Folding bicycles are a popular mode of transport for riders who wish to undertake a part of the journey on public transport, for example by train, and part of their journey by bicycle.

Some current designs of folding bicycles have as their principal design criterion the minimisation of the folded volume of the bicycle, so that it is easily stowable in the luggage compartments of public service vehicles. However, such folding bicycles often make use of complex and expensive sub-structures such as folding pedal assemblies. Furthermore, the disposition of the wheels in the folded condition makes it necessary to carry the folded bicycle rather than trail it.

Another type of folding cycle has a simple vertical- axis hinge in its frame, so that the front and rear frame halves may be brought to a side-by-side relation, with the wheels adjacent each other. While this allows the folded cycle to be trailed rather than carried, the size of the folded cycle is not minimised.

The present invention seeks to provide a folding bicycle which, while minimising the volume of the bicycle when folded, permits the folded bicycle to be trailed on its road wheels.

A further feature of the folding bicycle of the present invention is that, in the folded condition, the axis of the pedals of the bicycle is skewed in relation to the axes of the road wheels, in order that the road wheels may be placed closer together with the bicycle frame between them thus minimising the overall size of the folded cycle.

In a preferred embodiment of the bicycle of the present invention, the rear wheel of the bicycle is mounted on a single rear arm positioned to one side of the rear wheel, and the drive chain and transmission components of the bicycle are contained within the rear arm.

According to a first aspect of the present invention, there is provided a folding bicycle having frame members pivotally connected for movement between riding and folded positions, wherein wheels are mountable to the respective frame members at primary mounting points when the frame is in the riding position for riding, and are mountable to the frame at secondary mounting points when the frame is in the folded position, the wheels being substantially coaxial when mounted to the secondary mounting points when the frame is folded to enable trailing of the folded bicycle.

A further aspect of the invention provides a folding frame for a bicycle, having secondary attachment points for securing wheels to the folded frame in a substantially coaxial arrangement.

In a preferred embodiment, the secondary mounting points are so positioned that the wheel axes are

inclined relative to the axis of rotation of the bicycle pedals when the frame is folded and the wheels are attached at the secondary mounting points.

The secondary attachment points for the wheels may be on the same frame member as each other, or may be on different frame members. In the latter case, the secondary attachment points may be cooperable to secure the frame in the folded position.

An embodiment of the present invention will be now described in detail, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a folding bicycle according to the present invention, in the riding position; Figure 2 is a perspective view of the bicycle of Figure 1 in a partially folded position ; Figure 3 is an end view of the bicycle in the folded position of Figure 2; Figure 4 is a view of the bicycle in the completely folded position; and Figure 5 illustrates the trailing of the folded bicycle.

Referring now to the figures, Figure 1 shows the bicycle 1 in the riding position. The bicycle 1 comprises a main frame member 2, at the forward end of which is formed a steering head 3. The steering head comprises a steering shaft mounted in bearings in the

main frame member 2, having an upwardly-extending end 3a protruding from the main frame member 2, and a downwardly-protruding end 3b.

A handlebar stem 4 is mounted to the upwardly protruding end 3a (see Figure 5) of the steering shaft, by means of a clamp 5. The clamp 5 is provided with a quick-release cam lever 6 of conventional type, so that the handlebar stem 4 may be quickly secured to the shaft end 3a without the need for tools. The shaft end 3a and handlebar stem 4 may have non- circular cross-sections, or may be provided with splines or a key and keyway to ensure that the steering shaft rotates with the handlebar stem 4 when the two are fixed together by the clamp 5.

A fork assembly 7 is mounted to the lower end 3b of the steering shaft, by means of a clamp 8 similar to the clamp 5. The clamp 8 may have a quick-release cam arrangement 8a, for tool-free mounting and dismounting of the fork 7 to the steering shaft. The fork 7 and steering shaft may have complimentary non-circular section portions to ensure that the fork assembly 7 rotates with the steering shaft, as the handlebar stem 4 is turned.

The fork assembly 7 shown in Figure 1 is a single bladed fork, extending only on one side of the front wheel 9 of the bicycle. It is to be understood that a twin-bladed front fork may be used instead of the single-bladed fork assembly 7. However, an advantage of the single-bladed fork assembly is that the tyre 10 may be removed from the front wheel 9 without removing the front wheel 9 from the fork assembly 7. Puncture repair is therefore simplified.

Extending from the front fork assembly 7 coaxially with the front wheel 9 is a mounting stem 11. The mounting stem 11 is provided with a cradle 12. The purpose of the mounting stem 11 and cradle 12 will be described below.

At the upper end of handlebar stem 4 is a pair of handlebars 13, carrying brake levers 14. At their outboard ends, handlebars 13 have forwardly-extending horns 15 which provide alternative riding positions to the rider.

