GB2578641A

GB2578641A - Folding bicycle

Info

Publication number: GB2578641A
Application number: GB1817959.8A
Authority: GB
Inventors: Jones Timothy
Original assignee: Arcc Innovations Ltd
Current assignee: Arcc Innovations Ltd
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-05-20
Also published as: GB201817959D0

Abstract

A folding bicycle frame 2 comprising a main frame 20; a seat tube 21 rotatably connected to the main frame 20 at a seat tube pivot (25, figure 11): a down tube 22 rotatably connected to the main frame 20 at a down tube pivot (26, figure 11) and a toggle 24 which is rotatably connected to a lower end of the seat tube 21 at a first toggle pivot (27, figure 11) and a lower end of the down tube 22 at a second toggle pivot (28, figure 11). The frame 2 is foldable by rotation of the seat tube 21 about the seat tube pivot 25 and the down tube 22 about the down tube pivot 26; wherein the toggle 24 is configured to require the seat tube 21 to be rotated forwards, about the seat tube pivot 25, towards the down tube 22 to allow the folding bicycle frame 2 to be moved from the unfolded configuration to the folded configuration. A rear strut (80, figure 19) comprises first 81 and second 82 portions which may rotate relative to each other to allow the seat tube 21 to pivot forwards.

Description

Folding Bicycle

Technical Field

The disclosure relates to folding bicycles. The folding bicycles comprise a folding bicycle frame configured to allow the folding bicycle frame to be moved between an unfolded configuration and a folded configuration.

Background

W02017/199015 describes an example of a folding bicycle which comprises a steerable front wheel assembly including a front frame member, a rear wheel assembly including a lower frame member, a seat post member and a rear wheel. The lower frame member comprises a first hinge connected to the seat post member and operating on a horizontal axis to allow the bicycle to be folded. The steerable front wheel assembly comprises a hinged handlebar operable in use to position the handlebar in contact with the rear wheel, thereby reducing the size of the bicycle.

A problem with the folding bicycle of W02017/199015 is that the handlebars and front wheel must rotate 180 degrees before folding back towards the rear wheel. When riding the folding bicycle this means that the handlebar joint is completely reliant on the locking mechanism to stop the handlebars from collapsing forwards (which is the direction the largest forces act on the handlebars due to the user pushing forwards against them when the bike is decelerating due to braking).

A further problem with the folding bicycle of W02017/199015 is that the front frame member and the seat post member can be moved independently of one another which can lead to mis-alignment of the locking mechanism of the folding bicycle which comprises a sliding latch. In addition, both the front frame member and the seat post member must be operated manually to achieve the required movement of the sliding latch.

A further problem is the use of sliding parts in the locking mechanism which may in use quickly wear as engaging surfaces grind over one another during locking and unlocking movements. This may introduce a lot of disadvantageous "play" in the folding mechanism of the folding bicycle.

A further problem is that the sliding latch may be susceptible to the ingress of dirt and other foreign objects as the sliding parts are not fully enclosed.

A further problem is that the support stay of the folding bicycle is another independently hinged member which must be operated manually when folding and unfolding the folding bicycle.

Summary of the disclosure

The present disclosure provides in a first aspect a folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; a down tube rotatably connected to the main frame at a down tube pivot; and a toggle which is rotatably connected to a lower end of the seat tube at a first toggle pivot and a lower end of the down tube at a second toggle pivot; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; wherein the toggle is configured to require the seat tube to be rotated forwards, about the seat tube pivot, towards the down tube to allow the folding bicycle frame to be moved from the unfolded configuration to the folded configuration.

The toggle may be configured such that in the unfolded configuration the second toggle pivot is positioned to a first side of an imaginary line which extends between the seat tube pivot and the first toggle pivot; and such that in the folded configuration the second toggle pivot is positioned to a second side of the imaginary line; wherein rotation of the seat tube forwards, about the seat tube pivot, towards the down tube causes the second toggle pivot to move across the imaginary line from the first side to the second side.

The seat tube, down tube and toggle may be interlinked such that they do not move independently of one another. The seat tube and down tube may be interlinked only by the toggle and main frame such that the folding bicycle frame does not comprise a top tube.

The folding bicycle frame may be configured as a step-through bicycle frame.

Each of the seat tube pivot, the down tube pivot, the first toggle pivot and the second toggle pivot may have an axis of rotation that is horizontal.

The seat tube and the down tube may remain in a common plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration. The seat tube and down tube may lie on a centre plane of the folding bicycle frame.

The main frame may comprise a pair of frame members that are offset to either side of the centre plane; the seat tube and the down tube extending in between the pair of frame members.

The toggle may comprise one or more toggle plates.

The seat tube may comprise a pair of seat tube extensions at the lower end of the seat tube which may extend downwardly from the seat tube pivot to define a seat tube channel therebetween; the first toggle pivot may be located at a distal end of the seat tube extensions. The down tube and the toggle may move within the seat tube channel as the folding bicycle frame is folded between the folded configuration and the unfolded configuration.

The seat tube may comprise a seat tube end piece at the lower end of a seat tube tubular member. The down tube may comprise a down tube end piece at the lower end of a down tube tubular member. Each end piece may be configured with a connecting post which is received within the respective tubular member. The connecting post and tubular member may be joined together by a suitable means, for example welding or bonding. Alternatively, each end piece may be configured as a socket which receives the respective tubular member. The socket and tubular member may be joined together by a suitable means, for example welding or bonding. In a further alternative each end piece may be formed integrally with its respective tubular member.

