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Patent Searching and Data


Title:
BICYCLE FRAME
Document Type and Number:
WIPO Patent Application WO/2010/125356
Kind Code:
A1
Abstract:
The present invention proposes a bicycle frame for interconnecting a head tube and a seat tube of a bicycle. In one embodiment, the bicycle frame has connecting members which each comprise an outer tube and an inner tension member within the outer tube. The connecting members are each connected to a fastening which is attachable to the head or seat tube, with the outer tube abutting the fastening and the tension member being secured to the fastening in a way that applies a tensile force to the tension member. Thus, the tension members of the connecting members act to pull the parts of the frame together, which is resisted by the outer tubes so that those outer tubes are under compression. Alternatively, the bicycle frame may comprise trusses radiating from a central hub, each truss comprising two tubes and crossed tension members between the tubes. In another aspect of the invention the bicycle frame comprises a plurality of clamps, each clamp having a collar arranged to extend around the head tube or seat tube to be detachably clamped thereto.

Inventors:
MOULTON, Alexander, Eric (The Hall, Bradford-on-Avon, Wiltshire BA15 1AH, GB)
Application Number:
GB2010/000870
Publication Date:
November 04, 2010
Filing Date:
April 29, 2010
Export Citation:
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Assignee:
MOULTON DEVELOPMENTS LIMITED (The Hall, Bradford-on-Avon, Wiltshire BA15 1AH, GB)
MOULTON, Alexander, Eric (The Hall, Bradford-on-Avon, Wiltshire BA15 1AH, GB)
International Classes:
B62K3/08; B62K15/00; B62K19/00
Foreign References:
US20070273125A12007-11-29
US1428496A1922-09-05
US4577879A1986-03-25
US0591306A1897-10-05
US4813696A1989-03-21
DE45032C
EP0034864A21981-09-02
US3448997A1969-06-10
DE98421C
GB2130981A1984-06-13
USD535588S2007-01-23
US6012733A2000-01-11
Other References:
None
Attorney, Agent or Firm:
MEWBURN ELLIS LLP (33 Gutter Lane, London EC2V 8AS, GB)
Download PDF:
Claims:
Claims

1. A bicycle frame arranged to interconnect a head tube and a seat tube of a bicycle, the bicycle frame having a plurality of connecting members, each connecting member comprising an outer tube and an inner tension member within the outer tube, and each connecting member having a first end connected to a fastening adapted for attachment to the head tube or seat tube such that the outer tube abuts the fastening and the tension member is secured to the fastening, and each connecting member having a second end at which the tension member is connected to the outer tube, whereby the tension member is under a tensile force and the outer tube is under a corresponding compressive force by the forces applied to the outer tube due to the tensile force of the tension member.

2. A bicycle frame according to claim 1, wherein each fastening comprises a clamp having a collar arranged to extend around the head tube or seat tube to be detachably clamped thereto .

3. A bicycle frame according to claim 1 or claim 2, including a central hub, the connection of tension member and outer tube at the second end of each connecting member being via a connection to the central hub, whereby the outer tube abuts the central hub and the tension member is secured to the central hub.

4. A bicycle frame assembly including a bicycle frame according to claim 3 , and a head tube and a seat tube of a bicycle, wherein: one or more of the fastenings is attached to the head tube; one or more of the fastenings is attached to the seat tube; and the connecting members are arranged to form a plurality of trusses, each truss connecting the central hub with one of the plurality of fastenings, and each truss comprising two connecting members spaced apart at their second ends in a direction which is transverse to a plane formed by the longitudinal directions of the head and seat tubes.

5. A bicycle frame assembly according to claim 4, wherein the connecting members are arranged to form two trusses connecting the central hub with different positions along the seat tube, and two trusses connecting the central hub with different positions along the head tube.

6. A bicycle frame assembly according to claim 4 or claim 5, wherein the connecting members of one or more of the plurality of trusses are spaced apart in the transverse direction at their first ends such that a distance in the transverse direction between the first ends of the connecting members is smaller than a distance in the transverse direction between the second ends of the connecting members.

