ES2569374T3 - Machine for bending tubular products, and tube bending procedure - Google Patents

Abstract

Machine for bending tubular elements (11, 211) comprising bending means (12), provided with at least one bending arm (17) and a bending core (16) arranged, when in use, inside said tubular element (11, 211), the bending core (16) comprising a support bar (19), an opposite ogive (20) and a possible bending follow-up element (21) arranged in an articulated manner on the head of the opposite warhead (20), the machine also comprising displacement means (13, 113), for displacing said tubular element (11, 211) in a direction (F) towards said bending means (12), and means for cutout (22, 122) to cut a segment of the tube, characterized in that it also comprises retaining means (15, 115) arranged on the perimeter around said tubular element (11, 211) and configured to hold said core of bending (16) in a condition of substantial suspension within the said tubular element (11, 211) and because the displacement means (13) are of the type that have an unwinding roll (23) and the retaining means (15) are of the magnetic type and comprise at least one magnetic element ( 25) arranged downstream of said unwinding roll (23) in direction (F) and outside and around the tubular element (11), in such a way that a magnetic field is generated that collaborates with said support bar (19). ) and the bending core (16) is kept in magnetic suspension inside said tubular element (11).

Description

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DESCRIPTION

Machine for bending tubular products, and tube bending process FIELD OF THE INVENTION

The present invention relates to a machine for bending tubular products, for example metal tubes, to make dynamic tubes for fluids, canenas, machinery or others. In particular, the machine according to the present invention allows the curving of these tubular products in an automated manner and their substantially continuous feeding in a bending core.

The present invention also refers to the bending method for tubular elements.

Here and in the following description and in the claims, by the term continuous feeding we mean a feeding of the tubular product that starts from a product in a roller or a bar, but which, in any case, has an exit length which is higher in a multiple of the length of the segment that is the finished product.

BACKGROUND OF THE INVENTION

Machines for automatic or substantially automated bending of tubular elements are known, which allow to produce parts of pipes, machinery, tubena, fluid connections or others, according to the different curves designed.

The known bending machines for this type of product can be distinguished in substantially two groups, namely bending machines with a core and bending machines without a core.

In particular, in the bending machines with a core, the tubular elements are previously cut to the size required in the segments and then loaded into the machine to be supplied over the core.

Said type of known machine, although assuring a high quality of bending of tubular elements of large sizes with limited radii for each bending operation, requires a different auxiliary equipment both for pre-cutting with limited radii for each bending operation and also for loading the segments over the nucleus, prior to the bending steps.

This causes an increase in machine handling costs and increased complexity of operation and automation.

In addition, very often, this type of known machine has a mainly manual use, with consequent operating delays, the need for specialized personnel and an increase in production costs.

Additionally, the known bending machines with a core, due to their conformation and their concept of operation, perform a back bending, that is, they start at the opposite end of the tube with respect to the end that is fed.

Tail bending requires, for many products, to be sure that the length of the segment is appropriately longer than the current development length of the tubular element when it is curved, since it is necessary that the segment is still grasped by the uncurved part during the execution of the last bend.

Some types of known bending machines are also characterized by the formation of high amounts of waste caused by short straight sections at the end of the curved tubes.

Waste training has two main reasons. On the one hand, traditional core machines require, due to their operating concept, that the tube is supported at one end so that the section of the tube that acts as a support causes the waste to be eliminated at the end. On the other hand, waste is caused because, starting with the segment in the bending step, the external material is stretched and creates a deformation effect on the end of the cut tube, forcing a section to be removed.

The bending machines without a core, on the other hand, are applied in particular to bend tubular elements of a reduced diameter with high radii, and fed from a roller.

These known machines that provide a system of bending with matrix and clamp, and without a core, can imply, in the case that reduced radii of curvature are required, an ovalization of the section usable for the passage of the tubular element, and the characteristics of the Tubular element itself may vary.

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Under some conditions, a partial occlusion of the tubular element may occur at the curved point, with the consequent lack of performance of the final product.

US-A-2,996,100 discloses a method and an apparatus for bending tubes and canes comprising a rotary forming die, a holding die, a support jaw and a die die. The tube to be curved is fed and received inside the rotary die formed along a feed direction, and then advanced by means of rollers towards the support jaw and the pressure die along another direction of operation, contrary to said direction of feeding. Inside the tube can be mounted a mandrel that has a head portion, a stem portion and an end portion, used to bend thin sections of tube and cane wall, and is not usually necessary for tubes and walls with walls heavier The mandrel can be replaced by, or combined with, heating means to heat the tube before bending.

