CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom patent application number 2105839.1 filed on 23 April 2021 , which is incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to a variable diameter wheel. In particular, a variable diameter wheel that may be adjusted when moving from one terrain to a next terrain without sacrificing ease of transport or functionality.

BACKGROUND TO THE INVENTION

The performance of a wheel of a vehicle may be affected by a variety of parameters, one of which is wheel size. The wheel size is typically defined by the diameter, width, and weight of the wheel. The size of the wheel affects the stability of the vehicle as well as the traction of the wheel. The diameter of a wheel affects, amongst other things, the ease of manoeuvrability and steering of the vehicle, the potential speed of the vehicle, power requirements of the vehicle, and the force required to accelerate the vehicle.

The application of a vehicle may therefore be dependent on the wheel size of the vehicle. Vehicles are typically provided with a wheel or set of wheels that are dimensioned to optimise the vehicle for a particular application. This is particularly applicable to vehicles that are pushed such as pushchairs, prams, trolleys, etc.

A large diameter wheel, for example, is preferred for a vehicle that is to be used on uneven terrain. This may be any type of off-road vehicle, such as a jogging stroller, off-road cart, or wheelbarrow. However, a large diameter wheel is not suitable for compact vehicles or for use in small spaces where manoeuvrability is required.

A small diameter wheel on the other hand is preferred for a vehicle that is required to be agile as these wheels are typically lighter and more manoeuvrable. Vehicles that are required to be agile are often compact in size or compactible by collapsing to a stowage configuration. A compact vehicle, for example, a trolley, is suitable for use in a small space such as in a grocery store aisle, where a relatively smooth ground surface does not prevent the trolley wheels from revolving. The compact nature of the vehicle in combination with the small wheels allows for agility and manoeuvrability in such a space. A compactible vehicle is adjustable between an operative configuration and a stowage configuration. Like a compact vehicle, it is envisaged that the compactible vehicle would be relatively compact in its operative configuration, as the application of the vehicle may be similar to that of a compact vehicle. However, as a compactable vehicle is typically transported between locations, the vehicle in the stowage configuration is even more compact than that of the vehicle in the operative configuration. An example of a compactible vehicle may include a pram or a wheelchair where a user is required to load the vehicle into a car and transport it to and from locations, for example from home to a shopping centre and back.

The width of the wheel must be optimised for the application of the vehicle. A broad wheel provides stability to the vehicle but increases the traction of the wheel on a ground surface. The increased traction impacts the force required to translate movement to the vehicle. A broad wheel is also heavier than a narrow wheel. Thus, for a vehicle that is not driven by an engine, but instead has to be pushed or drawn by an animal or human, a balance must be struck between stability and traction to allow the vehicle to be moved by less force without sacrificing the stability of the vehicle.

For the purpose of this specification, the term “vehicle” refers to any wheeled means of transport for goods, people or animals including prams, pushchairs, trolleys, carts, wheelbarrows, wheelchairs, etc. Vehicles may be pushed or have some form of propulsion.

As already mentioned, the wheel size of a vehicle is generally set according to dimensions which are suitable for the application of the vehicle type. A vehicle is therefore limited in terms of versatility in as far as the functionality of the vehicle is determined by the size of the wheel. However, some vehicle types are used in more than one application and there is scope for versatility in respect of wheel size. Thus, some vehicles are provided in many different designs. A user looking for versatility in a vehicle may then be forced to obtain different versions of the vehicle for different applications.

As an example, there are multiple iterations of pram designs. Some prams may be optimized for exercise, such as running or hiking on moderately rough terrain, whereas others are optimised to be easily stowed and transported between locations where the pram is to be used. These are common activities for which a suitable pram is required, and many households therefore have more than one pram for use in different activities, such as for shopping, traveling, or exercise.

This diverse design approach has resulted in a fragmented and complicated product offering with some prams being capable of integrating with certain car seats or bassines but being too large to travel with easily. Other prams are only suitable for a single purpose such as running or off-road terrain purposes and not for day-to-day use in cities or to easily stow and travel with.

Similar issues are encountered with designs for other vehicles such as, for example, wheelchairs, wheelbarrows, push carts, etc. which are provided with set wheel sizes, requiring a user to potentially have to purchase more than one of the same types of vehicle to cater for varying needs in respect of the vehicle’s wheel size.

There is thus a need for a vehicle design capable of adjusting or adapting its configuration in ways other than already described to increase the versatility of the vehicle, allowing for a single vehicle to be useful in multiple applications. The means to adjust or adapt the vehicle’s configuration should not interfere with other requirements of the vehicle, for example, such as compactness or compatibility.

