GB1393358A - Rotary tower cranes - Google Patents

Abstract

1393358 Selt-erecting tower cranes CANDUELA SL 20 Dec 1973 [28 Dec 1972 20 Sept 1973] 59175/73 Heading B8B A rotary tower crane comprises a lower mast 8 articulated to an upper mast 20 at 12 and to a slewing ring 3 at 7. A boom 21 is articulated at 22 to the upper mast 20. A hoisting cable 18 runs from a hoist drum 4 over a fixed pulley 51 to a pulley block 10 on the lower mast 8 and then between the pulley block 10, pulley blocks 13, 16 pivoted to framework 34 and a moveable pulley block 15 before being attached to the framework 34. A tension cable 18<SP>1</SP> stretches from the pulley block 15 and is secured to a pulley 30 on A-frame 28. A safety cable 35 is attached to the tension cable 18<SP>1</SP> and passes intermediately over a pulley 11 on the lower mast 8. The pulley block 10 is mounted on one arm of a two armed lever 9 pivoted to the lower mast 8 at 31 and a roller 17 on the other arm engages the upper mast 20 during erection of the crane, as shown in Fig. 2, in the initial stages. At first the cable 35 takes the strain and the two masts 8, 20 are brought into line in a vertical position with the boom 21 alongside, the tension rope 18<SP>1</SP> now taking the strain, Fig. 3 (not shown). In this position the towers 8, 20 are held by brace 19 whereupon further operation of the drum 4 to wind the hoisting cable 18 draws down the movable block 15, which acts through the tension cable 18<SP>1</SP> to bring the boom 21 either to a horizontal or luffed position (as shown), through the members 22 to 30.