EP4658513A1

EP4658513A1 - Non-pneumatic tire with metal spokes formed by a thermo-mechanically controlled process

Info

Publication number: EP4658513A1
Application number: EP24750675.1A
Authority: EP
Inventors: Jared J. Griebel
Original assignee: Bridgestone Americas Tire Operations LLC
Current assignee: Bridgestone Americas Tire Operations LLC
Priority date: 2023-02-02
Filing date: 2024-01-03
Publication date: 2025-12-10
Also published as: JP2026506369A; WO2024163117A1; CN120677072A

Abstract

A method of making spokes for a non-pneumatic tire includes providing a steel plate, heating the steel plate to a temperature of at least 1000° C, and rolling the steel plate at a temperature of at least 900° C until a thickness of the steel plate has been reduced by at least 80%. The method also includes performing a first quenching of the steel plate and reheating the steel plate. The method further includes rolling the steel plate until the thickness of the steel plate has been further reduced by at least 80%, air cooling the steel plate, and reheating the steel plate. The method also includes performing a second quenching of the steel plate and tempering the steel plate. The method further includes cutting the steel plate into a plurality of steel strips and shaping the steel strips into a plurality of steel spokes.

Description

NON-PNEUMATIC TIRE WITH METAL SPOKES FORMED BY A THERMO-MECHANICALLY CONTROLLED PROCESS

FIELD OF INVENTION

[0001] The present disclosure relates to a non-pneumatic tire. More particularly, the present disclosure relates to a non-pneumatic tire having spokes that are formed by a thermos-mechanically controlled process. The resulting spokes may be formed of multiple layers.

BACKGROUND

[0002] Various tire constructions have been developed that 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 being punctured and becoming partially or completely depressurized, for extended periods of time and at relatively high speeds. Non-pneumatic tires may include support structure, such as spokes or webbing, that connects a lower ring to an upper ring. In some non- pneumatic tires, a circumferential tread may be attached to the upper ring of the tire. [0003] Non-pneumatic tire may use high strength, high toughness materials to achieve performance requirements. Steel components may be used as load carrying components of the non-pneumatic tire because of the multitude of options and preparation methods that can be utilized to generate the desired properties.

SUMMARY OF THE INVENTION

[0004] In one embodiment, a method of making a non-pneumatic tire includes providing a lower ring, providing an upper ring, providing a plurality of steel plates, and heating the plurality of steel plates to a temperature between 1000° C and 1200° C. The method further includes placing the plurality of steel plates on top of each other to form a layered steel plate having a first thickness, and rolling the layered steel plate at a temperature between 900° C and 1100° C until the layered steel plate has a second thickness less than the first thickness. The method also includes performing a first quenching of the layered steel plate and reheating the layered steel plate to a temperature between 400° C and 500° C. The method further includes rolling the layered steel plate until the layered steel plate has a third thickness less than the second thickness, and air cooling the layered steel plate to room temperature. The method also includes reheating the layered steel plate to a temperature between 790° C and 830° C, performing a second quenching of the layered steel plate, and tempering the layered steel plate at a temperature between 200° C and 300° C. The method also includes cutting the layered steel plate into a plurality of layered steel strips and shaping the layered steel strips into a plurality of layered steel spokes, with each of the plurality of layered steel spokes having a first end and a second end. The method also includes connecting the first end of each of the plurality of layered steel spokes to the lower ring and connecting the second end of each of the plurality of layered steel spokes to the upper ring. The method further includes applying a tread layer to an upper surface of the upper ring. [0005] In another embodiment, a non-pneumatic tire includes a lower ring having a first diameter and an upper ring coaxial with the lower ring and having a second diameter greater than the first diameter. The non-pneumatic tire also includes a plurality of spokes extending from the lower ring to the upper ring, with each of the plurality of spokes having a first end connected to the lower ring and a second end connected to the upper ring. Each of the plurality of spokes is formed of a plurality of layers of steel, with each layer of steel extending from the first end of the spoke to the second end of the spoke. The plurality of layers of steel includes at least one layer of a first steel having a first carbon content, a first strength, and a first elongation. The plurality of layers of steel also includes at least one layer of a second steel having a second carbon content, a second strength, and a second elongation, wherein the first carbon content is greater than the second carbon content, the first strength is greater than the second strength, and the first elongation is less than the second elongation.

