BACKGROUND OF THE INVENTION

Field of the Invention

[0001] This invention relates generally to tires, and more specifically to tire treads characterized as having a sacrificial groove separating an outer tread element and an inner tread element, the outer tread element being arranged adjacent to an outer, lateral side of the tread and being configured to protect the inner tread element.

Description of the Related Art

[0002] Tires are known to have treads upon which the tire rotates to generate traction. The portion of the tread that engages a ground surface to generate traction is referred to as an outer, ground-engaging side of the tread. To facilitate traction when having to navigate through water, snow, sand, or any other material, grooves and/or sipes are arranged along the outer, ground-engaging side. These grooves and/or sipes extend into the tread thickness to form a plurality of tread elements, which comprise either a block or a rib. During tire operation, however, tire treads are susceptible to irregular wear.

[0003] To better protect tread elements arranged nearest the lateral sides of the tread, where the lateral sides are spaced apart to define the tread width, one or more protective tread elements are arranged along the lateral sides to separate interior tread elements from the lateral sides of the tread. These protective tread elements may comprise a plurality of tread blocks or a rib, where such a rib is commonly referred to as a sacrificial rib. An intervening longitudinal groove, commonly referred to as a sacrificial groove, separates the outer, protective tread element from an inner, protected tread element, where the outer, protective tread element is arranged adjacent to an outer, lateral side of the tread. These sacrificial grooves, however, can develop cracks and tears, and there is a need to improve a sacrificial groove's resistance to cracking and tearing, such as those that may arise at or near the base of such grooves. By reducing the propensity of these grooves to develop cracks or tears, premature removal of tires will be avoided.

SUMMARY OF THE INVENTION

[0004] Embodiments of the invention include a tire tread comprising a length configured to extend annularly around a tire, a width extending in a transverse direction perpendicular to the length, and a pair of opposing lateral sides defining the width, and comprising a first lateral side and a second lateral side. The tread further includes an outer, ground-engaging side extending between the pair of opposing lateral sides, the ground- engaging side including a plurality of tread elements. The plurality of tread elements include an outer tread element arranged adjacent to the first lateral side and an inner tread element spaced apart by an intervening longitudinal groove from the outer tread element in the transverse direction towards a lateral centerline of the tread. The intervening longitudinal groove extends along a depthwise path into a thickness of the tread from the outer, ground- engaging side to a terminal end defining a height of the first groove. The depthwise path initiates at an entry location and extends into the thickness from the entry location and navigates along a first portion of the path to a widthwise extent of the path offset laterally from the entry location towards the first lateral side by a distance substantially equal to 1 mm to 6 mm. The depthwise path extends further into the thickness to the terminal end along a second portion of the path, the terminal end being offset laterally from the widthwise extent towards the lateral centerline of the tread.

[0005] Additional embodiments include a tire including any such tread described above and herein.

[0006] The foregoing and other embodiments, objects, features, and advantages of the invention will be apparent from the following more detailed descriptions of particular embodiments of the invention, as illustrated in the accompanying drawings wherein like reference numbers represent like parts of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a sectional view of a tire having a tire tread in accordance with an embodiment of the invention.

[0008] FIG. 2 is top view of the tire tread shown in FIG. 1.

[0009] FIG. 3 is partial sectional view of the tire tread shown in FIG. 1 taken at section 3.

[0010] FIG. 4 is a partial sectional view of a tire tread in accordance with an additional embodiment of the invention.

[0011] FIG. 5 is a partial sectional view of a reference tire tread for comparison with the tire tread shown in FIG. 4.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0012] Embodiments of the invention comprise a tire tread, and a tire including the tire tread, where the tire tread has a sacrificial groove separating a sacrificial tread element and an inner, protected tread element. A specific embodiment, exemplary of the invention, is further described in association with the figures included herewith. It is appreciated that the inventive tire tread may comprise any tire tread for use in forming a tire. For example, the tire tread may be an original tread formed with a new tire, or may be applied to a used tire during retreading operations.

