BACKGROUND OF THE INVENTION

Field of the Invention

[0001] This invention relates generally to pneumatic tires and methods for forming such tires, the tires having a belt comprised of at least three belt layers.

Description of the Related Art

[0002] Pneumatic tires generally include a tire carcass and a belt arranged about the tire carcass. In certain instances, the belt is formed of three stacked belt layers, where each layer includes a plurality of spaced-apart, elongate reinforcements. Commonly, with tires having three (or 4 or more) belt layers, the middle belt layer is arranged such that the elongate reinforcements of the middle belt layer are arranged at a substantially zero angle relative a widthwise centerline or an equatorial plane of the tire. Because the reinforcements of the middle belt ply are arranged at a zero angle, the reinforcements extend longitudinally in a circumferential direction of the belt or tire to provide an elevated circumferential or hoop strength for the belt and tire. Unfortunately, this substantially prevents the belt from stretching or expanding during methods of forming a tire, including curing tires during molding operations. Additionally, because the belt does not substantially expand, the belt is commonly assembled separate from the tire carcass, and later, after belt assembly, applied to the tire carcass to form an assembled, uncured tire. These and other issues are overcome by the invention described herein.

SUMMARY OF THE INVENTION

[0003] Embodiments of the invention include a pneumatic tire and methods for forming a pneumatic tire.

[0004] In particular embodiments of the invention, a cured pneumatic tire is provided comprising a tire carcass having one or more body layers extending between a pair of beads spaced apart in an axial direction of the tire. In such embodiments, the cured pneumatic tire also includes a belt arranged along the tire carcass between the pair of beads, the belt having three belt layers comprising a second belt layer arranged between a first belt layer and a third belt layer. Each of the three belt layers have a length extending in a circumferential direction of the tire and a width extending in the axial direction of the tire, each of the three belt layers including a plurality of elongate reinforcements spaced apart at least partially across the width of the respective belt layer and having a reinforcement length extending at least partially in the direction of the length of the respective belt layer. The length of each reinforcement in the first layer extends in a direction biased from an equatorial plane of the tire by an angle greater or less than zero, the length of each reinforcement in the second layer extends in a direction biased from an equatorial plane of the tire by an angle having an absolute value of 5 to 15 degrees, and the length of each reinforcement in the third layer extends in a direction biased from an equatorial plane of the tire by an angle greater or less than zero.

[0005] Particular embodiments of the present invention also include a method of forming a cured pneumatic tire, which includes a step of providing a tire carcass having one or more body layers extending between a pair of beads spaced apart in an axial direction of the tire. An additional step includes arranging a belt along a central portion of the tire carcass between the pair of beads, the belt having three belt layers comprising a second belt layer arranged between a first belt layer and a third belt layer, each of the three belt layers having a length extending in a circumferential direction of the tire and a width extending in the axial direction of the tire, each of the three belt layers including a plurality of elongate reinforcements spaced apart at least partially across the width of the respective belt layer and having a reinforcement length extending at least partially in the direction of the length of the respective belt layer. Yet a further step includes curing the belt to the tire carcass to form a cured tire, where the length of each reinforcement in the first layer extends in a direction biased from an equatorial plane of the tire by an angle greater or less than zero, the length of each reinforcement in the second layer extends in a direction biased from an equatorial plane of the tire by an angle having an absolute value of 5 to 15 degrees, and the length of each reinforcement in the third layer extends in a direction biased from an equatorial plane of the tire by an angle greater or less than zero.

[0006] Additional embodiments are described below.

DETAILED DESCRIPTION OF THE DRAWINGS

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

[0008] FIG. 2 is a partial top view of a belt of the tire of FIG. 1, showing three belt layers, in accordance with an embodiment of the invention. [0009] FIG 3 is a front sectional view of the tire being formed, where the belt is being applied and assembled on a tire carcass, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0010] Embodiments of the invention include cured pneumatic tires and methods for forming such tires, the tires having a belt comprised of at least three belt layers, where three belt layers are arranged such that the middle belt layer, which is also referred to a second belt layer herein, has elongate reinforcements, such as cords or the like, biased by a non-zero angle from an equatorial plane of the belt or tire.

