JPS637126B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rubber roll with a metal core.

Generally, corrugated rubber rolls (hereinafter simply referred to as rubber rolls) are widely used industrially as printing rolls, paper making rolls, spinning rolls, copying machine rolls, and the like. All of these rolls are characterized by having a metal core covered with elastic rubber, while functionally they have excellent abrasion resistance, high tear resistance, and no permanent deformation under load. It is required to be small and also have various properties such as heat resistance and chemical resistance depending on the application.

There are two general methods for producing rubber rolls that have been conventionally used. First, a mixture of raw rubber and necessary chemicals such as fillers, plasticizers, stabilizers, and vulcanizing agents is made into a sheet of the required thickness using two rolls or a calender.
Alternatively, the formulation may be wrapped around a metal core using an extruder. The steps that follow are common up to this point, but the first method is a molding method called press vulcanization, in which the core is covered with the aforementioned rubber compound and placed in a mold, and then inserted between the hot plates of the press. Then, pressure and heat are applied, and after a certain period of time, after vulcanization is complete, the mold is opened and the vulcanized rubber roll is taken out.

The second method is so-called rolling steaming, in which the rubber compound is further wrapped around a core coated with a similar rubber compound so as to press down the rubber compound, and then steamed or steamed in a pressure cooker. Vulcanization is performed by introducing heated air. In either case, the surface of the vulcanized rubber roll is polished to adjust the roll diameter and surface roughness to meet requirements.

Considering the advantages and disadvantages of the two manufacturing methods mentioned above, in the press vulcanization molding method, heat is transferred to the mold from the two upper and lower hot plates, but since the sides of the mold are in contact with the atmosphere, The way heat is transferred to the rubber inside is not uniform around the rubber roll. Of course, the rubber is compounded in such a way that it does not interfere with uneven heat transfer, and the mold is usually preheated to the temperature of the press. In press vulcanization, high pressure is generally applied, so a dense vulcanized rubber can be obtained, and
Rubber rolls with excellent mechanical strength and dimensional accuracy are manufactured. On the other hand, the seams of the mold often appear as stripes even after polishing, causing various problems during use. On the other hand, in vulcanization by rolling steaming, uniform vulcanization can be achieved throughout the roll due to the slow heating rate, especially for rolls with thick rubber walls.
Since the pressure is lower than that in press vulcanization, the mechanical strength is lower and a large amount of polishing allowance is required, but problems such as mold joints do not occur. The latter has the advantage of being able to vulcanize a large amount of rubber rolls at once depending on the size of the pressure cooker, but in either method, vulcanization is still performed in batches.

In order to eliminate the above-mentioned problems, the method for manufacturing a rubber roll according to the present invention has the advantages of both obtaining a dense vulcanized rubber with excellent mechanical strength through uniform heating and obtaining a surface layer with no mold seams. It is designed so that vulcanization molding can be carried out continuously.

That is, as shown in FIG. 1, the rubber compound 1 is injected under pressure into the gap between the molded cylinder 3 and the roll core 4 through the injection port 2 to fill it. The injection pressure at this time varies depending on the plasticity of the rubber compound, the shape of the injection port, the size of the gap to be filled, etc., but is usually 20 to 100 kg/cm ²
It is necessary to completely fill the rubber compound so that no voids remain in the gap. After filling the mold with the rubber compound, blind lids 6 and 6' are fixed to the outside of both ends to close the injection port 2 and the escape port 5 to prevent the mold from flowing out through the injection port 2 and the escape port 5.

In order to raise the temperature of the preformed product to the temperature required for vulcanization of the rubber, we adopted a method of directly heating the mold using high-frequency induction heating to raise the temperature of the rubber inside. Because of the seamless, cylindrical mold structure, the manufacturing cost of the mold is lower and more economical than the method of press vulcanization by placing it between two hot plates or the method of heating it in a sealed pot. In addition, the high-frequency induction heating method was made even more effective, resulting in much faster and more even heating.

In addition, as shown in FIG. 2, the plate-shaped heating coil 7
is placed vertically, an alternating current is passed through it, and when the mold 8 is rotated and moved in the direction of arrow A along its side wall, an induced current is generated on the mold surface and the mold 8 is heated by Joule heat. heats up quickly and evenly. As a result, the heat from the mold is evenly transferred to the rubber inside, and the vulcanization of the rubber progresses rapidly. At this time, due to the difference in thermal expansion between the mold 8 and the rubber compound, extremely high pressure is applied to the rubber itself depending on the volume of the rubber compound, resulting in a dense vulcanized rubber with excellent mechanical strength. However, due to this expansion pressure, it is impossible to take out the vulcanized rubber from the mold as it is. Therefore, after heating the mold 8, it is left at room temperature and waited for the temperature to drop to a certain level, then both ends of the mold are opened and the vulcanized rubber roll is taken out.

As an example, when a mold was moved to a position 3 cm away from a plate-shaped coil with a length of 1.2 m and a height of 1 m at a rotation speed of 6 rpm for 4 minutes, the surface temperature of the mold after 4 minutes was is 270℃, and the temperature of the roll core is 120℃.
The temperature rose to ℃. When this was left at room temperature for 10 minutes, the temperature of the roll core reached 170°C, and then gradually decreased to 120°C after 20 minutes, making it possible to take out the rubber roll. In this case, an alternating current of 20 KHz (100 A, 30 V) was applied to the coil.

In the general vulcanization method, in the case of press vulcanization,
The hot plate is heated by steam or electric heat, and the temperature of the hot plate is transferred to the mold, so the side that is in contact with the atmosphere is cooled, making the temperature rise rate of the mold slow and partially uneven. Therefore, it is usually necessary to preheat the mold, which is not very efficient. On the other hand, when vulcanizing in a pressure cooker, steam or heated air is sent into the pot to heat the rubber, so the rate of temperature rise of the rubber is much slower. This method is suitable for The method used in the present invention, in which the mold is directly heated by high-frequency induction heating, has the advantage of reducing energy loss, raising the temperature quickly, and heating the entire surface evenly. The molding process from start to finish of vulcanization can be carried out continuously, which helps improve productivity and contributes to cost reduction.

Furthermore, as mentioned above, by press-fitting the rubber compound from one end of a cylindrical mold, the surface of the finished rubber roll is completely smooth, with no traces of mold joints or deburring marks. It can be finished to a beautiful surface. Furthermore, the thermal expansion of the rubber is much greater than that of the mold, resulting in high pressure during vulcanization.
A dense vulcanized rubber with high mechanical strength is obtained. As a result, the durability of the rubber roll is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the invention, and FIG. 2 is a perspective view showing an embodiment of the invention. 1... Rubber compound, 2... Inlet, 3... Molding tube, 4... Roll, 5... Escape port, 6, 6'...
Blind lid, 7... heating coil, 8... mold.

Claims (1)

[Claims] 1. A metal core is held in a seamless cylindrical mold with lids attached at both ends that have an injection port on one side and an escape port on the other, and a rubber compound is injected into the internal cavity from the injection port of the mold. A method for manufacturing a rubber roll, characterized in that the mold is sequentially and continuously moved while rotating near a heating coil through which a high-frequency current is passed, and vulcanization is performed by heating the mold with an induced current.