GB2482509A

GB2482509A - Wheel

Info

Publication number: GB2482509A
Application number: GB1013121.7A
Authority: GB
Inventors: Samuel Blackburn Pearce
Original assignee: Jelly Products Ltd
Current assignee: Jelly Products Ltd
Priority date: 2010-08-04
Filing date: 2010-08-04
Publication date: 2012-02-08
Also published as: TW201210856A; WO2012017202A1; GB201104955D0; GB201013121D0

Abstract

A wheel (10) comprising a hub (12), a rim (14) and a plurality of resilient spokes (16) arranged to define pairs of opposed spokes (16a,16b) spaced circumferentially around the wheel (10). The hub (12) defines an axis of rotation (A) of the wheel (10) and each spoke (16) is connected at or towards one end to the hub (12) so as to extend tangentially from the hub (12) and being connected at or towards its other end to the rim (14). The spokes of each pair of opposed spokes (16a,16b) are connected to the hub (12) at spaced locations on opposite sides of a circumferential hub line (20) extending about the axis of rotation (A) of the wheel (10) so as to extend tangentially from the hub (12) generally towards each other. The spokes of each pair of opposed spokes (16a,16b) are connected to the rim (14) on a circumferential rim line (22) extending about the axis of rotation (A) of the wheel (10) and aligned with the circumferential hub line (20). The spokes (16a,16b) are shaped to pass each other as they extend generally towards each other from the hub (12) and thereafter follow curved profiles (24) extending back towards each other as they extend towards the rim (14).

Description

WHEEL

The invention relates to a wheel.

Wheel-based vehicles and machinery often experience shock and/or a loss of control when one or more of the wheels is subjected to an impact or is driven over an uneven driving surface. In order to overcome this problem such vehicles and machinery are often equipped with suspension systems including springs and dampers connected to each of the wheels so as to absorb impacts and to assist in the control of the wheels. The inclusion of such suspension also helps to ensure that the wheels of such vehicles and machinery remain in contact with a driving surface, regardless of the condition of the surface, and thereby helps to ensure the comfort and well-being of any occupants.

Conventionally the suspension systems used are distinct apparatus connected to each of the wheels. The inclusion of one or more suspension systems therefore increases the size, weight and manufacturing costs of wheel-based vehicles and machinery.

Wheels having integrated suspension systems are disclosed in US 1,445,522 and EP 2 308.

According to an aspect of the invention there is provided a wheel comprising a hub, a rim and a plurality of resilient spokes arranged to define pairs of opposed spokes spaced circumferentially around the wheel, the hub defining an axis of rotation of the wheel and each spoke being connected at or towards one end to the hub so as to extend tangentially from the hub and being connected at or towards its other end to the rim, wherein the spokes of each pair of opposed spokes are connected to the hub at spaced locations on opposite sides of a circumferential hub line extending about the axis of rotation of the wheel so as to extend tangentially from the hub generally towards each other and are connected to the rim on a circumferential rim line extending about the axis of rotation of the wheel and aligned with the circumferential hub line, the spokes being shaped to pass each other as they extend generally towards each other from the hub and thereafter follow curved profiles extending back towards each other as they extend towards the rim.

The use of resilient spokes defining curved profiles along at least part of their lengths allows displacement of the hub radially relative to the rim and thereby provides an integrated suspension system. Each of the spokes behaves as a resilient spring when,

I

for example, the hub experiences a force that results in displacement of the hub radially relative to the rim and the spoke is either elongated or compressed under the resultant radial load. This removes the need for external suspension and therefore reduces the number of components that would otherwise be associated with the wheel, thereby resulting in size and cost benefits.

Arranging the spokes to as to define pairs of spokes in which curved profiles of the spokes are oriented to oppose each other, and connecting the spokes of each pair to the hub at spaced locations, allows the spokes to apply opposing turning forces to the hub when a driving force is applied to either the hub or the rim. Consequently the arrangement of spokes acts to resist rotation of the hub relative to the rim and thereby reduces any lag between rotation of the hub and rotation of the rim when any such driving torque is applied. This is the case regardless of whether the driving torque acts to accelerate or decelerate rotation of the wheel, and regardless of the direction of the driving torque applied to the hub or rim.

Positioning of the spokes of each pair of opposed spokes relative to the circumferential hub and rim lines improves the lateral stability of the wheel by resisting lateral or twisting movement of the hub relative to the rim when a lateral force is applied to the rim or the hub.

Preferably each spoke is fixedly connected to the hub at or towards one end and pivotably connected to the rim at or towards the other end.

Rigidly connecting each spoke to the hub further improves the lateral stability of the wheel, further reducing the risk of any twisting movement of the hub relative to the rim.

Pivotably connecting each spoke to the rim allows pivoting movement of the spoke relative to the rim and reduces the stresses applied to the spoke during compression and elongation of the spoke. It therefore reduces the risk of the spokes snapping and allows the use of a material that is less flexible than might otherwise be required if the spokes were rigidly connected to the rim.