[0011] Commonly, with tires having three belt layers, the middle belt layer is arranged such that the elongate reinforcements of the middle belt layer are arranged at a substantially zero angle relative a widthwise centerline or an equatorial plane of the tire. Because the reinforcements of the middle belt ply are arranged at a zero angle, the reinforcements extend longitudinally in a circumferential direction of the belt or tire, which substantially prevents the belt from stretching or expanding during methods of tire curing, such as during molding operations. This is especially the case when the middle belt ply includes high strength, low elongation reinforcements, such as those used in truck tires. Therefore, because the belt does not substantially expand, the belt is commonly assembled separate from the tire carcass, and later, after belt assembly, applied to the tire carcass to form an assembled, uncured tire. Subsequently, the assembled, uncured tire is inserted into a mold and cured to form a cured tire. The invention described herein in accordance with various embodiments, provides various benefits, including eliminating the need to assemble a belt separate from the tire carcass, which eliminates certain complexities and additional time of prior methods for assembling an uncured pneumatic tire. While the invention provides belts that may be employed by any pneumatic tire, in particular embodiments, the cured pneumatic tires comprise truck and trailer tires or construction vehicle tires, where each such vehicle may be used for over-the-road or off-road purposes and may be configured to carry cargo or pull trailers carrying cargo or haul heavy machinery. Semi trucks, fire trucks, and ambulances are considered to be trucks for this purpose.

[0012] Accordingly, particular embodiments of the invention include a method of forming a cured pneumatic tire. In such methods, one step includes providing a tire carcass having one or more body layers extending between a pair of beads spaced apart in an axial direction of the tire. In such embodiments, the tire carcass is generally uncured, which is often referred to as being "green" within the industry, whereby the various components assembled to form the tire carcass are not permanently bonded together, and remain at least partially unbonded or separable while awaiting the addition of additional components to form an assembled tire, such as a belt and tire tread, for example. In a most basic form, the tire carcass includes at least one body layer extending between a pair of beads. The beads, each forming an annulus or ring, are spaced apart in an axial direction of the tire or tire carcass (that is, in other words, in a direction of the tire width). Each of the beads form an annulus or ring, and may comprise any bead desired or known to one of ordinary skill. The body layer comprises any material employed for such purpose, as known to one of ordinary skill. In particular embodiments, for example, the body layer comprises a composite sheet of material comprising a plurality of elongate reinforcements arranged within an elastomeric polymer matrix. In particular embodiments, the elastomeric polymer is a natural or synthetic rubber. Each of the reinforcements may comprise any cord known to one of ordinary skill. For example, such cords may be formed of metal (most commonly steel) or any fabric or textile, such as polyester, rayon, nylon, aramid, or fiberglass. Such cords may be formed of a plurality of wire (metal) or yarn/filaments (fabric/textile), arranged lengthwise and twisted along their lengths as desired.

[0013] Particular embodiments of the method of forming a cured pneumatic tire include a step of arranging a belt along a central portion of the tire carcass between the pair of beads. The belt has three belt layers, which are stacked, comprising a second belt layer arranged between a first belt layer and a third belt layer. Each of the three belt layers have a length extending in a circumferential direction of the tire and a width extending in the axial direction of the tire. Each of the three belt layers include a plurality of elongate reinforcements spaced apart at least partially across the width of the respective belt layer. Each of the plurality of elongate reinforcements also have a reinforcement length extending at least partially in the direction of the length of the respective belt layer. In arranging the belt along a central portion of the tire carcass, it is appreciated that the central portion consists of any portion of the tire carcass located between the pair of beads. For example, in more specific instances, the belt is arranged relative the central portion of the tire carcass such that a widthwise centerline of the belt extending lengthwise in a direction of the belt length (stated differently, in a circumferential direction of the belt) at the center of the belt width is arranged at the equator of the tire carcass (that is, at the widthwise centerline of the tire carcass between the pair of beads). It is also appreciated that the belt, which forms an annulus or ring, cannot significantly expand radially or circumferentially. Therefore, during the step of arranging a belt along a central portion of the tire carcass, the central portion is in an expanded state, such that the belt is formed a greater distance from the rotational axis of the tire, that is, at a distance that is much closer to its final, cured location. In an expanded state, the central portion has a perimeter, diameter, circumference, or perimeter that is greater than that of each bead of the pair of beads or portions of the body layer arranged adjacent to any such bead.

