[0001] This claims priority to, and the benefit of, U.S. Provisional Patent Application No. 61/909,746 filed on November 27, 2013 with the United States Patent Office, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

[0002] This invention relates generally to methods and apparatus for forming essentially zero-thickness sipes (also referred to herein more simply as "zero-thickness sipes"), and treads and tires having zero-thickness sipes.

Description of the Related Art

[0003] Tire treads are known to include a pattern of voids and such arranged along a ground-engaging side of the tread to provide sufficient traction and handling during particular conditions. For example, grooves provide void into which water, mud, or other environmental materials may be diverted to better allow the tread surface to engage a ground surface. It is also known to use sipes to create edges along the ground-engaging surface of the tread, which improve traction when operating in wet, snowy, or icy conditions. Commonly, sipes are formed by molding a narrow slot or groove into the tread. With the presence of void within a sipe, the stiffness of the tread may decrease, which may also reduce the tire traction and handling. Therefore, there is a desire to form zero-thickness sipes by reducing or generally eliminating the concurrent formation of void within the sipe. Also, it is desirous to form sipes without generating much or any additional void along the ground engaging side, as the addition of void reduces the amount of ground-engaging tread surface (also referred to as "contact surface") available for contacting the ground during tire operation. When reducing the amount of contact surface available, wear performance may also decrease.

SUMMARY OF THE INVENTION

[0004] Particular embodiments of the invention include a method of forming a tire. The method can include providing a mold configured to mold a tire tread, the mold having a molding cavity defined at least in part by an outermost molding surface configured to form a ground-engaging surface or side of the tire tread and a pair of opposing shoulder-forming portions configured to form a pair of opposing shoulders of the tire tread, and the outermost molding surface being arranged between the pair of opposing shoulder-forming portions. The mold further including a sipe-forming element spaced apart inwardly from each of the pair of opposing shoulder-forming portions, the sipe-forming element including a knife edge oriented towards a first shoulder-forming portion of the pair of opposing shoulder-forming portions and the knife edge having a length extending in a direction transverse to a direction extending between the pair of opposing shoulder-forming portions. The sipe-forming element further including a submerged void-forming portion extending in a direction towards the first shoulder-forming portion and from which a sipe-forming portion extends, the sipe- forming portion including the knife edge, such that in the step of molding, the submerged void-forming portion forms a submerged void spaced below the ground-engaging surface or side and extending to a first shoulder of the tread formed by the first shoulder-forming portion of the mold. Particular embodiments of the invention can further include arranging an uncured tire tread within the mold, the uncured tire tread having a thickness extending depthwise from the outermost molding surface such that a portion of the tire tread is arranged between the knife edge and the first shoulder-forming portion. The method can also include molding the tire tread arranged within the mold to form a cured molded tread having a thickness extending from a ground-engaging side or surface of the cured molded tread and a width extending between opposing lateral sides of the tread, the tread further including a pair of shoulders each arranged along one of the lateral sides of the tread, each of the shoulders extending in a direction of the tread thickness. Further, in embodiments, the method can include demolding the tire tread from the mold such that the sipe-forming element forms a sipe by the knife edge lacerating a thickness of the cured molded tread as the sipe-forming element is pulled in a direction toward the first shoulder-forming portion, the sipe comprising a laceration having a thickness substantially equal to zero and having length extending in a direction of the tread width from the first shoulder formed by the first shoulder-forming portion. It follows that particular embodiments of the invention comprises a molded tire formed by any of the methods recited above, or otherwise herein.

[0005] Particular embodiments of the invention also include a tire. The tire can include a pair of sidewalls extending radially outward to a central portion of the tire, the pair of sidewalls being spaced apart in an axial direction of the tire. The tire can further include a tire tread having a width extending in a lateral direction between a pair of opposing lateral sides of the tread and a pair of shoulders spaced apart and on opposing lateral sides of the tread width, the tread being arranged along a radially outer side of the central portion between the pair of sidewalls, the tire tread having a thickness extending from a ground-engaging side or surface to a bottom side within the central portion of the tire. In particular embodiments, the tire can include a sipe comprising a laceration having a thickness substantially equal to zero and having a length extending in a direction of the tread width from a first shoulder of the pair of shoulders of the tread, a depth extending in a direction of the tread thickness.

[0006] The foregoing and other 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 perspective, partial cutaway view of a tire, in accordance with an embodiment.

[0008] FIG. 2 is a side, partial cutaway, view of a tire tread arranged in a mold including a sipe-forming element for forming a zero-thickness sipe, in accordance with an embodiment.

[0009] FIG. 3 is a perspective view of the sipe-forming element shown in FIG. 2.

[0010] FIG. 4 is a top sectional view taken along line 4-4 in FIG. 2 showing the sipe- forming element arranged within a cavity of the groove-forming element.

[0011] FIG. 5 is a perspective view of a sipe-forming element having a sipe-forming portion substantially shaped and sized equivalent to the cross-sectional shape and size as the groove-forming element, in accordance with an alternative embodiment of the invention.

[0012] FIG. 6A is a chart showing the results of a simulation performed, where tire treads having zero-thickness zig-zag or straight sipes show an increase in transverse rigidity relative to tire treads having standard sipes.

