US Patent 11187326 Mechanical seal

A mechanical seal in which a rotary ring can be more reliably positioned. A rotary ring unit 100 includes: a sleeve 120 fixed to a rotary shaft 500; and a rotary ring 110 of which a movement in an axial direction and a rotation with respect to the sleeve 120 is restricted, a fixed ring unit 200 includes: a fixed ring 210 configured to slide on an end surface of the rotary ring 110; and a bellows 250 which presses the fixed ring 210 toward the rotary ring 110, and the sleeve 120 is provided with a stopper 140 which restricts a movement of the rotary ring 110 toward the fixed ring 210.