[0014] In particular instances, the belt is formed or assembled along the tire carcass by first applying the first belt layer to the tire carcass, then subsequently applying the second belt layer and then the third belt layer. While the first belt layer may be applied directly to the tire carcass, the second belt layer applied directly overtop the first belt layer, and the third belt layer applied directly overtop the second belt layer, it is appreciated that a thin layer of adhesive or bonding agent may be applied before the application of any belt layer without deviating from the invention. The layer of adhesive or bonding agent may comprise uncured elastomeric polymer, such as natural or synthetic rubber, or any other solid, liquid, or viscous material to facilitate sufficient bonding known to one of ordinary skill. In particular embodiments, the layer of adhesive or bonding agent is unreinforced, meaning that no elongate reinforcement is arranged within the layer, although other reinforcements may be employed in other embodiments. The thickness of the thin layer is generally less than the thickness of any such belt layer.

[0015] It is appreciated that each belt layer comprises a composite sheet of material comprising a plurality of elongate reinforcements arranged within an elastomeric polymer matrix. In particular embodiments, the elastomeric polymer is a natural or synthetic rubber. Each of the reinforcements may comprise any cord known to one of ordinary skill. For example, such cords may be formed of metal (most commonly steel) or any fabric or textile, such as polyester, rayon, nylon, aramid, or fiberglass. Such cords may be formed of a plurality of wire (metal) or yarn/filaments (fabric/textile), arranged lengthwise and twisted along their lengths as desired. For each belt layer, each reinforcement has a length extending at least partially in a direction of the belt layer length, which, when applied to the tire carcass, extend at least partially in a circumferential direction of the tire carcass. While it is noted that the belt includes three belt layers, it is appreciated that in different embodiments the belt comprises only three belt layers while in other embodiments more than three belt layers are provided. [0016] To ensure substantially all of the air or any other gases are evacuated and not trapped between belt layers, in particular embodiments, each of the three belt layers are forcibly applied, or after application a force is directionally applied to direct any air or other gas to a side edge each belt layer. This is referred to as "stitching" within the industry. Stitching may occur during application of a belt layer, after each belt layer is applied, or after all of the belt layers have been applied to form the belt. Whether due to forcible application of each belt layer, or due to the performance of stitching operations, in particular embodiments, the belt, and therefore each belt layer, is substantially applied to the tire carcass such that the belt and each belt layer is adapted to a contoured shape of the tire carcass central portion.

[0017] Upon completion of the step of arranging a belt along a tire carcass, the belt is an uncured or "green" belt. To complete the tire, additional components may be applied subsequent to application of the belt, such as applying a tire tread overtop the belt.

