[001] The present invention concerns a wheel and, in particular, a wheel for light weight vehicle, such as a car. The present invention also concerns a tire for use in the wheel of the present invention.

[002] Heavy goods vehicles are often provided with wheels with a double tire configuration to more evenly distribute heavy loads. In such arrangements it is typical for the vehicle' s wheel hub to have longer studs which enables the installation of two standard wheel rims onto a single hub. The inner wheel is thereby installed in a conventional position, and the outer wheel is installed the opposite way round so that it faces the inner wheel.

[003] As well as allowing for more even load distribution, the above double tire configuration provides the advantage that if one of the tires were to be punctured, the heavy goods vehicle is still able to remain relatively stable. This provides improved safety in the event of a tire blow out. Accordingly, there has been interest in adapting such a double tire arrangement for use in cars. [004] In this connection, the double tire configuration used in heavy goods vehicles is unsuitable for use in lighter weight vehicles, such as a car. One reason for this is that it results in a very wide wheel, which cannot normally be accommodated under a car's wheel arches. A further problem is that the maintenance of such an arrangement is often too involved and complex for most car users. For example, if a tire needs to be changed, considerable manual work is required because both wheels must be removed independently. Furthermore, shearing can occur between each of the two wheel rims, which can lead to fatigue failure of the studs or wheel nuts which secure the wheels. Therefore, such an arrangement necessitates regular maintenance to ensure the wheel nuts are appropriately tightened and there is no evidence of fatigue, which is too burdensome for most car users.

[005] In light of the above problems, various alternative configurations have been suggested. [006] US 2005/0088035 discloses one such wheel having a single wheel rim capable of simultaneously supporting at least two tires. In this case, the wheel is provided with a wheel rim having at least two grooves, each for positioning a standard tire. This arrangement provides increased stability in the event of one tire having a blow out, whilst still allowing for simple maintenance because both tires are provided on a single wheel rim.

[007] A problem with US 2005/0088035, however, is that in use, stones and other road debris has a tendency to become lodged in the space between the two tires. In instances where the debris is loosely held, this can lead to the debris being picked up and thrown by the wheel, which may be dangerous for other road users. Furthermore, where the debris becomes securely lodged, it can weaken both tires by projecting into the tire walls. Moreover, debris can also accumulate in the interior space created between the two tires, which may lead to mechanical malfunction. [008] WO 2005/084105 discloses another arrangement in which a wheel rim is provided in a number of segments which are screwed together to form a wheel rim unit, and a single tire is provided having a two or three independently inflatable compartments or chambers. Consequently, if one of the tire's compartments were to be punctured and deflate, the remaining compartments are able to remain inflated. As the tire is formed as a single membrane, this arrangement provides the advantage over US 2005/0088035 that debris is unable to become lodged in the tire. However, WO 2005/084105 suffers from the disadvantage that if one compartment becomes punctured, it is necessary replace the entire tire immediately, as the attached deflated sections may become dangerous during prolonged use or at higher speeds. Therefore, whist WO 2005/084105 may allow for a vehicle experiencing a blow out to come to a safe stop, it would not allow such a vehicle to easily continue their journey. Furthermore, the arrangement disclosed by WO 2005/084105 has a relatively complex construction which would require high levels of maintenance. For example, to replace the tire, each of the separate rim sections would need to be detached from one another.

[009] The present invention therefore seeks to overcome the above problems with known prior art arrangements.

[0010] According to a first aspect of the present invention there is provided an wheel for a vehicle comprising:

two or more tires;

a rim having two or more grooves, each groove for receiving one of the two or more tires;

