Traversing hoists – Boom position lock
Reexamination Certificate
2001-09-21
2003-08-05
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Boom position lock
C212S270000, C212S349000
Reexamination Certificate
active
06601719
ABSTRACT:
TECHNICAL FIELD
The present invention related generally to lifting devices, such as cranes or the like, and more particularly to a complementary locking and latching system for a telescoping boom.
BACKGROUND OF THE INVENTION
Various types of telescoping booms or boom assemblies for use in cranes or other lifting devices are known in the art. The conventional boom assembly includes a plurality of nested tubular sections, with each outer section having larger cross-sectional size than the next-adjacent inner section to permit the desired relative telescoping movement. In the typical arrangement, the proximal end of the outermost boom section is pivotally mounted on a turntable and the distal end of the innermost section carries one or more sheaves or equivalent structures for supporting the hoisting cable or the like.
Usually, to telescopingly move (extend or retract) a selected boom section relative to a next-adjacent boom section, a motive device such as a boom “extension” cylinder is employed. This extension cylinder is often positioned inside the innermost boom section, with the proximal end of the piston rod (often called the “rod end” of the cylinder) either pivotably or fixedly mounted to a stable structure, such as the endwall of the outermost boom section or an adjacent component of the crane. To couple the selected boom section to the “case” end of the extension cylinder, a latching device may be provided. Such devices often include opposed pairs of transversely movable structures that, in a latched position, project through corresponding apertures formed in the sidewalls of the boom section selected for telescoping movement. Hence, when the latching device is in the latched position and the extension cylinder is extended or retracted, the selected boom section telescopingly moves toward the corresponding extended or retracted position relative to the next-adjacent boom section.
Either after the latching operation is completed, or at substantially the same time, a locking device, such as a spring-loaded pin that is normally biased to securely hold the selected boom section in place, is retracted. Then, once the selected boom section reaches the desired position as the result of the relative telescoping movement, the operation is reversed such that the locking device is moved to the locked position and the latching device is retracted, in that order. Consequently, the boom section previously selected for telescoping movement is locked in the extended or retracted position. The latching device may then be used in combination with the extension cylinder to telescopingly move another selected boom section (with the locking device associated with that selected boom section being retracted and released as described above).
While this dual locking and latching arrangement works well for its intended purpose, efficiently and effectively moving the latching device between an unlatched and a latched position, retracting the locking device, and then reversing these operations when the selected boom section reaches the desired position is somewhat difficult in practice, especially within the confines of the boom assembly. Others in the past have proposed different types of motive devices for separately actuating the latching and locking devices, but most are exceedingly complex in design and in some instances may even be unreliable in operation (thus necessitating separate “fail-safe” devices, which may include auxiliary motive devices, including hydraulic cylinders, or even manually operated locks).
For example, some less than advantageous features required in a few past arrangements include the need for actuating the locking and latching devices using multiple, completely separate motive devices, such as hydraulic piston/cylinder combinations positioned orthogonally to each other (see, e.g., U.S. Pat. No. 5,628,416 to Frommelt et al.), or using multiple motive devices in combination with corresponding complicated hydraulic control systems (see, e.g., U.S. Pat. Nos. 4,433,515 and 4,490,951, both to Mentzer et al.). In addition to a separate latching device, a more recently proposed system requires two spring-loaded locking pins positioned in the opposing sidewalls of each telescoping boom section, with each pin being actuated by a separate hydraulic cylinder (see, e.g., U.S. Pat. No. 6,216,895 to Erdmann et al.). While these systems may be effective, the requirement of using more than one motive device to effect the locking and latching operations contributes to their complexity. A direct correlation exists between complexity of the locking or latching system and not only the expense to construct, operate, and service the boom assembly, but also the overall weight and minimum size requirements.
Accordingly, a need is identified for an improved, yet simplified, complementary locking and latching system for use. with a telescoping boom assembly. In one aspect, the locking and latching system would include locking and latching devices that are essentially independent of each other in form, but work together or complement each other in operation using a single motive device. As compared to past proposals, the resulting system would thus be somewhat less complicated in design, less expensive to manufacture and install, and easier to service. In another aspect, the invention would not necessarily be limited to the use of a single motive device, since a more efficient manner of automatically retracting or releasing a locking device immediately after moving a latching device between the latched and unlatched positions would be provided. In an even more specific aspect, the locking and latching system would be relatively compact, and thus would easily fit within the confines of a conventional boom assembly. In certain applications, the compact nature of the system would even allow for use with telescoping boom assemblies having smaller dimensions than previously thought possible, without compromising the strength and lifting capability, necessitating extensive redesign, or requiring special miniature components. In yet another aspect, the system would be designed so as to minimize the weight contribution to the overall boom assembly. In final analysis, the system in all respects would be an improvement over those in the prior art in terms of efficiency and reliability, which in turn would reduce operational costs.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, a system for selectively latching and unlocking a selected boom section for telescoping movement relative to a next-adjacent boom section is provided. The system is especially adapted for use in a crane or lifting device having a telescoping boom assembly including at least two boom sections and an extension device for telescopically moving the selected boom section relative to the next-adjacent boom section. The system comprises 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 single motive device. The motive device includes a locking and latching cylinder for moving the latching device to the latched position and moving the locking device to an unlocked position prior to telescopingly moving 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.
In one embodiment, the locking and latching cylinder is supported by and axially aligned with the extension device. The locking and latching cylinder is also coupled .to an engagement head forming part of the motive device for moving the latching device between a latched position and an unlatched position. The latching device may include at least two pivoting latching plates (and preferably two pairs of latching plates, with one pair positioned on each side of the extension cylinder). Each plate includes a hook-like portion for projecting through a corresponding ap
Brahan Thomas J.
King & Schickli PLLC
Link-Belt Construction Equipment Co. L.P. , LLLP
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