METHOD OF FORMING A BELT STRUCTURE FOR A PNEUMATIC TIRE

Abstract

A method of forming a belt structure for a tire includes providing a drum having a center section. A first drum edge is near a first edge of the center section and a second drum edge is near a second edge of the center section. A first end surface extends from the center section first edge to the drum first edge and a second end surface extends from the center section second edge to the drum second edge, and a radius of each end surface is smaller than the center section radius. A rubber strip reinforced by a plurality of cords includes an outer edge and an inner edge. The strip is wound about the drum, turning from a first winding angle to a second winding angle on an end surface to reduce the tension and length differential between cords at the outer edge and inner edge of the strip.

Claims

1. A method of forming a belt structure for a pneumatic tire, the method comprising the steps of: providing a drum, the drum including: an axially-extending circumferential center section, the center section including a first center section edge and a second center section edge, the center section being formed with a first radius of curvature, the first radius of curvature extending from the first center section edge to the second center section edge; an axially-disposed circumferential drum first edge near the first edge of the center section; an axially-disposed circumferential drum second edge near the second edge of the center section; a first end surface extending radially inwardly from the first edge of the center section to the drum first edge and including a second radius of curvature that is smaller than the first radius of curvature; a second end surface extending radially inwardly from the second edge of the center section to the drum second edge and including the second radius of curvature; and a surface recess for receiving a radially inner belt structure; providing at least one strip, the at least one strip being reinforced by a plurality of cords and including an axially outer edge and an axially inner edge; winding the at least one strip about the drum in a circumferential direction between the first and second drum edges; and turning the at least one strip from a first winding angle to a second winding angle on the first end surface, whereby the turning reduces a difference of at least one of a length between cords disposed adjacent the axially outer edge of the at least one strip and cords disposed adjacent the axially inner edge of the at least one strip, and a tension between the cords disposed adjacent the axially outer edge of the at least one strip and the cords disposed adjacent the axially inner edge of the at least one strip.

2. The method of forming the belt structure for the pneumatic tire of claim 1, further comprising the step of turning the at least one strip from the second winding angle back to the first winding angle on the second end surface.

3. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of turning the at least one strip includes the first winding angle being in a range of from about 5 to about 20 degrees.

4. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of turning the at least one strip includes the first winding angle and the second angle being at opposing angles such that an absolute value of the first winding angle is equal to an absolute value of the second winding angle.

5. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing the drum includes a ratio of a value of the first radius of curvature to a value of the second radius of curvature is from about 1.5 to about 30.

6. The method of forming the belt structure for the pneumatic tire of claim 5, wherein the ratio is from about 5 to about 15.

7. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the at least one strip is a first strip, and the method further comprises the step of offsetting a second strip in a circumferential manner from the first strip and winding the second strip about the drum.

8. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing at least one strip includes a width of the at least one strip being between about 0.25 inches and 1.0 inches.

9. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing at least one strip includes the cords being formed from at least one of nylon, aramid, a combination of nylon and aramid, polyester, and steel.

10. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing the drum includes reducing a traverse offset of the at least one strip.

11. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing the drum includes increasing a drum offset of the at least one strip.

12. The method of forming the belt structure for the pneumatic tire of claim 1, wherein the step of providing the drum includes the drum being formed with a second surface recess for receiving a second radially inner belt structure.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] The invention will be described by way of example and with reference to the accompanying drawings, in which:

[0024] FIG. 1 is a schematic cross-sectional view of an exemplary tire formed by the method of the present invention;

[0025] FIG. 2 is a schematic perspective view of an exemplary tire building drum with a zigzag belt structure of a tire of the present invention being formed;

[0026] FIG. 3 is a schematic end view of the tire building drum and zigzag belt structure shown in FIG. 2;

[0027] FIG. 4 is a fragmentary schematic representation of a portion of a strip of a zigzag belt structure formed by the method of the present invention;

[0028] FIG. 5 is a fragmentary schematic representation of a portion of an exemplary tire building drum with a strip of a zigzag belt structure formed by the method of the present invention;

[0029] FIG. 6A is schematic representation of a cross section of a tire building drum of the prior art;

[0030] FIG. 6B is a schematic representation of a cross section of an exemplary tire building drum used in the method of the present invention;

[0031] FIG. 6C is a schematic representation of a cross section of another exemplary tire building drum used in the method of the present invention; and

[0032] FIG. 6D is a schematic representation of a cross section of yet another exemplary tire building drum used in the method of the present invention.

