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Patent Searching and Data


Title:
BICYCLE FRAMES
Document Type and Number:
WIPO Patent Application WO/1996/003306
Kind Code:
A1
Abstract:
A bicycle frame (2) of shell-like form has zones (30, 32, 34 and 36) incorporating mountings for the handlebar/front fork assembly, crank assembly, seat, and rear wheel respectively. At least some of these zones are of a structure which permits the corresponding mounting to be fitted in a selected, but variable, position within the zone subsequent to production of the shell-like frame. The frame can thus be adapted to a different range of bicycle sizes without varying the basic tooling by which the frame is produced.

Inventors:
THOMPSON LACHLAN ARTHUR (AU)
Application Number:
PCT/AU1995/000444
Publication Date:
February 08, 1996
Filing Date:
July 21, 1995
Export Citation:
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Assignee:
MELBOURNE INST TECH (AU)
AUSTRIALIAN SPORTS COMMISSION (AU)
THOMPSON LACHLAN ARTHUR (AU)
International Classes:
B62K3/02; B62K19/16; (IPC1-7): B62K3/02; B62K19/02; B62K19/16; B62K19/30
Domestic Patent References:
WO1994026579A11994-11-24
Foreign References:
EP0198284A21986-10-22
GB2252537A1992-08-12
US5411280A1995-05-02
US3233916A1966-02-08
US5273303A1993-12-28
Other References:
PATENT ABSTRACTS OF JAPAN, M-1098, page 90; & JP,A,03 014 781 (MITSUBISHI RAYON CO LTD), 23 January 1991.
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Claims:
CLAIMS:
1. A method of producing a bicycle frame, comprising the steps of producing a frame of shelllike form without mountings for at least some from the group consisting of the crank assembly, the handlebar /front fork assembly, seat, and the rear wheel, and then installing said mountings at selected, but variable, positions within the frame.
2. A method as claimed in claim 1, wherein the frame comprises an upwardly directed extension for receiving a mounting for the seat, said method comprising reducing the length of the extension to a required length after production of the frame and then installing the mounting within the extension.
3. A method as claimed in claim 2, wherein the extension is substantially of tubular form.
4. A method as claimed in any one of claims 1 to 3, wherein the mounting for the crank assembly comprises a tubular insert, said method comprising drilling the frame in a selected, but variable, position and incorporating the tubular insert into the drilling thereby produced.
5. A method according to claim 4, wherein the construction of the frame permits the insert to be mounted anywhere within an area having a height dimension of approximately 100mm and a width dimension of approximately 80mm.
6. A method according to any one of claims 1 to 5, wherein the frame defines opposed stays each for receiving a mounting for the rear wheel, said method comprising reducing the length of the stays to a required length after production of the frame, and then installing the rear wheel mountings.
7. A method according to claim 6, wherein the construction of the frame permits the rear wheel mountings to be fitted to the stays anywhere within an area extending about 75mm forwardly from rear edges of the stays.
8. A method according to any one of claims 1 to 7, wherein the mounting for the handle bar/front fork assembly comprises a tubular insert for receiving a head tube, said method comprising drilling the frame at a seleαed, but variable, position and at a selected, but variable, inclination, and incorporating the insert.
9. A method according to claim 8, wherein the construction of the frame permits the head tube insert to be fitted anywhere within an area of a length of about 140mm and at an inclination which can vary within a range of about 12 \.
10. A method according to any one of claims 1 to 7, wherein a mounting for the handlebar/front fork assembly is incorporated into the frame at a predetermined position during manufacture of the frame.
11. A bicycle frame when manufactured by a method as defined in any one of claims 1 to 10.
12. A bicycle frame of shelllike form, said frame including zones having mountings for the handlebar /front fork assembly, crank assembly,, seat, and rear wheel, at least some of said zones having structure which permits the corresponding mounting to be fitted in a selected, but variable, position within the zone subsequent to production of the shelllike frame.
13. A bicycle frame according to claim 12, wherein the mounting zones for the handlebar/front fork assembly and/or the crank assembly are such that the zones can be drilled in a selected position to receive a mounting for the corresponding assembly.
14. A bicycle frame according to claim 12 or claim 13, wherein the zone at which the seat is mounted comprises an upwards extension of the frame, said extension being capable of being cut to a selected, but variable, length.
15. A bicycle frame according to any one of claims 12 to 14, wherein the zone at which the rear wheel is mounted comprises rearwardly directed stays capable of being cut to a selected, but variable, length.
16. A bicycle frame according to any one of claims 12 to 15, said frame being formed from two halfshells secured together.
17. A bicycle frame according to claim 16, wherein each half shall comprises a rearward extension which defines a respective rear wheel stay of the frame, the two half shells cooperating to at least partly define an enclosure forwardly of the rear wheel stays.
18. A bicycle frame according to claim 17, wherein the enclosure is closed at the rear by an insert incorporated between the two half shells.
19. A bicycle frame according to claim 18, wherein the insert also provides reinforcement for the rear wheel stays.
Description:
BICYCLE FRAMES

