WO2015155497A1

WO2015155497A1 - Powered unicycle device and drive arrangement for the same

Info

Publication number: WO2015155497A1
Application number: PCT/GB2015/050272
Authority: WO
Inventors: Timur Artemev
Original assignee: Timur Artemev
Priority date: 2014-04-11
Filing date: 2015-02-02
Publication date: 2015-10-15
Also published as: GB201406561D0; GB2525042A

Abstract

A self-balancing powered unicycle having a single hubless wheel (120) is disclosed, along with a drive arrangement (135) for the same. The drive arrangement (135) comprises: a pair of drive wheels adapted to apply a drive force to the rim of the single hubless wheel (120); and at least one motor (155) adapted to drive the pair of drive wheels. The drive wheels are inclined with respect to the plane of the single hubless wheel.

Description

POWERED UNICYCLE DEVICE AND DRIVE ARRANGEMENT FOR THE

SAME Field of Invention

The present invention relates to powered single-wheeled devices and more particularly to powered unicycles with self-balancing functionality. Background to the Invention

Powered self-balancing vehicles for use while standing are known. Such vehicles include two-wheeled vehicles and single-wheeled vehicles (i.e. unicycles).

In a powered self-balancing unicycle, an electronic or mechanical system that controls the wheel in the appropriate direction is typically used to achieve fore-and-aft balance. This type of automatic fore-and-aft balance technology is well known and described, for example, in United States Patent number 6,302,230. A sensor and electronic equipment are typically provided. Information detected by the sensor and the electronics is relayed to a motor. The motor drives the wheel in the appropriate direction and at sufficient speed to maintain fore-and-aft balance. Known embodiments of a powered self-balancing unicycle do not include a handle bar supported by a shaft. For example, United States Patent Application Serial Number 12/281 , 101 presents a single wheel, coupled to a frame to which two platforms (one on each side of the wheel) are attached. Summary of the invention

According to a first aspect of the invention, there is provided a drive arrangement for a self-balancing powered unicycle having a single hubless wheel, the drive arrangement comprising: a pair of drive wheels adapted to apply a drive force to the rim of a single hubless wheel; and at least one motor adapted to drive the pair of drive wheels, wherein the drive wheels are inclined with respect to the plane of the single hubless wheel. There is proposed a self-balancing powered unicycle drive arrangement comprising drive wheels that are arranged at an angle from the plane of the single wheel. Such a drive arrangement may provide more room between the drive wheels (thereby allowing for more components to be positioned between and/or near the drive wheels, such as braking, gearing, flywheel and/or control components for example) whilst also enabling use of a slimmer wheel rim. In other words, by inclining the drive wheels to the plane of the single hubless wheel, the lateral extent of the drive wheels at the point of contact with the wheel rim may be smaller than the lateral extent of the drive wheels at the point furthermost from the wheel rim. The increased spacing between the drive wheels at the point furthermost from the wheel rim may provide a larger space for accommodating components of the drive arrangement. Embodiments may therefore employ a larger, more powerful/complex drive motor arrangement without needing to increase in the width of the wheel rim. Also, the angled drive wheels may restrict or prevent lateral movement or slippage of the wheel rim with respect to the drive arrangement.

Embodiments may provide a drive arrangement which can be quickly and easily connected or removed to/from the unicycle wheel for repair or replacement, for example. Also, by being adapted to be fitted inside the wheel, embodiments may help to reduce the overall size or profile of the unicycle, thereby improving its portability.

In embodiments, the angle formed between at least one drive wheel and the plane of the single hubless wheel may be greater than 0° and less than 80°. Further, in some embodiments, the angle formed between the at least one drive wheel and the plane of the single hubless wheel may be less than 45°. The drive wheels may be adapted to contact the rim of the single hubless wheel at angle substantially perpendicular to the inner rim surface of the rim.

For the avoidance of doubt, reference to a single wheel should be taken to mean the generally circular unit that is positioned between the legs of a user and adapted to rotate about an axis to propel the unicycle in a direction during use. The single wheel may therefore be formed from one or more tyres and/or hubs that are coupled together (via a differential, for example). For example, an embodiment may comprise a single hubless wheel having a single hubless rim with a plurality of separate tyres fitted thereon. Alternatively, an embodiment may comprise a single hubless wheel formed from a plurality of hubless rims (each having a respective tyre fitted thereon), wherein the plurality of hubless rims are coupled together via a differential bearing arrangement.

