Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-03-29
2001-11-27
Ball, Michael W. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S526000, C152S527000, C152S538000
Reexamination Certificate
active
06321808
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to pneumatic tires and more particularly to a run flat pneumatic vehicle tire containing a thin annular band which acts as a structural compression member when the tire is in the unpressurized or uninflated state which allows loads to act over a substantial portion of the circumference of the tire to enable the tire to run in the unpressurized condition. More particularly, the invention relates to such a band element which is circumferentially expandable to enhance the process of manufacturing the run flat tire without materially sacrificing the run flat capability achieved by the tire.
2. Background Information
Various tire constructions have been developed over the years which enable a tire to run in an uninflated 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 uninflated tire. These tires are referred to as “run flat tires” and have been successful for certain applications and in certain types of tire constructions. One such type of run flat tire incorporates a thin annular high strength monolithic band which acts as a tension member when the tire is pressurized and acts as a structural compression member when the tire is in the unpressurized state, and are referred to as “banded run flat tires”. Some examples of such banded run flat tires are shown in U.S. Pat. Nos. 4,428,411; 4,673,014; 4,794,966; 4,456,084; 4,111,249; 4,318,434; 4,459,167; 4,734,144 and5,879,484.
Nearly all of the band elements used in these prior art run flat tires are in-extensible in the circumferential direction when placed in the green tire prior to curing. The inability of the band to sufficiently expand during curing can cause problems of tread rubber porosity and air entrapment between the outside surface of the band and the adjacent surface of the tread rubber. To eliminate such air entrapment it requires extremely accurate control of the amount of tread rubber placed in the mold, which with many existing molds and control equipment is difficult to achieve to prevent or reduce such air entrapment. Thus, existing run flat pneumatic tires using the known nonextensible rigid bands are difficult to economically manufacture in order to eliminate the tread rubber porosity and air entrapment between the tread rubber and outer surface of the run flat band. Likewise, this inextensibility of the band may inhibit the intimate contact necessary between the band element and surrounding rubber to form the desired adhesive bond therebetween when using conventional curing systems and equipment.
U.S. Pat. Nos. 4,428,411; 4,673,014 and 4,794,966 disclose run flat tires which have an annular structural compression element in the inside surface of the crown portion of the tire wherein the compression element is a helix formed by closely spaced coils wound from a rod of various solid and tubular cross sections. The coils are in a stressed condition and are applied following the second stage expansion of the green tire and are difficult to form as a separate element and then inserted into the inner crown portion of the tire prior to molding. Likewise, the band elements of these three prior art patents are difficult to economically produce and be used in a conventional tire building process as is the expandable band of the present invention which requires only minor changes to the existing tire manufacturing process.
In summary, the present invention provides a band element for a run flat tire which is expandable during curing to reduce the problems of tread rubber porosity and air entrapment between the band and adjacent tread rubber to provide more intimate contact therebetween to form a better adhesion bond than possible and at reduced costs than achieved with the heretofore inexpandable band elements.
SUMMARY OF THE INVENTION
The present invention provides a band element for a run flat tire formed of a prior rigid monolithic band structure in which a small helical cut is made from one edge in a circumferential helical manner to the other edge of the band to provide a circumferentially expandable band which does not materially affect its run flat support capability, yet enhances the manufacture of the tire and eliminates or materially reduces the porosity and entrapment of air between the band and tread rubber and providing better adhesion between the band and surrounding rubber.
The helical cut in the band of the present invention preferably extends 360 arcuate degrees or one complete revolution of the band, whereby the starting and ending locations of the cut at the band edges are spaced axially apart.
Another aspect of the invention enables the band to be produced initially as an inexpandable band element by usual manufacturing operations and then provided with the desired helical cut at sites completely separate from the manufacture of the final tire, and then subsequently incorporated with the green tire in the final building stage of the tire manufacture.
Another aspect of the invention provides incorporating an outer reinforcing layer around the helically cut band formed of a plurality of reinforcement cords in a rubber skim to stabilize the band element in the circumferential and axial directions upon curing so that no separation of the band occurs along the helical cut.
Still another aspect of the invention provides arranging the reinforcing cords in the outer reinforcing layer either in a parallel circumferentially extending direction or as pairs of overlapping cords biased at opposite angles with respect to each other and to the band axis.
Another feature of the invention is to provide a second expandable band similar to the first band, which is mounted concentrically to the first band and secured thereto by a thin intervening layer of rubber, wherein its axial cut preferably is equal in arcuate length to that of the other band but is a mirror image thereto.
Another aspect of the invention is to provide an outer reinforcing layerformed of circumferential or bias cords over the double band and rubber composite band to increase its stability during curing.
Another feature of the invention is forming the edges of the helical cut on a bevel whereby the cut edges overlap each other, preferably at a distance approximately equal to the thickness of the band.
Another aspect of the invention is forming the helical cut having an arcuate length of between 270° and 450°, with the preferred length of cut being one complete revolution or 360°.
Still another aspect of the invention is forming the reinforcing cords of the outer reinforcement layer of a material selected from the group consisting of nylon, polyester, steel and aramid and forming the band from a material selected from the group consisting of steel, aluminum, thermoplastic and thermosetting materials, and composites thereof.
Thus, the invention provides a band element which can be manufactured in an efficient and effective manner for subsequent incorporation into a run flat tire wherein the band is expandable circumferentially in the tire curing mold to form a better adhesion bond with the adjacent rubber without affecting the curing operation and equipment heretofore used, and which is achieved by modifying a heretofore used and constructed inextensible monolithic run flat band element.
The foregoing advantages, construction and operation of the present invention will become more readily apparent from the following description and accompanying drawings.
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patent: 3751316 (1973-08-01), Menough et al.
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patent: 3850219 (1974-11-01), Snyder
patent: 3933566 (1976-01-01), Seiberling
patent: 4094354 (1978-06-01), Ferrell et al.
patent: 4111249 (1978-09-01), Markow
patent: 4287924 (1981-09-01), Deck et al.
patent: 4318434 (1982-03-01), Markow
patent: 4428411 (1984-01-01),
Kirby James M.
Markow Edward G.
Spragg Charles D.
Ball Michael W.
Bridgestone Firestone Research, Inc.
Fischer Justin
Hornickel John H.
Kingsbury Thomas R.
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