Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-07-30
2002-01-08
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C152S453000, C156S121000, C156S130000, C156S133000, C156S135000, C156S156000
Reexamination Certificate
active
06336985
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a method of making a tire for vehicle wheels, comprising the steps of: forming an air tube of toroidal conformation, having a transverse profile in the form of a closed ring; covering the air tube with a carcass structure, accomplishment of which involves winding of at least one first thread element around the transverse profile of the air tube so as to form first turns disposed consecutively in side-by-side relationship along the circumferential extension of the air tube to define a first carcass ply integrally covering the air tube; and associating a circumferentially-inextensible belt structure and a tread band circumferentially external to the belt structure with the carcass structure at a radially-outer position.
In accordance with the invention, this method leads to achievement of a tire for vehicle wheels of the type comprising: an air tube or inflatable core of toroidal conformation, having a transverse profile in the form of a closed ring; a carcass structure comprising at least one first carcass ply formed of at least one first thread element wound around the transverse profile of the air tube to form first turns disposed consecutively in side-by-side relationship along the circumferential extension of the air tube; a pair of annular elements for anchoring to a rim, axially spaced apart from each other and extending circumferentially on the air tube surfaces at a radially-inner position; a belt structure circumscribing the carcass structure at a radially-outer position relative to the rotation axis of the tire; and a tread band disposed circumferentially at a radially-outer position relative to the belt structure. Still in accordance with the invention said tire can be coupled with one said rim of the type comprising a central portion for engagement with a hub of a vehicle wheel, and engagement means for said tire; the invention further relates to a wheel consisting of said tire and rim assembly.
It is known that tires for vehicle wheels currently have a toroidal conformation the profile of which seen in cross-section is open on its circumferentially-inner side. In more detail, the tire profile seen in cross-section is delimited between two inner circumferential edges defined by corresponding beads axially spaced apart from each other. An inextensible annular element, usually referred to as a bead core, is integrated into each bead and an elastomer filling, usually obtained by extrusion, is to be circumferentially applied to the outer surface of said bead core.
Turned up around the cross-sectional profile of the bead cores are the flaps of one or more carcass plies. Each carcass ply is made up of a plurality of textile cords disposed parallelly in side-by-side relationship and incorporated in an elastomer layer produced with the aid of appropriate calenders fed from an extrusion die. The rubberized fabric obtained from this step is then transversely cut into pieces of the desired length that are subsequently joined together at the respective side edges, optionally by slight mutual overlapping, in order to make a rubberized ply having transversely-disposed textile cords.
The assembly formed of one or more of said carcass plies and the bead cores with the respective elastomer filling form the so-called carcass structure of a tire.
Applied to the carcass structure, at a circumferentially-outer position, is a circumferentially-inextensible belt structure, comprising one or more superposed strips of rubberized fabric formed of textile and/or metallic cords. Circumferentially superposed on the belt structure is a tread band obtained by extrusion, by means of which the tire gets into contact with the ground.
Beads are so structured and shaped that they interact with respective circumferential portions of a rim with which the tire is associated to ensure a steady connection between these two components of a wheel.
In more detail, coupling between the bead and the corresponding circumferential portion of the rim enables the bead to be constantly pushed against an abutment flange by effect of the tire inflation pressure. In tubeless tires, that is, tires devoid of an air tube, coupling between the bead and the corresponding circumferential rim portion is conceived in such a manner that a hermetic seal of the air contained in the tire is also ensured.
In any case, both in tubeless tires and in tires providing employment of an air tube, the task of counteracting the inner inflating pressure of the tire relies on the rim.
In addition to the above described tires having a transverse profile of open section, use of which is almost universally spread for all types of road vehicles, several types of tire of a transverse sectional profile in the form of a closed ring have been proposed. For example, U.S. Pat. No. 4,232,723 discloses a tire having an air tube and a carcass structure essentially comprising a ribbon ply reinforced with radial threads which extends in the circumferential extension of the tire and is wound by its end flaps around the air tube so as to cover it over the whole transverse sectional profile thereof. A belt structure is interposed between the carcass ply and the air tube, at a circumferentially-outer position relative to the air tube; said belt structure has a substantially flat profile in cross-section and is essentially formed of one or more strips extending circumferentially of the tire and turned up around two inextensible annular elements located at the region usually referred to as the tire shoulder.
Coupling between the tire and rim is obtained by a circumferential ridge of one piece construction with the elastomer material forming the tire sidewalls, and extending at a radially internal and centered position relative to the tire.
Another type of tire having a closed cross-sectional profile is disclosed in U.S. Pat. No. 4,283,366, herein reported as an example of the most relevant state of the art in connection with the present invention.
This tire comprises an air tube having a substantially oval sectional profile, a pair of bead cores axially spaced apart from each other and located directly in contact with the air tube, on the side thereof turned towards the tire axis. The assembly formed of the air tube and bead cores is enclosed in a carcass structure essentially formed of a cord spirally-wound about the cross-sectional profile of the air tube. The cord thus wound forms a plurality of turns disposed consecutively in side-by-side relationship along the circumferential tire extension and oriented in respective planes substantially radial to the rotation axis of the tire itself.
Applied to the air tube at a radially-outer position thereof is a belt comprising one or more circumferentially-inextensible belt strips on which the tread band is superposed.
During the carcass structure formation, as well as during the following steps of the construction process, the air tube in a raw state is maintained to its toroidal conformation by an inner core susceptible of disintegration, said core giving the air tube sufficient consistency so as to enable it to bear any type of handling. This core, essentially consisting of powders aggregated by a binder, is disintegrated after vulcanization of the tire and the remaining powders are removed from the air tube through one or more tire inflating valves.
Use of a sufficiently rigid inner core susceptible of disintegration was made necessary in order to enable winding of the carcass cord around the air tube already shaped in an oval form, because the alternative solution of inflating the air tube to give it the necessary consistency during the tire construction steps inevitably caused the air tube to acquire a cross-section circular shape. To the ends of the present invention it is pointed out that “oval” and “elliptic” as herein considered are substantially equivalent terms.
The Applicant has become aware of the fact that laying down of the cord on the air tube having a circular shape in section would involve a variation in the radius of curvature of
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Knable Geoffrey L.
Pirelli Coordinamento Pneumatici S.p.A.
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