DEVICE FOR DRILLING Russian patent published in 1998 - IPC

FIELD: drilling units. SUBSTANCE: device has drilling unit submerged into drilled well. The latter has casing which accommodates at least during drilling a drilling set. Cutter head of drilling set has at least the first drilling means for drilling the center of well and the second drilling means for reaming the well center for sinking casing, and flushing means for removal of drillings from well. Rotary motion round longitudinal axis and percussive action in longitudinal direction from the first drilling means are transmitted with the help of joining device to the second drilling means connected with the first drilling means near the cutter head of drilling set. the second drilling means are made so that they are rotated together with casing head round central longitudinal axis with the help of joint and, in addition, they may be disconnected for retrieving the first drilling means from finished well. For optimization of at least sizes of the first drilling means, the effective diameter of the first drilling means amounts to at least 60% and in preferred version, more than 75% of casing inner diameter. EFFECT: reduced dimensions of device structure. 8 cl, 3 dwg