Mandrel for tube bending machine

Abstract

The mandrel for the tube bending machine has an elongated body (3) having a first end connected to the mandrel rod and a second end opposite the first end with a spherical seat (8), several intermediate articulation elements (10) and a final articulation element (11). Each of the intermediate and final articulation elements (10) has a peripheral portion (12) configured to rest against the inner wall of the tube (T) to be bent. Each intermediate articulation element (10) has a one-piece cup-shaped portion (13), a stem (19) extending from the cup-shaped portion (13), and a one-piece spherical portion (21) configured to be introduced into the cup-shaped portion (13) of the previous intermediate articulation element (10).

Description

[Technical Field]

[0001] The present invention relates to a mandrel for a tube bending machine.

[0002] Tube bending mandrels are known to be used to provide internal support for the tube being bent. The mandrel is inserted into the section of the tube to be bent, and as the bend occurs, the flexible portion of the mandrel bends with the tube, providing internal support and preventing the tube from unnecessarily collapsing or deforming. [Background technology]

[0003] Patent Document 1 discloses a mandrel for bending tubes, including a straight section and a flexible section. The straight section includes a rod that is received in a threaded coupling within a shank bore of the mandrel, which is then connected to a shank joint. The shank joint is formed in two mirror-image identical parts that are received within a male portion of an intermediate articulation element, which is also formed in two identical halves. The two identical halves are connected by an annular component having a spherical peripheral surface intended to contact the tube to be bent. The annular component is screwed onto the two halves of the articulation element. Each intermediate articulation element has a blind hole configured to accommodate a spring-loaded ball. The female seat on which the male portion of the articulation element is located has a recess at the bottom intended to receive and retain the ball. As a result, the articulation elements are aligned with each other in the non-operating position, facilitating the introduction of the mandrel into the tube to be bent. The final articulation element does not have a female component. This is because the final articulation element is not used to generate new connections to the articulation element and therefore does not need to be split into two halves.

[0004] It will be appreciated that such articulation elements need to be manufactured with considerable precision, as the internal thread of the annular component needs to be threaded into two external threads of two separate opposing pieces of the same articulation element.

[0005] To solve this problem, US Patent No. 5,629,999 describes a mandrel similar to that of the above patent in that both the shank joint and the intermediate articulation element are formed in two halves that can be assembled according to a central axial plane, but unlike the above patent, the annular component that connects the two halves and comes into contact with the wall of the tube to be bent is held by an elastic ring.

[0006] This solution eliminates the drawback of threading two parts together: the annular component and the articulation element. However, it still requires a fairly precise production of the two halves of the mandrel. As two halves, these parts have limited tolerances in use.

[0007] Patent Document 3 discloses a tube bending mandrel having a series of externally internally threaded ball members and a series of internally connected end-to-end ball link members, each having a spherical, split male portion formed at one end and a split female portion formed at the other end, the female portion having two externally threaded longitudinally extending parts whose inner surfaces cooperate to surround most of the spherical recess.

[0008] Thus, it will be understood that the female or bulbous portion is formed in two parts and not one piece.

[0009] Patent Document 4 provides a tube bending mandrel having a rigid tube and a flexible tube removably connected to the rigid tube. The mandrel's flexible tube is composed of multiple links, each of which has a male part, i.e., a link ball, movable within its respective female part, and a mandrel ball. Each link ball consists of two parts opposed along a meridian plane, the female part consisting of a cup-shaped part with an external thread extending into a cylindrical sector with a separate external thread, and both the cup-shaped part and the cylindrical sector are threaded onto the internal thread formed in the mandrel ball. To enable each female part to be removably attached to each link, it is necessary to remove the cylindrical sector of the female part so that one of the balls can be easily replaced if damaged.

[0010] It is therefore understood that both the female and male parts of the flexible tube of the mandrel according to US Pat. No. 5,649,999 are each made as two parts and not as one piece. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 4,635,464 [Patent Document 2] U.S. Patent No. 6,085,572 [Patent Document 3] U.S. Patent No. 3,408,850 [Patent Document 4] U.S. Patent No. 3,286,503 Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to overcome the drawbacks arising from the fact that in the prior art, the flexible portion of the mandrel is manufactured from link elements having a female component, a male component, or both, which are formed in at least two parts that are joined during assembly of the flexible portion of the mandrel prior to use.

[0013] It is an object of the present invention to form both the female and male components of the flexible portion of the mandrel in one piece.

[0014] Another object of the present invention is to provide a flexible portion of a mandrel that can be prepared for use in a simple and quick manner.

[0015] It is a further object of the present invention to provide a flexible portion of the mandrel that has higher mechanical strength characteristics than those of the prior art.

[0016] It is yet another object of the present invention to provide an articulation element that uses fewer parts than conventional articulation elements and is therefore easier and faster to assemble than previously possible.

[0017] It is a further object of the present invention to provide an articulating element formed of parts that are easily replaceable in the event of damage or wear. [Means for solving the problem]

[0018] The above and other objects are achieved by a mandrel for a tube bending machine comprising an elongated body having a first end connected to a mandrel rod and a second end opposite the first end where a spherical seat is present, at least an intermediate articulation element, and a final articulation element.

[0019] Each intermediate articulation element includes a ball joint, a one-piece cup-shaped portion having a spherical seat, a stem extending outwardly from the one-piece cup-shaped portion, and a one-piece spherical portion configured to be received in the spherical seat.

[0020] Because each spherical joint has only one male and one female component, the spherical joints do not require the precision of construction as the flexible portion of a conventional mandrel.

[0021] To allow the spherical part of the male component to be introduced into the spherical seat or the female component while maintaining the functionality of the ball joint where the male and female components fit closely together, the spherical part is configured like a sphere with a lightened periphery. The spherical part is preferably a solid cylindrical shape with opposite bases being spherical caps of the same sphere with the same axis perpendicular to the central axis of the spherical part. The diameter of the sphere is slightly smaller than that of the spherical seat of the female component.