The present invention relates to bicycle frames and more particularly to bicycle frames of shell-like construction.

Conventional tubular diamond-frames have changed little since their introduction in the 1890's and consist of steel tubes that are welded, brazed or soldered to a bottom bracket shell, head tube, seat tube and rear drop-outs to form the frame geometry. In volume production all the frame parts including the bottom bracket shell, head tube, seat tube and rear drop-outs are assembled into a welding jig for joining. Because the bottom bracket shell, head tube, seat tube and rear drop-outs must be included in the frame at assembly, the diamond-frame must be produced in a wide range of sizes to suit adult riders of different height. When the frame is used for athletic competition, the frame is normally built to suit the specific dimensions unique to the athlete. Seat tube and head tube angles of inclination are also variables that must be fixed on the assembly of the diamond frame resulting in an even greater variety of sizes.

In the late 1980's the Union Cyclist de International (UCI), the body that controls the sport of cycling, relaxed strict rules governing bicycle geometry and permitted the use of shell-like frames which reduced aerodynamic drag. This resulted in the introduction of lightweight frames consisting of an outer shell of a composite material such as carbon fibre, with a foam inner core. Frames of the type just described are produced in a mould or mould set, in which the mounting points for the seat, head tube, crank assembly and rear wheel are fitted so that the mounting points are incorporated into the frame at the time of moulding. This means that different tooling is required for each athlete for whom a frame is being produced, resulting in expensive manufacturing costs. For wider commercial application of this type frame, a range of sizes equivalent to that as for the steel tube diamond-frame would be required. This necessitates a mould (or mould set) for each size produced and would result in an extensive and expensive range of tooling.

According to the present invention, there is provided a method of producin a bicycle frame of shell-like form, comprising the steps of producing a frame of shell like form without mountings for at least some from the group consisting of the cran assembly, the handlebar /front fork assembly, seat, and the rear wheel, and the installing said mountings at selected, but variable, positions within the frame.

In a preferred embodiment, mounting inserts for mounting th handlebar/front fork assembly and the crank assembly are incorporated into th frame by drilling through the walls of the frame or otherwise forming a hole throug the frame and inserting one or more tubular inserts into the hole thus formed.

Preferably, an insert for mounting the seat is fitted to an upwardly extendin part of the frame which can be reduced in length by cutting or the like in order t provide a required height from the seat to the crank axis.

Preferably, the frame defines opposed rear wheel stays which can be reduce in length by cutting or the like to receive inserts for carrying the axle of the rea wheel.

Preferably, the frame is formed from left and right half shells assemble together, with an insert between the half-shells in the rear part of the frame to for a closure which closes the interior of the shell from the rear, the insert preferabl having rear extensions which act to reinforce rearwardly-extending parts of the half- shells which act as the rear wheel stays.

According to another aspect of the invention, there is provided a bicycl frame when manufactured in accordance with the method defined above.

According to yet another aspect of the invention, there is provided a bicycl frame of shell-like form with structure which permits at least some of th handlebar /front fork assembly, the crank assembly, the seat, and the rear wheel t be mounted at variable positions within the frame.