7. A bicycle frame assembly according to claim 4 or claim 5, wherein, in one or more of the plurality of trusses, the central axes of the connecting members intersect one another at the central axis of the head tube or seat tube.

8. A kit of parts for assembly of a bicycle frame, including: a head tube for mounting handlebars; a seat tube for mounting a seat; four pairs of outer tubes, and four pairs of tension members for mounting within the outer tubes; four fastenings, including two fastenings adapted for attachment to the head tube and two fastenings adapted for attachment to the seat tube, each fastening having securing means for securing first ends of a respective one of the pair of tension members, and each being adapted to abut first ends of one of the pairs of outer tubes with a secured tension member within each outer tube; and a central hub having securing means for securing second ends of each of the pairs of tension members, and being adapted to abut second ends of each of the pairs of outer tubes with a secured tension member within each outer tube.

9. A bicycle frame assembly including a head tube and a seat tube interconnected by a central hub, and a plurality of trusses, each truss comprising two tubes, each tube having a first end abutting the central hub and a second end connected to the seat tube or head tube, the tubes of each truss being spaced apart in a direction which is transverse to a plane formed by the longitudinal directions of the head and seat tubes, and each truss comprising two tension members arranged in a cross configuration such that each tension member extends from an end of one of the tubes to an opposite end of the other of the tubes, the tension members each being held under a tensile force such that the outer tubes are held under a corresponding compressive force.

10. A bicycle frame assembly according to claim 9, including two trusses connecting the central hub with different positions along the seat tube, and two trusses connecting the central hub with different positions along the head tube.

11. A bicycle frame according to claim 9 or claim 10, including a plurality of clamps, each clamp having a collar arranged to extend around the head tube or seat tube to be detachably clamped thereto, wherein in each truss the second end of each tube abuts one of the plurality of clamps.

12. A bicycle frame according to any of claims 9 to 11, wherein, in each truss, a distance in the transverse direction between the first ends of the connecting members is smaller than a distance in the transverse direction between the second ends of the connecting members.

13. A bicycle frame assembly including a seat tube and a head tube interconnected by a frame comprising a plurality of connecting members, the frame being connected to the seat tube and the head tube by a plurality of clamps, each clamp having a collar extending around the head tube or seat tube so that it is detachably clamped thereto.

14. A bicycle frame assembly according to claim 14, wherein the frame is connected to the seat tube by two clamps arranged at different positions along the seat tube and is connected to the head tube by two clamps arranged at different positions along the head tube .

Description:
BICYCLE FRAME

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention is concerned with bicycle frames, preferably bicycles with a frame structure of the open type, rather than the conventional quadrilateral frame. Such open frames are particularly, but not exclusively, appropriate for an adult bicycle with wheels of 20" diameter or less. However, the present invention is applicable to bicycles with larger wheels, and with other types of frames than those of the open type. Note that, in this specification, the term "frame" is used to refer to those parts of the structure connecting the head and seat tubes, as part of the overall structure of the bicycle itself, rather than to refer to that overall structure.

SUMMARY OF THE PRIOR ART

In a conventional frame, either a quadrilateral or open type, it is usual for the head and seat tubes to be connected by frame tubes, which are permanently secured to the head and seat tubes by brazing, welding, adhesives etc. The present invention seeks an alternative way of forming the structure which secures together the head and seat tubes to form the frame . SUMMARY OF THE INVENTION

According to a first aspect, at its most general, the present invention proposes that a bicycle has head and seat tubes which are interconnected by connecting members which comprise an outer tube and an inner tension member within the outer tube. The connecting members are connected to fastenings on the head or seat tubes, with the outer tubes abutting the fastening and the tension member being secured to the fastening (e.g. by a threaded engagement) in a way that applies a tensile force to the tension member. Thus, the tension members of the connecting members act to pull the parts of the frame together, which is resisted by the outer tubes so that those outer tubes are under compression.

Preferably, the connecting members are arranged to form trusses which radiate from a central hub to the head and seat tubes . Each truss preferably comprises two connecting members spaced apart in a direction generally perpendicular to the longitudinal direction of the head and seat tubes. Each truss is stiff in its plane, and the torsional stiffness of the frame then arises from that in-plane stiffness of the trusses . The ends of the connecting members of each truss are spaced apart, at the hub and at the head or seat tube, so that the truss may be considered to form a shear web or flange.