It is envisaged that in other embodiments, depending on the desired performance of the spokes, the spokes could be fixedly connected at both ends, pivotably connected at both ends or fixedly connected to the rim and pivotably connected to the hub.

In embodiments of the invention, each spoke may be formed from a laminated structure including two ore more alternate layers of reinforcing material and epoxy resin in order to achieve the required resilience.

In such embodiments, the reinforcing material may be chosen from glass fibre, carbon fibre, Kevlar (RTM) and hemp, and the reinforcing material is preferably arranged within the laminated structure so as to follow the shape of the spoke so as to provide a uni-directional strengthening effect and to enhance the performance of the spoke.

Preferably, each spoke is shaped to vary in width between the hub and the rim, in a direction parallel to the axis of rotation of the wheel, such that the width is greatest through the curved profile of the spoke.

Increasing the width of each spoke in the curved profile of the spoke helps to improve the lateral stability of the wheel, improving the spokes' ability to resist lateral and twisting forces applied to the hub and or rim. It also improves the strength of the spokes in the curved profiles, which are subjected to flexing and elongation upon the application of forces causing displacement of the hub relative to the rim.

The performance of the spokes on the application of a force causing radial displacement of the hub relative to the rim may be altered by varying the orientation of the spokes relative to each other as they extend towards the rim.

In embodiments of the invention the spokes of each pair of opposed spokes follow curved profiles extending back towards each other as they extend towards the rim so as meet substantially end to end at the rim. In other embodiments the spokes of each pair of opposed spokes follow curved profiles extending back towards each other as they extend towards the rim so as to pass each other as they extend towards the rim.

Shaping the spokes to extend past each other as they approach the rim increases the length of the curved profile of each spoke relative to the distance between the hub and the rim and thereby increases the extent to which the spokes may extend and compress on the application of a force resulting in displacement of the hub relative to the rim. This is particularly advantageous in small wheels where the space available to receive the spokes between the hub and the rim is limited. In small wheels, more rigid spokes might otherwise be required to absorb forces tending to cause radial displacement of the hub relative to the rim.

The length of the curved profile may be further increased through the use of a C-shaped profile.

It will be appreciated that compression of the spokes on radial movement of the hub towards the rim in the direction of the spokes will cause movement of adjacent spokes towards each other. So as to reduce the risk of the adjacent spokes colliding when they are compressed, each spoke may be connected at or towards the one end to the hub so as to extend tangentially from the hub at an angle to the circumferential hub line.

Alternatively, or in addition, each spoke may be connected at or towards the other end to the rim so as to extend from the rim at an angle to the circumferential rim line.

Angling the spokes relative to the hub and or rim of the wheel allows the curved profiles of the spokes to flex outwardly of the wheel, and the angle is preferably chosen so that each spoke follows its own trajectory in its own plane. This further reduces the risk of collisions between adjacent spokes and, in turn, allows a greater number of spokes to be incorporated into the wheel.

In embodiments in which the connection between the other end of each spoke and the rim is angled so that the spoke extends from the rim at an angle to the circumferential rim line, the curved profile of the spoke may be twisted so that the connection between the other end of each spoke and the rim is skewed relative to an inner circumferential surface of the rim.

Introducing a twist into the curved profile of each spoke further alters the direction in which the curved profile is able to compress on radial movement of the hub towards the rim and thereby reduces the risk of collisions between adjacent spokes whilst minimising the outward movement of the spokes.

In order to maximise the strength of the wheel, and facilitate construction of the wheel, each spoke of each pair of opposed spokes may be formed integrally with an opposed spoke of an adjacent pair of opposed spokes.

Depending on the shapes of the spokes and the positioning of the spokes relative to each other, and the resilient properties of the spokes, the spokes may be located circumferentially about the hub so as to form spring units arranged to balance the compression and elongation of the spokes on radial displacement of the hub relative to the rim. Balancing the compression and elongation in this manner assists balancing any displacement of the hub relative to the rim and increases the damping available from the spring units, thereby reducing the risk of uneven oscillation of the hub relative to the rim.

In embodiments in which the spokes of each pair of opposed spokes extend towards each other as they extend towards the rim but do not pass each other, the spokes of each pair of opposed spokes may form a spring unit, the spring units being circumferentially arranged about the hub to define co-operating pairs of opposed spring units such that movement of the hub towards the rim in the radial direction of one of the spring units of a co-operating pair of spring units causes compression of the spokes of the one spring unit and extension of the spokes of the other spring unit of the co-operating pair of spring units.

In other embodiments, in which the spokes of each pair of opposed spokes pass each other as they extend towards the rim, each spoke may form a spring unit in combination with the opposed spoke of an adjacent pair of opposed spokes.

It is envisaged that in further embodiments, the resilient properties of the spokes and the connections between each spoke and the hub and rim may be chosen such balancing of spring units circumferentially about the hub is not required to balance any displacement of the hub relative to the rim and to reduce the risk of uneven oscillation. In such embodiments, it will be appreciated that the number of spokes included in the wheel may be chosen to produce an odd number of pairs of opposing spokes or spring units.