[0013] An inventive tire tread includes a length configured to extend annularly around a tire and a width extending in a direction transverse to the length, where the transverse direction extends in a direction perpendicular to the tread length direction. The transverse direction of the tread is also referred to as a lateral or widthwise direction of the tread. The tread length extends in a direction also referred to as a lengthwise or longitudinal direction of the tread. The tire tread also includes a pair of opposing lateral sides spaced apart in the transverse direction to define the tread width. The pair of opposing lateral sides can be described as comprising a first lateral side and a second lateral side. The inventive tire tread also includes an outer, ground-engaging side extending between the pair of opposing lateral sides. The outer, ground-engaging side can be described as extending between the pair of opposing lateral sides along a lateral profile, where the lateral profile represents the general path defined by the outer side surface of each tread element, which does not account for any surface texture or other local anomalies, including any grooves or sipes that may be arranged between the tread elements and in communication with the outer, ground-engaging side of the tread. The tread also includes a thickness extending from the outer, ground- engaging side to a bottom side of the tread. The thickness extends in a direction perpendicular to the outer, ground-engaging side, that is, perpendicular to the lateral profile of the outer, ground-engaging side. The tread bottom side is configured to engage a tire when the tread is attached to the tire, and when attached to a tire the bottom side engages the tire. Most commonly, the bottom side is bonded to the tire, but there are other ways to attach a tread to a tire that may be employed to attach the inventive tread to a tire. In an exemplary embodiment of the inventive tire tread shown in FIGS. 1-3, a tread 12 is shown attached to a tire 10 having a length L12 and a width W12 defined by a pair of opposing lateral sides comprising a first lateral side 14A and a second lateral side 14B. The exemplary tread also includes a thickness T12 extending from an outer, ground-engaging side 16 of the tread to a bottom side 17 of the tread. The outer, ground-engaging side 16 has a lateral profile Pi6 along which the outer, ground-engaging side extends in the transverse direction of the tire tread.

[0014] The ground engaging side of an inventive tread includes a plurality of tread elements. The plurality of tread elements include a laterally outer or external (first) tread element arranged adjacent to the first lateral side and a laterally inner or interior (second) tread element spaced apart from the first tread element in the transverse direction of the tread by an intervening longitudinal groove. In being spaced apart from the outer tread element, the inner tread element is spaced towards a lateral centerline of the tread, or, stated differently, spaced away from the first lateral side and towards the second lateral side. The intervening groove is also referred to as a sacrificial groove, and the outer tread element also referred to as a sacrificial tread element. The intervening groove is a longitudinal groove, meaning the intervening groove has a length extending primarily, yet at least partially, in the direction of the tread length. Stated differently, a longitudinal groove either extends solely in the lengthwise direction of the tread, or is biased to the lengthwise direction, where the groove has vector components extending in the transverse and lengthwise directions of the tread, and where the vector component extending in the lengthwise direction is greater than the vector component extending in the transverse direction. It is appreciated that a tread may include a pair of outer tread elements arranged on opposing lateral sides of the tread, where in particular embodiments each outer tread element is arranged adjacent to the first lateral side and an inner tread element spaced apart from the outer tread element in the transverse direction of the tread by an intervening longitudinal groove. Each intervening longitudinal groove may each comprise any same or different intervening groove described herein. With reference to an exemplary embodiment of the inventive tread shown in FIGS. 1-3, a tread 12 includes a plurality of tread elements 18 extending into the tread thickness T12 from the outer, ground-engaging side 16. The plurality of tread elements 18 include an outer tread element 18 ₀ arranged adjacent to the first lateral side 12 and an inner tread element 18i spaced apart from the outer tread element in the transverse direction of the tread by an intervening longitudinal groove 20 having a length L2 ₀ extending along a length L12 of the tread. A lateral centerline of the tread is shown as CL. In the exemplary embodiment shown, each opposing lateral side 14A, 14B has an outer tread element 18 ₀ arranged in association with an intervening groove 20 and inner tread element 18j.

