Self-cleaning filter apparatus

Claim 1

Filter apparatus comprising means defining two fluid passages each containing a filter unit, said passages extending between a common upstream junction which is connected to means defining an inlet for fluid to be filtered, and a common downstream junction which is connected to means defining an outlet for filtered fluid, and the upstream portions of said passages each having parallel outer and inner walls, said outer walls being extended in an upstream direction to define an input nozzle interposed between said inlet and said common upstream junction for issuing a stream of fluid to be filtered into the space bounded by said outEr wall extensions and said inner walls being formed by the outer surfaces of a flow divider separating the entries to said passages at a point downstream of and in substantial axial alignment with said nozzle, the arrangement being such that a stream of fluid to be filtered issuing from said input nozzle automatically flows through one of said passages and its associated filter unit to said downstream junction from whence the major proportion of the filtered fluid flows through said outlet and a minor proportion of said fluid returns to said upstream junction through the other of said passages and the inoperative filter unit therein to clean the latter, and the flow of fluid through said passages is periodically switched solely in response to increased pressure difference between said upstream junction and said downstream junction through said temporarily operative filter.