Patent ID: 8915305

Claim:
A packer tool for a well, said tool comprising: a mandrel with a bore for receiving a tool-setting pressurized fluid, a hydraulic setting mechanism adapted to be driven by said pressurized fluid and packing seals around said mandrel and arranged to be set by said hydraulic setting mechanism in response to said pressurized fluid driving said hydraulic setting mechanism, said hydraulic setting mechanism comprising: a hydraulic chamber connected to said mandrel bore for receiving said pressurized fluid, a piston slidably mounted to said mandrel and adapted to be displaced, by said pressurized fluid entering said chamber, along said mandrel in a predetermined axial direction between a run-in position and a set position causing said packing seals to set, and a safety device for retaining said piston fast against displacement in said direction relative to said mandrel until said pressurized fluid has begun to pass from said mandrel bore into said chamber, thereby preventing premature setting of said tool, wherein said safety device is immune to shear forces applied by said piston, and wherein said safety device comprises: anti-setting segments loosely lodged in said piston and said mandrel thereby interlocking said piston and said mandrel to prevent relative axial movement therebetween in the run-in position, and a cylinder coaxial with said piston and adapted to displace along said mandrel in an axial direction opposite to said predetermined piston-displacement axial direction between a run-in position and a set position in response to said pressurized fluid entering said chamber, said cylinder forming a roof over said anti-setting segments lodged in said piston preventing said anti-setting segments from dislodging while said cylinder is in the run-in position, wherein said cylinder includes an inside step proximate to where the segments are lodged during run-in and adapted to create free space for said anti-setting segments to dislodge from said mandrel in response to tool-setting pressurized fluid entering said chamber and displacing said cylinder from its run-in position to its set position, whereby said anti-setting segments are able to dislodge to said free space thereby freeing said piston to be driven by said tool-setting pressurized fluid in said chamber to said set position.