Patent ID: 8161996

Claim:
A butterfly valve having interchangeable discs comprising: (a) a body having a rotatable shaft aligned with a vertical center-line of the body; (b) a circumferential seal affixed to a circumferential body seat; (c), wherein the interchangeable discs comprise an on-center disc affixed to the shaft or an off-center disc affixed to the shaft, the on-center disc and the off-center disc interchangeable with one another; (d) the circumferential seal surface comprising (i) a section of a sphere, the center of which is located on the intersection of the vertical center-line extending through the shaft and the horizontal center-line extending through the horizontal center of either disc; (ii) a spherical off-center seal region proximal to the inlet port; and (iii) a spherical on-center seal region distal from the inlet port; (e) the on-center disc comprising (i) a spherical sealing edge, the center of which is located on the intersection of the vertical center-line extending through the shaft and the horizontal center-line extending through the horizontal center of either disc; (ii) the spherical sealing edge configured for closure with the on-center seal region; and (iii) a front face of the on-center disc; and (f) the off-center disc comprising (i) a spherical sealing edge, the center of which is located on the intersection of the vertical center-line extending through the shaft and the horizontal center-line extending through the horizontal center of either disc; (ii) the spherical sealing edge configured for closure with the off-center seal region; and (iii) an eccentric front face of the off-center disc, the front face of which extends beyond the front face of the on-center disc.