Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2001-04-27
2004-11-23
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209500, C152S458000, C152S532000, C152S565000
Reexamination Certificate
active
06820666
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates tires and methods for making tires. More specifically, the present invention concerns a tire and a method for making a tire having a particular belt structure.
2. Description of the Related Art
As is known, a tire includes a carcass, a tread band, a pair of sidewalls and reinforcing layers between the tread band and the carcass. The carcass, usually at least a single ply, is turned out at its ends around a pair of bead cores. The bead cores, the ends of the carcass, and whatever filler that may be added between the bead cores and carcass form the beads on either side of the tire.
In the traditional (or known) tire, there are generally at least three rubber layers below the tread band, two belted layers and a 0 degree layer or nylon layer. The nylon layer contains reinforcing cords, preferably of a textile material, and more preferably of a heat-shrinkable material, such as nylon, oriented at 0° (i.e., in a circumferential direction) with respect to the equatorial plane of the tire. The reinforcing cords preferably are disposed in a sheet made of elastomeric compound. The nylon layer is located between the tread band and the belted layers. As understood by those skilled in the art, the nylon layer stabilizes the tire, improves its rolling resistance, and generally enhances its operational characteristics because the nylon layer helps the tire retain its shape when subjected to large centrifugal forces at high speeds. Without the nylon layer, the performance of the tire may be compromised, especially at high speeds.
The two belted layers comprise fine cords, preferably metallic cords, displaced in an elastomeric compound, that crisscross each other and are both angled with respect to the equatorial plane of the tire.
In addition to the three reinforcing layers, the traditional tire may also include a rubber sheet between the nylon layer and the tread band, which must be added because of the manner in which traditional tires are manufactured. As is known, the tread band is, often, a separately manufactured, extruded product. Because it is manufactured separately, the tread band cools to room temperature before it is incorporated into a tire. Upon cooling, the tread band loses tackiness and is less able to stick properly to the underlying layer during construction of the tire. To compensate for the loss of tackiness and to improve the adherence of the tread band to the underlying layer so that the tire may be assembled properly before it is vulcanized, a rubber sheet is added to the underside of the tread band. The rubber sheet is a calendered or coestruded (with the tread band) sheet of an elastomeric compound based on natural rubber that is well known in the art. The rubber sheet is usually 0.2 to 1.0 mm thick. Its tackiness may be attributed to the fact that the rubber sheet is typically made from a compound with a natural rubber content of more than about 50 percent of the polymer amount.
An alternate construction of the traditional tire, known as “cap and base tyre”, further includes an underlayer as part of the tread band on the side of the tread band facing the interior of the tire. The underlayer improves handling while reducing the rolling resistance of the tire and is incorporated into the tread band between the tread band and the underlying layer. In this alternate construction, the various layers of the tires are arranged in the following manner from the exterior of the tire to the interior: (1) the tread band, (2) the underlayer, which is incorporated into the underside of the tread band, (3) the rubber sheet, and (4) the 0° nylon layer, which is placed above the belted plies. The underlayer is made from a rubber-based compound and is usually between 1 and 2 mm thick. Since it does not have the same composition and characteristics as the tread band, the thickness of the underlayer is selected so that it will not come into contact with the road when the tire tread wears out.
In situations where the underlayer is made, for example, from a compound with a natural rubber content greater than 50 percent of the polymer amount, the rubber sheet may be omitted because the underlayer will have sufficient tackiness to properly adhere the tread band to the carcass, as described above in relation to the rubber sheet.
This does not mean, however, that the rubber sheet is omitted in every case where the natural rubber content of the overlaying layer is greater than 50%. In some cases, the rubber sheet can be omitted despite the fact that the rubber content of the overlaying layer is less than 50%, for example in the case that other material, able to make the overlaying layer with a good tackiness, are added to the compound, or for example when the tread band is not left to cool.
It is also known in the art to construct elastomeric compounds for tires that are reinforced through the addition of reinforcing fibers. One such example is U.S. Pat. No. 4,871,004 (“the '004 patent”), which describes the addition of Kevlar® pulp (a registered trademark of DuPont) to tire rubber to a point where the Kevlar® has a concentration of 0.2 to 20 parts per hundred of rubber (phr). In the '004 patent, the Kevlar® fibers are described as having a length (L) of 0.2 to 5 mm, a diameter (D) of 0.005 to 0.02 mm, and an aspect ratio (L/D) of greater than about 100. The resulting mixture of fibers and rubber can be used to prepare any one of the described components of a tire: apexes, filler strips, belts, belt overlay, and gum strips. The '004 patent describes some of the advantages of adding reinforcing fibers to an elastomer in the construction of a pneumatic tire, such as its reinforcing effect and the increased stiffness of the resulting tire.
European Patent Number 0 592 218 A1 (“the EPO '218 patent”) also describes some of the advantages of adding reinforcing fibers to the rubber for different parts of a pneumatic tire. The EPO '218 patent describes the addition of 16 to 30 parts per hundred of rubber (phr) of short fibers having an average diameter (D) of 0.1 to 0.5 &mgr;m, an average length (L) of 40 to 500 &mgr;m, and an aspect ratio (L/D) of 100 to 5000. Examples of the fibers that can be added are aramid fibers such as Kevlar®, cotton, nylon, polyester, rayon, and surface treated short fibers such as Nylon 6.
Similarly, European Patent Number 0 604 108 A1 (“the EPO '108 patent”) describes the addition of certain types of fibers to reinforce the rubber in a pneumatic tire. The specific fibers discussed by the EPO '108 patent are short fibers of UBEPOL-HE 0100 (available from UBE Industries Limited), i.e., Nylon-6. The fibers are described as having an average diameter (D) of 0.3 &mgr;m, an average length (L) of 300 &mgr;m, and an aspect ratio (L/D) of 1000. The fibers are incorporated into the rubber compound in a concentration of not less than 10 parts per 100 of rubber (phr), and preferably 10 to 30 phr.
SUMMARY OF THE INVENTION
The present invention concerns the construction of an elastomeric intermediate layer between the tread band and the belted plies of a pneumatic tire that replaces the nylon layer of the traditional tire but retains the beneficial characteristics of such structural element. Further, the intermediate layer may replace the rubber sheet if present. Similarly, for the second example of the traditional tire, the present invention provides a construction where the elastomeric intermediate layer replaces the 0° nylon layer, the underlayer, and the rubber sheet (if present), to achieve the same goals.
The Applicant found that replacing one or more layers in the traditional tire by introducing an elastomeric intermediate layer to the tread band made with a fiber-reinforcing material, the present invention realizes at least the same advantages in rolling resistance and handling that are previous realized by the structures of both of the traditional tire designs but it does so while reducing the overall weight of the tire.
Moreover, the replacement of the tradit
Brunacci Antonio
Nahmias Nanni Marco
Zanichelli Claudio
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Johnstone Adrienne C.
Pirelli Pneumatici S.p.A.
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