Tire groove with handlebar shape for heavy truck tread

Abstract

A heavy truck tire tread having ribs is provided. A sipe is located in a rib extending from a first side surface to a second side surface. A teardrop has a first end located at the first side surface and a second end located at the second side surface. A middle section of the teardrop is located between the first end and the second end in a lateral direction. A first transition is located between the first end and the middle section, and a second transition is located between the second end and the middle section, and they both extend in the lateral direction and a thickness direction. The entire middle section is farther from the upper surface in the thickness direction than any portion of the first end or the second end is from the upper surface in the thickness direction.

Description

Handlebar-shaped tire tread grooves for heavy-duty trucks Technical Field

[0001] The subject matter of this invention relates to teardrop-shaped tread grooves for tires, the teardrop having a specific geometry that minimizes or eliminates cracking within the teardrop. More specifically, this application relates to tread grooves with teardrops in the ribs, wherein the middle portion of the teardrop is farther from the upper surface than the tip of the teardrop, thereby minimizing or reducing cracking while achieving a trade-off between rolling resistance and end-of-service traction. Background Technology

[0002] Tires typically consist of a tread with a series of ribs extending circumferentially and separated axially by grooves. These ribs may have a series of tread grooves designed to improve traction under certain road conditions. Tread grooves are narrow slits cut into the ribs and can be formed in various ways. For example, the shape along the length of the grooves can be straight, zigzag, wavy, or angled into the tire element. The depth of the tread grooves can also vary or remain consistent along their length and can extend into the tread depth until the end of their lifespan. Tread grooves close within the tire's "footprint" on the road and increase the flexibility of the tread blocks containing them. The presence of tread grooves improves stopping distance, separation traction, and rolling traction on glare-covered ice. Additionally, tread grooves have been found to improve tire traction in snow, mud, and other types of ice.

[0003] Tread grooves with a teardrop shape are known to increase tire traction as the tire nears the end of its life. The teardrop feature in the tread grooves is an increase in the circumference of the groove in the radial direction closer to the tire center. This increased circumference results in a larger gap in the radially closer portion of the tread groove compared to the radially farther portion. As the tire tread wears down, this larger gap opens up and is exposed to the road surface, thus improving traction and water drainage as the tire nears the end of its life.

[0004] While including tread grooves can improve tire performance in certain areas, adding these cutting features to the tire ribs can also lead to the following risks: irregular wear on the ribs, increased rolling resistance, deterioration of tread robustness, and increased debris and fragmentation. Tread grooves present in the shoulder ribs of heavy-duty commercial truck tires can lead to irregular wear, increased rolling resistance, and tread groove attack. Tread groove attack is the cracking or breakage of the shoulder rib due to stress concentration caused by the tread grooves. When the driving tire is subjected to torque, cracking in the shoulder rib may occur at the bottom of the teardrop and then extend away from that starting point.

[0005] Known methods to prevent or minimize cracking at the base of the teardrop include increasing the size of the teardrop, which typically means increasing its diameter, resulting in a larger circumferential dimension of the tread. Increasing the teardrop radius increases end-of-service traction but reduces the stiffness of the tread blocks. This decrease in stiffness is due to less material constituting the tread blocks, making the material between the teardrop and the upper surface much less stiff. This has negative effects, as it reduces wear performance and rolling resistance. Another way to minimize or eliminate cracking at the base of the teardrop is to move the teardrop upwards in the thickness direction, bringing it closer to the upper surface of the tread, thus making the tread grooves as deep as they would otherwise be. However, moving the teardrop upwards closer to the upper surface of the tread reduces the end-of-service traction associated with the tread grooves. Therefore, there is still room for modification and improvement in the art. Attached Figure Description

[0006] Referring to the accompanying drawings, the complete and feasible disclosure of the invention for those skilled in the art, including its best mode, is set forth in the specification, wherein:

[0007] Figure 1 is a perspective view of a tire with a tread containing tread grooves in the shoulder as disclosed herein.

[0008] Figure 2 is a top view of the tread including the tread grooves in the shoulder, showing four tread grooves with different configurations.

[0009] Figure 3 is a cross-sectional view taken along line 3-3 in Figure 2.

[0010] Figure 4 is a cross-sectional view taken along line 4-4 in Figure 2.

[0011] Figure 5 is a cross-sectional view taken along line 5-5 in Figure 2.

[0012] Figure 6 is a cross-sectional view taken along line 6-6 in Figure 2.

[0013] Figure 7 is a cross-sectional view taken along line 7-7 in Figure 2.

[0014] Figure 8 is a cross-sectional view taken along line 8-8 in Figure 2.

[0015] Figure 9 is a cross-sectional view taken along line 9-9 in Figure 2.

[0016] Figure 10 is a cross-sectional view taken along line 10-10 in Figure 2.

[0017] Figure 11 is a cross-sectional view taken along line 11-11 in Figure 2.

[0018] Figure 12 is a cross-sectional view taken along line 12-12 in Figure 2.

[0019] Figure 13 is a top view of a tread with three different tread grooves according to another exemplary embodiment.

[0020] Figure 14 is a cross-sectional view taken along line 14-14 in Figure 13.

[0021] Figure 15 is a cross-sectional view taken along line 15-15 of Figure 13.

[0022] Figure 16 is a cross-sectional view taken along line 16-16 of Figure 13.

[0023] Figure 17 is a cross-sectional view taken along line 17-17 of Figure 13.

[0024] Figure 18 is a perspective view of a tread groove according to another exemplary embodiment, the tread groove having a middle section of the teardrop with a diameter larger than the end of the teardrop.

[0025] Figure 19 is a perspective view of a tread groove with a teardrop shape according to another exemplary embodiment, the teardrop having a middle section and an end section, the cross-sectional dimensions of which decrease / increase as the middle section and the end section extend in the lateral direction.

