Patent Description:
The commercial truck market is moving towards an increase in overall vehicle weight, which is due in part to the increase in weight of the motor and equipment. The increase in overall vehicle weight requires a tire capable of handling the additional loading. Thus, a tire with improved crown durability and increased load carrying capacity is desired.

<CIT> describes a tire in accordance with the preamble of claim <NUM>. A similar tire is also describes in <CIT>.

<CIT> describes a steel cord of the construction 4x4x0. <NUM> for use in tires.

<CIT> describes a steel cord for a protection ply of a tire having a 5x0. <NUM> construction.

The invention relates to a tire in accordance with claim <NUM>.

The invention provides in a first aspect a pneumatic tire for use on trucks, the tire comprising: a tread and a belt reinforcement structure located radially inward of the tread, the belt structure including a first and second working belt, wherein the angle of the first and second working belts range from <NUM> degrees to <NUM> degrees as measured relative to the circumferential direction, and wherein the angle of the first working belt is different than the angle of the second working belt, wherein the belt structure further comprises a relatively low angle belt having reinforcements angled at less than <NUM> degrees relative to the circumferential direction, and wherein the relatively low angle belt has extensible reinforcements.

The invention provides in a preferred aspect a pneumatic tire for use on trucks, the tire having a tread and a belt reinforcement structure located radially inward of the tread, the belt structure including a first and second working belts, wherein the angle of the first and second working belts range from <NUM> degrees to <NUM> degrees from the circumferential direction, wherein the belt structure further comprises a relatively low angle belt having reinforcements angled at less than <NUM> degrees, and further including a top protector belt located radially outwards of the working belts, wherein the top belt has a width greater than <NUM>% of the tread width.

The invention provides in a preferred aspect a pneumatic tire for use on trucks, the tire comprising: a tread and a belt reinforcement structure located radially inward of the tread, the belt structure including a first and second working belt, wherein the first and second working belt are formed of extensible reinforcements, wherein the angle of the first and second working belts range from <NUM> degrees to <NUM> degrees as measured relative to the circumferential direction, and wherein the angle of the first working belt is different than the angle of the second working belt, wherein the belt structure further comprises a relatively low angle belt having reinforcements angled at less than <NUM> degrees relative to the circumferential direction, wherein the relatively low angle belt has extensible reinforcements, and wherein the relatively low angle belt has a 4x4x0. <NUM> cord construction.

"Aspect Ratio" means the ratio of a tire's section height to its section width.

"Axial" and "axially" mean the lines or directions that are parallel to the axis of rotation of the tire.

"Belt Structure" or "Reinforcing Belts" means one or at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and preferably having both left and right cord angles in the range from <NUM>° to <NUM>° with respect to the equatorial plane of the tire.

"Carcass" means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.

"Circumferential" means lines or directions perpendicular to the axial direction within + or - <NUM> degrees.

"Cord" means one of the reinforcement strands, including fibers, which are used to reinforce the plies.

"Extensible" means a cord having a relative elongation of greater than <NUM>% at <NUM>% of the breaking load, when measured from a cord extracted from a cured tire. The tensile measurements for elongation at break (total elongation in %) are performed in accordance with ISO <NUM>-<NUM> B (<NUM>) at preload of no more than <NUM> MPa tested on a cable or cord when taken from a cured tire.

"Radial" and "radially" mean directions radially toward or away from the axis of rotation of the tire.

<FIG> illustrates a first embodiment of one half of a pneumatic tire <NUM>, suitable for use as a truck tire. The tire <NUM> has a tread <NUM> with a non-skid depth D. The tire tread <NUM> may comprise a plurality of circumferentially continuous ribs, which may vary, but are shown for example as ribs <NUM>, <NUM> and <NUM>. Positioned between each rib is a circumferential groove <NUM>, <NUM>, <NUM>, which are preferably continuous. The tread may also comprise optional sipes (not shown). The tread pattern is not limited to same, and may comprise, for example, a plurality of blocks and grooves (not shown).