It is also envisaged that in yet further embodiments, the intended use of the wheel is such that balancing of any displacement of the hub relative to the rim and to reduce the risk of uneven oscillation is not required. Again it will be appreciated that in such embodiments the number of spokes included in the wheel may be chosen to produce an odd number of pairs of opposing spokes or spring units.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a plan view of a wheel according to an embodiment of the invention; Figure 2 illustrates a pair of opposed spokes of the wheel of Figure 1; Figure 3 is a perspective view of the wheel of Figure 1; Figure 4 is a cross-sectional view along line I-I of Figure 1; Figure 5 is a plan view of a wheel according to another embodiment of the invention; Figure 6 illustrates a pair of opposed spokes of the wheel of Figure 5; Figure 7 is a perspective view of the wheel of Figure 5; Figure 8 illustrates an integrally formed pair of spokes of the wheel of Figure 5; Figure 9 is a plan view of a wheel according to a further embodiment of the invention; Figures 10 and 11 illustrate a pair of opposed spokes of the wheel of Figure 9; Figure 12 is a perspective view of the wheel of Figure 9; and Figure 13 illustrates an integrally formed pair of spokes of the wheel of Figure 9.

A wheel 10 according to an embodiment of the invention is shown in Figure 1.

The wheel 10 includes a hub 12, a rim 14 and a plurality of spokes 16 arranged circumferentially around the hub 12. Each spoke 16 is fixedly connected at one end to the hub 12 so as to extend tangentially from the hub 12, and pivotably connected at its other end to the rim 14 by means of a hinge assembly 18. The hub 12 defines an axis of rotation A of the wheel 10.

The spokes 16 include curved profiles 24 and are arranged to define pairs of opposed spokes 16a,16b spaced circumferentially about the wheel 10, the curved profiles of the opposed spokes 16a,16b being curved in opposite directions to each other, as shown in Figure 2.

Referring to Figures 3 and 4, the opposed spokes 16a,16b of each pair are connected to the hub 12 at spaced locations on opposite sides of a circumferential hub line 20 extending about the axis of rotation A of the wheel 10 so as to extend tangentially from the hub 12 generally towards each other. They are connected at their other ends to the rim 14 on a circumferential rim line 22 extending about the axis of rotation A of the wheel and aligned with the circumferential hub line 20.

The opposed spokes I 6a, I 6b of each pair are shaped to pass each other as they extend generally towards each other from the hub 12 and thereafter follow their curved profiles 24 so as to extend back towards each other as they extend towards the rim 14 so as to meet substantially end to end at a shared hinge assembly 18.

The spokes 16 are formed from laminated structures including a plurality of alternating layers of carbon fibre and epoxy resin. The layers of carbon fibre are arranged within the laminated structures so as to be aligned along the lengths of the spokes 16 and provide a uni-directional strengthening effect.

Each spoke 16 is shaped to vary in width W between the hub 12 and the rim 14, in a direction parallel to the axis of rotation A of the wheel 10, such that the width W is greatest through the curved profile 24 of the spoke 16.

In the embodiment shown in Figure 1, the pairs of opposed spokes 16a,16b are equidistantly spaced about the circumference of the wheel 10. Since all of the spokes are equal in length and define the same curved profile 24, this means the hub 12 is centrally located within the rim 14 in an unloaded or rest configuration of the wheel 10.

The resilient nature of the spokes 16 allows the curved profile 24 of each spoke to deform on the application of a compressive or tensile load, the curvature of the curved profile 24 of each spoke 16 increasing on the application of a compressive load and the curvature of the curved profile 24 of the spoke decreasing on the application of a tensile load. Consequently, on the application of a radial load to the hub 12, the spokes 16 deform as the hub 12 moves relative to the rim 14 in the direction of the radial load, the nature of the deformation of each spoke 16, i.e. elongation or compression, being determined by the direction of the applied load.

On removal of the radial load, the resilient nature of the spokes 16 means that each of the spokes 16 resumes its original shape and the hub 12 is thereby returned to its unloaded or rest position, centrally located within the rim 14.

Similarly, on the application of a radial load to the rim 14 so as to cause movement of the rim 14 towards the hub 12, the spokes 16 will deform in accordance with the direction of the radial load, as the rim 14 moves towards the hub 12, and will return the rim 14 to its unloaded or rest position relative to the hub 12 on removal of the load.

The arrangement of the spokes in each pair of opposed spokes 16a,16b relative to the circumferential hub and rim lines 20,22 improves the lateral stability of the wheel 10 by resisting twisting movement hub 12 relative to the rim 14 whilst at the same time facilitating the use of a relatively narrow rim 14. This is particularly advantageous when the size of the rim 14 is an important factor in terms of the performance of the wheel 10.

The use of a relatively narrow rim 14 is important, for example, in racing bicycle wheels.

The width W of the curved profile 24 of each spoke 16 also helps to improve the lateral stability of the wheel 10 by increasing the ability of the spokes 16 to resist twisting of the hub 12 relative to the rim 14.

