GB2475793A

GB2475793A - Folding bicycle

Info

Publication number: GB2475793A
Application number: GB1020256A
Authority: GB
Inventors: Stuart Gerald Lambert; William Jackson
Original assignee: CROSSHEAD Ltd
Current assignee: CROSSHEAD Ltd
Priority date: 2009-11-30
Filing date: 2010-11-30
Publication date: 2011-06-01
Anticipated expiration: 2030-11-30
Also published as: GB2475793B; GB201020256D0; GB201005525D0; GB0921103D0

Abstract

A folding bicycle 100 having a front fork assembly and a rear swing arm assembly 2 both coupled to a central frame assembly, and being such as to permit the front and rear wheels to be moved to a position generally alongside one another in the folded condition. The central frame assembly 1 includes a seat tube 15, and a bottom bracket assembly 3 coupled to the seat tube 15 by means of a rotary coupling which permits a limited amount of relative rotary movement about an axis coincident with the axis of the seat tube. The rear swing arm assembly 2 is pivotally coupled to the bottom bracket assembly 3, so that when the bicycle 100 is folded, the rear swing arm assembly is swung from an operative riding position to a folded condition, together with a concomitant rotation of the bottom bracket assembly 3 to permit the rear wheel to be positioned alongside the central frame assembly 1 and for permitting alignment of a chain transmission assembly. The front fork assembly may include forks comprising an upper fork part 4 and a left lower fork part 5 and a right lower fork part 5, each lower fork part 5 being connected to the upper fork 4 part by means of a respective pivotal coupling 42, which includes locking pawls 46 for retaining the fork parts 5 in an operative riding position, and the pawls 46 being releasable to permit the front wheel 18 to be pivoted towards the central frame assembly 1 to said folded configuration. In alternative embodiments, a pivotal coupling 60, 90 is provided on the central frame to enable the forks 61 to travel substantially within a first plane when they pivot from an operative riding configuration to a folded configuration.

Description

FOLDING BICYCLE

Field of the Invention

This invention relates to folding bicycles.

Background Art

GB-A-1580048 (Brompton Cycle Limited) discloses a folding bicycle, comprising a rear wheel assembly, which is pivoted to the main frame part so that it can be swung from an operative riding position to a folded condition, with the rear wheel directly beneath the main frame cross tube. A hinge coupling in the cross tube permits the front wheel to be located alongside the rear wheel in the fully folded condition. Although this provides a compact folded arrangement, the geometry of the frame and the radius of the rear wheel are restricted by the positioning of the rear wheel directly beneath the main frame cross tube when the bicycle is in the folded condition.

DE-A-431 3832 (Riese & Muller) discloses a folding bicycle with a rear wheel assembly foldable to a position beneath a main frame part, but wherein the pivot connection between the main frame part and the rear wheel assembly is pivoted obliquely to permit the rear wheel to be positioned to one side of the main frame part. A front fork assembly comprises a quadrilateral arrangement of fork parts pivoted together so as to pivotable to an open configuration from the quadrilateral shape, where the front wheel is alongside the rear wheel but on the opposite side of the main frame.

GB-A-2401589 (ATB Sales) discloses a folding bicycle with a rear wheel assembly foldable to a position beneath a main frame part, but wherein the pivot axis with the main frame part is skewed at a small angle so as to permit the rear wheel to be located to one side of the main frame part. Further, a front wheel folding assembly, as disclosed in GB-A- 2451689, requires the front wheel to be disengaged from the forks by a quick-release coupling, to permit a linkage to move the front wheel alongside the rear wheel.

A first problem with the Riese & Muller and ATB Sales rear wheel assemblies is that, by deliberately misaligning the rear wheel assembly, the chain must bend laterally from rear sprocket to chain ring when folded and therefore chain guides and methods for keeping the chain from falling off have to be employed. A second problem with the Riese & Muller and ATB Sales front wheel folding arrangements is that of complexity, and a simplified arrangement is desirable.

US-A-5,975,551 (Montague) discloses folding bicycles having a front frame part and a rear frame part, the rear frame part including a bottom bracket assembly for the chainset. The two frame parts are joined together by means of a pivotal coupling arrangement in the seat tube (extending from the saddle to the bottom bracket) which permits the two frame parts to be folded upon one another.

Currently the biggest manufacturer of folding bicycles by volume of sales is Dahon, but in general Dahon uses a simple folding mechanism including hinge couplings partway along the length of the main frame, which permit the bicycle to be folded in two, upon itself.

