Butterfly-valve seat ring and fixing structure of the same, and eccentric-type butterfly valve

An eccentric-type butterfly valve comprising:

• a cylindrical body having a flow path formed therein in a flow path direction;
• a disc axially and rotatably supported via a stem in the cylindrical body;
• an annular seat retainer;
• and
• an annular seat ring fixed by the annular seat retainer in the cylindrical body, the annular seat ring including:
• a ring-shaped base body part having a substantially rectangular shape in section,
• a flexible part with a predetermined material thickness, the flexible part being integrally provided on one side surface of an inner diameter of the ring-shaped base body part so as to extend therefrom,
• a fixing part being integrally provided on one side surface of an outer diameter of the ring-shaped base body part so as to extend therefrom, and
• a gasket part disposed on an annular periphery of an outer circumferential surface side of the ring-shaped base body part, the gasket part being integrally coupled to the ring-shaped base body part via a thin thickness part,
• wherein the disc is provided so as to be able to hermetically seal together with the annular seat ring,
• the annular seat ring includes a recess defining a concentric space part which is provided between an outer circumferential surface of the flexible part and an inner circumferential surface of the fixing part,
• an annular projection protrudes as a portion of the annular seat retainer at a position opposing the space part, the annular projection surrounding the entirety of the disc,
• a recessed-shaped groove is formed on an outer diameter side of the annular projection,
• a projecting part protrudes as a portion of the annular seat retainer and is disposed on an outer diameter side of the recessed-shaped groove,
• an attachment recessed groove is disposed on an outer diameter side of the projecting part,
• a seal contact part is provided to project at an inner diameter position of the flexible part, this seal contact part being positioned on an inner circumferential surface of the flexible part rather than a depth-side position of the space part,
• the gasket part is configured so as to fill in the attachment recessed groove,
• the fixing part is configured so as to fill in and be fixed in the recessed-shaped groove,
• a fixing base part, configured by an exterior of the ring-shaped base body part and the fixing part, is attached so as to fit between the cylindrical body and the annular seat retainer,
• a cylindrical body side of the fixing base part is in a close-contact seal state,
• the flexible part is deformable so as to warp with respect to the fixing base part,
• a first gap is formed between the ring-shaped base body part and the cylindrical body,
• a second gap is provided between an end surface of the flexible part along a direction intersecting the direction of the flow path and a side surface of the annular seat retainer along a direction intersecting the direction of the flow path,
• the flexible part is deformable to a side of the cylindrical body where the first gap is disposed and the flexible part is deformable to a side of the annular seat retainer where the second gap is disposed,
• an outer surface of the annular projection and an inside inner surface of the space part are in contact with each other at a contact position defining a supporting point part via which the flexible part can warp.