U.S. patent application number 10/590988 was filed with the patent office on 2008-10-23 for tyre for vehicles, in particular motor vehicles.
This patent application is currently assigned to FIAT AUTO S.P.A.. Invention is credited to Giovanni monfrino, Mario Palazzetti, Stefano Re Fiorentin.
Application Number | 20080257463 10/590988 |
Document ID | / |
Family ID | 34897824 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257463 |
Kind Code |
A1 |
Re Fiorentin; Stefano ; et
al. |
October 23, 2008 |
Tyre For Vehicles, In Particular Motor Vehicles
Abstract
A tyre for vehicles which does not require pressurisation by
means of a pressurised fluid has a tread, two sidewalls, and two
beads which are attached to a wheel rim made of elastomer material,
and is provided with at least one tubular reinforcement body which
is associated with the tread; each of the sidewalls having a
respective homogeneous resilient annular membrane, a straight
generatrix of which forms an angle (A) other than 90.degree. with
the axis of the tyre; the membranes being stretched radially
between the tread and the beads such as to be pre-tensioned in the
absence of external loads acting on the tyre.
Inventors: |
Re Fiorentin; Stefano;
(Grugliasco, IT) ; Palazzetti; Mario; (Avigliana,
IT) ; monfrino; Giovanni; (Moncalieri, IT) |
Correspondence
Address: |
MITCHELL P. BROOK;LUCE, FORWARD, HAMILTON & SCRIPPS LLP
11988 EL CAMINO REAL, SUITE 200
SAN DIEGO
CA
92130
US
|
Assignee: |
FIAT AUTO S.P.A.
Torino
IT
|
Family ID: |
34897824 |
Appl. No.: |
10/590988 |
Filed: |
June 15, 2004 |
PCT Filed: |
June 15, 2004 |
PCT NO: |
PCT/IT2004/000347 |
371 Date: |
July 1, 2008 |
Current U.S.
Class: |
152/173 |
Current CPC
Class: |
B60C 7/26 20130101; B60C
7/22 20130101; Y10T 152/10171 20150115; B60C 11/18 20130101; Y10T
152/10234 20150115; Y10T 152/10495 20150115; Y10T 152/1018
20150115 |
Class at
Publication: |
152/173 |
International
Class: |
B60C 7/22 20060101
B60C007/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2004 |
IT |
TO2004A000120 |
Claims
1. Tyre for vehicles, in particular for motor vehicles, which has
an axis of symmetry and comprises a tread, two sidewalls, two beads
which are attached to a wheel rim made of elastomer material, and
at least one tubular reinforcement body for coaxial reinforcement
on the said axis, which is surrounded by the said tread and extends
between the said sidewalls; each of the said sidewalls comprising a
respective resilient annular membrane with a straight generatrix
which forms an angle (A) other than 90.degree. with the axis of the
tyre; characterised in that the said tubular reinforcement body
comprises an annular belt and a plurality of blocks which are
supported by the said annular belt in positions adjacent to one
another, and can be forced against one another in order to apply
resistance to the circumferential actions of compression present on
the tyre during the rotation of the tyre itself.
2. Tyre according to claim 1, characterised in that the said
tubular body has a dimension measured parallel to the said axis
which is substantially the same as that of the tread measured in
the same direction.
3. Tyre according to claim 1, characterised in that the said
tubular body has lateral through-apertures.
4. Tyre according to claim 3, characterised in that at least some
of the said through-apertures are apertures which are elongate in
the circumferential direction.
5. Tyre according to claim 3, characterised in that at least some
of the said apertures are aligned with one another
circumferentially in order to form a circumferential row of
apertures.
6. Tyre according to claim 5, characterised in that the said
tubular body comprises at least one pair of the said
circumferential rows of apertures which are spaced from one another
in the axial direction.
7. Tyre according to claim 1, characterised in that the said
tubular body is delimited by respective cylindrical surfaces which
are coaxial to the axis; at least one of the said cylindrical
surfaces has a generatrix line which is straight and parallel to
the axis of the tyre.
