EP3377240A1

EP3377240A1 - Machine for bending pipes or sections in particular of metal, to obtain any shape

Info

Publication number: EP3377240A1
Application number: EP16815645.3A
Authority: EP
Inventors: Libero Angelo MASSARO
Original assignee: Massaro Libero Angelo
Current assignee: Massaro Libero Angelo
Priority date: 2015-11-20
Filing date: 2016-11-17
Publication date: 2018-09-26
Anticipated expiration: 2036-11-17
Also published as: ITUB20155771A1; WO2017085660A1; EP3377240B1

Abstract

Machine for bending metal pieces (14) comprising a matrix (2) and a counter-matrix (3), wherein the matrix (2) and the counter-matrix (3) are mounted on a work surface of the machine body (10), the matrix (2) being actuatable by first drive means, and the counter-matrix (3) being in turn actuatable by second drive means. A drive member (13) enables driving the metal piece (14) and the winding thereof around a portion of the peripheral edge (8) of the matrix (2). The machine provides for a rotary encoder associated to the rotational axis (1) of the matrix (2) and a linear encoder (5, 6) associated to the translation motion of the counter-matrix (3). The matrix (2) has a complex form, different from an arc of a circle, on said portion of the peripheral edge (8). Furthermore, a CNC control system is provided, adapted to control, during the bending of the metal piece (14), both the gear motor of the matrix (2) and that of the counter-matrix (3), by means of a system with two interpolated axes based on which said linear encoder can constantly communicate with said rotary encoder. A sensor (3) is necessarily provided that is adapted to acquire, by means of self-learning and before machining the piece, the form of the peripheral edge (8) not known to the CNC system of the machine.

Description

MACHINE FOR BENDING PIPES OR SECTIONS IN PARTICULAR OF METAL, TO OBTAIN ANY SHAPE

Description Technical field

The present invention generally refers to machines for bending pipes or sections made of any material, but preferably metal, without using an inner core. The machine subject of the invention is not a cambering machine, but an automatic machine with matrix and counter- matrix.

Prior art

In the prior art automatic machines for bending pipes or sections in particular metal (specifically aluminium, steel, iron, copper, titanium, etc.), as well as any other material using a matrix and a counter-matrix and without using an inner core (which is normally used as a contrast in case of rather small thicknesses and does not regard the present invention) have been known over the years.

Among others, also the inventor of the present invention overcame numerous problems in this field of the art and also features as an inventor for numerous patents in Italy and in some PCT and European applications. The Applicant of the present patent application is the proprietor or various patents in Italy and also features as an Applicant in some parallel PCT and European applications, which address problems different from the present invention. The pipe bending machine in question generally comprises a machine body with an upper operating plane on which the matrix and counter-matrix are mounted. The pipe is locked by a locking and drive member which is integrally joined to the matrix, while the counter- matrix presses against the matrix during the machining. The pipe is wound around the matrix just enough to complete the desired curve.

The Applicant filed industrial invention patent applications regarding the possibility of bending the pipe both to the right and to the left using the same pipe bending machine in which the matrix is simply tilted by 180° thus enabling the double bending direction; using a counter-matrix that reduces the friction that is generated during the bending of the pipe, thus enabling saving energy considering the same usage and reducing costs for the customer given the lower amount of materials used (for example Ampco 21) for manufacturing the counter- matrix; facilitating the assembly, disassembly and shipment, by manufacturing modular machines; using only one machine for bending pipes or pieces of variable dimensions and thicknesses, through a system for rotating and tilting the counter-matrix called "double twist" by the inventor.

The current pipe bending machines, of the type in question, do not yet have the capacity to adapt to any situation, in particular they do not allow the use of a matrix of any shape with a radius of curvature variable along the contour/perimeter of the matrix, and bending the pipe around at least one portion of this matrix with variable radius, or even around the entire matrix with variable radius and geometry. Were this possible (in particular even in combination with just a few or all innovations already present in the previous patent applications), there would be obtained an extremely versatile pipe bending machine, that would overcome one of the major problems of the industry.

