Programmed method of and apparatus for screening debris

Abstract

A programmed bar screen cleaner removes debris from a screen positioned in a channel to prevent the flow of the debris to a liquid treatment. A rake has tines for engaging the screen to move the debris toward and past an upper end of the screen to remove the debris from the screen. Automatic and controllable raking operations are provided to handle the situation in which there is debris jammed in the screen. The jammed debris resists the movement of the rake along the screen, which is sensed via rake motor overloaded, indicated by motor current in excess of a limit. The existence of a jammed rake causes positive release of the rake from the face of the bars, and further movement of the rake is controlled according to the nature of the problem which caused the jamming. If the rake jams during a raking stroke, the jam is sensed, and according to the nature of the problem, the rake may be positively removed from the face of the bars, and then either returned to an original position at the beginning of the stroke, or advanced in the direction of the original stroke and then returned to the face for completion of the stroke, or advanced in the direction of the original stroke, then returned to the face, and then moved toward the original position at the beginning of the stroke to remove the cause of the jamming from the face of the bars.