Lock-open mechanism for surface controlled subsurface safety valves. A lock-open sleeve can be positioned by wireline techniques to hold open the valve closure means for a subsurface safety valve.Cast Gate, Globe, Check Valves The operating tube of the safety valve can be used to return the valve closure means to normal operations. One embodiment of the present invention is particularly useful as a well tool which can readily be attached to the lower portion of presently available flapper type safety valves. Butterfly ValvesAlternative embodiments of the present invention can be built into both ball type and flapper type safety valves as an integral part of the complete safety valve assembly. A surface controlled subsurface safety valve having a housing means with a longitudinal passageway extending therethrough,SAFETY VALVES a valve closure means disposed in the longitudinal passageway having a first position blocking fluid flow therethrough and a second position allowing fluid flow through the longitudinal passageway, and an operating tube means slidably disposed in the longitudinal passageway to shift the valve closure means from its first to its second position, comprising: a lock-open sleeve slidably disposed in the longitudinal passageway having a first position which does not affect operation of the valve closure means and a second position which holds the valve closure means in its second position; the valve closure means located between the operating tube means and the lock-open sleeve; means for releasably securing the lock-open sleeve in its first position; the operating tube means engageable with the lock-open sleeve to shift the lock-open sleeve longitudinally from its second to its first position; means for biasing the lock-open sleeve to shift from its first to its second position; a sliding sleeve slidably disposed in the longitudinal passageway; a portion of the lock-open sleeve telescoped partially into the sliding sleeve; and means for contacting the releasable securing means by the sliding sleeve whereby the lock-open sleeve is released from its first position. The present invention discloses a well tool for locking open the valve closure means of a surface controlled subsurface safety valve, comprising housing means with a longitudinal passageway extending therethrough; means for attaching the housing means to the safety valve below its valve closure means; a lock-open sleeve slidably disposed in the longitudinal passageway having a first position which does not affect operation of the valve closure means and a second position which holds the valve closure means in its open position; means for releasably securing the lock-open sleeve in its first position; and means for biasing the lock-open sleeve to shift from its first to its second position. One object of the present invention is to provide a well tool which can be attached to any flapper type subsurface safety valve and allow the safety valve to be temporarily locked open. Another object of the present invention is to provide a surface controlled subsurface safety valve in which the operating tube for the valve closure means can unlock the valve closure means after being temporarily locked in its open position. A further object of the present invention is to provide a surface controlled subsurface safety valve which can be locked open and returned to its unlocked position as frequently as desired for the existing well conditions. Additional objects and advantages of the present invention will become readily apparent to those skilled in the art from studying the following written description in conjunction with the drawings and claims.

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