[0026] Figure 20 is a perspective view of the tread grooves in Figure 19 taken from different angles.

[0027] The same or similar reference numerals are used in different figures to indicate the same or similar features. Detailed Implementation

[0028] The present invention will now be described in detail with reference to embodiments thereof, and one or more examples of embodiments thereof are illustrated in the accompanying drawings. Each example is provided for illustrative purposes and is not intended to limit the invention. For example, a feature shown or described as part of one embodiment may be used with another embodiment to obtain a third embodiment. The invention is intended to include these and other modifications and variations.

[0029] This invention provides a tread groove 22 design for a tread 12 of a heavy-duty truck tire 10 that reduces or eliminates crack propagation while maintaining rigidity and performance at the end of its life. The tread groove 22 extends from a first side surface 18 to a second side surface 19 and has a teardrop 32 having a first end 34 at the first side surface 18 and a second end 36 at the second side surface 19. A middle section 38 of the teardrop 32 is positioned further away from the upper surface 16 in the thickness direction 24 than the ends 34, 36. A first transition portion 90 and a second transition portion 92 of the teardrop 32 are located between the middle section 38 and the ends 34, 36. The transition portions 90, 92 establish a geometric change in the shape of the teardrop 32 that reduces or eliminates crack propagation from the middle section 38 to the ends 34, 36. In some configurations of the teardrop 32, the provided geometry also reduces or eliminates crack initiation in the middle section 38, where crack initiation is most likely to occur. Through the geometric changes established by the transition sections 90 and 92, the total depth of the tread groove 22 in the thickness direction 24 does not need to be moved upward to the upper surface 16, and the cross-sectional dimension of the teardrop 32 along its entire length does not need to be increased.

[0030] Figure 1 shows a tire 10, which is a heavy-duty truck tire 10. At this point, tire 10 is not designed for automobiles, motorcycles, or light trucks (with a payload capacity of less than 4,000 pounds), but rather for use with heavy-duty trucks such as 18-wheelers, garbage trucks, or box trucks. Tire 10 can be a steering tire, drive tire, trailer tire, or all-position tire. In a preferred embodiment, tire 10 including tread grooves 22, as used herein, is a drive tire for a tractor-trailer. Tire 10 includes a carcass / body 76 on which a tread 12 is disposed. The central axis of tire 10 extends through the center of carcass 76, and the lateral / axial direction 28 of tire 10 is parallel to the central axis. The radial direction 24 (also referred to as the thickness direction 24) of tire 10 is perpendicular to the central axis, and the tread 12 is positioned further away from the central axis in the thickness direction 24 than the carcass 76. The tread 12 extends completely around the carcass 76 in the circumferential direction 26 of tire 10 and surrounds the central axis 360 degrees.

[0031] The tread 12 has five ribs, which are separated by four longitudinal grooves extending in the circumferential direction 26. These five ribs can be classified as a center rib, two intermediate ribs, and two shoulder ribs, one of which is designated as shoulder rib 14. Shoulder rib 14 is located on one side of the tread 12 in the lateral direction 28, and a second shoulder rib is located on the opposite side of the tread 12 in the lateral direction 28. A first side surface 18 of shoulder rib 14 is present at the first shoulder rib 14 and is the outermost surface of the tread 12 in the lateral direction 28. Each rib may consist of multiple tread blocks, and the tread blocks in shoulder rib 14 are designated as shoulder rib tread blocks 44, which may have various shapes, sizes, and structural features to give the tread 12 different performance characteristics. Rib grooves 42 separate the shoulder rib tread blocks 44 along the length of shoulder rib 14 in the circumferential direction 26. Rib grooves 42 may have a width greater than 2 mm. Although the shoulder rib 14 is composed of a series of shoulder rib tread blocks 44, in other embodiments, the shoulder rib does not need to have any shoulder rib tread blocks 44.

[0032] The tread 12 may include certain structural features capable of reducing tearing or crack initiation and propagation. One such structural feature, as shown with reference to Figure 2, may be a tread groove 22 extending across the entire lateral width of the shoulder rib 14 in the lateral direction 28. The tread groove 22 is a fine groove / cutout in the shoulder rib 14. The tread groove 22 at the upper surface 16 of the shoulder rib 14 may have a width of two millimeters or less. The tread groove 22 has a body 30 extending downwards from the upper surface 16 into the shoulder rib 14 in the thickness direction 24, and the body 30 has a width of less than 2 millimeters. At the bottom of the body 30, a teardrop 32 is included in the tread groove 22. The cross-sectional dimension or diameter of the teardrop 32 may be less than two millimeters or greater than or equal to two millimeters.

[0033] The tread groove 22 is shown and described as being located within the shoulder rib 14, but this is only one embodiment, as the tread groove 22 as described herein can be located in any one or more of the shoulder rib, intermediate rib, or central rib, or any rib of the tread 12. Thus, a rib can be the shoulder rib 14, intermediate rib, central rib, or any rib of the tread 12. When the rib is the shoulder rib 14, the first side surface 18 is the outer surface of the tread 14, and the second side surface 19 is the surface of the shoulder rib 14 facing the shoulder groove 20 and arguably defining a portion of the shoulder groove 20.

