So many sprayers feature additional secondary filters near each nozzle for capturing bits of debris that pass through the primary filter. Clogging of the secondary filters means downtime for the operator, who must stop spraying while the filters are cleaned out. Hoffman's nozzle system eliminates clogging and daily maintenance by automatically cleaning these secondary filters without interrupting the spraying process. In addition, the system reduces the exposure of operators to pesticides, yet provides an even application of chemicals to the area being sprayed. In his system, there are two flow lines to each nozzle, and each line has its own secondary filter near each nozzle.
Valves direct the liquid from the spray tank and pump to each flow line.
In essence, the water and the chemical mixture that are not sprayed out the nozzles are actually recirculated within the sprayer and eventually end up back in the spray tank. Liquid cannot pass through to the nozzle at the same rate the pump is set to discharge it from the tank. So a portion of the liquid passes into the second flow line and through its secondary filter to clean it out. This liquid, along with the debris it carries, will then exit the filter housing through the second flow line. The liquid and the debris flow through a valve system to a return line before going back to the spray tank.