Filtering elements

Abstract From the Canadian patent

A back-washable filtering element especially for, use with pumps, and more particularly for use with pumps that handle liquids with solid material entrained therein consists, of a helical coil spring disposed in a flow path for the liquid to be filtered. A movable element in the flow path is mechanically connected to the spring and compresses it axially under the effect of the back washing liquid to automatically reduce the flow capacity. The resultant "shrugging" of the spring also permits it to clear itself of filtered material to facilitate the back-washing.