Impact blow actuated pneumatic fastener driving tool

An air pressure actuated fastener driving tool comprising;

• a body having an upper end and a lower end;
• a work-piece engaging base secured to the lower end of said body and defining a passage for receiving a leading fastener from a supply of fasteners and for guiding said leading fastener into a work-piece underlying said base;
• a handle fixed relative to said body;
• a manually operated trigger operatively mounted to said handle so as to be movable between a rest position and an operating position;
• an air reservoir carried by said body with an inlet for connection to a supply of compressed air;
• an air operated cylinder and piston unit in said body, comprising a piston movable in a cylinder from an upper rest position to a lower fastener-driving position;
• a fastener driver secured to said piston and extending through said lower end of said body and into said base passage in said piston lower position for engaging and driving said leading fastener into the work-piece during downward operative stroke of said piston from its said upper position;
• a valve in said body including a valve seat carried by said body between said air reservoir and the cylinder of said unit and a valve member movable between a closed position seated on said valve seat and closing the communication between said air reservoir and said cylinder, and an opened position communicating said air reservoir with said cylinder to cause said operative stroke of said piston;
• an impact blow receiving anvil protruding from and movably carried by said upper end of said body for movement between an upper and a lower position;
• a lost motion system between said valve member and said anvil to prevent said valve member to move downwardly from said upper closed position when said anvil is moved to its lower position;
• and a lost motion disabling system connecting said trigger to and disabling said lost motion system when said trigger is in said operating position whereby said fastener driver can only drive said leading fastener if said trigger is moved into said operating position when a hammer blow is imparted on said anvil and moves said anvil to its lower position.