WO2010015802A1

WO2010015802A1 - Pedal mechanism

Info

Publication number: WO2010015802A1
Application number: PCT/GB2009/001855
Authority: WO
Inventors: George Frederic Galvin
Original assignee: George Frederic Galvin
Priority date: 2008-08-02
Filing date: 2009-07-28
Publication date: 2010-02-11
Also published as: GB2474215A; GB201102537D0; GB2474215B

Abstract

A pedal mechanism (4) for a bicycle comprises a pair of elongate members (5) attachable to the frame (1) of a bicycle on opposite sides thereof. A respective pedal (9) is associated with each of the elongate members and is mounted for reciprocation relative to the frame. A hub/scroll mechanism (6) is associated with a wheel (3) of the bicycle, and a pair of wires (10 are provided. The hub/scroll mechanism (6) comprises a wheel hub (16), a pair of scrolls (7) and a pair of one-way clutches (17), each scroll being associated with a respective elongate member/pedal carrier (5, 8). Each scroll (7) has a curved perimeter, and the scrolls are rotatably mounted on a scroll shaft (14) in such a manner that the radius of curvature of the curved perimeter of each scroll with respect to the axis of the scroll shaft is a minimum at one end (7c) of that curved perimeter and a maximum at the other end (7b) of that curved perimeter. One end of each wire (10) is associated with a respective elongate member (5), the other end of that wire being connected to a respective scroll (7) adjacent to said one end (7c) of that scroll, and an intermediate portion of that wire passes around the curved perimeter of that scroll. A respective one-way clutch (17) is provided between each scroll (7) and the hub ( 16), so that rotation of that scroll in one direction rotates the hub, and rotation of that scroll in the other direction results in that one-way clutch freewheeling

Description

Pedal mechanism

This invention relates to a pedal mechanism used to propel a bicycle, a tricycle or any other application converting a mechanical input to a rotary output.

A conventional bicycle pedal mechanism comprises two crank arms to which are attached pedals, the crank arms being displaced by 180°. One of the crank arms is attached to a drive sprocket which, via a chain, drives a driven sprocket fixed to a wheel (usually the rear wheel) of the bicycle. Getting a bicycle to move requires the rider to apply forces to the pedals. In doing so, the rider's force is transmitted over a distance by the crank arms, creating a moment which rotates the drive sprocket, thereby moving the chain and rotating the driven sprocket and hence the (rear) wheel.

In the case of a conventional bicycle, the drive sprocket usually has a greater diameter than the driven sprocket, but gearing arrangements may be provided depending upon the rider's requirements.

In a conventional arrangement, the pedals have to travel through 360° with force from each leg being applied one leg after the other. The maximum torque (turning force) that can be applied by this action occurs when the applied force through the rider's leg is when that force is normal (90°) to the crank arm, and, therefore, is a low torque both at the bottom and the top of travel.

The aim of the invention is to provide a pedal mechanism that permits increased torque to be applied virtually continuously, so that more efficient use is made of the rider=s input.

The present invention provides a pedal mechanism for a bicycle, the pedal mechanism comprising an elongate member attachable to the frame of a bicycle, a pedal associated with the elongate member and mounted for reciprocation relative to the frame, a hub/scroll mechanism associated with a wheel of the bicycle, and a wire, the hub/scroll mechanism comprising a wheel hub, a scroll and a one-way clutch, the scroll having a curved perimeter and being rotatably mounted on a scroll shaft in such a manner that the radius of curvature of its curved perimeter with respect to the axis of the scroll shaft is a minimum at one end of the curved perimeter and a maximum at the other end of the curved perimeter, one end of the wire being associated with the elongate member, the other end of the wire being connected to the scroll adjacent to said one end, and an intermediate portion of the wire passing around the curved perimeter of the scroll, the one-way clutch being provided between the scroll and the hub, so that rotation of the scroll in one direction rotates the hub, and rotation of the scroll in the other direction results in the one-way clutch freewheeling.