[0033] Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0034] An exemplary embodiment of a tire formed according to the method of the present invention is indicated generally at 10, and is shown in FIG. 1. The tire 10 includes a bead area 12 and a bead core 14 embedded in the bead area. A sidewall 16 extends radially outward from the bead area 12 to a ground-contacting tread 18. The tire 10 is reinforced by a carcass 20 that toroidally extends from one bead area 12 to a second bead area (not shown), as known to those skilled in the art. The carcass 20 includes at least one ply that preferably winds around each bead core 14.

[0035] A belt reinforcement package 22 is disposed between the carcass 20 and the tread 18. The belt reinforcement package 22 may employ specific configurations as desired. For example, the belt reinforcement package 22 may include at least one of a radially outer belt structure 24 and a radially inner belt structure 26. A zigzag belt package or belt structure 28 preferably is disposed between the radially outer belt structure 24 and the radially inner belt structure 26. Of course, different combinations of belt structures may be employed, and the outer belt structure 24 and inner belt structure 26 may be of any configuration, such as spiral, cut, zigzag, and the like.

[0036] Turning now to FIGS. 2 and 3, the method includes providing a tire building drum 30 for forming the zigzag belt structure 28. The tire building drum 30 includes an axially-extending circumferential center section 32, an axially-disposed circumferential first edge 34, and an axially-disposed circumferential second edge 36. The center section 32 preferably is formed with a slight radius as will be described in greater detail below, and includes a width indicated at W. At a first edge 38 of the center section 32, the drum 30 is formed with a first end surface indicated at 60 that extends radially inwardly to the drum first edge 34. At a second edge 40 of the center section 32, the drum 30 is formed with a second end surface indicated at 62 that extends radially inwardly to the drum second edge 36.

[0037] Referring to FIGS. 6B through 6D, aspects of the surface of the drum 30 are shown in comparison to the surface of a prior art drum 100, which is shown in FIG. 6A. The prior art drum 100 includes a surface 102 that extends from an axially-disposed circumferential first edge 104 to an axially-disposed circumferential second edge 106. The surface 102 of the prior art drum 100 is formed with a single slight curve or radius R1. In contrast, the tire building drum 30 used in the method of the invention is formed with a compound surface.

[0038] More particularly, as shown in FIGS. 3 and 6B, the center section 32 of the drum 30 is formed with the slight curve or radius R1, which is referred to as a first radius. The first radius R1 extends for the width W from the first edge 38 of the center section 32 to the second edge 40 of the center section. At the first edge 38 of the center section 32, the curvature of the drum 30 changes, as the first end surface 60 extends to the drum first edge 34 at a second radius R2, which is smaller than the radius R1. At the second edge 40 of the center section 32, the curvature of the drum 30 also changes, as the second end surface 62 extends to the drum second edge 36 again at the second radius R2. As mentioned above, the value of the second radius R2 is smaller than the value of the first radius R1. Preferably, a ratio of the value of the first radius R1 to the value of the second radius R2 is in a range of from about 1.5 to about 30, and is more preferably in range of from about 5 to about 15.

[0039] As shown in FIG. 6C, the drum 30 may include a recess 64, which provides a specific structural area on which the radially inner belt structure 24 (FIG. 1) may seat during the forming of the belt reinforcing package 22. As shown in FIG. 6D, the drum 30 may also include the first recess 64 and a second recess 66 to provide a structural area for multiple belt structures to seat during the forming of the belt reinforcing package 22. In any event, the center section 32 of the drum 30 is formed with the first radius R1, and each of the first end surface 60 and the second end surface 62 between the center section and each respective drum edge 34 and 36 is formed with the second radius R2.

