Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2000-06-22
2002-06-11
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209150, C152S209190, C152S209280
Reexamination Certificate
active
06401774
ABSTRACT:
TECHNICAL FIELD
This invention relates to off-road tires, more specifically, a preferred embodiment of this invention relates to a pneumatic all-terrain vehicle tire.
BACKGROUND OF THE INVENTION
As used in this patent the term off-the road tires means pneumatic tires that have a primary use or working surface condition that is not on a paved road. Such tires include earthmover, agricultural tires, lawn and garden tires, and all-terrain vehicles tires, including, but not limited to off-road dirt bike tires and ATV tires.
Of particular interest are tires that have low operating pressures and minimal belt reinforcements. Tires in this class include farm tires or ATV tires. ATV tires generally operate at less than 10 psi and often times have no belt reinforcing structure.
All-terrain vehicles are relatively lightweight with a relatively low center of gravity. Early three wheel versions had knobby tires having small square block elements and a relatively shallow tread depth.
Later versions of “Quad runners” or 4-wheel type ATV's were developed and have been more widely accepted due to their improved stability. Horsepower increases and improvements in both vehicle suspension and chassis has resulted in vehicles capable of relatively high speed and much greater load carrying capacity.
The tires used on these vehicles are operated at very low pressures in the 0.7 bar 10 psi or less range. The tires are very wide with relatively large air chambers, which assist in absorbing shock and vibration. The tires generally have nominal rim diameters of 36 cm 14 inches or less and overall diameters of 69 cm 27 inches or less.
Often the rear tires are of a slightly larger size than the more lightly loaded front tires.
In aggressive off-the-road applications, the tires must have a very open tread pattern that employs elongated lugs which provide effective straight-line or drawbar traction to enable the vehicle to climb hilly and rough terrain, as shown in U.S. Design Pat. No. 308,038. Additionally, the tread must provide excellent lateral traction for vehicle stability during turning maneuvers as is disclosed in U.S. Pat. No. 5,259,429.
The tire disclosed in that patent employs a repeating pattern of long, intermediate length and short lugs arranged to provide improved traction. The arrangement of these lugs is such that each lug wraps completely over the tread shoulder portion. The lugs are also circumferentially relatively closely spaced such that numerous lugs are in the footprint of the tire at any one time. The tire made according to this prior art invention is considered one of the best mud tires in its class according to its manufacturer.
In wet soils with heavy clay content there is a tendency for the tread to pack with mud between the elongated lugs. The circumferential space between the adjacent lugs is commonly referred to as a soil discharge channel. The channels extend generally from the centerplane of the tread axially outwardly over the tread shoulder. Once this area is packed with mud, the tread effectively looses its ability to provide any traction. This is because the lugs are buried in the packed mud giving the tire the appearance of a slick or racing tread devoid of grooves.
For the very reasons these tires have such good traction capabilities, they exhibit a relatively high potential for stubble damage in the area of the inner tread surface. This thin inner tread surface lies between the tread lugs and sharp objects such as the rocks, sticks, thorns or roots can penetrate this undertread causing the tire to deflate.
It is an object of the present invention to minimize this type of tire damage without increasing tire weight or losing tire performance.
A further objective of the present invention is to maintain the tread pattern, which is self-cleaning in wet clay soil conditions.
It is still a further objective that the tread design maintain its good handling and traction performance on firm soils without any penalties in tire weight.
SUMMARY OF THE INVENTION
An off-road tire having a casing and a tread radially outward of the casing is disclosed. The tread has an inner tread and a plurality of lugs extending radially outward from the inner tread.
The tread has a plurality of elongated pads, each elongated pad is oriented in a direction substantially parallel to the centerlines of circumferentially adjacent lugs. Each pad has a base width as measured from the inner tread and a radial height X also being measured from the inner tread. is at least three times greater than X. Each longitudinal sidewall has a slope of 30° or less as measured from the inner tread surface, preferably about 20° or less. The radial height is less than 0.2 inches (5 mm).
The elongated pads each have a pair of tapered ends extending across the sides. The tapered ends are inclined at an angle of about 45° or less relative to the inner tread surface.
In some cases whether there is a substantial circumferential space between adjacent lugs, it may be desirable to further include a radially outer or flat surface interposed between the pair of sloped longitudinal sides.
In the most preferred embodiment of the invention the off-road tire is an ATV tire. This ATV tire has the tread having the lugs arranged in an array of lugs oriented in a repeating directional pattern. The arrays are in rows around the circumference of the tread. A first array of lugs extends angularly from an axially inner end adjacent the centerplane (EP) of the tread toward a first lateral edge terminating an axially outer end. A second array of tread lugs extends angularly from an axially inner end adjacent the centerplane of the tread towards the second lateral edge terminating at an axially outer end. The space between each pair of first or second circumferentially adjacent arrays of lugs defines a soil discharge channel. Each pair of first or each pair of second arrays of lugs has the elongated pad located within the soil discharge channel and interposed between circumferentially adjacent arrays. The elongated pad is inclined in a direction similar to the inclination of the pairs of respective arrays.
Preferably the elongated pad interposed between circumferentially adjacent pairs of arrays is located substantially equal distance between centerlines of adjacent arrays. Each array of lugs has at least one circumferentially extending open channel between a pair of lugs within each array. At least one open channel intersects the soil discharge channel. It is believed desirable that the elongated pads have a length L of at least 35% of the tread arc width. Preferably the elongated pad extends from an axially inner end adjacent the equatorial plane outward to a lateral end covering substantially all of the soil discharge channels length.
The all terrain vehicle tire of the present invention preferably has a net-to-gross ratio of the tread as measured between the lateral edges around the entire circumference of the tread of less than 35%.
DEFINITIONS
“All-terrain Vehicle ATV” is any motorized off-highway vehicle 50 inches 1270 mm or less in overall width, with an unladen dry weight of 600 lbs. 275 kg or less, designed to travel on four or more low pressure tires, having a seat designed to be straddled by the operator and handlebars for steering control, and intended for use by a single operator and no passenger. Width and weight shall be exclusive of accessories and optional equipment. ATV's are subdivided into four categories as follows:
Category G General Use Model ATV: An ATV intended for general recreational and utility use;
Category S Sport Model ATV: An ATV intended for recreational use by experienced operators only;
Category U Utility Model ATV: An ATV intended primarily for utility use.
Category Y Youth Model ATV: An ATV intended for recreational off-road use under adult supervision by operators under age 16. Youth model ATV's can further be categorized as follows:
Category Y-6 ATV: A Category Y-6 ATV is a youth model ATV which is intended for use by children age 6 and older.
Category Y-12 ATV: A Category Y-12 ATV is
King David L.
Maki Steven D.
The Goodyear Tire & Rubber Company
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