Note: Descriptions are shown in the official language in which they were submitted.
105~494
This invention relates to pneumatic rubber tires,
and more particularly to pneumatic rubber tires suitable for
off-road vehicles (hereinafter referred to as a tire), which
are adapted for use in construction vehicles such as dump
truck, scraper, loader and so on, agricultural vehicles such
as log skidder, log forward and so on, or industrial vehicles
such as fork lift, platform truck, trailer and so on.
In general, the tires of this type run on off-road
area where obstructions such as sharp rocks, metal pieces,
glass pieces, stubs after felling and the like are scattered
thereon under a heavy load per tire. Therefore, such tire is
required to have a large resistance against damages due to
cut failure and a good durability for use in a long ~ime.
In this type of tire, a resistance to damage due to
tire cuts (hereinafter referred to as cut resistant property),
a resistance to separation of rubber around a reinforcing
layer in crown and other portions of the tire (hereinafter
referred to as separation resistant property), and a wear
resistance are most important requirements.
Heretofore, there have been made a few attempts for
improving the cut resistant property of the tire, but these
attempts are not always satisfactory. Besides, the separation
resistant property in the crown and other portions may be
considerably degraded. As a result, it is very difficult to
provide tires having a practical durability by any of these
attempts.
For instance, a first type of the conventionally
proposed pneumatic tires is so-called wire-under-tread type
tires (hereinafter referred to as W.T.U. tire), wherein a
rubberized layer containing thin metallic filaments of about
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105849~l
10 mm length embedded therein is arranged between a tread
rubber and a carcass body so as to prevent growth of the
damage due to cuts started from the tire tread into the
interior portion of ~he tire. The W.U.T. tire has been tried
to be sold in market. In practice, however, this first type
tire has such drawbacks that if an amount of the metallic
filaments enough to improve the cut resistant property is
embedded in rubber, the premature separation failure frequently
occurs inside the W.U.T. layer or between the W.U.T. layer
and the tread rubber or between the W.U.T. layer and the
carcass body before the tire will attain its advantageous
feature due to its large cut resistant property, while if the
amount of the metallic filaments used is decreased to such
an extent that the premature separation failure is not caused,
the aimed cut resistant property cannot be achieved. Thus,
the W.U.T. tires have not yet been put to practical use.
A second type of the conventional pneumtic tire is
tires provided with a steel cord breaker. As is well-known,
the steel cord for tire is prepared by twisting a plurality
of strands, each strand being formed by twisting a plurality
of elongated steel filaments each having a filament diameter
of about 0.15 to 0.3 mm. In this second type tire, the
breaker is formed by embodding such steel cords at equal
intervals in rubber and arranged between the carcass body
and the tread rubber so as to prevent growth of cut failure
passing through the crown portion of the tire. However, the
second type tire having such a steel cord breaker has an
unavoidable drawback that the separation failure is apt to
be caused at steel cord ends and the like.
It is, therefore, an object of the invention to
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eliminate the above mentioned drawbacks of the conventional
pneumatic tire. That is, the invention is to provide a
pneumatic rubber tire suitable for off-road vehicles having
improved cut resistant property, separation resistant property
and wear resistance.
According to the invention, there is provided a
pneumatic rubber tire for off-road vehicles, comprising a
- multi-layered carcass composed of rubberized laminated
plies, the cords of which are formed of organic fiber and
` 10 inclined at a given angle with respect to the circumferential
direction of tire, the cords of approximately one-half of
said carcass plies extending in an opposite direction to the
cords associated with the remaining plies to define a bias
construction, and a breaker circumferentially superimposed
about said multi-layered carcass and composed of at least
two rubberized layers containing reinforcing elements with
different properties embedded therein; said reinforcing
element in one of said breaker layers being composed of a
helically formed filament of material having a tensile
strength of not less than 140 kg/mm2 or a bundle thereof
together without twisting and said heli.cally formed filament
having a modulus o elasticity of 0.6 to 70 times higher
than that of said organic fiber cords of said carcass ply;
sai.d reinforcing element in said another breaker layer being
composed of a stranded cord of metallic filaments each
having a tensile strength equal to or larger than that of
steel and inclined in the circumferential direction of tire
at an angle of not larger than 8 and not smaller than 15
with respect to said given angle of the cords in said
carcass plies which are aligned with said stranded cord.
