Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a pneumatic
tire and in particular to a radial pneumatic tire which
is used at high speeds and which includes a belt
reinforcing cap or layer between the tread portion and
the belt portion.
A conventional radial pneumatic tire which
is used at high speeds includes a belt reinforcing
layer consistin~ of two layers each having a predeter-
mined width and disposed radially outwardly of a
lateral end portion of a belt. Each reinforcing layer
is composed of cords. The cords extend substantially
in the circumferential direction of the tire and are
covered with rubber. The lower reinforcing layer is
hooped around the belt, and then the longitudinal end
portions are overlapped with each other. Likewise, the
upper reinforcing layer is hooped on the lower
reinforcing layer previously hooped on the belt, and
the lon~itudinal end portions are overlapped with each
other and vulcanized. Thus, the reinforcing layers of
2~ the conventional tire form overlapped portions,
respectively. Another conventional radial pneumatic
tire which is used at high speeds includes a belt
reinforcing cap of a predetermined width disposed
radially outwardly of a belt and covering a full width
of the belt. The reinforcing cap is composed of cords.
The cords extend substantially in the circumferential
direction of the tire and are covered with rubber. The
reinforcing cap is hooped around the belt, and then the
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longitudinal end portions are overlapped with each
other and vulcanized. Thus, the rein~orcing cap of the
conventional tire also forms an overlapped portion.
In both cases of the reinforcing layer and
the reinforcing cap, at least one overlapped portion is
formed on the circumference of the tire, and therefore
the longitudinal end portions of the overlapped
portions slip relative to each other and loosen,
thereby weakening the tightening effect of the
reinforcing layer and cap. Also, the reinforcing layer
and the reinforcing cap are increased in thickness due
to the overlapped portions, thereby reducing a
uniformity level of the tire and degrading a
comfortable riding performance. Furthermore, in the
lateral end portion of the belt, the width of the upper
reinforcing layer can be reduced to a width smaller
than a full width of the lower reinforcing layer in
order that the belt is tightened by the reinforcing
layer, but if different layers of narrow and wide
widths are used, two kinds of reinforcing layers
different in width must be prepared. Furthermore, if
the reinforcing cap is further used, the cap of the
width must also be prepared in addition to the two
kinds of layers. As a result, there is the disadvan-
tage that various kinds of belt reinforcing layers and
caps are required.
It is accordingly an important object of the
present invention to provide an improved pneumatic tire
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which prevents and overcomes the a~orementioned
disadvantages attendant with the prior art.
In accordance with an important aspect of
the present invention, there is provided a pneumatic
tire comprising a carcass having two opposite beads and
extending from one bead to the other bead, a tread
portion disposed radially outwardly of the carcass and
extending in a circumferential direction of the tire, a
belt of steel cord material disposed between the
carcass and the tread portion, the belt having two
laterally opposite end portions, and a reinforcing
layer disposed between the tread portion and the belt.
; The reinforcing layer is formed by spirally hooping a
continuous ribbon material on the belt. The continuous
ribbon material is composed of a plurality of nylon
cords covered with rubber. The reinforcing layer is
varied in cord density laterally of the tire by varying
a hooping pitch of the ribbon material laterally of the
tire and hooping the ribbon material in two or more
layers.
The drawbacks of a prior-art pneumatic tire
and the features and advantages of a pneumatic tire
according to the present invention will be more clearly
understood from the following description taken in
; conjunction with the accompanying drawings in which:
Fig. 1 is a part-sectional view of a first
embodiment of the pneumatic tire in accordance with the
~- present invention;
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Fig. 2 is an enlarged sectional view of the
ribbon-like material and the belt shown in Fig. l;
: Fig. 3 is an enlarged sectional view showing
cord
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materials of the ribbon-like material shown in Fig. 2;
Fig. 4 is a part-sectional view showing a belt
reinforcing layer of a ribbon-like material hooped on a belt
in accordance with a second embodiment of the present
invention;
Fig. 5 is a part-sectional view showing a belt
reinforcing layer of a ribbon-like material hooped on a belt
in accordance with a third embodiment of the present
invention;
Fig. 6 is a part-sectional view showing a belt
reinforcing layer of a ribbon-like material hooped on a belt
according to a fourth embodiment of the present invention;
Fig. 7 is a view showing the manner in which a belt
reinforcing layer of a ribbon-like material is hooped on a
belt in accordance with a fifth embodiment of the present
invention;
- Fig. 8 is a view showing the manner in which two
belt reinforcing layer of a ribbon-like material are hooped on
a belt in accordance with a sixth embodiment of the present
invention;
Fig. 9 is a part-sectional view showing a pneumatic
tire of the prior art, two belt reinforcing layers being
hooped on a laterally end portion of the belt;
Fig. 10 is a side sectional view, taken from an
arrow B of Fig. 9, showing that longitudinal end portions of
the reinforclng layers are overlapped with each other;
Fig. 11 is a part-sectional view showing a pneumatic
tire of the prior art wherein the belt reinforcing cap is
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hooped over a full width of the belt;
Fig. 12 is a side sectional view, taken from
an arrow s of Fig. 11, showing that longitudinal end
portions of the reinforcing cap are overlapped with
each other;
Fig. 13 is a view showing the manner in
which a belt reinforcing layer of a ribbon-like
material is hooped on a belt in accordance with a
seventh embodiment of the present invention; and
10Fig. 14 is a view showing the manner in
which a belt reinforcing layer of a ribbon-like
material is hooped on a belt in accordance with an
eighth embodiment of the present invention.