Thus, currently in many cases (when required to bend an elliptical pipe just by way of example) the pipes are bent using another type of machine, i.e. using the aforementioned cambering machine. However, the latter reveals the drawback of not operating on a plane and thus there may be defects at the end of the pipe machining/bending operation, which require subsequent correction on other machines and/or by means of special tools. As of date, complex figures are obtained using cambering machines, albeit their drawback of not guaranteeing precision and repeatability of the result at "a single pass" (single pass in the machine) due to the fact that it does not have a fixed matrix.

On the other hand, as previously mentioned, in many situations (window, window frames, or sections/frames for walkways - for example of the camber arch type -, frames for lit advertising signs having a specific shape, etc.) it is necessary to bend the pipe/section with a variable radius, and it would be advantageous to have machine that is directly adaptable to the shape of the pipe/section meant to be obtained and enabling perfect and complete machining of the piece in just one machining pass.

There is currently the possibility of moving counter-matrix with respect to the matrix (which has a constant radius on the work portion) through a pic control system, in which the displacement of the counter-matrix and the rotation of the matrix are programmed in an entirely independent manner with respect to each other, and in which the displacements of the counter-matrix during machining are minimal or limited and solely aim at overcoming the problem related to eliminating the so-called "conical step" (or generally the defect visible to a naked eye) which is normally formed on the pipe or section immediately at the beginning or at the end of the rotation of the matrix, i.e. the machining.

Thus, an object of the present invention is to provide a pipe bending machine capable of bending pipes or sections according to variable radii of curvature i.e. with complex curves, even closed, on the same pipe bending machine and in a single machining pass (single pass).

Summary of the invention and advantages thereof

With the aim of overcoming the aforementioned problem, conferring total versatility to the pipe bending machine the inventor of the present invention firstly carried out numerous preliminary tests for exploring the possibilities of implementing the present inventive concept to be described hereinafter.

Thus, matrices of variable geometric shape (complex shapes, no longer circular shapes) were used and manual tests to move the worm screw that supports the counter-matrix were carried out, verifying the feasibility of the result, even using pipes of different diameters and materials (stainless steel, iron, aluminium, copper, titanium, and others). The movement of the worm screw, advancing and receding, was carried out to check the limit thickness up to which the same result was guaranteed, given that the pipes or sections of smaller thickness only require pipe bending machines with a core, i.e. those belonging to technologies different from the present invention.

The positive outcome of the executed tests also enabled the inventor to obtain a machine capable of overcoming the aforementioned problems.

However, a further drawback lay in the possible machining defects of the matrix, that could unacceptably differ from the prescribed mathematical model of a given figure. For example, a real oval matrix, that for example does not perfectly match (for example due to a manufacturing defect or tolerances) the prescribed mathematical figure would make it impossible to apply a control system based on a theoretical oval figure i.e. nominal, previously mentioned in the control unit or set by the user. The machining of the pipe or section in this case, would generate an unacceptable result given that it would apply a programme for displacing the rotating members exclusively based on the ideal oval geometrical shape i.e. theoretical.

Thus, the inventor realised that the problem that needed to be addressed, now lay in providing a system in which the counter-matrix is always moved at the same constant distance from the section/contour (generally with misaligned axis) of the matrix, which can now have any complex geometry, different from the conventional matrices with uniform radius, and also in that it may have small defects or imperfections. Thus doing, given that the counter-matrix "always moves strictly following the profile of the matrix", the radius (or the section) of the pipe to be machined would not be subjected to constriction, this for example being of major importance if the pipe is intended to be used in a hydraulic circuit, or another fluid circulation system, or to applications that require a perfect surface of the machined piece (for example parapets for luxury yachts).

In order to obtain the aforementioned objects, the inventor of the present invention applied for the first time in the industry a particular inventive concept, that consists in implementing a computerised numerical control (CNC) with interpolated axis in self-learning on conventional pipe bending machines of the type in question, for bending pipes or pieces using matrices and counter-matrices in which the matrix may have any complex and variable geometry.

This is a considerable step forward with respect to the prior art of the field, given that it is now possible to also guarantee the bending repeatability and the positive outcome with a single pass. As a matter fact, as mentioned, as of date the most complex shapes can be obtained only using cambering machines, which - by their nature - require a "multiple pass" process without guarantee of repeatability and only with highly specialised personnel.

