US Patent 7870818 Piston for a piston-cylinder unit

A piston-cylinder assembly includes a working cylinder, and a one-piece stamped and formed piston body which is attached to a piston rod, the piston body being axially movable in the cylinder and dividing the cylinder into two working spaces. The piston body has at least one first opening provided with a first valve for passing fluid when the piston moves in a pull direction, and at least one second opening provided with a second valve for passing fluid when the piston moves in a push direction. A circumferential surface of the piston body is formed with a shallow groove which holds a seal between the circumferential surface and the working cylinder.