Patent ID: 6601719
Filing Date: 2003-08-05
Classification: B66C

Abstract:
In a crane or lifting device having a telescoping boom assembly including at least two boom sections and an extension device for telescopically moving a selected boom section relative to at least one next-adjacent boom section, a system for selectively latching and unlocking the selected boom section for relative telescoping movement, comprising:a latching device for latching the selected boom section to the extension device in a latched position; a locking device for locking the selected boom section in place relative to the next-adjacent boom section; and a motive device including at least one locking and latching cylinder for moving said latching device into the latched position and moving said locking device to an unlocked position to permit the extension device to telescopingly move the selected boom section, and then moving the locking device to a locked position and moving the latching structure to an unlatched position when the telescoping movement is completed, wherein said latching device includes at least two pivoting latching plates, each having a portion capable of projecting into a corresponding aperture in the selected boom section in the latched position and a camming surface; wherein the locking and latching cylinder is supported by and axially aligned with the extension device and is coupled to an engagement structure forming part of the motive device for moving the latching device between the latched and unlatched positions, said engagement structure including a projection for engaging each camming surface to move the latching plates into the latched position during extension of the latching cylinder and to an unlatched position during retraction of the latching cylinder; whereby efficient and effective locking and latching action is reliably achieved.