The preliminary acquisition - by the CNC system - of the shape of the matrix by means of a self-learning process enables operating based on data regarding the actual shape of the matrix and not on memorised or set theoretical data, to which the matrix is expected to correspond ideally. Upon acquiring data regarding the shape of the matrix ("actual matrix"), the counter-matrix will move during the machining to a distance that is always constant from the acquired mathematical curve shape of the matrix), depending on the size of the section or pipe to be machined. Then, all that will be required is to set the transversal dimensions of the pipe to be machined, so as to perform the machining automatically. Then, given that all that will be required is to enter the relative geometrical data of the piece (pipe or section) the pipes (or sections) with different diameters (or sides) will be bent using the same matrix (within given limits obviously).

The preliminary acquisition of the data i.e. self-learning in the CNC system, occurs according to the invention using the following interpolated axes: 1) the rotational axis of the matrix, to which a rotary encoder and a relative gear motor are associated; 2) the linear displacement axis of the counter-matrix, to which a linear encoder and a relative gear motor are associated. The two interpolated axes (now no longer independent from each other), i.e. the rotational axis and linear axis (i.e. the respective encoders) communicate with each other during the machining so as to accurately meet the conditions of the previous self-learning process but to which the dimensional data of the piece should be added.

Thus, two gear motors operating in an interpolated fashion are required, one for the worm screw - i.e. for the advancement and recession of the counter-matrix - and one for the matrix. Each encoder will provide the respective instructions for the position of the matrix and counter-matrix for the CNC control system.

A method of self-learning acquisition of data regarding the geometric shape of the matrix consists in providing for a sensor preferably mechanical, that remains constantly at contact with the edge of the matrix while the latter rotates by the desired angle (at least corresponding to the rotational angle of the matrix during the future machining). The very same member that will press the pipe/section against the matrix during the future machining, i.e. the counter-matrix, a roller with a given shape or any other element suitable to perform such function of pressing the piece against the matrix during bending operations also being considered as a counter-matrix, may be preferably used as mechanical sensor.

Thus, the mechanical sensor could preferably be the same counter-matrix, which is preferably pressed by a spring against the edge of the matrix to remain constantly at contact with the latter during the self-learning process.

Once the self-learning process is completed, the counter- matrix that served the function of mechanical sensor in the self-learning process, will be connected to the movement mechanism (for example a worm screw) used for machining. In any case, the counter-matrix will thus no longer be, more or less freely slidable and subjected to the action of the spring alone, but it will be connected to the movement mechanism (for example a worm screw) moving during the future machining depending on the movement of the worm screw (or the like) which moves the slider/support of the counter-matrix.

It is thus clear that according to the present invention it is no longer possible to use a pic control system, in which the two movements (of the matrix and counter-matrix i.e. of the screw) could have been independent. Such pic system could have been used at most for eliminating funnel step deformations that would occur on the pipe at the beginning and at the end of the machining in a conventional machine, as described in a previous application of the Applicant.

Thus, the present invention is also applicable to the machining of pipes or sections even using manually made matrices, in which the matrix tolerances established by the turner could be such to lead to unacceptable machining were one to use a computer programme adapted to a theoretical/nominal geometrical shape to be copied. This is the actual advantage of the present invention, which, providing for a CNC with self-learning, makes the pipe bending machine flexible and adaptable to any shape (not known) and event. Should the piece (pipe, section), at the end of the bending operation be wound around the contour of the matrix totally or to an extent such to make it impossible to separate the piece from the matrix, then according to the present invention in this case it is possible to provide for a modular matrix, provided with a "cover", i.e. an upper part, and a "base", i.e. a lower part, which are rigidly connected during the machining but may be separated from each other along the axis of the matrix at the end of the machining. This enables the piece to be easily separated from the base of the matrix, for example, after removing said "cover" at the end of the machining. The two modular parts of the matrix may possibly be of the self-centring type providing for a system with a conical projection and a conical recess respectively, on one and respectively the other modular part.

