Title: Self-supporting tyre for vehicle wheels and method for manufacturing the same
Abstract: A self-supporting tyre (1) has reinforcing structures at the beads (4) defining rest surfaces (4a) for a corresponding rim (1a) which have a profile converging towards the tyre rotation axis away from the equatorial plane (X-X) of the tyre itself. The carcass plies (3a, 3b) are each made by sequential deposition of strip-like sections circumferentially distributed on a toroidal support (11). Elastic-support inserts (16, 21) are interposed between the side portions (13a, 14a) of axially internal sections (13), axial intermediate sections (15). In this manner around at least one of said support inserts opening degree of which can be modulated depending on requirements, by modifying the land/empty space ratio determined by the distance existing between the side portions (13a, 14a, 15a) of the strip-like sections (13, 14, 15) covering each of the axially opposite sides of the support insert itself.
Patent Number: 7,025,846 Issued on 04/11/2006 to Caretta
| Inventors:
|
Caretta; Renato (Gallarate (Varese), IT)
|
| Assignee:
|
Pirelli Pneumatici S.p.A. (Milan, IT)
|
| Appl. No.:
|
451390 |
| Filed:
|
December 3, 2001 |
| PCT Filed:
|
December 3, 2001
|
| PCT NO:
|
PCT/EP01/14100
|
| 371 Date:
|
June 23, 2003
|
| 102(e) Date:
|
June 23, 2003
|
| PCT PUB.NO.:
|
WO01/36185 |
| PCT PUB. Date:
|
May 25, 2001 |
Foreign Application Priority Data
| Current U.S. Class: |
156/110.1; 152/516; 152/517; 152/539; 152/548; 156/123; 156/133 |
| Current Intern'l Class: |
B60C 17/00 (20060101); B60C 17/04 (20060101); B29D 30/00 (20060101); B29D 30/08 (20060101) |
| Field of Search: |
152/516,517,539
156/110.1
|
References Cited [Referenced By]
U.S. Patent Documents
| 4215735 | Aug., 1980 | Sato.
| |
| 5634993 | Jun., 1997 | Drieux et al.
| |
| 5871602 | Feb., 1999 | Paonessa et al.
| |
| 5968294 | Oct., 1999 | Willard et al.
| |
| 5971047 | Oct., 1999 | Drieux et al.
| |
| 6374888 | Apr., 2002 | Willard et al.
| |
| 6814119 | Nov., 2004 | Caretta et al.
| |
| Foreign Patent Documents |
| 0 475 258 | Mar., 1992 | EP.
| |
| 0 542 252 | May., 1993 | EP.
| |
| 0 884 110 | May., 1998 | EP.
| |
| 0 919 406 | Jun., 1999 | EP.
| |
| 0 928 680 | Jul., 1999 | EP.
| |
| 0 928 702 | Jul., 1999 | EP.
| |
| 0 976 535 | Feb., 2000 | EP.
| |
| 2087805 | Jun., 1982 | GB.
| |
| WO 99/6422/5 | Dec., 1999 | WO.
| |
| WO 00/3566/6 | Jun., 2000 | WO.
| |
| WO 00/3890/6 | Jul., 2000 | WO.
| |
| WO 01/3618/5 | May., 2001 | WO.
| |
Primary Examiner: Copenheaver; Blaine
Assistant Examiner: Fischer; Justin
Attorney, Agent or Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national-phase entry under 35 U.S.C. § 371 from International
Application No. PCT/EP01/14100, filed Dec. 3, 2001, in the European Patent Office,
the contents of which are relied upon and incorporated herein by reference; additionally,
Applicant claims the right of priority under 35 U.S.C. § 119(a)-(d) based
on patent application No. 00830845.4, filed Dec. 22, 2000, in the European Patent
Office; further, Applicant claims the benefit under 35 U.S.C. § 119(e) based
on provisional application No. 60/265,616, filed Feb. 2, 2001, in the U.S. Patent
and Trademark Office.
Claims
The invention claimed is:
1. A self-supporting tyre for vehicle wheels, comprising:
a carcass structure having at least one carcass ply provided with end flaps in
engagement with respective annular reinforcing structures disposed in coaxial relationship
with a rotation axis of the tyre at positions axially spaced apart from each other
and each incorporated into a tyre bead, at least one of said beads exhibiting,
at a radially internal position thereof, a rest surface that, in a diametrical
section plane of the tyre, defines a profile converging towards the rotation axis
of the tyre and away from an equatorial plane of the tyre;
a belt structure applied to the carcass structure at a radially external position thereof;
a tread band applied to the belt structure at a radially external position thereof;
at least one pair of sidewalls each extending between one of said beads and a
side edge of the tread band, at a position axially external to the carcass structure;
at least one pair of elastic-support inserts incorporated into the carcass structure,
each at one of said sidewalls;
wherein the elastic-support inserts have respective radially internal apices
placed close to the beads, and radially external apices close to side edges of
the tread band,
wherein said at least one carcass ply comprises axially internal strip-like sections
and axially external strip-like sections,
wherein the axially internal and axially external strip-like sections are circumferentially
distributed around said rotation axis and each extends in a "U"-shaped configuration
around the cross-section profile of the carcass structure, to define: two side
portions mutually spaced apart in an axial direction, and a crown portion extending
at a radially external position between the side portions,
wherein said elastic-support inserts are each axially interposed between side
portions of the axially internal sections and side portions of the axially external sections.
