Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-07-30
2004-07-20
Knable, Geoffrey L. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S540000, C152S541000, C152S546000, C152S547000, C156S117000
Reexamination Certificate
active
06763868
ABSTRACT:
The present invention relates to a method of manufacturing a carcass structure for tyres, in particular for two-wheeled vehicles, comprising the steps of: preparing strip-like sections each comprising longitudinal and parallel thread-like elements at least partly coated with at least one layer of raw elastomer material; making at least one carcass ply by laying down and circumferentially distributing said strip-like sections on a toroidal support, each of said strip-like sections extending in a U-shaped configuration around the cross-section outline of the toroidal support, to define two side portions mutually spaced apart in an axial direction, and a crown portion extending at a radially outer position between the side portions; applying annular reinforcing structures to an area close to inner at circumferential edges of said at least one carcass ply.
The invention also relates to a carcass structure for tyres obtainable by the above mentioned method, said carcass structure comprising: at least one carcass ply comprising strip-like sections circumferentially distributed around a geometric rotation axis, and each comprising at least two thread-like elements disposed longitudinally and parallelly of each other and at least partly coated with at least one layer of raw elastomer material, each of said strip-like sections extending in a substantially U-shaped conformation 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.
Accomplishment of tyres for vehicle wheels involves formation of a carcass structure essentially made up of one or more carcass plies of a substantially toroidal conformation and having their axially opposite side edges in engagement with respective circumferentially-inextensible annular reinforcing elements, usually called “bead rings”.
Applied to the carcass structure, at a circumferentially outer position thereof, is a belt structure comprising one or more belt strips in the form of a closed ring, essentially consisting of textile or metal cords suitably oriented relative to each other and to the cords belonging to the adjacent carcass plies.
A tread band currently consisting of a strip of elastomer material of appropriate thickness is applied to the belt structure, at a circumferentially external position thereof.
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, that is the assembly made up of at least one polymer base suitably amalgamated with reinforcing fillers and/or process additives of various types.
Finally, to the opposite sides of the tyre being manufactured a pair of sidewalls is applied, each of them covering a side portion of the tyre included between a so-called shoulder region, located close to the corresponding side edge of the tread band, and a so-called bead located at the corresponding bead ring.
In accordance with traditional production methods, essentially, the above listed tyre components are first made separately from each other, to be then assembled during a tyre-manufacturing step.
It is the Applicant's feeling that these production methods are so far at least partly unsatisfactory in terms of quality of the finished product, and that they have some critical points as regards accomplishment of the process which is complicated and hardly governable.
For instance, for making the carcass ply or plies to be associated with the bead rings so as to form the carcass structure, it is required that, by an extrusion and/or calendering process, a rubberized fabric comprising longitudinally-disposed continuous textile or metal cords should be first produced. This rubberized fabric is submitted to a transverse-cutting operation to produce sections of predetermined sizes that are subsequently joined together so as to give origin to a continuous ribbon-like semifinished product, having transversely-disposed parallel cords.
This article of manufacture will be then cut into sections the length of which is correlated with the circumferential extension of the carcass to be made.
Production methods have been also proposed which, instead of resorting to the production of semifinished products, make the carcass structure directly during the tyre-manufacturing step.
For example, U.S. Pat. No. 5,362,343 discloses a method and an apparatus forming a carcass ply starting from a single cord previously wound around a reel.
According to the method and apparatus described in the above patent, at each operating cycle of the apparatus the cord drawn from the reel by power-driven idler rollers and maintained taut by a pneumatic tensioning system is cut to size to obtain a section of predetermined length.
The cord section is picked up by a pick-up element mounted on a belt wound over power-driven pulleys to be extended transversely on the outer surface of a toroidal support.
The section ends are then engaged by bending members of the belt type operating on the opposite sides of the toroidal support for radially applying the cord section to the toroidal support by means of slide elements acting like fingers along the side portions of the cord section.
Repetition of the above described operating cycle leads to deposition of a number of cord sections circumferentially disposed in side by side relationship until the whole circumferential extension of the toroidal support has been covered.
Necessarily, the toroidal support is previously coated with a layer of raw rubber having a dual function, i.e. that of adhering to the cords deposited thereon so as to conveniently hold them in a fixed positioning, and that of constituting an air-proof inner liner in the finished tyre.
Tyres obtained by this production method have a carcass structure in which the carcass ply or plies consist of individual cords each having two side portions axially spaced apart from each other and oriented radially of the rotation axis of the tyre, and a crown portion extending at a radially outer position between the side portions.
Within the scope of the carcass structure manufacture, it is also known that close to each of the tyre beads, the opposite ends of the individual cords forming a carcass ply are arranged, in an alternating sequence, at axially opposite positions relative to an annular anchoring element forming said bead ring, having the form of a crown made up of wire coils radially superposed on each other, as can be seen from patent EP 0 664 231 and patent U.S. Pat. No. 5,702,548. According to the teachings of these documents, a filling body of elastomer material is necessarily interposed between the anchoring annular insert and the threads or wires forming the carcass ply or plies.
In patent FR 384 231, to which referrence is herein made as an example of the most pertinent state of the art, accomplishment of a carcass structure is proposed which involves deposition, on a toroidal support, of a series of rectangular small bands of rubberized fabric circumferentially disposed in side by side relationship and arranged in radial planes relative to the geometric axis of the support drum itself. Deposition of the small bands is carried out in such a manner that the end flaps of two non-consecutive small bands are partly covered with the end flaps of the small band interposed therebetween. The existing spaces between the end flaps covered with the small bands are filled with trapezoidal inserts applied to the end flaps of the small band placed in an overlapping position thereon. Deposition of the small bands is carried out in different superposed layers, the number of which is correlated with the thickness to be given to the carcass structure. The presence of said trapezoidal inserts gives rise to thickening of the carcass structure at the bead regions so that thickness at the bead rings is twice that at the crown.
In U.S. Pat. No. 4,248,287 a method is disclosed according to which formation of the carcass structure contemplat
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Knable Geoffrey L.
Pirelli Pneumatici S.P.A.
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