At the rearward end of the main frame member 2, there is provided a socket 16 to accept a saddle stem 17, to the upper end of which a saddle 18 is mounted. The socket 16 is surrounded by a clamp 19 for securing the saddle stem 17 in the socket 16. The clamp 19 has a pair of rearwardly and downwardly extending webs 20 forming a clevis arrangement to receive the upper end of a spring and damper assembly 21. The clamp 19 is split between the webs 20, so that when the clamp 19 is released the spring and damper assembly 21 is disconnectable from the clamp 19, and the saddle stem 17 is removable from the socket 16. The clamp 19 is preferably provided with a quick-release cam lever 22.

The rear end of the main frame member 2 is pivotally connected to the front end of a swinging arm 23. A pair of pedals 24 mounted to a transversely-extending pedal axle 25 are supported in bearings mounted in the forward end of the swinging arm 23. An attachment socket 26 is provided on the forward end of the swinging arm 23, adjacent the near-side pedal. The purpose of this attachment socket 26 will be described later.

Intermediate the length of the swinging arm 23, the spring and damper assembly 21 is attached to a transversely-extending stud 27. The spring and damper assembly 21 is pivotally attached to stud 27, but with sufficient frictional engagement to prevent the spring and damper assembly 21 from rotating about the stud 27 under its own self-weight.

To the rear end of the swinging arm 23, rear wheel 28 is mounted to one side of the swinging arm 23. The swinging arm 23 comprises a stub axle to which the rear wheel 28 is detachably mounted, the stub axle being connected to the pedals 24 by means of sprockets and a chain which extend within the tubular swinging arm 23. The rear wheel 28 is detachable from the swinging arm 23 without disturbing the chain and sprockets, which are held in bearings mounted to the swinging arm 23 and rotatable relative thereto.

The rear wheel 28 has an axially-extending stub axle 29 extending away from the swinging arm 23.

Adjacent the rear end of the swinging arm 23, a tubular mounting socket 30 is provided on the swinging arm, the axis of the tubular mounting socket extending transversely to the swinging arm, but inclined at an angle to the pedal shaft 25 connecting the pedals 24.

The tubular mounting socket 30 is provided with a quick-release clamping arrangement 31 such as a cam lever. The tubular mounting socket 31 is dimensioned so as to be able to accept the mounting stem 11 of the front fork assembly 7. The mounting stem 11 is itself a tubular element, the lumen of the mounting stem 11 being dimensioned so as to accept the stub axle 29 mounted to rear wheel 28.

In order to minimise dimensions of the folded bicycle, the tubular mounting socket 30 is spaced from the rear end of the swinging arm 23 by a distance substantially equal to the radius of the rear wheel 28.

The stages in the folding of the bicycle will now be described in relation to Figures 2 to 4.

The first step in the folding procedure is to release the clamp 8 which attaches the front fork assembly 7 to the steering shaft, the rear wheel 28 is then released from its mounting to the swinging arm 23.

The clamp 19 is released to free the upper end of the spring-damper assembly 21 from the webs 20, and the rear swinging arm 23 may then be rotated about its pivot in order to bring the swinging arm 23 to a position below the main frame member 2 of the bicycle.

The mounting stem 11 of the front fork assembly 7 is then introduced into the tubular mounting socket 30 from the near-side of the bicycle frame. The stub axle 29 of the rear wheel is inserted into the off- side end of the tubular mounting socket 30, and is received within the lumen of the mounting stem 11.

The clamping arrangement 31 is then operated to secure the mounting stem 11 and the stub axle 29 to the mounting socket 30. The arrangement is such that the wheels 9 and 28 are coaxial, but their axes are skewed relative to the pedal axle, as is seen best in Figure 3. The skewing of the axes of the wheels relative to the pedal axis reduces to a minimum the transverse dimension T of the folded bicycle. The angle a between the mounting socket axes and the pedal axle is chosen in dependence on the throw of the pedal crank 24, and the width of the pedal in the direction of the

pedal axle axis. In the embodiment shown the angle is approximately 250, but may be greater or less than this angle depending on the dimensions of the wheels, the pedals and the cranks.

The next step in the folding procedure is to remove the saddle stem 17 from the now-loosened. clamp 19.

The mounting stem 11 of the front fork assembly 7 is so arranged that the front fork blade extends from the mounting stem 11 towards the steering head 3. The clamp 8 at the upper end of the fork assembly 7 and the steering head 3 define between them a gap into which the nose of the saddle 18 can be introduced, so that the saddle 18 is supported between the clamp 8 and the steering head 3. The saddle stem 17 is received in the cradle 12, and extends to a point below the rear end of the main frame member 2, adjacent the pedals 24.

The next stage in the folding procedure is to release the clamp 5 which attaches the handlebar stem 4 to the upper end 3a of the steering shaft, and remove the handlebars and handlebar stem. The handlebars 13 are provided, at the junction of the handlebars and the handlebar stem with a mounting spigot 32 which is engageable with the attachment socket 26 positioned on the swinging arm 23 adjacent the near-side pedal 24.

