JPS62121039A - Cover tape for tire bead core - Google Patents

Abstract

PURPOSE:To drastically improve unevenness of the inner circumferential surface of a bead core which is posterior to covering of a cover tape, by preventing a spatial area divided with warp and woof constituting plain cloth from being filled with unvulcanized rubber. CONSTITUTION:The material of plain cloth 11, for example, is a textile whose warp is of thread count of 58.5 piece/5cm at a piece of 20 count vinylon yarn and woof is of thread count of 53 piece/5cm at a piece of the 20 count vinylon yarn. Cement 12 obtained by dissolving unvulcanized rubber into a state of rubber paste with a solution is applied to the top of the plain cloth. Then directly after application of the same, the plain cloth is pressed by two rollers 13, then the same is led to a drying chamber and wound round after dryness. The wind-up roll of cloth 15 is cut out by a cutter or a slitter 16 in predetermined width and wound round as a cover tape 17. Although the unvulcanized rubber 12 is stuck round the cover tape centering round the warp and woof, at least a central area 10 out of a space divided with the warp and woof is not filled with the unvulcanized rubber 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cover tape for a bead core of a pneumatic tire.

(Prior Art) A bead core for a tire is made up of a single wire or a plurality of strands of wire twisted together with unvulcanized coated rubber a plurality of times, and is particularly commonly referred to as a strand bead.

With these bead cores, there are problems with workability during tire molding, especially tackiness (adhesion) when compressing to the carcass layer,
More importantly, due to the problem that the bead core is deformed during tire vulcanization and the shape of the bead core is disordered, conventionally it is made of plain woven organic fiber cloth called cover tape, and unvulcanized rubber is coated on both sides of the cloth. The coating has been used to tighten the outer periphery of the bead core to improve the tackiness and prevent the bead core from deforming during tire vulcanization.

Such cover tapes generally have warp and weft threads of 10 to 1 each.
The plain woven fabric is immersed in a rubber cement bath and then dried so that the space defined by the warp and weft is covered with unvulcanized rubber. It is formed.

The plain woven fabric covered with this rubber layer is cut to a predetermined width.
It has been used as a cover tape for bead cores.

(Problems with the Prior Art) However, the cover tapes for bead cores that have been conventionally used have the following problems.

First, as shown in the example of the method of covering a bead core with a cover tape in FIG. As a result, wrinkles occur on the inner circumferential surface to be covered, and as a result, unevenness occurs on the inner circumferential surface 5 of the bead core, and since the carcass ply cord is wound back around the bead core, the tension of the carcass ply cord becomes uneven. , resulting in poor tire uniformity.

In addition, in the figure, 6 is a bare wire, and 7 is an unvulcanized coated rubber. The bead core 3 is a strand bead core manufactured by rotating these.

The second problem is that in conventional cover tapes, the entire surface of the hand-woven fabric is covered with unvulcanized rubber, which increases the weight and cost of the bead core.

(Means for Solving the Problems) As a result of various studies regarding the above-mentioned problems, the present inventor found that wrinkles occur when covering the bead core with the cover tape, resulting in large irregularities on the inner peripheral surface of the tire. , because the unvulcanized rubber is filled up to the spatial area divided by the warp and weft yarns that make up the plain woven fabric. The causes are that it is difficult to follow length differences, (1) the degree of unevenness increases when wrinkles occur, and (3) the cover tape itself is highly rigid, reducing workability. I found out. Therefore, as a result of further investigation based on such causes, the present inventors succeeded in achieving the conventional function by not filling unvulcanized rubber into the spatial area divided by the warp and weft yarns that make up the plain woven fabric. We found that it was possible to significantly reduce the weight cost without sacrificing the cost, and at the same time significantly improve workability, and significantly improve the unevenness of the inner peripheral surface of the bead core after being coated with the cover tape, which was the initial objective. This discovery led to the completion of the present invention.

That is, the present invention provides a cover tape for a tire bead core made of a plain woven fabric of organic fibers and unvulcanized rubber, in which the warp and weft constituting the plain woven fabric are mainly covered with the unvulcanized rubber. The present invention relates to a cover tape for a tire bead core, characterized in that at least a central region of the space defined by the warp and weft is not substantially filled with the unvulcanized rubber.

Specifically, the cover tape of the present invention is a plain woven fabric of organic fibers composed of a plurality of warps and wefts, and the number of the warps and wefts is 10 to 100 and 15 cm. A process of attaching rubber cement to the fabric and squeezing out excess rubber cement to remove it, a process of drying the obtained plain woven fabric with rubber cement, and a process of cutting the dried plain woven fabric with rubber to a predetermined width. and more can be manufactured.

(Function) When the number of warps and wefts in the plain woven fabric of the present invention is less than 10, the area of the space defined by the warps and wefts expands, the amount of unvulcanized rubber per unit area decreases, and the unvulcanized rubber per unit area decreases. The adhesiveness of the vulcanized rubber cannot be sufficiently removed, and as a result, the workability of covering the bead core is reduced.

On the other hand, if the number of threads exceeds 100, unvulcanized rubber will fill the entire space defined by the warp and weft, and the number of threads will increase, reducing the rigidity of the cover tape itself. As a result, the workability of covering the bead core is reduced, and furthermore, deformation of the warp and weft to follow the difference in circumferential length is suppressed. As a result, wrinkles occur frequently on the inner circumferential surface of the bead, and the degree of unevenness also increases.

