JPH0413272Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an improvement in a bicycle frame, particularly a pedal crankshaft mounting portion.

[Conventional technology]

First, a conventional bicycle frame will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a perspective view showing a conventional bicycle frame, and FIG. 5 is a detailed view of a pedal crankshaft mounting portion of the bicycle frame. In the figure, 1 is a downwardly curved main frame, 2 is a handle frame into which the handle shaft is inserted, and is attached to the front end surface of the main frame 1 by horizontal welding. 3 is a hollow cylinder welded to the curved lower part of the main frame 1 and installed in the orthogonal direction, in order to increase the strength by widening the contact area with the main frame 1.
It has a notch 4 on its upper contact surface. 5a,
Reference numeral 5b denotes a cover plate attached to both end faces of the hollow cylinder 3 by means such as welding or by screwing together, and a crankshaft of a pedal (not shown) is rotatably mounted in the center of the cover plates 5a, 5b. A sleeve 6 for fitting is fixed to each cover plate 5a, 5b.
Reference numerals 7a and 7b are chainstays which are welded with their end surfaces in contact with the outer peripheral surface of the hollow cylinder 3, and FIG. 5 shows the state before welding. 8 is a seat stay whose one end is welded to the main frame 1;
9 is chain stay 7a, 7b and seat stay 8
A hole is drilled at the other end of each intersection to attach the rear wheel axle.

A conventional bicycle frame is constructed as described above, and in manufacturing this bicycle frame, the main frame 1 is curved and the handle frame 2 and seat stay 8 are welded and fixed thereto. On the other hand, each of the cover plates 5a and 5b was fixed by welding or screwing to both ends of the hollow cylinder 3 provided with the notch part 4, and then the sleeve 6 was inserted into the hole of the cover plates 5a and 5b and welded. After that, the chain stays 7a and 7b are brought into contact with the outer peripheral surface of the hollow cylinder 3, and the outer periphery of this contact portion is welded with a welding rod. Furthermore, the curved lower part of the main frame 1 is brought into contact with the notch 4 of the hollow cylinder 3 and welded. In this way, a bicycle frame as shown in FIG. 4 is manufactured.

[Problem that the invention attempts to solve]

As mentioned above, in conventional bicycle frames, each part is fixed by welding, so
It is necessary to streamline the welding work as much as possible, but in particular, the chain stays 7a and 7b are welded in contact with the hollow cylinder 3, and the hollow cylinder 3 to which the chain stays 7a and 7b are fixed is In order to perform curved surface welding while maintaining the required angular position with respect to the curved part of the frame 1, these parts have a high altitude where the outer periphery of the abutting part must be welded using a welding rod. However, there was a problem in that it required skilled work and was therefore significantly inferior in terms of working efficiency, appearance, and strength.

This idea was made to solve this problem, and the curved main frame after press molding and the hollow cylindrical member, which was also assembled only by press molding, were assembled using a series of welding operations, especially conventional methods. It can be easily assembled and fixed by spot welding, which does not require a welding rod, and this not only simplifies the installation of chainstays to cylindrical members, but also significantly reduces welding work and eliminates swelling of welded parts. The object of the present invention is to obtain a frame for a bicycle that has a good finish and can maintain sufficient strength.

[Means for solving problems]

In the bicycle frame according to this invention,
A cover plate covering both ends of the hollow cylinder is fastened by a pedal bearing sleeve inserted through the cover plate, and a protrusion for attaching a chain stay is integrally connected to this cover plate, so that the cover plate, that is, the chain stay The mounting protrusion is rotatably mounted to the hollow cylinder.

[Effect]

In this invention, the hollow cylinder, the cover plate, and the pedal bearing sleeve are assembled only by pressing, and the rotational positions of the chainstay attachment protrusions at both ends of the assembled hollow cylinder are set at different positions. This makes it easier to insert the welded part into a welding machine when spot welding the chainstay to this protruding part, and to weld the hollow cylinder to which the chainstay is fixed to the main frame. In this method, the notch of the hollow cylinder, which does not require consideration of the angular position at which the chainstay is attached to the main frame, is brought into contact with the curved lower edge of the main frame, and both chainstays are held at an angular position that does not get in the way. Welding can be easily performed. In this way, it is possible to quickly assemble the bicycle frame by joining each part after press molding and assembling by a series of spot welding.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a perspective view of the bicycle frame, which corresponds to FIG. 4, and FIG. 2 is a detailed view of the pedal crankshaft attachment portion, which corresponds to FIG. 5, before it is attached to the main frame 1. It represents. FIG. 3 is a sectional view taken along the - line in FIG. 2. In addition, in both Figures 2 and 3, the chain stay 7
Parts a and 7b are omitted.

