JP2008200974A - Manufacturing method for rubber cylinder, manufacturing method for rubber tube, and vulcanization mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a rubber tube, which also enables the manufacture of a medium-length rubber cylinder, while adopting a vulcanization molding system for covering an unvulcanized rubber cylinder with an outer mold and pressurizing it from the inside. <P>SOLUTION: A mandrel 7 is constituted by arranging a tubular rubber 5 around a metal tube 6. In the tubular rubber 5, two reinforcing cord layers 11 are provided by circumferentially arranging a reinforcing cord 12 while inclining it. The directions of the inclinations of the reinforcing cords 12 of the respective layers 11a and 11b are set to cross each other. The diameter of the tubular rubber 5 is reduced while angles (θ) of the inclinations of the reinforcing cords 12 are changed by pulling both ends of the tubular rubber 5. An unvulcanized rubber tube 8 is molded around the mandrel 7, and inserted into a vulcanizing pan 9. The reduction of the diameter of the tubular rubber 5 is released, and the unvulcanized rubber tube 8 is pressurized by being pressed against an inner peripheral surface of the vulcanizing pan 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a rubber cylinder, a method for producing a rubber tube, and a vulcanization mold for producing a rubber tube, for example.

  Generally, a rubber cylinder such as a rubber tube is manufactured by molding an unvulcanized rubber cylinder and vulcanizing and molding it by heating it while applying pressure. For vulcanization molding of an unvulcanized rubber cylinder, for example, a cloth fastening method, an outer bag method, a split outer mold method, or the like is employed as a method of placing a mandrel on the inside and pressurizing from the outside.

  Among the methods of pressurizing the unvulcanized rubber cylinder from the outside, the cloth fastening method and the outer bag method tend to lower the outer diameter accuracy of the rubber cylinder to be molded, and cannot obtain the desired surface gloss. In addition, the split outer mold method sets a larger amount of unvulcanized rubber in the unvulcanized rubber cylinder, so that the outer mold can be assembled and pressurized, and excess uncut rubber can be removed from the split surface of the outer mold. Vulcanized rubber flows out. The longer the rubber cylinder to be molded, the more difficult it is to adjust the amount of unvulcanized rubber. There is a risk that exposed reinforcing fibers may be exposed.

  On the other hand, as a vulcanization molding method in which an unvulcanized rubber cylinder is covered with an outer mold and pressurized from the inside, a method using an inner bag and an outer mold as disclosed in Patent Document 1, for example, may be adopted. is there. Since this method uses an outer mold, the outer diameter accuracy of the rubber cylinder after molding is high, a desired surface gloss can be obtained, and a split surface is unnecessary for the outer mold, There is no exposure of reinforcing fibers due to the outflow of unvulcanized rubber. However, when molding a medium-sized or larger rubber cylinder, this method is used because the inner bag cannot be inserted into the medium-sized unvulcanized rubber cylinder when setting the vulcanization mold. I can't do it.

On the other hand, a cylindrical rubber is arranged around the core material to form a mandrel, an unvulcanized rubber cylinder is molded around the mandrel, and the unvulcanized rubber cylinder is put together with the mandrel into an outer mold. A method of inserting and pressurizing can be considered. This method is to pressurize the unvulcanized rubber cylinder from the inside as in the case of the inner bag system by compressing and expanding the diameter of the cylindrical rubber in the direction of the central axis. In this molding, it is easy to set a vulcanization mold.
JP-A-5-237848

  However, the mandrel composed of the core material and the cylindrical rubber has a longer friction between the cylindrical rubber and the core material or the unvulcanized rubber cylinder as the unvulcanized rubber cylinder and the cylindrical rubber are longer. Applying force to both ends of the rubber to compress it in the direction of the central axis, the compression force is not transmitted to the central part, and the central part of the cylindrical rubber is sufficiently expanded to pressurize the unvulcanized rubber cylinder I can't.

  The present invention relates to a method for producing a rubber cylinder capable of producing a medium-sized rubber cylinder while adopting a vulcanization molding method in which an unvulcanized rubber cylinder is covered with an outer mold and pressurized from the inside. Another object is to provide a rubber tube manufacturing method and a vulcanization mold.

  In order to achieve the above object, a method for manufacturing a rubber cylinder according to the present invention is to vulcanize and mold an unvulcanized rubber cylinder around a mandrel, and the mandrel is around a core material. Cylindrical rubber is arranged, and in this cylindrical rubber, reinforcing cords are inclined with respect to the central axis of the mandrel and arranged in circumferential and even rows, and the reinforcing cords in a pair of rows intersect with each other in the inclination direction. A reinforcing cord layer is provided so as to be set.

