GB2358841A

GB2358841A - Bicycle frame

Info

Publication number: GB2358841A
Application number: GB0002683A
Authority: GB
Inventors: Jon Frank Ross Whyte
Original assignee: ATB Sales Ltd
Current assignee: ATB Sales Ltd
Priority date: 2000-02-04
Filing date: 2000-02-04
Publication date: 2001-08-08
Anticipated expiration: 2020-02-04
Also published as: GB0002683D0; GB2358841B

Abstract

The frame (10) comprises two monocoque frame members (11, 12) which each have relatively angled first and second length portions (11a, 11b; 12a, 12b) and which are arranged with the first length portions (11a, 12a) extending substantially parallel to and at a spacing from one another and the second length portions (11b, 12b) extending divergently from one another. The frame further includes a head tube (13) connecting the frame members together at the free ends of the first length portions (11a, 12a), a seat tube (14) connecting the members together at the free ends of the second length portions (11b, 12b) and a bracket (15) connecting the members together intermediate those ends and serving as a component attachment point, e.g. for a rear wheel suspension spring and damper unit. The members (11, 12) are each comprised of two parts, pressed out from metal sheet, and welded along the length of the members.

Description

1 2358841 1 BICYCLE FRAME The present invention relates to a bicycle frame

and to a method of producing such a frame.

Traditionally, bicycle frames consist of a quadrilateral tubular structure composed of a short head tube for a front wheel steering assembly, straight top tube and down tubes connected with and extending, respectively, horizontally and downwardly from the head tube, and an inclined seat tube connected with the top and down tubes. Such a structure is relatively lightweight and rigid and is uncomplicated to produce by cutting from stock tubing.

With the advent of rear wheel suspension systems and a need to provide space for a suspension spring and damper unit, the conventionally shaped structure constructed from tubes has become less suitable. Moreover, the addition of necessary mountings for the suspension system and the forces transmitted to the frame by the action of the suspension have the result that the frame is heavier and less rigid. These considerations have led to development of new frame designs, one such design being based on an approximately Yshaped monocoque member with the head tube connected with the post of the Y and the seat tube with the free ends of the arms of the Y. The monocoque member is usually produced by separately pressing lefthand and righthand shells and welding the shells together along a centre plane of the frame. This form of frame is adequately lightweight and rigid, but has a tendency to function like a soundbox in use and amplify noise. In addition, it is less convenient to manufacture due to the large and awkward basic Y-shape, which does not lend itself to tessellation in sheet material, and imposes restrictions on the routing of control cables because of the bulkiness of the frame elements. Different tooling is also necessary for different frame sizes and the cost of tooling is further increased by the need to provide reinforcement flutes or ribs to resist bending of the monocoque section.

It is therefore the primary object of the invention to provide a bicycle frame suitable for use with rear suspension systems and free or largely free of at least some of the mentioned disadvantages of known frames. A subsidiary object is the provision of a frame production method which can tend itself to mass production and which allows scope for adaptation to different frame sizes without necessarily requiring different tooling.

2 Other objects and advantages of the invention will be apparent from the following description.

According to a first aspect of the invention there is provided a bicycle frame comprising two elongate monocoque frame members arranged with first length portions thereof extending substantially parallel to one another and second length portions thereof extending divergently from one another, and connecting means connecting the frame members together.

A frame embodying the present invention represents a relatively lightweight and rigid structure offering sufficient space for components of a rear suspension system and greater freedom for routing cables and also for the positioning of cable stops on undersurfaces so as to reduce susceptibility to damage and to minimise the risk of causing injury to a rider. The two monocoque frame members can be individually small in size by comparison with the single large-size Y-shaped monocoque member of known frames and consequently can dispense with stiffening flutes or ribs. Similarly, the small size of the individual frame members largely or entirely eliminates any soundbox effect and thus a bicycle incorporating the frame may be less noisy when ridden.

For preference, the first and second length portions of each frame member extend at an angle relative to one another. It is, however, possible for one of the frame members to be straight or, for example, for either or each of the frame members to have a straight first length portion and a curved second length portion.

