[0001 ] The present invention generally relates to a transmission system. In particular the present invention relates to a transmission system for a belt or pulley driven system. The present invention also relates to a pulley which can be used in the transmission system.

BACKGROUND ART

[0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] Transmission systems are used in various vehicles to transfer power from a power source to an output, typically to a drive wheel to move the vehicle. One such vehicle which employs a drive train is a bicycle.

[0004] The transmission system of a bicycle is typically in the form of a centrally located chain ring integrating two crank arms. A rider engages the crank arms to rotate the chain ring. The chain ring is spaced from a rear sprocket but is interconnected using a chain which spans between the chain ring and the sprocket. As a result the torque exerted on the chain ring is transferred to the rear sprocket, which is also caused to rotate. The rear sprocket is secured to the axle of the rear wheel of the bicycle such that as the rear sprocket rotates the rear wheel will simultaneously rotate.

[0005] The transmission system of a bicycle will typically further comprise a gearing system to enable a rider to manipulate the effect the rotational force of the chain ring has on the rear wheel. This gear system general comprises a plurality of co-axially mounted rear sprockets of different diameter and a plurality of co-axially mounted chain rings (usually two or three) of different diameter. By activating a gear mechanism the rider can cause the chain to move to different sprockets or chain rings, enabling the rider to choose the gear ratio which best suits the conditions. [0006] Current drivetrains do, however, present disadvantages. This is particularly relevant to the field of competitive racing where a simple breakdown of equipment or inefficient gearing can cost the rider the race, or where a small reduction in bicycle weight can result in a win.

[0007] Current gearing systems are limited in the gear range they can achieve. A bike can either be set up with a large gearing range thereby not featuring the smallest possible gears, or with a small 'compact' gearing range thereby not featuring the largest possible gears. Therefore when setting up a bicycle it is necessary to choose one of the subset ranges.

[0008] A large gearing range is used for relatively flat terrain but inevitably leads to undesirable limitations when sections of the predominantly flat terrain lead uphill at a notable gradient, as these cannot be ridden with the preferred small gearing. This in turn leads to rider fatigue and a competitive disadvantage. A small gearing range is used for relatively steep uphill terrain but leads to undesirable limitations when riding downhill as large gearing to facilitate pedalling downhill at high speeds is not available. This leads to lower than possible speeds and hence a competitive disadvantage.

[0009] On a practical level the gear ratio range limitations of existing state of the art chain driven derailleur systems mean that riders and mechanics have to make a call on whether to install a large or small gear range. This not only compromises riding efficiency but also means a constant mechanical effort in changing and replacing the systems on the bike between race days of any tour event. The same applies to recreational riders who have to go through the effort of replacing drive trains depending on their intended type of riding if they want to expend riding energy efficiently.

[0010] While chain driven derailleur systems are highly efficient in transferring rider energy from the crankset to the rear wheel, this efficiency is significantly diminished when the chain is not set in a straight line between the plane of the front chain sprocket and the plane of the rear sprocket plane, i.e. all three elements are not in the same plane. Due to the inherent limitation of this type of drivetrain, straight line chain setting is only achievable for a small subset of gear settings of the drive train gearing range. [001 1 ] When a gear setting is chosen that causes the chain to deviate from the straight line between the chosen front chain ring and the chosen rear sprocket, the resultant strains and friction within the chain, and between chain and the chain ring and sprocket cause drive train efficiency to drop markedly. This means that up to 20% of the rider's energy provided at the crank set does not arrive at the rear wheel. The rider has no choice but to select terrain induced gear settings that feature this inefficiency because it would be even less desirable to force the rider's body to cope with too high or too low gear settings just for the sake of drive train efficiency.

[0012] Chain driven derailleur systems also feature inherent discontinuous securing when changing chain rings which result in the need to simultaneously change sprockets. This compounds the loss of momentum problem. It also presents a significant challenge to fatigued riders and frequently leads to inefficient riding.

[0013] A second major issue for chain driven derailleur systems is that the process of changing gears results in a temporary loss of power transmission for the time it takes the chain to relocate from one chain ring or sprocket to another one. This results in notable loss of rider energy in particular when riding uphill at steep gradient, as the resulting loss of momentum during gear change requires additional effort to bring the bicycle back to the speed before the gear change. It also leads to a time delay in the opportunity to respond to another rider's sprint during a race situation, all of which constitutes a competitive disadvantage and may make the difference between winning or not winning a road race.

[0014] Another disadvantage of conventional chain driven systems is the inability to change gear when stationary. Chain driven systems require a pedalling cadence to be applied in order to facilitate gear change. When a rider unexpectedly has to come to a stop or slow down there is a loss in rider energy and ultimately chain drive train efficiency, as the rider must first change to a smaller gear starting from a much too large gear. This consumes a disproportionate amount of energy and the cumulative effect of that over long rides leads to reduced rider endurance.

[0015] Chain and derailleur driven bicycle drive trains have been refined over several decades but still feature unavoidable weight in their components, particularly the chain itself which can only practically be manufactured from heavy steel. [0016] Chain driven derailleur systems are sensitive to physical shocks to the bike, lack of mechanical calibration quality or other misalignment, componentry mismatch, and lack of sensible rider operation. If any of the above exceeds the limitation of their operational design, the chain will come off the chain ring or the sprocket and, in the worst case, the chain can break. Chain derailment is common in recreational cycling and even regularly occurs during professional road racing even though great care is taken to provide equipment in peak condition. Other mechanical failures for conventional chain drives include blockage of some of the gear ratios by dirt ingress or ice formation.

