Method of forming a three-dimensional bend in a tubular product and method of manufacturing a tubular product

Abstract

Method for obtaining a three-dimensional bend in a tubular product (10') starting from a metal tube (10) extending along a rectilinear longitudinal axis (x), comprising the following steps: step a) performing a first bending operation on the tube (10) by means of first bending means (20) on a bending plane passing through the longitudinal axis (x) so that the tube (10) exiting the first bending means (20) comprises a bent portion (10b') lying on a curved plane; and step b) performing a second bending operation on the tube (10) exiting the first bending means (20) by means of second bending means (22) so that the bent portion (10b") of the tube (10) at the output of the second bending means (22) has, at its opposite ends, tangents (t1, t2) lying on a cylindrical surface having a generatrix orthogonal to the two planes (A1, A2) containing the tangents (t1, t2), respectively.

Description

Technical Field

[0001] This invention generally relates to methods for manufacturing tubular products. In particular, this invention relates to methods for manufacturing tubular products with complex curvature (i.e., having closely adjacent curved portions that are curved on respective planes of curvature).

[0002] As used in this application, the term "tubular product" refers to any product derived from a tube (whose cross-section may have different shapes, particularly circular), or similar elongated semi-finished products, such as rods or profiles. Background Technology

[0003] Various methods for obtaining tubular products by performing bending operations on metal tubes are known. Generally, depending on the geometry to be obtained and the material of the initial tube, bending operations can be performed using, for example, roller-type or shape-constrained bending devices.

[0004] When bending using a roller bending device, an initially straight metal tube is fed along its longitudinal axis and passed between at least three rollers alternately arranged on opposite sides of the tube, one of which is laterally movable, i.e., substantially orthogonal to the longitudinal axis of the tube. As the tube advances along its own longitudinal axis, the closer the movable roller is to the longitudinal axis of the tube, the smaller the bending radius of the resulting tube. By changing the relative orientation of the tube with respect to the bending device, i.e., with respect to the three rollers of the bending device, the spatial orientation of the bending plane of the tube can be altered.

[0005] While roller bending devices offer the advantage of ensuring high dimensional and geometric accuracy, it is practically impossible to obtain tubular products with complex curvatures by sequentially performing various bends on adjacent tube sections. In reality, roller bending devices cause plastic deformation of the tube at the intermediate roller, while the other rollers must rest against the curved or straight sections of the tube located on the tube's plane. In particular, if considering two adjacent bends, and the first bend to be manufactured also has a particularly small bending radius, it becomes especially difficult to address the problem of having adjacent bends with curvatures located on different bending planes.

[0006] A method for solving the above-mentioned problem is known from the same applicant's publication WO 2020 / 012376 A1, which is particularly conceived for manufacturing so-called ELM coils for nuclear fusion reactors, i.e., coils for controlling instability at the edge of plasma (ELM - Edge Localized Mode). The present invention relates to tubular products with particularly complex geometries, having a series of closely spaced curved portions and which must be manufactured with very tight tolerances. Known methods provide a first bending operation of the tube using a first bending device, thereby creating a plurality of first curved portions separated from a second straight portion. The tube is then subjected to a second bending operation using a second bending device, through which second curved portions are formed at intervals between the first curved portions. These second curved portions may have a reduced bending radius. WO2020 / 012376 A1 does not address the manufacturing of curved portions with a reduced bending radius and three-dimensional extension.

[0007] In the manufacture of the aforementioned ELM coil, it has been recognized that it is necessary to manufacture corner portions, wherein, in addition to the curvature required for manufacturing the corners of the basically rectangular coil, there are additional curvatures in different planes (overlapping and / or adjacent to the "main" plane), wherein the main objective of the present invention is to obtain a predetermined distance between the corners of the coil and its mounting surface. Summary of the Invention

[0008] Therefore, the object of the present invention is to provide a solution for manufacturing the aforementioned corner portions with a reduced bending radius, such that these curved portions have three-dimensional development.

[0009] More generally, another object of the present invention is to provide a solution for manufacturing curved portions with three-dimensional extension in tubular products.

[0010] Therefore, this invention is not limited to the manufacture of ELM coils, but can be applied to the manufacture of other types of complex curvature tubular products.

[0011] The method according to the present invention fully achieves the above-mentioned objectives.

