GB2613887A

GB2613887A - A derailleur assembly

Info

Publication number: GB2613887A
Application number: GB2118505.3A
Authority: GB
Inventors: Anthony Connell Richard
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-12-20
Filing date: 2021-12-20
Publication date: 2023-06-21
Anticipated expiration: 2041-12-20
Also published as: GB2613887B

Abstract

A derailleur assembly for a cycle 10, the cycle 10 having a multi-stage sprocket assembly 40 rotatable about an axis 64, the derailleur assembly comprising: a guide rail 80 extending substantially in a horizontal plane and angled to the axis 64; a chain guide 72 mounted on the guide rail 80, the chain guide 72 is slidingly moveable between a plurality of positions along the guide rail 80 each corresponding to a drive sprocket (40a-40d) of the multi-stage sprocket assembly 40; a guide sprocket 70 rotatably supported on the chain guide 72, the guide sprocket 70 is configured to guide displacement of a drive chain 42 parallel to the axis 64, wherein the separation between the guide sprocket 70 and the corresponding drive sprocket (40a-40d) is substantially the same at each of the positions.

Description

A DERAILLEUR ASSEMBLY

Field

The present application relates to a derailleur assembly, and in particular to a derailleur assembly for a cycle.

Background

With the exception of track bikes, almost all of the commercially available cycles employ a variable-ratio bicycle gearing system comprising a drive chain 113 connecting the front and rear sprocket sets. A derailleur is provided for each of the sprocket sets for shifting the drive chain from one sprocket to another in the sprocket set, so as to provide appropriate gearing to suit a rider's cadence at different speeds.

The derailleurs typically consist of a moveable chain guide operable by a Bowden cable that is attached to a gear lever. Upon actuating the gear lever, the change in cable tension moves the chain guide in a direction perpendicular to the rear axle, thus derailing the chain onto different sprockets in the sprocket set.

A conventional derailleur typically comprises a single derailleur frame that holds an upper guide sprocket and a lower tensioner sprocket. Together the two sprockets guide the chain in an S-shaped pattern to the sprocket set. By a parallelogram mechanism, the frame is configured to simultaneously displace in both the vertical and horizontal directions. The use of such a parallelogram mechanism ensures the derailleur frame, along with the two sprockets contained therein, are always aligned with the vertical plane, so as to minimise hindrance to the chain movement. Such an arrangement maintains a constant separation between the upper guide sprocket and the different sized sprockets in the sprockets set over the range of movement. The derailleur frame is spring-loaded and pivotable about the rear axle to take up any slack in the chain.

Such conventional derailleurs typically extend downwardly from the rear axle and require substantial ground clearance to accommodate the vertically extending derailleur frame. Whilst these derailleurs are perfectly acceptable for use in ordinary bicycles where the rear wheels are at least 26 inches in diameter, they often preclude the use of wheels that are measured less than 16 inches in size. Thus, the use of such derailleurs presents a challenge when reducing the overall height of a bicycle. For example, in collapsible bicycles, the overall height of the bicycle is often dictated by their wheel sizes.

Therefore, a vertically compact derailleur assembly is highly desirable.

Summary

The present invention offers a derailleur assembly having a guide sprocket that may only traverse in a horizontal plane when guiding the chain to the desired sprocket in the sprocket set. Advantageously, by removing the parallelogram commonly used in conventional bicycles, the guide sprocket is no longer required to displace in the vertical plane, thus substantially reducing the overall height of, and ground clearance required by, the derailleur assembly. Moreover, the guide sprocket and the tensioner sprocket in the derailleur assembly may move relative to each other, thus allowing the tensioner sprocket to be arranged with greater ground clearance in comparison to the conventional derailleurs. In addition, such an arrangement may allow the derailleur assembly to be more readily concealed in a monocoque frame.

According to a first aspect of the presently-claimed invention, there is provided a derailleur assembly for a cycle, the cycle having a multi-stage sprocket assembly rotatable about an axis, the derailleur assembly comprising: a guide rail extending substantially in a horizontal plane and angled to the axis; a chain guide mounted on the guide rail, the chain guide is slidingly moveable between a plurality of positions along the guide rail each corresponds to a drive sprocket of the multi-stage sprocket assembly; a guide sprocket rotatably supported on the chain guide, the guide sprocket is configured to guide displacement of a drive chain parallel to the axis, wherein the separation between the guide sprocket and the corresponding drive sprocket is substantially the same at each of the positions.

The cycle may be any cycle comprising a multi-stage sprocket assembly in its drive train, for example monocycles, bicycles, tricycles, quadricycles, cargo cycles and recumbent cycles. The cycle may be powered by the user alone, or by a combination of user input and a motor, e.g. an electric bike, or entirely by an electric motor or an internal combustion engine without the use of a foot pedal, e.g. a motorcycle.

The multi-stage sprocket assembly may commonly be referred to as a cassette, which may be the rear sprocket set and/or the front sprocket set of the cycle. For example, the guide sprocket is configured to guide displacement of a drive chain parallel to the axis corresponding to a rear axle or a crank axle of the cycle.

Therefore, the sprockets in the rear sprocket set may coaxially extend along a rear axis about which the rear axle rotates. Similarly, the sprockets in the front sprocket set may coaxially extend along a crank axis about which a crank axle rotates. Namely, the axis extends perpendicularly to the longitudinal axis of the cycle.

The guide rail may extend in a plane substantially parallel to the horizon when the cycle is set on levelled ground, i.e. in the horizontal plane, and the horizontal plane may be substantially parallel to a line extending through the front and rear axle of the bicycle.

