Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
2001-05-18
2003-04-29
Johnstone, Adrienne C. (Department: 1733)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C152S451000
Reexamination Certificate
active
06555212
ABSTRACT:
BACKGROUND AND BRIEF SUMMARY OF THE INVENTION
The present invention relates to articles made from elastomer-based material, defined in a general way in the remainder of the present description as elastomeric material or rubber compound; it relates specifically to the rubberized fabrics used for making the said articles and the corresponding reinforcing elements, and is more particularly concerned with pneumatic tires for vehicle wheels.
Rubberized fabrics are a semi-finished product of the greatest importance for the manufacture of products from elastomeric material: in general, they comprise a plurality of filamentary reinforcing elements having at least tensile strength, all being disposed parallel and adjacent to each other, and completely embedded in a sheet of rubber compound.
The said fabric is produced in the form of a continuous piece whose length is indefinite, in other words is far greater than its width, by incorporating in a layer of rubber compound, by known means and processes, the said reinforcing elements orientated in the longitudinal direction of the piece.
The piece is then cut transversely into portions of various sizes, with an angle of cut predetermined as necessary, and these portions are joined side by side to produce a continuous strip of fabric with reinforcing elements orientated at an angle of predetermined value with respect to the longitudinal direction of the strip.
Portions of appropriate size of the said strip form the textile elements used in the making of the product, assembled with other constituent elements of the product: for example, in the case of a pneumatic tire, as will be seen subsequently, these textile elements form the casing ply, the belts, rims, loops and other reinforcing fabrics disposed in various ways in the structure of the pneumatic tire.
The use of rubberized fabric enables the reinforcing elements to be disposed within the structure of the product, by the desired method and in the desired position, in a precise, simple and economical way.
The said filamentary reinforcing elements may be made from many different materials, textile or metal, natural or synthetic, and may consist either of monofilaments, in other words single wires or strands, or bundles of monofilaments placed together, or cords comprising a plurality of strands or bundles of monofilaments wound spirally with respect to each other in predetermined configurations.
In the present description, the word “wire” denotes the normal metal wire used in pneumatic tire technology, while the word “monofilament” or “floss” denotes textile fibres, natural or synthetic, which are also commonly used in the technology of rubber products.
Articles incorporating these reinforcing fabrics are, for example, pneumatic tires, transmission belts, conveyor belts and hoses for carrying fluids which may be pressurized.
The performance of rubber articles, in terms of service life, mechanical strength and, in the case of pneumatic tires, road performance, depends principally on the mechanical characteristics of the reinforcing elements which have the function of withstanding the stresses put upon it, which, in the case of a pneumatic tire, include the inflation pressure and the stresses arising from use on the road.
The pneumatic tire to which the invention relates comprises, in a general way, a casing of toroidal shape substantially consisting of at least one rubberized fabric (casing ply) having its edges wrapped around a pair of annular metal cores which are circumferentially inextensible (the ordinary bead cores), a tread band disposed on the crown of the said casing and a breaker structure interposed between the casing and the tread, formed by one or more radially superimposed layers of rubberized fabric (belts), wherein the said rubberized fabrics comprise a plurality of reinforcing elements, in other words the conventional cords, which have at least tensile strength, are parallel and adjacent to each other and orientated in a predetermined direction, and are incorporated in a sheet of rubber compound.
More precisely, the cords of the casing ply preferably lie in radial planes including the axis of rotation of the tire, while the cords of the belts preferably lie at angles to each other in adjacent belts and may be orientated parallel to the equatorial plane of the tire in the radially outermost belt.
In tires for motor vehicles, the said cords are preferably of the textile type in the casing ply and in the radially outermost belt, while they are metal cords in the radially innermost belts.
The textile cords are identified by a numerical symbol which represents the count of the fibre used and the number of strands used to form the cord. The term “strand” indicates a bundle of flosses or monofilaments twisted together; the term “count” indicates the weight in grams of a length of 10,000 meters of fibre, expressed in dTex units, or the weight in grams per length of 9000 meters, expressed in deniers.
At the present time, the textile cords used in rubberized fabrics for pneumatic tires comprise two or three strands twisted together and have a count in excess of 900 dTex units: for example, rayon cords with a count of 1840/2, 1840/3 or 2440/2, nylon6 or nylon66 cords with a count of 940/2 and 1400/2, or synthetic fibre (aramid or polyester) cords with a count of 1670/2, 1100/2 or 2440/2 are used for casing fabrics.
Known cords usually have diameters of the order of 0.7 mm and are incorporated in fabrics which have fabric thicknesses of approximately 1 mm, with a density of cords in the fabric of between 60 and 120 cords/dm, in other words cords per decimeter.
Fabrics for pneumatic tires reinforced with the said cords and corresponding tires are described, for example, in U.S. Pat. Nos. 3,616,832 and 3,929,180.
More particularly, U.S. Pat. No. 3,616,832 describes a tire with a radial casing formed by two casing plies provided with rayon cords with a count of 1650/2 denier and a density of 38 cords per 5 cm, in other words 76 cords/dm.
The belt assembly is formed by four fabric belts with rayon cords with a count of 1650/3 denier and 30 cords per 5 cm, in other words 60 cords/dm.
The tire is compared with another tire comprising the same rayon casing and a belt assembly formed by four fabric belts provided with cords of polyethylene naphthalene 2,6-dicarboxylate, known as PEN, with a count of 2000/2 denier, distributed with a density of 30 cords per 5 cm, in other words 60 cords/dm.
The cited patent describes, as an alternative to the rayon casing and with the same breaker structure with PEN cords, further casings with the same number of plies, comprising in one case polyethylene terephthalate, known as PET, fibre cords with a count of 1000/3 denier and a density of 35 cords per 5 cm, in other words 70 cords/dm, and in a second case having nylon6 cords with a count of 1260/2 denier and a density of 33 cords per 5 cm, in other words 66 cords/dm.
U.S. Pat. No. 3,929,180 describes, with a series of comparative examples, two pneumatic tires, both having a radial casing formed by two plies reinforced with 35 cords per 5 cm; the casing of the first tire comprises rayon cords having a count of 1650/3 denier, and that of the second has PEN cords with a count of 2000/2 denier. In both tires, the belt assembly is formed by four fabric belts with PEN cords having a count of 1000/2 denier, distributed with a density of 35 cords per 5 cm.
Given all this, the present development of pneumatic tire technology towards increasingly specialized products capable of providing increasingly high performance is a powerful stimulus to the search for increasingly lightweight tires.
In this context, the applicant became aware that one contribution to the solution of the problem might lie in the reduction of the weight of the pneumatic tire casing, though naturally without negative effects on the characteristics of mechanical strength and of the behaviour of the tire in use, and particularly on directional stability and comfort.
In this regard, it should be noted that the problem faced here is neither simple nor
Boiocchi Maurizio
Orjela Gurdey
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Johnstone Adrienne C.
Pirelli Coordinamento Pneumatici S.p.A.
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