Patent Description:
Manufacturers of heavy commercial vehicle tires have made progress in developing tire architectures and tire materials that allow increase in the wear resistance of tire treads and the reduction of the rolling resistance of tires while at the same time improving their level of grip and resistance to road hazard. Irregular tread wear (also called "uneven wear" or "abnormal wear") is a great concern for heavy commercial vehicle tires as it can progressively induce tire vibrations that become sensed by the driver through the steering wheel. It can also make for a poor looking wear pattern. Both of these undesired effects often lead to the tire being removed from service at an early stage of its wear life. Generally, the more the tire is put through a slow-wearing usage, the more irregular wear is affecting the removal mileage. This is why resistance to irregular wear is of paramount importance for truck tires in the so-called long haul steer usage.

It is known to include structural features in tires to fight irregular wear. For example, a sacrificial rib can be incorporated into the tread architecture to delay the onset of irregular wear. However, this feature is sensitive to curbing aggression and its use may not be practical outside of North American long haul applications. This design can on occasion lead to cracking at the bottom of the decoupling groove which may lead to early removal and customer dissatisfaction. Other sculptural features that can combat irregular wear include microsipes and inclined microsipes. These are small grooves that extend generally in the lateral, width direction of the tire. Unfortunately, these features are unusable in severe usage applications due to aggression concerns. Aggression on tires is a concern in growing or emerging markets that feature roadways that subject the tire to more severe usage that functions to tear up and wear down the tread at a higher rate than roads that are smoother and in better condition. Although mechanisms are known for reducing or eliminate irregular wear, there remains room for variation and improvement within the art.

The use of identical or similar reference numerals in different figures denotes identical or similar features.

Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations.

The present invention provides for a decoupling void sipe <NUM> that engages a decoupling void <NUM> in a heavy duty truck tire <NUM> that functions to reduce or eliminate aggression damage. The tread <NUM> has a shoulder rib <NUM> and an adjacent sacrificial rib <NUM> with the decoupling void <NUM> therebetween. The decoupling void sipe <NUM> is in the shoulder rib <NUM> and opens into the decoupling void <NUM>. Both the decoupling void sipe <NUM> and the decoupling void <NUM> extend in a thickness direction <NUM> of the tread <NUM> towards a bottom surface <NUM> of the tread <NUM>, with the decoupling void sipe <NUM> closer to the bottom surface <NUM> than the decoupling void <NUM>. This arrangement added a bridging effect across the bottom of the decoupling void <NUM> that functions to reduce or eliminate aggression damage to the tread <NUM> while maintaining the aspects of the decoupling void <NUM>. It is hypothesized that aggression damage is caused by impacts near the shoulder of the tire <NUM> by hitting curbs, pot holes, etc., and the bridging of the decoupling void sipe <NUM> will strengthen the bottom of the decoupling void <NUM> and minimize or eliminate this aggression damage.

<FIG> shows a tire <NUM> that is a heavy duty truck tire <NUM>. In this regard, the tire <NUM> is not designed for nor used with a car, motorcycle, or light truck (payload capacity less than <NUM>,<NUM> pounds), but is instead designed for and used with heavy duty trucks such as <NUM> wheelers, garbage trucks, or box trucks. The tire <NUM> may be a steer tire, a drive tire, a trailer tire, or an all position tire. The tire <NUM> includes a carcass <NUM> onto which a tread <NUM> is disposed thereon. The central axis <NUM> of the tire <NUM> extends through the center of the carcass <NUM>, and the axial direction <NUM>, which can be called the width direction <NUM>, of the tire <NUM> is parallel to the central axis <NUM>. The radial direction <NUM> of the tire <NUM> can be referred to as the thickness direction <NUM> and is perpendicular to the central axis <NUM>. The tread <NUM> is located farther from the central axis <NUM> in the thickness direction <NUM> than the carcass <NUM>. The tread <NUM> extends all the way around the carcass <NUM> in the circumferential direction <NUM> of the tire <NUM> and circles the central axis <NUM><NUM> degrees. The circumferential direction <NUM> can also be referred to as the longitudinal direction <NUM> of the tread <NUM>.