[0015] The intervening longitudinal groove of an inventive tire tread has a width taken in the transverse direction of the tread. The width is defined to extend between a groove outer side arranged along the outer tread element and a groove inner side arranged along the inner tread element. The intervening longitudinal groove of an inventive tire tread also extends depthwise into a thickness of the tread from an entry location and to a terminal end within the tread thickness. The entry location is arranged along the outer, ground- engaging side of the tread. The height of the groove extends in the direction of the tread thickness and defines the distance between deepest portion of the groove and the entry location of the groove. In the alternative, the height can be described as defining the distance between the deepest portion of the groove and the outer, ground-engaging side of the tread, which, in other words, is the depthwise offset distance between outer, ground-engaging side of the tread and the deepest portion of the groove. In particular embodiments, the deepest part of the groove is located at the terminal end. Accordingly, it is appreciated that the terminal end may not be the deepest part of the groove, and therefore, it is understood that in particular embodiments, the terminal end may be located above the deepest part of the groove towards the outer, ground-engaging side of the tread. The depthwise extension of the intervening longitudinal groove can be said to extend along a depthwise path initiating at an entry location and extending into the thickness from the entry location and to the terminal end. The depthwise path may be defined as an imaginary line along which a center of the groove extends long the length of the groove. This path ignores any grooves or other voids that may project from the intervening longitudinal groove. With reference to an exemplary embodiment of the inventive tread shown in FIGS. 1-3, an intervening longitudinal groove 20 is shown having a terminal end 24, the terminal end forming the deepest portion of the groove and defining a height !½ of the groove. The intervening longitudinal groove 20 extends along a depthwise path P2 ₀ into the tread thickness T12 from the entry location 22 and to the terminal end 24 of the groove. The intervening longitudinal groove 20 also has a width W2 ₀ , extending between a groove outer side 21 ₀ arranged along outer tread element 18 ₀ and a groove inner side 21j arranged along inner tread element 18j.

[0016] The depthwise path of an inventive tire tread can be described as navigating along a first portion extending from the entry location and to a widthwise extent of the path. From the entry location, the depthwise path may extend into the tread thickness from the entry location along any desired path. For example, in particular instances, the groove path extends into the thickness from the entry location in a direction relative to the direction of the tread thickness, which is perpendicular to the outer, ground-engaging side, by an angle of -15 degrees to 15 degrees. This includes the scenario where the groove path initially extends into the thickness from the entry location in a direction relative to the direction of the tread thickness by a zero-degree angle, which is the direction of the tread thickness and a direction normal to the outer, ground-engaging side. After entering the tread thickness from the entry location, the path may extend along any desired path to the widthwise extent of the path. It is appreciated that the widthwise extent of the path is offset from the entry location in the transverse direction of the tread towards the first lateral side by a lateral offset distance. In particular embodiments, the widthwise extent of the path, together with the corresponding groove width, defines the furthest deviation of the groove from the entry location in a transverse direction towards the first lateral side of the tread, which is referred to as the lateral offset distance of the groove outer side, as it measures the lateral distance between the entry location and the widthwise extend along the groove outer side.

