| 摘要 |
A valve for controlling flow to a burner of pulverized coal and air mixture in which valve has a body with an opening surrounded by an auxiliary metal valve seat portion and an annular sealing gasket formed of resilient material such as natural or synthetic rubber that can deteriorate under extraordinary conditions such as heat or explosion. A generally flat gate plate positioned within the valve body is mounted on a movable supporting member so it can be moved from an open position to a closed position in which it contacts the gasket or the auxiliary seat portion to seal the valve opening. The gate plate is movably mounted on the supporting member so it can tilt, within limits, relative to the supporting member to reduce scuffing of the gasket on opening or closing of the valve, and so it is resiliently urged away from the supporting member toward the valve opening when the member is in closed position to hold the gate plate in contact with the gasket or with the metal seat portion if the gasket is inoperative or absent due to deterioration. The supporting member is pivotally mounted and is moved by pivotally connected link members that are in an over-the-center position when the valve is closed, to hold the gate plate closed even if the actuating means becomes inoperative when the valve is closed.
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