A crank set

Abstract

The present invention relates to a crank set, for example for propelling a bicycle or driving a similar pedal powered machine or vehicle. A crank set comprises a left and right crank arm. Each crank arm has a piston- in-cylinder whose stroke reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied. A fluid pathway connects the two pistons via a flow control valve, whereby in use fluid urges a piston to lengthen a first crank arm, during part of its downwards stroke, and to shorten the length of a second crank arm, during part of its upwards stroke. An advantage of the flow control valve is that it enables a user to optimise crank length depending on the terrain or slope.

Description

[0001] A CRANK SET

[0002] Field of the Invention

[0003] The present invention relates to a crank set, for example for propelling a bicycle or driving a similar pedal powered machine or vehicle.

[0004] It is appreciated however the invention may also be used in pedal powered machines, such as static exercise equipment, for example exercise bicycles, treadmills or other pedal powered exercise apparatus which are operated by applying a force to a left and a right pedal in a cyclic manner. The pedals are each connected to a spindle by way of respective left and right cranks which each act as levers through which torque is applied to the spindle.

[0005] Typically, when cycling a cyclist presses down with one foot on one pedal and optionally applies an upwards force with their opposite foot on the other pedal, for example by way of toe clips or toe straps. Torque is applied to the spindle which turns a chain ring to transmit a force, via a chain to a sprocket on a rear wheel.

[0006] Background

[0007] In many societies there is an ever increasing interest in cycling and exercise bicycles and pedal powered exercise machines, for health and social purposes.

[0008] There are many styles of cycling and cyclists of many different abilities, and it is increasingly important for such cyclists to have more options and improvements in how the cycle.

[0009] Prior Art

[0010] International patent application WO 2008 031 135 (SCHEEPMAKER et al) discloses a crank where the length of each pedal crank of a bicycle varies so as to extend it on a downstroke and shorten the crank on an upstroke, thereby providing a greater mechanical advantage.

[0011] United states patent application US 20040 103 747 (HUNG) discloses a bicycle crank and pedal assembly with a self-extending and retracting crank arm. The assembly has three one-piece components that move relative to each other.

[0012] United states patent US 6 640 662 (BAXTER) discloses a variable length crank arm assembly for a bicycle having a frame and a rotatable spindle, the crank arm assembly comprising, a crank arm coupled to the spindle for rotation about the spindle.

[0013] UK patent application GB 2 368 322 A (SHAMSUTDINOV LUBECK) discloses a crank arm with two mutually telescopic parts, one fixed to a hub and the other slidable to provide varying pedal radial distance from the hub.

[0014] UK patent application GB 2 392 142 A (SHAMSUTDINOV LUBECK) discloses a hydraulic foot pedal crank arm assembly.

[0015] Korean patent application KR 20110000222U (GON MIN B) discloses a crank set connect to a bicycle rear wheel cassette gear.

[0016] Spanish patent application ES 2159222B1 (GARCIA MARTINEZ VICTOR) discloses a system for improving performance of crank connecting rod type motion transmission mechanisms.

[0017] The present invention arose in order to overcome drawbacks and disadvantages suffered by many prior art systems.

[0018] Another aim of the present invention is to provide an improved crank set which has a variable crank stroke. Another aim of the present invention is to provide an improved crank set which enables gear mashing.

[0019] Summary of the Invention

[0020] According to a first aspect of the present invention there is provided a crank set comprising: a left and right crank arm, each crank arm having a piston-in- cylinder whose stroke reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that a fluid pathway connects the two pistons via a flow control valve, whereby in use fluid urges a piston to lengthen a first crank arm, during part of its downwards stroke, and to shorten the length of a second crank arm, during part of its upwards stroke.

[0021] In some embodiments of the crank set the flow control valve is located in a bottom bracket.

[0022] In some embodiments of the crank set the flow control valve is adjustable to vary a rate of transfer of fluid between the two cylinders. Optionally the flow control valve may be automatically adjustable to provide an appropriate volume of hydraulic fluid in dependence upon one or more criteria. One example of an automatically adjustable flow control valve is one which increases supply of fluid in dependence upon a rotational speed of a crank (or a wheel) to supply an appropriate volume of hydraulic fluid.

[0023] In some embodiments of the crank set a fluid reservoir is provided in order to supply additional hydraulic fluid when required. Likewise, the reservoir is capable of receiving and storing excess hydraulic fluid when it is not required. It may comprise a flexible portion which is capable of expanding and contracting to accommodate varying volumes of fluid.

[0024] Optionally a bleed valve is provided to bleed fluid from the, or each, cylinder. The bleed valve may have a manual control. In some embodiments of the crank set, left and right cranks each comprise a sliding distal portion and fixed proximal portion. Preferably the distal portion of the crank includes a pedal socket. Alternatively, cranks may be supplied with pedals fitted thereto.

[0025] Pedal sockets may be threaded to receive a threaded pedal or they may be fitted with a quick release mechanism.