[0006] In yet another embodiment, a method of making spokes for a non- pneumatic tire includes providing a steel plate, heating the steel plate to a temperature of at least 1000° C, and rolling the steel plate at a temperature of at least 900° C until a thickness of the steel plate has been reduced by at least 80%. The method also includes performing a first quenching of the steel plate and reheating the steel plate to a temperature of at least 400° C. The method further includes rolling the steel plate until the thickness of the steel plate has been further reduced by at least 80%, air cooling the steel plate, and reheating the steel plate to a temperature of at least 790° C. The method also includes performing a second quenching of the steel plate and tempering the steel plate at a temperature of at least 200° C. The method further includes cutting the steel plate into a plurality of steel strips and shaping the steel strips into a plurality of steel spokes.

BRIEF DESCRIPTION OF DRAWINGS

[0007] In the accompanying drawings, structures are illustrated that, together with the detailed description provided below, describe exemplary embodiments of the claimed invention. Like elements are identified with the same reference numerals. It should be understood that elements shown as a single component may be replaced with multiple components, and elements shown as multiple components may be replaced with a single component. The drawings are not to scale and the proportion of certain elements may be exaggerated for the purpose of illustration.

[0008] Figure l is a side view of one embodiment of a non-pneumatic tire,

[0009] Figure l is a detail view of a portion of Figure 1 with some features removed for clarity,

[0010] Figure 3 is a perspective view of a steel plate,

[0011] Figure 4 is a time temperature graph of an exemplary method of processing steel plates,

[0012] Figures 5A and 5B are simplified drawings showing exemplary stacks of steel plates,

[0013] Figures 6A-6D are simplified drawings showing additional exemplary stacks of steel plates, and

[0014] Figures 7A and 7B are simplified drawings of layered spokes. DETAILED DESCRIPTION

[0015] The following includes definitions of selected terms employed herein. The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.

[0016] “Axial” and “axially” refer to a direction that is parallel to the axis of rotation of a tire.

[0017] Circumferential” and “circumferentially” refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

[0018] “Radial” and “radially” refer to a direction perpendicular to the axis of rotation of a tire.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] Figures 1 and 2 illustrate one embodiment of a non-pneumatic tire 10. The non-pneumatic tire 10 is merely an exemplary illustration and is not intended to be limiting. In the illustrated embodiment, the non-pneumatic tire 10 includes a generally annular lower ring 20. The lower ring 20 may engage a vehicle hub (not shown) for attaching the tire 10 to a vehicle. The lower ring 20 may be made of a polymeric material, an elastomeric material, a metal, a composite made up of polymers reinforced with glass or carbon fibers, or any other desired material or combination of materials.

[0024] The non-pneumatic tire 10 further includes a generally annular upper ring 30. The upper ring 30 has a diameter that is greater than a diameter of the lower ring 20, and is substantially coaxial with the lower ring 20. The upper ring 30 may be made of a polymeric material, an elastomeric material, a metal, a composite made up of polymers reinforced with glass or carbon fibers, or any other desired material or combination of materials. The lower ring 20 and upper ring 30 may be constructed of the same material, or of different materials.

[0025] A circumferential tread 40 is attached to the upper ring 30. The circumferential tread 40 may be attached to the upper ring 30 adhesively, mechanically, or by any other desired arrangement. The circumferential tread 40 may be made out of rubber, and may include tread elements (not shown) such as grooves, ribs, blocks, lugs, sipes, studs, or any other desired tread elements. The tread band may include a filament assembly.