8. Tyre according to claim 1, characterised in that the said
tubular body is a corrugated body.
9. Tyre according to claim 8, characterised in that the said
tubular body has at least one circumferential rib.
10. Tyre according to claim 1, characterised in that the said
tubular body is made of harmonic steel.
11. Tyre according to claim 1, characterised in that the said
tubular body is made of plastics material.
12. Tyre according to claim 1, characterised in that the tubular
body is at least partially embedded in the said tread.
13. Tyre according to claim 1, characterised in that the said
membranes are made of anisotropic material.
14. Tyre according to claim 13, characterised in that the said
membranes are reinforced with fibres which are disposed and
oriented such as to prevent localised deformations of the membranes
in a loaded condition.
15. Tyre according to claim 14, characterised in that the said
membranes are reinforced such as to contain the tension forces
which are present on the membranes themselves in static load
conditions above a dihedron which is tangent to the beads and has a
vertex parallel to the axis.
16. Tyre according to claims 1, characterised in that the
generatrices of the said membranes converge towards one another in
order to meet at a point outside the tread.
17. Tyre according to claim 1, characterised in that the
generatrices of the said membranes (24) converge towards one
another in order to meet at a point inside the tyre.
18. Tyre according to claim 1, characterised in that the said
membranes have cross-sections which are substantially constant in a
radial direction.
19. Tyre according to claim 18, characterised in that the said
cross-sections are substantially rectangular cross-sections.
20. Tyre according to claim 1, characterised in that the said beads
comprise at least one annular projection which can engage with a
corresponding retention seat when it is fitted onto the wheel
rim.
21. Tyre according to claim 1, characterised in that the said tread
comprises a plurality of apertures for communication with the
interior of the tyre; the said apertures being provided to
correspond with an equivalent number of apertures provided through
the said tubular body.
22. Tyre according to claim 21, characterised in that the said
apertures are closed by means of materials which are permeable to
water, and can prevent the intake of foreign bodies into the
tyre.
23. Tyre according to claim 22, characterised in that the said
materials which are permeable to water are porous materials.
24. Tyre according to claim 1, characterised in that the said tread
is vulcanised onto an outer surface of the said tubular body.
25. Tyre according to claim 1, characterised in that the said tread
comprises a plurality of outer circumferential grooves, and in that
the said grooves communicate with the interior of the tyre via a
plurality of through-radial passages.
26. Tyre according to claim 1, characterised in that the said
membranes are stretched radially between the said tread and the
said bead such as to be pre-tensioned in the absence of loads on
the tyre..
27. Tyre according to claim 1, characterised in that the said
membranes are made of homogeneous elastomer material.
28. Tyre according to claim 27, characterised in that the said
homogeneous material is an isotropic material.
29. Tyre according to claim 27, characterised in that the said
membranes are made of polybutadiene rubbers.
30. Tyre according to claim 27, characterised in that the said
membranes are made of polyisoprene rubbers.
31. Tyre according to claim 27, characterised in that the material
of which the said membranes are made comprises polycondensate of
dimethylsilanol, wherein the methyl units are substituted by vinyl
or phenolic units.
32. Tyre according to claim 1, characterised in that the said
blocks project from the said annular belt towards the interior of
the tyre.
33. Tyre according to claim 1, characterised in that the said
annular belt comprises a plurality of reinforcement threads or
strips.
34. Tyre according to claim 33, characterised in that the said
annular belt comprises a portion of elastomer material in which the
said reinforcement threads or strips are embedded.
35. Tyre according to claim 33, characterised in that the said
annular belt is connected integrally to the said tread.
36. Tyre according to claim 33, characterised in that the said
tread is connected to the said annular belt in a manner such that
it can be released, so that it can be replaced when it reaches a
wear limit.
37. Tyre according to claim 34, characterised in that the said
annular belt is glued to the said tread.