[0026] In some embodiments of the crank set for example for propelling a bicycle or similar pedal powered vehicle, there is provided a left and right crank arm each crank arm having a piston-in-cylinder whose stroke reciprocates to lengthen or shorten the respective crank arm thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied; a fluid pathway connects the two pistons via a flow control valve, and a drive sprocket for the cycle; arranged such that a chain engages the sprocket to propel the cycle; wherein each of the cranks comprises a lower crank portion located proximate the hub, and a distal upper crank portion to which a pedal is fitted; and wherein the upper crank portion is adapted to move on the crank from a first position further from the hub to a second position closer to the hub; characterised in that the hub comprises a fluid pathway through which fluid passes from the piston-in- cylinder in one crank to the piston-in-cylinder in the other crank.

[0027] Shafts on which pistons are supported are ideally square in cross-section to reduce any rotational torque being transmitted about a longitudinal axis of the crank.

[0028] One or more needle valves may be provided for connection between an inlet of the hydraulic cylinder.

[0029] Preferably the adjustable flow control valve adjusts fluid flow between each piston-in-cylinder according to the position of a crank. In this way each crank is adapted to extend on its downstroke towards a bottom dead centre (BDC) of the sprocket, in which position the opposing crank retracts, such that the left and right cranks reciprocate and oscillate thereby following an epicyclic pathway. As one crank returns to its top dead centre (TDC) faster, it becomes shorter. Therefore, it is appreciated that mashing or spinning of gears becomes easier and gear clash is avoided. Gear mashing is when the gears are close enough that gear teeth overlap.

[0030] In some embodiments the flow control valve controls the rate of flow of fluid through the fluid pathway which is ideally a hydraulic hose. In this way for example, fluid flow may be diverted for purposes of emptying or adding to the fluid level in a piston-in-cylinder.

[0031] In some embodiments the flow control valve allows a variation of available fluid in each piston-in-cylinder as fluid may be diverted to, or received from, a fluid reservoir. In this arrangement the flow control valve may be used to vary the length of the extension of each crank during a cycle.

[0032] Different settings for the flow control valve allow variation of supply of hydraulic fluid, for example to one or more selected cranks. Thus, the flow control valve is adjustable to switch between two or more different modes, such: as a ‘cross flow mode’ for regular use as hereindescribed; ‘access mode’ to enable for example topping up of hydraulic fluid or for repair / maintenance purposes; and ‘lock mode’ in which the two portions of the crank are immobilised mode for use as a conventional non-extending crank.

[0033] It is also appreciated that by using a flow control valve the crank length (or extension distance) can be shortened or lengthened by the user, and so crank length can be optimised for example in dependence upon a particular type of terrain or slope.

[0034] Optionally the flow control valve has a bleed valve, so as to enable hydraulic fluid to be bled, for example from a reservoir. According to a second aspect of the present invention there is provided a crank set comprising: a left and right crank arm, each crank reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that an interconnecting cable or connects the two cranks such that when a first crank arm extends during part of its downwards stroke the interconnecting cable shortens the length of a second crank arm during part of its upwards stroke.

[0035] In some embodiments, the crank comprises relatively sliding upper crank portion and lower crank portions, so that the overall length of each crank is variable.

[0036] In some embodiments crank portions are protected by an expandable cover or boot, so as to prevent ingress of debris or grit which may compromise extension and retraction of the sliding parts of the crank.

[0037] In some such embodiments the crank comprises a square portion or section profile in relation to the sliding parts of the crank, so as to prevent rotation during extension or retraction.

[0038] In some embodiments the crank comprises a pneumatic portion, which may be controlled by, or which may control, the extension and / or retraction, for example being within the crank(s).

[0039] In some such embodiments a pneumatic portion comprises a needle valve, so as to allow entry and exit of air to the portion.

[0040] In some embodiments the hub comprises a bespoke axle, for example with an in-built hydraulic fluid conduit. In some such embodiments the axle comprises a control means which is operative to extend and / or retract the crank. An example is a flow control valve which may be controlled by rotation of an axle on which the cranks are mounted.

[0041] For example, in some embodiments the axle comprises one part associated with a sprocket or gear crank and one part is associated with a distal crank.

[0042] In some such embodiments the crank comprises a flow control valve comprised in a spool flow control valve in the distal crank, for example being an annular valve, that may be located in a hub of a crank.

[0043] In some embodiments of the crank a spool valve allows reduction or control of available hydraulic fluid in the crank, allowing bleeding from a crank, or for example to allow diversion of hydraulic fluid to / from a reservoir.

[0044] In some such embodiments the crank comprises a sprung float or hydraulic fluid block within the spool valve, which defines a restriction to hydraulic fluid. The spool valve may be sprung to resist the hydraulic fluid, thereby ensuring that the hydraulic fluid is maintained under pressure.

[0045] In some such embodiments of the crank the spool valve is controlled by a two- part axle, which may be to displace the valve, and alter flow direction within the valve or crank.

