Patent ID: 7469934

Claim:
A pipe joint structure comprising: a connection flange member defining a through hole and an enlarged recess greater than an innermost diameter of said through hole, wherein said enlarged recess is located at one end of said through hole, the walls of said through hole and of said recess being substantially parallel to the central axis of said through hole; and a pipe having an outer diameter extending through said innermost diameter of said through hole and having a circular protrusion protruding radially outward from said pipe near an end of said pipe; wherein said enlarged recess has a serrated shape with a plurality of serrations and spaces disposed between adjacent serrations, an innermost diameter of said serrations being greater than said innermost diameter of said through hole; and said circular protrusion is press-fitted and fixed radially and axially to said enlarged recess such that an outer periphery of said circular protrusion is deformed into the serrated shape of said enlarged recess such that portions of the deformed circular protrusion are pushed into the spaces between the adjacent serrations and fixed in close relation against the serrations due to the deformation caused by the press-fitting fixation.