Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2000-05-23
2002-09-17
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209900, C152S209260, C152S209280, C152S903000
Reexamination Certificate
active
06450223
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to pneumatic tires which have improved wet traction and wet stopping and handling characteristics.
Hydroplaning of tires on wet pavement has long been a problem in the art. A tire hydroplanes when running on wet pavement because the tire pushes water in front of it as it advances, until the backpressure of the water is sufficient to lift the tire off the road. The pressure of the water is a function of the depth of the water and the speed of the tire. Various tire designs, adapted to channel water away from the tire, and thereby maintain rubber contact with the road, have been tried by the prior art to correct this problem. Although prior art rain tire designs have improved wet traction, it is a continuing goal in the art to further improve wet traction.
Traction on wet pavement, i.e. pavement that is moistened as opposed to having standing water, known as QGL wet traction (Government standard “Quality Grade Labeling”), is also an important characteristic for a tire.
Often, a tire designed for hydroplaning characteristics has diminished QGL wet traction characteristics because of the low net to gross usually associated with tires designed for hydroplaning properties. Conversely, a tire with good QGL wet traction usually has diminished hydroplaning properties, because of the high net to gross associated with tires designed for QGL wet traction.
It is an object of the present invention to provide a pneumatic tire having improved wet traction, both for hydroplaning and QGL, while having good handling, wet stopping ability, and improved noise and improved wear and irregular wear characteristics.
Other objects of the invention will be apparent from the following description and claims.
DEFINITIONS
“Aquachannel” refers to an extra wide circumferential groove with angled (non parallel), rounded groove walls designed specifically to channel water out of the footprint contact patch of the tire.
“Bead” means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
“Carcass” means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
“Contact Patch” refers to a section of footprint, in a footprint that is divided into sections by wide void areas, that maintains contact with the ground.
“Crown” refers to the circumferentially outermost portion of the carcass substantially within the width limits of the tread.
“Design rim” means a rim having a specified configuration and width.
“Directional tread” refers to a tread design which has a preferred direction of rotation in the forward direction of travel.
“Equatorial plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under design load and pressure.
“Footprint Net-to-gross” refers to the actual footprint of a deflected tire and is the ratio of the ground contacting surface area of the tread to the total tread footprint area including the groove void area.
“Groove” means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zig-zag manner. Grooves ordinarily remain open in the tire footprint. Circumferentially and laterally extending grooves sometimes have common portions and may be subclassified as “wide” or “narrow”. Grooves may be of varying depths in a tire. If such narrow or wide grooves are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming “tie bars” tending to maintain a rib-like character in the tread region involved.
“Lugs” refer to discontinuous radial rows of tread rubber in direct contact with the road surface.
“Net-to-gross” refers to the ratio of the ground-contacting surface of a tread to the total tread area.
“Normal load and inflation pressure” refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the design rim and service condition for a tire of specific size. Examples of standards are the Tire and Rim Association Manual and the European Tire and Rim Technical Organization.
“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. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.
“Radial” and “radially” are used to mean directions radially toward or away from the axis of rotation of the tire.
“Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential “wide groove” and either a second such groove or a lateral edge of the tread, the strip of rubber being laterally undivided by full-depth narrow or wide grooves.
“Shoulder” refers to the upper portion of sidewall just below the tread edge.
“Sidewall” means that component which comprises a portion of the outside surface of a tire between the tread and the bead.
“Sipes” refer to small slots molded into ribs of a tire that subdivide the tread surface and improves traction characteristics. Sipes tend to close completely in a tire footprint.
“Slots” are elongated void areas formed by steel blades inserted into a cast or machined mold or tread ring. Slots ordinarily remain open in a tire footprint. In the appended drawings, slots are illustrated by single lines because they are so narrow.
“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.
“Tread width” means the arc length of the road contacting tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.
“Turn-up ply” refers to an end of a carcass ply that wraps around one bead only.
SUMMARY OF THE INVENTION
A pneumatic tire for use on paved surfaces comprises a pair of annular beads, and at least one carcass ply wrapped around the annular beads, a tread disposed over the at least one carcass ply in a crown area of the tire. Sidewalls are disposed over the carcass ply between the tread and the beads. The tread comprises a center rib, shoulder lugs and center lugs disposed between the shoulder lugs and the center rib. The tread has a footprint net-to-gross ratio of 60% to 68% and two annular aquachannels each having a width of about 10% to 12% (as measured from tangents on the curve of the aquachannel walls adjacent to the land area of the lug) of total tread width based on the design of the tire, and a depth of 90% to 100% of total tread depth, and two circumferential grooves each having a width of 3% to 5% of the tread width based on the design width of the tread.
The illustrated tire may be viewed as having a tread having two aqua-tread portions, each aqua-tread portion comprising an aquachannel disposed between two circumferential rows of lugs, wherein the width of the aquachannel comprises 15% to 25% of the width of each aqua-tread portion. In various embodiments of the invention, the aquachannel may be symmetrical in cross section, and the aqua-tread portions may be substantially symmetrical within said tread, or the aqua-tread portions may be different, which causes asymmetry within the tread. In the illustrated embodiment, the aquachannel comprises 20% to 24% of the width of each aqua-tread portion.
In one embodiment of the invention, the tire has a tread wherein the shoulder lateral grooves and the center lateral grooves are angled in the same direction.
In an alternative embodiment, the shoulder lateral grooves and the center lateral grooves are angled in opposed directions.
Clark John Kevin
Landers Samuel Patrick
Miller Craig David
Ratliff, Jr. Billy Joe
Krawczyk Nancy T.
Maki Steven D.
Wheeler David E.
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