[0034] Figure 2 shows four tread grooves 22 in the shoulder rib 14 and four tread grooves 22 in the oppositely arranged shoulder ribs on the other side of the tread 12 in the lateral direction 28. Various tread grooves 22 are also located in the two central ribs and two intermediate ribs. The tread grooves 22 may all be constructed to have the same size and geometry, or they may have different sizes and / or geometries. In Figure 2, the four tread grooves 22 on the shoulder rib 14 all have different geometries from each other. The tread grooves 22 on the oppositely arranged shoulder ribs have the same geometric configuration as the tread grooves positioned at the same location relative to the circumferential direction 26 on the shoulder rib 14. According to various exemplary embodiments, any number of tread grooves 22 may be present in the tread 12, and the left-hand side shoulder rib 14 may or may not have the same number of tread grooves 22 as the right-hand side shoulder rib. It should be noted that the shoulder rib 14 is not located laterally on the outer side of the tread 12 in the lateral direction 28, but rather the sacrificial rib 54 is located on the outer side of the shoulder rib 14 in the lateral direction 28. The sacrificial rib groove 56 separates the sacrificial rib 54 from the shoulder rib 14, and the sacrificial rib 54 is designed to protect the shoulder rib 14 from abnormal wear during the use of the tread 12. As shown in Figure 3, the sacrificial rib 54 does not extend in the thickness direction 24 to the same position as the upper surface 16 in the thickness direction 24. The tread grooves 22 described herein are not those that may or may not be located in the sacrificial rib 54, but rather those tread grooves within the shoulder rib 14 that are separated from the sacrificial rib 54 and from the center rib, intermediate rib, or other ribs of the tread 12. In some embodiments, the sacrificial rib 54 has a height extending in the thickness direction 24 such that its upper surface is at the same height as the upper surface 16 in the thickness direction 24. It should be understood that, when used herein, the term shoulder rib 14 does not include sacrificial rib 54 of tread 12 if such sacrificial rib 54 is actually present in tread 12.

[0035] Figures 3 through 6 illustrate one configuration of the tread groove 22 as disclosed herein. The tread groove 22 leads to the sacrificial rib groove 56 and extends to the shoulder groove 20 from the first side surface 18 to the second side surface 19. As can be seen with particular reference to Figure 4, the teardrop 32 is composed of multiple segments that give the overall side view shape of the teardrop 32 a handle shape. The body 30 extends along the entire length of the teardrop 32 in the lateral direction 28 and extends along that entire length to the upper surface 16. The cross-sectional shape of the teardrop 32 is circular and has the same diameter along its entire length in the lateral direction 28. Figure 5 shows the first end 34 of the teardrop 32 as viewed from inside the sacrificial rib groove 56. The first end 34 is positioned higher in the thickness direction 24 than the bottom of the sacrificial rib groove 56, such that the bottom of the sacrificial rib groove 56 is farther from the upper surface 16 in the thickness direction 24 than the first end 34 is farther from the upper surface 16 in the thickness direction 24. The first end 34, together with the body 30, is located on the first side surface 18 of the shoulder rib 14. The cross-sectional shape of the first end 34 is circular and has the same diameter along its entire length in the lateral direction 28. The first end 34 is located in the same position along its entire length in the thickness direction 24 and does not move closer to or further away from the upper surface 16 in the thickness direction 24 at any point along its extension in the lateral direction 28. As shown, another portion of the teardrop 32, referred to as the middle segment 38, is positioned farther from the upper surface 16 in the thickness direction 24 than the first end 34 is farther from the upper surface 16 in the thickness direction 24. In this respect, the entire intermediate segment 38 is positioned away from the upper surface 16 such that no part of the first end 34 is in the same position as any part of the intermediate segment 38 in the thickness direction 24. The intermediate segment 38 is positioned in the thickness direction 24 such that it is partially above and partially below the bottom of the sacrificial rib groove 56 in the thickness direction.

[0036] Referring back to Figure 4, the first end 34 has a length 94 in the lateral direction 28, extending from the first side surface 18 to the first transition portion 90. The farthest extension point 48 of the first end is shown in Figure 4 and represents the farthest point of the first end 34 from the upper surface 16 in the thickness direction 24. The farthest extension point 48 extends along the entire length 94 because the first end 34 does not move upward or downward in the thickness direction 24 as it extends along the lateral direction 28. The intermediate segment 38 has a farthest extension point 52, which is also the farthest point of the intermediate segment 38 from the upper surface 16 in the thickness direction 24. Because the intermediate segment 38 does not extend upward or downward, the farthest extension point 52 extends along the entire length 98 of the intermediate segment 38 in the lateral direction 28. As shown in Figure 6, the cross-section of the intermediate segment 38 is circular and has the same diameter along the entire length 98. In various embodiments, the lengths 98 and 94 may be the same or they may be different. The distance from the farthest extension point 52 of the middle section to the upper surface 16 is greater than the distance from the farthest extension point 48 of the first end to the upper surface 16 in the thickness direction 24. The middle section 38 and the first end 34 may have the same diameter.

[0037] The first transition portion 90 of the teardrop 32, as shown in Figure 4, extends from the intermediate segment 38 to the first end 34 and connects the two portions 38, 34 of the teardrop 32. The first transition portion 90 extends in both the thickness direction 24 and the lateral direction 28 and has a circular cross-section with a diameter identical to that of the first end 34 and the intermediate segment 38. The first transition portion 90 has a length 100 extending from the first end 34 to the intermediate segment 38, and has a circular cross-section along its entire length 100. The distance of the length 100 may be the same as, or longer than, the lengths 94 and 98. Relative to the thickness direction 24, the first transition portion 90 has a portion located at the same position as the first end 34 and the intermediate segment 38, and this portion is located between the two portions 34, 38 of the teardrop 32.

[0038] The teardrop 32 has a second end 36 at the second side surface 19, which extends to the shoulder groove 20 and has a length 96 in the lateral direction 28. The second end 36 has a circular cross-section and a uniform diameter along its entire length 96, such that the farthest extension point 50 of the second end is located at the second end 36 and extends along its entire length 96. The farthest extension point 50 of the second end is the position of the second end 36 furthest from the upper surface 16 in the thickness direction 24. The farthest extension point 50 of the second end may be located in the same position as the farthest extension point 48 of the first end relative to the upper surface 16 in the thickness direction 24, and may be closer to the upper surface 16 in the thickness direction than the farthest extension point 52 of the intermediate segment. The entire second end 36 may be closer to the upper surface 16 in the thickness direction 24 than the entire intermediate segment 38, such that no part of the intermediate segment 38 is located at or above any part of the second end 36 in the thickness direction 24, thus being closer to the upper surface 16.

