Derrick crane with wide horizontal swinging range of boom

A derrick crane comprising:

• an upright derrick post having a hollow interior;
• a turning ring rotatably supported to rotate around a lower part of the derrick post about a vertical axis;
• a derrick boom pivotally supported at the inner proximal end thereof on the turning ring in a manner permitting up-and-down derricking movement of the boom;
• a swivel pulley rotatably supported at the top of the post to swivel freely about a vertical axis and rotatably supporting a plurality of sheaves;
• a derricking tackle connected between the swivel pulley and the top end of the boom and including a derricking cable passed around a sheave of the swivel pulley, extended downward therefrom to and around a stationary sheave, and wound around a powered winch;
• a cargo hoisting tackle connected between the top end of the boom and means for suspending a cargo article therefrom and including a hoisting cable passed around another sheave of the swivel pulley, extended downward therefrom to and around another stationary sheave, and wound around a powered winch;
• a mechanism for preventing mutual contacting of the derricking and hoisting cables comprising a plurality of vertically spaced-apart intermediate turntables rotatably supported in the hollow interior of the post to freely rotate about a vertical axis and located between the swivel pulley and the stationary sheaves, said turntable having spaced-apart sheaves for guiding and maintaining apart the derricking and hoisting cables, and means for so intercoupling the swivel pulley and the turntables that each of the differences between the rotational angles of the swivel pulley and the nearest turntable and between adjacent turntables does not exceed a specific angle thereby to prevent mutual contacting and rubbing of the derricking and hoisting cables;
• and a mechanism for controllably driving the turning ring comprising at least one slewing drum, motive power means for driving said drum in forward and reverse directions, and cables wound around the turning ring and the slewing drum and operating to transmit torque therebetween.