COLLET TOOL Russian patent published in 2006 - IPC E21B31/18 

FIELD: oil production industry, particularly for fishing or freeing objects in boreholes or wells.

SUBSTANCE: collet tool comprises collet with at least two opened leafs and tail, thrust case installed from collet outside and shaft with shear pin arranged inside the collet. The shaft has end of variable cross-section to provide movement and smooth opening of collet leafs. The thrust case has lower guiding means and slip is installed in the thrust case. The collet is provided with outer buttress thread formed on the tail and arranged under the slip. The buttress thread is adapted to regulate and limit collet stroke. Collet leafs have locking supporting collar arranged from inside and with thrust collar formed from outside thereof. Core with locking outer thrust collar is located inside the collet. The collar is put on the shaft and fixed from above by the shear pin. Shaft and/or core comprises fishing heads of lesser and larger diameters correspondingly and/or the collar has upper outer pipe or shaft thread. If the tool is installed in its initial position collet tail is fixed relative the core by shear pins and collet leafs may be pressed one to another to reduce diameter thereof during object fishing. If the tool is installed in its working position after object fixation by the tool for shear screws shearing by applying impact in top-down direction the core with shaft tail may slide into the collet and collet leafs may be opened as shaft tail moves inside the collet as outer thrust core collar is closed up with supporting collar of the collet to provide rigid fixation of initial or extended diameters thereof. If the tool is installed in tool releasing position after shear pin shearing by applying impact in down-top direction during object fishing the collet may be opened and the leaf diameter may be increased as the shaft tail moves through the leafs in return direction, wherein the core is released from locking supporting collar of the collet leafs to provide following pressing thereof during tool removing from the object.

EFFECT: increased efficiency and extended functional capabilities.

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