GB2414972A - Folding bicycle - Google Patents

Abstract

A folding bicycle (1) in which a rear sub-frame (4) of the bicycle, carrying a rear wheel (14), is pivotable about a transverse axis into the folded condition, and a front sub-frame of the bicycle (3), carrying a front wheel (11) and a front strut assembly (12) of the bicycle is also pivotable about a transverse axis into the folded condition, both sub-frames also being arranged for lateral displacement when pivoted with respect to the main frame so that in the folded condition the sub- frames and the wheels they carry are displaced laterally from the main frame. In the folded condition the rear sub-frame (4) and the wheel (14) it carries is displaced laterally on one side of the main frame (2), and the front sub-frame (3) and the wheel (11) it carries is displaced laterally on the other side of the main frame (2). A hinge (16) may allow the folding and lateral displacement to occur via arcuate cam surfaces (21-24).

Description

24 1 4972 Polding Bicycle This invention relates to a folding bicycle, and

to a hinge mechanism for use in such a bicycle but also capable of use in other applications.

Many different types of folding bicycle are known. Efforts have been made to make the folded bicycle more compact, but these frequently involve complex mechanisms which extend the time required to fold or erect the bicycle. Folding bicycles usually have wheels which are of significantly smaller diameter than those of rigid bicycles, and this has effects on stability and the riding experience.

EP0026800A discloses a folding bicycle in which a rear sub frame carrying the rear wheel is pivoted about a transverse, horizontal axis until the rear wheel meets the underside of the main frame of the bicycle, in the region of the crank assembly. A front sub assembly carrying the front wheel and handlebars is pivoted about an upwardly directed axis so that the front wheel lies generally alongside the rear wheel in its folded condition. A problem with this bicycle is that the rear wheel size is limited, not just because of the general design of the bicycle but also because the wheel can only pivot until it meets the underside of the main frame.

Accordingly, an invention disclosed herein provides a folding bicycle comprising a main frame and a sub-frame carrying a wheel, the sub-frame being pivotable about a transverse axis into a folded condition, characterized in that the sub-frame is also arranged for lateral displacement when pivoted with respect to the main frame so that in the folded condition the sub-frame and the wheel it carries are displaced laterally from the main frame.

Thus, the extent to which the sub-frame can be pivoted is not limited by the wheel coming into contact with the main frame. As a result, a more compact folded condition can be provided and /or wheels of a larger diameter can be used.

In one arrangement, the sub-frame is a rear sub frame of the bicycle, carrying the rear wheel. Preferably, in such an arrangement, the rear subframe pivots about the transverse crank axis of the bicycle. In another arrangement, the sub- frame is a front - 2 sub-frame of the bicycle, carrying the front wheel and the front strut assembly of the bicycle. The front sub-frame will also carry the steering assembly and handlebars, which may also be foldable separately, so as to further reduce the size of the folded bicycle. However, in the preferred embodiment of the invention both a front sub frame and a rear sub-frame are arranged for lateral displacement when pivoted with respect to the main frame so that in the folded condition the sub- frames and the wheels they carry are displaced laterally from the main frame. Preferably, in such an arrangement, the rear sub-frame and the wheel it carries is displaced laterally on one side of the main frame, and the front sub- frame and the wheel it carries is displaced laterally on the other side of the main frame. This provides a particularly compact arrangement.

The hinge arrangement between a sub-frame and the main frame could be such that the sub-frame is firstly displaced laterally by a user, before being pivoted into its folded condition. The arrangement could be such that a user must exert a lateral force whilst the sub-frame is being pivoted, so as to urge the sub-frame in the lateral direction. However, in the preferred arrangement there is provided a hinge which automatically displaces the sub-frame in a lateral direction whilst the sub-frame is being pivoted with respect to the main frame. Preferable, the hinge comprises two portions with cooperating cam surface so that they are urged apart in the lateral direction whilst being pivoted in the sense for folding the sub-frame, and move together whilst the sub-frame is being pivoted in the opposite direction. Preferably a biasing member such as a spring is provided, biasing the portions to the closed condition. Thus, pivoting the sub-frame into the folded condition will be against the force of the biasing member. A locking arrangement may be provided to lock the portions in the closed and / or open condition. The biasing member may resist lateral and / or pivotal movement. For example, a coil spring may be provided to resist lateral movement against its axial resilience, but may also be arranged so that it resists pivoting through its tensional resistance.