The advantages of the present invention may be combined with others already obtained in previous applications of the same Applicant (as previously mentioned in the description introductory part), in particular providing for - in the pipe bending machine of the invention - the innovative "pivot" or double twist system, or the controlled recession and advancement system of the counter-matrix only during an initial and respectively final step of the machining, even though, for the rest, the counter-matrix remains exactly at the pre- established or set distance/height, with respect to the self-learning curve.

According to a further aspect of the present invention, the CNC control system may comprise the possibility of bending the piece (pipe, section) more quickly on the almost straight portions of the matrix with respect to the portions with smaller radius of curvature. For example, this enables disassembling - into various portions on a display - the geometrical figure of the matrix acquired through self-learning (for example by clicking in the relative points of the perimeter of the matrix using the mouse of a computer that the machine may be provided with). For example, should the shape of the matrix be an ellipse, then when (during machining) the counter-matrix is at an apex of a greater semi-axis of the ellipse it is preferable that the matrix rotates slower than other portions, like in the area of the apex of the smaller axis of the ellipse. The advantage thereof lies in the reduction of the time required for each machining cycle, when required to perform (as it happens almost all the time) the same machining operation on a given batch of identical pieces. At the same time, this technical solution also enables reducing the possibility of machining defects, in that a uniform rotary speed of the matrix is not advantageous in the critical points (relatively small radius of curvature). The display of the machine which enables the functions described above could also be provided for directly on the body of the machine (control panel), instead of on a PC.

The matrices could be made of special steel with a better tenacity-elasticity ratio, while the counter-matrices could for example be made technopolymers in case of aluminium or copper pipes, and Ampco for steely materials in that this is the hardest material and with the lowest coefficient of friction currently available in the market.

The CNC control system shall also provide for a memory for storing the self-learning data of any complex curve. The control panel of the machine is preferably of the colour touch screen type, ideally divided into three pages: the first for the project data, the second for the executive projects of the figures - created or to be created -, whereas the third page will serve as a memory for all movements carried out by the matrix and by the counter-matrix, guaranteeing the repeatability of each movement of the machine.

In addition, the machine subject of the present invention is preferably provided with a USB port for saving data and an internet connection for facilitating remote assistance. This enables transferring - to another machine - the data acquired for a given shape of matrix and which enable performing a given machining on a batch of pieces. This enables using a second identical machine for continuing the machining, should the first machine have problems. Or one may simultaneously work on identical machines after carrying out self- learning on only one of them. In this case, one must ensure that the matrices are "identical" in the sense that they were manufactured with extremely strict/precise tolerances or that other variables cannot jeopardise an accurate and identical machining on all machines.

The rotational angles of the matrix and the linear paths of the screw (i.e. of the counter- matrix) during the machining of the piece may be drawn automatically (on a display) each time as a function of time, and/or put in graphical correlation with each other. Given that even during self-learning - though the motor of the driving screw is not operating then - similar graphic paths (x(t)) of the sensor/counter-matrix and of the rotation (\|/(t)) of the matrix may be drawn on the machine display by the CNC control system software, the "ideal path" of machining may be easily compared with the charts regarding the temporary actual machining, to check whether the machine operates within given tolerance brackets. This enables operating in the same manner, with said tolerance brackets, on a series of identical pipes. Should the data on the display reveal that the operating tolerances provided by the machine manufacturer have not been complied with, then this means that the pieces are not the same (casting and/or dimensional differences due to defects). Then, the user will have a wide range of options to check the compliance of the various pieces forming the batch with respect to the parameters provided by the manufacturer. This means that the machine can also carry out a self-diagnosis on the quality of the pieces.

The software should be preferably such to combine the data x(t) of the linear encoder and \|/(t) of the rotary encoder forming a two-dimensional shape (i.e. a curve) corresponding: a) in the case of self-learning, to the movement in a two-dimensional plane of the contact point between the sensor/counter-matrix and the matrix (two-dimensional shape of the matrix);

b) when machining a piece, to the movement in a two-dimensional plane of the contact point between the counter-matrix and the surface of the piece.

In the example of the elliptical matrix, the self-learning (case a) provides - on the display of the pipe bending machine - an elliptical shape corresponding (besides the scale) to the actual shape of the actual matrix (a mathematical ellipse besides the inevitable minimal imperfections due to manufacturing tolerances).