Preferably, the frame is formed from at least two half-shells bonded or otherwise secured together. Although it is preferred for the two half-shells to enclose a hollow interior space, in alternative constructions the half-shells may enclose an interior core, for example of a lightweight foamed material.

Embodiments of the invention will now be described, byway of example only, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a shell-type frame in accordance with one embodiment of the invention; Figure 2 is a side view of the frame shown in Figure 1;

Figure 3 is a plan view of the frame shown in Figure 1;

Figure 4 is a view showing two half-shells and an insert prior to assembly;

Figure 5 is a schematic side view showing variable mounting zones for components of the bicycle; and Figure 6 is a side view of a bicycle incorporating the frame of Figures 1 to 5.

In accordance with the preferred embodiment of the invention, a shell-type frame 2 is produced without the mounting points for a head tube of the handlebar /front fork assembly, the crank assembly and rear wheel, the mounting points then being fitted in required locations to produce a bicycle of required size, the construction of the frame being such that the mounting points can be varied within predetermined areas.

As shown in the accompanying drawings, the frame 2 is produced from separate left and right half-shells 4,6 of substantially identical shape, the edges 4a, 6a of which are joined over a substantial part of the periphery of the two half -shells except at the rear part of the frame where rearwardly-projecting extensions 8,10 of the two half-shells 4,6 are spaced to define stays between which the rear wheel is inserted. The connection of the two half-shells 4,6 at their adjoining edges forwardly of the rearwardly projecting stays 8,10 results in a structure of box section of significant structural rigidity. An insert 12 of bifurcated shape is incorporated between the opposing shell surfaces at the rear part of the frame and comprises an

arcuate base part 14 and opposed rearwardly extending and divergent arms 16,18. When located between the half-shells 4,6 the arcuate base part 14 of the insert 12 extends between and connects the opposing inner surfaces of the two half-shells 4,6 and forms a rear closure for the two half-shells in the zone forwardly of the arcuate base part. The divergent arms 16,18 of the insert 12 contact, and reinforce, the opposed rear extensions 8,10 of the half-shells 4,6. The arcuate base part 14 also defines the rear wheel arch. The closing of the shell-type frame at the rear wheel arch by the base part 14 of the insert 12 provides the frame with substantial torsional stiffness and the arms 16,18 of the insert 12 provide the rear extensions 8,10 of the half-shells 4,6 and which constitute the rear wheel stays, with compressive and bending stiffness.

The two half-shells 4,6 and the insert 12 which constitute the three components of the frame are formed separately and are then united in a final assembly stage. The half-shells 4,6 and insert 12 can be produced from composite materials such as fibre reinforced resinous materials using appropriate moulding techniques and are then bonded together in the final assembly stage. More particularly, the half-shells 4,6 are of thin-walled structure of single or multi-layer construction comprising resin reinforced with carbon fibres, glass fibres, or aramid fibres, or a combination of two or more such fibres. Alternatively, the two half-shells 4,6 and the insert 12 can be pressed from thin sheet metal and assembled together by welding and/or mechanical fasteners. It is to be noted that, to this point in its manufacture, the frame is not produced with mountings for the head tube, crank assembly, seat, or rear wheel.

The resulting frame as illustrated in the drawings thus comprises a main body part 20 with a forwardlyprojecting box section beam 22 which receives at its forward end a fitting for receiving the head tube of the handlebar/front fork assembly. The lower part of the main body portion 20 forwardly of the rear wheel arch defined by base 14 of the insert 12 forms an area into which a mounting for the crank assembly is fitted. An upwards extension 24 of the main body part 20 defines a tubular support for receiving a mounting for the seat. After production of the basic three

- 5 - component shell frame just described, the mountings are then incorporated into the frame in order to adapt the frame to provide a bicycle of required size. The mountings for the head tube and crank assembly are formed by tubular inserts, the frame being drilled at the required locations to accept these inserts with the exact position of the inserts being varied at that time to suit the bicycle being manufactured. The upwards extension 24 for receiving the seat mounting is formed to the maximum length which will be required, with appropriate adjustment being made by cutting the extension 24 to the required height and then incorporating a seat tube or other appropriate insert for mounting the seat within the extension of required length. The various inserts are anchored within the frame by appropriate fastening techniques such as bonding or welding.