The toggle may comprise a caster wheel, optionally a rigid caster wheel.

The folding bicycle frame may further comprise a rear strut having a first end that is rotatably connected to the seat tube and a second end that is rotatably connected to the main frame. The rear strut may form at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot.

The present disclosure further provides in a second aspect a folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; and a down tube rotatably connected to the main frame at a down tube pivot; a lower end of the seat tube being interlinked to a lower end of the down tube; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; wherein the main frame comprises a pair of frame members that are offset to either side of a centre plane of the folding bicycle frame.

The seat tube and the down tube may extend in between the pair of frame members. The seat tube and down tube may lie on the centre plane of the folding bicycle frame. The seat tube and the down tube may remain in the centre plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration.

The seat tube pivot may comprise a pivot joint that extends between the pair of frame members with the seat tube rotatably coupled to the pivot joint. The down tube pivot may comprise a pivot joint that extends between the pair of frame members with the down tube rotatably coupled to the pivot joint.

The main frame may further comprise a bottom bracket shell that extends between the pair of frame members.

The lower end of the seat tube may be interlinked to the lower end of the down tube by a toggle which is rotatably connected to the lower end of the seat tube at a first toggle pivot and the lower end of the down tube at a second toggle pivot; the toggle may be mounted in between the pair of frame members.

One or both of the pair of frame members may comprise a sheet member. Each frame member may be formed mainly or wholly from a single integral sheet of material. This is in contrast to a frame member formed from joining a plurality of separate parts, for example tubular members, to form a framework.

One or both of the pair of frame members may be configured with one or more openings, for example by cutting, stamping or pressing the sheet of material, to produce a truss-like structure.

One or both of the pair of frame members may comprise a generally triangular form, optionally including one or more internal openings. One or both of the pair of frame members may comprise a lower arm, a front upper arm and a rear upper arm; the front upper arm and the rear upper arm may meet at an upper apex.

The seat tube pivot and the down tube pivot may be located at a front of one or both of the frame members at or near a junction between the lower arm and the front upper arm.

A rear wheel drop-out may be provided at or near a junction between the lower arm and the rear upper arm.

The folding bicycle frame may further comprise a rear strut having a first end that is rotatably connected to the seat tube and a second end that is rotatably connected to the main frame. The second end may be rotatably connected to the pair of frame members at or near the upper apex.

The rear strut may comprise a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot.

Each of the seat tube pivot and the down tube pivot may have an axis of rotation that is horizontal.

The seat tube and down tube may be interlinked only by a toggle and the main frame such that the folding bicycle frame does not comprise a top tube.

The folding bicycle frame may be configured as a step-through bicycle frame.

The present disclosure further provides in a third aspect a folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; and a down tube rotatably connected to the main frame at a down tube pivot; a lower end of the seat tube being interlinked to a lower end of the down tube; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; the folding bicycle frame further comprising a rear strut having a first end that is rotatably connected to the seat tube and a second end that is connected to the main frame.

The rear strut may form at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot.

The locking mechanism may comprise a detent on one of the rear strut or the main frame and a catch on the other of the rear strut or the main frame.

The rear strut may be doubly-articulated: comprising a first articulation where the first portion is rotatably connected to the seat tube and a second articulation at an articulation pivot between the first portion and the second portion; and optionally wherein the rear strut may be triply-articulated: further comprising a third articulation between the second portion and the main frame.

The rear strut may form at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot; and the locking mechanism may comprise a detent at or near one of the articulation pivot of the rear strut or the main frame and a catch at or near the other of the articulation pivot of the rear strut or the main frame.

In the unfolded configuration the first portion and the second portion of the rear strut may be folded about the articulation pivot and the first portion of the rear strut may connect the seat tube with an abutment on the main frame. The articulation pivot may be coupled to a lock on the main frame. The rear strut may be configured to permit rotation of the seat tube forwardly away from the main frame by unfolding of the first portion and the second portion of the rear strut about the articulation pivot.

The rear strut may form a suspension member. The first portion of the rear strut may have a nominal length when the folding bicycle frame is in the unfolded configuration and the seat tube and main frame are unloaded; wherein the first portion of the rear strut may be compressible under loads imparted on the seat tube and or the main frame to reduce its length below the nominal length.

The main frame may comprise a pair of frame members that are offset to either side of a centre plane of the folding bicycle frame.

The rear strut, and optionally also the seat tube and the down tube, may extend in between the pair of frame members.

The rear strut, and optionally also the seat tube and down tube, may lie on the centre plane of the folding bicycle frame.

The rear strut, and optionally also the seat tube and the down tube, may remain in the centre plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration.

The present disclosure further provides a folding bicycle comprising a folding bicycle frame as described in any of the aspects above.

Brief description of the drawings

One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a side view of a folding bicycle according to the present disclosure; Figure 2 is a side view of a folding bicycle frame of the folding bicycle of Figure 1 in an unfolded configuration, together with a seat post and saddle; Figure 3 is a perspective view of the arrangement of Figure 2; Figure 4 is a top plan view of the arrangement of Figure 2; Figure 5 is a side view of the folding bicycle frame of Figure 2 in an over-centre position; Figure 6 is a perspective view of the arrangement of Figure 5; Figure 7 is a side view of the folding bicycle frame of Figure 2 in a folded configuration; Figure 8 is a perspective view of the arrangement of Figure 7; Figure 9 is a side view of the folding bicycle of Figure 1 in its folded configuration; Figure 10 is a perspective view of the arrangement of Figure 9; Figure 11 is a perspective view of a portion of the folding bicycle frame of Figure 2 showing a toggle of the folding bicycle frame; Figure 12 is a perspective view of a portion of the folding bicycle frame of Figure 2 showing the toggle and a portion of a main frame of the folding bicycle frame; Figures 13 to 16 are schematic illustrations of the movement of the toggle of Figure 11 during folding of the folding bicycle frame; Figure 17 is a perspective view of a portion of the folding bicycle of Figure 1 showing a rear strut of the folding bicycle frame; Figure 18 to 20 are schematic illustrations of the movement of the rear strut of Figure 17 during folding of the folding bicycle frame; and Figure 21 is a perspective view of another folding bicycle according to the present disclosure.

