In prior U.S. Pat. No. 5,052,627 of the present inventor issued Oct. 1, 1991 is disclosed a machine for spreading particulate material and particularly, but not exclusively, granular fertilizer in an agricultural situation. This machine includes a tank arranged to be mounted on a suitable transportation vehicle. At one end of the tank which is either the front end or the back end is mounted a pair of booms with each boom extending outwardly to a respective side of the tank for movement with the vehicle across the ground. Each boom includes a series of pipes which are horizontal and arranged either in a single row or in two rows so that the pipes are connected side by side. The tank has a pair of belts extending longitudinally of the tank side by side in a common horizontal plane. Each belt feeds out of the end of the tank for discharging material carried on the upper run of the belt into a guide duct system positioned underneath the end of the belt. The guide duct system includes a plurality of ducts equal to the number of pipes and arranged side by side across the width of the discharge end of the belt. The guide duct system thus receives portions of the material from different positions across the width of the belt and transfers that portion of material to a respective one of the pipes. The inner end of the pipes are connected to a manifold so that air from a fan blows through the pipes to carry the portion of material along the respective pipe to a spreader system at the end of the pipe. The spreader system can in some cases include two separate spreaders one directly at the end and one spaced inwardly from the end so as to split the material at the two separate spreaders thus reducing the number of individual pipes.
This machine has achieved considerable commercial success and is widely sold in North America.
The above patent also discloses a system for adding one or more additional components to the first component from the tank. Thus the belt carries the first component out of the tank using a gate at the exit of the tank for levelling the material on the belt at a predetermined thickness. Two further tanks are provided each of which has an individual metering system which meters an additional component from the additional tank onto the top of the same belt so that the same belt carries the additional material with the first material from the main tank to the guide system for discharge of the portions into the separate ducts of the guide system.
However the machine described above using the supplemental tanks does not provide sufficient flexibility of the materials to be supplied by the belt to accommodate the variations in the components of the fertilizer which are desired for modern agriculture.