[0039] The second transition portion 92 extends from the intermediate segment 38 to the second end 36 and has an extension component in both the lateral direction 28 and the thickness direction 24. The cross-sectional shape of the second transition portion 92 is circular, and the diameter of the cross-section of the second transition portion 92 is the same as the diameter of the second end 36, the intermediate segment 38, the first end 34, and the first transition portion 90. The second transition portion 92 has a length 102 extending from the second end 36 to the intermediate segment 38, and the second transition portion 92 has a circular cross-section along its entire length 102. The distance of the length 102 may be the same as, or longer than, the lengths 94, 98, 96, and 100. Relative to the thickness direction 24, the second transition portion 92 has a portion located at the same position as the second end 36 and the intermediate segment 38, and this portion is located between these two portions 36 and 38 of the teardrop 32.

[0040] Therefore, when viewed from the rear in the circumferential direction 26, the teardrop 32 has a "handle" shape, as shown, for example, in Figure 4. When the tread groove 22 first begins to crack, the cracking is most likely to begin at the bottom of the teardrop 32, in the middle of the teardrop 32 along the lateral direction 28. The lateral midpoint 40 of the teardrop 32 is located in the lateral direction 28, between the end point of the teardrop 32 on the first side surface 18 and the shoulder groove 20. This midpoint is located in the middle section 38, and in some embodiments, the middle section 38 is positioned relative to the lateral midpoint 40 such that half of the middle section 38 is outside the lateral midpoint 40, and the other half of the middle section 38 is inside the lateral midpoint 40 in the lateral direction 28. In some embodiments, half of the entire teardrop 32 is outside the lateral midpoint 40 in the lateral direction 28, and half of the entire teardrop 32 is inside the lateral midpoint 40 in the lateral direction 28. The intermediate segment 38 is located in the middle of the teardrop 32 in the lateral direction 28, and cracks that begin in the teardrop 32 will start at the farthest extension point 52 of the intermediate segment at the bottom of the intermediate segment 38. Transition portions 100, 102 on either side of the intermediate segment 38 in the lateral direction 28 serve to prevent cracks from extending from the intermediate segment 38 to the ends 34, 36. If crack propagation stops, the crack will not be visible to the user to maintain the aesthetic appearance of the tire 10 tread 12, and will not propagate to further degrade the performance of the tread 12.

[0041] Figure 2, and with reference to Figures 7 and 8, shows in more detail a tread groove 22 with a different configuration than the tread grooves just discussed. In this configuration, the tread groove 22 again has a handle shape, wherein the middle section 38 is farther from the upper surface 16 in the thickness direction 24 than the first end 34 and the second end 36 are. The ends 34, 36 are positioned so that they are closer to the upper surface 16 in the thickness direction 24 than any part of the middle section 38 is. The teardrop 32 also has a circular cross-sectional shape, however, the diameter is different in the different sections of the teardrop 32. The middle section 38 has a larger diameter cross-section than the first end 34 and the second end 36, which have the same cross-sectional diameter. The cross-sections of these sections 38, 34, 36 are constant along their entire width 98, 94, 96. The first transition portion 90 and the second transition portion 92 have a circular cross-sectional shape, wherein the diameter of the cross-section decreases from the middle section 38 to the ends 34, 36. The farthest extension points 48, 52, 50 are the same as those discussed with respect to the previous embodiments, as they extend along their respective entire lengths 94, 98, 96, and wherein the first farthest extension point 48 and the second farthest extension point 50 are equidistant from the upper surface 16 in the thickness direction 24. The farthest extension point 52 of the middle section is again farther from the upper surface 16 in the thickness direction 24 than the first farthest extension point 48 and the second farthest extension point 50.

[0042] The next tread groove 22 in sequence along the circumferential direction 26 is shown in the cross-sectional views in Figures 9 and 10, and has a geometrically different shape from the two previously discussed embodiments. The first end 34 and the second end 36 are constructed in the same manner as the two previously discussed embodiments, and it is not necessary to repeat this information. However, the intermediate segment 38 is constructed differently because its cross-sectional dimensions are not uniform along the entire length 98, but rather decrease continuously both inside and outside in the lateral direction 28 from the lateral midpoint 40. The intermediate segment 38 has a first intermediate segment base 66 located at the lateral midpoint 40 and a first intermediate segment end 68 located at the first transition 90. The shape of the intermediate segment 38 from the first intermediate segment base 66 to the first intermediate segment end 68 is a frustoconical shape, wherein the cross-sectional dimensions of the intermediate segment 38 decrease continuously in the lateral direction 28 from the first intermediate segment base 66 to the first intermediate segment end 68.

[0043] The other half of the intermediate segment 38 is a mirror image of the first half. The second half has a second intermediate segment base 70 that coincides with the first intermediate segment base 66 and the lateral midpoint 40. The intermediate segment 38 extends inwardly from the second intermediate segment base 70 in the lateral direction 28 to the second intermediate segment end 72 located at the beginning of the second transition portion 92. The cross-sectional diameter of the intermediate segment 38 decreases continuously in the lateral direction 28 from the second intermediate segment base 70 to the second intermediate segment end 72. The arrangement of the intermediate segment 38 results in the farthest extension point 52 of the intermediate segment being located at the lateral midpoint 40 and therefore also at the first intermediate segment base 66 and the second intermediate segment base 70. The farthest extension point 52 of the intermediate segment is therefore located at this particular position and does not extend along the entire length 98 as in the aforementioned embodiment. Therefore, the first intermediate segment end 68 and the second intermediate segment end 72 are closer to the upper surface 16 in the thickness direction 26 than the farthest extension point 52 of the intermediate segment. The farthest extension point 52 of the middle section is the farthest point of the entire teardrop 32 and tread groove 22 from the upper surface 16 in the thickness direction 24.

