Collapsible frame support for pivotal boom on a portable crane

In an apparatus including a transport vehicle and a crane structure mounted on said transport vehicle, said crane structure including a gantry structure and a generally vertical tower structure, said gantry structure including two boom portions and trolley tracks thereon, said boom portions further being pivotally attached to and supported by said generally vertical tower structure and extending outwardly therefrom in opposite directions and selectively alignable with said trolley tracks, substantially at an upper end thereof, and said crane structure further including an upper supporting structure attached to said generally vertical tower structure substantially at said upper end thereof and protruding generally upwardly relative to said tower structure and said boom portions, the improvement comprising pivot means for selectively pivoting said boom portions relative to said vertical tower structure between respective operating positions wherein said boom portions protrude generally horizontally from said vertical tower structure substantially at said upper end thereof and respective rest positions wherein said boom portions are lower than the top of said vertical tower structure, at least one link assembly distinct from said pivot means disconnectibly interconnecting each of said boom portions with said upper supporting structure for supporting said boom portions in said respective operating positions, said link assemblies each including a number of link members disconnectibly connected to one another, at least a pair of adjacent link members in each of said link assemblies being selectively disconnectible from one another in order to disconnect said boom portions from said upper supporting structures and to allow said pivoting of said boom portions to said respective rest positions lower than the top of said vertical tower structure, power means for pivoting said boom portions including actuators means selectively interconnecting said upper supporting structure and said tower structure for selectively collapsing said upper support structure in order to selectively reduce the overall height of said crane structure to allow said transport vehicle to pass under overhead obstructions, said upper support structure including an A-frame structure pivotally and collapsibly attached to the top of said vertical tower structure said A-frame structure being collapsible when said boom portions are in said respective rest positions, said pivot means including upper and lower hinge assemblies pivotally and selectively disconnectibly interconnecting each of said boom portions with said vertical tower structure, and separate upper and lower means for selectively disconnecting each of said upper and lower hinge assemblies, respectively, said upper hinge assemblies pivotally interconnecting said boom portions to said vertical tower structure for upward pivotal movement from said respective operating positions and relative to said vertical tower structure when said lower hinge assemblies are disconnected, and said lower hinge assembly pivotaly interconnecting said boom portions to said vertical tower structure for downward pivotal movement from said respective operating positions and relative to said vertical tower structure when said lower hinge assemblies are disconnected, said link members being disconnectible from one another when the respective boom portions are pivotally moved upwardly relative to said vertical tower structure.