Thus, for example, there may be four such trusses extending from a central hub, two to the head tube and two to the seat tube, to form an X- frame. Note that the spacing between the connecting members of the truss secured to a lower part of the seat tube (normally adjacent the bottom bracket) has to be greater at the attachment to the lower part of the seat tube than the spacing between the connecting members of the trusses which extend to an upper part of the seat tube and to the head tube, at the attachment to the head and seat tube. This is because the truss which extends to a lower part of the seat tube experiences more torsion when the user applies torsion to the handlebars when seeking to cycle quickly.

It should be noted that although there are preferably two connecting members in each truss, as discussed above, the present invention does not exclude the possibility that there is a single connecting member in each truss, or more than two connecting members.

The X- frame structure thus created provides torsional stiffness to the frame about a fore and aft axis, as well as the in-plane stiffness of each truss. Moreover, the X-shape of the frame provides torsional stiffness in the vertical plane with the frame acting as a shear web. Since each truss is stiff in its plane, and the resulting structure resists twisting particularly about the longitudinal axis of the main frame, thus giving the desired feel to the frame for the rider under the alternating loads applied as the rider thrusts on the pedals to propel the bicycle. Similarly, the vertical stiffness resists the load of the rider's weight. Finally, if the rider pulls back the handle bars, the resulting twisting of the head tube is resisted by the stiffness of the trusses.

As mentioned above, the connecting members of the frame need themselves to be connected to head and seat tubes. Preferably, connecting members are connected to the head and seat tubes by clamps, although it is also possible to use lugs brazed to the head and seat tubes. The clamps are releasable, allowing the frame to be detached from the head and seat tubes . It is preferable for there to be a single clamp for each truss, with the spacing between the connecting members of that truss at the head or seat tube being defined by clamps and the location of the connecting members to those clamp.

The tension member of each connecting member may be a metal rod corresponding to the spoke of a bicycle wheel. The term "spoke" will be used for such tension members in the following description. Thus, each spoke may be spigoted into the corresponding fastening and held thereto by a screw head at each end or a cap on one end of the spoke, in a similar manner to the securing of a spoke in a bicycle wheel. A similar arrangement may be used to secure the trusses to the hub, with the end of the connecting member remote from the fastening spigoting into a corresponding structure in the hub and held thereto by a screw head or cap. Note that if there is a screw head at the fastening there should be a cap at the hub and vice versa. The preferred arrangement is for the cap to be at the end of the truss adjacent the head and seat tube and the screw head to be at the hub. In the first aspect of the invention described above, connecting members are used which comprises an outer tube and an inner tension member. However, it is also possible to make the frame by using trusses radiating from a central hub, each of which trusses comprises two tubes and crossed tension members between the tubes. In such and arrangement, tension members extend from one end of a tube to the opposite end of the other tube. The two or more tubes, and the cross tension members, define the plane of the truss. This arrangement using tubes and crossed tension members is second, independent aspect of the present invention.

Again, this provides torsional stiffness to the frame, particularly when they are used to form an X- shape from a central hub. They each define a shear web, in a similar way to the trusses of the first aspect. Again, each truss is stiff in its plane, and the torsional stiffness of the frame then arises from the in-plane of the stiffness of the trusses. Moreover, it is again important that the trusses have a suitable width at the hub, and at their connections to the head and seat tubes. The truss which extends to a lower part of the seat tube may have to be wider at its connection to that seat tube than the other trusses are at their connections to the head and seat tubes, for the reasons discussed above.

Effectively, apart from using tension members external to the tubes, rather than internal of them, this aspect of the invention may be similar to the first aspect, and incorporate similar preferred features. The trusses may be connected to the head and seat tubes by clamps and the tension members may be a metal rod corresponding to the spoke of a bicycle wheel. Thus spokes may then be spigoted into the clamp, or other fastening, although the configuration of those spigots for the second aspect will have to be slightly different from that of the first aspect, in order to ensure that the spokes are crossed.

