Automatically deployable load-line receiving mast structure for limiting deflection of proportionally extendable boom section crane

In a crane having a base assembly including a rotatable turret and a base boom section pivotally carried by the turret, a series of proportionally extendable boom sections supported by the base boom section, a winch unit on the base assembly having a winch drum, a primary sheave on the outer end of the outermost of the extendable boom sections, and a flexible load line trained around the winch drum and extending over the sheave on the outermost boom section for lifting of a load by the crane, the improvement comprising:

• an erectable mast pivotally carried by one of the boom sections, said mast normally being positioned adjacent said one boom section on which it is mounted, said mast being movable to an erect position extending outwardly from said one boom section at an angle with respect to the latter in a direction toward the load line extending between the winch drum and the primary sheave,
• there being a secondary sheave on the mast disposed in a position for the load line to pass thereover between the winch drum and the primary sheave;
• and
• means on the boom sections and engageable with the mast for effecting erection of the mast after the boom sections have been partially extended to a predetermined extent and as the boom sections are further extended proportionally relative to the base boom section to an extent that a load to be picked up by the load line would otherwise impart an undesirable side deflection force on the extended boom,
• said mast and secondary sheave thereon being located such that upon initiation of erection of the mast, the load line extending from the winch drum over the secondary sheave to the primary sheave structure in conjunction with the longitudinal axis of the boom sections defines triangulation geometry,
• said load line serving to lift the load and also as a result of said triangulation geometry upon initiation of erection of the mast providing required offsetting boom deflection forces as a direct function of the overall length and angle of the boom during extension and retraction, and a direct function of the specific load being lifted by the crane boom sections.

In a crane having a base assembly including a rotatable turret and a base boom section pivotally carried by the turret, a series of proportionally extendable boom sections supported by the base boom section, a winch unit on the base assembly having a winch drum, a primary sheave on the outer end of the outermost of the extendable boom sections, and a flexible load line trained around the winch drum and extending over the sheave on the outermost boom section for lifting of a load by the crane, the improvement comprising:

• an erectable mast pivotally carried by one of the boom sections, said mast normally being positioned adjacent said one boom section on which it is mounted, said mast being movable to an erect position extending outwardly from said one boom section at an angle with respect to the latter in a direction toward the load line extending between the winch drum and the primary sheave,
• there being a secondary sheave on the mast disposed in a position for the load line to pass thereover between the winch drum and the primary sheave;
• and
• means on the boom sections and engageable with the mast for effecting erection of the mast after the boom sections have been partially extended to a predetermined extent and as the boom sections are further extended proportionally relative to the base boom section to an extent that the extendable boom sections no longer overlap the base boom section and one another relatively to an extent that undesirable side deflection of the boom sections would otherwise occur when a load is picked up by the load line,
• said mast and secondary sheave thereon being located such that upon initiation of erection of the mast, the load line extending from the winch drum over the secondary sheave to the primary sheave structure in conjunction with the longitudinal axis of the boom sections defines triangulation geometry,
• said load line serving to lift the load and also as a result of said triangulation geometry upon initiation of erection of the mast providing required offsetting boom deflection forces as a direct function of the overall length and angle of the boom during extension and retraction, and a direct function of the specific load being lifted by the crane boom sections.