Detailed description

In the following description terms such as 'upper and lower' and front and rear' are used to describe relative positions of features. Such terms are to be understood, unless the immediate context requires otherwise, as referring to a frame of reference when the folding bicycle is in an unfolded configuration and placed on a horizontal surface such as the ground. As such, the terms 'upper and lower' refer to relative distances from the horizontal surface. The terms 'front and rear' refer to being towards the front wheel and towards the rear wheel of the folding bicycle respectively.

In the following description a part may be described as comprising a 'pivot'. For example, a first part may be described as comprising a pivot for rotatably coupling the first part to a second part. Unless the immediate context requires otherwise, the term pivot encompasses any suitable construction allowing rotational coupling of the first part to the second part. As non-limiting examples, the pivot may comprise a pin, shaft or axle that rotates within an aperture, casing or bearing. The pivot or a part of the pivot may be integral with the first part or integral with the second part. The pivot may comprise one or more additional components that couple between the first part and the second part.

The folding bicycle will be described as adopting a plurality of configurations, including at least an unfolded configuration and a folded configuration. The unfolded configuration is to be understood as a configuration when the folding bicycle has been unfolded and made ready for riding. An example of the unfolded configuration is shown in Figure 1. The folded configuration is to be understood as a configuration when the bicycle has been folded, wholly or partially, into a more compact form to facilitate storage and or carrying by hand. An example of the folded configuration is shown in Figures 9 and 10.

As illustrated schematically in Figure 1, there is provided a first example of a folding bicycle 1 that comprises a frame 2 to which is connected a front wheel 3, a rear wheel 4, handle bars 8, a seat post 10 and a saddle 9. The folding bicycle 1 is further provided with pedals 5, cranks 6 and a drive means which may be in the form of a belt drive 11. A chain may be used in place of a belt drive 11 if desired. The front wheel 3 is connected to the frame 2 by a pair of front forks 7.

The folding bicycle 1 may be provided with ancillary components that are not shown in the drawings for reasons of clarity. These may include cables, lights, mudguards, etc. The front wheel 3, rear wheel 4, seat post 10, saddle 9, pedals 5, cranks 6 and belt drive 11 may be of conventional design as will be well known to the skilled reader and therefore will not be described in detail.

As most clearly shown in Figures 9 and 10, the handle bars 8 may comprise a handle bar joint 12 that permits the handle bars 8 to be folded and pivoted relative to the frame 2.

Similarly, the pair of front forks 7 may comprise a front fork joint 13 that permits the pair of front forks 7 to be folded and pivoted relative to the frame 2.

-10 -Figures 2 to 8 show the frame 2 of the folding bicycle 1 together with the seat post 10 and saddle 9. The frame 2 comprises a main frame 20, a seat tube 21, a down tube 22, a head tube 23, a toggle 24 and a rear strut 80.

The main frame 20 may comprise a pair of frame members in the form of a first frame member 50 and a second frame member 51, which will be referred to collectively as the frame members 50, 51. The frame members 50, 51 may be offset to either side of a centre plane 46 of the frame 2 as shown in Figure 4. In the example shown the centre plane 46 is vertical when the folding bicycle 1 is in the unfolded configuration ready for riding.

Each of the frame members 50, 51 may be formed wholly or partially from a sheet member. Each sheet member may be formed from a metal or composite material. Examples of suitable materials include steel, aluminium, titanium, carbon fibre or alloys or mixtures thereof.

Each sheet member may be formed by a process for example, pressing, stamping, or composite lay-up, which may require no brazing or additional joints.

Each of the frame members 50, 51 may comprise a lower arm 52, a front upper arm 53 and a rear upper arm 54. The front upper arms 53 and rear upper arms 54 may meet at upper apexes 55. Each front upper arm 53 and lower arm 52 may meet at a front end 63 of the respective frame member 50, 51. Each rear upper arm 54 and lower arm 52 may meet at a rear end 64 of the respective frame member 50, 51.

Each lower arm 52, front upper arm 53 and rear upper arm 54 may together produce a generally triangular form that may surround an internal opening in the form of a frame window 62.

As shown in Figure 3, each rear upper arm 54 and lower arm 52 may comprise one or more bends so that a rear end of each frame member 50, 51 is located further from the centre plane 46 than a front end of each frame members 50, 51 to accommodate attachment of the rear wheel 4. In the illustrated example of Figure 3, an upper bend 65 and a lower bend 66 are provided. The upper bend 65 may be concave (as viewed from outside the main frame 20) and the lower bend 66 may be convex. In this way the portion of the sheet member at the rear end 64 may be arranged parallel or substantially parallel to the portion of the sheet member at the front end 63, as shown in Figure 4.

A rear wheel drop-out 59 may be provided at or near a junction between the lower arm 52 and the rear upper arm 54. The rear wheel drop-out 59 may be formed integrally with the sheet member or may be a component affixed to the sheet member, for example by means of bolts 67 as shown in the example of Figure 3.

