Apparatus for and method of filtering solid particles from a particulate-bearing liquid

Claim 1

A method of filtering solid particles from a particulate-bearing liquid, comprising: supplying a head of water above a filter bed; pressurizing and dissolving a gas in the particulate-bearing liquid; ejecting and depressurizing said agitated liquid at a point below the surface of said head, the quantity of depressurization being controlled by a back pressure valve; sensing the presence and absence of an obstruction within said valve; opening said valve in response to said obstruction being sensed as present; closing said valve to a predetermined position after a predetermined period of time has elapsed from when said obstruction has been sensed as absent; removing said froth from the surface of said head; and withdrawing filtered water from a filtered water discharge port beneath said filter bed, thereby causing water to flow through said filter bed.

Claim 2

A method of filtering solid particles from a particulate-bearing liquid, comprising: supplying a head of water above a filter bed; pressurizing and dissolving a gas in the particulate-bearing liquid; ejecting and depressurizing said agitated liquid at a point below the surface of said head, the quantity of depressurization being controlled by a back pressure valve; sensing the presence and absence of an obstruction within said valve; opening said valve in response to said obstruction being sensed as present; closing said valve to a predetermined position after a predetermined period of time has elapsed from when said obstruction has been sensed as absent; removing said froth from the surface of said head; and withdrawing filtered water from a filtered water discharge port beneath said filter bed, thereby causing water to flow through said filter bed.

Claim 4

An apparatus for filtering solid particles from a particulate-bearing liquid, comprising: a tank; a head of water contained within said tank; a filter bed positioned at the bottom of said tank; means for pressurizing said particulate-bearing liquid and dissolving a gas therein; conduit means delivering said pressurized, gas-entrained liquid to a point beneath the surface of said head; a back pressure valve disposed within said conduit for controlling the pressure drop through said conduit; a valve actuator adapted to open and close said valve; a sensor for determining the presence and absence of an obstruction within said valve and for producing a signal indicative thereof; means for energizing said valve actuator to open said valve in response to said sensor indicating the presence of an obstruction within said valve; a time-delay relay adapted to energize said valve actuator to close said valve to a predetermined position a predetermined time after said time-delay relay is energized; means for energizing said time-delay relay in response to said sensors indicating the absence of an obstruction within said valve; a sludge collector for removing said froth from the surface of said head; and a filtered water discharge port beneath said filter bed.

Claim 5

An apparatus for filtering solid particles from a particulate-bearing liquid, comprising: a tank; a head of water contained within said tank; a filter bed positioned at the bottom of said tank; means for pressurizing said particulate-bearing liquid and dissolving a gas therein; conduit means delivering said pressurized, gas-entrained liquid to a point beneath the surface of said head; a back pressure valve disposed within said conduit for controlling the pressure drop through said conduit; a valve actuator adapted to open and close said valve; a sensor for determining the presence and absence of an obstruction within said valve and for producing a signal indicative thereof; means for energizing said valve actuator to open said valve in response to said sensor indicating the presence of an obstruction within said valve; a time-delay relay adapted to energize said valve actuator to close said valve to a predetermined position a predetermined time after said time-delay relay is energized; means for energizing said time-delay relay in response to said sensors indicating the absence of an obstruction within said valve; a sludge collector for removing said froth from the surface of said head; and a filtered water discharge port beneath said filter bed.