  The procedure for manufacturing the rubber cylinder will be described in detail. First, by pulling both ends of the cylindrical rubber, the cylindrical rubber is moved in the mandrel central axis direction while changing the inclination angle of the reinforcement cord with respect to the mandrel central axis. Reduce diameter while stretching. Next, after molding unvulcanized rubber cylinders around the mandrel and inserting them into the vulcanized can, the unvulcanized rubber cylinder is vulcanized by releasing the expansion of the cylindrical rubber and expanding the diameter. The vulcanization molding is carried out by applying pressure to the inner peripheral surface of the steel and heating it. Thereafter, the tubular rubber is reduced in diameter while being stretched again, and the rubber cylinder is taken out from the mandrel and the vulcanizing can.

  According to the above configuration, since the unvulcanized rubber is molded around the cylindrical rubber that has been stretched and reduced in diameter, it can be easily inserted into a vulcanizing can as an outer mold. Moreover, the diameter of the cylindrical rubber is expanded by releasing the expansion, and after the unvulcanized rubber cylinder is vulcanized and molded, the cylindrical rubber is stretched again to reduce the diameter. Removal can be facilitated.

  Furthermore, since a reinforcing cord layer is provided on the cylindrical rubber of the mandrel, even if the cylindrical rubber is set to a medium size so as to form a medium-sized rubber cylinder, the force pulling both ends of the cylindrical rubber is reduced by the core material. Alternatively, it can be transmitted to the central part in the mandrel central axis direction against friction with the unvulcanized rubber cylinder. In addition, since the inclination directions of the reinforcing cords in a pair of rows intersect each other, the so-called pantograph action of the reinforcing cords expands the entire length from both ends of the cylindrical rubber to the center while reducing the diameter or releasing the expansion. Can be calibrated.

  After inserting the mandrel and unvulcanized rubber cylinder into the vulcanized can, release the expansion of the cylindrical rubber, and compress the cylindrical rubber in the direction of the central axis of the mandrel, thereby expanding the diameter of the unvulcanized rubber cylinder. If pressure is applied by pressing against the inner peripheral surface of the vulcanized can, the physical properties of the rubber can be improved by pressing the unvulcanized rubber cylinder more strongly than simply releasing the expansion of the cylindrical rubber. .

  The production method of the present invention is preferably employed for the production of a rubber cylinder in which the ratio (L / D) of the length (L) to the outer diameter (D) in the central axis direction is set in the range of 3-20. It is.

  In other words, if (L / D) is less than 3, the cylindrical rubber can be sufficiently reduced in diameter and expanded by its release without providing a reinforcing cord layer on the cylindrical rubber. The effect of providing the reinforcing cord layer on the rubber cannot be obtained. On the other hand, if (L / D) exceeds 20, the friction with the core material becomes extremely large with the diameter reduction of the cylindrical rubber, so that the tensile force cannot be transmitted to the central part of the cylindrical rubber. It is not possible to reduce the diameter by stretching and to increase the diameter by releasing it.

  It is preferable to employ the method of the present invention for the production of the unvulcanized rubber cylinder in which the reinforcing fiber is embedded. That is, in the production method of the present invention, even in the production of a medium-sized rubber cylinder, the unvulcanized rubber cylinder is pressurized from the inside while being covered with a vulcanization can as an outer mold, so that the desired outer diameter accuracy is achieved. And it is not necessary to use a split outer mold to obtain surface gloss. Therefore, even if the reinforcing fibers are embedded in the unvulcanized rubber cylinder, the reinforcing fibers are not exposed due to the non-uniform outflow of the outer unvulcanized rubber from the split surface of the outer mold.

  The manufacturing method described above can be used to manufacture all types of rubber cylinders such as air spring diaphragms, tires, and pipe joints, but generally the ratio between the length in the central axis direction (L) and the outer diameter (D). For the rubber tube having a large (L / D), it is particularly preferable to employ the production method of the present invention for its production.

