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US 4,406,375 AGranted
Telescopic boom construction
AssigneeJLG Industries, Inc.
InventorJohn L. Hockensmith
Life of this patent
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AssigneeJLG Industries, Inc.
InventorJohn L. Hockensmith
Estimating the term…
A multi-section telescopic lifting boom which is extended and retracted at least in part by chains having their ends secured to one section, engaging sprockets carried by another section and connected at an intermediate point to a third section. Telescopic elements which are completely separated during boom extension are provided with inclined guide surfaces to insure entry of the smaller element into the surrounding element. Extension and retraction is effected by a linear hydraulic motor connected to a cylinder box which is pivoted to section adjacent the the base section; anti-friction pads are carried at the bottom of the outer end of the cylinder box and engage longitudinally extending tubes on the bottom plate of the next section, the tubes extending higher than the extension and retraction chains, which are positioned between the tubes. The chains are provided in parallel, at least one end of each chain being connected to a yoke which is adjustably secured by a threaded member.
A multi-section telescopic lifting boom includes a base section and movable sections, a motor for extending and retracting the boom movable sections, a cylinder box pivotally connected adjacent its inner end to a boom section adjacent the base section and having the motor connected to said cylinder box, means for moving one said movable section between a first position in which it is at least partially telescoped over said cylinder box and a second position in which the inner end thereof is beyond the outer end of the cylinder box, meeting portions on the outer end of said cylinder box and the inner end of of said one section, and guide surface means on at least one of the meeting portions for guiding said cylinder box into said one movable section;
A multi-section telescopic lifting boom comprising a base section, and at least three movable sections, a cylinder box, means for pivotally connecting the cylinder box and a first said movable section substantially adjacent the inner ends thereof, extensible motor means connected to said base section and to said cylinder box for extending and retracting said first movable section, anti-friction means on the bottom of the cylinder box adjacent the outer end thereof, means for extending and retracting the other movable sections upon extension and retraction of said first movable section by said motor means, a second said movable section having a first position in which it is at least partially telescoped over said cylinder box and a second position in which the inner end thereof is beyond the outer end of the cylinder box, and a third said movable section having longitudinally extending support surface means positioned for engagement by said anti-friction means when said second movable section is in a said second position thereof;
Dependencies are inferred from the claim text.