Arranging the spokes so as to define pairs of opposed spokes 16a,16b in which the curved profiles 24 of the spokes 16a,16b oppose each other, and connecting the opposed spokes 16a,16b of each pair to the hub 12 at spaced locations, enables the spokes to apply opposing turning forces to the hub 12 when a driving torque is applied to either the hub 12 or the rim 14. Consequently the spokes act on the hub 12 to resist rotation of the hub 12 relative to the rim 14. This is particularly advantageous in circumstances where the driving torque is applied to the hub 12 to either accelerate or decelerate rotation of the wheel 10.

Depending on the nature of the intended use of the wheel 10, and the size of driving torques intended to be applied to the hub 12 or rim 14, the size of the turning forces applied to the hub 12 by the spokes 16 may be increased by increasing the radial size of the hub 12 and by increasing the distance between the fixed ends of the opposed spokes 16a,16b of each pair.

Each pair of opposed spokes 16a,16b forms a spring unit arranged about the circumference of the hub 12 in co-operating pairs of spring units located on opposite sides of the hub 12. This arrangement provides a balanced response on the application of a radial load to the hub 12 or rim 14, one spring unit compressing whilst the co-operating spring unit elongates. When the wheel 10 is used on a vehicle or a bicycle, such balancing of the response to the spokes 16 to any such radial forces helps to provide a smooth ride for any occupant or rider as opposed to a bumpy ride that might otherwise result from an unbalanced arrangement of the spokes 16.

Consequently the resilient nature of the spokes 16, and the balanced arrangement of the pairs of opposed spokes 16a,16b, results in an enhanced suspension capability integrated within the wheel 10.

In other embodiments it is envisaged that balancing of the spring units may not be required. In such embodiments, the elastic nature of the reinforcing material, which defines the resilient nature of the spokes 16, and the connections between the spokes 16 and the hub 12 and rim 14 may be chosen to ensure that each spring unit provides a balanced response on its own. Alternatively the intended use of the wheel 10 may be such that balancing of any displacement and oscillatory movement of the hub 12 relative to the rim 14 is not required. In such embodiments, the wheel 10 may include an odd number of pairs of opposed spokes 16a,16b and thus an odd number of spring units.

The extent to which the spokes 16 provide an integrated suspension capability is however determined by the elastic nature of the reinforcing material used in the laminated structure of each spoke 16. The use of carbon fibre produces a relatively elastic response. As such, whilst spokes 16 formed using carbon fibre react relatively quickly to the application of a radial load to the hub 12 or rim 14, they provide limited damping capability and are perhaps less suitable for use over bumpy terrain. This is because the spokes 16 are more likely to reach their elastic limit on the application of a relatively large radial load to either the hub 12 or rim 14. This would lead to breakage of the spokes 16.

The damping capability of the spokes 16 may be increased in other embodiments through the use of a reinforcing material that is less elastic. Glass fibre is for example less elastic than carbon fibre, leading to the production of spokes 16 that react more slowly to radial forces applied to the hub 12 or rim 14 and thereby provide a greater damping effect. As such, the use of glass fibre may be considered more suitable for the use in a wheel 10 intended to be used over bumpy terrain. This is because the spokes 16 are less likely to reach their elastic limit on the application of a relatively large radial load to either the hub 12 or rim 14 and therefore less likely to snap.

In yet further embodiments, depending on the elastic response required from the spokes 16, Kevlar (RTM) or hemp may be used in the laminated structure used to form the spokes 16.

Regardless of the material used in the laminated structure, the width W of the curved profile 24 of each spoke 16 increases the strength of the spoke 16 in the curved profile 24. This increased strength of the portion of the spoke 16 that is required to deform during compression of the spoke 16 therefore reduces the risk of the spoke 16 snapping during compression.

The pivotable connection between each spoke 16 and the rim 14 also serves to reduce the risk of the spoke 16 snapping during compression by allowing limited movement of the spoke 16 relative to the rim 14. The pivoting movement of the spokes 16 at the rim 14 reduces the stresses applied to the spokes 16 at the connections with the rim 14 during compression of the spokes 16.

The spokes 16 are fixedly connected to the hub 12 so as to minimise flexing of the spokes 16 relative to the hub 12 and ensure that the spokes 16 are able to consistently apply the turning forces required to resist rotation of the hub 12 relative to the rim 14 on the application of a driving torque to the hub 12 or rim 14.

The strength of each spoke 16 at the connection between the spoke 16 and the hub 12 may be increased to cope with the stresses applied to the spokes 16 at the connections with the hub 12 through the use of one or more additional layers of carbon fibre in the laminated structure at the ends of the spokes 16 fixedly connected to the hub 12.

In other embodiments, depending on the size of radial forces and driving torques likely to be encountered by the wheel 10 and the amount of compression required from the spokes 16, it is envisaged the spokes 16 may be pivotably connected to the hub 12 instead of the rim 14, the spokes 16 may be fixedly connected at both ends to the hub 12 and the rim 14 or pivotably connected at both ends to the hub 12 and the rim 14.