The frame members 50, 51 may be held apart in a spaced relationship by a plurality of structures that span between the frame members 50, 51. One or more pillars 58 may span between the lower arms 52 of the frame members 50, 51. A bottom bracket shell 60 may be located to extend between the pair of frame members 50, 51 which in use may receive a bottom bracket cartridge that is to be coupled with the cranks 6 and pedals 5. A rear strut locking mechanism 61 may also span between the frame members 50, 51.

The down tube 22 may comprise a down tube tubular member 32 and a down tube end piece 31. The seat tube 21 may comprise a seat tube tubular member 30 and a seat tube end piece 29. The head tube 23 may comprise a head tube tubular member 34 and a head tube end piece 33 which may be integrally formed.

The down tube 22, seat tube 21 and head tube 23 may be formed from any suitable material, for example steel, aluminium, titanium, carbon fibre or alloys or mixtures thereof.

As shown in Figure 2, the down tube end piece 31 may be received in a lower end 37 of the down tube tubular member 32. An upper end 38 of the down tube tubular member 32 may have received therein a rear connecting post 42 of the head tube end piece 33. The handle bars 8 may be coupled to a connecting post (not shown) of the pair of front forks 7 with the connecting post extending through an internal channel of the head tube 23.

The down tube end piece 31 may comprise a connecting post 101 that is inserted into the down tube tubular member 32 and a tapered end piece 102 that terminates at a second toggle pivot 28. The connecting post 101 and the tapered end piece 102 may be formed integrally. A down tube pivot 26 may also be provided towards an upper end of the tapered end piece 102 so that the down tube pivot 26 is located part-way along the down tube 22 but at or near the lower end 37 of the down tube 22. An axis of rotation of the second -12 -toggle pivot 28 and the down tube pivot 26 may be horizontal in the unfolded configuration, i.e. parallel to the axis of rotation of the cranks 6.

The seat tube end piece 29 may comprise a connecting post 103 that is inserted into the seat tube tubular member 30 and a pair of seat tube extensions 39 that terminate at a first toggle pivot 27. The connecting post 103 and the seat tube extensions 39 may be formed integrally. A seat tube pivot 25 may also be provided towards an upper end of the pair of seat tube extensions 39 so that the seat tube pivot 25 is located part-way along the seat tube 21 but at or near the lower end 35 of the seat tube 21. An axis of rotation of the first toggle pivot 27 and the seat tube pivot 25 may be horizontal in the unfolded configuration, i.e. parallel to the axis of rotation of the cranks 6 and parallel to the axis of rotation of the second toggle pivot 28 and the down tube pivot 26.

Each of the seat tube end piece 29, the down tube end piece 31 and the head tube end piece 33 may be joined to the respective tubular members in which they are received by a suitable means, for example welding or bonding. This may be achieved, for example, by bonding of an external surface of the connection posts to an internal surface of the tubular members using an adhesive.

Alternatively, one or more of the seat tube end piece 29, the down tube end piece 31 and the head tube end piece 33 may be configured as a socket which receives the respective tubular member within it. Each socket and tubular member may then be joined together by a suitable means, for example welding or bonding. In a further alternative one or more of the seat tube end piece 29, the down tube end piece 31 and the head tube end piece 33 may be formed integrally with one or more of the tubular members.

The seat tube extensions 39 may form a pair of parallel members that are spaced apart to define a seat tube channel 40.

The down tube 22 and the seat tube 21 are rotatably coupled to the main frame 20. The down tube pivot 26 may be coupled to the front end 63 of the frame members 50, 51. The seat tube pivot 25 may be coupled also to the front end 63 but rearwards of the down tube pivot 26 as shown in Figure 12. When coupled to the main frame 20, both the seat tube 21 and the down tube 22 may extend in between the frame members 50, 51. Both may extend -13 -into a region between the frame members 50, 51 that is in front of the bottom bracket shell 60.

As shown in Figures 11 to 16, the down tube 22 may be interconnected to the seat tube 21 by means of the toggle 24. The toggle 24 may comprise a first toggle plate 70 and a second toggle plate 71 which will be referred to collectively as the toggle plates 70, 71. The toggle plates 70, 71 may be offset to either side of the centre plane 46 of the frame 2 as shown in Figure 12.

The toggle 24 may be formed from any suitable material, for example steel, aluminium, titanium, carbon fibre or alloys or mixtures thereof.

Each toggle plate 70, 71 may have a tri-lobed shape comprising a first lobe 73, a second lobe 74 and a third lobe 75. The first toggle pivot 27 at the distal end of the seat tube 21 may be coupled to the first lobe 73. The second toggle pivot 28 at the distal end of the down tube 22 may be coupled to the second lobe 74. A caster pivot 76 may be coupled to the third lobe 75. A caster wheel 72 may be rotatably mounted on the caster pivot 76.

The toggle plates 70, 71 may be held apart in a spaced arrangement by the first toggle pivot 27, the second toggle pivot 28 and the caster pivot 76. The external width of the toggle 24 may be less than the width of the seat tube channel 40 such that the toggle 24 may move within the seat tube channel 40 as shown in Figure 11. In addition, an internal distance between the inner faces of the toggle plates 70, 71 may be slightly larger than the external width of the tapered end piece 102 of the down tube end piece 31 such that the tapered end piece 102 may be rotatably coupled to the toggle 24 between the toggle plates 70, 71. Thus, the seat tube 21 and down tube 22 are rotatably coupled to one another and both may be orientated in the same plane, which is preferably the centre plane 46.