In a preferred arrangement, the hinge comprises two portions, at least one being provided with a cam surface in the form of an arcuate ramp extending around the pivot axis. Preferably, a plurality of cam surfaces are provided and in the preferred embodiment there are two symmetrically disposed cam surfaces. In such an arrangement, each cam surface may extend over an arc of 180 . In the preferred embodiment, each portion is provided with matching cam surfaces. Thus, each - 3 portion may have two symmetrically disposed, substantially identical, cam surfaces, each cam surface extending over an arc of 180 , the cam surfaces on one portion matching and cooperating with the cam surfaces on the other portion. Preferably, the higher end of each cam surface is provided with an undercut, so that in the closed S condition the two portions interlock.

The cam surface need not slope at a constant rate, and in a preferred embodiment each cam surface rises to an arcuate plateau portion. This can help to keep the bike in its folded condition until it is desired to erect it again.

In the preferred embodiment, the rear sub-frame is hinged about the axis of the crank shaft. However, it would be possible to displace the pivot axis of the rear sub frame from that of the main bearing. If the pivot axis is to the rear of the main bearing, as in EP0026800A, it will be necessary to deal with the lateral displacent of the front chain wheel and the gear(s) on the rear wheel, and it may be necessary to deal with chain tension. If the rear sub-frame pivots about an axis in front of the main bearing, then there will be no problems as the main bearing and rear wheel will pivot together and the chain tension and orientation will be unchanged. In practice, it may be desired to use a standard type of main bearing for reasons of convenience or expense, and whilst pivoting elsewhere will permit this, it would also be possible to accommodate it whilst still pivoting the rear sub-frame about the axis of the crank shaft. For example, the movable part of the hinge could carry a conventional main bearing, a main shaft and one pedal arm and pedal, and the stationary part of the hinge could carry the other pedal arm and pedal, and a stub shaft with an adaptor which meshes with the main shaft when the hinge is in the closed condition.

The invention also extends to a method of folding a bicycle, and thus viewed from another aspect of the invention there is provided a method of folding a bicycle comprising a main frame and a sub-frame carrying a wheel, the sub-frame being pivotable about a transverse axis into a folded condition, characterised in that the method comprises the steps of pivoting the sub-frame with respect to the main frame and also displacing the sub-frame laterally with respect to the main frame, so that in the folded condition the sub-frame and the wheel it carries lie alongside the main frame. Preferably, a rear sub frame of the bicycle, carrying a rear wheel, is pivoted about a transverse axis into the folded condition, and a front sub-frame of the bicycle, carrying a front wheel and a front strut assembly of the bicycle is also - 4 pivoted about a transverse axis into the folded condition, both sub-frames also being displaced laterally when pivoted with respect to the main frame, but in opposite directions, so that in the folded condition the sub-frames and the wheels they carry lie alongside the main frame, on opposite sides of the main frame. Preferably, in the folded condition the front wheel, main frame and rear wheel lie in substantially parallel planes. Preferably, in the folded condition the front wheel and rear wheel are substantially coaxial.

The hinge used in the preferred embodiment of the folding bicycle may be used in other contexts, for example on other folding articles such as baby buggies or folding chairs, or wherever it is desired to associate pivoting movement with lateral displacement. Thus, a further invention disclosed herein provides a hinge having an open and a closed condition, the hinge comprising two members arranged for relative pivotal movement about a pivot axis from the closed condition to the open condition, each member having a pair of arcuate cam surfaces disposed symmetrically about the pivot axis, the cam surfaces on one member cooperating with the cam surfaces on the other member so that upon relative pivotal movement of the members about the pivot axis, there is also relative translation of the members in the direction of the pivot axis, wherein each cam surface is in the form of a ramp provided with an undercut portion, and the undercut portions of one member interlock with the respective undercut portions of the other member when the hinge is in the closed condition. Preferably, a resilient member acts between the two members, providing a bias against movement from the closed condition to the open condition.

