Bicycle frame extension and bicycle

Abstract

To provide a bicycle frame extension tool and a bicycle which enable the position of a saddle to be adjusted higher than the length of a seat post. [Solution] The bicycle frame extension device 2 comprises a cylindrical extension standpipe 60 into which the seatpost 12 supporting the saddle 10 can be inserted and into which the seatpost 12 can be inserted from the top, and a support shaft 61 having one end connected to the top of the extension standpipe 60 and the other end connected to a fixed portion 25a formed in a portion of the backhawk 25 near the rear wheel 41, forming a triangular structure with the standpipe 21 into which the extension standpipe 60 has been inserted and the backhawk 25.

Description

[Technical field]

[0001] The present invention relates to a bicycle frame extension for use in adjusting the height of a saddle and to a bicycle. [Background technology]

[0002] A bicycle saddle is fixed to one end of a cylindrical seat post, the other end of which is inserted into a stand pipe located in the center of the frame, and is fixed to the bicycle frame by reducing the diameter of the upper part of the stand pipe using a tightening mechanism located at the top of the stand pipe. In addition, by loosening the tightening mechanism, the seat post can be made to freely expand and contract relative to the stand pipe, and the position of the saddle can be adjusted by extending the seat post to suit the user's height and tightening the tightening mechanism.

[0003] However, in this case, the range in which the saddle position can be raised is limited to the range of the seat post length. Therefore, it is difficult to raise the saddle position higher than the length of the seat post. A conventional technique for adjusting the saddle to a higher position is proposed in Patent Document 1. Patent Document 1 discloses that an extension post is inserted into the frame of a unicycle, and the saddle post is inserted into the extension post, so that the same unicycle can be used for both children and adults, even if the inseam is significantly different. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 1-89291 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the seat post of a two-wheeled bicycle extends obliquely relative to the vertical direction. For such a two-wheeled bicycle, if an extension post is inserted into the vertical pipe to raise the saddle as in the technology described in Patent Document 1, a large load is likely to be applied to the connection part between the vertical pipe and the extension post, and in the worst case, the extension post may be deformed. For this reason, it is difficult to raise the position of the saddle by extending the length of the vertical pipe. Thus, in the past, even a bicycle used in the early grades of elementary school could be used by extending the seat post and raising the saddle as the user grew. However, when the user grew further, it became difficult to raise the saddle beyond the length of the seat post, and as a result, it was difficult to continue using the bicycle used in the early grades of elementary school.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a bicycle frame extension device and a bicycle that can solve the above problems and allow the position of the saddle on a bicycle to be adjusted higher than the length of the seat post. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has the following configuration.

[0008] (1) A cylindrical extension standpipe (e.g., extension standpipe 60) into which a seat post (e.g., seat post 12) supporting a saddle (e.g., saddle 10) can be inserted and into a standpipe (e.g., standpipe 21) supporting the saddle, and into which the seat post can be inserted from above; A bicycle frame extension device comprising: a support shaft (e.g., support shaft 61) having one end connected to the upper part of the extension stand pipe and the other end connected to a predetermined portion of the frame body, the support shaft forming a triangular structure with the stand pipe into which the extension stand pipe is inserted and the frame body.

[0009] According to (1), by inserting the extension standpipe into the standpipe, the length of the standpipe can be extended, and the saddle can be adjusted to a higher position. In addition, a support shaft is disposed between the upper part of the extension standpipe and a predetermined part of the frame body to form a triangular structure, so that the load on the extension standpipe due to the weight of the user when using the bicycle can be dispersed, and deformation of the extension standpipe can be more reliably prevented. In this way, it is possible to adjust the position of the saddle on the bicycle to be higher than the length of the seat post.

[0010] (2) In paragraph (1), The support shaft is connected to the upper part of the extension vertical pipe in two pieces, The other ends of the two support shafts are connected to the frame body near both sides of the rear wheel rotation axis, forming a bicycle frame extension.

[0011] According to (2), since the two support shafts support the extension standpipe from the rear wheel side, it is possible to reduce the load on the extension standpipe and its connection part. This makes it possible to more reliably prevent the extension standpipe from being deformed due to the load applied to the extension standpipe by the weight of the user when using the bicycle.

[0012] (3) In paragraph (2), The support shaft is rotatably connected to the extension standpipe.