2. A tyre as claimed in claim 1, further comprising:
axially intermediate strip-like sections circumferentially distributed around
said rotation axis and each extending in a "U"-shaped configuration around the
cross-section profile of the carcass structure to define two side portions overlapping,
at an axially external position,
wherein the elastic-support inserts comprise:
a crown portion extending in a radially external position between the side portions, and
a pair of auxiliary elastic-support inserts each axially interposed between the
side portions of the axially intermediate sections and the side portions of the
axially external sections.
3. A tyre as claimed in claim 2, wherein:
the axially internal sections are distributed according to a circumferential
pitch corresponding to a multiple of their width;
the axially intermediate sections are distributed according to a circumferential
pitch corresponding to a multiple of their width and each have the respective crown
portion interposed in circumferential approaching relationship between the crown
portion of two axially internal sections, to define a first carcass ply therewith; and
the axially external sections are distributed according to a circumferential
pitch substantially corresponding to their width, to define a second carcass ply
radially superposed on the first carcass ply close to said crown portions.
4. A tyre as claimed in claim 2, further comprising:
a second axially intermediate strip-like sections circumferentially distributed
around said rotation axis and each extending in a "U"-shaped configuration around
the cross-section profile of the carcass structure to define two side portions
partly overlapping, at an axially external position, the side portions of the first
axially intermediate sections; and
a crown portion extending in a radially external position between the respective
side portions.
5. A tyre as claimed in claim 2, wherein:
the axially internal sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of their width;
the first axially intermediate sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections, with the respective crown portion interposed in
circumferential approaching relationship between the crown portions of two axially
internal sections, to define a first carcass ply therewith;
a second axially intermediate sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections; and
the axially external sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections, with the respective crown portion interposed in
circumferential approaching relationship between the crown portions of two of said
second axially intermediate sections, to define a second carcass ply therewith,
which second carcass ply is radially superposed on the first carcass ply close
to said crown portions.
6. A tyre as claimed in claim 2, wherein:
the axially internal sections are distributed according to a circumferential
pitch substantially corresponding to a width of each of the first axially intermediate
sections, to define a first carcass ply;
the axially intermediate sections are distributed according to a circumferential
pitch corresponding to a multiple of a width of each of the first axially intermediate
sections; and
the axially external sections are distributed according to a circumferential
pitch corresponding to a multiple of a width of each of the first axially intermediate
sections and each have the respective crown portion interposed in a circumferential
approaching relationship between the crown portions of two axially intermediate
sections, to define a second carcass ply therewith, said second carcass ply is
radially superposed on the first carcass ply close to said crown portions.
7. A tyre as claimed in claim 2, wherein the axially internal, intermediate and
external sections respectively, are distributed according to a circumferential
distribution pitch which is a multiple of a width of each of the first axially
intermediate sections, in accordance with a numerical factor corresponding to the
number of series of inner, intermediate and outer sections provided in forming
said at least one carcass ply.
8. A tyre as claimed in claim 7, wherein the crown portions of the individual
inner, intermediate and outer sections are sequentially interposed in a mutual
approaching relationship along a circumferential line, whereas the respective side
portions are axially offset from each other to house at least one of said elastic-support
inserts in empty spaces or gaps existing between the side portions of the inner
and intermediate sections and between the side portions of the intermediate and
outer sections.
9. A tyre as claimed in claim 2, wherein:
the axially internal sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections;
the axially intermediate sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections and each have the respective crown portion disposed
circumferentially close to the crown portion of an axially internal section; and
the axially external sections are distributed according to a circumferential
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections, each with its crown portion in circumferential approaching
relationship between the crown portion of one of the axially internal sections
and the crown portion of one of the axially intermediate sections, to define said
at least one carcass ply therewith.
10. A tyre as claimed in claim 1, wherein the axially internal sections are distributed
according to a circumferential pitch substantially corresponding to a multiple
of a width of each of the first axially intermediate sections, the axially external
sections each having the respective crown portion interposed in circumferential
approaching relationship between the crown portions of two axially internal sections.
11. A tyre as claimed in claim 1, wherein the axially internal sections and axially
external sections are distributed according to a circumferential pitch corresponding
to the width of each section, to define a first carcass ply and a second carcass
ply respectively, the second carcass ply being radially superposed on the first
carcass ply close to said crown portions.
12. A tyre as claimed in claim 1, further comprising a pair of auxiliary elastic-support
inserts each disposed at an axially internal position with respect to the axially
internal sections.
13. A tyre as claimed in claim 1, wherein each of said strip-like sections substantially
extends in a plane parallelly offset from a meridian plane of the tyre, so that
the respective crown portion, with respect to a radial reference plane passing
through the transition point between the crown portion itself and at least one
of the corresponding side portions, is oriented so that the crown portion forms
an angle of a value different from the inclination of the side portions.
14. A tyre as claimed in claim 13, wherein the axially internal sections and
axially external sections lie in deposition planes that at respectively opposite
sides are offset from said meridian plane, so that at least the side portions of
the axially internal sections have a crossed orientation relative to the side portions
of the axially external sections.