[0017] Conventional chain driven systems and also other hub gearing systems require lubrication in order to operate at peak efficiency possible. The systems are very sensitive to suboptimal lubrication which leads to regular maintenance requirements that are an operational overhead as well as a cost. Furthermore, new chains only become efficient after a 'break in' period that removes friction inefficiencies resulting from manufacturing processes. They then need to be regularly cleaned at short intervals or significant inefficiencies are introduced.

[0018] Chain driven derailleur and also hub planetary gearing systems are subject to high wear rates between the two metallic surfaces interacting, i.e. either the steel chain and the teeth on a sprocket or chain ring, or the planetary gear sprockets in a hub. This reduces part life cycles and means the entire drive train needs regular replacement in order to provide efficient power transfer.

SUMMARY OF INVENTION

[0019] It is an object of this invention to provide a transmission system which ameliorates, mitigates or overcomes, at least one disadvantage of the prior art, or which will at least provide the public with a practical choice.

[0020] While the invention has been shown and described with particular reference to a bicycle, the invention is equally applicable in many other applications. For example the invention has application in most chain/belt/pulley driven systems which currently use different gear ratios to achieve a particular outcome. These other applications include, but are not limited to transmission systems in vehicles, motorcycles, lawn mowers, quadbikes, industrial mobile equipment as well as fixed belt driven machinery.. These other applications, as well as those which would be obvious to the person skilled in the art, are considered to be included in the scope of the invention as defined herein.

[0021 ] Throughout the specification the term 'cable' is used to describe a rope, a belt, a chain, webbing or any other rope-like device which may be used to assist in transmitting force from a pulley to another object. Furthermore the term 'cable' can denote a single unitary cable, or a cable made from many smaller cables entwined or joined in an end to end arrangement.

[0022] The present invention provides a transmission system, the transmission system comprising a first pulley and an output which is spaced therefrom, a cable extends between the first pulley and the output such that movement of the first pulley causes rotation of the output, the first pulley comprising: a first side assembly spaced from a second side assembly, the first side assembly and second side assembly are co-axially mounted and rotatably fixed together; a variable annular recess defined between the first side assembly and the second side assembly, the annular recess being adapted to receive the cable to support the first pulley at a first diameter; each of the first side assembly and the second side assembly comprising at least one ring, the at least one ring being laterally movable between a first position and a second position, the first position being spaced outwardly from the second position, the at least one ring being adapted to engage the cable wherein when the at least one ring of each side assembly is in the second position the cable is supported at a second diameter.

[0023] The present invention further provides a transmission system, the transmission system comprising a first pulley and an output which is spaced therefrom, a cable extends between the first pulley and the output such that movement of the first pulley causes rotation of the output, the first pulley comprising: a first side assembly and a second side assembly spaced from each other, the first side assembly and second side assembly are co-axially mounted and rotatably fixed together; an annular recess between the first side assembly and second side assembly, the annular recess being adapted to receive the cable such that the cable is supported by the first pulley at a first diameter; each of the first side assembly and second side assembly comprising at least one ring, the at least one ring being laterally movable between at least a first position and a second position, the second position being spaced inwardly from the first position, the at least one ring being adapted to engage the cable wherein when the at least one ring of each side assembly is in the second position the cable is supported by the first pulley at a second diameter.

[0024] The first side assembly may be connected to the second side assembly.

[0025] Preferably when each of the at least one rings is in the first position the cable is supported by the first pulley at the first diameter. The first diameter is defined by the at least one ring of each of the first side assembly and second side assembly when in the first position.

[0026] Preferably during movement of each of the at least one rings from the first position to the second position the cable is supported at a constantly increasing diameter.

[0027] Preferably during movement of each of the at least one rings from the second position to the first position the cable is supported at a constantly decreasing diameter.

[0028] Preferably the at least one ring has a plurality of projections extending laterally from the ring in a generally central direction. That is to say the projections extend towards a central plane of the first pulley wherein the central plane is substantially perpendicular to the pulleys axis of rotation. The plurality of projections may be spaced around the ring. Each projection may provide a supporting surface which is adapted to engage the cable.

[0029] Preferably the projections of the at least one ring of the first side assembly are offset from the projections of the at least one ring of the second side assembly wherein movement of each of the at least one rings to the second position causes the projections of one ring to be received between the projections of the other ring. With this arrangement the rings effectively mesh together to provide a continuous groove/recess for supporting the cable.

[0030] In one aspect of the invention each of the first side assembly and second side assembly comprising a plurality of rings wherein the rings on the first side assembly are different diameters, and the rings on the second side assembly are different diameters, and the rings on the second side assembly have a corresponding ring on the first side assembly wherein corresponding rings move between at least a first position and a second position, the second position being spaced inwardly from the first position, corresponding rings being adapted to engage the cable wherein when the corresponding rings are in the second position the cable is supported by the first pulley at a different diameter to the diameter defined by the adjacent corresponding rings.

[0031 ] The cable may connect the first pulley and the output. The cable may extend between the first pulley and the output such that the cable loops partially around the pulley and partially around the output.