The invention also provides pedal mechanism for a bicycle, the pedal mechanism comprising an a pair of elongate members attachable to the frame of a bicycle on opposite sides thereof, a respective pedal associated with each of the elongate members and mounted for reciprocation relative to the frame, a hub/scroll mechanism associated with a wheel of the bicycle, and a pair of wires, the hub/scroll mechanism comprising a wheel hub, a pair of scrolls and a pair of oneway clutches, each scroll being associated with a respective elongate member/pedal carrier, each scroll having a curved perimeter, wherein the scrolls are rotatably mounted on a scroll shaft in such a manner that the radius of curvature of the curved perimeter of each scroll with respect to the axis of the scroll shaft is a minimum at one end of that curved perimeter and a maximum at the other end of that curved perimeter, one end of each wire being associated with a respective elongate member, the other end of that wire being connected to a respective scroll adjacent to said one end of that scroll, and an intermediate portion of that wire passing around the curved perimeter of that scroll, a respective oneway clutch being provided between each scroll and the hub, so that rotation of that scroll in one direction rotates the hub, and rotation of that scroll in the other direction results in that one-way clutch freewheeling

Advantageously, the curved perimeter of each of the scrolls extends over an angle greater than 360°, and preferably the curved perimeter of each of the scrolls extends over substantially 420°.

Conveniently, a respective groove is provided in the curved perimeter of each of the scrolls.

In a preferred embodiment, each of the scrolls is attached to a respective scroll carrier, a respective one-way clutch being provided between each scroll carrier and the hub.

Preferably, a respective crown gear wheel is fixed to each of the scroll carriers, the crown gear wheels meshing with a pair of pinions carried by a pinion shaft which is fixed to the scroll shaft for rotation therewith, the crown gear wheels and pinions defining a differential gear mechanism.

Advantageously, the pinion shaft passes at right-angles through the scroll shaft.

The pedal mechanism may further comprise a respective spring acting, in use, between each of the scrolls and the frame, each spring being effective to rotate the associated scroll back to its original position following rotation of that scroll in said one direction as a result of movement of the associated pedal carrier along the respective elongate member. The pedal mechanism may further comprise a friction band in engagement with a wheel fixed to the scroll shaft.

Alternatively, the pedal mechanism may further comprise an indent wheel fixed to the scroll shaft, the indent wheel being formed with a plurality of indents in its circumference, each of the indents being engageable with one end portion of a spring, the other end of that spring being fixable to the frame of the bicycle. Preferably, the indent wheel is provided with three equispaced indents.

Advantageously, a respective pedal carrier box constitutes each elongate member, each pedal carrier box being formed with a longitudinal slot within which the respective pedal carrier is reciprocably mounted.

Preferably, each pedal carrier is provided with rollers for rolling engagement with surfaces of the associated pedal carrier box, and each pedal carrier is provided with a further roller for rolling engagement within the longitudinal slot of the associated pedal carrier box.

In a preferred embodiment, a first end of each elongate member is pivotally attached to the frame, a respective pedal being attached to a second end of that elongate arm.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: -

Figure 1 is a side elevation of a bicycle incorporating a first form of pedal mechanism constructed in accordance with the invention;

Figure 2 is a schematic side elevation of the pedal mechanism of Figure l;

Figure 3 is a part-sectional perspective view of a hub/scroll mechanism forming part of the pedal mechanism;

Figure 4 is a perspective view of a crown wheel/pinion differential forming part of the hub/scroll mechanism;

Figure 5 is a side elevation of one of the scrolls of the hub/scroll mechanism;

Figure 6 is a side elevation of a bicycle incorporating a second form of pedal mechanism constructed in accordance with the invention;

Figure 7 is a schematic side elevation Of the pedal mechanism of Figure 6; and

Figure 8 is a perspective view of a pedal carrier box forming part of the pedal mechanism of Figure 7.

Referring to the drawings, Figure 1 shows a bicycle having a frame 1 , a front wheel 2, a rear wheel 3 and a pedal mechanism indicated generally by the reference numeral 4. The pedal mechanism 4 (see Figure 2) is constituted by a pair of elongate arms 5 positioned on opposite sides of the frame 1 , and by a hub/scroll mechanism 6 (see Figure 4) which includes a pair of scrolls 7.