[0017] Along the first portion, it is appreciated that the path may extend along any one or more segments, each of which may comprise any linear or curvilinear segment, until reaching the widthwise extent of the path. In particular embodiments, at the widthwise extent of the path, the widthwise extent coincides with a line extending in a direction of the tread thickness and perpendicular to the transverse direction, where the transverse direction extends in the direction of the tread width. In instances where the widthwise extent of the path coincides with a curvilinear portion of the path, the line extending in a direction of the tread thickness is tangent to the curvilinear portion and the widthwise extend of the path. With regard to the lateral offset distance of the path or of the groove outer side, in particular embodiments of the inventive tread the lateral offset distance extending from the entry location of the path and to the widthwise extent of the path is substantially equal to 1 millimeters (mm) to 6 mm, while in other embodiments, the lateral offset distance is greater than 6 mm. In further embodiments, the location of the widthwise extent of the path is offset from the entry location in the direction of the tread thickness by a distance substantially equal to 1/3 (one-third) to 4/5 (four-fifths) of the intervening longitudinal groove height. [0018] With reference to an exemplary embodiment of the inventive tread shown in FIG. 3, a first portion P20-1 of the depthwise path P20 is shown to extend from the entry location 22 in a direction of the tread thickness T12, that is, in a direction normal to the outer, ground-engaging side. The depthwise path P20 continues extending from the entry location 22 and to a widthwise extent 28 of the path towards the first lateral side 14A of the tread, that is, away from the lateral centerline CL of the tread, by a lateral offset distance D _lat In similar fashion, the distance between the entry location 22 and the widthwise extent 28 taken for the outer side 21 ₀ of groove 20 is shown as a lateral offset distance Di _at '. In the embodiment shown, a line L extending in a direction of the tread thickness and perpendicular to the transverse direction is tangent to the widthwise extent 28 of the depthwise path P20. The location of the widthwise extent 28 is shown to be offset from the entry location 22 in the direction of the tread thickness by a distance D _depth substantially equal to 1/3 (one-third) to 4/5 (four-fifths) of the intervening longitudinal groove height H20.

[0019] From the widthwise extent of the depthwise path of an inventive tread, the path extends further into the tread thickness from the widthwise extent and to the terminal end along a second portion of the path, where the terminal end is spaced apart from the widthwise extent of the path in the transverse direction of the tread toward the lateral centerline of the tread. In other words, the second portion of the path returns to a more inward location of the tread from the widthwise extent. In particular embodiments, the second portion of the depthwise path at least partly extends along an arc. It is appreciated that the arc may be defined by a curvilinear line having a desired radius, or may be an effective arc formed of a plurality of segments, each of which may be a curvilinear or linear segment. When the arc is formed of a plurality of segments, it is appreciated that the plurality may comprise at least two segments or three or more segments. In particular embodiments, any such arc is defined as having a radius of at least 2 mm, minus ½ the width of the groove. Or, in other words, an outer radius of the arc taken along the outer side of the groove is at least 2 mm. In particular embodiments, the second portion has an inner radius taken along an inner side of the groove. The width of the groove within the second portion may be constant or variable. For example, when the outer and inner sides within the second portion each extend along an arc, the groove width within the second portion is constant when the outer radius and the inner radius defining each such arc have the same origin. To the contrary, when the outer and inner sides within the second portion each extend along an arc, the groove width within the second portion is variable when the outer radius and the inner radius defining each such arc have a different origin. Optionally, an intervening portion of the path may extend between the first and second portions of the path. It is appreciated that the intervening portion of the path may comprise any linear or curvilinear path, which may be tangent with either or both the first and second portions. With reference to an exemplary embodiment of the inventive tread shown in FIG. 3, the depthwise path P20 of an intervening longitudinal groove 20 includes a second portion Ρ20-2· In the embodiment shown, the second portion P20-2 of the depthwise path P20 at least partly extends along an arc 30, which comprises a single curvilinear segment having a radius Γ2ο· The radius of the arc taken along the outer side 21 ₀ of the groove is represented as ¾ _<> · Second portion also has an inner radius 2 taken along an inner side 21j of the groove 20. The difference between the outer radius Γ2ο ₀ and the inner radius 2 is the width W20 of the groove at a given location along the second portion Ρ20-2· In the embodiment shown in FIG. 3, the groove width W20 along the second portion P20-2 is generally constant. This is because the inner radius 2 and the outer radius Γ2ο ₀ have the same origin, with the path radius r2o located between the inner and outer radii. To the contrary, in the embodiment shown in FIG. 4, the second portion P20-2 has a variable width W20. This is because the outer side extends along an outer radius ¾ _<> while the inner side does not extend along any arc, but instead is defined by a linear extension of the groove. An intervening portion P20 is shown extending from or along the widthwise extent 28 and to the second portion P20-2 of the path.