[0018] Once the uncured tire is assembled, particular embodiments of the method of forming a cured pneumatic tire further include a step of curing the belt to the tire carcass to form a cured tire. Curing may be achieved by any method known to one of ordinary skill in the art. For example, in particular embodiments, the assembled tire is placed within a mold, where elevated pressure and heat is applied to the tire to form and cure the assembled tire into a cured pneumatic tire. In any event, regardless of the method employed to cure the tire, in the cured tire: (1) the length of each reinforcement in the first belt layer extends in a direction biased relative to an equatorial plane of the belt or tire by an angle greater than or less than zero degrees (that is, in other words, by an angle having an absolute value greater than zero); (2) the length of each reinforcement in the second belt layer extends in a direction biased relative to an equatorial plane of the belt or tire by an angle substantially greater than or less than zero degrees (that is, in other words, by an angle having an absolute value substantially greater than zero); and, (3) the length of each reinforcement in the third belt layer extends in a direction biased relative to an equatorial plane of the belt or tire by an angle greater than or less than zero degrees. In more particular embodiments, for each of the first and third belt layers, the length of each reinforcement extends in a direction biased relative to an equatorial plane of the belt or tire by an angle having an absolute value of 18 to 30 degrees, or, in more specific embodiments 24 to 28 degrees. In any such embodiment, the length of each reinforcement in the second belt layer extends in a direction biased relative to an equatorial plane of the belt or tire by an angle having an absolute value substantially greater than zero, or, in more specific embodiments an absolute value of 5 degrees or more, and in even more specific embodiments 7 to 15 degrees or substantially 10 degrees. In any such embodiment, the reinforcement angle for the first belt layer is a positive value while the reinforcement angle for the third belt layer is a negative value, or vice versa, whether or not the absolute values for the reinforcement angles for the first and third belt layers are equal in absolute value.

[0019] In the cured tire, each of the belt layers have a width, which is referred to as a cured width, extending in the axial direction of the tire or belt. While the cured width of the belt and belt layers will vary depending upon the width of the tire being constructed, in particular embodiments there are differences in the width between the three belt layers. Specifically, in certain embodiments, the third belt layer, which is the outer belt layer of the three belt layers, has a width that is greater than the width of each of the first and second belt layers, which are referred to as the inner and the middle belt layers, respectively, of the three belt layers. In such certain embodiments, the width of the second belt layer is narrower than both the first and third belt layers. For example, in certain instances, the first and third belt layers are arranged such that each widthwise side edge of each respective belt layer extends at least 10 millimeters (mm) beyond a widthwise side edge of the second belt layer. In more specific embodiments, the width of the first layer extends at least 10 mm beyond the widthwise side edge of the second belt layer, and the third belt layer extends at least 20 mm beyond the widthwise side edge of the second belt layer.

[0020] The methods discussed above, and the cured tires formed by such methods, will now be discussed below in association with particular embodiments shown in the figures.

[0021] With reference to FIG. 1, a cross-sectional view of a cured, pneumatic tire 10 is shown in accordance with an embodiment of the invention, relative to a rotational axis A defining an axial direction of the tire, the radial direction R of the tire extending perpendicular to the rotational axis. The tire 10 includes a tread 12 arranged overtop a belt 20, all of which is bonded to a tire carcass 15. The tire includes a pair sidewalls 14 spaced apart in an axial direction of the tire, and a pair of beads 18 spaced apart in an axial direction of the tire. The axial direction of the tire is also a direction of the tire width, and a direction of the belt width and belt layer width. As part of the tire carcass 15, a body layer 16 extends between the pair of beads 18. A widthwise centerline CL is shown defining an equator extending around a perimeter of the tire 10. An equatorial plane EP extends through the tire 10 along the centerline CL. [0022] In FIG. 2, a top cutaway view of the belt 20 of FIG. 1 is shown, showing the three belt layers forming the belt. In particular, the three belt layers 22 comprise a first or inner belt layer 22i, a second or middle belt layer 22 ₂ , and a third or outer belt layer 22 ₃ . Each of the three belt layers form a sheet and include a plurality of reinforcements 24 arranged within a elastomeric polymer matrix 26. The reinforcements 24 in the second belt layer 22 ₂ are arranged at an angle Θ2 relative to the widthwise centerline CL of the tire or belt, or relative to the equatorial plane EP, where angle Θ2 is greater or less than zero degrees, that is, an angle that is non-zero. Likewise, the reinforcements 24 in each of the first and third belt layers 22^ 22 ₃ are arranged at a corresponding angle 0i, Θ3 relative to the widthwise centerline CL of the tire or belt, or relative to the equatorial plane EP, where the angle 0i, Θ3 is greater or less than zero degrees, that is, an angle that is non-zero. In the embodiment shown, while the absolute values for each of the first and third reinforcement angles 0i, Θ3 are equal, the reinforcement angle θι for the first layer 22i is a positive value while the reinforcement angle Θ3 for the third layer 22 ₃ is a negative value, or vice versa if using an alternative reference. In other variations, the absolute values for each of the first and third reinforcement angles 0i, Θ3 may not be equal (that is, may not be unequal or are different).