[0022] Advantageously, said solid body is defined by a flat surface using a secant plane perpendicular to said central axis, and in addition, said solid body has a main hole oriented along the central axis of the spherical part for the insertion of a stem.

[0023] Advantageously, the male component has at least one second threaded hole in a lateral direction or a third threaded hole that is angled for the insertion of a set screw. The set screw in the second threaded hole can prevent the threaded stem from unscrewing from the spherical portion, and the set screw in the third threaded hole can seal the smooth stem of the spherical portion.

[0024] The present invention will now be described with reference to preferred embodiments and associated variants, taken in conjunction with the accompanying drawings, which are described below. [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows an axial longitudinal section of a first embodiment of a mandrel for a tube bending machine according to the invention, showing the interior of the tube after a 90° bending operation. [Figure 2] FIG. 2 is an enlarged perspective view of the cup-shaped portion and stem of the intermediate articulation element of FIG. 1. [Figure 3]FIG. 3 is a rear end view of the cup-shaped portion and stem of the intermediate articulation element of FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 5] FIG. 2 is an enlarged perspective view of the male component or ball portion of the intermediate articulation element of FIG. 1. [Figure 6] FIG. 6 is an end view of the male component of FIG. 5. [Figure 7] FIG. 7 is a cross-sectional view taken along line BB in FIG. 6. [Figure 8] FIG. 6 is a side view of FIG. 5. [Figure 9] FIG. 6 is a top view of the male component of FIG. 5. [Figure 10] FIG. 6 is a bottom view of the male component of FIG. 5. [Figure 11] FIG. 1 is an axial longitudinal section of a second embodiment of a mandrel for a tube bending machine according to the invention, showing the interior of the tube after a 90° bending operation, in which a first variant of the cup-shaped part and stem of the intermediate articulation element is used; [Figure 12] 12 is an end view similar to FIG. 3 of a first variant of the cup-shaped portion and stem of the intermediate articulation element of FIG. 11; FIG. [Figure 13] FIG. 13 is a cross-sectional view taken along line CC in FIG. [Figure 14] FIG. 10 is an axial longitudinal section of a third embodiment of a mandrel for a tube bending machine according to the invention, showing the interior of the tube after a 90° bending operation, in which a second variant of the cup-shaped part and stem of the intermediate articulation element is used. [Figure 15] 15 is an end view similar to FIG. 3 of a second variant of the cup-shaped portion of the intermediate articulation element of FIG. 14. FIG. [Figure 16] FIG. 16 is a cross-sectional view taken along line DD in FIG. [Figure 17] FIG. 8 is a view similar to FIG. 7 showing a first modified example of the spherical portion. [Figure 18] 18 is a partial longitudinal cross-sectional view of two intermediate articulation elements using the second variant of the cup-shaped portion and stem of FIG. 16 and the first variant of the spherical portion of FIG. 17. FIG. [Figure 19] FIG. 10 is an axial longitudinal section of a fourth embodiment of a mandrel for a tube bending machine according to the invention, showing the interior of the tube after a 90° bending operation, in which a third variant of the cup-shaped portion and stem of the intermediate joining element is used. [Figure 20] FIG. 20 is a front end view of a third variation of the cup-shaped portion and stem of the intermediate articulation element of FIG. 19; [Figure 21] FIG. 21 is a cross-sectional view taken along line EE in FIG. 20. [Figure 22] 22 is a cross-sectional view similar to FIG. 21 of the outer cup-shaped portion and stem of the articulating end element of FIG. 19; [Figure 23] FIG. 10 is a side view of a fourth variant of the cup-shaped portion of the intermediate articulation element according to the present invention. [Figure 24] FIG. 24 is a cross-sectional view taken along line FF in FIG. 23. [Figure 25] FIG. 1 is an axonometric view of a first variant of a stem according to the invention. [Figure 26] FIG. 26 is a front end view of a first variant of the stem of FIG. 25. [Figure 27] FIG. 26 is a side view of a first variant of the stem of FIG. 25. [Figure 28] FIG. 28 is a cross-sectional view taken along line GG in FIG. 27. [Figure 29] 26 is a partial longitudinal cross-sectional view of two intermediate articulation elements using the fourth variant of the cup-shaped portion of FIG. 23 and the first variant of the stem of FIG. 25. FIG. [Figure 30] FIG. 10 is a side view of a fifth variant of the cup-shaped portion and stem of an intermediate articulation element according to the present invention. [Figure 31] FIG. 31 is a cross-sectional view taken along line HH in FIG. 30. [Figure 32] FIG. 31 is a front end view of a fifth variation of the cup-shaped portion of FIG. 30. [Figure 33] FIG. 10 is an axonometric view of a second variant of the spherical portion according to the invention. [Figure 34] 34 is a rear end of a second variation of the bulbous portion of FIG. 33. [Figure 35] FIG. 35 is a cross-sectional view taken along line II in FIG. 34. [Figure 36] FIG. 34 is a top view of a second variation of the bulbous portion of FIG. 33. [Figure 37] 33A and 33B are partial longitudinal cross-sectional views of two intermediate articulation elements using the fifth variant of the cup-shaped portion and stem of FIG. 30 and the second variant of the spherical portion of FIG. [Figure 38] FIG. 10 is a side view of a sixth variant of the cup-shaped portion of the intermediate articulation element according to the present invention; [Figure 39] FIG. 39 is a cross-sectional view taken along line LL in FIG. 38. [Figure 40] FIG. 39 is a front end view of a sixth variation of the cup-shaped portion of FIG. 38. [Figure 41] FIG. 10 is an axonometric view of a second variant of the stem according to the invention. [Figure 42] FIG. 42 is a front end view of a second variant of the stem of FIG. 41. [Figure 43] FIG. 42 is a side view of a second variant of the stem of FIG. 41. [Figure 44] FIG. 44 is a cross-sectional view taken along line MM in FIG. 43. [Figure 45] 42 is a partial longitudinal cross-sectional view of two intermediate articulation elements using the sixth variant of the cup-shaped portion of FIG. 38, the second variant of the spherical portion of FIG. 33, and the second variant of the stem of FIG. 41. FIG. [Figure 46] 1A-1C are partially exploded cross-sectional views illustrating the assembly steps of a mandrel according to the present invention. [Figure 47] 1A-1C are partially exploded cross-sectional views illustrating the assembly steps of a mandrel according to the present invention. [Figure 48] 1A-1C are partially exploded cross-sectional views illustrating the assembly steps of a mandrel according to the present invention. [Figure 49] 1A-1C are partially exploded cross-sectional views illustrating the assembly steps of a mandrel according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention is described in embodiments and variants shown in the drawings, in which the same or similar parts are given the same reference numerals.