This does not provide a very compact arrangement.

Summary of the Invention

It is an object of the invention to provide a folding bicycle wherein one or more of the above-noted problems are overcome, or at least reduced.

In a first aspect, the invention provides a folding bicycle having a front wheel assembly and a rear wheel assembly both coupled to a main frame assembly, and being such as to permit the front and rear wheels to be moved to a position generally alongside one another in the folded condition, wherein the main frame assembly includes a seat tube part, and a bottom bracket assembly coupled to the seat tube part by means of a rotary coupling which permits relative rotary movement, and the rear wheel assembly being pivotally coupled to the bottom bracket assembly, whereby, when the bicycle is folded, the rear wheel assembly may be swung from an operative riding position to a folded condition, together with a concomitant rotation of the bottom bracket assembly relative to said seat tube part, to permit the rear wheel to be positioned alongside the main frame part. The rotary coupling preferably permits a limited amount of relative rotary movement.

In accordance with the invention, the introduction of a degree of relative rotational movement between the seat tube part and a bottom bracket assembly, permits the front wheel assembly to sit alongside the rear wheel assembly in the folded position. In addition, the limited rotational movement permits the chain set to remain aligned with the rear sprocket, so that the requirement for guiding the chain during folding is avoided.

In a preferred embodiment, the main frame assembly includes a bottom bracket assembly which includes an inner tube extending into the seat tube part, about which a main frame part can rotate. The bottom bracket assembly is mounted to the main frame assembly by two moulded sleeves. The rear wheel assembly is coupled by means of a pivotal coupling to the bottom bracket assembly. The arrangement keeps the transmission system aligned between rear wheel and bottom bracket but allowing the rear wheel assembly to rotate from an operative riding position to a folded position. The main frame assembly can rotate permitting the front wheel to be positioned alongside the main frame part, the bottom bracket assembly and the rear wheel assembly remaining aligned relative to each other.

The bottom bracket assembly is the vertical and rotational axis for the main frame assembly and is coupled to the rear wheel assembly which has its rotational pivoting axis horizontal. The bottom bracket assembly has four means of keeping it aligned to the main frame assembly. 1; a lower contoured moulded sleeve, which may be a three point (or two-point or four-point) shape, which engages positively with the main frame assembly. 2.; an upper spring which is attached to the bottom bracket assembly via a washer and a fastener or retainer (for example a circlip) for retaining the main frame assembly, exerting downward pressure onto the main frame assembly keeping the lower three point moulded sleeve engaged with the main frame assembly. 3.; the rear wheel assembly has two blades which engage positively behind the main frame assembly seat tube and are locked by the means of a quick release clamp. 4.; The quick release clamp exerts pressure onto the two rear wheel assembly blades and additionally move two split barrel components closer together exerting pressure which passes through a hole in the main frame assembly and clamps the bottom bracket assembly within the main frame assembly seat tubing.

In a second aspect, the invention provides a folding bicycle comprising a front wheel assembly, a rear wheel assembly and a main frame; wherein a first pivotal coupling is provided on the main frame for pivotally mounting the front wheel assembly; the first pivotal coupling being arranged such that the front wheel assembly travels substantially within a first plane when it pivots from an operative riding configuration to a folded configuration.

The main frame defines a second plane. The first plane in which the front wheel assembly pivots can be angularly offset from the second plane. Thus, when the front wheel assembly is in the folded configuration, the front wheel can locate at least partially alongside the main frame. Preferably, the first plane and the second plane are offset from each other by an acute angle.

A locking means can be provided for locking the front wheel assembly in said operative riding configuration and/or said folded configuration.

The front wheel assembly also comprises a steering tube for steering the front wheel. The steering tube is mounted in a rotary coupling to enable rotational movement.

The rotary coupling is preferably distinct from the first pivotal coupling. When the front wheel assembly is pivoted relative to the frame, the rotary coupling can pivot with the front wheel assembly. The steering tube can also comprise a second coupling to enable the steering tube to be displaced to a folded configuration.

The rotation of the steering tube in the rotary coupling can move the front wheel out of the first plane. Preferably, the front wheel is centralised before it is pivoted about the first pivotal coupling. This can help prevent the front wheel interfering with the frame when the front wheel assembly is pivoted to its folded configuration.

The main frame preferably comprises a frame member extending from a seat post to the steering tube. The first pivotal coupling is preferably provided on said frame member. Preferably, the first pivotal coupling is provided proximal the steering tube. The frame member is preferably a top tube member.