The tread <NUM> features five ribs <NUM> that are separated by four longitudinal grooves that extend in the circumferential direction <NUM> completely about the tire <NUM>. The five ribs <NUM> can be classified as a central rib, two intermediate ribs, and two shoulder ribs. One of the longitudinal grooves is labeled as shoulder tread groove <NUM> and it is the longitudinal groove that separates a shoulder rib <NUM> from an intermediate rib <NUM> of the tread <NUM>. Although five ribs <NUM> are shown any number of ribs <NUM> can be present in other exemplary embodiments. The ribs <NUM> can each be made up of a number of tread blocks that can have various shapes, sizes, and configurations. The inclusion of these architectural features gives the tread <NUM> different performance properties in use. The tread <NUM> may include certain structural features that can reduce abnormal wear. One such structural feature may be sipes <NUM> that extend across the tread blocks of the ribs <NUM> in the width direction <NUM>. The tread <NUM> has a first tread edge and an oppositely disposed second tread edge in the width direction <NUM>. The rolling tread width of the tread <NUM> extends from one edge to the other edge and is the portion of the tread <NUM> that is designed to engage the ground when the tire <NUM> is new before any tread <NUM> wear has occurred. The tire <NUM> can be a brand new tire with the carcass <NUM> and tread <NUM> formed at the same time with both being brand new. Alternatively, the tread <NUM> may be provided as a retread band that is newly formed and then subsequently attached to an existing, used carcass <NUM> through a retread process. It is to be understood that the tire <NUM> illustrated in <FIG> does not include a sacrificial rib <NUM> or a decoupling void sipe <NUM> in accordance with the present invention.

<FIG> is a cross-sectional view of a tire <NUM> that incorporates a decoupling void sipe <NUM> in accordance with one exemplary embodiment. The tread <NUM> has ribs <NUM> that include a single center rib, a pair of intermediate ribs, and two shoulder ribs <NUM>. Also present is a pair of sacrificial ribs <NUM> that are adjacent the two shoulder ribs <NUM> and are on opposite ends of the tread <NUM> in the width direction <NUM>. The sacrificial ribs <NUM> are provided to protect the shoulder ribs <NUM> during use of the tire <NUM> and will normally wear first so that the shoulder ribs <NUM> are not subjected to irregular wear during use. The height of the shoulder ribs <NUM> in the thickness direction <NUM> is greater than the height of the sacrificial ribs <NUM> in the thickness direction <NUM>. The sacrificial rib <NUM> is separated from the shoulder rib <NUM> by a decoupling void <NUM> that can be made so as to have a variety of shapes. The <FIG> embodiment shows the decoupling void <NUM> as having a greater width deeper into the tread <NUM> formed by the overturned portion of the sacrificial rib <NUM>. The sacrificial rib <NUM> can be part of the tread <NUM> and can be formed with the rest of the ribs <NUM> and attached to the top of the carcass <NUM>.

A portion of the tread <NUM> of the tire <NUM> of <FIG> is shown in <FIG> and <FIG>. A plurality of decoupling void sipes <NUM> are located in the shoulder rib <NUM> and are spaced from one another in the longitudinal direction <NUM>. The shoulder rib <NUM> has an upper surface <NUM> that engages the road surface, and the decoupling void sipe <NUM> is open at this upper surface <NUM>. The decoupling void sipe <NUM> can be variously shaped and sized, and in the embodiment shown has a main portion <NUM>, that has a small width, and a teardrop <NUM> at the end of the main portion <NUM> that is circular in shape with a width greater than that of the main portion <NUM>. Both the main portion <NUM> and the teardrop <NUM> are open at the upper surface <NUM>. The decoupling void sipe <NUM> opens into the decoupling void <NUM>, and the main portion <NUM> is the part of the decoupling void sipe <NUM> that opens into this feature. The decoupling void sipe <NUM> extends into the tread <NUM> a greater depth than the decoupling void <NUM> in the thickness direction <NUM>. The decoupling void sipe <NUM> has a width that is less than <NUM> millimeters. This width may be measured at the main portion <NUM> so that the main portion <NUM> is less than <NUM> millimeters in width, and the teardrop <NUM> could be less than <NUM> millimeters, or the teardrop <NUM> may be <NUM> millimeters or greater in width. In some embodiments, no portion of the decoupling void sipe <NUM> has a width <NUM> millimeters or greater.

