Apparatus and method for reducing the cross section of a tubular hollow body by shaping the hollow body

An apparatus for reducing the cross-section of a tubular hollow body (2) by shaping the hollow body (2) which has a hollow body wall (3) made of a plastically deformable material and a hollow body axis (4) running in the longitudinal direction of the hollow body (2), the apparatus comprising:

• a shaping die (5) which is designed for arrangement on an outer side of the hollow body (2) and which has a die opening (7) designed for receiving the hollow body (2), the die opening (7) having an opening cross-section which is smaller than a hollow body cross-section of the hollow body (2) in an initial state,
• a mandrel (6) which is designed for arrangement in an interior of the hollow body (2),
• and
• a shaping drive (8) which has a die drive (10) and a drive controller (11),
• wherein the shaping die (5) arranged on the outer side of the hollow body (2) is movable with an axial movement of the die along the hollow body axis (4) in a direction (14) of the axial movement of the die relative to the hollow body (2) by means of the die drive (10) with the hollow body cross-section being reduced,
• wherein the shaping drive (8) has, in addition to the die drive (10), a mandrel drive (9) by means of which the mandrel (6) arranged in the interior of the hollow body (2) can be moved along the hollow body axis (4) through the die opening (7) with an axial mandrel movement directed counter to the axial die movement of the shaping die (5) arranged on the outer side of the hollow body (2),
• wherein the drive controller (11) of the shaping drive (8), is configured to control the mandrel drive (9) and the die drive (10) in such a way that the axial mandrel movement and the axial die movement of the shaping die (5) arranged on the outer side of the hollow body (2) are superposed on one another,
• wherein the apparatus is configured such that the mandrel (6) moving in a direction (13) of the axial mandrel movement is effectively supported on the hollow body wall (3) in a force-fit in the direction (13) of the axial mandrel movement such that the mandrel (6) moving in the direction (13) of the axial mandrel movement subjects the hollow body wall (3) to tensile stress in the direction (13) of the axial mandrel movement and the hollow body wall (3) is drawn through the die opening (7) relative to the shaping die (5) arranged on the outside of the hollow body (2) in the direction (13) of the axial mandrel movement.