[0023] As noted above, in particular exemplary embodiments, for each of the first and third belt layers 22^ 22 ₃ , the length of each reinforcement 24 extends in a direction biased relative to equatorial plane EP by a corresponding angle 0i, Θ3 having an absolute value of 18 to 30 degrees, or in more specific embodiments 24 to 28 degrees. In any such embodiment, the length of each reinforcement 24 in the second belt layer 22 ₂ extends in a direction biased relative to an equatorial plane of the belt or tire by an angle Θ2 having an absolute value substantially greater than zero, or, in more specific embodiments an absolute value of 5 to 15 degrees, and in even more specific embodiments 7 to 15 degrees or substantially 10 degrees. More generally, in certain embodiments, angle Θ2 is less than angles 0i, Θ3, where second belt layer 22 ₂ is a low angle reinforcement belt layer with angle Θ2 being a low angle measuring 5 to 15 degrees in absolute, such as 7 to 15 degrees or substantially 10 degrees a noted above. In other embodiments, for the three belt layers, it is understood that the first or third belt layer may be the low angle reinforcement belt layer, in lieu of the second belt layer. By employing these reinforcement angles, a compromise is met between maintaining a desired elevated level of circumferential hoop strength and allowing a tire to be more efficiently formed whereby the belt is formed directly onto the tire carcass in lieu of forming the belt separate from the tire carcass, where the belt is later applied in whole to the tire carcass. By employing a reinforcement angle of at least 5 degrees, each reinforcement will not extend completely around the circumference of the tire without terminating along a side edge of the respective belt layer, for belt layers of certain widths. By also ensuring a reinforcement angle does not extend substantially beyond 15 degrees, the desired elevated hoop strength of the belt is maintained while also allowing the belt to sufficiently expand during tire formation and/or after the uncured tire is placed within a mold.

[0024] Because reinforcement angle Θ2 in the second belt layer 222 is non-zero, or, more generally, because none of the three belt layers 22i, 222, 223 have reinforcements 24 extending longitudinally along a reinforcement angle 0i, Θ2, Θ3 equal to zero (that is, all are non-zero), the belt is able to expand as needed to allow the belt to be assembled and built directly onto the tire carcass, without having to assemble and build the belt separately from the tire carcass, such as on a different building drum or other platform. And because reinforcement angle Θ2 in the second belt layer 222 is a low angle somewhere from 5 to 15 degrees (as discussed above in different embodiments), or, more generally, because at least one of the three belt layers 22i, 222, 223 have reinforcements 24 extending longitudinally along a low angle reinforcement angle 0i, Θ2, Θ3 somewhere from 5 to 15 degrees, the belt 20 has a strength closely similar to a belt having a belt layer characterized as having reinforcements arranged at a zero degree relative to widthwise centerline CL or equatorial plane EP. Accordingly, by having a low angle reinforcement belt layer, the belt can be built on a tire carcass while also maintaining circumferential strength of the belt. In embodiments where the low angle reinforcement belt layer is the second belt layer, the low angle reinforcement belt layer distribute circumferential forces to the neighboring belt layers, namely, the first and third belt layers, which increases and optimizes the circumferential strength of the belt in total.