With respect to <FIG>, the tread <NUM> has a bottom surface <NUM> that engages the carcass <NUM>. The decoupling void sipe <NUM> extends to a point closer to the bottom surface <NUM> than does the decoupling void <NUM>. A distance <NUM> extends completely in the thickness direction <NUM> and is the closest distance of the decoupling void sipe <NUM> to the bottom surface <NUM>. The bottom surface <NUM> can be the bottom boundary of the extruded tread compound that is generally laid on top of the belt package that is also referred to as part of the carcass <NUM>. A distance <NUM> extends completely in the thickness direction <NUM> and is the closest distance of the decoupling void <NUM> to the bottom surface <NUM>. The distance <NUM> is smaller than the distance <NUM> which indicates that the decoupling void sipe <NUM> is closer to the bottom surface <NUM> and the decoupling void <NUM> is farther from the bottom surface <NUM> than the decoupling void sipe <NUM>.

The decoupling void sipe <NUM> extends outboard in the width direction <NUM> to a farthest outboard extent <NUM> which is the portion of the decoupling void sipe <NUM> closest to the outer edge of the tread <NUM> in the width direction <NUM>. The farthest outboard extent <NUM> may be at a position in the width direction <NUM> that is more outboard than the decoupling void <NUM>, or at the same outboard extent as the decoupling void <NUM> in the width direction <NUM>. In this particular embodiment, the farthest outboard extent <NUM> is the same as the farthest outboard extent of the decoupling void <NUM> in the width direction <NUM>. The sacrificial rib <NUM> has an upper surface <NUM> that is on the outer surface of the tread <NUM>. The decoupling void sipe <NUM> does not extend to the upper surface <NUM> and is not located in the sacrificial rib <NUM> in this embodiment. With reference now to <FIG>, it can be seen that the decoupling void sipe <NUM> is oriented completely in the width direction <NUM>. In this regard, a width angle <NUM> of the decoupling void sipe <NUM> is zero degrees. This width angle <NUM> can be measured by drawing a line though the center of the decoupling void sipe <NUM> and comparing the angle of this line relative to a line extending completely in the width direction <NUM>. The treardrop <NUM> is present at the farthest inboard and outboard portions of the decoupling void sipe <NUM>, and is present at the deepest portion of the decoupling void sipe <NUM> in the thickness direction <NUM>. The teardrop <NUM> need not be present in other exemplary embodiments. The decoupling void sipe <NUM> extends completely in the thickness direction <NUM>. The arrangement of the decoupling void sipe <NUM> thus causes it to extend below the decoupling void <NUM> and to extend across the entire width of the decoupling void <NUM>. Should the decoupling void sipe <NUM> have a geometry that makes it difficult to ascertain the width angle <NUM>, one could draw a straight line from a point at the intersection of the decoupling void sipe <NUM> and decoupling void <NUM>, to a point that is the most inboard extent of the decoupling void sipe <NUM> in the width direction <NUM>. The straight line drawn between these two points can then be measured relative to a line drawn completely in the width direction <NUM> to ascertain the width angle <NUM>.

Another embodiment of the tread <NUM> is illustrated with reference to <FIG> in which the relevant portions of the tread <NUM> are shown. The decoupling void sipes <NUM> are arranged as previously discussed with the exception that their width angle <NUM> is not zero. The width angle <NUM> is <NUM> degrees. The width angle <NUM> constant over the entire decoupling void sipe <NUM>. In other embodiments, the width angle <NUM> can be <NUM> degrees, <NUM> degrees, <NUM>, degrees, <NUM> degrees, or greater than zero to <NUM> degrees. The tread <NUM> may be directional in that the tread features are provided so that the tread <NUM> is designed to roll primarily in one direction. The designed for, forward, direction of roll is known as the rolling direction <NUM> and is noted in <FIG>. The width angle <NUM> is arranged so engagement of the decoupling void sipe <NUM> with the decoupling void <NUM> is forward relative to the rolling direction <NUM> of the end of the decoupling void sipe <NUM> that is most inboard into the shoulder rib <NUM> in the width direction <NUM>.