[0044] The point of the intermediate segment 38 closest to the upper surface 16 in the thickness direction 24 is located at the lateral midpoint 40, which is also located at both the first intermediate segment base 66 and the second intermediate segment base 70. The transition portions 90, 92 have the same cross-sectional diameter as the ends 34, 36. The intermediate segment 38 extends in the thickness direction 24 so as to be above a portion of the transition portions 90, 92, but still below the first furthest extension point 48 and the second furthest extension point 50. However, in other embodiments, the intermediate segment 38 may extend in the thickness direction 24 to be at or above the first furthest extension point 48 and the second furthest extension point 50.

[0045] The fourth tread groove 22 configuration of Figure 2 is shown in more detail in the cross-sectional views of Figures 11 and 12. This configuration of tread groove 22 has a “cigar”-shaped middle section 38, as previously discussed regarding the tread groove 22 described in Figures 9 and 10. The furthest extension point 52 of the middle section is the furthest point where the teardrop 32 and the tread groove 22 extend into the tread 12, and therefore the furthest point of the teardrop 32 and the tread groove 22 from the upper surface 16. The teardrop 32 differs in that the first end 34 and the second end 36 are not cylindrical in shape, but both are truncated cones. In this respect, the first end 34 has a first end base 58 located at the first transition portion 90 and a first end tip 60 located at the first side surface 18. The first end 34 has a circular cross-sectional shape with a diameter that continuously decreases in the lateral direction 28 from the first end base 58 to the first end tip 60. Therefore, the farthest extension point 48 of the first end is located at the boundary between the base 58 of the first end and the first transition portion 90. The farthest extension point 48 of the first end does not extend along the entire length 94, but is located at the innermost point of the first end 34.

[0046] The second end 36 is constructed in a similar manner to the first end 34, such that the second end base 62 is positioned at the second transition portion 92 and has a larger diameter than the second end tip 64 located at the second side surface 19. The second end 36 has a frustoconical shape, and its diameter decreases continuously in the lateral direction 28 from the second end base 62 to the second end tip 64. The furthest extension point 50 of the second end is located at the second end base 62 and does not extend along the entire length 96. The minimum cross-sectional diameter of the entire teardrop 32 is located at the first end tip 60 and the second end tip 64. The cross-sectional dimension of the first transition portion 90 does not change from the diameter of the first intermediate segment end 68 to the diameter of the first end base 58 and maintains the same diameter along the entire length 100. In a similar manner, the second transition portion 92 has a constant diameter along the entire length 102 and is the same as the diameter of the first transition portion 90. The entire ends 34, 36 are shown as being higher in the thickness direction 24 than the highest point of the middle section 38 at the lateral midpoint 40, making them closer to the upper surface 16. However, this is not necessary in other embodiments.

[0047] Figure 13 is a top view of a tread 12 according to another exemplary embodiment, wherein two differently constructed tread grooves 22 exist in the shoulder rib 14 on the left-hand side of the tread 12, and wherein a pair of tread grooves in the right-hand side shoulder rib are identical to each other but at an angle 74 to the lateral direction 28. The two center ribs also have tread grooves 22, which are constructed identically to the upper tread grooves 22 in the shoulder rib 14. The tread 12 differs from the tread shown in Figure 2 in that there is no sacrificial rib 54. Instead, the shoulder rib 14 is the outermost rib of the tread 12 in the lateral direction 28, and the tread grooves 22 extend completely from the first side surface 18 to the second side surface 19 located at the shoulder groove 20. One of the tread grooves 22 is shown in the cross-sectional views of Figures 14 and 15. The intermediate segment 38 has a shape different from the previously discussed shape. Here, the base 66 and end 68 of the first intermediate segment define half of the intermediate segment 38, which has a circular cross-sectional shape and whose dimensions decrease in the lateral direction 28 from the base 66 to the end 68. The base 70 of the second intermediate segment is also located at the lateral midpoint 40, and the diameter of the second half of the intermediate segment 38 continuously decreases from the base 70 to the end 72. The furthest extension point 52 of the intermediate segment extends along the entire length 98 from the end 68 of the first intermediate segment to the end 72 of the second intermediate segment. However, the distance between the side of the intermediate segment 38 closest to the upper surface 16 in the thickness direction 24 and the upper surface 16 varies. The intermediate segment 38 closest to the upper surface 16 in the thickness direction 24 is located at the lateral midpoint 40 and the bases 66 and 70. The position of the axis of the circular cross-section of the intermediate section 38 in the thickness direction 24 changes depending on the position of the intermediate section 38 in the lateral direction 28 on either side of the lateral midpoint 40.

[0048] End portions 34 and 36 are also constructed in a manner different from the ends disclosed in other embodiments. The farthest extension point 48 of the first end and the farthest extension point 50 of the second end both extend completely along lengths 94 and 96. However, the lengths of the opposite sides of the ends 34 and 36 closest to the upper surface 16 in the thickness direction 24 vary because the first end 60 and the second end 64 are farthest, and the first end base 58 and the second end base 62 are closest. The position of the axes of the first end 34 and the second end 36 in the thickness direction 24 varies depending on the position of the first end 34 and the second end 36 in the lateral direction 28. The transition portions 90 and 92 have a circular cross-section and the same diameter along their entire lengths 100 and 102, such that the diameter at the first intermediate segment end 68 and the second intermediate segment end 72 is the same as the diameter at the first end base 58 and the second end base 62. The cross-sectional diameter of the teardrop 32 is thus reduced, remains the same, and then decreases again in the lateral direction 28 as it extends inward and outward from the lateral midpoint 40. The entire length of the ends 34, 36 is closer to the upper surface 16 in the thickness direction 24 than any part of the intermediate segment 38 is closer to the upper surface 16 in that direction 24. The first end 60 and the second end 64 are the smallest segments of the entire teardrop 32 because they have the smallest cross-sectional diameter.

