Hydraulic lockout device for pressure controlled well tools

摘要

Well tools are provided which although pressure responsive, may be maintained by a hydraulic lockout in a nonresponsive condition until a threshold actuation step is performed. This lockout may be achieved by a hydraulic mechanism which allows pressure to be stored in a fluid spring during periods of increased pressure at the pressure source, and which traps these pressures even when pressure at the pressure source is reduced. When the tool is desired to be responsive to pressure cycles, a valve may be opened communicating the pressure in the fluid spring to a movable member in the well tool. This differential may be established by a differential between the pressure in the fluid spring and the pressure source. Communication of pressure in the fluid spring to a movable mandrel will then allow operation of the well tool in response to pressure cycles at the pressure source in accordance with the established design of the well tool.