In the wheel 10 shown in Figure 1, movement of the hub 12 relative to the rim 14 is limited by the space available between adjacent pairs of opposed spokes 16a,16b. The elastic nature of the reinforcing material included in the laminated structure used to form the spokes 16 must be chosen to ensure that the spokes of adjacent pairs of opposed spokes 16a,16b do not collide.

In order to reduce the risk of adjacent spokes colliding, the orientation of the curved portion 24 of each spoke 16 may be altered so that the curved profile 24 flexes outwardly from the wheel 10 during compression of the spoke 16.

A wheel 30 according to one such embodiment of the invention is shown in Figure 5.

The wheel 30 includes a hub 32, a rim 34 and a plurality of spokes 36 arranged circumferentially around the hub 32. Each spoke 36 is fixedly connected at one end to the hub 32 so as to extend tangentially from the hub 32 and pivotably connected at its other end to the rim 34 by means of a hinge assembly 38. The hub 32 defines an axis of rotation A of the wheel 30.

The spokes 36 include curved profiles 44 and are arranged to define pairs of opposed spokes 36a,36b spaced circumferentially about the wheel 30, the curved profiles 44 of the opposed spokes 36a,36b being curved in opposite directions to each other, as shown in Figure 6.

Referring to Figure 7, the opposed spokes 36a,36b of each pair are connected to the hub 32 at spaced locations on opposite sides of a circumferential hub line 40 extending about the axis of rotation A of the wheel 30 so as to extend tangentially from the hub 32, at an angle relative to the circumferential hub line 40, generally towards each other. They are connected at their other ends to the rim 34 on a circumferential rim line 42 extending about the axis of rotation A of the wheel 30 and aligned with the circumferential hub line 40.

The opposed spokes 36a,36b of each pair are shaped to pass each other as they extend generally towards each other from the hub 32 and thereafter follow their curved profiles 44 so as to extend back towards each other as they extend towards the rim 34 so as to meet substantially end to end at a shared hinge assembly 38. The spokes 36 are connected to the rim 34 at an angle to the circumferential rim line 42.

The curved profile 44 of each spoke 36 includes a twist so that the connection between the spokes 36 and the hinge assembly 38 is skewed relative to an inner circumferential surface 35 of the rim 34.

The spokes 36 are formed from laminated structures including a plurality of alternating layers of carbon fibre and epoxy resin. The layers of carbon fibre are arranged within the laminated structures so as to be aligned along the lengths of the spokes 36 and provide a u ni-directional strengthening effect.

As in the embodiment shown in Figure 1, each spoke 36 is shaped to vary in width W between the hub 32 and the rim 34, in a direction parallel to the axis of rotation A of the wheel 30, such that the width W is greatest through the curved profile 44 of the spoke 36.

The pairs of opposed spokes 36a,36b are equidistantly spaced about the circumference of the wheel 30. Since all of the spokes are equal in length and define the same curved profile 44, this means that the hub 32 is centrally located within the rim 34 in an unloaded or rest configuration of the wheel 30.

Each spoke of each pair of opposed spokes 36a,36b is formed integrally with an opposed spoke of an adjacent pair of opposed spokes 36a,36b, as shown in Figure 8.

The use of integrally formed spokes 36 strengthens the wheel 30 and facilitates construction of the wheel 30, connection portions 46 being received in angled receiving slots 48 formed on the outer circumferential surface of the hub 32.

The resilient nature of the spokes 36 allows the curved profile 44 of each spoke to deform on the application of a compressive or tensile load, the curvature of the curved profile 44 of each spoke 36 increasing on the application of a compressive load and the curvature of the curved profile 44 of the spoke decreasing on the application of a tensile load. Consequently, on the application of a radial load to the hub 32, the spokes 36 deform as the hub 32 moves relative to the rim 34 in the direction of the radial load, the nature of the deformation of each spoke 36, i.e. elongation or compression, being determined by the direction of the applied load.

On removal of the radial load, the resilient nature of the spokes 36 means that each of the spokes 36 resumes its original shape and the hub 32 is thereby returned to its unloaded or rest position, centrally located within the rim 34.

Similarly, on the application of a radial load to the rim 34 so as to cause movement of the rim 34 towards the hub 32, the spokes 36 will deform in accordance with the direction of the radial load, as the rim 34 moves towards the hub 32, and will return the rim 34 to its unloaded or rest position relative to the hub 32 on removal of the load.

The angle of the angled connections between the spokes 36 and the hub 32 and the skewed connection between the spokes 36 and the rim 34, is chosen so that the curved profiles 44 of the spokes 36 following their own trajectories in their own planes during deformation of the spokes 36, as opposed to deforming within the plane of the wheel 30.

As such, the spokes 36 do not collide during deformation. This allows a longer spoke 36 to be used than in the wheel 10 shown in Figure 1 and thus allows the response of the spokes 36 to the application of radial loads the hub 32 or rim 34 to be altered.

