Backwashing control for multipleseptum filter bed

Claim 1

A FILTER SYSTEM COMPRISING, IN COMBINATION: A FILTER TANK PROVIDING A CHAMBER HAVING INLET AND OUTLET OPENINGS SEPARATED BY A PLURALITY OF FILTER BEDS EACH PRESENTING A FILTERING SURFACE ON WHICH DIRT FILTERED FROM LIQUID FORCED THROUGH SAID TANK IN THE COURSE OF A FILTERING RUN IS DEPOSITED AS A COATING, MEANS OPERATING IN CYCLES FOR PUMPING SAID LIQUID THROUGH THE TANK WITH THE LIQUID ENTERING VIA THE INLET OPENING IN ONE CYCLE AND VIA THE OUTLET OPENING IN ANOTHER CYCLE SO AS IN THE FORMER INSTANCE TO FILTER THE LIQUID AND IN THE LATTER INSTANCE TO BACKWASH THE FILTER BEDS, A VALVING MEANS INCLUDING A RECIPROCALLY MOVABLE SHUTTLE VALVE AND MEANS TO CONNECTED SAID SHUTTLE VALVE WITH THE FILTER BEDS SUCH THAT WHEN THE SHUTTLE VALVE MOVES THROUGH ONE STROKE OF ITS RECIPROCATORY MOVEMENT FROM A NORMALLY OCCUPIED LOCALIZED POSITION AT ONE EXTREME THEREOF THE BACKWASH CYCLE IS PERFORMED IN SUCCESSIVE STAGES WHICH ARE ALL OF EQUAL DURATION AND DURING EACH OF WHICH STAGES SEPARATE GROUPS OF BEDS ARE BACKWASHED BY THE PUMPED LIQUID WITH EACH GROUP COMPOSED OF A RESPECTIVE GIVEN NUMBER OF THE BEDS LESS THAN THE WHOLE AND WHEN THE SHUTTLE VALVE HAS RETURNED TO SAID NORMAL POSITION THE FILTERING CYCLE IS THEN PERFORMED IN A SINGLE STAGE DURING WHICH ALL OF THE BEDS ARE CONCURRENTLY TRAVERSED BY THE PUMPED LIQUID, AN AIR CHAMBER WITHIN SAID TANK CHAMBER, SAID AIR CHAMBER INCLUDING TWO OPENINGS TO COMMUNICATE SAID AIR CHAMBER WITH THE ATMOSPHERE, A DIAPHRAGM HAVING ONE SIDE EXPOSED TO THE PRESSURE WHICH OBTAINS WITHIN THE TANK CHAMBER BETWEEN THE FILTER BEDS AND THE OPENING THROUGH WHICH LIQUID TO FILTERED ENTERS THE CHAMBER AND HAVING ITS OTHER SIDE EXPOSED TO THE PRESSURE WHICH OBTAINS IN SAID AIR CHAMBER, ONE OF SAID OPENINGS HAVING MEANS TO PERMIT ATMOSPHERIC AIR TO ENTER THE AIR CHAMBER AT A CHOKED RATE OF VOLUMETRIC FLOW, THE OTHER OF SAID OPENINGS HAVING A FITTING MEANS THEREIN PERMITTING RETURN UNIDIRECTIONAL FLOW TO THE ATMOSPHERE AT A FAST