first cylindrical member. The first and second cylindrical members are secured by a pin axle which is inserted through a pair of holes on the cylindrical surface of each of the first and second cylindrical members such that the first cylindrical member can be moved vertically within a confined distance in the interior space of the second cylindrical member. The single-tube suspension system of the present invention greatly reduces the weight and volume of the front part of a bicycle as compared to the conventional non-foldable or foldable bicycle which usually has a dual-tube suspension system. 
     In the following examples, an example of a foldable bicycle incorporating the foldable frame of the present invention is used for illustration purpose but the application of the foldable frame of the present invention is not limited to bicycle but also any two-wheel vehicle, e.g. electricity-driven or petroleum-driven motorcycle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side view of an embodiment of the foldable bicycle at its unfolded state. 
         FIG. 2  is a right side view of an embodiment of the foldable bicycle at its folded state. 
         FIG. 3  is a right side view of an exemplary embodiment of the foldable frame at its unfolded state in the absence of the seat, wheels and pedal. 
         FIG. 4A  is a right side view of an exemplary embodiment of the foldable frame at its unfolded state with three reference views showing the position of two locking systems at the front and rear ends of the foldable frame. 
         FIG. 4B  is a schematic diagram of the relationship between the rear locking system and the operation of the foldable bicycle from the unfolded state to folded state: the dotted and solid outlines represent the corresponding components at the unfolded and folded states of the foldable bicycle, respectively; arrows represent the direction of the movement of different corresponding components. 
         FIG. 5A  is an enlarged view of the rear locking system of the present invention: the dotted outline and the solid outline represent the position of the safety lock at the unfolded (locked) and folded (unlocked) states of the foldable bicycle, respectively. 
         FIG. 5B  shows different views of the rear locking system of the present invention: left panel is the view from the right hand side; middle panel is the view from the front side of the foldable frame; right panel shows the safety lock and the two arc-shaped structures (or notches) at the periphery of the bottom end of the screw-like member. 
         FIG. 6  includes a perspective view (A) and a side view (B) of the front locking system. 
         FIG. 7  includes a cross-sectional view (A) and a perspective view (B) of the single-tube suspension system. 
         FIG. 8  is a transactional view of the interior of the single-tube suspension system. 
         FIG. 9  is an exploded perspective view of the three cylindrical members and a pin axle of the single-tube suspension system. 
         FIG. 10  is an exploded perspective view of the foldable frame (without the front locking system, handle bars, saddle, and pedal). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is now explained more specifically by referring to the following examples with the aid of the corresponding drawings. These examples are given only for a better understanding of the present invention, and not intended to limit the scope of the invention in any way. 
       FIG. 1  is an example of a bicycle incorporated with the foldable frame of the present invention. In this example, the foldable frame  100  includes a crossbar  101 . The front end of the crossbar  101  has a ring structure  101   a  for holding a head tube  102  by passing the head tube  102  through the ring structure  101   a  while the rear end of the crossbar  101  is hinge joint with a seat tube  103  and a pair of rear forks  104 . In between the rear end of the crossbar  101  and the rear forks  104  is further releasably secured by a rear locking system  105 . The rear locking system  105  includes a flexible spring-like structure  106 , a screw-like member  107  and a safety lock  108 . One end of the flexible spring-like structure  106  is connected with the rear end of the crossbar  101  by a hinge joint and another end of the spring-like structure  106  is fixedly connected with one end of the screw-like member  107 ; another end of the screw-like member  107  is connected with the safety lock  108  which is for securing the rear locking system  105  on the rear forks  104  when the bicycle is in unfolded state  100 . The flexible spring-like structure  106  of the rear locking system  105  is designed for absorbing shock from the crossbar  101  and other parts of the foldable bicycle when it is in unfolded state  100 . Said another end of the screw-like member  107  is hollow and composed of two arc-shaped structures (notches) as a female member (not shown in  FIG. 1 ) for interlocking with the male member (not shown in  FIG. 1 ) on the rear forks  104  when the safety lock  108  is being clicked up. Detailed illustration of the interlocking relationship between the screw-like member  107 , the safety lock  108  and the rear forks  104  is shown in  FIGS. 4 ,  5 A and  5 B. In addition to the rear locking system  105 , there is another locking system at the front end of said crossbar  101 , which is situated on top of the head tube  102  which passes through the ring structure  101   a  at the front end of the crossbar  101 . The front locking system  109  is configured to have a cavity at the bottom side thereof ( 610  as shown in  FIG. 6A ) which is incorporated with a male member for interlocking with the female member formed by two arc-shaped structures (or notches) ( 601  as shown in  FIG. 6A ) at the periphery of the head tube  102 . Detailed illustration of the front locking system is shown in  FIG. 6A and 6B  while the suspension part or specifically called the single-tube suspension system is shown in  FIGS. 7-9 . 
