Well tools

Claim 1

A WALL TOOL INCLUDING: A TUBULAR MANDREL; A BARREL DISPOSED ABOUT SAID TUBULAR MANDREL AND PROVIDING WITH SAID TUBULAR MANDREL AN ANNULAR UPPER PISTON CHAMBER; AN ANNULAR PUMP PISTON LONGITUDINALLY MOVABLE IN SAID CHAMBER AND HAVING MEANS PROVIDING WITH SAID BARREL A LOWER ANNULAR CHAMBER WHOSE UPPER END IS IN COMMUNICATION WITH THE LOWER END OF SAID UPPER CHAMBER BY A BYPASS FLOW PASSAGE; AN ANNULAR OPERATOR PISTON LONGITUDINALLY MOVABLE IN SAID LOWER CHAMBER, SAID OPERATOR PISTON BEING MOVABLE DOWNWARDLY IN SAID LOWER CHAMBER RELATIVE TO SAID BARREL UPON DOWNWARD MOVEMENT OF SAID MANDREL AND SAID BARREL RELATIVE TO SAID PUMP PISTON BY LIQUID DISPLACED FROM THE UPPER END PORTION OF SAID UPPER CHAMBER BY SUCH DOWNWARD MOVEMENT OF SAID MANDREL AND SAID BARREL RELATIVE TO SAID PUMP PISTON, SAID PISTON HAVING MEANS ENGAGEABLE WITH AN OBJECT EXTENDING UPWARDLY IN SAID BARREL FOR PREVENTING DOWNWARD MOVEMENT OF SAID PUMP PISTON RELATIVE TO THE SAID OBJECT; GRIPPING MEANS DISPOSED IN SAID BARREL AND OPERABLE BY SAID OPERATOR PISTON FOR ENGAGING AN OBJECT EXTENDING UPWARDLY INTO SAID MANDREL, SAID GRIPPING MEANS AND SAID BARREL HAVING CO-ENGAGEABLE MEANS FOR MOVING SAID GRIPPING MEANS INWARDLY TO ENGAGE AN OBJECT IN SAID BARREL UPON DOWNWARD MOVEMENT OF SAID OPERATOR PISTON RELATIVE TO SAID BARREL, SAID BARREL AND SAID MANDREL HAVING CO-ENGAGEABLE MEANS FOR CONTROLLING MOVEMENT OF SAID MANDREL RELATIVE TO SAID BARREL, SAID BARREL AND SAID MANDREL HAVING MEANS CLOSING THE UPPER END OF SAID UPPER CHAMBER, SAID LAST MENTIONED MEANS OPENING THE UPPER END OF SAID UPPER CHAMBER TO THE EXTERIOR OF THE WELL TOOL UPON PREDETERMINED ROTATIONAL MOVEMENT OF SAID MANDREL RELATIVE TO SAID BARREL TO PERMIT DOWNWARD MOVEMENT OF SAID MANDREL RELATIVE TO SAID BARREL AND SAID PUMP PISTON TO FREE AND GRIPPING MEANS FOR MOVEMENT OUT OF ENGAGEMENT WITH AN OBJECT HELD THEREBY WHEREBY SAID RETRIEVING TOOL IS RELEASABLE FROM AN OBJECT PREVIOUSLY ENGAGED THEREBY.