[0012] The advantageous embodiments of the present invention should be understood as part of the following description.

[0013] In short, the present invention is based on the idea of ​​performing a method for manufacturing a three-dimensional bend in a tubular product, starting from a tube extending along a straight longitudinal axis, the method comprising the following steps:

[0014] a) A first bending operation is performed by a first bending device on a bending plane passing through the longitudinal axis, such that the tube exiting the first bending device includes a bent portion having two opposing ends; wherein the tangents of the bent portions at said ends (hereinafter referred to as the first tangent and the second tangent) lie on the bending plane; and

[0015] b) A second bending operation is performed on the tube exiting the first bending device by means of a second bending device, such that the bent portion of the tube has a tangent at the end of the tube on a cylindrical surface having a generatrix orthogonal to a plane containing a first tangent and a plane containing a second tangent.

[0016] The present invention also relates to a method for manufacturing a tubular product with complex curvature starting from a tube extending along a straight longitudinal axis, the method comprising the following steps:

[0017] a) A plurality of first bending operations are performed by a first bending device, each first bending operation being performed on a corresponding first straight portion of the tube and a corresponding second straight portion of the tube, and each first bending operation being performed in a bending plane passing through the longitudinal axis, thereby the tube exiting the first bending device comprising a plurality of first bending portions separated by second bending portions, wherein each bending portion comprises a first bending portion and a second bending portion located on the bending plane, each second bending portion having two opposing ends, wherein tangents (hereinafter referred to as first tangents and second tangents) at the ends of the second bending portions lie on the same bending plane; and

[0018] b) Performing a plurality of second bending operations on the tube exiting the first bending device by means of a second bending device, each second bending operation targeting one of the second bending portions, such that the tube exiting the second bending device includes a corresponding bent portion having a tangent at the end on a cylindrical surface between each pair of first consecutive bent portions, the cylindrical surface having a generatrix orthogonal to a plane containing the first tangent and a plane containing the second tangent, wherein the resulting tubular product includes the first bent portion and an adjacent corner bend.

[0019] Using this method, tubular products with complex curvature can be manufactured, i.e., products with adjacent curved sections or with three-dimensional curvature, such as ELM coils. Attached Figure Description

[0020] Other features and advantages of the invention will become clear from the following detailed description, which is given by way of non-limiting example only with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a perspective view of an ELM coil, which is an example of a complex curvature tubular product obtainable by the method according to the invention.

[0022] Figure 2 It is shown Figure 1 A perspective view of the corner section of a tubular product.

[0023] Figure 3 It is similar to Figure 2 A view showing only the central axis of the tube.

[0024] Figure 4 This schematically illustrates the method for obtaining according to the invention. Figure 1 The first step in the method for producing tubular products.

[0025] Figure 5 This is a front view of the turning portion obtained in the first step of the method according to the invention.

[0026] Figure 6 Schematic illustration of the method for obtaining according to the present invention Figure 1 The second step of the method for producing tubular products.

[0027] Figure 7 and Figure 8 This is a perspective view of a shape-constrained bending device for manufacturing tubular products according to the present invention. Detailed Implementation

[0028] First refer to Figure 1 The tubular product obtainable by the method of the present invention is generally designated as 10'. The tubular product 10' includes alternating and adjacent first curved portions 10a' and second bent portions (particularly corner portions 10b"). Specifically, the bending radius of the second bent portion or corner portion 10b" is smaller than the bending radius of the first curved portion 10a'. As an example of the tubular product 10' obtainable by the method of the present invention, Figure 1 An ELM coil is shown, which includes multiple turns.

[0029] 12. Each turn has multiple curved sides corresponding to the first curved portion 10a' and a connecting portion corresponding to a corner portion 10b” between each pair of consecutive curved sides, the bending radius of the connecting portion being smaller than the bending radius of the curved sides. For example, the coil (tubular product 10') may have six turns 12, each turn having four sides (first curved portion 10a'), the four sides being joined to each other through the corner portions 10b”. Obviously, the number of turns and sides can be arbitrarily chosen according to the requirements that the coil must meet.

