Patent Description:
The present disclosure relates to the rim of a wheel, and to a wheel comprising such a rim. In a particular form the present disclosure relates to the profile of a rim when viewed from the side, for a wheel of a bicycle, motorcycle, wheelchair, other wheeled vehicle, or any other function for a wheel. The present invention is applicable to a wheel that has spokes numbering from <NUM> to <NUM>, in singles or pairs, wherein the spokes are designed to supply support under both compression and tension.

A conventional wheel consists of a rim to support a tyre, a hub to support bearings connecting the wheel to the axle of the vehicle, and spokes to join the rim to the hub. The spokes may be flexible and function only under tension as is common on a bicycle wheel that commonly features <NUM>-<NUM> spokes, or the spokes may be rigid and function under both compression and tension as is common on street motorcycle and cars wheels.

Examples of wheels are known from <CIT> and <CIT>.

Where a high strength to weight ratio is desirable, designers must consider many aspects of the wheel design. The rim must adequately support the tyre under forces of acceleration, braking, lateral forces from cornering, and impact forces from bumps. The spokes must effectively transfer these forces, and the weight of the vehicle and its driver/rider between the rim and the hub. The hub must be adequately strong and well designed to support the spokes and provide an efficient connection between the wheel and the bearings that rotably connect to the vehicle at the axle or mounting point. Other desirable properties of a well-designed wheel may include favourable aerodynamics, stiffness or flex, and affordable cost of manufacture.

A high strength to weight ratio enables a lighter wheel and is favourable for its positive effect on acceleration and braking performance. It also reduces the unsprung mass. Reducing unsprung mass has a positive impact on performance, handling, and comfort over bumpy terrain. Because the wheel is rotating, it is subject to gyroscopic forces that magnify the felt effect of the wheels mass as the rotation speed increases. It thus becomes highly advantageous to the handling and performance of the bicycle, motorcycle, or other wheeled vehicle, to reduce the wheels mass where possible.

It is against this background and the problems and difficulties associated therewith that the present invention has been developed.

Certain objects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

According to the present invention there is provided a wheel as defined in claim <NUM>.

In one preferred embodiment the spokes rigidly connect the rim to the hub and provide support under forces of both compression and tension. The spoke numbers may vary from <NUM> to <NUM> and may number from <NUM> to <NUM> pairs. In a further embodiment, the wheel comprises a hub adapted to connect the wheel to a non-rotating axle or mounting point of a vehicle.

For ease of description, wheels embodying the various aspects of the present invention are described below in their usual assembled position as shown in the accompanying drawings and terms such as front, rear, upper, lower, horizontal, longitudinal et cetera may be used with reference to this usual position. However, the wheels may be manufactured, transported, sold, or used in orientations other than that described and shown here.

A detailed description of embodiments of the present invention is shown below reference to the accompanying figures that illustrate the principles of the invention. While the invention is described in connection with such embodiments, it should be understood that the invention is not limited to any embodiment. On the contrary, the scope of the invention is limited only by the appended claims and the invention encompasses numerous alternatives, modifications and equivalents. For the purpose of example, numerous specific details are set forth in the following description in order to provide a thorough understanding of the present invention.

The present invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the present invention is not unnecessarily obscured.

Embodiments of the present invention will be discussed with reference to the accompanying drawings wherein:.

In the following description, like reference characters designate like or corresponding parts throughout the Figures.

A conventional wheel for a bicycle or such includes a rim to support the tyre, a hub to connect the wheel rotably to the axle or mounting point of the fork / frame / or vehicle, and spokes to connect the rim to the hub. A first kind of wheel uses thin spokes to connect the rim to the hub. Spokes usually number <NUM> or more per wheel. The spokes are pre-tensioned, meaning that even when the wheel is not supporting any weight, the spokes are under tension. The spokes are commonly made from steel but may also be made from Titanium alloy, Aluminium alloy, composites such as carbon/epoxy, or any other material including high strength fibres. These thin spokes function under tension but provide negligible support under compression. A second kind of wheel uses spokes that provide support under tension and compression. Such spokes feature a larger diameter cross-section, and commonly number from <NUM> to <NUM> per wheel, and regularly occur in pairs ranging from <NUM> to <NUM>. These spokes are often made from plastic, magnesium alloy, aluminium alloy, or composites including carbon fibre. The rim, spokes, and part of the hub can often be made in one piece and cannot be disassembled.

For the purpose of this specification, the term "rim" should be construed as being inclusive of any member whose primary function is to support the tyre and provide adequate strength to support the tyre.

For the purpose of this specification, the term "hub" should be construed as being inclusive of any member whose primary function is to connect the rotatable wheel to an axle of, or mounting point of the bike or vehicle which is not rotating.

For the purpose of this specification, the term "spoke" or "spokes" should be construed as being inclusive of any member whose primary function is to connect the rim to the hub.

For the purpose of this specification, the term "depth of rim" should be construed as being the measurement from the outer diameter of the rim to the inner diameter of the rim at a cross-section viewed perpendicular to the outer diameter of the rim.

Referring now to <FIG>, there is shown a schematic representation of a rim <NUM> of wheel <NUM> according to an embodiment of the present invention. The rim <NUM> supports the tyre <NUM> and is connected to the hub <NUM> via spokes <NUM>.

