JAR Russian patent published in 2009 - IPC E21B31/107 

FIELD: oil and gas industry.

SUBSTANCE: invention is related to drilling equipment and may be used for liquidation of tool sticking in well in process of oil and gas wells drilling. Jar comprises hollow body with anvils, hollow stem with striker installed in body with the possibility of axial travel without mutual rotation, sub with striker installed on hollow stem, collet with free springing end, which has annular protrusion with support tapered end outside and replaceable ring inside, seals of fixed and movable joints. In hollow body bore is provided with tapered support protrusion for interaction in initial position with annular protrusion on free springing end of collet installed in hollow stem into annular space created between hollow body and hollow stem. Replaceable ring is arranged in the form of flexible elastic shell. Radial gap is provided between free springing end of collet and hollow stem, and its value is more than radial value of tapered support protrusion of hollow body radial bore.

EFFECT: higher accuracy of well making, device reliability and durability.

4 cl, 6 dwg