The arrangement of the spokes in each pair of opposed spokes 36a,36b relative to the circumferential hub and rim lines 40,42 improves the lateral stability of the wheel 30 by resisting twisting movement hub 32 relative to the rim 34 whilst at the same time facilitating the use of a relatively narrow rim 34. As outlined with reference to the embodiment show in Figure 1, this is particularly advantageous when the size of the rim 34 is an important factor in terms of the performance of the wheel 30. The use of a relatively narrow rim 34 is important, for example, in racing bicycle wheels.

The width W of the curved profile 44 of each spoke 36 also helps to improve the lateral stability of the wheel 30 by increasing the ability of the spokes 36 to resist twisting of the hub 32 relative to the rim 34.

Arranging the spokes so as to define pairs of opposed spokes 36a,13b in which the curved profiles 44 of the spokes 36a,36b oppose each other, and connecting the opposed spokes 36a,36b of each pair to the hub 32 at spaced locations, enables the spokes to apply opposing turning forces to the hub 32 when a driving torque is applied to either the hub 32 or the rim 34. Consequently the spokes act on the hub 32 to resist rotation of the hub 32 relative to the rim 34. This is particularly advantageous in circumstances where the driving torque is applied to the hub 32 to either accelerate or decelerate rotation of the wheel 30.

Depending on the nature of the intended use of the wheel 30, and the size of driving torques intended to be applied to the hub 32 or rim 34, the size of the turning forces applied to the hub 32 by the spokes 36 may be increased by increasing the radial size of the hub 32 and by increasing the distance between the fixed ends of the opposed spokes 36a,36b of each pair.

Each pair of opposed spokes 36a,36b forms a spring unit arranged about the circumference of the hub 32 in co-operating pairs of spring units located on opposite sides of the hub 32. This arrangement provides a balanced response on the application of a radial load to the hub 32 or rim 24, one spring unit compressing whilst the co-operating spring unit elongates. When the wheel 30 is used on a vehicle or a bicycle, such balancing of the response to the spokes 36 to any such radial forces helps to provide a smooth ride for any occupant or rider as opposed to a bumpy ride that might otherwise result from an unbalanced arrangement of the spokes 36.

Consequently the resilient nature of the spokes 36, and the balanced arrangement of the pairs of opposed spokes 36a,36b, results in an enhanced suspension capability integrated within the wheel 30.

As outlined previously, it is envisaged that in other embodiments the spring units are not arranged about the circumference of the hub 32 to provide a balanced arrangement. In such embodiments the wheel 30 may include an odd number of pairs of opposed spokes 36a,36b and thus an odd number of spring units.

The extent to which the spokes 36 provide an integrated suspension capability is however determined by the elastic nature of the reinforcing material used in the laminated structure of each spoke 36. The use of carbon fibre produces a relatively elastic response. As such, whilst spokes 16 formed using carbon fibre react relatively quickly to the application of a radial load to the hub 32 or rim 34, they provide limited damping capability and are perhaps less suitable for use over bumpy terrain. This is because the spokes 16 are more likely to reach their elastic limit on the application of a relatively large radial load to either the hub 32 or rim 34. This would lead to breakage of the spokes 36.

The damping capability of the spokes 36 may be increased in other embodiments through the use of a reinforcing material that is less elastic. Glass fibre is for example less elastic than carbon fibre, leading to the production of spokes 36 that react more slowly to radial forces applied to the hub 32 or rim 34 and thereby provide a greater damping effect. As such, the use of glass fibre may be considered more suitable for the use in a wheel 30 intended to be used over bumpy terrain. This is because the spokes 16 are less likely to reach their elastic limit on the application of a relatively large radial load to either the hub 32 or rim 34 and therefore less likely to snap.

In yet further embodiments, depending on the elastic response required from the spokes 36, Kevlar (RTM) or hemp may be used in the laminated structure used to form the spokes 36.

Regardless of the material used in the laminated structure, the width W of the curved profile 44 of each spoke 36 increases the strength of the spoke 36 in the curved profile 44. This increased strength of the portion of the spoke 36 that is required to deform during compression of the spoke 16 therefore reduces the risk of the spoke 36 snapping during compression.

The pivotable connection between each spoke 36 and the rim 34 also serves to reduce the risk of the spoke 36 snapping during compression by allowing limited movement of the spoke 36 relative to the rim 34. The pivoting movement of the spokes 36 at the rim 34 reduces the stresses applied to the spokes 36 at the connections with the rim 34 during compression of the spokes 36.

The spokes 36 are fixedly connected to the hub 32 so as to minimise flexing of the spokes 36 relative to the hub 32 and ensure that the spokes 36 are able to consistently apply the turning forces required to resist rotation of the hub 32 relative to the rim 34 on the application of a driving torque to the hub 32 or rim 34.

The strength of each spoke 36 at the connection between the spoke 36 and the hub 32 may be increased to cope with the stresses applied to the spokes 36 at the connections with the hub 32 through the use of one or more additional layers of carbon fibre in the laminated structure at the ends of the spokes 36 fixedly connected to the hub 32.