In most cases, the sizes of the sprockets in the multi-stage sprocket assembly may incrementally change with each sprocket. This provides a gradual change in gear ratio as the chain sequentially shifts through the different sprockets. For example, a nominal line may extend in the horizontal plane and joins the apexes, or leading teeth aligned at the horizontal plane, of all of the sprockets. In other words, the nominal line corresponds to the tapered side profile of the multi-stage sprocket assembly. The guide rail may extend parallel to the said nominal line, and therefore, the guide rail extends at an angle to the axis. The guide rail may linearly extend at an angle between 30° to 700 to the axis, or between 400 to 60° to the axis, or between 45° to 55° to the axis, or substantially 50° to the axis and/or it may extend parallel to the nominal line.

Alternatively, in some multi-stage sprocket assemblies, the sizes of sprockets in the multi-stage sprocket assembly may not change incrementally with each 35 sprocket. For example, the sprockets corresponding to the highest gears may decrease in size in a non-linear manner, which may result in a higher achievable top speed, or the sprockets corresponding to the lowest gears may increase in size in a non-linear manner, which may allow for more rapid acceleration. In these cases, the guide rail may non-linearly extend in the horizontal plane and complementary to a profile of the multi-stage sprocket assembly. For example, the guide rail may comprise, along its length, a curvature or plural consecutive segments extending at different angles to the axis, complementary to a curved or angled side profile of the multi-stage sprocket assembly.

Such arrangements may ensure the separation between the apexes (e.g. the opposing teeth that face each other) of the guide sprocket and the corresponding drive sprocket is substantially the same at each of the positions as the chain guide slides along the guide rail, and therefore reducing the amount of chain rattle, as well as the risk of accidental derailment.

In contrast to conventional derailleurs, the chain guide according to the present invention may only move in the horizontal plane. Advantageously, such an embodiment may substantially reduce the clearance required to accommodate the vertical displacement that is otherwise required in conventional derailleurs, thus resulting in a more vertically compact derailleur assembly.

Optionally, the derailleur assembly comprises an electronic actuator, the electrical actuator is configured to receive a signal from a gear selector, or shifter, to drive sliding movement in the chain guide. Optionally, the derailleur assembly comprises a rack and pinion gearing for translating a rotational motion of the electrical actuator to the sliding movement in the chain guide.

The gear selector may comprise an electronic shifter operable by hand or other means, and is configured to send a signal wirelessly, or by wire, to the electronic actuator for effecting gear selection. For example, the signal may be a signal for selecting a higher gear or a lower gear sequentially in the sprocket assembly, or for direct selection of any gear.

The electronic actuator may be an electrical motor that is fixed attached to the frame of the cycle. Upon receiving the signal, the electronic actuator may configure to drive rotational movement in a pinion gear, which in turn delivers linear motion in a corresponding rack gear to cause sliding movement in the chain guide.

In some other embodiment, a worm gear or other suitable gearing systems may be used in lieu of the rack and pinion gearing. In some other embodiment, a Shape Memory Alloy actuator or other direct-drive linear motors may be used for driving the sliding movement in the chain guide without the need for a gearbox.

Alternatively, the chain guide may be mechanically connectable to a shifter. For example, the chain guide may be directly connected to, and actuated by, the shifter by a Bowden cable, in a manner similar to the ordinary derailleurs. In these embodiments, the chain guide may slide in one direction by the tension in the Bowden cable, and a biasing means may be provided to bias the chain guide to slide in an opposite direction upon tension release in the Bowden cable.

Optionally, the movement of the chain guide along the angled guide rail is greater than the displacement in the drive chain along the axis. Since the guide rail extends at an angle to the axis, any movement in the chain guide would result in a relatively smaller translation in the drive chain parallel to the axis. Advantageously, such an arrangement may allow the displacement in the drive chain to be more precisely controlled.

Optionally, the guide rail having a first end fixedly attachable to a structure of the cycle proximal to, or adjacent to, or forward to, the multi-stage sprocket assembly and a second end fixedly attachable to the structure at a position forward of a rear wheel of the cycle. For example, when used for changing gear in a rear sprocket set, the first end of the guide rail may be attached to a fork end at the rear of the cycle frame commonly known as the derailleur hanger. The second end of the guide rail may be attached to the bottom bracket of the cycle or other parts of the frame forward of the cycle's rear wheel. Thus, the derailleur assembly may utilise a space that is otherwise left unoccupied in conventional cycles.

Optionally, the derailleur assembly further comprises a tensioner sprocket rotatably mounted on a tensioner member, the tensioner sprocket is configured to engage and tension the drive chain, wherein the tensioner member is fixedly attached to the chain guide. Such an arrangement may resemble the derailleur frame as used in conventional derailleurs.

Alternatively, the derailleur assembly further comprises a tensioner sprocket rotatably mounted on a tensioner member, the tensioner sprocket is configured to engage and tension the drive chain, wherein the tensioner member is moveable relative to the chain guide. The tensioner member may be moveable relative to the chain guide along the vertical plane. That is, in contrast to conventional derailleurs where the tensioner sprocket and the guide sprocket are mounted on a single derailleur frame, the derailleur assembly according to the present invention comprises an additional tensioner member for housing the tensioner sprocket. By the relative movement between the tensioner member and the chain guide, the tensioner sprocket may also move relative to the guide sprocket.

Such an arrangement may advantageously decouple the two functions in the derailleur assembly, e.g. chain tensioning and chain guidance. Thus, the vertical displacement as observed in conventional tensioner sprockets may be significantly reduced or eliminated. Moreover, since the movement in the chain guide is decoupled from in the tensioner member, the biasing force that is required for chain tensioning no longer acts directly upon the chain guide. Advantageously, less input force may be required from the rider, or the electronic actuator, to effect gear shifting.

