Dual-valve, dual-element, constant flow, filter assembly

Claim 1

A FILTER ASSEMBLY COMPRISING A HOUSING HAVING INLET AND OUTLET PASSAGES; A PRIMARY FILTER ELEMENT DISPOSED IN THE HOUSING; A PRIMARY PASSAGE LEADING FROM THE INLET ONLY TO THE PRIMARY FILTER ELEMENT; A SECONDARY FILTER ELEMENT DISPOSED IN THE HOUSING AND LOCATED ADJACENT TO AND DOWNSTREAM OF A DOWNSTREAM PORTION OF SAID PRIMARY FILTER ELEMENT; A SECONDARY PASSAGE LEADING FROM THE INLET TO THE SECONDARY FILTER ELEMENT, AND A FLOW CONTROL VALVE ASSEMBLY COMPRISING AN ORIFICE DISPOSED IN THE PRIMARY PASSAGE TO DIRECT ALL NORMAL FLOW TO AND THROUGH THE PRIMARY FILTER ELEMENT, THE PRIMARY FILTER ELEMENT RECEIVING FLUID IN A PREDETERMINED QUANTITY FOR FILTRATION AT ALL TIMES VIA THE ORIFICE, AND DELIVERING FILTERED FLUID FOR DELIVERY AT THE OUTLET PASSAGE OF THE HOUSING, AND A PRESSURE-SENSITIVE SPRING DISK VALVE, DISPOSED IN THE HOUSING ACROSS THE SECONDARY PASSAGE AND NORMALLY CLOSING OFF FLOW TO THE SECONDARY FILTER ELEMENT THROUGH THE SECONDARY PASSAGE, BUT RESPONSIVE TO A PREDETERMINED FLUID PRESSURE DIFFERENTIAL BETWEEN THE PRIMARY PASSAGE AND THE SECONDARY PASSAGE CAUSED BY AN EXCESSIVE VOLUME OF FLOW THROUGH THE ORIFICE, TO OPEN AND ALLOW SUCH EXCESS FLOW TO PASS DIRECTLY TO AND THROUGH THE SECONDARY FILTER ELEMENT, WHILE CONTINUING NORMAL FLOW TO AND THROUGH THE PRIMARY FILTER ELEMENT VIA THE ORIFICE, SO THAT BOTH NORMAL AND EXCESS FLOW THROUGH THE FILTER ASSEMBLY ARE FILTERED, AND NORMALLY NO UNFILTERED FLOW PASSES DIRECTLY TO THE SECONDARY FILTER ELEMENT.