| 摘要 |
Core barrel apparatus that includes an inner tube assembly that may fall under gravity or be fluidly propelled through a drill string to the bit end thereof for being retained at the bit end by latches and being retractable by an overshot assembly. The inner tube assembly includes an annular seal portion for forming a fluid seal with the drill string and a fluid by-pass channel with valving mechanism extending therein to permit outward flow but block inward flow while the inner tube assembly is being fluidly propelled inwardly. The inner tube assembly also includes control mechanism to prevent the valving mechanism being moved to permit significant inward flow through the channel only after fluid pressure has been applied to the inner tube assembly at the bit end of the drill string, the latches have moved to their latch seat engaging position and then inward fluid pressure has been significantly decreased. |