[0049] Figures 14 and 15 show a cross-section through the teardrop 32, and it should be understood that the bottom of the teardrop 32 has a concave shape and is not a straight line. The teardrop 32 is open because a continuous gap extends from the first side surface 18 through the shoulder rib 14 and reaches the second side surface 19 at the shoulder groove 20.

[0050] The continuous tread groove 22 in the circumferential direction 26 of Figure 13 is shown in more detail in the cross-sectional views of Figures 16 and 17, and is constructed in a different manner than the tread groove 22 discussed below. This tread groove 22 again extends along the entire lateral width of the shoulder rib 14, leading to the first side surface 18 and the second side surface 19. The teardrop 32 is also handle-shaped, but constructed in a different manner than any teardrop previously discussed. As shown, the teardrop 32 has a lateral midpoint 40, such that half of the middle segment 38 is inside in the lateral direction 28 and the other half is outside in the lateral direction 28. The teardrop 32 is arranged such that its cross-sectional size decreases constantly as it extends from the lateral midpoint 40 to the second end 64 in the lateral direction 28, and also decreases constantly as it extends from the lateral midpoint 40 to the first end 60 in the lateral direction 28. The teardrop 32 is furthest from the upper surface 16 at the furthest extension point 52 of the intermediate segment, and the teardrop 32 extends continuously from this point 52 toward the upper surface 16. The cross-sectional dimensions decrease continuously from the lateral midpoint 70 to the end 68 of the first intermediate segment. The cross-sectional dimensions of the first transition portion 90 also decrease continuously from the end 68 of the first intermediate segment to the first end base 58. At this point, the cross-sectional shape is circular, and therefore the diameter decreases as it extends. The first end 34 is constructed in a similar manner, as the diameter of the teardrop 32 at the first end decreases continuously from the first end base 58 to the first end end 60. The furthest extension point 48 of the first end is located at the first end base 58 and does not extend continuously along the entire length 94. The first end end 60 has the smallest diameter of the teardrop 32.

[0051] The teardrop 32, extending laterally inward from the lateral midpoint 40, is symmetrical to those segments just discussed extending laterally outward from the lateral midpoint 40. The cross-section is circular, and its dimensions continuously decrease from the lateral midpoint 70 to the end 72 of the second intermediate segment, and this decrease continues again along the entire length 102 of the second transition 92 to the second end base 62. The diameter of the second end 36 also continuously decreases from the second end base 62 to the second end end 64, which has the same dimensions as the first end end 60. The entire first end 34 and second end 36 are positioned closer to the upper surface 16 in the thickness direction 24 than any part of the intermediate segment 38, which is positioned entirely away from the upper surface 16 in the thickness direction 24. Therefore, the size of the teardrop 32 increases consistently from the first side surface 18 to the lateral midpoint 70, and then at this lateral midpoint, the teardrop reverses and the size of the shoulder groove 20 decreases consistently.

[0052] The various teardrop 32 designs discussed show segments 34, 36, 38, 90, 92 as either constantly increasing or decreasing in size, or maintaining the same size while extending in the lateral direction 28. However, other embodiments are also possible, wherein each segment 34, 36, 38, 90, 92 has portions that increase, decrease, or remain the same along their lengths 94, 96, 98, 100, 102, such that segments 34, 36, 38, 90, 92 may have the same or different varying cross-sectional dimensions along their lengths 94, 96, 98, 100, 102. A noticeable transition may or may not exist on the surface of the teardrop 32 between adjacent segments 34, 36, 38, 90, 92 and / or between portions of different sizes within segments 34, 36, 38, 90, 92.

[0053] Referring back to Figure 13, the tread groove 22 on the right-hand shoulder rib may include teardrops 32 constructed in any of the previously discussed manner. The tread groove 22 on the right-hand shoulder rib differs from the tread groove on the left-hand shoulder rib 14 in that the body 30 and the teardrop 32 are oriented at an angle 74 relative to the lateral direction 28. In contrast, the two tread grooves 22 on the left-hand shoulder rib 14 extend entirely in the lateral direction 28. According to various exemplary embodiments, the angle 74 of the two angled tread grooves 22 may be 5-10 degrees, 10-15 degrees, 5-20 degrees, 15-20 degrees, 20-25 degrees, 25-30 degrees, 2-7 degrees, 10-20 degrees, or up to 30 degrees. Angle 74 is the angle between the body 30 and the teardrop 32, as measured between their points of contact from the second side surface 19 to the first side surface 18, or as measured from their points of contact from the first side surface 18 to the second side surface 19. The tread grooves 22 can therefore be at different angles relative to the lateral direction 28 and are not limited to a specific single angle. All tread grooves 22 of the tread 12 can be oriented at the same angle 74, or various tread grooves 22 of the tread 12 can be oriented at different angles 74. Although a shoulder notch is not shown in any of the disclosed embodiments, it should be understood that the first side surface 18 may include a shoulder notch to which the tread grooves 22 lead.

[0054] Figure 18 is a perspective view of the tread groove 22 having a shape similar to the teardrop 32 previously discussed with respect to Figures 7 and 8, wherein the middle segment 38 is larger than the ends 34, 36. The shape of the body 30 differs from that of the body in other embodiments because it is not merely a linear shape, but a zigzag shape in both the lateral extension direction 28 and the thickness extension direction 24. The segments of the body 30 that move to engage the teardrop 32 are linear in shape. However, in other embodiments, the zigzag portions of the body 30 may engage some or all of the teardrop 32 along its lateral length. Therefore, it should be understood that the body 30 may be zigzag in certain areas, or may be entirely zigzag along its entire lateral length from the upper surface 16 to the teardrop 32. The body 30 may have different shapes depending on the specific exemplary embodiment.