38. Tyre according to claim 1, characterised in that the said
blocks are tapered towards the interior of the tyre.
39. Tyre according to claim 38, characterised in that the said
blocks delimit between one another notches which extend in a
direction substantially parallel to the said axis.
40. Tyre according to claim 38, characterised in that the said
blocks are distributed in order to form a plurality of axial rows
parallel to the said axis and a plurality of circumferential
rows.
41. Tyre according to claim 38, characterised in that the said
blocks are connected to one another by relative mobility means
which can permit displacement of the blocks relative to one another
during the rotation of the tyre.
42. Tyre according to claim 41, characterised in that the said
relative mobility means are virtual hinges.
43. Tyre according to claim 42, characterised in that the said
blocks are connected to one another by connection portions which
define the said relative mobility means; the said blocks and the
said connection portions constituting part of a body made in a
single piece.
44. Tyre according to claim 43, characterised in that it
additionally comprises means for reaction which, during the
rotation of the tyre, can apply action which opposes that which
generates the relative displacement of the said blocks.
45. Tyre according to claim 44, characterised in that the said
means for reaction are interposed between the belt and the
blocks.
46. Tyre according to claim 1, characterised in that the said
blocks are solid bodies.
47. Tyre according to claim 1, characterised in that the said
blocks are hollow bodies.
48. Tyre according to claim 47, characterised in that the said
tubular reinforcement body has an alveolar structure.
49. Tyre according to claim 44, characterised in that the said
blocks are connected integrally to the said belt by being glued or
vulcanised.
50. Wheel rim for vehicles, comprising an inner portion, two radial
annular portions which project from the said inner portion and
support respective seats for accommodation of corresponding beads,
and a tyre produced according to claim 1, and a wall which extends
between the said annular portions coaxially to an axis of the wheel
rim, and in use faces the said tyre, characterised in that the said
wall comprises a plurality of through-apertures which are
permanently open.
51. Wheel rim according to claim 50, characterised in that it
comprises an annular portion which is coaxial to the said axis and
is made of elastomer material; the said annular portion defining a
radial support stop for the said tread.
Description
TECHNICAL FIELD
[0001] The present invention relates to a tyre for vehicles.
BACKGROUND ART
[0002] In the field of tyres for vehicles in general, and of motor
vehicles in particular, it is known to produce tyres which have
radial half-sections in the shape of an omega and comprise a tread
and two convex sidewalls, each of which ends in a bead which, in
use, can co-operate in a flush manner with an annular portion of a
corresponding rim. When the tyre is connected to the rim, together
with the rim itself it delimits a chamber, which, again in use, is
filled with air or another pressurised fluid. The pressure of the
fluid in the said chamber is determined according to the type of
tyre, and to the stress conditions to which it is assumed that the
tyre itself may be subjected.
[0003] Although the known tyres are universally used, they suffer
from some disadvantages. Firstly, specifically because of their
shape and the fact that they are pressurised, they have high levels
of rolling resistance caused by high levels of hysteresis, which in
use are responsible for heating of the tyre and uncontrollable
variation of the efficiency and reliability of the tyre itself.
[0004] In addition, since it is necessary to meet specific
requirements of road hold, including when water is present on the
road surface, the tread is grooved to form a plurality of channels
which are transverse relative to the direction of running of the
vehicle, and which, since they open up to the exterior of the tyre,
discharge the water which is present into the area of interface of
the tyre/road surface. Although on the one hand the presence of
these transverse channels makes it possible to increase the road
hold in wet conditions, on the other hand it is a source of
troublesome noise emissions. The type, dimensions and distribution
of these transverse channels on the tread are therefore always a
compromise between the various requirements.
[0005] In addition, the known tyres require periodic checks on the
inflation pressure, which varies over a period of time as a result
of the inevitable leakages, and the tyres also need to be replaced
if they are punctured.