Thus, for a bicycle frame preferably of the open type, a form of 'space frame' construction is proposed, with all members of that * space frame' being essentially straight. The structure may thus comprise four trusses radiating from a central hub, the axis of which is transverse. Each shaft preferably comprise a flange at each edge. Each truss viewed in its flat plane tapers from its widest width at the hub in a triangle with the apex at the outer ends of the truss, or tapering in a trapezoidal shape with the width of the trapezoid being wider at the hub than at the outer ends of the trusses. The outer ends of the trusses may then terminate at the clamps on the head and seat tubes respectively. The span between the clamp except the head and seat tubes are as wide as possible to maximise the stiffness of the whole structure in the torsional sense about a fore and aft axis of the frame . The flanges of each truss may thus comprise tubes of relatively small diameter, which are maintained in compression by the action of pre-tensioned spokes which are located either inside the tubes (as in the first aspect) or externally in a cross form in or near to the plane of the truss (as in the second aspect) . The pre- tensioning of the spokes provides a load in excess of the tension or compression which the flanges experience under the varying loading of the frame so that at all times the tubes remain firmly seated, with one end in the hub and the other end in the clamp or other fastening.

There are then two manifestations of the resulting space frame construction. First is in which the trusses are fully triangulated in their plane with the apex of the triangle falling on the axial center line of the head and seat tubes respectively. In such as arrangement, no zig-zag shear members between the two flanges of the truss are needed to maintain shear stability in the plane of the truss . This corresponds to the first aspect of the invention, using spokes within tubes. The other manifestation is one in which the trusses each taper but are not truly triangulated, with the pretension spokes being outside the tubes (flanges) , which spokes are crossed and attached by screwing at one end (preferably at the hub end) and capped at the other end at the clamps or other fastenings to the head and seat tubes. In this way, the component of the force from the pre-tension spokes is sufficient to hold the tubes under compression in location under the alternating working loads on the frame. The pre-tensioning also eliminates back- lash from these loads. With either of these two constructions, the need for conventional welding/braising is avoided, allowing free choice of material, and minimising the skill levels for manufacture, etc. It may also be noted that the first and second aspects may be used in combination, by applying pretension spokes outside the tubes, as well as within them. Those spokes outside the tubes are crossed, as in the second aspect, and apply pre-compression to the tubes which are also pre-comprised by the spokes within the tubes, as in the first aspect. Thus the flanges of each truss may comprise tubes which are maintained under compression by the action of pre- tension spokes which are located both inside the tubes and externally in a cross form in or near to the plane of the truss. The crossed spokes provide additional stiffening in the plane of the truss, which may in some cases by desirable.

As mentioned above, in both the first and second aspects, it is preferable that the trusses are connected to the head and seat tubes by clamps. In fact, the use of clamps to hold together parts of a bicycle frame is a third, independent, aspect of the present invention. It may be used with other interconnection of those described in the first and second aspects. However, if the frame is clamped to the head and seat tubes, it may be connected thereto and disconnected therefrom by securing or releasing the clamps, to allow the bicycle to be assembled or dis-assembled.

The present invention offers the following advantages : a) to allow the assembly of the complete frame without the need for conventional brazing, welding, adhesive bonding or integral moulding, press forming etc. b) allows the use of any material for the head tube and seat tube and indeed for the tubes of the connecting members themselves but using spokes as members which are screwed at one end and capped at the other. c) the method of assembly is simply the insertion of the tubes at the hub and at the fixtures and threading the spoke from the hub to the aperture in the fixtures at the head tube and the seat tube; and then tightening the screwed nipple head on the spoke with a torque limiting key which can be a familiar power operated one. This is preferably done at the hub, and pre- tensions the whole frame . d) the apex of the triangle or quadrilateral of the trusses is at the axis of the head and seat tube respectively, and thus eliminates the need for the familiar zig-zags to take shear loads. Instead the alternating loads are simply tension and compression in the trusses . These loads are induced by forces from handlebar to pedals and the resistance constitutes the torsional stiffness of the frame. e) this elimination of the need for zig zags removes the need for fixing thereof to tubular members . Also it allows free access in the vertical plane of the volumes contained with and bounded by external covers or skins, providing a convenient access at the tope for stowage of items required in the use of the bicycle. f) to allow the assembly of the complete frame from a flat pack arrangement, in which the components are initially separated for transportation from the point of manufacture, and are put together later. g) because the frame may be assembled from separate components, those components may be fine painted individually, or left anodised, thereby avoiding the need for painting the completed frame. h) tooling to assemble the bicycle is simple, particularly when clamps are used to hold the frame to the head and seat tubes .

