WO2012160058A1

WO2012160058A1 - Apparatus for making stirrups

Info

Publication number: WO2012160058A1
Application number: PCT/EP2012/059478
Authority: WO
Inventors: Simone Rupoli
Original assignee: Schnell S.P.A.
Priority date: 2011-05-23
Filing date: 2012-05-22
Publication date: 2012-11-29
Also published as: EP2714296B1; ITBO20110293A1; EP2714296A1

Abstract

The apparatus for making stirrups, bidimensional and tridimensional, comprises guide means (4) to feed a metal rod (3) along a feed direction (A), a first fold unit (5) comprising a first central fold mandrel (8) and a first eccentric fold pin (9) rotatable about said first central mandrel (8) for folding said metal rod (3) on a work plane (2), a second fold unit (6) comprising a second central mandrel (10, 18) and a second fold pin (11, 110) mobile about said second central mandrel (10, 8) for folding said metal rod (3) on a folding plane inclined with respect to thework plane (2).

Description

APPARATUS FOR MAKING STIRRUPS

Technical Field

[01 ] The present invention regards an apparatus for making sti rru ps, i n particu lar tridimensional stirrups.

Background Art

[02] It has been known the use of apparatuses for making variously shaped metal stirrups starting from a metal rod. In particular, it has been known the requirement of making also tridimensional stirrups, intended, for example, to be used as spacing element suitable to be inserted between two metal nets. In order to accomplish this task, at present electro- welded lattice girders are also used, even though this solution proves to be expensive.

[03] The use of tridimensional stirrups, of suitable dimensions and therefore made to measure for every requirement, is vice versa cheaper and more practical.

[04] A problem generally complained in this specific field lays in the difficulty of producing tridimensional stirrups. At present there exist folding apparatuses able to fold an iron rod so as to make bidimensional stirrups, while the making of tridimensional stirrups has not yet found really efficacious solutions.

[05] EP 0519865 discloses a tridimensional apparatus which allows to make pieces of considerable size. Nevertheless such solution does not well suit to the use in the field of metal rods for reinforced concrete, furthermore it results to be very complicated and expensive to produce.

[06] EP 0396489 discloses a supplementary fold device suitable for apparatuses intended for the field of metal rods for reinforced concrete. Such device is able to create folds in a metal wire on different planes from the work plane, allowing in this way the shaping of tridimensional stirrups in an easy way. Known solutions of this type comprise two clearly distinct fold units operatively lined up along the feeding axis of the rod, which, therefore, do not allow to easily make structures of reduced size. Moreover, the presence of two fold units, besides burdening on the apparatus realization costs, may also be an obstacle to the working of bidimensional stirrups. In order to remedy this problem, the two fold units are arranged reciprocally spaced each other at a certain distance, penalizing nevertheless the production of tridimensional elements which often require the alternation of folding phases between the two fold units and the transfer from one unit to another till the product is complete.

Disclosure

[07] The task of the present invention is that of solving the aforementioned problems, devising an apparatus which allows to ma ke i n a n optimal manner both bidimensional and tridimensional stirrups.

[08] Within such task, it is a further scope of the present invention that of providing an apparatus which enables to make tridimensional stirrups having any size.

[09] Another scope of the present invention is that of providing an apparatus for making tridimensional stirrups having a simple conception and functioning, a securely reliable functioning and versatile use, as well as relatively economic costs.

[10] The cited scopes are attained, according to the present invention, by the apparatus for making stirrups according to claim 1.

[1 1 ] The apparatus comprises a first fold unit and a second fold unit which cooperate in the making of tridimensional stirrups starting from a metal rod fed along a feed direction through guide means.

[12] In particular the first fold unit comprises a first central mandrel and a first fold pin rotatable about the axis of the first central mandrel on a work plane, for folding the metal rod as it is in the apparatuses for making bidimensional stirrups of known type. The second fold unit comprises a second central mandrel and a second mobile fold pin working on an inclined folding plane, preferably orthogonal with respect to said work plane.

[13] The second mobile fold pin is arranged between the guide means of the metal rod and the first central mandrel of the first fold unit, for enabling the making of tridimensional stirrups with minimum length tracts. Such layout is particularly advantageous as, thanks to the spatial overlapping of the operating members of the first and the second fold units, the apparatus on the whole results very compact.

[14] In practice the second fold unit is arranged so as to overlap in space with the first fold unit, along the feed direction.

