Remote control actuation device

A remote controlled actuation device for the actuation of an appliance operatively connected to a drill-string having a bore of a substantially constant internal diameter that has an incompressible fluid circulating therein in an axial direction, the drill-string comprising a first end through which the incompressible fluid is introduced by a pumping means at an adjustable flow rate and a second end which is distant from the first end and wherein the incompressible fluid is used as a working fluid, the device being secured to the drill-string in a zone distant from the first end thereof, the device comprising:

• a body connected to the drill-string, said body having a central bore coaxial with the drill-string bore;
• a differential piston mounted so as to be movable in terms of translation in the axial direction and in terms of rotation about a longitudinal axis of said body within said central bore thereof, said piston having a tubular shape and having a central bore which is substantially coaxial with said body central bore and which comprises a profiled throttling portion the minimum internal diameter of which is smaller than the internal diameter of the central bore of the piston;
• a protruding profiled element secured to the body downstream of said differential piston and disposed coaxially with the differential piston, said element having a profiled frustoconical external surface widening in the direction of circulation of the fluid and facing the profiled throttling portion of the piston bore;
• a spring arranged between the piston and a part of the body for biasing the piston in a direction of movement opposite the direction of circulation of the incompressible fluid;
• and,
• a means for measuring the pressure of the incompressible fluid at the first end of the drill-string, the actuation device allowing for the circulation of the fluid in the drill-string at a first, operating flow rate without any movement of the piston, wherein a movement of the piston in the direction of circulation of the fluid occurs when the fluid circulates at a second and constant actuation flow rate greater than said first operating flow rate and wherein an increasing loss of head is caused when the piston moves in the direction of circulation of the fluid by a cooperation of the profiled throttling portion of the piston bore and the frustoconical external surface of the protruding profiled element, the movement being stopped after the actuation has been carried out at which point a loss of head and a pressure of the working fluid at the first end of the drill string are at a maximum but working fluid still flows through said central bore, and wherein the pressure of the fluid is continuously measured thereby allowing a remote monitoring of the movement of the piston;
• and
• wherein said differential piston further comprises, on its outer lateral surface, longitudinal grooves relative to the axis of the drill-string, arranged one after the other over the periphery of the piston and connected to one another by means of connecting grooves to form a continuous actuating surface for a step-by-step rotary movement of the piston and for its return into an initial position when the flow rate of the fluid is decreased to the operating flow rate, and at least one actuating finger interacting with the actuating surface at one end and a movable part of the appliance on the other end, to actuate the latter during the movement of the piston.