Abstract: A drill head (1) as part of a drill lance for an apparatus for drilling an underground tunnel, which drill head has a channel (10) extending along the center axis of the drill lance and is rotatable about the center axis, comprising at least one forwardly directed nozzle (2), the nozzle channel (21) of which communicates with the channel (10) and exits outside the center axis, the drill head (1) being characterized by at least one rearwardly directed nozzle (4) being provided, the nozzle channel (41) of which communicates with the channel (10).

Abstract: A corrugated tube consists of a one-piece metallic basic body with corrugations arranged concentrically about the tube axis and one behind the other, which corrugations each have an annular space in the radial zone between the corrugation trough and the corrugation apex. This annular space is closed at its interior by means of two mutually concentric annular wall parts which are seated on one another and are relatively slideable one within the other in the axial direction. On the axial side remote from the associated corrugation the annular wall parts adjoin a radial annular space which is opened towards the tube interior and dimensioned as narrowly as possible as regards its radial and axial width.

Abstract: A tubular bellows element for fluids is provided which has concentric corrugations. The corrugations include flanks separated by spaces which narrow towards inner ends of the corrugations. The inner corrugation ends have a conical shape, and act as scales to increase the degree to which the ends of the bellows element can be moved with respect to each other. The inner ends also serve to provide an essentially smooth inner surface for the bellows element, minimizing both flow disturbance and the creation of turbulence.