The elongate arm 5 shown in Figure 2 is pivoted to the frame 1 at a rear pivot point 8. The elongate member 5 supports a pedal 9 whose spindle (not shown) is fixed in an aperture (not shown) formed in the elongate member. A first end of a wire 10 is fixed within a slot 8b formed in the carrier 8, the second end of the wire 10 being fixed to the scroll 7 positioned in the same side of the frame 1 as that elongate member 5. The other elongate member 5 is the same as that described above, and its wire 10 is fixed to the scroll 7 positioned on the other side of the frame 1.

Referring to Figure 3, the hub/scroll mechanism 6 includes the two scrolls 7, each of which defines a curved perimeter which extends over about 420°. Each scroll 7 is fixed to a respective scroll carrier 12 for rotation therewith, and each scroll is formed with a groove 7a in its perimeter. Each scroll 7 is eccentrically mounted, via a respective support and thrust bearing 13 , with respect to a scroll shaft 14 so that one end 7b of its groove 7a is at a maximum distance from the axis of the scroll shaft, and the other end 7c of that groove is at a minimum distance from that axis. The scroll shaft 14 is mounted within a pair of rear suspension arms Ia (see Figures 1 and 2) forming part of the frame 1 by respective bearings 15. The scroll carriers 12 are mounted within the hub 16 of the rear wheel 3 with the interposition of one-way, needle roller clutches 17.

At its inner end, each scroll carrier 12 is provided with a crown gear wheel 19. The crown gear wheels 19 mesh with pinions 20 provided at the ends of a pinion shaft 21 which passes at right-angles through, and is fixed to, the scroll shaft 14. The crown gear wheels 19 and pinions 20 constitute a differential gear mechanism.

An indent wheel 23 is fixed to the scroll shaft 14 for rotation therewith. The indent wheel 23 is formed with three equispaced indents 24, each of which is engageable by the bent free end of a spring 25, the other end of which is fixed to one of the rear suspension arms Ia.

As best shown in Figure 2, the wires 10 pass around the scrolls 7 in the grooves 7a, and their second ends are fixed to the scrolls in respective slots (not shown) at the ends 7c. Each wire 10 thus enters its associated groove 7a at the end 7b thereof, and is fixed to the associated scroll in the slot at the end 7c. Each scroll 7 is fitted with a return spring 22, one end of which is fixed to the end 7b of that scroll, the other end being fixed to the frame 1 adjacent to the scroll shaft 14.

In use, when one of the pedals 9 (say the pedal at the right-hand side of the frame 1) is depressed, the associated elongate member 5 is forced down, carrying with it the wire 10. As the other end of that wire 10 is fixed to the respective scroll 7 in the slot at the end 7c, that scroll (and the associated scroll carrier 12) rotates in a clockwise direction winding up the associated spring 22. This rotation is transferred to the hub 16 by virtue of the respective one-way clutch 17. When pressure on that pedal 9 is relaxed, the scroll 7 is rotated in an anticlockwise direction by the spring 22 to be returned to its original position. During this return movement of the scroll 7, the associated one-way clutch 17 freewheels. The pedal 9 can then be depressed again to repeat this action.

It should be appreciated that a similar sequence of actions can be carried out by depressing and relaxing the pedal 9 on the other side of the frame 1. The two pedals 9 can be depressed either alternately, as with a conventional bicycle pedal mechanism, or they can be depressed simultaneously. It is also possible to power the bicycle using only one of the pedals 9.

When the pedals 9 are used alternately, the differential gear mechanism is effective to lift one pedal 9 as the other pedal is depressed. Thus, assuming one pedal 9 (say the right-hand pedal) is at the top of its movement and the other pedal is held stationary, as said one pedal is depressed, the associated scroll carrier 12 and scroll 7 are caused to rotate as described above. Rotation of the scroll 7 and the scroll carrier 12 causes rotation of the associated crown wheel gear 19. At the same time, the shaft 14 is held stationary by the other pedal 9, so that the shaft 21 is also held. Accordingly, further movement of said one pedal 9 causes the opposite pedal to rise, because rotation of the pinions 20 in contact with the rotating crown gear wheel 19 rotates the other crown gear wheel in the opposite direction (as indicated by the arrows in Figure 4). This causes that other crown gear wheel 19 to rotate the other scroll carrier 12 and the associated scroll 7 in the opposite direction, thereby causing the other pedal 9 to rise, the tension in the associated wire 10 maintaining that wire taut to enable this to occur.

