WO2005087576A1

WO2005087576A1 - Drive mechanism and vehicle

Info

Publication number: WO2005087576A1
Application number: PCT/GB2005/000880
Authority: WO
Inventors: Rad H. Dabbaj
Original assignee: Dabbaj Rad H
Priority date: 2004-03-09
Filing date: 2005-03-08
Publication date: 2005-09-22

Abstract

A vehicle drive mechanism for a vehicle such as a bicycle (20) includes a spring assembly (21) coupled to a shaft (23) and loadable via first and second pedals and levers (31-34). Once the spring passes a threshold, the spring (21) is able to contract by its own contraction force, which causes rotation of the shaft (23) and thus rotation of the wheel (35) to propel the bicycle forwards.

Description

D TVE MECHANISM AND VEHICLE

The present invention relates to a drive mechanism for driving a vehicle and to a vehicle incorporating a drive mechanism. An aspect of the present invention also relates to a sprung drive element. In many human-powered vehicle applications such as conventional bicycles, an input member (for example a pedal) drives an output member (or wheel) via a freewheel device to facilitate overrunning and freewheeling. For positive input-to-output drive to occur, the input needs to run at a speed at least as fast as the output in order to engage otherwise no drive occurs, thus making it exceedingly difficult for the rider to pedal fast enough for energy-coupling as speed increases. One way of dealing with this problem is by using step-up gears. A problem with such gears is that the rider constantly has to shift gears up or down to account for different drive conditions and terrains in order to conserve energy and reduce waste. Despite its success the bicycle has, however, a number of drawbacks mainly arising from its conventional drive mechanism and the many interacting spaced-out parts and components such as chain, sprockets, chain ring, lower bracket, gears, rotating cranks, rear and front derailleur mechanisms and controls. Attempts have been made to improve the design of conventional bicycles. For example, US-A-6,053,830 discloses a bicycle which uses an auxiliary power system formed of a set of cogs chain to tap some energy from the cranks, to store that in a spring and to hold it by a brake until the rider selectably releases it back into the conventional drive train. This complicates the drive system by having two drives, the usual one via the rider-pedal-chainring-chain-rear cog-wheel, as well as a rider-selected booster drive from the spring. In TJS-A-4, 108,459 a gear member is rotated by reciprocating levers to drive the normal chain ring of a conventional drive train, which in turn drives a spiral spring mounted on the rear wheel via additional gears. Up/down pedalling winds up the spring that drives the wheel. Both of these prior art systems increase complexity and cost and can potentially waste valuable rider's energy. Other less ambitious techniques to improve conventional bicycle drive were disclosed in TJS-A-1, 021,957 and US-A-6,244,135, in which spiral springs disposed between chairing and crank/lower bracket are used to couple better a rider's rotary pedalling to the drive train of a conventional bicycle. The present invention seeks to provide an improved drive mechanism and improved vehicle. According to an aspect of the present invention, there is provided a vehicle drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein said at least one input element is coupled directly to said axle assembly and thereby to the energy storage means. Preferably, the drive mechanism provides a first phase involving charging of the storage means and a second phase of discharging energy from the storage means. According to another aspect of the present invention, there is provided a vehicle drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein the energy storage means is operable in a first phase to store energy without such energy being releasable by the drive mechanism up to a threshold and in a subsequent second phase in which energy can be released. This aspect can provide an torque impulse for driving a vehicle. The at least one input element is preferably not linked to the second, energy release, phase of the energy storage element. Advantageously, the second phase is such as to allow rapid release of energy from the storage means relative to charging of the storage means during the first phase. In the preferred embodiment, the second phase provides discharge of energy from the energy storage means substantially back to a condition prior to the charging phase. The first and second phases may be included within one rotation of the axle assembly. The axle assembly may comprise a single drive shaft to which the energy storage means and the at least one input element are coupled. Preferably, the or each at least one input element is coupled to the axle assembly by means of a one-way freewheeling member. In an embodiment, the input members provide charging of the energy storage means through partial or full actuation of the input members. There may be provided a gear mechanism between the axle assembly and a wheel member, hub or output drive member. Advantageously, the energy storage means includes at least one sprung element chargeable by the at least one input means and dischargeable through operation of the axle assembly. Preferably, the or each sprung element is made from an elastomeric material such as rubber. In one embodiment, the or each sprung element includes a plurality of elastomeric members coupled at each end thereof to a common mounting member, which mounting member is provided with coupling means. There may be provided means to alter the configuration of the storage means and/or input means and/or crank/cam to alter the performance of the drive mechanism. The axle assembly may be in the form of a single unit which includes one or more of: a shaft; a hub located on the shaft with hub to shaft bearings; one or more input member bearings; one or more freewheeling members; a crank or crank coupling means; one or more gears; one or more fastening members. In many applications, the at least one input element may be driven by human or animal power. The invention also provides a vehicle including at least one drive mechanism as specified herein. The vehicle may a bicycle or other human powered vehicle including water and air craft. According to another aspect of the present invention, there is provided a