[0026] In the illustrated embodiment, the circumferential tread 40 is shown as a single layer. In alternative embodiments, the tread may be a multi-layer band. Such multi-layer tread bands may include one or more layers of substantially inextensible material. The layers may be formed of sheets of material, cords of material, filaments of material, or any other desired arrangement. In other alternative embodiments, the multi-layer tread band may include a layer of extensible material, such as an elastomer. In one exemplary embodiment, the tread band may include a pair of inextensible layers separated by a layer of extensible material. In other alternative embodiments, the tread band may include bands that are referred to as shear bands, shear elements, or thin annular high strength band elements.

[0027] Spokes 50 connect the lower ring 20 to the upper ring 30. Each spoke 50 has a first end connected to the lower ring 20 and a second end connected to the upper ring 30. In the illustrated embodiment, the spokes 50 are arranged into two axially spaced spoke groups, including a first spoke group extending in a first direction and a second spoke group extending in a second direction that is opposite to the first direction. In an alternative embodiment, a single group of spokes may be employed, with each spoke extending in the same direction. In another alternative embodiment, three or more axially spaced spoke groups may be employed.

[0028] In the illustrated embodiment, the first end of each spoke 50 is directly connected to the lower ring 20. The first end of the spoke 50 may be connected to the lower ring 20 by welding, brazing, soldering, adhesives, mechanical fasteners (e.g., bolts, rivets), key /key way connections, or any other desired arrangement. The second end of each spoke 50 is connected to a flexure member 60, which in turn is connected to the upper ring 30. In other words, the second end of the each spoke 50 is indirectly connected to the upper ring 30.

[0029] The flexure member 60 may be manufactured out of a polymer e.g., urethane or rubber), a thin, curved piece of metal, or any other desired material or combination of materials. In the illustrated embodiment, the flexure member 60 is provided as a rectangular cuboid and arranged so that an end of the flexure member 60 is aligned with the second end of the spoke 50. In other alternative embodiments, the flexure member may be arranged so that an end of the flexure member is set back from the second end of the spoke, or may be arranged so that an end of the flexure member extends beyond the second end of the spoke. In yet other alternative embodiments, the flexure member may be replaced with a mechanical pinned joint (i.e., hinge). [0030] The flexure member 60 includes a spoke facing surface and a ring facing surface. The spoke facing surface of the flexure member 60 is attached to the spoke 50 and the ring facing surface is attached to the upper ring 30. The attachment between the flexure member 60 and the spoke 50 or between the flexure member 60 and the upper ring 30 may be achieved using welding, brazing, soldering, adhesives, mechanical fasteners (e.g., bolts, rivets), key/keyway connections, or any other desired arrangement. For example, the attachment may be provided by casting urethane directly against the spoke, with or without the spoke being first coated in a primer.

[0031] While the illustrated embodiment shows a first end of each spoke 50 directly connected to the lower ring 20 and a second end indirectly connected to the upper ring 30, it should be understood that other arrangements may be used. For example, in an alternative embodiment, the first end of each spoke is indirectly connected to the lower ring and a second end of each spoke is directly connected to the upper ring. In another alternative embodiment, the first end of each spoke is indirectly connected to the lower ring and a second end of each spoke is likewise indirectly connected to the upper ring. In yet another alternative embodiment, the first end of each spoke is directly connected to the lower ring and a second end of each spoke is likewise directly connected to the upper ring.

[0032] Figure 2 is a detail view of a portion of the non-pneumatic tire 10 with some features removed for clarity. As can be seen in this view, each spoke 50 has a thickness Hn a generally circumferential direction. The thickness t may be between 1.5 mm and 5 mm. In one specific embodiment, each spoke 50 has a thickness t of 3 mm. In the illustrated embodiment, each spoke 50 has a constant thickness t. In alternative embodiments, the thickness of the spoke may vary between the first and second ends. For example, the spoke may have relatively thicker portions at the first and second ends and a relatively thinner portion between the ends. Each spoke also has a width in a generally axial direction.

[0033] In one embodiment, each of the spokes 50 are constructed of steel. More specifically, the spokes 50 are constructed of ultra high strength steel, produced through a Thermo-Mechanically Controlled Process (TMCP) production method. In one specific embodiment, the spokes 50 are layered spokes that are constructed of multiple layers of steel.