In a third aspect, the invention provides a folding bicycle having a front wheel assembly and a rear wheel assembly both coupled to a main frame assembly, and being such as to permit the front and rear wheels to be moved to a position generally alongside one another in the folded condition, wherein the front wheel assembly includes forks, comprising a fork head part and a left lower fork part and a right lower fork part, which hold the front wheel therebetween, and wherein each said lower fork part is connected to the fork head part by means of a respective pivotal coupling, which includes locking means for retaining the lower fork part in an operative riding position, and the locking means being releasable to permit the front wheel to be pivoted towards the main frame assembly to said folded configuration.

In accordance with the invention, the folding and locking assembly of left and right fork parts represents a significant simplification relative to the prior art discussed above, but without sacrificing structural strength.

Brief Descrirtion of the Drawings Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the frame and forks of a folding bicycle according to a first embodiment of the invention, comprising a rear swing arm assembly, central frame assembly, and front fork assembly; Figure 2 is an exploded view of the frame and forks shown in Figure 1; Figure 3 is a view from above of the folding bicycle according to the first embodiment of the invention, in a fully folded configuration; Figure 4 is a side view the folding bicycle according to the first embodiment of the invention, in the fully folded configuration; Figure 5 is a detailed view of the frame of the folding bicycle according to the first embodiment of the invention, showing a quick release clamp of the rear swing arm assembly; Figure 6 is a sectional view of the quick release clamp shown in Figure 5; Figure 7a is a side view of a bottom bracket assembly of the folding bicycle according to the first embodiment of the invention, comprising a bottom bracket shell and a vertical locating tube; Figure 7b is a rear view of the bottom bracket assembly shown in Figure 7a; Figure 7c is an exploded view of a spring-loading retention means of the bottom bracket assembly shown in Figure 7a; Figure 8 is a detailed view of the frame of the folding bicycle according to the first embodiment of the invention, showing a pivot connection of the rear swing arm assembly to the bottom bracket assembly, and coupling of a contoured surface with a cooperating contoured surface at the lower end of a seat tube of the central frame assembly; Figure 9 is a detailed view of the frame of the folding bicycle according to the first embodiment of the invention, showing a hinged coupling of a handlebar assembly to the front fork assembly; Figure 10 is a detailed view of the front fork assembly of the folding bicycle according to the first embodiment of the invention, showing a pawl locking assembly, and showing fork arm parts in a forward riding position; Figure 11 is a view similar to that of Figure 10, but showing the fork arm parts in a rearward retracted position; Figure 12 is a side view of a folding bicycle according to a second embodiment of the present invention, in an operative riding configuration; Figure 13 is a side view of the folding bicycle shown in Figure 12, in a fully folded configuration; Figure 14 is a perspective view of a pivoting coupling of the folding bicycle shown in Figure 12, when the folding bicycle is in the operative riding configuration; Figure 15 is a perspective view of the pivoting coupling shown in Figure 14, when the bicycle is in the fully folded configuration; Figure 16 is a perspective view of a front fork assembly of the folding bicycle shown in Figure 12; Figure 17 is an exploded perspective view of a portion of a frame of a folding bicycle according to a third preferred embodiment of the present invention; Figure 18 is a side view of another portion of the frame of the folding bicycle according to the third preferred embodiment of the present invention, showing a front fork assembly when the folding bicycle is in an operative riding configuration; and Figure 19 is a side view of the other portion of the frame of the folding bicycle shown in Figure 18, showing the front fork assembly when the folding bicycle is in a fully folded configuration.

Descrirtion of the Preferred Embodiments First Embodiment Referring to Figures 1 to 11, a folding bicycle 100 according to a first embodiment of the invention comprises a central frame assembly 1, a rear swing arm assembly 2 and a front fork assembly 12. The central frame assembly I has a top tube 13 extending from a head tube 14 to a seat tube 15, with the top tube 13 being primarily horizontal and the head tube 14 and seat tube 15 being primarily vertical in use. The central frame assembly 1 also has a down tube 16 extending from part way along the length of the top tube 13 to the seat tube 15, such that the top tube 13, seat tube 15 and down tube 16 form a triangle.

The folding bicycle 100 is arranged such that, when it is in a folded configuration, a rear wheel 17 of the folding bicycle 100 carried by the rear swing arm assembly 2 and a front wheel 18 of the folding bicycle 100 carried by the front fork assembly 12 are substantially alongside one another, one on each side of the central frame assembly 1.