The rear wheel stays formed by the rear extensions 8,10 of the two half-shells 4,6 are to the maximum required length but can be reduced in length by cutting. With the rear wheel stays made to the required length, drop-out inserts for receiving the rear wheel axle can then be fitted into the rear end portion of the stays by forming appropriate cut-outs, inserting the inserts and securing, for example by bonding, welding, or by using mechanical fasteners.

Other inserts to locate components such as derailiers for gear change, brakes, and water bottles can be mounted to the frame where desired by drilling and then fixing the insert by bonding, welding, or by mechanical fasteners.

Figure 5 shows the frame schematically and the cross-hatched areas 30, 32, 34, 36 indicate the areas within which the primary mounting inserts for the head tube, crank assembly, seat, and rear wheel are fitted. More particularly, and with reference to a main datum axis A-A coincident with the axis of the upwards extension 24 for the seat, the insert in the forward beam part 22 of the frame for receiving the head tube can be fitted anywhere within the area 30 which has a length of about 140 mm and which may be considered to be formed by distances of 70 mm forwardly or rearwardly of a median axis B-B which is itself approximately 470 mm forwardly of the datum axis A-A The insert for the head tube does not need to be

parallel to the axis B-B and can be inclined by up to plus or minus 6 °C from that axis to suit the required configuration. The insert for the crank assembly can be fitted anywhere within the approximately oval area 32 which has a major axis of about 100 mm in length and a minor axis of about 80 mm with the centre being located substantially on the datum axis A-A and about 400 mm beneath the lowest point to which the seat extension 24 can be cut. The seat extension itself extends to about 250 mm above the lowest point thereby providing the possibility for significant variation in seat height as indicated by the area 34. The inserts forming the rear wheel drop-outs can be fitted within an area 36 extending to about 75 mm forwardly from the rear edge of the stays 8,10. It is to be noted that the structure of the frame is such that this variation can be accommodated without adversely affecting the structural strength of the frame.

Accordingly, in the manner described, a single shell-type frame can be used to produce a wide range of bicycle sizes without the need for a special mould or tooling for each size, thereby leading to significant reduction in the costs of manufacture for frames of this type. Although a single basic frame would not be suitable for all different types of bicycle such as track racing, road racing mountain, nevertheless for each type of bicycle produced only one basic set of moulds or tooling is required to produce the range of adult sizes.

In the embodiment described above the mountings for the crank assembly, handlebar/front fork assembly, seat, and rear wheel are each incorporated into the frame at a selected position after production of the frame and this provides maximum possibility for variation in the dimensions and set-up of the completed bicycle within the overall parameters of a given frame. However, as mentioned earlier, it is within the scope of the invention for only some of the mountings to be fitted after production of the frame itself. Thus, one or more of the mountings could be incorporated into the frame at the time of manufacture of the frame, for example by incorporating an appropriate insert into a mold within which the frame is produced. Although this will inevitably reduce the wide range of variations which can be accommodated within the frame after manufacture of the frame itself,

nevertheless substantial variation can still be achieved with the advantage of some cost saving. As a particular example of this, a tubular insert for the head tube can be incorporated in the frame in a fixed position at the time of molding or other manufacture of the frame; although the handle bar /front fork assembly will then be in a fixed position for all frames thus produced, significant adaption to meet customer requirements can still be achieved by varying the position of the other mountings within the frame after manufacture of the frame.

The invention is not restricted to shell-like frames formed from two half shells in the manner described. For example the two half shells could enclose an inner core of a lightweight foamed material. Alternatively, the outer shell could be formed in one piece around an inner core. In a further alternative the outer shell could be constituted by an outer reinforced skin of an inner core, with the entire composite structure being produced in a single moulding operation.

Modifications are possible within the scope of the invention.