Method and apparatus for sinking a cased borehole for producing cased pile foundations

Apparatus for sinking a cased borehole, comprising:

• (a) a crane provided with a support cable,
• (b) a drilling appliance suspended from the cable to be lowered into a borehole, said drilling appliance being provided with a controllable clamping means for supporting the torque of a drive motor for a drilling tool on a drop tube, said clamping means being guided axially over a limited working stroke in a non-rotary manner on a housing supporting the drive motor, drilling tool, and power and control lines introduced into the drilling appliance from above,
• (c) an auger with a preceding rotary cutter head thereon as the drilling tool being provided with a double wing-shaped bit support with diametrically located swinging wings provided with drilling bits, said wings, in a working position being swung radially outwards and limited by a stop, cutting with their bits being free of the bit support and on reversing the direction of rotation, swinging back into their inner inoperative position, each swinging wing being provided on its radially outermost side face with a return strip inclined upwards in the drilling direction, which strips are located inside the inner diameter of the drop tube used in the inoperative position of the swinging wings, when the latter are swung inwards, and
• (d) a tube extraction maching located on the ground with a hydraulically actuated clamping collar guided in parallel by at least two double-acting lifting cylinders supported on a machine frame and which can be raised and lowered, vertical guides for anchoring bolts or tubes able to be driven into the ground being provided on the machine frame or on pressure shoes located on the ground, whereby the tube extraction machine is secured in a non-rotary manner above the ground.