Some forms of adjustable diameter wheels are known; however, the available designs for these wheels are complicated and not suitable for quick and simple adjustment.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a variable diameter wheel comprising: a hub defining a circumferential stowing zone; a plurality of spokes extending radially from the hub and movable relative to the hub; a rim component having segments connected to each other at consecutive hinge points to provide an articulated arrangement to expand and contract the rim component radially and with at least some of the hinge points mechanically linked with first ends of each spoke; and an expansion mechanism operatively engaging second ends of at least some spokes; wherein the expansion mechanism is configured to move the spokes and the rim component between a compact configuration wherein the spokes and the rim component are retracted into the stowing zone so that a perimeter of the hub is operable as a first ground-engaging surface of the wheel, and an expanded configuration wherein the spokes are deployed from the stowing zone to extend the rim component into a rim which defines a second ground-engaging surface of the wheel. In the expanded configuration, the spokes are fully deployed from the stowing zone and the components of each rim segment are fully extended relative to each other. In the compact configuration, the spokes are folded into the stowing zone and the rim component is retracted so that the segments overlap each other and the spokes.

The rim component may have a rim width that provides the second ground-engaging surface of the wheel in its expanded configuration, the rim width being supported on either side at radially spaced positions by the spokes cooperating in pairs.

Pairs of spokes may be mechanically linked to allow for simultaneous control by an actuating mechanism thereby to expand or retract the rim component.

A width of the wheel in the compact configuration may be formed of a width of the hub enclosing a width of a pair of the spokes and a width of the rim component retracted into the stowing zone.

The spokes may be arced in their elongate direction to facilitate overlapping of the spokes in the compact configuration and to accommodate a central portion of the hub.

A first set of spokes attached to one side of the rim component and a second set of spokes attached to the other side of the rim component may each expand and contract with movement within a plane for each set, with the two planes being in a parallel configuration.

Segments of the rim component may be connected to each other at consecutive hinge points, each hinge point being configured to bend in an opposite direction to an adjacent hinge point, to expand and collapse the rim component radially to move between a stowed position and an expanded operable position. Each alternate hinge point may be mechanically linked to a respective spoke to allow retraction of the rim component in an articulated or folding manner.

At least some of the hinge points may be in the form of locking hinges on the rim component, which allow for one-way pivotal movement of the hinge point to a pivot limit point to prevent the rim from buckling when the rim component is in the expanded configuration. The locking hinges may be configured to provide a preloading of compression of the rim component in the expanded configuration.

The rim component may include cut outs at the hinge points to allow for a tight retraction of the rim component in its compact configuration.

The expansion mechanism may be incorporated with the hub and located within the stowing zone. The expansion mechanism may be a planetary gear system comprising two subassemblies of sun gears and associated planet gears configured to mate with the sun gears, and a carrier formed of at least some spokes and accompanying hinges, wherein the subassemblies are mechanically linked by means of an axial arrangement to allow simultaneous rotation of the subassemblies.

The hub may be formed of two discs mounted at each end of the axial arrangement and the subassemblies may be disposed one from the other along a length of the axial arrangement on the inside of each of the two discs thereby defining the stowing zone between them, with the axial arrangement allowing relative rotation of the discs and subassemblies.

The planet gears may be fixed to a respective disc in a position that allows mating with the associated sun gear and wherein the planet gears are rotatable relative to the disc to allow the planet gears to move about a perimeter of the associated sun gear causing corresponding rotation of the sun gear relative to the disc.

Each planet gear may be operatively engaged with the second end of a spoke such that rotation of the planet gear is translated into rotation of a spoke.

The planet gears of consecutive spokes may mate in the alternate with the first sun gear and the second sun gear and the spokes are provided in pairs with one spoke being operatively associated with the first sun gear and the other spoke being operatively associated with the second sun gear.

An actuating mechanism may be provided to engage with the expansion mechanism and a locking mechanism is configured to lock the wheel in an expanded configuration or a contracted configuration. The actuating mechanism may be configured to actuate the expansion mechanism to cause expansion when a centrifugal force is applied to the wheel. The actuating mechanism may be configured to actuate the expansion mechanism to cause contraction by applying a braking force to the wheel.

The expansion mechanism may be spring loaded with a bias to the expanded configuration and wherein the actuation mechanism is configured to actuate the expansion mechanism to cause contraction by driving the wheel along a surface and using the frictional force of a contact with the surface to actuate the contraction when the locking mechanism is released.

The actuating mechanism and the rim component may form a back-drivable configuration with input from the actuating mechanism causing output in the expansion of the rim component and input from the contraction of the rim component causing output of the movement of the actuation mechanism. The actuating mechanism may include one or more levers that are each operatively engaged with one or more planet gears to move the planet gear relative to the respective sun gear to pivot one or more spokes, simultaneously, relative to the hub.

A locking mechanism in the form of a locking plate rotatable relative to at least one of the subassemblies may be provided and configured to disable the levers to lock the actuating mechanism to maintain the wheel in the expanded configuration or in the compact configuration.