[0055] Figures 19 and 20 show, in perspective, the tread groove 22 as discussed with reference back to Figures 11 and 12, wherein the ends 34, 36 are frustoconical in shape, and wherein the middle segment 34 has two frustoconical shapes extending from the lateral midpoint 40 in the lateral direction 28. The body 30 is zigzag in both the lateral direction 28 and the thickness direction 24, although in other embodiments it may be zigzag in only one of these directions 24, 28. The zigzag body 30 may engage some or all of the teardrop 32 along its lateral length, or may be completely spaced apart from the teardrop 32 such that no part of the zigzag body 30 engages the teardrop 32, as shown in Figures 19 and 20. Although shown as a combination of zigzag and linear shapes, it should be understood that various embodiments of the tread groove 22 disclosed herein may have a body 30 of any shape. When this portion of the shoulder rib 14 enters the contact patch, the zigzag shape "locks" the rubber forming the shoulder rib 14 together to increase rigidity.

[0056] The embodiments shown in Figures 4 to 6 have an intermediate segment 38 with the same dimensions as the ends 34 and 36. However, other disclosed embodiments have a teardrop 32 shape that is largest at the intermediate segment 38 compared to the ends 34 and 36, resulting in a larger volume and diameter. The intermediate segment 38 can therefore be larger in cross-sectional dimensions than the first end 34 or the second end 36. It has been found that cracks that might form in the teardrop 32 are more likely to form in the middle of the teardrop 32 and therefore in the intermediate segment 38, rather than at the ends of the teardrop 32 that include the first end 34 and the second end 36. The teardrop 32 will be better protected against tearing because the intermediate segment 32 is larger, since the teardrop 32 is most susceptible to tearing in the lateral direction 28 at the center of the shoulder rib 14, and the larger the size of the teardrop 32 in this region, the less likely a crack will form at that location. Since cracks are more likely to form and propagate at the middle section 38 than at the ends 34, 36, the cross-sectional dimensions / diameters of the first end 34 and the second end 36 can be made smaller than those of the middle section 38. This results in less rubber being missing from the shoulder rib 14 at the first end 34 and the second end 36, thus increasing the rigidity of the shoulder rib 14 at the tread groove 22. By making the ends 34, 36 smaller, the shoulder rib 14 will have more material, making it more rigid. This allows the teardrop 32 design to maintain wear and rolling resistance performance while reducing cracking, and eliminates the need to position the teardrop 32 closer to the upper surface 16 in the thickness direction 24, thus ensuring that end-of-service traction is not affected.

[0057] By having a handle-like shape (where the ends 34, 36 are closer to the upper surface 16 in the thickness direction 24 than any part of the middle section 38 is closer to the upper surface 16 in the thickness direction 24), the currently disclosed tread grooves 22 in the shoulder rib 14 allow end-of-life traction, minimize the impact on rolling resistance and wear, and minimize or eliminate cracking within the teardrop 32. The increased size of the teardrop 32 (if present) is positioned at the location where the teardrop 32 is most likely to experience cracking, which is the middle section 38. In some embodiments, the ends 34, 36 may be smaller, which increases the rigidity of the shoulder rib 14 at the tread grooves 22, minimizing the negative impact on rolling resistance and wear characteristics. The solution provided is a combination of end-of-life performance in reducing or minimizing crack formation within the tread grooves 22 and increased rigidity.

[0058] The disclosed teardrop geometry of the tread grooves 22 allows for end-of-life traction, minimizes the impact on rolling resistance and wear, and minimizes cracking. This geometry aids in rubber tearing while still maintaining traction on the tread 12. Alternatively, the tread grooves 22 may extend deeper into the tread 12 to achieve end-of-life performance, and the geometry of the tread grooves 22 maintains rigidity within the tread 12. Larger teardrops 32 result in less rubber, leading to less rigidity in the shoulder ribs 14, and the disclosed teardrop geometry prevents the presence of such larger voids. Because the geometry of the transitions 90, 92 moves upward / closer to the upper surface 16 from the intermediate section 38 to the ends 34, 36 in the thickness direction 24, the transitions 90, 92 make it difficult for cracks to move from the intermediate section 38 to the ends 34, 36. This handle geometry can be further enhanced by the aforementioned increase in the diameter or size of the intermediate section 38 at the first end 34 and the second end 36 to further minimize or prevent crack initiation. The applicant has discovered that the handle geometry is effective in preventing or minimizing cracking when the entire first end 34 and the second end 36 are closer to the upper surface 16 in the thickness direction 24 than the entire intermediate section 38 is closer to the upper surface 16 in the thickness direction 24, such that no part of the intermediate section 38 is closer to the upper surface 16 than any part of the first end 34 or the second end 36 is closer to the upper surface 16 in the thickness direction 24.

[0059] Although the tread groove 22 has been described as being located in the shoulder rib 14, as described herein, the tread groove 22 may be located in any rib 14 other than or in place of the shoulder rib 14. Therefore, the rib 14 in which the tread groove disclosed herein is located may be the center rib 14, the intermediate rib 14, or any rib of the tread 12. When located in the center rib 14 or the intermediate rib 14, the first side surface 18 and the second side surface 19 are the opposite lateral sides of that center rib 14 or intermediate rib 14. The tread groove 22 extends from one side of the opposite lateral side of the center rib 14 or the intermediate rib 14 to the other. Therefore, the tread groove 22 disclosed herein may be located in any one or all of the ribs 14 of the tread 12. In some cases, when a sacrificial rib 54 is present, the tread groove 22 may be located in all of the ribs 14 of the tread 12 except for the sacrificial rib 54.