[0013] According to (3), since the support shaft is rotatable relative to the extension standpipe, the other end of the support shaft is movable. This makes it easier to position the other end of the support shaft at the connection part with the frame body, and reduces the workload of installing the bicycle frame extension.

[0014] (4) A bicycle frame extension device according to (1) to (3), A bicycle equipped with a connecting portion (e.g., a fixed portion 25a) that connects to the other end of the support shaft.

[0015] According to (4), it becomes possible to change the shape of the bicycle to suit the user's physical growth. Effect of the Invention

[0016] According to the present invention, it is possible to provide a bicycle frame extension device and a bicycle that allow the position of the saddle on a bicycle to be adjusted higher than the length of the seat post. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a side view showing the schematic configuration of a bicycle 1 according to one embodiment of the present invention. [Diagram 2] 1 is a perspective view showing the appearance of a bicycle frame extension 2 of a bicycle 1 according to an embodiment of the present invention. [Diagram 3] 1 is a side view showing a state in which a bicycle frame extension 2 and a saddle 10 are attached to a bicycle 1 of an embodiment of the present invention. [Figure 4] 1 is an explanatory diagram showing the configuration of a modified example of a bicycle frame extension 2 for a bicycle 1 according to an embodiment of the present invention. [Diagram 5] 1 is a side view showing a modified example of the bicycle frame extension tool 2 attached to the frame body 20. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] <Bicycle 1 Configuration> 1 is a side view showing the schematic configuration of a bicycle 1 according to one embodiment of the present invention. The bicycle 1 includes a saddle 10, a seat post 12, a frame body 20, a handlebar 30, a front fork 31, a handle stem 32, a front wheel 40, a rear wheel 41, a gear crank 50, a crank 51, pedals 52, a freewheel 53, and a chain 54.

[0020] The saddle 10 is a member on which a user sits. The seat post 12 is a long, cylindrical member with the saddle 10 attached to one end. There are two types of seat posts 12: those that are attached directly to the frame body 20, and those that are attached to a bicycle frame extension 2 (see FIG. 3), which is an extension of the frame body 20 described below. In the following description, in order to distinguish between the two, the former may be referred to as seat post 12a and the latter as seat post 12b.

[0021] The frame body 20 is made of metal and includes a vertical pipe 21, a head pipe 22, an upper pipe 23, a lower pipe 24, a back fork 25, a chain stay 26, and a tightening mechanism 27.

[0022] The vertical pipe 21 is cylindrical and supports the saddle 10 by inserting and fixing the other end of the seat post 12. The head pipe 22 is cylindrical and rotatably supports a handlebar stem 32 (described later). The upper pipe 23 is a long member that connects an upper portion of the vertical pipe 21 to the head pipe 22. The lower pipe 24 is a long member that connects a lower portion of the vertical pipe 21 to the head pipe 22. The central axes of the vertical pipe 21, the head pipe 22, the upper pipe 23, and the lower pipe 24 are included in the same imaginary plane. A cylindrical bearing portion (not shown) is connected to the lower end of the vertical pipe 21. A crankshaft (not shown) is rotatably supported inside the bearing portion. The central axes of the bearing portion and the crankshaft are perpendicular to the imaginary plane described above.

[0023] The backhawk 25 is a long member having one end connected to the upper part of the standpipe 21 and extending from the upper part of the standpipe 21 to the opposite side to the head pipe 22. The chainstay 26 is a long member having one end connected to the lower part of the standpipe 21 and extending from the lower part of the standpipe 21 to the opposite side to the head pipe 22. The other end of the backhawk 25 and the other end of the chainstay 26 are connected, and the standpipe 21, the backhawk 25, and the chainstay 26 form a triangle.

[0024] Two back forks 25 and two chain stays 26 extend from the vertical pipe 21, and the other ends of the pair of back forks 25 and chain stays 26 face each other with a distance slightly larger than the width of the rear wheel 41. In addition, the pair of back forks 25 and chain stays 26 are line-symmetrical with respect to the above-mentioned imaginary plane.

[0025] The backhawk 25 also has a fixing portion 25a near the other end for fixing the other end of a support shaft 61 of the bicycle frame extension 2, which will be described later. The fixing portion 25a extends in a flat plate shape from the other end of the backhawk 25, and a bolt hole is formed in the flat surface of the extending portion.