[0046] In some such embodiments of the crank the spool valve is controlled by a switch means such as a push rod, which may hold components in place, for example under spring bias, detent or under pressure, such that displacement of the rod may release components and allow control or displacement of the axle, valve or parts thereof, to allow adjustment of the valve or flow direction. Displacement of the rod may act against a spring and be controlled by a button or other device, for example on an axle end. According to a third aspect of the present invention there is provided an energy storage system for use with a crank set as hereindefined, the energy storage system includes a hydraulic reservoir capable of receiving pressurised fluid and storing the fluid under pressure and a release valve which when operated releases pressurised hydraulic fluid to drive a piston-in-cylinder in either a left or a right crank arm to, each crank arm having a whose stroke reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that a fluid pathway connects the two pistons via a flow control valve, whereby in use fluid urges a first piston to lengthen a first crank arm, during part of its downwards stroke, and a second to retract to shorten the length of a second crank arm, during part of its upstroke.

[0047] According to a fourth aspect of the present invention there is provided a continuously variable transmission (CVT) system for a bicycle for mounting in a bottom bracket of a bicycle frame, the CVT system is driven by left and right cranks and comprises an epicyclic gear system which drives an auger that pumps an hydraulic fluid to a pressurised reservoir when the cranks are rotated in a first direction and when the cranks are driven in a reverse direction pressurised hydraulic fluid is released.

[0048] Preferably the continuously variable transmission (CVT) system includes a release valve which when actuated releases pressurised hydraulic fluid from a reservoir.

[0049] Preferably the continuously variable transmission (CVT) system has swash plates mounted on a rotating shaft within the housing and when rotated the shaft causes the swash plates to pressurise the hydraulic fluid.

[0050] In some embodiments the continuously variable transmission (CVT) system has a flow control valve that allows reduction of available hydraulic fluid from the reservoir. Preferred embodiments of the invention will now be described, by way of example only, and with reference to the Figures in which:

[0051] Brief Description of Figures

[0052] Figure 1 shows an isometric view of a first embodiment of a crank set according to the present invention;

[0053] Figure 2 shows a reverse isometric view of the embodiment of the crank set shown in Figure 1 ;

[0054] Figure 3 shows an exploded isometric view of the embodiment of the crank shown in Figures 1 and 2;

[0055] Figure 4 shows a detail isometric overall view of the embodiment of the crank shown in Figure 1 ;

[0056] Figure 5 shows a second isometric overall view of the embodiment of the crank shown in Figure 1 in an assembled form;

[0057] Figure 6 shows an isometric view of a second embodiment of the crank with a variable axle, according to the present invention;

[0058] Figure 7 shows a reverse isometric view of the embodiment of the crank shown in Figure 6;

[0059] Figure 8 shows a partially exploded view of the embodiment of the crank shown in Figures 6 and 7;

[0060] Figure 9 shows a fully exploded view of the embodiment of the crank shown in Figures 6 and 7; Figure 10 shows a second partially exploded view of the embodiment of the crank shown in Figures 6 and 7;

[0061] Figure 1 1 shows an exploded view of an alternative embodiment of the invention depicting constantly variable cranks and location of vacuum chamber connecting the two cranks;

[0062] Figure 12 shows an alternative embodiment of the invention with a reciprocating crank and balancing spring with an interconnecting cable or pulley;

[0063] Figure 13 shows an alternative improved embodiment of a reciprocating crank with fluid pathways for use in a reciprocating epicyclic crank;

[0064] Figure 14 shows an alternative embodiment with twin opposing sprag clutches and sun and planetary gears for providing a constantly variable transmission of torque;

[0065] Figure 15 shows an alternative embodiment of a basic reciprocating crank with balancing / dampening springs;

[0066] Figure 16A is a section through a planetary feed and shows variable displacement of axial pistons which act as an auger pump as part of a continuously variable transmission (CVT) means;

[0067] Figure 16B shows an overall isometric view part sectional detail of the continuously variable transmission (CVT) means shown in Figure 16A and details of a planetary gearbox in a cylindrical housing;

[0068] Figure 16C is a sectional view of the continuously variable transmission (CVT) means shown in Figures 16A and 16B showing a neutral position in which crank actuators are actuated and swash plates move in tandem; Figure 16D is a transverse sectional view which shows screw threads used to pressurise the continuously variable transmission (CVT) means by way of swash plates;

[0069] Figure 17A shows an overall view of an hydraulic energy storage reservoir with radial vanes of pressure valves which are used to pump hydraulic fluid under pressure;

[0070] Figure 17B is a diagrammatical sectional view of the energy storage reservoir shown in Figure 17A and depicts internal operation of a variable displacement vane pump;

[0071] Figure 17C is an external overall view of the hydraulic energy storage reservoir shown in Figures 17A and 17B; and

[0072] Figure 18 shows diagrammatical sectional views of an oil filled hydraulic vacuum centrifugal extendi ng / retracting crank used in the continuously variable transmission (CVT) means.