15. A tyre as claimed in claim 1, wherein at least one of said annular reinforcing
structures comprises:
at least one stiffening element applied against said at least one carcass ply
and having a cross-section profile extending away from the rotation axis of the
tyre; and
at least one annular circumferentially-inextensible anchoring insert having a
cross-section profile of flattened conformation, extending axially away from the
stiffening element in a direction converging towards the geometric rotation axis
of the tyre, away from the equatorial plane thereof.
16. A tyre as claimed in claim 15, wherein the cross-section profile of the annular
reinforcing structure has a geometric centre of gravity located at such a position
that an axially external end edge of said annular anchoring insert is pushed towards
the rotation axis of the tyre following a tension generated along said at least
one carcass ply by effect of an inflation pressure of the tyre.
17. A tyre as claimed in claim 15, wherein the cross-section profile of the annular
reinforcing structure has a geometric centre of gravity located at an axially external
position with respect to said stiffening element and at an axially internal position
with respect to an axially external end edge of said annular anchoring insert.
18. A tyre as claimed in claim 15, wherein said stiffening element is axially
positioned between a respective axially internal end flap and a respective axially
external end flap of said at least one carcass ply.
19. A tyre as claimed in claim 15, wherein said annular anchoring insert is applied
against an end portion of an outer end flap of the carcass ply, said end portion
extending axially away from the equatorial plane of the tyre.
20. A tyre as claimed in claim 19, wherein said annular anchoring insert is applied
at a radially external position with respect to said end portion of the outer end flap.
21. A tyre as claimed in claim 15, wherein said annular anchoring insert is disposed
substantially close to a radially internal edge of the stiffening element.
22. A tyre as claimed in claim 18, further comprising at least one auxiliary
annular anchoring insert parallel to and radially close to said annular anchoring insert.
23. A tyre as claimed in claim 22, wherein said auxiliary anchoring insert is
applied at a radially external position with respect to an end portion of said
inner end flap, extending axially away from an equatorial plane of the tyre.
24. A tyre as claimed in claim 23, wherein said auxiliary anchoring insert is
applied at a radially internal position relative to said end portion of the outer
end flap.
25. A tyre as claimed in claim 15, further comprising at least one auxiliary
circumferentially-inextensible stiffening element having a cross-section profile
radially extending at an axially internal position relative to said stiffening element.
26. A method of manufacturing a self-supporting tyre for vehicle wheels, comprising
the steps of:
preparing a carcass structure having at least one carcass ply provided with end
flaps in engagement with respective annular reinforcing structures disposed in
coaxial relationship with a rotation axis of the tyre at positions axially spaced
apart from each other and each incorporated into a tyre bead, wherein the at least
one of said beads exhibiting, at a radially internal position thereof, a rest surface
that, in a diametrical section plane of the tyre, defines a profile converging
towards the rotation axis of the tyre and away from an equatorial plane of the tyre;
wherein preparation of the carcass structure comprises:
arranging strip-like sections, each comprising longitudinal and parallel thread-like elements;
laying down axially internal strip-like sections circumferentially distributed
on the toroidal support, each of said axially internal strip-like sections extending
in a "U"-shaped configuration around the cross-section profile of the toroidal
support, to define two side portions that are mutually spaced apart in an axial
direction, and a crown portion extending in a radially external position between
the side portions;
applying at least one pair of elastic-support inserts at an axially external
position to the side portions of the axially internal sections, each at one of
said sidewalls, wherein the elastic-support inserts have respective radially internal
apices placed close to the beads, and radially external apices placed close to
side edges of the tread band;
laying down axially external strip-like sections circumferentially distributed
on the toroidal support, each of said axially external sections extending in a
"U"-shaped configuration around the cross-section profile of the toroidal support,
to define two side portions mutually spaced apart in an axial direction, each extending
in an axially external position relative to one of the elastic-support inserts,
and a crown portion extending in a radially external position between the side portions;
applying a belt structure to the carcass structure at a radially external position thereof;
applying a tread band to the belt structure at a radially external position thereof; and
applying a pair of sidewalls to the carcass structure, at laterally opposite
positions of the latter, each of said sidewalls extending between one of said beads
and a side edge of the tread band.
27. A method as claimed in claim 26, wherein before deposition of the axially
external sections the following further steps are carried out:
laying down axially intermediate strip-like sections circumferentially distributed
around said rotation axis and each extending in a "U"-shaped configuration around
the cross-section profile of the carcass structure to define two side portions
overlapping, in an axially external position, said elastic-support inserts, and
a crown portion extending in a radially external position between the side portions; and
applying a pair of auxiliary elastic-support inserts, at an axially external
position, to the side portions of the axially intermediate sections, before deposition
of the axially external sections.
28. A method as claimed in claim 27, wherein:
the axially internal sections are laid down according to a circumferential distribution
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections;
the axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of a width of each
of the first axially intermediate sections, with the respective crown portion interposed
in a circumferential approaching relationship between the crown portions of two
axially internal sections, to define a first carcass ply therewith; and
the axially external sections are laid down according to a circumferential distribution
pitch substantially corresponding to a width of each of the first axially intermediate
sections, to define a second carcass ply therewith, said carcass ply being radially
superposed on the first carcass ply.