As shown in Figures 17 to 20, the rear strut 80 may releasably interconnect the main frame 20 and the seat tube 21. The rear strut 80 may comprise a first portion 81 and a second portion 82 that are rotatably interconnected with one another by an articulation pivot 85. The first portion 81 may comprises a tubular structure that comprises first and second sections that are mobile relative to one another. The first and second sections may form a suspension strut that allows the length of the first portion 81 to increase and/or decrease from a nominal length under external loading The second portion 82 may comprise a pair -14 -of plate members that are coupled on either side to the first portion 81 and to respective frame members 50, 51.

A first end 83 of the first portion 81 may be rotatably connected at a seat tube mount pivot 86 to a seat tube sleeve 89 which is mounted to the seat tube 21. Alternatively, the seat tube mount pivot 86 may be formed as an integral boss projecting from the seat tube 21, for example where the seat tube 21 is laid up from carbon fibre composite. A second end 84 of the first portion 81 may be connected to the articulation pivot 85. A first end 90 of the second portion 82 may also be connected to the articulation pivot 85 while a second end 91 of the second portion 82 may be rotatably connected at a main frame mount pivot 87 to the frame members 50, 51. The main frame mount pivot 87 may be located on the front upper arm 53. The first end 90 of the second portion may be provided with a detent 92 that may be in the form of one or more transversely extending pins.

The rear strut locking mechanism 61 may be mounted between the frame members 50, 51 at or near the upper apexes 55. The rear strut locking mechanism 61 comprises a fixed part 93 that is mounted to the frame members 50, 51 and a mobile part 94 that is pivotally mounted to the fixed part 93. The mobile part 94 is biased anti-clockwise (as viewed in Figure 19) by a suitable means, for example a coil spring acting about the pivot. The fixed part 93 is provided with an arcuate surface 95 and the mobile part 94 is provided with a notch 96. A front lip 97 of the mobile part 94 projects forwards of the notch 96. The rear strut locking mechanism 61 provides a mechanism allowing an effective length of the rear strut 80 that spans between the seat tube 21 and the frame members 50, 51 to be selectively varied and as will be described further below.

Preferably, the seat tube 21, down tube 22 and toggle 24 are interlinked such that they do not move independently of one another.

An example method of folding the folding bicycle 1 will now be described starting from the unfolded configuration shown in Figure 1.

In this unfolded configuration, the handle bars 8 and front forks 7 are deployed and fixed for riding and the seat post 10 is extended such that the saddle 9 is at the required riding height. Further, the frame 2 is configured as shown in Figures 2 and 3. The orientation of the toggle 24 is shown in the enlarged view of Figure 13. The toggle 24 may be orientated -15 -with the first lobe 73 lowermost. An imaginary line 45 may be drawn extending through the first toggle pivot 27 and the seat tube pivot 25. The imaginary line 45 may be coincident on a longitudinal axis of the seat tube 21. In this unfolded configuration the second toggle pivot 28 may be located to one side of the imaginary line 45, which may be the rear side, which is to the right of the imaginary line 45 when viewed as shown in Figure 13. Further, the rear strut 80 is configured as shown in Figures 17 and 18 with the rear strut locking mechanism 61 in a locked configuration. In this configuration, the rear strut 80 may adopt a V-shape configuration with the first portion 81 structurally coupling the seat tube 21 to the main frame 20. A curved end surface of the second end 84 may rest against the arcuate surface 95. Further, in this configuration the detent 92 is retained by the notch 96 of the mobile part 94 as shown in Figure 18.

The seat post 10 and saddle 9 are preferably lowered before folding the frame 2. In the illustrated example, the seat post 10 and saddle 9 are lowered before carrying out the following steps.

In a first step the rear strut 80 is unlocked from the frame members 50, 51 by operating the rear strut locking mechanism 61. Unlocking is achieved by lifting on the front lip 97 to rotate the mobile part 94 clockwise to release the detent 92 from the notch 96. At this point the rear strut 80 may remain substantially in its V-shaped configuration.

Next, the seat tube 21 is pivoted forwards towards the down tube 22. This movement may be carried out by one hand of the user gripping, for example, the saddle 9. As shown in Figure 14, this pivoting causes the toggle 24 to rotate anti-clockwise (as viewed in Figure 14) moving the second toggle pivot 28 through the imaginary line 45 from the rear side of the imaginary line 45 to the front side of the imaginary line 45. Therefore, the toggle 24 may function as an over-centre toggle mechanism that moves from a first state 'over-centre' to a second state as the second toggle pivot 28 moves through the imaginary line 45, which may be the longitudinal axis of the seat tube 21.

In the first state of Figure 13 (which includes when the folding bicycle is being ridden) the largest forces act vertically upwards on the front wheel 3 which results in a clockwise turning moment acting at the down tube pivot 26 (as viewed in Figure 13). This moment will try to rotate the toggle 24 clockwise since the second toggle pivot 28 lies to the rear of the imaginary line 45. Thus, the upward force on the front wheel 3 will help to maintain the -16 -frame 2 in the unfolded configuration. In the second state the same clockwise turning moment acting at the down tube pivot 26 will act to try and rotate the toggle 24 anticlockwise since the second toggle pivot 28 now lies to the front of the imaginary line 45. Thus, the upward force on the front wheel 3 (e.g. a reaction force from the weight of the folding bicycle 1) will now assist in folding of the frame 2.

