Cooling system expansion tank

1. A tank for a cooling system of a liquid-cooled internal combustion engine, the tank comprising a plastic housing having an inlet port for connection to a supply of coolant discharged from the engine and an outlet port located at the bottom of the tank for the return of coolant to the engine, wherein a non-return valve is located in the outlet port to limit coolant backflow into the tank through the outlet port, wherein the non-return valve is molded as a single component, and wherein the outlet port has a surface forming a valve seat and the non-return valve has a valve head shaped for cooperation with the valve seat and wherein the valve head is dished having a concave side facing away from the valve seat and a convex side facing toward the valve seat.

2. A tank as claimed in claim 1 wherein the non-return valve is operable to close off the outlet port when there is a negative pressure differential above a threshold between the tank and a return conduit connecting the outlet port to the cooling system.

3. A tank as claimed in claim 1 wherein the convex side of the valve head is one of part conical and part spherical.

4. A tank as claimed in claim 1 wherein the non-return valve has an elongate body connecting the valve head to a retainer used to retain the non-return valve in the outlet port.

5. A tank as claimed in claim 4 wherein the retainer comprises at least two outwardly extending flexible arms attached to one end of the elongate body.

6. A tank as claimed in claim 1 wherein the non-return valve is connected to the outlet port by a thin flexible tether.

7. A tank as claimed in claim 1 wherein a flow restrictor is located in the inlet port which forms a restrictor housing.

8. A tank for a cooling system of a liquid-cooled internal combustion engine, the tank comprising a plastic housing having an inlet port for connection to a supply of coolant discharged from the engine and an outlet port located at the bottom of the tank for the return of coolant to the engine, wherein a non-return valve is located in the outlet port to limit coolant backflow into the tank through the outlet port, wherein the non-return valve is molded as a single component, wherein the outlet port has a surface forming a valve seat and the non-return valve has a valve head shaped for cooperation with the valve seat wherein the valve head is dished having a concave side facing away from the valve seat and a convex side facing toward the valve seat;

wherein a flow restrictor is located in the inlet port which forms a restrictor housing; and wherein the restrictor comprises a restrictor body fitted inside the restrictor housing wherein the restrictor body is an elongate body having a number of alternating first and second circumferentially extending passages formed therein, each first passage being separated from a respective adjacent second passage by a respective land and at least one transfer passage extending through each land so as to connect the first and second passages on each side of the land and in use produce a momentum loss as the coolant is transferred therethrough.

9. A tank as claimed in claim 8 wherein an outlet end of each transfer passage is inclined with respect to the flow of fluid through the first and second passages with which it cooperates at an acute angle and an inlet end of each transfer passage is inclined with respect to the flow of fluid through the first and second passages with which it cooperates at an obtuse angle.

10. A tank as claimed in claim 9 wherein the inclination of the outlets from the transfer passages causes fluid to flow in a first direction in the first passages and in a second opposite direction in the second passages.

11. A tank as claimed in claim 8 wherein the restrictor body is molded as a single component with the expansion tank.

12. A tank as claimed in claim 11 wherein the restrictor body is connected to the inlet port by an integrally formed thin flexible tether.

13. A tank for a cooling system of a liquid-cooled internal combustion engine, the tank comprising a plastic housing having an inlet port for connection to a supply of coolant discharged from the engine and an outlet port located at the bottom of the tank for the return of coolant to the engine, wherein a non-return valve is located in the outlet port to limit coolant backflow into the tank through the outlet port, wherein the outlet port has a surface forming a valve seat and the non-return valve has a valve head shaped for cooperation with the valve seat wherein the valve head is dished having a concave side facing away from the valve seat and a convex side facing toward the valve seat;

wherein a flow restrictor is located in the inlet port which forms a restrictor housing; and wherein the restrictor comprises an elongate plastic restrictor body fitted inside the restrictor housing, the restrictor body having a number of alternating first and second circumferentially extending passages formed therein, each first passage being separated from a respective adjacent second passage by a respective land and first and second transfer passages connecting the first and second passages on each side of the land to an internal swirl chamber used to produce a momentum loss as the coolant is transferred through the swirl chamber.

14. A tank as claimed in claim 13 wherein each first transfer passage is an inlet passage through which in use fluid flows from one of the circumferentially extending passages into the swirl chamber.

15. A tank circuit as claimed in claim 14 wherein each inlet passage is arranged tangentially with respect to the swirl chamber with which it cooperates so as to generate a circulatory flow within the swirl chamber.

16. A tank as claimed in claim 14 wherein the second transfer passage is an outlet passage to transfer fluid from the swirl chamber to a circumferentially extending passage and wherein each swirl chamber has a large diameter portion with which at least one inlet transfer passage cooperates and a small diameter portion with which at least one outlet transfer passage cooperates.

17. A tank as claimed in claim 13 wherein the second transfer passage is an outlet passage to transfer fluid from the swirl chamber to a circumferentially extending passage.

18. A tank as claimed in claim 13 wherein the flow restrictor includes at least two swirl chambers spaced out along its length.

19. An expansion tank for a cooling system of a liquid-cooled internal combustion engine, the tank comprising a plastic housing having an inlet port for connection to a supply of coolant discharged from the engine and an outlet port for connection to a return line through which coolant returns to the engine, wherein the tank has a top and a bottom, wherein the outlet port is located at the bottom of the tank, wherein a non-return valve is located in the outlet port to limit coolant backflow into the tank through the outlet port, wherein the non-return valve has an elongate body connecting the valve head to a retainer used to retain the non-return valve in the outlet port, and wherein the retainer comprises at least two outwardly extending flexible arms attached to one end of the elongate body.

20. An expansion tank for a cooling system of a liquid-cooled internal combustion engine, the tank comprising a plastic housing having an inlet port for connection to a supply of coolant discharged from the engine and an outlet port for connection to a return line through which coolant returns to the engine, wherein the tank has a top and a bottom, wherein the outlet port is located at the bottom of the tank, wherein a non-return valve is located in the outlet port to limit coolant backflow into the tank through the outlet port, and wherein a flow restrictor is located in the inlet port which forms a restrictor housing, wherein the restrictor comprises a restrictor body fitted inside the restrictor housing, wherein the restrictor body is an elongate body having a number of alternating first and second circumferentially extending passages formed therein, each first passage being separated from a respective adjacent second passage by a respective land and at least one transfer passage extending through each land so as to connect the first and second passages on each side of the land and in use produce a momentum loss as the coolant is transferred therethrough, wherein the non-return valve is molded as a single component, wherein the outlet port has a surface forming a valve seat and the non-return valve has a valve head shaped for cooperation with the valve seat and wherein the valve head is dished having a concave side facing away from the valve seat and a convex side facing toward the valve seat.

21. A tank as claimed in claim 20 wherein the restrictor body is connected to the inlet port by an integrally formed thin flexible tether.