Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-05-12
2003-06-03
Knable, Geoffrey L. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S331100, C152S342100, C152S511000, C152S512000, C156S119000, C425S028100, C425S035000, C425S047000
Reexamination Certificate
active
06571845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air tube for tires, to a process and related apparatus for its manufacture, and to wheels comprising tires provided with such an air tube; more particularly, the invention relates to an air tube intended for supporting the tire even in case of deflation thereof, as a result of a puncture for example.
More specifically, even if not exclusively, the air tube of the present invention is particularly suitable for tires of an elliptical transverse section in which the size of the minor axis parallel to the equatorial plane is smaller than the size of the major axis parallel to the rotation axis, and still more particularly for the so-called “low-section tires”, in which the ratio of the section height measured between the bead base and the tread band centre to the maximum tire width is equal to or lower than 0.7.
2. Description of Related Art
For better understanding the terminology used in he progress of the present specification the main features of a tire are hereinafter briefly set forth.
Generally, a tire comprises a carcass of toroidal shape having a crown portion and two axially opposite sidewalls, terminating with a pair of beads, each provided with at least one bead ring for anchoring of the tire to a corresponding mounting rim, a tread band disposed crownwise to said carcass, the carcass being provided with at least one reinforcing ply extending from the bead to bead and having its ends anchored to said bead rings.
In the case of radial tires, a belt structure, interposed between the carcass and tread band is also present, which bead structure may be comprised of two superposed layers of metallic cords disposed in crossed relationship with respect to each other and a radially outermost layer having textile cords directed parallelly to the equatorial plane of the tire.
These tires delimit an inner space between the carcass and rim which can be directly filled with air under pressure or occupied by an air tube of rubber material inflated with air under pressure.
In connection with the different solutions adopted, tires are identified as tubeless tires or tube type tires.
Many and varied solutions have already been provided for enabling tire running even in the case of partial or complete loss of air, as a result of punctures for example, over a fairly long length, at a moderate speed, to allow reaching of a service area where the necessary repairs or replacements can be carried out. These punctures mostly take place due to nails or other sharp pointed bodies spread on the ground, although these are not the only causes for possible deflation.
As regards tires provided with an air tube, the most widely proposed solutions contemplate use of an air tube divided into a plurality of circumferential or transverse compartments, independent of each other, by means of walls disposed parallel or perpendicular to the equatorial plane of the air tube itself.
The presence of several compartments independent of each other enables a sufficient inflation pressure to be maintained in the tire, thereby allowing the tire to run in an emergency condition even when one of said compartments has been punctured.
Examples of such a kind of tire are disclosed in U.S. Pat. No. 2,039,343 and GB 2 104 012, wherein one or more partition wall divide the the air-tube into two or more annular chambers. Reinforcement of each partition wall is provided for assuring suitable resistance to puncturing agents. However, suitable measures are necessarily taken for allowing the partition wall to spread itself, so as to be forced into engagement with the sidewall of the tube when the air within one chamber expand, as a consequence of deflation of the other chamber upon failure caused by a puncturing agent.
FR 2 524 849 discloses an apparatus for manufacturing an air tube of conventional type, i.e. not provided with partition walls, said apparatus comprising a pair of cheeks and a male die removably interposed therebetween. An elastomeric compound is injected into two distinct cavities defined between each cheek and the male die interposed therebetween, so as to form two parts of the air tube. The male die is then removed and the cheeks are approached one to the other to form the air tube by joining the two parts at their opposite edges.
As regards tubeless tires, the proposed solutions have directed their efforts towards modifications of the carcass structure by either strengthening the tire sidewalls to make the tire capable of self-support or, alternatively, creating independent compartments similar to those of the air tubes.
On the contrary, the solution of leaving the “tubeless” version in favour of the “tube type” version is not feasible with the so-called low-section tires, that is those having elliptical sections increasingly more elongated relative to the rotation axis, in which a great difficulty is found in employing known rubber air tubes.
Actually, traditional air tubes during inflation take a substantially circular profile in right section which badly matches with the elliptical tire profile, giving rise to folds overlapping each other that make it impossible to reach a correct and complete extension of the air tube walls over the inner surface of the toroidal cavity, in particular at the tire sidewalls, thereby generating a bad filling of the toroidal cavity and a dangerous state of inner stresses in the air tube wall, so that the air tube becomes quickly useless.
Consequently, in low-section tires, devoid of an air tube, the problem of ensuring a run under emergency conditions is now still solved by modifying the carcass structure, as previously stated.
The utility model DE 296 20 713 U1 discloses a tubeless tire comprising an inner central vertical wall disposed between the centre line of the tread band and the wheel rim on which the tire beads are mounted. The vertical wall is fitted, at the lower end thereof, into an appropriate rim seat so as to define two air spaces inside the tire, which air spaces are independent of each other, and each of which is inflated by a respective valve.
Practically the principle which informs this solution corresponds to that of having two twin tires mounted on one and the same rim.
Should one of the two carcass parts be punctured, the tire will be stabilized by the air pressure existing in the other part located at the side of the deflated one.
Patent application FR 2,605,269, in turn, discloses a tubeless tire formed of a plurality of distinct circumferential compartments, disposed axially in side by side relationship.
An appropriate inflating device comprises a tube passing through the lower part of all partitions generating the different circumferential compartments and is provided with a hole at each compartment: fitted in the tube is an axially drilled rod provided, on its side wall, with other holes which can be brought into communication with those of the tube to enable inflation of the tire by air inflated from the rod. Axial displacement of the rod relative to the tube enables the holes of the former to be made offset relative to those of the latter so as to stop air escape from the different compartments.
In conclusion, there is not yet the availability of an air tube adapted for being used with a low-section tire, which is capable of ensuring running under emergency conditions without being obliged to resort to an expensive and complicated modification of the tire carcass structure.
SUMMARY OF THE INVENTION
The Applicant has perceived the possibility of solving the problem by adopting an air tube divided into at least two distinct circumferential portions, separated from, each other by a longitudinal wall, while however assigning a greater rigidity to said wall and preferably also to the area surrounding it than the axially outermost portion thereof, that is the air tube sidewalls, in such a manner that during inflation of the air tube inside the tire the air tube expansion in an axial direction is greater than that in a radial direction, so as to bring its central po
Caretta Renato
Mancosu Federico
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Knable Geoffrey L.
Pirelli Pneumatici S.p.A.
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