GB2117719A - Bicycle frames - Google Patents

Abstract

A bicycle frame comprises, a seat-mounting tube 20, a cross bar 21 extended forwardly from the wall of the tube, an upper fork 23 extended upwardly from the upper portion of the rear wall of the tube, a lower fork 22 extended downwardly from the lower portion of the rear of the tube, and a rear fork 24 joining the free ends of the upper and lower forks. <IMAGE>

Description

SPECIFICATION Bicycle This invention relates to a bicycle frame.

Conventional bicycle frames are constructed in many forms, such as, diamond type (Fig.

la), staggered type (Fig. ib), loop type (Fig, ic, mixed type (Fig. id), H type (Fig. lie), U type (Fig. 1f) etc. All these types of frames have their individual advantages and disadvantages. Generally, the diamond type has a good load-bearing characteristic and is easy to manufacture, but its impact strength is unsatisfactory. In the staggered type a disadvantage is the occurrence of stress concentration at the seat tube. The loop type frame is acknowledged by its particular structure having a curvature formed at the connection between the cross bar and seat tube, thereby increasing the strength of the joint. The mixed type frame possesses higher strength and good stress distribution, but requires greater manufacturing time.The H type frame is employed in the portable and foldable bicycle, but results in stress concentration. In the U type frame, the lower curve portion is a significant portion that creates stress concentration.

According to the present invention, a bicycle frame comprises a cross bar; an upper fork; and a lower fork, the cross bar, upper and lower forks being interconnected at one end thereof; and a rear fork interconnecting the free ends of said upper and lower forks.

Advantageously the said one ends of the cross bar, upper and lower forks are interconnected at a tubular member.

Preferably, the connections of the tubular member, upper and lower forks form a five pipe connection.

Advantageously the cross bar is narrower at or adjacent its free end than adjacent its said one end.

A bicycle according to the present invention provides a simplified construction, good strength and stress distribution.

A bicycle frame according to the present invention is constructed according to requirements of design of seat and work place in terms of man's physical size, comfort, strength etc.

The present invention is further described hereinafter, by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic view illustrating various forms of bicycle frame in the prior art; Figure 2 is a perspective view of a bicycle constructed according to the present invention; and Figure 3 is a perspective view of a bicycle frame constructed according to the present invention.

As shown in Fig. 2 a bicycle 10 according to the present invention comprises, a frame 11 constructed according to the present invention, a back-rest type seat 12, a forwardly extending chain wheel 1 3 connected with a rear hub sprocket 1 6 through a chain 15, a handle grip 17, a front wheel 1 8 and rear wheel 19, and other parts that are required to constitute the whole assembly of a bicycle as conventionally constructed bicycles.

As shown in Fig. 3, the frame 11 includes a seat tube 20, and from the wall surface thereof, is welded a forwardly extending cross bar 21 of which the width is smaller at the forward portion thereof and larger at the rear portion thereof. An upper fork 23 is slopingly extending upward from an upper portion of the rear surface of the tube 20 and a lower fork 22 is extending downward from a lower portion of the rear surface of tube 20. The upper fork 23 and lower fork 22 are all in tube form and connected with the surface of the tube 20 by welding, forming a five-pipe connection which is a characteristic of the invention. A rear fork 24 is provided for connecting the upper and lower forks 23 and 22.

After assembling the bicycle 10, the cross bar 21 supports the seat portion 1 21 of the back seat 1 2 and the upper fork 23 supports the back portion 1 22. The forward portion of the cross bar 21 is extended beyond the front wheel 1 8 and supporting the chain wheel 1 3.

With this configuration, a rider can be allowed to ride on the bicycle in a comfortable backrest position.

As mentioned above, the frame 11 has a very simple construction and joints formed on the wall surface of the tube 20 are relatively good and of high strength. The additionally provided rear fork 24 offers a good stress distribution in the frame when carrying a load.

Furthermore, from Fig. 3 it can be seen that angles formed between the cross bar 21, upper fork 23 and lower fork 22 can be adjusted as practically required. The most suitable position of the frame can be so selected that the whole assembly of the bicycle suits for the corresponding geographical features and man's physical size, comfort, strength etc.

With the invention thus explained it is apparent that obvious modifications and variations can be made without departing from the scope of the invention. It is therefore intended that the invention be limited only as indicated in the appended claims.

1. A bicycle frame comprising a cross bar; an upper fork; and a lower fork, the cross bar, upper and lower forks being interconnected at one end thereof; and a rear fork interconnecting the free ends of said upper and lower forks.