Referring to Figs. 9 and 10, there is shown
a conventional radial pneumatic tire which is used at
high speeds and which includes a belt reinforcing layer
1 consisting of two layers la and lb each having a
` predetermined width Wl and disposed radially outwardly
of a lateral end portion 2a of a belt 2. Each
reinforcing layer is composed of cords. The cords
~; extend substantially in the circumferential direction
of the tire and are covered with rubber. The lower
; reinforcing layer lb is hooped around the belt 2, and
then the longitudinal end portions lbl (Fig. 10) are
overlapped with each other. Likewise, the upper
reinforcing layer la is hooped on the lower reinforcing
layer lb previously hooped on the belt 2, and the
longitudinal end portions lal (Fig. 10) are overlapped
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with each other and vulcanized. Thus, the reinforcing
layers la and lb of the conventional tire form
overlapped portions 4, respectively. In Figs. ll and
12, there is shown another conventional radial
pneumatic tire which is used at high speeds and which
includes a belt reinforcing cap 7 of a predetermined
width W7 disposed radially outwardly of a belt 9 and
covering a full width Wg of the belt 9. The re-
inforcing cap 7 is composed of cords. The cords extendlO substantially in the circumferential direction of the
tire and are covered with rubber. The reinforcing cap
7 is hooped around the belt 9, and then the
longitudinal end portions 7a (Fig. 12) are overlapped
with each other and vulcaniæed. Thus, the reinforcing
cap 7 of the conventional tire also forms an overlapped
portion ll.
In hoth cases of the reinforcing layer l and
the reinforcing cap 7, at least one overlapped portion
4 or ll is formed on the circumference of the tire, and
therefore the longitudinal end portions lal, lbl and 7a
of the overlapped portions 4 and ll slip relative to
each other and loosen, thereby weakening the tightening
effect of the reinforcing layer and cap. Also, since
the reinforcing layer l and the reinforcing cap 7 are
increased in thickness due to the overlapped portions 4
and ll, thereby reducing a uniformity level of the tire
and degradin~ a comfortable riding performance.
Furthermore, in the lateral end portion 2a of the belt
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2 shown in Fig. 9, the width of the upper reinforcing
layer la can be reduced to a width Wlc smaller than a
full width wl of the lower reinforcing layer lb in
order that the belt 2 i~ tightene~ by the reinforcing
layer 1, but if different layers of narrow and wide
widths are used, two kinds of reinforcing layers
different in width must be prepared. Furthermore, if
the reinforcing cap 7 as shown in Fig. 11 is further
used, the cap of the width W7 must also be prepared in
addition to the two kinds of layers. As a result,
there is the disadvantage that various kinds of belt
reinforcing layers and caps are required.