vehicle drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein the energy storage means comprises an elastomeric energy storage member. According to another aspect of the present invention, there is provided a spring assembly comprising a plurality of elastomeric elements and a mounting member including a plurality of holding locations for holding an end of each elastomeric element such that the elastomeric elements are arranged in parallel to one another. It will be apparent that the preferred embodiments can provide a bicycle which has no chains or sprocket wheels as in conventional bicycles and a drive mechanism which can help propel the vehicle by virtue of the force of the spring means. In this regard, the propulsion force and in particular torque is provided by the spring and thus not limited to that which can be provided by the input members. Thus, a good propulsive force and speed can be generated even by relatively slow inputs through the input members. The preferred embodiments can provide an alternative drive mechanism capable of relatively rapid input to output energy coupling and drive. It has applications in a number of human-powered vehicles such as push bikes. The drive mechanism can store mechanical energy applied at any input rate(s) and subsequently release and/or couple such energy to an output member at the same or different rate(s). When applied to bicycle applications, the drive mechanism can produce a radically different pulsating-drive bicycle or pulse-bicycle. Various embodiments of the present invention are described below, by way of example only, with reference to the illustrative accompanying drawings, in which: Figure 1 shows an embodiment of drive mechanism using a drive crank arrangement; Figure 2 shows an embodiment of drive mechanism using a drive cam arrangement; Figure 3 shows an embodiment of bicycle incorporating a drive mechanism as shown in Figure 1; Figure 4 shows a view of the rear hub and some of the other parts of the bicycle of Figure 3; Figure 5 shows an embodiment of drive mechanism provided with hub gears; Figures 6a to 6c show an embodiment of sprung element and fastening method; Figure 7 shows an alternative fastening method; Figure 8 shows an example of variable length crank; Figure 9 shows an alternative embodiment of drive mechanism with a concealed spring element, fixed to the inside of a frame; Figure 10 shows an example of coupled bicycle levers embodiment; and Figure 11 shows an example of another coupled bicycle levers embodiment. Figure 1 shows in outline an embodiment of a crank-type drive mechanism 10 comprising an appropriate energy storage device like a spring or a spring assembly 1, one end of which is appropriately connected by a pivotable mounting to a frame or chassis member 8 through pin 7. The other end of the spring assembly 1 is connected to crank 2 via crankpin 4, for example through needle roller bearings. The crank 2 is fixed to crankshaft or axle 3 which is itself rotatably supported on frame member 8 via appropriate bearings (not shown). Crank 2 and shaft 3 can both rotate about the axis of shaft 3 as shown by arrow 6. Although not shown in Figure 1, shaft 3 may drive a wheel hub and wheel via one or more appropriate overrunning clutch or freewheeling members such as roller or sprag types. In other words, the shaft 3 locks to and drives the wheel in one direction of rotation (in this example when rotating clockwise) but when the speed of shaft 3 falls below that of the wheel, it unlocks the wheel and allows it to freewheel in the same direction. Suitable freewheeling members are supplied by STIEBER and produced by MARLAND Clutch, 650 East Elm Avenue, La Grange, IL 60525-0308 USA. Mechanical energy may be applied to the crankshaft 3 by any appropriate input means (such as the levers 31, 33 shown in Figure 3) to rotate the shaft 3 and crank 2 in a clockwise direction 6, extending spring 1 to store mechanical energy therein. More and more energy is stored until the crank 2 reaches the 180° position, that is until the spring 1 reaches its maximum extension and energy storage state. The angles refer to those between crank 2 and a line running between crankshaft 3 and spring end at pivot 7. Substantially within the 0°-180° angular range (referred to hereinafter as the energy storage phase), the spring 1 stores energy and exerts torque on crank 2 and shaft 3 trying to rotate them in a counter-clockwise direction. The latter can be prevented by means similar to that of embodiment 20. As the crank 2 turns beyond 180°, the spring 1 begins to exert a clockwise torque on the crank 2 since the torque arm now lies on the opposite side, that is substantially within angular range 180°-360° (referred to hereinafter as the energy release phase). This allows spring 1 to release its stored energy and to drive crankshaft 3 clockwise until crank 2 returns back to the starting position approximately around the 0° position, when the storage and release cycle may then be repeated. The trigger point or threshold lies substantially near 180°, when the spring line of force acting on pivot 4 crosses the shaft centre. In order to provide freewheeling facility and/or appropriately apply input energy, one or more one-way freewheeling members may be used on the crankshaft 3, that is for coupling input energy to the crankshaft (see members 44, 45 in Figure 4) and one or more for coupling output energy to the wheel (see member 48 in Figure 4). The spring size, rating, capability and other parameters of the spring 1 and other elements can be appropriately chosen so as to enable the drive mechanism to drive a output load throughout the desired speed range (rpm). Additional freewheeling members between the crankshaft and the frame 8 may be used if desired to prevent the crankshaft 3 from turning in the reverse direction (counter-clockwise), such as the freewheel 46 shown in Figure 4 or by other means similar to embodiment 20. While the spring 1 is exerting a torque on the crank 2, it also exerts reaction torque on the frame 8 in the opposite direction, that is clockwise during the 0°-180° phase and counter-clockwise during the 180°-360° phase, which can be counter-balanced by any appropriate means if considered necessary in any particular implementation. Figure 9 shows an alternative embodiment of drive mechanism 100 comprising a crankshaft 103 connected to crank 102 which rotates clockwise