Reinforcement belt for a pneumatic tire

A reinforcement belt for a pneumatic tire includes at least three superpositioned plies of filiform elements. A first ply having two free lateral edges has at least one lateral edge portion folded over to create a skirt with the balance of the first ply forming a main portion having an axial width substantially equal to the axial width of the reinforcement belt. The filiform elements in this first ply are of aromatic polyamide composition and have a high modulus of elasticity. A second ply extends parallel to the first ply over an axial distance at least equal to the axial spacing of the two free lateral edges of the first ply. The filiform elements in the second ply may be either of aromatic polyamide or steel composition. A third ply of filiform elements of steel extends into the median zone of the belt and has an axial width which is less than, equal to or greater than the distance separating the free edges of the first ply. Various orientations of the plies are disclosed.

BACKGROUND OF THE INVENTION 
1. Field Of The Invention 
This invention relates to pneumatic tires, and more particularly to tread 
reinforcements or reinforcement belts for radial ply tires. 
2. Prior Art 
It is known in the tire industry to provide pneumatic tire constructions 
which include an annular reinforcement belt or breaker assembly about the 
periphery of the tire between the tread and the carcass. It has been found 
that such a pneumatic tire construction enhances the road stability of the 
tire and increases the tread life in both radial and bias ply 
constructions. Usually, the reinforcement belt consists of one or more 
annular bands which may be positioned parallel and concentrically adjacent 
to one another. These bands almost universally contain cords of organic, 
steel or glass materials which may be oriented on a bias angle from the 
equatorial plane of the tire. A major problem attending such reinforcement 
belt constructions is that of belt edge separation which generally arises 
from road stresses acting in the shoulder regions of the tire where the 
edges of the belts lie. These stresses are caused primarily by the 
rotation of the load-bearing tire into its contact patch with the 
pavement. It is the continual change in shape of the cross-section of the 
tire that causes the stresses, concentrating them in the shoulder regions. 
Since the belt edges within the shoulder region usually contain exposed 
ends of the bias oriented inextensible cords, the interface between the 
cords and the surrounding rubber is often the weakest bond area between 
the belts and the tire carcass. The shoulder region stresses have a 
tendency to cause a separation of the cord ends from the adjacent rubber, 
therefore resulting in a gradual ply separation. 
Several variations in reinforcement belt constructions have been designed 
in an attempt to overcome the above difficulties. Specifically, there is 
disclosed in U.S. Pat. No. 3,881,538 a multi-ply reinforcing breaker 
consisting of a plurality of superimposed plies which decrease 
successively in span axially of the tire from the radially innermost ply 
to the radially outermost ply. The innermost ply is folded at its end to 
in part overlap at least one of the other plies to resist edge separation 
of the plies. Other reinforcement belts containing folded plies are 
described in U.S. Pat. Nos. 3,757,844, 3,949,797 and Canadian Pat. No. 
952,419. 
Usually, the various plies consist of steel cables or cords encased in 
rubber. The use of steel cables in the plies which give the belt increased 
structural rigidity leads to a harsher riding tire. It has been proposed 
to use materials consisting of aromatic polyamides, for instance those 
referred to as Aramides which have a modulus of elasticity preferably in 
excess of 3,500 kg/sq. mm or 260 gram/denier. Indeed, this material has 
attractive qualities of elasticity, toughness, low elongation, low 
specific mass, etc., under such conditions that it reduces the tendancy to 
separate or tear off the belt plies, specifically in the areas of the 
lateral edges of the plies, at least as long as an excessive speed has not 
been attained. 
Construction for reinforcement belts including one or more non-metallic 
cord plies are detailed in U.S. Pat. Nos. 3,404,721, 3,690,364, 3,881,538, 
3,949,797 and French Pat. No. 1,228,241. In several instances in which 
non-metallic cords are used, the softer riding characteristics and lighter 
weight attributable to the non-metallic cords are outweighed by the 
reduced structural integrity of the reinforcement belt structure. 
Furthermore, known approaches to reinforcement belt designs do not provide 
completely satisfactory solutions to the problems of tire stiffness and 
shoulder fatigue. 
It is toward the elimination of these and other drawbacks that the present 
invention is directed. 
