| 摘要 |
<p>A valve (10) comprises a unitary valve housing (12), a valve stem (26) disposed in the housing having a lower portion (32) with a recess for a gasket (46). The valve stem further having a recess in its base for receiving an incompressible, free-falling object (44). The free-falling object is disposed within the valve housing such that the valve is precluded from opening when the valvel is in an upright position.</p> |