The rear swing arm assembly 2 is mounted to the central frame assembly I by a bottom bracket assembly 3. The rear swing arm assembly 2, the central frame assembly 1 and the bottom bracket assembly 3 are attached together to create either a compact folded structure rotated in two different planes or a rigid structure in an open for riding position.

The rear swing arm assembly 2 comprises two seat stays 19, each a extending from one of a pair of dropouts 20 for receiving an axle (not shown) of the rear wheel 17 to one of a pair of blades 21 for securing the seat stays 19 to the central frame assembly 1.

The rear swing arm assembly 2 also has two chain stays 22, each extending from part way along a respective one of the seat stays 19 to a rear swing arm support 23. A bracing member 24 is provided, extending from the ends of the seat stays 22 proximal to the blades 21 to the rear swing arm support 23.

The bottom bracket assembly 3 comprises a locating tube 24 arranged to extend inside the seat tube 15 of the central frame assembly 1. At one end of the locating tube 24 is a bottom bracket housing 25. The bottom bracket housing 25 comprises a bottom bracket shell 26 for receiving a bottom bracket (not shown) of the folding bicycle 100. The bottom bracket shell 26 is located to one side of the locating tube 24, with the main axes of the bottom bracket shell 26 and the locating tube 24 being perpendicular to one another.

The bottom bracket housing 25 also has a rear swing arm bracket 27 for mounting the rear swing arm support 23. The rear swing arm support 23 is mounted to the rear swing arm bracket 27 by a pivot 28, such that the rear swing arm support 23 may pivot about an axis parallel to the main axis of the bottom bracket shell 26. This allows the rear swing arm assembly 2 to pivot relative to the rear swing arm bracket 27, and hence the bottom bracket assembly 3, about the axis perpendicular to the main axis of the locating tube 24.

In other words, the rear swing arm assembly 2 rotates around the bottom bracket assembly 3, allowing approximately 180 degrees of rotating travel aligned with the bottom bracket (not shown).

At the other end of the locating tube 24 is a seat post assembly 30. The seat post assembly 30 comprises a seat post 31 for supporting a saddle 37 of the folding bicycle 100. As can be seen most clearly in Figure 6, the seat post 31 is arranged to extend inside the locating tube 24, which in turn extends inside the seat tube 15. A seat clamp 32 is provided at the end of the locating tube 24 into which the seat post 31 extends, in order to clamp the seat post 31 to the locating tube 24. An upper bush 10 supports the locating tube 24 in the seat tube 15 at a rim of the seat tube 15 proximal to the top tube 13, such that the locating tube 24 can rotate within the seat tube 15. A seat tube spring 34, a C-clip and a washer 36 are provided between the seat clamp 21 and the upper bush 10. The seat tube spring 34 coils around the outside of the locating tube 24 and can be compressed between the washer 36 and the upper bush 10 so as to urge the locating tube 24 in a direction along the main axis of the locating tube 24 towards the saddle 37.

A lower contoured bush 9 is provided at a rim of the seat tube 15 proximal to the down tube 16 to support the locating tube 24 such that it can rotate within the seat tube 15.

A surface 33 of the lower contoured bush 9 facing along the main axis of the seat tube 15 towards the bottom bracket housing 25 has cam projections 38 that provide cam surface.

An opposing surface of the lower contoured bush 9 has locating projections 39 that cooperate with locating recesses in the rim of the seat tube 15 to prevent rotational movement of the lower contoured bush 9 in the seat tube 15.

A surface 29 of the bottom bracket housing 25 facing along the main axis of the locating tube 24 towards the end of the locating tube 24 distal to the bottom bracket housing 25 provides one or more cam followers. Force exerted by the spring 34 urges the cam followers and cam surface towards one another. When the bottom bracket assembly 3 is rotated in the seat tube 15 such that the rear swing arm assembly 2 and the central frame assembly I are in line with one another, the cam followers dwell, with compression of the spring 34 minimised. As the bottom bracket assembly 3 is rotated in the seat tube 15 such that the rear swing arm assembly 2 and the central frame assembly I are out of alignment, it is displaced outward of the seat tube 15 by the cam surface of the lower contoured bush 9 against the force exerted by the spring 34. In this embodiment, the cam followers and cam surface correspond in profile and conform to one another when the cam dwells.