SUMMARY OF THE INVENTION 
1. Purposes Of The Invention 
It is an object of the present invention to provide a pneumatic tire having 
an improved reinforcement belt. 
Another object of the present invention is to provide a novel and improved 
belted pneumatic tire with a reinforcement belt constructed to provide 
desirable qualities of road-holding ability, driving comfort, lightness in 
weight, high speed capability and high wear resistance. 
Other objects of the present invention, in part will be obvious and in part 
will become apparent as the description proceeds. 
2. Brief Description Of The Invention 
Generally, the above and other objects of the present invention are 
accomplished by a pneumatic tire having a radial carcass and a 
reinforcement belt or breaker placed between the crown region of the 
carcass and the tread. The reinforcement belt includes at least three 
radially superpositioned plies of filiform elements which elements are 
substantially parallel to one another in each ply. A first ply having free 
lateral edges has at least one lateral edge portion folded over to form a 
skirt with the balance of the first ply forming a main portion having an 
axial width substantially equal to the width of the reinforcement belt. 
The filiformm elements in this first ply are of an aromatic polyamide 
having a high modulus of elasticity. A second ply extends parallel to the 
first ply over an axial extent at least equal to the axial spacing of the 
two free lateral edges of the folded first ply. Preferably the second ply 
has an axial extent substantially equal to that of the main portion of the 
folded ply. In the second ply the filiform elements are either of aromatic 
polyamide or steel composition. A third ply of steel elements is provided 
which extends into the median zone of the reinforcement belt and has an 
axial width which may be less than, equal to or greater than the axial 
distance between the two free ends of the folded over first ply. 
The three plies may be superimposed in various combinations as will be 
detailed hereinbelow. The invention consists of the features of 
construction and arrangement of parts which will be detailed hereinafter 
and described in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the specification and the claims, the terms "axially inward" and 
"axially outward" are used with reference to a sidewall of the tire, that 
is, "axially inward" refers to a vector extending from the sidewall to the 
opposite sidewall. Conversely, "axially outward" refers to a vector 
extending outwardly away from a sidewall. The terms "radially inward" and 
"radially outward" are used with reference to the axis of rotation of the 
tire, that is, "radially inward" refers to a vector extending from the 
tread profile of the tire to the axis, while, the term "radially outward" 
refers to a vector extending from the axis toward the tread profile. The 
term "filiform element" designates either a twisted cord composed of 
strands, an isolated strand or a spun yarn. 
Referring now to the drawings, there is illustrated in FIG. 1, a portion of 
a pneumatic tire identifed generally by the reference numeral 10. The tire 
10 has a crownn region 12 defined by the shoulders 14 and 16 any by a 
tread portion 18. In addition, the tire 10 is provided with a carcass 20 
which may be built in any conventional manner and if of radial 
construction includes radially extending reinforcing threads or cords (not 
shown). 
Positioned between the carcass 20 and the tread portion 18 is a 
reinforcement belt or breaker in accordance with one embodiment of the 
present invention which is identified generally by the reference numeral 
22. The reinforcement belt 22 is substantially coextensive with the tread 
portion 18 and it circles, peripherially, the carcass 20. 
The reinforcement belt 22 includes at least three plies of filiform 
elements in which the elements are substantially parallel to one another 
in each ply and coated with a natural or synthetic elastomer. 
A first ply 24 constitutes the radially innermost ply of the reinforcement 
belt and has two free lateral edges or free edges 26 and 28. The ply has 
two foldings 30 and 32 lying substantially at each lateral edge of the 
reinforcement belt in order to create two lateral skirts 34 and 36, folded 
radially outwardly with respect to a main portion 38. The main portion 38 
has an axial extent substantially equal to the axial width of the 
reinforcement belt. As noted hereinabove the first ply 24 contains 
filiform elements and these are of an aromatic polyamide composition 
having a high modulus of elasticity, preferably in excess of 3,500 kg/sq. 
mm. 
A second ply 40 is superimposed on the main portion 38 on its radially 
outward side and extends parallel to the first ply 24. It has an axial 
width at least equal to the distance between the two free edges 26 and 28 
so that the skirts 34 and 36 can be folded over the lateral edges 42 and 
44 of the second ply 40 as shown. The filiform elements in the second ply 
40 may be either or an aromatic polyamide, similar to that utilized in the 
first ply 24, or may be of steel. 
