Method of winding reinforcement layer of pneumatic radial tire

A method of winding a reinforcement layer of a pneumatic radial tire, which comprises providing at circumferentially spaced locations opposite to a front face of an outer peripheral surface of a building drum, a pair of traverse devices each having a fiber cord feed guide and constructed so as to be reciprocated along the axial direction of the building drum; and moving the pair of traverse devices by independent driving devices along the axial direction of the building drum while rotating the building drum, thereby simultaneously feeding rubberized fiber cords respectively from each feed device to a reinforcement belt on the building drum.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of winding a reinforcement layer 
comprising a fiber cord composed of at least one textile cord on a 
reinforcement belt wound round a building drum in the production process 
of a pneumatic radial tire, and more particularly to a method of 
efficiently forming a reinforcement layer free from a spliced part through 
continuous winding of a fiber cord round a reinforcement belt provided on 
a building drum. 
In some pneumatic radial tires for a passenger car, a reinforcement layer 
having a cord angle of substantially 0.degree. relative to the 
circumferential direction of the tire is wound round at least both edges 
of at least two reinforcement belts provided on a tread for the purpose of 
improving high speed durability. FIGS. 6 and 7 are each an example of the 
tread of a high-performance tire having high speed durability. In FIG. 6, 
two reinforcement belts B each comprising steel cords are provided on a 
carcass C of a tread T so that the cord angles cross each other, and both 
edges of the reinforcement belts B are covered with a reinforcement layer 
L comprising fiber cords having a cord angle of substantially 0.degree. 
relative to the circumferential direction of the tire. 
When the above-described radial tire travels at a high speed, both edges of 
the reinforcement belt B are forced up towards the outside in the radial 
direction by centrifugal force, which causes unfavorable separation. 
However, the above-described reinforcement layer L serves to inhibit the 
edges of the reinforcement belt B from being forced up to prevent the 
occurrence of the separation, which contributes to an improvement in the 
high speed durability. In order to improve the high speed durability, 
sometimes the reinforcement layer L is provided so as to cover not only 
both edges of the reinforcement belt B but also the full width of the 
reinforcement belt B as shown in FIG. 7. 
In the production process of a tire, the winding of the reinforcement layer 
L round the above-described belt B is conducted on a building drum. As 
with the reinforcement belt B, the winding of the reinforcement layer L is 
generally conducted by splicing both ends of a ribbon belt formed by 
doubling a plurality of fiber cords in parallel. Since the fiber cords of 
the reinforcement layer are provided in the circumferential direction of 
the tire, Japanese Patent Laid-Open No. 251203/1987 proposes formation of 
a reinforcement layer through continuous winding of a single fiber cord 
coated with rubber in a spiral form in the circumferential direction of 
the tire without splicing the ribbon belt. 
This method of winding a reinforcement layer is excellent in an improvement 
in the uniformity of a tire because no spliced part is formed. However, in 
this method, a single fiber cord coated with rubber should be continuously 
wound several hundred times on a building drum. This takes a very long 
period of time until the reinforcement layer is formed, which brings about 
a problem with efficiency. Further, when a reinforcement layer is formed 
separately on each of the left and right edges of the belt the fiber cord 
must be cut after winding of one reinforcement layer is completed, and the 
fiber cord end should be then switched for formation of another 
reinforcement layer. This takes not only a long time but also much labor. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a method of winding a 
reinforcement layer of a pneumatic radial tire which comprises 
continuously winding a fiber cord on a reinforcement belt wound round a 
building drum to form a reinforcement layer free from a spliced part. 
Another object of the present invention is to provide a method of winding a 
reinforcement layer of a pneumatic radial tire which enables efficient 
winding in a short time when a reinforcement layer free from a spliced 
part is formed by continuously winding a fiber cord on a reinforcement 
belt wound round a building drum. 
In order to attain the above-described objects in the present invention, a 
pair of traverse devices each having a fiber cord feed guide and 
constructed so as to be reciprocated along the axial direction of a 
building drum are provided as a winding device opposite to the front face 
of the outer peripheral surface of the building drum. In the 
above-described structure, said pair of traverse devices are moved along 
the axial direction of the building drum while rotating the building drum, 
thereby feeding a rubberized fiber cord composed of at least one textile 
cord from each feed guide, and thereafter the fed fiber cords are spirally 
wound along substantially the circumferential direction on at least two 
reinforcement belts wound on the building drum to form at least one 
reinforcement layer comprising the fiber cords. 
A desired reinforcement layer can be wound in a short time on the 
reinforcement belts by providing a pair of traverse devices in front of 
the outer peripheral surface of the building drum and simultaneously 
feeding rubberized fiber cords from the feed guide of each of the traverse 
devices. As opposed to the prior art method, a reinforcement layer can be 
formed separately on each of the left and right edges of the belt 
simultaneously without the necessity of suspending the feed of the fiber 
cords.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the winding apparatus shown in FIGS. 1 and 2, numeral 1 designates a 
building drum for building a reinforcement belt B and a reinforcement 
layer L. The reinforcement belt B comprises at least two layers crossing 
each other in the direction of the cords, and at least one of them 
comprises steel cords. The reinforcement layer L comprises at least one 
layer provided so as to cover at least both edges of the reinforcement 
belt B and is formed by spirally winding a rubberized fiber cord Y in a 
continuous manner along substantially the circumferential direction of the 
building drum. The rubberized fiber cord is composed of at least one 
textile cord which is preferably an organic fiber cord and most preferably 
a nylon cord. In case the rubberized fiber cord is composed of more than 
two textile cords, those textile cords are formed to be flat. 