[0060] Although the subject matter of the invention has been described in detail with respect to specific embodiments and methods, it should be understood that modifications, variations, and equivalents of such embodiments can be readily conceived by those skilled in the art upon understanding the foregoing. Therefore, the scope of this disclosure is by way of example rather than limitation, and this disclosure does not exclude obvious such modifications, variations, and / or additions to the subject matter.

Claims

1. A heavy-duty truck tire tread, the heavy-duty truck tire tread having a lateral direction, a thickness direction, and a circumferential direction, the heavy-duty truck tire tread comprising: Rib, the rib having a first side surface and a second side surface, wherein the rib has an upper surface; The tread groove is located in the rib and extends from the first side surface to the second side surface. The tread groove has a body and a teardrop, wherein a first end of the teardrop is located on the first side surface, a second end of the teardrop is located on the second side surface, and the teardrop has a middle section located in the lateral direction between the first end and the second end of the teardrop, and wherein the lateral midpoint of the teardrop in the lateral direction is located at the middle section. The teardrop has a first transition portion located between the first end and the middle section and extending in both the lateral and thickness directions. The teardrop has a second transition portion located between the second end and the middle section and extending in both the lateral and thickness directions. The entire middle section is farther from the upper surface in the thickness direction than any portion of the first end is farther from the upper surface in the thickness direction, and the entire middle section is farther from the upper surface in the thickness direction than any portion of the second end is farther from the upper surface in the thickness direction.

2. The tread according to claim 1, wherein the rib is a shoulder rib, and wherein the tread has a shoulder groove adjacent to the shoulder rib in the lateral direction, and wherein the second side surface faces the shoulder groove.

3. The tread according to claim 2, wherein the shoulder rib has a plurality of rib grooves, the plurality of rib grooves such that the shoulder rib is arranged as a plurality of shoulder rib tread blocks.

4. The tread according to claim 1, wherein the first end, the second end and the intermediate segment all have a circular cross-section, the cross-section having the same diameter along the entire length of the first end, the second end and the intermediate segment.

5. The tread according to claim 4, wherein the first transition portion and the second transition portion have a circular cross-section, the cross-section having the same diameter along the entire length of the first transition portion and the second transition portion, and wherein the diameter of the first transition portion and the second transition portion is the same as the diameter of the first end, the second end and the intermediate segment.

6. The tread according to claim 1, wherein the first end and the second end have circular cross-sections having the same diameter along the entire length of the first end and the second end; wherein the intermediate segment has a circular cross-section having the same diameter along the entire length of the intermediate segment, wherein the diameter of the intermediate segment is greater than the diameter of the first end and the second end; wherein the first transition portion and the second transition portion have circular cross-sections having varying diameters along the entire length of the first transition portion and the second transition portion.

7. The tread of claim 1, wherein the intermediate segment has a point extending furthest from the upper surface in the thickness direction along the entire lateral length of the intermediate segment, and wherein the distance from the upper surface to the furthest point extending from the upper surface in the thickness direction does not change at any point along the entire lateral length of the intermediate segment.

8. The tread of claim 1, wherein the intermediate segment is closest to the upper surface at the lateral midpoint in the thickness direction; wherein the intermediate segment of the teardrop has a first intermediate segment truncated cone shape extending outward from the lateral midpoint in the lateral direction, such that the base of the first intermediate segment is located at the lateral midpoint and the end of the first intermediate segment engages the first transition portion; wherein the intermediate segment of the teardrop has a second intermediate segment truncated cone shape extending inward from the lateral midpoint in the lateral direction, such that the base of the second intermediate segment is located at the lateral midpoint and the end of the second intermediate segment engages the second transition portion.

9. The tread according to claim 1, wherein the first end of the teardrop is a truncated cone shape, the truncated cone having a first end base located inside the first end in the lateral direction, the first end located at the first side surface, wherein the first end base engages the first transition portion; wherein the second end of the teardrop is a truncated cone shape, the truncated cone having a second end base located outside the second end in the lateral direction, the second end located at the second side surface, wherein the second end base engages the second transition portion.

10. The tread according to claim 1, wherein the body is zigzag-shaped.

11. The tread according to claim 1, wherein the cross-section of the teardrop in the entire middle section is circular, wherein the cross-section of the teardrop in the entire first end is circular, wherein the cross-section of the teardrop in the entire second end is circular, wherein the cross-section of the teardrop in the entire first transition section is circular, and wherein the cross-section of the teardrop in the entire second transition section is circular.

12. The tread of claim 11, wherein the first end has a point extending farthest from the upper surface in the thickness direction along the entire lateral length of the first end, wherein the second end has a point extending farthest from the upper surface in the thickness direction along the entire lateral length of the second end, wherein the intermediate segment has a point extending farthest from the upper surface in the thickness direction along the entire lateral length of the intermediate segment; wherein the distances of the farthest points of the first end and the second end to the upper surface in the thickness direction are the same, and wherein the distance of the farthest point of the intermediate segment to the upper surface in the thickness direction is greater than the distance of the farthest point of the first end to the upper surface in the thickness direction; and wherein the cross-sectional dimensions of the entire first end, the entire second end, and the entire intermediate segment change as the first end, the second end, and the intermediate segment extend in the lateral direction.

13. The tread of claim 1, wherein the cross-sectional dimension of the teardrop extending from the lateral midpoint to the first side surface in the lateral direction continuously decreases from the lateral midpoint to the first side surface; wherein the cross-sectional dimension of the teardrop extending from the lateral midpoint to the second side surface in the lateral direction continuously decreases from the lateral midpoint to the second side surface.

14. The tread of claim 2, further comprising a sacrificial rib located outside the shoulder rib in the lateral direction, wherein a sacrificial rib groove is located between the shoulder rib and the sacrificial rib in the lateral direction.

15. The tread according to claim 1, wherein the tread grooves form an angle of 5 to 20 degrees relative to the lateral direction as they extend from the first side surface to the second side surface.

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