부산대학교 도서관

Disclosed is a fluid driven pulsating, hammering tool operational when pressurized fluid is pumped into the tool's upper sub, having a poppet valve which can seal the upper end of a slidable outer valve assembly when closed; an inner valve assembly slidable within the outer valve assembly; wherein the inner and outer valve assemblies remain in selective fluid communication with the poppet valve even when the poppet valve is closed, wherein interruption of said fluid communication occurs from movement of the inner and/or outer valve assemblies to particular positions along their sliding paths; and further including a lower valve which is preferably a Tesla valve having channels which are also in fluid communication with the poppet valve.