GB1158028A - Improvements relating to Levelling Devices - Google Patents

Abstract

1,158,028. Levelling mobile tower cranes. PRIESTMAN BROS. Ltd. 20 June, 1968 [13 July, 1967], No. 32353/67. Addition to 1,120,164. Heading B8B. To level a bedplate 7, Fig. 1, which supports a tower crane or other civil engineering machine, an operator turns a switch 22, Fig. 2 (not shown) to position B to lower a hook 9 into engagement with an anchor pin 11 and lock the superstructure relative to the chassis by engaging locks 14, 16. The ground level is next determined by rotating a control box casing 23, Figs. 3, 5 until a spirit level 30 gives a zero reading and a second level 31 extends away down the line of maximum slope of the ground. One of the hand wheels 33 is now rotated to tilt a plate 28 upwards until the spirit level 31, which is mounted on it, gives a zero reading. Simultaneously a shutter 36 moves under a cut-out 39 so that the intersections X, Y between red and green halves of the shutter with the outer edge of the semicircular cut-out 39 indicate the two directions to which thicker parts of the two wedge rings 12, 13, Fig. 1, must be rotated to level the superstructure. Movement of the switch 22 to position C disengages the lock 14 between the lower wedge ring 12 and the chassis 8. The two wedge rings are now rotated by a slewing pinion 18 until a green pointer arm 41b, Fig. 3, overlies the intersection X between the green half 36b of the shutter and the edge of the cut-out 39. This puts the lower wedge ring 12 in its final position. The control switch 22 is now turned to position D to re-engage the lock 14 and indicate this engagement. Rotation of the switch to position E, disengages the lock 16 between the upper and lower wedge rings and produces a signal that this lock is disengaged whilst the upper wedge ring 13 is rotated until a red pointer arm 41a overlies the intersection Y of the red half 36a of the shutter and the cut-out 39. The upper wedge ring is now in its final position. The switch 22 is next turned successively to positions F and A which respectively re-engage the lock 16 and disengage the hook 9 so that the superstructure may be slewed about a truly vertical axis.