4 -
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In a preferred embodiment of the invention 7 the
reinforcing element composed of the helically formed filament
or bundle thereof in one of the breaker layers is inclined
at an angle of not larger than 5 and not smaller than 10
with respect to the angle of the stranded cord as the
reinforcing element in another breaker layer.
The breaker layer containing the helically formed
filament or bundle thereof as the reinforcing element may be
terminated at suitable positions in the widthwise direction
of the tread, but the end portion of the breaker layer
containing the stranded cord as the reinforcing element is
not located at a hump portion of the tire.
According to the invention, the carcass is a multi-
layered bias structure composed of rubberized laminated plies
;....................................................................... . .
lS each containing cords formed of organic fiber and inclined
at a given angle, preferably an angle of 23 to 45, with
respect to the circumferential direction of tire, provided
that the cords of approximately one-half of the carcass plies
extend in an opposite direction to the cords associated with
the remaining plies.
The formation of a tire body comprising such multi-
layered bias carcass is substantially followed by the prior
- art in the fundamental construction as a so-called bias type
tire. However, the invention is particularly aimed at to
adapt such tire for travel on off-road under peculiar and
severe service conditions.
In such multi-layered bias carcass, if the cord
angle of the carcass ply is smaller than 23, it is difficult
to deform the carcass into a toroidal shape in the tire
building step. On the contrary, if the cord angle of the
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~584g4
carcass ply is larger than 45, an undesirable flexibility
is given to the side portions of the tire so that the
stability and safety of the tire are degraded.
According to the invention, as the breaker circum-
ferentially superimposed about the carcass there are used
at least two rubberized layers each containing a reinforcing
element embedded therein. The reinforcing element used in
one of the breaker layers is composed of a helically formed
filament or a bundle thereof together without twisting.
A tensile strength required for such helically formed filament
is defined by a balanced resistance to cuts penetrating into
the tire which resistance is present in the tire immediately
before the tread cut is produced by sharp rocks and the like
when the tire rides on or is urged against these rocks.
The tensile strength of the filament is made at least
1~0 kg/mm2 preferably at least 170 kg/mm2 when the tire is
used under such condition that a comparatively mild tread
cut is produced, and at least 200 kg/mm2 when a maximum cut
resistant property is required.
As the breaker for the tire according to the
invention, the rubberized layer containing the reinforcing
element composed of the above mentioned helically formed
filament or bundle thereof is used together with a rubberized
layer containing a reinforcing element composed of a stranded
cord of metallic filaments each having a tensile strength
equal to or larger than that of steel. The reason why such
two rubberized layers are used as the breaker is as follows.
Heretofore, there was used a steel cord breaker
composed of a rubberized layer containing steel cords
embedded therein. As mentioned above, such steel cords are
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1058~94
prepared by twisting a plurality of strands, each strand
being formed by twisting a plurality of thin steel filaments
each having a filament diameter of about 0.15 to 0.3 mm.
Since the steel cord has a very high modulus of
elasticity and a high flexural rigidity, if the crown
portion of the tire as a whole is largely deformed during
; the running under a load, the steel cord intends to hold
linearity and original length of the crown portion. On the
contrary, the rubber surrounding the steel cord is small in
the modulus of elasticity and flexible. As a result, a
large shearing strain is caused between the steel cord and
the tread rubber contacting therewith. Especially, the
shearing strain becomes maximum at ends of the steel cord
and hence the damage due to separation occurs at an early
; 15 time in use. If the tire is repeatedly used for a long time
in such a damaged state, the range of the damage due to
separation becomes wide and the use of such tire becomes
: ~ impossible . '
The term "modulus of elasticity" used herein means
a value calculated from the following equation on the basis
of a relationship between an elongation and a force obtained
by drawing the organic fiber cord or the reinforcing element
composed of steel cord or helically formed filament or
bundle of such filaments under a tension;
ModuIus of elasticity = S [kg/mm2], wherein F
represents a force ~kg) at an elongation of 1%, S represents
a sectional area (mm2) of a material to be drawn and Q ~ ;
represent an elongation of 1%. According to this equation, .
the modulus of elasticity of the nylon cord is about ;~
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1058494
1.2 x 102 kg/mm2 and that of the steel cord is about
200 x 102 kg/mm2.
According to the invention, a helically formed thin
filament of a metal such as steel and the like having a
filament diameter of 0.1 to 1.0 mm, preferably about 0.13 to
0.5 mm, or a bundle obtained by gathering a plurality of such
helically formed filaments together without twisting is used
as a new reinforcing element having an improved cut resistant
property for use in a rubberized breaker layer.
