| 摘要 |
A dockboard comprises a main plate hinged at its rear edge to a frame and having a lip plate hinged at its front edge. Upwardly acting springs beneath the main plate are sufficiently strong to move the board upwards in the absence of a weight thereon. A cable is connected between the frame and the board, one end of the cable being wound around a ratchet-controlled reel which holds the board in any position to which it is set; a manually controlled release is provided for the ratchet. The lip plate is automatically elevated as the main plate rises by a snatch chain acting on one end of an articulated linkage which just reaches top dead center as the lip plate reaches the elevated position and locks it in that position. The linkage is mounted to move backward and thereby trip the latch upon an impact applied to the elevated lip, for example by a transport backing into the lip.
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