[0032] The cable may be in the form of a continuous belt which frictionally engages the first pulley. The cross section of the belt may be V-shaped, and may be truncated. The belt may comprise a plurality of wedge shaped segments depending from a belt portion. Preferably the cross sectional profile of the belt changes between a tensioned state wherein the profile represents a narrow V-shape, and a relaxed state wherein the profile represents a broader V-shape. The belt may adopt the tensioned state when it spans between the pulley and the output. The belt may adopt the relaxed state when the belt engages the pulley and when the belt engages the output. When the belt is in the relaxed state the broader V-cross section presents a greater surface area to engage the annular recess of the pulley, and the output. In this regard the V-shape complements the annular recess. When in the tensioned state the narrower V- shape presents a reduced surface area such that the cross section is narrower than the cross section of the annular recess. As a result the belt does not engage with the pulley until further around the pulley, and disengages from the pulley earlier than if the belt only had one state. This configuration reduces friction losses encountered at the transition of the belt engaging and disengaging from the pulley. [0033] In one aspect of the invention the frictional forces between the belt and the pulley are the same when considered from all directions.

[0034] In another aspect of the invention the ratio of the friction between the belt and the pulley in the belt driving direction to the friction between the belt and the pulley in a direction at or near normal to the driving direction is as high as possible, being higher than 1 :1 , in that the driving direction friction is lower than the normal friction. When friction between the belt and the pulley in the belt driven direction is high, and the friction between the belt and the pulley in a direction normal to the driven direction is low, power transmission is possible without belt slip. It also allows for feasible and practical shifting of gearing that otherwise would have to cope with high forces to overcome non-drive directional friction between belt and pulley.

[0035] , In one aspect of the invention the surface of the belt and/or the surface of the pulley may comprise surface irregularities such as projections and/or knurls, to increase friction between the belt and the pulley.

[0036] In another aspect of the invention the surface of the belt and/or the surface of the pulley may comprise surface irregularities such as projections, knurls, grooves, and/or patterns to assist in increasing the ratio of the friction between the belt and the pulley in the belt driving direction to the friction between the belt and the pulley in a direction at or near normal to the driving direction.

[0037] The cable may be in the form of a composite material. The cable may have a core. The core may be formed from a non-yielding material such as carbon fibre. While the core is flexible the length of the core, once formed into the belt, does not change.

[0038] Preferably the output is in the form of a second pulley. The second pulley may be a smaller, or larger, version of the first pulley. The second pulley may comprise a first side assembly and a second side assembly spaced from each other, the first side assembly being connected to the second side assembly such that the first side assembly and second side assembly are co-axially mounted. Preferably each of the first side assembly and second side assembly of the second pulley comprise at least one ring,

[0039] In one aspect of the invention the first pulley comprises an activation means to cause movement of the at least one ring of each side assembly between the first position and the second position. Using the activation means the first pulley controls the position of the cable, effectively determining the gearing of the transmission system. Preferably the second pulley reacts to the movement of the at least one ring of each side assembly of the first pulley. In this regard the second pulley is a passive pulley. The at least one ring of each side assembly of the second pulley is preferably biased to its first position.

[0040] In another aspect of the invention the second pulley comprises an activation means to cause movement of the at least one ring of each side assembly between the first position and the second position. Using the activation means the second pulley controls the position of the cable, effectively determining the gearing of the transmission system. Preferably the first pulley reacts to the movement of the at least one ring of each side assembly of the second pulley.

[0041 ] The activation means may comprise a biasing means wherein the biasing means biases the at least one ring towards the first position.

[0042] Preferably the transmission system is arranged such that as the first pulley moves from the first diameter to the second diameter, the second pulley moves from the second diameter to the first diameter. As the belt is fixed in length, the belt must move relative to the second pulley in order to compensate for movement of the belt relative to the first pulley. Therefore, as the belt is positioned to rotate about the larger second diameter of the first pulley, the belt is caused to move to rotate about the smaller first diameter of the second pulley or vice versa.

[0043] The present invention provides a transmission system, the transmission system comprising a first pulley connected to an output by a cable such that movement of the first pulley causes rotation of the output, the first pulley comprising: an annular recess between a first side of the first pulley and a second side of the first pulley, the annular recess being adapted to receive the cable such that the cable is supported by the first pulley at a first diameter; at least one pair of rings located in the annular recess, the at least one pair of rings being moveable in a lateral direction relative to the sides of the pulley between a spaced condition, wherein the pair of rings do not engage the cable, and a meshed condition, wherein the pair of rings support the cable at a second diameter, the second diameter being larger than the first diameter.

[0044] The present invention provides a variable diameter pulley, the pulley comprising: an annular recess for receiving a cable such that the cable is supported by the pulley at a first diameter of the pulley; at least one pair of rings located in the annular recess, the at least one pair of rings being moveable in a lateral direction between a spaced condition, wherein the pair of rings do not engage the cable, and a meshed condition, wherein the pair of rings support the cable at a second diameter, the second diameter being larger than the first diameter.

[0045] The present invention provides a variable diameter pulley, the pulley comprising: an annular recess for receiving a cable at a first diameter of the pulley; the annular recess providing a support surface for supporting the cable, the support surface being movable between the first diameter and a second diameter; wherein the support surface is positionable at any diameter between the first diameter and the second diameter.

