| 摘要 |
<p>The lifting gantry for prestressed concrete girders, as in the main patent, has two uprights (1, 2) joined at the top by a girder (3), and running on wheels (4) at the bottom. The girder (3) has a jack (7) for lifting, to the top of which are fixed two cables (8, 9) for keeping the girder horizontal whilst being lifted. The cable (8) runs over guide pulleys (11, 12) above the ends of the lower girder (5), and is hooked onto one (13) of the ends of the lower girder. The other cable (9) runs over the guide pulley (14) positioned straight above the other end (15) of the lower girder to which it is attached. Alternatively, the mobile girder acts as a hoist and bracing for the two uprights.</p> |
