| 摘要 |
<p>A telescopic boom, for portable cranes, having one or more hydraulically operated telescopic slides, and one or more mechanically operated telescopic slides. The extension or retraction of the mechanically operated telescopic slide is effected by means of a detachable retaining rod, one end of which is connected with the non-telescopic main boom by means of a bolt inserted transversely therethrough. The other free end of the retaining rod is provided with a pressure piece, for maintaining the boom in some of its positions during extension thereof, and a tensioning device, which is located 180 DEG opposite from the pressure piece, for maintaining the boom in some of its positions during retraction thereof. A plurality of slots are arranged along the mechanically operated telescopic slide transverse to the direction of operation. These slots respectively cooperate with a cam of the pressure piece or with a stop cam of a pawl during extension and retraction of the telescopic slide.</p> |
