Filter with automatic backwash control

Claim 1

A FILTER COMPRISING, A FILTER CHAMBER CONTAINING A FILTER BED, A BACKWASH WATER STORAGE COMPARTMENT EXTENDING ABOVE SAID CHAMBER, AN UNDERDRAIN COMPARTMENT EXTENDING BELOW SAID FILTER CHAMBER AND IN CONTINUOUS COMMUNICATION WITH SAID STORAGE COMPARTMENT, A FILTERED WATER OUTLET CONNECTED TO SAID UNDERDRAIN COMPARTMENT, A WATER INLET CONNECTED TO THE TOP OF SAID FILTER CHAMBER, A BACKWASH CONDUIT HAVING AN INLET END CONNECTED TO THE UPPER PORTION OF SAID FILTER CHAMBER AND AN OUTLET END DISPOSED AT AN ELEVATION BELOW SAID UNDERDRAIN COMPARTMENT, A WASTE OUTLET DISPOSED TO RECEIVE LIQUID FROM THE OUTLET END OF SAID BACKWASH CONDUIT, A BACKWASH CONTROL VALVE INTERPOSED IN SAID BACKWASH CONDUIT, A VERTICALLY ELONGATED FLOAT CHAMBER EXTENDING UPWARDLY FROM SAID VALVE TO AN ELEVATION SUBSTANTIALLY ABOVE THE TOP OF SAID STORAGE COMPARTMENT, THE LOWER END OF SAID FLOAT CHAMBER BEING IN COMMUNICATION WITH SAID BACKWASH CONDUIT, AND A FLOAT IN SAID FLOAT CHAMBER OPERATIVELY CONNECTED TO SAID VALVE AND MOVABLE IN RESPONSE TO CHANGES IN LEVEL OF LIQUID IN SAID FLOAT CHAMBER TO ACTUATE SAID VALVE TO AND FROM CLOSED POSITION, WHEREBY BACKWASH FLOW THROUGH SAID FILTER CHAMBER IS INITIATED BY THE OPENING OF SAID VALVE WHEN PRESSURE LOSS ACROSS THE FILTER BED CAUSES A PREDETERMINED RISE IN THE HEAD OF WATER IN SAID FLOAT CHAMBER, AND MEANS FOR TERMINATING THE BACKWASH FLOW UPON A DROP OF THE LIQUID LEVEL IN SAID STORAGE COMPARTMENT TO A PREDETERMINED LOW LEVEL.