along 106. Spring assembly 101 is anchored to frame 108 at one end and, at the other, to crank 102 by pivot 104 via a cable 105. Two cable guides or pulleys 107 confine the cable 105 to substantially lengthwise movement 109 between spring assembly 101 and pulleys 107. More cable guides may be used to redirect cable 105 about one or more axes. Advantages of this embodiment 100 include a smaller spring assembly swept area, a more compact design, at least part of the assembly 100 (for example, spring 101 and part of cable 105) can be concealable inside a frame or chassis, if desired, and the provision of alternative torque versus angle relationships. The preferred embodiments of drive mechanism include the following principal advantages: the capability of the spring assembly automatically to transform input power (power = rate of delivering energy) to the same or different output power depending on output load and drive conditions. As Power (P)=Torque (T) x Angular Speed (ω), the spring can release its stored input energy at variable rates, for example, applying higher T when load runs at low ω and lower T at higher ω, thus providing built-in continuously variable input-to-output drive ratios in a manner akin to an automatic transmission. Additionally, the drive mechanism is capable of delivering output power at sufficiently high or fast speeds so as actively to engage a freewheel-driven member (for example a wheel as in bicycles and other human-powered applications) and couple more energy to the output load even when it is rotating at relatively faster speeds relative to the input speed. Other advantages include the continuous cyclic operation and self-trigger capability. Figure 2 shows an outline of an embodiment of cam-type drive mechanism 10a which comprises an appropriate energy storage device like extension spring 11. One end of spring 11 may be appropriately connected to frame or chassis 18 or pivotally mounted via pin 17, the other end being connected to a bracket member or cam follower 19. Roller 14a is pivotally mounted on the other end of follower 19 on pin 14 and bears on cam 12 of appropriately shaped profile with a reference line 15a. Cam 12 is fixed to shaft 13 and rotates in a clockwise direction 16 such that line 15a can traverse an angle with reference to a vertical line between pivot 17 and the shaft-centre, like angle 15. Cam follower 19 may include any appropriate one or more guides, railings, sliding members, rollers and bearings to prevent lateral motions while enabling it to slide smoothly substantially along 19a. For example, the cam's inner surfaces may slide over the shaft 13 via appropriate bearings (not shown). Mechanical input energy may be applied to shaft 13 by appropriate means (similar to 10) that rotates shaft 13 and cam 12 along direction 16, causing cam 12 to push roller 14a along 19a, thus pulling follower 19 along and extending spring 11 to store mechanical energy. It continues to do so more and more until spring 11 reaches its maximum extension and energy storage state, approximately around 180°. Reverse rotation (counter-clockwise) torque can be prevented as in the first described embodiment. As cam 12 (and 15 a) turns beyond 180° its profile will have progressively reduced radii, which enables the spring 11 to release its energy and exert a clockwise torque on cam 12 substantially within angular range 180° -360°. This drives shaft 13 clockwise until cam 12 returns back to the starting position approximately around 0°, when the storage and release cycle may then be repeated. Other details are similar to the first described embodiment. Alternative cam-profiles (for example, circular, curved) may be used with equal or non-equal storage and release cycles or phases. For example, they could be designed to provide a storage cycle through 0°-90° and a release or drive cycle through 90°-360°, if desired. Instead of follower 19, roller 14a may by itself be appropriately guided and connected to spring 11 via a cable or rod. Among the features of the embodiment 10a, the following can be provided: more than one energy storage and release cycles of equal or different angular range per revolution can be achieved which may be advantageous in some applications, and providing more flexibility in the cam's position on the shaft. Furthermore, the torque versus angle relation may be altered by an appropriate cam-profile, for example to provide more distributed drive and related advantages. The cam embodiments may use compression or extension springs, and those skilled in the art will know how to apply and couple these springs appropriately to the cams and vice versa. The drive mechanisms 10 and 10a may alternatively drive the output member (wheel hub) via gears of any appropriate type and ratio, for example hub gears (inside the hub), further to improve and enhance drive capability, for example at starting and low- speeds, such as in embodiment 60 of Figure 5 (see below). The drive mechanisms disclosed herein can be used in a number of applications, like the bicycle embodiment 20 of Figure 3. Figure 3 shows the main components which, in part, are similar to a conventional bicycle but using the drive mechanism disclosed above, two oscillating foot levers and a different frame. With reference to Figures 3 and 4, bicycle 20 comprises a rear wheel drive mechanism 20a similar to 10 (see Figure 4 for more detail), frame 29, fork 39, handlebar 38 and saddle 37, front wheel hub 39a, front wheel 36 and rear wheel 35 with spokes (not shown). Frame 29 may have a number of appropriately joined parts, for example by welding, comprising a head tube 29a, top tubes 29b, seat tube 29c, a rear fork-like member 29d with left and right legs terminated with bearings housings 53 and 52, respectively. At least one member of housings 53 and 52 may be demountable for easy assembly and servicing. Drive mechanism 20a comprises crank 22, crankshaft 23 and spring or spring assembly 21 (for example similar to 80 of Figure 6a). The assembly 21 is attached to the right leg of member 29d via pin 27 at one end and, at the other end, to crank 22 via crankpin 24. Crankshaft 23 is driven by right 31 and left 33 levers on which right and left pedals 32 and 34, respectively, are mounted. Levers 31, 33 move in an oscillating motion 25 to rotate crankshaft 23 and crank 22 clockwise to extend spring 21 and store energy substantially through the crank's angular