2. A bicycle frame as claimed in claim 1, wherein said one ends of the cross bar, upper

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Bicycle This invention relates to a bicycle frame. Conventional bicycle frames are constructed in many forms, such as, diamond type (Fig. la), staggered type (Fig. ib), loop type (Fig, ic, mixed type (Fig. id), H type (Fig. lie), U type (Fig. 1f) etc. All these types of frames have their individual advantages and disadvantages. Generally, the diamond type has a good load-bearing characteristic and is easy to manufacture, but its impact strength is unsatisfactory. In the staggered type a disadvantage is the occurrence of stress concentration at the seat tube. The loop type frame is acknowledged by its particular structure having a curvature formed at the connection between the cross bar and seat tube, thereby increasing the strength of the joint. The mixed type frame possesses higher strength and good stress distribution, but requires greater manufacturing time.The H type frame is employed in the portable and foldable bicycle, but results in stress concentration. In the U type frame, the lower curve portion is a significant portion that creates stress concentration. According to the present invention, a bicycle frame comprises a cross bar; an upper fork; and a lower fork, the cross bar, upper and lower forks being interconnected at one end thereof; and a rear fork interconnecting the free ends of said upper and lower forks. Advantageously the said one ends of the cross bar, upper and lower forks are interconnected at a tubular member. Preferably, the connections of the tubular member, upper and lower forks form a five pipe connection. Advantageously the cross bar is narrower at or adjacent its free end than adjacent its said one end. A bicycle according to the present invention provides a simplified construction, good strength and stress distribution. A bicycle frame according to the present invention is constructed according to requirements of design of seat and work place in terms of man's physical size, comfort, strength etc. The present invention is further described hereinafter, by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic view illustrating various forms of bicycle frame in the prior art; Figure 2 is a perspective view of a bicycle constructed according to the present invention; and Figure 3 is a perspective view of a bicycle frame constructed according to the present invention. As shown in Fig. 2 a bicycle 10 according to the present invention comprises, a frame 11 constructed according to the present invention, a back-rest type seat 12, a forwardly extending chain wheel 1 3 connected with a rear hub sprocket 1 6 through a chain 15, a handle grip 17, a front wheel 1 8 and rear wheel 19, and other parts that are required to constitute the whole assembly of a bicycle as conventionally constructed bicycles. As shown in Fig. 3, the frame 11 includes a seat tube 20, and from the wall surface thereof, is welded a forwardly extending cross bar 21 of which the width is smaller at the forward portion thereof and larger at the rear portion thereof. An upper fork 23 is slopingly extending upward from an upper portion of the rear surface of the tube 20 and a lower fork 22 is extending downward from a lower portion of the rear surface of tube 20. The upper fork 23 and lower fork 22 are all in tube form and connected with the surface of the tube 20 by welding, forming a five-pipe connection which is a characteristic of the invention. A rear fork 24 is provided for connecting the upper and lower forks 23 and 22. After assembling the bicycle 10, the cross bar 21 supports the seat portion 1 21 of the back seat 1 2 and the upper fork 23 supports the back portion 1 22. The forward portion of the cross bar 21 is extended beyond the front wheel 1 8 and supporting the chain wheel 1 3. With this configuration, a rider can be allowed to ride on the bicycle in a comfortable backrest position. As mentioned above, the frame 11 has a very simple construction and joints formed on the wall surface of the tube 20 are relatively good and of high strength. The additionally provided rear fork 24 offers a good stress distribution in the frame when carrying a load. Furthermore, from Fig. 3 it can be seen that angles formed between the cross bar 21, upper fork 23 and lower fork 22 can be adjusted as practically required. The most suitable position of the frame can be so selected that the whole assembly of the bicycle suits for the corresponding geographical features and man's physical size, comfort, strength etc. With the invention thus explained it is apparent that obvious modifications and variations can be made without departing from the scope of the invention. It is therefore intended that the invention be limited only as indicated in the appended claims. CLAIMS

1. A bicycle frame comprising a cross bar; an upper fork; and a lower fork, the cross bar, upper and lower forks being interconnected at one end thereof; and a rear fork interconnecting the free ends of said upper and lower forks.

2. A bicycle frame as claimed in claim 1, wherein said one ends of the cross bar, upper and lower forks are interconnected at a tubular member.

3. A bicycle frame as claimed in claim 2, wherein said cross bar extends forwardly from a front portion of the wall of said tubular member, said upper fork extends upwardly from an upper portion of the rear wall of said tubular member and said lower fork extends downwardly from a lower portion of the rear of said tubular member.

4. A bicycle frame as claimed in claim 2 or 3, wherein said tubular member, said cross bar, and upper and lower forks form a fivepipe connection.

5. A bicycle frame as claimed in claim 1, 2, 3, or 4 wherein the said cross bar is narrower near its free end than adjacent its said one end.

A bicycle frame substantially as hereinbefore described with reference to Figs. 2 and 3 of the accompanying drawings.