DETACHABLE ADAPTER Russian patent published in 2018 - IPC E21B17/06 E21B17/42 

FIELD: mining.

SUBSTANCE: detachable adapter comprises a nipple and a coupling connected to each other by a two-thread cylindrical thread of a large pitch. The average thread diameter is determined by expression D_cp=|(D²+d²-2h²)/2|^0.5. Torque moments of connection tightening meet the conditions T_wa=T_us and T_ua>T_us, where D and d are outer and inner diameters of the adapter; h is the height of the thread profile; T_wa - working torque of adapter threaded connection; T_us - ultimate tightening torque of the drill string threaded connections (σ_z=σ_y); T_ua - ultimate tightening torque of adapter threaded connection (σ_z=σ_y); σ_z - tightening tension in dangerous section of the threaded connection; σ_y - yield strength of the threaded joint material.

EFFECT: providing strength, tightness, and high reliability when drilling and disconnecting the drill string from stuck core tool or bit.

2 dwg, 1 tbl