Patent ID: 7997583

Claim:
A mechanical sealing device comprising: a stationary slide ring hermetically fixed in a housing; a rotary slide ring which slides and closely contacts with said stationary slide ring, the rotary slide ring being rotatable with a rotary shaft inserted to an inner bore; an O-ring housed in an annular ramp portion of an inner bore of said rotary slide ring; and an annular ring member forming a triangle shape in axial section housed in said annular ramp portion of said inner bore of said rotary slide ring as adjoining said O-ring at an atmosphere side; wherein said rotary slide ring is provided on an outer circumference face of said rotary shaft is movable in the axial direction of said rotary shaft via said O-ring, wherein said annular ramp portion of said inner bore of said rotary slide ring comprises an inner circumference face tapered to become gradually narrower from a high pressure environment side toward an atmosphere side, wherein said annular ring member is made of material having a relatively lower gas permeability than that of said O-ring, and comprises a tapered outer circumference face of which an outer diameter becomes smaller from the high pressure environment side towards the atmosphere side to correspond to the tapered inner circumference face of said annular ramp portion of said inner bore of said rotary slide ring and an inner circumferential face in which an annular projected portion is provided at an end portion adjacent to said O-ring in a cross-section along an axial direction of said annular ring member, said annular projected portion projecting radially inward, wherein said tapered outer circumferential face of said ring member and said tapered inner circumferential face of said rotary slide ring contact each other, and wherein an expression D 1 <D 2 <D 3 is satisfied in which D 1 is a diameter of said rotary shaft, D 2 is an inner diameter of said annular projected portion of said ring member, and D 3 is an inner diameter of a portion at said atmosphere side from said ring member in the inner bore of said rotary slide ring.