| 摘要 |
The lift valve comprises a body (1) in which is formed a cylindrical chamber (2) provided with a lateral inlet (14) and with an outlet (3). This chamber contains a piston (4) on which acts a spring (22) and which is solidly fixed to a rod (6) whose end constitutes a valve seal. The rod (6) is further provided with a crosssection reducer (9) formed, for example, by a perforated cylindrical bearing surface. The inlet aperture (14) opens out between the piston (4) and the cross-section reducer (9). The difference between the forces acting on the piston and on the cross-section reducer causes the piston to retract, thus opening the lift valve. The cross-section reducer seals the inlet aperture (14) to a greater or lesser extent.
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