29. A method as claimed in claim 28, wherein before application of said auxiliary
elastic support insert, and wherein the axially intermediate strip-like sections
are first axially intermediate strip-like sections, the method comprising:
laying down second axially-intermediate strip-like sections circumferentially
distributed around said rotation axis and each extending in a "U"-shaped configuration
around the cross-section profile of carcass structure to define two side portions
partly overlapping, at an axially external position, the side portions of the first
axially intermediate sections being previously laid down, and a crown portion extending
in a radially external position between the respective side portions.
30. A method as claimed in claim 29, wherein:
the axially internal sections are laid down according to a circumferential distribution
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections;
the first axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of a width of each
of the first axially intermediate sections, each having the respective crown portion
interposed in a circumferential approaching relationship between the crown portions
of two axially internal sections, to define a first carcass ply therewith;
the second axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of a width of each
of the first axially intermediate sections; and
the axially external sections are laid down according to a circumferential distribution
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections, each having the respective crown portion interposed
in a circumferential approaching relationship between the crown portions of two
of said second axially intermediate sections, to define a second carcass ply therewith.
31. A method as claimed in claim 27, wherein:
the axially internal sections are laid down according to a circumferential distribution
pitch substantially corresponding to a width of each of the first axially intermediate
sections, to define a first carcass ply;
the axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of a width of each
of the first axially intermediate sections; and
the axially external sections are laid down according to a circumferential distribution
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections, each having the respective crown portion interposed
in a circumferential approaching relationship between the crown portions of two
of said intermediate sections, to define a second carcass ply therewith, which
carcass ply is radially superposed on the first carcass ply close to said crown portions.
32. A method as claimed in claim 27, wherein:
the axially internal sections are laid down according to a circumferential distribution
pitch substantially corresponding to a multiple of a width of each of the first
axially intermediate sections;
the axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of a width of each
of the first axially intermediate sections, each having the respective crown portion
disposed circumferentially close to the crown portion of an axially internal section; and
the axially external sections are laid down according to a circumferential pitch
substantially corresponding to a multiple of a width of each of the first axially
intermediate sections, each having its crown portion in circumferential approaching
relationship between the crown portion of one of the axially internal sections
and the crown portion of one of the axially intermediate sections, to define said
at least one carcass ply therewith.
33. A method as claimed in claim 26, wherein the axially internal sections are
distributed according to a circumferential pitch substantially corresponding to
a multiple of a width of each of the first axially intermediate sections, the axially
external sections being each laid down with the crown portion in circumferential
approaching relationship between the crown portions of two axially internal sections.
34. A method as claimed in claim 26, wherein the axially internal sections are
distributed according to a circumferential pitch substantially corresponding to
a width of each of the first axially intermediate sections to define a first carcass
ply, and the axially external sections are distributed according to a circumferential
pitch substantially corresponding to a width of each of the first axially intermediate
sections to define a second carcass ply radially superposed on the first carcass
ply close to said crown portions.
35. A method as claimed in claim 26, further comprising the step of arranging
a pair of auxiliary elastic-support inserts, each at an axially internal position
with respect to the axially internal sections.
36. A method as claimed in claim 26, wherein each of said strip-like sections
is laid down in a plane parallelly offset from a meridian plane of the toroidal support.
37. A method as claimed in claim 36, wherein the axially internal sections and
axially external sections are respectively laid down in deposition planes that
are offset at respectively opposite sides from said meridian plane, so that the
side portions of the axially internal and axially external sections have respectively
inclined orientations.
38. A method as claimed in claim 26, wherein accomplishment of at least one of
said annular anchoring structures comprises the steps of:
applying at least one annular circumferentially-inextensible anchoring insert
in radial superposed relationship with an end portion of at least one of said end
flaps, said anchoring insert having a cross-section profile of flattened conformation
extending axially away from the corresponding inner end flap and from an equatorial
plane of the tyre; and
applying at least one stiffening element against said at least one end flap,
said stiffening element being substantially placed at an axially internal position
relative to said annular anchoring insert and having a cross-section profile extending
away from said rotation axis.
39. A method as claimed in claim 38, wherein application of said annular anchoring
insert takes place by winding at least one thread-like element in concentric coils
disposed axially close to each other around the toroidal support.
40. A method as claimed in claim 38, wherein application of said annular anchoring
insert is carried out subsequently to deposition of the axially external sections.
41. A method as claimed in claim 38, wherein application of the stiffening element
is carried out before application of the annular anchoring insert.
42. A method as claimed in claim 38, wherein application of said at least one
stiffening element is carried out before deposition of the axially external sections.
43. A method as claimed in claim 38, wherein application of said at least one
stiffening element is carried out by winding at least one thread-like element in
concentric coils that are radially superposed around the toroidal support.
44. A method as claimed in claim 38, further comprising the step of applying
an auxiliary circumferentially-inextensible annular anchoring insert disposed substantially
parallel and radially close to said annular anchoring insert.
45. A method as claimed in claim 38, wherein an auxiliary anchoring insert is
applied subsequently to deposition of the radially internal sections and before
deposition of the radially external sections.