From the above, the cover tape for tire bead core of the present invention has a warp and weft thread count of 10 to 1.
00 lines/5 cm works well.

In addition, it is most preferable that the unvulcanized rubber filling rate in the spatial area divided by the warp and weft is 100% of the total spatial area, but if it is 50% or more, the desired effect can be obtained. , preferably 70% or more.

(Example) Next, the present invention will be explained by examples.

Manufacture of Cover Tape An example of the method of manufacturing the cover tape of the present invention will be explained based on the drawings.

FIG. 2 is a schematic diagram showing how to apply rubber to a handwoven fabric in a method of manufacturing a cover tape. In the figure, the material of the plain woven fabric 11 has one warp of vinylon number 20, and the number of threads is 58.
It is a fabric with 5 threads/5 cm, one weft of vinylon count 20, and a thread count of 53 threads/5 am.

This plain woven fabric with a width of 1.35m x length of 2400m,
First, a rubber cementing process was carried out, in which a cement layer 2 in which unvulcanized rubber was dissolved in a solution to form a rubber paste was adhered to the upper surface of the hand-woven fabric. Immediately thereafter, the cement was squeezed by two rollers 13 to remove the cement in the space defined by the warp and weft, and then led to the drying chamber 14, where it was dried and wound up as a roll 15.

FIG. 3 is a schematic diagram of the cutting process. In the figure, winding roll 1
5 is cut into a predetermined width with a cutter or slitter 16 to make a cover tape 17, and wound up as the cover tape 17.The conventional method of covering unvulcanized rubber is to first soak cement in the upper surface of the plain woven fabric. Immediately after adhesion, the excess cement layer was scraped off by placing a knife on the top surface of the plain woven fabric, and then dried in the next step (not shown). Other than that, all the steps are the same as in this example.

The cover tape of the present invention manufactured according to the above manufacturing method and the conventional cover tape manufactured for comparison are shown in plan views in FIGS. 4 and 5, respectively.

In the cover tape of the present invention shown in FIG.
The unvulcanized rubber 12 is attached around the warp yarns 18 and the weft yarns 19, but at least the central area 10 of the space defined by the warp yarns 18 and the weft yarns 19 is not filled with the unvulcanized rubber 12.

On the other hand, in the conventional cover tape shown in FIG. 5, unvulcanized rubber 12 is filled not only in the warp threads 18 and the weft threads 19 but also in the space area defined by the warp threads 18 and the weft threads 19.

Incidentally, when we measured the filling rate of 2000 spatial areas for the above two types of cover tapes, it was confirmed that about 83% of the cover tapes of the above embodiments of the present invention were not filled with unvulcanized rubber. Ta. In contrast, in conventional cover tapes, only 2.0-3.0% was unfilled with unvulcanized rubber, and almost all the spatial areas were filled with unvulcanized rubber.

The cover tape of the present invention manufactured by a cover tape evaluation company and the conventional cover tape were respectively tested in tire size PSR165'SR131PR.
For the bead cores used in the above, evaluations were conducted on the degree of unevenness of the inner circumferential surface after the bead core cover, weight, and cost. The results are shown in Table 1 below.

In Table 1, the results are shown as an index when the prior art is set as 100, and the smaller the index, the better the result.

The method of wrapping the cover tape of the present invention around the bead core is not limited to the above-mentioned embodiments; for example, a method of folding the cover tape from the inner periphery of the bead core to the outer periphery, or a method of wrapping the cover tape in a spiral shape along the circumference of the bead core can be used. be.

(Effects of the Invention) As explained above, in the cover tape for tire bead core of the present invention, by not filling unvulcanized rubber into the spatial area divided by the warp and weft that constitute the plain woven fabric, , it is possible to significantly reduce weight and cost without sacrificing conventional functions, and at the same time significantly improve workability, and also to significantly improve the unevenness of the inner circumferential surface of the bead core after being coated with cover tape. This has the effect of being able to.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a method of covering a bead core with a cover tape, Fig. 2 is a schematic diagram showing an example of the rubber attachment process in the method for manufacturing a cover tape of the present invention, and Fig. A schematic diagram showing an example of a cutting process following the process; FIG. 4 is a plan view of the cover tape of the present invention; and FIG. 5 is a plan view of a conventional cover tape. 1... Cover tape 2... Broken line 3... Bead core 4... Outer circumferential side 5... Inner circumferential surface
6...Element wire 7...Unvulcanized coated rubber 1
0... Central area 11... Plain woven fabric 12.
...Cement 13...Roller 14...
Drying chamber 15... Winding cloth 16... Cutter or slitter 17... Cover tape 18...
・Warp 19...Weft

Claims (1)

[Claims] 1. In a tire bead core cover tape made of a plain woven fabric of organic fibers and unvulcanized rubber, the warp and weft constituting the plain woven fabric are mainly covered with the unvulcanized rubber, and the warp and weft are covered with the unvulcanized rubber. and a cover tape for a tire bead core, characterized in that at least a central region of the space defined by the wefts is not substantially filled with the unvulcanized rubber.