ANNULAR CROWN BIT Russian patent published in 2006 - IPC E21B10/02 

FIELD: rock drilling tools, particularly crowns adapted to drill through fractured and intermittent ground.

SUBSTANCE: crown bit comprises body with cuts formed in lower bit part. The cuts are inclined in direction opposite to body rotation direction and divide the crown bit into several sectors reinforced with cutters. The crown bit also has guiding bush arranged inside the body. The guiding bush has safety means to prevent cutters from damage arranged in each body sector in front of the cutters and having dimensions equal to multiple cutting edge width of the cutters defined in direction of crown bit rotation. Each safety means is made as a rod with spherical working head and annular groove or slot created in outer surface thereof for fixer receiving. The fixer is made as retaining corrugated ring. The body has mating axial channel for axially movable rod insertion and annular boring formed in inner body side. The boring crosses axial channels for rods receiving.

EFFECT: increased operational efficiency.

2 cl, 5 dwg