<FIG> shows a cross-sectional view of another embodiment of the tread <NUM> taken from inside the decoupling void <NUM> where the side wall of the shoulder rib <NUM> that defines part of the decoupling void <NUM> is visible. The decoupling void sipe <NUM> can be seen to open through the side wall of the shoulder rib <NUM> and into the decoupling void <NUM>. The decoupling void sipe <NUM> also extends below the bottom of the decoupling void <NUM> in the thickness direction <NUM> so as to be closer to the bottom surface <NUM> than is the bottom of the decoupling void <NUM>. The distance <NUM> is shorter than the distance <NUM> and these distances <NUM>, <NUM> represent the closest approaches of the decoupling void <NUM> and the decoupling void sipe <NUM> to the bottom surface <NUM>. The decoupling void sipe <NUM> is angled relative to the width direction <NUM> so that the width angle <NUM> is again not zero, and in the disclosed embodiment is <NUM> degrees. Additionally, the orientation of the decoupling void sipe <NUM> is angled relative to the thickness direction <NUM> so that it does not extend completely in the thickness direction <NUM>. The orientation of the decoupling void sipe <NUM> to thickness direction <NUM> can be measured via a thickness angle <NUM>. The thickness angle <NUM> is measured starting from the point the decoupling void sipe <NUM> engages the upper surface <NUM>. A line drawn completely in the thickness direction <NUM> extends through this point, and the thickness angle <NUM> is measured between this vertical line and the decoupling void sipe <NUM>. It may be the case that the decoupling void sipe <NUM> has a shape that makes it difficult for its orientation relative to the thickness direction <NUM> to be measured, for example the decoupling void sipe <NUM> may have an undulating shape and be linear. In these instances, a point can be located at the opening of the decoupling void sipe <NUM> at the upper surface <NUM>, and a second point can be located at the deepest location of the decoupling void sipe <NUM> into the tread <NUM> in the thickness direction <NUM>, and a straight line can be drawn between these two points. The thickness angle <NUM> is measured between this straight line, and the straight line extending completely in the thickness direction <NUM> that goes through the intersection of the decoupling void sipe <NUM> and the upper surface <NUM>.

The thickness angle <NUM> in <FIG> is <NUM> degrees. The thickness angle <NUM> may be different in other embodiments and can be from greater than <NUM> to <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, from greater than <NUM> to <NUM> degrees, <NUM> degrees, from <NUM> to <NUM> degrees, from <NUM> to <NUM> degrees, from <NUM> to <NUM> degrees, from greater than <NUM> degrees to <NUM> degrees, or from <NUM> to <NUM> degrees in other embodiments. The entire height of the decoupling void sipe <NUM> may have the same thickness angle <NUM> orientation relative to the thickness direction <NUM>. The rolling direction <NUM> is noted, and the decoupling void sipe <NUM> is oriented so that upon extension into the tread <NUM> from the upper surface <NUM> the decoupling void sipe <NUM> extends opposite to the rolling direction <NUM> in the circumferential direction <NUM>. However, other embodiments are possible in which the thickness angle <NUM> causes the decoupling void sipe <NUM> to extend from the upper surface <NUM> so that the bottom of the decoupling void sipe <NUM> is located forward in the rolling direction <NUM> from the point of the decoupling void sipe <NUM> at the upper surface <NUM>. Also, the tread <NUM> may not be a directional tread <NUM> so that it does not have a rolling direction <NUM> and the thickness angle <NUM> in these instances can be positive or negative. <FIG> shows a portion of the tread <NUM> that includes the decoupling void sipes <NUM> that are oriented so that they have both a width angle <NUM> and a thickness angle <NUM> that are not zero degrees. In this particular embodiment, the width angle <NUM> is <NUM> degrees and the thickness angle <NUM> is <NUM> degrees. However, it is to be understood that in other embodiments, the thickness angle <NUM> could be greater than zero, while the width angle <NUM> is zero degrees. The decoupling void sipe <NUM> may be arranged to extend into the sacrificial rib <NUM> but remain hidden in the sacrificial rib <NUM>.