Next, further pivoting of the seat tube 21 forwards towards the down tube causes the down tube 22 to start to pivot rearwards, as shown in Figures 5, 6 and 15, due to the interconnection of the seat tube 21, down tube 22, toggle 24 and main frame 20. As before, this movement may be carried out by one hand of the user gripping, for example, the saddle 9 and optionally another hand gripping the handle bars 8. The movement may be assisted by the clockwise turning moment acting at the down tube pivot 26. The toggle 24 continues to rotate anti-clockwise so that the caster wheel 72 moves into a lowermost position extending below the toggle plates 70, 71 where it may be brought into contact with the ground to aid rolling of the frame 2.

Movement into the position of Figures 5, 6 and 15 is accompanied by extension of the rear strut 80 as shown in Figures 5 and 19. This extension results in unfolding of the first portion 81 and second portion 82, with the first portion 81 turning clockwise and the second portion 82 turning anti-clockwise (as viewed in Figure 18) until they are substantially straight and aligned with one another as shown in Figure 19.

Next, once the position of Figures 5, 6 and 15 is obtained the down tube 22 continues to be pivoted rearwards accompanied now by rearward pivoting of the seat tube 21 into the folded configuration of Figure 16. The seat tube 21 may be pushed rearward by the user but again the motion is assisted by the clockwise turning moment acting at the down tube pivot 26. The toggle 24 completes its anti-clockwise rotation. It is to be noted that the folding of the frame 2 is thus achieved by the seat tube 21 first being pivoted forwards and then pivoted backwards.

Movement into the position of Figure 16 is accompanied by folding of the rear strut 80 as shown in Figures 7 and 20. The first portion 81 turns clockwise and the second portion 82 turns anti-clockwise (as viewed in Figure 19) until they are substantially overlapped with one another as shown in Figure 20 with the articulation pivot 85 beneath the main frame mount pivot 87.

-17 -Now that the folding frame is in the folded configuration the handle bars 8 and the front forks 7 may be optionally folded into the configuration shown in Figures 9 and 10 by rotating the front wheel 3 to lie against an outer face of the frame member 50 and the handle bars 8 to lie against an outer face of the frame member 51.

To unfold the folding bicycle 1 the steps described above are reversed.

Figure 21 illustrates a second example of a folding bicycle according to the present disclosure, and the same reference numerals denote equivalent features to those of the first example. Whether or not shown, the second example may include any combination of features from the first example described above with reference to Figures 1 to 20.

The main difference with the second example is that one or more of the lower arm 52, front upper arm 53 and rear upper arm 54 of the frame members 51 are provided with a plurality of apertures 68. These may be in addition to the frame window 62 within the bounds of the lower arm 52, front upper arm 53 and rear upper arm 54.

The plurality of apertures 68 produce a truss-like structure for one or more of the lower arm 52, front upper arm 53 and rear upper arm 54 which may lead to weight savings. The plurality of apertures 68 may be formed, for example by cutting, stamping or pressing the sheet of material of the frame members 50, 51.

Industrial Applicability

The present disclosure finds application in providing a folding bicycle 1 that is configured with a frame 2 to allow the frame 2 to be moved between an unfolded configuration and a folded configuration.

The frame 2 of the present disclosure may in particular provide a step-through bicycle frame. Preferably the frame 2 does not require a top tube extending between the seat tube 21 and the down tube 22. Rather, the seat tube 21 and the down tube 22 may only be interlinked by the main frame 20 and the toggle 24. Advantageously, this may lead to an improved step-through bicycle frame that may be easier to mount and dismount for the rider.

-18 -Advantageously, the main frame 20 may be configured as two frame members 50, 51 that are offset from the centre plane 46. This may permit the frame 2 to be configured with both the seat tube 21 and the down tube 22 aligned in the centre plane 46 and moving during folding and unfolding so as to remain in the centre plane 46. Advantageously, this may permit use of a single down tube end piece 31 and a single seat tube end piece 29. This may lead to weight savings compared to a folding bicycle that comprises pairs of end pieces positioned either side of a central main frame. Also, the couplings, such as the down tube pivot 26, seat tube pivot 25, first toggle pivot 27 and second toggle pivot 28 may extend between the frame members 50, 51 so as to be wholly or substantially within an interior of the main frame 20. This may reduce the likelihood of the couplings being damaged by impacts and reduce the ingress of contaminants into the couplings compared to couplings mounted to one or both sides of a central main frame.

Advantageously, the main frame 20 fixes the location of both the rear wheel drop out 59 and the bottom bracket shell 60 and the spacing of these components preferably does not change during folding of the frame 2. This enables use of a belt drive 11 without the need for any belt or chain tensioning device.

Advantageously, folding of the frame 2 may require movement of the seat tube 21 in the opposite direction to the main forces acting on the frame 2 when in the unfolded configuration (during ride mode) to unlock the mechanism. For example, the configuration of the toggle 24 in the unfolded configuration means that forces acting up through the front wheel 3 (from bumps etc.) and forces due to the rider's weight would only attempt to push the toggle 24 and seat tube 21 further in a locking direction.

Advantageously, the locking of the toggle 24, seat tube 21 and down tube 22 in the unfolded configuration makes use of the strength of the down tube end piece 31 as a cantilever beam and the strength of the seat tube end piece 29 in tension.

Advantageously, all of the down tube 22, seat tube 21 and toggle 24 are interlinked so that their movement is co-ordinated and none can move independently of one another. This may result in a folding bicycle that is easier for a user to fold and unfold because the relative movement of the parts may be constrained by their interlinking and the user is not required to remember a sequential order of separate tube movements to fold or unfold the folding bicycle.