This reinforcing element composed of the helically
formed filament has a modulus of elasticity within a range of
0.2 x 102 to 80 x 102 ~kg/mm2), preferably 0.7 x 102 to
60 x 102 (kg/mm2), which is very close to the value of the
organic fiber cord and is fairly smaller than the value of
the steel cord commonly used. That is, the modulus of
elasticity of the reinforcing element composed of the
helically formed filament is 0.6 to 70 times higher than that
of the organic fiber cord used in the carcass ply, while the
modulus of elasticity of the steel cord is about 200 times
higher than that of the organic fiber cord.
According to the invention, the modulus of elasticity
of the reinforcing element composed of the helically formed
filament is so selected that a ratio in modulus of elasticity
of such reinforcing element to the organic fiber cord is
within a range of 0.6 to 70, preferably 0.6 to 50. If such
a ratio is larger than 70, a difference between the modulus
of elasticity of the reinforcing element and that of the
tread rubber becomes considerably large, and as a result, the
shearing strain between the reinforcing element and the
adjoining tread rubber becomes large during the rotation of
1C~58494
the tire and the damage due to separation is liable to be
caused When the modulus of elasticity of the reinforcing
element comes near that of the organic fiber cord, the damage
due to separation hardly occurs. However, if the ratio is
smaller than 0.6, the rigidity of the reinforcing element
becomes excessively small, so that the tire is apt to be
deformed more and hence the wearing of the tread rubber is
accelerated.
According to the invention, by using at least two
rubberized layers each containing the different reinforcing
element as the breaker, there is provided pneumatic rubber
tires for off-road vehicles which prevent occurrence of the
damage due to separation, which was liable to be caused in
the conventional steel cord breaker, sufficiently utilize a
high cut resistant property inherent to steel and have
excellent wear resistance and high durability as compared
with those of the breaker using only the helically formed
filament. That is, the rubberized layer containing steel
cords as the reinforcing element for the breaker according
to the invention is not effective to a certain special cut
but exhibits an excellent cut resistant property against
general cuts. ~urther, this breaker layer increases the
rigidity of the crown portion and hence exhibits an excellent
wear resistance owing to its high modulus of elasticity.
However, such a high modulus of elasticity causes a large
relative strain between the steel cord and the adjoining
tread rubber and as a result, the separation resistant
property is considerably degraded. Therefore, it is obliged
to considerably limit the position, number and the like of
this breaker layer in use. On the other hand, the rubberized
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~ 05~494
layer containing the helically formed filament or bundle
thereof as the reinforcing element for the breaker according
to the invention considerably decreases the relative strain
between the reinforcing element and the adjoining tread
rubber as compared with the case of using the steel cord
hecause the modulus of elasticity of this reinforcing element
is lower than that of the steel cord and as a result, such a
layer exihibits not only a very high separation resistant
- property but also a considerably improved cut resistant
,~ 10 property against any kind of cuts. Therefore, there is no
limitation relating to the position, number and the like of
the layer in use.
The inventors have confirmed from many experimental
results that a synergetic effect is developed by optionally
combining the steel cord reinforced layer with the helically
formed filament reinforced layer as the breaker and as a
result, very excellent properties are given to the tire for
; use in off-road vehicles.
That is, the invention makes it possible to combine
the rubberized layers containing two different reinforcing
elements in various forms in practice. For instance, a
first rubberized layer containing the helically formed
filament or bundle thereof as the reinforcing element is
arranged outside a second rubberized layer containing the
steel cord as the reinforcing element, and vice versa.
Furthermore, the second rubberized layer is sandwiched
between the two first rubberized layers, and vice versa.
In any case the number of each of the first and
second rubberized layers used may be one or more. Such
modified constructions of the breaker are optionally selected
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1~358494
depending upon matters for tire design inclusive of use
conditions of tire, production cost and the like. Moreover,
an additional rubberized layer containing fiber cords made
of a suitable material as a reinforcing element may be used
in the breaker besides the first and second rubberized
layers. Alternatively, such fiber cords may be incorporated
into any one of the first and second rubberized layers as a
part of the reinforcing element, if necessary.
According to the invention, the rubberized layer
containing the steel cords as the reinforcing element for
the breaker should be arranged in the circumferential direction
of tire so that its steel cord angle is not larger than 8
and not smaller than 15 with respect to the given angle of
the cords in the carcass plies which is aligned with the
steel cord.
