Patent ID: 7377413

Claim:
A pneumatic nail gun comprising: a gun body, which has a main air housing collecting a compressed high pressure air with a constant pressure, and a trigger at one end of the main air housing driving the high pressure air to shoot a nail; a movable cylinder disposed in the main air housing, which moves upward when the trigger is pressed, and moves downward for reposition when the trigger is released; a piston slidably movable in the cylinder, which has a driver blade extending from the piston, which protrudes out of the gun body for punching against a nail in accordance with a downward movement of the piston; a slidable sleeve valve assembled at an outer peripheral surface of the cylinder, which moves upward and introduces high pressure air to drive the piston move upward when the cylinder moves downward to a lower dead center thereof, and is driven downward for reposition by high pressure air after the piston moves to an upper dead center thereof; a head valve positioned above and integrated on the cylinder; a first air chamber formed between a top end of the head valve and an inner peripheral surface of the gun body, which receives the high pressure air from the main air housing when the trigger is released, and exhausts the high pressure air when the trigger is pressed; a second air chamber formed between the head valve and inner peripheral surface of the gun body, which receives the high pressure air from the main air housing and drives the cylinder move upward when the high-pressure air in the first air chamber is discharged; a third air chamber positioned between the slidable sleeve valve and the inner peripheral surface of the gun body, which receives the high pressure air from the main air housing for driving the slidable sleeve valve to move downward; a plurality of top vent holes formed on the cylinder, which connect with the third air chamber for guiding the high-pressure air in the second air chamber continuously into the cylinder for driving the piston to move downwardly to punch the nail when the trigger is pressed to move the cylinder upward and guiding the high-pressure air in the third air chamber into the cylinder when the trigger is released to move the cylinder downward; a fourth air chamber formed between an inner peripheral surface of the gun body and an outer peripheral surface of the slidable sleeve valve, which receives the high pressure air from the main air housing for driving the slidable sleeve valve to move upwardly when the high-pressure air in the third air chamber is discharged; a plurality of bottom vent holes formed at a bottom region of the cylinder; and a bottom valve fixedly positioned at a lower end portion of the slidable sleeve valve, which can close the fluid communication between the fourth air chamber and the bottom vent holes when the slidable sleeve valve moves downward, and guide the high-pressure air in the fourth air chamber into the cylinder to drive the piston for reposition when the slidable sleeve valve moves upward.