Frame unit for bicycle and method of manufacturing the same

A frame unit for a bicycle may include a left frame body in which a part of a head tube, a part of a seat tube, a part of a frame, and a left stay are integrally formed, and a right frame body in which a part of the head tube, a part of the seat tube, a part of the frame, and a right stay are integrally formed, wherein the left frame body and the right frame body may be coupled so as to integrally form the head tube, the seat tube, and the frame, and a seat pipe formed to have a cylinder shape by step-by-step press processing may be inserted into the seat tube and then coupled to the seat tube.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent Application Number 10-2013-0097434 filed Aug. 16, 2013, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a frame unit for a bicycle and a method of manufacturing the same, and more particularly, to a frame unit for a bicycle which includes a head tube, a seat tube, a frame, and left and right stays and a method of manufacturing the same.

2. Description of Related Art

In general, a frame unit for a bicycle is a constituent component that forms an overall structure of a bicycle, and manufactured by mutually joining constituent components such as a head tube, a seat tube, a frame, and left and right stays.

In general, a frame unit for a bicycle is a constituent component that forms an overall structure of a bicycle, and manufactured by mutually joining constituent components such as a head tube, a seat tube, a frame, and left and right stays.

Recently, in order to implement various designs and secure rigidity for safety, materials such as aluminum, chromium-molybdenum steel, carbon, and titanium are used instead of a high tensile steel material that is generally used.

FIG. 1is a configuration diagram of a frame unit for a bicycle according to the related art.

Referring toFIG. 1, a frame unit100for a bicycle of the related art includes a head tube101, a seat tube103, an upper frame105, a lower frame107, and upper and lower stays109and111disposed at both sides.

A steering shaft (not illustrated) to which a steering handle is connected is installed on the head tube101, and a seat pipe (not illustrated) connected to a seat is installed on the seat tube103.

The upper and lower frames105and107connect and support the head tube101and the seat tube103.

Rear ends of both the upper and lower stays109and111are connected to each other so as to form a rotating body fork113to which a rear wheel is mounted.

A front end of the lower stay111is connected to a pedal assembly115that is configured at a lower end of the seat tube103.

Meanwhile, the frame unit100for a bicycle mostly includes both the upper frame105and the lower frame107, but in some cases, only a single frame, that is, only the upper frame105may be applied between the head tube101and the seat tube103.

However, according to the frame unit100for a bicycle of the related art, which has the aforementioned configuration, when the head tube101, the seat tube103, the upper frame105, the lower frame107, and the upper and lower stays109and111are joined to each other by a welding process, residual stress due to welding heat is distributed to joining portions. Particularly, impact loads are directly applied when the bicycle runs, thereby causing a serious problem with respect to safety such as cracks or damage occurring at the periphery of the joining portions.

Particularly, because welding work is performed after the head tube101passes through a separate preheating process in accordance with a difference in thickness between the upper and lower frames105and107when the head tube101is joined to the upper and lower frames105and107, there is a drawback in that a welding defect occurs if the preheating process is not properly performed.

In addition, since the process of welding the joining portions is manually performed, an inferiority rate is high because there is a difference in welding quality in accordance with skill of workers and working environment, and thereby, there are drawbacks in that an excessive working time is required and productivity deteriorates.

BRIEF SUMMARY

Various aspects of the present invention provide for a frame unit for a bicycle and a method of manufacturing the same having advantages of improving rigidity and design quality.

Various aspects of the present invention provide for a frame unit for a bicycle that may include a left frame body in which a part of a head tube, a part of a seat tube, a part of a frame, and a left stay are integrally formed, and a right frame body in which a part of the head tube, a part of the seat tube, a part of the frame, and a right stay are integrally formed, wherein the left frame body and the right frame body may be coupled so as to integrally form the head tube, the seat tube, and the frame, and a seat pipe formed to have a cylinder shape by step-by-step press processing may be inserted into the seat tube and then coupled to the seat tube.

The seat pipe may include a stepped portion protruding at an exterior circumference of an upper portion of the seat tube for a seat clamper to be mounted to the exterior circumference of the stepped portion, and a seating protrusion protruding at the middle portion of the seat pipe to form a welding surface portion welded to the seat tube.

The seat pipe may have a thickness same or similar to a thickness of the seat tube.

The left frame body and the right frame body may be coupled by a welding method.

Various aspects of the present invention provide for a method of manufacturing a frame unit for a bicycle that may include press-forming a left frame body in which a part of a head tube where a steering shaft is mounted thereto, a part of a seat tube where a seat pipe is mounted thereto, a part of a frame configured to integrally connect the head tube and the seat tube and form a body of a bicycle, and a left stay are integrally formed, press-forming a right frame body in which a part of the head tube, a part of the seat tube, and a right stay are integrally formed, coupling the left frame body and the right frame body each other along edges of the left and right frame bodies, and inserting a seat pipe formed to have a cylinder shape by step-by-step press processing into the seat tube and coupling the seat pipe to the seat tube.

