Abstract: A differential pressure indicator for use with a filter providing dual indication to indicate both a bypass condition as well as an impending bypass condition. The indicator includes a pressure detector in the form of a piston carrying a pair of permanent magnets. A pair of cylinders each carrying a permanent magnet are concentrically disposed around the permanent magnets carried by the piston. As the differential pressure increases, the piston moves pulling the permanent magnets affixed thereto through the concentrically disposed magnets and as a result of magnetic force interaction the concentrically disposed cylinders move to expose first one and then the other of the cylinders to provide the signals representative of the impending bypass as well as bypass differential pressure being sensed.

Abstract: A differential fluid pressure indicator including a bypass valve which provides an indication that the filter is in the bypass condition. The bypass valve includes a differential area piston which includes at the outlet port thereof a restriction orifice adapted to insure a predetermined stroke of the poppet in the bypass valve, thereby to insure actuation of the indicator.

Abstract: A filter comprising a center tube and a porous metal filter pack surrounding the center tube. The filter pack has a plurality of pleats extending longitudinally of the center tube with each of the plates having first and second ends. A metal-to-metal bond seals the first and second ends of the pleats closed. An additional metal-to-metal bond attaches the filter pack to the center tube and seals the filter pack to the center tube. The conventional filter end caps are eliminated to reduce entrapment of debris at the ends of the filter pack and to facilitate cleaning of the filter.