| 摘要 |
<p>A valve assembly has a valve lid (3) assembly which can be fitted in sealing relation on a valve seat (2), an over-centre device can serve to force the lid on to the seat; a drive shaft (A) connected to the lid assembly and drive means (10) for rotating the shaft to open and close the valve seat, the over-centre device serving to oppose rotation of the shaft up to a critical position whereupon the device assists in rotation of the shaft to open the valve seat.</p> |