The seat pipe may include a stepped portion protruding at an exterior circumference of an upper portion of the seat tube for a seat clamper to be mounted to the exterior circumference of the stepped portion, and a seating protrusion protruding at the middle portion of the seat pipe to form a welding surface portion welded to the seat tube.

The seat pipe may have a thickness same or similar to a thickness of the seat tube.

The seat pipe may be formed by press forming a flat sheet to have a stepped portion and a seating protrusion, press forming the flat sheet to be a cylinder shape, press forming a protrusion and a depressed portion at ends of the sheet, and welding the protrusion and the depressed portion.

According to the frame unit for a bicycle according to various aspects of the present invention, a head tube, a seat tube, a frame, a pedal assembly and a left and right stays are integrally formed with the main frame without a joining portion such that residual stress due to welding heat at a joining portion in the related art may be removed, and a factor, which causes joint rigidity deterioration due to the residual stress, may be eliminated.

Accordingly, rigidity and durability between the head tube and the frame with respect to an impact load transmitted from a road surface and a fatigue load of the frame unit per se are firmly maintained, thereby preventing damage such as cracks, and securing safety.

In addition, welding work is performed along edges of the left and right frame bodies when the left and right frame bodies are joined, such that welding processes may be automated, working times may be reduced due to the automation, and welding quality and productivity may be improved.

Since the seat pipe is formed to have a thickness that is the same as or similar to a thickness of the seat tube, the seat pipe may be instantly joined to the seat tube without a separate preheating process, thereby improving welding quality and reducing time needed during the work process.

Since the seat pipe is formed to have a thickness that is the same as or similar to a thickness of the seat tube by press forming, the seat pipe may be compatible for other seats, and productivity may be improved.

DETAILED DESCRIPTION

A part irrelevant to the description will be omitted to clearly describe the present invention, and the same or similar elements will be designated by the same reference numerals throughout the specification.

The size and thickness of each component illustrated in the drawings are arbitrarily shown for understanding and ease of description, but the present invention is not limited thereto. Thicknesses of several portions and regions are enlarged for clear expressions.

Further, in the following detailed description, names of constituents, which are in the same relationship, are divided into “the first”, “the second”, and the like, but the present invention is not limited to the order in the following description.

Throughout the specification and the claims, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

In addition, “unit”, “means”, “part”, “member”, or the like, which is described in the specification, means a unit of a comprehensive configuration that performs at least one function or operation.

FIG. 2is a side view of a bicycle to which a frame unit for a bicycle according to various embodiments of the present invention is applied,FIG. 3is a perspective view of the frame unit for a bicycle according to various embodiments of the present invention, andFIG. 4is an exploded perspective view of the frame unit for a bicycle according to various embodiments of the present invention.

Referring toFIGS. 2 to 4, a frame unit1for a bicycle according to various embodiments of the present invention includes a head tube3, a seat tube5, a frame7, a pedal assembly9, and left and right stays11and11a.

A steering shaft15to which a handle13is mounted is installed to the head tube3, and a front wheel19is installed by a fork17configured at a lower side of the steering shaft15.

A seat23is installed to the seat tube5by a seat pipe21.

The frame7may include an upper extension frame25configured to integrally connect the head tube3and the seat tube5, and a lower extension frame27integrally connected to the pedal assembly9, and forms a body of a bicycle29. One will appreciate that such integral components may be monolithically formed.

The left and right stays11and11ainclude an upper stay31, and a lower stay33, respectively, and rear ends of both the upper stays31and rear ends of both the lower stays33are connected to each other so as to form a rotating body fork37to which a rear wheel35is mounted.

Further, front ends of both the upper stays31are connected to the seat tube5, and front ends of both the lower stays33are connected to the pedal assembly9configured at a lower side of the seat tube5.

The pedal assembly9may be formed to protrude downward at a lower side between the frame7and both the lower stays33, and a pedal9a, which is connected to the rear wheel35by a chain39, is installed on the pedal assembly9.

Here, the head tube3, the seat tube5, the frame7, the pedal assembly9, and the left and right stays11and11aare formed by a left frame body41and a right frame body43, which are integrally formed. One will appreciate that such integral components may be monolithically formed.

Further, the left and right frame bodies41and43are joined along edges thereof so as to form an overall configuration of the frame unit1for a bicycle.

The left and right frame bodies41and43are joined to each other by a welding method, and in this case, the welding method may be an arc welding method or the like.