The frame preferably comprises first connecting means connecting the frame members together at the free ends of the first length portions, for example a head tube for a front wheel steering assembly, and preferably also second connecting means connecting the members together at the free ends of the second length portions, for example a seat tube for a seat post. The monocoque members can thus be completed as a frame with the use of simple tube lengths of desired diameters.

In addition, a third connecting means is preferably present to connect the frame members together intermediate the free ends of their first and second length portions, preferably in the region of a junction of those length portions. The third connecting means, which can 3 be a bracket also serving for attachment of a component such as a spring and damper unit, enhances the rigidity of the frame and can act to distribute loads from a rear suspension system to the two monocoque frame members.

The first length portions of the frame members are, for preference, disposed at a spacing from one another. The spacing, if present, can be selected in dependence on the frame dimensions as indicated further below. The first and second length portions of each member preferably taper towards their free ends, so that the material mass and thus strength of the member is greater in the vicinity of the junction, where bending stress is concentrated, of the relatively angled length portions. The members themselves can each be formed from two parts joined together longitudinally of the member, preferably at sides of the member respectively facing towards and away from the other member. Each of the parts can be, for example, a metal pressing or stamping.

According to a second aspect of the invention there is provided a method of producing a bicycle frame as described above when each of the frame members is formed from two parts, the method comprising the steps of forming the parts of the frame members from sheet metal, joining the parts together to form the two frame members, disposing the frame members so that the first length portions thereof extend substantially parallel to one another and the second length portions thereof extend divergently from one another and connecting the frame members together by the connecting means.

The first length portions of the frame members can be disposed so as to be spaced apart by a predetermined amount dependent on a predetermined final height of the frame. Similarly, the first andlor second length portions can be shortened by a predetermined amou nt dependent on a predetermined final length of the frame. As a result, the same tooling can be used for frame component production regardless of eventual frame size and adjustments can be subsequently made to component spacing and lengths to adapt to different desired frame dimensions.

The parts of the frame members can, with advantage, be formed from tessellated regions of a single sheet of metal, which can result in an appreciable saving in material. The frame member parts, which have, for example, the shape of a flattened or shallow V, are capable of nesting together in a multiple chevron manner and corresponding regions of a sheet of metal can be allocated for multiple pressings or stampings of the parts. This 4 advantage is particularly marked in the case of a method for series frame production, as a single sheet can provide the material for the frame parts of several frames.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic elevation of a bicycle frame embodying the invention; and Fig. 2 is a cross-section, to enlarged scale, along the line 11-11 of Fig. 1.

Referring now to the drawings there is shown a bicycle frame 10 basically composed of two metallic monocoque frame members 11 and 12, a metallic head tube 13 for a front wheel steering assembly (not shown) and a metallic seat tube 14 for a seat post (also not shown). The frame member 11 comprises a relatively angled first length portion 11 a and second length portion 11 b, which include a large obtuse angle in the vicinity of 140 to 1500. The length portions 1 la and 1 lb taper towards their free ends and are connected at those ends with, respectively, the head tube 13 and seat tube 14, preferably by welding. The frame member 12 similarly comprises a relatively angled first length portion 12a and second length portion 12b, which are shaped and connected in similar manner to the length portions 11 a and 11 b of the member 11. A tubular mounting element for a sprocket and pedal crank drive assembly is disposed at the lower end of the seat tube 14.

As evident from Fig. 1, the frame members 11 and 12 are arranged with the first length portions 11 a and 12a extending at a spacing from and approximately parallel to each other and the second length portions 11 b and 12b extending divergently from one another. The frame members are additionally connected together by a U-section bracket 15 which is located in the region of the junctions of the length portions of the members and which additionally serves as an attachment point for a spring and damper unit 16 of a rear wheel suspension (shown only partially). The bracket 15 can be connected to the two frame members by welding.