46. A method as claimed in claim 45, wherein application of said auxiliary anchoring
insert takes place by winding up of at least one thread-like element in concentric
coils disposed axially close to each other around the toroidal support.
47. A method as claimed in claim 38, wherein before applying said stiffening
element, application of at least one auxiliary stiffening element radially extending
in an axially internal position relative to the stiffening element is carried out.
48. A method as claimed in claim 47, wherein application of said auxiliary stiffening
element preferably takes place by winding at least one thread-like element in concentric
coils disposed radially close to each other around the toroidal support.
49. A method as claimed in claim 26, wherein each of said elastic-support inserts
is formed by winding at least one continuous strip-like element of elastomer material
so as to form coils that are disposed axially close to and/or radially superposed
on each other around the geometric axis of the toroidal support.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a self-supporting tyre for vehicle wheels, comprising:
a carcass structure having at least one carcass ply provided with end flaps in
engagement with respective annular reinforcing structures disposed in coaxial relationship
with a rotation axis of the tyre at positions axially spaced apart from each other
and each incorporated into a tyre bead, at least one of said beads exhibiting,
at a radially internal position thereof, a rest surface that, in a diametrical
section plane of the tyre, defines a profile converging towards the rotation axis
of the tyre itself away from an equatorial plane of the same; a belt structure
applied to the carcass structure at a radially external position thereof; a tread
band applied to the belt structure at a radially external position thereof; at
least one pair of sidewalls each extending between one of said beads and a side
edge of the tread band, at an axially external position with respect to the carcass structure.
The present invention also relates to a method of manufacturing a self-supporting
tyre for vehicle wheels, comprising the steps of: preparing a carcass structure
having at least one carcass ply provided with end flaps in engagement with respective
annular reinforcing structures disposed in coaxial relationship with a rotation
axis of the tyre at positions axially spaced apart from each other and each incorporated
into a tyre bead, at least one of said beads exhibiting, at a radially internal
position thereof, a rest surface that, in a diametrical section plane of the tyre,
defines a profile converging towards the rotation axis of the tyre itself away
from an equatorial plane thereof; applying a belt structure to the carcass structure
at a radially external position thereof; applying a tread band to the belt structure
at a radially external position of same; applying a pair of sidewalls to the carcass
structure, at laterally opposite positions of the latter, each of said sidewalls
extending between one of said beads and a side edge of the tread band.
Tyres for vehicle wheels essentially comprise a carcass structure made up of
one or more carcass plies that, in the most typical solutions, have the respective
inner circumferential edges turned up around inextensible annular inserts being
part of annular reinforcing structures and placed at axially opposite positions
in the regions usually identified as tyre "beads".
Applied to the carcass ply or plies, at a radially external position, is
a belt structure comprising one or more belt layers radially superposed in succession.
Radially superposed on the belt structure is a tread band of elastomer material.
The outer sides of the carcass structure are also covered with respective sidewalls
made of elastomer material as well.
It is to be pointed out that, to the aims of the present invention, by the term
"elastomer material" it is intended a rubber blend in its entirety, that is the
assembly made up of at least one base polymer suitably amalgamated with reinforcing
fillers and/or process additives of various types.
Usually the tyre beads, and in particular the annular reinforcing structures
incorporated thereinto, are conveniently structured and shaped so as to match with
the respective circumferential seats arranged on a rim with which the tyre is to
be associated, to ensure a steady connection between the two components of a wheel.
In more detail, coupling between each bead and the corresponding circumferential
seat of the rim is of such a nature that the bead is constantly pushed, by effect
of the tyre inflation pressure, against an abutment shoulder radially jutting out
away from the rotation axis of the tyre and defining the axially external edge
of the rim. At least in tubeless tyres, i.e. tyres devoid of an air tube, each
circumferential seat for engagement of the bead has a frusto-conical surface, hereinafter
referred to as "flange", having an extension converging towards the rotation axis
on moving close to the equatorial plane of the tyre. Each bead, axially pushed
away from the equatorial plane by effect of the inflation pressure, acts in axial
thrust relationship against the respective flange so as to ensure a perfect air-tightness
to the tyre.
Recently wheels for vehicles have been proposed in which the engagement
seats of the tyre beads have a frusto-conical conformation with an extension converging
towards the rotation axis away from the equatorial plane. An example of such a
rim-tyre assembly is described in U.S. Pat. No. 5,634,993. In the embodiment proposed
in such a patent, the tyre beads the shape of which matches that of the corresponding
rim seats, have annular reinforcing structures comprising usual rings around which
the end flaps of the carcass ply are axially turned up. As a whole the carcass
structure, of the radial type, has a cross-section profile with a constant bending
direction, the tangent of which close to the rings is substantially parallel to
the equatorial plane.
In document U.S. Pat. No. 5,971,047 a tyre is described which has beads particularly
adapted for use on rims having frusto-conical flanges axially facing outwardly,
hereinafter referred to, for the sake of simplicity, as "reverse-flange" rims.
The Applicant has already proposed, in document WO 99/64225, technical improvements
particularly addressed to simplification of the production process for tyres provided
with beads adapted for a reverse-flange rim.