In the rubberized layer containing the helically
formed filament or bundle thereof as the reinforcing element,
the modulus of elasticity of the reinforcing element is very
small as compared with that of the steel cord and comes near
that of the tread rubber. Thus, it will be anticipated that
the rigidity of this rubberized layer as a whole becomes
small due to the decrease of the modulus of elasticity and
hence the wear resistance of the tread rubber is degraded.
Therefore, in order to approach the rigidity of the helically
formed filament reinforced layer to that of the steel cord
reinforced layer to thereby improve the wear resistance of
the tread rubber, the helically formed filament reinforced
layer is arranged in the circumferential direction of tire
so that the angle of the helically formed filament reinforce-
ment is not larger than 5 and not smaller than 10 with
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1~358494
respect to the angle of the steel cord used as the reinforcing
element for the breaker.
In order to prevent growth of the damage due to
cuts started from the tread portion in the pneumatic bias
tire for off-road vehicles, it has been the common practice
to arrange the breaker composed of two or more steel cord
reinforced layers between the carcass ply and the tread
rubber wherein one of the steel cord layers has a width
somewhat larger than the tread width and also the other
steel cord layer near the tread portion has a width narrower
than the tread width. In such a bias tire, it has been
well-known that the radius of that portion of the tire which
makes contact with ground ~effective rotational radius)
becomes small during the rotation of tire under a load and
at the same time the cread width of said portion becomes
narrow, while when that portion of the tire which makes
contact with ground is not subjected to the load in the
course of the rotation, the radius becomes large and at the
same time the tread width is turned to the original width.
Upon the observation of such phenomenon, particularly behavior
in the internal portion of tread, it has been confirmed that
the angle of the organic fiber cord used in the carcass ply
; as well as the angle of the steel cord used in the breaker
at that portion of the tire which makes contact with ground
under a load are variously changed. Such change of cord
angles is indefinitely repeated until the tire becomes
useless. On the other hand, the modulus of elasticity of
the steel cord is considerably higher than that of the tread
rubber. This considerably large difference between the
modulus of elasticity of the steel cord and that of the
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~ 058494
tread rubber results in occurrance of large shearing strain
between the steel cord and the tread rubber contacting
therewith when that steel cord which makes contact with
ground under a load is forced to be subjected to change of
cord angle. This pnenomenon has been examined in detail
with respect to the damaged tires provided with the steel
cord breaker to recognize the followings; that is, the
damage due to separation is not observed at end portions of
the breaker extending near the side portions over the tread
width because the shearing strain between the steel cord and
the adjoining tread rubber during the rotation of tire under ~-
a load becomes gradually increased from a crown center to a
hump portion, and is maximum at the hump portion and becomes
rapidly decreased beyond the hump portion. On the contrary,
at end portions of the steel cord terminated at the hump
portion there is caused a considerably large shearing strain ~ -
between the steel cord and the adjoining tread rubber due to
the change of the steel cord angle as described above, and
as a result, the damage due to separation is caused and
gradually spreaded by repeating such phenomenon. Therefore,
-; there have been frequently seen the case that the steel cord
; breaker tires become useless at a relatively early time in
use though they possess a considrably high cut resistant
property. On the basis of such recognition, according to
the invention, th0 breaker composed of at least two rubberized
layers is so arranged that the breaker layer containing
steel cords as the reinforcing element is arranged so as not
to be located at the hump portion where is liable to cause
the damage due to separation, while the breaker layer
contaiDing the helically formed filament or bundle thereof
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~058494
as the reinforcing element may be located at any position
because such layer itself does not cause the damage due to
separation as mentioned above.
The term "tread width" used herein means a distance
on tread surface between the most thick portions o-f tread
rubber gauge a~ both ends of the crown portion when the tire
is cut along a plane including a rotational axis of tire.
The term "hump line" used herein means a normal line drawn
from the tread surface having the most thick portion of the
tread rubber toward the carcass ply, and hence the term
"hump portion" used herein means a vicinity of a point
intersecting the hump line with the outermost ply of the
carcass plies or the tread rubber near the carcass plies.