[15] Therefore the apparatus is able to make a series of extremely close folds, for example, a first fold on the work plane issuing from the first fold unit and a second fold on the inclined folding plane, issuing from the second fold unit, oblique with respect to the work plane. Consequently, limits of apparatuses of known type, with two separate and distinct fold units in which repeated transfers of working operations from one fold unit to another are necessary, with a noticeable waste of energy and time despite the apparatus overall productivity, prove to be overcome. It is necessary to underline, as well, that the apparatus according to the invention will bring no risks with regard to the correct positioning of the forming stirrup during work steps, while in known apparatuses, given the need of repeated transfers, such risk is the highest, even up to the complete discharge of the piece out of the working members, also because of the inevitable deformations of row materials.

[16] It is worth noting that the first fold unit and the second fold unit do not interfere in the respective working. Therefore the apparatus allows to make a series of folds on reciprocally oblique planes, for making bidimensional and tridimensional pieces without interruption, that is without needing to interrupt the production cycle. In practice the apparatus provides for making both one kind and the other kind of stirrups without distinction.

[17] In particular the second fold pin of the second fold unit is mobile between an active folding position of the metal rod about the second central mandrel, protruding from the work plan of the first fold unit, and an inactive position in which the second mobile fold pin hides, at least partially, behind the above mentioned work plane, in order to give the first fold unit a full working efficacy.

[18] Preferably the second central mandrel is shaped by the same guide means of the metal rod. For example, the second central mandrel can be made through a profiled edge, suitably shaped at the end of the guide means of the metal rod. In other words, the second central mandrel can be advantageously shaped by a fixed member already present in the apparatus for making bidimensional stirrups, having a main function, for example as a guide and a stop of the metal rod during the folding phase, and a second auxiliary function, relevant for the making of tridimensional stirrups.

[19] As an alternative or as an addition, the second central mandrel of the second fold unit can be made through a suitable mobile auxiliary member for the folding, which can be alternately operated on the work plane. For example such mobile auxiliary member can be advantageously interposed between the guide means of the metal rod and the first fold unit, so as to allow the construction of tridimensional stirrups of very reduced size, through the substantial reduction of the distance between the second mobile fold pin and the respective fold axis.

[20] According to an aspect of the invention, the second central mandrel of the second fold unit can be usefully shaped, as an alternative or as an addition, through a suitable appendix profiled on the first central mandrel, for example a tooth-shaped one, turned toward the collecting zone of made stirrups, so as to facilitate their discharge.

[21 ] The second mobile fold pin of the second fold unit is preferably operated rotatably between a hidden position with respect to the work plane of the apparatus and a protruding rotated position, suitable to fold the metal rod around the respective auxiliary member or fixed mandrel or mobile mandrel, interposed between the guide means and the first fold unit. In particular the second mobile fold pin in preferably shaped by an arm swinging around a shaft suitably operated, in inclined position, preferably orthogonally, with respect to the first central fold mandrel of the first fold unit, so as to allow the construction of corresponding folds on reciprocally inclined planes.

[22] The above mentioned folding arm can be borne, more precisely, by a lever radial with respect to the above mentioned shaft or eccentric with respect to it. [23] Moreover, the folding arm can be arranged downstream of the second fold unit. In this case, at the aforesaid inactive position, the folding arm does not interfere with the work plane of the first fold unit, so as to let free the handling zone of the stirrup being formed.

[24] As an alternative the folding arm can be instead interposed between the guide means of the metal rod and the first fold unit. According to a particularly advantageous embodiment, the folding arm can perform a double working function: a first folding function in which, in the aforementioned active position, the folding arm works as a mobile folding member in the protruding position from the work plane, and a second working function when in the aforementioned inactive position, in which the folding arm works as an auxiliary guide member for the first fold unit and is partially covered by the work plane. I n order to accomplish this second working task, the folding arm usefully bears stopping bodies combined with the second mobile fold pin, as to define auxiliary guide means lined up to the main guide means and the stopping body of the metal rod being formed through the first fold unit.

Description of Drawings

[25] Details of the invention shall be more apparent from the detailed description of a preferred embodiment of the apparatus for making tridimensional stirrups, illustrated for indicative purposes in the attached drawings, wherein:

[26] figures 1 - 4 show a perspective view of the apparatus for making tridimensional stirrups, in successive operating steps;

[27] figure 5 shows a perspective view of the apparatus according to the present invention in a different embodiment;

[28] figures 6 - 1 1 show a perspective view of a further embodiment of the apparatus in successive operating steps.

Best Mode

[29] With particular reference firstly to figures 1 - 4, the apparatus for making bidimensional and tridimensional stirrups is indicated in its entirety with 1 . The apparatus for making stirrups comprises a work plane 2 on which a metal rod 3 is fed along a feed direction A. For example the metal rod 3 is unrolled from a reel, not illustrated, and subsequently straightened through a straightening device, comprising for example counter-rotating rolls, before reaching the work plane 2 where it is folded in bidimensional and tridimensional stirrups.

