Importance

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Abstract

A memory aboard a boom-type crane stores the coefficients of several polynomials of at least the fifth order closely approximating respective curves giving the maximum permissible load for different boom lengths as a function of the elevational angle of the boom (or the horizontal projection of its length). The set of coefficients read out under the control of a boom-length sensor is fed to a processor which calculates, for a given angle (or projection) as measured by another sensor, the numerical value of the maximum load corresponding to the selected polynomial. The actual value of the load, e.g. as detected by the hydraulic pressure of a jack engaging the boom at an intermediate point, is compared with the permissible maximum calculated by the processor; if that maximum is exceeded, an alarm is given.

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First Claim