The tire <NUM> further comprises a casing <NUM> which includes two opposed sidewalls <NUM> which extend down from the tread <NUM> to the bead area. The casing of the tire may optionally include an inner liner <NUM> which is typically formed of halobutyl rubber which forms an air impervious barrier. The tire casing <NUM> further includes one or more radial plies <NUM> extending from the tread, down the sidewall to the tire bead <NUM>. Preferably, the radial ply <NUM> is wrapped about or otherwise secured to each annular bead <NUM>. In the embodiment illustrated and not limited to same, there is only one ply <NUM> and it is wrapped around the bead in an inside out manner such that the ply ending <NUM> is located axially outward and radially outwards of the bead. The beads <NUM> may be any desired shape, but in this embodiment, it is shown as a hexagonal configuration with steel filaments.

The tire may further optionally include an apex <NUM> which may be shaped like a triangle. The ply turnup in the bead area may be optionally reinforced with a chipper <NUM> wrapped about the bead ply <NUM>.

The tire <NUM> further includes a belt package <NUM> which is located between the tread <NUM> and the one or more plies <NUM>. The belt package may comprise one or more layers of reinforcement. The ply <NUM> and the belt reinforcing structure <NUM> are made from cord reinforced elastomeric material, wherein the cords are typically steel wire or polyamide filaments and the elastomer preferably being rubber.

The belt reinforcing package <NUM> may include an optional transitional belt <NUM> that is the radially innermost belt of the belt package <NUM>. The transition belt <NUM> preferably has an axial belt width in a range of from <NUM>% to <NUM>% of the tread arc width. The transition belt <NUM> preferably has an orientation that has an angle of between <NUM> to <NUM> degrees (preferably right). The transition belt <NUM> is preferably made of ultra tensile steel with a construction of <NUM>+2x0.

Belt reinforcing structure <NUM> further includes a first extensible working belt <NUM> and a second extensible working belt <NUM>. The first working belt <NUM> is located radially inwards of the second working belt <NUM>. Preferably, the first working belt <NUM> has an axial belt width substantially equal to the tread arc width and is preferably the widest belt of the belt package <NUM>. The breaker angle of first working belt <NUM> is between <NUM> and <NUM> degrees, preferably with a right orientation, more preferably in the range of from <NUM> to <NUM> degrees or in the range of from <NUM> to <NUM> degrees. The first working belt <NUM> preferably comprises extensible or high elongation wire as cord reinforcement having a % elongation at <NUM>% of breaking load of greater than <NUM>%, as measured from a cord taken from a cured tire. Preferably, the % elongation at the <NUM>% of breaking load is greater than <NUM> %, and more preferably greater than <NUM>%, and most preferably greater than <NUM>%. The first working belt construction is preferably formed of wire having a wire construction of 3x7x, 3x4x, 4x4x. Preferably the wire has a construction of <NUM>+3x, and more preferably, a wire construction of <NUM>+3x0. <NUM> UT (UT = ultra-tensile steel). The EPI ("ends per <NUM>") preferably range from <NUM> to <NUM>.

The second working belt <NUM> is located radially outward of the first working belt, and preferably has an axial width less than the width of first working belt <NUM>. Preferably, the second working belt <NUM> has a width less than the axial width of the first working belt <NUM> by a step off, which preferably ranges from <NUM> to <NUM>. The second working belt <NUM> has a breaker angle between <NUM> to <NUM> degrees, and more preferably in the range of <NUM> to <NUM> degrees, preferably with a left orientation, and more preferably in the range of from <NUM> to <NUM> degrees. The angle of the first working belt <NUM> is different from the angle of the second working belt <NUM>. The angle of either the first or second working belt <NUM>, <NUM> is the angle of the parallel reinforcement cords relative to the circumferential direction of the tire <NUM>. The angle of the first working belt α<NUM> is greater than the angle of the second working belt α<NUM>. Preferably, the absolute difference of |α<NUM> - α<NUM>| is greater than <NUM> degrees. The second working belt <NUM> preferably comprises extensible or high elongation wire as cord reinforcement preferably having the same construction with the same but opposite angular orientation as the first working belt <NUM>.

