The cross section dimensions range today, with rod diameter ranging currently from 6 or 8 mm up to 40mm.

The produced pieces are mainly used in construction and generally in manufacturing projects as concrete reinforcing material and as structural elements in metal constructions.

The various product geometries, shown in figure 1, are produced by originally straightened rods, which are undergoing consecutive bending operations at both ends at the appropriate angle, without excluding bending in the middle part. The products may be symmetric about an axis, as in figure la, or symmetric about a point, as in figure I c, or asymmetrical, as in figure I b and d. The bending angles are usually 90° but they can also vary depending on particular construction requirements.

The various product geometries, shown in figure 1, are produced by originally straightened rods, undergoing successive bending operations at the desired angles, starting from the rod ends and proceeding towards the inner section but not necessarily the middle of the rod. In figure la and b bending is implemented by rotation towards one direction, whereas in figure I c and d bending is implemented towards both directions.

The usual process for production of these pieces is the following: Two bending mechanisms, which move along guides from the ends of the initially straightened rod towards the middle section, execute successive bending operations. The material to be bent is usually restrained by a gripper at some point at the middle section. Bending is implemented by wrapping the rod around a pin, where the pin diameter specifies the curvature radius of the bent rods. The curvature radius of the product at the bending locations is proportional to the rod diameter, according to regulations. In order to implement bending towards both directions, two fixed and two rotating pins are used.

Even though this solution is simple as a mechanical construction, in case of large diameter material, it results in large bending mechanisms, which cannot move very close to each other, and therefore do not allow for formation of pieces with short sides. In addition, the two rotating pins cannot form 180° angles.

In order for the bending mechanisms to move very close to each other, some manufacturers employ only one fixed pin and one rotating pin. These bending mechanisms can only bend the material towards one direction and they can form, completely automatically, products where bending is implemented towards one direction only, such as in figure la and b. For bending operations towards the other direction, the machine operator must intervene and manually bend the semi-finished piece in order to implement the opposite direction bending.

In order to avoid manual intervention, some manufacturers developed a transfer mechanism, where grippers hold the semi-finished product, remove it from the plane of bending, and transport it in a parallel direction to the opposite side of the fixed pin, consequently the rotating pin is rotated by 180°, and the grippers relocate the semi-finished product on the bending mechanisms. The bending mechanisms are now able to implement bending angles at the opposite direction.

Transferring of the semi-finished product is a disadvantage for this method. In the case of long pieces, the three grippers, which are necessarily required, are located at large distances with each other, and hence lifting, transfer and relocation on the bending mechanisms is implemented slowly and in a complicated manner.

The purpose of this invention is to present a method, which resolves the problems exhibited by existing methods and machines, and which leads to fabrication of a machine, which allows bending in both directions in a simple, quick and reliable manner.

The objective of the present invention is the development of a machine, which automates the process for production of various products, allows bending in both directions, is very flexible, very simple in design, user friendly and reliable in operation.

The method of the present invention is explained in the form of an example, as in figure 3, where the process for production of the piece shown in figure 2 is schematically described. The product shown in figure 2 is formed by a straightened part of appropriate length and is characterized by the lengths and angles xl, al and x2, a2 at the left end and the lengths and angles yl, pi and y2, p2 at the right end. The straightened wire (1) is placed on the bending units (6).

The bending units (6) consist of a fixed pin (2), which is located along the bending mechanism's rotation axis and of a rotating pin (3), able to rotate about the fixed pin. The two pins (2) and (3) are placed on a flat disc (4). The bending pins alone or with their mechanisms can be withdrawn from the bending plane, where the material to be bent is placed, so that the material to be bent is no more entrapped between the pair of pins (2) and (3).

The material to be bent (1) is held by a gripper (5), which is located at the interior side of the bending mechanism. The grippers (5) can move transversely to the longitudinal axis of the material (1).

The process for production of the piece of figure 2 is the following : The straightened material (1) is placed, as in figure 3a, between the pins (2) and (3) of the two bending units, which are located at distances xl and yl from the left and the right end respectively.

Upon rotation of the rotating pins (3) about fixed pins (2), as in figure 3b, the bending units bend the material at angles al and pi respectively, while the grippers (5) restrain the material. Next, the rotating pins (3) return to their initial location, as in figure 3c.

The bending units and the grippers move towards the inner section of the semi- finished product, at x2 for the left one and at x2 for the right one, as in figure 3d.

Next, the bending pins (2) and (3) and the discs (4) or alternatively, the bending pins (2) and (3) only, are withdrawn under the bending plane, as in figure 3e, so that the material to bent is freed. The elements under the plane of bending are drawn with a broken line.

frame (6) executes motion Z1, driven by a motor (13), which drives it via a rack (12) and pinion assembly.

The machine is presented schematically in figure 5. It consists of two bending mechanisms, which are placed on two moving frames (6a) and (6b) for the left and right carriers, which are placed on the metal structure (7) and can move along guides.

Its operation is as following: The moving frames are relocated at the appropriate locations for performing the first bending operation at the left and right ends.

The material to be bent (1) is placed manually or automatically on the bending mechanisms.

Next, both the two bending mechanisms perform bending.

The bending mechanisms return to their initial position and the process of the successive bending operations follows, as presented in the explanation of the present method.

In case bending towards the opposite direction is required, the process which is followed is the one explained previously, during the presentation of the method.

As already mentioned during the presentation of the method, bending can be implemented in two ways. They can be successive, with one mechanism restraining and bending, while the other mechanism is moving towards the next bending location.

A gripper at the interior section can be activated, in order to restrain the material to be bent, while the two bending mechanisms bend simultaneously and move simultaneously towards another location. In this case, the gripper can move transversely to the axis of the material, just like the grippers on the bending mechanisms.

Existence of only one fixed and one rotating pin on each bending mechanism is a definite advantage of the present method, since the bending mechanism dimensions are kept reasonable, and the two bending mechanisms can move very close to each another, so that they can bend sides of a short length as well.

Furthermore, due to the capability for bending at both directions, the machine can produce whatever shape is required.