Pneumatic door closer

A pneumatic door closer, including:

• a rotary energy-storing mechanism, including a housing and a driving mechanism connected thereto;
• the driving mechanism includes a cylinder, a second piston assembly having one end configured within the cylinder, and a sealing element sleeving on the second piston assembly;
• the sealing element is in an air tight connection with the cylinder and the second piston assembly, to form a closed space filled with high pressure gas in the cylinder;
• the second piston assembly divides the closed space into a first air chamber and a second air chamber in communication with each other, the first air chamber is configured between the second piston assembly and the sealing element;
• the driving mechanism further includes a first piston assembly configured in the housing, and the first piston assembly is connected to the other end of the second piston assembly;
• the pneumatic door closer further includes a transmission mechanism having one end received in the housing and another end connected to the door frame;
• when the door is opening, the transmission mechanism drives the first piston assembly to move toward the cylinder, and thus drives the second piston assembly to move away from the sealing element, squeezing the high pressure gas in the second air chamber, forcing the high pressure gas in the second air chamber to flow into the first air chamber, thereby the second air chamber will decrease in size;
• when the external force applied on the door disappears, the second piston assembly moves toward the sealing element because a first action force, which is a pressure force exerted by a high pressure gas of the first air chamber onto the second piston assembly, is smaller than a second action force, which is a pressure force exerted by a high pressure gas of the second air chamber onto the second piston assembly, and the first action force is in a contrary direction to the second action force thereby the first air chamber decreases in size, and the high pressure gas in the first air chamber will flow into the second air chamber, to drive the first piston assembly away from the cylinder, whereby the transmission mechanism is driven to close the door.