Patent ID: 8439330

Claim:
A stem shoulder seal with double rings, comprising: a sealing ring, a clamping ring and a spherical or conical stem shoulder, wherein the sealing ring is made of a low strength material and responsible for sealing the spherical or conical stem shoulder and a valve body, the clamping ring is made of a high strength material and responsible for pressing the sealing ring tight, and the spherical or conical stem shoulder is assembled to press at the same time the sealing ring and the clamping ring supported mutually; the sealing ring has a cross-sectional shape of an equilateral triangle (ABC), the sealing ring including: a first surface formed by revolving an arc opposite a first side AB of the triangle ABC or by revolving the first side AB around an axis of a valve stem, the first surface engaging a surface of the spherical or conical stem shoulder for sealing the spherical or conical stem shoulder, a second surface formed by revolving a second side BC around the axis of the valve stem, the second surface of the sealing ring engaging the clamping ring, and a third surface formed by revolving a third side CA around the axis of the valve stem, the third surface being perpendicular to the axis of the valve stem for sealing a surface of the valve body; and the clamping ring has a cross-sectional shape of a truncated right trapezoid, a first side and a second side of the truncated right trapezoid are parallel with each other and perpendicular to an axis of a valve stem, a height side of the truncated right trapezoid is the generatrix of a cylindrical surface of the clamping ring, the clamping ring being accommodated by a bore of the valve body that has a clearance fit with the cylindrical surface, an oblique side of the truncated right trapezoid is the generatrix of a conical surface of the clamping ring, the conical surface engaging the third surface of the sealing ring for clamping the sealing ring, a fifth side of the truncated right trapezoid is formed by cutting away an acute corner formed by the oblique side and the second side of the truncated right trapezoid, the fifth side is the generatrix of an engaging surface of the clamping ring that is pressed against by the surface of the spherical or conical stem shoulder.