Patent Publication Number: US-2019184760-A1

Title: Apparatuses and methods for improving chunking and cracking resistance of tires

Description:
FIELD 
     This application generally to apparatuses and methods of improving chunking and cracking resistance of tires. 
     BACKGROUND OF THE DISCLOSURE 
     Sipes are sometimes cut or molded into tread to improve traction. Sipes may be formed in ribs and blocks of a tread and may exhibit the effect of cutting through water films on road surfaces, similar to edges of grooves. Sipes may also facilitate deformation of ribs and blocks, and may inhibit tire hysteresis loss. A sipe pattern can be within one or more blocks, ribs or lugs of the tire tread and included within the boundary of each tread element. Sipes may be cut straight across the tire tread, or at a constant a bias angle within tread elements. Sipes may weaken the tread blocks, and make them more susceptible to tearing or chunking off pieces of rubber. This may cause some tearing and chipping to occur at the edges of the tread blocks when the tire is subjected to side scrub. 
     BRIEF SUMMARY 
     Some embodiments relate to methods and apparatus for increasing chunking and cracking resistance of tire treads, and more particularly, apparatus and methods in which chevron or offset chevron shaped sipes are provided on a tire tread causing significant increase in chunking and cracking resistance of the tire tread. 
     In some embodiments, a tire may include a tire tread defining a rotational axis. A plurality of tread elements may be positioned on the tire tread surface so as to provide a tread pattern. The plurality of tread elements may be positioned at least one of axially or circumferentially on the tire tread surface. A plurality of grooves may be provided between the plurality of tread elements. A first set of sipes may extend from a circumferential axis of the tire tread towards a first axial end of the tire tread at a non-zero angle with respect to an axial axis of the tire tread. A second set of sipes may extend from the circumferential axis towards a second axial end of the tire tread opposite the first axial end at the non-zero angle with respect to the axial axis such that a first sipe end of each of the first set of sipes may be positioned proximate to a second sipe end of each of the second set of sipes. Each of the first set of sipes and the second set of sipes may extend beyond 50% of a half width of the tire tread measured from the circumferential axis. Moreover, each of the first set of sipes and the second set of sipes may have a sipe depth greater than 50% of a height of the plurality of tread elements. 
     In some embodiments, a tread pattern for a tire tread may include a plurality of tread elements positioned on a tire tread first surface so as to provide the tread pattern. The plurality of tread elements may be positioned at least one of axially or circumferentially on the tire tread surface. A plurality of grooves may be provided between the plurality of tread elements. A first set of sipes may extend from a circumferential axis of the tire tread towards a first axial end of the tire tread at a non-zero angle with respect to an axial axis of the tire tread. A second set of sipes may extend from the circumferential axis towards a second axial end of the tire tread opposite the first axial end at the non-zero angle with respect to the axial axis such that a first sipe end of each of the first set of sipes may be positioned proximate to a second sipe end of each of the second set of sipes. Each of the first set of sipes and the second set of sipes may extend beyond 50% of a half width of the tire measured from the circumferential axis. Moreover, each of the first set of sipes and the second set of sipes may have a sipe depth greater than 50% of a height of the plurality of tread elements. 
     In some embodiments, a method of increasing chunking and cracking resistance of a tire tread of a tire, which includes a plurality of tread elements, includes defining a first set of sipes in the tire tread. The first set of sipes may extend from a circumferential axis of the tire tread towards a first axial end of the tire tread at a non-zero angle with respect to an axial axis of the tire tread. A second set of sipes are provided in the tire tread extending from the circumferential axis towards a second axial end of the tire tread opposite the first axial end at the non-zero angle with respect to the axial axis such that a first sipe end of each of the first set of sipes may be positioned proximate to a second sipe end of each of the second set of sipes. Each of the first set of sipes and the second set of sipes may extend beyond 50% of a half width of the tire tread measured from the circumferential axis, and may have a sipe depth greater than 50% of a height of the plurality of tread elements. 