Optionally, the derailleur assembly further comprises a biasing means connected between a structure of the cycle and the tensioner member, the biasing means is configured to apply a biasing force on the tensioner member so as to tension the drive chain. In contrast to conventional derailleurs where the biasing means is connected between a fixed portion and a moveable portion of the derailleur, the biasing means in the present invention is configured to connect directly between the tensioner member and a structure of the cycle, e.g. the bicycle frame. For example, the biasing means may comprise a tension spring, and wherein the derailleur assembly may further comprise one or more pulleys attached to the structure of the cycle for routing the tension spring around the axis.

Advantageously, such an arrangement may allow the biasing means to be routed around the axis, thereby offering sufficient ground clearance when smaller wheels, e.g. less than 16 inches in size, are used.

Optionally, the tensioner member is arranged at a vertical position below the chain guide and an apex of each of the sprockets in the multi-stage sprocket assembly.

More specifically, the tensioner member is positioned below the lowest tooth of the largest sprocket so as to provide sufficient clearance therebetween.

Optionally, the tensioner member is configured to be suspended by the biasing force applied by the biasing means and the tension in the drive chain. That is, the tensioner member may not fixedly attach to the frame of the cycle. Rather, it may be suspended by the biasing means and the drive chain. Thus, the tensioner member may move in any direction and around any axes.

Optionally, the tensioner member is moveable in a direction parallel to the axis by the displacement in the drive chain. More specifically, since the tensioner member is not fixedly attached to the frame, it may trail the drive chain in a direction parallel to the axis. Advantageously, such an arrangement may allow the tensioner sprocket to maintain adequate alignment with the guide sprocket, and thus minimising rattle and resistance during pedalling.

According to a second aspect of the presently-claimed invention, there is provided a derailleur assembly for a cycle, the cycle having a multi-stage sprocket assembly rotatable about an axis, the derailleur assembly comprising: a chain guide moveable to a plurality of positions each corresponds to a drive sprocket of the multi-stage sprocket assembly; a guide sprocket rotatably supported on the chain guide, the guide sprocket is configured to guide displacement of a drive chain parallel to the axis, wherein the separation between the guide sprocket and the corresponding drive sprocket is substantially constant at each of the positions; and a tensioner sprocket rotatably mounted on a tensioner member, the tensioner sprocket is configured to engage and tension the drive chain, wherein the tensioner member is moveable relative to the chain guide.

The chain guide may be moveable in both vertical and horizontal directions. For example, the chain guide may be connected to the cycle frame by a parallelogram as featured in conventional derailleurs, whilst remaining moveable relative to the tensioner member.

Alternatively, the derailleur assembly may further comprise a guide rail extending at an angle to the axis; wherein the chain guide is mounted on the guide rail and is slidingly moveable to the plurality of positions. In some embodiments, the guide rail may extend at an angle to the horizontal plane, therefore, the chain guide is 113 slideable along a direction angled to both the axis and the horizontal plane. In the preferred embodiment, the guide rail may extend substantially in the horizontal plane and thus the chain guide may only slide along the guide rail in the horizontal plane.

Optionally, the derailleur assembly further comprises a biasing means connected between a structure of the cycle and the tensioner member, the biasing means is configured to apply a biasing force on the tensioner member so as to tension the drive chain.

Optionally, the biasing means comprises a tension spring, and wherein the derailleur assembly further comprises one or more pulleys attached to the structure of the cycle for routing the tension spring around the axis.

Optionally, the tension guide member is configured to be suspended by the biasing force applied by the biasing means and the tension in the drive chain.

According to a third aspect of the presently-claimed invention, there is provided a cycle, comprising the multi-stage sprocket assembly, the drive chain and the derailleur assembly of the first aspect and/or the second aspect.

Optionally, the cycle further comprises a monocoque frame that forms a load-bearing structure to which a rear wheel of the cycle is mounted onto, the monocoque frame at least partially encloses the multi-stage sprocket assembly, the derailleur assembly, the drive chain and other drivetrain components that drives the rear wheel. In a preferred embodiment, the monocoque frame completely encloses the entire derailleur assembly, the drive chain and other drivetrain components that drive the rear wheel. The monocoque frame may generally be defined as an exoskeleton frame and may form from two monocoque shells. The monocoque frame may shield the drivetrain components including the front and rear sprocket sets, the derailleur assembly, as well as the drive chain that connects the two sprocket sets. Thus, not only the monocoque frame helps concealing the drivetrain components thus offering an additional layer of protection, it may shield the user from the grease and grit commonly associated with a bicycle drivetrain system.

Optionally, the monocoque frame comprises a channel extending along the longitudinal axis of the monocoque frame.

Optionally, the cyle further comprises a subassembly to which a front wheel of the cycle is mounted onto, the subassembly comprises a guide frame slidably received inside the channel of the monocoque frame for varying the overall length of the cycle.

The guide frame may extend in a longitudinal axis of the cycle and parallel to the horizontal plane, whereby the relative sliding movement between the subassembly and the monocoque frame may allow the length of the cycle to be adjusted to different user sizes. The guide frame may alternatively extend at an angle to the horizontal plane, whereby the relative sliding movement between the subassembly and the monocoque frame may allow the height and the length of the cycle to be adjusted to different user sizes. The channel may be a receiving tube that coaxially extends with, and configured to receive, the guide frame, or it may be a guide rail extending parallel to the guide frame for receiving a protruded part of the guide frame.