[0040] Returning to FIGS. 2 and 3, to form the zigzag belt structure 28, the drum 30 is rotated as each one of individual strips 28a, 28b, 28c and 28d, which are shown by way of example, are wound about the drum in a circumferential direction extending in an alternating fashion between the drum edges 34 and 36, as will be explained in greater detail below. Each strip 28a, 28b, 28c and 28d is formed of rubber and is reinforced with a plurality of cords. The width of each strip 28a, 28b, 28c and 28d is typically between about 0.25 inches and 1.0 inches, and the cords preferably are formed from nylon, aramid, a combination of nylon and aramid, polyester or steel.

[0041] During winding, a first strip 28a is wound about the drum 30 at a first predetermined winding angle indicated by β. As the first strip 28a passes the first edge 38 of the center section 32 heading toward the first drum edge 34, the strip reaches a first plane 42 on the first end surface 60, which is the axial outer limit for the strip winding. At that point, referred to as a turn 46, the first strip 28a is turned in a shallow U-direction and angled at a second winding angle, which preferably is an opposing winding angle, indicated by −β. As the first strip 28a passes the second edge 40 of the center section 32 hearing toward the second drum edge 36, the strip reaches a second plane 44 on the second end surface 62 that is the opposing axial limit for the strip winding. At that point, referred to as a turn 48, the first strip 28a is turned in a shallow U-direction and angled at the winding angle of β. Preferably, the winding angle β is in a range of from about 5 to about 20 degrees.

[0042] After the first strip 28a has been wrapped about the drum 30 in this manner, a second strip 28b is shifted or offset in a circumferential manner from the first strip and then wrapped about the drum adjacent the first strip in a manner similar to that as the first strip. The second strip 28b thus includes turns 50 and 52 that are offset from the respective turns 46 and 48 of the first strip 28a. A third strip 28c and a fourth strip 28d are each wrapped about the drum 30 in a similar offset fashion, continuing to create multiple layers and thus form a belt, which continues again for multiple belts that form the zigzag belt package 28. It is to be understood that the strips 28a, 28b, 28c and 28d may be disposed in abutment with one another, overlapping one another, or spaced apart from one another. Moreover, while the strips 28a, 28b, 28c and 28d of the exemplary belt package 28 include two turns, depending on the winding angle of each strip, the diameter of the drum 30, the width of the drum and other characteristics, the strips may include more than two turns.

[0043] As described above, in the prior art, the change of direction of the strips using a single-curved or flat-surfaced drum may create a length differential between the cords on the outside edge of the strip and the cords on the inside of the strip, as well as a difference in tension between the cords on the outside edge of the strip and the inside edge of the strip, and non-uniform spacing between the cords. The drum 30 for forming the tire 10 reduces these issues by providing a center section 32 with a first radius R1 and end surfaces 60 and 62 that each have a second radius R2, which is referred to as a double-curved drum.

[0044] More particularly, referring to FIG. 4, the strip 28a includes an axially outer edge 54, an axially inner edge 56 and a thickness BW. The cords in the axially outer edge region 54 would have a higher tension, longer length and compressed spacing compared to the cords in the region of the axially inner edge 56 using a prior art drum. Winding the strip 28a on the double curved drum 30 reduces the differential between the cords in the outer edge 54 and the inner edge 56 to zero or near-zero. When the cord lengths are equal, they are also in equal tension and have generally uniform spacing after curing. Such reduction of the length and tension differential between the cords in the strip outer edge 54 and the strip inner edge 56 is accomplished by optimizing certain parameters.

[0045] First, as shown in FIGS. 4 and 5, by making the turn 46 on the first end surface 60 of the drum 30 (as well as the turn 48 on the second end surface 62, which is not shown in FIGS. 4 and 5), the contoured surface of the drum compensates for the winding angle β (FIG. 3) of the strip with the radius R2 on the drum. The radius R2 of the first end surface 60 of the drum 30 thus creates equal tension in each edge 54 and 56 of the strip 28a. To enable such equal tension, a ratio of the value of the radius R1 of the center section 32 to the value of the radius R2 of the first end surface 60 (as well as to the value of the radius R2 of the second end surface 62) preferably is in a range of from about 1.5 to about 30. For example, when the winding angle β of the belts 28a, 28b, 28c and 28d is between about 5 degrees to about 20 degrees, the ratio of radius R1 to radius R2 may be in a range of from about 5 to about 15. When the strips 28a, 28b, 28c and 28d are of a relatively wide width, the ratio of R1 to radius R2 will be higher than when the strips are of a relatively narrow width.

