Metal gasket, vacuum flange for the metal gasket, and vacuum seal structure using the metal gasket

A vacuum seal structure using a reusable metal gasket, comprising:

• a pair of flanges with a sealing groove in the surface of said flange, at least an inner side wall section of said sealing groove being inclined with respect to the flange surface in such a fashion that the width of a cross section of aid sealing groove decreases in the direction of the depth thereof, and an outer sidewall section of said sealing groove being substantially perpendicular to the flange surface, with a difference in level being provided so that said flange surface positioned to the inside of said sealing groove is lower than said flange surface positioned to the outside of said sealing groove, there being no protruding section on said flange surface on the inside of said sealing groove,
• wherein said difference in level is in the range of 0.3 mm to 1.0 mm;
• and
• a ring-shaped reusable gasket member with a substantially rectangular cross-section, which is accepted and pressed into said sealing groove opposing said flanges, with the ratio (t/w) of the thickness t of said ring-shaped gasket member to the width w thereof being in the range of 0.5 to 4, having a Vickers hardness in the range of 50 to 120,
• wherein no portion of the ring-shaped reusable gasket member extends out of the sealing groove, and wherein the ratio (t/w) and the Vickers hardness are chosen such that the reusable metal gasket is not deformed when pressed in the sealing groove and may be reused.