Variable bore ram rubber

Abstract

An improved sealing element for variable bore ram blowout preventers of the type using two semicircular ram blocks to urge a resilient sealing member into sealing circumferential contact with the circumferential surface of a tubular drill string component includes a generally uniform thickness member having in plan view the shape of a semi-circular arch with bar-shaped legs extending laterally outwards from opposite base ends of the arch. A plurality of metal inserts forms a skeletal structure around which is molded a rubber matrix to form the sealing member. Each insert has a pair of generally flat and parallel upper and lower plates joined together by a pedestal and interleaved with and slidable with respect to the plates of an adjacent insert. Two outer generally rectangular plan-view end inserts have inner lateral edges which slidably interleave with the two outer elongated rectangular lateral ends of each of two intermediate corner inserts. Each of the two corner inserts has an arcuate inner end which slidably interleaves with opposite ends of a single arcuate center insert. The pedestals joining the upper and lower halves of the two corner inserts, and the pedestal joining upper and lower halves of the center insert, each have different tear-drop shaped cross-sectional shapes which promote rubber flow into the sealing area when the seal is compressed.