[0030] refer to Figure 2 and Figure 3 Specifically, it shows a single second bend or corner portion 10b” of the tubular product or coil 10', particularly arranged at a corner of the lower corner or Figure 1 The corner portion at the upper right corner of the coil. The central axis of the tubular product 10' is represented by x. From Figure 3 As can be seen, the corner portion 10b” has a three-dimensional extension; in other words, the central axis x is not on the plane. In the corner portion 10b”, the opposite ends 11b” and 12b” can be identified, at which the corner portion 10b” joins the corresponding first curved portion 10a’.

[0031] This invention stems from a general observation that, for two straight oblique lines in space, there exist two parallel planes, each containing one of these lines; these planes (hereinafter referred to as A1 and A2) are positioned a distance d from each other. The tangents t1 and t2 of the corner portion 10b” at the opposite ends 11b” and 12b” of the corner portion 10b” (more precisely, the tangents t1 and t2 of the central axis x of the corner portion 10b”) therefore lie on two corresponding planes A1 and A2, which are parallel to each other and positioned a distance d from each other.

[0032] In the example shown, the corner portion 10b” is formed by the superposition or combination of a smooth double S-curve and a sharp curve. Specifically, the tangent t1 of the corner portion 10b” at the first end 11b” lies on the first plane A1, and the tangent t2 of the corner portion 10b” at the second end 12b” lies on a second plane A2 parallel to the first plane A1. The distance between the two planes A1 and A2 is... Figure 2 and 3 The central axis x at the corner 10b” is shaped as a double S-curve on a cylindrical surface, the generatrix of which is orthogonal to planes A1 and A2. More generally, the central axis x at the corner 10b” is shaped as a double S-curve, the tangent of which to the end of the hyperbola lies on a cylindrical surface, the generatrix of which is orthogonal to planes A1 and A2.

[0033] Now for reference Figures 4 to 6 The following describes a method for manufacturing a tubular product 10', starting with a tube 10 made of metallic material.

[0034] Pipe 10 is shown in the accompanying drawings as a pipe with a circular cross-section, but its cross-section may have a shape other than a circle.

[0035] The longitudinal axis x (initially straight) of tube 10 is denoted by x. 10a represents the first straight portion of tube 10, which corresponds to the aforementioned first curved portion 10a' in the final tubular product 10', while 10b represents the second straight portion of tube 10, which corresponds to the aforementioned second bend or corner portion 10b' in the final tubular product 10'. Figure 4As shown, the first straight portion 10a and the second straight portion 10b alternate and extend immediately adjacent to the second straight portion 10b.

[0036] According to the present invention, a tubular product 10' is obtained by a manufacturing method that substantially includes the following steps:

[0037] a) A plurality of first bending operations are performed by the first bending device 20, each first bending operation being performed on a corresponding first straight portion 10a and a corresponding second straight portion 10b of the tube 10, and

[0038] b) A plurality of second bending operations are performed by the second bending device 22, each second bending operation being performed on the corresponding second straight portion 10b of the tube 10 that has already undergone the corresponding first bending operation.

[0039] In particular, Figure 4 The aforementioned step a) is shown, wherein the tube 10 is fed to the first bending device 20 via a feeding device 18 (which is of a known type and is therefore only shown very schematically in the figures) to perform the aforementioned first bending operation.

[0040] The first bending operations are performed on the corresponding first straight portion 10a and corresponding second straight portion 10b of the tube 10, respectively, and each operation is performed on a bending plane passing through the longitudinal axis x of the tube, such that the tube 10 leaving the first bending device 20 includes a plurality of corresponding first bent portions 10a' separated by second bent portions 10b'. The first bent portions 10a' and the second bent portions 10b' may be located on the same bending plane or on different bending planes. The curvature of the second bent portion 10b' is very small and therefore... Figure 4 Invisible in the view. Each of these second curved portions 10b' corresponds to the aforementioned double S-shaped curve, however, and lies on a plane passing through the longitudinal axis x of the pipe. One of these second curved portions 10b' is in Figure 5 The figure is shown in detail. In this figure, for clarity, the curvature of the second curved portion 10b' is magnified. The second curved portion 10b' includes a first curved portion 11b' and a second curved portion 12b' located on the same bending plane. This first curved portion 11b' and this second curved portion 12b' have corresponding bending radii R1 and R2 (more precisely, the central axis x), in... Figure 5 They are represented as the same value; however, this condition is not required. The inflection point 13b' lies between the first bend 11b' and the second bend 12b'. For reference, Figure 5 Ends 11b” and 12b” are also shown, which are related to Figure 2 and Figure 3 The differences shown are still located in the same plane, namely, the plane of the first curved portion 11b' and the second curved portion 12b'. Figure 5 The distance d between tangents t1 and t2 and planes A1 and A2 is also shown.

