Tri stable actuator apparatus and method

Abstract

An actuator to direct a downhole drilling tool includes a stator and an armature configured to be electromagnetically displaced into one of three stable positions. A cavity within the stator is in communication with a high-pressure fluid and hydraulic ports in the stator allow the high-pressure fluid to communicate with low-pressure regions. Plungers on the armature selectively block either or none of the hydraulic ports, allowing for three control options from the actuator to the downhole drilling tool.

1 . An actuator to direct a rotary steerable tool, the actuator comprising:
 a stator having an internal cavity in communication with a high-pressure zone, a first hydraulic port and a second hydraulic port;   an armature housed within said internal cavity, said armature including a first valve plunger and a second valve plunger;   said first valve plunger configured to block said first hydraulic port from said high-pressure zone when said armature is in a first position;   said second valve plunger configured to block said second hydraulic port from said high-pressure zone when said armature is in a second position;   said first and said second hydraulic ports in communication with said high-pressure zone when said armature is in a third position; and   said actuator configured to be electromagnetically displaced into said first and said second positions.   
   
   
       2 . The actuator of  claim 1  wherein said armature includes an electromagnetic coil to generate electromagnetic force when energized by a power source. 
   
   
       3 . The actuator of  claim 1  wherein said stator comprises a ferromagnetic material. 
   
   
       4 . The actuator of  claim 1  wherein said stator comprises an electromagnetic coil to generate electromagnetic force when energized by a power source. 
   
   
       5 . The actuator of  claim 1  wherein said armature comprises a ferromagnetic material. 
   
   
       6 . The actuator of  claim 1  further comprising a first spring to bias said first valve plunger away from said first hydraulic port and a second spring to bias said second valve plunger away from said second hydraulic port. 
   
   
       7 . The actuator of  claim 6  wherein said first and said second springs act as electrical leads in communication with an electromagnetic coil of said armature. 
   
   
       8 . The actuator of  claim 1  wherein said armature is held into said first position by the force of fluids flowing from said high-pressure zone through said second port. 
   
   
       9 . The actuator of  claim 1  wherein said armature is held into said second position by the force of fluids flowing from said high-pressure zone through said first port. 
   
   
       10 . The actuator of  claim 1  wherein said armature is held into said third position through electromagnetic force. 
   
   
       11 . The actuator of  claim 1  wherein said armature is held into said third position by the force of fluids flowing from said high-pressure zone simultaneously through said first and said second ports. 
   
   
       12 . A method to operate a rotary steerable tool with a tri-stable actuator, the method comprising:
 installing an armature within an internal cavity of a stator, the stator having a first hydraulic port and a second hydraulic port;   hydraulically communicating between a high-pressure zone and the internal cavity;   blocking the first hydraulic port and communicating between the high-pressure zone and the second hydraulic port when the stator is in a first position;   blocking the second hydraulic port and communicating between the high-pressure zone and the first hydraulic port when the stator is in a first position;   communicating between the high-pressure zone and both first and second hydraulic ports when the stator is in a third position; and   displacing the stator into the first and the second positions with electromagnetic force.   
   
   
       13 . The method of  claim 12  further comprising biasing the armature away from the first position with a first spring. 
   
   
       14 . The method of  claim 12  further comprising biasing the armature away from the second position with a second spring. 
   
   
       15 . The method of  claim 12  further comprising retaining the armature in the first position with the force of fluid flowing from the high-pressure zone through the second hydraulic port. 
   
   
       16 . The method of  claim 12  further comprising retaining the armature in the second position with the force of fluid flowing from the high-pressure zone through the third hydraulic port. 
   
   
       17 . The method of  claim 12  further comprising retaining the armature in the third position with electromagnetic force. 
   
   
       18 . A tri-stable actuator comprising:
 a stator having an internal cavity in communication with a high-pressure zone, a first hydraulic port and a second hydraulic port;   an armature housed within said internal cavity, said armature including a first valve plunger and a second valve plunger;   said first valve plunger configured to block said first hydraulic port from said high-pressure zone when said armature is in a first stable position;   said second valve plunger configured to block said second hydraulic port from said high-pressure zone when said armature is in a second stable position;   said first and second hydraulic ports in communication with said high-pressure zone when said armature is in a third stable position;   said actuator configured to be electromagnetically displaced into said first and said second stable positions; and   said armature is configured to be held into said first stable position by a force of fluids flowing from said high-pressure zone through said second port and held into said second stable position by said force of fluids flowing from said high-pressure zone through said first port.   
   
   
       19 . The tri-stable actuator of  claim 18  further comprising a first spring to bias said first valve plunger away from said first hydraulic port and a second spring to bias said second valve plunger away from said second hydraulic port.