[0073] Detailed Description of Figures

[0074] Referring generally to the Figures, and in particular Figure 1 , there is shown an embodiment of a crank set comprising: two cranks 1 , 2. Each crank 1 , 2 has a connection hub 3, 4 each of which respectively connects crank 1 , 2 to a sprocket 12. In use sprocket 12 receives a drive chain (not shown) for transferring torque from pedals (not shown) attached to the cranks 1 , 2 in order to propel a bicycle (not shown), for example.

[0075] The cranks 1 , 2 each include a lower portion 9, 7 in which connection hubs 3, 4 are formed. Lower portions 9 and 7 of cranks 1 and 2, are connected to the sprocket 12 at their hubs 3 and 4. The cranks 1 and 2 each have upper portions 10 which each have a threaded pedal socket 14 each of which receives a pedal (not shown). Each upper portion 10 is adapted to move in an axial direction on the crank from a first position, where a pedal is further from the hub 3, 4; to a second position where a pedal is closer to the hub.

[0076] By varying the length of the crank, the distance of a pedal to a centre of rotation extends on the down stroke towards a bottom dead centre (BDC) whilst simultaneously the opposing crank retracts. This reciprocating motion effectively defines an epicycle path. On an upstroke as the crank returns to a top dead centre (TDC) it does so faster than in conventional (non-extending) cranks as it becomes shorter. Thus so-called ‘mashing’ or spinning of gears therefore becomes easier.

[0077] With reference to the embodiment shown in Figures 1 to 10 a crank set comprises a gear wheel for use with a chain propulsion bicycle, or similar. The gear wheel comprises a standard sprocket 12, connected to a crank set for a bicycle with two cranks, namely a sprocket side crank 1 and a distal side crank 2, the cranks joined by a hollow axle 15, (shown in Figure 3) that allows hydraulic fluid to pass from one crank to the other, having within the axle a hydraulic hose 6.

[0078] The cranks adjust in length from the centre of rotation as the user pedals. The cranks are provided with two portions, namely an upper pedal end and a lower portion, wherein the upper slides within the lower and the sliding is covered by a resilient flexible bellows 8.

[0079] The flexible bellows 8 on each crank protects the internal components of the crank portions when they are extending and retracting. They also prevent dirt build-up and cover a potential trapping area. Alternatively, a telescopic cover may be deployed.

[0080] The crank portions comprise an oblong sectional profile piston which reduces torsional forces exerted on the portions. A shroud bearing between the portions distributes the forces from a user and helps the pedal portions extend and retract smoothly.

[0081] The lower crank portions 9, 7 are a continuation of the hubs 3, 4 on either side, and internally include a dual purpose chamber or cylinder within a hydraulic piston outer sleeve, wherein the hydraulic piston is driven outwards by the hydraulic fluid filling the cylinder, and wherein the piston extends into a pneumatic chamber upon extension of a hydraulic piston block.

[0082] The extension forces air from the pneumatic chamber through a needle valve, and air is subsequently drawn into the pneumatic chamber through the needle valve when the crank contracts, and the hydraulic cylinder retracts.

[0083] The hydraulic cylinder has a stroke of 25 mm and a 7 mm square piston into the upper portion, to limit rotational torque. The cranks are 170 mm extended and 145 mm retracted.

[0084] The embodiment comes with a single 36 tooth (36T) chainring sprocket 12 which can be upgraded to suit terrain and style of riding.

[0085] The crank may be provided in a range of crank sizes including 170 mm, 172.5 mm and 175 mm.

[0086] A hydraulic reservoir located in the hub of the distal side, ensures the hydraulic system always has sufficient hydraulic fluid.

[0087] A bleed valve 5 for hydraulic fluid within the reservoir and thereby present within the cranks and hose of the embodiment, sits under a removable rubber cap at the end of the reservoir and perimetric the hub 4. This bleed valve allows the hydraulic fluid to be topped up and remove air bubbles.

[0088] The hydraulic reservoir is a flexible membrane allowing it to expand and contract depending on hydraulic fluid levels. A 4 mm hydraulic hose 6 transmits hydraulic fluid from one cylinder on one crank to the other as the cranks extend and retract.

[0089] Two pedal end grub screws are used to secure pedals (not shown) in sockets in the extending pedal ends, which form the upper crank portions, in a manner known in the art, wherein the pedals screw into threaded sockets in the pedal ends 10. Alternatively quick release fittings may enable pedals to be fitted and locked to the cranks.

[0090] The pedal sockets 14 comprise a raised outer face around the sockets to prevent a user’s leg from catching as cycling and the sockets comprise tapped holes at the ends of the cranks to allow the user to attach their desired pedals.

[0091] A flow control valve 1 1 is located on the hub 4 distal side, inline within the hose and arranged to control flow through the hose from the sprocket side crank 1 to the distal crank and thereby subsequent extension and retraction, and to the reservoir 5.