wherein each of said two or more tires comprises a lateral mating formation for engaging with an opposing mating formation of the adjacent tire. [0011] In this way, once fitted to a vehicle, if one of the tires were to be punctured during use, the remaining tire(s) allow the vehicle to remain stable and the wheel to continue to be used. Furthermore, as each tire is provided on the rim separately, if one tires is damaged, it may be removed to prevent it compromising the stability and operation of the remaining tires, and can be replaced independently when convenient to return the wheel to its original condition. Moreover, as the tire is provided on a single rim, maintenance of the vehicle's wheels is simplified, allowing for use of the present invention with domestic vehicles. Finally, the lateral mating formations act to form a mating engagement between adjacent tires. This allows the wheel to be substantially the same width as a conventional wheel and provides the appearance of a single tire. This is functionally and aesthetically advantageous because it allows the wheel to be used on both the front and rear of a vehicle, and on light weight domestic vehicles, such as luxury cars. Furthermore, this construction also acts to prevent stones or debris becoming lodged between the tires. This avoids stones and other debris being picked up by the wheel and helps to avoid premature tire damage which may occur at the side walls of the tires if stones were to become lodged here. [0012] Conveniently, the lateral mating formations are configured for mating with opposing lateral mating formations from the tire tread radially inwards along at least a portion of the sidewalls between the adjacent tires. In this way, engagement between opposing side walls of adjacent tires occurs over a large surface area, from the periphery of the tire inwards. This provides a stable engagement between the two mating formations and prevents debris from being forced between the tires' sidewalls. [0013] Conveniently, said lateral mating formations engage with one another at the radial periphery of the tires for forming a continuous tread across the two or more tires. In this way, functionality of the tread patten can be achieved across all of the wheel's tires. For example, the tread pattern may include rain grooves which extend over all of the tires. Moreover, the wheel thereby provides the appearance of a single tire, which allows the present invention to be used in domestic applications where tire appearance is more important. For example, the wheel may be used with luxury vehicles.

[0014] Conveniently, the continuous tread comprises a continuous tread pattern across the two or more tires. [0015] Conveniently, the lateral mating formations project from the opposing shoulders of adjacent tires.

[0016] Preferably, said lateral mating formations comprise a stiffened portion adjacent to their engaging surfaces for preventing disengagement from the adjacent mating formation. In this way, the opposing surfaces of the mating formations act to retain their shape, and hence engagement with one another. This helps to prevent debris from entering the joint between the tires.

[0017] Preferably, said stiffened portion forms part of the wheel ' s tread .

[0018] Conveniently, the stiffened portion comprises a stiffened portion of rubber.

[0019] Conveniently, each of said two or more tires comprises an internal air chamber. [0020] Preferably, adjacent tires define a void radially inwards of said lateral mating formations for providing a space into which the internal air chamber' s of the tires may expand into. This allow space for the air chambers to expand into as they are compressed by a load placed on the wheel. [0021] In an embodiment, the internal air chamber is shaped for forming said lateral mating formations.

[0022] In an embodiment there is provided three of said two or more tires and wherein said rim comprises three of said two or more grooves for receiving said three tires.

[0023] Conveniently, said vehicle is a light weight vehicle. [0024] Preferably, said light weight vehicle is a car.

[0025] According to a second aspect of the present invention there is provided a tire for use in the wheel described above, wherein the tire comprises a lateral mating formation in use for engaging with an opposing mating formation on an adjacent tire.

[0026] Illustrative embodiments of the present invention will now be described with reference to the accompanying drawing in which:

Figure 1 shows a cross sectional view of a wheel according to a first embodiment of the present invention;

Figure 2 shows a cross sectional view of a wheel according to a second embodiment of the present invention; and

Figure 3 shows a cross sectional view of a wheel according to a third embodiment of the present invention.

[0027] Figure 1 shows a cross sectional view of a wheel 1 according to a first embodiment of the present invention. The wheel 1 is provided with a wheel rim 2 which supports two tires 5a and 5b. The wheel rim 2 is formed as a single unitary piece and is provided with two grooves 3a and 3b which are defined between outer ridges 2a and 2b, and the rim's central ridge. Grooves 3a and 3b respectively support tires 5a and 5b, which each sit into their respective groove. Apertures 4a and 4b are provided in the outer ridges 2a and 2b and accommodate the air valve stems (not shown) to permit the inflation of the tires.

[0028] Each of tires 5a and 5b comprises two side walls and a tread 11 provided around its outer circumference. An inflatable air chamber is provided in the interior of each tire. The grooves 3a and 3b of wheel rim 2 are configured such that they hold the tires' opposing side walls in contact with one another when the tires are inflated.

[0029] In this connection, the walls of the tires 5a and 5b are respectively provided with mating formations 6a and 6b which project from the shoulder sections of the tire's sidewalls, from the normal contour of each of the tire's air chambers. These mating formations form a mating surface between the two tires and engage with one another along their opposing side walls at joint 8. As can be seen, the mating surfaces extend radially inwards from the tire's tread at the wheel's periphery. The mating formations 6a and 6b are provided with stiffened sections 7a and 7b, respectively. These sections act to stiffen the joint 8 between the two tires 5a and 5b.

[0030] In this embodiment, radially inwards of the mating formations 6a and 6b, the normal contours of the inner inflatable air chambers define a cavity 9. This provides a space into which the air chambers can expand into when the wheel 1 is bearing a load.