According to another aspect of the invention, there is provided a self- balancing powered unicycle comprising: a single hubless wheel; and a drive arrangement according to an embodiment. Embodiments may provide a self-balancing powered unicycle that is modular in nature. The drive arrangement may be easily engaged and disengaged to/from the wheel to facilitate rapid and simple repair or replacement.

Brief description of the drawings

An example of the invention will now be described with reference to the accompanying diagrams, in which:

FIG. 1 is an isometric view of an embodiment of a powered unicycle device in a closed configuration;

FIG. 2 is an exploded diagram of components internal to the casing of FIG. 1 ,

FIGS. 3A & 3B are side and front elevations, respectively, of the embodiment of FIG. 1 , wherein the casing is moving between a closed and open configuration; FIGS. 4A & 4B are side and front elevations, respectively, of the embodiment of FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in a stowed configuration;

FIG. 5 is an isometric view of the embodiment of FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in a stowed configuration;

FIGS. 6A & 6B are side and front elevations, respectively, of the embodiment of FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in an active configuration;

FIG. 7 is an isometric view of the embodiment of FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in an active configuration;

FIGS. 8A & 8B are side and front elevations, respectively, of a drive arrangement according to an embodiment;

FIG. 9 is a cross sectional view of the drive arrangement of FIG. 8 taken along the line C-C;

FIG. 10 is a side elevation of the drive arrangement of FIG. 8 wherein internal components are depicted by dashed lines;

FIGS. 1 1A-1 1C depict part of a drive arrangement according to an embodiment of the invention; and

FIGS. 12A-12D illustrate various motor and drive wheel arrangements according to embodiments in combination with various inner rim surface profile shapes. Detailed description

FIGS. 1 -5 show one embodiment of a powered unicycle device 100. FIG. 1 shows the powered unicycle device 100 with a casing 110 in a closed configuration so that it encases a single wheel 120. Here, the casing 1 10 is formed from a first, upper portion 1 10A that covers the top (uppermost) half of the wheel 120, and a second, lower portion 1 10B that covers the bottom (lowermost) half of the wheel 120. FIG 2 illustrates an exploded view of components internal to the casing 1 10, namely a wheel 120 and drive arrangement 135. Referring back to FIG. 1 , the wheel 120 spins about a central axis 125. The first, upper portion 1 10A of the casing is retained in a fixed position relative to the central axis 125, whereas the second, lower portion 1 10B of the casing is adapted to rotate about the central axis 125. Rotation of the second lower portion 1 10B about the central axis 125 moves the casing between closed and open configurations (as illustrated by FIGS. 3-4). In the closed configuration (shown in FIG.1 ), the casing 1 10 encloses the wheel 120 so that the outer rim 130 of the wheel 120 is not exposed. In the open configuration (shown in FIG. 5), the outer rim 130 of the wheel 120 is exposed so that it can contact a ground surface.

Referring now to FIG. 2, rotation of the single wheel 120 is driven by a drive arrangement 135 according to an embodiment. The drive arrangement 135 includes guide wheels 40 attached to an outwardly facing side of respective batteries 145. In this embodiment, there are two pairs of angled guide wheels 140, wherein the two guide wheels in each pair share are tapered or conical such that they have a sloped surface which is not perpendicular to the radial plane of the single wheel 120. Put another way, the contact surface of each guide wheel is inclined with respect to the radial plane of the single wheel 120. The guide wheels 140 of each pair are also positioned spaced apart to provide a gap between the two guide wheels of a pair.

A rib 150 is provided around the inner rim of the wheel 120 and fits into the gap between the two guide wheels 140 in each pair. The guide wheels 140 are therefore adapted to contact with the inner rim of wheel 120 where they spin along with wheel 120 and hold wheel 120 in place by way of the rib 150. Of course, it will be appreciated that other arrangements, including those with only one guide wheel per battery 145, are possible.