[0092] The flow control valve may be deployed to be T shaped and may be screwed between three positions thereby enabling three different modes.

[0093] These are: ‘crossflow’ mode, being right-angled with a blocked arm, for extension and retraction of the cranks; ‘access mode’ in which the valve is open with the hose to the axle and gear wheel crank blocked, (for example to allow a user to replenish the reservoir; and a ‘lock’ mode in which position fluid flow is prevented through the hose to / from the axle and crank and so the reservoir is blocked. This prevents extension and retraction of the cranks.

[0094] Using the flow control valve, a reduction of hydraulic fluid may enable crank length extension can be set shorter depending on the terrain. 4 mm hose connectors screw into the flow control valve, reservoir and connect bottom feeds on the hydraulic cylinders.

[0095] Each crank arm consists of two machined portions that are bolted together, which allows the cylinder and internal tubing to be assembled easily.

[0096] The crank mounting system, bottom bracket axle and fixings are based on standard components.

[0097] Crank parts may be formed hollow or may be ‘bored out’ to reduce weight. They are ideally dimensioned to fit with and connect to a standard chain ring.

[0098] With reference to the second embodiment 199, shown in Figures 6 to 8 two cranks 47, 67 are arranged such that a chain engages the sprocket 12 wherein each of the cranks comprise a hub 64, 63, a lower portion 67, 47, and a distal second end 70 providing a pedal in use; and wherein the upper portions 67, 47 are adapted to move from a first position further from the hub, 64, 63 respectively, to a second position closer to the hub; characterised in that the hub comprises a hydraulic fluid pathway provided by a hydraulic hose, such that hydraulic fluid passes from one crank to the other according to position, and wherein one of the hubs comprises a flow control means controlled by the other hub.

[0099] In the second pictured embodiment an axle 66 between the cranks is provided in two parts, wherein one part is associated with the sprocket crank 47 and another part is associated with the distal opposing crank 67.

[0100] In the hub 64 of the opposing side crank there is internally provided a flow control annular or spool valve, which comprises a spool valve reservoir.

[0101] The reservoir is an annular reservoir located within the valve in the hub of the crank side opposing the gear wheel. The annular reservoir comprises a float that travels in the annular reservoir, which float is spring-loaded, such that this spring-loaded float provides a block helps maintain pressure.

[0102] A bleed valve 72 allows access into the reservoir when addition or bleeding of hydraulic fluid is needed. The bleed valve screws into the reservoir to the far side of the block, such that when the spool valve is in the correct flow position hydraulic fluid may be added to the hose, and cranks.

[0103] The axle 66 comprises a first part 65 connected to the chain side crank, and a second part 56 connected to the opposing side crank or valve side axle part. The two parts are concentric and mutually limited in rotational movement by axle engagement pins or studs from the first part which protrude through limiting slots in the second part, permitting counter-rotation through only 90 degrees.

[0104] The chain side crank is connected to the annular or spool valve, comprising the control and the reservoir.

[0105] The opposing side crank is secured to the second part of the axle, wherein the spool valve may thereby be rotated by the chain side crank within the second axle part. The hydraulic hose passes through the axle and spool valve into the cylinder on the opposing side crank.

[0106] In this way the spool valve may be rotated in relation to the hydraulic fluid pathway, such that the crank and half of axle rotate so pedals are no longer in line.

[0107] On the drive or chain side there is a push button lock 36 at end of the axle 66, which provides a release to allow access to the reservoir and / or control extension or retraction by movement of the valve in relation to the hydraulic fluid pathway. On the opposing side crank there is a slider which moves the flow control valve between positions and provides a rotating spool valve actuation lug. The push button lock is at the end of a push rod, which push rod at another end engages or disengages the slider.

[0108] An inner core connects both halves of the axle. The inner core is precision riveted to one-half of the axle.

[0109] A user is enabled by this embodiment to either use the push lock and slider to control the spool valve, or: push the spring-loaded rod to allow crank separation.

[0110] In some embodiments actuation of the spool valve may be achieved by reversing the direction of rotation of crank (backpedalling) or manually rotating the chainring (a cranks) in a reverse direction.

[0111] The crank mounting system, bottom bracket axle and fixings are based on standard components.

[0112] With reference to the second pictured embodiment the embodiment comprises a simplified version of the first embodiment’s crank portion arrangement, having a sliding telescopic cover instead of a bellows cover to avoid ingress of debris and dirt.

[0113] Figure 10 shows a second partially exploded view of the embodiment of the crank shown in Figure 6. Crank 100 relies on a reciprocating motion generated by a linear actuator.

[0114] Referring now to the embodiments shown in Figures 11 to 16 and 18, Figure 1 1 shows an alternative embodiment of a crank set 200 with a constantly variable crank. Crank 200 includes an upper extending retracting half crank 201 , a fine adjustment ferrule 202, a piston and ram 203, a cylinder head 204, a damper spring 205 housed in cylinder 206. An actuator base 207 connects cylinder 206 to a bottom half of crank with actuator housing 208. There is also shown a compression fitting 209 and a valve fill / bleed 210.