[0034] The basis behind TMCP steel production is that a controlled temperature profile within the steel plate ensures development of desired steel microstructure. Simultaneous utilization of heavy warm rolling is used to mechanically reduce the gauge of the steel, decrease the grain size of constituents within the matrix, and accelerate production of microstructure capable of achieving an ultra high strength (z.e., strength greater than or equal to 2000 MPa) while maintaining an acceptable elongation (z.e., an elongation of at least 3%). TMCP has been previously used for large applications involving thick plates, such as steel plates for ship hulls. TMCP is challenging at thinner gauges, however, because it is more difficult to control the properties of the resulting product. For this reason, TMCP has long been thought to be unsuitable for small applications that require thin sheets of steel, such as sheets that are less than a centimeter thick.

[0035] Figure 3 is a perspective view of an exemplary steel plate 100 that is used to form a plurality of spokes. In one embodiment, a single steel plate is used to form the spokes. In an alternative embodiment, a plurality of steel plates may be stacked and processed to ultimately form layered spokes. The steel plate 100 may be formed from any number of steel types. For example, the steel plate 100 may be Damascus or katana steel, or a similar steel type. Such steel types have a high carbon content of at least 0.60%, ultra high strength (z.e., an ultimate tensile strength of at least 2000 MPa, or 290 ksi), and moderate elongation (z.e. elongation of at least 3%). As another example, the steel plate 100 may be formed of steel with a low-medium carbon content of less than 0.60%, high strength (z.e., an ultimate tensile strength of 1200-2000 MPa, or 174-290 ksi), and high elongation (z.e., elongation of at least 10%). In another example, plates of both steel types may be employed.

[0036] The plate 100 has an initial thickness to that is significantly greater than the thickness t of each spoke 50. Where the spoke 50 is formed from a single steel plate 100, the plate may have an initial thickness to between 50 mm and 500 mm. Where the spoke 50 is formed from a plurality of stacked plates, the stack may have a combined initial thickness between 50 mm and 500 mm.

[0037] Figure 4 is a time temperature graph of an exemplary method of processing steel plates using TMCP. The graph is not to scale. While certain temperature values and other notations are present on the graph, it should be understood that these values are merely exemplary.

[0038] The process starts by heating the steel plate 100 (or a plurality of steel plates) to a high temperature. In the time temperature graph, the plate is heated to a temperature of 1200° C and then held at that temperature for two hours. In one embodiment, it takes 30 minutes for each inch of thickness to reach a temperature of 1200° C. In alternative embodiments, the plate may be heated to a temperature between 900° C and 1300° C and held at that temperature for two hours. Heating the plate to such a temperature homogenizes the steel. The temperature may be selected based on the carbon content in the steel. A temperature between 900° C and 1300° C may be appropriate for steel with 0.15%-0.80% carbon content.

[0039] Where multiple plates are being used, the plurality of steel plates are stacked on top of each other during the initial heating phase or directly after the heating phase. The stacking of the plurality of plates results in a layered steel plate. [0040] Figures 5A and 5B are simplified drawings showing exemplary stacks of steel plates 200. Figure 5A illustrates a stack of steel plates 200A with alternating layers of high carbon steel plates 210 and a low carbon steel plate 220. Each high carbon steel plate 210 has a carbon content of at least 0.60%, while the low carbon steel plate 220 has a carbon content of less than 0.60%. In Figure 5A, the high carbon steel plates 210 form the outermost layers, and sandwich the low carbon steel plate 220.

[0041] The high carbon steel plates 210 may be referred to as a plurality of first steel plates having a first strength and a first elongation, and the low carbon steel plate 220 may be referred to as a second steel plate having a second strength and a second elongation. The first strength is greater than the second strength, and the second elongation is greater than the first elongation. For example, the first strength of the finished product may be at least 2000 MPa, while the second strength is between 1200-2000 MPa. The first elongation of the finished product may be at least 3%, while the second elongation is at least 10%.