The mounting spigot 32 is introduced into the attachment socket 26, and is clamped therein by means of a quick-release clamp 33. In this position, the handlebars 13 extend substantially vertically and the handlebar stem 4 extends above the saddle stem 17, optionally to rest on the main frame member 2 at its end remote from the mounting spigot 32. The folded position is shown in Figures 4 and 5, and in this

position the upper of the two handlebar horns 15 extends substantially parallel to the axis of the tubular mounting socket 30, and therefore parallel to the axes of wheels 9 and 28. As shown in Figure 5, the folded bicycle can be trailed by grasping the upper handlebar horn 15, and lifting and pulling the folded cycle so that it rolls on its wheels 9 and 28.

Since the front wheel 9 is not disconnected from the fork assembly 7 during the folding procedure, the front wheel brake (not shown) is not disturbed. The front wheel brake may therefore be of any conventional type in which brake blocks engage the wheel rim, or may be a disc brake arrangement or a drum brake mounted to the hub of the front wheel.

Since the rear wheel is disconnected from the swinging arm 23 during the folding procedure, the preferred braking arrangement for the rear wheel is a hub- mounted brake which is retained to the swinging arm 23. Alternative brake arrangements such as caliper or disc brakes may be used.

During the folding operation, brake cables extending from the front and rear brakes to brake levers 14 on the handlebars 13 will wrap round the folded parts of the bicycle, particularly retaining the saddle 18 and saddle stem 17 in their folded positions.

To deploy the folded bicycle for riding, the folding procedure is simply undertaken in reverse. First, the handlebars and handlebar stem are disconnected from the attachment sockets 26, and attached to the upper end 3a of steering shaft 3 using the clamp 5. The saddle 18 and saddle stem 17 are then withdrawn from

their folded position in cradle 12, and the lower end of saddle stem 17 is introduced into the socket 16.

The clamp 31 of the tubular mounting socket 30 is then released, and the front and rear wheels released from the swinging arm 23.

The swinging arm 23 is then swung downwardly and rearwardly, until the upper end of the spring-damper assembly 21 re-engages with the webs 20 of the clamp 19. The clamp 19 is then tightened to secure the spring-damper assembly.

The front fork assembly 7 is then mounted to the lower end of the steering shaft by means of clamp 8, and the rear wheel is mounted again to the rear end of swinging arm 23. After checking that all clamps have been properly tightened the bicycle is ready for riding again.

In the embodiment described, both the front and rear wheels are mounted to the bicycle frame at one side only. It will however be understood that a twin- bladed front fork assembly may be used instead of the single-bladed assembly shown. Furthermore, the bicycle may not be provided with rear suspension but may have a swinging arm 23 which is pivotable in relation to the main frame member 2 about a transverse axis, and lockable in folded and extended positions, respectively.

In the folded condition of the bicycle frame, the wheels of the bicycle are coaxial, and are skewed in relation to the axis of the bicycle pedals so that the lateral dimension of the folded bicycle frame is

minimised without the use of folding pedal assemblies.

In the embodiment illustrated the tubular mounting socket 30 which provides a second mounting point on the bicycle frame for the bicycle wheels, is provided on the swinging arm 23. It will be understood that the tubular mounting socket 30 may alternatively be provided on the main frame member 2, aligned transversely to the main frame member 2 and set at an inclined angle relative to the pedal axle.

In a further alternative embodiment, the tubular mounting socket 30 may be provided as two separate components mounted on respective parts of the bicycle frame such that, when the frame is in its folded condition, the parts of the tubular mounting socket are coaxial, and the front and rear wheels of the bicycle may be attached to respective parts of the tubular mounting socket.

In an advantageous embodiment, one part of the tubular mounting socket 30 may be provided on the swinging arm and another part on the underside of the main frame member 2. When the frame is folded, mounting spigot 29 will extend through both parts of the tubular mounting portion 30 and will prevent"unfolding"of the frame. The secondary mounting arrangement for the wheels may thus be used to secure the frame in its folded position during storage and trailing of the folded bicycle.

In the embodiments described above, the front and rear wheels of the bicycle are of the same diameter. It is, however, foreseen that the front and rear wheels may have different diameters. In such an embodiment,

each wheel will be secured to the folded frame at a respective secondary mounting point, with the axes of the front and rear wheels parallel and spaced vertically by a distance equal to the difference in the wheel diameters. The wheel axes will preferably be inclined to the pedal shaft axis, to reduce the lateral dimension of the folded bicycle. It is further foreseen that the two secondary mounting points necessary to mount wheels of different diameters may be mounted on the same frame element, rather than on different and relatively movable frame elements.

The folding bicycle described hereinabove may be provided as a complete bicycle or as a bare frame or as a kit of parts for assembly.