Separation nut

Claim 1

A separation nut for releasably engaging a threaded element, said separation nut having an engagement axis and comprising: a housing forming an internal cavity and an aperture entering the cavity to receive the element to be engaged by the separation nut; a seat member on the housing facing into the cavity and tapering inwardly as it extends into the cavity; antirotation means fixed relative to the housing; a plurality of individually disconnected nut setments in grouped configuration around the engagement axis to form a segmented nut, each nut segment including a concave surface facing the engagement axis, a thread fragment on the concave surface, which fragment is part of the same thread as is formed on the other segments, a lock surface, a relief surface, a cam surface, and a brace surface, all facing away from the engagement axis; an abutment surface facing the seat member, and a fulcrum surface axially spaced from the abutment surface, the nut segments engaging the anti-rotation means, whereby to be held against rotation around the engagement axis; a lock plunger axially movable in said cavity, a bounding wall in said lock plunger which bounds an opening that receives the nut segments in their grouped configuration, a lock surface, a drive cylinder, a drive face, a cam surface, and a brace surface, all on said bounding wall, the lock surface being so disposed and arranged as to embrace the lock surfaces of the nut segments in an engagement condition of the separation nut, at which condition the brace surfaces abut each other and the abutment surface bears against the seat member; a drive piston making an axially sliding fit in said drive cylinder and having a drive face facing toward the drive face of the lock plunger, whereby to form a power chamber in the drive cylinder, and a fulcrum surface so disposed and arranged as to bear against the fulcrum faces of the nut segments and disposed radially inwardly of the cam surfaces; and conduit means to convey fluid under pressure to said power chamber whereby to move the lock plunger axially to an unengaged position wherein its lock surface does not embrace the lock surfaces of the nut segments and does overlay the relief surfaces, wherein the cam faces engage one another to rotate the nut segments around the fulcrum surfaces as a consequence of a torque couple exerted at the cam surfaces and on the fulcrum surfaces, and the thread fragments move arcuately away from the engagement axis to release the element which was engaged by the previously-grouped nut segments, while the nut segments are retained in the housing by the drive piston.