[0115] A modified captive bolt 21 1 retains a slotted plate 1 12 and a sliding slotted plated 213.

[0116] An extension spring 214 and a piston cup and seal 215 are positioned at ends of an extension spring and vacuum chamber 216. A displacement hole enables hollow axle 217 to be modified for compatibility with a modified captive bolt by way of a clamp ring 218.

[0117] Figure 12 shows an alternative embodiment of the crank 300 with a reciprocating crank and balancing spring 300 which comprises an upper half 301 with linear slideways movement. A cable attachment point 302 for receiving a cable 308. Lower half of crank 303 is connected to hollow axle 304 by way of a clamp ring 305.

[0118] A captive bolt 306 is retained by a captive fastener 307. There is also shown a cable assembly 308 which has a loop ferrule at its end. A jockey wheel 309 is housed at either end of hollow axle 304 and a locking pin 310 ensures that jockey wheel housing 31 1 fits inside hollow axle 304 and is retained therein by modified captive fasteners 312 and 313.

[0119] This embodiment relies on the cable 308 to transfer tension being transferred from one crank to another crank under control of an adjustable friction setting provided by a balancing spring 300 and control devices housed within the hollow axle 304.

[0120] Figure 13 shows a yet further embodiment of a reciprocating crank 400 with fluid pathways for use in a reciprocating epicyclic crank set according to the invention in which a left 431 A and right 431 B crank arm each has a piston-in- cylinder whose stroke reciprocates to lengthen or shorten the respective crank arm 431 A, 431 B. This ensures a force applied to each pedal (not shown) connected to respective ends 401 A and 401 B of each crank arm, to cause a variable torque to be transferred to a chainring (not shown).

[0121] A flexible hydraulic reservoir 413 is housed within a chainring spline and includes a bladder 414. Hollow axle 415 has a machined feature for feed pipes 416 (which act as hydraulic fluid via pathways) and a clamp ring 417 retains these components within hollow axle 415.

[0122] An optional sun and planetary gear 418 includes compression springs 419 for clutches, ball bearings 420, a flow regulator screw 421 , a compression olive 422 and right hand hollow stud 423. Also depicted are a bottle screw ferrule 424 which has a left hand threaded hollow stud 425 and a modified captive bolt (manifold) 426.

[0123] Left crank 431 A includes a linear actuator 402 and lower part of left crank has an aperture for receiving the linear actuator 403. This houses a piston (not shown) which delivers hydraulic fluid via pathways 416 to a second piston housed in right hand crank 431 B via a flow control valve, whereby in use hydraulic fluid urges a piston to lengthen crank arm 431 A (in direction of arrow A) during part of its downwards stroke, and to shorten the length of a crank arm 431 B (in direction of arrow B), during part of its upwards stroke.

[0124] A captive bolt 404 has a manifold and a housing front cover 405. A rotary spool valve 406 is retained by a spool valve cover 407 and a sprung ball catch 408. A spur gear unidirectional clutch 409 spools a shaft to which spur planets 410 and a unidirectional ring gear 411 are connected.

[0125] A confined space compression spring 412 enables a captive fastener 427 to ensure jacking lock ring 428 remains in position for linear actuation and holds damper spring 429 in place. Base of actuator 430 is in the form of a cylinder 431 and includes a piston and ram 432 housed within a cylinder head 433. Fine adjustment of the stroke of the includes a piston and ram 432 is by way of adjustment ferrule 434.

[0126] Referring to Figure 14 there is shown an alternative embodiment of a crank 500 with twin opposing sprag clutches 513 and a sun and planetary gear box for providing a constantly variable transmission of torque.

[0127] Upper part of crank pedal attachment 501 slides linearly in left hand (L / H) and right hand ( R / H) threaded ferrule 502. Lower part of crank 503 has an aperture for receiving linear actuator 504. Cross flow tubes 505 have two optional augers 506 which each have hollow axles 507. Manifold 508 includes a flexible bladder 509 which acts as a reservoir for hydraulic fluid.

[0128] A captive bolt 510 arrests a spool valve which has built in flow passages (not shown) and is compatible with standard parts of a bottom bracket in a bicycle frame. A compression seal 51 1 and indexing spool 512 operate in combination with a lost action sprag clutch 513.

[0129] Sun and planetary gears 515 and carrier operate effectively as a torque limiter with slip drive 516. An orbital toothed feature has a captive bolt is shown with a slotted plate 517. A toothed orbital gear 518 is shown in detail with the hollow axle 507.

[0130] A unidirectional clutch 1 19 is provided to oppose the direction of operation of sprag clutch 513. A lock cap 520 has a spool 521 .