[0041] Preferably, the first bending device 20 is a free-form bending device, wherein the desired bend is applied to the tube by a moving part of the device, which applies a deformation force on the advancing tube. An example of this type of bending device is a roller bending machine.

[0042] Roller bending machines are typically only able to bend tubes within a specific bending plane that passes through the tube's longitudinal axis. To change the bending plane, the relative orientation of the rollers to the tube can be altered.

[0043] Another example of a free-form bending device is the so-called insert bending machine, such as that described in US5111675A. With such a machine, it is easier to change the plane of curvature of the tube.

[0044] Figure 6 The method according to the invention is also shown in step b), wherein the tube 10 leaving the first bending device 20 undergoes the aforementioned second bending operation via a second bending device 22 located downstream of the first bending device 20.

[0045] A second bending operation is performed on the corresponding second bending portion 10b' of the tube 10, such that the tubular product 10' leaving the second bending device 22 includes a corresponding second bending portion or corner portion 10b between each pair of first continuous bending portions 10a'.

[0046] Special reference Figure 7 and Figure 8 The second bending device 22 is preferably a form-bound bending device, which includes, in a manner known per se, a mold or die 24 having a groove 28a, and at least one clamping shoe or clamp 26 having a corresponding groove 28b. The clamping shoe or clamp 26 is provided to cooperate with the mold 24 and act on the tube 10 to bend the tube 10 according to a given curve. The second bending device 22 is configured to perform a corner bend, which overlaps on the second bend portion 10b' and is located at a position having a... Figure 2 and Figure 3 The cylindrical surface of the generatrices orthogonal to planes A1 and A2 shown. More generally, the second bending device is configured to perform a corner bend superimposed on the second bending portion 10b', such that the resulting three-dimensional bending portion has tangents to the opposite ends of the bending portion, the bending portion being located on a surface having a bend with a bend that is perpendicular to the planes A1 and A2 shown. Figure 2On the cylindrical surface of the generatrices orthogonal to planes A1 and A2. In the example shown, grooves 28a and 28b are shaped to accommodate double S-shaped curves, and groove 28a of mold 24 extends along surface 28c of mold 24, which may be at least partially cylindrical. Specifically, the dimensions of grooves 28a and 28b can be designed such that the bending radius R3 of the corner bend (more precisely, the bending radius R3 at the central axis x) is smaller than the bending radii R1 and R2 of the first bends 11b' and 12b'. This results in... Figure 2 and Figure 3 The corner section 10b' shown.

[0047] Optionally, the method may also include measuring the advance of the tube 10 and / or marking the operation of the tube 10 during its advance by means of a measuring device (not shown, but in any case known in itself) and a marking device (not shown, but in any case known in itself), such as an ink or laser marking device.

[0048] The method according to the invention can be performed, for example, by performing all first bending operations by a first bending device 20 to obtain all first bent portions 10a' and second bent portions 10b' of the tubular product 10', and then performing all second bending operations by a second bending device 22 to obtain all second corner portions 10b' of the tubular product 10'.

[0049] Alternatively, the method according to the invention can be carried out, for example, by performing a first bending operation and a second bending operation sequentially by a first bending device 20 and a second bending device 22 to obtain a portion of a tubular product 10' at one time, which includes at least two first bent portions 10a' and a second corner portion 10b between each pair of first bent portions 10a'.

[0050] In particular, when used to manufacture an ELM coil having a plurality of turns 12, the method according to the invention can be performed in the following manner: manufacturing all turns together, i.e., first performing all first bending operations and then performing all second bending operations, or manufacturing turn by turn, i.e., first performing the first bending operation conceived for the first coil, and then performing the second bending operation conceived for the first coil, and then repeating these operations for subsequent turns.

[0051] As already mentioned, another aspect of the invention relates to an apparatus for manufacturing tubular products with complex curvatures starting from a metal tube extending along a straight longitudinal axis x. In addition to the aforementioned feeding device 18, first bending device 20, and second bending device 22, this apparatus includes a support device (not shown, but of a known type in any case) arranged between the first bending device 20 and the second bending device 22 to support the tube 10 exiting the first bending device 20.