During machining, (case b) the drawn shape should ideally follow the curve around the self- learning ellipse, moved orthogonally with respect to the learning ellipse by a constant distance d. The admissible tolerance brackets could correspond to a curve diverging by d+ε, just by way of example, thus forming a substantially elliptical tolerance bracket, established by the manufacturer of the pipe bending machine. The pipe bending machine of the invention also offers the possibility of checking whether the matrix or counter-matrix are worn out, or whether the machine is not operating correctly due to a failure. This can be observed from the display in that the tolerances established by the machine manufacturer for machining a given piece are no longer complied with. The curves corresponding to the current movements of the matrix and the counter-matrix exceed the established tolerance brackets (d+ε) with respect to the initial self-learning curves.

Even when operating with the same matrix, the self-learning process must be repeated periodically by the user.

Brief description of the drawings

The present invention will now be illustrated purely by way of non-limiting example according to an embodiment thereof, shown in the figures, wherein:

Fig. la shows an elliptical shape of the piece (pipe or section) obtained by the pipe bending machine according to the present invention;

Fig. lb shows a camber arch profile, usable for obtaining frames/profiles on which people can walk through, provided with doors or large doors;

Figs. 2a-2o show a series of non-limiting examples of pieces, in cross-sectional view, obtainable by means of a machine of the present invention;

Figs. 3a-3d show (in a plan view) the machine of the present invention, in particular solely regarding the portion thereof used (i.e. the means utilised) in the self-learning process, a matrix used for obtaining the camber arch of Fig. lb in the example; these figures show the various positions of the matrix and sensor in the self-learning process;

Figs. 4a-4d show steps similar to those of figures 3a-3d, but in the actual process for machining a piece whose final shape at the end of the machining is of a camber arch type (see Figs. 4d and lb);

Fig. 5 is a lateral view of Fig. 4d.

Detailed description of the preferred embodiment of the invention

Fig. la shows an example of a machined piece, ellipse-shaped, with R1-R4 radii of curvature, wherein R1=R3 > R2=R4. In this case, it is preferable that the bending of the pipe, initially straight, proceeds faster along the portion with Rl and R3 radius of curvature with respect to the portion with R2 and R4 radius of curvature. The software of the CNC control system may be adapted to solve this problem. This reduces the cycle times for machining identical pipes to obtain identical shapes, for example the shape shown in Fig. la or in Fig. lb. In the latter figure, the machined piece takes a camber arch shape; even in this case, the machining may be carried out more rapidly along the portion with greater radius of curvature, R2, with respect to a portion with smaller radius of curvature R1=R3. In the case of Fig. la the operator may programme the machining dividing on the machine display the shape of the final ellipse into four portions, or in the case of fig. lb he may programme the machining dividing, into three portions, the camber arch-shaped curve which will appear on the display after the learning and insertion of the geometrical data of the piece, for example. The operator may allocate to the various portions different rotational speeds of the matrix and the linear movement of the counter-matrix. Obviously, the areas of passage from one selected portion to the adjacent selected portion provide for the passage - with continuity - from one speed to another, through a "smoothing" operation.

Fig. 2 shows only a few examples of various pieces a-o etc., of the transversal sections of a part that can be machined. It should be observed that the material may also be solid material. The possibility of also machining solid material is given by a suitable choice of the power and the torque that can be exerted by the gear motor associated to the rotational axis of the matrix.

Now focusing on Figs. 3a-3d, they illustrate four "shots" in the self-learning process of the outer shape/profile of the matrix in the specific example (but non-limiting) of a camber arch- shaped matrix.

Figures 3-4-5 in the present patent application just represent the four mechanical parts of the pipe bending machine regarding the specific object of the present invention.

Fig. 3a shows the starting point, in point "0". The gear motor (not shown) associated to the matrix 2 is yet to begin rotating the rotational axis 1. It should be observed that the rotational axis 1 is no longer coincident with the symmetry centre, like it occurs in conventional matrices, which are always circular shaped (at least in the machining part of the piece). Obviously, in order to transmit motion to the matrix 2 the rotational axis 1 must have a non- circular portion contrary to the illustration in the figures (these and other things, are obvious to a man skilled in the art and will not be addressed in detail).