<FIG> illustrate another embodiment of the tread <NUM>. The decoupling void <NUM> has a teardrop at its bottom end and has a main section that is linear in shape. The decoupling void <NUM> may extend completely in the longitudinal direction <NUM>, or can be wavy or angled upon its extension in the longitudinal direction <NUM>. The decoupling void sipe <NUM> again extends from the upper surface <NUM> into the tread <NUM> so that the distance <NUM> is less than the distance <NUM>. However, the decoupling void sipe <NUM> extends outboard beyond the decoupling void <NUM> in the width direction <NUM> so that the farthest outboard extent <NUM> is outboard of the entire decoupling void <NUM> in the width direction <NUM>. The decoupling void sipe <NUM> extends to the upper surface <NUM> and is open at the upper surface <NUM>. The teardrop portion <NUM> is located at the farthest outboard and inboard extents of the decoupling void sipe <NUM> in the width direction <NUM>, and at the location of the decoupling void sipe <NUM> deepest into the tread <NUM> and closest to the bottom surface <NUM> in the thickness direction <NUM>. The remaining edges of the decoupling void sipe <NUM> are the main portion <NUM> and do not have a teardrop portion <NUM> and these portions engage the upper surfaces <NUM>, <NUM> and the decoupling void <NUM>. The width angle <NUM> and thickness angle <NUM> are both zero degrees in the illustrated embodiment. The decoupling void <NUM> has a width <NUM> that can be two millimeters or greater in some embodiments. In these cases the decoupling void <NUM> may be referred to a decoupling groove as a groove is a void having a width <NUM> millimeters or greater. In instances where the decoupling void <NUM> has a width <NUM> that is less than <NUM> millimeters, the decoupling void <NUM> could be called a decoupling sipe. The width <NUM> can be measured as the maximum width of the decoupling void <NUM>, which could be the width <NUM> of the teardrop of the decoupling void <NUM> in the width direction <NUM>, or may be measured as the width of the majority of the decoupling void <NUM> that has the same shape/size which in the present instance would be the portion of the decoupling void <NUM> above the teardrop portion in the thickness direction <NUM>. The decoupling void sipe <NUM> extends into the sacrificial rib <NUM> and is not hidden in the sacrificial rib <NUM> because it is open at the upper surface <NUM>.

A shoulder tread groove <NUM> separates the shoulder rib <NUM> from the intermediate rib <NUM>. The shoulder tread groove <NUM> has a bottom that is a distance from the bottom surface <NUM> in the thickness direction <NUM> that is greater than the distance <NUM>. In other embodiments, the distance from the bottom surface <NUM> to the bottom of the shoulder tread groove <NUM> in the thickness direction <NUM> is the same as distance <NUM>. The decoupling void sipe <NUM> is located in the shoulder rib <NUM> and does not extend to the shoulder tread groove <NUM> so that it does not open into the shoulder tread groove <NUM>.

Another embodiment of the tread <NUM> is shown in top view in <FIG> which illustrates the relevant portions of the design. The decoupling void sipe <NUM> is again open at the upper surface <NUM>. However, it is to be understood that the decoupling void sipe <NUM> need not be open at the upper surface <NUM> and/or the upper surface <NUM> in other embodiments. The decoupling void sipe <NUM> is oriented at a width angle <NUM> that is greater than zero, and is <NUM> degrees in this embodiment. The portion of the decoupling void sipe <NUM> inboard of the decoupling void <NUM> in the width direction <NUM> is oriented differently relative to the width direction <NUM> than the portion of the decoupling void sipe <NUM> outboard of the decoupling void <NUM> in the width direction <NUM>. The portion of the decoupling void sipe <NUM> outboard of the decoupling void <NUM> in the width direction <NUM> has a width angle <NUM> that likewise has a magnitude of <NUM> degrees. Both portions on either side of the decoupling void <NUM> extend from the decoupling void <NUM> at the same magnitude of the width angle <NUM> rearward relative to the rolling direction <NUM> in the circumferential direction <NUM>. The decoupling void sipe <NUM> is symmetrical with respect to the decoupling void <NUM>, but need not be symmetrical relative to the decoupling void <NUM> in other embodiments. The decoupling void sipe <NUM> also has a thickness angle <NUM> that is not zero, <NUM> degrees in this embodiment, and extends rearward relative to the rolling direction <NUM> so that the bottom of the decoupling void sipe <NUM> is rearward of the openings at the upper surfaces <NUM>, <NUM> in the circumferential direction <NUM>.