It is the Applicant's feeling that the technical problem to be solved for the
purposes of the present invention is to obtain further functional improvements
in the above mentioned tyre, particularly in connection with ride comfort, by envisaging
new technical solutions aiming at achieving the desired self-support qualities,
i.e. the capability of ensuring ride over short-medium runs in the absence of inflation
pressure, following a puncture for example.
In the above United States documents U.S. Pat. Nos. 5,674,993 and 5,971,047,
for
self-support purposes, use of a big ring of elastomer material is proposed which
is fitted on the rim and arranged to provide a rest seat at the tyre belt to conveniently
support the structure during running under deflated conditions. Unlike the solutions
found in traditional tyres to be used on rims having flanges diverging away from
the equatorial plane, hereinafter referred to as "right-flange" rims, the tyre
structure having beads adapted for a reverse flange is capable of ensuring by itself,
at least within limits, a good anchoring of the beads to the corresponding rim
flanges even under deflated conditions of the tyre. Use of the elastomer support
ring fitted on the rim is therefore presently preferred to the other known solutions
commonly adopted on tyres having beads for right flanges, as described in documents
GB 2087805, EP 475258 and EP 542252 for example, which obtain self-support by arranging
appropriate elastomer reinforcement inserts, usually referred to as "lunettes"
at the sidewalls, in combination with suitably strengthened beads to promote steadiness
of engagement of the latter on the respective flanges.
Examples of such embodiments are described in documents GB 2087805, EP 475258
and EP 542252, in which at least one of the elastic-support inserts present at
each sidewall is enclosed between two carcass plies forming a sort of closed container
around it, so as to achieve good results particularly in connection with the self-supporting
capability of the tyre under deflated conditions.
The Applicant has however understood that, above all on low-section tyres, i.e.
tyres in which the height/width ratio is, just as an indication, lower than 0.60,
the presence of the annular elastomer insert within the tyre as described in documents
U.S. Pat. Nos. 5,674,993 and 5,971,047 may impair ride comfort of the tyre even
under normal use conditions. In fact, the tyre crown portion may easily come into
contact with the radially external portion of the annular insert, at the ground-contacting
area, above all following impacts transmitted by unevennesses in the road surface,
causing direct transmission of the impacts to the vehicle suspensions. In addition,
the annular elastomer insert greatly reduces the amount of air in the tyre, the
elastic behaviour of which is one of the decisive factors for ride comfort purposes.
The Applicant has also understood that location of the elastic-support inserts
in a sort of closed container defined by the carcass plies turned up around the
annular anchoring structures, as suggested in documents GB 2087805, EP 475258 and
EP 542252, tends to greatly increase stiffness of the tyre sidewall not only with
reference to its vertical flexibility, i.e. in connection with substantially radial
stresses with respect to the rotation axis of the tyre, but also with reference
to its torsional flexibility, i.e. in connection with stresses directed tangentially
of the circumferential extension of the tyre itself.
By adopting particular expedients, as described in documents EP 475258 and EP
542252 in the name of the same Applicant for example, the possibility of restricting,
within limits, the vertical stiffness of the sidewall under running conditions
with an inflated tyre is achieved. On the other hand, these technical solutions
tend to make the tyre structure heavier and more complicated and are not efficient
for the purpose of limiting the torsional stiffness which, as found out by the
Applicant, is one of the decisive factors in terms of ride comfort, particularly
at medium/high speed. in fact, the tyre capability of absorbing impacts transmitted
by potholes or other unevennesses present in a road surface depends on the torsional
stiffness of the tyre.
The Applicant has also understood that during running under normal inflated conditions
and, even more so, under deflated conditions, the presence of the elastic-support
inserts completely enclosed between two carcass plies imposes strong stresses and/or
deformations to the inserts themselves as well as to the other tyre construction
components that are present close to the sidewalls, which will bring about an increase
in the operating temperatures and softening of the materials. Thus use of materials
having high moduli of elasticity is compulsory, in order to further increase ride
comfort with an inflated tyre.
In accordance with the present invention, it has been found that if in tyres
having
reverse-flange beads technical solutions are adopted that aim at achieving self-support
qualities through insertion of elastomer inserts within the sidewalls, instead
of the traditional elastomer ring fitted on the rim, unexpected improvements in
the tyre behaviour can be reached, above all in terms of ride comfort.
It has also been found that use of these technical solutions make it surprisingly
possible to manufacture a tyre using simplified production processes based on the
principles described in the above mentioned document WO 99/64225, also obtaining
the possibility of modulating at will, depending on requirements, the containment
degree exerted by the carcass structure on the elastomer inserts disposed at the sidewalls.
In more detail, it is an object of the present invention to provide a self-supporting
tyre for vehicle wheels, characterized in that it further comprises at least one
pair of elastic-support inserts incorporated into the carcass structure, each at
one of said sidewalls.
More particularly, the elastic-support inserts have respective radially internal
apices placed close to the beads, and radially external apices placed close to
the side edges of the tread band.
In a preferential embodiment of the-invention, said at least one carcass ply
comprises:
axially internal strip-like sections and axially external strip-like sections,
said axially internal and axially external sections being circumferentially distributed
around said rotation axis and each extending in a "U"-shaped configuration around
the cross-section profile of the carcass structure, to define two side portions
mutually spaced apart in an axial direction and a crown portion extending in a
radially external position between the side portions, said elastic-support inserts
being each axially interposed between side portions of the axially internal sections
and side portions of the axially external sections.