  The present invention also provides a vulcanization mold used in the above production method. That is, the present invention includes a mandrel that forms an unvulcanized rubber cylinder around the mandrel, and a vulcanization can that pressurizes and heats the unvulcanized rubber cylinder inserted together with the mandrel. Cylindrical rubber is arranged around, and the reinforcing cords are arranged in the circumferential direction and even rows while inclining the reinforcing cords with respect to the central axis of the mandrel, and the inclination directions of the reinforcing cords in a pair of rows are arranged. Provided is a vulcanization molding die provided with a reinforcing cord layer set so as to cross each other.

  By adopting the configuration of the vulcanization mold, it is possible to obtain the same effect as that obtained by adopting the configuration of the rubber cylinder and the rubber tube manufacturing method. In addition, as the reinforcement cord, any heat-resistant material that can withstand the temperature at the time of vulcanization molding may be used, but in order to transmit the tensile force to the central portion of the cylindrical rubber, a material having a small elongation with respect to tension is preferable, Examples include aramid cords and steel cords. In particular, an aramid fiber cord that is a spun yarn is suitable because it does not require treatment with an adhesive or the like.

  If the inclination angle of the reinforcing cord with respect to the mandrel central axis is set larger toward the center than both ends of the mandrel, the cylindrical rubber can be uniformly reduced in diameter over its entire length and expanded by releasing it. In other words, since the tensile force received from both ends tends to be small due to the influence of friction with the core material etc. at the central part of the cylindrical rubber, the inclination angle of the reinforcing cord at this central part is set large, By making the rigidity of the central portion smaller than both end portions, it is possible to make the diameter reduction and diameter expansion of the cylindrical rubber uniform over the entire length.

  The cylindrical rubber may be formed from a heat-resistant rubber that can withstand the temperature at the time of vulcanization molding. However, if silicon rubber having a high coefficient of thermal expansion is used as this heat-resistant rubber, the cylindrical rubber will be Due to the thermal expansion of the cylindrical rubber, the unvulcanized rubber cylinder can be more strongly pressurized and the physical properties of the rubber can be enhanced.

  As described above, according to the present invention, the cylindrical rubber is arranged around the core material to form the mandrel, and the cylindrical rubber is provided with the reinforcing cord layer. The rubber can be reduced in diameter and expanded over the entire length. As a result, a vulcanization molding method in which an unvulcanized rubber cylinder is covered with an outer mold and pressed from the inside can be adopted for the production of a medium-sized rubber cylinder, and the rubber cylinder after molding is It is possible to improve the diameter accuracy and obtain a desired surface gloss.

  The best mode for carrying out a method for producing a rubber cylinder, a method for producing a rubber tube, and a vulcanization mold according to the present invention will be described below with reference to the drawings.

  First, the structure of the rubber tube as a rubber cylinder manufactured by the method according to the present invention will be described. FIG. 1 is a view showing a rubber tube manufactured by the method according to the present invention, wherein the upper half is a sectional view and the lower half is a side view.

  The rubber tube 1 is used, for example, as a pumping tube equipped in a squeeze pump for pumping ready-mixed concrete or the like. The rubber tube 1 has a structure in which a reinforcing fiber 3 is embedded in a medium-sized rubber cylinder 2 and its center. The ratio (L / D) between the axial length (L) and the outer diameter (D) is set in the range of 3-20.

  Next, the manufacturing method of the rubber tube which concerns on this invention is demonstrated. FIG. 2 is a view showing a mandrel, in which the upper half is a sectional view and the lower half is a side view. In FIG. 2, the center portion of the lower half shows the reinforcing cord layers on the outer surface side and the inner surface side by peeling the outer surface rubber of the cylindrical rubber. FIG. 3 is a diagram showing the first half of the rubber tube manufacturing method, and FIG. 4 is a diagram showing the second half of the rubber tube manufacturing method.

  First, the configuration of the vulcanization mold according to the present invention will be described.

  The vulcanization mold 4 includes a mandrel 7 in which a sufficiently thick cylindrical rubber 5 is disposed around a metal tube 6 as a core, and an unvulcanized rubber cylinder 8 molded around the mandrel 7 as a mandrel. 7 and a vulcanizing can 9 inserted into the vulcanizing can 9 and an end pressing metal fitting 10 for pressing the end of the unvulcanized rubber cylinder 8 inserted into the vulcanizing can 9. The unvulcanized rubber cylinder 8 is connected to the cylindrical rubber 5. While expanding and pressurizing, vulcanization molding is carried out by heating from inside and outside through the mandrel 7 and the vulcanizing can 9.