<FIG> show another embodiment of the tread <NUM> in which the decoupling void <NUM>, decoupling void sipes <NUM>, and orientations of the shoulder ribs <NUM> and sacrificial ribs <NUM> are shown. The decoupling void sipes <NUM> are oriented both in the width <NUM> and thickness <NUM> directions so that they are not at zero angles in these directions. Further, the width and thickness orientations of the decoupling void sipes <NUM> are not the same along their entire lengths but instead change. The decoupling void sipe <NUM> has a first portion <NUM> that originates at the upper surface <NUM> and this first portion <NUM> is oriented at a first width angle <NUM> to the width direction <NUM>. The first portion <NUM> is also oriented at a first thickness angle <NUM> relative to the thickness direction <NUM>. The width angle <NUM> and thickness angle <NUM> can be measured the same as previously discussed with respect to the angles <NUM>, <NUM>, and may have magnitudes as previously discussed. The bottom of the decoupling void sipe <NUM> "twists" so that it has a different width angle. The first portion <NUM> transitions to a second portion <NUM> at a location at the top of the teardrop portion of the decoupling void <NUM> and maintains this second portion <NUM> for the rest of the decoupling void sipe <NUM> which terminates on the opposite side of the decoupling void <NUM> from the first portion <NUM>. The second portion <NUM> terminates below the upper surface <NUM> and does not open at the upper surface <NUM>. The second portion <NUM> includes the part of the decoupling void sipe <NUM> that is below the decoupling void <NUM> and is closer to the bottom surface <NUM> than the decoupling void <NUM>. The second portion <NUM> has a second width angle <NUM> that is not zero degrees, and is different in magnitude from the first width angle <NUM>. Additionally, the second portion <NUM> has a second thickness angle <NUM> that is not zero degrees, and that is different in magnitude from the first thickness angle <NUM>. Aside from having different width and thickness angles, the portions <NUM>, <NUM> can have widths different from one another such that the second portion <NUM> is wider than the width of the first portion <NUM>. It is thus the case that the width angles <NUM> and <NUM> of the decoupling void sipe <NUM> need not be the same across the entire decoupling void sipe <NUM>, but can be different at different locations of the decoupling void sipe <NUM>. Variation of the width angles <NUM>, <NUM> of the decoupling void sipe <NUM> will impact the function of the decoupling void <NUM> and resistance to aggression damage. The smaller the magnitude of the width angle, the more laterally oriented the decoupling void sipe <NUM> will be and the more coupled the shoulder and sacrificial ribs <NUM>, <NUM> will become. Increasing the magnitude of the width angle will cause the shoulder rib <NUM> and the sacrificial rib <NUM> to be less coupled to one another.

Another embodiment of the tread <NUM> is shown with reference to <FIG> in which only the relevant portion of the tread <NUM> that includes the decoupling void sipe <NUM> is shown. The decoupling void sipe <NUM> extends outboard in the lateral direction <NUM> so that the farthest outboard extent <NUM> is outboard of the entire decoupling void <NUM> in the width direction <NUM>, but the decoupling void sipe <NUM> does not extend to the upper surface <NUM> and is not open at the upper surface <NUM>. The decoupling void sipe <NUM> is made of three portions <NUM>, <NUM>, <NUM> which have different orientations relative to the width and thickness directions <NUM>, <NUM>. Although three portions are shown in this embodiment, any number of portions of the decoupling void sipe <NUM> can be present in yet other versions of the tread <NUM>. The top view of the tread <NUM> is shown in <FIG> and is the tread <NUM> in an unworn state. The decoupling void sipe <NUM> has a first portion <NUM> that is at a first width angle <NUM> relative to the width direction <NUM>. The first width angle <NUM> is <NUM> degrees and can be measured in the manners as previously discussed. The first portion <NUM> extends a distance into the tread <NUM> in the thickness direction <NUM> until transitioning into a second portion <NUM> of the decoupling void sipe <NUM>. The first portion <NUM> extends a longer length in the thickness direction <NUM> than does the amount of extension of the second portion <NUM> in the thickness direction <NUM>. The second portion <NUM> can be seen in <FIG> which is a cross-sectional view taken along line <NUM>-<NUM> of <FIG>. The second portion <NUM> is oriented at a second width angle <NUM> to the width direction <NUM>. The second width angle <NUM> is less than the first width angle <NUM> and is <NUM> degrees in this embodiment. The cross-sectional shape of the second portion <NUM> is the same as the cross-sectional shape of the first portion <NUM>. The second portion <NUM> extends in the thickness direction <NUM> to a height that is the same as the bottom of the decoupling void <NUM> such that the very bottom of the decoupling void <NUM> and the very bottom of the second portion <NUM> are the same distance to the bottom surface <NUM> in the thickness direction <NUM>.

