JPS60127121A - Manufacture of tubular rubber molded article - Google Patents

Abstract

PURPOSE:To enable to enhance the strength of a finished product and to finish the external appearance homogeneously and smoothly by a method wherein specified-length band-shaped bodies having trapezoidal section are used as member for forming preformed body and the outer surface of a preformed body is covered by unvulcanized rubber layer and, after that, vulcanized. CONSTITUTION:Firstly, a large number of specified-length band-shaped bodies 11 consisting in cutting an unvulcanized band-shaped body having a trapezoidal section formed by an extruder in length are successively laminated upwards from the base of the outer surface of a conical inner mold 4 in order to gorm a preformed body 13 made of unvulcanized rubber. Secondly, the outer surface of the preformed body 13 is covered by an outer mold 5 in order to be clamped and fixed together with an inner mold 4. Thirdly, fluidized unvulcanized rubber, which is stored in a storage chamber 16, is pushed by means of the movement of a piston 18 through a push platen 17 into a gap 14 between the preformed body 13 and the outer mold 5. Fourthly, a pushing-in device 15 is removed and the mold is blocked, clamped and fixed. Finally, the mold is vulcanized by heating under pressure in order to be able to obtain a final product.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a cylindrical rubber molded article having a conical or truncated conical shape. More specifically, the present invention relates to a novel method for manufacturing the cylindrical rubber molded product, which completely eliminates defects such as insufficient polymer, insufficient strength, and poor appearance by molding the surface of the preform more precisely.

Description of Prior Art Conventionally, conical cylindrical rubber molded products, for example, Utility Model Application No. 58-14
In order to manufacture the cone-shaped or truncated cone-shaped cylindrical fender disclosed in Japanese Patent No. 5321, the following method was adopted.

That is, as shown in FIG. 1, first, unvulcanized rubber is made into a sheet by extrusion molding, cut into a predetermined length to form a strip-shaped member 1, and the required number of strips are arranged to form a substantially square shape. After forming the plate 2, the ring-shaped member 3 is cut out using an appropriate circular drawing tool. Following a similar operation, a plurality of ring-shaped members were obtained by gradually decreasing the inner and outer diameters, and these were placed on the outer circumferential surface of the conical inner mold 4, as shown in the vertical section in FIG.
They are stacked in order from large diameter to small diameter.

After reaching a predetermined height, the outer mold 5 was placed to close the mold, and the mold was vulcanized under heat and pressure to produce a truncated 1'11e-shaped cylindrical rubber molded product.

However, with such conventional molding methods, it is difficult to produce a 1M truncated conical cylindrical rubber molded product with high strength, uniform dimensions, and beautiful appearance. This is because, as is already well known, the thickness of the extruded rubber sheet varies slightly from patch to patch due to cross-wires, variations in the degree of heating, or variations in extrusion temperature. The rubber sheets obtained as described above are lined up and cut, and each ring is different for each piece and between the rings, so these rings are cut into inner molds as shown in FIG. This is because the shape of the preform obtained by laminating along the outer circumferential surface of No. 4 will also be irregular.

Furthermore, in the conventional method, the cross section of the unvulcanized rubber sheet to be extruded was rectangular. A stepped gap is formed between the outer surface of the preform and the outer mold. Therefore, the finished product obtained by vulcanization molding also has drawbacks such as insufficient volume in some parts, the formation of recesses called hairs, and insufficient strength. Naturally, the appearance was also unsatisfactory.

In addition, with this method, as mentioned above, it is necessary to prepare ring-shaped members with many different diameters in order to manufacture one conical cylindrical rubber molded product, and of course, a circular drawing tool is also required for this purpose. It is necessary to use a tool with variable dimensions or prepare and use a large number of circle drawing tools with different sizes. In addition, creating various ring-shaped members to manufacture one product requires creating unvulcanized rubber sheets of various sizes, and furthermore, it is necessary to create unvulcanized rubber sheets of various sizes, and the remaining after the ring-shaped member is cut out. The problem of disposal of waste rubber also arises. Therefore, such conventional methods are also disadvantageous from the viewpoint of industrial production.