[0013] FIG. 6B is a diagram of a tread thickness cross-section showing various parameters, as referenced in the chart of FIG. 6A, describing the location and size of a sipe and a submerged void arranged within a tread thickness, in accordance with a particular embodiment of the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0014] Particular embodiments of the invention provide a tire including zero- thickness sipes (also referred to as "lamelles"), tire molds and methods for forming such sipes, as well as treads and tires having such treads having substantially zero-thickness sipes (also referred to herein more simply as "zero-thickness sipes").

[0015] Disclosed in this application a method of forming a tire tread or tire having a tire tread, each of which include one or more sipes each comprising a laceration or slice extending through a thickness of the tire tread.

[0016] In particular embodiments, such methods include a step of providing a mold having a molding cavity configured to mold a tire tread. The mold may comprise a tire mold, which is configured to receive a tire having a tire tread for molding, or only a tire tread, such as when forming a tread for later application to a tire carcass in retreading operations, for example. Any such mold generally has an annular molding cavity, and may comprise any type of mold, such as a clamshell mold or a segmented mold, for example. In any event, any such mold includes a molding cavity defined at least in part by an outermost molding surface configured to form a ground-engaging side or surface of the tire tread. The outermost molding surface can also be referred to as the ground-engaging molding surface or portion of the mold or molding cavity. The outermost molding surface is arranged along an outer cavity side, which is generally annular or circumferential in shape. Therefore, when relating any feature of the mold or tire tread to the outermost molding surface, the same relation can be made or drawn relative to the outer cavity side by substituting the outer cavity side for the outermost molding surface. Any such mold also includes a pair of opposing shoulder- molding portions configured to form a pair of opposing shoulders of the tire tread, the outermost molding surface being arranged between the pair of opposing shoulder-molding portions. It can also be said that the pair of opposing shoulders are spaced apart and arranged on opposing lateral sides of the tread width.

[0017] Any such mold further includes a sipe-forming element spaced apart inwardly from each of the pair of opposing shoulder-molding portions, such that the sipe-forming element is arranged between the pair of opposing shoulder-molding portions in a direction of a molding cavity width, where the width of the molding cavity is configured to form a width of the tire tread. Because sipe-forming element is configured to be removed from the tire tread to cut or lacerate a sipe into a thickness of the tread, by being spaced apart, an area is formed between one of the pair of opposing shoulder-molding portions and the sipe-forming element for receiving tread material in which a sipe will be cut during a demolding operation. Accordingly, the sipe-forming element, and more specifically, a sipe-forming portion of the sipe-forming element, includes a knife edge, which is also referred to as a cutting or lacerating edge. The knife-edge may be sufficiently sharp, that is, as sharp as needed to lacerate or slice a thickness of the tread. A laceration or slice is also referred to as a discontinuity. When the sipe-forming element is arranged in the mold, the knife edge is oriented towards a first shoulder-molding portion of the pair of opposing shoulder-molding portions. This is desired so that the knife edge can cut through a thickness of the tread as the sipe-forming element is pulled in a lateral direction of the tire tread and toward a shoulder. To form a desired depth of the sipe, the knife edge has a length. The length generally extends in a direction transverse to a direction extending between the pair of opposing shoulder- molding portions, which means the length extends in a direction having a vector extending in the direction transverse to a direction extending between the pair of opposing shoulder- molding portions. This means the length of the knife edge may be entirely transverse or may be inclined in the direction extending between the pair of opposing shoulder-molding portions. It is also appreciated that the knife edge may be arranged below, or spaced apart, from the outermost molding surface to form a sipe recessed below the ground-engaging side within the thickness of the cured molded tread. It is also appreciated that the knife edge may be arranged to be arranged adjacent to, or to extend into a cavity within, the outermost molding surface so to form a sipe extending up to and along the ground-engaging side of the cured molded tread. Finally, it is also appreciated that the knife edge may form any sipe extending at any depth within the thickness of the cured molded tread, and at any depth relative to any other void formed within the thickness of the cured molded tread. It is also noted that the knife edge may be jagged or saw-tooth, for example, to improve its ability to cut or lacerate the tread.

[0018] In particular embodiments, the length of the knife edge extends along a linear path. In other embodiments, to increase the rigidity of the tread element or the tread, the length of the knife edge extends along a non-linear path. By extending along a non-linear path, the sipe-forming element is able to form a sipe having a depth or height extending along a non-linear path in a direction of the tread thickness. By providing a non-linear extension of the sipe depth or height, the local stiffness or rigidity of the tread is increased in a direction transverse to a direction of the sipe height or depth or to a direction of the tread thickness. This may further reclaim the loss in rigidity that naturally occurs when forming a sipe within the tread. It is noted that the non-linear path can be an undulating path having a plurality of peaks and valleys (that is, apexes and troughs), such as a sinusoidal path, a saw-tooth path, or a square-wave path, for example. Therefore, it is contemplated that the non-linear path may be curvilinear or comprise a plurality of linear segments, or any combination thereof.