The remaining section of the decoupling void sipe <NUM> is made of the third portion <NUM> and this part includes the bottom of the decoupling void sipe <NUM> that is closest to the bottom surface <NUM>, and the part of the decoupling void sipe <NUM> that is outboard from the decoupling void <NUM> in the width direction <NUM>. The third portion <NUM> can be seen in the cross-sectional view of <FIG> and is likewise oriented relative to the width direction <NUM> at a non-zero angle. The third portion is oriented at a third width angle <NUM> that can be calculated as previously discussed and has a magnitude that is less than the magnitude of the first width angle <NUM>, and is less than the magnitude of the second width angle <NUM>. The third width angle <NUM> may be <NUM> degrees in the illustrated embodiment. The third width angle <NUM> is measured by comparing a line drawn through the third portion <NUM> originating from the most outboard portion of the third portion <NUM> in the width direction <NUM> to a line extending completely in the width direction <NUM>. The cross-sectional shape of the third portion <NUM> is different than the cross-sectional shapes of the first and second portions <NUM>, <NUM> due to the absence of the decoupling void <NUM> through parts of the third portion <NUM>. As the tread <NUM> wears, different portions <NUM>, <NUM>, <NUM> with their resultant different orientations and shapes can be presented to the road so that the tread <NUM> exhibits different tread features at different points in its wear life.

Aside from having different width angles <NUM>, <NUM>, <NUM>, the various portions <NUM>, <NUM>, <NUM> also feature different thickness angles <NUM>, <NUM>, <NUM>. <FIG> shows the extension of the decoupling void sipe <NUM> in the thickness direction <NUM>. The first portion <NUM> is oriented at a first thickness angle <NUM>, and the second portion <NUM> is oriented at a second thickness angle <NUM>. The first thickness angle <NUM> has a magnitude greater than the magnitude of the second thickness angle <NUM>. The third portion <NUM> is oriented at a third thickness angle <NUM> to the thickness direction <NUM> which has a magnitude less than the magnitudes of the first and second thickness angles <NUM>, <NUM>. In one embodiment, the first thickness angle <NUM> is <NUM> degrees, the second thickness angle <NUM> is <NUM> degrees, and the third thickness angle <NUM> is <NUM> degrees.

Claim 1:
A tread (<NUM>) for a heavy truck tire (<NUM>), comprising:
a bottom surface (<NUM>);
a shoulder rib (<NUM>) having a shoulder rib upper surface (<NUM>);
a sacrificial rib (<NUM>) having a sacrificial rib upper surface (<NUM>), wherein the sacrificial rib (<NUM>) is located outboard from the shoulder rib (<NUM>) in a width direction (<NUM>);
a decoupling void (<NUM>) that is located between the shoulder rib (<NUM>) and the sacrificial rib (<NUM>) in the width direction (<NUM>), wherein the decoupling void (<NUM>) extends in a thickness direction (<NUM>); and
a decoupling void sipe (<NUM>) that is in the shoulder rib (<NUM>) and that opens at the shoulder rib upper surface (<NUM>) and that opens at the decoupling void (<NUM>), wherein the decoupling void sipe (<NUM>) extends in the thickness direction (<NUM>), wherein the decoupling void sipe (<NUM>) is closer to the bottom surface (<NUM>) than the decoupling void (<NUM>) in the thickness direction (<NUM>);
characterized in that the decoupling void sipe (<NUM>) extends in the width direction (<NUM>) to a farthest outboard extent (<NUM>) of the decoupling void sipe (<NUM>), wherein no portion of the decoupling void (<NUM>) is farther outboard in the width direction (<NUM>) than the farthest outboard extent (<NUM>) of the decoupling void sipe (<NUM>).