[0006] Finally, the known tyres determine the geometry of the rim,
which must have a perimetric tubular portion which is free from
apertures, in order to delimit the chamber for the pressurised
fluid, and must permit fitting of the inflation valve. For these
reasons, in the known solutions, the wheel/rim assembly has
relatively high weights which generate inevitable forces of
inertia, which, as is known, affect both the acceleration and the
braking.
DISCLOSURE OF INVENTION
[0007] The object of the invention is thus to provide a tyre for
vehicles which makes it possible to solve the above-described
problems simply and economically, and in particular which makes it
possible to obtain a high level of driving comfort in any condition
in which it is used.
[0008] According to the present invention, a tyre is provided for
vehicles, in particular for motor vehicles, which has an axis of
symmetry and comprises a tread, two sidewalls, and two beads which
are attached to a wheel rim made of elastomer material,
characterised in that it additionally comprises at least one
tubular reinforcement body which is coaxial to the said axis, is
surrounded by the said tread, and extends between the said
sidewalls; each of the said sidewalls comprising a respective
resilient annular membrane with a straight generatrix which forms
an angle other than 90.degree. with the axis of the tyre.
[0009] Preferably, in the above-defined tyre, the said tubular body
has a dimension, measured parallel to the said axis, which is
substantially the same as that of the tread measured in the same
direction. Also preferably, the said membranes are stretched
between the said tread and the said beads, such as to be
pre-tensioned in the absence of loads on the tyre.
[0010] Also preferably, the generatrices of the said membranes
converge towards one another such as to meet at a point outside the
tread. Alternatively, the generatrices of the said membranes
converge towards one another such as to meet at a point inside the
tyre.
[0011] Advantageously, the said tubular reinforcement body
comprises an annular belt and a plurality of blocks which are
supported by the said annular belt in positions which are adjacent
to one another, and can be forced against one another in order to
apply resistance to the circumferential actions of compression
which are present on the tyre during rotation of the tyre
itself.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described with reference to the
attached figures, which illustrate some non-limiting embodiments of
it, in which:
[0013] FIG. 1 illustrates in front elevation a preferred embodiment
of a tyre produced according to the dictates of the present
invention;
[0014] FIG. 2 is a half-section of the tyre according to the line
II-II in FIG. 1, fitted onto a wheel rim;
[0015] FIG. 3 is a figure similar to FIG. 2, and illustrates a
variant of a portion of the tyre in FIG. 1;
[0016] FIG. 4 illustrates a variant of a detail of FIGS. 2 and
3;
[0017] FIG. 5 illustrates schematically a tyre showing areas with
different stresses;
[0018] FIG. 6 illustrates a variant of some details of FIGS. 2 and
3;
[0019] FIG. 7 is a further variant of the detail of FIG. 4,
disposed in a deformed condition;
[0020] FIG. 8 illustrates schematically the detail of FIG. 7 in two
different functional conditions; and
[0021] FIGS. 9 and 10 illustrate in cross-section two different
variants of a detail of FIG. 7.
BEST MODE FOR CARRYING OUT THE INVENTION
[0022] In FIG. 1, 1 indicates as a whole a wheel unit for a
vehicle, and in particular a motor vehicle (not illustrated),
comprising a wheel rim 2 (FIGS. 2 and 3), and a tyre 3 fitted onto
the wheel rim 2 itself.
[0023] The wheel rim 2 comprises a central attachment portion 5,
and two radial annular flanges 6 which project from the portion 5
and support respective seats 1, each of which accommodates a
corresponding bead 8 of the tyre 3. The beads 8 each have their own
anchorage projection 9, and are engaged with the seats 7 by
respective annular discs 10 which are connected to the respective
flanges 6 by means of screws 11. The portion 5 comprises a
cylindrical wall 12, which extends coaxially to the axis 13 of the
wheel rim 2 in the position facing the tyre 3, in order to connect
the flanges 6 to one another, and is provided with a plurality of
permanently open through-apertures 14, only one of which can be
seen in FIGS. 2 and 3.
