Butterfly valve

A butterfly valve comprising,

• an annular valve body,
• a ring-shaped elastic valve seat fitted to an inner circumference of the valve body, said valve seat having diametrically opposed annular protrusions, each of which is formed with an opening at the center thereof, an upper face of each said protrusion defining an annular flat sliding face with at least a pair of recesses for charging with lubricant, each said pair of recesses being disposed symmetrically with respect to a respective opening of the valve seat,
• a valve stem pivotally fitted to the valve body through the openings of the valve seat, and
• a rigid valve disk fitted to the valve stem, said valve disk having a pair of annular flat sliding faces around the valve stem corresponding to the sliding face of the valve seat, each sliding face of the valve disk slidably contacting a respective corresponding sliding face of the valve seat during rotation of the valve disk.

A butterfly valve comprising

• an annular valve body,
• a ring-shaped elastic valve seat fitted to an inner circumference of the valve body, said valve seat having diametrically opposed openings, an annular flat sliding face around each of the openings and cavities charged with lubricant on the sliding face, each of said cavities having a semi-spherical profile, at least a pair of the cavities disposed symmetrically in respect to each respective opening of the valve seat in each of concentrical annular zones with the opening, dividing imaginarily each sliding face of the valve seat,
• a valve stem pivotally fitted to the valve body through the openings of the valve seat, and
• a rigid valve disk fitted to the valve stem, said valve disk having a pair of annular flat sliding faces around the valve stem, each sliding face of the valve disk slidably contacting a respective corresponding sliding face of the valve seat during rotation of the valve disk.