In other embodiments, depending on the size of radial forces and driving torques likely to be encountered by the wheel 30 and the amount of compression required from the spokes 36, it is envisaged the spokes 36 may be pivotably connected to the hub 32 instead of the rim 34, the spokes 36 may be fixedly connected at both ends to the hub 32 and the rim 34 or pivotably connected at both ends to the hub 32 and the rim 34.

A wheel 50 according to a further embodiment of the invention is shown in Figure 9.

The wheel 50 includes a hub 52, a rim 54 and a plurality of spokes 56 arranged circumferentially about the hub 52. Each spoke is fixedly connected at one end to the hub 52 so as to extend tangentially from the hub 52, and fixedly connected at its other end to the rim 54. The hub 52 defines an axis of rotation A of the wheel 50.

The spokes 56 include curved C-sections 64 and are arranged to define pairs of opposed spokes 56a,56b spaced circumferentially about the wheel 50, the C-sections 64 being curved in opposite directions to each other, as shown in Figure 10.

Referring to Figures 11 and 12, the opposed spokes 56a,56b of each pair are connected to the hub 52 at spaced locations on opposite sides of a circumferential hub line 60 extending about the axis of rotation A of the wheel 50 so as to extend tangentially from the hub 52, at an angle relative to the circumferential hub line 60, generally towards each other. They are not connected at their other ends to the rim 54 on a circumferential rim line 62 extending about the axis of rotation A of the wheel 50 and aligned with the circumferential hub line 60.

The opposed spokes 56a,56b of each pair are shaped to pass each other as they extend generally towards each other from the hub 52 and thereafter follow their curved profiles 64 so as to extend back towards each other as they extend towards the rim 54 so as to pass each other as they extend towards the rim 54. The spokes 56 of each opposed pair are connected to the rim 54 at circumferentially spaced locations and at an angle to the circumferential rim line 62.

The spokes 56 are formed from laminated structures including a plurality of alternating layers of carbon fibre and epoxy resin. The layers of carbon fibre are arranged within the laminated structures so as to be aligned along the lengths of the spokes 56 and provide a uni-directional strengthening effect.

Each spoke of each pair of opposed spokes 56a,56b is formed integrally with an opposed spoke of an adjacent pair of opposed spokes 56a,56b, as shown in Figure 13.

The pairs of opposed spokes 56a,56b are equidistantly spaced about the circumference of the wheel 50. Since all of the spokes are equal in length and define the same C-sections 64, this means the hub 52 is centrally located within the rim 54 in an unloaded or rest configuration of the wheel 50.

The resilient nature of the spokes 56 allows the C-sections 64 of each spoke to deform on the application of a compressive or tensile load, the curvature of the C-section 64 of each spoke 56 increasing on the application of a compressive load and the curvature of the C-section 54 of the spoke decreasing on the application of a tensile load.

Consequently, on the application of a radial load to the hub 52, the spokes 56 deform as the hub 52 moves relative to the rim 54 in the direction of the radial load, the nature of the deformation of each spoke 56, i.e. elongation or compression, being determined by the direction of the applied load.

On removal of the radial load, the resilient nature of the spokes 56 means that each of the spokes 56 resumes its original shape and the hub 52 is thereby returned to its unloaded or rest position, centrally located within the rim 54.

Similarly, on the application of a radial load to the rim 54 so as to cause movement of the rim 54 towards the hub 52, the spokes 56 will deform in accordance with the direction of the radial load, as the rim 54 moves towards the hub 52, and will return the rim 54 to its unloaded or rest position relative to the hub 52 on removal of the load.

Arranging the spokes so as to define pairs of opposed spokes 56a,56b in which the C-sections 64 of the spokes 56a,56b oppose each other, and connecting the opposed spokes 56a,56b of each pair to the hub 52 at spaced locations, enables the spokes to apply opposing turning forces to the hub 52 when a driving torque is applied to either the hub 52 or the rim 54. Consequently the spokes act on the hub 52 to resist rotation of the hub 52 relative to the rim 54. This is particularly advantageous in circumstances where the driving torque is applied to the hub 52 to either accelerate or decelerate rotation of the wheel 50.

Each integrally formed pair of spokes 56a,56b forms a spring unit arranged about the circumference of the hub 52 in co-operating pairs of spring units located on opposite sides of the hub 52. This arrangement provides a balanced response on the application of a radial load to the hub 52 or rim 54, one spring unit compressing whilst the co-operating spring unit elongates.

The angle of the angled connections between the spokes 56 and the hub 52 and the rim 54 is chosen so that the spring units follow their own trajectories in their own planes during deformation of the spokes 56, as opposed to deforming within the plane of the wheel 50. As such, the spokes 56 do not collide during deformation. This allows a longer C-section 64 to be used and thus allows the response of the spokes to the application of radial loads to the hub 52 or rim 54 to be tailored. This ability to alter the length of the C-sections renders the structure of the wheel 50 shown in Figure 9 suitable for use in relatively smaller wheels, such as those used on strollers, pushchairs and scooters. This is because the C-section is able to accommodate deformation of the spokes 56 within a relatively small region between the hub 52 and the rim 54.