A bicycle and a hinge in accordance with the inventions will now be described by way of example, and with reference to the accompanying drawings, in which: Figure 1 is a side view of a folding bicycle in its erected condition; Figure 2 is a top plan view of the bicycle in its erected condition; Figure 3 is a top plan view of the bicycle in a partially folded condition; Figure 4 is a top plan view of the bicycle in its fully folded condition; - 5 Figure 5 is a side view of the bicycle in its fully folded condition; Pigure 6 is a perspective view of a hinge for use in the bicycle, shown when the bicycle is in its erected condition; Pigure 7 is a perspective view of the hinge, shown when the bicycle is in its fully folded condition; Figure 8 is a top plan view of one of the pivotal members constituting the hinge; Pigure 9 is a side view of the pivotal member, Figure 10 is a section on the line A-A of Pigure 8; Figure 1 1 is a perspective section through the hinge at the front of the bicycle, shown when the bicycle is in its erected condition; Pigure 12 is a perspective section through the hinge at the front of the bicycle, shown when the bicycle is in its fully folded condition; Pigure 13 is a perspective section through the hinge at the rear of the bicycle, accommodating the main crank bearing, shown when the bicycle is in its erected condition; and Pigure 14 is a perspective section through the hinge at the rear of the bicycle, shown when the bicycle is in its erected condition.

Referring now to the drawings in detail, in Figures 1 and 2 there is shown a folding bicycle 1, comprising a main frame 2, a front sub-frame 3 and a rear sub-frame 4.

The main frame carries a saddle post 5 and a saddle 6, as well as a crank assembly 7 with a chain wheel 8 and pedals 9. The front sub frame carries a front strut 10 to which the front wheel l 1 is attached. As shown, the front strut is a single strut on one side of the wheel 11, although a conventional front fork arrangement could be used. The front strut 10 is supported in a bearing 12, and is attached to a handlebar assembly 1 3. The rear sub-frame 4 carries a rear wheel 14 driven by a chain 15 connected to the chain wheel 8. - 6

The front sub-frame 3 is pivotably attached to the main frame by a transverse hinge 16. This allows the sub-frame 3 to pivot with respect to the main frame 2 and simultaneously to undergo lateral translation to the left as viewed from above in Figure 2. The rear sub-frame 4 is pivotably attached to the main frame by a transverse hinge 17. This allows the sub-frame 4 to pivot with respect to the main frame 2 and simultaneously to undergo lateral translation to the right as viewed from above in Figure 2. The hinge 17 is arranged coaxially with the main bearing for the crank assembly 7.

The manner in which the bicycle is folded from its erected state, shown in Figures I and 2, will now be described with reference to Figures 3, 4 and 5. Firstly, the front sub-frame 3 carrying wheel 11 is pivoted about the hinge 16 in the clockwise direction as viewed in Figure I. Simultaneously, it undergoes lateral translation to the left of the main frame, until it takes up the partly folded position shown in Figure 3, where the front wheel I I lies partially alongside the main frame 2. Further pivoting brings the sub-frame 3 to the fully folded position shown in Figure 4, where the front wheel 11 lies entirely alongside the main frame 2. As shown in Figure 4, the rear sub-frame 4 carrying wheel 14 has also been pivoted about the hinge 17 in the anti-clockwise direction as viewed in Figure 1. Simultaneously, it has undergone lateral translation to the right of the main frame, until it takes up the position shown in Figure 4, where the rear wheel 14 lies fully alongside the main frame 2, parallel to wheel I I and with their axes of rotation coinciding. The order in which the sub frames are pivoted can be reversed. In the folded condition, the front wheel, rear wheel and main frame are in substantially parallel planes. The single front strut 10 is on the side of the front wheel 11 in the direction of lateral displacement when the bicycle is folded, so that it is on the outside of the bicycle when folded and does not limit the extent to which the wheel 11 can be positioned close to the main frame 2.

