Patent Description:
Various tire constructions have been developed which enable a tire to run in an uninflated or underinflated condition. Non-pneumatic tires do not require inflation, while "run flat tires" may continue to operate after receiving a puncture and a complete or partial loss of pressurized air, for extended periods of time and at relatively high speeds. Non-pneumatic tires may include a plurality of spokes, a webbing, or other support structure that connects a lower ring to an upper ring.

According to its abstract, <CIT> describes an improved spoke edge geometry for a non-pneumatic or hybrid tire that is less prone to fatigue when used. It also provides a way to manufacture such geometry in a mold, In particular the spoke edge geometry is provided with a reduced cross-section that reduces the bending stresses locally and allows a unique mold construction that changes the placement and orientation of potential flash and reduces other potential molding flaws when a liquid such as polyurethane is introduced into the cavity of the mold to form a spoke. This change results in a reduction in the possibility of a stress riser being found near the edge of the spoke, enhancing the durability of the tire.

According to its abstract, <CIT> describes an airless tire thats purpose is to minimize decline in endurance, while improving vibration performance. The spokes of an airless tire are provided, as an integrated unit, with an outside annular portion joined to the inside peripheral surface of a tread ring, an inside annular portion joined to the outside peripheral surface of a hub, and a spoke plate portion of constant thickness providing linkage therebetween. The radial inner edge and the radial outer edge of the center plane of thickness of the spoke plate portion are respectively diagonal with respect to a tire axial-direction line. The intersection line at which the center plane of thickness intersects a plane that is at a right angle to the tire axial-direction line constitutes a straight line. The spoke length, which is the length from the radial inner edge to the radial outer edge along the intersection line, is constant for any given location in the tire axial direction.

Described herein is a non-pneumatic tire that includes a lower ring having a first diameter and an upper ring having a second diameter greater than the first diameter. The upper ring is substantially coaxial with the lower ring. A plurality of spokes extends between the lower ring and the upper ring. Each one of the plurality of spokes includes a first face and a second face opposite the first face, a first axial edge and a second axial edge. The first and second axial edges space the first face from the second face. At least one of the first edge and the second edge has a geometry that provides the spoke with a semi-elliptical cross section.

Also described herein is a method of making a non-pneumatic tire that includes providing a lower ring having a first diameter, providing an upper ring having a second diameter greater than the first diameter, and arranging the upper ring to be substantially coaxially with the lower ring. The method further includes forming a plurality of spokes with a nonrectangular cross section. Each one of the plurality of spokes includes a first face and a second face opposite the first face, and a first axial edge and a second axial edge. The first and second axial edges space the first face from the second face. At least one of the first edge and the second edge has a semi-elliptical cross section geometry that provides the spoke with the nonrectangular cross section. The method further includes attaching the lower ring and the lower ring to one another using the plurality of spokes.

The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation.

"Axial" and "axially" refer to a direction that is parallel to the axis of rotation of a tire.

"Circumferential" and "circumferentially" refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

"Radial" and "radially" refer to a direction perpendicular to the axis of rotation of a tire.

"Tread" as used herein, refers to that portion of the tire that comes into contact with the road or ground under normal inflation and normal load.

While similar terms used in the following descriptions describe common tire components, it should be understood that because the terms carry slightly different connotations, one of ordinary skill in the art would not consider any one of the following terms to be purely interchangeable with another term used to describe a common tire component.

Directions are stated herein with reference to the axis of rotation of the tire. The terms "upward" and "upwardly" refer to a general direction towards the tread of the tire, whereas "downward" and "downwardly" refer to the general direction towards the axis of rotation of the tire. Thus, when relative directional terms such as "upper" and "lower" or "top" and "bottom" are used in connection with an element, the "upper" or "top" element is spaced closer to the tread than the "lower" or "bottom" element. Additionally, when relative directional terms such as "above" or "below" are used in connection with an element, an element that is "above" another element is closer to the tread than the other element.

The terms "inward" and "inwardly" refer to a general direction towards the equatorial plane of the tire, whereas "outward" and "outwardly" refer to a general direction away from the equatorial plane of the tire and towards the side of the tire. Thus, when relative directional terms such as "inner" and "outer" are used in connection with an element, the "inner" element is spaced closer to the equatorial plane of the tire than the "outer" element.

<FIG> and <FIG> are front views of one embodiment of a non-pneumatic tire <NUM>. The non-pneumatic tire <NUM> includes a lower ring <NUM> having a first diameter, and an upper ring <NUM> having a second diameter greater than the first diameter. The upper ring <NUM> is substantially coaxial with the lower ring <NUM>. In the illustrated embodiment, the lower ring <NUM> is shown as being attached to a hub <NUM>.

