JPH04224826A - Bonding of cord-filled raw rubber sheet material - Google Patents

Abstract

PURPOSE:To obtain a product of improved uniformity by abutting raw rubber sheets against each other and irradiating the joint with electron beams. CONSTITUTION:A process for bonding raw rubber sheets 1 in each of which many cords are embedded in parallel with each other, wherein the ends each of which is parallel with the embedded cords 2 of the corresponding sheet material are abutted, pulled nearer and pressed against each other, and the joint is irradiated with electron beams into a semivulcanized state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for butt-joining corded raw rubber sheet materials.

0002

[Prior Art] Corded sheet materials are mainly used for the plies and belts of pneumatic tires, and in particular are used in layers for belts, etc. In the process of manufacturing such pneumatic tires, sheet materials are Work to join the starting and ending ends of materials is frequently performed, and the quality of the joining affects the quality of the tire.

[0003] There are two main methods for joining sheet materials:
There are two methods: overlap bonding and butt bonding.

[0004] As shown in FIG. 11, the overlap bonding method uses a sheet material 01 in which a cord 02 is embedded up to the end.
In this method, the starting end and the ending end are overlapped, and the overlapping portion is pressed with a roller or press to join. In the case of using the same method, the ends of the sheet material 01 are overlapped and the cords 02 are lined up and down at equal intervals (see Figure 11), and when this overlapping part is pressed and joined, the upper and lower cords 02 bit into each other alternately, the interval between the cords becomes narrower, and the joint becomes uneven compared to other cords.

[0005]Therefore, there is a special joining method to solve this problem, and the method shown in FIG. Kaisho 55-614
In the method shown in Figure 13, one cord is removed from the end of the sheet material 05, and one cord is buried at the starting end of the other sheet material 06 apart from the others. This is a method of overlapping and crimp-bonding the single cord so that the starting end of the isolated cord is positioned above the cord that has been pulled out. According to the above joining method, the cords are arranged substantially uniformly at the joining part.

On the other hand, the method of butt joining sheet materials is as follows:
As shown in FIG. 14, this is a method in which the starting end and the ending end of the sheet material 07 are butted against each other, and the end surfaces are brought into contact with each other and pressed together.

[0007] As a special method of this butt joining, as shown in FIG. 15, the starting end and the ending end of the sheet material 08 are butted together, and a narrow material 09 in which two or less cords are embedded is superimposed on the butted part. There is a joining method in which the narrow material 09 is pushed in from above (Japanese Patent Laid-Open No. 63-98
Publication No. 424).

[0008]

[Problem to be solved] In the manufacture of pneumatic tires, etc., in addition to plies and belts that use corded sheet materials, there are many other materials that are used to provide the strength and performance required for pneumatic tires, such as treads, sidewalls, beads, etc. After the parts are bonded and laminated on the flat drum of a molding machine, or during the process, it is expanded into a tire shape or a shape close to the tire shape, or the raw tire after molding is turned into a final tire in a vulcanization press. The joints of each component are stretched from time to time to perform expansion.

In the case of sheet materials, the following problems arise when using the conventional joining method. In other words, with the overlap bonding method, the intervals between the cords embedded in the bonded portion become uneven as described above, and in order to solve this problem, a special bonding method shown in FIGS. 12 and 13 has been proposed. Even if the cord spacing becomes uniform when overlapping the cords, the joint will inevitably have a thick wall, and when such a joint is stretched, as shown in Figure 16, the thick joint will remain as it is, and a tensile force will be applied to both ends of the thick wall. This results in a concentrated and significant elongation and thinning of the wall thickness, which poses a problem in terms of uniformity and causes a problem in which the strength is partially reduced.

In the case of conventional butt joints, when a tensile force is applied to the joint, the joint itself stretches and becomes thinner, as shown in FIG. 17. If the sheet material is in such a condition, the uniformity of the tire will be impaired and there will be a problem that the quality of the tire will be poor.

