Tire with outside-in ply construction

#This invention relates to pneumatic tires. In particular, the invention relates to a ply construction for truck tires and bus tires, which are collectively referred to herein as “truck tires.”

#Motor vehicle tires are designed to satisfy a number of performance criteria, such as durability, low rolling resistance, low tendency for hydroplaning, high wet traction, good handling characteristics and low noise. These criteria are particularly important for truck tires, which are frequently operated at highway speeds for long periods of time and over many miles under varying environmental conditions.

#In addition to satisfying performance criteria it is desirable to design a truck tire that is lightweight. There are several motivations for reducing tire weight. For example, a lighter tire improves fuel economy by lowering the total vehicle weight, which in turn lowers the amount of loading on the truck's engine. Lighter tires also run cooler, which lessens heat build-up damage to rubber compounds that can reduce the service life of the tire. Unfortunately, designing a tire that satisfies the necessary performance criteria for truck service often requires trade-offs that result in a heavier tire than desired.

#In the accompanying drawings:

#FIG. 1 is a cross-sectional view of the general construction of a prior art tire;

#FIG. 2 illustrates an expanded cross-sectional view of the bead region of the tire of FIG. 1;

#In the drawings the same numbers are used for the same components or items in the several views. With particular reference to FIG. 1, there is illustrated a cross-sectional view of the general construction of a prior art tire 10. The tire has a tread portion 12 and a pair of sidewalls 16 wherein the sidewalls are connected to the tread portion by shoulder regions 14. The tire may have one or more reinforcing belts 24. A carcass 18 of the tire includes one or more continuous radial plies 15, such as steel radial plies, extending from side to side. Bead regions 19 of the tire have a pair of axially spaced bead cores 26 around which are wrapped turn-up ends 20 of the radial plies 15. An apex 22 is sandwiched between the main body of the carcass 18 and the turn-up ends 20. Toes 36 and heels 37 provide a base for fitting the tire 10 to a wheel rim (not shown). FIG. 1 also illustrates the equatorial plane (“EP”) and the tread arc width (“TAW”) of the tire 10.

#FIG. 2 illustrates an expanded cross-sectional view of the bead region 19 of a prior art tire. Each of the bead cores 26 have a substantially inextensible coil of round metal filaments 27. The wire gauge of the filaments may range from 0.050 to 0.080 inches. Typical sizes are 0.080, 0.072, 0.063 and 0.050 inch diameter. The bead may be made by winding a single filament into an annular configuration or by using multiple individual filaments. The number of winds or filaments may vary, depending upon the size of the tire. A small truck tire may have as few as 20 filaments or winds, while larger truck tires may utilize as many as 65 winds or filaments. A flipper 40, such as a nylon fabric ply, is wrapped around the bead 26 to prevent the filaments 27 from cutting through the surrounding plies and rubber. The flipper 40 is surrounded by a turn-up end 20 of a radial ply 15. The radial ply 15 is routed generally parallel to the interior 30 of the tire, wraps around the bead 26, and terminates with a turn-up end 20 generally parallel to the exterior 32 of the tire. A chipper 34 may be wrapped around a portion of the turn-up end 20 to act as a stiffness transition gradient.

#A schematic diagram of a prior art tire is illustrated in FIG. 3. The tire may have one or more reinforcing belts 24. As can be seen, the turn-up ends 20 wrap around the bead cores 26 in an inside-out fashion with reference to the interior 30 and exterior 32. Under the pressure of inflation, the radial ply 15 exerts an inherent upward force F1 as seen in FIG. 3. The force F1 exerted by the radial ply 15 causes the bead cores 26 to rotate in a direction R1, causing the toe 36 to lift away from the rim (not shown). Over time this lifting creates a permanent set in the bead area making it difficult if not impossible to remount the tire if it is ever removed from the rim. Additionally under the pressure of inflation and the forces experienced during use, the ply in a conventional tire tends to move toward the rim and rubber adjacent the rim is displaced. This results in a noticeable rim indentation.