JPS6325939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a retreaded tire that can improve the static imbalance of the retreaded tire.

Conventional retreaded tires are manufactured using the following procedure. That is, first, the remaining tread and damaged breakers of a tire with a worn tread are removed, the removed surface is buffed using a buffing machine, and the recesses and through holes are repaired to obtain the base tire 1 shown in FIG. Next, a new unvulcanized cushion rubber and breaker are attached, and the cut end surfaces of an unvulcanized band-shaped tread rubber 2 extruded from an extruder and cut to a predetermined length dimension are butted and attached thereon. Then, the tread portion is vulcanized using a mold and a pattern is formed on the tread surface. Finally, we perform a finishing inspection, at which time we measure the amount of static unbalance using a balancing machine.
This is completed by adding an unbalance mark at the lightest point of the tire.

Retreaded tires manufactured in this manner generally tend to have poorer static balance than new tires. When this static imbalance amount is large,
This causes steering wheel shake and has a negative impact on vehicle performance (handling stability), so after assembling the tire rim, one correction weight is added to each side of the wheel to mainly correct the dynamic imbalance. . If the static unbalance amount is large, the dynamic unbalance correction weight amount will also be correspondingly large, increasing the correction cost. For this reason, some users have been demanding that the amount of static imbalance be reduced in retreaded tires for trucks and buses, and the yield of retreaded tires has not always been good. Therefore, a balance patch is attached to the retreaded tire manufactured by the method described above to correct the static unbalance amount based on the measured static unbalance amount, and the static unbalance amount is measured again. It is now possible to complete the work by adding a mark. Although this had the effect of improving the yield of retreaded tires and reducing the amount of dynamic unbalance correction weight, it required the process of applying balance patches and measuring the amount of static unbalance again, The cost of manufacturing tires has increased. Then, if you apply a balance patch,
Problems arose when it turned over or came off, and methods such as natural vulcanization or heat baking were applied to solve this problem.
Manufacturing costs were further increased due to modification costs. In the case of the above-mentioned retreaded tire manufacturing method, although not all tires require correction using the balance patch, 85% to 95% of the tires require correction using the balance patch.

The present invention provides a method for manufacturing a retreaded tire with improved uniformity, which can reduce the amount of correction for static unbalance of the retreaded tire.

The first invention differs from the conventional manufacturing method described above in the following two points. The first step is to detect the lightest point in the circumferential direction of the base tire before winding and adhering the unvulcanized tread rubber. Part 2
The method is to position both cut ends to be joined to each other, that is, both end joints, at the lightest point position when performing winding bonding of unvulcanized tread rubber. The second invention, in addition to the differences of the first invention, is that, compared to the conventional manufacturing method, the third invention is that the length of the tread rubber is cut within 20 mm longer than the circumference of the tire of the predetermined base. be.

In the first invention, positioning the both end joints at the lightest point is because unvulcanized rubber extruded from an extruder in a strip shape is used in the winding bonding of treaded rubber, and the leading cut end of the unvulcanized rubber is used. The contracted state of the tire is naturally different from that of other parts, and the weight per unit length is greater, so the unbalance of the tire is corrected by the increased weight.

In the second invention, the amount by which the length of the tread rubber is cut within 20 mm from the circumference of the predetermined tire is about 5 to 10 mm, 20 mm at most, and the extra length of rubber is cut at both ends. They are compressed in the longitudinal direction or overlapped and joined in the vicinity of the joint, and the amount of rubber in the extra length increases at the joint, thereby correcting the unbalance of the tire to a greater extent.

Examples of the present invention will be described below. 10 in FIGS. 4 and 5 is an example of an apparatus used in the method of the present invention. In the same figure, 11 is a stand main body, 12 is a free roller, and the stand main body 11 has necessary tools built in (not shown), and a stand for tools etc. is formed at the upper part and in the middle, and a free roller is provided. Two rollers 12 are cantilevered in parallel in a freely rotatable manner on each side of the stand main body 11, and each roller has an enlarged central portion. This apparatus 10 is used in the examples.

First, the remaining tread and damaged breakers of the tire are removed and buffed using the same conventional method to obtain the base tire 1. This base tire 1 is mounted on two free rollers 12 at the bead portion 5 as shown in FIGS. 4 and 5.
While rotating the base tire 1 by hand, repair the recesses, through holes, etc. on the outer circumferential surface of the tire. Then, the repaired base tire 1 is rotated, and when the rotation stops, rubber is attached to the sidewall portion corresponding to the top position of the base tire 1.
Put a small mark 4 on the chiyoke. This mark position is the lightest point position of the base tire 1 in the circumferential direction.

