Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-12-05
2004-09-14
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S539000, C152S544000, C152S547000, C152S550000, C152S552000, C156S133000, C156S135000
Reexamination Certificate
active
06789590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a tire for vehicle wheels, comprising the following steps: forming a carcass structure having at least one carcass ply with terminal zones engaged with respective annular reinforcing structures which are axially spaced from one another; applying a belt structure in a position circumferentially outside the carcass structure; applying a tread band in a position circumferentially outside the belt structure and at least one pair of sidewalls in laterally opposite positions on the carcass structure.
The present invention also relates to a tire for vehicle wheels which can be obtained by means of the above-mentioned method, comprising: a carcass structure having at least one carcass ply with terminal zones engaged with respective annular reinforcing structures axially spaced from one another; a belt structure applied in a position circumferentially outside the carcass structure; a tread band applied in a position circumferentially outside the belt structure; at least one pair of sidewalls applied in laterally opposite positions on the carcass structure.
The invention also relates to a tire wheel comprising a mounting rim provided with bead seats defined by frustoconical surfaces converging towards the axis of rotation of the tire, away from the equatorial plane thereof, and a tire obtained with the method according to the invention provided with beads designed to fit precisely into the above-mentioned seats.
2. Description of the Related Art
The manufacture of tires for vehicle wheels involves the manufacturing of a carcass structure essentially composed of one or more carcass plies shaped in a substantially toroidal configuration and having its axially opposite lateral edges engaged with respective annular reinforcing structures, each of which normally comprises a circumferentially unextendable, metal, annular insert, usually called a bead core, and a filling element made of elastomeric material and combined with the bead core in a radially external position.
The carcass structure has, applied to it, in a circumferentially outer position, a belt structure comprising one or more belt layers formed in a closed ring, which are essentially made up of textile or metal cords suitably oriented relative to each other and to the cords belonging to the adjacent carcass plies. Then, at a circumferentially outer position of the belt structure a tread band is applied, which usually consists of a strip of elastomer material of suitable thickness.
It is to point out that, to the aims of the present description, by the term “elastomer material” it is intended a rubber blend in its entirety, i.e. the assembly formed of at least one base polymer suitably amalgamated with reinforcing fillers and/or process additives of various types.
Ultimately, a pair of sidewalls is applied to the opposite sides of a tire being manufactured, each of said sidewalls covering a side portion of the tire comprised between a so-called shoulder region, arranged close to the corresponding side edge of the tread band, and a so-called bead arranged at the corresponding bead core.
The traditional production methods essentially envisage that the above listed tire components are first made separately from one another, to be then assembled during a step of the tire manufacture.
Production methods have also been proposed, whereby, instead of resorting to the production of semi-finished products, part or all of the carcass structure components are made directly during the tire manufacturing steps.
For example, U.S. Pat. No. 5,453,140, discloses a method and an apparatus which form a carcass ply by laying down, on a toroidal support shaped so as to match the tire, a plurality of cord sections arranged circumferentially in side by side relationship and sequentially obtained by cutting an individual cord supplied from a reel.
For the purposes of manufacturing the annular reinforcing structures, it is also known that, in the vicinity of each of the tire beads, the opposite ends of the individual cords forming a carcass ply are arranged, in an alternate sequence, in axially opposite positions with respect to an annular anchoring insert formed substantially in the manner of a circular crown and composed of coils of metal wire arranged in concentric circumferences, as can be understood from the patent EP 0,664,231 and the patent U.S. Pat. No. 5,702,548.
In the above mentioned art, all the cords forming the carcass ply or plies are however substantially arranged along the neutral axis of resistance to bending of the respective bead. Under this circumstance, the structural strength of the beads must necessarily rely on the rigidity of the filling inserts made of very hard elastomer material incorporated into the bead structure, the behaviour of which is affected by temperature changes due both to environmental factors and to stresses induced during normal operation.
The Applicant has found that important advantages can be achieved both in terms of simplification in the production processes and in terms of improvement of the behavioural features of the tire if the carcass ply or plies are made by suitably laying down strip-like sections on a rigid toroidal support, each comprising a plurality of cords parallel to each other, incorporated into an elastomer layer.
In this connection, the Applicant has already developed different manufacturing methods being the object of respective European Patent Applications.
For instance, in European Patent Application Nos. 97830731.2 (EP 0928680) and 97830733.8 (EP 0928702) a manufacturing method and a tire are respectively disclosed in which the carcass structure is obtained by making a first and a second carcass plies, each obtained by means of strip-like sections sequentially laid down in circumferential mutual side by side relationship.
Tires obtained following the method described in such patent applications have the end portions of the strip-like sections belonging to the first and second carcass plies disposed on respectively opposite sides relative to the annular reinforcing structures of the beads.
This expedient, in combination with the respectively crossed orientation of the strip-like sections belonging to one and the other plies, offers considerable advantages in terms of structural strength of the tire close to the beads and sidewalls.
In the European Patent Application No. 98830472.1(EP0976535), in the name of the Applicant as well, accomplishment of a carcass ply is proposed which is made by laying down a first and a second series of strip-like sections in an alternate sequence, the sections belonging to the first and second series terminating at respectively opposite sides relative to the bead reinforcing structures.
Thus, advantages can be achieved in terms of structural strength at the tire beads and sidewalls, even in the presence of a single carcass ply.
Usually tire beads, and in particular the annular reinforcing structures integrated thereinto, are conceived and shaped in a manner suitable for coupling with the respective circumferential seats provided on a rim with which the tire is to be associated, for the purpose of ensuring a steady connection between these two wheel components.
In greater detail, the engagement between each bead and the corresponding circumferential seat of the rim is such that the bead is constantly pushed, owing to the inflation pressure of the tire, against an abutment shoulder projecting radially away from the axis of rotation of the tire and defining the axially external edge of the rim. At least in tubeless tires, i.e. those without inner tubes, each circumferential seat for engagement of the bead has a frustoconical surface—usually called a “bead seat”—having an extension converging towards the rotation axis into the vicinity of the equatorial plane of the tire. Each bead, which is pushed axially away from the equatorial plane owing to the inflation pressure, acts in an axial thrust relationship against the respective bead seat so as to ensu
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Johnstone Adrienne C.
Pirelli Pneumatici S.p.A.
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