US Patent 7775291 Retrievable surface controlled subsurface safety valve

A safety valve apparatus has a housing with a bore and a projection disposed in the bore. A locking dog disposed on the housing is movable to engage an inner conduit wall surrounding the housing, and a flapper rotatably disposed on the housing is movable between opened and closed positions. A first sleeve disposed within the bore above the projection is mechanically movable between locked positions. In one locked position, the sleeve moves the locking dog to engage the wall. A piston disposed in the housing hydraulically communicates with a port in the projection and couples to a second sleeve disposed within the bore below the projection. The second sleeve conceals the piston and is hydraulically movable to open and close the flapper.