[0019] The sipe-forming element further includes a submerged void-forming portion extending in a direction towards the first shoulder and from which the knife edge and/or sipe- forming portion extends (the sipe-forming portion including the knife edge), such that in the step of molding, the submerged void-forming portion forms a submerged void spaced below the ground-engaging side or surface and extending to a first shoulder of the tread formed by the first shoulder-forming portion of the mold. It is appreciated that the submerged void may comprise any void. For example, in different embodiments, the submerged void comprises a lateral groove or a conventional/traditional sipe having a thickness substantially greater than zero (a sipe thickness as used herein is also referred to as a sipe width). It is also appreciated that the knife edge or sipe-forming portion may extend in any direction from the submerged void- forming portion. For example, in particular embodiments, the knife edge extends above the submerged void-forming portion (that is, in a direction towards the outermost molding surface), below the submerged void-forming portion (that is, in a direction opposite the outermost molding surface), or both above and below the submerged void-forming portion.

[0020] In particular embodiments, the mold further includes a void-forming element extending inward from the outermost molding surface, or in other words, into the molding cavity from the outermost molding surface. It is appreciated that any mold may comprise one or more (that is, one or a plurality of) void-forming elements. In an example where the mold cavity is substantially annular, it can be said that the void-forming element extends radially inward from the outermost molding surface. The void-forming element may be configured to form any desired void having a length extending in a longitudinal direction of the tread (that is, in a direction of the tread length). By extending in a longitudinal direction of the tread, it is appreciated that the longitudinal direction may be biased to a true longitudinal direction orthogonal to a the direction of the tread width, such that a vector component of the void length extends in a direction of the tread width but such vector component is less than the vector component extending in a direction of the tread length. In particular embodiments, a void-forming element is configured to form a groove (operating as a groove-forming element), and more particularly a longitudinal groove (operating as a longitudinal groove- forming element) or a traditional sipe having a thickness substantially greater than zero. It is to be appreciated that the void-forming element may also be configured to form any desired void having a length extending in a lateral direction of the tread (that is, in a direction of the tread width).

[0021] It is appreciated that a sipe-forming element may be operably arranged in the mold in any manner sufficient to maintain the sipe-forming element in an arrangement spaced-apart from a shoulder-forming portion of the mold. It is appreciated that in any such arrangement, the sipe-forming element may be arranged to form a sipe having a length extending partially or fully across a tread element, such as a rib or tread block. For example, when the mold includes a void-forming element, in particular embodiments, the sipe-forming element is spaced apart from the void-forming element, such as a longitudinal groove- forming element, for example, in a direction towards the first shoulder-molding portion, such that in the step of demolding, the sipe formed is spaced apart from the void formed by the void-forming element. In other embodiments, the sipe-forming portion is arranged within a cavity of the void-forming element, such as the longitudinal groove-forming element, such that in the step of demolding, the sipe formed extends to the shoulder from the void formed by the void-forming element. It is appreciated that the cavity arranged within the void- forming element may extend partially or fully across a full width of the void-forming element. When extending fully across a full width of the void-forming element, the length of the knife edge may extend along a portion of the cross-sectional profile or outer perimeter of the void-forming element. Accordingly, in particular embodiments, the knife edge length extends to form, or is shaped to generally match, a portion of the cross-sectional profile of the void-forming element. In other words, the knife edge length extends in a direction substantially the same as a cross-sectional profile of the longitudinal groove. In even further embodiments, the sipe-forming portion has a shape substantially equal to the cross-sectional shape of the void-forming element. This occurs when the cavity extends through or substantially through the void-forming element. It is appreciated that the sipe-forming element may extend from a shoulder-molding portion and through a void-forming element to a more central region of the tire tread(longitudinal void-forming element), where the sipe- forming element forms a sipe within a tread elements arranged more central or inward from any tread elements arranged along the shoulder of the tread.

[0022] Additional embodiments of the method include a step of arranging an uncured tire tread within the mold. The uncured tire tread has a thickness extending depthwise from the outermost molding surface such that a portion of the tire tread is arranged between the knife edge and the first shoulder-molding portion. That is, a gap exists between the sipe- forming portion (and particularly the knife edge) and the first shoulder-molding portion to enable tread material to flow there between. After arranging the uncured tire tread within the mold, embodiments of the method include a step of molding the tire tread to form a cured molded tread having a thickness extending from a ground-engaging side of the tread. The ground-engaging side is also referred to as a top side, an outer side, or an exterior side of the tread. The ground-engaging side also includes at least one ground-engaging surface. Accordingly, when referencing a ground-engaging side of the tread, such as when describing the tread thickness or the location of a sipe or void, a ground-engaging surface may be substituted for the ground-engaging side for reference purposes. The cured molded tread also includes a pair of opposing shoulders extending along the lateral sides of the tread width in a direction of the tread thickness. As mentioned elsewhere herein, the tire tread may be molded alone (that is, separately from the tire) or while attached to a tire. During the molding process, the tread is cured, as the tread is generally formed of a curable elastomeric material, such as natural or synthetic rubber or any other polymeric material.