Referring to Fig. 1 of the drawings, a
radial pneumatic tire according to a first embodiment
of the present invention is generally designated by
reference numeral 21. The radial pneumatic tire 21
comprises a carcass 23 made up of layers of cord
materials and extending from one bead to the other
bead, a tread portion 25 disposed radially ou~wardly of
;~ 20 the carcass 23 and extending in a circumferential
direction of the tire, a belt 27 disposed between the
carcass 23 and the tread portion 25, and a belt
reinforcing layer 30 disposed between the tread portion
25 and the belt 27. The reinforcing la~ver 30 is formed
by hooping a continuous ribbon-like material 36, which
is composed of one to twelve cord materials 32 covered
with rubber 34, on the belt 27 spirally in the
circumferential direction o~ the tire. In this embodi-
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g
ment, the cord materials 32 of the ribbon-like material
36 comprises two nylon cords as shown in Fig . 3. When
the ribbon-like material 36 of two cord materials 32 is
used, there is the advantage that the number of hoops
of the continuous ribbon-like material 36 can be
reduced by half as compared with a ribbon-like material
of one cord, thereby enhancing an efficiency of
production. The continuous ribbon-like material 36
forming the belt reinforcing layer 30 is capable of
being hooped with a variable hooping density in a
lateral direction of the tire indicated by an arrow A
in Fig. 2. More particularly, the reinforcing layer 30
of a laterally outer end portion 27a of the belt 27
comprises an outer reinforcing layer 30a and an inner
reinforcing layer 30b, and in the outer reinforcing
layer 30a, the ribbon-like material 36 is hooped in two
lay~rs, and in the inner reinforcing layer 30b, the
ribbon-like material 36 is hooped in one layer. Thus,
the hooping density of the hooped ribbon-like material
36 is reduced at the inner reinforcing layer 30b than
at the outer reinorcing layer 30a.
The operation of the aforementioned first
embodiment according to the present invention will be
hereinafter described.
As mentioned above, the continuous ribbon-
like material 36 forming the belt reinforcing layer 30
is capable of being spirally hooped with a variable
hooping density in the lateral direction of the tire,
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and therefore, the hooping density can be increased
gradually toward the outer end portion 27a of the belt
27 which should be more tightened, and decreased
gradually toward a mid-circumferential portion E of the
belt 27 which should be less tightened. Furthermore,
the reinforcing layer 30 is ~ormed by hooping spirally
many times the continuous ribbon-like material 36
composed of one to twelve cord materials 32 covered
with rubber 36, and therefore there is no overlapped
longitudinal end portions which are formed in the
aforementioned prior art. As a consequence, the belt
reinforcing layer 30 according to the present invention
is effectively prevented from slipping and loosening,
thereby considerably enhancing the tightening effect of
the belt and the tire durability performance at high
speeds. In addition, since the continuous ribbon-like
material 36 is hooped spirally, the leading and
trailing end portions thereof are effectively prevented
from being overlapped ~ith each other and therefore a
~0 uniformity level of the tire cannot be reduced and a
comfortable riding performance of the tire cannot be
degraded. Furthermore, since a narrow reinforcing
layer and a wide reinforcing layer can be made by
varying the hooping density of the continuous ribbon-
like material 36, only one kind of a material is
required to make the ribbon-like material 36, thereby
considerably reducing the cost of production.
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Referring to Fig. 4, there is shown a belt
reinforcing layer 40 of a ribbon-like material 46
~pirally hooped on a belt 27 in accordance with a
second embodiment of the present invention. The
reinforcing layer 40 comprises a laterally inner
reinforcing layer 42 which is spixally hooped on a
laterally outer end portion 27a of the belt 27 with a
predetermined spacing in the lateral direction of the
tire, and a laterally outer reinforcing layer 44 which
is hooped on the laterally outer end portion 27a of the
belt 27 without the spacing. As a result, the hooping
density of the continuous ribbon-like material 46
forming the reinforcing layer 40 is reduced from the
outer reinforcing layer 44 toward the inner reinforcing
layer 42. Other members are substantially identical in
construction and operation to those of the first
- embodiment and therefore the description will be
hereinafter omitted.
Referring to Fig. 5, there is shown a third
embodiment of the present invention. In this embodi-
ment, a reinforcing layer 50 is used as a cap. That
is, a continuous ribbon-like material 52 forming the
reinforcing layer 50 is hooped over the full width o~
the belt 27 so that the spacing between the adjacent
looped portions is gradually reduced from a mid-
circumferential portion E of the tire toward opposite
outer end portions 27a of the belt 27. More parti-
cularly, at the opposite outer end portions 27a, the
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ribbon-like material 52 is spirally hooped without the
spacing between the adjacent looped portions thereof.