Spoke supporting blocks may be provided adjacent each spoke to prevent over extension of the spokes thereby retaining the integrity of the wheel in the expanded configuration so that the rim component remains radially aligned. Spoke supporting blocks may be provided on each disc to support the spokes in position relative to the respective sun gear and each other, to prevent over extension of the spokes thereby retaining the integrity of the wheel in the expanded configuration so that the rim component remains radially aligned.

The wheel may be for a vehicle for carrying goods or people. For example, the vehicle may be a conveyance configured to be pushed or propelled by a person including one or more of the group of: a pushchair, a pram, a wheelchair, a bicycle, a tricycle, a scooter, a trolley.

According to another aspect of the present invention there is provided a vehicle for carrying goods or people which incorporates at least one wheel according to the first aspect of the invention, wherein the vehicle is configured to be operable with the wheel in either the expanded configuration or the compact configuration.

The vehicle may be adjustable between an operative configuration and a stowage configuration and wherein, in the operative configuration, the wheel is adjustable between the expanded configuration and the compact configuration.

In the stowage configuration, the wheel may be configured to be in the compact configuration to contribute to the compactness of the vehicle within the stowage configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is a perspective view of a self-contained variable diameter wheel according to the invention in its compact configuration; Figure 2 is a perspective view of the self-contained variable diameter wheel according to the invention in its expanded configuration;

Figure 3 is a perspective view of the self-contained variable diameter wheel being adjusted between the configurations of Figures 1 and 2;

Figure 4 is a side view of the self-contained variable diameter wheel shown in Figure 1 ;

Figure 5 is a side view of the self-contained variable diameter wheel shown in Figure 2;

Figure 6 is a side view of the self-contained variable diameter wheel shown in Figure 3;

Figure 7 is a cross-sectional view through the axis of the self-contained variable diameter wheel in Figure 4;

Figure 8 is a cross-sectional view through the axis of the self-contained variable diameter wheel in Figure 5;

Figure 9 is a cross-sectional view through the axis of the self-contained variable diameter wheel in Figure 6;

Figure 10 is a perspective view of the self-contained variable diameter wheel of Figure 2, excluding hub components, to show an expansion mechanism operable to move the self-contained variable wheel between configurations shown in Figures 1 and 2; and

Figures 11 to 13 show a locking mechanism in locked and unlocked positions, used to lock the wheel in the configurations of Figure 1 and Figure 2.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

The described wheel is a variable diameter wheel which is selectively movable between a compact configuration with a smaller diameter and an expanded configuration with a larger diameter. Applying the described wheel to a vehicle increases the versatility of the vehicle by allowing the vehicle to be used in situations where different sizes of wheel are desirable. In the expanded configuration, the larger diameter wheel allows for the vehicle to move across rougher terrain. Whilst in the compact configuration, the smaller diameter wheel allows for manoeuvrability of the vehicle and improves the overall compactness of the vehicle. The variable diameter wheel has a central portion that is referred to as a hub that is formed of two parallel discs attached together via an axial arrangement. The hub defines a stowing zone between the parallel discs. In the contracted configuration, a perimeter of the hub is operable as a first ground-engaging surface of the wheel. The perimeter of the hub may be provided by the rims of the parallel discs that may have a suitable surface for engaging with the ground.

A plurality of spokes are provided attached to the hub in a spaced apart arrangement around the circumference of the hub. The spokes are attached to the hub such that they are selectively moveable relative to the hub via an expansion mechanism operated by an actuation mechanism.

The expansion mechanism moves the spokes from a retracted position within the stowing zone of the hub (when they are not needed in the contracted configuration of the wheel) to an extended position in which the spokes extend from the hub to support a rim component having a larger diameter than the hub that defines a second ground-engaging surface of the wheel. The rim component has a width that provides the ground-engaging surface and pairs of the spokes are attached to and support each side of width of the rim component. The rim component is a segmented rim component formed of hinged segments such that the rim component can be folded away within the stowing zone when the wheel is in the contracted configuration. The rim component has locking hinges joining rim component segments between points of spoke attachment, where the locking hinges include levers that are asymmetrical to allow compression of the rim component to be pre-loaded to reduce flexion on the rim component that may increase rolling resistance.

When the spokes are deployed from the stowing zone, the spokes in each pair cooperate to draw out retracted segments of the rim component supported by the pair of spokes, causing the rim component to expand and form a large diameter wheel. When the spokes are withdrawn into the stowing zone, the drawn out segments of the rim component collapse and are retracted, with the spokes, within the stowing zone forming a small diameter the wheel comprising of the hub itself.