As with the embodiments shown in Figures 1 and 5, the extent to which the spokes 56 provide an integrated suspension capability is however determined by the elastic nature of the reinforcing material used in the laminated structure of each spoke 56. The use of carbon fibre produces a relatively elastic response. As such, whilst spokes 56 formed using carbon fibre react relatively quickly to the application of a radial load to the hub 52 or rim 54, they provide limited damping capability and are perhaps less suitable for use over bumpy terrain. This is because the spokes 56 are more likely to reach their elastic limit on the application of a relatively large radial load to either the hub 52 or rim 54. This would lead to breakage of the spokes 56.

As outlined previously, it is envisaged that in other embodiments the spring units are not arranged about the circumference of the hub 52 to provide a balanced arrangement. In such embodiments the wheel 50 may include an odd number of pairs of opposed spokes 56a,56b and an odd number of spring units.

The damping capability of the spokes 56 may be increased in other embodiments through the use of a reinforcing material that is less elastic. Glass fibre is for example less elastic than carbon fibre, leading to the production of spokes 56 that react more slowly to radial forces applied to the hub 52 or rim 54 and thereby provide a greater damping effect. As such, the use of glass fibre may be considered more suitable for the use in a wheel 50 intended to be used over bumpy terrain. This is because the spokes 16 are less likely to reach their elastic limit on the application of a relatively large radial load to either the hub 52 or rim 4 and therefore less likely to snap.

Claims

CLAIMS1. A wheel comprising a hub, a rim and a plurality of resilient spokes arranged to define pairs of opposed spokes spaced circumferentially around the wheel, the hub defining an axis of rotation of the wheel and each spoke being connected at or towards one end to the hub so as to extend tangentially from the hub and being connected at or towards its other end to the rim, wherein the spokes of each pair of opposed spokes are connected to the hub at spaced locations on opposite sides of a circumferential hub line extending about the axis of rotation of the wheel so as to extend tangentially from the hub generally towards each other and are connected to the rim on a circumferential rim line extending about the axis of rotation of the wheel and aligned with the circumferential hub line, the spokes being shaped to pass each other as they extend generally towards each other from the hub and thereafter follow curved profiles extending back towards each other as they extend towards the rim.
2. A wheel according to Claim I wherein each spoke is fixedly connected to the hub at or towards one end and pivotably connected to the rim at or towards the other end.
3. A wheel according to Claim I or Claim 2 wherein each spoke is formed from a laminated structure including two or more alternate layers of reinforcing material and epoxy resin.
4. A wheel according to Claim 3 wherein the reinforcing material is chosen from glass fibre, carbon fibre, Kevlar (RTM) and hemp.
5. A wheel according to Claim 3 or Claim 4 wherein the or each layer of reinforcing material is arranged within the laminated structure so as to follow the shape of the spoke.
6. A wheel according to any one of Claims 3 to 5 wherein each spoke is shaped to vary in width between the hub and the rim, in a direction parallel to the axis of rotation of the wheel, such that the width is greatest through the curved profile of the spoke.
7. A wheel according to any preceding claim wherein the spokes of each pair of opposed spokes follow curved profiles extending back towards each other as they extend towards the rim so as to meet substantially end to end at the rim.
8. A wheel according to any of Claims I to 6 wherein the spokes of each pair of opposed spokes follow curved profiles extending back towards each other as they extend towards the rim so as to pass each other as they extend towards the rim.
9. A wheel according to any preceding claim wherein each spoke defines a C-shaped profile along at least part of its length between the hub and the rim.
10. A wheel according to any preceding claim wherein each spoke is connected at or towards one end to the hub so as to extend tangentially from the hub at an angle to the circumferential hub line.
11. A wheel according to any preceding claim wherein each spoke is connected at or towards the other end to the rim so as to extend from the rim at an angle relative to the circumferential rim line.
12. A wheel according to Claim 11 wherein the profile of each spoke is twisted so that the connection between the other end of the spoke and the rim is skewed relative to an inner circumferential surface of the rim.
13. A wheel according to any preceding claim wherein each spoke of each pair of opposed spokes is formed integrally with an opposed spoke of an adjacent pair of opposed spokes.
14. A wheel according to any preceding claim wherein each pair of opposed spokes defines a spring unit and the spring units are arranged circumferentially about the hub to define co-operating pairs of opposed spring units such that movement of the hub towards the rim in the radial direction of one of the spring units of a co-operating pair of spring units causes compression of the spokes of the one spring unit and extension of the spokes of the other spring unit of the co-operating pair of spring units.
15. A wheel according to Claim 8 wherein the integrally formed spokes define spring units and the spring units are arranged circumferentially about the hub to define co-operating pairs of opposed spring units such that movement of the hub towards the rim in the radial direction of one of the spring units of a co-operating pair of spring units causes compression of the spokes of the one spring unit and extension of the spokes of the other spring unit of the co-operating pair of spring units.
16. A wheel generally as herein described with reference to and/or as illustrated in the accompanying drawings.