US Patent 10883333 Buoyant system for installing a casing string

A sealing device includes a tubular body having a bore; a collet seat having a plurality of collets; a frangible sealing element disposed in the collet seat and blocking fluid communication through the bore; and a releasable sleeve releasably attached to the tubular body and retaining the collet seat against the tubular body. In one embodiment, the plurality of the collets includes threads mated with threads on the tubular body. In another embodiment, the plurality of the collets is attached to the sleeve.