WO-A-03/045603 discloses a bending machine for obtaining molded elements from previously cut profiles, equipped with a traction assembly that pulls the profiles, the first shearing means, bending means and second water shearing means below the bending means.

Document NL-A-7.512.602 discloses a bending machine for bending tubular elements that includes compression means, configured as a steel cable, a chain, or a chain made of L-shaped links, with protrusions to be inserted into along the tubular element to act as a contrast for the bending operation. The compression means disclosed in NL-A-7,512,602 exert a compression force from the inside along the entire length of the tubular element and, in particular, in the case of the chain, contact, oppose and push at least along the entire surface of the interior of the wall of the tubular element, exerting a perpendicular force with respect to the axis of the tubular element.

An objective of the present invention is to produce a machine for curving tubular elements that allows efficient bending of both the tubular elements with a wide diameter and with reduced radii of curvature, and the tubular elements of a limited diameter with wide radii of curvature.

A further objective of the present invention is to make a machine for bending tubular elements that is simple and economical, that allows a high automation of operations, that uses a bending core and can be fed in a continuously continuous way.

Another object of the present invention is to improve a method for curving tubular elements that provides a remedy to the drawbacks of the state of the art.

The Applicant has conceived, tested and carried out the present invention in order to overcome the inconveniences of the state of the art and to achieve these and other objectives and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other features of the invention or variants of the main inventive idea.

According to the above-mentioned objectives, a machine for bending tubular elements according to the present invention comprises bending means provided with at least one bending arm capable of acting on an external surface of the tubular element in order to produce a bend, and with a bending core capable of being arranged inside the tubular element to contrast from inside the action of the bending arm, and to form, in a desired manner, the bend of the tubular element.

The machine according to the present invention also comprises displacement means capable of moving the tubular element in a linear manner, both in the first feeding step towards the bending means and also during the bending steps.

In accordance with a distinctive feature of the present invention, the bending machine also comprises retention means selectively connected to the bending core in order to maintain the latter in a condition of substantial suspension inside the tubular element.

The suspension condition defined by the retaining means is such that the displacement means supply the tubular element towards the bending means in one direction and one direction that coincide with a working direction of the bending means in the tubular element.

In this way, the tubular element is worked from the front, namely, starting at the same end with which the tubular element is fed.

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This working condition allows the tubular element to be fed sustainably continuously, exploiting the advantages of automation of known machines devoid of core. Contrary to these known machines, the machine according to the present invention also exploits the advantageous features of using the core to carry out the bending.

In this way it is possible to provide a machine for the bending of tubular elements that is substantially automated, or can be automated, more or less completely, allowing bending with both wide and small radii, substantially of the full range of dimensions of the elements. tubular

With the present invention there is a reduction in the operation and management costs of the machine, optimizing performance.

According to the invention, the retention means are of the magnetic type, that is, they provide at least one magnetic element arranged on the penimeter around the area where the tubular element is arranged in the operative condition. By magnetic element we understand, here and in the following description and the claims, any element capable of exerting a magnetic force of attraction on an element, which is also magnetic, magnetized or has magnetic means (in this case, the bending core), therefore including magnets, electromagnets, elements that can be magnetized and any other element suitable for the purpose.

The magnetic element that is at least one, or the plurality of magnetic elements, is / are arranged around the tubular element in order to generate a magnetic field that maintains the nucleus in a suspension condition inside the tubular element .

The position of the magnetic element (s) is lateral, that is, it does not interfere with the feeding axis of the tubular element, and this determines a considerable operating advantage, promoting the automation of the feed and feed movements of the tubular element towards the bending means.

The bending core is arranged axially in accordance with the central zone of magnetic equilibrium, thus remaining in a condition of substantial suspension within the space defined by the magnetic elements.

In this way, the tubular element is supplied by the displacement means in the direction of the feed, being inserted in the defined space between the magnetic elements and the bending core, without any interference by any possible support of the bending core or of the proper tubular element In this arrangement, the tubular element is further fed by the displacement means in the same direction and in the same direction, in a coordinated manner with the impulse of the bending means in order to carry out the required bends.