     All combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being included within this disclosure. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being included within this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
         FIG. 1  is a front view of a portion of a tire tread including chevron shaped sipes, according to some embodiments. 
         FIG. 2  is a side cross-section view of a tread element of the tire tread of  FIG. 1 . 
         FIG. 3  is a front view of a portion of a tire tread including offset chevron shaped sipes, according to some embodiments. 
         FIG. 4  is a front view of a portion of a tire tread including offset chevron shaped sipes, according to some embodiments. 
         FIG. 5  is a front view of a portion of a tire tread including chevron shaped sipes, according to some embodiments. 
         FIG. 6  is a schematic flow diagram of an example method for increasing chunking and cracking resistance of a tire tread, according to some embodiments. 
     
    
    
     Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the disclosure. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure. 
     DETAILED DESCRIPTION 
     Some embodiments relate to methods and apparatus for increasing resistance of tire treads to chunking and cracking, and more particularly, apparatus and methods in which chevron or offset chevron shaped sipe pattern is provided on a tire tread causing significant increase in chunking and cracking resistance of the tire tread. 
     For ease of understanding this disclosure the following terms are disclosed: 
     “Aspect ratio” of the tire may refer to the ratio of its section height (SH) to its section width (Sw) multiplied by 100% for expression as a percentage. 
     “Asymmetric tread” may refer to a tread that has a tread pattern not symmetrical about the centerplane or an equatorial plane EP of the tire. 
     “Axial” and “axially” may refer to lines or directions that are parallel to an axis of rotation of the tire. 
     “Circumferential” may refer to lines or directions extending along the perimeter of the surface of the annular tire tread perpendicular to an axial direction. 
     “Groove” may refer to an elongated void area in a tire tread that may extend circumferentially or laterally about the tire tread in a straight, curved, zigzag or any other suitable manner. Circumferentially and laterally extending grooves may sometimes have common portions. The “groove width” may be equal to a tread surface area occupied by a groove or groove portion, thus, the groove width may be its average width over its length. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. In some embodiments, the depth of the groove may be constant along the tire. If such narrow or wide grooves are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they may be regarded as forming “tie bars” tending to maintain a rib-like character in the tread region involved. 
     “Net-to-gross ratio” may refer to the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges. 
     “Non-directional tread” may refer to a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern may have a preferred direction of travel requiring specific wheel positioning. 
     “Radial” and “radially” may refer to directions radially toward or away from the axis of rotation of the tire. 
     “Rib” may refer to a circumferentially extending strip of rubber on the tread with at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves. 
     “Sipe” may refer to small slots molded or cut into the tread elements of the tire that subdivide the tread surface and may improve traction. 
     “Tread element” or “traction element” may refer to a rib, lug or a block element. 
     “Lugs” may refer to the section of the tread element that make contact with a surface. 
     “Voids” may refer to spaces that are located between the lugs. 
       FIG. 1  is a front view of a portion of a tire tread  100  of a tire, according to some embodiments. The tire may include a pneumatic tire. The tire tread  100  may include a rotational axis and a tread pattern  110 . Specifically, the tire tread  100  may include a plurality of tread elements  112  positioned on a surface of the tire tread  100  that provide the tread pattern  110 . The tire tread  100  may be molded with the tire, or molded separately and thereafter coupled to an outer surface of the tire (e.g., via an adhesive, curing, fusion bonding, heat bonding, etc.). 
     The plurality of tread elements  112  may include a plurality of circumferential lugs  113  separated by voids  114 . A connecting block  115  may be positioned in the void  114  between each of the lugs  113 , and coupled to each of the adjacent lugs  113 .  FIG. 2  is a side cross-section view of a portion of the tire tread  100  including single tread element  112 . As seen in  FIG. 2 , each tread element has a height “h”. A height of each of the connecting block  115  may be smaller than the height h of the tread elements  112  such that the connecting blocks  115  do not contact the surface on which the tire tread  100  is positioned. Furthermore, the tire tread  100  may have a half width “w” ( FIG. 1 ) measured from a circumferential axis A C  of the tire tread  100  to an axial end thereof. 
