DOWNHOLE OVERSHOT DEVICE Russian patent published in 2006 - IPC E21B31/18 E21B31/12 

FIELD: fishing for or freeing objects in boreholes or wells, particularly to eliminate drilling string breakdown in large-size well.

SUBSTANCE: device comprises hollow body with end thrust bearing coaxially installed and supported by radial-axial bearings, as well as overshot member having ends fixedly secured to lower body part. Device also comprises rotary means, which rotate the end thrust bearing only in one direction. The end thrust bearing has conical guiding cavity and arranged in upper part of body interior. The overshot member is made as flexible link movably connected with the end thrust bearing. The flexible link comprises filament member having central part passing through diametrical channel formed in the end thrust bearing so that the filament member may be displaced relative the end thrust bearing.

EFFECT: increased operational reliability and simplified structure.

3 cl, 2 dwg