[0052] The device 30 may also include the aforementioned measuring device and / or marking device.

[0053] In the preceding description, a method for obtaining a three-dimensional bend in a tubular product 10' has been described, the method being applied to the manufacture of a complex curvature tubular product including a first bend portion 10a' and a second corner portion 10b". It will be understood that this particular method may have a more general application if a three-dimensional bend is required, the three-dimensional bend including a first bend component having opposing ends extending in a plane and a second bend component obtained by bending the plane on which the end of the first bend component lies in a cylindrical surface.

[0054] Naturally, without prejudice to the principles of the invention, embodiments and construction details may vary widely relative to the embodiments and construction details described and illustrated purely by way of non-limiting examples, without departing from the scope of the invention as defined by the appended claims. For example, the method according to the invention is not limited to the presence of the first and second bending operations described above, but may provide other bending operations performed before the first bending operation, between the first and second bending operations, or after the second bending operation.

Claims

1. A method for forming a three-dimensional bend in a tubular product (10') starting from a tube (10) extending along a longitudinal axis (x) in a straight line, the method comprising the steps of: Step a) A first bending operation is performed by a first bending device (20) in a bending plane passing through the longitudinal axis (x) such that the tube (10) exiting the first bending device (20) includes a bent portion (10b') having two opposing ends (11b'', 12b''), wherein a first tangent (t1) and a second tangent (t2) tangent to the bent portion (10b') at the two ends lie in the bending plane; and Step b) A second bending operation is performed on the bent portion (10b') of the tube (10) exiting the first bending device (20) by the second bending device (22) to obtain a bent portion (10b'') of the tube (10), wherein the tangents (t1, t2) of the bent portion at the end are located in a cylindrical plane having generatrices orthogonal to the plane (A1) containing the first tangent (t1) and the plane (A2) containing the second tangent (t2). Step a) includes performing the first bending operation such that the bent portion (10b') of the tube (10) leaving the first bending device (20) includes a first bent portion (11b') and a second bent portion (12b') located in the bending plane, wherein the inflection point (13b') is located between the first bent portion and the second bent portion.

2. The method according to claim 1, wherein, The first bending device (20) is a free-form bending device.

3. The method according to claim 1 or 2, wherein, The second bending device (22) is a shape-constrained bending device.

4. A method for manufacturing a complex curvature tubular product (10') starting from a tube (10) extending along a longitudinal axis (x) in a straight line, the method comprising the steps of: Step a) Perform a plurality of first bending operations by a first bending device (20), each first bending operation being performed on a corresponding first straight portion (10a) and a corresponding second straight portion (10b) of the tube (10), and each first bending operation being performed in a bending plane passing through the longitudinal axis (x), such that the tube (10) leaving the first bending device (20) includes a plurality of corresponding first bent portions (10a') separated by second bent portions (10b'), each second bent portion (10b') having two opposing ends (11b'', 12b''), wherein a first tangent (t1) and a second tangent (t2) tangent to the second bent portion (10b') at the two ends lie in the same bending plane; and Step b) Perform a plurality of second bending operations on the tube (10) exiting the first bending device (20) by means of a second bending device (22), each second bending operation being performed on a second bending portion (10b') such that the tube (10) exiting the second bending device (22) includes a corresponding second bending portion (10b'') between each pair of consecutive first bending portions (10a'), the second bending portion having a first tangent (t1) and a second tangent (t2) located in a cylindrical surface at the end, the cylindrical surface having a generatrix orthogonal to a plane (A1) containing the first tangent (t1) and a plane (A2) containing the second tangent (t2), wherein the tubular product (10') thus obtained includes the first bending portion (10a') and the second bending portion (10b'') adjacent to each other.

5. The method according to claim 4, wherein, Step a) includes: performing the first bending operation such that each second bending portion (10b') of the tube (10) leaving the first bending device (20) includes a first bending portion (11b') and a second bending portion (12b') located in the same bending plane, wherein the inflection point (13b') is between the first bending portion and the second bending portion.

6. The method according to claim 4 or 5, wherein, The first bending device (20) is a free-form bending device.

7. The method according to claim 4 or 5, wherein, The second bending device (22) is a shape-constrained bending device.

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