The direction in which hinges of the rim component pivot allows for optimal radial retraction and expansion of the wheel. In addition, the spokes are arced to facilitate overlapping of the spokes and the rim component when the wheel is in the compact configuration. Arcing of the spokes allows them to wrap around the axial arrangement of the hub thereby extending the total travel of the radial end of the spoke (from the expanded to retracted positions) and hence the change in diameter of the wheel. Based on the requirement for a mechanically sound rim component of a reasonable width and thickness, the spokes are provided in two planes parallel to the rim component. In order to obtain a sufficient ratio between the diameter of the compact configuration and the expanded configuration, the stowing volume of the hub is kept to a minimum and the stowing of the spokes in parallel planes enables this compact arrangement. The “packing factor” of the spokes is also achieved by alternating the spokes from one side of the rim to the other.

In the expanded position, the spokes may be orientated radially such that the loads applied to the wheel primarily load the spokes in compression or tension minimizing the bending load and hence the required size and weight of the spoke.

The expansion mechanism may be provided by a planetary gear system coordinating the expansion and retraction of the spokes between the compact configuration and the expanded configuration. Actuation of the expansion mechanism causes the spokes to be deployed or retracted relative to the hub. The actuation may use a centrifugal force of rotation of the wheel to cause expansion. A braking force on a rotating wheel may be used to collapse the wheel. More specifically that the expansion mechanism is back drivable.

An example embodiment of a variable diameter wheel (100) is described with reference to the figures. Figures 1 , 2 and 3 show the example embodiment of a variable diameter wheel (100) in different states namely: a compact configuration (100A) shown in Figure 1 ; an expanded configuration (100B) shown in Figure 2; and an intermediate state (100C) shown in Figure 3 between the compact configuration (100A) and the expanded configuration (100B).

Figures 4, 5 and 6 show side views of the wheels in the configurations of Figures 1 , 2 and 3 respectively. Figures 7, 8 and 9 are cross-sectional views through the axis of the wheels in the configurations of Figures 1 , 2 and 3.

In the expanded configuration (100B) shown in Figure 2, a diameter of the wheel is substantially larger than in the compact configuration (100A) of Figure 1 . To capitalise on the available volume in the stowage zone whilst providing a mechanically sound rim of a reasonable width and thickness, the spokes are situated in planes parallel to the rim and alternate from one side of the rim to the other.

The wheel (100) includes a hub (200) with an expansion mechanism (300) supported on the hub (200) that is controlled by an actuating mechanism (500) that is operated by a user. A locking mechanism (700) is provided to enable or disable the actuating mechanism (500). The wheel (100) is selectively changed between the expanded configuration (100A) and the compact configuration by a user operating the expansion mechanism (300) with the actuating mechanism (500).

Spokes (400) are extendable from the hub (200) to expand the diameter of the wheel with the spokes (400) operatively engaged with components of the expansion arrangement (300). A collapsible segmented rim component (600) is attached to the spokes (400) such that it can be moved between a stowed collapsed arrangement and an expanded operational condition as the larger diameter second ground-engaging surface.

Figures 1 , 4 and 7 show the wheel in the contracted configuration (100A) in which the smaller diameter of the wheel is defined by the hub (200). The hub (200) comprises a first disc (202A) and a second disc (202B) supported on either end of an axial arrangement (204) that provides the axis of the wheel. The first disc (202A) and the second disc (202B) are displaced from each other to define a stowing zone (206) between the first disc (202A) and the second disc (202B). The volume of the stowing zone (206) is sufficient to contain the expansion mechanism (300), the spokes (400), and the rim component (600). The width of the stowing zone (206) corresponds to the combined width of the rim component (600) and the widths of the supporting spokes (400) on either side of the rim component (600). The spokes (200) are of an elongate arced form to aid in the stowed configuration within the hub (200) and have a flat form such that their width is minimized to reduce the width of the hub (200) required.

A width of the wheel (100A) in the contracted configuration is defined by the hub having the spokes (400) and the rim component (600) fully retracted into the stowing zone (206) and is thus determined by the width of discs (202A) and (202B) and the width of the stowing zone (206). Due to the compact nature of overlapping retracted spokes and rim component, the stowing volume is minimized and the width of the wheel is thus relatively narrow, contributing to the compactness of the wheel by minimizing the required width of the wheel in the compact configuration.

Figures 2, 5 and 8 show the wheel in the expanded configuration (100B) in which the larger diameter of the wheel is defined by the expanded rim component (600). The rim component (600) has a width that provides the ground-engaging surface of the wheel in its expanded form. Pairs of the spokes (400) are attached to and support each side of width of the rim component (600). The rim component (600) is a segmented rim component formed of hinged segments such that the rim component can be extended from the stowing zone (206) when the wheel is in the expanded configuration (100B). In the expanded configuration (100B), the hub (200) forms an inner hub of the expanded wheel.