The drum 1 is fixed to one end of a drum shaft 2 supported by a bearing 3 
and rotated by a motor 4 mounted on the opposite side of the bearing 3. A 
support frame 5 is provided opposite to the front face of the outer 
peripheral surface of the building drum 1, and a pair of traverse devices 
6a and 6b are provided on the support frame 5. Both the traverse devices 
6a and 6bhave support plates 8a and 8b, respectively. The support plates 
8a and 8b are provided with feed guides 7a and 7b for a fiber cord Y, 
respectively. The feed guides 7a and 7b each comprise a grooved roller. 
The fiber cords Y, Y are guided to the grooves and fed on the building 
drum 1. 
The support frame 5 is provided with one ball screw 9 and two guide rods 
12, 12. The ball screw 9 has a right-handed screw 9r in one moiety and a 
left-handed screw 9s in the other moiety of its length, and provided so 
that it can be rotated by a motor 13 in any of the forward and backward 
directions. One support plate 8aout of the two support plates 8a and 8b is 
engaged with the right-handed screw of the ball screw 9 through a nut 10a, 
while the other support plate 8b is engaged with the left-handed screw 9s 
of the ball screw 9 through a nut 10b. The support plates 8a, 8b are 
slidably fitted with guide rods 12, 12 through guides 11a, 11b, 
respectively. Therefore, the rotation of the ball screw 9 with the motor 
13 enables the traverse devices 6a, 6b to be moved together with the feed 
guides 7a, 7b in the directions opposite to each other. The rubberized 
fiber cords Y, Y simultaneously fed from both the feed guides 7a, 7b for 
moving the fiber cords are spirally wound in a continuous manner on a 
reinforcement belt B provided on the building drum 1 driven by a motor 4 
to form reinforcement layers L, L. 
When winding initiating points S, S of the two feed guides 7a, 7b are 
provided a little inside both edges of the reinforcement belt B and 
outwardly moved as shown in, for example, FIG. 5(A), reinforcement layers 
L, L are respectively formed on both edges of the reinforcement belt B. 
Further, reinforcement layers L, L overlapped to have a double layer 
structure as shown in FIG. 5(B) can be formed by, as shown in FIG. 5(A), 
moving the feed guides 7a and 7b toward both edges of the reinforcement 
belt and then turning back the guides toward the inside of the 
reinforcement belt. Further, as shown in FIG. 5(C), reinforcement layers 
L, L each having a double-layer structure can be formed also by placing 
the winding initiating points S, S of the feed guides 7a and 7b at the 
edges, inwardly moving both the feed guides and outwardly turning back the 
feed guides. As shown in FIG. 5(D), reinforcement layers L, L covering 
substantially the full width of the reinforcement belt can be formed by 
placing the winding initiating points S, S at a center, moving the feed 
guides respectively toward the edges and turning back the feed guides 
toward the center. 
Thus, the left and right reinforcement layers L, L can be symmetrically and 
simultaneously formed on the reinforcement belt B by feeding a pair of 
fiber cords Y, Y on the reinforcement belt B while traversing the fiber 
cords in the directions opposite to each other. Further, the winding can 
be efficiently completed in a short time by simultaneously feeding a pair 
of fiber cords. 
FIGS. 3 and 4 relate to another example of the winding device. In this 
device, a pair of traverse devices 6a, 6b are supported by frames 5a and 
5b separately provided respectively as upper and lower frames and provided 
so that they are driven by separately provided ball screws 9a, 9b. The two 
ball screws 9a, 9b are the same with each other in the direction of the 
thread and driven by motors 13a, 13b, respectively. When the two motors 
13a and 13b rotate in a same direction each other, the two traverse 
devices 6aand 6b can be moved together with the feed guides 7a, 7b along 
the axial direction of the building drum 1 in the same directions, while 
they rotate in opposite directions each other, the two traverse devices 
6a, 6b can be moved in the directions opposed to each other. 
In the first Example shown in FIGS. 1 and 2, since the traverse devices 6a, 
6b are driven with one ball screw, they cannot traverse fiber cords 
overlapping each other. On the other hand, in the second Example shown in 
FIGS. 3 and 4, since the traverse devices 6a, 6b are separately provided 
respectively as upper and lower traverse devices and driven by separate 
ball screws 9a, 9b, they can traverse fiber cord overlapped with each 
other. For this reason, in the first Example, as shown in FIGS. 5(A) to 
(D), only reinforcement layers L, L not overlapping each other can be 
formed, while in the second Example, it is possible to form not only the 
reinforcement layers L, L not overlapping each other as shown in FIGS. 
5(A) to 9D but also various reinforcement layers L, L overlapping each 
other shown in FIGS. 5(E) to (H). 
As described above, according to the present invention, two fiber cords are 
simultaneously fed to form a reinforcement layer, which enables the 
winding to be efficiently conducted in a short time as opposed to the 
prior art method wherein the reinforcement layer is formed with only one 
fiber cord. Further, also in the case of the formation of the 
reinforcement layers separately in both the left and right edges, as 
opposed to the prior art method, there is no necessity of replacing the 
fiber cord, which contributes to an improvement in the workability.