Trigger mechanism for ball activated device

Abstract

A trigger mechanism for a ball activated device ( 100 ) comprises a seat sleeve ( 130 ) with seat defining members ( 132 ) forming a fluid tight seal with a ball ( 300 ) in an initial state and allowing the ball ( 300 ) to pass in a final state. An alternating member ( 125 ) can move radially in an aperture ( 124 ) through an inner sleeve ( 120 ) and abuts an outer surface on the seat sleeve ( 130 ) in the initial state, is received in a recess ( 134 ) on the seat sleeve ( 130 ) in an intermediate state, and is received in a groove ( 114 ) in the outer sleeve ( 110 ) in the final state. A protective sleeve ( 150 ) may extend axially from the seat sleeve ( 130 ) over a seat receiving area ( 115 ). The mechanism is suitable for cementing and fracturing as particles cannot penetrate to its moving parts.

1 . A trigger mechanism for a ball activated device, the trigger mechanism comprising:
 an inner sleeve axially slidably disposed within an outer sleeve from an initial state wherein the ball activated device is inactive to a final state wherein the ball activated device is activated;   a seat sleeve axially slidably disposed within the inner sleeve, the seat sleeve comprising radially moveable seat defining members configured to form a fluid tight seal with a ball in the initial state and allowing the ball to pass in the final state; and   an alternating member is disposed radially moveably in a radial aperture through a wall of the inner sleeve, wherein the alternating member:   abuts an upstream side of a first axial stopper on an inner surface of the outer sleeve and a radially exterior surface on the seat sleeve in the initial state,   is received in a recess on the seat sleeve in an intermediate state, and   is received in a groove in the inner surface in the final state.   
     
     
         2 . The trigger mechanism of  claim 1  wherein the spaces between and behind the sleeves are filled with an incompressible, water-repelling fluid kept at the pressure of the ambient well fluid. 
     
     
         3 . The trigger mechanism of  claim 1  wherein the alternating member is radially biased. 
     
     
         4 . The trigger mechanism of  claim 3  wherein the seat sleeve is retained by the alternating member and an initial state holding shoulder on the seat sleeve in the initial state. 
     
     
         5 . The trigger mechanism of  claim 1  wherein the seat sleeve is retained by the alternating member and a final state holding shoulder on the seat sleeve in the final state. 
     
     
         6 . The trigger mechanism of  claim 1  further comprising a separate axial stopper on the seat sleeve and a complementary member configured to temporarily halt the axial motion of the seat sleeve at a position wherein the alternating member can enter the recess. 
     
     
         7 . The trigger mechanism of  claim 1  wherein an inner surface of the seat sleeve further comprises key grooves configured to receive a fishing tool. 
     
     
         8 . The trigger mechanism of  claim 1  wherein the seat defining members comprise axially extending collet fingers disposed in close contact with each other around the circumference of the seat sleeve. 
     
     
         9 . The trigger mechanism of any  claim 1  wherein the seat defining members are slidably mounted on guides oriented radially and perpendicular to a central axis of the seat sleeve. 
     
     
         10 . The trigger mechanism of  claim 1  further comprising a protective sleeve extending axially from the seat sleeve over a seat receiving area in the initial state, the protective sleeve permitting the seat defining members to enter into the seat receiving area in the final state.