| 摘要 |
CORE DRILLING TOOL FOR BOREHOLES IN ROCK A core drilling tool for bore-holes in rock comprises a stem to be attached to a pipe string and rotatably mounting an outer tube having a drilling bit at its lower end. A core tube is mounted in a central passage in the tool by latch means engaging in a locating recess in the stem whereby the lower end of the core tube is located adjacent the bit but spaced slightly therefrom to allow passage of drilling fluid. The outer tube and drilling bit are rotated by a motor having a stator fixed to the stem by a connector element preventing rotation of the stator but allowing its transverse movement and a cooperating rotor fixed to the outer tube, so that as the rotor rotates, driven by drilling fluid, the stator executes an eccentric orbit. The diameter of the central passage in the stem slightly exceeds the maximum external diameter of the core tube. The central passage through the connector element and stator has a diameter equal to the maximum external diameter of the core tube plus the eccentricity of the stator whereby the core tube can be readily introduced into and withdrawn from the central passage. Drilling fluid is suitably supplied to the motor through the central passage above the core tube (which is desirably sealed by a seal, at its upper end, to the stem) and thence to an annular space between the outer tube and the connecting element the annular space leading to the working chamber of the motor from which it flows to the bit though an annular space between the outer tube and the core tube. |
