Fluid pump and outlet check valve assembly thereof

A fluid pump comprising:

• a housing;
• an inlet passage through which fluid enters said housing;
• an outlet conduit through which fluid leaves said housing;
• a pumping element within said housing, said pumping element being configured to draw fluid into said inlet passage and pressurize said fluid which is discharged through said outlet conduit;
• and
• a check valve assembly, which allows flow through said outlet conduit in a first direction and prevents flow through said outlet conduit in a second direction which is opposite said first direction, said check valve assembly comprising:
• said outlet conduit;
• and
• a valve stem within said outlet conduit such that a flow path is created radially between said outlet conduit and said valve stem, said valve stem moving along a check valve assembly axis between a closed position which prevents fluid flow through said flow path and an open position which permits fluid flow through said flow path;
• wherein said flow path includes a first restriction which increases velocity of fluid passing through said flow path;
• a first expansion, downstream of said first restriction, which decreases velocity of fluid passing through said flow path;
• a second restriction, downstream of said first expansion, which increases velocity of fluid passing through said flow path;
• and a second expansion, downstream of said second restriction, which decreases velocity of fluid passing through said flow path;
• wherein said outlet conduit includes an inner wall surface;
• wherein said valve stem includes a valve stem seating surface which 1) seats against said inner wall surface when said valve stem is in said closed position, thereby preventing fluid flow through said flow path and 2) is spaced apart from said inner wall surface when said valve stem is in said open position, thereby permitting fluid flow through said flow path;
• wherein said first restriction is formed between said valve stem seating surface and said inner wall surface;
• wherein said inner wall surface has an inner wall surface diverging section which diverges away from said check valve assembly axis when moving along said check valve assembly axis in said first direction;
• wherein said valve stem seating surface seats against said inner wall surface diverging section when said valve stem is in said closed position;
• wherein said inner wall surface has an inner wall surface converging section, downstream of said inner wall surface diverging section, which converges toward said check valve assembly axis in said first direction;
• wherein said valve stem has a valve stem converging section which converges toward said check valve assembly axis in said first direction;
• and
• wherein said first expansion is located radially between said inner wall surface converging section and said valve stem converging section.