[0026] The tightening mechanism 27 is provided at the upper end of the stand pipe 21 and fixes the seat post 12 to the stand pipe 21 by reducing the diameter of the stand pipe 21.

[0027] Here, the tightening mechanism 27 cannot tighten and fix a seat post 12 having an outer diameter smaller than a specified outer diameter. According to this embodiment, the seat post 12a and the seat post 12b do not have the same diameter, but the diameter of the seat post 12b is set to be smaller. Therefore, the tightening mechanism 27 can tighten and fix the seat post 12a, but cannot tighten and fix the seat post 12b.

[0028] According to this embodiment, a plurality of (for example, three) slits extending downward are formed in a part of the upper end of the standpipe 21, and the upper end of the standpipe 21 is divided into a plurality of curved extension pieces. A plate-shaped member curved in a U-shape is disposed on the upper end of the standpipe 21, and this plate-shaped member is welded and fixed to one of the extension pieces. Bolt holes are formed on the flat surface at both ends of the plate-shaped member, and a nut is fixed to the edge of one of the bolt holes. Then, a bolt is passed through the other bolt hole and screwed into the nut to form the tightening mechanism 27. By loosening the bolt, it becomes possible to slide the seat post 12a relative to the standpipe 21, and the saddle 10 can be adjusted to a desired height. By tightening the bolt, the upper part of the standpipe 21 is reduced in diameter, and the seat post 12a is fixed in close contact with the standpipe 21.

[0029] The handlebar 30 is a handle body operated by the user while driving. The front fork 31 is equipped with a cylindrical fork column 31a inserted into the head pipe 22, and a long U-shaped fork portion 31b. One end of the fork column 31a is connected to the center of the fork portion 31b, and the other end extends in the opposite direction to the extension direction of the fork portion 31b. The handle stem 32 is a member that connects the handlebar 30 and the front fork 31.

[0030] When the fork column 31a is inserted into the head pipe 22, it is rotatable around the axis of the head pipe 22 inside the head pipe 22, and an upper part of the fork column 31a protrudes from the head pipe 22. A handle stem 32 is fixed to this protruding part, and the handle bar 30 is attached to the handle stem 32.

[0031] The front wheel 40 is composed of an annular rim 40a, a hub 40b at the center of the rim, spokes (not shown) connecting the rim 40a and the hub 40b, and a tire 40c arranged on the outer periphery of the rim 40a. The rear wheel 41 has a similar structure to the front wheel 40, so a detailed description will be omitted.

[0032] The front wheel 40 is disposed inside the fork portion 31b of the front fork 31, and the hub 40b is fixed to the tip of the fork portion 31b, thereby attaching the front wheel 40 to the front fork 31. As a result, when the user operates the handlebar 30, the fork column 31a rotates in conjunction with the handlebar 30, and the fork portion 31b also rotates, making it possible to change the direction of the front wheel 40.

[0033] The rear wheel 41 is disposed between a pair of back forks 25 and chain stays 26, and is attached to the frame body 20 by fixing a hub (not shown) of the rear wheel 41 to the other end of the pair of back forks 25 and chain stays 26.

[0034] The gear crank 50 has a gear-shaped sprocket around which the chain 54 is hung, and a rod-shaped crank fixed to the sprocket and extending radially from the center of the sprocket. The gear crank 50 is attached to the frame body 20 by fixing the center of the sprocket to one end of a crankshaft rotatably attached to the lower end of the vertical pipe 21. The crank 51 is a rod-shaped member having the same length as the crank of the gear crank 50, and is fixed to the other end of the crankshaft. The crank of the gear crank 50 and the crank 51 face in opposite directions by 180 degrees from each other. The pedal 52 is a rectangular parallelepiped member rotatably attached to the crank of the gear crank 50 and the other end of the crank 51. The direction of the rotation axis of the pedal 52 is perpendicular to the longitudinal direction of the crank 51. In other words, the rotation axis of the pedal 52 and the central axis of the crankshaft provided at the lower end of the vertical pipe 21 are parallel to each other.

[0035] The freewheel 53 is a member that transmits rotation to the rear wheel 41. The chain 54 is an annular member that is wound around the outer periphery of the sprocket of the gear crank 50 and the freewheel 53, and transmits the rotation of the gear crank 50 to the freewheel 53.