Optionally, the monocoque frame further comprises a seat post, the seat post is arranged to extend through, and angled to, the channel of the monocoque frame in a ridable configuration, and is configured to be stowed in the channel parallel to the guide frame in a collapsed configuration. Thus, the channel of the monocoque frame may extend through the monocoque frame where one end is configured to receive the guide frame and the other for receiving the seat post.

More specifically, in the ridable configuration, the rider may ride on a seat of the seat post, whereby the monocoque frame bears the weight of the rider. In the collapsed configuration, the guide frame may be fully stowed in the channel with the seat post may be received in the guide frame such that the channel, the guide frame and the seat post may coextend along the longitudinal axis of the cycle.

According to a fourth aspect of the presently-claimed invention, there is provided a monocoque frame that forms a load-bearing structure to which a rear wheel of the cycle is mounted onto, the monocoque frame at least partially encloses a gear selector and other drivetrain components that drives the rear wheel; the monocoque frame comprises a channel extending along the longitudinal axis of the monocoque frame; a subassembly to which a front wheel of the cycle is mounted onto, the subassembly having a guide frame slidably received inside the channel of the monocoque frame for varying the overall length of the cycle.

Optionally, the monocoque frame further comprises a seat post, the seat post is arranged to extend through, and angled to, the channel of the monocoque frame in a ridable configuration, and is configured to be stowed in the channel parallel to the guide frame in a collapsed position.

Features from any one of the first to the fourth aspects of the present invention may be applicable with any other feature from the other aspects.

Brief Description of the Drawings

Certain embodiments of the presently-claimed invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a bicycle in a ridable configuration according to a first embodiment of the present invention; Figure 2 is a side view of the bicycle of Figure 1 in a collapsed configuration; Figure 3 is a cross-sectional plan view of a derailleur assembly according to a second embodiment in which the drive chain engages the largest sprocket in the rear sprocket set; Figure 4 is a cross-sectional plan view of the derailleur assembly of Figure 4 in which the drive chain engages the smallest sprocket in the rear sprocket set; Figure 5 is a side view of a derailleur assembly according to a third embodiment in which the drive chain engages the largest sprocket in the rear sprocket set; and Figure 6 is a side view of the derailleur assembly of Figure 5 in which the drive chain engages the smallest sprocket in the rear sprocket set.

Detailed Description

Collapsible bicycle comprising a monocoque frame Figures 1 and 2 are side views of a bicycle 10 in respectively a ridable configuration and a collapsed configuration according to a first embodiment of the present invention. The bicycle 10 is a collapsible bicycle where the overall length of the bicycle 10 can be varied to suit riders of different sizes in a ridable configuration as shown in Figure 1, as well as being put into a collapsed configuration as shown in Figure 2 during transportation.

Towards the front of the bicycle 10 there is provided a subassembly 22, comprising a front wheel 34 rotatably mounted onto a fork 24 by a front axle 36. The fork 24 having a steerer tube at its top end that extends through a headtube 26, wherein bearings are provided in the headtube 26 to aid relative rotation between the said steerer tube and the headtube 26. The steerer tube of the fork 24 is coupled to a handlebar stem 25 fixed attached to a handlebar (not shown). The handlebar stem 25 is partly enclosed in a stem sleeve 27 extending upwardly from the headtube 26. Thus, a rider may rotate a handlebar about the headtube 26 to steer the bicycle 10 into the desired direction.

The stem sleeve 27 is configured to pivot about a hinge 29 to convert between the ridable configuration and the collapsed configuration. More specifically, in the rideable configuration, the handle stem 25 extends at an angle to the longitudinal axis of the bicycle 10 and is locked in position by a hinged lever. On the other hand, the handle stem 25 is substantially parallel to the longitudinal axis of the bicycle 10 when the stem sleeve 27 the bicycle 10 is put into the collapsed configuration. Such an arrangement reduces the overall height of the bicycle when it is collapsed.

113 The subassembly 22 further comprises an elongated guide frame 28 welded to the headtube 26. The guide frame 28 extends in a horizontal plane along the longitudinal axis of the bicycle 10. The guide frame 28 is of conventional tubular frame construction and may form from any suitable material. The phrase horizonal plane generally refers to a plane parallel to the horizon when the bicycle 10 is set on levelled ground, and may be substantially parallel to a line extending through the front and rear axle of the bicycle.

Referring to Figure 1, a rearward portion of the bicycle 10 comprises a monocoque frame 12 rotatably supported on a rear wheel 30 by a rear axle 32. The monocoque frame 12 forms a load-bearing structure of the bicycle 10 that is configured to distribute some of the weight of the rider (not shown) and the bicycle 10 to the rear axle 32. That is, the monocoque frame 12 is the only load-bearing member connected between a seat post 16 and a crank axle 200 of the bicycle 10 to the rear axle 32. The monocoque frame 12 may be formed from any suitable material such as steel, aluminium, and other composite materials such as a carbon fibre composite. The rear wheel 30 and the front wheel 34 are compact bicycle wheels each having an overall diameter of less than 350mm, commonly referred to as 12 or 14 inches wheels.

The monocoque frame 12 is formed from two monocoque shells joint together along a longitudinal centreline of the bicycle 10. As shown in Figure 1, the monocoque frame 12 fully encloses a rear sprockets set 40, a front sprockets set 50 and their respective derailleurs, as well as the drive chain 42 connecting the sprocket sets 40, 50.