[0042] Figure 5B illustrates a stack of steel plates 200B with alternating layers of high carbon steel plates 210 and a low carbon steel plate 220. The high carbon and low carbon steel plates 210, 220 are substantially the same as those described above with respect to Figure 5A. In Figure 5B, the low carbon steel plates 220 form the outermost layers, and sandwich the high carbon steel plate 210.

[0043] Figures 5A and 5B each show three layers for illustrative purposes. In practice, it may be desirable to form spokes of many more layers. Figures 6A-6D are simplified drawings showing additional exemplary layers of steel plates. Figure 6A illustrates a stack of steel plates 200C with three high carbon steel plates 210 and three low carbon steel plates 220. In this embodiment one high carbon steel plate 210 forms a first outer layer, while one low carbon steel plate 220 forms a second outer layer opposite the first outer layer.

[0044] Figure 6B illustrates a stack of steel plates 200D with five high carbon steel plates 210 and five low carbon steel plates 220. In this embodiment one high carbon steel plate 210 forms a first outer layer, while one low carbon steel plate 220 forms a second outer layer opposite the first outer layer.

[0045] Figure 6C illustrates a stack of steel plates 200E with ten high carbon steel plates 210 and ten low carbon steel plates 220. In this embodiment one high carbon steel plate 210 forms a first outer layer, while one low carbon steel plate 220 forms a second outer layer opposite the first outer layer.

[0046] Figure 6D illustrates a stack of steel plates 200F with twenty high carbon steel plates 210 and twenty low carbon steel plates 220. In this embodiment one high carbon steel plate 210 forms a first outer layer, while one low carbon steel plate 220 forms a second outer layer opposite the first outer layer.

[0047] The embodiments illustrated in Figures 5A-B and 6A-D are merely exemplary and are not intended to be limiting. In one known embodiment, each steel spoke is made from a stack of 10-20 steel plates. In another known embodiment, each steel spoke is made from a stack of 20-30 steel plates. In yet another known embodiment, each steel spoke is made from a stack of 30-40 steel plates. In still another known embodiment, each steel spoke is made from a stack of 40-50 steel plates. In other words, each steel spoke may be made from a stack of 10-50 steel plates. In each case, the layers may alternate between first steel plates and second steel plates. In alternative embodiments, it may be desirable to use consecutive plates of the same material. In other alternative embodiments, it may be desirable to use three or more different types of steel plates. The outer layers of each stack may be formed of the same steel type, or of different steel type. [0048] Returning to Figure 4, after the initial heating step is complete, steel plate 100 (or the stack of steel plates 200) is rolled at a normalized temperature between 900° C and 1100° C until the thickness of the plate 100 (or the stack of steel plates) has been reduced by 90%. This rolling step may be referred to as a hot rolling process. In other embodiments, the plate may be rolled until its thickness has been reduced by between 80-99%. In other words, the thickness of the steel plate 100 (or the stack of steel plates 200) after this rolling process may be between 1% and 20% of the original thickness. In one embodiment, the thickness of the steel plate or stack of steel plates is between 10 mm and 100 mm at this stage.

[0049] After the rolling process, the steel plate 100 (or the stack of steel plates 200) is rapidly cooled by a first quenching. As shown in the temperature time graph, the quenching is an oil quenching. Oil quenching cools the steel at a rate between 5° C/min and 10° C/min, and generates a martensite structure within the steel plate 100. In other embodiments, another quenching medium may be used, such as glycol, water, or nitrogen.

[0050] The steel plate 100 (or the stack of steel plates 200) is then subjected to a tempforming (“TF”) step, in which the plate is reheated to a temperature between of 500° C at a rate between 5° C/min and 10° C/min. The heat rate will impact the growth of grains within each plate.