range from 0°-180°. Pedalling beyond 180° releases energy stored in the spring 21 and rotates crank 22 and crankshaft 23 approximately through the 180°-360° phase to turn wheel 35 in the direction of arrow 26 and thereby to propel the bicycle forward along direction 41. Levers 31, 33 may have appropriate stops to limit their maximum angular travel, and may also have one or more appropriate rebound spring(s) (not shown) to urge them to an upper rest position, coming to rest at an upper stop ready for the next stroke. For example, lever 31 may have a top stop (not shown) and a bottom stop 28b attached to frame 29d via support member 28. These stops may preferably be resilient and/or provided with rubber bumpers to soften impact and/or reduce noise, with capabilities at least to handle spring 21 reverse torque (counter-clockwise) and the rider's weight for the top and bottom stops, respectively. Although not shown, lever 33 may have a similar support stops and spring on the other side. Lever stops may be placed anywhere appropriate, including in front of wheel 35, in which case they may share a common support similar to 28. The pedals are pivotally mounted on the levers but since they do not have to do a full turn they may be non-pivotally mounted, for example resiliently twistable. Figure 4 shows a view of drive mechanism 20a (and 20) showing most parts in more detail. It comprises crankshaft 23 rotatably mounted on fork 29d by appropriate shaft-support bearings inside right and left housings 52 and 53 respectively, a rear wheel hub 42 (shown in cross-section with spokes 51) mounted on crankshaft 23 via one-way freewheeling member 48 at one end and bearings 54 at the other, right and left levers 31 and 33 mounted on shaft 23 via one-way freewheeling members 44 and 45, respectively, capable of independently turning crankshaft 23 clockwise and freewheel back in counter-clockwise direction. Crank 22 is fixed to the right end (as seen in this Figure) of shaft 23, while spring or spring assembly 21 is pivotally connected to crank 22 at crankpin 24 (with appropriate needle roller bearings). Spring 21 is also mounted pivotally on fork 29d by pin 27 (for example, via needle roller bearings). Pin member 27 may be supported on fork 29d at one of a plurality of positions or steps to alter the spring's pre-extension and its energy storage capability in order to provide additional means to control drive-level magnitude and/or to furnish the rider with a range of cycling modes or schemes of various effort levels. For example, if the amount of pre-stressing of the spring is increased it will require more energy to extend it to the threshold and the spring will thus store more energy compared to when it is not or less pre-stressed. Such positions could either be used by moving pin 27 manually into a desired hole or position in the fork 29d, or pin 27 may be mounted on an additional member with an appropriate handle or lever that can be latched into any of these positions which can be controlled during riding (preferably when the spring is discharged). Another example of a rider controlled system would be by cable such as a Bowden cable, coupled to a control lever and controlling a pre-tensioning member attaching the spring 21 to the fork 29d, the pre-tensioning member being for example a suitable form of lever. The skilled person will readily be able to envisage suitable mechanisms. As in conventional bicycles, both legs of fork 29d may be inclined at an angle relative to the plane of wheel 35 such that they are closer to this plane near the top end (27) and spring 21 may also be inclined likewise. Alternatively, fork 29d and spring 21 may run parallel to the plane of the wheel 35. The various parts in 20a of Figure 4 may be made de-mountable and may be assembled together in place and appropriately separated by a number of spacers such as 55 and secured on the shaft 23 by one or more keyways and keys and/or interference-fitting and may be fastened by a bolt 47. The crank 22 may be fixed to shaft 23 (for example welded) or may be demountable with a sliding part into shaft 23, fixed by pins or dowels that may lie under a one-way freewheeling member or bearings. The operation of the bicycle 20 may now be explained with reference to Figures 3 and 4. The rider can drive and propel the bicycle 20 by applying a series of strokes, each being a downward push on the respective pedal and lever, which forces crankshaft 23 and crank 22 to turn clockwise by an angle dependent on stroke and lever lengths. In this example, the stroke is approximately 30 to 35° but this depends, of course, on the length and arrangements of the levers 31, 33. Each stroke of one of the levers 31, 33 causes a progressive turn of the crank 22, thus extending the spring 21 and storing mechanical energy progressively, through the angular range from 0°-180° (see Figure 1). After each stroke, the rider can briefly cease pushing downwardly and may lift his/her foot upward so that the respective lever 31, 33 may rebound back towards the upper stop (for this purpose they are suitably sprung). Although the levers 31, 33 may be stroked at the same or different times, it may be preferable to stroke them alternately in a one-at-a- time fashion, releasing one lever (after a stroke) then commencing the other, and so on. In this way, at least one lever 31, 33 will rest against its respective upper stop through the 0°- 180° degree range, which prevents crankshaft 23 and the levers 31, 33 from rotating counter-clockwise, with consequent energy loss. Alternatively or in addition to the latter, an appropriate one-way freewheeling element between shaft 23 and fork 29d, such as 46, may be used to prevent such reverse rotation, irrespective of whether or not a lever 31, 33 is resting on its stop. Instead of element 46, one or more of shaft-support bearings (inside housings 52 and 53) may have a built-in freewheeling capability. Speed and output power may be controlled by, among others, spring energy, crank length, pedal forces, lever length and stroke angles, pedalling frequency and rider's forward lean. In addition to spring assembly energy storage, a part of a rider's energy applied to the crankshaft 23 can be used to drive the wheel 35 and bicycle 20 via direct- drive, that is in parallel to and independently of spring assembly. Once the crank 22 moves over the 180° position (see the embodiments shown in