The batteries 145 are mounted on a motor 155 which drives a pair of drive wheels 160 positioned at the lowermost point along the inner rim of the wheel 120. The batteries 145 supply power to motor 155 and, this embodiment, there are two batteries in order to create a balanced distribution of volume and weight. However, it is not necessary to employ two batteries 145. Also, alternative energy storage arrangements may be used, such as a flywheel, capacitors, and other known power storage devices, for example. The drive arrangement 135 is adapted to be fitted inside the wheel. In other words, the drive arrangement is sized and shaped so that it can be positioned in the void define by the inner rim of the wheel 120. Further, the drive arrangement 135 is movable between a locked configuration and an unlocked configuration.

In the locked configuration, when fitted inside the wheel 120, the drive arrangement 135 engages with the rim of the wheel 120 to prevent its removal from the wheel. Here, in the embodiment shown, the guide wheels 140 contact the inner rim of wheel 120 and hold wheel 120 in place by way of the rib 150 when the drive arrangement is in the locked configuration.

In the unlocked configuration, when fitted inside the wheel 120, the drive arrangement 135 disengages with the rim of the wheel 120 to permit its removal from the wheel. Here, in the embodiment shown, the drive arrangement contracts in size when moved from the locked configuration to the unlocked configuration so that the guide wheels 140 no longer contact the inner rim of wheel 120 and no longer hold the wheel 120 in place by way of the rib 150. Such reduced size (e.g. diameter) of the drive arrangement 135 when in the unlocked configuration thus enables the drive arrangement 135 to be removed from the wheel 120.

It will therefore be understood that the drive arrangement 135 of the illustrated embodiment can be quickly and easily connected or removed to/from the wheel 120 for repair or replacement, for example. Arranging the drive arrangement 135 in the unlocked configuration permits its removal or fitting from/to the wheel 120 (because, for example, its dimensions when in the unlocked configuration permit its fitting inside the wheel). When fitted inside the wheel 120, the drive arrangement can be arranged in the locked configuration so that it engages with the rim of the wheel 120 to prevent its removal (because, for example, its dimensions when in the locked configuration prevent the drive arrangement from being removed from the wheel). When the drive arrangement 135 is fitted inside the wheel and in the locked configuration, a pair of drive wheels (not visible in Figure 2) is adapted to contact the inner rim of the wheel 120. Here, the pair of drive wheels comprises first and second rollers that are inclined with respect to the radial plane of the wheel. By way of contact with the inner rim of the wheel 120, the drive wheels transmit torque from the motor 155 to the wheel 120. It will be understood that this drive system operates by friction and it may be preferable to avoid slippage between the drive wheels and the inner rim of wheel 120. Positioning the drive wheels at the lowermost point enables the weight of a user to provide a force which presses the drive wheels against the inner rim of the wheel 120, thereby helping to reduce or avoid slippage.

Referring to FIGS. 5-7, two foot platforms 165 are coupled to the second, lower portion 1 10B of the casing 1 10, with one on each side of wheel 120. In the open configuration, the foot platforms 165 are movable between a stowed configuration, wherein the foot platforms are substantially parallel with the plane of the wheel (as shown in FIG. 5), and an active configuration, wherein the foot platforms are substantially perpendicular to the plane of the wheel (as shown in FIGS. 6-7) so as to support a user's weight. Thus, in this embodiment, the foot platforms 165 are movable between: (i) a stowed configuration wherein they are flat against the side of the wheel and can be rotated (with the second, lower portion 1 10B of the casing) about the central axis 125 so as to be positioned inside (and covered by) the first, upper portion 1 1 OA of the casing; and (ii) an active configuration, wherein they project outwardly from the side of the wheel to provide a support surface for the feet of a user. Accordingly, the foot platforms 165 are upwardly foldable into a stowed configuration that narrows the profile of the unicycle 100 to aid in storage and carrying. In use, the foot platforms are moved to the active configuration, and the user stands with one foot on each platform 165. The drive arrangement 135 includes a gyroscope or accelerometer system 170 which senses forward and backward tilt of the device in relation to the ground surface and regulates the motor 155 accordingly to keep the device upright. In this way, the user is provided a way of controlling the acceleration and deceleration of the unicycle by varying the pressure applied to various areas of the foot platforms 165. It also enables the unicycle to self-regulate its balance in the fore-and-aft plane.

