Patent ID: 7364044
Filing Date: 2008-04-29
Classification: B66C

Abstract:
1. A safety device against crane overturning which operates in a crawler crane comprising at least four outriggers and a frame, the four outriggers operable to make allowance for variation so as to maximize or minimize an overhang distance, an attaching member rotatively movable in a horizontal direction and supported by the frame, a base end arm supported by the attaching member so that the base end arm can be freely raised and laid, an intermediate arm supported by the base end are so that the intermediate arm can be freely raised and laid, a leading end arm in slidable contact with the intermediate arm, an outrigger cylinder provided between the attaching member and the base end arm and operable to raise and lay the base end arm; the safety device comprising: a load detector that detects a ground reaction to each of the outriggers; and an alarm output section operable to calculate sums of detected values for ground reactions to every two adjacent outriggers to find a minimum value of the sums, to compare the minimum value with a preliminary reference value that represents a preliminary alarm state prior to the crane reaching a stability limitation and a limit reference value that represents a need to stop the crane so that the crane reaches the stability limitation in its maximum overhang state or in its minimum overhang state, and to output a preliminary alarm signal when the minimum value is smaller than the preliminary reference value or output a limit alarm signal when the minimum value is smaller than the limit reference value.