[0051] In other embodiments, the plate is reheated to a temperature between 400° C and 600° C. Importantly, the plate is reheated to a temperature below the point at which ferrite transitions to austenite, which is depicted as Ai in the temperature time graph. [0052] While the steel is at the heightened temperature, the steel plate 100 (or the stack of steel plates 200) is rolled again. This process may be referred to as heavy warm rolling. As shown in the time temperature graph of Figure 4, the steel plate 100 (or the stack of steel plates 200) is rolled until its thickness has been reduced by another 85%. In other embodiments, the plate is rolled until its thickness has been reduced by between 80-99%. In other words, the thickness of the steel plate 100 (or the stack of steel plates 200) may be between 1% and 20% of the previous thickness. This thickness is the final plate gauge. In one embodiment, the thickness of the steel plate or stack of steel plates is between 2 mm and 5 mm at this stage. Where a stack of steel plates has been used, each layer of steel may be between and 0.04 mm and 0.5 mm (40-500 pm) at this stage.

[0053] The heavy warm rolling process may result in the production of the ultrafine elongated ferrite grain microstructure and fine carbides that are evenly distributed throughout the matrix. The deformation at these lower temperatures requires a significant amount of force as the steel is rather stiff but is necessary to introduce plastic deformation into the steel.

[0054] After the warm rolling process is complete, the steel plate 100 (or the stack of steel plates 200) is air cooled until it reaches room temperature. After it has been cooled, the steel plate 100 (or the stack of steel plates 200) is reheated again. This time it is reheated to a temperature A2 above the point where ferrite transitions to austenite. For example, the plate may be heated to a temperature between 790° C and 830° C. The plate is then held at this temperature to allow for dissolution of carbides, which then allows for growth of the grain size in the final martensite. In one embodiment, this may occur in less than ten minutes. In other embodiments, it may be held for a significantly longer period of time.

[0055] The steel plate 100 (or the stack of steel plates 200) is then quenched a second time. In one embodiment, the second quenching is a water quenching, which reduces the temperature at a rate between 10° C/min and 20° C/min, depending on the water temperature. In alternative embodiments, the second quenching may be performed with oil, glycol, or nitrogen. The second quenching generates a final, ultrafine martensite structure. The steel plate 100 (or stack of steel plates 200) is then tempered at relatively low temperatures (200-300 °C) to relieve internal stresses and improve the overall percent elongation of the material. The steel plate 100 (or stack of steel plates 200) is then air cooled once again to room temperature.

[0056] After the TMCP process is complete, the steel plate 100 (or stack of steel plates 200) may then be formed into spokes. Figures 7A and 7B are simplified drawings of layered spokes 300. In both drawings, each layer extends along the entire length of the spoke 300 from a first end of the spoke to a second end of the spoke.

[0057] Figure 7A illustrates a spoke 300A with high carbon steel layers 310 surrounding a low carbon steel layer 320. This arrangement corresponds to the stack of steel plates 200A shown in Figure 5A.

[0058] Figure 7B illustrates a spoke 300B with low carbon steel layers 320 surrounding a high carbon steel layer 310. This arrangement corresponds to the stack of steel plates 200A shown in Figure 5A.

[0059] It should be understood that the spokes 300 in Figures 7A and 7B are merely exemplary. Spokes may be formed from a single plate, or any of the stacks of plates that are described above.

[0060] To form the spokes, an operator cuts the steel plate 100 (or stack of steel plates 200) into a plurality of steel strips. The steel strips may be solid steel strips or layered steel strips. The operator then shapes the steel strips into a plurality of steel spokes, each of the plurality of layered steel spokes having a first end and a second end. In one embodiment, the operator forms at least one curve in the steel strip to form a spoke. In the embodiments shown in Figures 7A and 7B, the operator forms multiple curves in the steel strip to form the spokes 300. The operator then connects the first end of each of the steel spokes to a lower ring and connects the second end of each of the plurality of layered steel spokes to an upper ring. This forms a non-pneumatic tire structure, such as the structure shown in Figure 1. The operator may then apply a tread layer to an upper surface of the upper ring to complete construction of the non-pneumatic tire. [0061] In one embodiment, the spokes are formed after the TF process but before the reheating and the second quench. In another embodiment, the spokes are formed after the reheating and the second quench. Forming the spokes before the reheating and second quench may prevent parts from fracturing during forming [0062] 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 624 (2d. Ed. 1995). 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.