[30] The apparatus 1 also comprises guide means 4 of the fed rod 3, a first fold unit 5 and a second fold unit 6 suitable to cooperate for the folding of the rod 3 fed on the work plane 2.

[31 ] I n particular, the guide means 4 is preferably constructed through a body fixed with respect to the work plane 2 and having a passage channel 7 substantially rectilinear and aligned, in use, to the feed direction A of the metal rod 3. Besides serving as a guide along the above mentioned feed direction A, the guide body 4 also serves as a stop member during the folding phase of the rod for both the first fold unit 5 and the second fold unit 6, as it is described hereafter.

[32] The passage channel 7 can for example be obtained by drilling the guide body 4 or simply by approaching a wall of the body 4 to the work plane 2 of the apparatus 1.

[33] The first fold unit 5 is arranged along the feed direction A of the metal rod 3 to be folded for making stirrups. Preferably, the first fold unit 5 is a unit of traditional type, provided, in a known manner, with for example a first central mandrel 8 or profile body and a first eccentric fold pin 9 having reciprocally parallel axes and substantially orthogonal to the work plane 2 of the apparatus 1 , so as to fold the metal rod 3 on the same plane 2. More precisely the first eccentric fold pin 9 is operated rotatably about the first central mandrel 8, so as to fold the metal rod 3 on the work plane 2 according to the rolling produced around the first central mandrel 8. Nevertheless, it is possible to use a fold unit of a different kind which is otherwise suitable to fold the metal rod 3 on the work plane 2.

[34] The second fold unit 6 is actually arranged so as to overlap with the space occupied, along the feed direction A, by the first fold unit 5. More precisely the second fold unit 6 comprises a guide and stop member, for example, advantageously shared with the first fold unit 5 and then inserted in the same guide body 4, a second central folding mandrel 10 and a second mobile fold pin 1 1 , which can subsequently return in an inactive position of rest hidden upstream or downstream of the first fold unit 5.

[35] Preferably the second mandrel 10 is borne by the same aforementioned guide means 4.

More precisely, the second mandrel 1 0 is shaped by the guide body 4 through a respective profiled edge of the passage channel 7, turned towards the first fold unit 5. Such profiled edge 10 has a curved shape suitable to perform as rolling profile for the folding of the metal rod 3 around the corresponding folding axis, that is on a laying plane inclined or preferably orthogonal to the plane 2. The profiled edge 10 can be directly obtained on the guide body 4 or arranged as a separated insert.

[36] The second mobile fold pin 1 1 is preferably shaped by an arm, bearing rotatably at its end a roll 12, coaxial to the same arm, suitable to reduce friction between the mobile fold member and the rod 3 during the active folding phase, in which the rod 3 is wound in a plastic manner around the profiled edge 10 of the passage channel 7.

[37] The arm 1 1 is borne by a lever 13 assembled on a shaft 14 suitable to be operated in suitable oscillation for the folding of the rod 3 around the respective axis. The swinging shaft 14 is oblique, preferably orthogonally to the axis of the first central mandrel 8 of the first fold unit 5, so as to make the folding of the rod 3 on a corresponding second folding plane orthogonal to the work plane 2. Nevertheless different embodiments are possible for making folding on oblique planes of different inclination with respect to the work plane 2.

[38] In particular the lever 13 can be radially borne by a disc 15 assembled to the shaft 14. As an alternative the lever 1 3 can be borne eccentrically to the shaft 14, for performing oscillating motions correspondingly different, for the folding of the metal rod 3 around the second central mandrel 10. The second fold pin 1 1 is anyway mobile between an inactive position, where it allows the passage of the rod 3 on the work plane 2 toward and further the first fold unit 5 for the corresponding folding around the first central mandrel 8 (see figures 1 and 4) and an active position, where the second mobile fold pin 1 1 protrudes from the work plane 2 through a corresponding opening 16 of the work plane 2 for folding the metal rod 3 around the second mandrel 10 (see figures 2 and 3).

[39] Finally the apparatus 1 comprises a cutting member 17, preferably arranged downstream of the guide means 4, so as to make the separation of the stirrup already shaped by the rod 3. The cutting member 17 comprises, in a known manner, a couple of blades opposite with respect to the rod 3, preferably a fixed blade borne at the edge of the guide body 4 and a mobile opposite one, distanced during the feeding phase, suitable to cooperate for intercepting a rod 3 section and to be operated according to a relative cutting motion during the corresponding working phase.

[40] As an alternative or as an addition to what disclosed so far the second mandrel 10 can be shaped by a suitable appendix of the cutting member 17, for example integral with one of the above mentioned blades.

