| 摘要 |
<p>A crane which is admirably suited for shipboard use essentially removes the danger of a swinging block or a swinging load, and provides a simplified boom construction. The boom is a three-part articulated boom with both of the forward parts swinging downwardly from the fully extended horizontal position. In one form a winching means is preferably carried entirely by the outermost boom section. Preferably there are two hoist lines, each with its own winching means which may be of drum or cylinder type. In use of this form, the boom will be operated to place its tip at or only slightly above the load to be lifted so that the swinging of the hook hanging from it will be negligible even when swells cause movement of the ship. Once the hook or hooks have been secured to the load, the line or lines may be winched in for snugness and the load lifted and moved to deck or hatch position with virtually no swinging. With another form of the invention, a lift fork is carried at the end of the boom. Because the extent of angular swing excludes the use of the ordinary cylinder-leveling of the lift fork, it is hung on a pivot. The necessary control for thrusting under a load is achieved by applying a disc brake to the pivoting action.</p> |
