Dual filter device

Claim 1

A FILTER DEVICE COMPRISING (A) A HOUSING PROVIDED WITH A FILTER CHAMBER, (B) AN INLET AND AN OUTLET PROVIDED IN SAID HOUSING AND COMMUICATING WITH SAID FILTER CHAMBER, (C) A CARRIER STRUCTURE AXIALLY SLIDABLY MOUNTED WITHIN SAID FILTER CHAMBER, (D) A FIRST AND A SECOND FILTER ELEMENT CARRIED BY SAID CARRIER STRUCTURE IN AN AXIALLY ALIGNED POSITION, (E) VALVE MEANS CARRIED IN SAID HOUSING INTERMEDIATE SAID FILTER ELEMENTS AND INCLUDING A VALVE MEMBER CARRIED BY SAID CARRIER STRUCTURE AND MOVABLE WITH SAID CARRIER STRUCTURE INTERMEDIATE A POSITION SUBSTANTIALLY CLOSING COMMUNICATION BETWEEN THE OUTLET SIDES OF SAID FILTER ELEMENTS AND A POSITION OPENING COMMUNICATION BETWEEN THE OUTLET SIDES OF SAID FILTER ELEMENTS, (F) MEANS URGING SAID CARRIER STRUCTURE TOWARD A POSITION IN WHICH SAID VALVE MEMBER IS IN THE CLOSED POSITION, (G) PRESSURE RESPONSIVE MEANS CARRIED BY SAID CARRIER STRUCTURE AND OPERABLE TO RESPOND TO INCREASES IN THE PRESSURE DIFFERENTIAL ACROSS ONE OF SAID FILTER ELEMENTS TO MOVE SAID CARRIER STRTUCTURE TOWARD A POSITION IN WHICH SAID VALVE MEMBER IS IN THE OPEN POSITION, (H) MEANS ACTUATED BY SAID CARRIER STRUCTURE TO OPEN FLUID FLOW DIRECTLY FROM THE INLET SIDE OF SAID FIRST FILTER ELEMENT TO SAID OUTLET IN RESPONSE TO A PREDETERMINED DIFFERENTIAL PRESSURE INCREASE BETWEEN THE INLET AND THE OUTLET SIDES OF SAID FIRST FILTER ELEMENT.