[0063] While the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the application, in its broader aspects, is not limited to the specific details, the representative apparatus and method, and illustrative examples shown and described. For example, each spoke may be provided with a rubber coating to soften impact when contact between adjacent spokes occurs. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant’s general inventive concept.

Claims

CLAIMS What is claimed is:

1. A method of making a non-pneumatic tire, the method comprising: providing a lower ring; providing an upper ring; providing a plurality of steel plates; heating the plurality of steel plates to a temperature between 1000° C and 1200° C; placing the plurality of steel plates on top of each other to form a layered steel plate having a first thickness; rolling the layered steel plate at a temperature between 900° C and 1100° C until the layered steel plate has a second thickness less than the first thickness; performing a first quenching of the layered steel plate; reheating the layered steel plate to a temperature between 400° C and 500° C; rolling the layered steel plate until the layered steel plate has a third thickness less than the second thickness; air cooling the layered steel plate to room temperature; reheating the layered steel plate to a temperature between 790° C and 830° C; performing a second quenching of the layered steel plate; tempering the layered steel plate at a temperature between 200° C and 300° C; cutting the layered steel plate into a plurality of layered steel strips; shaping the layered steel strips into a plurality of layered steel spokes, each of the plurality of layered steel spokes having a first end and a second end; connecting the first end of each of the plurality of layered steel spokes to the lower ring; connecting the second end of each of the plurality of layered steel spokes to the upper ring; and applying a tread layer to an upper surface of the upper ring.

2. The method of claim 1, wherein the plurality of steel plates includes a plurality of first steel plates having a first strength and a first elongation, and a plurality of second steel plates having a second strength and a second elongation, wherein the first strength is greater than the second strength, and wherein the second elongation is greater than the first elongation.

3. The method of claim 2, wherein the first strength is at least 2000 MPa and the second strength is between 1200-2000 MPa.

4. The method of claim 2, wherein the first elongation is at least 3% and the second elongation is at least 10%.

5. The method of claim 1, wherein the second thickness is 1-20% of the first thickness, and wherein the third thickness is 1-20% of the second thickness.

6. The method of claim 1, wherein the third thickness is between 2-5 mm.

7. The method of claim 1, wherein the first quenching is performed with oil.

8. The method of claim 1, wherein the second quenching is performed with water.

9. A non-pneumatic tire comprising: a lower ring having a first diameter; an upper ring having a second diameter greater than the first diameter, the upper ring being coaxial with the lower ring; a plurality of spokes extending from the lower ring to the upper ring, wherein each of the plurality of spokes has a first end connected to the lower ring and a second end connected to the upper ring, wherein each of the plurality of spokes is formed of a plurality of layers of steel, wherein each of the plurality of layers of steel extends from the first end of the spoke to the second end of the spoke, wherein the plurality of layers of steel includes at least one layer of a first steel having a first carbon content, a first strength, and a first elongation, wherein the plurality of layers of steel includes at least one layer of a second steel having a second carbon content, a second strength, and a second elongation, wherein the first carbon content is greater than the second carbon content, wherein the first strength is greater than the second strength, and wherein the first elongation is less than the second elongation.

10. The non-pneumatic tire of claim 9, wherein the first end of each of the plurality of spokes is directly connected to the lower ring, and wherein the second end of each of the plurality of spokes is indirectly connected to the upper ring.

11. The non-pneumatic tire of claim 9, wherein the plurality of layers of steel includes at least ten layers of steel.

12. The non-pneumatic tire of claim 9, wherein the plurality of layers of steel includes 30 to 50 layers of steel.

13. The non-pneumatic tire of claim 9, wherein each of the plurality of spokes has a thickness of less than 5 mm.

14. The non-pneumatic tire of claim 9, wherein the first carbon content is at least 0.60% and wherein the second carbon content is less than 0.60%.

15. The non-pneumatic tire of claim 9, wherein the plurality of layers of steel includes alternating layers of the first steel and the second steel.