The monocoque frame 12 further comprises a guide channel 14 extending along the longitudinal axis of the bicycle 10 and in the same horizontal plane as the guide frame 28. In the illustrated embodiment, the guide channel 14 extends internally through a front and rear opening of the monocoque frame 12. In some other embodiments, the guide channel 14 only extends through the front opening of the monocoque frame 12 whilst the rear end of the monocoque frame 12 is sealed, e.g. the guide channel 14 does not extend all the way through the monocoque frame in these embodiments.

113 The guide channel 14 is configured to slidingly receive the guide frame 28. The guide channel 14 has a cross-sectional profile complementary to that of the guide frame 28. The cross-section profiles of the guide channel 14 and the guide frame 28 are non-circular to prevent relative rotation between the subassembly 22 and the monocoque frame 12. By the sliding connection, the monocoque frame 12 joints the subassembly 22 to form the bicycle 10.

The overall length of the bicycle 10 can be adjusted by sliding the guide frame 28 along the guide channel 14 within a movement range to suit riders of different sizes. Furthermore, the guide channel 14 comprises a retaining means for moveably retaining the guide frame 28 at any desired position within the said movement range. For example, the retaining means may be an indexing arrangement.

For example, to suit a taller rider, the bicycle may be lengthened to its greatest extent by sliding the guide frame 28 towards a first end of the movement range, e.g. towards the front of the monocoque frame 12. On the other hand, as shown in Figure 2, the bicycle 10 may be put into the collapsed configuration by sliding guide frame 28 towards a second end of the movement range, which significantly shortens the overall length of the bicycle. To suit shorter or smaller riders, the guide frame 28 may be slide to a position between the two ends of the movement range.

As shown in Figure 2, the seat post 16 is configured to be inserted into the guide channel 14 through a rear opening of the monocoque frame 12 when the bicycle 10 is put into the collapsed configuration. More specifically, the seat post 14 may be received in, and coextends with, both the guide channel 14 and the guide frame 28. Such an arrangement reduces the overall height of the bicycle 10 when it is put into the collapsed configuration.

The bicycle 10 further comprises a support wheel 38 rotatably supported at the rear end of the monocoque frame 12. The support wheel 38 extends in the same plane as the front wheel 34 and the rear wheel 30, and is positioned upward of the rear wheel 30 as shown in Figures 1 and 2. When the bicycle 10 is put into the collapsed configuration as shown in Figure 2, the bicycle 10 may be pivoted about the rear axle 32 and be supported on both the rear wheel 30 and the support wheel 38. Thus, the rider may transport the bicycle 10 with relative ease by the support wheel 38 and the rear wheel 30.

Referring back to Figure 1, the front sprocket set 50 is mechanically connected to the rear sprocket set 40 by the drive chain 42. In use, a rider may push on a pedal 121 to rotate the crank axle 200 and the front sprocket set 50 in a first rotational direction 202. By the drive chain 42 and the rear sprocket set 50, the driving force is transferred to rear wheel 30 for driving forward motion in the cycle 10.

The drive chain 42 loops around a sprocket in each of the rear and front sprocket sets 40, 50, as well as engaging with a guide sprocket 70 and a tensioner sprocket 90 in a rear derailleur assembly. In the illustrated embodiment, the front sprocket set 50 comprises a single sprocket whilst the rear sprocket set 40 comprises four sprockets of different sizes, thus only the rear derailleur assembly is featured. In other embodiments, the front and rear sprocket sets may have any number of sprockets as required and may feature an additional front derailleur.

The guide sprocket 70 is configured to move in a direction parallel to the rear axle 32 so as to displace the drive chain 42 to other sprockets in the rear sprocket set 40. The tensioner sprocket 90, biased by a biasing means, is configured to maintain the tension in the drive chain as it loops around the various sprockets of the rear sprocket set 40.

Horizontally Movable Guide Sprocket In conventional derailleurs, the guide sprocket is arranged to displace in both the vertical plane and the horizontal direction by a parallelogram. As such, they require a substantial ground clearance and therefore preclude the use of smaller sized wheels, e.g. less than 16 inches in diameter. In the present invention, the guide sprocket moves only in a horizontal plane, resulting in a more vertically compact derailleur assembly.

Figures 3 and 4 are cross-sectional plan views of a derailleur assembly according to a second embodiment of the present invention, taken across a horizontal plane through the rear axle 32. Figures 3 and 4 respectively shows the drive chain 42 engages with the largest sprocket 40d and the smallest sprocket 40a in the rear sprocket set 40.

The derailleur assembly as shown in Figure 3 is a rear derailleur assembly installed at the rear axle 32 of the bicycle 10, but it may also serve as a front derailleur for the crank axle in other embodiments. In the illustrated embodiment, the derailleur assembly is installed onto the collapsible bicycle 10 as shown in Figures 1 and 2 as an example, but the derailleur assembly may nevertheless be used with any suitable cycle.

As shown in Figure 3, the rear axle 32 is rotationally mounted onto the monocoque frame 12 by suitable bearings (not shown). The rear axle 32 defines a rear axis 64 having the rear sprocket set 40, the rear wheel 30, and a brake disc 226 coaxially mounted thereon. The rear sprocket set 40 is connected with the front sprocket set 50 by the drive chain 42.

The rear sprocket set 40 comprises a series of four sprockets 40a-40d that incrementally increase in diameter, or size. For example, the sprockets 40a, 40b, 40c and 40d respectively having 14, 17, 20, 24 teeth provided around their circumferences. As the drive chain 42 sequentially shifts through the sprockets 40a-40d they result in a gradual change in pedalling cadence. Due to the differences in the sprockets sizes, the rear sprocket set 40 have a generally tapered side profile, represented by a nominal line 44 extending across the apexes (or leading teeth aligned in the horizonal plane) of all of the sprockets 40a-40d.

