Ball valve

Claim 1

A valve comprising: a body having a central passage of generally cylindrical crosssection; a ball valve member positioned in said passage and mounted for selective rotation about an axis extending perpendicular to the axis of said passage, said ball mounted for limited movement in directions axially of said passage; a pair of radially inwardly extending shoulders in said passageway located generally equal distances from said ball on opposite sides thereof, each said shoulder being circumferentially continuous and having a surface facing said ball which is substantially perpendicular to the axis of the passageway; a pair of resilient seat ring members with one of said ring members positioned between each shoulder and the ball member, each seat ring member having a central opening and a first continuous surface facing said ball and a second continuous surface facing said shoulder, said first surface being of concave spherical configuration of a radius greater than the radius of said ball member and said second surface being generally planar and extending generally parallel to said shoulder; a disc spring between the second face of each ring and the associated shoulder, each disc spring having a central opening and in its unstressed condition having a truncated conical shape, each disc being positioned with its smaller diameter end pointing toward the ball and sized so that when the ball member, the seat ring members, and the disc springs are assembled between the shoulders, the disc springs are stressed to a flat configuration against the shoulder, and only the radial innermost portion of the first surface of each seat ring is biased against the ball member under a predetermined load, the remaining portion of the first surface being spaced from the ball because of its concave spherical configuration having a radius greater than the radius of the ball member.