[0020] As stated previously, the intervening longitudinal groove extends lengthwise to a terminal end located within the tread thickness. In particular embodiments, the terminal end is located at the end of the second portion. It is appreciated that in certain instances, the terminal end is arranged directly below the entry location of the groove in a direction of the tread thickness, while in other instances the terminal end is offset laterally from a location located below the entry location in a direction of the tread thickness either towards the first lateral side or towards the lateral centerline of the tread. In embodiments where the terminal end is offset laterally from a location located below the entry location in a direction of the tread thickness, it is appreciated that the offset distance may be any desired distance; however, in certain instances, the terminal end is laterally offset relative to the entry location between -5 mm and 5 mm. It is appreciated that in embodiments where the second portion extends at least partially along an arc, in certain instances the arc terminates to form the terminal end while in other instances the length of the groove extends further from the arc before reaching the terminal end. With reference to an exemplary embodiment of the inventive tread shown in FIG. 3, the terminal end 24 is arranged at the end of the arc of the second portion P20-2 and directly below the entry location 22 of the groove 20 in a direction of the tread thickness T12, such that the lateral offset distance from the entry location is substantially zero.

[0021] It is appreciated that the intervening longitudinal groove has a width, which may be variable or constant along the entire length or any partial length of the groove. In particular embodiments, at least the second portion of the path has a substantially constant width. With reference to an exemplary embodiment shown in FIG. 3, the groove 20 has a width W20 that is substantially constant along the entire depthwise extension of the groove, including the second portion Ρ20-2· To the contrary, groove 20 in the embodiment shown in FIG. 4 has a variable width W20 along the depthwise extension of the groove. While it is appreciated that the intervening longitudinal groove may have any sized width, in particular embodiments, the groove has a width substantially equal to 0.3 mm to 3 mm for a variable or constant width.

[0022] It is appreciated that each of the inner and outer tread elements may comprise any of a tread block or tread rib. Each of a tread block and tread rib have a defined width extending at least partially in a direction of the tread width. As to length, a tread rib has a length extending the substantially full length of the tread, and which may be continuous or discontinuous, such as when a sipe extends through the rib width. The length of a tread block, however, extends less than the length of the tire tread, where the opposing ends of the block length are arranged adjacent to a lateral groove. In the exemplary embodiment shown in FIGS. 1-3, for example, each of the outer tread element 18 ₀ and inner tread element 18i is a rib.

[0023] It is appreciated that each of the outer and inner tread elements have a width extending at least partially in the transverse direction of the tread. Each such width may comprise any desired width. In particular embodiments, however, such as is exemplarily shown in FIG. 3, however, the width Wis ₀ of the outer tread element 18 ₀ is less than the width Wisi of the inner tread element 18j. [0024] It is also appreciated that each of the outer and inner tread elements have a height extending toward the outer, ground-engaging side from a bottom of the intervening longitudinal groove in a direction of the tread thickness and normal to the outer, ground- engaging side. Each such height may comprise any desired height. In particular instances, there is a difference in height between the outer and inner tread elements, which is termed a tread element height offset distance. While such offset distance may comprise any desired distance, in certain embodiments, the tread element height offset distance is substantially equal to 1 mm to ½ of the inner tread element height. It is appreciated that any offset distance may be employed; however, in particular instances, the height offset distance is such that the inner tread element height is greater than the outer tread element height, or, stated differently, the height of the outer tread element is offset below the profile of the outer, ground-engaging side. In one embodiment shown in FIG. 3, for example, the height His ₀ of an outer tread element 18 ₀ is less than the height Higi of an inner tread element 18j. Accordingly, a difference in height exists between the outer and inner tread elements, which represents a tread element height offset distance ΔΗ.

