A pipe bending die is known from EP 1 591 174 B1, in which the bending head is actuated via a total of three rotational axis. A first rotational drive rotates the bending mandrel itself, a second rotational drive rotates the bending arm with the clamp die attached thereto, and a third drive finally rotates a cam disk in which a guide element runs which is connected with the clamp die and radially displaces the same during the rotation. This known construction is relatively complex and expensive as a result of the numerous mechanical elements with which the bending arm is provided. Moreover, there is a limitation in the bending freedom as a result of its large interference contour.
EP 1 543892 B1 describes a bending apparatus in which the clamp die rests on a toothed rack which is displaceable via a gearwheel attached to the bending axis. In order to cause the forward feed motion of the clamp die towards the bending mandrel, the bending drive needs to be actuated which then causes the pivoting of the bending mandrel together with the clamp die after the forward feed motion and clamping has been completed. In this case however it is necessary to rotate the bending axis by actuating the bending drive until the forward feed motion of the clamp die occurs and the workpiece is clamped between clamp die and mandrel. Bending is only performed afterwards. The bending mandrel must be provided with a completely round configuration, with right and left bending not being easily possible.
In the case of EP 1 543 891 A 1, the clamp dies are disposed on a support which is moved on its part by means of a horizontally disposed worm radially towards the bending mandrel or away from the same. This known construction is very complex, large and relatively expensive and three different drives are required for actuation.
In the bending machine as known from EP 1 396 294 A 1, the clamp dies are disposed on guide paths on which they are moved radially by a spindle drive. Drive and spindle are integrated in the bending arm. This leads to the disadvantage of a very heavy and complex bending arm.
WO 2007122346 A 1 describes a bending die arrangement in which a second rotary disk sits on a first rotary disk in an eccentric manner relative to its bending axis. A clamp die is rotatably attached in an eccentric manner on the second disk. The forward feed motion of the clamp die and the bending movement can be performed by a respective control of the three rotational movements and their superposition. However, a large basic rotary disk with a large interference contour and three drives are necessary again and the controlled drive of the various rotational axes is very complex.
A rotary bending die of the kind mentioned above is known from GB 1 319 581 A, in which the bending mandrel sits on its rotational axis in a freely rotatable manner. The clamp die which is guided in a recess of a further rotary plate in the manner of a motion link in the tensioning or releasing direction is connected in an articulated manner with a swivel axis which is also disposed eccentrically to the rotational axis of the bending mandrel on a driven rotary disk which is concentric to the bending mandrel, which connection occurs via a swiveling lever which is linked to its swivel axis. By twisting the rotary disk relative to the bending mandrel, a workpiece to be bent can be clamped between clamp die and bending mandrel and thereafter be bent around the same by further rotation of the rotary disk together with the bending mandrel. The clamp die can be moved away from the bending mandrel and the workpiece can be released again by means of rotation of the rotary disk in the opposite direction after completed bending. In this case, since there is only one driven rotational axis it needs to be rotated by actuating the drive that is also responsible for the bending until the forward feed motion of the clamp die occurs and the workpiece is clamped on the bending mandrel. Bending is performed only afterwards. The bending mandrel needs to be provided with a completely round configuration. Right and left bending is not easily possible. Since the guidance of the clamp die occurs over its entire path of adjustment in a motion link recess of a rotary plate, a large rotary plate with a large interference contour in respect of a limitation of the bending freedom is necessary for this purpose.