Pressure sensible valve for exhaust muffler and method of assembling same

A valve for use with a passing pipe installed in an exhaust muffler, comprising:

• a valve seat structure adapted to be secured to an outlet end of said passing pipe, said valve seat structure including a flat seat surface portion which extends around the outlet end of said passing pipe;
• a valve plate structure pivotally connected to said valve seat structure, said valve plate structure including a valve plate portion and a flat sealing portion which forms a peripheral part of said valve plate portion, said valve plate structure having a closed position wherein said valve plate portion closes the outlet end of said passing pipe having said flat sealing portion entirely pressed against the flat seat surface of said valve seat structure and an open position wherein said valve plate portion opens the outlet end of said passing pipe having the flat sealing portion separated from said flat seat surface;
• a biasing structure which biases said valve plate structure to assume said closed position;
• and
• a pivot structure which includes:
• a first pair of side wall portions defined by said valve seat structure, said first side wall portions being formed with first aligned openings respectively;
• a second pair of side wall portions defined by said valve plate structure, said second side wall portions being formed with second aligned openings respectively, said second side wall portions being put between said first side wall portions in such a manner that the first and second aligned openings are all aligned;
• and
• a pivot shaft passing through said aligned first and second openings of the first and second side wall portions,
• wherein the entire pressing of said flat sealing portion against said flat seat surface is carried out on a common imaginary flat surface.

A method of assembling a valve, comprising the steps of:

• (a) preparing a valve seat structure and a valve plate structure, said valve seat structure including a first pair of side wall portions which are formed with first aligned openings which are elliptic in shape, said valve plate structure including a second pair of side wall portions which are formed with second aligned openings which are circular in shape;
• (b) putting said second side wall portions between said first side wall portions and keeping the first and second side wall portions in such a manner that the first and second aligned openings are all aligned;
• (c) inserting a pivot shaft into the aligned first and second openings so that upon insertion of the pivot shaft, the valve plate structure becomes pivotal relative to said valve seat structure about the pivot shaft;
• (d) positioning said valve plate structure relative to said valve seat structure by moving the pivot shaft in the first aligned openings;
• and
• (e) fixing said pivot shaft to said first side wall portions while keeping the positioning between the valve plate structure and said valve seat structure.