Therefore, the inventors of the present invention have carried out various inspections and researches in order to eliminate the various drawbacks of the conventional method. This variation is caused by the extruder forming a band of unvulcanized rubber with a trapezoidal cross section.
We learned that this problem could be solved by laminating regular length strips obtained by cutting them to a certain length, and filed a separate patent application.

However, even with this method, there are still problems that need to be improved. That is, in this method, a preform is formed by arranging and stacking a large number of regular length strips having a trapezoidal cross section on the outer surface of an inner mold such as a conical shape, so that irregularities on the inner and outer surfaces of the preform are Although it is not as good as the conventional method (see FIG. 2), it still remains. Therefore, by improving this point, it will be possible to further improve the appearance, strength, lack of volume, and other properties of the final product.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a novel method that solves the above-mentioned problems and makes it possible to manufacture a cylindrical rubber molded product having even more hidden properties.

Structure of the Invention The object of the present invention is to form an unvulcanized strip having a trapezoidal cross section using an extruder, cut the strip to a certain length to obtain a large number of fixed length strips, and cut the strip to a fixed length. The bodies are laid out circumferentially from below the outer surface of the conical inner mold, and are sequentially stacked upward along the ridge of the conical inner mold to form a preformed unvulcanized rubber on the outer surface of the inner mold. Then, an outer mold is placed on the outer surface of the preform, the inner mold and the outer mold are fastened and fixed, and a press-fitting device for unvulcanized rubber in several stages is used to press the unvulcanized rubber onto the outer surface of the preform. This can be achieved by press-fitting unvulcanized rubber into the rubber and then vulcanizing it under heat and pressure.

In the conventional manufacturing method of tubular rubber products, the sheet-like member used for preforming is manufactured by extrusion molding, but in extrusion molding, as mentioned above, kneading and heating are performed for each loft. Due to slight differences in extrusion level or extrusion temperature, it was inevitable that the dimensions would vary. Such dimensional variations remain as variations in thickness even in the four annular members in the preforming, and as a result, the thickness is not constant even within one annular member.

Furthermore, in the conventional method, the unvulcanized rubber sheet obtained by extrusion must be cut into various predetermined sizes, and a large amount of waste rubber is generated after cutting out the ring.

However, according to the method of the present invention, first, a strip of unvulcanized rubber having a trapezoidal cross section is formed by extrusion molding, and then the strip is cut into a certain length to obtain a large number of fixed length strips. Form. Therefore, unlike in the conventional method, there is no need for the troublesome operation of cutting the extruded sheet into various predetermined dimensions, arranging the extruded sheets, and cutting out the ring-shaped bodies with a circular side tool. It is only necessary to cut it into regular length strips. Furthermore, the reason why the strip that is first formed by extrusion molding has a trapezoidal cross section is that when manufacturing the preform, the preform is formed by laying out and stacking strips of a fixed length, resulting in the slope and conical shape of the inner surface of the preform. This is to match the slope of the outer surface of the inner mold and bring them into close contact with each other.

Forming the strip in this way makes it possible to improve the strength and appearance of the finished product obtained after vulcanization. This point is one of the important features of the method of the present invention.

Next, the fixed length strips obtained as described above are laid out along the circumferential direction from below the outer surface of the conical inner mold, and are sequentially laminated upward along the ridge of the inner mold.

In addition, when the cylindrical rubber molded product is a fender material, when forming the preform, a reinforcing iron plate that should be buried in the quay wall attachment part covered in advance with unvulcanized rubber is placed at the lowest part of the outer surface of the conical inner mold. Place. Furthermore, if the upper part of the cylindrical rubber molded body is desired to be cylindrical, regular length strips having a rectangular cross section are used and arranged and laminated. Also, there is no problem of step-like gap formation as in the conventional method shown in FIG.

Even in the method of the present invention, since the strip is formed by extrusion molding, variations in thickness still remain. However, by cutting this into short lengths′ζ, randomly selecting and arranging them,
Since the preform is laminated and preformed, variations in the thickness of each layer of the preform and between adjacent layers are dispersed as a whole. Therefore, at this stage, the quality has already been improved to a considerable extent, especially in terms of strength and appearance.
Further improvements must be made to increase the commercial value of the final product.