To complete the folding operation, the saddle 6 is lowered, for example using a conventional quick release mechanism. The folded state of the bicycle is shown from the side in Figure 5. The main frame 2 is provided with an aperture 18 along its length, so that in the folded condition the main frame 2 provides a handle for carrying the folded bicycle. As an additional feature, an arrangement could be provided for folding the handlebars to make the folded structure even more compact. - 7

Erecting the bicycle involves carrying out the above steps in reverse.

The bicycle may be manufactured from any suitable material but in one preferred embodiment a number of components such as the wheels and the main frame are made from a lightweight plastics or composite material.

The basic structure and operation of the hinges 16 and 17 will now be described in more detail. Figure 6 is a perspective view of hinge 16 when the bicycle is in the fully extended condition, and Figure 7 is a perspective view when the bicycle is in l O the fully folded condition. Hinge 16 has two hinge portions l 9 and 20, each with a pair of symmetrically disposed arcuate cam surfaces in the form of ramps 21, 22 on portion 19 and matching ramps 23, 24 on portion 20. Each ramp has a plateau at its highest point and is provided with an undercut 25, 26, 27, 28 (the second undercut 26 on portion] 9 is not shown in Figures 6 and 7 but can be seen in Figure 8. In the closed condition shown in Figure 6, the undercuts 25, 27 and 26, 28 are interlocked, thus resisting unwanted lateral movement. When portion 20 is pivoted with respect to portion 19, the ramps cooperate so that the portions move apart in the direction of the pivot axis.

Portion 19 is shown in more detail in Figures 8, 9 and l O. Portion 20 is identical.

Figure 8 shows how the arcuate ramps 21 and 22 are arranged symmetrically, displaced by 180 . Figure 9 shows that the ramps 21 and 22 have identical profiles, with a straight inclined portion joined by a short curve to a plateau portion, respectively 29, 30, at the highest point. Figure 10 shows more clearly the nature of the undercut 26.

Figures 11 and 12 show a more complex front hinge 16' which incorporates a locking mechanism for locking the bicycle in the fully erected condition, and a biasing spring. A fixed hinge portion 31 is attached to the main frame 2, and a rotatable hinge portion 32 is attached to the front sub-frame 3. These portions have cam surfaces arranged as described with reference to Figures 6 to 10 and operate in the manner described previously to provide lateral translation upon being pivoted with respect to each other. A cylindrical part 33 of portion 31 extends into a cavity in portion 32, and terminates in a flange 34. Similarly, cylindrical part 35 of portion 32 extends into a cavity in portion 31, and terminates in a flange 36. There is thus defined an annular space between the two flanges 34 and 36 and a coil spring 37 is - 8 positioned in this space. As the two portions 31 and 32 move apart, upon rotation, towards the position shown in Figure 12, the spring 37 is compressed between the flanges 34 and 38, and thus provides a biasing force resisting lateral translation.

Figures 11 and 12 also show a locking mechanism for use when the bicycle is in the erected condition and the hinge portions are as shown in Figure 11. Portion 31 is provided with a threaded hole 38 and portion 32 is provided with a captive threaded bolt 39 which is screwed into the threaded hole to lock the portions 31 and 32 in the closed condition. The head 40 of the bolt can be provided with a gripping portion 4 l so that a user can easily lock and unlock the hinge. A small coil spring 42 around the bolt acts between portion 31 and the head 40 of the bolt to provide an anti-backlash function.

Figures 13 and 14 show a rear hinge 17'. A fixed hinge portion 43 is attached to the main frame 2, and a rotatable hinge portion 44 is attached to the rear sub-frame 4.