[0046] Next, the width BW of the strip 28a may be optimized to promote a length and tension of the cords in the axially outer edge region 54 that are equal to the length and tension of the cords in the axially inner edge 56 region, taking into account the double-curved drum 30. For example, the width BW of the strip 28a preferably is between about 0.25 inches and about 1.0 inches. In addition, the width of the entire belt package 28 may be optimized to promote a length and tension of the cords in the axially outer edge region 54 of each respective strip 28a, 28b, 28c and 28d that are equal to the length and tension of the cords in the axially inner edge 56 region of each strip.

[0047] Another parameter that may be optimized is the traverse offset TO. The traverse offset TO is the axial distance at the center of the strip 28a from the center of the turn 46 to the point 58 at which the turn ends and the strip continues in a straight line along the drum 30. A higher traverse offset TO undesirably increases the length and tension differential between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56. The double-curved drum 30 desirably reduces the traverse offset TO effect, thereby decreasing the length and tension differential between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56 to zero or near zero.

[0048] A further parameter that may be optimized is the drum offset DO. The drum offset DO is the circumferential distance at the center of the strip 28a from the center of the turn 46 to the point 58 at which the turn ends and the strip continues in a straight line along the drum 30. A lower drum offset DO creates a sharper turn 46 that undesirably increases the length and tension differential between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56. The double-curved drum 30 desirably reduces the drum offset DO effect, thereby creating a smoother turn 46, which decreases the length and tension differential between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56 to zero or near zero.

[0049] These parameters may be optimized in several ways. For example, when the contour of the double-curved drum 30 has been established, the remaining winding parameters may be adjusted to reach equal tension between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56 of the strip 28a. Alternatively, the contour of the double-curved drum 30 may be adjusted in view of established remaining winding parameters to reach equal tension between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56 of the strip 28a. As another alternative, the contour of the double-curved drum 30 and the remaining winding parameters may all be adjusted during design to reach equal tension between the cords in the axially outer edge region 54 and the cords in the axially inner edge region 56 of the strip 28a.

[0050] Therefore, the present invention includes a method of forming a belt structure 28 for a tire 10. The method includes steps in accordance with the description that is presented above and shown in FIGS. 1 through 5 and 6B through 6D.

[0051] In this manner, the tire 10 including the zigzag belt structure 28 formed on the double-curved drum 30 optimizes zigzag winding parameters of the strips 28a, 28b, 28c and 28d to promote a uniform tension on the cords in each strip, a uniform length of the cords across each strip, and uniform spacing between the cords in each strip. Such uniform tension, length and spacing of the cords in each strip 28a, 28b, 28c and 28d desirably increases the strength of zigzag belt structure 28 and thus the belt reinforcing package 22. The uniform tension, length and spacing also balances the strain and stress of the cords in each strip 28a, 28b, 28c and 28d to desirably increase the durability of the edge of the zigzag belt structure 28. Moreover, the uniform tension, length and spacing of the cords in each strip 28a, 28b, 28c and 28d improves the uniformity of the zigzag belt structure 28 and thus the belt reinforcing package 22 to promote desirable uniform wear of the tire tread 18.

[0052] It is to be understood that the method of forming and/or the structure of the above-described tire 10, zigzag belt structure 28 and/or double-curved drum 30 may be altered or rearranged, or components or steps known to those skilled in the art omitted or added, without affecting the overall concept or operation of the invention. In addition, the number, arrangement, sequence of winding and/or compositions of the strips 28a, 28b, 28c and 28d and their manner of forming belt layers and the zigzag belt structure 28 may be adjusted or changed based upon particular design considerations without affecting the overall concept or operation of the invention.

[0053] The invention has been described with reference to a preferred embodiment. Potential modifications and alterations will occur to others upon a reading and understanding of this description. It is to be understood that all such modifications and alterations are included in the scope of the invention as set forth in the appended claims, or the equivalents thereof.