Also provided may be the presence of axially intermediate strip-like sections
circumferentially distributed around said rotation axis and each extending in a
"U"-shaped configuration around the cross-section profile of the carcass structure
to define two side portions overlapping, in an axially external position, said
elastic-support inserts, and a crown portion extending in a radially external position
between the side portions; a pair of auxiliary elastic-support inserts being each
axially interposed between the side portions of the axially intermediate sections
and the side portions of the axially external sections.
In more detail, the axially internal sections are preferably distributed according
to a circumferential pitch corresponding to a multiple of their width, the axially
intermediate sections are distributed according to a circumferential pitch corresponding
to a multiple of their width and each have the respective crown portion interposed
in circumferential approaching relationship between the crown portion of two axially
internal sections, to define a first carcass ply therewith, and the axially external
sections are distributed according to a circumferential pitch substantially corresponding
to their width, to define a second carcass ply radially superposed on the first
carcass ply close to said crown portions.
In addition to the above, the presence of second axially intermediate strip-like
sections may be also provided, which second sections are circumferentially distributed
around said rotation axis and each extend in a "U"-shaped configuration around
the cross-section profile of the carcass structure to define two side portions
partly overlapping, at an axially external position, the side portions of the first
axially intermediate sections, and a crown portion extending in a radially external-position
between the respective side portions.
In a possible preferential alternative embodiment, the axially internal sections
are distributed according to a circumferential pitch substantially corresponding
to a multiple of their width, the first axially intermediate sections are distributed
according to a circumferential pitch substantially corresponding to a multiple
of their width, each with the respective crown portion interposed in circumferential
approaching relationship between the crown portion of two axially internal sections,
to define a first carcass ply therewith, the second axially intermediate sections
are distributed according to a circumferential pitch substantially corresponding
to a multiple of their width, and the axially external sections are distributed
according to a circumferential pitch substantially corresponding to a multiple
of their width, each with the respective crown portion interposed in circumferential
approaching relationship between the crown portions of two of said second axially
intermediate sections, to define a second carcass ply therewith, which second carcass
ply is radially superposed on the first carcass ply close to said crown portions.
According to a further preferential alternative embodiment, the axially
internal sections are distributed according to a circumferential pitch substantially
corresponding to their width, to define a first carcass ply, the axially intermediate
sections are distributed according to a circumferential pitch corresponding to
a multiple of their width and the axially external sections are distributed according
to a circumferential pitch corresponding to a multiple of their width and each
have the respective crown portion interposed in a circumferential approaching relationship
between the crown portions of two axially intermediate sections, to define a second
carcass ply therewith, which second carcass ply is radially superposed on the first
carcass ply close to said crown portions.
The inner, intermediate and outer sections respectively can also be distributed
according to a circumferential distribution pitch which is a multiple of their
width in accordance with a numerical factor corresponding to the number of series
of inner, intermediate and outer sections provided in the formation process of
said at least one carcass ply.
Under this circumstance, the crown portions of the individual inner, intermediate
and outer sections are sequentially alternated in mutual approaching relationship
along one and the same circumferential line, whereas the respective side portions
are axially offset from each other to house at least one of said elastic-support
inserts in the spaces existing between the side portions of the inner and intermediate
sections, and between the side portions of the intermediate and outer sections.
In accordance with a further alternative embodiment, the axially internal sections
are distributed according to a circumferential pitch substantially corresponding
to a multiple of their width, the axially intermediate sections are distributed
according to a circumferential pitch substantially corresponding to a multiple
of their width and each have the respective crown portion disposed circumferentially
close to the crown portion of an axially internal section, and the axially external
sections are distributed according to a circumferential pitch substantially corresponding
to a multiple of their width, each with its crown portion in circumferential approaching
relationship between the crown portion of one of the axially internal sections
and the crown portion of one of the axially intermediate sections to define said
at least one carcass ply therewith.
In a further possible embodiment, the axially internal sections are distributed
according to a circumferential pitch substantially corresponding to a multiple
of their width, the axially external sections each having the respective crown
portion interposed in circumferential approaching relationship between the crown
portions of two axially internal sections.
Alternatively, the axially internal sections and axially external
sections are distributed according to a circumferential pitch corresponding to
the width of each section, to define a first carcass ply and a second carcass ply
respectively, the second carcass ply being radially superposed on the first carcass
ply close to said crown portions.
Also provided may be the presence of a pair of auxiliary elastic-support inserts
each disposed at an axially internal position with respect to the axially internal sections.
In a further preferential alternative embodiment, each of said strip-like sections
substantially extends in a plane parallelly offset from a meridian plane of the
tyre, so that the respective crown portion, with respect to a radial reference
plane passing through the transition point between the crown portion and at least
one of the corresponding side portions, is oriented in such a manner as to form
an angle of a value different from the inclination exhibited by the side portions.
In more detail, the axially internal sections and axially external sections lie
in deposition planes that at respectively opposite sides are offset from said meridian
plane, so that at least the side portions of the axially internal sections have
a crossed orientation relative to the side portions of the axially external sections.