[0024] The tyre 3, which can support the load transmitted by the
wheel rim 2 without needing to be pressurised by air or other
pressurised fluids, comprises two sidewalls 15, which are connected
firstly to the beads 8 and secondly to a tread 16. The beads 8, the
tread 16 and the sidewalls 15 are made of elastomer material, as
will become more apparent from the following description.
[0025] The tyre 3 additionally comprises a homogenous tubular
reinforcement body 18 (FIGS. 2 and 3), which extends coaxially to
the axis 13, and is made of a material other than the said
elastomer material, and preferably of harmonic steel or of
fibre-reinforced plastics material of the thermoplastic or
thermosetting type. As also illustrated in FIGS. 2 and 3, the
tubular body 18 has a dimension measured parallel to the axis 13
which is substantially the same as that of the tread 16 measured in
the same direction, and is delimited radially by two cylindrical
lateral surfaces 18a and 18b which are coaxial to the axis 13 and
have generatrix lines which are straight, and are parallel to one
another and to the axis 13. According to the variant illustrated in
FIG. 4, the tubular body 18 is a corrugated body with a plurality
of circumferential ribs 19, which delimit between one another a
plurality of circumferential grooves 20. The tread 16 is vulcanised
on the outer surface of the tubular body 18, which is thus at least
partially embedded in the elastomer material of the tread 16
itself. The tread 16 is provided with a plurality of radial
through-apertures 20, each of which communicates with a
corresponding through-aperture 21 provided in the tubular body
18.
[0026] Advantageously, the apertures 20 and 21 are elongate in the
circumferential direction, and are aligned with one another in
order to form circumferential rows of apertures which are spaced
from one another in an axial direction. Advantageously, the
apertures 20 are closed by means of materials 20a which are
permeable only to water, and advantageously by means of porous
materials.
[0027] The tread 16 is grooved by producing only a plurality of
circumferential grooves 22, into which there open the
through-apertures 20 provided through the tread 16.
[0028] As illustrated in FIG. 1, and in particular in FIGS. 2 and
3, each of the sidewalls 15 comprises a respective frusto-conical
resilient annular membrane 24 with a straight generatrix which
forms an angle A other than 90.degree. with the axis 13, and is
advantageously variable between 75 and 85.degree.. In FIG. 3, the
generatrices of the membranes 24 converge towards one another and
towards the tread 16, meeting at a point, not illustrated, outside
the tread 16 itself, whereas in FIG. 2, the generatrices diverge
from the wheel rim 2 and thus meet at a point inside the tyre
3.
[0029] Again with reference to FIGS. 2 and 3, the membranes 24 have
cross-sections which are substantially constant in a radial
direction, and radial half-sections which are substantially
rectangular, and, according to a first embodiment, are reinforced
by means of fibre materials not shown in the attached figures, such
as to be anisotropic. The fibres of the fibre material are
distributed and oriented such as to prevent localised deformations
of the membranes 24 under static load, in particular in the area
immediately beneath the wheel rim 2. Specifically, the fibres are
distributed and oriented such that the tension stresses present in
the different points of the membranes in conditions in which a load
is applied, are contained within a dihedron 26 which is tangent to
the beads 8, has a vertex parallel to the axis 13, and is disposed
in use below the axis 13 itself, as illustrated in FIG. 5. By this
means, the portions A (FIG. 5) of the membranes 24 which are
contained within the dihedron 26 are stretched between the
corresponding portions of the tubular body 18 and the wheel rim 2,
whereas the portions B of the membranes below the dihedron 26 are
not subjected in practice to tension stresses, and can thus be
deformed freely under the action of the load transmitted by the
wheel rim 2. As a result of the deformation of the portions B, the
actual radius of curvature of the part of the tyre beneath the
dihedron 26 increases, tending towards infinity at the vertical
plane which passes through the axis 13 (FIG. 5). The part of the
tyre which is subjected to traction stress, i.e. which is contained
within the dihedron 26, supports the load, thus guaranteeing the
resilience required for satisfactory driving comfort. In other
words, in the wheel unit 1, the wheel rim 2, which, as is known,
transmits the load to the tyre, is "suspended" from the portions A
of the membranes 24, by this means "releasing" the portions B.
