Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-06-13
2002-09-03
Ball, Michael W. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S517000, C152S544000, C152S549000, C152S552000, C152S548000
Reexamination Certificate
active
06443201
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to pneumatic tires, specifically tires with modified sidewall ply lines and bead sections to increase the load carrying capacity.
BACKGROUND OF THE INVENTION
The sidewalls of conventional pneumatic tires provide these conventional tires with desirable flexibility in the radial direction. This radial flexibility allows the tread surface to move radially inward to accommodate irregularities in the road surface. However, the sidewalls of conventional tires also limit the performance of the tire with undesirable axial and circumferential flexibility. Axial sidewall flexibility limits the responsiveness of the tire in cornering, and circumferential flexibility limits the tire's capacity to handle the torsional forces encountered in acceleration and deceleration. In addition, the space required for the sidewall limits the maximum size of the wheel and the size of the brake mechanism that can be fit within the wheel for a given overall tire diameter.
When normally inflated, the sidewalls of conventional tires protect the rim from possible contact with the road surface. Also, conventional sidewalls distribute the weight of the vehicle and the force of impacts with road hazards by acting in tension to confine the compressive force provided by the air in a normally inflated tire. However, when normal inflation air pressure is lost, such as when the tire is punctured, the relatively thin and flexible sidewalls of a conventional tire collapse and buckle in such a manner that the sidewall fails to provide its normal functions of radial flexibility, rim flange protection, or the distribution of forces from the wheel to the road.
The load carrying capacity (LCC), typically represented by the Load Index (LI), of a pneumatic tire is related to the tire fill pressure (P) and the volume (V) contained within the tire. The European Tire and Rim Technical Organization (ETRTO) expresses this relationship with the equation:
LCC=&agr;V
&bgr;
(
P+P
0
)
where the &agr; (alpha) and &bgr; (beta) coefficients are fixed by the ETRTO by interpreting the results of tire durability and endurance tests. Tire pressure (P) is the ETRTO basic inflation pressure. Similar calculations are employed in the United States by the Tire and Rim Association (TRA) to determine a “Load Index” (LI) comparable to the ETRTO's load carrying capacity. A limitation on pneumatic tire sidewall changes is presented by the LCC (and LI). For example, if a shorter sidewall is desired (lower aspect ratio), then the tire width and/or outside diameter is usually increased to maintain approximately the same tire volume V at fill pressure P in order to maintain the same load carrying capacity LCC. Alternatively, the design of the tire can be changed in order to produce higher values for the LCC alpha and/or beta coefficients in ETRTO testing, thereby achieving the same LCC with a reduced tire volume V. Conventional radial ply tires with low aspect ratios have been developed in part to address the limitations of sidewalls. As noted by U.S. Pat. No. 4,811,771 ('771), there are basically two different shapes of passenger tires on the road today: high aspect ratio tires (aspect ratio >65) and low aspect ratio tires (aspect ratio <65). The low aspect ratio tires, where the radial height of the sidewall is reduced relative to the tire width, have better cornering characteristics and less rolling resistance than the high aspect ratio tires. Patent '771 discloses the use of a special low aspect ratio tire (aspect ratio of 40 to 45) used in conjunction with a new larger diameter wheel and rim (18 to 20 inches).
Recognition of the advantages of reducing the radial height of the sidewall is not new. U.S. Pat. No. 1,293,528 discloses the use of a plurality of chain rings as an “inexpansible” bond to provide a pneumatic tire having a cross section under inflation to present a most advantageous width for weight carrying capacity and which will have only the minimum radial height necessary to provide the requisite cushioning action, so that the wheel rim may be as close as practicable to the surface traveled over and the driving power thereby most efficiently transmitted.
U.S. Pat. No. 1,456,062 ('062) discloses a tire that has no straight sidewalls or belly part, independent of its wide gable-like tread, as in existing types of inflated tires. In fact the whole of the tire cover, with the exception of its suitable inextensible base beads is a shock absorbing tread, which “may be used to replace existing types of solid rubber band tires”. The tread is arced, with a narrow blunt apex on its centerline, so that the footprint varies in size with the applied load. As best it can be determined from the description in this 1923 patent, the tire does not have belts or beads in the same sense as modern-day tires. The patent mentions “inextensible base beads” but describes and illustrates these beads as being part of “an abnormally strong and preferably thin supple foundation . . . which may be manufactured from woven cord and be endless and abnormally strong in every direction. This unbelted, non-radial ply tire also provides rim flange protection and limited run flat capability as seen in
FIG. 3
of the '062 Patent, where the flattened, deflated tire is thick enough to support the vehicle by pressing against the substantially flat well of the wheel without loading the wheel rim flanges.
Other patents describe tires, such as racing tires, with aspect ratios as low as 25% but still having sidewalls. For example, German Patent No. 25 34 840 discloses a low aspect ratio tire with a running tread having a width which is at least half the total width of the tire, and preferably less than two-thirds of the total width of the tire. The remainder of the tire width comprises sidewalls which are radially diverted towards the seating surfaces of the tire rim.
German Patent No. 2 127 588 discloses a very low profile pneumatic tire for racing cars (aspect ratio less than 25%) having a broad tread molded in a concave shape so that it becomes flat when the tire is inflated at low pressure. The maximum width of the rim is 120% of the wheel diameter. The tire may be of radial or crossply construction. The outside surface of the sidewall is substantially flat and vertical in an un-inflated tire, however the ply line has a standard curvature from the bead into the sidewall.
U.S. Pat. No. 5,785,781 discloses a tire with relatively straight sidewalls combined with a tread-supporting ring on a specially-designed rim, in order to provide support for the tire when running at low or zero pressure. The tire has a radial ply casing on which the points that are furthest apart axially are radially apart close to seats of outwardly sloping beads, which engage sloping seats on the rim which also features an extra rim flange axially interior to the bead. When mounted on the specially-designed rim and inflated to service pressure, the tire's carcass reinforcement (ply) has a constant direction of curvature from the bead area to the corresponding sidewall wherein a tangent to the point of tangency of the [ply line] with the [bead] reinforcement ring forms with the axis of rotation an angle &phgr;, open towards the outside, of at least 70°, preferably at least 80°, and even more preferably greater than 90° as mentioned on column 5, lines 40-61. The base of each rim bead seat slopes at an angle formed with the axis of rotation wherein the angle is open axially inward and radially outward and is greater than 0°, preferably between 10° and 40°. The axially outside rim flange delimits the bead tip with a face which forms with the axis of rotation an angle &ggr;, open radially and axially towards the outside, of less than 90° and preferably between 40° and 50°.
While it may not be readily apparent, there exists a potential to develop a pneumatic radial tire with revolutionary dimension properties providing superior performance when compared to conventional pneumatic radial ti
Colantonio Laurent
Nguyen Gia Van
Philpott Frank
Roesgen Alain Emile Francois
Ball Michael W.
Cohn Howard M.
Fischer Justin
The Goodyear Tire & Rubber Company
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