[0027] Conventionally, as shown in the axial longitudinal sections of Figures 1, 11, 14 and 19, within a tube T already bent by 90°, the mandrel for bending the tube has a straight section 1 and a flexible section 2. The tube may have a circular or polygonal cross section.

[0028] The straight section 1 has an elongated body 3, which is connected in a conventional manner by a screw thread 4 to a mandrel rod (not shown). The elongated body 3 has an axis t that coincides with the axis of the bent tube T. The elongated body 3 has a preferably cylindrical cavity therein, in which an insert 5 having a spherical seat 8 for a spherical joint is housed. The insert 5 is held in place by a screw 6, which is shown in the drawings as a hexagonal threaded bolt. The elongated body 3 conventionally has a lubrication passage, generally designated 7, communicating with the interior of the tube T. According to the invention, the insert 5 is formed in one piece coaxially with the tube T, which also coincides with the axial center t of the elongated body 3. Obviously, the straight section 1 is intended to remain in the straight section of the bent tube T during the bending operation. The spherical seat 8 of the insert 5 communicates with the elongated body 3 through at least one hole 9.

[0029] The flexible part 2 comprises at least one intermediate articulation element 10 and a final articulation element 11, each of which is surrounded by a periphery 12 configured to rest against the inner wall of the bendable tube T. If the tube is cylindrical, the periphery is in the shape of a spherical segment intended to contact the cylindrical wall of the bendable tube T. If the bendable tube T is polygonal, for example square or rectangular, the periphery is accordingly shaped. According to a first embodiment of the invention, each intermediate articulation element 10 and final articulation element 11 is inserted into a central hole in their periphery 12 and is held there in the conventional manner.

[0030] Reference is made to Figures 2, 3 and 4, which are an enlarged perspective view of the cup-shaped portion and stem of the articulation element in Figure 1, a rear end view of the cup-shaped portion and stem of the intermediate articulation element in Figure 2, and a cross-sectional view along line AA in Figure 3. Each intermediate articulation element 10 comprises a cup-shaped portion 13 of a ball-joint having a central axis c. The cup-shaped portion 13 has a spherical seat 14 with a determined inner diameter. The spherical seat 14 is substantially in the shape of a part-spherical cavity bounded on the outside by a laterally projecting peripheral edge 15 at a projection 48.

[0031] At least one hole 16, two in the illustrated embodiment, is formed according to a transverse axis d perpendicular to the central axis c, the purpose of which will be explained later.

[0032] The peripheral edge 15 prevents the male component of the ball joint from disengaging, as will be shown below. When the cup-shaped portion 13 is inserted into the peripheral portion 12, the peripheral edge 15 extends laterally outward at a projection 48 that abuts, in a known manner, against a corresponding shoulder formed on the peripheral portion 12. The cup-shaped portion 13 is retained in the peripheral portion 12 by a resilient ring 17 (FIG. 1) received in a groove 18 in the cup-shaped portion 13.

[0033] The cup-shaped portion 13 of the intermediate articulation element extends along a central axis c to a stem 19 that extends outwardly from the cup-shaped portion. The stem 19 is threaded. Between the cup-shaped portion 13 and the stem 19 there is an annular surface 20 that serves as the abutment surface for the male component of the ball joint, hereafter referred to as the spherical portion 21. The spherical portion 21 is shown in enlarged perspective views, orthogonal cross-sections in Figures 5, 6, 7, 8, 9 and 10 and in a cross-section along line BB in Figure 6.

[0034] The spherical portion 21 is one piece and has a central axis s. It is configured to be introduced into and held in the spherical seat 8 of the insert 5 of the elongated body 3 or in the spherical seat 14 of the cup-shaped portion 13 of the intermediate articulation element. For this purpose, the spherical portion 21 can be considered to be a substantially lightweight sphere, the opposite bases of which are formed by cylinders 22 with spherical caps 23, 23. The cylinder 22 connecting the two spherical caps 23, 23 may be replaced by a prism or other elongated shape, since only the spherical caps 23, 23 come into contact with the spherical seat 8 of the insert 5 or the spherical seat 14 of the cup-shaped portion 13 of the intermediate articulation element. The spherical portion 21 has a main threaded hole 24 in the direction of the central axis s and is defined by a flat surface 25 using a secant plane perpendicular to the central axis s. A stem 19 extending from the cup-shaped portion 13 is threaded into a threaded main bore 24 of the spherical portion 21. Additionally, the spherical portion 21 is formed with at least one second threaded bore 26 having a transverse axis r perpendicular to the axis s of the threaded main bore 24. The second threaded bore 26 is configured to receive a set screw 27 ( FIG. 1 ) capable of locking the stem 19 threaded into the spherical portion 21. The set screw 27 is inserted into both the cup-shaped portion 13 of the intermediate articulation element 10 through the hole 16 and the ball-joint insert 5 of the elongated body 3 through the hole 9 before the intermediate articulation element 10 is inserted into the peripheral portion 12 and the insert 5 is inserted into the elongated body 3.

[0035] According to a first embodiment shown in Figure 1, the stem 19 has a free end in which is provided a blind hole 31 (Figure 4) coaxial with the central axis c of the cup-shaped portion 13. The blind hole 31 is suitable for accommodating a pre-compressed helical spring 28 and a ball 29. Both the spherical seat 14 of the cup-shaped portion 13 of the intermediate articulation element 10 and the spherical seat 8 of the insert 5 of the elongated body 3 have a recess 30 in the shape of a spherical cap with axes coinciding with the central axes t and c, respectively. The recess 30 in the shape of a spherical cap is configured to receive and hold the ball 29 loaded by the helical spring 28 in the blind hole 31 of the stem 19. As shown, this arrangement serves to keep the flexible portion 2 of the mandrel straight when the mandrel is not in place and needs to be inserted into a new bendable tube.

