Liquid filter system having automatic filter back wash control and method of operation

Claim 2

The combination with a liquid filter for removing solid particles from a liquid, comprising a stationary housing containing therein an inner chamber having a filter screen mounted thereon, a shaft in the interior of and along an axis of said inner chamber, backwasher arms fixedly mounted on said shaft, means for producing relative motion between said arms and screen, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating with the interior of said screen over a path devoid of screening for carrying away the liquid which has been filtered by said screen, of pressure responsive means coupled to said filtered liquid outlet and responsive to an absolute drop in pressure in said filtered liquid outlet below a predetermined pressure, said pressure responsive means connected to and controlling a valve for introducing into said filtered liquid outlet backwash liquid free of debris at an appreciably higher pressure than the normal pressures in either said inlet or said filtered liquid outlet, a second pressure responsive means coupled to said inlet and responsive to a pressure appreciably higher than the normal pressure in said inlet, said second pressure responsive means controlling said valve for terminating the flow of said backwash liquid into said filtered liquid outlet.

Claim 3

The combination of claim 1 wherein said first pressure-responsive means is a first pressure switch, said valve is a double-acting electrically controlled valve, said second pressure responsive means is a second pressure switch, and including electrical connections from said switches to said double-acting electrically controlled valve.

Claim 4

The combination of claim 2 wherein said double-acting electrically controlled valve includes a solenoid having double coils, said first pressure switch being connected to one coil and said second pressure switch being connected to the other coil.

Claim 5

The combination of claim 3, including a horizontal check valve positioned between said valve and said filtered liquid outlet, a gate valve in said inlet, and another horizontal check valve positioned in said inlet between said gate valve and said filter.

Claim 6

The combination of claim 3, including means for maintaining constanT input pressure in said inlet, a gate valve in said outlet to adjust the pressure differential between inlet and outlet, a horizontal check valve positioned between said solenoid valve and said filtered liquid outlet, a gate valve in said inlet, and another horizontal check valve positioned in said inlet between said last gate valve and said filter.

Claim 7

The combination of claim 5, wherein there is provided a shut-off valve for said source of back wash liquid.

Claim 8

The combination of claim 1, wherein said filter includes a liquid distribution arrangement between said inlet and the exterior surface of said screen for distributing the incoming liquid from said inlet substantially uniformly over the length of said screen, and including means for maintaining a normal substantially constant input pressure in said inlet.

Claim 9

In a backwash filter comprising a housing containing a hollow screen, inlet means for distributing the incoming liquid substantially uniformly onto the exterior surface of and over the length of said screen, an outlet communicating with the interior of said screen over a path devoid of screening, the method of operation which includes introducing in said outlet in response to an absolute drop in pressure in said outlet below a predetermined pressure a backwash liquid at a pressure appreciably higher than the normal operating pressures in either said inlet or outlet, whereby the backwash liquid enters the interior of said screen to thereby exert an outwardly directed force for dislodging particles tending to clog the exterior surface of the screen, and terminating the flow of backwash liquid in response to an increase in pressure in said inlet appreciably higher than the normal pressure in said inlet whereby said termination permits inlet pressure to return to normal operating pressure and filtration resumes.

Claim 10

In a backwash filter comprising a housing containing a hollow screen, inlet means for distributing the incoming liquid substantially uniformly onto the exterior surface of and over the length of said screen, an outlet communicating with the interior of said screen over a path devoid of screening, the method of operation which includes introducing in said outlet in response to an absolute drop in pressure in said outlet below a predetermined pressure a backwash liquid at a pressure appreciably higher than the normal operating pressures in either said inlet or outlet, whereby the backwash liquid enters the interior of said screen to thereby exert an outwardly directed force for dislodging particles tending to clog the exterior surface of the screen, and terminating the flow of backwash liquid in response to an increase in pressure in said inlet appreciably higher than the normal pressure in said inlet whereby said termination permits inlet pressure to return to normal operating pressure and filtration resumes.

Claim 11

The combination with a liquid filter for removing solid particles from a liquid, comprising a housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating directly with the interior of said screen for carrying away the filtered liquid over a path substantially unimpeded to the flow of liquid therethrough, of means coupled to said outlet responsive to an absolute drop in pressure in said outlet below a predetermined pressure connected to means for introducing into said outlet backwash liquid free of debris at a pressure appreciably higher than the normal pressures in either said inlet or said outlet, and means coupled to said inlet and responsive to an appreciable increase in pressure above the normal inlet pressure caused by the introduction of said backwash liquid connected to means for terminating the flow of said backwash liquid into said outlet.

