CROWN BIT Russian patent published in 2012 - IPC E21B10/02 

FIELD: mining.

SUBSTANCE: crown bit comprises a body with a circular bore, telescopically joined crown rings with splines on contact surfaces and stepwise working ends reinforced with rock-breaking elements, and a unit of crown ring fixation against axial displacement relative to the body. The fixation unit of the lower crown ring is arranged in the form of a chamber filled with liquid and having channels closed in the initial position with a valve and a rod. The lower end of the rod is fixed in the body of a lower crown ring and is displaced from its working end towards the side opposite to the bottomhole. The opposite end of the rod is installed with a gap relative to the upper wall of the chamber. The circular bore is arranged in the form of a circular slot open at the side of the well bottomhole.

EFFECT: higher performance indices of a crown.

2 cl, 3 dwg