[0025] Because the belt is configured to expand when placed under tension as the tire pressurized during a curing process, such as when the tire is molded, the angles of the reinforcements decrease as the belt expands between an uncured and cured state of the tire. Therefore, the angle of the reinforcements in each of the three belt layers when applied to the tire carcass are greater than the angles of the reinforcements in each of the three belt layers in the cured tire. Because the amount of expansion may vary from curing process to curing process, such as when different molds are used, the requisite angle of the reinforcements in the uncured tire will vary as is known to one of ordinary skill in the art. Accordingly, one of ordinary skill in the art will know, without undue experimentation, how to select an angle of the reinforcement for each of the three belt layers as applied to the tire carcass for the purpose of achieving the desired angles of the reinforcements in each of the three belt layers in the cured tire.

[0026] With continued reference to FIG. 2, cured widths of the three belt layers of cured, pneumatic tire 10 are shown. In particular, first belt layer 22i has a width Wi, second belt layer 22 ₂ has a width W2, and third belt layer 22 ₃ has a width W3. In the embodiment shown, third belt layer 22 ₃ has a width W3 that is greater than the width Wi, W2 of each of the first and second belt layers 22i, 22 ₂ . It is also shown that width W2 of the second belt layer 22 ₂ is narrower than the width Wi, W3 both the first and third belt layers. The three belt layers can also be described such that the first belt layer 22i is arranged such that each widthwise side edge SEi of the first belt layer 22i extends by a distance Δ1.2 at least 10 millimeters (mm) beyond a widthwise side edge SE2 of the second belt layer 22 ₂ , and the widthwise side edge SE ₃ of the third belt layer 22 ₃ extends a distance Δ3.2 at least 20 mm beyond the widthwise side edge SE2 of the second belt layer.

[0027] With continued reference to FIG. 2, the widths of the belt layers 22i, 22 ₂ , 22 ₃ may each be expressed as a percentage of a width of the tread 12. In particular embodiments, the width of the tread 12 can be effectively referred to as a width or a tread arc. The tread arc width WTA is defined to extend between locations P arranged on opposing sides of centerline CL along the tread width, where at each location P a tangent line LTAN extends by an angle a substantially equal to 20 degrees in a direction toward centerline CL from a radial reference line L _R . In other words, at each location P, tangent line L _TAN intersects the radial reference line LR. It is appreciated that radial reference line LR extends in a radial direction R of the tire, and parallel to centerline CL and therefore perpendicular to the axial direction A of the tire, while tangent line LTAN is arranged tangent to the tread or tread arc, where the tangent line extends along a plane defined radial direction R and axial direction A of the tire (in other words, the tangent line is formed of two vectors, one extending in the radial direction and the other in the axial direction). In particular embodiments, the third layer width W3 is substantially equal to or less than 85 percent (85%) of the tread arc width WTA, and where the second layer width W2 is substantially equal to or less than 80 percent (80%) of the third layer width and the first layer width Wi is substantially equal to 95 to 105 percent (95-105%) of the third layer width.

[0028] With reference to FIG. 3, an uncured tire carcass 15 is shown along a building platform comprising a building drum 30, where a central portion 17 of the tire carcass is in an expanded state with a belt 20 being assembled or built thereon. By way of example, one manner employed to achieve this, a sleeve 32 is expanded with a pneumatic bladder 34. First belt layer 22i is shown applied to central portion 17 of the tire carcass 15. Subsequently, the second belt layer 22 ₂ is awaiting application overtop the first belt layer 22i with third belt layer 22 ₃ being arranged overtop the second belt layer. A stitching wheel 36 is shown directionally applying forces to the first belt layer 22i to direct air or other gases out a side edge SEi of the first belt layer. In this embodiment, each of the three belt layers are applied and then stitched prior to application of a subsequent belt layer to remove any air or gas trapped underneath each such belt layer.

[0029] 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.

[0030] 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.