Patent ID: 6145605
Filing Date: 2000-11-14
Classification: E21B

Abstract:
Rotary drill bit for the rotary crushing drilling of rock, said bit comprising a bit body and three roller cutters, each roller cutter being rotatably mounted on a journal protruding from the bit body, each roller cutter including a roller body having a generally conical shape with a rear end facing generally towards the periphery of the drill bit and a front end facing generally towards a rotational center of the drill bit, wherein a number of rock-crushing buttons are provided in each roller body to form at least first, second and third circumferential rows of buttons, the first, second and third rows of buttons being arranged successively from the rear end toward the front end of the roller cutter, each button having a working end which projects from the roller body and which during rotation of the roller cutter comes into engagement with the rock, wherein each button of the first and second rows having a length of attack which is longer in a direction of rotation of the roller cutter than in a direction perpendicular thereto, the buttons of the third row having a length of attack in the rotational direction which is shorter than the lengths of attack of the buttons of the first and second rows in the rotational direction.