When not in use, the foot platforms 165 are moved to the stowed configuration and then rotated (with the second, lower portion 1 1 OB of the casing) about the central axis 125 so as to move the casing to the closed configuration. Thus, in the closed configuration, the foot platforms 165 are stored inside the casing (covered by the first, upper portion 1 10A of the casing).

The embodiment of FIGS. 1 -7 also comprises a lifting handle 180 coupled to the drive arrangement 135 via a plurality of rods 185. The lifting handle 180 is positioned at the top of the casing 1 10, above the wheel 120, and may be used to hold the unicycle 100 above the ground, for example to enable a user to lift, carry, convey or place the unicycle 100.

A retractable carrying strap 190 is also provided and attached to the top of the casing 100. The carrying strap 190 may be used to carry the unicycle 100, for example over the shoulder of user. A hook may be provided on the bottom of the case to create rucksack-like belts from the carrying strap 190.

Here, the handle 180 is also adapted to trigger an activating system which moves the casing between the closed and open configurations. More specifically, movement of the handle relative to the casing 1 10 in an outward direction (away from the center of the wheel 120) as depicted by an arrow labeled "A", triggers the activating system which in turn causes the second, lower portion 1 10B of the casing to rotate about the central axis to move from the closed configuration to the open configuration. This process of rotating the second, lower portion 1 10B of the casing from the closed configuration to the open configuration is depicted by FIGS. 3-4.

It will therefore be understood that, in this embodiment, the lifting handle 180 may be used to initiate the activating system and move the casing from the closed configuration to the open configuration. Thus, when a user holds the unicycle 100 by the handle above the ground, the force of the unicycle pulling downwards under the influence of gravity causes upward movement of the lifting handle 180 relative to the casing 1 10 (as depicted by an arrow labeled "A") which triggers the activating system. In response to this trigger, the activating system moves the casing to the open configuration (depicted in FIGS. 4 & 5) so that the lowermost portion of the wheel is exposed and can be brought into contact with a ground surface. In other words, when lifted by the lifting handle 180, the unicycle may be arranged in an open configuration ready for deployment (e.g. placement on a ground surface).

Further, when placed on the ground and the balance control system is activated, the depression of the handle in a downward/inward direction (towards the centre of the wheel 120) as depicted by an arrow labeled "B" moves the rods 185 and cause the foot platforms to move from the stowed configuration (shown in FIGS. 4 & 5) to the active configuration (shown in FIGS. 6 & 7). Here, downward movement of the rods causes the foot platforms 165 to rotate about an axis and the rods then hold the foot platforms 165 in place to support the feet of user.

When the user no longer desires to use the unicycle, the user pulls on the lifting handle to lift the unicycle from the ground. This results in upward movement of the lifting handle 180 and the associated rods 185 relative to the casing 1 10 (as depicted by an arrow labeled "A") which then causes the foot platforms to move from the active configuration (shown in FIGS. 6 & 7) to the stowed configuration (shown in FIGS. 4 & 5).

Turning now to FIGS. 8-10, there is depicted a drive arrangement 200 according to an embodiment of the invention. Such a drive arrangement 200 is adapted to fit inside the wheel of a hubless unicycle so that it may be used to drive (e.g. rotate) the wheel.

The drive arrangement 200 is adapted to be movable between a locked (or expanded) configuration, in which when fitted inside a hubless wheel the drive arrangement engages with the rim of the wheel to prevent its removal from the wheel, and an unlocked (or contracted) configuration, in which when fitted inside the hubless wheel the drive arrangement 200 disengages the rim of the wheel to permit its removal from the wheel. The drive arrangement 200 may therefore be quickly and easily connected to (or removed from) the hubless wheel for repair or replacement.