[0046] Preferably the support surface presents a substantially continuous surface to the cable when received on the pulley. The cross sectional profile of the support surface may be complementary to the cross sectional shape of that portion of the cable which engages the support surface so that the cable is retained in the annular recess.

[0047] Preferably as the support surface moves between the first diameter and the second diameter, the cable, when supported thereon, remains in the same radial plane.

[0048] Preferably the support surface is formed from a first set of support surface units and a second set of support surface units.

[0049] The first set of support surface units and the second set of support surface units may mesh together or overlap with each other to form the support surface. [0050] The first set of support surface units and the second set of support surface units being moveable in a lateral direction between a spaced condition, wherein the cable may be supported at the first diameter, and a meshed condition, wherein the cable may be supported at the second diameter, whereby during movement of the set of support surface units between conditions the cable may be supported on the support surface which is changing diameter.

[0051 ] Each set of set of support surface units may be arranged so that the support surface units define a plurality of rings. Each ring may comprise a hoop from which the support surface units of that ring project.

[0052] Each ring of the plurality of rings of the first set of support surface units, has a complementary ring of the plurality of rings of the second set of support surface units, whereby complementary rings are in a staggered relation to each other to provide a ring pair. Meshing of each ring pair provides the support surface.

[0053] Each ring pair may move between a first position and a second position.

[0054] In the first position the complementary rings of a ring pair may be spaced away from each other in the axial/lateral direction. In this position the cable cannot be supported by the ring pair.

[0055] In the second position the complementary rings of the ring pair may be in the meshed condition to provide the support surface. In this position the cable is supported by the ring pair.

[0056] Each ring pair may move to a third position which is between the first position and the second position.

[0057] The plurality of rings of each set of support surface units may be arranged so that as a ring approaches the second position the adjacent upper/outer ring thereto commences moving towards the second position.

[0058] The plurality of rings of each set of support surface units may be arranged so that as a ring approaches the first position the adjacent lower/inner ring thereto commences its movement towards the first position. [0059] The plurality of rings of each set of support surface units may be arranged so that as a ring of the first set of support surface units approaches the first position the adjacent lower/inner ring of the second set of support surface units moves to the third position.

[0060] The plurality of rings of each set of support surface units may be arranged so that as a ring of the second set of support surface units approaches the first position the adjacent lower/inner ring of the first set of support surface units moves to the third position.

[0061 ] Each support surface unit may be wedge shaped to provide a sloped surface which engages the cable. Each support surface unit of the first ring and last ring may be smaller than the support surface units of adjacent rings therebetween.

[0062] The pulley may comprise a first side housing for housing the plurality of rings of the first set of support surface units.

[0063] The pulley may comprise a second side housing for housing the plurality of rings of the second set of support surface units.

[0064] The first side housing and the second side housing may be co-axially mounted with respect to each other to define the annular recess therebetween.

[0065] The pulley may comprise activation means to cause movement of the ring pairs between the first position and the second position.

[0066] The activation means may cause movement of the ring pairs between the first position, the second position and the third position.

[0067] The activation means may comprise a biasing means wherein the biasing means biases each ring towards the first position.

[0068] The biasing means may be provided by springs or magnets.

[0069] The activation means may also comprise a plurality of actuator arms. Each actuator arm may be movable in a radial direction between a first position, central of the pulley and a second position, adjacent the outer diameter of the pulley. Each actuator arm may have a head adapted to cause movement of the ring pairs as the actuator arm moves between positions. [0070] A first set of actuator arms may be supported in recesses in the first side housing. The first set of actuator arms may be spaced radially in a spider web type arrangement.

[0071 ] A second set of actuator arms may be supported in recesses in the second side housing. The second set of actuator arms may be spaced radially in a spider web type arrangement.

[0072] As the actuator arms move from their first position towards their second position they cause the ring pairs to move from their first position to their second position.

[0073] As or after the head of each actuator arm passes a ring when moving in a radially outward direction the ring may move to its third position.

[0074] As or after the head of each actuator arm passes a ring when moving in a radially inward direction the ring may move back to its first position.

[0075] The activation means may be manually activated or automatically activated.

[0076] In one aspect of the invention the activation means may be activated mechanically as a result of an input force from an operator.

[0077] In another aspect of the invention the activation means may be activated by a motor wherein the motor is adapted to cause movement of the actuator arms.

[0078] The motor may be an electric motor. The motor may be located in the pulley or a central hub/spindle between the first side housing and the second side housing. The motor may cause rotation of a gear system wherein the set of gears cause movement of the actuator arms. The motor may be reversed to cause movement of the actuator arms in the reverse direction.

[0079] The motor may be powered by a power supply. The power supply may be located in the bicycle frame, the pulley, the crank arm and/or spindle. The power supply may be recharged through a charging socket located on the external surface of the bicycle frame, the pulley or the crank arm. [0080] The present invention provides a transmission system, the transmission system comprising a variable diameter pulley as herein before described connected to an output by a belt such that movement of the pulley causes rotation of the output, the activating means being activated by a motor wherein the motor is powered by a power supply located within the spatial foot print of the transmission system, such as for example, in the crank arm or inside the spindle. The power supply may be recharged through a charging socket, eliminating the need to remove the battery for re-charging.

