Principle of pneumatic nail gun


Pneumatic nail gun is the most commonly used nail gun. In this kind of equipment, the hammering force comes from the compressed air, which is usually produced by an independent air compressor. The working principle of a standard air compressor and water pump is the same. It has one or more piston barrels, which can draw air from the atmosphere during the up stroke and output and press the air into the nail gun during the down stroke. In this way, compressed air can be continuously input into the air storage chamber of the nail gun through the hose.
Petrol powered air compressor manufactured by Hitachi
Hitachi Power Tools
Petrol powered air compressor manufactured by Hitachi
The hammering device of the pneumatic nail gun is the same as that of the solenoid nail gun: it also uses a sliding piston to drive a long blade. When the air pressure at the head of the piston is greater than that at the bottom, the piston is pushed downward. When the air pressure at the bottom of the piston is greater than that at the top, the piston remains stationary. The trigger device changes the balance state by guiding the flow of compressed air. The following figure shows the typical valve system used by this nail gun:
In this design, the piston head (b) has a movable plug (a). When the trigger is released, compressed air will flow to both ends of the valve plug. The compressed air flows directly to the bottom edge of the valve plug through the air chamber on one side, and through the trigger valve (c) and a small plastic pipe (d) on the other side until it finally reaches the upper part of the valve plug. Since compressed air can flow to either end of the valve plug, the air pressure is balanced with each other. However, the valve plug is also connected to the spring (e), which moves it downward. This changes the pressure balance: when the trigger is released, the pressure above the valve plug is always greater than the pressure below it.
This imbalance allows the valve plug to compress the seal ring surrounding the piston head. When the valve plug is in this position, the compressed air flowing into the nail gun cannot reach the top of the piston to push the piston downward.
Here's what happens when you pull the pneumatic nail gun:
The trigger valve closes and opens a channel to the atmosphere. When the trigger valve is in place, compressed air cannot flow to the space above the valve plug.
The lower part of the valve plug has more air pressure than the upper part. The valve plug rises and compressed air can flow to the top of the piston.
Compressed air causes the piston and blade to move downward and shoots the shot pin out of the gun chamber.
When the piston moves downward, the air in the piston barrel is pushed into the return chamber (f) through a series of holes.
As more and more air flows into the chamber, the pressure increases. When you release the trigger, compressed air returns the plug to its original position and prevents air from flowing to the head of the piston. Since there is no downward air pressure, the compressed air in the return chamber will jack up the piston head. The air above the piston head is discharged into the atmosphere from the nail gun.