Device for applying plant-protecting compositions

An apparatus for applying a diluted liquid composition of predetermined concentration to a substrate, said apparatus comprising:

• a tank which holds a carrier fluid;
• a feed pump which pumps the carrier fluid from the tank through the apparatus;
• a metering device through which all of the carrier fluid flows;
• and
• a dosing device which is connected to said metering device and to a reservoir for a concentrated liquid composition, wherein said dosing device pumps the concentrated liquid composition from the reservoir directly into the carrier fluid in said metering device to form the diluted liquid composition;
• said metering device having a drive element which moves in direct proportion to the amount of the carrier fluid flowing through said metering device and being driven only by the flow of the carrier fluid through said metering device, said drive element in turn providing all of the energy required to drive said dosing device;
• said dosing device being connected to the drive element in a manner such that the amount of the concentrated liquid composition pumped into the carrier fluid is directly proportional to the amount of the carrier fluid pumped through said metering device;
• the drive element being a movable piston which defines a moveable barrier between a first chamber and a second chamber in said metering device, said first chamber and said second chamber each comprising an inlet valve and an outlet valve;
• each of said first and second chambers having a volume which increases and decreases relative to the motion of said movable piston, such that the volume of said second chamber will decrease as the volume of said first chamber increases and vice versa;
• wherein, for each of said first and second chambers, said carrier fluid enters said chamber through its respective inlet valve, which is open as its volume increases, with its respective outlet valve being closed, and exiting through its respective outlet valve, which is open as its volume decreases, with its respective inlet valve being closed, the inlet valve of said second chamber being closed when the inlet valve of said first chamber is open, and the outlet valve of said second chamber being closed when the outlet valve of said first chamber is open, and vice versa, such that one of said first and second chambers is filling while the other is emptying, with the amount of carrier fluid passing through said metering device being equal to the product of volume of said chambers and the number of pumping cycles;
• and,
• wherein said dosing device comprises a hollow metering piston with a return valve, said hollow metering piston being displaceable in a dosing chamber, wherein said hollow metering piston is connected to the drive element such that movement of the drive element results in proportional movement of said hollow metering piston, such that the dosing chamber fills with the concentrated liquid composition as said second chamber fills with the carrier fluid, and the concentrated liquid composition is pumped into said first chamber through the hollow metering piston as said first chamber fills with carrier fluid.