1.  Technical Field
The present invention relates to a discharge valve apparatus, a flush water tank apparatus including this discharge valve apparatus, and a flush toilet including this flush water tank apparatus; in particular, it relates to a discharge valve apparatus attached to a discharge port on a flush water tank for storing flush water used to flush a toilet, a flush water tank including this discharge valve apparatus, and a flush toilet including this flush water tank apparatus. 
2.  Description of Related Art
As shown in Patent Document 1 (Japanese Patent Unexamined Publication No.  2013-104271), what are known as direct drive discharge valve apparatuses have been known for some time, in which an operating member extending from a manual operating apparatus is attached to a primary shaft member of a valve body disposed inside a discharge valve apparatus casing, and the valve body and valve body primary shaft member are pulled up from a valve port through a lifting action by the operating member moving in tandem with the manual operation. 
In such discharge valve apparatuses, an operating member extending from a manual operating device is attached to the primary shaft member of a valve body inside a casing when manufactured at a factory or the like, and the exterior casing of the discharge valve apparatus is assembled so as not to be easily removable and disassembled.