FIG. 5is a side cross-sectional view illustrating a configuration of a seat pipe according to various embodiments of the present invention, andFIG. 6is a perspective view of a seat pipe according to various embodiments of the present invention.

Referring toFIG. 5andFIG. 6, the seat pipe21mounted to the seat tube5is formed to have a cylinder shape by step-by-step press processing, and a stepped portion45and a seating protrusion47are formed to an upper portion and a middle portion thereof.

The stepped portion45protrudes at an exterior circumference of the seat tube5, and a seat clamper51is mounted to the exterior circumference of the stepped portion45for clamping a seat post49where the seat23is mounted.

The seating protrusion47protrudes at the middle portion thereof to form a welding surface portion53contacting the seat tube5.

The seat pipe21may have a thickness same or similar to that of the seat tube5.

An interior diameter of the seat pipe21is determined for corresponding to an exterior circumference of the seat post49.

In this case, a gap may be formed between the interior diameter of the seat pipe21and the exterior circumference of the seat post49. However, the seat clamper51may prevent movement of the seat post49by clamping the seat post49.

Thus, the seat pipe21may adapt various seat posts49with various sizes.

According to the frame unit1for a bicycle according to various embodiments of the present invention, which has the aforementioned configuration, the head tube3, the seat tube5, the frame7, the pedal assembly9and the left and right stays11and11aare integrally formed without a joining portion such that residual stress due to welding heat at a joining portion in the related art may be removed, and a factor, which causes joint rigidity deterioration due to the residual stress, may be eliminated.

In addition, an occurrence of a safety accident due to cracks and damage which have occurred at the joining portion is reduced, and rigidity and durability between the head tube3and the frame7with respect to an impact load transmitted from a road surface and a fatigue load of the frame unit per se are firmly maintained.

Further, the left and right frame bodies41and43, which form the frame unit1for a bicycle, are integrally formed, thereby making the entire outer appearance of the frame unit1for a bicycle be aesthetically attractive.

In addition, welding beads, which occur when the left and right frame bodies41and43are joined, are not directly exposed to a surface, such that an influence on the entire outer appearance design of the frame unit1for a bicycle is minimized.

In addition, welding work is performed along edges of the left and right frame bodies23and25when the left and right frame bodies41and43are joined, such that welding processes may be automated, working times may be reduced due to the automation, and welding quality and productivity may be improved.

In addition, since the seat pipe21is formed to have a thickness that is the same as or similar to a thickness of the seat tube5, the seat pipe21may be instantly joined to the seat tube5without a separate preheating process, thereby improving welding quality and reducing time needed during the work process.

Hereinafter, a method of manufacturing the frame unit1for a bicycle according to various embodiments of the present invention, which has been described above, will be described with reference toFIGS. 3 to 6.

First, the seat tube5, the frame7, the pedal assembly9, and the left and right stays11and11aare integrally formed, and the left and right frame bodies41and43, which are symmetric to each other, are press-formed, respectively as shown inFIG. 4.

Thereafter, the left and right frame bodies41and43formed by a press are joined to each other by welding along edges of the left and right frame bodies41and43, and manufactured as the frame unit1for a bicycle, as illustrated inFIG. 3.

The seat pipe21formed to have a cylinder shape by step-by-step press processing is inserted into the seat tube5and then coupled to the seat tube5.

The stepped portion45protrudes at the exterior circumference of the seat tube5, and the seat clamper51is mounted to the exterior circumference of the stepped portion45for clamping the seat post49. And the seating protrusion47protrudes at the middle portion thereof to form the welding surface portion53to weld to the seat tube5.

The seat pipe21is formed by step-by-step press processing.

That is, a flat sheet is press formed to form the stepped portion45and the seating protrusion47, and then formed in a cylinder shape by a series of press forming processes to be the seat pipe21.

A protrusion55and a depressed portion57are formed by press forming at ends of the sheet (the seat pipe21) then the protrusion55and the depressed portion57are coupled.

The seat pipe21may have a thickness same or similar to that of the seat tube5.

In addition, since the seat pipe21is formed to have a thickness that is the same as or similar to a thickness of the seat tube5, the seat pipe21may be instantly joined to the seat tube5without a separate preheating process, thereby improving welding quality and reducing time needed during the work process.

Since the seat pipe21is formed to have a thickness that is the same as or similar to a thickness of the seat tube5, the seat pipe21may be compatible for other seats.

Since the seat pipe21is formed by press forming process, quality of the seat pipe21is stable and thickness of the seat tube5may be reduced so that total weight of the frame unit1may be reduced.

For convenience in explanation and accurate definition in the appended claims, the terms upper or lower, front or rear, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.