In addition, although the fixed length strip is not formed along the arc of the inner mold, unvulcanized rubber has excellent elasticity and flexibility, and has adhesive properties, so it can be molded to fit around the circumference of the inner mold with a large curvature. It is easy to arrange the regular length strips along the length and form a layer.

Next, after covering the preformed product as described in "-" with an outer mold in the same manner as in the past, an unvulcanized rubber press-in device is used to inject heated and plasticized unvulcanized rubber into the gap between the preform and the outer mold. Press-fit the vulcanized rubber. In this way, it is possible to compensate for the lack of volume on the outer surface of the preform, fill in the slight step gap, and further improve the strength and appearance of the molded product. In particular, when the dimensions and thickness of the standard length strips are uneven,
Since these are arranged and laminated, the inner surface of the preform obtained by pressing it against the outer surface of the inner mold is relatively smooth and has few gaps, but on the contrary, the degree of irregularity on the outer surface of the preform is significant. Therefore, heat plasticization (
Pressing in unvulcanized rubber (fluidized) to form a layer of unvulcanized rubber on the outer surface is extremely important in improving the strength, appearance, etc. of the finished product.

In order to facilitate the press-fitting of fluid unvulcanized rubber and obtain an even more beautiful appearance, when covering the preform with an outer mold, the specified length is set so that the inner surface of the outer mold and the outer surface of the preform do not come into contact. It is desirable to design the dimensions of the band as well as the inner diameter of the outer mold.

Various modes can be considered for press-fitting the unvulcanized rubber.

For example, by inserting a thin hollow tube to the bottom of the gap and connecting it to a pump means for pumping unvulcanized rubber, a fluidized unvulcanized rubber storage chamber having a cylindrical shape with an outer diameter equal to the outer mold; A press plate having a diameter equal to that of the storage chamber, a piston, and a driving device for the piston (which may be hydraulic or hydraulic) are provided, and a plurality of press plates are provided at positions corresponding to the gap between the outer surface of the preform and the outer mold. This can be carried out by using an unvulcanized rubber press-fitting device having a bottom press-fitting hole for fluidized rubber and a plurality of holes for venting air communicating with the outside.

Furthermore, since there is a risk that the volume will be insufficient if only the rubber is press-fitted from the top as described above, in such a case, a structure that can be separated into two upper and lower parts 4fA is used, and the lower part 8
The rubber can be completely press-fitted into the gaps by using an outer mold in which the No. 15 member is provided with rubber reservoirs that communicate with several of the above-mentioned gaps, and applying pressure together with the above-mentioned press-fitting device.

Then, unvulcanized rubber is press-fitted into the gap between the inner surface of the outer mold and the outer surface of the preform to form an unvulcanized rubber layer on the outer surface of the preform, and after cooling, the outer mold and the inner mold are are fastened and fixed, and vulcanized under heat and pressure to obtain the final product as in the conventional method.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. However, these Examples are merely for illustrating the present invention, and are not intended to limit the scope of the present invention.

FIG. 3 shows a perspective view of a preforming member used in the method of the present invention, that is, a regular length strip 11 having a trapezoidal cross section. As described above, this was produced by forming a band of unvulcanized rubber having a trapezoidal cross section using an extruder, and then cutting the band into a predetermined length.

In addition, since the fixed length strip is made of unvulcanized rubber, it has excellent elasticity and flexibility as well as good adhesion, so when forming the preform, it can be curved into a predetermined shape and Moreover, it can be easily adhered to the outer surface of the inner mold 4.

Furthermore, FIG. 4 is a diagram showing a method for forming a conical cylindrical molded article of the present invention. In FIG. 4, as an example, the cross section shows a state in which the regular length strips 11 of FIG. Furthermore, a gap 14 is provided between the mold outer mold 5 and the preform 13, and a press-fitting device for fluidized unvulcanized rubber is attached to the upper part of the mold. The press-fitting device 15 consists of a cylindrical press-fitting fluidized unvulcanized rubber storage chamber 16 having a shape equal to the outer diameter of the outer mold 5, an unvulcanized rubber press-fitting press ff 117, and a piston 18, and a bottom portion of the storage chamber. is provided with a plurality of unvulcanized rubber press-fit holes 19 which are provided in communication with the gap 14 and a plurality of holes (not shown) which communicate with the outside air for extracting the air in the gap 14. ing.