[0023] As a result of the step of molding, the tire tread includes a tread pattern, which is a predetermined arrangement of voids to provide a particular volumetric void ratio, surface void ratio, and layout of void and contact surfaces along a width and length of the tread. Volumetric void ratio is the ratio of volumetric void available at a particular worn depth of the tread relative to the total volume of the tread at the particular worn depth - where the total volume includes both void and tread material available. Surface void ratio is the ratio of surface void arranged along the outer side, or ground-engaging side, of the tread at a particular worn depth of the tread relative to the total surface area available of the tread at the particular worn depth - where the total area includes both void and tread areas arranged along the outer side.

[0024] As used in this application, the term "discontinuity" comprises any void, such as a groove or traditional sipe having a thickness or width substantially greater than zero, or any laceration, such as a zero-thickness sipe discussed herein, where any such discontinuity has a depth extending into the tread thickness. A void may be arranged along the ground- engaging side of the tread, or offset below the ground-engaging side of the tread to form a submerged void within the tread thickness. It is appreciated that a discontinuity may have a length extending in any direction transverse to the tread thickness, such as in a direction of the tread length and/or width. For example, the sipe or groove may be a longitudinal or lateral sipe or groove. Longitudinal grooves or sipe generally extend in a direction of the tread length, which may extend circumferentially around the tire. It is also contemplated that a longitudinal groove or sipe may extend at an angle biased to a circumferential direction of the tire. Lateral grooves or sipes generally extend in a direction of the tread width, where the lateral groove or sipe generally extends in a direction perpendicular to a longitudinal centerline of the tread (which extends in a direction of the tread length) or at an angle biased to the longitudinal centerline. It is appreciated that the length of any discontinuity may extend along any linear or non-linear path as desired, where a non-linear path is more fully described herein. Moreover, unless otherwise specified herein, any groove discussed herein may comprise a lateral or longitudinal groove and any sipe, whether or not a zero-thickness sipe, may comprise a lateral or longitudinal sipe. Accordingly, unless otherwise specified, a groove-forming element may be a longitudinal or lateral groove-forming element, which is configured to form a longitudinal or lateral groove, respectively. Likewise, unless otherwise specified, a sipe-forming element may be a longitudinal or lateral sipe-forming element, which is configured to form a longitudinal or lateral sipe, respectively.

[0025] With particular regard to the zero-thickness sipe, such sipe is a discontinuity comprising a laceration or slice extending through a thickness of the tread to define a depth or height of the sipe, the sipe having a length extending in a direction transverse to a thickness of the tread and a width or thickness extending transverse to both the length and depth of the sipe. Because the sipe is a laceration, the width or thickness of the sipe is substantially zero, as no material is being removed to form the sipe in the tread. Moreover, the sipe is formed such that the sipe is in a substantially zero-thickness arrangement when the tread is arranged annularly around the tire, where the sipe is in closed arrangement and appears as an slit or slice along the ground-engaging surface of the tread. In other words, when the tire tread is generally in an undeformed arrangement, the sipe is in a closed arrangement, where cut surfaces of the tread thickness on opposing sides of the sipe are in contact or in an abutting arrangement to define the substantially zero thickness of the sipe. In particular embodiments, it is understood that "substantially equal to zero" ranges from zero (0) to 0.2 mm, or 0 to 0.1 mm in other embodiments. Further, it is to be appreciated that, while the sipe described above may have a zero width or thickness at a moment of formation such that it appears closed, thermal expansion and/or contraction effects can result in a slight opening such that the opposing sides are no longer in full contact. Nonetheless, such a sipe is a zero-thickness sipe since, at the moment of formation, the opposing sides will be in contact since no material is removed.

[0026] In addition, such a sipe is a zero-thickness sipe even though the sipe may also open as the tire rolls through a contact patch during tire operation, where in the open arrangement the cut surfaces on opposing sides of the sipe are at least partially separated such that the sipe opens to a thickness greater than zero. The tire contact patch is the portion of the tread contacting a ground surface at any time during tire operation. In general, the sipe is closed in the contact patch. In instances where the tire operates under driving or braking torque, the sipe may open when located in a leading or trailing edge of the contact patch. In addition, as the sipe may open as it rolls through areas just before and/or just after the contact patch.

[0027] In contrast to a sipe as described above, a groove generally has perceptible width or opposing sides which are not in contact. It is also noted that an arrangement of grooves generally define a tread element, such as a rib or a lug. A rib is defined as a portion of ground-engaging surface arranged between spaced-apart longitudinal grooves or a longitudinal groove and one of opposing sides of the tread defining the width of the tread, extending substantially the full length of the tread. That is, the rib extends substantially continuously around the circumference of the tire. If a rib is discontinuous, for example, due to the presence of one or more lateral grooves extending fully across a rib, the separated portions of the rib are referred to as lugs or blocks. More generally, a portion of the ground- engaging surface defined by a pair of spaced-apart longitudinal grooves, or a longitudinal groove and one of the lateral sides of the tread width, and a pair of spaced-apart lateral grooves is known as a tread lug or block. The rib can be a shoulder rib located at a lateral side of the tread width (which may be adjacent to the sidewall when installed on a tire) or a center rib located between a pair of spaced-apart longitudinal grooves.