[0025] In particular embodiments, as noted above, the tire tread is operably attached to a tire. It is appreciated that the tire may comprise any known tire having a tread, which may comprise any pneumatic or non-pneumatic tire. Additionally, for any such tire, the tread may be attached using any known manner. For example, in particular instances, the tire tread may be: (1) bonded to the tire by vulcanization after undergoing a curing operation; (2) attached using an adhesive; and/or, (3) even using mechanical means. It is appreciated that in different instances, the tire tread is either an original tread attached to a new tire or a replacement tread for use in forming a retreaded tire.

[0026] A comparison between an inventive tire tread represented by FIG. 4 and a reference tire tread represented by FIG. 5 was conducted using finite element analysis, where a model of each was created changing only the configuration of the sacrificial groove.

[0027] With reference to a particular embodiment of the inventive tread shown in FIG. 4, the intervening longitudinal groove ("sacrificial groove") 20 is characterized as having a variable groove width W20, where the groove width remains substantially constant up to the groove's second portion P20-2, upon which the groove width widens to its maximum width. In conducting the comparison, the groove width W20 initially equaled 0.5 mm and expanded to a maximum width of 1.5 mm in the second portion P ₂ 0- ₂ , where the second portion initiates at a depth of 8.78 mm from inlet 22. Additional parameters characterizing the sacrificial groove of FIG. 4 as used in the comparison include: a lateral offset D'i _a t equal to 2.5 mm; an outer radius ¾ _<> equal to 2.75 mm; an inner radius ₂ equal to 2.25 mm; and a groove height H ₂ 0 equal to 12.48 mm.

[0028] With regard to the reference sacrificial groove used in the comparison, with reference to FIG. 5, the reference sacrificial groove is characterized by the following parameters: an initial width W ₂ o,ref equal to 1 mm and remaining constant until reaching a groove depth of 6.35 mm, upon which the groove width widens to a maximum width of 2.13 mm before tapering to a terminal end; a lateral offset D' _lat ,ref equal to 1. 13 mm; a radius i"20o,ref equal to 1.63 mm; and a groove height H ₂ o, _re f equal to 12.48 mm. This reference sacrificial groove does not have an inner radius. Instead, the inner side of the initial portion of the groove continues in the same direction, extending linearly to the terminal end.

[0029] Upon applying a lateral force directed away from the lateral centerline of the tread, where the force generated a bending moment on the outer tread element to deform and bend the outer tread element outwardly toward the adjacent lateral side of the tread, which in effect widened the sacrificial groove arranged between the outer tread element and an inner tread element to simulate strain energy density at the bottom of each groove within the tread thickness. For each such test, the strain energy was measured. As a result, the inventive sacrificial groove of FIG. 4 achieved a substantial improvement over the sacrificial groove of FIG. 5 by generating more than a 30% reduction in strain energy, indicating a potential of more than 30% improvement in cracking and tearing resistance of the sacrificial groove along the second portion of the groove path.

[0030] The terms "comprising," "including," and "having," as used in the claims and specification herein, shall be considered as indicating an open group that may include other elements not specified. The terms "a," "an," and the singular forms of words shall be taken to include the plural form of the same words, such that the terms mean that one or more of something is provided. The terms "at least one" and "one or more" are used interchangeably. The term "single" shall be used to indicate that one and only one of something is intended. Similarly, other specific integer values, such as "two," are used when a specific number of things is intended. The terms "preferably," "preferred," "prefer," "optionally," "may," and similar terms are used to indicate that an item, condition or step being referred to is an optional (i.e., not required) feature of the invention. Ranges that are described as being "between a and b" are inclusive of the values for "a" and "b" unless otherwise specified.

[0031] While this invention has been described with reference to particular embodiments thereof, it shall be understood that such description is by way of illustration only and should not be construed as limiting the scope of the claimed invention. Accordingly, the scope and content of the invention are to be defined only by the terms of the following claims. Furthermore, it is understood that the features of any specific embodiment discussed herein may be combined with one or more features of any one or more embodiments otherwise discussed or contemplated herein unless otherwise stated.