[0131] The sub-assembly components are listed for the sake of completeness:

[0132] 522 Base of linear actuator

[0133] 523 Tube cylinder

[0134] 524 Cap with restrictor

[0135] 525 Piston 526 Dual push compression fitting

[0136] 527 Compression fitting (olive)

[0137] 528 Planet carrier and clutch shaft

[0138] 529 Ball bearing

[0139] 530 Compression springs

[0140] 531 Spur gear planets with unidirectional clutch (Sprag gear) 531 a Spur gear planets with special flow through feature,

[0141] Referring now to Figure 15 there is shown an alternative embodiment of a basic reciprocating crank 888 with balancing / dampening springs. A modified standard captive bolt and contra free rotating, opposing sprag clutches and compound planetary gear set or single clutch and simple planetary set ball catch assists spool valve selection. The embodiment shown in Figure 15 operates in forwards and reverse pedalling modes.

[0142] As mentioned above the other modes include an ‘access mode’ in which the valve is open with the hose to the axle and gear wheel crank blocked, (for example to allow a user to replenish the reservoir; and a ‘lock’ mode in which position fluid flow is prevented through the hose to / from the axle and crank and so the reservoir is blocked.

[0143] Referring now to Figures 16A to 16D, Figure 16A shows a section through a continuously variable transmission (CVT) means and shows variable displacement of two sets of six axial pistons 630 which act with Archimedean screws (or augers) 610 and 620 to pump hydraulic fluid as part of a continuously variable transmission (CVT) means. Each set of six pistons 630 is arranged in the form of a carrousel in capstans 640 and 650 (Figure 16D) and are driven by augers 610 and 620. Pairs of sprung valve plates 660A and 660B and 670A and 670B retain the pistons in the capstans 640 and 650.

[0144] The continuously variable transmission (CVT) means enables a user to pedal backwards to operate a spool valve (not shown), so that in cross flow mode, fluid is forced from the reservoir to operate the cranks in a reciprocating manner. When operating in this mode the two-part axle allows the two cranks to disengage one from another and actuate a reservoir or release a lock extension of the pedals. The two cranks have a return mechanism, such as a spring, to enable the pedals to return to their normal orientation, that is extending in diametrically opposed directions.

[0145] Figure 16B shows an overall isometric, part sectional view of the continuously variable transmission (CVT) means and shows the augers 610 and 620 housed within a capstans 640 and 650 and augers 610 and 620 removed. The operation of the contra-rotating augers 610 and 620 pressurises the hydraulic fluid.

[0146] Figure 16C is a sectional view of the continuously variable transmission (CVT) means and shows a neutral position in which contra-rotating augers 610 and 620 are actuated and acts as swash plates that move in tandem. Figure 16D is a transverse sectional view which shows screw threads of contra-rotating augers 610 and 620 used to pressurise the continuously variable transmission (CVT) means by way of swash plates.

[0147] In another embodiment an oval chainring (not shown) may be used as an offset epicyclic which in use becomes epi-trochoidal path to create a double power peak which may be deployed for example in sprints or uphill stretches. Such an arrangement is adapted with standard features to enable it to be retrofitted to bicycles axles housings and to operate with existing chainrings and pedals.

[0148] Figures 17A to 17D show views of radial vanes of pressure valves which are used to pressurise hydraulic fluid and store it under pressure. Figure 17C shows an external plan view of the displacement axle vane pump.

[0149] Referring to Figure 17B is an exploded diagrammatical view and shows internal components of a variable displacement axle vane pump 700 which acts as an energy storage device. Pistons 750, 752, 754, 756, 758 and 760 are arranged equidistantly around a circumference of a cylinder 720. Six cups or recesses are shown in hidden detail within axle housing 710. A bleed valve 740 is also shown. The pistons 750, 752, 754, 756, 758 and 760 are housed within housing 730 of the variable displacement axle vane pump 700. When rotated a hydraulic fluid, stored within the housing 730 is compressed and stored for subsequent use

[0150] Figure 18 shows diagrammatical sectional views of an oil filled hydraulic vacuum centrifugal extendi ng / retracting crank used in the continuously variable transmission (CVT) means.

[0151] In the embodiment depicted in the right hand pane, a two-part axle 920 has separate left and right hollow portions each defining a first hydraulic reservoir or chamber 809 and a second hydraulic reservoir or chamber 810. Springs 931 , 932 and 933 are shown connecting pistons 935 and 936. As hydraulic fluid is drawn from each reservoir or chamber 809 and 810 to extend either a left or right crank as described above, the springs 931 , 932 and 933 extend, so storing energy in the springs which recover on a reverse stroke and acts to suck the hydraulic fluid to its respective chamber or reservoir.

[0152] At the end of a downward part of a pedalling motion, the force exerted by a pedal reduces and either the left or right crank starts to retract as it moves on an upward path of its cycle. Springs 931 , 932 and 933 act to retract either piston 935 or 936 and so increase the rate at which hydraulic fluid is returned from a crank to the reservoir speed. Therefore, as one reservoir on one side fills, the reservoir on the opposite side empties and this pattern repeats as a cyclists turns the left and right pedals. Thus springs 931 , 932 and 933 attached to pistons 935, 936 in each of the hydraulic fluid chambers or reservoirs 809, 810, extend and retract as hydraulic fluid exhausts from and returns to the chamber or reservoir 809, 810 to / from a piston-and-cylinder in the crank. The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of protection as defined by the claims.