[0030] The variant illustrated in FIG. 6 relates to a tyre 30 which
differs from the tyre 3 only in that the membranes 24 are made of
isotropic and homogeneous elastomer material. Advantageously, the
membranes 24 are made of polybutadiene rubbers or polyisoprene
rubbers, treated in order to withstand atmospheric agents, or of
polycondensate of dimethylsilanol and derivatives, when the methyl
groups are replaced by vinyl or phenolic groups. At rest, i.e. in a
non-deformed condition, each of the membranes 24 has radial
dimensions which are smaller than the radial distance between the
tread 16 and the corresponding bead 8. When it is connected to the
tread and to the corresponding bead 8, each membrane 24 is
stretched radially such that in the condition in which the tyre is
at rest, i.e. in the absence of external stresses, it is perfectly
pre-tensioned. The level of pre-tensioning of the membranes 24 is
selected according to the load which acts on the tyre, and in each
case such that in use, i.e. when the tyre is in a loaded condition,
the portions B of the membranes 24 still have a residual traction
load. By this means, the generatrix of the membranes 24 is always
kept straight in practice, including on the vertical plane which
passes through the axis of the tyre.
[0031] In order to avoid excessive deformations of the membranes 24
in conditions of sudden stresses, for example when the wheel
encounters a "step", the wheel rim comprises an annular portion 31
(FIG. 6) made of elastomer material, which in use is disposed
coaxially to the axis of the wheel rim and faces the body 18, such
as to constitute under limit conditions a support or a stop for the
body 18 itself. The portion 31 is supported by a metal portion 32
of the wheel rim, which portion is supported by a plurality of
spokes 33.
[0032] FIGS. 7 and a illustrate partially a tubular reinforcement
body 35, which is always associated with the tread 16, has a
dimension measured parallel to the axis 13 which is substantially
the same as that of the tread 16 measured in the same direction,
and differs from the reinforcement body 18 in that it has
predetermined differentiated resistance to stress, i.e. which is
dependent on the stress to which it is subjected. Specifically, the
tubular body 35 comprises a continuous outer annular belt 36 and a
plurality of blocks 37 which are supported by the belt 36 itself.
The belt 36 is flexible and can withstand the circumferential
tension actions which act on the reinforcement body 35, and
preferably comprises a portion 38 of elastomer material and a
plurality of reinforcement threads or fibres 39 which may or may
not be braided, embedded in the portion 38 of elastomer material.
The belt 36, which extends along the entire width of the tread 16,
is connected integrally to the tread 16 itself, for example by
means of vulcanisation or by being glued, or in a manner such that
it can be dismantled or detached, such as to permit replacement of
the tread 16 alone when it has reached a limit wear value.
According to a variant, the belt 36 does not have the portion 38 of
elastomer material, and comprises only a braid of threads or
strips.