Figures 1 and 2) the spring 21 is allowed to contract, rotating the crank 22 and crankshaft 23 during such contraction, thus rotating the wheel 35. At this point, it is the power released from the spring 21 which propels the bicycle 20, rather than just the cyclist's power in pedalling. The release of energy from the spring 21 produces reaction forces on the bicycle

20 which, in the drive cycle, producing counter-clockwise torque that may tend to lift the front wheel 36 off the ground. One or more methods may be used to counteract this, such as the rider's forward lean on the handlebar 38, appropriate positioning of the saddle 37 to provide more forward weight, pressing down on the pedals 32, 34 and appropriate bicycle/frame design. The bicycle can provide a number of new and interesting riding possibilities and features, among them: 1- Starting. The rider may ride first while bicycle 20 is stationary and then stroke to move forwards via direct-drive as well as storing energy in the spring 21. After a few strokes, the drive mechanism kicks in (that is, the crank cam moves over centre so that the spring is allowed to contract) to accelerate the bicycle forwards. Alternatively, the rider may start by first rolling the bicycle forwards against the ground, then riding on and stroking to build up speed. 2-Riding. The rider may ride the bicycle 20 in a similar manner to a conventional bicycle but instead of the usual pedalling, the rider now applies continuous (or even discontinuous) oscillating up/down full or partial strokes at any desirable frequency/rate and magnitude depending on desired speed and driving conditions, to propel the bicycle forwards. Other actions such as balancing, steering and braking may be as in a conventional bicycle. 3 -Power Start. The rider may prefer to prime the drive mechanism first by applying a few lever strokes while, for example, lifting the rear- wheel 35 off the ground (possibly by using an appropriate stand) to store some energy in the spring 21 up to just before the trigger point (that is the 180° position). He/she can then, once the bicycle is fully on the ground, apply a short stroke to trigger the drive mechanism and obtain accelerated forward push. Unlike a conventional bike, this makes for a pleasurable start and in traffic situations a faster and thus possibly safer start by providing increased acceleration. 4-Stopping. The rider may slow down and stop by applying the brakes and/or reduce or halt stroking. With some practice, the rider may quickly learn how to feel or sense the varying magnitude of pedalling forces under his/her feet and the time of the next imminent kick-in (that is release of spring power) and make optimum use of his/her resources. For example, with temporary stops such as at traffic lights, the rider may prefer to coordinate his/her actions so as to keep at least some stored energy reserve. For example, the rider may effect a prior stroking action so as to stop at the traffic light with a charged spring, preferably up to just before the trigger point. The spring can later be triggered by a small pedal stroke to get a forward push or power start. At the end of a ride, the rider may coordinate or control slowing down and stopping so as to end up with little or no stored energy reserve, if desired. 5- Alternating lever-at-a-time fashion may provide a natural rhythm of stroking. In addition, the rider may also use one lever alone, or both simultaneously, if desired. The advantages of the bicycle 20 include: a built-in automatic drive capability of the drive mechanism (mentioned above) by driving the load at an appropriate power level to suit the various load conditions, for example by applying higher torque when speed is low (such as at start-up or when going uphill) and lower torque at higher speeds. Other advantages include alleviating the need for the following parts used in conventional bicycles: chain, chain rings, sprockets, lower bracket, rear and front derailleur mechanisms and the inefficient rider's feet circular motion. An integrated wheel-hub cluster similar to 20a with or without the spring may be made as a standard component or unit comprising one or more of the following parts, among other parts: shaft, wheel hub, fixed or variable ratio gears, hub-to-shaft bearings, one-way freewheeling elements and bearings, keyways, keys, freewheeling elements and supports on which to mount levers, shaft-to-frame bearings and housing and others, some of which may share one or more common members such as inner and/or outer races and so on. Such standard components can be well-engineered, compact, reliable and cost-effective for use in a range of bicycle designs worldwide, thus help to popularise the bicycle. Additional drive and speed control means or mechanisms may be used to allow the rider to control manually (for example by one or more selectable positions such as via cable or other members) one or more of: the effective crank-arm 22 length, the spring 21 length and its pre-extension and levers 31 and 33 lengths, to account for certain drive conditions such as when going uphill, and/or to increase rider's comfort. In lever length control, for example, each pedal may be mounted on a mini-lever pivoted at the end of the lever, which can be flicked by the rider into one or more positions of varying effective lever-lengths. Braking of appropriate strength may also be used to reduce drive, for example when stopping or slow-turning. It is envisaged that in some embodiments it would be desired to have some form of gear mechanism. For example, fixed ratio gears of any appropriate type such as hub gears, planetary and others may be used in the drive mechanism of bicycle 20, to suit the various types of output loads and conditions, for example to improve direct-drive at low speeds, starting and uphill, amongst other features. Of course, similar improvements to the latter may also be obtained by using a more powerful spring. One embodiment of gear 60 is shown in Figure 5, showing a view of the top half of shaft and hub (the bottom half is omitted for clarity) with shaft centre running along 73 a. It comprises epicyclic or planetary gears 60a disposed between shaft 73 and wheel hub 71. Wheel hub 71 is supported on shaft 73 via bearings 74, 75 and 76. The wheel hub 71 can therefore be driven by gears 60a via the spring assembly, by direct drive or both. Gears 60a comprise sun gear 61 which meshes with one or more (for example, four) planet gears 62 mounted on carriers 64a and 64b via appropriate pins or bearings 65 with carriers 64a and 64b being fixed to shaft 73. Ring gear 63 meshes with planet gears 62 at one end and extends outside the hub 71 at its other end 63 a through bearings 74 and 75 such that it is supported on outer and inner races of bearings 74 and 75, respectively, to facilitate clamping gear 63 without interfering with hub 71 or shaft 73. Bearings 74, 75 may also comprise a triple-race bearings with ring gear 63 appropriately connected to the middle race near 63a. Sun gear 61 drives hub 71 via a one-way freewheeling member 67 such that hub 71 can freewheel when not driven. Appropriate spacers 78 may be used. Gear 61 may have a clearance with shaft 73 or may be supported on it via needle roller bearings. If ring gear 63 is anchored or clamped at 63 a to frame of bicycle 20 for example, shaft 73 can drive sun gear 61, member 67 and hub 71 at its designed gear ratio, such as 3:1. Gears 60a may also be used as a de-coupling clutch if ring gear 63 is left undamped (floating and free to rotate) which can be used advantageously for wheeling the bicycle backward. Additionally, clamping 63a may be a partial clamp (to restrict its rotation) to effect a means of drive-level control, for example, a disc-brake type member appropriately attached to ring gear 63 at 63a with appropriate spring-biased brake pads and cable such that the default may be a fully clamped condition corresponding to maximum drive-level, and the rider may release the clamp partially or fully to reduce drive-level, or to wheel the bicycle backward. If desired the action of gears 60a may be cancelled (equivalent to 1:1 ratio) by clamping ring gear 63 to shaft 73. Planetary gears 60a may have one or more magnification stages. Other alternative arrangements may be used, for example sun gear 61 may be appropriately clamped while ring gear 63 may drive hub 71 via a one-way freewheeling element. The gears may preferably be low noise. The benefits of gears include: increasing direct-drive magnitude and speeds, improved uphill performance and starting, de-coupling clutch facility, reduced peak torque magnitudes, improved wheel-to-ground coupling efficiency and tractions, reduced localised tyre deformation and associated coupling losses. Gears may alter or modify the drive characteristics of the spring assembly and drive mechanism, and the range or level of automatic drive throughout the speed range. Instead of fixed ratio gears, variable ratio gears may be used if so desired for example similar to Sturmey Archer and others wherein one appropriate gear member is clamped while others are used as input and output to provide a range of desirable ratios, as known to those skilled in the art. The spring 1, 11, 21, 101 may comprise a spring assembly having one or more springs in parallel, series and/or a combination, of appropriate energy rating and characteristics compatible with the input source, for example optimised for a rider's performance and capability. The spring or assembly may be mounted around the crankshaft at any desirable angle and orientation, that is at 0°-360° and can be fixed to any appropriate part of the frame. Any appropriate spring type including coil extension, compression, drawbar and elastomeric (for example rubber) springs may be used.

