Runflat tire with tread stiffening member

Details Runflat tire with tread stiffening member Runflat tire with tread stiffening member

2000-07-18

2002-08-27

Johnstone, Adrienne C. (Department: 1733)

Resilient tires and wheels

Tires, resilient

Armored

C152S209100, C152S209180, C152S517000, C152S526000, C152S527000, C152S531000, C152S532000, C152S533000, C152S534000, C152S546000, C152SDIG001

Reexamination Certificate

active

06439283

ABSTRACT:

TECHNICAL FIELD
This invention relates to a tire; more particularly to a pneumatic tire capable of being used in the uninflated condition.
BACKGROUND ART
Various tire constructions have been suggested for pneumatic runflat tires, that is, tires capable of being used in the uninflated condition. One approach described in U.S. Pat. No. 4,111,249 entitled “Banded Tires” was to provide a hoop or annular band directed under and approximately as wide as the tread. The hoop in combination with the rest of the tire structure could support the vehicle weight in the uninflated condition. This banded tire actually tensioned the ply cords even in the uninflated condition. Another U.S. Pat. No. 5,685,927; combined the use of sidewall inserts in combination with an annular bead placed directly under the tread. In this approach, the sidewall inserts were assisted in load carrying capacity by the addition of this tread bead. The resultant tire was able to carry more load with less sidewall material. Unfortunately, the hoop or beads under the tread created additional rolling resistance problems and presented a much stiffer tread area which could inhibit ride performance.
In a 1998 article entitled “Self-Supporting Tire Performance Criteria in Testing”, the author Walter Lee Willard, Jr. of Michelin America Research and Development corporation, reported to the Society of Automotive Engineers, Inc. a rather comprehensive study of self-supporting tires. He reported that self-supporting tires share the same basic design objectives: minimize the differences relative to conventional tires (inflated), enhance low pressure handling capability, acceptable zero PSI handling on suitable vehicles, enhance low pressure and zero PSI bead retention; and provide sufficient zero PSI durability to avoid a less than ideal roadside situation.
It is applicants' belief that the ideal self-supporting or runflat tires is one that can operate at zero PSI indefinitely and this theoretical tire should provide the same ride performance and handling characteristics of the pneumatic tire. Having set that, as a design goal, current technology falls far short in several areas, however, it is improving rapidly. In order to approach the theoretical goal, applicants have discovered several unique relationship with regard to runflat tires, and in discovering these relationships, they have developed several embodiments that have improved characteristics and are a great step forward in the achievement of the theoretical runflat tire.
SUMMARY OF THE INVENTION
A pneumatic runflat tire
1
,
2
,
3
,
4
,
5
or
6
having a radially outer tread
12
, a belt reinforcing structure radially inward of the tread, the belt reinforcing structure having at least two cord reinforced layers
24
,
26
, and a carcass reinforcing structure including at least one cord reinforced ply
30
,
32
extending to a pair of annular beads
36
a
,
36
b
is disclosed. The tire when mounted on a design rim when normally inflated but unloaded has a section height (H), a section width W, wherein W is greater than (H). The tire has a pair of sidewalls
16
,
18
extending from the tread
12
radially inward toward the bead cores
36
a
,
36
b
. Each sidewall
16
,
18
has at least one elastomeric filler
40
a
,
40
b
,
42
a
,
42
b
radially inward of the ply
30
,
32
. The normally inflated 30 PSI deflection D
30
of the tire when under normal vehicle load is less than 20 mms. The zero PSI deflection D
0
under normal load is less than 40 mms. The difference between the vehicle loaded uninflated deflection D
0
minus the D
30
deflection is substantially equal to or less than the amount of deflection D
30.
The tire
1
,
2
,
3
,
4
,
5
and
6
when mounted on a design rim and normally inflated and placed under normal vehicle load, has a dynamic tread contact patch
55
at 4 kph or greater characterized by a substantially rectangular shape having a width W
n
and a average circumferential length L
n
and a length L
n
+&Dgr;L and width W
0
; wherein W
0
is less the 120% of W
n
when under normal vehicle load and zero inflation pressure. The contact patch
55
has a parimeter shape wherein at least the leading edge
54
and preferably some or all the trailing edge
56
maintains tread element contact in the range of inflation pressures from zero to normal inflation pressure. The ratio of the contact patch length L
n
+&Dgr;L at zero PSI to the length L
n
is 225 percent or less. The tire
1
,
2
,
3
,
4
,
5
and
6
has a net contact area when normally vehicle loaded and inflated that is less than 150 percent of the normally vehicle loaded and zero PSI net contact area, preferably less than 125%, most preferably the same contact area.
The pneumatic runflat tires achieving this deflection at 30 PSI and zero PSI and the footprint contact shape are defined by a combination of composite structures which include the tread
12
, the belt reinforcing structure
24
,
26
and the at least one cord reinforced ply
30
,
32
and one or more tread stiffening members
101
selected from a group of one or more of the following: a) a fabric overlay
28
having at least three layers of cord reinforced material located between the tread
12
and the belt reinforcing structure
24
,
26
, b) at least three or more annular bands
29
positioned in an array laterally across the tire
4
interposed between the belt reinforcing structure
24
,
26
and the carcass ply
30
,
32
, the array of bands
29
having axial width at least
70
percent of the tread width, c) one or more layers of elastomeric spacers
27
—one layer located between two belt layers
24
,
25
,
26
or a belt layer
26
and a carcass ply
30
,
32
, d) a third belt layer
25
having steel cords inclined in a range of 18° to 30° relative to the tires equatorial plane, e) a third belt layer
25
having cords in a range of 50° to 80° relative to the equatorial plane and located between the belt structure and the carcass ply, f) one or more fabric underply layers
70
located between the belt reinforcing structure
24
,
26
and the carcass reinforcing structure
30
,
32
, g) one or more helically wound coils
60
extending circumferentially around and radially inward of the belt reinforcing structure
24
,
26
, the combination of elements forming a composite structure yielding the contact patch
55
at normal inflation and zero PSI whereby the tread elements maintain at least parimeter contact around the contact patch
55
, at both shoulder regions
50
,
52
and the leading edge
54
, preferably at both shoulder regions
50
,
52
, and leading edge
55
and trailing edge
56
.
The tire
1
,
2
,
3
,
4
,
5
or
6
when employing one or more of the stiffening members
101
described above achieves the desired zero PSI driving and handling performance without sacrificing the tire's ride and handling at normal inflation pressures.
A preferred embodiment tire
1
includes a fabric overlay
28
interposed between the tread
12
and the belt reinforcing structure
24
,
26
, the fabric overlay
28
being made of three or more spirally wound layers of aramid reinforced strips. The cords of the fabric overlay
28
are oriented at an angle &thgr; of less than 5° relative to an equatorial plane of the tire
1
. The fabric overlay
28
is preferably composed of strips which are spirally wound about the tire, its spiral revolution having a pitch of about 25 mm or less. In tires
1
having an aspect ratio greater than 50% the strips overlap sufficiently to create at least three layers of overlay fabric
28
across the entire width of the overlay
28
. In tires
1
having an aspect ratio of less than 50% the strips are overlapped in three layers in at least the central region and the shoulder regions, the three layers covering at least 60% of the overlay width.
Another embodiment tire
2
according to the invention has a belt reinforcing structure having three belt layers
24
,
25
,
26
, each belt layer
24
,
25
,
26
having parallel cords oriented angularly relative to the equatorial pl

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