The folding frame design keeps the complete transmission system aligned between the bottom bracket and rear dropouts 20 when the rear swing arm assembly 2 pivots from fully open to folded. The bottom bracket shell 26 and locating tube 24 (or seat tube component) is fixed via a fixed pivot point to the rear swing arm assembly 2 and additionally forms a pivoting axis for the central frame assembly I (or central triangulated frame) which allows the central frame assembly I to swing out of alignment. The central frame assembly 3 sits on a three-pointed radial articulation near the bottom bracket and visibly slides in and out of alignment controlled via an upper seat tube external spring which allows vertical and rotational movement. The rear swing arm assembly 2 is held in line by a seat tube split insert 40. Rearward of the seat tube 15, at the end of the seat tube proximal to the top tube 13, is a seat tube split pin housing 39. The seat tube split pin housing 39 is generally cylindrical and has a main axis perpendicular to and offset from the main axis of the seat tube 15. A side wall of the seat tube 15 is open to the inside of the seat tube split pin housing 39, such that the seat tube split pin housing 39 can engage the locating tube 24 of the bottom bracket assembly 3. In other words, the locating tube 24 (or inner tube part) of the bottom bracket assembly 3 passes through the centre of the seat tube 15 and emerges visibly behind the seat tube 15 within the split pin housing 39. The seat tube split insert 40 is clamped together by a frame quick release clamp 41. The seat tube split pin insert 40 holds the blades 21 of the rear swing arm assembly 2 in place and additionally exerts pressure on the bottom bracket assembly 3.

When the rear swing arm assembly 2 is being folded and the blades 21 of rear swing arm assembly are clear of the frame quick release clamp 41, the central frame assembly I is free to rotate around the locating tube 24 (or inner tube) of the bottom bracket assembly 3. This rotating action allows the central frame assembly I to move out of alignment with the fixed relationship of the transmission system between rear dropout and bottom bracket. Full alignment is re-established when the blades 21 of the rear swing arm assembly 2 and frame quick release clamp are re-united and locked.

During the rotational movement of the central frame assembly I around the bottom bracket assembly 3, the lower contoured bush 9 and upper bush 10 reduce friction between the two tube sections and additionally the lower contoured bush 9 raises the central frame assembly I a small distance compressing the seat tube spring 34 at the top of the seat tube 15 an equal distance. Above the seat tube spring 34 the C-clip 35 and washer 36 are attached to the locating tube 24 of the bottom bracket assembly 3. The raised high points around the circumference of the lower contoured bush 9 correspond to the shaping at the bottom of the bottom bracket assembly 3. The resulting mechanical action of the raised high points in the lower contoured bush 9 is to provide an engaged and locked structure when the central frame assembly 1, rear swing arm assembly 2 and bottom bracket assembly 3 are held in place by the frame quick release clamp 41.

The front fork assembly 12 comprises a fork head part 4 and a fork arm part 5.

The fork head part 4 is attached to the central frame assembly I via a 1-1/8 inch steerer tube 42 inserted into headset bearings (not shown) within the central frame assembly 1.

The fork head part 4 is completed as an assembly with two fork arm parts 5. The three components forming the front fork assembly 12 are held together by two rotational joints 42, which are attached via a threaded fork bush 43 and washer 44. The front fork assembly 12 holds the front wheel 18 in two fixed positions, open for riding and folded for transportation or storage. The fork arm parts 5 when rotated have two fixed positions, which are locked by a spring 45 and tapered pawl 46.

A steerer clamp and hinge assembly 47 is provided for mounting the front fork assembly 12 to the central frame assembly I. The steerer clamp and hinge assembly 47 has two key functions. Firstly, the steerer clamp and hinge assembly 47 retains the fork steerer tube 42 in a fixed position through a clamping action, allowing the head tube 14 and bearings (not shown) to remain stable without any undesirable play between the two.

Secondly, the steerer clamp and hinge assembly 47 provides a pivoting and lockable hinge allowing an upper steering tube 48, which is attached to handlebars (not shown), to rotate into two positions; open for riding and folded for transportation or storage. -1O-

The complete steerer clamp and hinge assembly 47 comprises: a steerer clamp part 49, upper steering tube part 50, external v clamp 51, rod shaped linkage (not shown), sleeved bushes 52, two-piece bolt 53 and quick release lever 54. The steerer clamp part 49 is of cast aluminium construction having an internal locatable protrusion which slots into the fork steerer tube 42 aligning the two for ease of assembly. There is an internal centrally placed hole for pre-tensioning the steerer clamp part 49 using an industry standard, sprung steel star insert and bolt for pre-tensioning the whole headset assembly before two-piece bolt 53 on the steerer clamp part 49 is tightened resulting in the clamping of the component onto the fork steerer tube 42.