A third ply 46 of steel elements is superimposed on the second ply 40 and 
extends from the free edge 26 to the free edge 28. 
In the embodiment illustrated in FIG. 1, and also shown in FIG. 1A, the 
axial width "m" of the skirt 36 plus the axial width "p" of the skirt 34 
plus the axial width "n" of the third ply 46 are equal to "1", the axial 
width of the reinforcement belt. In other words, the third ply 46 abuts 
the free edges 26 and 28 on the skirts 34 and 36 respectively. The third 
ply 46 also extends into the median zone of the reinforcement belt as 
shown. 
In the alternative embodiments of the present invention which are 
illustrated in FIGS. 2-11, and which will be discussed hereinbelow, only 
the reinforcement belts are illustrated. 
In the alternative embodiment illustrated in FIG. 2, a first ply 50 has 
radially outwardly folded portions or skirts 52 and 54. The second ply 56 
has an axial extent which is less than the axial width of the main portion 
58 of the first ply which corresponds to the axial width of the 
reinforcement belt, but which is greater than the distance between the 
free edges 60 and 62 on the skirts 52 and 54 respectively. In this 
embodiment as in the one illustrated in FIGS. 1 and 1A, the skirts 52 and 
54 are folded onto the lateral edges 56a and 56b of the second ply 56. A 
third ply 64 is positioned between the free edges 60 and 62. In this 
embodiment, the axial width of the skirt 52 denoted by the letter "p" plus 
the axial width of the skirt 54 denoted by the letter "m" plus the axial 
width of the third ply 64, "n", is less than the axial width "1" of the 
reinforcement belt. Third ply 64 does not abut the free edges 60 and 62. 
Moreover, as shown, the axial width "p" of the skirt 52 may be greater 
than the axial width "m" of the skirt 54. 
Another alternative embodiment for the reinforcement belt is illustrated in 
FIG. 3 and incorporates a first ply 68 having skirts 70 and 72 which are 
folded radially outwardly over both a second ply 74 and a third ply 76 
which is positioned between the first and second plies. The third ply 76 
has an axial width "n" less than the axial width "q" of the second ply 74 
The width "q" of the second ply 74 is, as in the embodiments illustrated 
in FIGS. 1 and 2 above, less than the full axial width of the 
reinforcement belt but greater than the distance between the free edges 78 
and 80 on the skirts 70 and 72 respectively. 
Another alternative embodiment is shown in FIG. 4 in which a first ply 82 
has radially outwardly folded skirts 84 and 86 as shown. A second ply 88 
is superimposed upon the skirts 84 and 86 and is of an axial width 
sufficient to bridge the two free edges 90 and 92 on the skirts 84 and 86 
respectively. A third ply 94 is positioned axially between the edges 90 
and 92 and radially between the main portion 96 of the first ply 82 and 
the second ply 88. In this embodiment the second ply 88 overlaps the third 
ply 94 in its entirety as well as the free edges 90 and 92. 
The alternative embodiment illustrated in FIG. 5 includes a folded first 
ply 98 with skirts 100 and 102. Positioned on the skirts 100 and 102 in a 
manner similar to that embodiment illustrated in FIG. 4 is a second ply 
104 which extends over the free edges 106 and 108. Superimposed upon the 
second ply 104 is a third ply 110 which has an axial extent greater than 
the distance between the free edges 106 and 108. 
In FIG. 6, a further alternative embodiment is shown in which a first ply 
112 has radially outwardly folded skirts 114 and 116 over which is 
positioned a second ply 118 in direct contact with the skirts 114 and 116. 
This embodiment differs from those discussed hereinabove in that a third 
ply 120 is positioned radially inwardly of the main portion 122 on the 
first ply 122. The third ply 120 may have an axial width equal to or 
grater than the spece between the free edges 124 and 126 of the first ply. 
The alternative embodiment of FIG. 7 has a first ply 128 with skirts 130 
and 132. A third ply 134 is positioned between free edges 136 and 138 
respectively. Positioned radially inwardly of the main portion 140 is a 
second ply 142. 
