GB1385113A - Folding tower cranes - Google Patents

Abstract

1385113 Folding tower cranes POTAIN 7 Aug 1972 [6 Aug 1971] 36796/72 Heading B8B A folding tower crane has a telescopic mast 5, 4 pivoted on a slewing platform 1 at a pivot 3 on a support 2. A jib 7 is pivoted at 6 to mast upper section 5. In the lowered position, Fig. 1 (not shown), the jib 7 and mast 5, 4 lie substantially horizontally adjacent the platform 1. A rod 9 is pivoted at 8 to the mast upper section 5 arid a fixed length tie cable 12 connects its end to the free end of the jib at 14. In the lowered position the end 13 of the rod 9 lies towards the jib point 14 and the cable 12 is slack. A cable 15, taut at all times, is connected at 16 to the lower end of lower mast section 4, passes over a pulley 17 at the upper end of section 4, over a pulley 18 on the support 2, over a pulley 19 on the platform 1 and over a pulley 11 on a fixed rear arm 10 to be attached to end 13 of the rod 9. A winch arrangement (not shown), is used to pivot the mast from its lowered to its erect position and this movement pivots the rod 9 to take up the slack in the cable 12 (as shown) and raise the jib 7 to its horizontal operating position as the cable 15 leaves the pulley 11 to run vertically and act to balance the jib 7, Figs. 3, 4 (not shown), as the mast becomes vertical. The mast is then locked in position and may be extended as required, the jib 7 remaining horizontal as the extra cable required between the pulley 19 and the point 13 is paid out from between the point 16 and the pulley 17.