Means for backwashing a filter bed

Claim 1

IN COMBINATION WITH A CHAMBER HAVING INLET AND OUTLET OPENINGS SEPARATED BY A FILTER BED, A SOURCE OF LIQUID, A REVERSIBLE PUMP HAVING OPENINGS WHICHSERVE INTERCHANGEABLY AS INLET AND OUTLET DEPENDING UPON THE DIRECTION IN WHICH SAID REVERSIBLE PUMP IS DRIVEN, A CONDUIT BETWEEN SAID LIQUID SOURCE AND THE SIDE OF SAID PUMP WHICH NORMALLY OPERATES AS THE INLET OR SUCTION SIDE, A CONDUIT BETWEEN THE INLET OPENING OF THE CHAMBER AND THE OTHER OR NORMAL OUTLET OR PRESSURE SIDE OF THE PUMP, A CONDUIT BETWEEN THE OUTLET OPENING OF THE CHAMBER AND THE LIQUID SOURCE, A NORMALLY ISOLATED WASTE CONDUIT, AND MEANS OPERATED AUTOMATICALLY BY THE ACT OF REVERSING SAID PUMP, SO AS TO BACKWASH THE FILTER BED, SERVING TO COINCIDENTLY BRING THE THEN DISHCARGE SIDE OF THE PUMP INTO COMMUNICATION WITH THE WASTE CONDUIT AND ISOLATING SAID DISCHARGE SIDE FROM THE LIQUID SOURCE, SAID PUMP BEING OF THE PROPELLER TYPE COMPRISED OF MULTIPLE INLINE PROPELLER BLADES OCUPYING A TUBULAR CASING OF SUBSTANTIALLY UNIFORM DIAMETER THROUGHOUT ITS LENGTH AND DRIVEN IN OPPOSITE DIRECTIONS OF ROTATION, SELECTIVELY, AND HAVING THE SEVERAL BLADES SEPARATED ONE FROM ANOTHER BY STATIONARY STRAIGHTENER VANES.