The fluidized unvulcanized rubber is press-fitted into the gap between the preform 13 and the mold 5 by operating a driving means (not shown) for the piston 18, and the fluid stored in the storage chamber 16 is moved by the movement of the piston. This is done by pressurizing the unvulcanized rubber through the press plate 17, thereby forcing the unvulcanized rubber into the press-in hole 19 and expelling the air in the gap through the air vent hole.

The impact receiving portion is obtained by arranging and stacking strips 20 of a fixed length each having a rectangular cross section. However, since it is cylindrical, a stepped gap is not formed as in the conventional method. This fixed length strip 20 having a rectangular cross section can also be formed in the same manner as the fixed length strip 11 having a trapezoidal cross section.

After the press-fitting of the unvulcanized rubber is completed, the press-fitting device 15 is removed,
Close the mold and fasten it. Next, the final product is obtained by vulcanization under heat and pressure according to a conventional method.

As described above, when the press-fitting device 15 shown in FIG. 4 is used to press-fit rubber only from the upper part, insufficient volume may occur. In order to solve this problem, an outer mold 5 as shown in FIG. 5 is used which can be separated into two parts 21 and 22.

Rubber reservoirs 23 are provided at several locations in the lower member 21 of the outer mold 5, and after a predetermined amount of fluidized rubber is injected into these reservoirs, the above-mentioned press-fitting device 15 and the upper mold upper portion 22 are attached. By configuring the outer mold in this way, the press-fitting device 1
It is possible to compensate for the lack of volume due to only 5.

As described in detail in "2. Effects of the Invention", according to the method for manufacturing a cylindrical rubber molded product of the present invention, a regular length strip having a trapezoidal cross section is used as a member for producing a preform, and the preform is By covering the outer surface with an unvulcanized rubber layer and then vulcanizing it, it is possible to increase the strength of the finished product and to make the appearance more homogeneous and smooth, thereby increasing the commercial value of the product. It becomes possible to do so.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a method for producing a ring-shaped body for fine molding, which is a fourth method for producing a conventional conical cylindrical rubber molded product. FIG. 3 is a diagram showing a method for manufacturing a cylindrical rubber molded product. FIG. 3 is a diagram showing a fixed length strip used in manufacturing the conical cylindrical rubber molded product of the present invention. FIG. FIG. 5 is a diagram showing a method for manufacturing a conical cylindrical rubber molded product according to the invention. FIG. 5 is a diagram showing another embodiment of the method for manufacturing a conical cylindrical rubber molded product according to the invention. (Main reference Number> 1: Strip-shaped member, 3: Ring-shaped member, 4: Mold inner mold, 5: Molding F outer mold, 11: Standard length strip, 12: Impact receiving part, 13: Preformed body, 14: Gap, 15: Press-fitting device>16: Storage chamber, 17: Pressing plate, 18: Piston, 19: Press-fitting hole, 20: Regular-length strip body having a rectangular cross section, 21: Outer mold lower member, 22: Outer mold lower member, 23 : Rubber reservoir patent applicant Sumitomo Rubber Industries Co., Ltd. Representative Patent attorney Arai Noise stop Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A band of unvulcanized rubber having a trapezoidal cross section is formed by an extruder, and the band is cut into a certain length to obtain a large number of fixed-length bands, and the fixed-length band is cut into a conical or truncated conical shape. A preformed body of unvulcanized rubber is formed on the outer surface of the inner mold by arranging them circumferentially from below the outer surface of the inner mold and sequentially stacking them upward along the ridge of the inner mold. An outer mold is placed on the outer surface of the preform, the inner mold and the core outer mold are fastened and fixed, and unvulcanized rubber is applied onto the outer surface of the preform using a press-fitting device with several stages of unvulcanized rubber into the outer mold. A method for producing a cylindrical rubber molded product, which comprises press-fitting rubber and then vulcanizing it under heat and pressure.