In the alternative embodiment shown in FIG. 8, a first ply 144 is provided 
with skirts 146 and 147. Superimposed upon the first ply 144 radially 
inwardly of the main portion 148 is a second ply 149. A third ply 150 is 
positioned immediately adjacent the second ply 149 and radially inwardly 
of the first ply 144. 
A further alternative embodiment is shown in FIG. 9 wherein a first ply 152 
is provided with radially outwardly folded skirts 154 and 156 which 
overlap a second ply 158 as shown. A third ply 160 is superimposed upon 
the skirts 154 and 156 and extends axially beyond the free edges 162 and 
164 on the skirts 154 and 156 respectively. 
In the alternative embodiment of FIG. 10, a first ply 166 has skirts 168 
and 170 folded radially outwardly upon a second ply 172. The free edges 
174 and 176 on the skirts 168 and 170 respectively may be spaced slightly 
from each other or may abut each other. Superimposed on the free edges 174 
and 176 is a third ply 178. 
There is shown in FIG. 11 yet another embodiment of the present invention 
in which a first ply 180 has only one radially outward fold 82 to create a 
skirt 184. Placed adjacent but spaced from the free edge 186 of the first 
ply 180 on the skirt 184 is a third ply 188 which extends into the median 
zone of the reinforcement belt. A second ply 190 extends from the fold 182 
over the skirt 184, the free edge 186 as well as the third ply 188 as 
shown. In this embodiment, the fold 182 may be located on either the 
axially inward, or axially outward edge of the reinforcement belt. 
In the embodiments illustrated in FIGS. 1-11 the axis of the pneumatic tire 
containing the reinforcement belt is situated beneath the particular 
cross-sectional representation so that the skirts created by the folds in 
the first ply are positioned radially outwardly of the main portion of the 
first ply. It is to be understood that without deviating from the intent 
of the present invention, the axis could be situated above the 
reinforcement belts illustrated so that the skirts created by the folds in 
the first ply will be positioned radially inwardly of the main portion of 
the first ply. Furthermore, where the skirts of the first ply are shown 
folded radially outwardly, they may alternatively be folded radially 
inwardly with the orientation of the three plies remaining unchanged. 
In the various embodiments discussed hereinabove, the filiform elements of 
the first ply are formed from an aromatic polyamide composition having a 
modulus of elasticity preferably in excess of 3,500 kg/sq. mm. The 
filiform elements in the second ply may be of either steel or aromatic 
polyamide and preferably are of the latter. The filiform elements in the 
third ply are of steel. As to the angle of orientation of the elements in 
the various plies, the elements in the main portions of the first ply lie 
at an angle of from about 10.degree. to about 30.degree. with respect to 
the equatorial plane X--X of the tire. Consequently, the filiform elements 
in the skirt portions of the first ply will lie at an angle intersecting 
the filiform elements of the main portion, with the angle accordingly 
being between 20.degree. and 60.degree.. The filiform elements in the 
second plies lie at an angle of from about 10.degree. to about 30.degree. 
with respect to the equatorial plane X--X of the tire and the filiform 
elements in the third plies lie at an angle of from about 20.degree. to 
about 90.degree. with respect to the equatorial plane. 
It can be seen from the foregoing that the objects of the present invention 
namely, to achieve an improved reinforcement belt for a pneumatic tire, 
are accomplished by the utilization of a first ply of aromatic polyamide 
filiform elements which is folded along at least one lateral edge to 
create at least one skirt. A second ply of filiform elements which may be 
either steel or aromatic polyamide is positioned with respect to the skirt 
so as to extend beyond the free edge on the skirt. A third ply of steel 
filiform elements extends into the median zone of the belt and is located 
with respect to the first and second plies to contribute structural 
rigidity to the reinforcement belt. The utilization of the first two plies 
of aromatic polyamide filiform elements results in the reinforcement belt 
being considerably lighter in weight than those manufactured pursuant to 
current designs. 
While in accordance with the patent statutes preferred embodiments of the 
present invention are set forth and described in detail, it is to be 
understood that the present invention is not limited thereto or thereby.