Figures 3, 6 and 9 show the wheel in an intermediate state (100C) in which it is in the process of being converted from the compact configuration (100A) and the expanded configuration (100B) or vice versa. These figures show the rim component (600) being expanded or collapsed radially by folding its hinged segments (602). The hinged segments (602) are controlled by the spokes (400) that are attached between alternate hinge points (604) of the rim component (600) and an expansion mechanism (300) provided at the hub (200). The expansion mechanism (300) in this example embodiment is a gear mechanism described further below. The expansion mechanism (300) is activated by an actuating mechanism (500) and locked by a locking mechanism (700). In this example embodiment, the actuating mechanism (500) is provided by one or more levers with locking arrangements as described further below.

The expansion mechanism (300) may be a planetary gear system operable to rotate the spokes (400) which in turn control the hinging of the segmented rim component (600) to expand/contract the wheel. The planetary gear system includes two sun gear components which may be mechanically coupled via the axial arrangement (204) to causes the sun gear components to rotate simultaneously, resulting in a single linkage system.

Figures 7, 8, 9 and 10 show an example embodiment of the expansion mechanism (300) in the form of a planetary gear arrangement comprising two subassemblies, each including a sun gear (302) and associated planet gears (306). The subassemblies are mechanically linked via the axial arrangement (204) enabling simultaneous rotation of the sun gears (302A) and (302B).

The axial arrangement (204) may be provided around a central shaft operable as a free-spinning axel which mounts the wheel to the vehicle. A first coaxial sleeve around the central shaft rigidly connects the first disc (202A) to the second disc (202B) and a second coaxial sleeve rigidly connects the first subassembly to the second subassembly. This axial arrangement (204) synchronizes the movement of the spokes and the function of the wheel.

The expansion mechanism (300) is located within the stowing zone (206) of the hub (200). The sun gears (302A) and (302B) are coaxial with the discs (202A) and (202B). The sun gears (302A) and (302B) are disposed from each other at either end of the axial arrangement (204), within the confines of the stowing zone (206).

The planet gears (306) are equispaced radially about an associated sun gear (302) and are rotatably fixed to an inner surface of a disc (202A) or (202B) and are positioned relative to the associated sun gear (302) to allow mating between the planet gears (306) and the associated sun gear (302) and causing rotation of the planet gears (306) as the sun gear (302) is rotated.

A first set of the planet gears (306Ai, 306A ₂ , 306A ₃ , 306A ) mate with the first sun gear (302A) to form a first subassembly of the planetary gear system (306) and a second set of the planet gears (306Bi, 3O6B ₂ , 306B ₃ , 306B ) mate with the second sun gear (302B) to form a second sub assembly of the planetary gear system (300).

As shown in Figure 4, a diameter (D _d ) of the discs (202A, 202B) is larger than a diameter (D _sg ) of the sun gears (302A, 302B) and associated planet gears (306A, 306B), so that the planetary gear system is fully contained withing the stowing zone (206).

The spokes (400) are arranged about the hub (200) in pairs, with one spoke within each pair connected to a planet gear (306A) that mates with the first sun gear (302A) and the other spoke connected to a planet gear (306B) that mates with the second sun gear (302B). The spokes (400) within each pair are staggered so that the spokes extend about the hub (200) in an alternating pattern. Rotation of a planet gear (306A, 306B) causes the connected spoke to pivot one way or the other, depending on the direction in which the planet gear is rotated, extending or retracting the spokes (400).

In this example embodiment, spokes (400Ai, 400A ₂ , 400A ₃ and 400A ₄ ) are connected to planet gears (306Ai, 306A ₂ , 306A ₃ , 306A ) and spokes (400Bi, 400B ₂ , 400B ₃ and 400B ) are connected to planet gears (306Bi, 306B ₂ , 306B ₃ , 306B ₄ ). The alternating pattern is thus in the following order: 400Ai, 400Bi, 400A ₂ , 400B ₂ , 400A ₃ , 400B ₃ , 400A ₄ , 400B ₄ such as shown in Figure 10.

The first set of the planet gears (306Ai, 306A ₂ , 306A ₃ , 306A ₄ ) mates with the first sun gear (302A) which is fixed to the first disc (202A) and the second set of the planet gears (306Bi, 306B ₂ , 306B ₃ , 306B ₄ ) mates with the second sun gear (302B) which is fixed to the second disc (202B).

The actuating mechanism (500) is configured to cause rotation of at least one of the planet gears, to set in motion the rotation of the planetary gear system (300). Rotation of any one planet gear causes rotation of an associated sun gear (302), in an opposite direction, about the axis of the axial arrangement (204), resulting in rotation of the mechanically linked subassemblies. Spokes (400), which are fixed to the planet gears (306) are deployed or retracted by the rotation of an associated planet gear (306).

