Harnischfeger Corporation

Lembit Vaerk

Narahari Gattu

Robert A Fritsch

Ram N Rathi

David Moravec

A mobile crane having a boom and a boom extension connected thereto with a toggle linkage for connecting the boom extension to the boom to allow the boom extension to be offset from the boom by one of a plurality of predetermined angles. A pair of double links is pivotably attached to the boom extension while a pair of single links is pivotably attached to the upper sheave pin in the boom head. Both the single and double links have a hole in the opposite end. Either the single or double links also have a hole in at least one intermediate position. The link having one hole is then pinned to the other link having two holes, the hole selected in the second link determining the angles of offset when tension is applied to the linkage by pivoting the boom extension about the lower sheave pin after removal of the upper boom foot pins. Biasing devices are provided to cause the linkage, which pivots freely at both ends and in the middle, to toggle upward when tension thereon is released. A storage position is provided for storing the double links and the link connector pins so as to prevent interference with the other apparatus and loss of the connector pins when the linkage is not in use.

Crane boom having variable angle offset capability

Apparatus and method for extending a fly section of a telescopic crane boom which fly section does not have its own power extension/retraction unit. The crane boom comprises at least a first or fly section, a second section, and a third or base section. Linearly extendable power screws are located within the boom for extending the second section from the base section, being connected between the base section and the second section to effect movement of the latter. To set up the crane for operation, the power screws extend the second section from the base section, a load pin connecting the fly section and the second section is released, and a pair of stop pins engages the fly section in its sides. The stop pins prevent movement of the fly section relative to the base section. Thus, when the second section is thereafter retracted into the base section, the fly section is left extended from the second section. A hole at the inside of the fly section and the load pin are at this point in alignment and the load pin may be inserted to engage both sections. The power screws are now in readiness to independently operate the second section, with the fly section fully extended on the second section.

Telescoping crane boom

A high-strength light-weight hollow boom section for a multi-section telescopic crane boom comprises a top wall, a bottom wall, and a pair of lateral walls, each lateral wall being located between the top wall and the bottom wall. Each of the four walls comprises a pair of spaced apart longitudinally extending members, a relatively thin plate extending between, overlapping and welded to the pair of longitudinal members, and a plurality of longitudinally spaced part transversely extending stiffeners of U-shaped cross-sections, each stiffener being welded to the plate and to the pair of longitudinal members. Each longitudinal member of a lateral wall is in edge-wise abutting relationship with and welded to the surface of a longitudinal member of one of the top and bottom walls. Each stiffener of a lateral wall also has its ends in abutting relationship with and welded to the surface of a longitudinal member of the top and bottom walls. Novel slide pad arrangements are also disclosed.

High-strength light-weight boom section for telescopic crane boom

A large light-weight deflection-resistant telescopic boom section of hollow rectangular cross-section comprises spaced apart top and bottom plates and spaced apart vertical side plates welded therebetween inwardly of the side edges thereof. Longitudinal corner stiffeners of angular cross-section are welded between the outwardly extending portion of the top and bottom plates and the associated vertical side plate to shorten the effective height of the side plate, to stiffen the top and bottom plates, to increase the mechanical section properties, and to provide a flat built-in slide pad bearing surface. Vertical side stiffeners of U-shaped cross-section are welded to the vertical side plates at intervals therealong and to the longitudinal corner stiffeners to provide the buckling resistance and increased shear load capacity of side plates.

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Cedar Rapids, IA, United States of America

Lembit Vaerk