Apparatus for monitoring and recording the load of a crane with a pivotal boom

Claim 1

In a crane with a chassis, a boom, mounting means pivotally securing said boom on said chassis for movement in a vertical plane about a horizontal axis, actuating means for swinging said boom about said axis, and hoist means on said boom for raising and lowering a load, the improvement comprising a monitoring device for recording the load on the crane for a finite period, said device including: first sensing means operatively connected to said actuating means for determining the instantaneous load moment thereof and producing a first electrical signal representing said instantaneous load moment; second sensing means operatively connected to said mounting means and responsive to the position of said boom for producing a second electrical signal representing the instantaneous maximum permissible load moment thereof; a quotient-forming comparator connected to said first and second sensing means and responsive to said first and second signals for producing an electrical output signal representing the ratio of the instantaneous load moment and the maximum permissible load moment of said boom; stop means connected to said actuating means and responsive to said output signal for immobilizing said actuating means upon said instantaneous load moment equaling said maximum permissible load moment; and a recorder connected to said quotient-forming comparator means and including timing means for registering said output signal as a function of time over said finite period.