Patent Description:
Tires for service on aircraft landing gears are exposed to severe operating conditions of load and acceleration/speed. In particular, aviation tires coupled with the landing gears of large commercial airliners are susceptible to severe deformation upon landing, takeoffs, and controlled movement of the aircraft under its own power while on the ground (e.g., taxiing, parking, etc.). Loss of a landing gear tire on takeoff (e.g., a blowout, mechanical failure, etc.) may result in an aborted take-off or an emergency landing. Loss of a landing gear tire upon landing may result in an inability to halt the airliner's momentum, leading to runway overshoot. Airliners often elevate tire temperature by taxiing long distances and/or by taxiing at high speed, which may increase the susceptibility to blowouts during takeoff or after landing.

Typically, the belt package incorporated into conventional aviation tires includes a number of cut belt layers and a number of spiral wound layers formed from cord reinforced strip(s) wound about the circumference of belt layers of the tire with a zero degree spiral overlay. The spiral wound layers terminate proximate the tire shoulder of the tire with little or no overlap, as the winding direction is reversed to apply the successive spiral wound layers.

One conventional approach for improving tire durability is a uniform increase in the number of belt layers from crown to shoulder. However, this approach may result in significant tire weight increases. Tire weight increases from the added layers is contrary to another tire design parameter for minimizing the net weight of the airliner. Increasing the number of belt layers uniformly between the crown and the shoulder also significantly increases the tire's production cost (e.g., more material, more complexity, more waste, etc.). For these and other reasons, it would be desirable to provide a lightweight tire for airliner landing gears characterized by improved durability and greater load capability.

<CIT>, <CIT> and <CIT> describe a tire in accordance with the preamble of claim <NUM>.

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

A tire in accordance with a preferred aspect of the invention includes a carcass, a tread disposed radially outward of the carcass, a sidewall including a shoulder extends toward the tread, and a reinforcing structure positioned radially between the carcass and the tread. The reinforcing structure includes one or a plurality of belts extending axially toward the shoulder and an overlapping spiral wound strip positioned at a radially outermost portion of the reinforcing structure. The overlapping spiral wound strip includes a uniform width having groups of four first cords with a single second cord therebetween. The first cords include a hybrid construction, and the second cords include a single material construction.

A method of constructing a tire in accordance with a preferred aspect of the invention includes the steps of: axially extending a carcass from a first bead portion to a second bead portion, axially extending a tread radially outward of the carcass, extending a sidewall radially outward to a shoulder adjacent the tread; positioning a reinforcing structure radially between the carcass and the tread, spirally winding an overlapping strip at a radially outermost portion of the reinforcing structure. The overlapping strip includes a uniform width having groups of four first cords with a single second cord therebetween. The first cords include a hybrid construction, and the second cords includes a single material construction.

According to a preferred aspect of the invention, the first cords have a hybrid construction of nylon and aramid.

According to a preferred aspect of the invention, the second cords have a full nylon construction.

According to a preferred aspect of the invention, the first cords have a hybrid construction, and the second cords have a 1400dtex/<NUM> single material construction.

According to a preferred aspect of the invention, the first cords have a full nylon construction, and the second cords have a <NUM> dtex/<NUM> full rayon construction.

According to a preferred aspect of the invention, the first cords have a full aramid construction.

According to a preferred aspect of the invention, the second cords have a <NUM> + <NUM> full nylon construction.

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

"Carcass" means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.

"Cord" means one of the reinforcement strands which the plies in the tire comprise.

"Crown" refers to substantially the outer circumference of a tire where the tread is disposed.

"Circumferential" means circular lines or directions extending along the surface of the sidewall perpendicular to the axial direction.

"Equatorial plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

"Inner" means toward the inside of the tire.

"Lateral" means a direction parallel to the axial direction, as in across the width of the tread or crown region.

"Outer" means toward the tire's exterior.

"Pneumatic tire" means a laminated mechanical device of generally toroidal shape, usually an open-torus having beads and a tread and made of rubber, chemicals, fabric and steel or other materials.

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

"Shoulder" means the upper portion of the sidewall just below the tread edge.

"Sidewall" means that portion of a tire between the tread and the bead area.

"Tread" means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.

With reference to <FIG>, an example pneumatic aviation tire <NUM> suitable for airliner service as a nose gear tire for instance includes a carcass <NUM>, a ground-engaging tread <NUM>, a sidewall <NUM>, and a shoulder <NUM> defined by the junction of the sidewall <NUM> and the tread <NUM>. When mounted on the airliner, the tread <NUM> provides traction and the tire <NUM> contains a fluid (e.g., air, nitrogen, etc.) that sustains part of the airliner load. The example tire <NUM> preferably has a mirror symmetry reflecting about an equatorial plane <NUM> bisecting tire <NUM>. Arranged between the carcass <NUM> and the tread <NUM> is a belt package, generally indicated by reference numeral <NUM>, comprising one belt, two belts or preferably a plurality of, for example five, six or seven, individual cut belt plies or layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and a plurality of, for example one, two or three, spiral wound belt layers <NUM>, <NUM> positioned radially-outward from the one or more cut belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The number of cut belt layers and spiral wound layers in the belt package <NUM> may vary according to the tire construction. If the tire <NUM> is a passenger tire, it may be sufficient for instance to use just one or two belt layers, i.e., only one or two of the individual cut belt plies or layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, in the belt package <NUM>.