BRIEF DESCRIPTION OF THE DRAWINGS

[0081 ] Further features of the present invention are more fully described in the following description of a non-limiting embodiment thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

Figure 1 is a side view of a front pulley assembly of a transmission system of a bicycle according to a first embodiment of the invention;

Figure 2 is a cross sectional side view of figure 1 taken through line CC;

Figure 3 is a perspective exploded view of figure 1 ;

Figures 4, 5 and 6 are different views of figure 2 with the left hand side shown in an exploded condition and the right hand side in an assembled condition;

Figure 7 is a perspective view of a plurality of rings of the present embodiment;

Figure 8 is a perspective view of the right hand side of figure 2 in an assembled condition;

Figure 9 is a perspective view of the left hand side of figure 2 in an assembled condition;

Figure 10 is a perspective view of an actuator means of the present embodiment;

Figure 1 1 is a side view of figure 10; Figure 12 is a part perspective view of figure 1 1 showing a cross section through a hub/spindle;

Figure 13 is a front view of figure 12 without the crank;

Figure 14 is a perspective view of the motor and gear system;

Figure 15 is a schematic representation of part of the transmission system of the first embodiment when at the largest/highest gear ratio (one side of the pulleys being removed for illustrative purposes);

Figure 16 is a schematic representation of the transmission system of the first embodiment when at the smallest/lowest gear ratio (one side of the pulleys being removed for illustrative purposes);

Figure 17 is a perspective schematic representation of figure 15;

Figure 18 is a front view of the front pulley of figure 17 without the cable;

Figure 19 is a cross section view of a section of the front pulley of figure 18;

Figure 20 and 21 are schematic representations showing the position of the plurality of rings of the pulley of figure 18 when supporting the cable;

Figure 22 is a perspective schematic representation of the transmission system of the first embodiment when moving from the largest gear ratio;

Figure 23 is a front view of the front pulley of figure 22 without the cable;

Figure 24 is a cross section view of a section of the front pulley of figure 23;

Figure 25 and 26 are schematic representations showing the position of the plurality of rings of the pulley of figure 23 when supporting the cable;

Figure 27 is a perspective schematic representation of the transmission system of the first embodiment when moving towards the smallest gear ratio;

Figure 28 is a front view of the front pulley of figure 27without the cable;

Figure 29 is a cross section view of a section of the front pulley of figure 28; Figure 30 and 31 are schematic representations showing the position of the plurality of rings of the pulley of figure 28 when supporting the cable;

Figure 32 is a perspective schematic representation of figure 16;

Figure 33 is a front view of the front pulley of figure 32 without the cable;

Figure 34 is a cross section view of a section of the front pulley of figure 33; and

Figure 35 and 36 are schematic representations showing the position of the plurality of rings of the pulley of figure 33 when supporting the cable.

DESCRIPTION OF EMBODIMENTS

[0082] The present invention according to a first embodiment of the invention is in the form of a transmission system 12 comprising a variable diameter pulley 1 1 . The pulley 1 1 is particularly adapted for use with a transmission system which functions in a similar/same manner as a continuously variable transmission (CVT).

[0083] As will be highlighted in the below discussion, a difference between the present invention and the continuously variable transmissions of the prior art is that the pulley of the present invention is configured to maintain a relatively narrow gauge. This enables the pulley and associated transmission system to be used in applications which have minimal space for a transmission system, such as, for example, bicycles including conventional bicycles, e-bicycles and pedelecs.

[0084] Previous CVT's comprise relatively thick front and/or rear pulley arrangements which could not be readily applied in applications which have limited space to house the pulley arrangement. For example, these CVTs could not be applied to bicycles as it would impede the pedal action, not provide a sufficient range in gear ratios, place significant stress on the chain and/or is too heavy. The relatively narrow pulley of the present invention provides the transmission system with a practical and efficient drive train geometry. When applied to a bicycle the thickness of the pulley of the present invention is similar to the thickness of a chain ring of a conventional bicycle wherein the chain ring comprises two sprockets. [0085] The present invention also allows the diameter of the pulley to be increased with minimal or no change in the width of the pulley. This provides for a large range of gear ratios. This further enhances the vast array of applications the present invention is suited.

[0086] The below embodiments discuss the present invention as applied to a bicycle. However, there are many more applications in other types of driven equipment. These include applications in vehicles, lawnmowers, motorised scooters, quad-bikes, snowmobiles, mobile or fixed industrial equipment. These other applications are considered to be within the scope of this invention.

[0087] In the present embodiment the pulley 1 1 is adapted to support two crank arms 13 to which peddles/clips 15 are secured. A rider (not shown) can engage the peddles 15 to cause the pulley 1 1 to rotate, as is well known.

[0088] The pulley 1 1 comprises a first side housing 17 and a second side housing 19. The first side housing 17 and the second side housing 19 are co-axially mounted and secured to each other via a shaft 21 . The pulley 1 1 is secured to a frame of the bicycle (not shown) so that the pulley 1 1 is located adjacent the frame.

[0089] One of the crank arms 13a is connected to a shaft which passes through a spindle/hub 23 of the bicycle frame before being secured relative to the second side housing 19. The second crank arm 13b is secured directly to an outer surface of the first side housing 17.

[0090] The first side housing 17 and the second side housing 19 are spaced a distance from each other to define an annular recess 25 therebetween.

