TECHNICAL FIELD

The present invention relates to a pneumatic fender and a method of manufacturing the same, and particularly, relates to a pneumatic fender and a method of manufacturing the same in which the boundary region between a body portion and a hemispherical portion is expanded smoothly together with the expanding body portion when a body is loaded with a specified internal pressure to make it easier to ensure the body with a predetermined shape.

BACKGROUND ART

Pneumatic fenders typically include a body provided with a hemispherical portion having a bowl shape at both ends of a body portion having a cylindrical shape, and the body is constituted by a plurality of reinforcing layers layered between an inner layer rubber and an outer layer rubber. In the body portion, each of the reinforcing layers is formed of multiple cords aligned in parallel, and the cords are disposed at a predetermined cord angle with respect to the cylinder axial direction. The cords of the reinforcing layers layered adjacently are in an intersecting state (so-called bias structure). When the cord angle in the neutral state where the body is not expanded is set to approximately the angle of repose (from 54° to 55°), the size (length and outer diameter) of the body does not change so much even when the inside of the body is filled with air and loaded with a specified internal pressure.

A pneumatic fender in which a cord angle of the reinforcing layers of a body portion is set to 15° or more and 45° or less in a neutral state where a body is not expanded has been proposed (see Patent Document 1). In the fender of this proposal, when the inside of the body is filled with air and loaded with a specified internal pressure, the cord angle of the reinforcing layer of the body portion will increase to approximately the angle of repose. Accordingly, since the body portion is expanded greatly in diameter, excellent cushioning performance (counter force) can be obtained when used while being compact when not in use.

However, unlike the reinforcing layer of the body portion, the cord angle of the reinforcing layer of the hemispherical portion in a neutral state in which the body is not expanded is not set to 15° or more and 45° or less. Thus, even when the body is loaded with the specified internal pressure, the boundary region between the hemispherical portion and the body portion does not expand greatly in diameter smoothly. As a result, since strain occurs at or near the boundary between the hemispherical portion and the body portion, a body that has been expanded to a predetermined shape cannot be ensured.

CITATION LIST

Patent Literature

Patent Document 1: JP 2013-231297 A

SUMMARY OF INVENTION

Technical Problem

An object of the present invention is to provide a pneumatic fender and a method of manufacturing the same in which the boundary region between a body portion and a hemispherical portion is expanded smoothly together with the expanding body portion when the body is loaded with a specified internal pressure to make it easier to ensure the body with a predetermined shape.

Solution to Problem

To achieve the object described above, the pneumatic fender according to embodiments of the present invention is a pneumatic fender which includes a body including a body portion having a cylindrical shape, and a hemispherical portion having a bowl shape connected to both ends of the body portion, in which the body is constituted by a plurality of reinforcing layers layered between an inner layer rubber and an outer layer rubber, each of the reinforcing layers in the body portion is formed of multiple cords aligned to extend in parallel at a predetermined cord angle with respect to a cylinder axial direction, the cords of the reinforcing layers layered adjacently have an intersecting bias structure, and the cord angle in a neutral state where the body is not expanded is set to 25° or more and 45° or less, both end portions in the cylinder axial direction of each of the reinforcing layers of the body portion and each of the corresponding reinforcing layers of the hemispherical portion facing each other with a space, members facing each other being bonded with a bonding member interposed between the members facing each other, the bonding member disposed in each of the spaces, each of the bonding members being formed of multiple cords aligned to extend in parallel, the multiple cords of the bonding members extending in an orientation identical to an orientation of the cords of a corresponding bonding target reinforcing layer of the body portion, a cord angle of the cords of the bonding members being set to ±10° of the cord angle of the cords of the bonding target reinforcing layer in a neutral state where the body is not expanded, the spaces having a plurality of different sizes, one set of ends of the spaces being set to a plurality of different positions, and an other set of ends of the spaces being set to a plurality of different positions, with respect to a circumferential direction of the hemispherical portion having an arcuate shape in a side view of the body.

The method of manufacturing the pneumatic fender according to embodiments of the present invention is a method of manufacturing the pneumatic fender described above, the method including: using a molding mold for the body portion having a cylindrical shape and a molding mold for the hemispherical portion having a bowl shape connected to both ends of the molding mold for the body portion to create a state in which the molding mold for the body portion and the molding molds for the hemispherical portion are separated; layering the reinforcing layers constituting the body portion on an inner side of the molding mold for the body portion; layering the reinforcing layers constituting the hemispherical portion on an inner side of each of the molding molds for the hemispherical portion; connecting the molding molds for the hemispherical portion to both ends of the molding mold for the body portion so that both end portions in the cylinder axial direction of each of the reinforcing layers constituting the body portion and each of the corresponding reinforcing layers of the hemispherical portion face each other with a space; sequentially disposing the bonding members in the respective spaces to form a reinforcing body formed of the reinforcing layers; and vulcanizing a bladder in which unvulcanized rubbers that form the outer layer rubber and the inner layer rubber are layered on an outer surface and an inner surface of the reinforcing body under predetermined conditions to obtain the body.

Advantageous Effects of Invention

According to the pneumatic fender according to embodiments of the present invention, not only the reinforcing layers constituting the body portion, but also the bonding members disposed in each space between the reinforcing layers and the reinforcing layers constituting the hemispherical portion and disposed facing the reinforcing layers have a bias structure in which the cords layered adjacently intersect each other. In the neutral state where the body is not expanded, the cord angle of the reinforcing layer of the body portion is set to 25° or more and 45° or less, and the cord angle of the reinforcing layer is set to be approximately identical to the cord angle of the bonding member. Accordingly, when the body is filled with air and loaded with the specified internal pressure, since the cord angle of each of the reinforcing layer of the body portion and the bonding members will increase to approximately a stable angle of repose, the body portion and the boundary region between the body portion and the hemispherical portion will also easily expand. Furthermore, since the respective spaces have a plurality of different types of sizes, one set of ends of the spaces are set to a plurality of different positions, and the other set of ends of the spaces are also set to a plurality of different positions, with respect to the circumferential direction of the hemispherical portion having an arcuate shape in a side view of the body. Thus, since the bonding positions between the bonding members and the respective reinforcing layers are dispersed with respect to the circumferential direction, the difference in rigidity of the body in the circumferential direction is suppressed. Accordingly, when the body is loaded with the specified internal pressure, the strain occurring at or near the boundary between the body portion and the hemispherical portion is rectified, and it becomes easy to obtain the body that has been expanded to a predetermined shape.

According to the method of manufacturing the pneumatic fender according to embodiments of the present invention, after a multilayer structure of the reinforcing layers constituting the body portion and a multilayer structure of the reinforcing layers constituting the hemispherical portions are separately formed using a molding mold for the body portion having a cylindrical shape and a molding mold for the hemispherical portion having a bowl shape connected to both ends of the molding mold for the body portion, the multilayer structures are bonded by the bonding member to form a reinforcing body formed of the reinforcing layers. Accordingly, the pneumatic fender described above can be efficiently manufactured.