The present invention may also encompass a kit of parts for making the frame described previously, of any aspect, comprising head and seat tubes, fastenings for attachment to the head and seat tubes (or already attached thereto) , at least one hub and tubes and spokes for assembling the X-frame. The invention also includes a method of assembly of a bicycle frame from such components .

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a side view of a bicycle frame according to a first embodiment of the present invention;

Fig. 2 is a view in the direction of arrow "A" in Fig. 1 of two of the trusses of the frame of the bicycle of Fig 1,

Fig. 3 is a view in the direction of arrow "C" in Fig. 1 of another two of the trusses of the frame of the bicycle of Fig 1.

Fig. 4 shows the securing of the tubular members to the fastenings;

Fig. 5 shows an alternative arrangement of a tubular member, spoke and fastenings;

Fig. 6 shows trusses of a second embodiment of the present invention, used in the frame of a bicycle;

Fig. 7 shows other trusses of the second embodiment; Figs 8a and 8b show details of the clamp which connects the suspension component of the rear fork assembly of the embodiment of Fig 1 to the seat tube, Fig 8b being a sectional view along the line X A' to 'A' in Fig 8a; and

Figs 9a, 9b and 9c show clamps used to attach the frame of the bicycle Fig 1 to the head tube, Fig 9a being an upper clamp, Fig 9b being a lower clamp, and Fig 9c being a sectional view along the line 1 B' to λ B' and also yC to X C in Figs 9a and 9b.

DETAILED DESCRIPTION

Referring first to Fig. 1, a bicycle has a head tube 10 and a seat tube 12 interconnected by an X- frame, one side of which is generally indicated at 14. The X-frame comprises connecting members 16 to 22 which radiate from a central hub part 24. The connecting members 16, 18 extend to respective clamps 26, 28 on the head tube and the connecting members 20, 22 extend to respective clamps 30, 32 on the seat tube 12.

In the embodiment of Fig. 1, the X-frame 14 also has a lower bracing tie 34 extending between the clamps 28, 30 and having a connection member 36 which connects the bracing tie 34 to the hub part 24. In accordance with the first aspect of the present invention, in this first embodiment each of the connecting members 16, 18, 20 and 22 (and also the tie 34) comprises an outer tube and an inner spoke. Each of the spokes of the connecting members 16, 18, 20, 22 is connected to the hub 24 at one end, and to one of the clamps 26, 28, 30, 32 at the other. The spoke of the tie 34 is connected to the clamps 28, 30. Thus, the outer tube of each of the connecting members 16, 18, 20, 22 is put under compression by tension from the spoke that extends within it.

Fig. 1 also shows the bicycle rear fork assembly 40 which supports the rear wheel 42 and is connected to the clamp 32 by a suspension component 44, and also connected to the bottom bracket 46 of the bicycle, which bottom bracket is adjacent the clamp 30. This rear fork assembly is already known, and thus will not be described in further detail.

Although not visible in Fig. 1, the X- frame of four trusses has another side (one behind the other in the figure) connecting the head tube 10 and seat tube 12. This is illustrated in Fig. 2 and the sides 14, 14a have exactly the same shape and are connected to the same clamps 26, 28, 30, 32. Their respective hub parts 24,

24a are interconnected by a hollow rod 50 which holds the hub parts 24, 24a apart so as to form a hub for the X- frame consisting of the hub parts 24, 24a and the rod 50. The resulting structure thus has torsional strength in several different directions, as previously discussed. Although not shown in Fig. 2, the frame 14a has lower connecting members (below the connecting members 16a, 22a) corresponding to connecting members of the X- frame. In a similar way, Fig. 3 shows that the bracing tie 34 (which is not shown in Fig. 2) is connected to the hub parts 24, 24a by respective connection members 36, 36a.