[0012] From the point of view of tire uniformity, the butt joining method is more preferable, but the environmental conditions, materials, reliability of joining machines and equipment including the joining method, left conditions of green tires, and tire processing are important. Due to various factors in the sulfurization process, various problems arise in the bonding state as described above.

Therefore, a special method shown in FIG. 15 has been proposed as an improvement to the butt joining method.
9, it was found that in tires that require high quality and high performance, slight differences in the density of the cords at the joints affect uniformity. Note that the quality of the bonding of sheet materials, not just tires, has a great impact on the quality of the product.

[0014] The present invention has been made in view of the above points.
The objective is to provide a method for joining sheet materials that has excellent uniformity and can improve product quality.

[0015]

Means for Solving the Problems and Effects In order to achieve the above object, the present invention provides a method for joining raw rubber sheet materials in which a large number of cords are buried parallel to each other. Butt the parallel ends together, pull the butt ends together and press them together,
A method for joining corded raw rubber sheet materials is to press the pressed ends to join, and then irradiate the joined part with an electron beam to bring it into a semi-vulcanized state.

[0016] By irradiating the bonded parts of the sheet materials by butting, pressing, and squeezing to a semi-vulcanized state by irradiating them with electron beams, the green strength of the bonded parts increases compared to other parts, as shown in FIG. 17. There is no need to reduce the wall thickness of the butt joint, and uniformity is improved throughout.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention illustrated in FIGS. 1 to 9 will be described below.

FIGS. 1 and 2 are a plan view and a sectional view showing a starting end 1a and a terminal end 1b of a sheet material 1 containing a cord, and a steel cord 2 is embedded inside the sheet material 1. As shown in FIG. This sheet material 1 is made by coating both sides of a steel cord 2 stretched in parallel with rubber in a calendering process and cutting it to the required length parallel to the steel cord 2. It is buried oriented perpendicularly to the longitudinal direction, and has a starting end 1a and a terminal end 1b.
The cut plane is also perpendicular to the longitudinal direction of the sheet material 1. The sheet material 1 used here has a thickness of about 2.2 mm, and the embedded steel cords 2 have a diameter of 1.2 mm and are arranged at a pitch of about 1.8 mm.

The starting end 1a and the ending end 1b of the sheet material 1
In the step of butting together, a known splicing device 10 (Japanese Unexamined Patent Publication No. 123472/1983) is used,
The process will be briefly explained based on FIGS. 3 and 4.

The splicing device 10 has splicing members 11 and 11u disposed vertically symmetrically, and the splicing member 1 on the lower side.
1u is provided below the conveyance path 9 with a fixed height, and the upper joining member 11 is provided so as to be movable up and down by a cylinder (not shown). Upper and lower joining members 11, 1
1u have the same structure, so the upper joint member 11
Regarding the lower joining member 11u, the same reference numerals and suffix u are added to the corresponding members, and the explanation thereof will be omitted.

A plate-shaped body 13 is fixed to the lower end of the cylinder rod 12 that projects downward from the cylinder, and is connected to a pair of front and rear brackets 14 and 15 hanging downward from the plate-shaped body 13 via pivots 16 and 17. Joint plates 18 and 19 are pivotally supported. A plurality of upstream joining plates 18 and downstream joining plates 19 are arranged alternately, and their ends partially overlap at the center. Teeth 20 and 21 are arranged in an arc shape on the lower end surface of these overlapping ends.

Further, a pressing plate 22 is in contact with the upper end of the overlapping ends, and a support shaft 23 extending upward from the pressing plate 22 is slidable into a hole bored in the plate-shaped body 13. A spring 24 is inserted between the pressing plate 22 and the plate-like body 13 by being fitted. Stopper pins 25 and 26 are provided at mutually distant ends of the joining plates 18 and 19 to project upward and come into contact with the plate-like body 13.

The lower joint member 11u has the same structure except that its height is fixed by a support member 27.

