Torque converter for use when drilling with a rotating drill bit
A torque converter for use in drilling with a rotating drill bit, the purpose of the torque converter being to absorb impacts and bring about an axial movement of the drill bit when the torque exceeds a predetermined value. For this purpose the torque converter is composed of two cylindrical string parts connected through the bearing elements. The string parts are connected to each other through helical elements in such a way that relative rotation of the two cylindrical string parts brings about axial movement, which unloads the drill bit.
1. In a drill string that extends along an axis from an uphole direction to a downhole direction, a torque converter comprising:
upper and lower cylindrical string parts, each comprising an uphole end and a downhole end;
helical spring elements operatively connecting the downhole end of the upper cylindrical string part to the uphole end of the lower cylindrical string part;
wherein the helical spring elements limit otherwise free relative axial and counter-rotational movement of the upper and lower cylindrical string parts with respect to each other;
wherein relative counter-rotational movement of the upper and lower cylindrical parts in a first direction causes the helical spring elements to contract along the axis, and thus move the lower cylindrical string part in the uphole direction;
wherein relative counter-rotational movement of the upper and lower cylindrical parts in a second, opposite direction causes the helical spring elements to expand along the axis, and thus move the lower cylindrical string part in the downhole direction; and
wherein a predetermined amount of torque applied to the drill string during drill string operation causes relative counter-rotational movement of the upper and lower cylindrical parts in the first direction and thus results in movement of the lower cylindrical string part in the uphole direction.
2. The torque converter according to claim 1 , comprising at least one guide element disposed between the upper and lower cylindrical string parts.
3. The torque converter according to claim 1 , comprising at least one seal disposed between the upper and lower cylindrical string parts.
4. The torque converter according to claim 1 , comprising a drill string having a downhole end and a drill bit operably connected to the downhole end, and wherein the torque converter is incorporated into a drill string such that relative rotation movement of the upper and lower cylindrical parts causes the drill bit to retract in the uphole direction away from a drilling surface.
5. A method of operating the torque converter of claim 4 comprising the step of operating the drill string until a predetermined amount of torque is applied to the helical spring elements to thus retract the drill bit in the uphole direction away form the drilling device.