Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-02-18
2002-04-02
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S526000, C152S537000, C152S565000
Reexamination Certificate
active
06363986
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to reinforced resilient pneumatic tires and more particularly to a vehicle tire reinforced by a thin high strength annular band which is stabilized by a plurality of radial elements in a tire sidewall to enable the tire to run in an unpressurized condition. More particularly, the invention relates to a method of building such a run flat tire wherein the band is coated with an elastomeric material and partially cured to enable the band to achieve a proper bond within the finished tire between the carcass and tread package.
2. Background Information
Various tire constructions have been devised over the years which enable a tire to run in an under-inflated or non-inflated condition, such as after receiving a puncture and loss of pressurized air, for extended periods of time and at relatively high speeds. This enables the vehicle operator to safely drive the vehicle to an appropriate location for repair or replacement of the punctured tire. Certain of these safety tires, referred to as “run flat tires”, have been successful for certain applications and certain types of tire constructions. Most of these run flat tires achieve their run flat capability, by the placement of reinforcing layers or members of relatively stiff elastomeric material in the side walls of the tire which enable the tire to support the vehicle weight even with the complete loss of internal air pressure. Examples of such prior art run flat tire constructions which use such sidewall inserts are shown in U.S. Pat. Nos. 3,911,987; 3,949,798; 3,954,131; 4,067,372; 4,202,393; 4,203,481; 4,261,405; 4,265,288; 4,287,924; 4,365,659; 4,917,164; and 4,929,684.
Another type of run flat tire is referred to as a “banded tire.” These banded tires have been promoted in literature and patents as a pneumatic tire reinforced by a radially stabilized compression element such that operation of the tire is independent of pressure. The compression element is commonly referred to as a band or band element, and as indicated above, tires incorporating this compression element are known as banded tires. Examples of such banded run flat tires are shown in U.S. Pat. Nos. 4,428,411; 4,673,014; 4,794,966; 4,456,048; 4,111,249; 4,318,434; 4,459,167; and 4,734,144.
Prior banded tires have concentrated primarily on the compression element consisting of at least one solid, thin annular band of high strength material, which behaves as a tension member when the tire is pressurized and which acts as a structural compression member when the tire is in the unpressurized state which allows loads to act over a substantial portion of the circumference of the tire. Various band designs achieve dual band stiffness capabilities suitable for the stress conditions imposed by both the pressurized and unpressurized tire states. Various methods have been developed to manufacture the band element. One of these methods imparts a prestressing of band fibers in order to improve band performance, described in application Ser. No. 08/782,364, now U.S. Pat. No. 5,879,484. These band elements have various characteristics relating to dimensions, length, width and thicknesses and have preferred modulus of elasticity and resulting bending stiffness. A number of the above referenced patents disclose various methods for forming the band element.
However, one problem that exists is in the manufacturing of the run flat safety tires having the band incorporated therein. Although careful preparation may be utilized in preparation of the band, prior to its incorporation into the green tire, several problems occur when forming the finalized tire containing such a band.
FIG. 1
shows a prior art tire containing a banded element when formed satisfactory with
FIG. 2
showing a major problem which occurs during the formation of a run flat banded tire discussed further below.
Banded tires are made of either rigid or nearly rigid non-extensible circular bands which may be made of one or more of the known rigid non-extensible band elements formed of steel, aluminum, thermoplastic and thermosetting materials and multi-layered composites.
It has been determined that several difficulties must be overcome in order to successfully produce a banded tire on equipment intended for conventional radial tire productions. The two major problems that occur is the entrapment of air axially outwards towards the end of the band on the inside diameter as shown in FIG.
2
and the entrapment of air on the outside diameter of the band. Since the band element is rigid and changes imperceptibly from the green state to the final cure state, it results in the green tire profile of the banded tire being essentially the same as the final cure profile as shown in FIG.
1
. The band is essentially flat across the crown portion of the banded tire in both the green tire and the cured tire and the sidewalls have minimum bulge in both cases. Thus, the green tire and cured tire profiles are approximately rectangular with axially extending crown portion and outwardly extending sidewalls. In other words, the shaping and expansion at the conventional second stage machine of a tire building process must deliver the final green tire profile as shown in FIG.
1
.
In the manufacturing of a tire, the second stage tire building machine expands a first stage carcass outwardly and unites it with the band/tread package and then stitches the assembled pieces together, preferably without air entrapment. The banded tire first stage carcass consists of a usual innerliner, body plies, sidewalls and beads and when mounted on the second stage tire building machine will lie flat against the shaping bladder so as to be in a cylindrical or tubular configuration. Similarly, the band with the tread is positioned in an axial alignment over this assembly.
In operation, the tire forming bladder upon which the banded tire first stage carcass rests expands and moves the banded tire first stage carcass outwardly until it contacts the inside diameter of the band. Herein lies the first problem in that the body cords contained in the body ply are resistant to being expanded so as to transform from lying flat against the shaping bladder of the second stage tire building machine to the shape or expanded condition in order to maintain an essentially rectangular profile. This resistance of the body ply cords to assume a rectangular profile as shown in
FIG. 1
is most noticeable near the axial ends of the band. The second stage shaping results in air being trapped between the inside diameter of the band and the adjacent first stage carcass near the band edges as shown in FIG.
2
. This condition is unlikely to produce a usable tire in that curing the green tire with air trapped within the carcass is unacceptable.
Two other factors besides the natural resistance due to tension in the cords which are likely to contribute to the air entrapment between the inside diameter of the band and the adjacent rubber is as follows: The first relates to the difficulty in shaping the body cords so that they contact the band completely out to the edges of the band. This requires the second stage shaping bladder to be able to expand is the body cords outward and into the required rectangular shape as shown in FIG.
1
. However, the second stage shaping bladder relies upon pneumatic pressure for expansion and has limited ability to achieve a shaped rectangular profile. Even if reinforcement is utilized in the crown portion of the second stage shaping bladder, the rectangular profile is still difficult to achieve consistently. Thus, frequently this second stage shaping operation is unsuccessful, resulting in an imperfect banded green tire. This condition can be easily detected by non destructively examining the band edges on the inside of the tire.
Another contributing factor to air entrapment between the inside diameter of the band and the adjacent rubber within the banded green tire carcass relates to adhesion at the band/rubber interface. Even if the expansion as described above is successful, the b
Kirby James M.
Markow Edward G.
Spragg Charles D.
Bridgestone Firestone Research, Inc.
Hornickel John H.
Johnstone Adrienne C.
Kingsbury Thomas R.
Sand Michael
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