The pedal mechanism 4 described above has an inbuilt gear mechanism constituted by the indent wheel 23 and the associated spring 25. Thus, assuming that both pedals 9 are at the tops of their movement, and one of the pedals (say the right-hand pedal) is depressed, the rear wheel 3 is rotated, via rotation of the right- hand scroll 7, the associated scroll carrier 12, one-way clutch 17 and the hub 16. However, because the other pedal 9 is at the top of its movement, it cannot move upwards, so the associated scroll 7 and scroll carrier 12 cannot rotate. As a result, rotation of the crown gear wheel 19 associated with the right-hand scroll 7 rotates the two pinions 20, but this rotation cannot be transferred to the crown gear wheel 19 associated with the left-hand scroll 7 which is held stationary. Accordingly, the scroll shaft 14 and the pinion shaft 21 are rotated carrying the pinions 20.

When the left-hand pedal 9 is then depressed, the rear wheel 3 is rotated, via rotation of the left-hand scroll 7, the associated scroll carrier 12, one-way clutch 17 and the hub 16. As this occurs, the right-hand pedal 9 is raised as described above.

The inbuilt gear mechanism depends upon the working strokes of the two pedals 9. Thus, if the right-hand pedal 9 is initially depressed until the bent free end of the spring 25 engages in the first of the indents 24, that is to say the associated elongate member 5 travels along about one third of its total possible travel length, the associated scroll 7 rotates through only about one third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a large moment arm from the axis of the scroll shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being at the portion adjacent to the end 7b), a low gearing is achieved. The bicycle can then be driven in this low gear by alternately depressing the two pedals 9 over that same travel distance. After travelling for a while, a rider will need to change Agear≤ as is the case with a conventional bicycle. To do this, both the pedals 9 are held at the bottoms of their current travel. One pedal 9 is then depressed until the bent free end of the spring 25 engages in the second of the indents 24, so that the associated elongate member 5 travels along the next third of its possible total travel length, so that the associated scroll 7 rotates through only about the next third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a medium moment arm from the axis of the shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being in the middle of the perimeter substantially midway between the two ends 7b and 7c), a medium gearing is achieved. The bicycle can then be driven in this medium gear by alternately depressing the two pedals 9 over that same travel distance.

In order to move up to a higher gear, this process is repeated, so that the bent free end of the spring 25 engages in the third of the indents 24, so that the associated elongate member 5 travels along the last third of its possible total travel length, and so that the associated scroll 7 rotates through only about the last third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a small moment arm from the axis of the scroll shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being at the portion adjacent to the end 7c), a high gearing is achieved. The pedals 9 are alternately depressed over the last third of their total travel distance.

Thus, when starting to ride, a rider depresses one pedal 9 until the shaft 14 carries the indent wheel around by 120° until the bent of the end of the spring 25 snaps into the first of the indents 24 to engage first gear. As this happens, the rider feels the resistance to further movement of that pedal 9, commences cycling by depressing the other pedal 9, and continues by alternate depression of the pedals, over the first third of their total travel distance, until second gear needs to be engaged.

As mentioned above, in order to engage second gear, both pedals 9 are held at the bottoms of their current travel, and one of the pedals is then depressed until the bent end of the spring 25 snaps into the next indent 24. Cycling can then continue by alternate depression of the two pedals 9 over the next third of their total travel distance.

Similarly, in order to engage third gear, this process is repeated, so that cycling in third gear occurs by alternate depression of the two pedals 9 over the last third of their total travel distance.

In a modified embodiment, not shown, the indent wheel 23 is replaced by an unindented wheel, and the spring 25 is replaced by a friction band passing around the unindented wheel, a portion of the friction band being fixed to the frame of the bicycle. In this case, the gearing arrangement is more fluid, as there are no indents to define the three gears, as was the case with the embodiment described above with respect to Figure 3. Gear changing then depends on the rider choosing the degree of depression of the pedals 9.