The inventors have already confirmed from experi-
mental results relating to the filament diameter of thehelically formed filament that when the helically formed
filament of the same material is used as the reinforcing
element against any type of cuts, the cut resistant property
as a tire depends upon the total sectional area of the
filaments included in the section of the tire due to cut
failure but does not depend upon a size of sectional area or
diameter of each filament. Therefore, it is preferable that
the filament diameter of the helically formed filament
becomes small as far as possible in order to make internal
stress of the filament uniform. In this connection, according
to the invention, there are used helically formed filaments
having a filament diameter of 0.1 mm to 1.0 mm.
If the filament diameter is smaller than 0.1 mm,
- the filament is frequently breaked in allowable extent in
the step of forming the helically formed filament. As a
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1058494
result, it is clear that the use of such thin filament is
not economical. On the contrary, if the filament diameter
is larger than 1.0 mm, the internal stress produced in the
step of forming the helically formed filament becomes excessive.
In addition, the torsional shearing stress produced when the
force for expanding or contracting the filament is applied
thereto in its lengthwise direction is concentrated toward
the outer portion of the filament. As a result, in order to ;~
give the filament a strength necessary for withstanding the
same exterior force, a total sectional area of the large
diameter filament must be larger than that of the thin
filament, so that a more greater amount of the material is
required. Hence, it is clear that the use of such large ;~
diameter filament is not economical. As seen from the above
reasons, the filament diameter should lie within the above
mentioned range of 0.1 mm to 1.0 mm.
In the practice of the invention, the breaker of
,,'J the above mentioned construction is usually arranged between
the tread rubber and the carcass ply. Further, the breaker
may be arranged in the tread rubber or in the carcass plies
near the tread in dependence with the use of tires. Moreover,
the breaker may be divided at suitable intervals in its
widthwise direction.
According to the invention, the breaker is not
t 25 always symmetrical with respect to the equatorial plane oftire and may be unsymmetrical in dependence with the use of
tires.
In addition, at least one rubberized layer of
cords made of an organic fiber such as nylon and the like
~breaker protect layer) may be arranged as a cut protect by
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~05849~
superimposing it outside the breaker (near the tread) with a
width larger than that of the breaker or along both side
edges of the breaker so as to improve a recap property of
the tire.
According to the invention, the organic fiber cord
used in the carcass ply and the breaker protect layer may be
made of rayon, vinylon, polyester or the like in addition to
nylon. As the helically formed filament and the stranded
cord composed of metallic filaments constituting the rein-
forcing element for the breaker, there is preferably used
filament materials having a good adherence to rubber or
subjected to a treatment for adhering to rubber, for example,
a brass plated steel filament, an aromatic polyamide fiber
having a high modulus of elasticity, a glass fiber and the
like.
The invention will now be described in greater
detail with reference to the accompanying drawings, wherein:
Fig. 1 is a cross-sectional view of one-half of a
tire embodying the invention;
Fig. 2 is a graph illustrating experimental test
results of separation resistant property of tires according
to the invention compared with those of conventional tires;
and
Figs. 3 to 5 are cross-sectional views of modified
forms of a tire embodying the present invention, respectively.
Pneumatic tires for construction vehicle wheels
embodying the invention will now be described with reference
to Examples.
Example 1
In Fig. 1 is shown a radial cross-sectional view
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105~494
of one-half of a tire embodying the invention, the section
containing the rotational axis of tire. This tire is of
17.5-25 12PR in size (12PR indicates the size on the basis
of cotton yarn). In the present example, a bead member 1 is
composed of two sets of bead cores la, lb. A carcass 2 is
composed of 8 plies in total, each ply being composed of
nylon cord of 1,260 denier/two strands.
~ our plies 2a of the total 8 plies of the carcass
2 are wound around the bead core la from the inside toward
the outside thereof and secured to the bead member 1. The
other two plies 2b are wound around the bead core lb from
the inside toward the outside thereof and secured to the
bead member 1. The remaining two outside plies 2c are
extended from the outside toward the inside of the bead
cores la, lb along their lower surfaces and secured at their
ends to a toe portion lc of the bead member 1.
The cords of each ply of the carcass 2 are inclined
at an angle of about 36 with respect to the circumferential
direction of tire as measured at a center of a tire crown
portion. These cords of the carcass plies are alternately
extended along two opposite directions symmetrically inclined
at about 36 with respect to the circumferential direction
of the tire crown portion.
In the crown portion 3 of the tire, about the
outside of the carcass 2 is superimposed a breaker 4 of two-
layered structure. In the breaker 4, a layer 4a is composed
of a rubberized fabric containing a plurality of stranded
steel cords having a strand construction of 1 x 4 + 6 x 4 + 1
~the filament diameter is 0.175 mm and the cord diameter is
1.26 mm) embedded therein as a reinforcing element.
