Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1998-03-02
2001-06-19
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S532000
Reexamination Certificate
active
06247512
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a new and improved pneumatic vehicle tire and, more particularly, to a new and improved pneumatic tire having a radial ply carcass or having a bias ply carcass.
The present invention relates to a pneumatic vehicle tire, especially for commercial vehicles, having a radial carcass, the plies of which are made of steel or of a material of comparable high strength, and the ends of which terminate at or around the tire beads. The tire has a centrally disposed tread strip and a multi-ply belt. Typically, in such a tire, the shoulders or lateral areas of the tire tread tend to wear at a greater rate than the central portion of the tread. This necessitates the premature scrapping of such tires due to their total wear in the shoulder area although the central portion of the tread is still satisfactory for substantial additional service. The severe conditions during the service life of a commercial tire as well as the differing impact of certain forces or stresses on the tire tread across its lateral or widthwise extent significantly contributes to the non-uniform distribution of tread wear.
In an attempt to overcome the drawbacks in presently known tires, it has been suggested to provide a tire specifically having a rubber component of a different property to beneficially affect the tire tread performance. For example, it has been suggested that additional rubber be incorporated in the laterally outward areas of the tread so that both the central and lateral portions of the tread will wear out at approximately the same time, notwithstanding the fact that the laterally outward areas of the tread wear more quickly than the central area. This solution may, however, cause an unwanted weight increase in the shoulder region which increases the heat build-up in the tire, thereby adversely affecting tire life. Moreover, increasing the quantity of material in the shoulder regions adds to the cost of manufacture of the tire.
U.S. Pat. No. 3,853,164 to Mirtain proposes another solution to the problem of disproportionate tread wear. Mirtain discloses a cushion, formed of a material harder than the material of the remainder of the tread, disposed between the tread and the breaker of the tire. The cushion extends to one or both of the lateral or outside walls of the tire. This solution also is not completely satisfactory because the use of such a hard cushion results in a ride quality which is substantially rougher than that of conventional tires. Furthermore, it has been found that the use of such a hard cushion tends to reduce the traction of the tire.
U.S. Pat. No. 4,671,333 to Rohde et al. discloses a tire with a low-damping rubber layer disposed between plies of a multi-ply breaker belt. Such tires achieve their best results when used with commercial vehicles. By providing a step in the shoulder region, by having the belt plies extend laterally into the stepped portions, and by possibly introducing a low-damping rubber layer between plies of the belt, it was hoped to achieve a tire having a reduced resistance to rolling. German Auslegeschrift 10 07 644 to Fletcher discloses a vehicle tire having a belt of steel cord fabric with a resilient rubber underlayer of a carcass rubber mixture disposed radially outwardly from an eight ply diagonal carcass of textile fabric. The belt plies extend at an angle of 45 degrees relative to the circumferential direction of the tire. The rubber underlayer serves to prevent detachment of the belt from the carcass due to the overall rigidity of the tire and the relative movement between the tread strip and the carcass resulting therefrom. The rubber underlayer is at least 2 to 5 mm thick.
U.S. Pat. No. 3,931,844 to Mirtain discloses a pneumatic tire having a cushion-like support under the tread member. The support is more supple, or softer, than the rubber mixture of the tread member. The cushion extends over the tire width and has a greater thickness in the midcircumferential plane region of the tire. The cushion has only a relatively small thickness in the shoulder regions of the tire. The disclosed tire is intended to provide uniform tire wear and improved traction.
Nonetheless, in spite of the attempts to ameliorate the problems of the tire tread performance through the strategic placement of special property rubbers, there still remains room for improvement in this approach to an improved tire.
SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to provide a tire with improved tread performance.
It is a further object of the present invention to provide a tire having improved tread wear resistance.
It is a further object of the present invention to provide a tire that exhibits reduced stresses in the contact patch.
It is a further object of the present invention to provide a tread having a soft rubber compound which reduces the stresses in the contact patch.
It is a further object of the present invention to provide a tire that exhibits a phase lag between the stresses and strains occurring in the contact patch.
It is a further object of the present invention to provide a tread having a highly hysteretic material to produce a phase lag between the stresses and strains occurring in the contact patch.
These and other objects of the present invention are achieved by a tire comprising a pair of beads; a carcass ply having ends, each ends anchored to a respective bead; at least one belt ply extending circumferentially around the tire and disposed radially outward of the carcass ply; and a tread portion disposed radially outward of the belt ply. The tread portion has a plurality of tread ribs or blocks and at least one groove disposed between adjacent tread ribs or blocks.
One aspect of the invention is achieved by forming the tread portion from first and second rubber portions. The second rubber portion has a hysteresis value greater than the first rubber portion and a modulus value less than first rubber portion.
Another aspect of the invention is achieved by forming the tread portion from a first and second tread compound. The hysteresis value of the second tread compound is greater than the hysteresis value of the first tread compound and the modulus value of the first tread compound is less than the modulus value of the second tread compound.
Another aspect of the present invention is achieved by forming the tread portion from a rubber with a modulus of between approximately 2 and 3 N/mm
2
, and a tan &dgr; value of between approximately 0.2 and 0.4 when the tread is at ten percent (10%) deformation and 40° C.
REFERENCES:
patent: 3486545 (1969-12-01), Niclas et al.
patent: 3853164 (1974-12-01), Mirtain
patent: 3931844 (1976-01-01), Mirtain
patent: 4249588 (1981-02-01), Egan
patent: 4273177 (1981-06-01), Nybakken
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patent: 4603721 (1986-08-01), Kogure et al.
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patent: 4675349 (1987-06-01), Palombo et al.
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patent: 5109902 (1992-05-01), Kobayashi
patent: 5176765 (1993-01-01), Yamaguchi et al.
patent: 5181976 (1993-01-01), Iwafune et al.
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patent: 5479977 (1996-01-01), Tamano et al.
patent: 5614041 (1997-03-01), Dumke et al.
patent: 557 101 (1993-08-01), None
patent: 2 215 331 (1974-08-01), None
patent: 753533 (1956-07-01), None
patent: 753963 (1956-08-01), None
patent: 1 255 952 (1971-12-01), None
patent: 54-38004 (1979-03-01), None
patent: 59-120639 (1984-07-01), None
patent: 62-283001 (1987-12-01), None
Translation for Japan 54-38004.*
Blow, Rubber Technology and Manufacture, p. 349-356, 1971.*
Clark, Mechanics of Pneumatic Tires, p. 25-29, 1981.*
EPO Search Report for application No. 97113215.4—2306 (counterpart to parent application 08/706,951).
Csontos Alan A.
Farrell Martin
Maki Steven D.
Michelin Recherche ET Technique S.A.
Reed Robert R.
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