Claim 12

The combination with a liquid filter for removing solid particles from a liquid, comprising a housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating directly with the interior of said screen for carrying away the filtered liquid over a path substantially unimpeded to the flow of liquid therethrough, of means coupled to said outlet responsive to an absolute drop in pressure in said outlet below a predetermined pressure connected to means for introducing into said outlet backwash liquid free of debris at a pressure appreciably higher than the normal pressures in either said inlet or said outlet, and means coupled to said inlet and responsive to an appreciable increase in pressure above the normal inlet pressure caused by the introduction of said backwash liquid connected to means for terminating the flow of said backwash liquid into said outlet.

Claim 13

The combination with a liquid filter for removing solid particles from a liquid, comprising a stationary housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, a shaft in the interior of and along an axis of said inner chamber, backwasher arms fixedly mounted on said shaft, means for producing relative motion between said arms and screen, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating with the interior of said screen for carrying away the filtered liquid, of means responsive to a drop in pressure in said filtered liquid outlet below a predetermined pressure controlling means for introducing into said filtered liquid outlet backwash liquid free of debris at a pressure appreciably higher than the pressures in either said inlet or said filtered liquid outlet, said last means including a conduit extending from said filtered liquid outlet to a source of said backwash liquid, and also iNcluding a double-acting electrically controlled valve in said conduit, a first pressure switch communicating with and responsive to a pressure in said inlet greater than the normal inlet pressure due to the pressure of said backwash liquid, a second pressure switch communicating with and responsive to a drop in pressure in said filtered liquid outlet, and electrical connections from said switches to said double-acting controlled valve, said double-acting electrically controlled valve comprising a solenoid having double coils, said first pressure switch being connected to one coil and said second pressure switch being connected to the other coil, said first pressure switch being responsive to said increased pressure in said inlet for operating said solenoid valve to close said conduit, said second switch being responsive to a lowering in pressure in said filtered liquid outlet below a predetermined amount for operating said solenoid to open said conduit and permit the inflow of said backwash liquid into said filtered liquid outlet.

Claim 14

The combination with a liquid filter for removing solid particles from a liquid, comprising a stationary housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, a shaft in the interior of and along an axis of said inner chamber, backwasher arms fixedly mounted on said shaft, means for producing relative motion between said arms and screen, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating with the interior of said screen for carrying away the filtered liquid, of means responsive to a drop in pressure in said filtered liquid outlet below a predetermined pressure controlling means for introducing into said filtered liquid outlet backwash liquid free of debris at a pressure appreciably higher than the pressures in either said inlet or said filtered liquid outlet, said last means including a conduit extending from said filtered liquid outlet to a source of said backwash liquid, and also iNcluding a double-acting electrically controlled valve in said conduit, a first pressure switch communicating with and responsive to a pressure in said inlet greater than the normal inlet pressure due to the pressure of said backwash liquid, a second pressure switch communicating with and responsive to a drop in pressure in said filtered liquid outlet, and electrical connections from said switches to said double-acting controlled valve, said double-acting electrically controlled valve comprising a solenoid having double coils, said first pressure switch being connected to one coil and said second pressure switch being connected to the other coil, said first pressure switch being responsive to said increased pressure in said inlet for operating said solenoid valve to close said conduit, said second switch being responsive to a lowering in pressure in said filtered liquid outlet below a predetermined amount for operating said solenoid to open said conduit and permit the inflow of said backwash liquid into said filtered liquid outlet.

Claim 15

The combination with a liquid filter for removing solid particles from a liquid, comprising a housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating with the interior of said screen for carrying away the filtered liquid, of a valve for introducing into said outlet a source of backwash liquid free of debris at a pressure appreciably higher than the normal pressures in either said inlet or said outlet, a low pressure switch coupled to said outlet and responsive to a drop in pressure in said outlet below a predetermined pressure for opening said valve, a connection between said low pressure switch and said valve, and a high pressure switch coupled to said inlet responsive to an increase in pressure in said inlet above the normal pressure therein caused by the flow of said backwash liquid for closing said valve to terminate the flow of backwash liquid into said outlet.

Claim 16

The combination with a liquid filter for removing solid particles from a liquid, comprising a housing containing therein an inner chamber spaced therefrom, said inner chamber having a filter screen mounted thereon, an inlet for introducing the liquid to be filtered through an opening in said housing and onto the exterior surface of said screen, a filtered liquid outlet communicating with the interior of said screen for carrying away the filtered liquid, of a valve for introducing into said outlet a source of backwash liquid free of debris at a pressure appreciably higher than the normal pressures in either said inlet or said outlet, a low pressure switch coupled to said outlet and responsive to a drop in pressure in said outlet below a predetermined pressure for opening said valve, a connection between said low pressure switch and said valve, and a high pressure switch coupled to said inlet responsive to an increase in pressure in said inlet above the normal pressure therein caused by the flow of said backwash liquid for closing said valve to terminate the flow of backwash liquid into said outlet.