Fluid system fittings

Claim 1

A FILTERING MEANS FOR A REVERSE FLOW FLUID SYSTEM COMPRISING (A) A CENTRAL MOUNTING BLOCK HAVING A FIRST AND A SECOND PORT THEREIN EACH ADAPTED FOR CONNECTION WITH A FLUID SYSTEM, (B) A FIRST AND A SECOND ENCLOSED FILTER DEVICE MOUNTED ON OPPOSED FACES OF SAID MOUNTING BLOCK, EACH FILTER DEVICE HAVING A FLUID INLET AND A FLUID OUTLET PASSAGE, (C) A FIRST PASSAGE BEING PROVIDED IN SAID MOUNTING BLOCK CONNECTING SAID FLUID INLET PASSAGE OF SAID FIRST FILTER DEVICE AND SAID FLUID OUTLET PASSAGE OF SAID SECOND FILTER DEVICE WITH SAID FIRST MOUNTING BLOCK PORT, AND A SECOND PASSAGE WITH SAID FIRST MOUNTING BLOCK PORT, BLOCK CONNECTING SAID FLUID INLET PASSAGE OF SAID SECOND FILTER DEVICE AND SAID FLUID OUTLET PASSAGE OF SAID FIRST OUTLET PASSAGE OF SAID FIRST FILTER DEVICE WITH SAID SECOND MOUNTING BLOCK PORT, (D) A FIRST CHECK VALVE MEANS AND A SECOND CHECK VALVE MEANS EACH MOUNTED IN SAID MOUNTING BLOCK, (C) SAID FIRST CHECK VALVE MEANS BEING MOUNTED IN SAID FIRST PASSAGE INTERMEDIATE SAID FLUID OUTLET PASSAGE OF SAID SECOND FILTER DEVICE AND SAID FIRST PORT AND BEING OPERABLE TO BLOCK FLUID FLOW IN A DIRECTION FROM SAID FIRST PORT TO SAID FLUID INLET PASSAGE SAID SECOND FILTE DEVICE AND TO PERMIT FLUID FLOW FROM SAID FLUID OUTLET PASSAGE OF SAID SECOND FILTER DEVICE TO SAID FIRST PORT, (F) SAID SECOND CHECK VALVE MEANS BEING MOUNTED IN SAID SECOND PASSAGE INTERMEDIATE SAID FLUID OUTLET PASSAGE AND BEING OPERABLE TO BLOCK FLUID FLOW IN A PORT AND BEING OPERABLE TO BLOCK FLUID FLOW IN A DIRECTION FROM SAID SECOND PORT TO SAID FLUID OUTLET PASSAGE OF SAID FIRST FILTER DEVICE AND TO PERMIT FLUID FLOW FROM SAID FLUID OUTLET PASSAGE OF SAID FIRST FILTER DEVICE TO SAID SECOND PORT.