A self-sealing and self-centering piston has a domed piston plate and a substantially cylindrical skirt section. The skirt section joins the rear of the piston plate. A gap having a depth is formed between a first portion of the skirt section and a front lamella. A rear lamella adjoins the front lamella. In addition, a second section of the skirt section has a first seal and a second seal.

A self-sealing and self-centering piston has a domed piston plate and a substantially cylindrical skirt section. The skirt section joins the rear of the piston plate. A gap having a depth is formed between a first portion of the skirt section and a front lamella. A rear lamella adjoins the front lamella. In addition, a second section of the skirt section has a first seal and a second seal.

A piston assembly including a shaft having a piston arrangement. The piston arrangement has a retract-area on one side and a extend-area on the opposite side. The retract-area is larger than the extend-area so that when fluid exerts a force on the retract-area the piston arrangement generates and applies a retract force to the shaft. Upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft. The retract force is greater than or equal to the extend force.

A piston assembly including a shaft having a piston arrangement. The piston arrangement has a retract-area on one side and a extend-area on the opposite side. The retract-area is larger than the extend-area so that when fluid exerts a force on the retract-area the piston arrangement generates and applies a retract force to the shaft. Upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft. The retract force is greater than or equal to the extend force.

A piston with an oil return channel may include a piston head, a piston skirt, and an oil return hole. The piston head may include a ring groove. The piston skirt may be connected to the piston head. The piston skirt may have a surface including a concave face window. A connection between the face window and the ring groove may form a residual ring bank. The oil return hole may be formed by milling on the residual ring bank. The oil return hole may connect the ring groove close to the piston skirt with the face window. A depth of the oil return hole may be greater than a depth of the ring groove.

A piston with an oil return channel may include a piston head, a piston skirt, and an oil return hole. The piston head may include a ring groove. The piston skirt may be connected to the piston head. The piston skirt may have a surface including a concave face window. A connection between the face window and the ring groove may form a residual ring bank. The oil return hole may be formed by milling on the residual ring bank. The oil return hole may connect the ring groove close to the piston skirt with the face window. A depth of the oil return hole may be greater than a depth of the ring groove.

A piston assembly including a shaft having a piston arrangement. The piston arrangement has a retract-area on one side and a extend-area on the opposite side. The retract-area is larger than the extend-area so that when fluid exerts a force on the retract-area the piston arrangement generates and applies a retract force to the shaft. Upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft. The retract force is greater than or equal to the extend force.

A piston assembly including a shaft having a piston arrangement. The piston arrangement has a retract-area on one side and a extend-area on the opposite side. The retract-area is larger than the extend-area so that when fluid exerts a force on the retract-area the piston arrangement generates and applies a retract force to the shaft. Upon release of the fluid pressure to the retract-area and application of the fluid pressure to the extend-area the piston arrangement generates and applies an extend force to the shaft. The retract force is greater than or equal to the extend force.

A piston for an internal combustion engine has a plurality of recesses formed in a skirt including an upper, a lower, and a central portion. The recesses in the upper portion close to an upper boundary of the central portion have lower ends located upwardly at a given distance away from the upper boundary. The recesses in the central portion close to the upper boundary have upper ends located downwardly at the given distance away from the upper boundary. The recesses in the lower portion close to the lower boundary have upper ends located downwardly at the given distance away from the lower boundary. The recesses in the central portion closer to the lower boundary have lower ends located upwardly at the given distance away from the lower boundary. This enhances lubrication between the piston and an inner wall of a cylinder bore and reduces a friction loss of the piston.

A piston for an internal combustion engine has a plurality of recesses formed in a skirt including an upper, a lower, and a central portion. The recesses in the upper portion close to an upper boundary of the central portion have lower ends located upwardly at a given distance away from the upper boundary. The recesses in the central portion close to the upper boundary have upper ends located downwardly at the given distance away from the upper boundary. The recesses in the lower portion close to the lower boundary have upper ends located downwardly at the given distance away from the lower boundary. The recesses in the central portion closer to the lower boundary have lower ends located upwardly at the given distance away from the lower boundary. This enhances lubrication between the piston and an inner wall of a cylinder bore and reduces a friction loss of the piston.