In this solution, it is clear that no work waste is produced, and that, once a first portion of the tubular element has been curved according to the desired pattern, the tubular element can be cut exactly to size, separating only The curved portion. In this condition, the rear end of the rest of the tubular element coincides with the front end of the new portion to be curved, etc.

According to a variant, the magnetic elements can be shaped in such a way that they send an axial recovery movement of the core subsequently to the bending steps.

According to a further variant, the retaining means comprise a first gripping member arranged in collaboration with a first end, or rear end, of the bending core, and capable of maintaining the bending core in the suspended condition during the steps of feeding of the tubular element in the direction of the feeding.

In this variant solution, the retaining means also comprise a second gripping organ arranged in collaboration with a second end, or rear end, of the bending core, and capable of maintaining the bending core in the suspended condition during the steps of curved tubular element.

Also in this solution, as in the preceding one, the retention means are arranged and act laterally with respect to the position of the tubular element, so that there is no interference by the retention means with respect to the feeding axis of the tubular element .

In this variant solution, the tubular element is initially supplied from the front by the displacement means. Next, the tubular element is cut or sheared in order to define a segment of desired length.

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Subsequently, the segment is supplied along the feed direction so that it releases the rear end of the bending core.

In this condition, the second grip organ is activated and the first grip organ is deactivated in such a way that the displacement means can supply the segment in the same direction and the same direction to put it in collaboration with the bending means and carry Out the required bends.

The suspended condition of the bending core is guaranteed at the rear by the second grip.

With this variant, the bending occurs only in a segment that coincides with the size of the development of the portion to be curved, so that the operations of moving the segment are facilitated, and that the quality results of the led bending are further improved. finished.

According to an additional variant, the retaining means comprise a support member, for example made of a flexible material, articulated meshes or others, which support and feed the core inside a tubular bar from which a plurality of curved portions.

In this variant solution, the core is displaced through the displacement means, axially with respect to the tubular bar by a rear end of the latter, until the front end is reached, and then it is positioned in collaboration with the arm of bending of the bending means.

However, the movement of the tubular bar to bend its portions is carried out from the front.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present invention will become apparent from the following description of some preferred embodiments, given as a non-restrictive example with respect to the attached drawings in which:

- fig. 1 is a schematic, side and partially sectioned view of a first embodiment of a machine for curving tubular elements according to the present invention, in a first step of operation;

- fig. 2 is a schematic, side and partially sectioned view of the bending machine in fig. 1, in a second operation step;

- fig. 3 is a schematic, side and partially sectioned view of the bending machine in fig. 1, in a third step of operation;

- fig. 4 is a schematic, side and partially sectioned view of a second embodiment of a machine for bending tubular elements, in a first operation step;

- fig. 5 is a schematic, side and partially sectioned view of the bending machine in fig. 4, in a second step of operation;

- fig. 6 is a schematic, side and partially sectioned view of the bending machine in fig. 4, in a third step of operation;

- fig. 7 is a schematic, side and partially sectioned view of a third embodiment of a machine for bending tubular elements, in a first step of operation;

- fig. 8 is a schematic, side and partially sectioned view of the bending machine in fig. 7, in a second step of operation;

- fig. 9 is a schematic, side and partially sectioned view of the bending machine in fig. 7, in a third step of operation.

In order to facilitate understanding, the same reference numbers have been used, where possible, to identify common elements in drawings that are substantially identical. It is understood that the elements and features of an embodiment can be conveniently incorporated into other embodiments without further clarification.

DETAILED DESCRIPTION OF SOME FORMS OF EMBODIMENT

With reference to figs. 1, 2 and 3, a first embodiment of a machine 10 used for the bending of tubular elements, or tubes 11, is shown.

Both for this described embodiment and for the embodiments described below, the relative representations are deliberately schematic, in order to better understand the characteristics of the machine according to the present invention.

The operating details such as, for example, the diameter of the tubes, the radii of curvature obtained, the sizes of the core and others, have been chosen deliberately at random, so as not to restrict the individual embodiments to solutions of specific operation, also considering the fact that one of the main advantages of the present invention is the excellent ability of the bending machine to be applied for essentially any type of tube with any radius of curvature.

