Abstract: The invention relates to a trench cutter comprising a cutter frame, at least one rotatably drivable cutter wheel, which has cutting teeth on its outer circumference for removing ground material, at least one bearing shield, which is arranged on the underside of the cutter frame and is configured to support the at least one cutter wheel, at least one conveyor box, which has at least one opening for discharging removed ground material and/or for feeding a suspension and is arranged in the region of the at least one bearing shield, wherein the at least one cutter wheel has, on its side facing the bearing shield, at least one flap tooth which can be adjusted between an unfolded position, in which the flap tooth removes ground material below the bearing shield, and a folded position for running past at the bearing shield.

Abstract: A top drive for a drill string, and an apparatus and method for calibrating the top drive. The top drive includes a rotationally driven shaft that is rotatably mounted by a bearing arrangement having at least one axial bearing and at least one load measuring cell for measuring an axial load of the at least one axial bearing. A calibration device including a pressure element is placed at an upper end portion of the drive shaft. The pressure element exerts a defined calibration force onto the drive shaft in an axial direction. The at least one load measuring cell measures the axial load and transmits a measured load value to a comparing unit, which compares the measured load value with the defined calibration force to determine a differential value. The differential value is then used to calibrate the at least one load measuring cell.

Abstract: A top drive for a drill string, and an apparatus and method for calibrating the top drive. The top drive includes a rotationally driven shaft that is rotatably mounted by a bearing arrangement having at least one axial bearing and at least one load measuring cell for measuring an axial load of the at least one axial bearing. A calibration device including a pressure element is placed at an upper end portion of the drive shaft. The pressure element exerts a defined calibration force onto the drive shaft in an axial direction. The at least one load measuring cell measures the axial load and transmits a measured load value to a comparing unit, which compares the measured load value with the defined calibration force to determine a differential value. The differential value is then used to calibrate the at least one load measuring cell.

Abstract: A drill drive for a drilling rig includes a motor, by which a drive shaft is rotationally driven which is supported in a rotatable manner in a housing with a bearing arrangement having at least a radial bearing, a first axial bearing and a second axial bearing. On the first axial bearing a first force measuring device is arranged for determining a first axial force on the first axial bearing and on the second axial bearing a second force measuring device is arranged for determining a second axial force on the second axial bearing. A drilling rig, in particular for oil or gas drilling, with a drill mast, along which a drill string with a drilling tool is arranged, wherein on the drill mast a drill drive according to the invention is supported in a displaceable manner for rotationally driving the drill string.