Thus, if the right-hand pedal 9 is initially depressed by one third of its total possible travel length, the associated scroll 7 rotates through only about one third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a large moment arm from the axis of the scroll shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being at the portion adjacent to the end 7b), a low gearing is achieved. The bicycle can then be driven in this low gear by alternately depressing the two pedals 9 over that same travel distance.

After travelling for a while, a rider will need to change Agear≤ as is the case with a conventional bicycle. To do this, both the pedals 9 are held at the bottoms of their current travel. One pedal 9 is then depressed so that the associated elongate member 5 travels along the next third of its possible total travel length, so that the associated scroll 7 rotates through only about the next third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a medium moment arm from the axis of the scroll shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being in the middle of the perimeter substantially midway between the two ends 7b and 7c), a medium gearing is achieved. The bicycle can then be driven in this medium gear by alternately depressing the two pedals 9 over that same travel distance.

In order to move up to a higher gear, this process is repeated, so that the associated elongate member 5 travels along the last third of its possible total travel length, and so that the associated scroll 7 rotates through only about the last third of its possible arc of rotation. As the rotation of that scroll 7 occurs with a small moment arm from the axis of the scroll shaft 14 to where the wire 10 engages the perimeter of that scroll (that engagement being at the portion adjacent to the end 7c), a high gearing is achieved. The pedals 9 are alternately depressed over the last third of their total travel distance.

This gearing arrangement is suitable for an experienced rider, and it will be apparent that the gearing arrangement is capable of continuous adjustment to suit the rider=s requirements. The friction band enables the scroll shaft 14 to be positioned in any desired position by the rider, to provide an infinitely adjustable gearing arrangement.

Although the pedals 9 can be depressed simultaneously, it is preferable to cycle by alternate depression of the two pedals, as with a conventional bicycle. Simultaneous pedal operation is, therefore, used to change Agear≡, that is the arc through which the scrolls 7 are operated. Otherwise, simultaneous pedal depression would lead to unnecessary friction that would be felt by the rider. When both pedals 9 are operated over the same range, only then will the scroll shaft 14 not rotate, with either the indent wheel 23 or the friction band holding the scroll shaft 14 so that the differential gear mechanism can function as described above.

As mentioned above, any combination of pedal movement can be utilised to suit the prevailing conditions, the gear change being created by the chosen range over which the pedals 9 travel. Both pedals 9 can be used at the same time, or any combination of pedal movement overlap can be used. However, when both pedals are depressed simultaneously, some friction will be felt (due either to the engagement of the spring 25 in an indent 24 of the indent wheel, or to the engagement of the friction band with the unindented wheel), as the scroll shaft 14 is rotated, this friction being provided so that the rider can Afeel≤ the positions of the pedals 9, and experience the upwards movement of the inactive pedal about the position set. Unlike a conventional pedal crank mechanism, torque can be applied to the rear wheel 3 over the entire length of pedal travel.

In addition, the described pedal configuration allows the conventional chain to be replaced by the wires 10, thereby removing a source of constant problems of wear, adjustment and lubrication. The action of the conventional crank mechanism allows the active pedal to raise the other pedal, and hence the rider=s inactive leg. This action is incorporated in the pedal mechanism described above by incorporating the differential gear mechanism 19, 20 between the two scrolls 7 and their carriers 12, so that the downwards movement of one pedal 9 causes the other pedal to rise, whilst downwards movement of both pedals changes the arcs over which the scrolls 7 operate, thereby changing the output gear ratio. To reduce the Agearing≡, the pedals 9 can be raised by the rider=s legs, either independently or both together, the wires 10 being prevented from parting from their scrolls 7 by the springs 22.

The two pedals 9 are also not required to rotate as with a conventional crank mechanism, so they can be locked in any position chosen by the rider, making access to the pedal toe caps (if present) extremely easy on first starting to pedal.

By having two pedals 9 that can be used independently, it can be seen that pedalling can be maintained when negotiating a corner without fear of a pedal striking the ground, particularly with fixed wheel bicycles, as the pedals can be simply prevented by the rider from going near the ground, without loss of drive action, unlike conventional pedal crank mechanisms.

