| 摘要 |
<p>A downhole tool coupling for selectively transmitting torque downhole between a drive portion and a rotatable portion, such as between teeth 72 on resilient collet fingers 74 on an outer sleeve 63 and teeth 70 on an inner sleeves 62 of a directional drill drive assembly 26 which are axially alignable with each other to enable adjustment of the orientation of a drill bit, also incorporates a torque limiter. Torque limitation may be achieved by bearing surfaces (75,77, figure 3)between teeth 70,72 having radially offset angles providing non-tangential forces which urge outer sleeve collet teeth 72 outwards, and out of engagement with inner sleeve teeth 70 above a predetermined threshold torque. The collet fingers 74 may extend axially (figure 4) or alternatively extend circumferentially around the outer sleeve (163, figure 7).</p> |