Compression springs may alternatively be used with the near-end fixed to the frame while an appropriate member (for example a cable) connects the far-end to a crankpin, and other necessary modifications. At least part of spring assembly and/or drive mechanism may be appropriately enclosed or covered, for aesthetic reasons and rider and parts protection. Rider weight and forward lean, bicycle mass, inertial aspects, saddle position, frame rigidity, weight distribution and so on may be optimised so as to improve spring energy coupling and drive, and also to counteract the spring's reaction force on the frame. The spring assembly may be made of one or more parallel cord(s) of appropriate elastomeric material, for example natural rubber. Each cord may comprise a bundle of multiple strands covered with one or more appropriate protective coverings and braids. One example is spring 80 shown in Figures 6a-c (6a is top view, 6b and 6c are end views of termination block and hole 87, respectively). This comprises one or more cords 85 in one or more rows, two end-termination members or termination blocks 81, 82, with mounting holes 83, 84 respectively, pivoting on mounting pins, for example via needle roller bearings. It may be desirable to cut the cord ends after fastening to appropriate lengths to facilitate fraying of strands and enhance fastening, which may also be pressed down (axially) by an additional fastening member, if desired. In one fastening method shown in Figures 6a-6c, cords 85 may pass through passages 87 first via inner sleeve 86a, and then an outer sleeve 86b may be forced over inner sleeve 86a to effect fastening of cords 85 to members 81, 82. The inner and outer sleeves 86a and 86b may have appropriate design, dimensions, slots, openings, shaped-ends and edges so as to facilitate assembly and fastening, and may also have lips/ridges to prevent sliding through passages 87 during operation. For example, inner sleeve 86a may be inserted into passages 87 from the outer face of member 81 (or 82) until its lips rest on member 81, then followed by the forced-insertion of the outer sleeve 86b from the inside face of member 81 (or 82) to complete the fastening process. Inner sleeve and/or outer sleeve may be made of one or more parts or segments (four being shown for inner sleeve 86a in Figures 6b and 6c). The diameters of passages 87 and sleeves 86a and 86b may be appropriately chosen to suit the diameter of the cords 85 in order to facilitate fastening on the one hand and, on the other, preferably to make the crimped effective cord-diameter inside the segments smaller than the minimum operating cord diameter (corresponding to maximum operating extension). Thus the cords 85 can be fastened by the constriction inside the inner sleeve 86a and friction. The advantages of spring assembly 80 include: flexible dimensions, compact design, controllable aspect ratio, facilitated trade-off between spring force, spring energy, cord length and diameter. The width of spring assembly 80 can be reduced further by, alternatively, moving mountings 83, 84 further out from members 81, 82 and placing them on an extended part of members 81, 82 (not shown), if desired. Alternatively, cord 85 may comprise a single continuous cord appropriately threaded or laced back and forth through passages 87. Figure 7 shows alternative cord fastening method, wherein the holes 97 in termination-block 91 may have appropriate grooves or openings 92 thorough which an appropriate crimping or pressing tool may be inserted to surround the holes (and their inserted cords) and facilitate crimp fastening by constricting cord diameter. Member 91 can be mounted via hole 94. Alternatively, an appropriate sleeve having one or more segments, for example segments with overlapping (circumferential) fingers sliding into each other during crimping, may be inserted around the cord first before crimping. Holes 97 may also be open on the outside. Other alternative cord-fastenings to termination blocks may be used, including: one or more pins/rods (preferably lockable in place) of one or more rows and/or columns may be forced through appropriate holes from the side (for example normal to holes 87 in Figure 6) to squeeze and compress the cord 85 and secure fastening accordingly. The holes may be circular or of any other appropriate shape. Alternatively, the cords may be cut to length first, then crimped at their free ends with a sleeve or inner and outer sleeves, then each cord may be hanged or slotted into appropriately shaped holes in termination blocks. In order to take advantage of the available long service life of a rubber spring, it may be preferable to confine its extension to a certain range as recommended by manufacturers, typically 15%-90% at all times. This condition can be readily met by simply making a minimum extension point (for example 15%) substantially correspond to the zero-degree crank/cam angle, and a maximum extension (for example at 85%) substantially correspond to the trigger point (180°). Additional spring assembly protection against the environment may be used if desired. The rubber spring may alternatively be made of a rectangular shape of strand bundles appropriately clamped at the ends, if desired. The springs may also be made of moulded material with appropriately mounted/clamped dumb-bell like ends. At least part of the spring assembly may be concealed inside the bicycle's frame for compactness, improved protection, aesthetic reasons and others, with either direct connection to the crankpin or, alternatively, as shown in embodiment 100 of Figure 9. The cyclic variation of effective crank torque-arm length may be modified through at least part of 0°-360° range, so as to modify the torque versus crank angle relation and characteristics with the following benefits: reduce torque demand on bearings and freewheeling members, reduce wheel slippage on the ground, reduce localised tyre deformation and flexing that may give rise to some losses, reduce stresses on bearings and other parts and reduce reaction forces, amongst others. Preferably, torque may be made to vary with angle in a more uniform manner with reduced torque peaks during the energy storage and/or release phases. For example, this can be automatic, such as with a crank having one or more members appropriately supported and disposed so as to undergo bending, flexing, deformation and the like radially and/or at an angle to radial, such as that shown in Figure 8. In Figure 8, a relatively flexible crank 2 (a single crank shown at nine different angular positions) is mounted on shaft 3 and connected to the spring assembly at crankpin 4, wherein spring assembly pulls crank 2 in a top-right direction 89, and rotates it clockwise in the direction of arrow 6. Other details may be similar to the previously described embodiments. The crank bends elastically under the force (F) of the spring and in the direction of spring such that its effective arm-length (r), namely the radial distance between crank pin 4 and shaft 3 centre, and torque are advantageously modified (T=F x r). This variation can result in broader relation with reduced peak torques. The energy storage and release cycles may have the same or different torque versus angle characteristics. Other methods include using cranks made of one or more pivoting, sliding of otherwise adjustable members capable of varying r radially or at an angle to radial. Another method of alternative effective r change is that shown in Figure 9, in which the spring assembly line of force acting on the crank is cyclically altered and may be adjusted by the distance between 107 and 103. A number of alternative embodiments to assembly 20a may be made without departing from the teachings herein. For example, the levers and their freewheeling elements may be mounted on the crankshaft 23 on the outside of the frame, or the spring 21 may alternatively be connected to an appropriate crankpin on the crankshaft 23 situated on an inside centre crank (for example within the legs of forks 29d). The hub may alternatively be mounted on crankshaft 23 via two bearings one at each end, with a one-way freewheeling member in between or a one-way freewheeling member (with bearings) at each end. The one-way freewheeling members may be of any desirable type, size, rating and characteristics. The crank may use a counter-weight if desired. An appropriate rider-controlled coupling/de-coupling clutch between the drive