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In this case, the machine 10 comprises a bending organ 12 and a displacement organ 13, in this case represented by a rewind roll 23. The movement of the tube 11, in a manner known in the state of the art, is achieved by means of a motorized roller conveyor or with other systems of an alternative type, such as a clamp, or similar means, not shown here in detail, which carry out both the first supply of the tubes 11 towards the bending organ 12 as the advance of the tubes 11 during the work steps.

In the following description, reference numbers 13, 113, 213 are used to indicate in a general manner the organ that moves the tube 11 linearly in the direction of feeding which, as is known, is not represented in detail in the drawings.

The machine 10 according to the present invention also comprises a retention organ 15 whose function will be described in detail below.

The bending organ 12 comprises a bending core 16 and a bending arm 17, which is movable with respect to the bending core 16 in order to bend the supplied tubes 11.

In particular, the bending core 16 is disposed inside the tubes 11 in such a way that it opposes, inside the tube 11, the bending action that is exerted outside by the bending arm 17.

The bending core 16, on the other hand, comprises a polarized support bar 19, an opposite warhead 20 and, in the case represented in the drawings, at least one bending follower element 21 arranged in an articulated manner to the head of the opposite warhead 20.

There may be only one bending element 21, as in the drawings, or there may be none, if the type of bending and / or machine does not need it.

The bending arm 17 is of the type that is substantially known and is only shown schematically in the drawings. The bending arm 17 acts outside the tube 11 to be curved to confer on the latter, in coordination with the feed transmitted by the movement organ 13, depending on the radius of curvature. The bending arm 17 can be selectively positioned in different transverse planes with respect to the direction F, in order to bend the tubes 11 in different planes.

The machine 10 also comprises a cutting tool 22, for example a milling cutter or another, in this case, arranged downstream of the retaining organ 15 and upstream of the bending organ 12, which allows a segment of the tube to be cut to size. 11 at the end of the bending steps.

Within the context of the present invention, here and in the variant solutions shown below, it is understood that the cutting tool 22 must also be disposed downstream of the bending organ 12, or there may be one or more cutting bodies 22 waters up and one or more cutting tools downstream of the bending organ 12.

The tube 11 is fed in the same feed direction "F", and in the same direction, both in the feed passage of the tube 11 towards the bending organ 12, as well as during the bending steps. The direction and direction of the feed define a supply in front and an operation in front of the tube 11.

The retention organ 15 comprises at least one magnetic element 25; by this term we understand permanent magnets, electromagnets or other similar or comparable element. The magnetic element (s) 25 are arranged in the form of a ring around an area in which the tube 11 is supplied, near the bending organ 12, defining a space between it and the bending core 16 in which tube 11 can be inserted.

The permanent magnets 25 arranged in this way define, with their magnetic fields, a median, axial zone with respect to the feeding direction "F", of magnetic equilibrium. The bending core 16 is arranged with its support bar 19 in this medium zone of magnetic equilibrium. The support bar 19, being polarized, remains substantially suspended in correspondence to this area, and also absorbs, among other things, the axial forces that they generate during bending.

Therefore, the entire bending core 16 is kept in suspension by the action of the magnetic fields generated by the magnet or permanent magnets 25, to allow the feed in the required direction "F", without danger or interference with possible structures for the support of the bending core 16 in its operative position.

As shown in sequence in figs. 1, 2 and 3, in this embodiment of the machine 10, the tube 11 is fed from a roller by the action of the unwind roll 23 in the feed direction "F", and is directed forward to the bending organ 12.

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Before reaching the bending arm 17, the front end of the tube 11 is led to pass through the interior of the retention organ in the space defined between the permanent magnet or the magnets 25 and the bending core 16, so that the latter It is arranged in suspension inside the tube 11.

In the embodiment shown in figs. 4, 5 and 6, a second embodiment of the machine 110 is schematically represented.

In this case, the machine 110 comprises a bending organ 12, a displacement organ 113, and a retention organ 115, the last two of which have a different conformation from the one described so far.

The bending organ 12 is the same as described for the solution in figs. 1, 2 and 3, and comprises the bending core 16 and the bending arm 17, to bend the supplied tubes 11.

The displacement organ 113 comprises, in this case, a motorized unwind roll 23 capable of unwinding from a roller the tube 11 to be curved, and displacement tongs 123 arranged downstream of the unwinding roll 23 and upstream of the organ of curved 12, with respect to the feed direction "F".

In this case, other feeding organs may also be present, but not shown here, such as a roller conveyor, etc.