A circumferential tread <NUM> is disposed about the upper ring <NUM>. The tread <NUM> may include tread elements such as grooves, ribs, blocks, lugs, sipes, studs, and other elements. A shear band or other shear element or reinforcement structure (not shown) may be disposed between the upper ring <NUM> and the tread <NUM>. In an alternative embodiment, the separate tread may be omitted and instead tread elements may be formed directly on the upper ring.

In the illustrated embodiment, a plurality of spokes <NUM> extend between the lower ring <NUM> and the upper ring <NUM>. In this embodiment, the design of each one of the plurality of spokes <NUM> is substantially identical. Accordingly, further description of the plurality of spokes <NUM> will be made with reference to a single spoke. However, in an alternative embodiment, the plurality of spokes may include spokes having different designs.

Referring to <FIG> and <FIG>, the spoke <NUM> extends between a first end <NUM> and a second end <NUM> along a generally radial direction of the non-pneumatic tire <NUM> to define a spoke length L. The first end <NUM> is attached to the lower ring <NUM>. The second end <NUM> is attached to the upper ring <NUM>. Non-limiting examples of how the spoke ends <NUM>, <NUM> may be attached to the lower ring <NUM> and the upper ring <NUM> include adhesive, molding, or mechanical fasteners. Alternatively, the spoke <NUM> and at least one of the lower ring <NUM> and the upper ring <NUM> may be a single, unitary construction.

In the illustrated embodiment, the first end <NUM> and the second end <NUM> are each directly attached to the lower ring <NUM> and the upper ring <NUM>, respectively. In an alternative embodiment, the first end <NUM> or the second end <NUM> may be indirectly attached to the lower ring <NUM> and the upper ring <NUM>, respectively. For example, the first end <NUM> and /or the second end <NUM> may be attached to the respective lower ring <NUM> and outer <NUM> ring by a damper, spacer, or any desired structure.

The spoke <NUM> also extends between a first edge <NUM> and a second edge <NUM> along a generally axial direction of the non-pneumatic tire <NUM> to define a spoke width W. In the illustrated embodiment, the spoke width W is less than the width of both the lower ring <NUM> and the upper ring <NUM>, and the width of the lower ring <NUM> is equal to the width of the upper ring <NUM>. In an alternative embodiment, the width of the spoke may be greater than, equal to, or less than the width of the lower ring or the upper ring. In another alternative embodiment, the width of the lower ring may be greater than or less than the width of the upper ring.

In the illustrated embodiment, the spoke width W is constant along the spoke length L. In an alternative embodiment, the width W of the spoke <NUM> may vary along the spoke length L. Such variable width may provide the spoke <NUM> with desired performance characteristics. For example, beginning from an intermediate point between the first end <NUM> and the second end <NUM>, the spoke <NUM> may taper outwards such that the spoke width W at the first and second ends <NUM>, <NUM> is greater than the spoke width at the intermediate point. According to this example, the intermediate point defines a reduced width portion. This tapered arrangement is shown in phantom with dotted lines in <FIG>. The reduced width of the intermediate point may encourage bending/flexing of the spoke <NUM> at the intermediate point, which may be a desirable characteristic in certain applications. In an alternative embodiment, the reduced width portion may be located at any desired point along the length L of the spoke <NUM>. In another alternative embodiment, the spoke <NUM> may have multiple reduced width portions.

The spoke <NUM> includes a first face <NUM> and a second face <NUM>, as can be best seen in <FIG>. In the illustrated embodiment, each of the first face <NUM> and the second face <NUM> extend linearly in the axial direction and extends substantially parallel with the axial direction of the non-pneumatic tire <NUM>. In an alternative embodiment, the first face or the second face may extend in a non-linear fashion in the axial direction. In another alternative embodiment, the first face or the second face may be angled relative to the axial direction of the non-pneumatic tire.

The first and second edges <NUM>, <NUM> space the first face <NUM> from the second face <NUM>. The spoke <NUM> extends between the first face <NUM> and the second face <NUM> along a circumferential direction of the non-pneumatic tire <NUM> to define a spoke thickness T. In the illustrated embodiment, the spoke thickness T is constant along the spoke length L. In one example, the spoke thickness T is between <NUM>-<NUM> inches. However, the spoke may have any desired thickness.

In an alternative embodiment, the thickness T of the spoke <NUM> may vary along the spoke length L. Such variable thickness may provide the spoke <NUM> with desired performance characteristics. For example, beginning from an intermediate point between the first end <NUM> and the second end <NUM>, the spoke <NUM> may taper outwards such that the spoke thickness T at the first and second ends <NUM>, <NUM> is greater than the spoke thickness at the intermediate point. According to this example, the intermediate point defines a reduced thickness portion. This tapered arrangement is shown in phantom with dotted lines on one of the spokes in <FIG>. The relatively reduced thickness of the intermediate point may encourage bending/flexing of the spoke <NUM> at the intermediate point, which may be a desirable characteristic in certain applications. In an alternative embodiment, the reduced thickness portion may be located at any desired point along the length L of the spoke <NUM>. In another alternative embodiment, the spoke <NUM> may have multiple reduced thickness portions.