  The cylindrical rubber 5 has heat resistance that can withstand the vulcanization temperature, is easily deformed, and is formed of silicon rubber having a high coefficient of thermal expansion, so that it can be sufficiently compressed in the central axis direction of the mandrel. It is set longer than the unvulcanized rubber cylinder 8 and the vulcanized can 9 that are molded into the same. The cylindrical rubber 5 has a sufficient thickness of, for example, about 7 mm, and is stretched in the mandrel central axis direction along the metal tube 6 to reduce the diameter, and the release of the reduced diameter, compression in the mandrel central axis direction, In addition, the diameter is expanded by thermal expansion during vulcanization molding.

  In the vicinity of the outer surface of the cylindrical rubber 5, a reinforcing cord layer 11 is provided for transmitting the tensile force applied to both ends to the central portion.

  The reinforcing cord layer 11 is formed by arranging reinforcing cords 12 made of, for example, 0.3 mm thick aramid middle fibers in a circumferential direction and two layers with a number density of 6 / cm while inclining with respect to the mandrel central axis. The inclination directions of the reinforcing cords 12 of the layers 11a and 11b are set to intersect each other. The inclination angle (θ) of the reinforcing cord 12 with respect to the central axis of the mandrel ranges from the inclination angle (θ1, for example, 46 °) at both ends of the cylindrical rubber 5 to the inclination angle (θ2, for example, 58 °) at the center. It is set to be larger toward the center than at both ends (θ1 ≦ θ ≦ θ2).

  The metal pipe 6 heats the unvulcanized rubber cylinder 8 from the inside through the cylindrical rubber 5 by supplying and circulating a heat medium such as silicon oil or glycerin inside the metal pipe 6. . The metal tube 6 is set to be sufficiently longer than the cylindrical rubber 5 disposed around the central portion thereof, and functions as a guide when the cylindrical rubber 5 is stretched or compressed in the mandrel central axis direction. .

  The vulcanizing can 9 is a double pipe having an inner diameter equal to the outer diameter of the rubber tube 1, having connection flanges 13 at both ends and having a cavity 14 on the entire circumference, and from the inlet (not shown) to the cavity 14. The unvulcanized rubber cylinder 8 is heated from the outside by supplying and circulating a heat medium such as silicon oil or glycerin. The vulcanized can 9 is set longer than the unvulcanized rubber cylinder 8 so that the unvulcanized rubber cylinder 8 can be accommodated over its entire length.

  The end holding metal fitting 10 has an L-shaped cylindrical rubber holding metal fitting 16 that holds the cylindrical rubber end collar 15 provided at the end of the cylindrical rubber 5 and the end shape of the unvulcanized rubber cylinder 8. An end collar 17 to be formed, an unvulcanized rubber cylinder pressing metal fitting 18 having an L-shaped cross section for holding the end collar 17, and a flange of the cylindrical rubber pressing metal fitting 16 are penetrated and screwed to the connection flange 13 of the vulcanizing can 9. The unvulcanized rubber cylinder retainer bolt that is screwed to the flange of the tubular rubber retainer bolt 19 and the tubular rubber retainer bracket 16 to be joined, and whose tip is brought into contact with the flange of the unvulcanized rubber cylinder retainer bracket 18. 20.

  The end holding metal fitting 10 adjusts the unvulcanized rubber cylinder holding bolt 20 and adjusts the unvulcanized rubber cylinder 8 while adjusting the cylindrical rubber holding bolt 19 to stretch or compress the cylindrical rubber 5. It is designed to hold down the length.

  Next, a method for producing a rubber tube using the above vulcanization mold will be described. As shown in FIG. 3A, the cylindrical rubber 5 of the mandrel 7 has a length L1 and an outer diameter D1 (for example, φ36 mm) in a free state.

  First, as shown in FIG. 3B, the end collar 17 is disposed at a predetermined position outside the cylindrical rubber 5. At the same time, by pulling both ends of the cylindrical rubber 5 in the mandrel central axis direction, the outer diameter of the cylindrical rubber 5 is reduced to D2 (for example, φ34 mm) while extending the length of the cylindrical rubber 5 to L2.

  At this time, the cylindrical rubber 5 is reduced in diameter while being stretched in the mandrel central axis direction by changing the inclination angle (θ) of the reinforcing cord 12 with respect to the mandrel central axis by the pantograph action of the reinforcing cord layer 11. In addition, since the inclination angle (θ) of the reinforcing cord 12 is increased at the center portion where the tensile force is smaller, and the rigidity of the tubular rubber 5 against tension is reduced, the tubular rubber 5 is uniform over the entire length. Reduce to diameter.