In this solution variant too, the tube 11 is fed from the front, in the same feed direction "F", and in the same direction, both by means of the unwind roll 23 and also through the sliding tongs 123.

The retention member 115 comprises first grippers 26 and second grippers 27 arranged in collaboration with the bending core 16, in order to keep it in a suspended condition, which acts on one side of the tube 11.

In particular, the first grip pliers 26 are suitable for collaborating with a rear end of the support bar 19 of the bending core 16; while the second grip tongs 27 are suitable for collaborating with the opposite nose 20 of the bending core 16. The sequence of operation of the two grip tongs 26 and 27 will be described in detail below.

In this case, the machine 110 also comprises a cutting tool 122, for example a milling cutter or another, disposed in this case upstream of the first gripping tongs 26, and capable of cutting a pipe segment 11 to the extent previously bent.

As depicted in sequence in figs. 4, 5 and 6, in this embodiment of the machine 110, the tube 11 is initially unwound from a roller through the action of the unwind roll 23, and moved in the feed direction "F" by means of the organ of feed 113, and directed from the front towards the bending organ 12.

During the supply of the tube 11, the bending core 16 is maintained in a suspended condition by the action of the second grip tongs 27.

Before reaching the second grippers with the front end of the tube 11, the unwinding roll 23 for feeding the tube 11 and the cutting tool 122 cut the tube segment 11 to be curved to size. Prior to the definitive cutting of the tube segment 11, the segment is associated with the sliding pliers 123. In a variant of this solution two cutting units can be provided, in which a first one cuts a segment made from multiple of the product , and a second one is positioned behind the bending organ 12 and cut to size in a curved tube.

Once the custom cut has been made, the unwind roll 23 partially covers the tube 11, separates from the cut segment, and releases a back section of the support bar 19 of the bending core 16.

In this condition, the first grip tongs 26 are placed in collaboration with this back section of the support rod 19, and subsequently the second grip tongs 27 are discharged, releasing the opposing warhead 20.

At this point, the movement tongs 123 supply the segment forward in the direction F in the same direction of feeding that follows with the unwind roll 23, such that it is put in cooperation with the bending organ 12 and performs the curves required.

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In the embodiment shown in figs. 7, 8 and 9, the bending machine is represented in its entirety with the reference number 210.

In this case, the machine 210 comprises a bending organ 12, a displacement organ 213, and a retaining organ 215, of which the last two have a different conformation of both the solutions described so far.

The bending organ 12 is the same as described for the previous solutions and comprises the bending core 16 and the bending arm 17.

In this case, the tube, instead of being fed from a roller, is fed into bars 211 of a substantially multiple length with respect to the length of the individual segments to be curved.

In this case, the displacement organ 213 comprises displacement tongs 223 arranged in collaboration with a rear end of the bar 211, in order to determine a movement thereof towards the bending organ 12 in the feed direction F.

The retaining member 215 comprises a support bar 219 directly connected to the rear of the opposite warhead 20 of the bending core 16.

The support bar 219 is made of a flexible material, with articulated meshes or another, in such a way that it is able to feed the opposing warhead 20 from a rear surface of the tubular bar 211, with a curved path, and in any case ensures sufficient rigidity in the operative position of the opposite warhead 20.

The machine 210 also comprises in this case a cutting tool 222, for example a milling cutter or another, disposed in this case upstream of the bending arm 17, and capable of cutting a segment of tube 11 after the bending to size.

As shown in sequence in figs. 7, 8 and 9, in this embodiment of the machine 210, the tubular bar 211 is initially fed from a storage and arranged in the feed direction F. From there, the sliding pliers 223 supply the bar 211 from the front to the bending organ 12.

Once the bar 211 has been positioned in collaboration with the bending organ 12, the bending core 16 is axially inserted into the bar 211 from a rear end thereof, until it reaches the cooperative position, in the inside of the bar 21, with the bending arm 17.

Next, the bar 211 is progressively supplied by the sliding pliers 233 in order to carry out the desired bends.

At the end of the bending, the cutting tool 222 cuts the segment to its measurement, to summarize the bending cycle of a new section of the bar 211, always fed from the front.

It is evident that it is possible to make modifications and / or additions of parts or steps with respect to the machine 10 and the cutting method as described above, without departing from the field and scope of the present invention.