The connecting members 16, 18 which are attached to the head tube 10 are both in the same vertical plane (when the bicycle is upright) , and similarly the connecting members 20, 22 of that X- frame 14 are in the same vertical plane. As shown in figs 2 and 3, those planes are inclined to each other due to the greater lateral separation of the points of attachment of the connecting members 16, 18, 20, 22 to the hub 24 from the median plane 52 of the frame, as compared with the separation of the points of attachment of the connecting members 16, 18, 20, 22 to the fastenings 26, 28 from the median plane 52. The same is true of the other side 14a of the X-frame. Thus a truss is formed by connecting members 16 and 16a and the fact that the truss has two separate elements gives it structural integrity in torsion, when those elements are connected by the hub. The connecting members 16 and 16a act as flanges of the truss. Similar trusses are formed by the pairs of connecting members 18 and 18a, 20 and 20a, and 22 and 22a. In this structure, the X- frame provides torsional stiffness by the in-plane stiffness of each truss. The ends of the trusses at the head and seat tubes are in plane, and are deflected in opposite senses when the rider thrusts to drive the bicycle forward. The torsional stiffness is a function of the square of the separation of the ends of the trusses at the head and seat tubes (the 'span') .

The structure of the connecting members 16, 18, 20 and 22 and their connection to the clamps 26, 28, 30, 32 will now be described with reference to Fig. 4. Fig. 4 shows the connection of truss 16 (and also connection 16a) to the clamp 26. The connections of the other connecting members to the other clamps 28, 30, 32 is the same. Thus, the clamp 26 comprises an annular part 60 which extends around the head tube 10, and has a split 62 therein. Fixings 64 on each side of the split 62 are connected by e.g. a screw, and brought towards each other so as to clamp the clamp 26 to the head tube 10. Arms

66, 66a integral with the rest of the clamp 26 extend from the annular part 60, and terminate in a spigot to which the connecting members 16, 16a are respectively connected.

Fig. 4 illustrates that the connecting members 16, 16a each comprise an outer tube 68, 68a and an inner spoke 70, 70a.

The arms 66, 66a each terminate in spigots, comprising a first bore 72, 72a at the end of the bushing, which receives the ends of the tubes 68, 68a, a second bore 74, 74a, narrower than the first bore 72, 72a, through which the respective spokes 70, 70a pass, and a third bore 76, 76a wider than the second bore 74, 74a which contains a screw head or other connector 78, 78a which is threaded on the end of the spoke 70, 70a and extends into the second bore 74, 74a. Thus, the tube 68 abuts against the junction between the bores 72, 74, and the screw head 78 abuts against the junction between the bores 74, 76. There is a similar structure at the hub 24 but with a cap on the end of the spoke . Altenatively the cap could be at the end of the spoke at the fastening and the screw head at the hub. Thus, the spoke 70 is put under tension when the screw head 78 is threaded thereto, and that tension compresses the outer tube 68. A similar arrangement occurs at tube 68a and spoke 70a relative to the bores 72a, 74a, 76a and screw head 78a, and indeed there is a similar effect for all the trusses of the X- frames 14, 14a.

Although not illustrated in the drawings, the securing of the connecting members 16, 18, 20 and 22 to the hub 24, and the securing of the connecting members 16a, 18a, 20a and 22a to the hub 24a may be similar to that illustrated in Fig. 4, but with a cap at the end of the spoke, so that the tube of each connecting member abuts a part of the hub, and the spoke is secured via the cap to an adjacent part of the hub so that it is under tension. By adjusting the screw head at the hub or fastening end of the connecting member, and appropriate tension may be applied to the spoke.