Machining a piece using a matrix 2 with such a complex shape requires - according to the invention - performing a self-learning process first. This occurs through a mechanical sensor 3 which electronically "reads" the perimeter external profile (of the camber arch type in this case) of the matrix 2. Specifically, the machine of the invention provides for a slider 4 integrally joined to a linear encoder 5, in the present non-limiting case constituted by a magnetic reader 5, interacting with an underlying magnetic band 6 (material measure). The slider 4 is freely slidable along a guide 7 (just schematised) and it supports - at the front part - said mechanical sensor 3, in the present case formed by a support roller 3, which - in the self-learning - remains constantly abutting against the external profile 8 of the matrix, thanks to the action exerted by an elastic means 9 which constantly presses against the rear side of the slider 4.

In Fig. 3b it should be observed that the thrust spring 9 (elastic means) expanded to enable the support roller 3 to remain at contact against the external profile 8 to be acquired. The matrix 2 has been rotated clockwise (arched arrow) by means of a gear motor by acting on the rotational axis 1. Fig. 3c shows the subsequent step, in which the thrust spring 9 has reached the maximum expansion thereof, the support roller 3 (rotatably mounted on the slider 4) maintaining contact with the profile 8 of the matrix 2. The final step of the self- learning process is shown in Fig. 3d (maximum compression of the spring 9 like in Fig. 3a). The linear encoder 5 and the rotary encoder (not shown but associated to the rotational axis 1 of the matrix 2) have in the meanwhile transmitted to the CNC control system all data regarding the shape of the matrix 2. In other words, a precise correlation F(x, ψ) = 0, between the linear displacement x(t) and the rotational angle \|/(t) of the support roller 3 and respectively of the matrix 2 was acquired. For instance, one may choose χ=ψ=0 for the initial position shown in Fig. 3a. Furthermore, figures 3-4-5 also show a stationary block with respect to the machine plane, indicated with 10. Number 11 schematically indicates the block of the gear motor that actuates the worm screw (see the following description and figures 4, 5) not used during the self-learning (Figs. 3a-3d).

The following figures, 4a up to 4d, instead show the process for the actual machining on the matrix 2 of the camber arch type (non-limiting example), for example using a piece obtained using a metal pipe with circular section and initially straight shaped. In this case, the spring 9 is removed and the worm screw 12 of the gear motor 11 is mounted to actuate the slider 4 in a driven fashion. Regarding this, implementation details may vary: for example, the spring 9 could be left where it is, if the latter is designated to be arranged beneath the position occupied subsequently by the worm screw. Such alternative solutions are simple to a man skilled in the art and shall not be addressed in detail.

Fig. 4a shows the initial position (position "0") of the machining process, the anchoring bracket 13 securing, as known, the pipe 14 to the matrix 2. The anchoring bracket 13 is removably mounted on the matrix 2 and it could be obtained in any manner, for example in two modular parts, etc. The anchoring bracket 13 operates as usual, already known from the conventional circular bending of pipes and sections, as a member for driving the pipe/piece 14 to be machined. The slider 4, driven by the worm screw 12, holds the piece 14 closely at contact with the groove (with shape complementary to the piece) obtained in the peripheral part 8, also called profile or shape, of the matrix 2. This type of machining (bending) of the piece 14, without an inner core, to which the present invention exclusively refers, obviously works for a given type of pieces 14 which have a sufficient thickness and resistance of the material to be machined.

According to the present invention it is crucial that the control of the machine be a CNC control with interpolated axes, i.e. the rotary encoder associated to the rotational axis 1 of the matrix 2 constantly communicates with the linear encoder 5 associated to the slider 4 during machining. The geometrical data of the matrix 2 acquired during the self-learning (Figs. 3a up to 3d) are used in the actual machining process (Fig. 4a up to 4d) together with the geometrical data (for example the diameter) of the transversal section of the piece 14, to rotate the worm screw 12 in both directions and with speed that can be set by the operator, while the matrix 2 still rotates in the clockwise direction (but also with speed that can be set by the operator in various aforementioned portions).