As best shown in <FIG> and <FIG>, both of the spiral wound belt layers <NUM>, <NUM> are formed by a continuous rubberized flat strip <NUM> that is wound circumferentially (e.g., with a -<NUM> degree to +<NUM> degree spiral overlay) about the tire <NUM>. The overlay <NUM>, <NUM> extends one tire shoulder <NUM> to the other tire shoulder (not shown). The flat strip <NUM> is reinforced with multiple embedded preferably high modulus, preferably essentially inextensible, cords <NUM> of, for example, nylon, rayon, polyester, aramid, glass, and/or metal disposed spatially with a substantially parallel arrangement of one to another and covered by an elastomer matrix, such as a cured rubber casing. The width Ws of flat strip <NUM> preferably ranges from <NUM> to <NUM> or from <NUM> to <NUM> such as <NUM>. The thickness of the flat strip <NUM> may approximate several millimeters. The density of cords <NUM> of the flat strip <NUM> is preferably from <NUM> to <NUM> per <NUM> ("ends per inch"). During construction of tire <NUM>, the flat strip <NUM> is wound circumferentially about a crowned building drum with the flat strip <NUM> being shifted by a transverse, or axial, distance approximately equal to, or slightly greater than, the width Ws with each individual turn.

The axial dimension of the one or more cut belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is preferably selected such that corresponding lateral side edges are tiered or staggered with an overlapping relationship near the tire shoulder <NUM>. For example, the cut belt layer <NUM> preferably extends laterally/axially for a greater lateral distance from the equatorial plane <NUM> than the cut belt layer <NUM> so that the terminal side edge of the cut belt layer <NUM> overlaps between layers <NUM> and <NUM>.

A plurality of overlapping spiral wound shoulder layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, preferably <NUM> to <NUM> or <NUM> to <NUM> such shoulder layers, is provided in the tire shoulder <NUM>.

Each of the spiral wound shoulder layers <NUM>, <NUM>, <NUM> is preferably defined by a single circumferential flat strip, similar to the flat strip <NUM>, in which adjacent turns are shifted laterally by less than one strip width (Ws) so that the shoulder layers <NUM>, <NUM>, <NUM> have a partially overlapping, or staggered relationship (<FIG>). In other words, the winding pitch for spiral wound shoulder layers <NUM>, <NUM>, <NUM> is preferably less than one strip width (Ws) per revolution. The remaining spiral wound shoulder layers <NUM>, <NUM>, <NUM>, <NUM> are preferably applied with a winding pitch equal to one strip width (Ws) per revolution such that there is no overlapping build up in the tire crown region beyond the overlap afforded by spiral wound belt layers <NUM>, <NUM>. The lateral shift of less than one strip width (Ws) is shown in <FIG> as adjacent turns of the flat strip <NUM> contribute to the partially overlapping relationship. In a central region of the tire shoulder <NUM>, an overlapping relationship may thereby be established to provide an ultimate thickness equivalent to for instance six strip thicknesses.

With continued reference to <FIG>, to apply the spiral wound shoulder layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, the first spiral wound belt layer <NUM> is applied to the tire <NUM>. After the shoulder layer <NUM> is applied, the winding pitch is changed from greater than or equal to one strip width (Ws) per revolution (e.g., a -<NUM> degree to +<NUM> degree pitch) to a winding pitch that is less than one strip width (Ws) per revolution. In the example belt package <NUM> of <FIG>, the spiral wound shoulder layers <NUM>, <NUM>, <NUM> is shifted laterally by approximately <NUM> of the strip width (Ws) per revolution. The spiral wound shoulder layers <NUM>, <NUM>, <NUM> are for instance applied serially or sequentially from left to right, as best visible in <FIG>. The spiral wound shoulder layers <NUM>, <NUM> are preferably applied with a winding pitch of approximately zero degrees so that the shoulder layers <NUM>, <NUM> roughly overlap the shoulder layer <NUM>. Then, the winding pitch is preferably reverted to greater than or equal to one strip width (Ws) per revolution. The spiral wound shoulder layer <NUM> is preferably applied with a unitary winding pitch of one strip width (Ws), in an opposite or reverse winding direction from the shoulder layers <NUM>, <NUM>, <NUM>. After the shoulder layer <NUM> is applied, the circumferential turns of the flat strip <NUM> transitions into forming the spiral wound belt layer <NUM>. At the tire shoulder opposite the tire shoulder <NUM>, another set of spiral wound shoulder layers (not shown but similar to spiral wound shoulder layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are preferably applied to tire <NUM>.