In accordance with a further inventive aspect, at least one of said annular reinforcing
structures comprises: at least one stiffening element applied against said at least
one carcass ply and having a cross-section profile extending away from the rotation
axis of the tyre; at least one annular circumferentially-inextensible anchoring
insert having a cross-section profile of flattened conformation, extending axially
away from,the stiffening element in a direction converging towards the geometric
rotation axis of the tyre away from the equatorial plane thereof.
The cross-section profile of the annular reinforcing structure is advantageously
provided to have a geometric centre of gravity located at such a position that
an axially external end edge of said annular anchoring insert is pushed towards
the rotation axis of the tyre following a tension generated along said at least
one carcass ply by effect of the inflation pressure of the tyre.
In more detail, the cross-section profile of the annular reinforcing structure
has a geometric centre of gravity located at an axially external position relative
to said stiffening element and at an axially internal position relative to an axially
external end edge of said annular anchoring insert.
Preferably, said stiffening element is axially positioned between a respective
axially internal end flap and a respective axially external end flap of said at
least one carcass ply.
Said annular anchoring insert is also provided to be applied against an end
portion of the outer end flap, extending axially away from the equatorial plane
of the tyre. In more detail, said annular anchoring insert is applied at a radially
external position with respect to said end portion of the outer end flap.
It is also provided that the annular anchoring insert should be disposed substantially
close to a radially internal edge of the stiffening element.
The annular reinforcing structure may further comprise at least one auxiliary
annular anchoring insert parallel to and radially close to said annular anchoring insert.
Such an auxiliary anchoring insert is preferably applied at a radially external
position with respect to an end portion of said inner end flap, and extends axially
away from an equatorial plane of the tyre.
The auxiliary anchoring insert is preferably applied at a radially internal position
relative to said end portion of the outer end flap.
The presence of at least one auxiliary circumferentially-inextensible stiffening
element may be also provided, which auxiliary element has a cross-section profile
radially extending at an axially internal position relative to said stiffening element.
It is a further object of the present invention a tyred wheel for vehicles comprising
a mounting rim to be associated with a hub of a vehicle and a tyre mounted on said
rim, said tyre comprising the above described features.
In accordance with a further aspect of the present invention, said tyre can be
obtained by a method of manufacturing a self-supporting tyre for vehicle wheels,
characterized in that, concurrently with preparation of said at least one carcass
ply, also carried out is a step of incorporating into the carcass structure at
least one pair of elastic-support inserts, each at one of said sidewalls. Preparation
of the carcass structure preferably comprises the following steps: arranging strip-like
sections each comprising longitudinal and parallel thread-like elements; laying
down axially internal strip-like sections circumferentially distributed on the
toroidal support, each of said axially internal sections extending in a "U"-shaped
configuration around the cross-section profile of the toroidal support, to define
two side portions that are mutually spaced apart in an axial direction, and a crown
portion extending in a radially external position between the side portions; applying
said elastic-support inserts in a position axially external to the side portions
of the axially internal sections; laying down axially external strip-like sections
circumferentially distributed on the toroidal support, each of said axially external
sections extending in a "U"-shaped configuration around the cross-section profile
of the toroidal support, to define two side portions that are mutually spaced apart
in an axial direction, each extending in an axially external position relative
to one of the elastic-support inserts, and a crown portion extending in a radially
external position between the side portions.
In a possible embodiment, before laying down the axially external sections the
following further steps are carried out: laying down axially intermediate strip-like
sections circumferentially distributed around said rotation axis and each extending
in a "U"-shaped configuration around the cross-section profile of the carcass structure
to define two side portions overlapping, at an axially external position, said
elastic-support inserts, and a crown portion extending in a radially external position
between the side portions; applying a pair of auxiliary elastic-support inserts,
at an axially external position, to the side portions of the axially intermediate
sections, before deposition of the axially external sections.
In particular, it may be provided that the axially internal sections should be
laid down according to a circumferential distribution pitch substantially corresponding
to a multiple of their width, the axially intermediate sections should be laid
down according to a circumferential distribution pitch substantially corresponding
to a multiple of their width, each with the respective crown portion interposed
in a circumferential approaching relationship between the crown portions of two
axially internal sections, to define a first carcass ply therewith, and the axially
external sections should be laid down according to a circumferential distribution
pitch substantially corresponding to their width, to define a second carcass ply
therewith, which carcass ply is radially superposed on the first carcass ply.
In a possible preferential embodiment, before application of said auxiliary elastic-support
insert, also carried out is the step of laying down second axially-intermediate
strip-like sections circumferentially distributed around said rotation axis and
each extending in a "U"-shaped configuration around the cross-section profile of
the toroidal support to define two side portions partly overlapping, at an axially
external position, the side portions of the first axially intermediate sections
previously laid down, and a crown portion extending in a radially external position
between the respective side portions.
In particular, the axially internal sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of their width, the
first axially intermediate sections are laid down according to a circumferential
distribution pitch substantially corresponding to a multiple of their width, each
having the respective crown portion interposed in a circumferential approaching
relationship between the crown portions of two axially internal sections, to define
a first carcass ply therewith, the second axially intermediate sections are laid
down according to a circumferential distribution pitch substantially corresponding
to a multiple of their width, and the axially external sections are laid down according
to a circumferential distribution pitch substantially corresponding to a multiple
of their width, each having