For a shape of the matrix 2 like the one shown in Figs. 3 and 4 it is not difficult to separate the pipe (or piece in general) 14 at the end of the machining, after removing the drive bracket 13, in that the two free ends of the pipe 14 in Fig. 4d are straight. Normally, the cycle times are reduced by rotating the matrix 2 in the opposite direction (anticlockwise direction) to return it to the cycle start position of Fig. 4a, while the slider 4 is simultaneously slightly receded so that it does not represent a hindrance when the pipe 14 already machined is removed from the matrix 2 after removing (or after actuating to open) the anchoring bracket 13.

However, in many cases it would be impossible to separate the already machined piece 14 from the matrix 2; this for example applies for a machined piece 14 shaped to form a closed curve (the ellipse of Fig. la). Thus, according to a further aspect of the present invention, the matrix 2 is obtained in the shape of the modular matrix, constituted by a cover (upper part) and a base (lower part). Thus, it will be sufficient to remove the upper part of the matrix 2 from the rotational axis 1 thereof, to remove the machined piece 14 from the machine. The two modular parts of the matrix may also be provided with self-centring means, for example a conical projection on a first component and a conical cavity on the other component.

Fig. 5 shows a lateral view in the position of Fig. 4d regarding the completion of machining. Thus, this figure does not require further explanation.

For the best completion of the machining, in case of a closed curve formed by the piece 14 - such as for example the ellipse shown in Fig. la -, there can be provided two identical brackets 13 on the matrix 2, slightly spaced from each other along the perimeter 8 of the matrix 2 and each forming two vertically openable and closable clamps, in which the first bracket 13 serves as a drive bracket and the other as a retention bracket for completing the machining. Specifically, once the pipe bending is almost complete, with the matrix 2 stationary, the retention bracket (preferably located in proximity of the drive bracket) blocks the piece 14 on the matrix 2 closing, and immediately thereafter the drive bracket 13 opens to enable the passage of the counter-matrix on the remaining unprocessed part of the piece 14 which was still covered/blocked by the drive bracket slightly earlier. Obviously, to complete the machining, the matrix 2 must be slightly rotated again, by an angle substantially corresponding to the angle subtending (from the centre of the axis 1) the perimeter portion 8 of the matrix 2 previously blocked by the drive bracket 13.

The present invention has been described without getting into technical execution details that would be obvious to a man skilled in the art. Furthermore, the embodiment, shown and described, simply represents one of the various ways of implementing the present inventive concept.

Specifically, just to mention a few examples, the self-learning process could occur even by means of an optical sensor or a ultrasonic sensor for measuring the distance (variable over time) between a fixed point (for example along the longitudinal axis X-X of Fig. 3a) and the peripheral edge 8 of the matrix 2 while the latter rotates as described regarding Figs. 3a up to 3d. Furthermore, the sensor could be possibly provided at another point, e.g. still along axis X-X but on the opposite side of the matrix 2 with respect to the rotational axis 1 of the latter. In the figures, the mechanical sensor coincides with the member (counter- matrix) 3 which is also used when bending the piece 14. This does not necessarily have to be. The sensor could be an element different from the counter-matrix. These and other modifications are obvious to a man skilled in the art intending to apply the inventive concept of the present innovation to obtain a machine for bending pipes or sections using a matrix of any complex shape. Lastly, it should be observed that the initial shape of the piece 14 must not be necessarily be straight, given that the machine of the invention could be used for subsequently bending various portions of a single piece 14 obtaining subsequent curves of the same or different shape (in this case changing the matrix between one machining operation and the other). The subsequent machining of the various portions of the same pipe is for example known from the conventional machines that use matrices 2 of the perfectly circular arch type 8. LIST OF REFERENCE SYMBOLS