It will be apparent that the force applied to the pedals 9 has a direct affect on the scrolls 7, so that there is no loss of torque through the Abottom dead centres, as is exhibited by a conventional pedal crank mechanism. It is this Atop and bottoms positioning of a conventional pedal crank mechanism that leads to failure of momentum when travelling uphill. This can be avoided with the pedal mechanism 4 described above, as the second pedal can be acted upon before the first pedal reaches the end of its desired travel. This feature will be particularly advantageous in trishaw applications. It should also be noted that a conventional pedal crank mechanism can be replace by the pedal crank mechanism described above. Alternatively, the pedal crank mechanism described above can be built into a bicycle at the manufacturing stage.

Figures 6 to 8 show a second form of pedal mechanism, in which the elongate arms of the first form of pedal mechanism are supplemented by pedal carrier boxes described below. This second form of pedal mechanism has the same hub/scroll mechanism as that of the first form (as shown in Figures 3 to 5). Accordingly, that hub/scroll mechanism will not be described in detail below.

Figure 6 shows a bicycle having a frame 101, a front wheel 102, a rear wheel 103 and a pedal mechanism indicated generally by the reference numeral 104. The pedal mechanism 104 (see Figure 7) is constituted by a pair of pedal carrier boxes 105 positioned on opposite sides of the frame 101, and by the hub/scroll mechanism 6 of Figure 3 which includes a pair of scrolls 7.

The pedal carrier box 105 shown in Figure 7 is formed (see Figure 8) with a longitudinal channel 105a in which a pedal carrier 108 is reciprocally mounted. The pedal carrier 108 is provided with two pairs of side-mounted rollers (not shown) at opposite ends thereof, which are engageable with surfaces of the pedal carrier box 105, and with a further roller (not shown) which is engageable within the slot 105a. The rollers enable the pedal carrier 108 to move smoothly with respect to the pedal carrier box 105. The pedal carrier 108 supports a pedal 109 whose spindle (not shown) is fixed in an aperture 108a formed in the pedal carrier. A first end of a wire 10 forming part of the hub/scroll mechanism is fixed within a slot 108b formed in the carrier 108, the wire exiting the pedal carrier box 105 via a roller 111 positioned at the upper end of the box. The second end of the wire 10 is fixed to the scroll 7 positioned in the same side of the frame 101 as that pedal carrier box 105. The other pedal carrier box 105 is the same as that described above, and its wire 10 is fixed to the scroll 7 positioned on the other side of the frame 1.

The second form of pedal mechanism operates in substantially the same way as the first form of pedal mechanism apart from the minor differences described below.

Thus, in use, when one of the pedals 109 (say the pedal at the right-hand side of the frame 101) is depressed, the associated pedal carrier 108 is forced down its channel 105a, carrying with it the wire 10. As the other end of that wire 10 is fixed to the respective scroll 7 in the slot at the end 7c, that scroll (and the associated scroll carrier 12) rotates in a clockwise direction winding up the associated spring 22. Thereafter, operation of the hub/scroll mechanism is the same as that for the first form of pedal mechanism. In particular, the pedals 109 can be used together, separately or alternately, and gear change is the same as for the first form of pedal mechanism, with the proviso that it is movement of the pedal carriers 108 in the respective channels 105a that results in gear changes rather than the pivotal movement of the elongate arms 5.

It will be apparent that the pedal mechanism described above could be modified. For example, the wires 10 need not be metallic, but could be made of any elongate wire-like material that is sufficiently strong and pliable to carry out the required functionality.

It will also be apparent that the pedal mechanism described above could be used in any application where manual input, either by arms or legs, needs to be converted into rotary motion, for example in a pedalo.

Claims

1. A pedal mechanism for a bicycle, the pedal mechanism comprising an elongate member attachable to the frame of a bicycle, a pedal associated with the elongate member and mounted for reciprocation relative to the frame, a hub/scroll mechanism associated with a wheel of the bicycle, and a wire, the hub/scroll mechanism comprising a wheel hub, a scroll and a one-way clutch, the scroll having a curved perimeter and being rotatably mounted on a scroll shaft in such a manner that the radius of curvature of its curved perimeter with respect to the axis of the scroll shaft is a minimum at one end of the curved perimeter and a maximum at the other end of the curved perimeter, one end of the wire being associated with the elongate member, the other end of the wire being connected to the scroll adjacent to said one end, and an intermediate portion of the wire passing around the curved perimeter of the scroll, the one-way clutch being provided between the scroll and the hub, so that rotation of the scroll in one direction rotates the hub, and rotation of the scroll in the other direction results in the one-way clutch freewheeling.