It can thus be seen that it is simple to assemble the frame, by positioning the various parts and threading the screw heads on to the ends of the spokes, to hold the whole structure together. In Fig. 4, the outer tubes 68, 68a (and indeed the tubes of the other parts of the X-frames 14, 14a) may be of carbon fibre. Fig. 5 illustrates an alternative arrangement in which there is an aluminium tube 90 but containing a spoke 92 in a similar manner to the spoke 70 in the tube 68. The arm 94 and bushing into which the spoke 92 is received may be the same as the arm 66, with similar bores 96, 98, 100 and nut 102, corresponding to the bores 72, 74, 76 and nut 78. A second embodiment of the invention will now be described with reference to Fig 1, and Figs 6 and 7. In side view of Fig 1, the bicycle of the second embodiment appears similar to that of the first embodiment. However, the configuration of the trusses joining the hub of the X- frame to the head and seat tubes 10, 12 is different, as can be seen from Figs 6 and 7. In the first embodiment, each branch of the X- frame comprises two connecting members, each of which comprises an outer tubular member and a spoke within that tubular member. In the second embodiment, however, the branches of the X- frame are formed by tubes and crossed external spokes. The pairs of tubes and crossed spokes form trusses, having the same function as the trusses o the first embodiment . Thus, two pairs of tubes 116, 116a and 118, 118a extend from the hub to the head tube 10, and are connected by respective clamps 26, 28 as before. Similarly, two pairs of tubes 120, 12a and 122, 122a extend from the hub to the seat tube 12 , and are connected thereto by clamps 30, 32. The hub has the same configuration as in the first embodiment, with two hub parts 24, 24a connected by a rod 50 to provide appropriate spacing of the ends of the trusses at the hub. Instead of using spokes internal of the tubes, there are then crossed spokes associated with each pair of tubes. Each spoke extends from an end (or close to an end) of one of the tubes to the opposite end (or close to the opposite end) of the other tube. Thus, for the pair of tubes 116, 116a, one spoke 116b extends from the hub end of the tube 116 to the head tube end of the tube 116a, and similarly a spoke 116c extends from the hub end of the tube 116a to the head tube end of the tube 116. The spokes 116b and 116c are under tension between the hub and clamp 26, and so apply compressive forces to the tubes 116, 116a.

Thus, again, a truss is formed by the tubes 116, 116a, and spokes 116b, 116c which is stiff in its plane because of the tensioning provided by the spokes 116b, 116c. The arrangement is the same for the other trusses, so that tubes 120 and 120a (corresponding to the tubes 20 and 20a of the first embodiment) are put in the tension by spokes 120b, 120c between the hub and clamp 30, for tubes 118 and 118a (corresponding to the tubes 18, 18a in the first embodiment) are put under tension by the spokes 118b, 118c between the hub and the clamp 28, and the tubes 122, 122a (corresponding to the connecting members 22, 22a in the first embodiment) are put under tension by the spokes 122b, 122c between the hub and the clamp 32. The resulting X- frame again has high torsional strength. Moreover, again, the frame may be easy to assemble by suitable design of the clamps 26, 28, 30, 32. The compressive forces applied by the spokes to the tubes can force the tubes into bushes in the clamps and the hub, and the spokes themselves may be fixed to the hub and to the clamps using suitable fixing in a similar way to those of the first embodiment. For example, one end of the spokes (usually the hub end) may be threaded and screwed into a bush, with the other end of the spoke (e.g. at the connector end) passing through a bore, and having a nut screwed on its end which abuts against an end of the bore, to apply tension to the spoke when the nut is tightened. Thus, the second embodiment gives similar advantage to the first embodiment in terms of ease of assembly. It should be noted that in both the first and second embodiments, clamps are used to hold the connecting members, tubes, spokes, etc to the head and seat tubes. As mentioned previously, the use of clamps to hold parts of a frame to the head and seat tubes represents an independent aspect of the present invention. The use of clamps enables the frame to be attached to the head and seat tubes in a releasable way.

Figs 8a and 8b show in more detail the clamp 32 of Fig 1 in more detail . Fig 8b is a sectional view along the line 'A' to λ A' in Fig 8a. Thus, the suspension component 44 has a projection 140 which is received between flanges 142, 144 of clamp 32 and held thereto by a bolt 146 and nut 148. The flanges 142, 144 extend from respective curved clamp parts 150, 152 which extend partially around the seat tube 12 and terminate, at the ends of those clamp parts 150, 152 remote from the flanges 142, 144 in further flanges 154, 156 respectively. A block 158 is received between the flanges 154, 156 and held thereto by bolt 160 and nut 162. The block 158 receives the ends of the connecting members 22, 22a in Fig 1.