These portions have cam surfaces arranged as described with reference to Figures 6 to 10 and operate in the manner described previously to provide lateral translation upon being pivoted with respect to each other. A cylindrical part 45 of portion 43 extends into a cavity in portion 44, and terminates in a flange 46. Similarly, cylindrical part 47 of portion 44 extends into a cavity in portion 43, and terminates in a flange 48. There is thus defined an annular space between the two flanges 46 and 48, and a coil spring 49 is positioned in this space. As the two portions 43 and 44 move apart, upon rotation, towards the position shown in Figure 14, the spring 49 is compressed between the flanges 46 and 48, and thus provides a biasing force resisting lateral translation Hinge portion 43 is provided with a main bearing 50 for the pedal crank shaft 51, and hinge portion 44 is also provided with a main bearing 52 for the pedal crank shaft 51, the shaft extending along the pivot axis of the hinge. Within the hinge 17', the crank shaft is telescopic, so that it can change length as the hinge portions move apart or together. Thus, in this region the crank shaft 51 comprises a first portion 53 which extends telescopically into a second portion 54. Portion 53 is provided with a pin 55 which is slidably received in a longitudinally extending slot 56 provided in the second portion 54. A number of pin and slot arrangements may be provided if desired, spaced circumferentially around the shaft, to provide balance and to permit the transmission of greater forces. 9 -

There is no need for a locking mechanism for the rear hinge 17 or 17' of the bicycle although one could be incorporated if desired. The engagement of the undercut portions and the effect of the spring 49 resist lateral movement, and the nature of the S forces on the hinge when there is a load, provides a reaction force tending to keep the hinge in the closed condition.

The bicycle will normally incorporate other features such as brakes and gears. Either or both of these may be hub mounted if desired.

In the preferred embodiment there is provided a folding bicycles which is easy to fold and erect, and which forms a compact package when folded, whilst enabling the use of wheels of a larger diameter than those normally associated with folding bicycles. -

Claims (30)

1. A folding bicycle comprising a main frame and a sub-frame carrying a wheel, the sub-frame being pivotable about a transverse axis into a folded condition, characterised in that the sub-frame is also arranged for lateral displacement when pivoted with respect to the main frame so that in the folded condition the sub-frame and the wheel it carries are displaced laterally from the main frame.

2. A folding bicycle as claimed in claim 1, characterised in that the subframe is a rear sub frame of the bicycle, carrying a rear wheel.

3. A folding bicycle as claimed in claim 2, characterised in that the rear sub- frame pivots about a transverse crank axis of the bicycle.

4. A folding bicycle as claimed in claim 1, characterised in that the subframe is a front sub-frame of the bicycle, carrying a front wheel and a front strut assembly of the bicycle.

5. A folding bicycle as claimed in claim 1, characterised in that a rear sub frame of the bicycle, carrying a rear wheel, is pivotable about a transverse axis into the folded condition, and a front sub-frame of the bicycle, carrying a front wheel and a front strut assembly of the bicycle is also pivotable about a transverse axis into the folded condition, both sub-frames also being arranged for lateral displacement when pivoted with respect to the main frame so that in the folded condition the sub-frames and the wheels they carry are displaced laterally from the main frame.

6. A folding bicycle as claimed in claim 5, characterised in that in the folded condition the rear sub-frame and the wheel it carries is displaced laterally on one side of the main frame, and the front sub- frame and the wheel it carries is displaced laterally on the other side of the main frame.

7. A folding bicycle as claimed in claim 5 or 6, characterised in that each sub frame is pivotal connected to the main frame by a hinge which automatically displaces the sub-frame in a lateral direction whilst the sub-frame is being pivoted with respect to the main frame.

8 A folding bicycle as claimed in claim 7, characterised in that each hinge comprises two portions with cooperating cam surface so that they are urged apart in the lateral direction whilst being pivoted in the sense for folding the respective sub frame, and move together whilst the sub-frame is being pivoted in the opposite direction.

9. A folding bicycle as claimed in claim 8, characterised in that a biasing member is provided, biasing the hinge portions to the closed condition.

10. A folding bicycle as claimed in claim 8 or 9, characterised in that at least one of the hinges is provided with a locking arrangement to lock the portions in the closed condition.

11. A folding bicycle as claimed in claim 10 characterised in that only the hinge for the front sub-frame is provided with a locking arrangement.

12. A folding bicycle as claimed in any of claims 8 to 11, characterised in that the hinge portions are provided with cooperating cam surfaces in the form of arcuate ramps extending around the pivot axis.

