| 摘要 |
A roller bit (10) is described, to the body (12) of which roller bodies (22) are connected in a fully offset position. The fully offset position is established by an axis of rotation of each roller body (22), a longitudinal axis (17) of the roller bit (10) and end bearing points of the roller bodies (22). The axes of rotation of the roller bodies (22) are at right angles to the longitudinal axis (17) of the roller bit (10). In a primary direction (19) of rotation of the drill-pipe string and of the roller bit (10), rows (25) of cutting elements abrade the bottom and the side walls of a borehole (13) when the roller body (22) acts on the earth formation during the rotation of the roller bit (10). The striking of the earth formation by the cutting elements of the roller body (22) gives the roller bodies (22) a secondary rotation which is caused by the primary rotation and enables the rows (25) of cutting elements to bite the side wall of the borehole (13) and finish the borehole to size as well as abrade material from the bottom of the borehole (13). A lubricating system is provided in the body (12) of the roller bit (10).
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