[0036] When the user depresses the pedal 52 to rotate the crank shaft at the lower end of the standpipe 21, the gear crank 50 rotates, and the rotation is transmitted to the freewheel 53 via the chain 54, causing the rear wheel 41 to rotate. When the user stops rotating the pedal 52, the rear wheel 41 rotates by inertia due to the function of the freewheel 53.

[0037] <Configuration of bicycle frame extension tool 2> FIG. 2 is a perspective view showing the exterior of the bicycle frame extension 2 of the bicycle 1 according to one embodiment of the present invention.

[0038] The bicycle frame extension tool 2 includes an extension vertical pipe 60, two support shafts 61, 61, and a tightening mechanism 62.

[0039] The extension stand pipe 60 is configured in a cylindrical shape with the same outer diameter as the seat post 12a, and can be inserted into the stand pipe 21. In other words, the inner diameter of the extension stand pipe 60 is smaller than the inner diameter of the stand pipe 21. The extension stand pipe 60 is formed with an indicator 60a that indicates the length to be inserted into the stand pipe 21.

[0040] One end of each of the two support shafts 61, 61 is fixed by welding to the upper part of the extension standpipe 60 and extends obliquely downward. The other end of each of the support shafts 61, 61 is formed into a flat plate by crushing, and a bolt hole is formed in the flat plate surface. The length of the support shafts 61, 61 and the direction of extension of the support shafts 61, 61 relative to the extension standpipe 60 are set so that the other end of each of the support shafts 61, 61 faces the fixing part 25a formed on the backhawk 25 when the extension standpipe 60 is inserted into the standpipe 21 up to the position of the indicator 60a.

[0041] The tightening mechanism 62 is provided at the upper end of the extension standing pipe 60, and fixes the seat post 12b to the extension standing pipe 60 by reducing the diameter of the extension standing pipe 60. The tightening mechanism 62 has a configuration substantially similar to that of the tightening mechanism 27 provided at the top of the standing pipe 21, and includes a plate-shaped member 62a curved in a U-shape, a bolt 62b passed through both ends of the plate-shaped member 62a, and a nut 62c screwed onto the bolt 62b. However, since the outer diameter of the extension standing pipe 60 is smaller than the outer diameter of the standing pipe 21, the curvature of the U-shape of the plate-shaped member 62a is smaller than the curvature of the U-shape of the plate-shaped member of the standing pipe 21. A single slit 60b extending downward from the upper end is formed at the upper part of the extension standing pipe 60, and the plate-shaped member 62a is disposed on the upper part of the extension standing pipe 60 so that both ends of the plate-shaped member 62a are positioned on both sides of the slit 60b, and is fixed by welding. By loosening the bolt 62b, the seat post 12b can be slid relative to the extension pipe 60, and the saddle 10 can be adjusted to a desired height. By tightening the bolt 62b, the upper part of the extension pipe 60 is reduced in diameter, and the seat post 12b is fixed in close contact with the extension pipe 60.

[0042] FIG. 3 is a side view showing the state in which the bicycle frame extension 2 and the saddle 10 are attached to the bicycle 1 of one embodiment of the present invention.

[0043] When attaching the bicycle frame extension 2 to the bicycle 1, the extension standpipe 60 is inserted into the standpipe 21, the indicator 60a is aligned with the standpipe 21, and the other end of the support shafts 61, 61 is opposed to the fixing part 25a of the backhawk 25. In this state, the bolt of the tightening mechanism 27 is rotated to fix the extension standpipe 60 to the standpipe 21. Furthermore, the other end of the support shafts 61, 61 is connected to the backhawk 25 by passing a bolt through the bolt hole of the other end of the support shafts 61, 61 and the bolt hole of the fixing part 25a and tightening the nut. As a result, a triangular structure is formed by the support shaft 61, the backhawk 25, and the standpipe 21 into which the extension standpipe 60 is inserted, and the bicycle frame extension 2 is fixed to the frame body 20.

[0044] Finally, the seat post 12b is inserted into the extension standpipe 60 and the bolt 62b of the tightening mechanism 62 is rotated to fix the seat post 12b to the extension standpipe 60, thereby making the bicycle 1 ready for use.