[0091 ] As best shown in figures 6 and 7, the first side housing 17 houses nine rings 27 of different diameters. Each ring 27 comprises a hoop 29 which has a plurality of wedged shaped projections 31 projecting therefrom in a spaced apart arrangement to define a gap 33 therebetween. Each projection 31 provides a support surface 35 for reasons which will be discussed below.

[0092] Referring to figure 7, the projections 31 are arranged so that projections 31 on one ring are offset relative to the projections 31 on adjacent rings 27. The projections 31 on each ring 27 are spaced apart to define a gap 33. The gaps are sized so that projections 31 of adjacent rings 27 can be received in the gaps 33 so that adjacent rings 27, when assembled, can nestle together, as represented by the second side housing 19 shown in at least figure 4, 5 and 6.

[0093] The projections 31 a on the first ring 27a are approximately half the size of the projections 31 on the ring adjacent thereto. The first ring 27a has the smallest diameter.

[0094] The last ring 27i also comprises a second set of projections 32i which are approximately half the size of the projections 31 i. The projections 32i may be located between projections 31 i on the rings adjacent these two rings 27a, 27i. The last ring 27i has the largest diameter.

[0095] Each ring 27 is movable in a lateral direction relative to the first side housing 17. With the exception of the first ring 27a, each ring 27 is movable between a first position, as shown in figure 9, wherein each ring is adjacent to an inner side 37 of the first side housing 17, and a second position, wherein the ring 27 is spaced away from the inner side 37. In this embodiment each ring 27, with the exception of the last ring 27i, is also movable to a third position which is located laterally between the first position and the second position.

[0096] The transmission system 12 also comprises an activation means 39. The activation means 39 co-operates with the pulley 1 1 to cause movement of each ring 27 between the first position, the second position and the third position.

[0097] The activation means 39 comprises a biasing means, which in this embodiment is in the form of a set of magnets 41 , which bias each ring to the first position. The magnets co-operate with a set of metal pins 43 retained in each ring 27. In alternative embodiments the biasing means can be in the form of springs.

[0098] The activation means 39 also comprise a plurality of actuator arms 45 supported in recesses 47, wherein a first set of the actuator arms 45 are located on the inner side 37 of the first side housing 17, and a second set of the actuator arms 45 are located on the inner side of the second side housing 19. The actuator arms 45 are spaced radially in a spider web type arrangement. Each actuator arm 45 is movable along its recess 47 in a radial direction (as indicated by the arrows in figure 1 1 ) between an innermost position, central of the first side housing 17, as shown in figure 1 1 , and an outermost position, adjacent the outer diameter of the first side housing 17. [0099] Each actuator arm 45 has a head 49 adapted to cause movement of the ring pairs as the actuator arm 45 moves between positions. In this particular embodiment each head 49 provide a sloping upper face 51 for engaging a sloping lower face 151 of the rings 27. Each head 49 also comprises a sloping lower face 52 for engaging a sloping upper face 152 of the rings 27 for reasons which will be described below.

[00100] The activation means 39 is activated by an electric motor 53 which cooperates with a gearing system 55 to move the actuator arms 45 along the recesses 47 so that the actuator arms 45 are caused to move outwardly or inwardly. The activation means 39 is also able to hold the actuator arms 45 at any location between their innermost position and outermost position. This is achieved by controlling the electric motor 53 accordingly.

[00101 ] When the actuator arms 45 are at their innermost position their heads 49 aligns with the first ring 27a such that the ring is in the second position.

[00102] The configuration of the second side assembly 19 is largely identical to that of the first side assembly 17. The second side assembly 19 comprises an activation means which has the same components as those of the first side assembly 17. In this regard the activation means and its features are numbered the same for the second side assembly 19 as those of the first side assembly 17. The activation means of the second side assembly 19 is activated by the electric motor 53 and the gearing system 55 such that the activation means of the second side assembly 19 operates simultaneously with that of the first side assembly 17.

[00103] The second side assembly 19 also comprises an identical set of nine rings 27. In this regard the set of nine rings 27 and their features are numbered the same as those of the first side assembly 17.

[00104] The difference between the two sets of rings is the orientation of the rings of the second side assembly 19 relative to the rings of the first side assembly 17. In this regard each of the rings of the second side assembly 19 has a corresponding ring 27 on the first side assembly 17 to provide a ring pair. The corresponding rings of the ring pair are the same as each other but when the pulley is assembled the corresponding rings are offset to each other. As the corresponding rings are offset, when the corresponding rings move from the first position to the second position the projections 31 from the ring of the first side assembly are received in the gaps 33 of the corresponding ring of the second side assembly 19 such that in the second position the ring pair are meshed together, as best shown in figure 18.

[00105] When the pulley 1 1 is assembled the first side assembly 17 and second side assembly 19 define the annular recess 25 therebetween. The annular recess is adapted to receive a cable in the form of a V-shaped belt 59.

[00106] When the first ring 27a of the first side assembly 17 and the first ring 27a of the second side assembly 19 are each in their second position, and the remaining rings of the first side assembly 17 and the remaining rings of the second side assembly 19 are each in their first position, the belt 59 is supported by the pulley 1 1 at the systems smallest diameter, as best represented by figures 33 to 35.

[00107] When the last set of rings 27i of each of the first side assembly 17 and second side assembly 19 are in their second position the belt 59 is supported by the pulley 1 1 at the system's largest diameter, as best represented by figures 18 to 21 .

