| 摘要 |
A safety and fixing mechanism allows a movable shape to move in one direction relative to a fixed shaped along an axis but automatically stops the moving shape from moving in the other direction. A ratchet machanism fastened to the fixed shape includes a ratchet element that is movably guided by a support in a direction substantially perpendicular to the axis. The ratchet element has an end portion that protrudes form the fixed shape toward the movable shape, the end portion having a flat end surface and an inclined end surface inclined to the axis. A spring biases the ratchet element relative to the fixed shape toward the movable shape. A perforated strip fastened to the movable shape has a plurality of spaced-apart holes lying in a row parallel to the axis, each hole being adapted to receive the end portion of the element.
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