The frame member 11 is formed from two halves 11 A and 11 B (Fig. 2) which are pressed from sheet metal, such as aluminium, and joined together by welding longitudinally of the member along its top and bottom sides, in particular in a plane S of symmetry of the frame. The frame member is formed from two halves 12A and 12B (Fig. 2) produced and joined together in similar manner. The lower frame member 12, which in the completed frame may be subjected to greater loads than the upper frame member 11, is deeper in crosssection than the member 11. As can be seen from Fig. 2, each member has a cur ved top wall, a flat bottom wall and flat side walls at right angles to the bottom wall, the junctions of the bottom wall and side walls being radiussed. possible.

Other cross-sectional shapes are Locating points 17 for control cables are provided at the undersides of the two frame members 11 and 12, the cable runs thus being able to be routed in locations with reduced exposure to damage.

A frame embodying the invention as described above can be produced in simple manner by pressing out the halves 11 A, 11 B, 12A and 12B for the frame members of the frame and additionally for the frame members of further frames from a single sheet of suitable gauge aluminium or other preferred metal or metal alloy. The section depths of the halves can be selected in accordance with the desired bending strength of the finished members and the lengths of the halves can be selected to be oversize with respect to the intended final lengths of the frame members. The shallow or flattened 'V' shapes of the frame member halves allow a considerable number to be produced from a single sheet of material by assignment, to the halves, of respective regions of the sheet which adjoin one another in a multiple chevron arrangement. Various other arrangements are possible, the flattened 'V' shapes being capable of tessellation in a sheet format in different ways still with optimum use of the sheet material.

The pressed-out frame member halves can then be welded together, in the manner previously described, to form the individual frame members 11 and 12 or pairs of such frame members. The members, if produced oversize in length in relation to the intended frame size, are trimmed to the appropriate length and connected together, by welding, by the tubes 13 and 14 and bracket 15 to form the complete frame, with the length portions 11 a and 12a of the frame members disposed at a mutual spacing also dependent on the frame size. Consequently, adjustments in frame size are achieved in the assembly stage rather than the pressing stage and a single tool can be employed for the pressing step. The connecting process can be carried out with use of a suitable jig. The order of connecting of the tubes 13 and 14 and bracket 15 and the stage at which the frame members are trimmed in length prior to final welding can be varied as desired.

6 The finished frame has an advantageous strength-to-weight ratio and is compatible with typical space requirements for rear suspension systems. It can be completed into a bicycle by fitment of usual sub-assemblies and components, including brake and gear cable runs employing the locating points 17.

7

Claims

1. A bicycle frame comprising two elongate monocoque frame members arranged with first length portions thereof extending substantially parallel to one another and second length portions thereof extending divergently from one another, and connecting means connecting the frame members together.

2. A frame as claimed in claim 1, wherein the first and second length portions of each frame member extend at an angle relative to one another.

3. A frame as claimed in claim 1 or claim 2, comprising first connecting means connecting the frame members together at the free ends of the first length portions.

4. A frame as claimed in claim 3, wherein the first connecting means comprises a head tube for a front wheel steering assembly.

5. A frame as claimed in any one of the preceding claims, comprising second connecting means connecting the frame members together at the free ends of the second length portion.

6. A frame as claimed in claim 5, wherein the second connecting means comprises a seat tube for a seat post.

7. A frame as claimed in any one of the preceding claims, comprising third connecting means connecting the frame members together intermediate the free ends of the first and second length portions.

8. A frame as claimed in claim 7, wherein the third connecting means connects the frame members together in the region of a junction of the first and second length portions of each member.

9. A frame as claimed in claim 7 or claim 8, wherein the third connecting means comprises a bracket for attachment of a component.

8 11. A frame as claimed in any one of the preceding claims, wherein the first and second length portions of each frame member taper towards their free ends.

12. A frame as claimed in any one of the preceding claims, wherein each of the frame members is formed from two parts joined together longitudinally of the member.

13. A frame as claimed in claim 12, wherein the two parts of each frame member are joined together at a side thereof facing towards and a side thereof facing away from the respective other frame member.

