US 4,045,923 AGranted

Telescopic swingaway jib

AssigneeWalter Kidde & Company, Inc.

InventorVenkatachalam Shanmugasundaram

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Abstract

A telescopic extension jib for crane booms increases the reach of the boom and therefore increases the utility of the construction crane. To facilitate manual extension and retraction of the movable jib section relative to the fixed base section, a system of rollers is employed between the relatively movable jib sections. In the socketing area of the jib at full jib extension, upper and lower rollers are spring-mounted and can bear the dead weight of the movable jib section when the same is unloaded. Coacting bearing pads engage the top and bottom faces of the movable jib section under loading to distribute stresses over larger areas, the spring-mounted rollers retracting automatically to enable the movable jib section to engage the bearing pads in the socketing area. A locating pin is provided to lock the jib sections against accidental relative movement in both the extended and retracted positions of the jib.

Claims8

Dependent claims

An extension jib for crane booms comprising a stationary jib base section adapted for attachment to a crane boom, and an extensible and retractable movable jib section slidably mounted within said stationary jib section, said movable jib having top, bottom and side walls, longitudinally spaced opposing spring-urged rollers mounted on the stationary jib section, said rollers engaging the top and bottom walls of said movable jib section;

each spring-urged roller comprising a freely rotatable transverse axis cylindrical roller of sufficient length to substantially span the width of the movable jib section, a mounting plate carrying said roller, headed guide pins engaged slidably with the mounting plate and allowing the mounting plate and roller to move toward and away from the adjacent wall of the movable jib section, and compression springs on said headed guide pins urging the mounting plate and roller toward the adjacent wall of the movable jib section, whereby the rollers bear the dead weight of the moving jib section when the latter is extended from the stationary jib section;
and longitudinal spaced opposing bearing pad units mounted on the stationary jib adjacent the spring-urged rollers and engaging the top and bottom walls of the movable jib when the spring-urged rollers yield due to a load being placed on said movable jib section.

Dependencies are inferred from the claim text.