- 17 -
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~05~494
The number of steel cords per 5 cm is approximately 18 and
these cords are inclined at an angle of about 36 with
respect to the circumferential direction of tire. Another
layer 4b for the breaker is composed of a rubberized fabric
containing a plurality of bundles made of helically formed
filaments ~the filament diameter is 0.25 mm and the number
of filaments is 14) embedded therein as a reinforcing element.
The number of the bundles per 5 cm is approximately 18 and
these bundles are inclined at an angle of about 36 with - -
respect to the circumferential direction of tire.
In Fig. 2 are shown improved separation resistant
property and durability of the tire built as above described
manner. This figure shows an examples of experimental tests
obtained by an indoor drum testing machine by plotting
running time in hour on abscissa and plotting load speed per
hour in ton-kilometer per hour on ordinate. In the present
' experimental test, the tire was pressurized to the standard
internal pressure of 3.5 kg/cm2, the speed was made constant
as 11 km/hr, and the load was increased from 60% to 170% in
a stepwise manner as shown in Fig. 2. In this case, 100%
load corresponds to 6.135 kg (standard load for 17.5-25
tire as defined according to JIS).
In Fig. 2, a point A represents a test result of a
conventional steel breaker tire, a point B a test result of
a conventional nylon breaker tire, and a point C a test
` result of the tire according to the example 1 of the invention.
As shown by the point A, the conventional steel breaker tire
exceeded its limit temperature at the third load step, thus
resulting in the breaker end separation. On the contrary,
as shown by the point C, the tire according to the example 1
. ~
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~051~494
of the invention safely passed the third load step and
arrived at the fifth load step where the tire exceeded its
limit temperature and caused separation at the breaker due
to overheating. In this case, there was not observed the
occurrence of separation at ends of each bundle made of the
helically formed filaments in the breaker layer 4b.
The above experimental tests have yielded the
- surprising result ~hat the invention brings the same effectas the conventional nylon breaker tire which causes separation
at the point B of the fifth load step although the steel
cords liable to cause the separation in itself are used as
the reinforcing element for the breaker.
Example 2
In Fig. 3 is shown a radial cross-sectional view
of one-half of a tire having the same structure as described
in Example 1, except that the breaker 4 is composed of two
t layers 4a and two layers 4b and the arrangement of the
breaker layers 4a, 4b is reversed to the case of Example 1.
The tire of the present example gave the substan-
tially same result as the tire of Example 1 when the durability
of the tire is examined by an indoor drum testing machine in
the same manner as described in Example 1.
In the examples of Figs. 1 and 3, the modulus of
elasticity of the nylon cord used in each ply of the carcass
2 was 1.2 x 102 kg/mm2, and that of the reinforcing element
composed of the bundle of helically formed steel filaments
in the breaker layer 4b was 2.5 x 102 kg/mm2. Further, the
tensile strength of the helically formed steel filament was
27n kg/mm2.
In Fig. 4 is shown another embodiment of the tire
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~058494
according to the invention. In this embodiment, the arrange-
ment of the breaker 4 composed of an outer layer 4a and an
inner layer 4b is the same as in Fig. 3 except that both
ends of the breaker 4 are not located in the vicinity of
hump portions 5 of the tire, and further an additional
reinforcing layer 6 is arranged between the breaker layers
~` 4a and 4b. This additional reinforcing layer 6 is composed
of a rubberized ply containing 40 stranded nylon cords per
5 cm, the stranded nylon cord being composed of 1,260 denier/
two strands. These cords are inclined at the same angle as
` that of the breaker 4, but extended in a direction opposite
~ to the breaker layer 4b.
r In Fig- 5 is shown a further embodiment of the
tire according to the invention. In this embodiment, the
arrangement of the breaker 4 composed of an inner layer 4a
and an outer layer 4b is the same as in Fig. 1 except that
the ends of the breaker layer 4a are not located in the
vicinity of the hump portions 5 of tire but the ends of the
breaker layer 4b are terminated in the vicinity of the hump
portion 5.
In Figs 4 and 5, a dot-dash-line represents a
hump line of tire.
As stated hereinbefore, according to the invention,
the cut resistant property, separation resistant property
and wear resistance of pneumatic rubber tire for off-road
vehicles can be improved remarkably.
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