The nominal line 44 extends at an angle a to the rear axis 64. In this particular example, the angle a is 500.

In some other embodiments, the rear sprocket set may comprise any plural number of sprockets each having different sizes, resulting in a change in the gradient of the nominal line. Thus, the angle a in these embodiments may range between 30° to 70°, or between 400 to 600, or between 45° to 55° to the rear axis.

The derailleur assembly comprises a guide rail 80 extending substantially in the horizontal plane and at an angle a to the rear axis 64. More specifically, the guide rail extends parallel to the nominal line 44 and thus it is separated to teeth of all of the sprockets 40a-40d by substantially the same gap. In the illustrated embodiment, the guide rail 80 extends diagonally across the longitudinal axis 66 of the bicycle 10, and fixedly mounts onto opposite sides of the monocoque frame 12 by suitable brackets. The brackets are suitably sized to offset the position of the guide rail 80 along the longitudinal axis 66, so as to provide sufficient clearance between the guide rail 80 and the rear sprocket set 40.

In some other embodiments, in particular ones that feature a conventional bicycle frame, the guide rail may not extend across the longitudinal axis, but instead, the first end of the guide rail may attach to a fork end of the frame that mounts the rear axle, and the second end attached to a bottom bracket of the bicycle.

The guide rail 80 is positioned forward of the rear wheel 30, and is shielded from grit by a mudguard 34 surrounding the rear wheel 30. Such an arrangement utilises a space that is normally left unoccupied in conventional bicycles.

As shown in Figure 3, a chain guide 72 is slidably mounted on the guide rail 80 by suitable bearings (not shown). The chain guide 72 comprises arms 73 onto which the guide sprocket 70 is rotatably mounted. The guide sprocket 70 is aligned with a vertical plane and is rotatable about an axis parallel to the rear axis 64.

The chain guide 72 is slidingly moveable between a plurality of positions along the guide rail 80 each corresponds to a sprocket 40a-40d of the rear sprocket set 40.

For example, the chain guide 72 as shown in Figure 3 is at a position corresponding to the largest sprocket 40d, and at a position corresponding to the smaller sprocket 40a as shown in Figure 4. Thus, at each of the positions, the guide sprocket 70 is parallel to, and separated by a substantially constant gap to, the corresponding sprocket 40a-40d. More specifically, the parallelity between the guide rail 80 and the tapered side profile of the rear sprocket set 40, e.g. the nominal line 44, maintains a substantially constant separation through the range of sliding movement and advantageously minimises rattling and the risk of chain derailment.

As shown in Figures 3 and 4, the movement of the chain guide 72 along the angled guide rail 80 is greater than the displacement in the drive chain 42 parallel to the rear axis 64. More specifically, since the guide rail 80 extends at an angle to the axis, any movement in the chain guide 72 parallel to the nominal line 44 would result in a relatively smaller displacement in the drive chain 42. Advantageously, such an arrangement may allow the displacement in the drive chain 42 to be more precisely controlled.

The relative sliding movement between the chain guide 72 and the guide rail 80 is driven by a motor 78 in combination with a rack 76a and pinion 76b gearing.

The motor 78 is fixed attached to the monocoque frame 12. The pinion gear 76b is mounted onto an output shaft of the motor 78, and is configured to engage the corresponding rack 76a that is fixed attached to the chain guide 72. This allows the rotational movement at the output shaft to be converted to a linear sliding movement in the chain guide 72. For example, upon receiving an upshift or a downshift signal from an electronic shifter (not shown), the output shaft of the motor 78 rotates in a direction corresponding to the signal. By the rack and pinion gearing 76a, 76b, the chain guide 72 slides along the guide rail 80 to a different position corresponding to the desired sprocket 40a-40d in the rear sprocket set 40. This causes the guide sprocket 70 to displace the drive chain 42 onto the desired sprocket and provides the rider with suitable cadence.

In some other embodiments, other types of gearing may be used. For example, a worm gear may be used instead of the rack and pinion gearing. In some other embodiment, other actuators may be used in lieu of the motor, for example Shape Memory Alloy actuators and other direct-drive linear motors.

A sprung ball indexing arrangement (not shown) is provided to movably retain the chain guide at each of the positions. More specifically, the guide rail 80 is provided with a notch at each of the positions for receiving a sprung ball mechanism that fitted to the chain guide 72. This advantageously allows the chain guide 72 to be retained, by the biasing force from the sprung ball mechanism, at each of the positions when the motor 78 is not actuated. In order to initiate sliding movement in the chain guide 72, the motor 78 would have to first overcome the biasing force to dislodge the sprung ball mechanism from the notch and thereby freeing up the chain guide 72.

In some other embodiments, the sliding movement in the chain guide may be effected by a direct mechanical connection to the shifter, instead of an electronic actuator. For example, the chain guide may be connected to a shifter by Bowden cables. In these cases, the rider may toggle the shifter to change vary the tension in the Bowden cable, which in turn drive sliding movement in the chain guide for displacing the drive chain to the desired sprocket.

In some other embodiments, the rear sprocket set may comprise a series of sprockets through which their sizes do not increase incrementally with each sprocket. In these cases, the guide rail may non-linearly extend in the horizontal plane and complementary to a profile of the multi-stage sprocket assembly. For example, the guide rail may comprise, along its length, a curvature or plural consecutive segments extending at different angles to the axis, complementary to a curved or angled side profile of the multi-stage sprocket assembly.

