| 摘要 |
<p>The device reduces or stops the flow of a medium, the diaphragm or plug used having hydraulic dampers for reducing its speed of movement, so as to avoid a shock on encountering the seat. The dampers have pistons working in liq-filled cylinders which are closed at the ends. Speed can be reduced by the continuous braking effect of a hydraulic fluid flowing through a calibrated passage between two chambers formed by a piston in a cylinder, and by a dashpot effect at the end of the stroke near the closing point.</p> |