2. A pedal mechanism for a bicycle, the pedal mechanism comprising an a pair of elongate members attachable to the frame of a bicycle on opposite sides thereof, a respective pedal associated with each of the elongate members and mounted for reciprocation relative to the frame, a hub/scroll mechanism associated with a wheel of the bicycle, and a pair of wires, the hub/scroll mechanism comprising a wheel hub, a pair of scrolls and a pair of one-way clutches, each scroll being associated with a respective elongate member/pedal carrier, each scroll having a curved perimeter, wherein the scrolls are rotatably mounted on a scroll shaft in such a manner that the radius of curvature of the curved perimeter of each scroll with respect to the axis of the scroll shaft is a minimum at one end of that curved perimeter and a maximum at the other end of that curved perimeter, one end of each wire being associated with a respective elongate member, the other end of that wire being connected to a respective scroll adjacent to said one end of that scroll, and an intermediate portion of that wire passing around the curved perimeter of that scroll, a respective one-way clutch being provided between each scroll and the hub, so that rotation of that scroll in one direction rotates the hub, and rotation of that scroll in the other direction results in that oneway clutch freewheeling

3. A pedal mechanism as claimed in claim 2, wherein the curved perimeter of each of the scrolls extends over an angle greater than 360 .

4. A pedal mechanism as claimed in claim 3 , wherein the curved perimeter of each of the scrolls extends over substantially 420°.

5. A pedal mechanism as claimed in any one of claims 2 to 4, wherein a respective groove is provided in the curved perimeter of each of the scrolls.

6. A pedal mechanism as claimed in any one of claims 2 to 5 , wherein each of the scrolls is attached to a respective scroll carrier, a respective one-way clutch being provided between each scroll carrier and the hub.

7. A pedal mechanism as claimed in claim 6, wherein a respective crown gear wheel is fixed to each of the scroll carriers, the crown gear wheels meshing with a pair of pinions carried by a pinion shaft which is fixed to the scroll shaft for rotation therewith, the crown gear wheels and pinions defining a differential gear mechanism.

8. A pedal mechanism as claimed in claim 7, wherein the pinion shaft passes at right-angles through the scroll shaft.

9. A pedal mechanism as claimed in any one of claims 2 to 8, further comprising a respective spring acting, in use, between each of the scrolls and the frame, each spring being effective to rotate the associated scroll back to its original position following rotation of that scroll in said one direction as a result of movement of the associated pedal carrier along the respective elongate member.

10. A pedal mechanism as claimed in any one of claims 2 to 9, further comprising a friction band in engagement with a wheel fixed to the scroll shaft.

11. A pedal mechanism as claimed in any one of claims 2 to 9, further comprising an indent wheel fixed to the scroll shaft, the indent wheel being formed with a plurality of indents in its circumference, each of the indents being engageable with one end portion of a spring, the other end of that spring being fixable to the frame of the bicycle.

12. A pedal mechanism as claimed in claim 11 , wherein the indent wheel is provided with three equispaced indents.

13. A pedal mechanism as claimed in any one of claims 2 to 12, wherein a respective pedal carrier box is associated with each elongate member, each pedal carrier box being formed with a longitudinal slot within which the respective pedal carrier is reciprocably mounted.

14. A pedal mechanism as claimed in claim 13, wherein each pedal carrier is provided with rollers for rolling engagement with surfaces of the associated pedal carrier box.

15. A pedal mechanism as claimed in claim 14, wherein each pedal carrier is provided with a further roller for rolling engagement within the longitudinal slot of the associated pedal carrier box.

16. A pedal mechanism as claimed in any one of claims 2 to 12, wherein a first end of each elongate member is pivotally attached to the frame, a respective pedal being attached to a second end of that elongate arm.

17. A pedal mechanism substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 5 or Figures 6 to 8 as modified by Figures 3 to 5 of the drawings.

18. A bicycle substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 5 or Figures 6 to 8 as modified by Figures 3 to 5 of the drawings.