[0036] 11 which shows an axial longitudinal section of a second embodiment of a mandrel according to the invention, in which the insert 5, the intermediate articulation element 101 and the final articulation element 111 all differ slightly from the first embodiment. In FIG. 11 it can be seen that the variant of the insert 5 of the elongate body 3 and the first variant of the cup-shaped portion 131 of the intermediate articulation element 101 have a blind hole 32.

[0037] Figures 12 and 13 show a rear end view and a cross-sectional view along line CC of a first variant of the cup-shaped portion 131. In particular, Figure 13 shows in detail the blind hole 32 in the cup-shaped portion 131 that is coaxial with the central axis c. The blind hole 32 is configured to receive the pre-compressed helical spring 28 and the ball 29. The stems 191 of the intermediate articulation element 101 and the final articulation element 111 are also threaded.

[0038] Like that of the final articulation element 111, the stem 191 of the intermediate articulation element 101 also has in its free end 40 a recess 33 in the shape of a spherical cap having an axis coinciding with the central axis c of the cup-shaped portion 131. As in the first embodiment, the recess 33 in the shape of a spherical cap is configured to receive and retain the insert 5 of the elongate body 3 and the ball 29 loaded by the helical spring 28 in the blind hole 32 in the cup-shaped portion 131 of the intermediate articulation element 101.

[0039] Reference is made to Figure 14, which shows an axial longitudinal section of a third embodiment of a mandrel according to the invention, in which the insert 5, the intermediate articulation element 102 and the final articulation element 112 are all slightly different from those of the second embodiment. Figures 15 and 16 show an end view and a section along line DD of a second variant of the cup-shaped portion 132. Figure 17 shows a first variant of the spherical portion, similar to Figure 7, but with slight modifications that will be explained later. Due to the minor differences, the spherical portion retains the reference number 21. Figure 18 is a partial longitudinal section of two intermediate articulation elements using the second variant of the cup-shaped portion 132 of Figure 16 and the first variant of the spherical portion 21 of Figure 17.

[0040] It will be noted in Figure 14 that both the insert 5 of the elongated body 3 and the cup-shaped portion 132 of the intermediate articulation element 102 preferably have a cylindrical blind hole 34. Figure 16 shows in detail the blind hole 34 in the cup-shaped portion 132 coaxial with the central axis c. The blind hole 34 is configured to accommodate a permanent magnet 35 (Figure 14), which is preferably a neodymium magnet. The permanent magnet 35 is dimensioned to be received and retained in the blind hole 34. The stem 192 of the intermediate articulation element 102 and the stem 193 of the final articulation element 112, both of which are threaded and made from steel, are attracted to the permanent magnet 35, causing the flexible portion 2 of the mandrel to automatically remain straight against gravity before being introduced into the tube to be bent.

[0041] As already mentioned before, the spherical portion 21 is inserted into the spherical seat 14 of the cup-shaped portion 132 after the permanent magnet 35 has been inserted into the cavity of the blind hole 34. At this point, the stem 192 of the intermediate articulation element 102 or the stem 193 of the final articulation element 112 can be screwed into the spherical portion 21. The spherical portion 21 has a seat 39 that receives an abutment 45 located between the cup-shaped portion 132 and the threaded stem 192. The abutment 45 adds a shoulder 46 intended to abut the flat surface 25 of the spherical portion 21 when the stem 192 is fully screwed into the main bore 24 of the spherical portion 21. In this position, the annular surface 20 of the threaded stem 192 contacts the base 47 of the seat 39 of the spherical portion 21. Thanks to the abutment 45 of the stem 192, which is positioned after being screwed into the seat 39 of the spherical portion 21, the rattle of the interconnection is reduced, thus reducing the risk of wear and failure of parts when using a mandrel according to the invention.

[0042] To improve the sealing of the ball joint thus produced, a set screw 27 is inserted into the hole 16 in the cup-shaped portion 132 to prevent the threaded portions of the stem 192 or stem 193 from loosening.

[0043] 19, which shows an axial longitudinal section of a fourth embodiment of a mandrel according to the invention. The elongated body 300, the intermediate articulation element 103 and the final articulation element 113 have been modified. It should be noted that, unlike the previous embodiments in which the spherical seat 8 was formed in the insert 5 of the elongated body 3, in the straight section 1 of the mandrel according to the fourth embodiment, the spherical seat 8 is obtained directly in the elongated body 300. At a first end, the elongated body 300 is configured to be connected to a mandrel rod (not shown) by means of a threaded coupling 4, which has a lubrication passage, generally designated 7, communicating with the interior of the tube T. At a second end, the elongated body 300 has at least one hole 90 (two in FIG. 19), which is perpendicular to the central axis t of the elongated body 300 and communicates with the interior of the tube T. As shown in Figures 5, 6, 7, 8, 9 and 10, the hole 90 allows for the passage of the set screw 27 when the spherical portion 21 is inserted into the spherical seat 8 and the hole 90 is coaxial with the second threaded hole 26 of the spherical portion 21.

[0044] In the fourth embodiment, the flexible portion 2 of the mandrel also has some differences from the previous embodiments.

[0045] In the intermediate joint element 103, the peripheral portion 121 is one piece with the cup-shaped portion 133, as shown in detail in FIG. 20, an enlarged front end view of the cup-shaped portion of the intermediate joint element of FIG. 19, and in FIG. 21, a cross-sectional view along line E-E of FIG. 20. The peripheral portion 121 is represented as a spherical segment, in this case a mandrel intended for use with cylindrical bendable tubes. A hole 160 is formed in the peripheral portion 121, connecting the interior of the tube T with the spherical seat 14 of the cup-shaped portion 133. The hole 160, which is perpendicular to the central axis c of the cup-shaped portion 133, is configured to allow passage of the set screw 27 when the spherical portion 21 is inserted into the spherical seat 14 and the hole 160 is coaxial with the second threaded hole 26 of the spherical portion 21 (FIG. 19).