The upper steering tube part 48 has a tube, hinge plate (not shown) and external clamping face (not shown) which is either fabricated or alternatively the hinge plate and external clamping face are cast in aluminium as a single component.

The front wheel assembly 12 consists of one upper fork part 4 and two lower fork parts 5, two trigger locks 46 (pawls) with wound springs 45, two large washers 44 and threaded bushes 43 which intentionally bottom out providing the correct contact pressure within pivoting joint 42. The pivoting fork arrangement with trigger lock 46 allow the front wheel assembly to either pivot and lock into an open riding position or pivot and lock into the folded position, during this mechanical action the upper fork part 4 remains fixed and the two lower fork parts 5 rotate about a fixed pivotal point.

The trigger locks 46 are released on either side of the upper fork part 4 to achieve the open position for riding or closed for folding. The wound springs 45 positioned behind the trigger locks 46 stop the locking feature from bouncing out of the locked position whilst riding on rough or bumpy surfaces. The trigger locks 46 have a tapered shape, which provides them with a natural tendency to remain fully engaged avoiding any unwanted rattling or vibration.

When the front fork assembly 12 is in the open position for riding there is a fixed contact surface feature between upper fork part 4 and lower fork parts 5 which limits any further rotational movement removing rotational impact stresses from the trigger locks 46.

Second Embodiment Referring to Figures 12 to 16, a folding bicycle 200 according to a second embodiment of the present invention has several features in common with the first embodiment and like reference numerals have been used for like components and assemblies. However, folding bicycle 200 according to the second embodiment has a top tube hinge lock 60, which enables the head tube 14 and front forks 61 to move into two positions, utilising a front fork quick release lever 62, which has corresponding two position locking points.

The folding bicycle 200 according to the second embodiment is shown in an operative riding configuration in Figure 12, and in a folded configuration in Figure 13. The chain and seat clamp have been omitted from Figures 12 and 13 for the sake of clarity.

The rear swing arm assembly 2 of the folding bicycle 200 according to the second embodiment is unchanged from that of the folding bicycle 100 according to the first embodiment. However, the mounting of the front forks 61 on the central frame assembly 1 differs in the second embodiment. In particular, the central frame assembly I is provided with the top tube hinge lock 60 (or frame coupling) to enable the front forks 61 and the head tube 14 to pivot together to the folded configuration. As shown in Figure 12, the front fork assembly 12 is provided with a steerer clamp and hinge assembly 47 which is unchanged from the first embodiment.

The top tube hinge lock 60 is shown in perspective in Figures 14 and 15. The top tube hinge lock 60 is shown in an operative riding configuration in Figure 14, and in a folded configuration in Figure 15. The top tube hinge lock 60 comprises a frame coupling member 63 pivotally connected to a head tube coupling member 64 by a hinge pivot pin 65. The frame coupling member 63 fixedly mounts onto the central frame assembly 1.

The head tube coupling member 64 carries a fixedly mounted collar which forms a rotary coupling for rotatably mounting the fork assembly 12.

A quick release locking assembly 66 is provided selectively to lock the head tube coupling member 64 at each end of its travel. As shown in exploded form in Figure 15, the quick release locking assembly 66 comprises a guide pin quick release threaded pin 67 which travels within an aperture 68 formed in the head tube coupling member 64. The aperture 68 is arcuate having a centre coincident with the centre of the hinge pivot pin 65 to facilitate pivoting of the head tube coupling member 64. An enlarged recess 69 is formed at each end of the arcuate aperture 68 to receive a quick release sleeve nut 70 and quick release threaded sleeve nut 71 mounted on the quick release threaded pin 67.

quick release coil springs 72 are provided to centralise the quick release locking assembly 66. A quick release lever 73 allows a user selectively to release the quick release locking assembly 66 by lifting the quick release sleeve nut 70 and quick release threaded sleeve nut 71 out of the associated enlarged recess 69. The quick release lever 73 is shown in its locked position in Figure 14. -12-

The axis of the hinge pivot pin 65 is oriented at an acute angle relative to a longitudinal axis X of the central frame assembly I such that, when the front fork assembly 12 and the steerer clamp 47 pivot to the folded configuration, the front wheel moves to a position alongside the central frame assembly 1. The fork head part 4 and the steerer clamp 6 undergo movement at least substantially within a single plane when they pivot from the operative riding configuration to the folded configuration.

At least in preferred embodiments, the top tube hinge lock 60 provides a robust mechanism that can readily be operated. Moreover, the offset arrangement of the hinge pivot pin 65 allows the front wheel 18 to be swung alongside the central frame assembly I when the bicycle 200 is in its folded configuration.

