GB1409373A - Collapsible crane - Google Patents

Abstract

1409373 Collapsible cranes POTAIN 15 Jan 1973 [14 Jan 1972] 1961/73 Heading B8B A collapsible crane comprises a frame 1 with an integral stand 2 provided at its top with a pivot pin 15 about which mast 3 can pivot between a vertical working position and the horizontal transport position shown, jib 4 also being horizontal in this position. A compensation bar 6 is pivoted at 7 to the stand 2 at its lower end, its upper end having rollers 8 engaging the underside of the jib 4. A cable 11 from lifting winch 5 on the frame 1 extends between sets of pulleys 9 and 10, respectively on the bar 6 adjacent the rollers 8 and on the upper face of the mast 3 between the pivot pin 15 and the top of the mast 3 where the jib 4 is pivoted. A flexible sling 12 is hooked at one end to the upper end of the bar 6 and at its other end to the stand 2. To erect the crane the cable 11 is wound in, the jib 4 being raised to about 20 degrees to the horizontal by the bar 6 swinging anticlockwise until it is locked by the sling 12 tightening. During this stage the mast 3 remains horizontal as the torque required to raise it is greater than that required to raise the jib 4. In this position, Fig. 2 (not shown), the pulleys 9, 10 are now out of their original horizontal position in line with the pivot pin 15 and have a sufficient lever arm to raise the mast 3. When the mast 3 has been raised sufficiently, by continuing to wind in the cable 11, for the jib 4 to become horizontal, Fig. 3 (not shown), a jib sling 13 tightens and during the final stages of erection the jib 4 leaves the rollers 8 and thereafter remains substantially horizontal.