DEVICE FOR EXPANDING WELL BOREHOLE

FIELD: mining industry, possible use for expanding drilled well borehole in process of its construction. ^ SUBSTANCE: device consists of body with central axial and radial channels. Grooves are made on external side surface of body along ascending helical curve. Upper and lower parts of body are made mutually shifted in diametrically opposite sides. Outside the body, rock-destroying tools are mounted in form of milling cutters with through radial channels. Milling cutters are mounted on the body with possible rotation and axial movement. External surface of milling cutters is equipped with wear-resistant cutting structures. Between end surfaces of milling cutter and body, supporting washers are mounted. Between lower ends of milling cutter and supporting washers, spring washers are positioned. To limit rotation of each milling cutter relatively to body, fingers are used. These fingers provide for turn of each milling cutter within limits of angle, equal to 180°, which is appropriate for maximal increase of external diameter of expander. Expansion of drilled borehole of well by means of given device is performed due to simultaneous rotation and axial movement of drilling column, and also forcing of washing liquid into it. To return device to transporting position it is sufficient to stop rotation of drilling column and washing of well. Under effect of their own weight rolling cutters will move to transport position. ^ EFFECT: increased reliability and safety of operation of device for expanding well borehole. ^ 4 dwg