HYDRAULIC JAR Russian patent published in 2006 - IPC E21B31/113 

FIELD: oil production industry, particularly for underground well repair to release stuck tool.

SUBSTANCE: device comprises cylinder having bored portion, cylinder, piston connected to traction and compensating rods and sealed with gaskets. Device also has bush with outer flat installed over the piston on compensating rod. The bush and piston end define annular gap with slot-like channel formed in bottom thereof. The device also has valve unit with shutoff member arranged in the annular gap and made as O-ring of elastomeric material. The shutoff member closes liquid flow directed from cavity located above the piston to cavity under the piston. The piston is spaced from the cylinder. Channel, which communicate cylinder cavities divided with piston, is made as annular space between compensating rod and piston and may be connected with slot-like channel.

EFFECT: simplified structure and increased reliability.

2 dwg