Device for controlling the load of a lifting appliance

A device for enabling the load on a lifting appliance to be controlled, comprising a first potentiometer unit formed by a series of potentiometers, each having multiple tappings and a movable contact arm, means for mechanically coupling together the arms of said potentiometers, first means for controlling the position of the arms of the said potentiometers as a function of the value of a first geometric parameter of the appliance, a second potentiometer unit comprising a potentiometer having multiple tappings and a movable contact arm, each tapping being electrically connected to the arm of a corresponding potentiometer of the first unit, a second means for controlling the position of the arm of the said second unit potentiometer as a function of the value of a second geometric parameter of the appliance, third means serving to assign reference voltages to the tappings of the potentiometers of the first unit, fourth means serving to establish a voltage representing the instantaneous load actually applied to the appliance, fifth means serving to compare the voltage taken from the arm of the second unit potentiometer and the said voltage representing the load applied to the appliance, said third means including for each tapping, a system of polarisation comprising a series of polarisation circuits in parallel, associated with the position in which the appliance is brought into operation, each circuit having a member suitable for providing a regulated voltage and controlled by a switching device defining the instantaneous position of operation and simultaneously controlling all the circuits of all the systems of polarisation of the tappings of the first unit potentiometers.