DE3161931D1 - Tower crane - Google Patents

Abstract

1. Tower crane comprising a pylon (1) and a telescopic jib (2, 3) mounted thereon, with a crab (14), said jib (2, 3) comprising at least two extensible parts (2 and 3), namely a foot part (2) secured to the pylon (1) and a sliding point part (3), each said parts having a running track extending along the lengthwise direction thereof for the crab (14), the jib (2, 3) being provided with means for locking both parts (2 and 3) relative to one another, the crane having a winch (28) and a cable (26, 27) secured thereto for extending and retracting the jib (2, 3) as well for travelling of the crab (14) on the jib (2, 3), a first part of which (26), which can cause the crab (14) to move away from the pylon, being integral with said crab (14) and extending through at least one cable pulley (29) mounted on the end removed from the pylon (1), of the point part (3) of the jib towards the winch (28), while a second part (27) which can cause the crab (14) to move towards the jib (1), is also secured to said crab (14) and extends through at least one cable pulley (30) mounted on that end located on the pylon (1) side, of the foot part (2) of the jib (2, 3), towards the winch (28), both cable parts (26 and 27) being so wound on the winch (28) drum that the one part be unwound from said drum when the other part is wound thereon, characterized in that the first cable part (26) extends through the cable pulley (29) on that end removed from the pylon (1) of the point part of the jib (3), directly towards the pylon (1), at least up to the foot part (2) of the jib (2, 3), in such a way that said cable part (26) may not only travel the crab (14) towards that end of the jib (2, 3) removed from the pylon (1) but also, when the movement of the crab (14) in the direction of that end removed from the pylon (1) of the point part (3) of the jib (2, 3) is prevented, may pull said point part (3) into the foot part (2) of the jib, while the second cable part (27) first passes over the cable pulley (30) on that end lying on the pylon (1) side, of the foot part (2) of the jib (2, 3), but then extends away again from the pylon (1) to a cable pulley (31) which is mounted on that end removed from the pylon (1), of said foot part (2) of the jib (2, 3), returns about said pulley (31) in the direction of the pylon (1), passes at least over a cable pulley (32) on that end facing the pylon (1), of the point end (3) of the jib, then extends away again from the pylon (1) and finally by passing over a second cable pulley (33) mounted on that end removed from pylon (1) of the foot part (2) of the jib (2, 3), returns in the direction of the pylon (1), in such a way that said second cable part (27) not only may cause the crab (14) to move towards the pylon (1), but also when the movement of the crab (14) in the direction of the end lying on the pylon (1) side, of the foot part (2) of the jib (2, 3) is prevented, may extend the point part (3) of the jib (2, 3) out of said foot part (2).