The drive arrangement 200 comprises a motor 210 adapted to drive a hubless wheel by applying a force to the inner rim of the hubless wheel. Here, the drive arrangement 200 comprises a pair of drive wheel 220A and 220B which are driven by respective motors 210 and adapted to contact the inner rim of the wheel (when the drive arrangement is fitted inside the wheel and in a locked configuration). The drive wheels 220A and 220B are angled with respect to the radial plane of the hubless wheel so that the radial plane of each drive wheel 220A and 220B is inclined with respect to the radial plane of the hubless wheel. Thus, the drive wheels 220A and 220B are arranged in a V-shape, wherein the vertex of the V-shape point towards the center of the drive arrangement 200.

The drive arrangement 200 also comprises guide wheels 230 attached to an outwardly facing side of respective batteries 240. Here, there are two pairs of guide wheels 230. The two guide wheels in each pair share are angled in opposing directions away from the radial plane of the hubless wheel. Thus, when viewed from directly above the drive arrangement 200, the radial planes of a pair of guide wheels 230 form a V-shape with the vertex of the V-shape pointing towards the center of the drive arrangement 200. In other words, the radial plane of each guide wheel is inclined with respect to the radial plane of the hubless wheel (driven by the drive arrangement 200). The guide wheels I 1

230 of each pair are also positioned spaced apart to provide a gap between the two guide wheels of a pair.

When the drive arrangement is fitted inside the wheel and in a locked configuration, a rib provided around the inner rim of the wheel fits into the gap between the two guide wheels 230 in each pair. The guide wheels 230 are therefore adapted to contact with the inner rim of wheel where they spin along with the wheel and prevent its removal in the locked configuration. The batteries 240 are mounted on the motor 210. The batteries 240 supply power to motor 210. Alternative energy storage arrangements may of course be used, such as a flywheel, capacitors, and other known power storage devices, for example. Also mounted on the motor 210, and provided in-between the batteries 240, is a balance control system 250. The balance control system 250 is adapted to maintain fore-aft balance of the unicycle device by controlling the motor.

Within the balance control system 250, there is provided a locking system which is adapted to move the drive arrangement 200 from the unlocked configuration to the locked configuration when activated. Here, the locking system comprises a rotatably mounted locking bar 270 (visible in FIG. 10) that can be rotated (using an exposed portion 280) between a locked and unlocked position. In the locked position (depicted in FIG. 10), the locking bar 270 extends into the batteries 240 to exert an outwardly extending pressing force on the batteries which tends to move the batteries in an outward direction (i.e. a direction extending radially outward from the center of the drive arrangement 200). This pushes the batteries outwardly so as to increase the diametrical extent of the drive arrangement 200. In other words, moving (e.g. rotating) the locking bar 270 to the locked position expands the size of the drive arrangement 200 by moving the batteries outwards (from the centre of the drive arrangement 200). Conversely, when the locking bar 270 is moved to the unlocked position, the pressing force is removed from the batteries 240 and they move in an inward direction (i.e. a direction extending radially inward towards the center of the drive arrangement 200), due to a biasing force from a spring for example. This moves the batteries inwardly so as to decrease the diametrical extent of the drive arrangement 200. Put another way, moving (e.g. rotating) the locking bar 270 to the unlocked position contracts the size of the drive arrangement 200 by moving the batteries inwards (towards the centre of the drive arrangement 200).

The locking bar 270 of this embodiment is adapted to be turned manually by a user. However, in alternative embodiments, the locking bar 270 may be turned using a motor arrangement which is activated in response to a signal provided by the user for example. It will therefore be appreciated that the locking system may comprise an electrical or mechanical locking arrangement (or a combination thereof) which moves the drive arrangement 200 between the locked and unlocked configuration.

Here, the locking bar 270 is formed from an electrically conductive material (such as metal) so that it forms an electrical connection between the batteries 240 and the balance control system 250 and the motor 210 when in the locked position. Thus, when in the unlocked position, the balance control system 250, the motor 210 and the batteries 240 may be electrically isolated from each other, thereby preventing operation of the drive arrangement 200. This may therefore provide a safety feature which prevents the motor 210 or control system 250 from operating, for example, when the drive arrangement 200 is placed into the unlocked configuration (for removal, replacement or repair, for example).

