| 摘要 |
A check valve includes an outer valve body and an inner poppet valve moveable relative to the valve body and spring-biased into a closed position. The inner poppet valve has first and second stage openings. The first stage preferably has a single, relatively small through-hole into the chamber of the poppet valve, while the second stage preferably has multiple openings of a larger diameter. The first and second stage openings are spaced axially along the poppet valve, with the first stage opening being located closer to the valve head of the poppet valve than the second stage openings. In the closed position, fluid flow is blocked through both the first and second stage openings. When the cracking force of the valve is exceeded and the valve head moves away from the valve seat, fill flow occurs through the first stage opening and is restricted through the second stage openings. The restricted fluid flow causes the pressure drop across the check valve to be satisfactory at low flow rates to cause the poppet valve to stroke long enough such that particles will pass easily between the valve head and the valve seat. The flow increases through the second stage openings as the poppet valve moves toward its open position. The pressure drop is minimized at high flow rates to maximize the efficiency of the check valve. The check valve also has relatively few parts, and can be easily assembled and installed within the housing of a fuel nozzle.
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