| 摘要 |
The eclipsable double fixed lock is pushed towards its lower position by the hydraulic pressure of the injection pump pushed boring liquid. Thus, an hydraulic seal is made between the interior tube and the exterior tube of the bore, when the liquid pressure exceeds a predetermined value. - The lock also allows the fluid to circulate when the pressure is less than the predetermined value, but above the recall force necessary to open the liquid flow regulation valve.
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