Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2001-11-29
2004-11-09
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S539000, C152S543000, C152S548000, C152S550000, C152S558000, C152S560000, C156S133000
Reexamination Certificate
active
06814119
ABSTRACT:
The present invention relates to a self-supporting tire for vehicle wheels, comprising: a carcass structure having at least one carcass ply provided with end flaps in engagement with respective annular anchoring structures disposed in coaxial relation with a geometric rotation axis of the tire at axially spaced apart positions with respect to each other; a belt structure applied to the carcass structure at a radially outer position thereof; a tread band applied to the belt structure at a radially outer position thereof; at least one pair of sidewalls applied to the carcass structure at opposite side positions; at least one pair of resilient stiffening inserts incorporated into the carcass structure, each at one of said sidewalls.
The present invention also relates to a method of manufacturing a self-supporting tire for vehicle wheels, comprising the steps of: preparing a carcass structure comprising at least one carcass ply having end flaps in engagement with respective annular anchoring structures disposed concentric with a geometric rotation axis of the tire at axially spaced apart positions with respect to each other; applying a belt structure to the carcass structure at a radially outer position thereof; applying a tread band to the belt structure at a radially outer position thereof; applying a pair of sidewalls to the carcass structure at opposite side positions; incorporating at least one pair of resilient stiffening inserts into the carcass structure concurrently with preparation of said at least one carcass ply.
DESCRIPTION OF THE RELATED ART
Tires for vehicle wheels essentially comprise a carcass structure consisting of one or more carcass plies that, in the most classic embodiments, have the respective inner circumferential edges turned up around inextensible annular inserts being part of annular reinforcing structures, disposed at radially opposite positions at the tire regions usually identified as “tire beads”.
A belt structure is applied to the carcass ply or plies at a radially outer position thereof, which belt structure comprises one or more belt layers radially superposed upon each other. A tread band of elastomer material radially overlaps the belt structure. The outer sides of the carcass structure are also covered with respective sidewalls also made of elastomer material.
It should be also pointed out, for the purposes of the present description, that by the term “elastomer material” it is meant the rubber blend in its entirety, i.e. the assembly formed of at least one base polymer suitably amalgamated with reinforcing charges and/or process additives of different types.
In order to give the tire self-supporting qualities, i.e. the capability of ensuring short/medium runs in the absence of inflating pressure when a puncture occurs for example, the expedient of integrating into the tire, close to the sidewalls thereof, one or more reinforcing inserts of elastomer material is known, which inserts of semicircular outline and usually identified as “lunettes” conveniently support the vehicle load when the normal inflating pressure of the tire fails.
In this connection, different embodiments have been proposed aiming at giving the required self-supporting features to the tire, without impairing ride comfort too much when the tire is inflated. These solutions are essentially diversified both in the physico-chemical features of the elastomer materials employed in making the resilient stiffening inserts, and in the contemplated insert number, and also in their positioning in relation to the carcass ply or plies.
Good results, particularly in connection with the tire self-supporting capability under deflated conditions have been achieved with embodiments in which at least one of the resilient stiffening inserts which are present at each sidewall is enclosed between two carcass plies forming a sort of closed container around it, as described in documents GB 2087805, EP 475258 and EP 542252, for example.
The Applicant has however sensed that placing the resilient stiffening inserts in a sort of closed container defined by the carcass plies turned up around the annular anchoring structures tends to increase the tire sidewall rigidity too much not only with reference to its vertical flexibility, i.e. in connection with stresses substantially radial to the rotation axis of the tire, but also with reference to its torsional sensitivity, i.e. in connection with stresses directed tangentially of the circumferential extension of the tire itself.
By adopting particular expedients, as described for example in documents EP 475258 and EP 542252 in the name of the same Applicant, the possibility of restricting, within some limits, the vertical rigidity of the tire sidewall with an inflated tire under running conditions has been achieved. On the other hand, these technical solutions tend to make the tire structure more complicated and heavy and do not appear to be efficient for the purpose of controlling torsional rigidity which has been identified by the Applicant as one of the decisive factors for ride comfort above all at medium/high speeds. In fact, the tire capability of absorbing impacts transmitted by potholes or other unevennesses present on the roadway depends on the torsional rigidity of the tire itself.
The Applicant has also sensed that when the tire runs under normal inflated conditions and, all the more reason, under deflated conditions, the presence of resilient stiffening inserts completely enclosed between two carcass plies imposes strong stresses and/or deformations to the inserts themselves and also to the other constructional components of the tire that are present close to the sidewalls, which will bring about an increase in the operation temperatures and softening of the materials. Due to the above, use of materials having high moduli of elasticity is imposed, which will further reduce ride comfort with an inflated tire.
SUMMARY OF THE INVENTION
In accordance with the present invention it has been found that as regards manufacture of self-supporting tires, unexpected advantages can be achieved if the tire carcass structure is formed with a plurality of strip-like lengths sequentially disposed along the circumferential extension of the tire. In this way it is in fact possible to regulate, depending on requirements, the control degree exerted by the carcass structure on the resilient stiffening inserts present therein.
In more detail, it is an object of the present invention to provide a self-supporting tire for vehicle wheels, characterized in that said at least one carcass ply comprises: axially inner strip-like lengths and axially outer strip-like lengths, said axially inner and axially outer lengths being circumferentially distributed around said rotation axis and extending each in a U-shaped configuration around the cross-section outline of the carcass structure, to define two side portions spaced apart from each other in an axial direction and a crown portion extending at a radially outer position between the side portions, said resilient stiffening inserts being each axially interposed between side portions of the axially inner lengths and side portions of the axially outer lengths.
The presence of axially intermediate strip-like lengths may be also provided and they are circumferentially distributed around said rotation axis and extend each in a U-shaped configuration around the cross-section outline of the carcass structure, to define two side portions that, at an axially outer position, overlap said resilient stiffening inserts, and a crown portion extending at a radially outer position between the side portions; and a pair of auxiliary resilient stiffening inserts each axially interposed between the side portions of the axially intermediate lengths and the side portions of the axially outer lengths.
In more detail, the axially inner lengths can be distributed following a circumferential pitch corresponding to a multiple of their width, the axially intermediate lengths are distributed following a circumferential pitch corresponding to a multiple of
Caretta Renato
Frisiani Luca
Misani Pierangelo
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Johnstone Adrienne C.
Pirelli Pneumatici S.p.A.
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