     The following is a brief description of how the foldable frame of the present invention is transformed from its unfolded state into folded state using the three simple steps. The first step is to unlock the safety lock  108  of the rear locking system  105  such that the connection between the crossbar  101  and the rear forks  104  by the rear locking system  105  can be released easily. The only connection between the crossbar  101  and the rear forks  104  are two hinge joints but it allows the rear forks  104  to move about the hinge joints towards the crossbar  101  when the bicycle is being folded up. The second step is to unlock the front locking system  109  by releasing a lock  110  at the handle bars  111  such that the top end of the head tube  102  can be plugged out from the cavity ( 610  as shown in  FIG. 6A ) of the front locking system  109  in order to release the handle bars  111  from the head tube  102 . The first and second steps can be reversed in order. Since the only connection between the crossbar  101  and the pair of rear forks  104  are two separate hinge joints, the rear forks  104  become movable and can be folded about the hinge joints towards the front wheel until the rear forks and the head tube are placed in parallel to each other vertically. In such state, the foldable frame of the present invention is transformed into its folded state. In order to reduce the volume and bulkiness of the foldable bicycle, the seat tube  103  is also hinge joint with the crossbar  101  such that the seat tube  103  is movable towards the crossbar  101 . The pedal part is also movable towards the crossbar  101 . A schematic example of the foldable bicycle at its fully folded state  200  is shown in  FIG. 2 .  FIG. 3  shows the bicycle frame  300  of the foldable bicycle without the associated parts such as the seat, wheels, handle bars and pedal. 
       FIG. 4A  shows the position of the front and rear locking systems in the foldable frame. The dotted outline represents the original position of the parts at the unfolded state of the foldable frame, which can be detached or moved. For example, the rear forks  104  can be moved about the hinge joints with the crossbar  101  towards the front wheel after the rear locking system is unlocked. The seat tube  103  can also be moved about the hinge joint with the crossbar  101  towards the crossbar.  FIG. 4B  is an enlarged view of the rear end of the crossbar to further illustrate the working principle of the rear locking system and the path of movement of different movable parts which are hinge joint with the rear end of the crossbar after the rear locking system is released from the rear forks. According to the sequence of the three simple steps as described in the example to transform the foldable bicycle from its unfolded state into folded state, the safety lock  108  should be released first by turning from its its horizontal position (locked) towards its vertical position (unlocked). The screw-like member  107  is subsequently released from an anchoring point  104   a  on the rear forks such that the releasable connection between the crossbar  101  and the rear forks through the rear locking system is released. The rear forks  104  are then moved pivotally about the hinge joint  201  to a position at about a right angle to the crossbar  101 . The seat tube  103  is optionally moved pivotally about the hinge joint  202  to a position at about a right angle to the crossbar  101  in order to further reduce the volume and bulkiness of the foldable bicycle when it is in folded state.  FIG. 5A  is the enlarged view of the rear locking system. Solid outline represents the safety lock  108  at its unlocked position which is held in an upright position which is almost parallel to the screw-like member  107 ; whereas the dotted outline represents the safety lock  108  at its locked position which forms an acute angle with the screw-like member  107 .  FIG. 5B  shows different views of the rear locking system  105 , especially the screw-like member  107  and the safety lock  108 . In the right panel, the safety lock  108  is shown to include a spring  501  for loosening or tightening the safety lock  108 . Also, two arc-shaped structures (or notches)  502  are also applied to the rear locking system  105  to interlock with a male member incorporated into the corresponding connection point at the rear forks. 
       FIG. 6  shows how the suspension system inside the head tube is detached from the front locking system. In  FIG. 6A , the front locking system includes a cavity  610  incorporated with a male member  602  for interlocking with the top end of the suspension system where there is a pair of arc-shaped structures (notches)  601  acting as a female member to fit into the male member in the cavity  610  at the bottom side of the front locking system.  FIG. 6B  is the side view (right side) of the front locking system  109  where the dotted outline represents the top end of the head tube  102  plugged inside the cavity  610  of the front locking system  109  when the female and male members are interlocked together. 
       FIGS. 7-9  are different views of the suspension system of the present invention. To reduce the weight of the frame, the suspension system employs a single-tube suspension system  700  mainly composed of three cylindrical members, a suspension spring and a pin axle. In  FIG. 7 , a first cylindrical member (the longest cylindrical member)  701  is configured to interact with a second and third cylindrical members ( 703 ,  702 ). The suspension spring  704  is situated at the bottom in the interior space of the second cylindrical member  703 .  FIG. 8  shows that each of the first and second cylindrical members ( 701 ,  703 ) is configured to have two pairs of holes ( 705   a ,  705   b ) at two opposite sides along the cylindrical wall of the cylindrical member. A pin axle  706  is inserted through the two pairs of holes ( 705   a ,  705   b ) such that the first and second cylindrical members ( 701 ,  703 ) are secured with each other while the first cylindrical member  701  is allowed to have a vertical movement within a confined distance corresponding to the vertical height of the holes ( 705   a ,  705   b ).  FIG. 9  shows that the third cylindrical member  702  has a peripheral ring  901  surrounding the top open end thereof. The third cylindrical member  702  serves to fill up the space between the first and the third cylindrical members ( 701 ,  703 ) in order to enhance the stability during the vertical movement of the first cylindrical member  701  onto the suspension spring  704  inside the second cylindrical member  703 . In an exemplary embodiment, the third cylindrical member  702  is made of rubber for the purpose of providing elasticity when the first cylindrical member  701  moves vertically inside the .  FIG. 10  shows the main components composing the foldable frame of the present invention. It is noteworthy that every component in the present foldable frame is non-welded, and the connection from one component to the other is either by hinge joint or other mechanisms such as the locking system as described in the present invention. 
     If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. 
     Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims. 
     It is also noted herein that while the above describes exemplary embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.