The expansion mechanism (300) may be driven by rotating one or more levers (504) that form the actuating mechanism (500). In this embodiment, the expansion mechanism (300) is a planetary gear system and the levers (504) are linked to planet gears (306) that mate with the sun gears (302A, 302B). The planet gears (306) support the second ends of the spokes (400), and the rotation of the planet gears (306) cause the associated spokes (400) to rotate about the planet gears (306) to cause deployment or retraction of the spokes (400) from and into the stowing zone (206) by rotation of the spokes (400) as the planet gear (306) engages with a sun gear (202).

The actuating mechanism (500) includes levers (504) arranged on the outer surface of the discs (202) of the hub (200) as shown in Figures 1 , 2, 3 and 11 . The levers (504) are each operatively engaged with a planet gear (306) associated with one of the subassemblies. The levers (504) are swivelled to cause rotation of the associated planet gears (306) in the direction that the levers are being swivelled in. The levers (504) are rotatably fixed on an outer surface of the disc (202A or 202B). Due to the linked nature of the planetary gear system (300), it is not necessarily required to operate a lever (504) for each planet gear (306) and a single lever associated with a single planet gear could be sufficient to set in motion the planetary gear system (300).

To allow the levers (504), located on the outer face of the disc (202), to actuate the planet gears (306) located on an inner surface of the disc (202), connecting members (502) are fixed to and extend axially from each planet gear (306) through apertures formed in the disc (202) and connect with a respective lever (504) to establish a mechanical link between the levers (504) and the planet gears (306). The connecting members include bearing surfaces to reduce friction between the connecting members (502) and the apertures when the connecting members (502) are rotated.

Spoke support blocks (308) may also be provided on an inner surface of the discs (202) adjacent the planet gears (306) to prevent over extension of the spokes (400) to protect the integrity of the wheel in the expanded configuration by keeping the spokes (400) radially aligned.

The rim component (600) is described further with reference to Figures 2, 3 and 8. The rim component (600) includes hinged rim segments (602) that enable the radial expansion and contraction of the rim component (600). A first hinge set (604A) and a second hinge set (604B) are provided for the segments (602) of the rim component (600) and define hinge points on the rim component. The second hinge set (604B) comprises of one-way locking hinges. In the expanded configuration, the locking hinges (604B) prevent the hinge points from collapsing or buckling, thus increasing the load bearing capacity of the wheel whilst maintaining the expanded configuration. The locking hinges also allow for pre-loaded compression of the rim component so that, when expanded, the rim component is in a preloaded compressed state to reduce flexion of the rim, which leads to a corresponding reduction of rolling resistance of the wheel. The locking hinges (604B) alternate with non-locking hinges (604A) provided at spoke attachment points.

The segments (602) which are pivotally connected to each other at the hinge points form a closed, mechanically linked structure which, in an expanded form, defines a continuous surface (608) on the perimeter of a felloes (606). A width of the felloes (606) is determined by a width of the linked segments that are drawn into alignment and locked in the aligned position in the expanded configuration of the wheel (100B). The locking hinges (604B) prevent buckling or distorting of the wheel in the expanded configuration and increases the stability of the wheel.

Each alternate hinge (604A) is configured to open and close in an opposite direction to the one way locking hinge (604B) adjacent thereto to radially expand and contract the rim component. The first set of the hinges (604A) are configured to open and close inwardly in a direction facing the hub (200) whereas a second set of the one-way locking hinges (604B) are configured to open and close outwardly in a direction away from the hub (200) to allow the segmented rim component to expand or collapse radially as shown in Figure 3 and Figure 9.

The first set of hinges (604A) are pivotally connected to a first end of a spoke (400) to establish a mechanical connection between the rim component (600) and the expansion mechanism (300) via the spokes (400). The hinges (604A) are configured to bend the rim component inwards to collapse the rim component as the spokes are retracted into the stowing zone. In the expanded configuration, the position of the spokes at the hinge points prevents the rim component from bending inwards and collapsing. The one-way locking hinges (604B) are interposed between consecutive spokes (400). The hinges (604A) are attached alternately to spokes (400) that engage with each of the first and second subassemblies.

The rim component includes cut outs (610) of a shaped cut out design on an inner surface of the rim component (600) as shown in Figure 3 which allows the rim component (600) to fold in tightly on itself in the compact configuration of the wheel (100A). Each cut out (610) may be configured to receive a portion of an adjacent segment (602) of the rim component (600).

The segmented rim component (600), the spokes (400), the planetary gears (306), and the levers (504) are linked to form a mechanical linkage system and movement of any one of the components of the linkage system will cause a corresponding movement in the other components. For example, actuation of any one of the levers (504) will cause the linked planet gear (306) to rotate relative to the respective sun gear, causing the entire system to expand or retract. Upon actuation of the levers (504), each pair of spokes (400) cooperates to draw out or retract the rim segments (602) supported by the pair to expand or retract the rim component (600). The felloes (606) is supported on either side of its width by spoke pairs.

