SELF-RELEASING CASE SPEAR Russian patent published in 2005 - IPC

FIELD: earth or rock drilling, particularly grappling tools for removing broken pipe string sections from wells by internal gripping thereof.

SUBSTANCE: case spear has smooth body with inclined planes offset relative axis, gripping members displaceable only along inclined planes, rests, coupler, guiding surface and longitudinal flushing orifice. Inclined surfaces taper downwards and are spaced equal angles one from another across diameter. Gripping members are composite and consist of anvils and guiding means tapering upwards and cooperating with inclined planes from inside. Anvils are located outside and installed on guiding means so that anvils may move only along guiding means. Rests are arranged on guiding means from below and adapted to limit anvil movement. In transportation position guiding means are fixed relative inclined planes by shear members.

EFFECT: increased reliability and extended operational capabilities.

2 dwg