| 摘要 |
An apparatus includes a cylinder, a piston, a first mechanism and a second mechanism. The cylinder includes a first end, a second end and a chamber. The piston extends into the chamber from the second end. The piston is movable to reciprocate within the chamber. The first mechanism is adapted to move the piston toward the first end. A second mechanism constantly biases the piston toward the second end. A method of controlling the piston is also provided. |
