GB1593987A

GB1593987A - Bicycle frame and frame and front fork combination

Info

Publication number: GB1593987A
Application number: GB50565/77A
Authority: GB
Original assignee: Vereinigte Metallwerke Ranshoffen Berndorf AG
Current assignee: Vereinigte Metallwerke Ranshoffen Berndorf AG
Priority date: 1976-12-07
Filing date: 1977-12-05
Publication date: 1981-07-22
Also published as: SE7713829L; DK540477A; NL7713464A; DE2753432A1; ES464879A1; AT370371B; FR2373436B3; ATA903876A; BE861524A; NO774146L; NO802071L; FR2373436A1

Description

(54) BICYCLE FRAME AND FRAME AND FRONT FORK COMBINATION (71) We, VEREINIGTE METALL WERKE RANSHOFEN-BERNDORF AKTIENGESELLSCHAFT, a body corporated organised and existing under the laws of Austria, of 5282 Braunau am Inn Ranshofen, Austria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a bicycle frame and to a bicycle frame and front fork in combination.

In a conventional bicycle, the front wheel mounting fork, and the frame are made from seamless steel tubes and connecting lugs into which the steel tubes are brazed.

The steel tubes are generally of small dimensions, in the region of from 24 to 26 mm in diameter, but in spite of these dimensions such a bicycle suffers from relatively high weight besides being liable to rust.

A frame construction has therefore been proposed, which, using tubes of approximately the same outside dimensions, provides connecting lugs and tubes, of light metal or alloy. As it is not possible to fix the tubes and lugs together by brazing, for considerations concerning mechanical strength and corrosion, the tubes are screwed into the lugs by means of fine screw threads. In order to some extent to compensate for the weakening effect caused by cutting the screw threads in the tubes, the tubes are strengthened in the region of the connecting positions of tubular sleeves which are pushed into the tubes, this therefore giving rise to a further considerable amount of work and an increase in weight. In addition, such a bicycle does not have the necessary strength of the steel construction, so that the frame tends to flex when under load.

According to one aspect of the invention, there is provided a bicycle frame comprising light metal or light alloy tube members each connected to a respective fixing lug, wherein each tube member is connected to the respective lug by means of a twocomponent adhesive resin, and wherein the frame tube members include a seat tube member and at least one down tube member, with the external diameter of the down tube and seat tube members being at least 30 millimetres.

According to another aspect of the invention there is provided such a bicycle frame in combination with a front fork comprising light metal or light alloy tube members each connected to a respective fixing lug, wherein each fork tube member is connected to the respective lug by means of a two-component adhesive resin, and wherein the fork tube members have, at the region thereof connected to the respective fixing lug, an oval cross-section with a largest dimension of at least 30 millimetres or a round cross-section with a largest diameter of at least 25 millimeters.

A bicycle frame and front fork according to the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a side view of a frame according to the invention, and Figure 2 shows a front wheel fork for the Figure 1 frame.

Referring to Figure 1, the primarily loaded part of a bicycle frame, namely the triangular main frame assembly, is formed from hollow tube members 7, 8 and 9 of light metal or light alloy, namely an optional horizontal tube 7 or cross-bar, a down tube 8 and a seat tube 9, which at their ends are inserted into and secured in fixing lugs in the form of socket sleeves as indicated at 1, 2, 3, 4 and 5, exclusively by means of a twocomponent adhesive resin. Lugs 1 and 2 are part of the frame steering head, lugs 3 and 4 are part of the bottom bracket, and lug 5 is part of a seat pillar mounting bracket. The tubes 7 to 9 are in the form of seamless drawn extrusions, while the members providing lugs 1 to 5 may be in the form of castings, forgings or die-castings or they may comprise structures which are welded together from pressed sheet metal parts or tubes. Preferably hardenable eloxadizable alloys of the AlMgSi or AlMgZn type are used. The eloxation operation not only provides a decorative surface protection, but also provides a good bonding surface for the adhesive although a satisfactory bonding surface can also be produced by a chemical preliminary treatment such as etching or pickling. A suitable bonding surface is essential to achieve the mechanical strength of the adhesive joint, and such a surface is produced when the relationship between the lengths of bonding or adhesive coated surface at the tube ends, and the diameter of the tubes, is at least 0.3:1 at positions 1 and 2 and at least 0.25:1 at positions 3, 4 and 5.

The external diameter of the tubes of the frame is at least 28 mm as regards the tube 7 and at least 30 mm as regards the tubes 8 and 9. In the event that the socket sleeves have a profiled edge or outline the ratio between the mean value of the sum of all the individual adhesive coated tube member length of bonding surfaces of the tubes, and the diameter of the tube is at least 0.3:1 at positions 1 and 2 and at least 0.12:1 at positions 3, 4 and 5. Reference 15 denotes the bracket for receiving a saddle-mounting pillar, while reference 16 denotes a lug of the bottom bracket to which the bottom stays of the rear wheel mounting sub-frame are secured e.g. also by adhesive. The other stays of the rear wheel mounting sub-frame are also secured to appropriate sockets on bracket 15, as by adhesive.

