| 摘要 |
A drilling tool, for example a core barrel inner tube assembly or a drilling bit, is attached to the inner end of a latch body which is removably seatable on a landing shoulder of a drill string. The inner end of the latch body mounts a drilling tool such as a core receiving tool or a drag bit. An overcenter toggle latch assembly is mounted to the latch body, the latch assembly including a pair of latches having inner ends pivotally mounted to the latch body, toggle links that at their one ends are pivotally connected to the outer ends of the latches and at their opposite ends have a retractor link extended through elongated slots. The retractor pin is extended through an axially elongated slot in the latch body to limit the axial movement of the pin between a position that the latches are locked in a latch seated position and a position retracting the latch body and the drilling tool attached thereto. An overshot coupling member and a latch retractor tube are provided for retracting the retractor pin including moving the latch body and the structure depending therefrom outwardly through the drill string.
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