Mechanical seal

A mechanical seal for preventing leakage of fluid, said seal comprising:

• (a) a rotary shaft;
• (b) a seat ring having an annular sliding contact surface;
• and
• (c) a follower ring having an annular sliding contact surface in sliding contact with said sliding contact surface of said seat ring, one of said seat ring and said follower ring being rotated by said rotary shaft, and the other ring allowing said rotary shaft to rotatably pass therethrough, wherein sliding contact between said sliding contact surfaces prevents said fluid from leaking from the outside to the inside of said sliding contact surfaces, so as to maintain fluid-tightness at an outer peripheral portion of an outer one of said follower ring and said seat ring, and wherein
• (d) at least one of said sliding contact surfaces has formed therein a plurality of recesses, each of which is defined by a forward edge and a rear edge, each of said recesses opening only to an inner circumferential surface of said one of said rings, said forward edge being inclined from said inner circumferential surface to a rear side extending radially outwardly and circumferentially from the intersection of said forward edge and said inner circumferential surface in a direction of a relative motion between said seat ring and said follower ring, said intersection within each recess being defined by an acute angle, said rear edge extending radially inwardly from the radial and circumferential outer end of said forward edge at least partially along a radial line extending through substantially a center of said rotary shaft, said forward edge being longer than said rear edge and the rear edge and forward edge intersecting at an acute angle, said rear edge being forwardly bulged in the direction of relative motion between said seat ring and said follower ring to an extent that it is not subjected to thermal deformation.