HYDRAULIC DRILLING JAR Russian patent published in 1994 - IPC

FIELD: fishing of objects stuck in wellbore. SUBSTANCE: hydraulic drilling jar is provided with upper dosing mechanism which is located in annular space between mandrel and body above lower dosing mechanism and additional annular protrusion with seal located between dosing mechanisms and separating the annular space between them into lower and upper high-pressure chambers and annular stage with radial channel. Annular stage is located above upper dosing mechanism. Additional ring pistons are located on both sides of annular stage and spring-loaded relative to it. Upper and lower dosing mechanisms are made in form of cylindrical sleeve rigidly connected with body. Cylindrical sleeve has seals and bypass channels, hollow seat with cylindrical inner surface and valve installed in seat. Valve is made in form of cylindrical pin spring-loaded to seat. Cylindrical pin has slots on lower end and forms together with seat inner surface the overflow channels hydraulically communicated with bypass channels. EFFECT: higher operate reliability and increased service life. 3 cl, 8 dwg