shaft and the wheel may be used (for example similar to 60a with floating ring gear 63), if desired, to facilitate a number of functions, including: stored energy-dissipation without propulsion (for example via the brake), bicycle backward wheeling, disengaging or de-activating the drive, and priming without bicycle rolling. Also, an appropriate rider-controlled manual locking mechanism may be used to halt crank or shaft rotation at one or more positions for example by causing a pin to intercept the crank or other additional member attached to the shaft, if desired. In this specification, one-way freewheeling members and all other freewheels refer to overrunning clutches that lock to the shaft in one direction (to transmit torque) and unlock in the opposite direction (to freewheel), and may preferably be of fast acting, low backlash, smooth and low noise type such as a roller or sprag types, and may have built-in internal or external bearings and normally comprise inner and outer races. If desired, ratchet and pawl type freewheels may be used. One-way freewheeling members may have radial bearings and/or separate or built-in appropriate thrust bearings on one or both sides so as to appropriately handle the load condition at hand, for example against torsion and twisting. The bearings may be of the sealed types (ball or roller bearings), and/or of loose de-mountable balls like the cup-and-cone types as in conventional bicycles, or loose rollers. The levers 31, 33 may have any appropriate lengths which, together with their maximum vertical travel or arc, define the maximum stroke angle, which in turn controls the ratio between the maximum stroke and crank turning angle, in other words determining the number of full strokes required to rotate the crankshaft though 0°-180°. The levers 31, 33 may have appropriately-shaped profiles and may be straight or bent along their lengths in up/down directions (as in 20) and/or laterally, for example by spreading out and away from each other so as to achieve a desired separating distance between the pedals. In order to improve bicycle rider's pedalling and reduce his/her leg losses, it may be desirable to reduce the need for rider's leg deceleration at end of strokes by providing one or more of the following means: making torque increase towards stroke-end, for example with appropriate lever rebound springs and/or other springs, saddle adjustment for maximum leg extension, making torque versus angle relation more uniform. In addition, bicycle levers (like 31, 33 of Figure 3) may be coupled together by any appropriate means such that they move in out-of-phase fashion and in opposite direction; that is if one goes down it forces the other to go up as in embodiments 130 and 140 of Figures 10 and 11, respectively. In Figure 10, embodiment 130 comprises right lever 131 and left lever 132 coupled together by a flexible cable 133, cable 133 supported on pulley 135 which is in turn pivotally mounted on frame 138 via support member 137. Pulley 135 can rotate by cable 133 back and forth in direction 134. When lever 131 is pushed down via its respective pedal (not shown), it pulls the other upwards via cable 133 and vice versa. Member 137 may be attached to frame at an appropriate position such as to seat tube 29c or fork 29d of bicycle 20. If desired, lever 131 and/or 132 may also have rebound springs and/or stops (as described in embodiment 20). Appropriate means may be used to prevent cable 133 from coming off pulley 135. Instead of one pulley, cable 133 may pass over two pulleys left and right disposed side by side. Figure 11 shows another embodiment 140 of coupled bicycle levers, comprising right lever 141 with slot 141a, and lever 142 with slot 142a, gears 143 and 144 meshing with one another and rotatably supported on member 148. Appropriately shaped member 145 is coupled to lever 141 via an appropriate pivoted roller 141b which slides in slot 141a, and a similar member 146 is coupled to lever 142 via an appropriate pivoted roller 142b which slides in slot 142a. The other ends of member 145 and 146 are fixed to gears 143 and 144, respectively. Support member 148 may be anchored to the bicycle frame. Thus, pushing one lever down will automatically push the other up and vice versa, with the rollers sliding in the respective slots. Members 145 and 146 may alternatively be pivotally supported on a respective lever, while member 148 may be allowed to slide horizontally appropriately on the frame. The advantages of coupled embodiments 130 and 140 include: improvement to a rider pedalling efficiency, reduction in leg and feet losses and enhancement in rider's comfort. Additional foot-rest(s) and/or appropriately adjusted lever re-bound spring-force to suit rider, may be used. Additional means, such as mechanical and electronics audio/visual, may be used to monitor the approach of trigger points (for example the 180° position) and alert the rider to take appropriate action like halting stroking and stopping, if desired. The various parts of drive mechanism and bicycle can be appropriately designed for strength, rigidity, inertial aspects of wheel and other rotating parts, stiffness, drive forces, spring action and reaction forces to achieve desired performance, rider's comfort and so on. Some parts may be similar to those used in conventional bicycles, such as front fork, brakes, low air resistance, low rolling friction and so on. Those skilled in the art know how to modify, adapt and apply similar design techniques used in conventional bicycles to benefit from the teachings herein. The bicycle can be appropriately designed for various age groups with varying sizes and weights, and also be tailor made for specific activities or applications like speeds and mountain bikes and so on. Both pedal and/or saddle heights and saddle position may be made adjustable for optimum riding conditions. A foldable bicycle may be made by providing appropriate demountable mechanism with lockable parts (for example by snap-fit) or hinges (for example with locks) along member 29b, allowing the frame to fold back for easy transport and storage. In addition, the levers may be foldable or telescopic and the pedals may also fold on levers, for example by a flick-action, to alter lever-length. At least one drive mechanism can be provided per driven wheel/crankshaft, and the drive mechanism may drive more than one wheel, each may have its own freewheeling member. The drive mechanism may drive one or more wheel(s) that may share a common crankshaft or shaft e.g. as in tricycle applications. One or more drive mechanisms of the same or different drive characteristics (T and ω) may drive one or more wheel(s), for example two drive mechanisms, one on either side of the wheel, may share a common shaft and levers driving the wheel, and each may have its own spring, crank and crankpin. For long spring assembly, it may be folded over the wheel, for example via cable and pulleys, and anchored to frame on the other side of crank. Applications include human-powered vehicles on the ground, water and in air including cars, bicycles, tricycles, quadricycles, tandems and rickshaws with at least one drive mechanism driving one or more wheels. Others include drives for electric generators, linear to rotary motion conversion, internal combustion engine starting mechanism (for example lawnmowers and other garden equipments, generators and so on), and any other appropriate energy conversion devices, also in water-crafts applications. For non-vehicle applications it is envisaged, in one aspect, that the drive mechanism will include energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein said at least one input element is coupled directly to said axle assembly and thereby to the energy storage means. In another aspect, it is envisaged for non-vehicle applications the drive mechanism will include energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein the energy storage means is operable in a first phase to store energy without such energy being releasable by the drive mechanism up to a threshold and in a subsequent second phase in which energy can be released. Of course, all the other preferred features disclosed herein in particular in connection with the described vehicle applications can also be used for non-vehicle applications. The disclosures in UK patent applications No 0405246.0 and No. 0418819.9, from which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.

