Valve disk of double eccentric butterfly valve, and double eccentric butterfly valve

1. A valve disk of a double eccentric butterfly valve, the valve disk having a circular outer shape and comprising:

a boss section for accommodating a stem; and

a rib section extending toward both outer edge portions of the valve disk in a direction intersecting the stem from the boss section,

wherein the boss section and the rib section are provided on a surface on one side of a disc, and a stem center axis passing through a center of the stem is at a position shifted from a valve disk center axis,

wherein the boss section is divided into a plurality of boss sections such that the stem is partially exposed, the rib section is provided in each of the boss sections obtained by the division, and the rib section and the boss section are consecutively connected to each other such that there occurs no step in a height direction viewed from the surface of the disc and there occurs no linear boundary portion on a side wall surface of the boss section, and

wherein the boss section is divided into two boss sections such that the stem is exposed in the vicinity of a center of the valve disk, the rib section is formed nearer the center side of the valve disk in each of the boss sections, and a sidewall surface, on the center side of the valve disk, of the boss section and a sidewall surface, on the center side of the valve disk, of the rib section are provided to form a consecutive single plane.

2. The valve disk of the double eccentric butterfly valve according to claim 1 , wherein the rib section is provided so as to gradually increase in height toward the boss section from an end portion on the outer edge side of the valve disk.

3. The valve disk of the double eccentric butterfly valve according to claim 1 , wherein an upper surface of the rib section is inclined so as to decrease at a substantially constant angle toward the outer edge portions of the valve disk from the boss section, and a rib center axis obtained by virtually extending inclined surfaces toward a center of the valve disk and connecting the inclined surfaces to each other is positioned on the opposite side to the stem center axis with respect to the valve disk center axis.

4. A double eccentric butterfly valve including the valve disk according to claim 1 , wherein the valve disc is openable and closable via the stem by pivotally mounting the stem on upper and lower pivotal mounting sections of a body having a cylindrical shape and providing the valve disk in the body.

5. A valve disk of a double eccentric butterfly valve having a circular outer shape, wherein a boss section for accommodating a stem and a rib section extending toward both outer edge portions of the valve disk in a direction intersecting the stem from the boss section are provided on a surface on one side of a disc, a stem center axis passing through a center of the stem is at a position shifted from a valve disk center axis, and the rib section excluding the boss section is provided such that a height from the surface of the disc on the side on which a distance to an end on the edge portion side of the valve disk is long is larger than that on the side on which a distance to an end on the edge portion side of the valve disk is short when the heights are respectively compared at positions spaced an equal distance apart from the stem center axis,

wherein the boss section is divided into a plurality of boss sections such that the stem is partially exposed, the rib section is provided in each of the boss sections obtained by the division, and the rib section and the boss section are consecutively connected to each other such that there occurs no step in a height direction viewed from the surface of the disc and there occurs no linear boundary portion on a side wall surface of the boss section, and

wherein the boss section is divided into two boss sections such that the stem is exposed in the vicinity of a center of the valve disk, the rib section is formed nearer the center side of the valve disk in each of the boss sections, and a sidewall surface, on the center side of the valve disk, of the boss section and a sidewall surface, on the center side of the valve disk, of the rib section are provided to form a consecutive single plane.

6. The valve disk of the double eccentric butterfly valve according to claim 5 , wherein the rib section gradually increases in height toward the boss section from an end portion on the outer edge side of the valve disk.

7. The valve disk of the double eccentric butterfly valve according to claim 5 , wherein an upper surface of the rib section is inclined to decrease at a substantially constant angle toward the outer edge portions of the valve disk from the boss section, and a rib center axis obtained by virtually extending inclined surfaces toward a center of the valve disk and connecting the inclined surfaces to each other is positioned on the opposite side to the stem center axis with respect to the valve disk center axis.

8. A double eccentric butterfly including the valve disk according to claim 5 , wherein the valve disk is provided so as to be openable and closable via the stem by pivotally mounting the stem on upper and lower pivotal mounting sections of a body having a short cylindrical shape and providing the valve disk in the body.