[0031] Once the tires 5a and 5b are fitted to the wheel rim 2 and inflated, their tire treads 11 form a continuous tread across both tires and around the radial periphery of the wheel. A continuous tread pattern is provided on the tread across the two tires 5a and 5b.

[0032] As will be understood, once the tires 5a and 5b are fitted to the wheel rim 2, they are engaged with one another along mating formation 6a and 6b. This provides the appearance of a single tire and makes the present invention suitable for use in luxury vehicles, as well as for commercial applications. [0033] Furthermore, as the tire tread 11 forms a continuous tread pattern across the tires, the tread functionality of a single tire is achieved. This allows, for example, the tires in combination to channel away heat and surface water from the tire material and from beneath the wheel's footprint in use.

[0034] Moreover, because of the engagement of mating formations 6a and 6b around the periphery of the tire, stones and other debris are prevented from becoming lodged between the two tires. This effect is enhanced by formations 6a and 6b being provided with stiffened sections 7a and 7b. These stiffened sections render the joint 8 relatively incompressible and thereby help to maintain engagement between the side walls of the tires for preventing stones and other debris from becoming stuck between them.

[0035] Figure 2 shows a second embodiment of the present invention. This embodiment is substantially similar to the first embodiment described in relation to Figure 1, although in this embodiment, three tires are provided rather than two. The description of like features described in reference to the first embodiment has therefore been omitted for conciseness . [0036] In this connection, wheel rim 2 is provided with three grooves which support three tires 5a, 5b, and 5c. The tire tread 11 extends and forms a continuous pattern across all three tires. In addition, the second embodiment is further provided with central aperture 4c for accommodating an air valve stem for the middle tire 5c.

[0037] As with the first embodiment, each of the three tires of the second embodiment is provided with a mating formation 6 on their side walls for engagement with one another. The mating formation 6c on middle tire 5c, however, is formed on both its left and right side walls so that this tire engages with both adjacent tires.

[0038] The second embodiment provides the same advantages as those described in relation to the first embodiment. In addition, the second embodiment provides an additional level of safety in that in the event that one of the three tires were to deflate, two thirds of the tire remains inflated to provide additional stability. Furthermore, the second embodiment allows the air pressure in each of the three tires to be independently modified. For example, in snowy conditions, in may be helpful to partially deflate the middle tire, or to remove it completely, in order to provide additional grip.

[0039] Figure 3 shows a third embodiment of the present invention. This embodiment is substantially similar to the first embodiment described in relation to Figure 1, although in this embodiment, an air vent 12 is provided which allows air to pass in or out of cavity 9 through the wheel rim 2, to thereby equalise air pressure in the cavity with the external atmosphere.

[0040] With the present invention, there is therefore provided a wheel which can accommodate two or more tires on a single rim. In this way, if one of the tires were to deflate during use, the wheel is still able to run using the remaining tires. Furthermore, as each of the tires is provided separately, they can be removed and replace independently of one another. This allows any damaged tire components to be removed if it is necessary to run the wheel using the remaining tires. It also reduces the cost of replacement tires in the event of a puncture. Moreover, as the tires are provided on a single rim, the wheel of the present invention allows for simple maintenance and replacement. At the same time, the construction of the present invention prevents stones and other debris being caught between adjacent tires, as well as permitting a continuous tire tread to be provided across all of the tires. Consequently, the present invention provides the appearance of a single tire and can be used on all types of light vehicles, including luxury cars or commercial vehicles.

[0041] It will be understood that the embodiments illustrated above show applications of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0042] In this respect, although the first and second embodiments of the invention accommodate two and three tires respectively, it is envisaged that embodiments may be provided which accommodate four or more tires.

[0043] Moreover, it is envisaged that embodiments of the invention may be provided in which two or more tires of differing shapes and/or sizes are supported on the same wheel rim. [0044] Furthermore, although in the above embodiments, cavity 9 is provided beneath the adjoining mating formations, it is also envisaged that this section may be filled. [0045] Furthermore, in the above embodiment, the mating formations are formed as projections in the tire material. However, these projections may instead be formed by the internal air chamber. That is, each tire's air chamber may be shaped so as to form its mating formation. In such a case, the stiffened sections of the projections may be formed in the walls of the air chamber on adjacent sides of the tires. These stiffened sections thereby help to retain the shape of the mating projections and prevent stones from becoming trapped between the tires.