14. A frame as claimed in claim 13, wherein each of the parts is a metal pressing or stamping.

15- A bicycle frame substantially as hereinbefore described with reference to the accompanying drawings.

16. A bicycle comprising a frame as claimed in any one of the preceding claims.

17. A method of producing a bicycle frame as claimed in claim 12, comprising the steps of forming the parts of the frame members from sheet metal, joining the parts together to form the two frame members, disposing the frame members so that the first length portions thereof extend substantially parallel to one another and the second length portions thereof extend divergently from one another and connecting the frame members together by the connecting means.

18. A method as claimed in claim 17, wherein the step of disposing comprises spacing the first length portions of the frame members apart by a predetermined amount dependent on a predetermined final height of the frame.

19. A method as claimed in claim 17 or claim 18, comprising the step of shortening the first length portions of the frame members by a predetermined amount dependent on a predetermined final length of the frame.

9 20. A method as claimed in any one of claims 17 to 19, comprising the step of shortening the second length portions of the frame members by a predetermined amount dependent on a predetermined final length of the frame.

21. A method as claimed in any one of claims 17 to 20, wherein the parts of the frame members are respectively formed from tessellated regions of a single sheet of metal.

22. A method of producing a plurality of bicycle frames each by a method as claimed in any one of claims 17 to 21, wherein the parts of the frame members of all the frames are respectively formed from tessellated regions of a single sheet of metal.

23. A method as claimed in claim 17 and substantially as hereinbefore described with reference to the accompanying drawings.

Amended claims have been filed as t'ollows 1. A bicycle frame comprising two elongate monocoque frame members which are arranged with first length portions thereof extending in substantially the same direction and second length portions thereof extending divergently from one another and which are separately fabricated from individual parts to each form a respective load-bearing hollow body, and connecting means connecting the frame members together.

3. A frame as claimed in claim 1 or claim 2, wherein the connecting means comprises first length portion connecting means connecting the frame members together at the free ends of the first length portions.

4. A frame as claimed in claim 3, wherein the first length portion connecting means comprises a head tube for a front wheel steering assembly.

5. A frame as claimed in any one of the preceding claims, wherein the connecting means comprises second length portion connecting means connecting the frame members together at the free ends of the second length portions.

6. A frame as claimed in claim 5, wherein the second length portion connecting means comprises a seat tube for a seat post.

7. A frame as claimed in any one of the preceding claims, wherein the connecting means comprises intermediate connecting means connecting the frame members together intermediate the free ends of the first and second length portions.

8. A frame as claimed in claim 7, wherein the intermediate connecting means connects the frame members together in the region of a junction of the first and second length portions of each member.

9. A frame as claimed in claim 7 or claim 8, wherein the intermediate connecting means comprises a bracket for attachment of a component.

10. A frame as claimed in any one of the preceding claims, wherein the first length portions of the frame members are spaced from one another.

11. A frame as claimed in any one of the preceding claims, wherein the first and second length portions of each frame member taper towards their free ends.

12. A frame as claimed in any one of the preceding claims, wherein the parts from which each of the frame members is fabricated comprise two parts joined together longitudinally of the member.

15. A bicycle frame substantially as hereinbefore described with reference to the accompanying drawings.

16. A bicycle comprising a frame as claimed in any one of the preceding claims.

17. A method of producing a bicycle frame as claimed in claim 12, comprising the steps of forming the parts of the frame members from sheet metal, joining the parts together to form the two frame members, disposing the frame members so that the first length portions thereof extend in substantially the same direction and the second length portions thereof extend divergently from one another and connecting the frame members together by the connecting means.

X 2- 19. A method as claimed in claim 17 or claim 18, comprising the step of shortening the first length portions of the frame members by a predetermined amount dependent on a predetermined final length of the frame.

20. A method as claimed in any one of claims 17 to 19, comprising the step of shortening the second length portions of the frame members by a predetermined amount dependent on a predetermined final length of the frame.