A Deformable Wheel

Field of Invention

The invention relates to modes of transport and in particular modes of transport over uneven terrain including travelling along discontinuous surfaces. Specifically, the invention relates to the mechanism for contacting said surfaces which in the prior art may be in the form of a wheel.

Background

A vehicle may be fundamentally described as comprising a means to contain a load such as freight passengers, etc, a driving means for propelling the vehicle whether by engine, motor or manually biased by person and a means to travel across the ground such as one or more wheels.

Basically, wheels are designed to traverse flat surfaces. Of course, not all surfaces will be flat and even, but nevertheless still require traversing for the transportation of a load.

One means of overcoming the unevenness of a surface is to increase the diameter of a wheel. Where the height of an obstacle on a surface approaches the radius of the wheel, the ability of the wheel to rotate to pass over the obstacle is diminished, requiring greater force to maintain the overturning moment of the wheel. In the case of a child's pram, the greater the diameter of the wheel, the less force is required to

traverse a specific obstacle, such as a step. The larger the wheel for a given obstacle, the lower the force that is required, with the force vary in inverse proportion to the length of the lever arm between to top of the obstacle and the centre line of the wheel axle.

For large vehicles, a caterpillar track may be used in place of a wheel so as to provide a flexible surface about which the track can wrap. Thus, by providing sufficient drive, the caterpillar track wraps around the obstacle and climbs over the surface, thus negating the requirement to overcome the lever arm created between the radius of a wheel and an obstacle.

A caterpillar track however is not particularly useful unless there is sufficient- drive to climb over the obstacle, which is not practical for smaller vehicles or manually operable vehicles such as a child's pram or hand trolley.

Thus, whilst a caterpillar track is useful in some instances, the reduced motive force required to rotate a wheel is preferable when capacity to apply sufficient motive force is an issue.

Statement of the Invention

It is therefore an object of the present invention to provide a replacement for a wheel that is capable of traversing certain uneven surfaces.

In a first aspect, the invention provides a deformable wheel for a vehicle comprising, an internal frame, said frame having a hub at a centre of the frame and connectable to an axle,a plurality of members projecting radially from said hub, each member terminating at a- support end, a flexible peripheral band having an outer contact surface, said band continuously spanning the support ends, wherein each member is resiliently deformable such that on application of an external load to the outer contact surface, at least one of said members at least partially deforms.

In a second aspect, the invention provides a vehicle having at least one deformable wheel, said deformable wheel comprising, an internal frame, said frame having a hub at a centre of the frame and connectable to an axle of the vehicle, a plurality of members projecting radially from said hub, each member terminating at a support end, a flexible peripheral band having an outer contact surface, said band continuously spanning the support ends, wherein each member is resiliently deformable such that on application of an external load to the outer contact surface, at least one of said members at least partially deforms.

Thus, the deformable wheel according to the present invention differs from the prior art in that the internal structure is deformable on application of an external load such as that provided by discontinuity or obstruction along an even surface. Whereby certain types of wheels, according to the prior art, may have spokes to ensure the rigidity of the wheel, deformation of the wheel according to the present invention is required in order to accommodate this discontinuity. In a preferred embodiment, the stiffness of the resilient deformability of each member will depend on the application of

the deformable wheel. Such issues in determining the stiffness of the resiliency may include the load being borne by the wheel, the size of the obstructions that the deformable wheel must traverse or the speed by which the vehicle will be operating. It follows that a heavier load may require a greater stiffness to prevent the members from over deforming. Further, if the deformable wheel is subjected to high speed due to a high speed of the vehicle, the type of terrain may well determine the stiffness of the deformability due to impact loads upon the deformable wheel and also preventing resonance of the deformability of the wheel through repeated contact with obstructions.

In a further preferred embodiment, the resiliently deformable members may further include a dampening means to dampen any resonance that may occur through said deformation.

In a preferred embodiment, the deformable members may be laterally deformable such as a flexural spring. Alternatively, the deformable members may be axially deformable such as using a compression spring. In a preferred embodiment, the deformable members may be a composite construction of members moving in a reciprocal action so as to telescope within the axis of adjacent portions of the member. The resiliency may therefore be provided by one or more springs within the elongate member to ensure resilient recovery of the shape of the deformable wheel.

In a further preferred embodiment, the members may contact the flexible peripheral band through support wheels. In this embodiment, the wheels may facilitate movement of the band about the periphery of the deformable wheel. Said movement of

the band may assist in the deformable .wheel traversing an obstruction. In a further embodiment, the movement of the band may provide for movement of the deformable wheel along an even surface without rotation of the deformable wheel.

In a preferred embodiment, the deformable wheel may have at least three members such that the deformable wheel takes the shape of a triangle. Alternatively, the wheel may have four members to form a square shape. In further embodiments of the invention, the wheel may have a plurality of said members so as to better emulate a circular shape such as is available with 5, 6, 7 or more said members.

In a further preferred embodiment, the resilient means providing resilient deformation of the members may be sufficient to extend out so as to keep the band in tension. Such an arrangement may be useful for maintaining the band in shape and also to ensure good distribution of load from the band to the deformable members.