  Next, as shown in FIG. 3 (c), the inner surface unvulcanized rubber is wound around the cylindrical rubber 5, the reinforcing fiber 3 is arranged on the outer side, and the outer surface unvulcanized rubber is wound on the outer side. Then, the unvulcanized rubber cylinder 8 in which the reinforcing fiber 3 is embedded is molded. The unvulcanized rubber cylinder 8 has an inner diameter and an outer diameter smaller than those of the rubber tube 1 and is set to a thickness that can obtain the rubber tube 1 having a desired thickness after vulcanization molding. In addition, as shown in FIG.4 (d), the cylindrical rubber 5 tries to return to the free state of length L1 and outer diameter D1 by canceling | extracting extension.

  As shown in FIG. 4 (e), the mandrel 7 and the unvulcanized rubber cylinder 8 are inserted into the vulcanizing can 9. At this time, since the outer diameter of the cylindrical rubber 5 is reduced to D2, the outer diameter of the unvulcanized rubber cylinder 8 is smaller than the outer diameter of the rubber tube 1, that is, the inner diameter of the vulcanized can 9, and its insertion Is easy.

  Further, the end holding metal fitting 10 is attached to the vulcanized can 9 and the unvulcanized rubber cylinder holding bolt 20 is adjusted to hold the end of the unvulcanized rubber cylinder 8. In addition, the unvulcanized rubber cylinder 8 is heated from inside and outside by supplying a heat medium to the metal tube 6 and the vulcanizing can 9 and circulating it. As the heating starts, the cylindrical rubber holding bolt 19 of the end holding metal fitting 10 is adjusted to release the expansion of the cylindrical rubber 5, and the outer diameter is expanded to D1 while the length of the cylindrical rubber 5 is set to L1. After the diameter, the cylindrical rubber pressing bolt 19 is further adjusted to expand the outer diameter while compressing the length of the cylindrical rubber 5 to L3. Further, the outer diameter of the cylindrical rubber 5 is expanded to D3 (for example, φ38 mm) by thermal expansion. As a result, the unvulcanized rubber cylinder 8 is heated and pressed against the inner peripheral surface of the vulcanizing can 9 to be vulcanized and molded.

  Thereafter, as shown in FIG. 4 (f), the length of the cylindrical rubber 5 is again extended to L2, the outer diameter is reduced to D2, and the rubber after vulcanization molding from the mandrel 7 and the vulcanizing can 9 is obtained. Remove tube 1. At this time, since the diameter of the cylindrical rubber 5 is reduced to D2, the rubber tube 1 can be easily taken out.

  According to the above configuration, since the reinforcing cord layer 11 is provided on the cylindrical rubber 5, the force applied to both ends of the cylindrical rubber 5 is transmitted to the central portion, and the pantograph action of the reinforcing cord layer 11 causes the cylindrical rubber 5 to be transmitted. Can be reduced in diameter and expanded. Moreover, since the inclination angle (θ) of the reinforcing cord 12 is set to be larger toward the center of the cylindrical rubber 5, the cylindrical rubber 5 can be uniformly reduced in diameter and expanded over the entire length, and unvulcanized rubber. The cylinder 8 can be pressed strongly and uniformly over the entire length.

  As a result, it is possible to manufacture a rubber tube 1 having a medium size and high quality with a small diameter of about 3 to 20 (L / D) between the length (L) in the central axis direction and the outer diameter (D). . Moreover, since the cylindrical rubber 5 is inserted into the vulcanizing can 9 with a reduced diameter and pulled out, the vulcanizing mold 4 can be easily set and removed.

  Since the unvulcanized rubber cylinder 8 is covered with a vulcanizing can 9 as an outer mold and pressurized from the inside, the outer diameter accuracy of the rubber tube 1 can be increased and a desired surface gloss can be obtained. Further, since the split outer mold is not used, the reinforcing fiber 3 is not exposed by the non-uniform flow of the unvulcanized rubber from the split surface, and the rubber tube having the reinforcing fiber and having the thin outer rubber is formed. Can be manufactured.

  The vulcanizing can 9 is inexpensive because the split outer mold is unnecessary, and the cylindrical rubber 5 made of silicon rubber that is inexpensive and has a long life is used. Therefore, the initial cost of the vulcanizing mold 4 and its consumables Costs can be reduced.