-19 -Advantageously, each of the down tube pivot 26, seat tube pivot 25, first toggle pivot 27 and second toggle pivot 28 may have an axis of rotation that is horizontal. This allows the frame 2 to fold and unfold in a 'linear' manner with the tubes remaining on the centre plane 46. This may result in a slimmer overall package of the folding bicycle 1 in the folded configuration.

Advantageously, the frame members 50, 51 may be sheet members. The frame members 50, 51 may present an uninterrupted exterior surface for parts to fold up against. The uninterrupted exterior surfaces may also present fewer snag points to brush against by a user whilst the folding bicycle 1 is carried. The sheet members may be manufactured through a process (for example, pressing, stamping, or composite lay-up) which requires no brazing or additional joints (unlike a tubular structure). The sheet members may be manufactured in a range of materials (for example, aluminium, titanium, carbon fibre, etc.).

Advantageously, the use of sheet members for the frame members 50, 51 may permit the sheet members to be cut and then formed to give the required shape (for example slim where the rear strut 80 is connected but wide at the rear wheel drop-out 59) which may simplify manufacture. The use of sheet members may also allow for a highly automated manufacturing process and allows for simple mounting of components using mechanical fasteners.

Advantageously, the front wheel 3 and the rear wheel 4 may remain in contact with the ground during folding and unfolding of the folding bicycle 1. This avoids the need for the rider to lift the weight of the folding bicycle, for example to swing the rear wheel 4 below a remainder of the folding bicycle as is required in some prior art designs. Further the weight of the folding bicycle 1 is continuously supported by the ground reducing the effort required by the rider to fold and unfold the folding bicycle 1.

