METHOD AND DEVICE FOR EXPANDING AND CONTAINING JIB OF WHEEL TYPE CRANE

PURPOSE:To reduce a protrusion amount of a jib protruding sideways of a boom in a jig lateral embracing containing state by a method wherein after a jib is moved from a lateral embracing containing position to a lower position centering around a first shaft once, the jib is rotated around a second shaft and set in a down embracing position. CONSTITUTION:Simultaneously with release of the tip side of a jib 2 from fixing, the containing lock pin of an intermediate support mechanism 14 is dislocated. With this state, the jib 2 is supported to a boom 1 at two points in the direction of the length of an intermediate part by means of an automatic coupling pin 22 and a containing fixing pin 26. After, with the boom 1 slightly expanded, a jib support shaft 3 is moved more in front than a coupling part 4, the jib 2 is rotated around a first shaft B through expansion of a jib elevation cylinder 21, and moved in a horizontal placing posture to a lower position where it is positioned on the under surface side of the boom. Through expansion of a jib rotary cylinder 19, the jib 2 is rotated, as shown by a virtual line, around the second shaft and set to a down embracing position wherein coupling parts 4 and 4 on both sides are positioned facing the jib support shafts 3 and 3 on both sides.