Patent ID: 8118551

Claim:
A casing having an upper casing and a lower casing that are joined together in a dividable manner, and a sealing structure that prevents outward leakage of gas from a joint area between the upper casing and the lower casing, the casing comprising: an upper protruding element that protrudes from an outer circumference of the upper casing; a lower protruding element that protrudes from an outer circumference of the lower casing; and an intermediary member that is arranged on the outer circumferences of the upper protruding element and the lower protruding element, wherein the joint area between the upper casing and the lower casing is extended by the upper protruding element and the lower protruding element; and the intermediary member is welded to the upper protruding element and the lower protruding element, at a position offset from the joint area, the upper protruding element and the lower protruding element are welded with the intermediary member to have flexible structures, so that they can be deformed.