Abstract: A specific feature of the apparatus according to the invention which incorates a percussion unit to a tail piece whereof there is attached a rope connecting to a means of extracting is that fitted into said tail piece coaxially therewith and with a clearance is a ring, the clearance between said ring and said tail piece containing a resilient member with passages reeved wherethrough are the ends of the rope and the inside surface of said tail piece being provided with stops in the body whereof there are also passages for reeving the ends of the rope.