[00108] As the actuation arms 45 can be set at any position between their innermost position and outermost position the location of the belt 59 can be supported by the pulley at any diameter between the smallest diameter and the largest diameter.

[00109] The variable diameter pulley 1 1 can be combined with a second variable diameter pulley 1 1 1 to complete the transmission system 12. As can be noted in the figures, the belt 56, which is a continuous loop, extends between the two pulleys 1 1 , 1 1 1 to transfer movement from the first pulley 1 1 to the second pulley 1 1 1 .

[001 10] The second pulley 1 1 1 acts as a slave pulley whereby it reacts to changes of the first pulley 1 1 . In this regard the second pulley 1 1 1 is a smaller version of the first pulley 1 1 without the need to incorporate an activation means 39, electric motor 53 and gearing system 55 in the second pulley 1 1 1 .

[001 1 1 ] Owing to the configuration of the rings the pulley presents a substantially continuous support surface to the belt as the belt moves relative to the pulley between the smallest diameter and the largest diameter. [001 12] Figures 17 to 36 show various views of the transmission system. The transmission system 12 comprises the first variable diameter pulley 1 1 , and second variable diameter 1 1 1 interconnected by the belt 59. The various views show the belt 59 at various positions of the transmission system 12 wherein the various positions correspond to various gear positions of a conventional bicycle chain driven derailleur system.

[001 13] Referring to figures 17 to 21 , the transmission system 12 is shown at a position relating to the largest/highest gear ratio wherein the actuator arms 45 are at their outermost position, whereby the sloping upper face 51 of actuator head 49 engages the sloping lower face 151 of the ring 27i. In this position the last set of rings 27i of the first side assembly 17 of the first pulley 1 1 , and the last set of rings 27i of the second side assembly 19 of the first pulley 1 1 are each in their second position to support the belt 59 at the largest diameter. When in this position the remaining rings of the first pulley 1 1 are in their third position.

[001 14] When the belt 59 is supported by the first pulley 1 1 in the largest diameter the configuration of the pulley ensures that the recess 25 which receives the belt limits the ability of the belt 59 to disengage from the pulley 1 1 .

[001 15] When the belt 59 is supported by the first pulley 1 1 in the largest diameter, the belt 59 is supported by the second pulley 1 1 1 in the smallest diameter, as shown in figure 17. In this embodiment the second pulley 1 1 1 is a reactionary pulley wherein the operation of the second pulley 1 1 1 is dictated by the operation of the first pulley 1 1 . As the first pulley 1 1 is actively caused to move to a new operative position by the activation means 39, the change in tension in the belt 59 causes the second pulley 1 1 1 to react to support the belt 59 in a new position.

[001 16] In this position the first ring 27a of the first side assembly 17 of the second pulley 1 1 1 , and the first ring 27a of the second side assembly 19 of the second pulley 1 1 1 are each in their second position, with the remaining rings in their first position. [001 17] Referring to figures 22 to 26, the transmission system 12 is shown at a first intermediary position. Referring to figures 27 to 31 , the transmission system 12 is shown at a second intermediary position. In these sets of figures the transmission system 12 moves away from the largest/highest gear ratio. This is achieved by activating the activation means 39 to cause the actuator arms 45 to move inwardly towards their innermost position.

[001 18] As the head 49 of the actuator arms 45 moves inwardly the sloping upper face 51 of actuator head 49 moves away from the sloping lower face 151 of the ring 27i , allowing the last set of rings 27i to return to their first position by the biasing action of the magnets 41 . As this happens, the sloping lower face 52 of actuator head 49 engages the sloping upper face 152 of the ring 27h adjacent the last ring 27i to cause it to move from the third position to the second position to support the belt 59.

[001 19] When in this position the rings of the first pulley 1 1 which are smaller in diameter to ring 27h are in their third position, while the last set of rings 27i are in their first position.

[00120] As the head 49 of the actuator arms 45 moves further inwardly the sloping upper face 51 of actuator head 49 moves away from the sloping lower face 151 of the ring 27h, allowing the rings 27h to return to their first position by the biasing action of the magnets 41 . As this happens, the sloping lower face 52 of actuator head 49 engages the sloping upper face 152 of the ring 27g adjacent the ring 27h to cause it to move from the third position to the second position to support the belt 59.

[00121 ] When in this position the rings of the first pulley 1 1 which are smaller in diameter to ring 27g are in their third position, while the rings of larger diameter to ring 27g are in their first position.

[00122] This sequence continues for subsequent rings as the actuator arms 45 are caused to move further inward.

[00123] When the belt 59 is supported by the first pulley 1 1 in any intermediary position, the second pulley 1 1 1 reacts so that the belt 59 is suitably supported. [00124] Referring to figures 32 to 36, the transmission system 12 is shown at a position relating to the smallest/lowest gear ratio wherein the actuator arms 45 are at their innermost position, whereby the sloping upper face 51 of actuator head 49 engages the sloping lower face 151 of the ring 27a. In this position the first ring 27a of the first side assembly 17 of the first pulley 1 1 , and the first ring 27a of the second side assembly 19 of the first pulley 1 1 are each in their second position. When in this position the remaining rings of the first pulley 1 1 are in their first position.