Claims

1. A vehicle drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein said at least one input element is coupled directly to said axle assembly and thereby to the energy storage means.

2. A vehicle drive mechanism according to claim 1, wherein the drive mechanism provides a first phase involving charging of the storage means and a second phase of discharging energy from the storage means.

3. A vehicle drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein the energy storage means is operable in a first phase to store energy without such energy being releasable by the drive mechanism up to a threshold and in a subsequent second phase in which energy can be released.

4. A vehicle drive mechanism according to claim 2 or 3, wherein the at least one input element is not linked to the second, energy release, phase of the energy storage means.

5. A vehicle drive mechanism according to claim 2, 3 or 4, wherein the second phase can allow rapid release of energy from the storage means relative to charging of the storage means during the first phase.

6. A vehicle drive mechanism according to claim 2, 3, 4 or 5, wherein the second phase provides discharge of energy from the energy storage means substantially back to a condition prior to the charging phase.

7. A vehicle drive mechanism according to any preceding claim, wherein the axle assembly comprises a single drive shaft to which the energy storage means and the at least one input element are coupled.

8. A vehicle drive mechanism according to claims 7, wherein the first and second phases are included within one rotation of the drive shaft.

9. A vehicle drive mechanism according to any preceding claim, wherein the or each at least one input element is coupled to the axle assembly by means of a one-way freewheeling member.

10. A vehicle drive mechanism according to any preceding claim, wherein the input elements provide charging of the energy storage means through partial or full actuation of the input elements.

11. A vehicle drive mechanism according to any preceding claim, including a gear mechanism between the axle assembly and a wheel member, hub or output drive member.

12. A vehicle drive mechanism according to any preceding claim, wherein the energy storage means includes at least one sprung element chargeable by the at least one input element and dischargeable through operation of the axle assembly.

13. A vehicle drive mechanism according to claim 12 , wherein the or each sprung element is extendible to store energy therein and returnable to an original state to release energy.

14. A vehicle drive mechanism according to claim 12 or 13, wherein the or each sprung element is made from an elastomeric material such as rubber.

15. A vehicle drive mechanism according to claim 12, 13 or 14, wherein the or each sprung element includes a plurality of elastomeric members coupled at each end thereof to a common mounting member, which mounting member is provided with coupling means.

16. A vehicle drive mechanism according to any preceding claim, wherein the or each input element is arranged to drive the axle assembly.

17. A vehicle drive mechanism according to any preceding claim, including means to alter the configuration of the storage means and/or input element and/or crank/cam to alter the performance of the drive mechanism.

18. A vehicle drive mechanism according to any preceding claim, wherein the axle assembly is in the form of a single unit which includes one or more of: a shaft; a hub located on the shaft with hub to shaft bearings; one or more input element bearings; one or more freewheeling members; a crank or cam coupling means; one or more gears; one or more fastening members.

19. A vehicle drive mechanism according to any preceding claim, wherein the at least one input element is driven by human, animal power or wind power.

20. A vehicle including at least one drive mechanism according to any preceding claim.

21. A vehicle according to claim 20, wherein the vehicle is a bicycle or other human powered vehicle.

22. A drive mechanism including energy storage means, a rotatable axle assembly coupled to the energy storage means and rotatable by energy released from the storage means; and at least one input element operable to input energy into the storage means; wherein the energy storage means comprises an elastomeric energy storage element.

23. A spring assembly comprising a plurality of elastomeric elements and a mounting member including a plurality of holding locations for holding an end of each elastomeric element such that the elastomeric elements are arranged substantially in parallel to one another.