The tensile strength measurements on the working belts <NUM>, <NUM> such as the load at break (maximum load in N), strength at break (in MPa) and elongation at break (total elongation in %) are performed in tension in accordance with ISO <NUM>-<NUM> B (<NUM>) at a pre-load no more than <NUM> MPa tested on a cable or wire when taken from a cured tire.

The belt structure <NUM> further comprises a relatively low angle belt <NUM> which is preferably located between the first and second working belts <NUM>, <NUM>. The relatively low angle belt <NUM> may also be located between the transition belt <NUM> and the first working belt <NUM>, or radially outward of the second working belt <NUM>.

The relatively low angle belt <NUM> has reinforcements that are oriented circumferentially at <NUM> degrees or less, preferably <NUM> degrees or less such as <NUM> degrees or <NUM> degrees. The relatively low angle belt <NUM> is preferably formed from spirally winding a rubberized strip of one or more cords. Preferably, the strip has <NUM>-<NUM> steel cords and has a strip width less than <NUM> such as <NUM> or <NUM> to <NUM>. Alternatively, the relatively low angle belt <NUM> may be formed of a cut belt with the reinforcements oriented in the range of <NUM> to <NUM> degrees from the circumferential direction, or more preferably in the range of <NUM> to <NUM> degrees from the circumferential direction. The relatively low angle belt <NUM> has a width sized to avoid compression in the shoulder area. The axial belt width of the relatively low angle belt <NUM> is preferably less than the axial belt width of the first and second working belts <NUM>, <NUM> and is preferably wider than the top protector belt <NUM>.

The relatively low angle belt <NUM> preferably comprises reinforcement cords, preferably steel wire cords, of a 3x7 construction, a 3x4 construction, or a 4x4 construction. More preferably, the reinforcement cords are steel wire cords of a 3x7x0. <NUM> construction, a 3x4x0. <NUM> construction, or a 4x4x0. <NUM> construction, and preferably formed of high tensile steel.

The reinforcement cords of the relatively low angle belt <NUM> are extensible.

For measurements taken from bare cords taken from a cured tire, the % elongation at <NUM>% of breaking load is <NUM> or more, and preferably <NUM> % or more, and more preferably <NUM>% or more, and most preferably <NUM>%. Alternatively, the relatively low angle belt may be formed of non-metal reinforcements such as aramid, carbon fiber, or polyketone or POK.

The tensile measurements such as the load at break (maximum load in N), strength at break (in MPa) and elongation at break (total elongation in %) are performed in tension in accordance with ISO <NUM>-<NUM> B (<NUM>) at a pre-load no more than <NUM> MPa tested on a cable or wire when taken from a cured tire.

The relatively low angle belt <NUM> has a central portion <NUM> located between the two outer lateral ends <NUM>. Preferably, the central portion <NUM> of the relatively low angle belt <NUM> has an axial width in the range of from <NUM>% to <NUM>% of the total relatively low angle belt width, and more preferably about <NUM>% or <NUM>% to <NUM>% of the total relatively low angle belt width. The reinforcement cords of the relatively low angle belt are typically coated with a rubber compound before layup. During cure or vulcanization, the rubber penetrates the cord.

The degree to which the rubber penetrates the free zones of a cord (called rubber penetration) is expressed as a percentage of the free zones occupied by a rubber compound after curing and is determined by an air-permeability test. This test is performed on cords extracted directly from the relatively low angle belt <NUM> of a cured tire which has therefore been penetrated with the cured rubber compound.

The air permeability test is run as per protocol described in: <NPL>.