[0045] According to this embodiment, the inner diameter of the extension standpipe 60 is smaller than the inner diameter of the standpipe 21. Therefore, when using the bicycle frame extension tool 2, it is desirable to attach a seatpost 12b, the outer diameter of which is slightly smaller than the seatpost 12a of the saddle 10 shown in FIG. 2, to the saddle 10, or to prepare a dedicated saddle 10 having a seatpost 12b that can be inserted into the extension standpipe 60. Since the seatpost 12b can be inserted into the extension standpipe 60 and partially inserted into the standpipe 21, the seatpost 12b can be made longer than the seatpost 12a. As a result, the range in which the height of the saddle 10 can be adjusted can be made wider.

[0046] If the user is short, the bicycle is used without attaching the bicycle frame extension 2, as shown in Figure 1. If the user is tall, the bicycle frame extension 2 is attached and the handlebars 30 are rotated 180 degrees forward to position the grip portion of the handlebars 30 in front of the head pipe 22, as shown in Figure 3. This makes it possible to make large adjustments to the height of the saddle 10 and the grip position of the handlebars 30 as the user grows.

[0047] According to the present embodiment configured in this manner, it is possible to change the form of the bicycle according to the height of the user, and the user can use the bicycle in the form most suitable for the user. For example, when the user is in the lower grades of elementary school, the bicycle is used in the form shown in FIG. 1, and when the user is in the upper grades of elementary school or above and is taller, the bicycle is used in the form shown in FIG. 3. In this way, the bicycle can be used for a long period of time. In addition, by inserting the extension standpipe 60 into the standpipe 21, the length of the standpipe 21 can be extended, and the saddle 10 can be adjusted to a higher position. Here, if the support shafts 61, 61 were not present, the extension standpipe 60 would be inclined obliquely along the standpipe 21 toward the rear wheel, so that when the user sits on the saddle 10, a large load would be applied to the connection portion of the extension standpipe 60 with the standpipe 21. According to the present embodiment, the extension standpipe 60 is supported from the rear by the support shafts 61, 61, so that the load applied to the extension standpipe 60 when the user sits on the saddle 10 is distributed, and it is possible to prevent the extension standpipe 60 from being deformed while the bicycle 1 is in use.

[0048] <Modifications of the bicycle frame extension 2> Fig. 4 is an explanatory diagram showing the configuration of a modified bicycle frame extension 2 for bicycle 1 according to an embodiment of the present invention, Fig. 4(a) is a plan view seen from above along the central axis of the extension vertical pipe 60, and Fig. 4(b) is a side view. Fig. 5 is a side view showing the modified bicycle frame extension 2 attached to the frame body 20. Note that the same members or members with the same functions as those in the bicycle frame extension 2 shown in Fig. 2 are given the same reference numerals and detailed description will be omitted.

[0049] In the bicycle frame extension 2 shown in FIG. 2, the support shafts 61, 61 are welded and fixed to the extension standpipe 60. In contrast, in the modified bicycle frame extension 2 shown in FIG. 4, the support shafts 61, 61 are rotatably connected to the extension standpipe 60. Specifically, one end of the support shafts 61, 61 is also formed into a flat plate shape by crushing, and a bolt hole is formed in this flat plate portion. Then, the bolt of the tightening mechanism 62 is inserted into this bolt hole, and one end of the support shafts 61, 61 is positioned between the flat plate portion at the top of the extension standpipe 60 and the nut 62c, and between the flat plate portion at the top of the extension standpipe 60 and the head of the bolt 62b. As a result, the support shafts 61, 61 are rotatably supported by the tightening mechanism 62.

[0050] In addition, in the bicycle 1 shown in Fig. 2, the other end of the back fork 25 and the other end of the chain stay 26 are connected. In contrast, in the bicycle 1 shown in Fig. 4, the other end of the back fork 25 and the other end of the chain stay 26 are connected to the rear claw 28 that supports the rear wheel 41, as shown in Fig. 5. Furthermore, the other ends of the support shafts 61, 61 are connected to the rear claw 28 by bolting or the like.

