COMBINED HYDRAULIC UNDERREAMER

The invention relates to drilling equipment and can be used for borehole enlargement in drilling process within needed range of diameters. A combined hydraulic underreamer consists of a body with central washing channel in which a spring-supported pusher is placed with possibility of displacement, and pads of executive elements placed on the body, the last ones interact with the pusher, at that in the body side washing channels are provided, those are placed with possibility to bring into coincidence the cavities of those with the central washing channel after bringing the pads to working position. According to the invention, the body is arranged of assembled elements that include the main cylindrical section, the upper connecting muff and the lower closed nipple with threaded joints, tightness of those is provided with tightening rings. In the walls of the cylindrical part of the body six horizontal cylindrical cuts are provided, those are symmetrically shifted one with respect to another by angle 60°, those with alternation, one by one, have reamed cells shifted one with respect to another by angle 120°, there executive elements are placed, as pads equipped with destructive instrument. In the inner cylindrical section of the body a pusher is placed, this is arranged as a movable cylindrical piston the lower part of which has conical shape, its lower end goes to a cylindrical rod placed on the spring-supported prop, the spring of that one is installed in a stepped cylindrical recess of a closed nipple with possibility of interaction with the conical section of the piston-pusher with at least three working elements installed in the walls of the cylindrical section of the piston-pusher in horizontal cylindrical cuts with possibility of displacement in axial direction, fixed on the cylindrical rod with an elastic ring-stopper, that for the pads have inner cylindrical support, outside of that one a circular recess for the ring-stopper is provided, and the upper part of the cylindrical support of each pad has skewed surface for conical section of the piston, at that the number of the side washing channels is proportional to the number of executive elements, the channels are provided in the walls of the cylindrical section of the body in zigzag-like way, of two inclined down sections and one vertical section, placed with possibility of bringing to coincidence the cavities of those with the central washing channel after bringing the piston to working position, w