Here, the drive arrangement 200 also comprises a charging interface 290 for connecting to a power supply and charging the batteries 240. The charging interface 290 comprises a universal plug 295 attached to a retractable cable 300. The universal plug 295 can be fitted in an electrical socket so as to supply electrical energy to the batteries via the cable 300. Other arrangements for charging the batteries may be used, such as an inductive (or "wireless") charging arrangement for example. Embodiments may therefore provide a self-balancing powered unicycle that is modular in nature. The drive arrangement may be easily engaged and disengaged to/from the wheel to facilitate rapid and simple repair or replacement.

Turning now to FIGS. 11A-1 1 C, there is depicted part of a drive arrangement according to an embodiment of the invention. The part of a drive arrangement is depicted without other parts of the drive arrangement, such as guide wheels, batteries, foot platforms, and balance control system. Instead, depicted is motor and drive wheel arrangement which is coupled to a support framework 420.

Here, the motor and drive wheel arrangement comprises first 430 and second 440 motors coupled to first 450 and second 460 drive wheels, respectively. The first motor 430 is arranged to drive rotation of the first drive wheel 450, and the second motor 440 is arranged to drive rotation of the second drive wheel 460. The first 450 and second 460 drive wheels are adapted to contact the inner rim of a single hubless wheel (not shown in Figures 11A-1 1 C) and drive rotation of the single hubless wheel.

Here, the first 430 and second 440 motors may be independent from each, thus providing for redundancy in the motors. If one motor fails, the other motor may still continue to operate. Other embodiment may employ a single motor to drive both the first 430 and second 440 motors.

A protective covering 470 is provided above the first 450 and second 460 drive wheels so as to partially cover the drive wheels and protect against dust/dirt ingress. Both the first 450 and second 460 drive wheels are inclined with respect to the plane X of a single hubless wheel that the drive arrangement is adapted to drive. In other words, rather than being parallel to the radial plane X of the single hubless wheel to be driven by the drive wheels, the drive wheels are titled from parallel to the radial plane X of the single hubless wheel (i.e. tilted from vertical in Figure 1 1 C) so that there is a non-zero angle Θ formed between the plane of a drive wheel and the plane X of the single hubless wheel. Here, the angle Θ formed between the plane of each drive wheel and the plane X of the single hubless wheel is approximately 25°. Of course, other angles may be formed between the plane of each drive wheel and the plane X of the single hubless wheel, and such angles may be in the range of 0 < Θ <= 90° for example. Also, the first 450 and second 460 drive wheels need not be inclined with respect to the plane of the single hubless wheel by the same angle. The first 450 and second 460 drive wheels may therefore be inclined (with respect to the radial plane X of single hubless wheel) by differing angles.

Turning now to FIGS. 12A-12D, there is depicted various motor and drive wheel arrangements in combination with various inner rim surface profile shapes.

Figure 12A shows a single hubless wheel having a tyre 480 mounted on a rim 490. The rim 490 has an inner rim surface with a non-flat profile. More specifically, the inner rim surface comprises two sloped flat surfaces that form a peak projecting inwardly towards the center of the single hubless wheel (i.e. projecting upwardly in Figure 12A).

The first 450 and second 460 drive wheels are adapted to apply a drive force to the inner rim 490 of the single hubless wheel. The drive wheels 450 and 460 are inclined with respect to the radial plane X of the single hubless wheel. Thus, each of the first and second drive wheels form an angle Θ between their radial plane and the radial plane X of the single hubless wheel. Here, the angle Θ formed between the radial plane of each drive wheel and the plane X of the single hubless wheel is approximately 20°.

It is noted that, in this example, the drive wheels 450 and 460 are angled from vertical by the same angle Θ that the sloped flat surfaces of the inner rim surface are inclined from horizontal so that the drive wheels 450 and 460 contact the inner rim 490 of the single hubless wheel at angle approximately perpendicular to the surface of the inner rim 490.

Figure 12B shows a single hubless wheel having an inner rim surface with a non-flat profile, wherein the inner rim surface comprises two curved and sloped surfaces that form a peak projecting inwardly towards the center of the single hubless wheel (i.e. projecting upwardly in Figure 12B).