1 rotational axis

2 matrix

3 counter-matrix

4 slider

5 magnetic reader

6 magnetic band

7 slider sliding guide

8 peripheral edge of the matrix

9 elastic means, spring

10 machine body

11 gear motor block

12 thrust worm screw

13 anchoring/drive bracket

14 Piece (to be machined and respectively already machined)

X X longitudinal axis

Claims

1. Machine for bending pieces (14) of elongated form, in particular metal pieces with constant cross section, without the use of an inner core, in particular pipes and sections, comprising a matrix (2) and a counter-matrix (3), wherein the matrix (2) and the counter- matrix (3) are mounted on a work surface of a machine body (10), the matrix (2) being connected to a vertical rotation axis (1) thereof actuatable by first actuation means, and the counter-matrix (3) being in turn actuatable by second actuation means so as to be able to translate in both directions along a translation axis (X-X) on said work surface in order to press the piece (14) during the machining against a peripheral edge (8) of the matrix (2) while this rotates around the vertical rotation axis (1) thereof, said matrix (2) also being provided with a drive member (13) in order to allow driving the metal piece (14) and its winding around a portion of said peripheral edge (8) in order to be able to form a bending in accordance with the form of the peripheral edge (8) itself, the matrix (2) having at the latter a groove with form complementary to that of a part of the section of the metal piece (14) to be bent, wherein in addition the machine provides for a rotary encoder associated with said rotation axis (1) of the matrix (2) and a linear encoder (5, 6) associated with the translation motion of the counter-matrix (3),

characterised in that

- the matrix (2) has a complex form, different from an arc of a circle, on said portion of the peripheral edge (8),

- a CNC control system is provided, adapted to control, during the bending of the piece (14), both said means for actuating the matrix (2) and said means for actuating the counter-matrix (3), by means of a system with two interpolated axes based on which said linear encoder (5, 6) can constantly communicate with said rotary encoder,

- a sensor is provided that is adapted to acquire, by means of self-learning and before machining the piece (14), the form of the peripheral edge (8) not known to the CNC system of the machine.

2. Machine according to claim 1, characterised in that said sensor is a mechanical, optical or ultrasonic sensor.

3. Machine according to claim 2, characterised in that said mechanical sensor comprises a slider (4) slidable along a linear guide (7) and adapted to remain constantly in abutment by means of a roller against said peripheral edge (8) under the action of pressure means (9); said slider (4) supporting a reader interacting with a material measure (6) provided in a stationary manner on the block (10) of the machine in order to determine the temporary position of the slider (4).

4. Machine according to claim 3, characterised in that the pressure means (9) are elastic means (9), the reader (5) being a magnetic reader (5) interacting with a magnetic band (6) provided in a stationary manner on the block (10) of the machine.

5. Machine according to any one of the preceding claims, characterised in that the counter-matrix (3) is comprised in the sensor and corresponds to a roller (3) of the sensor in abutment against the matrix (2) during the self-learning.

6. Machine according to any one of the preceding claims, characterised in that the matrix (2) comprises a cover, or upper part, and a base, or lower part, which can be fit together, and whose plane of separation intersects said groove of the matrix (2).

7. Machine according to any one of the preceding claims, characterised in that it is adapted to carry out a self-diagnosis of the quality of the piece (14) by means of the comparison of the flat trajectory of a point of contact between the counter-matrix (3) and the piece (14), indicated by the CNC control system on a display of the machine during machining, on one hand, and on the other hand the shape of the same matrix (2) obtained in the self-learning process that corresponds with the profile of the peripheral edge (8) apart from a possible scale factor.

8. Machine according to any one of the preceding claims, characterised in that the means for actuating the matrix (2) and/or the means for actuating the counter-matrix (3) are gear motors.

9. Machine according to any one of the preceding claims, characterised in that it comprises a retention bracket mounted on the matrix (2) in a position close to the drive bracket (13).

10. Machine according to claim 9, characterised in that the retention bracket and the drive bracket (13) of the piece (14) each form two vertically openable and closable jaws, in order to tighten or release the metal piece (14).

11. Machine according to any one of the preceding claims, characterised in that it comprises means for storing, for a predetermined long time period, or for an unlimited time period, the data obtained from the self-learning process, and for transferring the stored data to another machine for bending pieces (14), for example by means of a USB port.

12. Machine according to any one of the preceding claims, characterised in that it comprises a CNC control system with an industrial touch screen for use with an Internet connection, usable for remote service.

13. Machine according to any one of the preceding claims, characterised in that the self- learning process can be periodically executed on the same matrix (2), also on the basis of an indicator or signal of the number of machined pieces.