When no external force is applied to the joining plates 18 and 19, the spring 24 causes the pressing plate 22 to force the overlapping ends of the joining plates 18 and 19 downward, as shown in FIG. The teeth 20 and 21 of the mating plates 18 and 19 are in an open state. In this state, the teeth 20u, 21u of the lower joining member 11u are located in the notched portion of the conveyance path 9 and are on the same plane as the conveyance path 9.

Terminal end 1b of the preceding downstream sheet material 1
and the starting end 1a of the next upstream sheet material 1 are positioned on the teeth 20u, 21u of the lower splicing member 11u with a slight distance between them, and the upper splicing member 11 is lowered.
The upper teeth 20, 21 sandwich the starting end 1a and the ending end 1b of the sheet material 1 between the upper teeth 20, 21 and the lower teeth 20u, 21u.

When the joining member 11 is further lowered, the joining plates 18, 19, 1 resist the springs 24, 24u.
Teeth 20, 21, 20 where 8u and 19u swing and overlap
Since u and 21u are closed, the sheet material 1 on the upstream side and the sheet material 1 on the downstream side are drawn together and the starting end 1a and the ending end 1b are butted together. When the joining member 11 is further lowered, the starting end 1a and the ending end 1b are further crimped together with the teeth 20, 21.
20u and 21u are arranged alternately, so that the joints are pressed together in a zigzag manner. Thereafter, although not shown, the joint is pressed with a press to join the two.

The joined state is illustrated in FIGS. 5 and 6. Although the joint is zigzag, the spacing between the steel cords 2 at the joint is slightly larger than the pitch of 1.8 mm in other parts, and the joint is not particularly thick.

[0029] The sheet material 1, which has been successively joined in this way and formed into a long piece, is conveyed to the next electron beam irradiation step. The electron beam irradiation device 30 is illustrated in FIGS. 7 and 8. The electron beam irradiation device 30 has an electron gun 31 with an accelerating voltage of 500 kv above.
A skirt portion 32 extending in a fan shape in the width direction is vertically provided below the skirt portion 32. The skirt portion 32 is flat in the flow direction of the sheet material 1, and the lower end opening is in the form of a long slit in the width direction. A beam shutter 33 that can freely appear and retract is provided below the opening. Note that the arrows in FIGS. 7 and 8 indicate the direction of electron beam irradiation.

When the long sheet material 1 described above is being conveyed below the electron beam irradiation device 30, the beam shutter 33 protrudes and blocks the bottom of the skirt portion 32 of the electron beam irradiation device 30, thereby preventing unintentional use. The electron beam is prevented from being irradiated onto the sheet material 1 during this period. When the bonded portion of the sheet material 1 is conveyed to the lower part of the electron beam irradiation device 30, the bonded portion is fixed corresponding to the opening of the electron beam irradiation device 30, and the stage is reached for electron beam irradiation, the beam shutter 33 moves. to remove the shield.

[0031] Then, an electron beam is irradiated by the electron gun 31 toward the joint portion of the sheet material 1. Irradiation with the electron beam is performed within a range of 10 mm (preferably 5 mm) on one side from the bonding surface.
An irradiation dose of 3-10 Mrad is applied. The joints of the sheet material 1 are somewhat vulcanized (semi-vulcanized) by being irradiated with the electron beam, increasing the green strength. Within such a range of irradiation conditions, there is no change in shape due to electron beam irradiation.

The sheet material 1 whose joint portions have been irradiated with electron beams in this manner is used as a constituent material of a tire and is molded and expanded in a vulcanizing press to manufacture a tire. As shown in Figure 9, the steel cords at the joint were only slightly stretched due to their large green strength, and the distance between the steel cords 2 was slightly wider due to the stretching of other parts. It almost matches the interval between the cords 2, the thickness is not much different, and it is in a homogeneous state as a whole. Therefore, the uniformity is much better and the quality of the tire is also improved.