[0028] In further embodiments, the method includes a step of demolding the tire tread from the mold. In doing so, the knife edge of the sipe-forming element lacerates a thickness of the cured molded tread as the sipe-forming element is pulled in a direction toward the first shoulder-molding portion, or the shoulder that is has formed, the sipe having length extending in a direction of the tread width from the shoulder formed by the first shoulder- molding portion. In particular embodiments, the sipe comprises a laceration having a thickness substantially equal to zero. As noted above, in particular embodiments, it is understood that "substantially equal to zero" ranges from zero (0) to 0.2 mm, or 0 to 0.1 mm in other embodiments. The resultant sipe has a length extending in a direction of the tread width. Further, it is noted that since tread material is not removed by the action of lacerating the tread thickness by the knife edge, the sipe has a substantially zero thickness or width extending transverse to the sipe length and by a depth into the cured molded tread thickness from the ground-engaging side of the cured molded tread. It is appreciated that the length of the sipe may extend fully across a tread element, or partially across a tread element, such as when the sipe extends from a groove or other void on a first side of the tread element and terminates within the length or width of a tread element inward a second, opposing side of the tread element. Such a tread element may be a shoulder rib or shoulder tread block. It is also appreciated that in partially extending across a tread element, the sipe may be fully arranged inward of both first and second opposing sides of the tread element length or width. Accordingly, the length of the sipe can extend across substantially any portion of the tread element without intersecting any grooves, intersecting only one groove, or intersecting two grooves.

[0029] It is also appreciated that the sipe-forming element can assume various cross- sectional shapes, such as when the sipe-forming element forms more than a zero-thickness sipe. For example, in particular embodiments, the sipe-forming element includes a submerged void-forming portion extending from the knife edge. In the step of molding, the submerged void-forming portion forms a submerged void, such as a groove or traditional sipe, spaced below the ground-engaging surface and arranged below and in communication with the zero-thickness sipe within the thickness of the cured molded tread. Accordingly, the sipe, having a substantially zero width, extends into the thickness of the tread and to the submerged void having a non-zero width. The submerged void-forming portion has a width for forming a thickness or width of the void in which it forms, the width extending is in a direction transverse to the length and a height of the submerged void-forming portion and sipe-forming element. The width of the submerged void-forming portion can be constant over a depth extending in a direction of the tread thickness. For example, the width can be substantially greater than the width or thickness of a lacerated sipe, and up to 10 mm or more. In an exemplary embodiment, the submerged void-forming portion is of variable width over its depth. For instance, the submerged void- forming portion can have a teardrop-shaped cross section where a maximum width is at a depth farthest from the outermost molding surface of the mold or the ground-engaging side in terms of the submerged void formed in the tread thickness by such submerged void-forming element. The width generally decreases with depth upwards towards the ground-engaging side of the tread to a minimum width at a bottom of the sipe. The width can decrease linearly or non-linearly and, moreover, the depth corresponding to the maximum width is not limited to the depth farthest from the ground- engaging side of the tread. Just as the width remains constant or vary as described above, so may the height of the submerged void or submerged void-forming element.

[0030] Particular embodiments of the tires and methods discussed above will now be described in further detail below in association with the figures filed herewith exemplifying the performance of the methods in association with particular embodiments of the tires.

[0031] With reference to FIG. 1, a molded tire 10 according to an exemplary embodiment of the present invention is shown. The tire 10 includes a pair of sidewalls 12 each extending radially outward from a rotational axis of the tire to a central portion 14 of the tire 10. The central portion 14 of the tire extends annularly and includes a tread 20 having a thickness T20 extending in a radial direction from a ground-engaging side 22 of the tread to a bottom side 24 for attachment and bonding to the tire. The tread also has a width W20 extending in a lateral direction between the pair of opposing, lateral sides or side edges 21 of the tread arranged adjacent sidewalls 12. The tread also includes a pair of shoulders 21s arranged along each side 21 extending along the tread thickness T20.

[0032] With regard to the ground-engaging side 22 of the tread 20, it is shown to include a plurality of voids 26 comprising longitudinal grooves having a length extending in a direction of the tread length, which is in a circumferential direction of the tire. Each void 26 comprising a longitudinal groove also has a depth (I26 extending into the tread thickness T20 from the ground-engaging side 22. The longitudinal grooves 26 define a plurality of tread elements comprising ribs also extending in a direction of the tread length. The plurality of ribs include both shoulder ribs 28s bounded by a lateral side 21 of the tread width W20 and a longitudinal groove 26 and center ribs 28c bounded on both sides by a pair of spaced apart longitudinal grooves 26. Center ribs 28c are arranged intermediately between shoulder ribs 28s- While FIG. 1 illustrates a 4-rib tire, it is to be appreciated that the methods described herein can be utilized with tires having more or less ribs than tire 10.