Figures 11 , 12 and 13 show a locking mechanism (700), which is provided to prevent unintended contraction or expansion by disabling the actuating mechanism (500). In this example embodiment, the locking mechanism (700) stops the rotation of the levers (504). The locking mechanism (700) may be in the form of a locking plate (702) secured via a locking arrangement located in the hub (200).

The locking plate (702) is located on the outer face (210A) of the hub (200) and is rotatably engaged with an axial componentwhich extends from the outer surface (210A). The locking plate (702) is configured to be movable between either of two locked positions (a locked contracted position and a locked expanded position), with the plate (702) secured by the locking arrangement, and an unlocked position, with the plate disengaged from the locking arrangement. In the locked positions, the corners of the plate (702) are engaged with levers (504), to prevent actuation thereof. In the unlocked position, the plate (702) is dislodged to release the levers (504), to allow actuation thereof.

In this embodiment, the locking mechanism comprises of a spring/bail assembly with a ball (704) positioned to interface with one of corresponding holes (706) in the locking plate (702) to secure the locking plate in selected positions relative to the hub (200).

As shown in Figure 11 and 13, there are first and second locking positions that are determined by the hole (706A) or 706(B) which interfaces with the ball (704) and the orientation of the levers (504). Due to the synchronized operation of the locking mechanism (700), the actuating mechanism (500) and the expansion mechanism (300), a first locking position as shown in Figure 11 is associated with the collapsed configuration of the wheel and a second locking position as shown in Figure 13 is associated with the expanded configuration of the wheel. In the first locking position, the levers are oriented in a particular direction and a first hole (706A) interfaces with the ball (704) whereas in the second locking position, the levers are oriented in an opposite direction and a second hole (706B) interfaces with the ball (704).

Each lever has an irregular shape such that, in the expanded state, the locking plate and the levers interact in such a way that the spokes are preloaded by the tension generated between the levers and the locking plate in the second locking position.

The size and shape of the levers are determined by a position of an axis of rotation of each spoke relative to the hub. The size and shape of the levers are optimised to produce sufficient tension between the levers and the locking plate, particularly in the second locking position, to preload the spokes in the expanded configuration of the wheel, while still ensuring that the levers do not protrude beyond the diameter of the wheel in the compact configuration.

The wheel (100) is intended to be used in either the expanded configuration or the compact configuration. In the expanded configuration, the continuous surface (608) defined by the felloes (606) is operable as a ground engaging surface. In the compact configuration, rims of the first disc (202A) and the second disc (202B) define surfaces (212A) and (212B) which are operable as the ground engaging surfaces. During use of the wheel (100), the locking plate is generally in the locked position to prevent involuntary expansion or collapse of the wheel (100).

To adjust the wheel (100) between the expanded configuration and the compact configuration, the locking plate (702) is sprung from the ball (704) to allow rotation of the plate (702) to release the levers (504).

To expand the wheel, at least one of the released levers (504) is actuated in a first direction causing corresponding movement of all the planet gears (306) relative to the respective sun gears (302). As the planet gears (306) are rotated, the spokes are deployed from the stowing zone (208), forcing locking joints (604A and 604B) to extend and lock to form the felloes (606).

To adjust the wheel (100) into the compact configuration, at least one of the levers (504) is rotated in a second opposed direction to cause corresponding movement of the planet gear (306) associated with the particular lever, in turn causing the entire linkage system to retract. Hinges (604A) and (604B) buckle and collapse to allow the rim segment component (600) and the spokes (400) to fold into the stowing zone (206).

Actuation of a single lever (504) is sufficient to cause corresponding movement of all components in the linkage system. An alternative expansion or retraction technique might allow for the segmented rim component (600) to be drawn out or pushed in manually to expand or collapse the rim component (600). The expansion may use centrifugal force to cause expansion. A braking force on a rotating wheel may be used to collapse the wheel. The expansion mechanism may be back drivable.

The wheel may be configured to use a centrifugal force to cause expansion. The centrifugal force may be applied by lifting the wheel from the ground with any expansion locks released, and then spinning the wheel electrically or mechanically beyond a threshold velocity with the centrifugal forces causing the wheel to open. The centrifugal force may generate sufficient momentum for the spokes to move radially outward causing the wheel to open. Once the spokes are in the expanded configuration any expansion locks may be engaged, locking the wheel in the expanded configuration. The wheel may by spun electrically by an actuation means, causing all of the wheels of the vehicle to expand either simultaneously or individually. The centrifugal forces may also originate from manually spinning the wheel.

The wheel may be configured to use a braking force to cause contraction. The wheel may be spun up electrically or mechanically, with any expansion locks released, and then a brake applied to cause the contraction. Applying a brake causes a static friction force to exist between the outer rim and the contact surface. When the frictional force becomes greater than the stiffness or tension of the spokes, it will force the spokes to move against the spokes’ tensional direction, in the contracting direction, causing the wheel to contract. Once the spokes are in the contracted configuration any locks may be engaged, locking the wheel in the contracted configuration. The frictional force may also exist by applying pressure on the outer rim manually.