Reference will now be made to Figure 2 showing a front fork for use in combination with the Figure 1 frame. The fork comprises a pair of fork legs 11 secured by adhesive to a crown bracket providing two fixing lugs 13 and carried by a steering column or pillar 12. The crown bracket 13 and pillar 12 are preferably made in one piece as by casting, to avoid further joints. The fork is made in a similar manner to the Figure 1 frame, the fork legs 11 being made of light metal or light alloy tube of circular or oval crosssection, or a section varying along the length of the legs 11. The legs 11 are fixed in the lugs in the bracket 13 by adhesive, at position 14. The relationship between the adhesive lengths i.e. the length of bonding surface on the tubes of legs 11, and the largest dimension of the cross-section of the fork legs 11 is at least 0.3:1, at position 14, while the largest dimension of the crosssection of the fork leg 11, when the tube is of oval cross-section, is at least 30 mm, at position 14, and at least 25 mm when the leg is a round cross-section. As indicated above, the term adhesive length is intended to mean the length of tube which is pushed into the sleeve or socket of the lug and secured by adhesive therein. When a profiled edge is used on the lugs of the crown bracket 13, the relationship between the mean value of the sum of all the individual adhesive coated tube lengths and the largest dimension of the cross-section of the fork leg 11, is at least 0.15:1, at the position 14.

The adhesive used for the frame and fork described above is preferably a twocomponent Araldite (Registered Trade Mark) metal adhesive AW 136 and hardener HY 994 produced by Ciba-Geigy, which provides a satisfactory degree of strength over a prolonged working life and at a temperature of up to 800C. Solidification of the adhesive occurs, after cooling of the adhesive joint, subsequent to the curing operation.

Various modifications may be made.

without thereby departing from the scope of the invention as defined by the appended claims. For example, instead of external socket sleeves i.e. lugs as shown which provide recesses into which the tubes are inserted, it is alternatively possible to use lugs with internal sleeves which are pushed into the tubes and secured therein by adhesive. Also, other components such as the steering column 12 and a handlebar (not shown) can be made from light metal or alloy tube with sleeve connections, and likewise the mounting lugs for the front and rear wheel spindles may be secured by adhesive joints. Further, although the Figure 1 frame has a horizontal cross bar 7, this may be omitted to form a frame for a ladies' bicycle, a second down tube extending between lug 1 and the seat tube 9 at a position spaced along the tube 9 from the lug 4.

It will be appreciated that a conventionally built fork i.e. built by brazing, may be used on the abovedescribed frame according to the invention.

The use of a high-strength adhesive makes it possible to produce a light-weight connection which reduces the amount of work involved in building the frame or frame and fork and which is capable of withstanding the loadings which occur thereon, if it is ensured that the adhesive surfaces are of certain minimum dimensions. As the tubes are of larger outside dimensions than previous conventional steel frame and fork members, the larger outside dimensions provide a degree of rigidity which is virtually equivalent to that of the conventional steel bicycle frame, while the bicycle is substantially lighter due to the low specitic weight and wall thickness of the light metal or light alloy members.

WHAT WE CLAIM IS: 1. A bicycle frame comprising light metal or light alloy tube members each connected to a respective fixing lug, wherein each tube member is connected to the respective lug by means of a two-component adhesive resin, and wherein the frame tube members include a seat tube member and at least one down tube member, with the external diameter of the down tube and seat tube members being at least 30 millimeters.

2. A bicycle frame according to claim 1, wherein the frame tube members include a horizontal tube member with the external diameter thereof being at least 28 millimeters.

3. A bicycle frame according to claim 1 or claim 2, wherein the seat tube member, the down tube member and the horizontal tube member, when present, are secured together in a triangular configuration by fixing lugs at the steering head, bottom bracket and seat pillar mounting bracket, and wherein the ratio between the lengths of tube member secured to the respective lugs and the diameter of the tubes is at least 0.3:1 at the connections between the horizontal and down tube members and the steering head lugs, and at least 0.25:1 at the connections between the down tube, the seat tube and the horizontal tube members, and the bottom bracket lug and the seat pillar mounting lug respectively.

4. A bicycle frame according to claim 3, wherein the lugs have profiled edges, the ends of the tube members also have a profiled edge, and the ratio between the mean value of the sum of all the individual adhesive coated tube member lengths secured to the respective lug and the diameter of the tube member is at least 0.3:1 at the connections between the horizontal and down tube members and the steering head lugs, and at least 0.12:1 at the connections between the down tube member, the seat tube and the horizontal tube members, and the bottom bracket lug and the seat pillar mounting lug respectively.

5. A bicycle frame substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

6. A bicycle frame according to any one of claims 1 to 5 in combination with a front fork comprising light metal or light alloy tube members each connected to a respective fixing lug, wherein each fork tube member is connected to the respective lug by means of a two-component adhesive resin, and wherein the fork tube members have, at the region thereof connected to the respective fixing lug, an oval cross-section with a largest dimension of at least 30 millimeters or a round cross-section with a largest diameter of at least 25 millimeters.

7. The combination according to claim 6, wherein the fork comprises a pair of leg tube members each secured to a respective lug of a crown bracket providing the two lugs, the lugs having an oval or round crosssection at least in their region in which they are connected to the lugs of the crown bracket and the ratio between the adhesive coated leg tube length secured to the crown lug by adhesive and the largest dimension of the cross section of the fork leg is at least 0.3:1 at the connection to the crown lug, the largest dimension of the cross section of the fork leg being at least 30 mm, when the leg has an oval cross-section, at said connection, and at least 25 mm when the leg has a round cross-section, at said connection.

8. The combination according to claim 7, wherein the crown lug has profiled edges and the ends of the fork legs also have profiled edge, the ratio between the mean value of the sum of all the individual adhesive coated leg tube lengths secured in the crown lug, and the largest dimension of the cross section of the fork leg being at least 0.15:1 at said connection.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. substantially lighter due to the low specitic weight and wall thickness of the light metal or light alloy members. WHAT WE CLAIM IS:

1. A bicycle frame comprising light metal or light alloy tube members each connected to a respective fixing lug, wherein each tube member is connected to the respective lug by means of a two-component adhesive resin, and wherein the frame tube members include a seat tube member and at least one down tube member, with the external diameter of the down tube and seat tube members being at least 30 millimeters.