13. A folding bicycle as claimed in claim 12, characterised in that a plurality of arcuately displaced cam surfaces are provided on each hinge portion.

14. A folding bicycle as claimed in claim 13, characterised in that the higher end of the ramp of each cam surface is provided with an undercut, so that in the closed condition the two hinge portions interlock.

15. A folding bicycle as claimed in any of claims 7 to 14, characterised in that the rear hinge is coaxial with and extends around a main crank shaft for the bicycle.

16. A folding bicycle as claimed in claim 15, characterised in that the rear hinge has a crank shaft bearing on each side of the main frame.

17. A folding bicycle as claimed in claim 16, characterised in that a portion of the crank shaft extending between the two crank shaft bearings is telescopic.

18. A folding bicycle as claimed in any of claims 5 to 17, characterised in that the front strut assembly comprises a single strut to which the front wheel is attached, the single strut being on the side of the wheel in the direction of lateral displacement when the bicycle is folded. s

19. A folding bicycle as claimed in any of claims 5 to 18, characterised in that in the folded condition the front wheel, main frame and rear wheel lie in substantially parallel planes.

20. A folding bicycle as claimed in claim 19, characterised in that in the folded condition the front wheel and rear wheel are substantially coaxial.

21. A method of folding a bicycle comprising a main frame and a sub-frame carrying a wheel, the sub-frame being pivotable about a transverse axis into a folded condition, characterised in that the method comprises the steps of pivoting the sub frame with respect to the main frame and also displacing the sub-frame laterally with respect to the main frame, so that in the folded condition the sub-frame and the wheel it carries lie alongside the main frame.

22. A method as claimed in claim 21, characterised in that a rear sub frame of the bicycle, carrying a rear wheel, is pivoted about a transverse axis into the folded condition, and a front sub-frame of the bicycle, carrying a front wheel and a front strut assembly of the bicycle is also pivoted about a transverse axis into the folded condition, both sub-frames also being displaced laterally when pivoted with respect to the main frame, but in opposite directions, so that in the folded condition the sub frames and the wheels they carry lie alongside the main frame, on opposite sides of the main frame.

23. A method as claimed in claim 22, characterised in that in the folded condition the front wheel, main frame and rear wheel lie in substantially parallel planes.

24. A method as claimed in claim 23, characterised in that in the folded condition the front wheel and rear wheel are substantially coaxial.

A folding bicycle as claimed in claim 1, characterized in that the subframe is pivotable by means of a hinge having an open and a closed condition, the hinge comprising two members arranged for relative pivotal movement about a pivot axis from the closed condition to the open condition, each member having a pair of arcuate cam surfaces disposed symmetrically about the pivot axis, the cam surfaces on one member cooperating with the cam surfaces on the other member so that upon relative pivotal movement of the members about the pivot axis, there is also relative translation of the members in the direction of the pivot axis, wherein each cam surface is in the form of a ramp provided with an undercut portion, and the undercut portions of one member interlock with the respective undercut portions of the other member when the hinge is in the closed condition.

26. A folding bicycle substantially as hereinbefore described and with reference to the accompanying drawings.

27. A method of folding a bicycle, substantially as hereinbefore described and with reference to the accompanying drawings.

28. A hinge having an open and a closed condition, the hinge comprising two members arranged for relative pivotal movement about a pivot axis from the closed condition to the open condition, each member having a pair of arcuate cam surfaces disposed symmetrically about the pivot axis, the cam surfaces on one member cooperating with the cam surfaces on the other member so that upon relative pivotal movement of the members about the pivot axis, there is also relative translation of the members in the direction of the pivot axis, wherein each cam surface is in the form of a ramp provided with an undercut portion, and the undercut portions of one member interlock with the respective undercut portions of the other member when the hinge is in the closed condition.

29. A hinge as claimed in claim 28, characterized in that it incorporates a resilient biasing element acting between the two members and resisting relative translation of the two members apart.

30. A hinge substantially as hereinbefore described and with reference to the accompanying drawings.