[0033] According to the exemplary embodiment shown in FIG. 1, the tread 20 includes a plurality of sipes 30 comprising a laceration formed during a demolding operation, the sipe. In particular embodiments, the sipe has a thickness substantially equal to zero. Each sipe 30 extends into the tread thickness from the ground-engaging side 22 by a depth (I30, which in particular embodiments is equivalent to the length of the knife edge L 8 shown in FIGS. 2 and 3. It is appreciated that the depth (I30 of each sipe 30 may extend into the thickness of the tread 20 by a depth equal to, less than, or greater than the depth of any groove 26. Each sipe 30 also has a length extending transversely to the tread thickness and the sipe depth, which is represented as length L30 in FIG. 1. With continued reference to the embodiment of FIG. 1, certain sipes 30 are shown to have a length extending fully across a tread element (which comprises a rib in the embodiment shown) from a first groove 26 to a second groove 26 or to a lateral side 21 or shoulder 21s of the tread width W2 ₀ , while other sipes 30 are shown to have a length extending partial across a tread element from a first groove 26 and spaced apart from a second groove 26. Though shown in FIG. 1 as being aligned or co-linear, it is to be appreciated that sipes 30 can be otherwise arranged.

[0034] In the embodiment shown in FIG. 1, the sipes 30 arranged along the center ribs 28c have lengths extending along linear paths. Further, the depth of each sipe 30 is shown to extend along a non-linear path, each of which are more specifically an undulating path. It is appreciated, however, that in other embodiments, the depth of any such void may extend along a linear path.

[0035] In particular embodiments, such as in the embodiment shown in FIG. 1, each sipe 30 extends toward the ground-engaging side 22 from a submerged void 32 offset or spaced below the ground-engaging side within the tread thickness. In other words, each sipe 30 extends into the thickness of the tread 20 from the ground-engaging side and into a submerged void 32. In the embodiment shown, the submerged void 32 is a submerged groove, and more specifically a submerged lateral groove. As discussed above, the submerged void 32 may comprise any cross-sectional shape. Each submerged void 32 has a width that is wider than the width or thickness of the sipe 30, which is substantially zero. While the submerged void may comprise any desired void, in other embodiments, in lieu of a groove, the submerged void is a submerged traditional sipe having a thickness substantially greater than zero. Regardless, in any event, any submerged void 32 has a length extending in a direction transverse to the tread thickness and to the width or thickness of the submerged void. The length of the submerged void may extend in a linear path or a non-linear path, regardless of whether the sipe length extends along the same or different path, or in a linear or non-linear path, where the non-linear path may be any non-linear path as contemplated above with regard to the sipe or sipe-forming element. It is appreciated that by forming a zero-thickness sipe, the stiffness of the tread element and therefore the tread increases relative to using traditional sipe having a thickness substantially greater than zero. It is also appreciated that having a depth of the sipe-forming element extend along a non-linear path, the rigidity of the tread element and therefore the tread increases. [0036] As discussed above in association with various methods, a zero-thickness sipe is formed by way of molding and demolding operations. In an exemplary embodiment in FIG. 2, a zero-thickness sipe 30 is formed in a tread 20 using a mold 40. Specifically, in FIG. 2, a portion of a tread 20 as a portion of tire 10 formed in mold 40, which includes an outermost molding side or surface 42 from which void-forming elements 44 extend into a molding cavity. The void-forming elements 44 are configured to form longitudinal grooves, such as the grooves 26 of FIG. 1, although in other embodiments the void-forming elements are used to form any other void, such as a traditional sipe having a thickness substantially greater than zero, lateral grooves, etc. The void-forming elements 44 are also shown to extend into the molding cavity by a distance less than the tread thickness T20, but may extend fully through the tread thickness in other embodiments.

[0037] In the embodiment shown, the mold further includes a sipe-forming element 46 configured to form a zero-thickness sipe in tread 20, such as sipe 30 of FIG. 1. The sipe- forming element 46 includes a sipe-forming portion 50 with a knife edge 48 for lacerating a thickness of the tread as the sipe-forming element is removed from the tread by pulling the element outwardly from the tread thickness and towards a shoulder of the tread. To achieve its intended purpose, the knife edge 48 is spaced a distance dug from the shoulder-forming portion 43 of the mold, which is arranged adjacent to tread shoulder 21 _s or side edge 21 of the tread in FIG. 2. By doing so, an area or gap (cits) is formed between the shoulder-forming portion 43 and the knife edge 48 for receiving tread material. During the molding operation, tread material is arranged in the area between the shoulder-forming portion 43 and the knife edge 48. Once the tire tread 20 is cured, the tire 10 is demolded from mold 40. During removal, the sipe-forming element 46 is drawn outwardly through the tread thickness between the shoulder-forming portion 43 and the knife edge 48 to form a sipe comprising a laceration as exemplarily shown in FIG. 1. It is appreciated that, in particular embodiments where the tread is molded separately from the tire, such as when forming an annular tread for retreading operations, the sipe-forming element may be arranged below the tread thickness, so that the knife edge is pulled through the entire thickness of the tread to form a full-depth zero-thickness sipe.

[0038] As discussed above, the sipe-forming element may optionally include a submerged void-forming portion extending from the knife edge in a direction away from the outermost molding surface or outer side of the molding cavity. In an exemplary embodiment shown in FIG. 2, the sipe-forming element 46 includes a submerged void-forming portion 52 comprising a submerged groove-forming portion configured to form a submerged lateral groove within the tread thickness. As contemplated above, the submerged void-forming portion may form any desired void having any desired cross-sectional shape, and has a length that extends in a direction generally transverse to the height and width of the sipe-forming element and of the groove-forming portion. Moreover, while shown the submerged void forming portion 52 is shown to be straight, it is to be appreciated that the submerged void- forming portion 52 can extend along a path that follows a profile of the ground-engaging side 22 in region of the shoulders 21s and/or the lateral side 21 through the same region. During demolding, the sipe-forming element 46 is drawn outwardly along the same path along which the void-forming portion 52 extends.