Advantageously, by eliminating vertical displacement in the guide sprocket, the derailleur assembly according to the present invention can be made more vertically compact, as well as significantly reduce the amount of ground clearance required.

Decoupled tensioner member and chain guide A conventional derailleur typically comprises a single derailleur frame that holds both the guide sprocket and the tensioner sprocket, and therefore the two sprockets move in unison along in both vertical and horizontal directions during a gear change.

In a derailleur assembly according to a third embodiment of the present invention, the guide sprocket and the tensioner sprocket are rotatably mounted on respective chain guide and tensioner member, and wherein the chain guide and the tensioner member are moveable relative to each other. Such an arrangement may advantageously decouple the two functions, chain tensioning and chain guidance, in the derailleur assembly. Thus, the vertical displacement as observed in conventional tensioner sprockets may be significantly reduced or eliminated. Moreover, since the movement in the chain guide is decoupled from the tensioner member, the biasing force that is required for chain tensioning no longer acts directly upon the chain guide. Advantageously, less input force may be required from the rider, or the electronic actuator, to effect gear shifting.

Figures 5 and 6 show an enlarged side view of the bicycle 10 of Figure 1 in combination with the horizontally moveable chain guide 72 of Figures 3 and 4. For simplicity reasons, the guide rail and other components are not shown again.

Figures 5 and 6 respectively shows the drive chain 42 engages with the largest sprocket and the smallest sprocket in the rear sprocket set 40.

As shown in Figure 5, the chain guide 72 and tensioner member 92 are distinct elements and are connected by the drive chain 42. More specifically, the drive chain 42 sequentially routes through the tensioner sprocket 90 at tensioner member 92 and the guide sprocket 70 at the chain guide 72 before feeding to a sprocket of the rear sprocket set 40.

A biasing means, in this example a tension spring 94, is fixedly attached between the monocoque frame 12 at fixing point 98 and the tensioner member 92. The monocoque frame also comprises a plurality of tensioner pulleys 96a, 96b are rotatably mounted thereon and are distributed around the rear axle 32. The tension spring 94 is routed through the plurality of tensioner pulleys 96a, 96b such that it is wound around the rear axle 32. Advantageously, this allows a relatively long tension spring 94 to be neatly concealed in the monocoque frame 12, as shown in Figures 5 and 6, as well as providing increased ground clearance to cater for smaller wheels.

The length of the tensioner spring and the number of tensioner pulleys may vary across different embodiments. For example, in some embodiments, more tensioner pulleys may be provided for routing a lengthier tensioner spring, e.g. to provide a larger overall biasing force or to utilise longer tension springs with lower spring constants. In some embodiments, to reduce complexity a shorter length of tension spring may be used which accordingly reduces the number of tensioner pulleys required. This reduces the complexity of the derailleur assembly. In some other embodiments, shorter coil springs or torsion springs with higher spring constants may be used to provide the required biasing force, without the need for any tensioner pulley, e.g. the coil spring or the torsion spring may directly connect between the monocoque frame and the tensioner member.

The tensioner spring 94 is configured to bias the tensioner member 92 away from the front sprocket set 50 and therefore tensions the drive chain 42 to reduce or eliminate slack in the drive chain 42. The tensioner member 92 is suspended by the biasing force in the tensioner spring 94 and the tension in the drive chain 42, and therefore it is moveable in all directions and about all axes.

For example, when shifting the drive chain 42 from the largest sprocket in Figure 5 to the smallest sprocket in Figure 6, the tensioner spring 94 pulls the tensioner member 92 further away from the front sprocket set 50 in order to maintain sufficient tension in the drive chain 42 to eliminate slack, e.g. the tensioner member 92 moves along the longitudinal axis of the bicycle 10.

Since the movement in the chain guide 72 is decoupled from the tensioner member 92, the biasing force that is required for chain tensioning no longer acts directly upon the chain guide 72. Advantageously, less input force may be required from the rider, or the electronic actuator, to effect gear shifting.

The displacement in the drive chain 42 along the rear axis 64 during shifting also displaces the tensioner member 92 horizontally. More specifically, since the tensioner member 92 is not fixedly attached to the frame, it trails the drive chain 42 and the chain guide 72 in a direction parallel to the rear axis 64. For example, in the illustrated embodiment where four sprockets are featured in the rear sprocket set 40, the tensioner member may displace up to 20mm in a direction parallel to the rear axis 64 as it displaces the drive chain 42 through the four sprockets. Advantageously, such an arrangement may allow the tensioner sprocket to maintain adequate alignment with the guide sprocket, and thus minimising rattle and resistance during pedalling.

113 As shown in Figures 5 and 6, the tensioner member 92 is arranged at a position below the chain guide and an apex of each of the sprockets in the multi-stage sprocket assembly. More specifically, the tensioner member is positioned below the bottom teeth of the largest sprocket in the rear sprocket set 40 so as to provide sufficient clearance when it trails the drive chain 42 in a direction parallel to the rear axis 64.

As shown in Figure 5, one of the tensioner pulley 96b is mounted at a position on the monocoque frame 12 such that a section of the tension spring 94 extends substantially parallel to the section of the drive chain 42 connecting the tensioner sprocket 90 and the front sprocket set 50. Thus, during shifting the tensioner member 92 moves along the direction of the drive chain 42. This advantageously minimises vertical displacement in the tensioner member 92 during a gear change. In some embodiments, the tensioner pulley is positioned such that a section of the tension spring and the section of the drive chain connecting the tensioner sprocket and the front sprocket set extend parallel to the horizontal plane. Thus, during shifting the tensioner member moves only in the horizontal direction.