When the reinforcing layer is one layer at the outer
end portion of the belt as shown in Figs. 4 and 5, it
is desirable that the width of the ribbon-like material
52 be between 4 mm and 6 mm. If the width is less than
4 mm, the cost of production is increased, and if the
width is more than 6 mm, the ribbon-like material of
the reinforcing layer protrudes from the lateral end of
the belt when it i5 hooped, so that cracks occur at the
protruded portion. Other members are substantially
identical in construction and operation to those of the
second embodiment and therefore the description will be
hersinafter omitted.
Referring to Fig. 6, there is shown a fourth
embodiment of the present invention. A reinforcing
layer 60 is provided over the full width of the belt
27. A continuous ribbon-like material 62 forming the
reinforcing layer 60 is spirally hooped so that the
spacing between the adjacent looped portions thereof is
gradually reduced from a mid-circumferential portion E
of the tire toward the opposite outer end portion 27a
of the belt 27. At the outer end portion 27a, the
ribbon-like material 62 is hooped in two layers without
the spacing between the adjacent looped portions
thereof. Thus, in this embodiment, the hoopin~ density
is increased at the opposite outer end portion 27a than
the third embodiment shown in Fig. 5. When the
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reinforcing layer is hooped in two layers at the outer
~nd portion of the belt as shown in Fig. 6, it is
desirable that the width of the ribbon-like material be
between 4 mm and 11 mm. If the width is less than 4
mm, the cost of production is increased, and if the
width is more than 11 mm, the ribbon-like material of
the reinforcing layer protrudes from the lateral end of
the belt when it is hooped, so that cracks occur at the
protruded portion. Other members are substantially
identical in construction and operation to those of the
third embodiment and therefore the description will be
hereinafter omitted.
Referring to Fig. 7, there is shown the
manner in which a belt reinforcing layer 70 of a
ribbon-like material 72 is spirally hooped on the belt
27 in accordance with a fifth embodiment of the present
invention. The ribbon-like material 72 is first hooped
leftward of Fig. 7 from a position B to a lateral left
end C. At the lateral end C, the hooping direction of
~O the ribbon-like material 72 is turned to the position B
so that the ribbon material can be hooped in two
layers. The reinforcing layer 70 becomes one layer
from the positon B and the hooping density is gradually
decreased toward the mid-circumferential positon E.
After passing the mid-circumferential position E, the
ribbon-like material 72 is hooped so that the hooping
density is gradually increased toward a lateral right
end D. At the lateral right end D, the ribbon-like
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material 72 is again turned back to the mid-
circumferential position E to be in two layers, and the
hooping is completed at a position F. Thus, the
ribbon-like material 72 is hooped with a locus of a
generally inverted letter ~ indicated by the arrow in
Fig. 7. As a result, the reinforcing la~er 70 as shown
in Fig. 7 can be easily formed continuously by a single
ribbon-like material 72.
Referring to Fig. 8, there is shown a sixth
embodiment according to the present invention. The
sixth embodiment is identical to the fifth embodiment
of Fig. 7 except that two ribbon-like materials 82
forming a reinforcing layer 80 are used. The two
ribbon-like materials 82 are hooped in opposite direc-
tions from the mid-circumferential position E to
opposite ends D and D, and turned back at the ends D
and D toward the mid-circumferential position E, and
the hooping of the two ribbon-like materials 82 are
completed at positions F and F. In this embodiment,
two ribbon-like materials are used, but the reinforcing
layer 80 aan also be
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easily formed.
Fig. 13 shows the manner in which a belt reinforcing
layer 90 of a ribbon-like material 92 is hooped on the belt 27
in accordance with a seventh embodiment of the present
invention. The ribbon-like material 92 is flrst hooped
laterally outward from a position H to the lateral edge of the
belt 27, and turned back toward the mid-circumferential
position E and turned back again at the other lateral edge of
the belt 27 and terminated at a postion G. It is noted that
two ribbon-like materials 92 may be hooped from the positions
H and E at the same time.
Fig. 14 shows the manner in which a belt reinforcing
layer 100 of a ribbon-like material 102 is hooped on the belt
27 in accordance with an eighth embodiment of the present
invention. In this embodiment, the ribbon-like material 102
is hooped so as be three layers at the opposite outer end
portions 27a of the beIt 27. It is noted that two ribbon-like
materials ln2 may be hooped from positions K and L at the same
time.
While certain representative embodiments and details
have been shown for the purpose of illustrating the invention,
i~t will be apparent to those skilled in this art that various
changes and modifications may be made therein without
departing rom the spirit or scope of the invention.
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