     A plurality of circumferential grooves  116  may be provided between each of the plurality of tread elements  113 . The tread elements  112  may also include shoulder blocks  118  positioned at axial ends of the tire tread  110 . A plurality of notches  119  or slots may be provided in the shoulder blocks  118 . 
     It is to be appreciated that while the tire tread  100  is shown as having a particular tread pattern  110 , the tire tread  100  may have any suitable tread pattern. For example, the plurality of tread elements  112  may be axially or circumferentially positioned on a surface of the tire tread  100 , include straight, curved or zig zag grooves, a pitch pattern, a non-directional tread pattern, a symmetric tread or an asymmetric tread. Furthermore, the tire tread  100  may have any suitable aspect ratio or net-to-gross ratio. 
     The tire tread  100  may include a first set of sipes  122   a  extending from the circumferential axis of the tire tread  100  towards a first axial end  111   a  of the tire tread  100  at a non-zero angle α with respect to an axial axis A A  of the tire tread  100  (e.g., in the range of about 5-40 degrees inclusive of all ranges and values therebetween). The tire tread  100  may also include a second set of sipes  122   b  extending from the circumferential axis A C  towards a second axial end  111   b  of the tire tread  100  opposite the first axial end. Each of the second set of sipes  122   b  may be inclined at the non-zero angle α with respect to the axial axis A A . The first set of sipes  122   a  and the second set of sipes  122   b  (collectively referred to herein as “the sipes  122 ”) may be molded into the tire tread  100 , for example during a molding operation of the tire tread  100 , or cut into the tread elements  112  after molding of the tire tread  100 . Moreover, the sipes  122  may be inclined towards a direction of rotation of the tire tread  100  or away from the direction of rotation. 
     Each sipe included in the first set of sipes  122   a  and the second set of sipes  122   b , respectively may be positioned parallel to an adjacent sipe at any suitable pitch or distance therefrom. In some embodiments, the distance may be in a range of 5 mm to 40 mm inclusive of all ranges and values therebetween. Furthermore, the distance or pitch may be fixed or variable. 
     A first sipe end  123   a  of each of the first set of sipes  122   a  may be positioned proximate to a second sipe end  123   b  of each of the second set of sipes  122   b . For example, the first sipe end  123   a  and the second sipe end  123   b  of each of the first set of sipes  122   a  and the second set of sipes  122   b , respectively may intersect the circumferential axis A C . In some embodiments, the first sipe end  123   a  and the second sipe end  123   b  may intersect each other such that the combination of the sipes  122  may comprise a chevron shape, as shown for example in  FIG. 1 . In some embodiments, the first sipe end  123   a  and the second sipe end  123   b  may be offset from each other so that the combination of each of the sipes  122  comprise an offset chevron shape. 
     Each of the sipes  122  may extend beyond 50% of a half width of the tire tread  100  measured from the circumferential axis A C . For example, each of the sipes  122  may extend between 60% to 100% of the half width w of the tire tread  100  inclusive of all ranges and values therebetween. Furthermore, each of the sipes  122  may have a sipe depth d greater than 50% of the height h of each of the plurality of tread elements  112 , measured from a top surface of the tread element  112  positioned opposite the surface of the tire tread  100  on which the tread elements  112  are positioned. For example, each of the sipes  122  may have a sipe depth d in a range of 60% to 100% of the height h of the plurality of tread elements  112  inclusive of all ranges and values therebetween. In some embodiments, each of the sipes  122  may have a sipe depth greater than 100% of the height of the plurality of tread elements (e.g., about 101% to 110% of the height h of the plurality of tread elements  112  inclusive of all ranges and values therebetween). 