The wheel may utilise centrifugal forces to expand and frictional forces to collapse in another embodiment, for example, having a different gearing arrangement. For the wheel to optimise the aid of centrifugal and frictional forces for expansion and contraction, the spokes need to operate in a uniform manner. This allows for the centre of gravity to be located at the centre axis of the wheel wherefrom the centrifugal force originates, causing the wheel to expand uniformly.

The expansion mechanism may also include a spring assistance by being spring loaded with a bias towards expansion. The actuation mechanism is then configured to actuate the expansion mechanism, causing expansion and through enabling the locking mechanism the wheel will operate in the expanded configuration. When the locking mechanism is released, and a frictional force is applied between the outer rim and a contact surface the wheel will collapse to the contracted configuration. The contraction may also include a spring assistance.

By locking the locking mechanism in the contracted configuration, the wheel will not expand even when a centrifugal force is applied. In the same manner, if the locking mechanism is locked when the wheel is in the expanded configuration, the wheel will not collapse when in a frictional force is applied. Releasing the lock of the locking mechanism enables the wheel to freely expand or collapse, depending on the actuation means and the forces applied.

Without the locking plate activated, the wheel components are free moving and as such will follow the natural gearing bias state of either open or closed depending on the external forces applied to it.

It is also envisaged that with the expansion locks released, by driving the wheel along the driving surface (i.e. pushing a pram) the contact with the road/path may force the wheel to contract. This feature may be used, for example, if the wheel is spring loaded in the expanded position and then contracted by this means.

The described features may rely on a "back-drivable" aspect of the wheel. To clarify this, in the field of mechanical mechanism and gearing systems there is generally an input side and an output side. Some systems, by way of internal friction or other mechanisms, can only transfer motion from the input to the output. If one attempted to move the output to cause movement of the input the system would lock and no motion would result. An example is a jack for a car where the crank handle can lift the car but the weight of the car does not close the jack. In contrast to this, a back- drivable system is one where motion of the output can and will cause motion of the input. The expanding wheel is an example of this type of system. The levers are the "input" and the movement of the segments is the "output" and the point is that the segments can be moved by either moving the levers and hence the gearing system or by moving the segments which will then turn the gears and the rest of the mechanism.

The locking mechanism is operated in a specific way during adjustment of the wheel. To allow contraction, the locking plate (702) is turned slightly counter clockwise to release the levers (504). The locking plate (702) then remains in position until the levers are rotated clockwise such that the wheel is fully contracted in the compact configuration (100A). Finally, the locking plate is then rotated further counter clockwise until the hole (706A) is engaged via the spring/bail assembly (704) in the first locking position with the wheel in the contracted configuration as shown in Figure 11.

The expansion of the wheel (100) is initiated through the same procedure with rotation directions reversed. The locking plate (702) is rotated sightly clockwise until the levers (504) are released. One or more levers are then rotated counter clockwise until the wheel is fully expanded. The locking plate (702) may then be rotated clockwise until the hole (706B) latches with the spring/bail (704) assembly in the second locking position with the wheel in the expanded configuration as shown in Figure 13.

In use, a vehicle having wheels (100) according to the invention can easily be adapted or adjusted between configurations suitable for different applications. For example, a pram which has a wheel according to the invention could be easily stowed or transported with its wheel (100) in the compact configuration (100A). With the wheel in the compact configuration, the pram will also be easily manoeuvrable in small spaces with smooth ground surfaces, such as aisles in a shop.

For outdoor use, the wheel (100) of the pram could be adjusted to the expanded configuration (100B) to allow for exercise activities on uneven terrain, such running or walking on a pavement, gravel, the beach etc.

The expansion mechanism (300) is operated by the actuating mechanism (500), in a straightforward manner. The locking mechanism (700) is easy to operate and may be configured to facilitate operation of the actuating mechanism (500). The wheel expands and retracts in a radial sense only and there is no need for a complicated linkage system to provide for axial expansion.

The wheel (100) is suitable for use on everyday vehicles of the kind previously mentioned and the ease in moving the wheel between configurations allows a user to adjust the wheel as many times as needed during a single trip which may traverse different terrains. Referring to the pram example, a user could adjust the wheel from the compact configuration used for pushing the pram through a shopping centre to the expanded configuration to push the pram from the shopping centre to a car parked in a parking area. Once at the car, the wheel could again be adjusted to the compact configuration to facilitate stowage of the pram in a boot of the car.

The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention to be set forth in any accompanying claims.

Finally, throughout the specification and any accompanying claims, unless the context requires otherwise, the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.