[0039] In FIG. 3, the sipe-forming element 46 of FIG. 2 is shown in further detail. In particular, the sipe-forming element 46 has a knife edge having a length L 8 extending along a non-linear path, which in particular forms an undulating path. While it is appreciated that the knife edge may extend along any desired non-linear path, the path may also be linear. For example, an exemplary sipe-forming element 46 is shown in FIG. 5 where the knife edge 48 extends along a linear path. It is also noted that in the embodiment shown, the cross-sectional shape of the submerged void-forming portion 52 forms a teardrop-like shape, where the width W is at a maximum at an end opposite the knife edge 48 and decreases to a minimum width at the knife edge.

[0040] As discussed above, it is appreciated that a sipe-forming element may be operably arranged in the mold in any manner sufficient to maintain the sipe-forming element in an arrangement spaced-apart from a shoulder-forming portion of the mold to form a sipe having a length extending partially or fully across a tread element, such as a rib or tread block. While in particular embodiments the sipe-forming element is spaced apart from a void-forming element, such as a longitudinal groove-forming element, for example, in a direction towards the first shoulder-molding portion, in other embodiments, such as exemplarily shown in FIGS 2 and 4, the sipe-forming portion 50 is arranged within a cavity 45 of the void-forming element 44, such that in the step of demolding, the sipe formed extends to the shoulder from the void formed by the void-forming element. In the embodiment shown, the cavity 45 arranged within the void-forming element 44 extends partially across a full width of the void-forming element, although as discussed above it is appreciated that the cavity may extend across the full width of the void-forming element. As best shown in FIG. 2, the knife edge 48 is shaped to match a portion of the cross-sectional outer profile (or outer perimeter) 44 _P of the void-forming element. When the cavity extends through the void-forming element 44, it is appreciated that the sipe-forming element 46 may extend from a shoulder-forming portion 43 and through the void-forming element 44 to a more central region of the tire tread, where the sipe-forming element forms a sipe within a tread elements (such as tread elements 28c in FIG. 1) arranged more central or inward from any tread elements arranged along the shoulder of the tread (such as shoulder tread elements 28s in FIG. 1).

[0041] In accordance with certain finite element simulations conducted, benefits of zero-thickness sipes, as generally described herein, are exemplified in the chart shown in FIG. 6A in cooperation with various parameters identified in FIG. 6B. In FIG. 6A, the chart shown generally illustrates a percentage increase in rigidity for zero-thickness sipes over standard sipes, for different changes in the parameters describing the arrangement of a sipe extending to a ground-engaging side of the tread from a submerged void arranged within the tread thickness. This increase in rigidity (also referred to as "transverse rigidity") occurs in a direction transverse to the direction of the tread thickness and transverse to a direction of the sipe length. For example, if a length of the sipe extends in a direction of the tread width, the transverse rigidity comprises longitudinal rigidity. By further example, if a length of the sipe extends in a direction of the tread length, the transverse rigidity comprises lateral rigidity.

[0042] With particular reference to FIG. 6B, various parameters are shown describing the height and depth of a sipe arranged in conjunction with a submerged void within a tread thickness, where a tire tread thickness T ₂ o is shown to include a submerged void X (i.e. , submerged void 32) extending into the tread thickness by a depth Z2 and a sipe S extending into the tread thickness by a depth Z3 to the submerged void. It is appreciated that for the evaluation, sipe S either comprised a zero-thickness sipe 30 or a standard sipe having a thickness of approximately 0.4 mm. With regard to depth Z3, it can be said that depth Z3 represents, in certain embodiments, knife edge length L 8 as discussed elsewhere herein. Finally, depth Zi represents the sum of depth Z2 and depth Z3. In particular embodiments, total depth Zi is equal to substantially 3 to 14 mm, although other depths may be employed in other embodiments. For example, it is appreciated that the total depth Zi may comprise a larger range, such as substantially 2 to 15 mm, or a sub-range, such as 5 to 10 mm.

[0043] In addition, the total depth Zi can be described as a function of total tread thickness T2 ₀ . For example, in particular embodiments, the total depth Zi is substantially equal to 50 to 90% of the total tread thickness T2 ₀ . Accordingly, by virtue of being described as a function of the total tread thickness T ₂ o, the total depth Ζχ can be proportionally employed by any type of tire tread having any total tread thickness T ₂ o- For example, such treads may be employed by high-performance tire or a light truck tire. In particular embodiments of such examples, Zi is at least equal to 26 to 86% of the tread thickness T2 ₀ , but less than the tread thickness, such that the submerged void is arranged within the tread thickness offset a distance from the bottom side of the tread.