In the figure, the same reference numerals as in FIGS. 4 and 5 indicate the same or corresponding parts. A hollow cylinder 3 is attached to the lower part of the main frame 1 which is curved downward, and is provided with a notch 4 as in the conventional example described above. 5a, 5b
is a cover plate that is fitted over both end faces of the hollow cylinder 3, and has holes 12a and 12b in the center, and protrusions 10a and 10b that are U-shaped in cross section and are integrally connected to the sides. It is set up. Reference numeral 6a denotes a sleeve for rotatably fitting the crankshaft of a pedal (not shown), and by expanding and caulking both ends of the sleeve, the cover plates 5a and 5b are rotatably attached to the hollow cylinder 3. ing. Note that the protrusions 10a, 10
A plurality of uneven portions 11 for spot welding (for example, three locations) are provided on b. Chain stays 7a and 7b are held by protrusions 10a and 10b of cover plates 5a and 5b and fixed by spot welding.

In this case, the hollow cylinder 3 and the cover plates 5a and 5b are
The auxiliary members 5a and 5b were not firmly fixed to each other, but were attached slightly loosely to the extent that they could rotate as described above when an external force was applied, and furthermore, before the main frame and chain stays 7a and 7b were attached, The protrusions 10a and 10b are mutually connected to the sleeve 6.
For example, they are arranged to be shifted by about 90 degrees so as not to face in the same direction with respect to the plane perpendicular to the axis of a.

Therefore, when manufacturing a bicycle frame configured as described above, first the auxiliary members 5a and 5b are attached to both ends of the hollow cylinder 3, and then one end is attached to the sleeve which has already been expanded. 6a into the holes 12a, 12b formed in the cover plates 5a, 5b, and then expand and caulk the other end portion of the sleeve 6a that protrudes outward from the outer surface of the cover plates 5a, 5b. , cover plates 5a and 5b are attached to the hollow cylinder 3. At this time, the protrusion 10
When spot welding the chainstays 7a, 10b and the chainstays 7a, 7b, the protrusions 10 are installed as described above so that they can be easily set in a spot welding machine.
a and 10b so that they are not in the same direction with respect to the plane perpendicular to the axis of the sleeve 6a, for example, at an angle of about 90°.
(See Figure 2). Next, the protrusion 10a
While holding the chainstay 7a in the groove, the two are welded together by spot welding. In this case, the plurality of uneven portions 11 for spot welding are replaced by the protruding portion 1.
0a, the chain stay 7a is firmly welded to the protrusion 10a at the uneven portion 11.

After the chain stay 7b is welded to the protrusion 10b in the same manner as described above, one of the chain stays 7a, 7b is rotated so that both the chain stays 7a, 7b are oriented in the same direction.

After the lower part of the curved main frame 1 is inserted into the notch 4 of the hollow cylinder 3, welding is performed.

In this case, the hollow cylinder 3, which does not require consideration of the mounting angle position of the chain stays 7a, 7b with respect to the main frame 1,
Hold b at a rotating angle position that does not get in the way,
It can be set in a spot welding machine with the notch 4 in contact with the curved lower edge of the main frame 1, and welding work can be easily performed.

As is clear from the above, by performing a series of mechanical welding operations on the main frame 1 after press forming and the hollow cylinder 3 assembled by press forming, welding operations using conventional welding rods can be achieved. It is possible to quickly assemble a bicycle frame without having to do this.

Note that the handle frame 2 and seat stay 8 are attached to the main frame 1 in the same manner as in the prior art.

In addition, seat stay 8 and chain stay 7
By slightly bending the peripheries of the spot welded portions at the ends of a and 7b toward the contact surfaces, the welding effect can be further improved when spot welding these parts.

Further, the order of assembling the frames is not limited to the above order, but may be, for example, the most efficient order.

Although this bicycle frame is usually used for children's bicycles, it goes without saying that it can also be used for adult bicycles.

Furthermore, although the above embodiments have been described in terms of spot welding, other welding equipment may be used.

[Effect of idea]

As explained above, this invention has a simple structure in which the chainstay is rotatably fixed to the hollow cylinder via the cover plate, so the number of welding points can be reduced, and mechanical welding methods such as spot welding can be used. This makes it possible to significantly shorten the time required, and has the advantage of being strong enough and having an excellent appearance.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of this invention, Fig. 2 is a detailed view of the pedal crankshaft mounting part in the above embodiment, Fig. 3 is a sectional view taken along the - line in Fig. 2, FIG. 4 is a perspective view showing a conventional bicycle frame, and FIG. 5 is a detailed view of a conventional pedal crankshaft mounting portion. 1... Main frame, 3... Hollow cylinder, 5a, 5
b... Lid plate, 7a, 7b... Chain stays. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] In a bicycle frame in which a hollow cylinder for supporting pedal shafts is fixed perpendicularly to the curved lower edge of the main frame, the hollow cylinder has at both ends thereof,
Lid plates covering these end surfaces are fitted, and protrusions for attaching chainstays are integrally formed on these lid plates to extend laterally from the lid surfaces, and both lid plates are inserted through their centers. A bicycle frame, characterized in that both cover plates are rotatably attached to the hollow cylinder by being fastened with sleeves for receiving pedal shafts.