Patent ID: 8708309

Claim:
A positioning device assembly for regulating the flow of a fluid through a fluid flow-path of a regulator, the positioning device assembly comprising: a tubular control member; a central rod disposed at least partly within the tubular control member and adapted to be fixed to a casing of the regulator; a first spring seat disposed within the tubular control member and fixed relative to the central rod; a second spring seat at least partly disposed within the tubular control member and defining an opening through which the central rod extends; and a spring disposed between the first and second spring seats, the spring adapted to bias the tubular control member into a predetermined position relative to the casing of the regulator, wherein the second spring seat comprises a spring seat adaptor fixed relative to the control member and a seat ring engaging an upper portion of the spring and adapted for displacement relative to the spring seat adaptor to thereby self-align the spring within the tubular control member, the seat ring having opposing first and second axial ends and the spring seat adaptor extending axially beyond each of the first and second axial ends such that the spring seat adaptor is disposed radially between the seat ring and the central rod along the entire axial dimension of the seat ring, the seat ring including an L-shaped cross-section defining a seating surface and an alignment surface disposed perpendicular to each other, the seating surface engaged by the upper portion of the spring and the alignment surface disposed axially and radially inward of the upper portion of the spring, wherein the spring seat adaptor comprises a partial spherical convex surface and the seat ring comprises a partial spherical concave surface that engages the partial spherical convex surface of the spring seat adaptor, and wherein the partial spherical convex surface and the partial spherical concave surface have the same radii of curvature.