[0033] Again with reference to FIGS. 7 and 8, the belt 36 supports
the blocks 38, which are connected integrally to the belt 36, for
example by being vulcanised or simply by being glued, project
towards the interior of the tyre 3, and can create action which
resists the circumferential actions of compression which act on the
reinforcement body 35 during rotation of the tyre 3. The blocks 37,
which can consist of solid bodies, as illustrated in FIGS. 7 and 8,
or of hollow bodies as illustrated in FIGS. 9 and 10, are adjacent
to one another and aligned in order to define a plurality of axial
rows 41 of blocks, i.e. which are parallel to the axis 13 of the
tyre, and a plurality of circumferential rows 42 of blocks. In the
example illustrated, the blocks 37 have the same dimensions and
geometry as one another, and each have a frusto-conical form with a
quadrangular base, which is advantageously rectangular with the
larger side parallel to the axis 13. The blocks 37 are tapered
towards the interior of the tyre 3 and each have a respective
larger base which faces the belt 36 and is connected to the larger
base of the adjacent block 37 by means of a respective flexible
joining portion 43 (FIG. 8 and 9). The joining portions 43 define
respective virtual hinges 44 which hinge each block 37 on the one
adjacent to it. In the embodiment illustrated in FIGS. 9 and 10,
the blocks 37 constitute together with the flexible joining
portions 43 parts of a flexible thermoplastic material alveolar
body 45 made in a single piece, advantageously from polypropylene
or polyamide material. Alternatively, the blocks 37 are solid
bodies made of plastics or elastomer material, and are connected to
one another in order to define a monolithic body. In both cases,
the blocks 37 are shaped such that, if the tyre 3 is unloaded,
their lateral walls 46 are simply disposed adjacent to one another,
or are forced against one another in order to define a preloaded
reinforcement body.
[0034] In use, when the wheel rim 2 transmits the load to the tyre
3, the various portions of the reinforcement body 35 act
differently according to the position which they occupy in relation
to the area of contact with the support surface of the wheel unit
1. Specifically, in the area of contact of the wheel unit--support
surface, as a result of the load transmitted to the tread 16, the
blocks 37 are rotated relative to one another in opposite
directions around a respective axis of pivoting (as illustrated in
FIG. 8a), and define between one another respective V-shaped
notches 49 which widen towards the interior of the tyre 3, whereas
in the areas to the right and left of the said area of contact,
they are forced against one another (as illustrated in FIG. 8b), in
order to withstand the load transmitted to the tyre 3 by the wheel
rim 2.
[0035] When the wheel unit encounters "a step", indicated as 50
(FIG. 7), or when a concentrated load is applied to it from the
exterior, as illustrated in FIG. 7, the virtual hinges 44 apply
minimal resistance to the deflection of the reinforcement body
towards the interior of the tyre 2, such that the various blocks 37
rotate in opposite directions to one another, thus becoming spaced
from one another progressively and in proportion with their
distance from the step 50, as illustrated in FIG. 7. In this
situation also, the blocks 37 which are disposed in the vicinity of
the step 50 delimit between one another a series of V-shaped
notches 49, the widening of which, again as can be seen from FIG.
7, is variable, and reaches a maximum value at the step 50, and
values which gradually decrease as the distance from the step 50
itself increases.
[0036] In order to limit the rotation of the blocks 37,
particularly in the presence of pronounced steps, the portions 43
are replaced by reinforced portions 52, as illustrated in FIG. 10.
Each portion 52 comprises a solid bead 52a, from which there extend
integrally the resilient lateral walls 46 of the respective blocks
37. By this means, the virtual hinge 44 which is disposed in the
solution in FIG. 9 between two adjacent blocks 37, is replaced by
two virtual hinges 53 and 54, which are each defined by a section
of the wall of the corresponding block 37 adjacent to the bead 53.
In relation to the hinges 44 the hinges 53 and 54 are thus
displaced towards the free ends of the blocks 37, such that in
addition to a predetermined angle of rotation of the blocks 37, the
solid beads 52a apply torque which opposes that which rotates the
blocks 37 opening up, thus limiting the deformation of the
reinforcement body 35 and of the tread 16 towards the interior of
the tyre 3.
[0037] It is apparent from the preceding description that in
comparison with the known solutions, the wheel unit 1 described
firstly does not need to be pressurised, thus solving all the
functional and maintenance problems associated with the presence of
air or another pressurised fluid.
[0038] Furthermore, and again in comparison with the known
solutions, the tyres 3,30 described ensure optimum resilience and
deformability when loaded, and simultaneously a reduced hysteresis.
