| 摘要 |
<p>A method and apparatus for shielding a valve gate (3B) from potentially harmful environmental conditions. A valve gate can be moved from a closed position, in which the valve gate closes a valve passage (11) and is potentially exposed to harmful environmental conditions, to a retracted position, in which the valve gate is shielded from the harmful environmental conditions. For example, the valve gate can be retracted inside a housing (51) and a door (63) can be closed over and opening (62, 67) in the housing to protect the valve gate. Other portions of the valve (100), such as a valve seat (2), can also be protected from harmful conditions, e.g., by closing a valve seat opening to prevent substances or other environmental conditions form leaving the valve passage.</p> |
