Abstract: An extension and retraction system for a four section telescopic boom having simultaneous and equal extension and retraction of the telescopic sections, wherein a pair of hydraulic cylinders are mounted exteriorly of the boom for extending and retracting the inner mid section relative to the base section; a pair of extension chains or cables are connected between the base section and the outer mid section, and between the fly section and the inner mid section; and a pair of retraction cables are connected between the base section and the outer mid section, and between the fly section and the inner mid section. The extension and retraction chains and cables are positioned within the boom sections to thereby be protected from damage.

Abstract: A multi-section hydraulically operated telescoping crane boom includes a manual fly section (23) which may be safely extended and retracted, securely latched in the extended position and pin locked by remote operation of a biased hydraulically powered latching plunger (33) and a biased cooperative hydraulically powered locking pin (52) both embodied in a static hydraulic circuit which includes in one form a pressure fluid circuit safety interlock portion (FIG. 4) with a pressure-responsive indicator (123) to indicate when the latching plunger (33) is engaged (48), and in another form an electrical switch circuit safety interlock portion (FIG. 7) controlling the hydraulic circuit, with an electric switch (131) operated indicator (159) to indicate when the latching plunger (33) is engaged (48). The safety interlock portions of both circuits for the cooperative latching plunger (33) and locking pin (52) prevent their operation in improper sequence so one is engaged at all times before the other is disengaged.

Abstract: A swing-around side stowable jib for crane booms is safely supported at all times during movement from its use position to its stowed position, and vice versa. In the short transitional movement of the jib following its release from its nose assembly pivot and immediately prior to re-engaging this pivot, the jib is always securely held by a strongly biased safety latch in supportive engagement with a side mounting assembly located between the nose assembly pivot and a second mounting assembly on the boom rearwardly of the first mounting assembly. The safety latch at proper times is easily released by operation of a hand lever near ground level. Locks for the safety latch and its release lever are also provided. The safety latch is swiveled and biased to meet the swing-around jib squarely as it approaches the stowed position.

Abstract: A multi-section hydraulically operated telescoping crane boom includes a manual fly section which may be safely extended and retracted, securely latched in the extended position and pin locked by remote operation of a biased hydraulically powered latching plunger and a biased cooperative hydraulically powered locking pin both embodied in a static pressure hydraulic circuit which includes a pressure-responsive indicator to indicate when the latching plunger is engaged. The circuit also includes safety interlocks for the cooperative latching plunger and locking pin preventing their operation in improper sequence.