A possible modification to the top tube hinge lock 60 would be to provide an automatic locking mechanism. It is envisaged that such an automatic locking mechanism would be biased towards, or secured in a locked configuration unless positively disengaged by a user.

Although the hinge pivot pin 65 is shown in the second embodiment as being positioned towards the bottom of the central frame assembly 1, the hinge pivot pin 65 could be located centrally or towards the top of the central frame assembly 1.

Third Embodiment Referring to Figures 17 to 19, a folding bicycle 300 according to a third embodiment of the present invention has several features in common with the first embodiment and second embodiment and like reference numerals have been used for like components and assemblies. However, the folding bicycle 300 according to the third embodiment has a bottom bracket housing 80 and bottom contoured bush 81 that cooperate to limit rotation of the locating tube 24 in the seat tube 15, as shown in Figure 17. The folding bicycle 300 according to the third embodiment also has a top tube hinge lock 90 that automatically locks the front forks 61 in the operative riding configuration.

Referring to Figure 17, the bottom bracket housing 80 of the third embodiment has a surface 82 facing along the main axis of the locating tube 24 towards the saddle, which surface 82 comprises one or more projections 83 and one or more recesses 84. In this embodiment, there are four projections 83 and four recesses 84. The recesses 84 are inclined in one direction around the circumference of the locating tube 24. This means that the recesses 84 are closer to the tops of the projections 83 on one side than on the other. -13-

In this embodiment, the incline is away from the bottom bracket housing 80, anti-clockwise around the circumference of the locating tube 24.

The lower contoured bush 81 also has one or more projections 85. The projections of the lower contoured bush 81 cooperate with the recesses 84 of the bottom bracket housing 80. In this embodiment, the lower contoured bush 81 has four projections 85, corresponding with the four recesses 84 of the bottom bracket housing 80.

When the locating tube 24 is mounted in the seat tube 15, the projections 82 of the bottom bracket housing 80 and the projections 85 of the lower contoured bush 81 interlock. The interlocking limits the amount by which the locating tube 24 can rotate in the seat tube 15. Typically, the maximum angle of rotation is limited to a maximum angle that is between 10° and 40°. In this embodiment, the rotation is limited to a maximum of around 30°, which is optimum for allowing easy pivoting of the rear swing arm assembly 2, whilst ensuring that the bicycle is compact in the folded configuration. In addition, the incline of the recesses 84 of the bottom bracket housing 80, in combination with the force exerted by the seat tube spring 34, urges the rear swing arm assembly 2 into alignment with the central frame assembly 1.

Referring to Figures 18 and 19, the top tube hinge lock 90 of the third embodiment has a hinge pivot pin 91 located adjacent the head tube 14. The hinge pivot pin 91 of the third embodiment is oriented similarly to the hinge pivot pin 65 of the second embodiment.

A locking mechanism 92 of the top tube hinge lock 90 comprises an L-shaped slot 92 with a first element aligned with the top tube 13 of the central frame assembly I and a second element inclined transverse to the top tube 13 and circumferentially to a pivot axis 94 of a locking lever 93. The locking lever 93 is pivotally mounted on the head tube 14 and has a pawl 95 located in the slot 92.

When the folding bicycle 300 of the third embodiment is in its operative riding configuration, the pawl 95 is located in the smaller element of the slot 92. The length and arrangement of the locking lever 94 is such that, when the pawl 95 is in this location, the front forks 61 are positioned for the bicycle 300 to be ridden. More specifically, the locking lever 93 braces the head tube 14 against a stop (not shown) about the hinge pivot pin 91.

In order to fold the bicycle 300, the user lifts the pawl out of the second element of the slot 92, by rotating the locking lever 93 around the pivot axis 94, in order to allow the pawl 95 to slide along the first element of the slot 92. As the first element is aligned with the top tube 13 and radially to the pivot axis 94 of the locking lever 93, this allows the head tube 14 to pivot around the hinge pivot pin 91. -14-

It will be appreciated that various changes and modifications can be made to the embodiments of invention without departing from the scope of the claims. In particular, whilst some features are described in the context of only one embodiment of the invention, they may equally be employed in other embodiments of the invention, resulting in further embodiments of the invention comprising features selected from the different embodiments that are described. -15-

