Patent ID: 7228788

Claim:
A piston for an air pump comprising a valve sealing plate, an upper piston plate, an air ring, a piston rod, locking component, a bearing and a bearing protection cap, wherein the valve sealing plate is flatly mounted by a pegging plate and a peg onto a venting hole provided on the upper piston plate, the upper piston plate has a bottom with an external edge having a circular protruded edge, and the piston plate has a venting hole in combination with the valve sealing plate, and the bottom section of the upper piston plate is provided with a positioning screw rod for combination with a recess at a lower piston plate, and the locking component is used to lock the lower piston plate; the air ring is mounted between the upper and the lower piston plate and has a hollow bowl cavity and is made from temperature resistant and wear-resistant material, and the diameter of the air ring is larger than that of the inner wall of the cylinder, and the external edge is a converging face inwardly inclined; the piston rod is formed together with the lower piston plate and an axle hole at a lower section of the piston rod; and the lower piston late and the upper piston plate are locked with the locking component, and the lower piston plate has a recessed slot and through holes; the external side of the recessed slot is provided with at least one inlet, the axle hole having a blocking edge at the inner side, and the external edge of the axle hole is locked and protected with the bearing protection cap to protect the bearing positioned within the axle hole; the bearing is positioned within the axle hole of the piston rod; and the bearing protection cap locks the external edge of the axle hole of the piston rod and a protruded edge of the protection cap urges the bearing within the axle hole.