Next, the base tire 1 is set on a molding former, a required number of new unvulcanized cushion rubber or breakers are attached, and then rubber glue is applied onto the breakers. Separately, the winding start point of the leading cut end 3 of the unvulcanized band-shaped tread rubber 2 extruded from the extruder and not subjected to cooling treatment is aligned with the unbalance mark 4 of the base tire 1 as shown in FIG. Wrap it around once, cut it, and join both cut ends together. The leading cut end 3 of the band-shaped tread 2 extruded from the extruder shrinks in the length direction in a short time due to not being subjected to cooling treatment, resulting in localized width and thickness dimension shrinkage. As a result, the amount of rubber at the cut end 3 is relatively increased compared to other parts, resulting in an insufficient amount of rubber at the position of the unbalance mark 4, that is, the lightest point of the base tire (static unbalance). will be compensated. Fig. 3 shows that when the extruded tread rubber 2 is not subjected to cooling treatment, its leading cut end 3 contracts by an amount l in the length direction, and as a result, the dimensions W in the width direction and D in the thickness direction locally change. This is an exaggerated representation of the increasing situation.

Furthermore, when a large amount of correction is required, the following method is added. That is, the tread rubber to be wound around and adhered to the base tire is cut to be somewhat longer than the predetermined circumference of the base tire, for example within 20 mm, preferably 5 mm to 10 mm. Then, the cut end surfaces are joined by either overlapping or abutting each other so that the joining portion is located at the lightest point position. Note that if the excess tread rubber exceeds 20 mm in the circumferential direction, it will be difficult to bring the joint into close contact with the base tire.

When using this additional method, for example, if the tread length is 3.2 m, the tread width is 35 cm, and the tread thickness is 1.8 cm, and the length is cut by about 10 mm, the weight will be about 50 g. A joint is obtained, and the unbalance of approximately 2.5 kg cm can be corrected.

The tire that has been molded with the unvulcanized tread rubber 2 pasted thereon is loaded into a known vulcanizer, and the tread portion is pressurized and heated using a patterned mold to be vulcanized.

After vulcanization, the tire is completed in a finish inspection step by detecting the lightest point position of the tire using the device 10 or a conventional balancing machine and marking that position.

Since the unvulcanized tread rubber 2 is attached to the retreaded tire manufactured in this manner so as to correct the unbalance of the base tire 1 itself, the finished tire has a small amount of static unbalance. That is, the uniformity is improved compared to conventional retreaded tires of this type. According to the results of experiments to date, it is possible to correct the amount of unbalance by 4 kg·cm to 10 kg·cm using retreaded tires for trucks and buses. This means that the amount of unbalance in conventional retreaded truck and bus tires is 5 to 20.
Since it is Kg・cm, it can be said that this can be halved. In addition, according to the retreaded tire inspection management table at a retreaded tire manufacturing factory that implemented this method, it was necessary to apply balance patches to 85% to 95% of retreaded tires before the method, but after the method The number of items that require the application of balance patches has been significantly reduced to 5% to 15%.

As described above, according to the present invention, the uniformity of a retreaded tire can be greatly improved, the amount of correction of static and dynamic imbalance can be significantly reduced, and the cost of correction can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a conventional retreaded tire at a stage in which tread rubber is attached, and FIGS. 2a, b, and c are schematic side views of different states showing the order in which tread rubber is attached according to an embodiment of the present invention. Fig. 3 is an explanatory view showing the contracted state of the leading cut end of extruded unvulcanized tread rubber, where a is a plan view, b is a side view, and Fig. 4 shows the workbench used in the same example together with the platform tire. A schematic side view, and FIG. 5 is a longitudinal sectional front view of a portion of FIG. 4 with parts omitted. 1... stand tire, 4... unbalance mark (lightest point position of stand tire), 2... unvulcanized tread rubber.

Claims (1)

[Claims] 1. A process of removing the remaining tread of a worn tire and buffing the removed surface, and repairing any damaged parts to obtain a stand tire, and a step of detecting the lightest point position; a step of winding and gluing a band-shaped unvulcanized tread rubber around the outer periphery of the base tire so that both end joints are located at the lightest point position; A method for producing a retreaded tire comprising the steps of loading a rolled and bonded base tire into a vulcanizer and vulcanizing the tread portion. 2 The process of removing the remaining tread of a worn tire and buffing the removed surface, and repairing any damaged parts to obtain a base tire, and detecting the position of the lightest point in the circumferential direction of the base tire. Then, a strip of unvulcanized tread rubber is cut to a length within 20 mm from the circumference of the base tire and wound around the outer circumference of the base tire so that the joints at both ends are located at the lightest point. A method for manufacturing a retreaded tire, which comprises a step of gluing, and a step of loading the base tire with the unvulcanized tread rubber wound and bonded into a vulcanizer to vulcanize the tread portion.