The rim <NUM> of the wheel <NUM> includes a midsection <NUM> that is deeper in its cross-section than area <NUM> where the spoke <NUM> connects, and is deeper than area <NUM> located between the midsection <NUM> and the spoke connection area <NUM>. The spoke connection area <NUM> is shallower in its cross-section than the midsection <NUM> but deeper in its cross-section than area <NUM>. The area <NUM> is shallower in its cross-section with respect to area <NUM> and <NUM>.

It is to be noted that for the embodiments shown in <FIG>, only three spokes <NUM> are illustrated and described. In certain embodiments spokes may number from two to nine, or in pairs numbering from two to nine. In <FIG> the connection of spokes <NUM> to rim <NUM> is not illustrated to aid understanding of the rim <NUM> profile.

The profile of the rim <NUM> of the wheel <NUM> of <FIG> is considerably unique and offers a superior strength-to-weight ratio than any known arrangement of the prior art. Stiffness and flex properties under both lateral and torsional forces are more consistent and superior also to any known arrangement of the prior art. In general terms, the depth of the rim <NUM>, the distance between the outer diameter <NUM> and the inner diameter <NUM> at location <NUM> may be characterised as being between twenty and sixty percent greater than the depth of the rim <NUM>, the distance between the outer diameter <NUM> and inner diameter <NUM> at area <NUM>. The location of the shallowest section <NUM> of the rim <NUM> can be defined as being between <NUM>% and <NUM>% of the distance between the spoke connection point <NUM> and the midsection <NUM> of the rim <NUM>.

Referring now to <FIG>, there is shown a schematic representation of a rim <NUM> and wheel <NUM> according to an embodiment of the present invention. The rim <NUM> is connected to the hub <NUM> via spokes <NUM>. The profile of the connection <NUM> of the spokes <NUM> to the rim <NUM> is illustrated in a manner similar to production versions of the wheel <NUM>.

The rim <NUM> of the wheel <NUM> includes a midsection <NUM> that is deeper in its cross-section than area <NUM>. The designed depth of the rim <NUM> at area <NUM> where the spoke <NUM> connects to the rim <NUM> is visibly obscured by the profile of the connection <NUM> of the spokes <NUM> to the rim <NUM>. Area <NUM> of the rim is shallower in its cross-section with respect to any other area of the rim <NUM>.

Referring now to <FIG>, there is shown a schematic representation of a rim <NUM> and wheel <NUM> according to an embodiment of the invention. Cross-section depth of the rim <NUM> at locations <NUM>, <NUM>, and <NUM> is here shown for clarity with a dashed line. The outer diameter <NUM> of the rim <NUM> remains constant. The distance from the outer diameter <NUM> to the inner diameter <NUM> of the rim <NUM> is greatest at area <NUM>. The distance from the outer diameter <NUM> to the inner diameter <NUM> is smallest at area <NUM>.

The benefits of the invention can be understood from two known observations of beam bending theory in physics.

Referring now to <FIG>. If a beam <NUM> is laid horizontally between two supports <NUM>, <NUM>, at either end (a simply supported beam) and equal downward forces are applied interchangeably at various locations along the beam, the centre-point 61of the beam <NUM> between the supports <NUM>,<NUM>, will emerge as the most highly stressed and flexed. Optimising the strength-to-weight ratio of this beam <NUM>, along with achieving more consistent flex characteristics can be achieved by adding depth to the cross-section of the beam <NUM> about the mid-section <NUM> while decreasing its depth about the locations <NUM>, <NUM>, nearest the supports <NUM>,<NUM>.

Referring now to <FIG>. If a beam <NUM> is laid horizontally and is clamped rigidly both top and bottom about each end <NUM>, <NUM>, and a downward force <NUM> is applied, say <NUM>% of the distance from one end of the beam to the other, the section <NUM> of the beam <NUM> most closely located to the nearest clamp <NUM> will be the most flexed and highly stressed. This is because support <NUM> is so far away that support <NUM> is bearing the majority of the load. In this instance the beam <NUM> is acting like a cantilever beam that is only clamped and supported about one end <NUM>. Optimising the strength-to-weight ratio of the beam <NUM> under this load can be achieved by adding depth to the cross-section of the beam <NUM> nearest the clamp area <NUM> while reducing the depth of the beam <NUM> as it nears clamp area <NUM>.

When the above physical phenomena are combined and observed in combination with the circular profile of a rim (acting as the beam) and the spokes (acting as the supports and clamps), the rim profile <NUM> of the invention herein described emerges as the optimum design for strength-to-weight properties and consistencies in flex.

Claim 1:
A wheel having a rim (<NUM>) for supporting a tyre (<NUM>), a hub (<NUM>) and a plurality of spokes (<NUM>) having spoke connection points (<NUM>) connecting the rim (<NUM>) to the hub (<NUM>), wherein the depth of the rim (<NUM>) between its outer diameter and its inner diameter at a cross section viewed perpendicular to the outer diameter is varied, wherein
a midsection of the rim (<NUM>) approximately halfway between adjacent spoke connection points (<NUM>) has the greatest depth and
characterised in that an area (<NUM>) of the rim (<NUM>) between the midsection (<NUM>) and an adjacent spoke connection point (<NUM>) has the shallowest depth.