Claims

Claims1 . A crank set comprising: a left and right crank arm, each crank arm having a piston-in-cylinder whose stroke reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that a hydraulic fluid pathway connects the two pistons via a flow control valve, whereby in use hydraulic fluid urges a piston to lengthen a first crank arm, during part of its downwards stroke, and to shorten the length of a second crank arm, during part of its upwards stroke.

2. A crank set according to claim 1 wherein the flow control valve is located in a bottom bracket.

3. A crank set according to claim 1 or 2 wherein the flow control valve is adjustable to vary a rate of transfer of hydraulic fluid between the two cylinders.

4. A crank set according to any preceding claim includes first and second hydraulic fluid chambers or reservoirs.

5. A crank set according to claim 4 wherein springs attach to pistons in each of the hydraulic fluid chambers or reservoirs, the springs extend and retract as hydraulic fluid exhaust from and return to the chamber or reservoir from a piston-and-cylinder.

6. A crank set according to any preceding claim wherein each crank arm comprises a sliding distal portion and fixed proximal portion.

7. A crank set according to claim 6 wherein the distal portion includes a pedal socket.

8. A crank set according to claim 7 wherein the pedal socket is threaded to receive a threaded pedal.

9. A crank set according to any of claims 1 to 7 wherein the pedal socket includes a quick release means to receive a pedal.

10. A crank set according to any of claims 6 to 9 wherein a shroud bearing is fitted between the sliding distal portion and the fixed proximal portion for distributing a force applied to a pedal.

11. A crank set according to claim 10 wherein the shroud bearing is oblong shaped to resist bending.

12. A crank set according to any preceding claim wherein a crank has a sliding telescopic cover or a bellows cover.

13. A crank set according to any preceding claim wherein a chain ring is fitted to one of the cranks.

14. A crank set according to any preceding claim wherein a means is provided in a chamber which is in fluid communication with each piston-in- cylinder and allows variable adjustment of a length of a crank according to a rotational position of a crank.

15. A crank set according to any preceding claim wherein the flow control valve is adjustable to switch between modes.

16. A crank set according to any preceding claim comprises a protected by a flexible boot.

17. A continuously variable transmission (CVT) system for a bicycle is mounted in a bottom bracket of a bicycle frame and is driven by left and right cranks, the CVT system comprises an epicyclic gear system which drives an auger that pumps an hydraulic fluid to a pressurised reservoir when the cranks are rotated in a first direction and when the cranks are driven in a reverse direction pressurised hydraulic fluid is released.

18. A continuously variable transmission (CVT) system according to claim 17 wherein a release valve is provided which when actuated releases pressurised hydraulic fluid.

19. A continuously variable transmission (CVT) system according to claim 17 or 18 includes swash plates which when counter-rotated pressurise the hydraulic fluid.

20. A continuously variable transmission (CVT) system according to any of claims 17 to 19 wherein a flow control valve allows reduction of available hydraulic fluid from the reservoir.21 . A crank set comprising: two cranks arranged such that a chain engages the sprocket wherein each of the cranks comprise a hub, a lower portion , and a distal second end providing a pedal in use; and wherein the upper portions are adapted to move from a first position further from the hub, to a second position closer to the hub; characterised in that the hub comprises a fluid pathway such that fluid passes from one crank to the other according to the position, and wherein one of the hubs comprises a flow control means controlled by the other hub.

22. An energy storage system for use with a crank set as hereindefined, the energy storage system includes a hydraulic reservoir capable of receiving pressurised fluid and storing the fluid under pressure and a release valve which when operated releases pressurised hydraulic fluid to drive a piston-in-cylinder in either a left or a right crank arm to, each crank arm having a whose stroke reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that a fluid pathway connects the two pistons via a flow control valve, whereby in use fluid urges a first piston to lengthen a first crank arm, during part of its downwards stroke, and a second to retract to shorten the length of a second crank arm, during part of its upstroke.

23. A crank set comprising: a left and right crank arm, each crank reciprocates to lengthen or shorten the respective crank arm, thereby enabling a torque, applied to a pedal connected to an end of each crank arm, to be varied, characterised in that an interconnecting cable or connects the two cranks such that when a first crank arm extends during part of its downwards stroke, the interconnecting cable shortens the length of a second crank arm during part of its upwards stroke.

24. A bicycle or driven pedal powered machine or vehicle fitted with a crank set according to any of claims 1 to 16, 21 or 23.

25. A static exercise machine, for example an exercise bicycle, treadmill or other pedal powered exercise apparatus fitted with a crank set according to any of claims 1 to 16, 21 or 23.

Images