[0044] With reference now to the depth or height of the submerged void, which is represented as Z2 in FIG. 6B, in particular embodiments the submerged void height Z2 is substantially equal to at least 2 mm and up to substantially 70% of the total depth Zi, taken in the direction of the tread thickness. It is appreciated that Z2 may be equal to less than 2 mm if achieving sufficient sipe robustness and greater than 70% of Zi if achieving further increasing or maintaining the transverse rigidity of the tread. As mentioned above with regard to Zi, the height Z2 can also be described as a function of total tread thickness T2 ₀ .

[0045] With regard now to the length of the sipe extending from the submerged void, which is represented as Z3 in FIG. 6B, in particular embodiments the distance from which the sipe extends upwards towards the ground-engaging side of the tread from the submerged void is substantially equal to at least 10% of the total depth Zi and up to the total depth Zi less 2 mm (that is, up to Zi - 2 mm). In other words, the depth Z3 of the sipe can be a function of the total depth Zi and the height Z2 of the submerged void, as shown in FIG. 6. As mentioned above with regard to Ζχ and Z ₂ , the height Z3 can also be described as a function of total tread thickness T ₂ o-

[0046] As mentioned above, any two of the three parameters described can be utilized to derive the third. It is appreciated, however, that alternative dimensions can be employed in connection with the methods described herein and the attached claims are not limited to the specific parameters described above.

[0047] With regard now to the chart shown in FIG. 6A, a comparison of simulation results between tread blocks having zero-thickness sipes as generally described above and tread blocks having standard sipes having a thickness of approximately 0.4 mm, for submerged voids of different heights Z2 (expressed as a percentage of total depth Zi). For the zero-thickness sipes, both straight and zig-zag configurations were tested, where straight sipes extended into the tread thickness along a straight path and the zig-zag sipes extended into the tread thickness along a zig-zag or undulating path. For the standard sipe, the sipe was a straight sipe extending into the tread thickness along a straight path. For these simulations, the tire tread thickness T ₂ o is 8.5 mm and the total depth Ζχ is 8 mm. The simulations were performed using finite element analysis (FEA) on a 2-dimensional tread model generally shown in FIG. 6B, where the bottom side of the tread was fixed (that is, constrained in all directions) while a lateral shearing load was applied to the ground-engaging side by way of imposing a lateral displacement on the tread. Upon review of the results, which are reflected in FIG. 6A, an increase in transverse rigidity is realized in all tread blocks having zero-thickness sipes as compared to tread blocks having standard sipes when the height Z ₂ is less than 90% of the total depth Zi. An increase in transverse rigidity is obtained regardless as to whether the sipes are zig-zag sipes (e.g. , sipes made with with the sipe- forming element 46 of FIG. 3, for example) or straight sipes (e.g., sipes made the sipe- forming element of 46 of FIG. 5, for example). With a height Z2 equal to 70% or less of the total depth Zi, at least a 5% increase in transverse rigidity is realized for the values of total tread thickness T2 ₀ and total depth Zi utilized for the tests. In particular, a straight sipe provides a 5% increase in transverse rigidity while a zig-zag sipe provides approximately a 7% increase in transverse rigidity when Z ₂ is equal to 70% of total depth Ζχ. In instances when Z ₂ is equal to 50% of total depth Ζχ, a straight sipe provides approximately an 11% increase in transverse rigidity while a zig-zag sipe provides approximately a 14% increase in transverse rigidity. Finally, in instances when Z ₂ is equal to approximately 35% of total depth Zi, a straight sipe provides approximately an 16% increase in transverse rigidity while a zig-zag sipe provides a 20% increase in transverse rigidity.

[0048] While the tests results provide an overall increase in transverse rigidity when the % value of Z ₂ decreases, a growing or escalating increase is also obtained when employing zig-zag sipes (i.e. , undulating sipes) when compared to the use of straight sipes. For example, with reference again to the results shown in FIG. 6A, when using a zig-zag sipe in lieu of a straight sipe: there is an approximately 32% increase in transverse rigidity when Z ₂ is equal to 70% or less of total depth Zi; there is an approximately 28% increase in transverse rigidity when Z ₂ is equal to 50% of total depth Zi; and, there is an approximately 27% increase in transverse rigidity when Z ₂ is equal to 35% of total depth Zi.

[0049] Based upon these results, in view of the broader invention, because the substantially zero-thickness sipes may extend lengthwise in any direction of the tire or tire tread, it can be said that increases in transverse rigidity are realized in a direction transverse to the length of the sipe. Therefore, when employing substantially zero-thickness sipes as described herein, an increase in transverse rigidity is obtained in any direction of the tire or tire tread transverse to both the tread thickness and the length of the sipe, which may comprise a longitudinal or lateral direction of the tire or tire tread, or any direction there between. Therefore, the increase in rigidity may be an increase in longitudinal or lateral rigidity, for example. It is noted that the simulations evaluate the benefit of employing substantially zero-thickness sipes without considering any benefits associated with the length of the sipe extending along a non-linear path.

[0050] It is appreciated that formation of zero-thickness sipes on the outer side of the tread may be performed by any manual or automated process or machine, of which may contain a processor and memory storage device configured to store instructions for performing the method steps discussed and contemplated herein.

[0051] 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.

[0052] 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.