[0046] 19 and 22, which are cross-sectional views similar to FIG. 21 of the final articulation element 113 according to the fourth embodiment, the periphery 121 having spherical segments is also in one piece with the cup-shaped portion 122. It is self-evident that if the bendable tube has a square portion, the periphery of the intermediate articulation element and the final articulation element will have a square outer shape together with the elongated body 300.

[0047] It will be appreciated that the one-piece construction of the peripheral cup-shaped portion of the final articulation element 113 reduces the number of parts to manufacture the mandrel and therefore manufacturing costs, and also makes assembly easier and faster.

[0048] In the rest, the flexible portion 2 of the fourth embodiment of the invention is the same as in the third embodiment. In fact, both the elongated body 300 and the cup-shaped portion 133 of the intermediate articulation element 103 have blind holes 34. Figure 21 shows in detail the blind holes 34 of the cup-shaped portion 133, which are coaxial with the central axis c. The blind holes 34 are suitable for accommodating and properly holding permanent magnets 35 (Figure 19). The threaded stem 192 of the intermediate articulation element 103 and the threaded stem 193 of the cup-shaped portion 122 of the final articulation element 113, both made of steel, are attracted by the permanent magnets 35, as a result of which the flexible portion 2 of the mandrel is straightened before being introduced into the tube to be bent. It is clear that the variants of the intermediate and final articulation elements having a periphery integral with the cup-shaped portion, as well as the variants of the straight portion of the mandrel having a spherical seat obtained in the elongated body, are also applicable to the other embodiments of the invention described above.

[0049] 23 and 24, which show a side view and a cross-sectional view along line FF in Fig. 23, of a fourth variant of the cup-shaped portion of the intermediate articulation element according to the present invention. Comparing the fourth variant of the cup-shaped portion 134 with the first embodiment (Fig. 4), it should be noted that the cup-shaped portion 134 of the intermediate articulation element has a through-hole 140 coaxial with the central axis c. The through-hole 140 is provided with an abutment portion 141.

[0050] Inserted into the through-hole 140 is a stem 194, which, unlike the previous embodiment, is made up of a body separate from the cup-shaped portion 134 and can be considered a first modified example of a stem according to the present invention.

[0051] The stem 194 is shown in an axonometric view in Figure 25, a front end view in Figure 26, a side view in Figure 27, and a cross-sectional view in Figure 28 taken along line GG in Figure 27. Similar to the cup-shaped portion, the stem 194 of axis c comprises a head 37, a smooth proximal portion 41, and a threaded distal portion 42.

[0052] At the end of the head 37, the stem 194 has a recess 43 with a spherical cap, coaxial with the axis c, and a preferably hexagonal recess 44 for screwing in the stem 194. Using the fourth variant of the cup-shaped part of Figure 23 and the first variant of the stem of Figure 25, at the end 40 opposite the head 37, a blind hole 34 is formed as a seat for a permanent magnet 35, which is shown in Figure 29, a partial longitudinal section of two intermediate articulation elements 104.

[0053] To assemble the embodiment of the mandrel shown in the intermediate articulation element 104, 104, the spherical portion 21 is inserted into the spherical seat 14 of the cup-shaped portion 134. A stem 194, which forms part of the continuous intermediate articulation element 104 with a permanent magnet 35 in its cylindrical seat 34, is screwed into the main threaded hole 24 of the spherical portion 21 by using a key to act on the recess 44 in the head 37 of the stem 194. To complete the ball joint, a set screw 27 is inserted into the second hole 16 until it contacts the thread 42 of the stem 194. The spherical portion 21 is thus constrained in the spherical seat 14 of the cup-shaped portion 134 and holds the articulation element. Due to the mutual contact of the free end 40 of the stem and the head 37 of said stem, the spherical cup-shaped recess 43 allows the intermediate articulation element 104 to rock relative to the previous element.

[0054] The fourth variant of the cup-shaped portion 134 and the second variant of the stem 194 cooperate to produce an intermediate articulation element 104 that is formed by adding components compared to the previous variants, but which allows for easy manufacture of the mandrel and quick replacement of damaged or worn parts.

[0055] 30, 31 and 32, which are a side view of a fifth variant of the one-piece cup-shaped portion 135 with stem 195 of the present invention, a cross-sectional view along line HH in FIG. 30, and a front end view of the fifth variant of the cup-shaped portion of FIG. 30.

[0056] The fifth variant of the cup-shaped portion 135 cooperates with the first variant of the spherical portion 210 represented in Figures 33, 34, 35 and 36 to produce the intermediate articulation element 105 shown in partial longitudinal section in Figure 37, which show an axonometric view, a rear end view, a section along line II in Figure 34 and a top view of the spherical portion 210.

[0057] The main difference between the intermediate articulation element 105 and, for example, the articulation element 102 of the third embodiment of the mandrel is that the stem 195 is unthreaded, smooth, and has a lateral indentation 36. Preferably, the lateral indentation 36 is angled in a longitudinal section on one side, approximately perpendicular to the axis c of the intermediate articulation element 195. The spherical portion 210 has a third threaded hole 260 with an axis i that is inclined relative to the central axis s of the smooth, i.e., unthreaded, main bore 240. The third threaded hole 260, which communicates with the main bore 240 of the spherical portion 210, is adapted to receive a set screw 270. The set screw 270 has a head located below and a flat end opposite. A recess 38 is formed in the peripheral edge 15 of the cup-shaped portion 135 to allow the set screw to be easily threaded into the third threaded hole 260. When it is coaxial with the third threaded hole 260, the set screw 270 can reach the lateral recess 36 of the stem 195, with its flat end abutting the side of the lateral recess 36 approximately perpendicular to the axis c. In this way, when inserted into the main hole 240 of the spherical portion 210, the position of the stem 195 of the articulation element is locked, preventing rotation and movement of the stem 195. As a result, rotation and movement of the cup-shaped portion 135, which is one piece with the stem 195, are also prevented. Although not shown, a stem 195 with a fifth variation of the cup-shaped portion 135 can be used in the final articulation element.

