Spreader devices having a controlled output

Claim 1

A spreader device for mounting on a vehicle mounted on wheels so that the output of the spreader device is controlled by the speed of displacement of the vehicle, said device comprising a tank for containing a liquid product to be spread, a pump having an output and an input which is connected to the tank, a spreader system for said liquid product, a supply pipe connecting the output of the pump to the spreader system, a return pipe connecting the tank to the supply pipe, a regulating valve inserted in the return pipe, first transducer means to sense the pressure in said supply pipe and to produce a first fluidic signal proportional to said pressure; second transducer means to sense the displacement speed of said vehicle and to produce a second fluidic signal which is linearly proportional to said displacement speed; corrector fluid circuit means comprising an input connected to said second transducer means to receive said second fluidic signal, an output, a first passageway putting the input in communication with the output, a fluid discharge passageway connected to said first passageway, an adjustable throttle, valve means inserted in said discharge passageway, and setting means for adjusting said throttle valve means whereby to produce at said output a third fluidic signal which is also linearly proportional to said displacement speed but of a selected different slope from said second signal; regulator means adapted to compare said first and said third fluidic signals and to adjust the position of said regulating valve through a valve operator as a function of the difference between said fluidic signals, said third fluidic signal from said corrector fluid circuit means varying in accordance with a slope corresponding to any selected one of a family of linear curves approximating supply pipe pressure plotted as a function of displacement speed of said vehicle at pressures in excess of 1 bar and displacement speeds of said vehicle greater than 4 kph.