Patent ID: 8567610

Claim:
A fuel filter system ( 10 ) of a fuel supply system of an internal combustion engine comprising: a fuel pump ( 18 ) delivering fuel to the internal combustion engine; at least one fuel filter ( 14 ) filtering fuel serving to operate the internal combustion engine; a pressure line ( 16 ) connecting an outlet of said fuel pump ( 18 ) to said at least one fuel filter ( 14 ) and a high pressure section ( 15 ) of said fuel supply system; a water separation device ( 20 separating water from the fuel delivered in said pressure line ( 16 ); a water collecting chamber ( 24 ) connected by a drain line ( 22 ) to said water separation device ( 20 ) to receive the water separated from the fuel; a controllable water discharge valve ( 30 ) arranged in a second water drain line ( 26 ) and operative to open or close said second drain line ( 26 ) to flow, said second drain line interconnecting said water collecting chamber ( 24 ) to said water discharge valve ( 30 ); a cleaning component ( 32 ) operative to clean said separated water of hydrocarbons, said cleaning component ( 32 ) arranged in said second water drain line ( 26 , 28 ) downstream of said water discharge valve ( 30 ); a suction line ( 38 ) connecting and delivering fuel from a fuel tank ( 40 ) to an inlet of said fuel pump ( 18 ); wherein a bidirectional stop-and-check valve ( 44 ; 144 ) is arranged in a connecting line ( 36 ) that interconnects said suction line ( 38 ) and said second water drain line ( 26 ) at a portion ( 28 ) of said second water drain line ( 26 ) between said water collecting chamber ( 24 ) and said cleaning component ( 32 ); wherein said bidirectional stop-and-check valve ( 44 ; 144 ) is operative, at least depending on the pressure in the second water drain line ( 26 ), to block flow between said second water drain line ( 26 ) and said suction line ( 38 ) when a pressure in said second water drain line ( 26 ) is less than pressure in said suction line ( 38 ); wherein said bidirectional stop-and-check valve ( 44 ; 144 ) is operative to open permitting flow between said second water drain line ( 26 ) and said suction line ( 38 ) when a pressure in said second water drain line ( 26 ) is greater than pressure in said suction line ( 38 ) and pressure difference is smaller than a limit pressure difference; wherein said bidirectional stop-and-check valve ( 44 ; 144 ) is operative to block flow between said second water drain line ( 26 ) and said suction line ( 38 ) when a pressure in said second water drain line ( 26 ) is greater than pressure in said suction line ( 38 ) and pressure difference is at least as great as said limit pressure difference.