These particular features are derived partly from the presence of
the membranes 24, and partly from the design characteristics of the
reinforcement bodies 18 and 37. In the case of the body 37, it is
obvious in particular that the belt 36 and the blocks 37 allow the
tyre to adapt to the different load conditions and according to the
obstacles encountered during rolling, thus becoming deformed
differently and in a controlled manner according to the stress to
which it is subjected. The tyre consequently obtains fluidity of
performance even in conditions in which there are substantial
obstacles, and therefore a high level of driving comfort in any
situation, for the same road hold conditions.
[0039] Furthermore, the absence of pressurised fluid makes it
possible to provide through-apertures, both through the tread 16
and the tubular reinforcement bodies 19 and 35, and through the
wheel rim 2, and in particular through the wall of the wheel rim
which, in the known solutions, delimits the pressure chamber,
together with the tyre. In fact, in the specific case of the
reinforcement body 35, it is apparent that through apertures can be
obtained by removing one or more blocks 37, or through the smaller
bases or the lateral wall of the blocks 37 themselves.
[0040] The passages provided through the tread and the tubular
reinforcement body 18 serve a dual purpose. Firstly, in fact, they
permit discharge of the water alone which is present in the
tread/road surface interface, towards the interior of the tyre, and
from there to the exterior, via the apertures 14 in the wheel rim
2. The presence of the passages 20 and 21 through the tread 16 and
the reinforcement body 18 thus provides greater freedom in the
grooving of the tread 16 itself, since it avoids creation of the
conventional transverse channels for lateral discharge of the
water, which are essential in the known solutions in order to
obtain the required hold on the road surface, but are a source of
undesirable acoustic emissions. In addition, the presence of the
passages 20 and 21 makes it possible to reduce and control the
temperature of use of the tyre, with an obvious increase in the
efficiency and reliability of the tyre itself. The fact of
providing porous materials for closure of the apertures 20 prevents
intake into the tyre of solid bodies such as stones, gravel and/or
sand.
[0041] The fact of not having to provide a chamber for the
pressurised fluid also increases the freedom of design and
production of the wheel rim 2, which can thus have forms and
geometries which are not permitted by the type of tyres now used.
Finally, the greater freedom of form of the wheel rim comprises a
substantial reduction in the weight of the. wheel unit, as well as
a further reduction in the hysteresis of the wheel unit itself.
[0042] It is apparent from the preceding description that
modifications and variations which do not depart from the field of
protection of the claims, can be made to the wheel unit 1
described. In particular, a different method could be provided for
connection of the beads 8 to the wheel rim 2, and an additional
tubular body could be disposed on the interior or exterior of the
body 18, 35 in contact with the body 18,35 itself or in a position
spaced from the latter.
[0043] In addition, both the tubular bodies 18 and 35 and the tread
16 could dispense with the respective apertures 20 and 21, and the
wheel rim could dispense with the apertures 14, and could comprise
other through-apertures, provided for example through the flanges
6. Furthermore, when they exist, the apertures 20 and 21 could have
dimensions and/or geometries which are also very different from
those illustrated by way of example, and in particular they could
have axial dimensions which are particularly small, in order to
prevent the intake of foreign bodies into the tyre.
[0044] Finally, the membranes 24 could constitute only an
intermediate or end part of the respective sidewalls 15, or they
could have cross-sections which are variable in a radial direction.
If the membranes are pre-tensioned, when "at rest" they have a
radial dimension smaller than the distance between the beads and
the tread.
[0045] In addition, as far as the body 35 is concerned, it is
apparent that the blocks 37 could have forms and dimensions other
than those described by way of example, and the distribution and
orientation of the blocks 37 could also be different. In
particular, a plurality of continuous axial blocks could be
provided which are or are not parallel to the axis 13, extending
along the entire width of the tread and delimiting between one
another respective continuous axial notches. Furthermore, in order
to adapt to particular curvatures of the tread 16, in particular at
the shoulders of the tyre, the blocks 37 could have heights which
differ from one area to another, and in particular could have a
reduced height in the vicinity of the said shoulders.
* * * * *