Check valve with improved response time

1. A check valve comprising:

a valve housing including a well defined in the valve housing, a retainer associated with the valve housing and a valve seat; and

a valve member which is movable between a closed seated position and an open position to allow fluid flow in one direction from an inlet port to an outlet port, wherein said valve member is disc shaped and comprises:

i. a central portion which maintains a substantially continuous convex curvature occupying substantially all the central portion and extending towards the outlet port extending in the direction of fluid flow when in either the closed seated position or the open position,

ii. a flat peripheral portion around the substantially continuous convex curvature of the central portion, the flat peripheral portion in contact with a cooperative sealing surface of the valve seat when said valve member is in the closed seated position, and

iii. a guide portion that surrounds said central portion and said flat peripheral portion, said guide portion being thinner than said central portion and said flat peripheral portion and having a weight to area ratio that is smaller than the weight to area ratio of said central portion; and

wherein said guide portion travels within said well defined in said valve housing between the valve seat when in the seated position and said retainer when in a fully open position.

2. The check valve of claim 1 wherein said central portion comprises a material which resists deflection, fatigue and deformation.

3. The check valve of claim 1 wherein said guide portion defines several orifices therein through which said fluid can flow when said valve member is in said open position.

4. The check valve of claim 3 wherein said orifices are shaped to increase the cross-sectional flow area through said valve and reduce pressure drop.

5. The check valve of claim 4 wherein said orifices have a kidney-shaped cross-sectional area.

6. The check valve of claim 1 wherein said guide portion comprises a plurality of arms which are connected to said central portion.

7. The check valve of claim 6 further comprising a guiding mechanism having a shape that cooperates with one of said plurality of arms.

8. The check valve of claim 7 wherein said guiding mechanism is a pin, the pin being aligned with an orifice associated with the one of said plurality of arms whereby said pin guides movement of the valve member when it moves between said seated and said open position.

9. The check valve of claim 8 further comprising an elastic element disposed between said valve member and said valve housing and associated with said pin.

10. The check valve of claim 7 wherein said guiding mechanism comprises a channel provided in said valve housing, said channel receiving said one of said plurality of arms and guiding said one of said plurality of arms when said valve member moves between said seated and said open position.

11. The check valve of claim 1 wherein said valve member has a composite structure, said central portion made from a material heavier than a material from which said guide portion is made.

12. The check valve of claim 1 wherein said central portion of said valve member is made from metal and said guide portion is made from a polymeric material.

13. The check valve of claim 1 wherein said central portion comprises a core made of metal, said core being coated with a polymeric layer which extends beyond said central portion and forms said guide portion.

14. The check valve of claim 1 wherein said central portion further comprises a side that faces an inlet port which has a substantially convex shape with a central convex curvature extending towards said inlet port.

15. The check valve of claim 14 wherein said central portion comprises a hollow volume between said opposing convex curvatures.

16. The check valve of claim 1 , wherein the valve member is free-floating.

17. A piston pump comprising a piston which is moved within a pump cavity to increase the pressure of a fluid which enters the pump through an inlet port and which is delivered to a fluid system through an outlet port, the piston pump further comprising the check valve of claim 1 whose inlet port is in fluid communication with said inlet port of said pump.

18. The piston pump of claim 17 wherein said guide portion of said valve member comprises a plurality of orifices through which said fluid can flow when said valve member is in said open position.

19. The piston pump of claim 18 wherein said orifices of said guide portion of said valve member are shaped to increase the cross-sectional flow area through said valve and reduce pressure drop.

20. The piston pump of claim 19 wherein said orifices have a kidney-shaped cross-sectional flow area.

21. The piston pump of claim 17 wherein said central portion of said valve member is made of metal and wherein said piston pump further comprises a mechanism for reducing the fluid forces needed to lift said valve member from said valve seat, said mechanism comprising a permanent magnet mounted in said piston of said pump.

22. A check valve comprising:

a valve housing including a well defined in the valve housing, a retainer associated with the valve housing and a valve seat; and

a valve member which is movable between a closed seated position and an open position to allow fluid flow in one direction from an inlet port to an outlet port, wherein said valve member is disc shaped having an outer circumferential edge and comprises;

i. a central portion which maintains a substantially continuous convex curvature extending towards the outlet port in the direction of fluid flow when in either the closed seated position or the open position,

ii. a flat peripheral portion around the substantially continuous convex curvature of the central portion, the flat peripheral portion substantially perpendicular to the direction of fluid flow and in contact with a cooperative sealing surface of the valve seat when said valve member is in the closed seated position, and

iii. a guide portion that surrounds said central portion and said flat peripheral portion and is defined in part by said outer circumferential edge, said guide portion being thinner than said central portion and said flat peripheral portion and having a weight to area ratio that is smaller than the weight to area ratio of said central portion; and

wherein said outer circumferential edge of said valve member travels within said well defined in said valve housing between the valve seat when said valve member is in the seated position and said retainer when in a fully open position.