     Expanding further, in some embodiments as shown in  FIG. 1 , the first sipe end  123   a  and the second sipe end  123   b  of the first set of sipes  122   a  and the second set of sipes  122   b , respectively intersect each other such that the sipes  122  provide a chevron shape. Each of the sipes  122  of the tire tread  100  of  FIG. 1  may extend from the circumferential axis A C  at an angle α of about 35 degrees to a corresponding axial end  111   a/b  of the tire tread  110  so that the sipes  122  may extend to 100% of the half width of the tire tread  110 . The sipes  122  may have a sipe depth d of about 60% of the height h of each tread element  112 , but may be cut to have a deeper sipe depth (e.g., 60%, 70%, 80%, 90%, 100% or 110% of the height h of the tread element  112  inclusive of all ranges and values therebetween). 
       FIG. 3  is a top view of a portion of a tire tread  200  of a tire according to some embodiments. The tire tread  200  includes a tread pattern  210 . The tread pattern  210  may be substantially similarly to the tread pattern  110  of the tire tread  100  and is therefore, not described in further detail herein. 
     A first set of sipes  222   a  and a second set of sipes  222   b  (collectively referred to herein as “the sipes  222 ”) extend from a circumferential axis A C  towards opposite axial ends of the tire tread  200 . For example, each of the sipes  222  may extend to 100% of a half width w of the tire tread  200 , as shown in  FIG. 3 . Each of the second set of sipes  222   b  is also inclined at the non-zero angle α with respect to the axial axis A A , for example at an angle of about 35 degrees. Furthermore, the sipes  222  may have any suitable sipe depth, for example in the range of 60% to 110% of a height of a plurality of tread elements of the tire tread  200 , as described with respect to  FIG. 1 . 
     Each sipe included in the first set of sipes  222   a  and the second set of sipes  222   b , respectively may be positioned parallel to an adjacent sipe at any suitable pitch or distance therefrom. In some embodiments, the distance may be in a range of 5 mm to 40 mm inclusive of all ranges and values therebetween. Furthermore, the distance or pitch may be fixed or variable. 
     A first sipe end  223   a  of each of the first set of sipes  222   a  may be positioned proximate to a second sipe end  223   b  of each of the second set of sipes  222   b . For example, the first sipe end  223   a  and the second sipe end  223   b  of each of the first set of sipes  222   a  and the second set of sipes  222   b  may intersect the circumferential axis A C . The first sipe end  222   a  and the second sipe end  223   b  may be offset from each other so that the combination of each of the sipes  222  provides an offset chevron shape, as shown in  FIG. 3 . 
       FIG. 4  is a top view of a portion of a tire tread  300  of a tire according to some embodiments. The tire tread  300  includes a tread pattern  310 . The tread pattern  310  may be substantially similarly to the tread pattern  110  of the tire tread  100 . 
     A first set of sipes  322   a  and a second set of sipes  322   b  (collectively referred to herein as “the sipes  322 ”) extend from a circumferential axis A C  towards opposite axial ends of the tire tread  200 , and are positioned in an offset chevron pattern. As shown in  FIG. 4 , each of the sipes  322  may extend greater than 50% of a half width w of the tire tread  200 , for example about 60% of the half width w. Each of the second set of sipes  322   b  is also inclined at the non-zero angle α with respect to the axial axis A A , for example an angle of about 20 degrees. Furthermore, the sipes  322  may have any suitable sipe depth, for example in the range of 60% to 110% of a height of a plurality of tread elements of the tire tread  300 , such as described with respect to  FIG. 1 . 
       FIG. 5  is a top view of a portion of a tire tread  400  of a tire according to an embodiment. The tire tread  400  includes a tread pattern  410 . The tread pattern  410  may be substantially similarly to the tread pattern  110  of the tire tread  100 . 
     A first set of sipes  422   a  and a second set of sipes  422   b  (collectively referred to herein as “the sipes  422 ”) extend from a circumferential axis A C  towards opposite axial ends of the tire tread  400 , and are positioned in a chevron pattern. As shown in  FIG. 5 , each of the sipes  422  may extend greater than 50% of a half width w of the tire tread  400 , for example about 80% of the half width w. Each of the second set of sipes  422   b  is also inclined at the non-zero angle α with respect to the axial axis A A , for example an angle of about 20 degrees. Furthermore, the sipes  422  may have any suitable sipe depth, for example in the range of 60% to 110% of a height of a plurality of tread elements of the tire tread  400 , such as described with respect to  FIG. 1 . 