[0058] Referring to FIG. 37, in which two intermediate articulation elements 105 use the fifth variation of the cup-shaped portion of FIG. 30 and the second variation of the spherical portion 210 of FIG. 33, assembly of the aforementioned intermediate articulation elements 105 is shown.

[0059] First, the spherical portion 210 is inserted into the spherical seat 14 of the cup-shaped portion 135, and then the permanent magnet 35 is inserted into the blind hole 34. The stem 195 of the continuous intermediate articulation element 105 is introduced into the spherical portion 210. Then, a set screw 270 is screwed through a third threaded hole 260 arranged along and coaxially with the recess 38 in the peripheral edge 15 of the cup-shaped portion 135 until its top penetrates into the recess 36 on the side of the stem 195 in the appropriate rotational position. The free end 40 of the stem is beveled to allow the cup-shaped portion 135 to swing relative to the permanent magnet 35.

[0060] It will be appreciated that the advantages of the cup-shaped portion 135 and the associated fifth variant of the stem 195 and the second variant of the spherical portion 210 lie, inter alia, in their structural simplicity, which does not require a threaded connection of the stem 195 and the spherical portion 210. The number of components of the articulation element 105 is less than that of the articulation element 104.

[0061] Reference is made to Figures 38, 39 and 40, which are a side view of a sixth variant of the cup-shaped portion 136 according to the present invention, a cross-sectional view along line LL in Figure 39 and a front view of the sixth variant of the cup-shaped portion in Figure 38.

[0062] The sixth variant is similar to the fourth variant in that the cup-shaped portion 134 (FIG. 23) has a through hole 140 coaxial with the central axis and is provided with an abutment surface 141. Like the cup-shaped portion 135 of the fifth variant, the cup-shaped portion 136 has a recess 38 in the peripheral edge 15 and does not have the second lateral hole 16 of the fourth variant.

[0063] Inserted into the through hole 140 is a second variant of stem 196, which, like the stem 195 of the fifth variant, is unthreaded and, like the first variant of stem 194, has a body separate from the cup-shaped portion 136, and can be considered the second variant of the stem according to the present invention.

[0064] The stem 196 is shown in Figure 41 in an axonometric view, in Figure 42 in a rear end view, in Figure 43 in a side view, and in Figure 44 in a cross section taken along line MM in Figure 43. The stem 196, of axis c similar to the cup-shaped portion, is provided with a head 37 having a spherical cup-shaped recess 43 and is smooth. At the end 40 opposite the head 37 is a blind hole 34 for a permanent magnet 35. The sixth variant of the cup-shaped portion 136 cooperates with the second variant of the spherical portion 210 depicted in Figures 33, 34, 35 and 36 described above to produce the intermediate articulation element 106.

[0065] The main difference of the intermediate articulation element 106 with respect to the articulation element 105 is the fact that the stem 196 is not one piece with the cup-shaped portion 136. As already mentioned, the spherical portion 210 has a third threaded hole 260 with an axis i inclined relative to the central axis s of the smooth, i.e., unthreaded, main bore 240. The third threaded hole 260, which communicates with the main bore 240 of the spherical portion 210, is configured to receive a set screw 270. To facilitate threading the set screw into the third threaded hole 260, a recess 38 is provided in the peripheral edge 15 of the cup-shaped portion 136, as in the fifth variant of the cup-shaped portion 135 of FIG. 31. When the recess 38 is coaxial with the third threaded hole 260, the set screw 270 can reach the recess 36 laterally of the stem 196, as already described for the stem 195 of the fifth variant of the cup-shaped portion 135. In this manner, when inserted into the main bore 240 of the spherical portion 210, the position of the articulation element stem 196 is locked and prevented from rotation and translation.

[0066] 45, which is a partial longitudinal cross-sectional view of two intermediate articulation elements 106, the assembly of the aforementioned intermediate articulation elements 106 is shown. Each intermediate articulation element 106 uses the sixth variant of the cup-shaped portion 136 of FIG. 38, the second variant of the stem 196, and the second variant of the spherical portion 210 of FIG. 33.

[0067] First, the spherical portion 210 is inserted into the spherical seat 14 of the cup-shaped portion 136. Then, after the permanent magnet 35 has been inserted into the blind hole 34, the second variant of the rod 36 is inserted into the main hole 240. Afterwards, a set screw 270 is threaded through a third threaded hole 260 arranged along and coaxially with the recess 38 in the peripheral edge 15 of the cup-shaped portion 136 until its top penetrates into the lateral recess 36 of the stem 196 in the appropriate rotational position. The free end 40 of the stem 196 is received in the spherical cup-shaped recess 43 of the continuous stem 196, allowing the intermediate articulation element 106 to swing.

[0068] It will be appreciated that the advantages of the cup-shaped portion 136 and the associated sixth variant of the stem 196 and the second variant of the spherical portion 210 lie, inter alia, in their structural simplicity, which does not require a threaded connection of the stem 196 and the spherical portion 210, and the number of components of the articulation element 106 is the same as that of the articulation element 104.

[0069] It should be understood that the present invention, in its various embodiments and variants, achieves its intended purpose, particularly in that each articulation element is not manufactured in two symmetrically identical parts that remain constant even when the mandrel is disassembled. Assembly time of the mandrel is reduced while durability in use is increased. In particular, the integral shape of the elongated body 300 of the intermediate articulation element 103 and the final articulation element 113 further reduces the manufacturing cost and assembly time of the mandrel while increasing durability in use.

