Abstract: A kelly-bar apparatus includes, for example, an inner kelly-bar, a second kelly-bar and an outer kelly-bar. These kelly-bars are relatively telescopically operable and torque is transmitted from outside to inside. When the second and outer kelly-bar are in a contracted position, they are supported by a spring on a spring support fixed to the inner kelly-bar. The bottom end of a torque transmitting projection of the inner kelly-bar is fitted into and welded to the spring support. The spring support is fixed onto an engagement member formed integrally with the inner kelly-bar. In addition, a stop member for preventing the second kelly-bar from coming away from the outer kelly-bar projects from the inner periphery of the outer kelly-bar at a location above the torque transmitting portion.

Abstract: A shaft drilling rig with which a shaft is drilled into the earth with a turning force and thrust of drilling imparted to at least the drill bit of a drill string, down to a predetermined depth, and then a new drill string component is added to the drill string, for further drilling.The subject of the present invention lies in enabling the work of adding a new drill string component to the drill string safely and in a reduced time.To solve the above problem, the shaft drilling rig according to the present invention comprises a means of receiving an additional drill string component at least at the bottom end thereof, means of supporting said receiving means so as to be stably movable between a position where a drill string component is to be added and a parking position, and a means of holding the additional drill string component.

Abstract: A rotatable cutter head for a pit boring machine used in reverse circulation drilling. The cutter head has cutter arrays including rotary cutters and drag cutters and disposed radially and circumferentially spaced positions on the cutter head, the drag cutters having the cutting ends lying generally in a conical plane having the axis coaxial with the axis of rotation of the cutter head. The rotary cutters each have cutting teeth around the circumference thereof and each tooth has an inclined side face lying in a further conical plane the central axis of which is coaxial with the axis of rotation of the rotary cutter, the inclined side face of each tooth facing generally along the inclination of the conical plane in which the cutting ends of the drag cutters lie, and the tip of each cutting tooth of each rotary cutter projecting beyond the plane in which the cutting ends of the drag cutters lie.