Claims

CLAIMS1. A folding bicycle having a front wheel assembly and a rear wheel assembly both coupled to a main frame assembly, and being such as to permit the front and rear wheels to be moved to a position generally alongside one another in the folded condition, wherein the main frame assembly includes a seat tube part, and a bottom bracket assembly coupled to the seat tube part by means of a rotary coupling which permits relative rotary movement, and the rear wheel assembly being pivotally coupled to the bottom bracket assembly, whereby, when the bicycle is folded, the rear wheel assembly may be swung from an operative riding position to a folded condition, together with a concomitant rotation of the bottom bracket assembly relative to said seat tube part, to permit the rear wheel to be positioned alongside the main frame part.
2. A folding bicycle according to claim 1, wherein the rotary coupling permits a limited amount of relative rotary movement between the bottom bracket assembly and the seat tube part.3. A folding bicycle according to claim I or claim 2, wherein said bottom bracket assembly has a tube portion inserted into the seat tube part to provide said rotary coupling.
3. A folding bicycle according to any one of claims I to 3, wherein the bottom bracket assembly has a contoured portion for engagement with a contoured lower edge portion of the seat tube part, and spring bias means for maintaining engagement between the contoured portions, whereby to restore alignment of the bottom bracket assembly when the rear wheel assembly is unfolded.
4. A folding bicycle according to claim 3, wherein the bottom bracket assembly includes a contoured sleeve, and said bias means includes a spring and retainer assembly, which acts to retain the bottom bracket assembly with the seat tube part and to exert pressure onto the seat tube part to keep the contoured sleeve engaged with the seat tube part.
5. A folding bicycle according to any one of claims I to 4, wherein the rear wheel assembly has first and second blades arranged to engage within first and second locations -16-at an upper end of said seat tube part, and including a quick release clamp, for locking said blades in said locations.
6. A folding bicycle according to claim 5, wherein the quick release clamp is arranged to exert pressure on the rear wheel assembly blades and additionally to clamp a seat pin together with the bottom bracket assembly within the seat tube part.
7. A folding bicycle according to any of the preceding claims, wherein a seat pin is slidable within the tube portion of the bottom bracket assembly, and including a clamp means arrangement at the upper end of said tube part for clamping the seat pin in a desired position.
8. A folding bicycle according to any preceding claim, including a steerer clamp and hinge means for clamping the handlebars to the front fork assembly, and to permit hinging of the handle bars from an operative riding position to a folded configuration.
9. A folding bicycle according to any one of the preceding claims, wherein a first pivotal coupling is provided for pivotally mounting the front wheel assembly; the first pivotal coupling being arranged such that the front wheel assembly travels substantially within a first plane when it pivots from an operative riding configuration to a folded configuration.
10. A folding bicycle according to claim 9, wherein the first plane in which the front wheel assembly travels is angularly offset from the main frame.
11. A folding bicycle according to claim 10, wherein an axis about which the first plane is angularly offset from the main frame is substantially vertical when the bicycle is oriented for normal use.
12. A folding bicycle according to any one of claims 9 to II, further comprising a locking means for locking the front wheel assembly in said operative riding position and/or said folded configuration.
13. A folding bicycle according to any one of claims I to 8, wherein the front wheel assembly includes forks, comprising an upper fork part and a left lower fork part and a right lower fork part which hold the front wheel therebetween, and wherein each said lower -17-fork part is connected to the upper fork part by means of a respective pivotal coupling, which includes locking means for retaining the lower fork parts in an operative riding position, and the locking means being releasable to permit the front wheel to be pivoted towards the main frame assembly to said folded configuration.
14. A folding bicycle according to claim 13, wherein said locking means includes pawl means for engaging within respective first and second locations within said pivotal coupling to maintain the respective lower fork part either in an operative riding position or in a rearwardly folded position.
15. A folding bicycle according to claim 14, wherein said pawl means is spring biased into engagement with said pivotal coupling, and includes a finger grippable portion for releasing the pawl means from the pivotal coupling.
16. A folding bicycle according to claim 15, wherein said pawl means has a portion tapering towards its free end for engaging within similarly shaped recesses at said first and second locations.
17. A folding bicycle according to any of claims 13 to 16, wherein said pivotal coupling includes a washer and a threaded bush for providing a predetermined contact pressure within the pivotal coupling.
18. A folding bicycle according to any one of claims the preceding claims, wherein the front wheel assembly further comprises a steering tube mounted in a rotary coupling.
19. A folding bicycle according to claim 18, wherein the steering tube comprises a pivotal coupling to enable it to be displaced to a folded configuration.
20. A folding bicycle substantially as described herein with reference to the accompanying drawings.