     The chevron or offset chevron sipes described herein may significantly improve chunking or cracking resistance of the tire tread irrespective of the tire tread pattern of the tire tread. A scale of 0-5 rating points was developed to quantify chunking resistance of tires, with 0 being the worst to 5 being the best. Straight sipes, chevron shaped sipes and offset chevron sipes were cut in bus tires, and dumpster truck tires. The cracking and chunking performance of the tires was rated on the scale. Changing the sipes from straight sipes to chevron shaped or offset chevron shaped sipes resulted in an improvement in cracking and chunking resistance in a range of 0.2 rating points to as much as 1.81 rating points on the scale. 
       FIG. 6  is a schematic flow diagram of an example method  500  for improving chunking and cracking resistance of a tire tread (e.g., the tire tread  100 / 200 / 300 / 400 ) of a tire. The tire tread includes a plurality of tread elements (e.g., the tread elements  112 ) which provide a tread pattern (e.g., the tread pattern  110 / 210 / 310 / 410 ). 
     The method  500  includes defining a first set of sipes in the tire tread extending from a circumferential axis of the tire tread towards a first axial end of the tire tread at a non-zero angle with respect to an axial axis of the tire tread at  502 . For example, the first set of sipes  122   a / 222   a / 322 / 422   a  may be cut in the tread elements  112 / 212 / 312 / 412 . The non-zero angle may be in the range of 5 degrees to 40 degrees. 
     Furthermore, a second set of sipes are provided in the tire tread extending from the circumferential axis towards a second axial end of the tire tread opposite the first axial end at the non-zero angle with respect to the axial axis at  504 . For example, the second set of sipes  122   b / 222   b / 322   b / 422   b  may be cut in the tread elements  112 / 212 / 312 / 412 . A first sipe end of each of the first set of sipes is positioned proximate to a second sipe end of each of the second set of sipes, so that the first set of sipes and the second set of sipes in combination comprise a chevron or offset chevron pattern. 
     Each sipe included in the first set of sipes and the second set of sipes, respectively may be positioned parallel to an adjacent sipe at any suitable pitch or distance therefrom (e.g., a range of 5 mm to 40 mm inclusive of all ranges and values therebetween. Furthermore, the distance or pitch may be fixed or variable. 
     Each of the first set of sipes and the second set of sipes extend beyond 50% of a half width of the tire tread measured from the circumferential axis. For example, each of the sipes may extend between 60% to 100% of the half width w of the tire tread inclusive of all ranges and values therebetween. Furthermore, each of the sipes may have a sipe depth d greater than 50% of the height h of each of the plurality of tread elements, measured from a top surface of the tread element positioned opposite the surface of the tire tread on which the tread elements are positioned. For example, each of the sipes may have a sipe depth d in a range of 60% to 100% of the height h of the plurality of tread elements inclusive of all ranges and values therebetween. In some embodiments, each of the sipes may have a sipe depth greater than 100% of the height of the plurality of tread elements (e.g., about 101% to 110% of the height h of the plurality of tread elements inclusive of all ranges and values therebetween). 
     The use of the terms “a” and “an” and “the” and similar referents refer to both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are open-ended terms (e.g., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the subject matter and does not pose a limitation unless otherwise claimed. No language in the specification should be construed as being absolute on a scale but should only indicate relative improvement, nothing should be construed as indicating any non-claimed element as essential. 
     It should be noted that the term “example” as used herein to describe some embodiments is intended to indicate that some embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to connote that some embodiments are necessarily extraordinary or superlative examples). 
     As used herein, the terms “about” and “approximately” generally mean plus or minus 10% of the stated value. For example, about 0.5 would include 0.45 and 0.55, about 10 would include 9 to 11, about 1000 would include 900 to 1100. 
     The terms “coupled,” “connected,” and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. 
     Preferred embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed unless otherwise indicated herein or otherwise clearly contradicted by context. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of this disclosure or of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.