In the illustrated embodiments, the first edge and the second edge <NUM>, <NUM> of the spoke <NUM> has a geometry that gives the spoke <NUM> a nonrectangular cross section. In each of these embodiments, the edges may be described as tapered. <FIG> illustrates one example in which the edges are rounded. In other words, the geometry of each of the first edge and the second edge 215a, 220a is a continuously curved surface having a semi-circle cross section. The radius of curvature of the continuously curved surface may be one half the thickness of the spoke (i.e., <NUM>T). However, the radius of curvature of the continuously curved surface may be any desired value.

Known spokes having a rectangular cross section with orthogonal axial edges may be sensitive to surface imperfections (e.g., scratches, gouges, nicks) that could grow into a crack that may result in failure of the spoke. The continuously curved surface geometry of the first and second edges 215a, 220a of the spoke <NUM> shown in <FIG> eliminates the orthogonal axial edges and provides the spoke <NUM> with a nonrectangular cross section. This arrangement may reduce the sensitivity of the spoke <NUM> to such minor imperfections and enhance fatigue life of the spoke <NUM>, thereby increasing the robustness of the spoke <NUM> over known spoke designs.

<FIG> illustrate alternative edge geometries that may be employed. It should be understood that these embodiments are merely exemplary, and additional geometries may be employed that provide greater complexity than a rectangular cross-section. In the embodiment shown in <FIG>, the geometry of the first edge and the second edge 215b, 220b is a continuously curved surface having a semi-elliptical cross section. In another alternative embodiment, the geometry of the first or second edges <NUM>, <NUM> may be a continuously curved surface defined by a plurality of radii. In yet another alternative embodiment, which is not used in an embodiment of a non-pneumatic tire or in a method of making a non-pneumatic tire according to the present invention, the first or second edges <NUM>, <NUM> may be a continuously curved surface having any desired cross section. In yet another alternative embodiment, the geometry of only one of the first and second edges <NUM>, <NUM> may be provided as a continuously curved surface.

As shown in <FIG>, rather than a continuously curved surface, the geometry of the first and second edges <NUM>, <NUM> may include a respective straight portion <NUM>, <NUM>. The embodiments according to <FIG> are not used in an embodiment of a non-pneumatic tire or in a method of making a non-pneumatic tire according to the present invention. In this case, as shown in <FIG>, the geometry of the first edge and the second edge 215c, 220c includes a curved surface between the straight portions <NUM>, <NUM> and the faces <NUM>, <NUM>. In other words, the first and second edges 215c, 220c have rounded corners. In another example, as shown in <FIG>, the geometry of the first edge and the second edge 215d, 220d includes a linear surface between the straight portions <NUM>, <NUM> and the faces <NUM>, <NUM>. In other words, the first and second edges 215d, 220d have chamfered corners.

In each of the foregoing examples, the geometry of the first edge and the second edge <NUM>, <NUM> eliminates the orthogonal axial edge of known spoke designs. Regardless of the specific geometry employed, providing a spoke that is free from orthogonal axial edges enhances fatigue life and reduces sensitivity of the spoke to surface imperfections, thus improving spoke robustness.

The geometries of the first and second edges <NUM>, <NUM> may be formed using any desired manufacturing process. Non-limiting examples of manufacturing processes that may be used to form the geometries of the first and second edges <NUM>, <NUM> include rolling, shot peening, hydroforming, flow forming, or roll forming.

According to one example, the geometry of the first edge or the second edge <NUM>, <NUM> may be provided by initially forming the edge using laser cutting, skiving, or any other desired cutting process. Then, the cut edges may be subsequently treated with a rolling process, shot peening process, or both to provide a rounded edge with a desired smoothness. In alternative embodiments, the first edge or the second edge may be treated with a rolling process, shot peening process, or both without prior edge forming.

To further improve the robustness of the spoke <NUM>, the faces <NUM>, <NUM> or the edges <NUM>, <NUM> of the spoke <NUM> may be provided with a specific surface roughness. In one example, the average surface roughness of the spoke <NUM> is less than <NUM> microns, preferably less than <NUM> microns, and ideally less than <NUM> microns. These specific roughness values are considered when measuring the surface roughness of the spoke <NUM> along the radial direction of the non-pneumatic tire <NUM> and also along axial direction of the non-pneumatic tire <NUM>. In another embodiment, the specific roughness values are considered when measuring the surface roughness of the spoke <NUM> along the radial direction of the non-pneumatic tire <NUM>, but not the axial direction A of the non-pneumatic tire <NUM>. For example, in one such embodiment, the surface may be relatively smooth in the axial direction, and relatively rough in the radial direction. Smoothing the surface in a single direction may be less time consuming and less costly. In yet another embodiment, the specific roughness values are considered when measuring the surface roughness of the spoke <NUM> along the axial direction of the non-pneumatic tire <NUM>, but not the radial direction of the non-pneumatic tire <NUM>.