[0070] Figures 46 to 49 are partially exploded cross-sectional views that schematically summarize the successive assembly steps of a mandrel according to the invention. In particular, the connection of an intermediate articulation element to the elongated body of the mandrel is shown. First, a one-piece spherical portion 21, shaped like a square and lightened at the periphery, is introduced into the spherical seat 8 of the insert 5 of the elongated body 3 of the mandrel. This is made possible by the fact that the spherical portion 21 is defined by a flat surface 25 using a secant plane perpendicular to the central axis s of the spherical portion. As shown in Figure 46, the spherical portion 21 is introduced into the spherical seat 8 in an arrangement such that the central axis s is perpendicular to the central axis t of the elongated body 3, i.e., the insert 5. Figure 47 shows that the spherical portion 21 is rotated 90° to be accommodated in the spherical seat 8 of the elongated body 3. Afterwards (Figure 48), the one-piece intermediate articulation element 10 is introduced into the periphery 12 and held there by the elastic element 17. As shown in FIG. 49, the intermediate articulation element 10 has its stem 19 threaded onto the spherical portion 21 and inserted into the spherical cavity 8 of the insert 5 where it is held by the set screw 27 .

[0071] It will be appreciated that, according to the present invention, both the spherical portions and the intermediate articulation element are made in one piece. This allows for easy manufacture of the mandrel components, easy assembly and, above all, improves the overall mechanical strength of the mandrel. In fact, unlike the prior art, there are no means for retaining the spherical portions in their respective spherical seats. In fact, the retaining means are more prone than others to wear out, rendering a mandrel made according to the teachings of the prior art unusable. [Explanation of symbols]

[0072] 3;300 Long and slender body 5 Insert 7 screws 8 Spherical seat 9 holes 10;101;102;103;104;105;106 Intermediate articulating element 11;111;112;113 Final articulating element 12;121 Periphery 13;131;132;133;134;135:136 Cup-shaped part 14 Spherical seat 15 Peripheral margin 16 holes 17 Elastic Ring 18 Groove 19;191;192;194;195;196 stem 21;210 Spherical part 24;240 Main hole 25 flat surface 26 Second screw hole 27 Set screw 28 Pre-compressed coil spring 29 balls 30 depression 31 blind hole 32 blind hole 33 Depression 34 blind hole 35 Permanent Magnets 36 Side notch 37 Head 38 Recess 40 Stem end 90 holes 120;122 The outer cup-shaped part 140 through hole 141 Contact part 193 Final Articulating Element Stem 260 Third screw hole c Center axis i-axis r horizontal axis s center axis t center axis T-tube

Claims

1. 1. A mandrel for a tube bending machine, comprising: an elongated body (3; 300) having a central axis (t), a first end connected to the mandrel rod, and a second end opposite said first end, on which a spherical seat (8) is located; at least one intermediate articulation element (10; 101; 102; 103; 104; 105; 106) and a final articulation element (11; 111; 112; 113), both of which have a periphery (12; 121) adapted to rest against the inner wall of the tube (T) to be curved, Equipped with The at least one intermediate articulation element (10; 101; 102; 103; 104; 105; 106) a cup-shaped portion (13; 131; 132; 133; 134; 135; 136) in one piece, having a central axis (c) and comprising a spherical seat (14) with an opening defined by a peripheral edge (15), and an articulation element stem (19; 191; 192; 194; 195; 196) in said intermediate articulation element (10; 101; 102; 103; 104; 105; 106) extending outwardly from said cup-shaped portion (13; 131; 132; 133; 134; 135; 136) along said central axis (c) of said cup-shaped portion (13; 131; 132; 133; 134; 135; 136) and terminating in a stem end (40), a one-piece spherical part (21; 210) having a central axis (s) and a main hole (24; 240) oriented along the central axis (s) of the spherical part (21; 210), the main hole (24; 240) being defined by a flat surface (25) by a secant plane perpendicular to the central axis (s) so that the spherical part (21; 210) has a height that allows it to be introduced into the spherical seat (8) of the elongate body (3; 300) and held by the peripheral edge (15); A mandrel comprising:

2. The final articulation element (11; 111; 112; 113) a cup-shaped portion (120; 122) in one piece and having a central axis and a final articulation element stem (193) extending outwardly from said cup-shaped portion (120; 122) along said central axis; a one-piece spherical part (21; 210) having a central axis (s) and a main hole (24; 240) oriented along the central axis (s) of the spherical part (21; 210), the main hole (24; 240) being defined by a flat surface (25) by a secant plane perpendicular to the central axis (s) so that the spherical part (21; 210) has a height that allows it to be introduced into the spherical seat (14) of the cup-shaped part (13; 131; 132; 133; 134; 135; 136) and held by the peripheral edge (15), The mandrel of claim 1 , having

3. - said main hole (24) of said spherical part (21) is threaded; - said articulation element stem (19; 191; 192; 193; 194) is threaded, 3. A mandrel according to claim 1 or 2, wherein the spherical portion (21) comprises at least one second threaded hole (26) having a transverse axis (r) perpendicular to the central axis (s) of the main hole (24) and suitable for receiving a set screw (27) capable of locking the articulation element stem (19; 191; 192; 193; 194) screwed into the main hole (24) of the spherical portion (21).

4. - said cup-shaped portion (135; 136) has a recess (38) in said peripheral edge (15); - said articulating element stem (195; 196) is smooth and has a lateral notch (36); - said main hole (240) of said spherical portion (210) is smooth; 3. The mandrel according to claim 1, wherein the spherical portion (210) has a third threaded hole (260) having an axis (i) inclined with respect to the central axis (s) of the main bore (240), the third threaded hole (260) communicating with the main bore (240) and capable of receiving a set screw (270) when the recess (38) is coaxial with the third threaded hole (260), the set screw (270) being suitable, when inserted into the main bore (240) of the spherical portion (210), to reach the side notches (36) of the articulation element stem (195; 196) and lock the position of the articulation element stem (195; 196) to prevent any rotation and movement of the articulation element stem (195; 196).

5. 5. A mandrel according to claim 3 or 4, wherein the articulation element stem (19; 191; 192; 195) is in one piece with the cup-shaped portion (13; 131; 132; 135) of the intermediate articulation element.

