| 摘要 |
<p>For achieving a shut-off function, a mainstream communicates with a control stream into which an outlet for the mainstream opens laterally. By reciprocating the control stream back and forth across the outlet, for example by alternate pressurisation of reservoirs to which the control stream is connected at its ends, access of the mainstream to the outlet is inhibited. When the reciprocation is discontinued full flow of the mainstream to or through the outlet can take place.</p> |