The specific surface roughness may be imparted to the spoke <NUM> using any desired manufacturing process. Examples of manufacturing processes that may be used to impart the specific surface roughness include, but are not limited to shot peening, laser shock peening, low plasticity burnishing, machining, grinding, polishing, or lapping. Alternatively, the surface rough may be provided by an isotropic etching process, or by a chemical treatment. Using any of the foregoing processes to provide the spoke <NUM> with a surface roughness of less than <NUM> microns eliminates, or at least substantially reduces, surface imperfections on the spoke that may propagate through the spoke and result in spoke failure. The specified surface roughness of less than <NUM> microns enhances fatigue life of the spoke <NUM>. Accordingly, providing a surface roughness of less than <NUM> microns may improve robustness of the spoke <NUM>. Providing a roughness of less than <NUM> microns, or less than <NUM> microns may further enhance these benefits.

In one example embodiment, shown in <FIG>, the spoke <NUM> is substantially U-shaped. In another example embodiment, shown in <FIG>, the spoke <NUM> is substantially V-shaped. Compared to the U-shaped spoke, the V-shaped spoke has a more pronounced point between the lower ring <NUM> and the upper ring <NUM>. In yet another example embodiment, shown in <FIG>, the spoke <NUM> is serpentine shaped with two or more bends. In other example embodiments the spoke <NUM> may be any desired shape (e.g., straight spoke). The shape of the spoke <NUM> may be selected to provide desired performance characteristics.

The spoke <NUM> may be manufactured out of any desired material. For example, the spoke <NUM> may be manufactured out of high strength steels such as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. As another example, the spoke <NUM> may be manufactured out of reinforced polymers/plastics such as those reinforced with carbon fiber, glass fiber, or aramid fiber. The spoke <NUM> may manufactured out of a single strip of material, or may be formed as multiple strips of material that are subsequently secured together. The spoke <NUM> may be provided with a coating to enhance performance characteristics of the spoke and provide physical protection, corrosion resistance, or vibration damping.

While <FIG> illustrate embodiments of non-pneumatic tires having spokes, it should be understood that other support structures may be used instead of spokes, wherein such embodiments are neither used in embodiments of a non-pneumatic tire according to the present invention, nor in embodiments of a method of making a non-pneumatic tire according to the present invention. For example, <FIG> illustrates one embodiment of a non-pneumatic tire <NUM> having a lower ring <NUM>, an upper ring <NUM>, and a webbing <NUM> extending between the upper ring and the lower ring. Aside from the use of a webbing instead of spokes, the non-pneumatic tire of <FIG> is otherwise substantially the same as the non-pneumatic tire <NUM> described above with respect to <FIG>. In other words, the webbing <NUM> may have any of the edge geometries described above. Likewise, the webbing <NUM> may be constructed of any of the spoke materials discussed above.

The geometry of the webbing <NUM> shown in <FIG> is merely exemplary. It should be understood that the webbing may have any geometry. In other alternative embodiments (not shown), support structures other than spokes or webbing may be employed.

To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both. " When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage <NUM> (2d. Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto. " Furthermore, to the extent the term "connect" is used in the specification or claims, it is intended to mean not only "directly connected to," but also "indirectly connected to" such as connected through another component or components.

Claim 1:
A non-pneumatic tire (<NUM>) comprising:
a lower ring (<NUM>) having a first diameter;
an upper ring (<NUM>) having a second diameter greater than the first diameter, the upper ring being (<NUM>) substantially coaxial with the lower ring (<NUM>);
a plurality of spokes (<NUM>) extending between the lower ring (<NUM>) and the upper ring (<NUM>), each one of the plurality of spokes (<NUM>) including:
a first face (<NUM>) and a second face (<NUM>) opposite the first face (<NUM>), and
a first axial edge (<NUM>; 215a; 215b; 215c; 215d) and a second axial edge (<NUM>; 220a; 220b; 220c; 220d), the first and second axial edges (<NUM>, <NUM>) spacing the first face (<NUM>) from the second face (<NUM>),
characterised in that
at least one of the first edge (<NUM>) and the second edge (<NUM>) includes a semi-elliptical cross section geometry that provides the spoke (<NUM>) with a nonrectangular cross section, the semi-elliptical cross section geometry having a semi-major axis and a semi-minor axis, a length of the semi-major axis being greater than a length of the semi-minor axis.