When the electron beam irradiation dose is 20 Mrad, the vulcanization progresses too much and the green strength is too large, and the state of the joint after molding and vulcanization is as shown in FIG. Since the other parts were elongated while remaining unchanged, only the wall thickness at the joint became relatively thick, and the spacing between the cords 2 became relatively narrow only at the joint, resulting in poor uniformity.

Therefore, when the sheet material 1 is used as a constituent material of a tire, an irradiation dose of about 3 to 10 Mrad is suitable. When the RFV (longitudinal variation) of the tire manufactured using the sheet material 1 according to this example was measured, the RFV was reduced by 0.2 to 0.5 kg compared to the tire that was butt-jointed and not subjected to electron beam irradiation. It has been proven that even in RFV, it is uniform over the entire circumference. In addition, the RFV of the tire subjected to 20 Mrad electron beam irradiation was comparable to that of the conventional butt joint.

[0035] When the sheet material is used as a constituent material of a tire, the butt joint part is 3 to 10M.
By performing rad electron beam irradiation, the uniformity of the tire can be significantly improved. The tests conducted here have been repeated and have always yielded consistent and reproducible results.

[0036] In this example, a method for joining corded sheet materials as tire constituent members is shown, but the method can be applied not only to tire constituent members but also to other corded sheet materials, and can improve the uniformity of the product. You can improve your performance. In this embodiment, the steel cord 2 is embedded in the sheet material 1, but the embedded cord is not limited to steel, and may be made of synthetic fibers such as polyester, nylon, and rayon. Furthermore, the buried cord is not limited to being buried perpendicular to the longitudinal direction of the sheet material, but may be buried diagonally, and the ends cut diagonally parallel to the cord may be joined together. Of course you can.

[0037]

Effects of the Invention The present invention improves the uniformity of products manufactured using the sheet materials by butting and joining corded sheet materials and then irradiating the joint with an electron beam to make it semi-vulcanized. can be improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the starting and ending ends of a corded sheet material.

FIG. 2 is a sectional view of the same.

FIG. 3 is a schematic side view of the splicing device.

FIG. 4 is a schematic side view showing another state of the device.

FIG. 5 is a plan view showing a joint of sheet materials.

FIG. 6 is a sectional view of the same.

FIG. 7 is a side view of the electron beam irradiation device.

FIG. 8 is a front view of the same.

FIG. 9 is a cross-sectional view of a sheet material joint after tire manufacture.

FIG. 10 is a cross-sectional view of a sheet material joint after tire manufacture when irradiated with an electron beam of 20 Mrad.

FIG. 11 is a cross-sectional view showing a conventional overlap joint.

FIG. 12 is a sectional view showing a conventional special joint.

FIG. 13 is a sectional view showing a conventional special joint.

FIG. 14 is a sectional view showing a conventional butt joint.

FIG. 15 is a sectional view showing a special case of a conventional butt joint.

FIG. 16 is a cross-sectional view of a sheet material joint of a tire using conventional overlap-joined sheet materials.

FIG. 17 is a cross-sectional view of a sheet material joint of a tire using conventional butt-jointed sheet materials.

[Explanation of symbols]

1... Sheet material, 2... Steel cord, 9... Conveyance path, 1
0... Joining device, 11... Joining member, 12... Cylinder rod, 13... Plate, 14... Bracket, 15... Bracket, 16... Pivot, 17... Pivot, 18... Joining plate, 19... Joining plate , 20...teeth, 21...teeth, 22...pressing plate, 23...support shaft, 24...spring, 25, 26...
Stopper pin, 30... Electron beam irradiation device, 31... Electron gun, 32... Skirt portion, 33... Beam shutter.

Claims (1)

[Claims] Claim 1. A method for joining raw rubber sheet materials in which a large number of cords are buried parallel to each other, comprising butting ends of the sheet materials parallel to the buried cords;
A corded raw rubber sheet material characterized in that the abutted ends are brought together and pressed together, the pressed ends are pressed and joined, and then the joined part is irradiated with an electron beam to bring it into a semi-vulcanized state. Joining method.