Advantageously, the vertical displacement as observed in conventional tensioner sprockets may be significantly reduced or eliminated.

Claims

Claims 1. A derailleur assembly for a cycle, the cycle having a multi-stage sprocket assembly rotatable about an axis, the derailleur assembly comprising: a guide rail extending substantially in a horizontal plane and angled to the axis; a chain guide mounted on the guide rail, the chain guide is slidingly moveable between a plurality of positions along the guide rail each corresponds to a drive sprocket of the multi-stage sprocket assembly; lo a guide sprocket rotatably supported on the chain guide, the guide sprocket is configured to guide displacement of a drive chain parallel to the axis, wherein the separation between the guide sprocket and the corresponding drive sprocket is substantially the same at each of the positions.
2. The derailleur assembly of claim 1, wherein the guide rail linearly extends at an angle between 300 to 70°, or between 40° to 60°, or between 45° to 55°, or substantially 50° to the axis.
3. The derailleur assembly of claim 1, wherein the guide rail non-linearly extends in the horizontal plane and is complementary to a profile of the multi-stage sprocket assembly.
4. The derailleur assembly of any one of the preceding claims, wherein the guide rail comprises retaining means for movably retaining the chain guide at each of the positions.
5. The derailleur assembly of any one of the preceding claims, further comprises an electronic actuator, the electronic actuator is configured to receive a signal from a gear selector to drive sliding movement in the chain guide.
6. The derailleur assembly of claim 5, further comprises a rack and pinion gearing for translating a rotational motion of the electrical actuator to the sliding movement in the chain guide.
7. The derailleur assembly of any one of the claims 1 to 4, wherein the chain guide is mechanically connectable to a gear selector for effecting sliding movement in the chain guide.
8. The derailleur assembly of any one of the preceding claims, wherein the movement of the chain guide along the angled guide rail being greater than the displacement in the drive chain along the axis.
9. The derailleur assembly of any one of the preceding claims, wherein the guide rail having a first end fixedly attachable to a structure of the cycle proximal to the multi-stage sprocket assembly and a second end fixedly attachable to the structure at a position forward of a rear wheel of the cycle.
10. The derailleur assembly of any one of the preceding claims, wherein the guide sprocket is configured to guide displacement of the drive chain parallel to the axis corresponds to a rear axle or a crank axle of the cycle.
11. The derailleur assembly of any one of the preceding claims, further comprises a tensioner sprocket rotatably mounted on a tensioner member, the tensioner sprocket is configured to engage and tension the drive chain, wherein the tensioner member is moveable relative to the chain guide.
12. The derailleur assembly of claim 11, further comprises a biasing means connected between a structure of the cycle and the tensioner member, the biasing means is configured to apply a biasing force on the tensioner member so as to tension the drive chain.
13. The derailleur assembly of claim 12, wherein the biasing means comprises a tension spring, and wherein the derailleur assembly further comprises one or more pulleys attached to the structure of the cycle for routing the tension spring around the axis.
14. The derailleur assembly of any one of the claims 11 to 13, wherein the tensioner member is arranged at a position below the chain guide and an apex of each of the sprockets in the multi-stage sprocket assembly.
15. The derailleur assembly of any one of the claims 11 to 14, wherein the tensioner member is configured to be suspended by the biasing force applicable by the biasing means and the tension in the drive chain.
16. The derailleur assembly of any one of the claims 11 to 15, the tension guide member is moveable in a direction parallel to the axis by the displacement in the drive chain.
17. A derailleur assembly for a cycle, the cycle having a multi-stage sprocket assembly rotatable about an axis, the derailleur assembly comprising: a chain guide moveable to a plurality of positions each corresponds to a drive sprocket of the multi-stage sprocket assembly; a guide sprocket rotatably supported on the chain guide, the guide sprocket is configured to guide displacement of a drive chain parallel to the axis, wherein the separation between the guide sprocket and the corresponding drive sprocket is substantially constant at each of the positions; and a tensioner sprocket rotatably mounted on a tensioner member, the tensioner sprocket is configured to engage and tension the drive chain, wherein the tensioner member is moveable relative to the chain guide.
18. The derailleur assembly of claim 17, further comprises a biasing means connected between a structure of the cycle and the tensioner member, the biasing means is configured to apply a biasing force on the tensioner member so as to tension the drive chain.
19. The derailleur assembly of claim 18, wherein the biasing means comprises a tension spring, and wherein the derailleur assembly further comprises one or more pulleys attached to the structure of the cycle for routing the tension spring around the axis.
20. The derailleur assembly of claims 18 or 19, wherein the tension guide member is configured to be suspended by the biasing force applicable by the biasing means and the tension in the drive chain.
21. The derailleur assembly of any one of the claims 17 to 20, further comprises a guide rail extending at an angle to the axis; wherein the chain guide is mounted on the guide rail and is slidingly moveable to the plurality of positions.
22. The derailleur assembly of claim 21, wherein the guide rail extends substantially in a horizontal plane.
23. A cycle, comprising the multi-stage sprocket assembly, the drive chain and the derailleur assembly of any one of the preceding claims.
24. The cycle of claim 23, further comprises a monocoque frame that forms a load-bearing structure to which a rear wheel of the cycle is mounted onto, the monocoque frame at least partially encloses the multi-stage sprocket assembly, the derailleur assembly, the drive chain and other drivetrain components that drives the rear wheel.
25. The cycle of claim 24, further comprises a subassembly to which a front wheel of the cycle is mounted onto, the subassembly comprises a guide frame slidably received inside the monocoque frame for varying the overall length of the 20 cycle.