Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2000-01-24
2001-07-17
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209120, C152S209210, C152S209280
Reexamination Certificate
active
06260594
ABSTRACT:
TECHNICAL FIELD
A pneumatic tire for small construction type vehicles such a skid steer vehicle and loader back hoe vehicles has a tread pattern designed for improved wear and reduced vibration.
BACKGROUND ART
Construction vehicles work in a variety of service conditions exposing the tires to loose soft wet clay and mud, paved roads, gravel and to broken concrete, glass and debris at demolition sites. These conditions result in rapid wearing of the treads for such tires.
A particularly difficult application for the tire is when mounted on skid steer vehicles. These vehicles provide turning capability by braking or locking one side of the vehicle's tires while driving the opposite side of the vehicle tires, thus the name skid steer. The tires actually skid to perform a turning maneuver over the terrain conditions stated above. Rapid wearing of tread results as a direct result of this scuffing action. The prior art tread pattern
10
shown in FIG.
1
and as taught in U.S. Pat. No. 4,481,993 is particularly prone to this rapid wearing.
At the leading edge
5
of the lugs
6
,
8
at the location of the intersection
3
of the inclined shoulder portion
2
and the lateral portion
4
this wear induced by turning is most apparent. The tread
10
is supported by the lateral portions
4
of lugs
6
and
8
when turning right or left and as the tire turns and rotates the maximum resistance to the tuning moment M as illustrated occurs at locations
3
. On hard paved surfaces this location abrades rapidly. In broken debris and concrete the location
3
can be chipped and chunked away.
A second phenomenon detrimental to good tire performance results in the unsupported nature of the vehicle load as the tire groove
7
enters the footprint. As can be readily seen, the unsupported region is very large and shifts from left to right as the tire
10
rotates. This results in increased vibration and a non-uniform loading of the underlying tire carcass which in turn transmits these vibrations through the wheel back to the vehicle and the operator.
The resultant transmission of this vibration is bad under straight line driving but becomes worse under rapid turning maneuvers. The operator can actually transmit steering inputs, which can cause the tire carcass to be twisted, and contorted resulting in a vibration transmission commonly referred to as “tire hop.” Those skilled in the art have attempted solutions of stiffening and shortening the tire sidewalls which can lessen these vibrations. This solution, however, requires the vehicle owner to replace all his rims and accept a tire with less air damping volume resulting in a stiffer less comfortable overall ride. Due to the stiffer carcass structure an even more rapid wearing of the tread lugs is expected when such a design is employed.
The tire of the present invention provides a tread pattern specifically designed to improve treadwear, reduce vibration and minimize the phenomena of “tire hopping.”
DISCLOSURE OF INVENTION
Summary of the Invention
A pneumatic tire
20
for a small construction type vehicle has a nominal rim diameter of 762 mm (30 inches) or less, an aspect ratio of less than 70%, and an annular tread
32
.
The tread
32
has a plurality of lugs
40
,
60
projecting radially outwardly from the tread
32
, an equatorial plane EP dividing the tread into a first tread half
32
A and a second tread half
32
B, the equatorial plane EP being perpendicular to the axis of rotation of the tire
20
.
The plurality of tread lugs
40
,
60
is divided into a first row
40
and second row
60
of lugs. Each lug
40
,
60
extends from a first or second tread half. The lugs
40
,
60
each have an inclined axially outer portion
46
,
66
and a laterally extending axially inner portion
44
,
64
. The axially inner portion
44
,
64
cross the equatorial plane and extend into an opposite tread half. Each axially inner portion
44
,
64
of a lug within a first or second row
40
,
60
is located between a pair of axially inner portions
44
,
64
of lugs from an opposite row with the axially inner portions
44
,
64
of circumferentially adjacent lugs of opposite rows being substantially parallel and spaced a circumferential distance D from an adjacent lug
40
,
60
.
Each lug
40
,
60
has a leading edge projection
47
,
67
. The leading edge projection
47
,
67
is located at the junction of the axially inner portion
44
,
64
and the inclined axially outer portion
46
,
66
along a leading edge
41
,
61
of each lug
40
,
60
. Each projection
47
,
67
extends circumferentially a distance of about 50%, preferably at least 50% into the spaced distance D between the adjacent lugs
40
,
60
.
Preferably the projection
47
,
67
is axially located such that the axially inner end
45
,
65
of a lug from a first or second row
40
,
60
is substantially axially aligned with a portion of the leading edge projection
47
,
67
of a circumferentially adjacent lug of the opposite row.
In the preferred embodiment a line
70
tangent to the leading edge
41
,
61
of the axially inner portion
44
,
64
of a lug if extended to intersect the leading edge
41
,
61
of the axially outer portion
46
,
66
would exhibit a radially outer surface area A defining the leading edge projection. Preferably the surface area A is substantially trapezoidal in shape having a circumferential length of at least 10 mm, a long base of greater than 25 mm and a short base of greater than 12 mm for a 12-16.5 NHS size or greater, smaller sizes being proportionately smaller.
The tread
32
most preferably has a net-to-gross ratio as measured around the entire circumference of the tread of about 50% or less.
Definitions
“Aspect Ratio” means the ratio of a tire's section height to its section width.
“Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire.
“Bead” or “Bead Core” means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers.
“Belt Structure” or “Reinforcing Belts” means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 27° with respect to the equatorial plane of the tire.
“Bias Ply Tire” means that the reinforcing cords in the carcass ply extend diagonally across the tire from bead-to-bead at about a 25-65° angle with respect to the equatorial plane of the tire, the ply cords running at opposite angles in alternate layers.
“Carcass” means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Design Rim” means a rim having a specified configuration and width. For the purposes of this specification, the design rim and design rim width are as specified by the industry standards in effect in the location in which the tire is made. For example, in the United States, the design rims are as specified by the Tire and Rim Association. In Europe, the rims are as specified in the European Tire and Rim Technical Organization--Standards Manual and the term design rim means the same as the standard measurement rims. In Japan, the standard organization is The Japan Automobile Tire Manufacturer's Association.
“Design Rim Width” is the specific commercially available rim width assigned to each tire size and typically is between 75% and 90% of the specific tire's section width.
“Equatorial Plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing trough the center of its tread.
Bonko Mark Leonard
Rooney Timothy Michael
King David L.
Maki Steven D.
The Goodyear Tire & Rubber Company
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