Pneumatic tire having 80 to 105 pitches

Details Pneumatic tire having 80 to 105 pitches Pneumatic tire having 80 to 105 pitches

2000-06-14

2002-09-10

Maki, Steven D. (Department: 1733)

Resilient tires and wheels

Tires, resilient

Anti-skid devices

C152S209180, C152S209220, C152S209250, C152S902000, C152SDIG003

Reexamination Certificate

active

06446689

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to pneumatic tires which have improved snow traction and tread wear, and improved noise and wet and dry handling characteristics.
It is a continuing goal in the art to improve the properties of pneumatic tires. This continuous improvement is driven by competition between the tire manufacturers and also, to some extent, by a drive for improvement by vehicle manufacturers. To some extent, improvements in original equipment (OE) tires are driven by competition between the automobile manufacturers.
Sometimes, improvements manifest themselves in entirely new and revolutionary tire constructions, and sometimes the improvements comprise incremental changes that are required of a tire manufacturer by a vehicle manufacturer to meet OE specifications. Relatively small changes in tread design, and changes in and use of materials, can cause significant differences in tire properties, and such differences may mean the difference between meeting specifications and being rejected by the OE customer.
Tires similar to the tire of the invention have been used in OE accounts in previous years with satisfactory performance. As changes in vehicle design, and especially the design of the suspension of a vehicle takes place, changes in the tires are required, always with the goal of improving the performance of the tire/vehicle combination.
It is an object of the present invention to improve the performance of a tire line that is currently in commercial use.
Other objects of the invention will be apparent from the following description and claims.
Definitions
“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.
“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 sub-classified 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.
“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.
“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 comprises at least a pair of annular beads, at least one carcass ply wrapped around the beads, tread disposed over the carcass ply in a crown area of the tire, and sidewalls disposed between the tread and the beads, the tread pattern having lugs formed by the intersection of lateral grooves and circumferential grooves, the improvement comprising a tread pattern having 80 to 105 pitches and a sipe density in the lugs of 1.0 to 1.1 sipes per pitch.
In the illustrated embodiment, the tire has 4 circumferential grooves, and 85 pitches in a PJ-5 pitch sequence. The tire has a combined net-to-gross ratio in the center and intermediate lug portions of 0.58 to 0.62, and a net-to-gross ratio in the shoulder portions of 0.75 to 0.8 and an overall net-to-gross ratio of 0.646.
The illustrated tire has a square footprint shape and a footprint factor of 1.0 to 1.25.
The sipes in the shoulder region of the tire are at substantially 90° with respect to the equatorial plane of the tire. Also, the lateral grooves are at substantially full tread depth in the shoulder region of the tire and are graded to less than fill tread depth at the center of the tire. Specifically, the lateral grooves are at substantially full tread depth in the shoulder region of the tire with tie bars ½ tread depth, and are graded to about ⅔ tread depth at the center of the tire.


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