Abstract: 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.degree. 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.

Abstract: A telescopic boom for movable cranes with at least one hydraulically operable telescopic slide and with at least one mechanically operable telescopic slide. The pushing out movement and the retracting movement of the mechanically actuated telescopic slide is effected by means of a holding bar having a free end portion provided with a pressing or pushing member and with a pulling member offset by 180.degree. with regard to the pressing or pushing member. The other end of the holding bar is provided with a transverse bolt for engagement with a bearing on the at least one hydraulically operable slide. The mechanically operable telescopic slide is provided with cams extending transverse to its longitudinal direction of movement for cooperation with the holding bar.