| 摘要 |
A cap for a fill pipe of a fluid container, such as a gas tank, is provided. It has a vent hole which is normally held unsealed by the weight of a ball which impinges against and thereby tilts a spring loaded pin carrying an O-ring. When the cap tips away from the vertical by more than a pre-selected angle, the ball rolls away from the pin and the spring urges the pin to an orientation where the O-ring seals the hole. When the container is tipped beyond the pre-selected angle, should the internal tank pressure exceed a pre-determined level, the pressure overcomes the force of the spring allowing relief venting.
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