  In addition, this invention is not limited to said embodiment, A change can be suitably added within the scope of the present invention. For example, instead of the rubber tube 1, all rubber cylinders such as an air spring diaphragm, a tire, and a pipe joint can be manufactured.

  The reinforcing cord layer 11 may be formed by repeatedly winding one reinforcing cord 12 while changing the inclination angle (θ), or by forming several reinforcing cords 12 while changing the cord interval. May be. Further, instead of the two reinforcing cord layers 11, the reinforcing cords 12 may be arranged in even rows. In this case, the reinforcing cords 11 may be arranged in the circumferential direction and even rows while being inclined with respect to the central axis of the mandrel, and the inclination directions (θ) of the reinforcing cords 12 in a pair of rows may be set to intersect each other.

  The cylindrical rubber 5 can also be formed from a heat resistant rubber other than silicon rubber. As the reinforcing cord 12, instead of a cord made of aramid medium fiber, other cords such as a steel cord which does not easily stretch can be used.

It is a figure which shows the rubber tube manufactured with the method which concerns on this invention, an upper half is sectional drawing, a lower half is a side view It is a figure which shows a mandrel, an upper half is sectional drawing, a lower half is a side view The figure which shows the process of the first half of the manufacturing method of a rubber tube The figure which shows the process of the latter half of the manufacturing method of a rubber tube

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rubber tube 3 Reinforcing fiber 4 Vulcanization mold 5 Cylindrical rubber 6 Metal tube 7 Mandrel 8 Unvulcanized rubber cylinder 9 Vulcanized can 11 Reinforcement cord layer 12 Reinforcement cord

Claims (8)

A method for producing a rubber cylinder in which an unvulcanized rubber cylinder is molded around a mandrel and vulcanized,
The mandrel is formed by arranging a cylindrical rubber around a core material, and in the cylindrical rubber, reinforcing cords are arranged in a circumferential direction and even rows while being inclined with respect to the central axis of the mandrel, and a pair of rows. Reinforcement cord layer formed by setting the inclination directions of the reinforcement cords to cross each other is provided,
By pulling both ends of the cylindrical rubber, the diameter of the cylindrical rubber is reduced while extending in the direction of the central axis of the mandrel while changing the inclination angle of the reinforcing cord with respect to the central axis of the mandrel, and then unvulcanized around the mandrel. After the rubber cylinders are molded and inserted into the vulcanizing can, the unvulcanized rubber cylinder is pressed against the inner peripheral surface of the vulcanizing can by releasing the expansion of the cylindrical rubber and expanding the diameter. A method for producing a rubber cylinder, wherein the rubber cylinder is vulcanized by heating while pressing, and then the diameter of the cylindrical rubber is reduced while being stretched again, and the rubber cylinder is taken out of the mandrel and the vulcanizing can.   After inserting the mandrel and the unvulcanized rubber cylinder into the vulcanized can, releasing the expansion of the cylindrical rubber and compressing the cylindrical rubber in the direction of the central axis of the mandrel to expand the diameter, the unvulcanized rubber 2. The method for producing a rubber cylinder according to claim 1, wherein the cylinder is pressed against the inner peripheral surface of the vulcanizing can and pressurized.   The ratio (L / D) between the length (L) in the central axis direction of the rubber cylinder and the outer diameter (D) is set in the range of 3 to 20, according to claim 1 or 2. Manufacturing method of rubber cylinder.   The method for producing a rubber cylinder according to claim 1, 2 or 3, wherein reinforcing fibers are embedded in the unvulcanized rubber cylinder.   A rubber tube is manufactured by the method in any one of Claims 1-4, The manufacturing method of the rubber tube characterized by the above-mentioned.   A mandrel that molds an unvulcanized rubber cylinder around the mandrel; and a vulcanization can that pressurizes and heats the unvulcanized rubber cylinder inserted together with the mandrel. The mandrel has a cylindrical rubber around the core. The reinforcing cords are arranged on the cylindrical rubber in a circumferential direction and even rows while being inclined with respect to the central axis of the mandrel, and the inclination directions of the reinforcing cords in a pair of rows are set to intersect each other. A vulcanization mold characterized in that a reinforcing cord layer is provided.   The vulcanization mold according to claim 6, wherein the reinforcing cord has a larger inclination angle with respect to the mandrel central axis toward the center than both ends of the mandrel.   The vulcanization mold according to claim 6 or 7, wherein the cylindrical rubber is made of silicon rubber.

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