With reference to <FIG>, another example belt package <NUM> for use with the present invention is shown. The belt package <NUM> for an example tire (not shown, but similar to the tire <NUM> of <FIG>) includes one, two or preferably a plurality of cut belts <NUM>, <NUM> and a plurality of spiral wound belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> wound with a zero degree spiral. The laterally outermost turn of the spiral wound belt layer <NUM> is preferably aligned radially with the free side edge of the underlying cut belt <NUM>. The laterally outermost turn of the spiral wound belt layer <NUM> are preferably shifted laterally by less than one strip width (Ws), although the winding pitch remains constant at greater than or equal to about one strip width (Ws). Each successive spiral wound belt layer <NUM>, <NUM>, <NUM>, <NUM> may likewise be shifted laterally by less than one strip width (Ws) while the winding pitch remains constant at greater than or equal to about one strip width (Ws). In other words, when the winding direction is reversed at the turn around positions at each tire shoulder <NUM> (<FIG>), an initial strip turn of each spiral wound belt layer <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be shifted laterally by less than one strip width (Ws) so that radially adjacent pairs of the spiral wound belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> only partially overlap. Alternating spiral wound belt layers, for example spiral wound belt layers <NUM>, <NUM>, <NUM>, preferably include multiple overlapping initial turns of the flat strip <NUM> wound with a zero pitch. In the example shown, two cut belts and six spiral wound belt layers are provided in the belt package <NUM> and the lateral shift distance for successive spiral wound belt layers is about <NUM> of the strip width (Ws).

The overlapping turns of flat strip <NUM> at the lateral edge of the spiral wound belt layers create a tiered arrangement such that the lateral shift in the starting location for successive spiral wound belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the lateral edges among successive spiral wound belt layers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are not coincident. The spiral wound belt layer <NUM> contributes for instance three overlapping spiral wound shoulder layers. The spiral wound belt layer <NUM> for instance contributes one partially overlapping spiral wound shoulder layer. The spiral wound belt layer <NUM> for instance contributes three partially overlapping spiral wound shoulder layers.

In accordance with the present invention, an overlay construction, such as above described <NUM>, <NUM>, <NUM>, includes multiple cord materials. Current manufacturing methods allow an overlay construction in accordance with the present invention to include multiple reinforcement cords co-extruded in a single step. An overlay strip, such as the flat strip <NUM>, thus preferably comprises two or more single end dipped cords of different materials. The overlay strip preferably has a width between <NUM> and <NUM>, or <NUM>. For example, the overlay strip width preferably includes seven hybrid cords of aramid/nylon and two nylon cords, in place of eight cords of hybrid material for a conventional overlay strip, such as the spiral layers <NUM>, <NUM> and the flat strip <NUM>.

Conventional overlay strips have been made entirely of a single reinforcement material, such as full nylon, hybrid nylon and aramid, or full aramid. The application of single dipped fabrics (made of a single cord type), one at a time, for calendering/slitting operations allows varying cord types within a single overlay strip. Such a combination of different cord materials within a single strip may thereby enhances functional properties while decreasing cost and/or weight of the overlay package. The insertion of one of more full nylon cords into an overlay strip usually made entirely of hybrid cords further increases shrink force at higher speeds when the tire starts to heat-up, leading to a more stable tire circumference at high speeds, with potential benefits in high speed performance.

As shown in <FIG>, the width of an example overlay strip <NUM> in accordance with the present invention includes groups of four first cords <NUM> with a single second cord <NUM> therebetween. Alternatively, <NUM> to <NUM> such first cords <NUM> with <NUM> to <NUM> such second singe cords <NUM> therebetween may be used.

The first cords <NUM> preferably include a hybrid construction, a full nylon construction, or a full aramid constriction. The second cords <NUM> preferably include a hybrid construction, a full nylon construction, or a full aramid constriction.

Claim 1:
A tire comprising a carcass, a tread (<NUM>) disposed radially outward of the carcass (<NUM>), a sidewall (<NUM>) including a shoulder (<NUM>) extending toward the tread (<NUM>), and a reinforcing structure (<NUM>, <NUM>) positioned radially between the carcass (<NUM>) and the tread (<NUM>), the reinforcing structure (<NUM>, <NUM>) including one, two or a plurality of belts (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) extending axially toward the shoulder (<NUM>) and an overlapping spirally wound strip (<NUM>) positioned at a radially outermost portion of the reinforcing structure (<NUM>, <NUM>), wherein the overlapping spirally wound strip (<NUM>) has a preferably uniform width and comprises groups of from <NUM> to <NUM> first cords (<NUM>) together with of from <NUM> to <NUM> second cords (<NUM>) therebetween, characterized in that (i) the material of the first cords (<NUM>) is different from the material of the second cords (<NUM>) and in that the tire is an aircraft tire; and/or (ii) in that the diameter of the first cords (<NUM>) is different from the diameter of the second cords (<NUM>).