Multiple filter devices

Claim 1

A FILTER DEVICE ADAPTED TO BE CONNECTED TO AN OUTLET PIPE AND TO BE SUBMERGED IN A FLUID RESERVOIR, SAID DEVICE COMPRISING (A) A FILTER CARRIER STRUCTURE SUBMERGED IN SAID RESERVOIR AND HAVING AN OUTLET ADAPTED FOR CONNECTION TO SAID OUTLET PIPE, (B) SAID CARRIER STRUCTURE COMPRISING A FIRST ANNULAR MEMBER AND A SECOND ANNULAR MEMBER, (C) A FIRST FILTER ELEMENT AND A SECOND FILTER ELEMENT CARRIED BY SAID STRUCTURE INTERMEDIATE SAID ANNULAR MEMBERS AND EACH HAVING AN INLET SIDE EXPOSED TO THE FLUID IN SAID RESERVOIR AND AN OUTLET SIDE COMMUNICATING WITH SAID OUTLET. (D) A NORMALLY CLOSED VALVE MEANS CARRIED BY SAID STRUCTURE INTERMEDIATE THE OUTLET SIDES OF SAID FILTER ELEMENTS AND OPERABLE TO REGULATE FLUID FLOW FROM THE OUTLET SIDE OF SAID OF FIRST FILTER ELEMENT IN RESPONSE TO CHANGES IN THE PRESSURE DIFFERENTIAL BETWEEN THE OUTLET SIDES OF SAID FILTER ELEMENTS, AND (E) SAID VALVE MEANS COMPRISING A ROD CARRIED BY SAID CARRIER STRUCTURE AND SECURING SAID ANNULAR MEMBERS TOGETHER AND SAID FILTER ELEMENTS THEREBETWEEN, A WALL CARRIED BY SAID CARRIER STRUCTURE INTERMEDIATE SAID FIRST FILTER ELEMENT AND SAID SECOND FILTER ELEMENT AND HAVING AN OPENING THEREIN, A VALVE MEMBER COMPRISING A HOLLOW BODY NORMALLY EXTENDING INTO SAID OPENING AND HAVING A CLOSED END OPPOSITE SIDES OF WHICH ARE EXPOSED TO THE OUTLET SIDES OF SAID FILTER ELEMENTS, A SHOULDER PORTION ON THE OUTER SURFACE OF SAID BODY AXIALLY SPACED FROM SAID CLOSED END, AND A PLURALITY OF ANNULARLY SPACED SLOTS EXTENDING AXIALLY FROM THE OPEN END OF SAID BODY TO A POINT ADJACENT SAID SHOULDER PORTION, AND BIASING MEANS ENGAGING SAID SHOULDER PORTION AND NORMALLY URGING SAID BODY TOWARD A POSITION IN WHICH SAID SHOULDER PORTION ENGAGES SAID WALL TO CLOSE FLUID FLOW THROUGH SAID OPENING.