6. - said cup-shaped part (134; 136) of the intermediate articulation element has a through-hole (140) coaxial with said central axis (c) of said cup-shaped part (134; 136) and provided with an abutment (141); A mandrel according to claim 3 or 4, wherein the articulation element stem (194; 196) comprises a head (37) and is adapted to be inserted into the through hole (140) of the cup-shaped portion (134; 136) with the head (37) in contact with the abutment portion (141).

7. - said elongate body (3) has a cylindrical cavity formed at said second end of said elongate body (3); - an insert (5) is housed in said cylindrical cavity and is connected to said elongated body (3) by means of a screw (7), said elongated body (3) being connected at said first end of said elongated body (3) to said mandrel rod by means of a threaded connection; The mandrel according to claim 3, wherein the spherical seat (8) is in the insert (5) and has at least one hole (9), the at least one hole (9) being perpendicular to the central axis (t) of the elongated body (3) and suitable for allowing the passage of the set screw (27) when the spherical portion (21) is inserted into the spherical seat (8) and the hole (9) is coaxial with the second threaded hole (26) of the spherical portion (21).

8. 4. The mandrel of claim 3, wherein the elongated body (300) is adapted to have the first end of the elongated body (300) connected to a mandrel rod by a threaded connection, and the second end of the elongated body (300) has the spherical seat (8) with at least one hole (90), the at least one hole (90) being perpendicular to the central axis (t) of the elongated body (3) and communicating with the interior of the tube (T), the hole (90) being adapted to allow passage of the set screw (27) when the spherical portion (21) is inserted into the spherical seat (8) and the hole (90) is coaxial with the second threaded hole (26) of the spherical portion (21).

9. 5. A mandrel according to claim 4, wherein the peripheral portion (12) has a central hole into which the intermediate articulation element (10; 101; 102) is inserted and held, on the one hand, by abutments formed on the cup-shaped portion (135; 136) and, on the other hand, by an elastic ring (17) accommodated in a groove (18) obtained in the cup-shaped portion (153; 136).

10. - said peripheral part (12) has a central hole into which said intermediate articulation element (10; 101; 102; 104) is inserted and held, on the one hand, by abutments formed on said cup-shaped part (13; 131; 132; 134) and, on the other hand, by an elastic ring (17) accommodated in a groove (18) obtained in said cup-shaped part (13; 131; 132; 134); A mandrel according to claim 3, wherein the cup-shaped portion (13; 131; 132; 134) being one piece has at least one hole (16) perpendicular to the central axis (c) of the cup-shaped portion (13; 131; 132; 134) and suitable for allowing the passage of the set screw (27) when the spherical portion (21) is inserted in the spherical seat (14) and the hole (16) is coaxial with the second threaded hole (26) of the spherical portion (21).

11. A mandrel according to claim 3, wherein said peripheral part (121) is in one piece with the cup-shaped part (133) of its intermediate articulation element (103) and has at least one hole (160) connecting the interior of said tube (T) with said spherical seat (14) of said cup-shaped part (133) of said intermediate articulation element (103), said hole (160) being perpendicular to its central axis (c) and suitable for allowing the passage of said set screw (27) when said spherical part (21) is inserted in said spherical seat (14) and said hole (160) is coaxial with said second threaded hole (26) of said spherical part (21).

12. 3. A mandrel according to claim 2, wherein the peripheral portion (12) has a central hole and the cup-shaped portion (120) of the final articulation element (11; 111; 112) is inserted into and held in the central hole of the peripheral portion (12) by an abutment formed on the cup-shaped portion (120) of the final articulation element (11; 111; 112) on the one hand and by an elastic ring (17) accommodated in a groove (18) formed in the cup-shaped portion (120) of the final articulation element (11; 111; 112) on the other hand.

13. 3. A mandrel according to claim 2, wherein said peripheral portion (121) is one piece with said cup-shaped portion (122) of said final articulation element (113).

14. - said articulation element stem (19) of each intermediate articulation element (10) has a blind hole (31) suitable for accommodating a pre-compressed coil spring (28) and a ball (29); A mandrel according to claim 1, wherein the spherical seat (8) of the elongate body (3) and the spherical seat (14) of the cup-shaped portion (13) of each intermediate articulation element (10) have a recess (30) in the form of a spherical cap having an axis coinciding with the central axis (t) of the elongate body (3) and the central axis (c) of the cup-shaped portion (13), respectively, said recess (30) being suitable for receiving and retaining the ball (29) loaded by the coil spring (28) in the blind hole (31) of the articulation element stem (19).

15. - the spherical seat (8) of the elongated body (3) and the spherical seat (14) of the cup-shaped portion (131) of the intermediate articulation element (101) have blind holes (32) extending in the elongated body (3) along the central axis (t) and in the cup-shaped portion (131) along the central axis (c), in which a pre-compressed coil spring (28) and a ball (29) are accommodated; The mandrel according to claim 1, wherein the articulation element stems (191) of the intermediate articulation element (101) and the final articulation element (111) have recesses (33) in the form of spherical caps with an axis coinciding with the central axis (c) of the cup-shaped portion (131) configured to receive and retain the ball (29) loaded by the coil spring (28) in the blind holes (32) of the elongate body (3) and the intermediate articulation element (101).

16. 2. A mandrel according to claim 1, wherein the spherical seats (8) of the elongate body (3) and the spherical seats (14) of the cup-shaped portions (132; 133; 135) of the intermediate articulation elements (102; 103) have blind holes (34) extending from the respective spherical seats (8; 14) along the central axis (t, c), the blind holes (34) accommodating permanent magnets (35) suitable for exerting an attractive force on successive intermediate articulation elements (102, 103) and the final articulation element (112; 113) to keep the mandrel straight against gravity when not in use.

17. 2. The mandrel of claim 1, wherein the articulation element stems (194; 196) extending outwardly from the cup-shaped portions (134; 136) have blind holes (34) at their ends (40) that receive permanent magnets (35) configured to exert an attractive force on successive intermediate and final articulation elements to keep the mandrel straight against gravity when not in use.

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