Nail gun having safety device for preventing accidental firings

A pneumatically operated nail gun for striking a head of a nail into a workpiece, including:

• a housing frame (2) for providing a compressed air chamber (4) connected to a compressed air source (C),
• a cylinder (9) disposed in the frame,
• a piston (10) slidably movable in the cylinder and driven by the compressed air,
• a bit (20) connected integrally to the piston for striking the head of the nail (30),
• a trigger lever (11) for selectively applying the compressed air in the compressed air chamber to the piston to move the bit,
• a bit guide fixed to a lower end of the housing frame for guiding reciprocal travel of the bit,
• a nail guide (24) slidably supported on the bit guide, the nail guide having an inner diameter greater than an outer diameter of a head of the nail, the nail having a sufficient length which is protruding from the nail guide when inserted and set therein, the improvement comprising:
• said nail guide (24) being formed with an axially oriented slit (24a) at one side thereof;
• a movable segment (25, 125) having a pipe-shaped portion (25a, 125a) and an arm portion (25b, 125b) connected to the pipe-shaped portion, the pipe-shaped portion being movably disposed within the nail guide (24) and having an inner diameter greater than an outer diameter of the bit, the arm portion being movable within the slit, the bit being operative to protrude through the pipe-shaped portion for striking the head of the nail;
• a safety arm (26) having one end positioned adjacent the trigger lever (11) and another end coupled to the arm portion (25b, 125b), said one end of the safety arm being selectively engageable with the trigger lever to render the latter inoperative, and
• a biasing spring (33) connected to the safety arm (26) for urging the safety arm in one direction to maintain engagement between the one end of the safety arm and the trigger lever.