In a further embodiment, the support wheels may be driven so as to further facilitate movement of the band about the periphery of the deformable wheel.

Applications of the deformable wheel according to the present invention may include all terrain vehicles, amphibious vehicles, recreational vehicles and other such self-driving vehicles. Alternatively, the deformable wheel may be applicable to manually driven vehicles such as a child's pram, hand trolley or devices used to move heavy loads over uneven surfaces.

Brief Description of Drawings

Figure Ia shows a defoπnable wheel according to an embodiment of the present invention;

Figure Ib shows a detailed view of the deformable wheel according to Figure Ia;

Figure 2 shows the deformable wheel according to Figure 1, commencing to ascend a step;

Figure 3 shows the deformable wheel according to Figure 1, at a further stage in ascending the step; Figure 4 shows a schematic diagram comparing an axle path between a conventional wheel and a deformable wheel according to Figure 1.

It will be convenient to further describe the present invention with respect to the accompanying drawings, which illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

Description of the Embodiment Figure Ia shows an deformable wheel 1 according to an embodiment of the present invention. The wheel 1 comprises a flexible band 5 for contacting a surface 30 wrapped around an internal structure 7. The internal structure comprises a plurality of spokes, in this case four, giving the wheel 1 a square shape. Each spoke comprises an

elongate member 15a to d attached to a hub 20 and radially extending outward with a wheel 10a to d at each opposed end.

The hub 20 has an axle 22, which permits rotation of the deformable wheel. In this embodiment, the wheel 1 is shown connected to a frame 25. The frame 25 is representative of a connection to a vehicle which may be applicable to any number of vehicles including both driven vehicles and manually operated vehicles such as a child's pram or a hand trolley.

Figure Ib shows a detailed view of one embodiment of a "spoke", in this case the elongate member 15. The member 15 comprises an upper section 16 and a lower section 18 arranged so as to permit reciprocal movement of the upper section 16 within the body of the lower section 18. The reciprocal motion is controlled by a resilient device (not shown), whereby the movement may be elastic through control of a spring, with or without a dampening device to dampen the elastic response of the spoke. Thus the elongate member permits deformation of the wheel 10 when a force is applied thereto, but returning the wheel to its original shape on release of said force.

Figure 2 shows the deformable wheel as it comes in contact with a discontinuity. In this embodiment of the deformable wheel 1, movement along the even surface 30 may be through movement of the band 5 around the peripheral of the deformable wheel 1. Movement of the band 5 is facilitated by rotation of each of the wheels 10a to d and thus movement along an even surface may be similar to that of a caterpillar track though functioning in a different way. A significant departure from the caterpillar track of the

prior art however, is the combination with the internal structure 7 and its interaction with a discontinuity. In this case, the even surface 30 is interrupted by an obstacle 35 in the form of a single step. The direction 45 of the deformable wheel 1 requires the deformable wheel 1 to move from the even surface 30 to the upper surface 40 and so traverse the step 35. The upper portion 55 of the step 35 contacts one face 50 of the deformable wheel 1, deforming the band 56. The band 5 forming the outer surface of the deformable wheel 1 is both flexible and sufficiently strong to transmit the deformation loads to adjacent wheels 10c, d. It will be clear to the person skilled in the art that the types of material the band 5 can comprise, for instance, it could be a nylon or polypropylene fabric or similar tough flexible material and/or may be fibre reinforced to provide sufficient tensile strength.

The load 60a, b transmitted to the adjacent wheels 10c, d causes a deformation 65a, b of the respective elongate members. Thus, the deformable wheel 1 on contact with the step 35 with the resiliency of the elongate member sufficient to deform about the discontinuity, but stiff enough to not fully retract under the applied load which is supported by the deformable wheel 1.

Further, as with a conventional wheel subjected to a discontinuity, the deformable wheel 1 also rotates about the axle, and so achieving both a climbing effect through the deformity of the band 5 and structure 7, but also to traverse the continuity in the same manner as a conventional wheel.

Figure 3 shows a further progression of the deformable wheel 1 travelling in the same direction 45. It will be noted that the portion of band 50 in contact with the step 35 has a different deformed shape 67. As the deformable wheel 1 rotates further so as to imminently contact the upper surface 40, the band correspondingly moves 70 following a rotation of the individual wheels 10a, d. Thus, in addition to deformation around the obstruction and rotation of the deformable wheel 1, this embodiment of the present invention has a further means by which it can traverse the obstruction being rotation of the band 5 through translation movements 70 and rotation 75 a, d of the individual wheels 10a to d of the internal structure 7.

Figure 4 shows a schematic view of the path followed by an axle supporting a load. In one case, the path 80 followed by a conventional fixed wheel arrangement follows the line of the obstruction 35. It can be seen that to overcome the obstruction, the path 80 of the axle is equally discontinuous and suggests a significant motive force in order to overcome the obstruction 35. An alternative path 85 followed by the axle of the deformable wheel 1, according to one embodiment shows a continuous path despite the discontinuity of the obstruction 35. It can thus be seen that the features of the embodiment are sufficient to smooth over the discontinuity 80 of the axle path, which may correspond to a reduction in required motive force and disruption to the load supported by the deformable wheel 1.