Claims

-20 -CLAIMS: 1. A folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; a down tube rotatably connected to the main frame at a down tube pivot; and a toggle which is rotatably connected to a lower end of the seat tube at a first toggle pivot and a lower end of the down tube at a second toggle pivot; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; wherein the toggle is configured to require the seat tube to be rotated forwards, about the seat tube pivot, towards the down tube to allow the folding bicycle frame to be moved from the unfolded configuration to the folded configuration.
2. A folding bicycle frame as claimed in claim 1, wherein the toggle is configured such that in the unfolded configuration the second toggle pivot is positioned to a first side of an imaginary line which extends between the seat tube pivot and the first toggle pivot; and such that in the folded configuration the second toggle pivot is positioned to a second side of the imaginary line; wherein rotation of the seat tube forwards, about the seat tube pivot, towards the down tube causes the second toggle pivot to move across the imaginary line from the first side to the second side.
3. A folding bicycle frame as claimed in claim 1 or claim 2, wherein the seat tube, down tube and toggle are interlinked such that they do not move independently of one another.
4. A folding bicycle frame as claimed in any preceding claim, wherein the seat tube and down tube are interlinked only by the toggle and main frame such that the folding bicycle frame does not comprise a top tube.
5. A folding bicycle frame as claimed in any preceding claim, wherein the folding bicycle frame is configured as a step-through bicycle frame.
-21 - 6. A folding bicycle frame as claimed in any preceding claim, wherein each of the seat tube pivot, the down tube pivot, the first toggle pivot and the second toggle pivot have an axis of rotation that is horizontal.
7. A folding bicycle frame as claimed in any preceding claim, wherein the seat tube and the down tube remain in a common plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration.
8. A folding bicycle frame as claimed in any preceding claim, wherein the seat tube and down tube lie on a centre plane of the folding bicycle frame; and, optionally, wherein the main frame comprises a pair of frame members that are offset to either side of the centre plane; the seat tube and the down tube extending in between the pair of frame members.
9. A folding bicycle frame as claimed in any preceding claim, wherein the toggle comprises one or more toggle plates.
10. A folding bicycle frame as claimed in any preceding claim, wherein the seat tube comprises a pair of seat tube extensions at the lower end of the seat tube which extend downwardly from the seat tube pivot to define a seat tube channel therebetween; the first toggle pivot being located at a distal end of the seat tube extensions; and, optionally, wherein the down tube and the toggle move within the seat tube channel as the folding bicycle frame is folded between the folded configuration and the unfolded configuration.
11. A folding bicycle frame as claimed in any preceding claim, wherein the seat tube comprises a seat tube end piece at the lower end of a seat tube tubular member.
12. A folding bicycle frame as claimed in any preceding claim, wherein the down tube comprises a down tube end piece at the lower end of a down tube tubular member.
13. A folding bicycle frame as claimed in any preceding claim, wherein the toggle comprises a caster wheel, optionally a rigid caster wheel.
-22 - 14. A folding bicycle frame as claimed in any preceding claim, further comprising a rear strut having a first end that is rotatably connected to the seat tube and a second end that is rotatably connected to the main frame; and, optionally, wherein the rear strut forms at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot.
15. A folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; and a down tube rotatably connected to the main frame at a down tube pivot; a lower end of the seat tube being interlinked to a lower end of the down tube; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; wherein the main frame comprises a pair of frame members that are offset to either side of a centre plane of the folding bicycle frame.
16. A folding bicycle frame as claimed in claim 15, wherein the seat tube and the down tube extend in between the pair of frame members.
17. A folding bicycle frame as claimed in claim 15 or claim 16, wherein the seat tube and down tube lie on the centre plane of the folding bicycle frame; and, optionally, wherein the seat tube and the down tube remain in the centre plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration.
18. A folding bicycle frame as claimed in any one of claims 15 to 17, wherein the seat tube pivot comprises a pivot joint that extends between the pair of frame members with the seat tube rotatably coupled to the pivot joint.
19. A folding bicycle frame as claimed in any one of claims 15 to 18, wherein the down tube pivot comprises a pivot joint that extends between the pair of frame members with the down tube rotatably coupled to the pivot joint.
-23 - 20. A folding bicycle frame as claimed in any one of claims 15 to 19, wherein the main frame further comprises a bottom bracket shell that extends between the pair of frame members.
21. A folding bicycle frame as claimed in any one of claims 15 to 20, wherein the lower end of the seat tube is interlinked to the lower end of the down tube by a toggle which is rotatably connected to the lower end of the seat tube at a first toggle pivot and the lower end of the down tube at a second toggle pivot; the toggle being mounted in between the pair of frame members.
22. A folding bicycle frame as claimed in any one of claims 15 to 21, wherein one or both of the pair of frame members comprises a sheet member.
23. A folding bicycle frame as claimed in any one of claims 15 to 22, wherein one or both of the pair of frame members comprises a generally triangular form, optionally including one or more internal openings.
24. A folding bicycle frame as claimed in any one of claims 15 to 23, wherein one or both of the pair of frame members comprises a lower arm, a front upper arm and a rear upper arm; the front upper arm and the rear upper arm meeting at an upper apex; and, optionally, wherein the seat tube pivot and the down tube pivot are located at a front of one or both of the frame members at or near a junction between the lower arm and the front upper arm; and, optionally, wherein a rear wheel drop-out is provided at or near a junction between the lower arm and the rear upper arm.
25. A folding bicycle frame as claimed in claim 24, further comprising a rear strut having a first end that is rotatably connected to the seat tube and a second end that is rotatably connected to the main frame; and, optionally, wherein the second end is rotatably connected to the pair of frame members at or near the upper apex; and, optionally, wherein the rear strut comprises a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot.
26. A folding bicycle frame as claimed in any one of claims 15 to 25, wherein each of the seat tube pivot and the down tube pivot have an axis of rotation that is horizontal.
-24 - 27. A folding bicycle frame as claimed in any one of claims 15 to 26, wherein the seat tube and down tube are interlinked only by a toggle and the main frame such that the folding bicycle frame does not comprise a top tube.
28. A folding bicycle frame as claimed in any one of claims 15 to 27, wherein the folding bicycle frame is configured as a step-through bicycle frame.
29. A folding bicycle frame comprising: a main frame; a seat tube rotatably connected to the main frame at a seat tube pivot; and a down tube rotatably connected to the main frame at a down tube pivot; a lower end of the seat tube being interlinked to a lower end of the down tube; the folding bicycle frame being foldable between a folded configuration for storage or carrying and an unfolded configuration for use as a bicycle frame; the folding bicycle frame being foldable by rotation of the seat tube about the seat tube pivot and the down tube about the down tube pivot; the folding bicycle frame further comprising a rear strut having a first end that is rotatably connected to the seat tube and a second end that is connected to the main frame.
30. A folding bicycle frame as claimed in claim 29, wherein the rear strut forms at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot; and, optionally, wherein the locking mechanism comprises a detent on one of the rear strut or the main frame and a catch on the other of the rear strut or the main frame.
31. A folding bicycle frame as claimed in any one of claims 29 to 30, wherein the rear strut is doubly-articulated: comprising a first articulation where the first portion is rotatably connected to the seat tube and a second articulation at an articulation pivot between the first portion and the second portion; and optionally wherein the rear strut is triply-articulated: further comprising a third articulation between the second portion and the main frame; and, optionally, wherein the rear strut forms at least a portion of a locking mechanism to selectively lock the seat tube to prevent the seat tube rotating forwards about the seat tube pivot; and the locking mechanism comprises a detent at or near one of the articulation pivot of the rear strut or the main frame and a catch at or near the other of the articulation pivot of the rear strut or the main frame.
-25 - 32. A folding bicycle frame as claimed in claim 31, wherein in the unfolded configuration the first portion and the second portion of the rear strut are folded about the articulation pivot and the first portion of the rear strut connects the seat tube with the main frame; and, optionally, wherein the articulation pivot is coupled to a lock on the main frame.
33. A folding bicycle frame as claimed in any one of claims 31 to 32, wherein the rear strut is configured to permit rotation of the seat tube forwardly away from the main frame by unfolding of the first portion and the second portion of the rear strut about the articulation pivot.
34. A folding bicycle frame as claimed in any one of claims 31 to 33, wherein the rear strut forms a suspension member.
35. A folding bicycle frame as claimed in any one of claims 31 to 34, wherein the first portion of the rear strut has a nominal length when the folding bicycle frame is in the unfolded configuration and the seat tube and main frame are unloaded; wherein the first portion of the rear strut is compressible under loads imparted on the seat tube and or the main frame to reduce its length below the nominal length.
36. A folding bicycle frame as claimed in any one of claims 29 to 35, wherein the main frame comprises a pair of frame members that are offset to either side of a centre plane of the folding bicycle frame; and, optionally, wherein the rear strut, and optionally also the seat tube and the down tube, extends in between the pair of frame members; and, optionally, wherein the rear strut, and optionally also the seat tube and down tube, lies on the centre plane of the folding bicycle frame; and, optionally, wherein the rear strut, and optionally also the seat tube and the down tube, remains in the centre plane in the folded configuration and the unfolded configuration and during folding between the folded configuration and the unfolded configuration.
37. A folding bicycle comprising a folding bicycle frame as claimed in any preceding claim.