Method and Apparatus for Locking Expandable Cutters of Well Bore Casing Mill

Abstract

A casing mill for downhole casing milling has multiple elongated cutter bases hingedly connected to a main body by a plurality of positioning arms. An operating mechanism within the main body of the casing mill, actuated by fluid flow, moves the cutter bases to an extended position. Multiple cutters fixed to the cutter bases are then positioned to engage a casing surface. An internal fluid operated locking mechanism can be selectively actuated to secure the cutter bases in an extended position.

What is claimed is: 
     
         1 . An apparatus for downhole cutting or milling in a wellbore comprising:
 a) a body member having a central through bore;   b) at least one cutter base hingedly attached to said body member, wherein said at least one cutter base is configured to alternate between a first radially collapsed position and a second radially extended position;   c) a piston, having a central through bore, moveably disposed within said through bore of said body member, wherein said piston is configured to alternate between a first position, and a second position wherein said piston forces said at least one cutter base to shift from said first collapsed position to said second extended position; and   d) at least one cutter disposed on said at least one cutter base.   
     
     
         2 . The apparatus of  claim 1 , further comprising a locking assembly configured to lock said at least one cutter base in said second radially extended position. 
     
     
         3 . The apparatus of  claim 2 , wherein said locking assembly further comprises:
 a) a locking sleeve disposed in said central bore through bore of said body member between said body member and said piston;   b) at least one lock button operationally attached to said piston, wherein said at least lock button is configured to alternate between a first retracted position and a second extended position in engagement with said locking sleeve.   
     
     
         4 . The apparatus of  claim 3 , wherein said locking sleeve further comprises ridges disposed on an inner surface of said locking sleeve, and said at least one lock button further comprises ridges disposed on an outer surface of said at least one lock button. 
     
     
         5 . The apparatus of  claim 4 , wherein said at least one lock button is received within a recess in said piston. 
     
     
         6 . The apparatus of  claim 5 , wherein said locking sleeve is secured to said body member with at least one shear pin. 
     
     
         7 . The apparatus of  claim 6 , wherein said at least one shear pin is configured to separate in response to a predetermined force, causing said locking sleeve to detach from said body member. 
     
     
         8 . The apparatus of  claim 1 , further comprising a nozzle having a predetermined opening disposed in said central through bore of said piston. 
     
     
         9 . An apparatus for downhole cutting or milling in a wellbore comprising:
 a) a body member having a central through bore;   b) at least one cutter base hingedly attached to said body member, wherein each of said at least one cutter base has a heel member protruding into said central bore of said body member;   c) a piston, having a central through bore, moveably disposed within said through bore of said body member, wherein said piston is configured to alternate between a first position, and a second position wherein said piston acts on said heel member and forces said at least one cutter base to shift from a first collapsed position to second radially extended position; and   d) at least one cutter disposed on said at least one cutter base.   
     
     
         10 . The apparatus of  claim 9 , further comprising a locking assembly configured to lock said at least one cutter base in said second radially extended position. 
     
     
         11 . The apparatus of  claim 10 , wherein said locking assembly further comprises
 a) a locking sleeve disposed in said central bore through bore of said body member between said body member and said piston;   b) at least one lock button operationally attached to said piston, wherein said at least lock button is configured to alternate between a first retracted position and a second extended position in engagement with said locking sleeve.   
     
     
         12 . The apparatus of  claim 11 , wherein said locking sleeve further comprises ridges disposed on an inner surface of said locking sleeve, and said at least one lock button further comprises ridges disposed on an outer surface of said at least one lock button. 
     
     
         13 . The apparatus of  claim 12 , wherein said at least one lock button is received within a recess in said piston. 
     
     
         14 . The apparatus of  claim 13 , wherein said locking sleeve is secured to said body member with at least one shear pin. 
     
     
         15 . The apparatus of  claim 14 , wherein said at least one shear pin is configured to separate in response to a predetermined force, causing said locking sleeve to detach from said body member. 
     
     
         16 . The apparatus of  claim 9 , further comprising a nozzle having a predetermined opening disposed in said central through bore of said piston.