A tool for activating the firing head of a perforating gun located below a packer by applying pressure to the upper well annulus while maintaining an unimpeded bore between the perforating gun and the pipe string. The tool is provided with a flow valve to prevent flow through the flow bore when closed,...http://www.google.fr/patents/US4804044?utm_source=gb-gplus-shareBrevet US4804044 - Perforating gun firing tool and method of operation
Perforating gun firing tool and method of operation