The first 450 and second 460 drive wheels are adapted to apply a drive force to the inner rim 490 of the single hubless wheel. As with the previous example, the drive wheels 450 and 460 are inclined with respect to the radial plane X of the single hubless wheel. Each of the first and second drive wheels therefore form an angle Θ between their radial plane and the radial plane X of the single hubless wheel. Further, the drive wheels 450 and 460 are angled from vertical so that the drive wheels 450 and 460 contact the inner rim 490 of the single hubless wheel at angle approximately perpendicular to the surface of the inner rim 490.

Figure 12C shows a single hubless wheel having an inner rim surface with a non-flat profile, wherein the inner rim surface comprise has a flange or rib 500 projecting inwardly towards the center of the single hubless wheel (i.e. projecting upwardly in Figure 12C).

The first 450 and second 460 drive wheels are adapted to apply a drive force to the inner rim 490 of the single hubless wheel. The drive wheels 450 and 460 are inclined with respect to the radial plane X of the single hubless wheel. Each of the first and second drive wheels therefore form an angle Θ between their radial plane and the radial plane X of the single hubless wheel. Here, the drive wheels 450 and 460 are positioned on either side of the flange/rib 500 so that the flange or rib 500 is situated in the gap between the drive wheels 450 and 460. Figure 12D shows a single hubless wheel having an inner rim surface with a non-flat profile, wherein the inner rim surface comprise two sloped flat surfaces that form a trough projecting into the inner rim (i.e. projecting downwardly in Figure 12D).

The first 450 and second 460 drive wheels are adapted to apply a drive force to the inner rim 490 of the single hubless wheel. The drive wheels 450 and 460 are tilted or slanted with respect to the radial plane X of the single hubless wheel. Thus, each of the first and second drive wheels form an angle Θ between their radial plane and the radial plane X of the single hubless wheel. Here, the angle Θ formed between the radial plane of each drive wheel and the plane X of the single hubless wheel is approximately 15°.

It is noted that, in this example, the drive wheels 450 and 460 are angled from vertical by the same angle Θ that the sloped flat surfaces of the inner rim surface are inclined from horizontal so that the drive wheels 450 and 460 contact the inner rim 490 of the single hubless wheel at angle approximately perpendicular to the surface of the inner rim 490. Thus, when viewed from the viewing angle depicted in Figure 12D, the drive wheels 450 and 460 appear to overlap each other (although they are offset from each other in the Z-direction extending in to page).

While specific embodiments have been described herein for purposes of illustration, various modifications will be apparent to a person skilled in the art and may be made without departing from the scope of the invention.

It will be appreciated that a variation on the hubless drive arrangement described above may be based on gear transmission instead of friction. The drive wheels may thus be replaced by circular gears for example, and accordingly the inner rim of the hubless wheel may have alternating protruding and indented segments (i.e. "teeth").

Claims

1. A drive arrangement for a self-balancing powered unicycle having a single hubless wheel, the drive arrangement comprising:

a pair of drive wheels adapted to apply a drive force to the rim of a single hubless wheel; and

at least one motor adapted to drive the pair of drive wheels, wherein the drive wheels are inclined with respect to the plane of the single hubless wheel.

2. The drive arrangement of claim 1 , wherein the angle formed between at least one drive wheel and the plane of the single hubless wheel is greater than 0° and less than 80°.

3. The drive arrangement of claim 2, wherein the angle formed between the at least one drive wheel and the plane of the single hubless wheel is less than 45°.

4. The drive arrangement of any preceding claim, wherein the drive wheels are adapted to contact the rim of the single hubless wheel at angle substantially perpendicular to the inner rim surface of the rim.

5. The drive arrangement of any preceding claim, further comprising a pair of tapered guide wheels.

6. A self-balancing powered unicycle comprising:

a single hubless wheel; and

a drive arrangement according to any preceding claim.

7. The self-balancing power unicycle of claim 6, wherein the single hubless wheel comprises a rim having an inner rim surface with a non-flat profile.

8. A drive arrangement for a self-balancing powered unicycle substantially as herein described above with reference to the accompanying figures.

9. A self-balancing powered unicycle substantially as herein desc ibed above with reference to the accompanying figures.