Abstract: A mechanical seal for sealing a slurry liquid between a casing and a rotary shaft comprises a fixed seat ring; a rotatable slide ring in the casing and abutting against the seat ring to form a sealing face therebetween; a helical spring in the casing and surrounding the rotary shaft, and biassing the rotatable slide ring toward the seat ring; and a rotatable ring on the rotary shaft and rotatable with the rotary shaft and holding the spring at a predetermined position relative to the rotary shaft, the spring being interposed between the rotatable slide ring and the rotatable ring. A small space is provided between the casing and the rotatable ring and the rotatable ring has a helical projection on the outer surface thereof. The helical projection of the rotatable ring and the helical spring are directed such that upon rotation thereof a force is produced in a direction away from the sealing face and toward the interior of the casing.

Abstract: A sealing device for a rotary shaft is provided with a spiral member having a determined pitch and a determined thickness on a rotating portion and/or a stationary portion corresponding to the rotating portion. The spiral member may be provided via a shaft sleeve, or may be directly attached on a rotating portion and/or a stationary portion corresponding to the rotating portion. The spiral member may be in advance shaped in a spiral form, or may be a string-like flexible member which may be shaped in a spiral form.

Abstract: A mechanical seal has a seal ring whose sealing face is divided into an inner part and an outer part by a circular groove through which sealing liquid is fed. The inner part of the sealing face is concave in the axial direction thereof.