[00125] When the belt 59 is supported by the first pulley 1 1 in the smallest diameter, the belt 59 is supported by the second pulley 1 1 1 in the largest diameter, as shown in figure 35. In this position the last ring 27i of the first side assembly 17 of the second pulley 1 1 1 , and the last ring 27i of the second side assembly 19 of the second pulley 1 1 1 are each in their second position, with the remaining rings in their third position.

[00126] In reverse operation the first pulley 1 1 undergoes a similar sequence of events. As the actuator arms 45 moves outwardly toward a ring, the sloping upper face 51 of actuator head 49 engages the sloping lower face 151 of the ring 27, overcoming the biasing action of the magnets 41 to cause the ring to move from its first position to its second position.

[00127] As the actuator head 49 moves past a ring 27 the sloping lower face 52 of actuator head 49 passes the ring, the biasing action of the magnets 41 causes the sloping upper face 152 of the ring 27 to slide along the sloping lower face 52 of actuator head 49 allowing the ring to move to the third position. An arm 50 of the actuator arm 49 prevents the ring returning to its first position after the actuator arm 49 has passed the ring in the outward direction.

[00128] Similarly, the rings of the second pulley 1 1 1 are caused to move such that the belt 59 is supported at smaller diameters.

[00129] As can be seen by the operation of the present embodiment, the transmission system 12 presents a substantially continuous support surface on both the first pulley 1 1 and the second pulley 1 1 1 as the transmission system moves between the largest/highest gear ratio and the smallest/lowest gear ratio. Furthermore, the activation means 39 is operable such that the actuator arms 45 may be positioned anywhere between their lowermost and outermost position (inclusive) and may be held in that position. As such the surface which supports the belts can be at any diameter between the largest diameter and smallest diameter.

[00130] Considering bicycles, prior art chain driven derailleur systems have been prone to mechanical malfunction or even failure. These include chains coming off sprockets or chain rings when bicycles are subject to shock (e.g. riders going through holes in the road or over edges) or excessively aggressive gear change events. At best these failures lead to considerable inconvenience, distortion of race results, or at worst it leads to rider injury.

[00131 ] The reason why this malfunction or failure is possible is due to the design and construction of prior art derailleur driven cassette and chain ring systems which do not physically force the chain to be retained in place. The present invention is designed such that it is relatively impossible for the belt to come off the front or rear pulleys because no jockey wheels are in use and the edge perimeters of the pulleys physically constrain the belt under any load including shocks induced by road conditions. This increases the safety for the ride and, in competition, levels the playing field.

[00132] The present invention mitigates loss of power during gear ratio changes as it provides continuous power transmission during those gear ratio changes. This does not apply to derailleur systems of prior art bicycles which suffer from loss of momentum during gear (chain ring or sprocket) changes

[00133] Loss of momentum is particularly significant for prior art derailleur systems when changing between chain rings requiring associated multiple sprocket (typically 3- 4) changes in the cassette at the same time in order to avoid excessive gear ratio adjustments from the current setting.

[00134] The present embodiment can be activated by single trigger up or down shifting (using existing handle bar mounted shifter hardware) on the front crank set. The rear wheel gearing adjusts automatically to the crank setting through belt pretension and a spring-like mechanism. Prior art derailleur drive trains require the rider to separately coordinate shifting of rear sprockets as well as front chain rings to achieve continuous gearing during up or down shifts which is not only inefficient as it leads to loss of momentum as between 3 and 4 gears have to be traversed when chain rings are changed, but it also places a strain on the riders in a state of fatigue or needing to respond to race situations without warning. [00135] The present embodiment removes the manual coordination requirement of rear (cassette) and front (chain ring) changes making shifting much simpler. This is particularly desirable when riders are fatigued. The present embodiment also removes gear ratio duplication which exists in all prior art chain ring and cassette combinations, thereby simplifying the system further.

[00136] The present embodiment eliminates the need for drivetrain lubrication which reduces maintenance and does not compromise drive efficiency.

[00137] The gearing ratio of the present embodiment combines existing standard and compact gearing ratios of prior art systems so that there is no need to swap chain rings and or cassettes from race day to race day which is currently the case. This further reduces maintenance.

[00138] The present embodiment also expands on the largest as well as the smallest gear ratios available from prior art derailleur systems.

[00139] As the present embodiment is continuously variable riders are no longer forced to use comparably energy sapping large gear steps inherent in prior art drive trains.

[00140] The efficiency of the present embodiment is superior to that of the prior art systems as traditional systems suffer from inefficiencies when using smallest sprockets and when using cross chain gear settings. The efficiency of the present embodiment ensures more rider energy input at the crank set arrive at the rear wheel.

[00141 ] Many of the abovementioned advantages of the present embodiment are also realised in one form or another in other applications/embodiments of the present invention. For example changing between gears is no longer associated with a loss of/drop in power as the gears change. The present invention allows for the smooth transition between gear ratios whereby the transfer of power is maintained at all times.

[00142] The present invention provides a transmission system having a relatively narrow, fixed width, pulley which is capable of being designed to have near unlimited gear ratios. This is in contrast to current CVT systems which must increase in width as gear ratios increase. [00143] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[00144] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprise", "comprises," "comprising," "including," and "having," or variations thereof are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[00145] When an element or layer is referred to as being "on", "engaged to", "connected to" or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to", "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[00146] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[00147] Spatially relative terms, such as "inner," "outer," "beneath", "below", "lower", "above", "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.