Patent ID: 7487833

Claim:
Safety apparatus for providing ballistic train interruption in a perforating system comprising perforating guns and a firing head, said safety apparatus comprising a generally tubular-shaped housing which has first and second ends and which is fabricated to permit the housing to be positioned at any location in the perforating system, comprising: a first ballistic section in the housing which extends from the first end of the housing to the middle portion of the housing; a second ballistic section in the housing which extends from the second end of the housing to the middle portion of the housing; a third ballistic section which is rotatably mounted in the middle portion of the housing to move between a disarmed position and an armed position, the third ballistics section being misaligned with the first and second ballistic sections in the disarmed position and the third ballistic section being aligned with the first and second ballistic sections in the armed position; an annular piston in the housing which is in a first position when there is no pressure on the safety apparatus and which moves from the first position to a second position when the safety apparatus is subjected to downhole pressure, said movement of the annular piston from the first to second positions causing the third ballistic section to rotate from the disarmed to the armed position; and a compression spring in the housing for exerting a force on the annular piston to hold it in its first position when the safety apparatus is not subjected to pressure and which is compressed by movement of the annular piston from its first to its second position.