Butterfly valve

Claim 1

In a butterfly valve assembly for installation in a pipe line between flanges having spaced parallel planar annular faces, each face extending transversely of and centered upon the lengthwise axis of said pipe line; said valve assembly comprising: a tubular valve body made of rigid material and having parallel planar annular end walls centered upon said axis of the pipe line in which said assembly is to be installed, each of said end walls being adapted to make face-to-face contact with one of said faces of said flange, said valve body having an inner circumferential valve-seat-supporting surface extending axially of said pipe line, said valve body having a pair of annular grooves each of said grooves being defined by a radially outwardly positioned wall extending axially inwardly from the radially inward circumference of one of said end walls and a radially inwardly positioned wall, each of said grooves having a predetermined depth measured axially of said valve body, and said valve body having a pair of oppositely disposed annular ribs each of said ribs extending axially outwardly from said valve-seat-supporting surface and each of said ribs terminating axially inwardly of the plane of one of said end walls in a rib surface which intersects said radially inwardly positioned wall of one of said grooves; and a valve seat insert made of elastomeric material having a tubular seat portion the exterior circumferential surface of which is shaped to engage said valve-seat-supporting surface and the interior circumferential surface of which is shaped to define a tubular fluid passageway extending axially through said valve assembly when said seat insert is fitted upon said valve body; the improvement comprising a pair of flange-sealing portions integral with and extending axially outwardly and radially outwardly from the opposite axial ends of the tubular seat portion of said valve seat insert, each of said flange-sealing portions having a recess facing axially inwardly and shaped to fit upon one of said ribs, an axially inwardly extending annular bead formed radially outwardly of said recess and shaped to enter one of said grooves, and an annular flange-engaging surface which when said insert is fitted upon said valve body ready for installation between flanges of a pipe line slopes axially outwardly with respect to the plane of the adjacent one of said end walls of said valve body, the radially outward periphery of said flange-engaging surface on each of said flange-sealing portions lying approximately within said plane of the adjacent one of said end walls and the radially inward periphery thereof forming an intersection with an axially outward extension of said inner circumferential surface of said insert in a plane axially outwardly disposed with respect to said plane of said adjacent end wall, and said annular bead on each of said flange-sealing portions having a volume of elastomeric material which is less than the volume of the one of said annular grooves which said bead is shaped to enter by an amount sufficient to insure that space is left unfilled by elastomeric material within each of said grooves when said valve body with said valve seat insert fitted thereoN is installed between flanges of a pipe line.