METHOD AND BENDING TOOL FOR BENDING PIPES OVER A MANDREL WITH AN ADJUSTABLE MANDREL RETAINER MEANS BENDING TOOL AND ROTATING BENDING TOOL WITH SUCH A BENDING TOOL

摘要

The invention relates to a method and a device for bending pipes (3) over a mandrel (6), in particular pipes having thin walls, on a rotary draw bending tool (1), which comprises a bending template (2), a slide rail (4) which is arranged above the pipe and which holds the pipe and the mandrel in position, and at least one upper, outer clamping jaw (7), which, rotating by a bending angle, presses the pipe (3) against the bending template (2). The invention also relates to a bending tool (1) and to a beading tool suitable for the method or for the bending tool. According to the method, in order to prevent the formation of folds, a tensile force applied to the pipe (3) during the bending process and therefore the trailing of pipe material in the bending zone on the inside (3b) of the pipe bend (3a) are retarded by at least one mandrel retaining means which can be placed against the mandrel shaft, wherein tensile stress is introduced at the pipe bend inner radius and the critical compressive stress leading to fold formation is no longer met.