For a 3x7x0. <NUM> construction, the rubber penetration at the outer lateral ends <NUM> of the relatively low angle belt <NUM> can be set to be either equal to, or less than, the rubber penetration at the central portion <NUM>. Preferably, it is less than the rubber penetration at the central portion <NUM> such as <NUM>% at the axially outer ends <NUM> and <NUM> % at the central portion.

For a 4x4x0. <NUM> cord construction, the rubber penetration at the outer lateral ends <NUM> of the relatively low angle belt <NUM> was determined to be greater than the rubber penetration at the central portion <NUM>. For this 4x4x0. <NUM> configuration, it was found that the rubber penetration at the outer lateral ends <NUM> was in a range of from <NUM>% to <NUM>%, while the rubber penetration at the central portion <NUM> was <NUM>% or less.

The belt structure further includes a top protector belt <NUM> that is the radially outermost belt. The top protector belt <NUM> preferably has a width that is in the range of from <NUM>% to <NUM>% of the width of the relatively low angle belt <NUM>. Preferably, the belt <NUM> has the same angle and orientation as the adjacent working belt <NUM>.

The top protector belt <NUM> preferably has reinforcement cords made of high impact steel cord wherein the cord preferably has full rubber penetration, i.e., at least <NUM>% up to <NUM>%, that helps in avoiding corrosion and enable excellent retreadability. It also provides high impact resistance as it exhibits more work to break because of its enhanced % elongation (> <NUM>%) even after embedded in rubber.

Preferably, the reinforcement cords of the top protector belt <NUM> have a cord construction of 5x, and more preferably, 5x0. <NUM> or 5x0.

The reinforcement cords of the top protector belt <NUM> are preferably made of steel, and are high impact cords (HI), with a very high energy absorption with energy/cord > <NUM> J/mm2, using a Charpy Impact Tester in a <NUM> strip with <NUM> EPI (ends per <NUM>).

Maximum compressive stresses of such cords are preferably above <NUM> MPa at maximum deformation at kinking of > <NUM>%.

Having a top protective belt with a high impact cord helps in absorbing the shock created during an impact and relieves the stresses on the tread shoulder grooves.

The aspect ratio of the tire described above may vary.

The aspect ratio is preferably in the range of <NUM> to <NUM>.

The tire preferably has a net to gross ratio in the range of <NUM> to <NUM>, more preferably in the range of from <NUM> to <NUM> or from <NUM> to <NUM>.

Claim 1:
A pneumatic tire for use on trucks, the tire (<NUM>) comprising a tread (<NUM>) and a belt structure (<NUM>) located radially inward of the tread (<NUM>), the belt structure (<NUM>) including a first working belt (<NUM>) and a second working belt (<NUM>), wherein the angle of the first and second working belts (<NUM>, <NUM>) each range from <NUM> degrees to <NUM> degrees as measured relative to the circumferential direction of the tire (<NUM>), and wherein the angle of the first working belt (<NUM>) is greater than the angle of the second working belt (<NUM>), wherein the belt structure (<NUM>) further comprises a relatively low angle belt (<NUM>) having reinforcements angled at less than <NUM> degrees relative to the circumferential direction of the tire (<NUM>), wherein the relatively low angle belt (<NUM>) has extensible reinforcement cords, i. e. cords having a relative elongation of greater than <NUM>% at <NUM>% of the breaking load, when measured from a cord extracted from a cured tire, characterized in that the tire (<NUM>) further includes a radially outermost top protector belt (<NUM>) comprising reinforcement cords having an impact energy absorption of > <NUM> J/mm<NUM> measured using a Charpy Impact Tester in a <NUM> strip with <NUM> ends per <NUM>, and wherein the rubber penetration at the outer lateral ends (<NUM>) of the relatively low angle belt (<NUM>) is greater than the rubber penetration at a central portion (<NUM>) of the relatively low angle belt (<NUM>).