[0051] In this way, the support shafts 61, 61 are rotatable relative to the extension stand pipe 60, so that the other end of the support shafts 61, 61 can move. In addition, the support shafts 61, 61 are rotatable relative to the extension stand pipe 60, and further, the rear jaw 28 is formed with a plurality of holes arranged in the front-rear direction for bolting the other end of the extension stand pipe 60. This allows the other end of the extension stand pipe 60 to be fixed to the rear jaw 28 when the length of the extension stand pipe 60 extended from the stand pipe 21 is changed. This makes it easy to position the other end of the support shafts 61, 61 at the connection portion in the rear jaw 28, and reduces the workload for attaching the bicycle frame extension 2.

[0052] Although the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the other end of the support shaft 61, 61 is directly connected to the frame body 20, but the present invention is not limited to this. An optional metal fitting may be attached to the frame body 20 near the support part of the rear wheel, and the other end of the support shaft 61, 61 may be connected to the frame body 20 via this metal fitting.

[0053] In addition, in the above-described embodiment, bolts and nuts are used to connect the frame body 20 to the other ends of the support shafts 61, 61, but the fixing method is not important as long as the frame body 20 and the support shafts 61, 61 can be firmly connected to each other.

[0054] In the above embodiment, the bicycle 1 is described as being a bicycle frame for a child in the lower grades of elementary school with the bicycle frame extension 2 attached to it, but a bicycle frame extension 2 for an adult may also be attached. In addition, if a user who has used the bicycle 1 with the bicycle frame extension 2 attached thereto feels that the saddle of the bicycle is too high as they get older, they may remove the bicycle frame extension 2 and lower the saddle. In this way, the bicycle frame extension 2 may be attached in advance to a bicycle for seniors.

[0055] In the above embodiment, the other ends of the support shafts 61, 61 are connected to the frame body 20 near the rear wheel 41, but a support shaft 61 may be added to connect the upper part of the extension stand pipe 60 to the upper pipe 23, forming a triangular structure by the stand pipe 21 into which the extension stand pipe 60 is inserted, the support shaft 61, and the upper pipe 23. This more reliably prevents the extension stand pipe 60 from being deformed due to a load applied to the extension stand pipe 60 by the weight of the user when using the bicycle 1.

[0056] It should be noted that within the scope of the concept of the present invention, a person skilled in the art may come up with various modifications and alterations. It is understood that such modifications and alterations fall within the scope of the present invention. For example, even if a person skilled in the art appropriately adds, deletes, or modifies the design of the above-described embodiment, or adds, omits, or modifies the conditions of a process, these modifications and alterations are included in the scope of the present invention as long as they include the gist of the present invention. [Explanation of symbols]

[0057] 1. Bicycle 2 Bicycle frame extensions 10. Saddle 12 Seat pipe 20 Frame body 21 Standpipe 22 Head pipe 23 Upper Pipe 24 Lower pipe 25 Backhawk 25a Fixed part 26 Chainstay 27 Tightening mechanism 28 Rear 30 Handlebar 31 Front Hawk 31a Hawk Column 31b Hawk Club 32 Handle stem 40 Front wheel 40a rim 40b hub 40c tyres 41 Rear wheel 50 Gear crank 51 Crank 52 Pedals 53 Freewheel 54 Chain 60 Extension vertical pipe 60a indicator 60b Slit 61 Support shaft 62 Tightening mechanism 62a Plate-shaped member 62b Bolt 62c Nut

Claims

1. A bicycle frame extension tool that forms part of a bicycle frame body, is inclined at a certain angle toward the rear wheel of the bicycle, and extends the length of a vertical pipe that supports a saddle, a cylindrical extension standpipe into which a seat post supporting the saddle can be inserted and into which the seat post can be inserted from an upper portion of the standpipe; a support shaft having one end connected to the upper portion of the extension standpipe and the other end connected to a predetermined portion of the frame body, the support shaft forming a triangular structure with the extension standpipe, the standpipe into which the extension standpipe is inserted, and the frame body; When the extension standpipe is inserted into the standpipe, the other end of the support shaft is positioned at the predetermined position, The support shaft is connected to the upper part of the extension vertical pipe in two pieces, The other ends of the two support shafts are connected to the frame body near both sides of the rotation axis of the rear wheel.

2. 2. The bicycle frame extension of claim 1, The support shaft is rotatably connected to the extension standpipe.

3. A bicycle frame extension according to claim 1 or 2; A connecting portion that connects to the other end of the support shaft.

Images