For example, it is encompassed within the scope of the present invention to provide that cutting tools 22, 122, 222 are arranged downstream of the bending organ 12, or in a different position with respect to the bending organ 12, dependent on the different Operating conditions.

According to another variant, the support bar 19 is polarized by means of a magnetic core, or an electric current or other known polarization system, capable of generating a magnetic field that opposes the action of the field generated by the permanent magnets. 25, or by electromagnets.

It is also clear that, although the present invention has been described with reference to specific examples, a person with experience in the field will surely be able to achieve many other equivalent forms of the machine for bending tubular products and the related method of cutting , without departing from the scope of the claims.

Claims (7)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 1. Machine for bending tubular elements (11, 211) comprising bending means (12), provided with at least one bending arm (17) and a bending core (16) arranged, when in use, in the inside said tubular element (11, 211), the bending core (16) comprising a support bar (19), an opposite warhead (20) and a possible bending tracking element (21) arranged in an articulated manner in the head of the opposing warhead (20), the machine also comprising means of movement (13, 113), to move said tubular element (11, 211) in a direction (F) towards said bending means (12), and about trimming means (22, 122) for cutting a segment of the tube, characterized in that it also comprises retaining means (15, 115) arranged on the penimeter around said tubular element (11, 211) and configured to maintain said bending core (16) in a condition of substantial suspension inside d and said tubular element (11, 211) and because the displacement means (13) are of the type that have a rewind roll (23) and the retention means (15) are of the magnetic type and comprise at least one magnetic element (25) disposed downstream of said unwind roll (23) in the direction (F) and outside and around the tubular element (11), such that a magnetic field is generated that collaborates with said support bar ( 19) and the bending core (16) is kept in magnetic suspension inside said tubular element (11). 2. Machine according to claim 1, characterized in that said support bar (19) is provided with a magnetic polarization. 3. Machine according to claim 1, characterized in that said magnetic elements (25) and said bending core (16) define between them a space in which the tubular element (11) is inserted around said bending core (16 ). 4. Machine according to claim 1, characterized in that the feeding means (13) are of the combined type, with a rewind roll (113) and a sliding pliers (123), and the retention means (115) comprise a first gripping organ (26), arranged on one side of the penimeter of the tubular element (11) in cooperation with a first end (19) of the bending core (16), in order to selectively maintain said bending core (16) in the suspended condition inside the tubular element (11) during the feeding steps of said tubular element (11) in the feeding direction (F) and towards said bending means (12), and a second grip organ (27), spaced longitudinally with respect to said first grip organ (26), and arranged in cooperation with a second end (20) of the bending core (16), and capable of maintaining the core of curved (16) in the suspended condition inside the tubular element (11) during the bending steps of said tubular element (11), in which the tubular element (11) is displaced by said pliers (123). 5. Machine according to claim 1 or 4, characterized in that it comprises at least one cutting organ (22, 122) disposed upstream and / or downstream of the gripping organ with respect to the feeding direction ( F), and apt to divide the tubular element (11) into segments of the desired length. 6. Method for curving tubular elements (11) comprising at least one bending step, wherein bending means (12) provided with at least one bending arm (17) act on an external surface of said tubular element (11,211 ), and a bending core (16) disposed inside said tubular element (11, 211) opposes the action of said bending arm (17) from the inside and forms the bending of said tubular element (11) in a desired manner, and at least one displacement step in which displacement means (13, 113) move said tubular element (11,211), both to feed it towards said bending means (12) and also during the bending step , wherein both in said bending step and in said displacement step, said bending core (16) is maintained in a condition of substantial suspension inside said tubular element (11) through retaining means (15 , 115), arranged on the surrounding penimeter or of said tubular element (11), characterized in that said method provides for an activation of the retention means (15) of the magnetic type comprising at least one magnetic element (25) that collaborates with a support bar (19 ) of the bending core (16) and arranged on the penimeter around the tubular element (11, 211) in an operative condition, to generate respective magnetic fields, defining a central zone of magnetic equilibrium in which the bending core (16 ) is arranged axially creating a substantial magnetic suspension, to allow a substantially continuous feed through the displacement means (13, 113). 7. Method according to claim 6, characterized in that the bending core (16) is axially displaced towards the tubular element (11, 211) by a rear end of the tubular element (11, 211), until the front end is reached, and then it is positioned in cooperation with the bending means (12) and the movement of the tubular element (11, 211) to bend its portions is carried out from the front.