The transverse thicknesses (in the plane of the paper in Fig 8b) of the projection 140 and block 158 is selected so that, when the flanges 142, 144, 154, 156 are clamped thereto by the bolts and nuts 146, 148, 160, 162, the clamp parts 150, 152 are forced into contact with the seat tube 12, to clamp the projection 140 and block 156 to the seat tube 12, and hence to clamp the suspension 44 and connecting members 22, 22a to the seat tube 12.

However, to prevent any slippage of the clamp parts 150, 152 on the seat tube 12, pop rivets 164, 166 are provided which extend through aligned bores in the clamp parts 150, 152 and the seat tube 12, so that the clamp parts 150, 152 cannot rotate around the axis of the seat tube 12, or slide along the seat tube 12. Thus, the combination of the clamping force and the pop rivets 164, 166 fix the clamp 32 in the correct position on the seat tube 12. In the arrangement of Figs 8a and 8b, the clamp parts 150, 152 and the flanges 142, 144, 154, 156 may be of stainless steel, with the projection 140 and the block 158 being of aluminium.

Fig 9a then shows a similar arrangement, but of the clamp 26. Note that this clamp is slightly different from that shown in Fig 4. In particular, and as is evident from the sectional view of Fig 9c, taken along the line λ B' to X B' in Fig 9a, the clamp 26 comprises a clamp part 170 which extends the majority of the circumference of the head tube 10 and terminates in flanges 172, 174. A block 176 is received between those flanges 172, 174 and secured thereto by a bolt 178 and nut 180. The block 176 receives the connecting members 16, 16a. It may be noted that the internal structure of the block 176 may, to enable those connecting members 16, 16a to be connected thereto, be the same as shown in Fig 4. The only difference is then that the block 76 is a separate component from the clamp 26, rather than being integral therewith as in Fig 4. Moreover, in a similar manner to the clamp 32, the clamp 26 may have a pop rivet 180 which passes through aligned bores in the clamp parts 170 and head tube 10, to prevent the clamp 26 rotating or sliding on head tube 10. The clamping force of the clamp 26, determined by the width of the block 176 relative to the spacing of the flanges 172, 174 represents the primary force holding the clamp 26 onto the head tube 10 but the pop rivet 182 provides additional securing.

The clamp 28 in Fig 1 may be very similar to the clamp 26, as can be seen from comparison of Figs 9a and 9b. Indeed, the sectional view along the line λ C to X C in Fig 9b is the same as that along the line 'B' to X B' in Fig 9a, and so Fig 9c shows both views. Therefore, the same reference numerals are used to indicate corresponding parts. However, in Fig 9b the block 190 received between the flanges 172, 174 has a different shape from the block 176, because it must receive both the bracing ties 18, 18a and the lower bracing tie 34. Again, therefore, the clamp 28 is held to the head tube 10 by the combined effect of the clamping force due to bolt and nut 178, 180 on the flanges 172, 174 and the pop rivet 182 extending through a bore in the clamp part 170 and the head tube .

Moreover, as in the arrangement of Figs 8a and 8b, the clamp part 170 and flanges 172, 174 may be of stainless steel, and the blocks 176, 190 may be of aluminium .

Thus, the present invention in its various aspects provides a frame for a bicycle which is simple to assemble. The frame may be transported in a disassembled state ( e.g. in a 'flat-pack' arrangement) and assembled quickly using relatively unskilled labour. The arrangement in which the tubes are put under compression by abutment of the ends of those tubes fastenings and/or a hub, with a spoke under tension secured to the fastening and/or hub putting the tube under compression. By locating the spoke within the tube or using crossed spokes, a frame is formed which has an appearance which presents a new and simplified appearance, as compared with the known space frame. Of course, the present invention is not limited to the use of caps on the end of the spokes, to attach the spokes to the fastenings and/or hub, and other configurations may be possible, such as flanges at one end of the spoke, or sliding arrangements. It may also be possible to clamp one or both ends of the spoke .