[41 ] In the embodiment illustrated in figures from 1 to 4 the second mobile fold pin 1 1 is in particular disposed downstream of the first fold unit 5 so as to cooperate with the second mandrel 10 disposed upstream of the same first fold unit 5.

[42] According to a particular embodiment, similar as for the rest to the ones disclosed so far, it is useful to arrange a reference member or auxiliary mandrel 18 for the folding on the aforementioned second plane, associated in use with the second fold unit 6, for making tridimensional stirrups with central tracts, that is which can be made by the second fold unit 6 in the third dimension with respect to the work plane 2, of length inferior than the distance between the second fixed mandrel 10 and the second mobile fold pin 1 1 . In this case the auxiliary reference member 18 is preferably mobile between an active position of interception of the metal rod 3 (see figure 5) and a disengagement position of the metal rod 3, in which the auxiliary member 18 is distanced from the metal rod 3.

[43] The auxiliary member 18 can be made for example through a rod suitable to oscillate, bearing a profiled portion 19 suitable to intercept the metal rod 3 so as to perform as fold mandrel. Around such profiled position 19 suitably operated in gripping, the second mobile fold pin 1 1 is suitable to operate the folding of the metal rod 3.

[44] According to a different embodiment illustrated in figures from 6 to 1 1 , the arm 1 10 is instead interposed between the guide means 4 and the first fold unit 5. In practice the oscillation lever 130 has a quite reduced length with respect to the lever 13 of the above disclosed embodiment, so as to allow the second fold unit 6 to operate the folding of reduced length tracts as well.

[45] In such case it is possible to make the folding arm 1 10 bear auxiliary guide means 20 as well, suitable to perform as guide and stop member of the metal rod 3 when the folding arm 1 10 is in inactive position. In particular, such auxiliary guide means 20 can be constructed through suitable guide bodies borne at the end of the folding arm 1 10, suitably associated with the folding roll 12. For example the folding arm 1 10 can shape a first appendix 21 for guiding the feeding rod 3 and an opposed second guide appendix 22, the first appendix 21 and the second appendix 22 being substantially distanced by the folding roll 12 so as to shape a second passage channel 23 for the metal rod 3, aligned with the passage channel 7 defined by the main guide means 4 (see figure 7). In such case the arm 1 10 is mobile to partially hide in the inactive position, protruding from the work plane 2 in such condition as well, because of the presence of the cited auxiliary guide means associated with it. It is important to note that the second passage channel 23 performs an advantageous stopping function as well during the folding phases performed by the first fold unit 5. I n such case the stopping made by the contrasting of folding operations takes place in a portion of the rod 3 closer to the central mandrel 8, reducing the free tract of the rod 3 inevitably subject to deflection because of the folding stress. Such reduction minimizes also the entity of the vibrations of the rod 3 which generate because of the folding action driven by the members of the first fold unit 5. Therefore, such embodiment allows to obtain a high productivity. The first appendix 21 and/or the second appendix 22 can advantageously be mobile according to a mutual approaching motion for tightening the rod 3 during the folding phase.

[46] According a further embodiment not illustrated in the figures, the second central mandrel 10 of the second fold unit 6 can be usefully shaped as an alternative or as an addition to what above disclosed by a suitable appendix profiled on the first central mandrel 8, for example a tooth-shaped one, turned towards the collecting zone of the shaped stirrups, so as to ease their discharge. I n this case the second fold pin 1 1 is arranged mobile downstream of the first fold unit 5.

[47] The functioning of the apparatus for making bidimensional and tridimensional stirrups turns easily out from the preceding description.

[48] The metal rod 3 is fed on the work plane 2 of the apparatus 1 , in the feed direction A, through the guide means 4. More precisely the rod 3 is fed between the first central mandrel 8 and the first eccentric fold pin 9 of the first fold unit 5 (see for example figure 6), for example, starting from a position underneath the work plane 2. The first fold unit 9 is in an initial position, distanced from the rod 3 and suitable to allow the feeding along the feed direction A.

[49] In a following phase, the metal rod 3 is folded, practically on the work plane 2, through the operated rotation of the first fold pin 9 around the axis of the first central mandrel 8. Therefore the metal rod 3 receives a first folding, for example a right angle one, which arranges a first folded tract 31 (see figures 1 and 7) substantially rotated perpendicularly to the feed axis A, and a second tract 32 arranged in this phase along the feed axis A (for the respective embodiments of the apparatus according the invention, see figures 2 and 8).

[50] The first eccentric fold pin 9 performs a reversal oscillation to the initial position in order to avoid interfering with the further feeding phase of the rod 3. In practice, the metal rod 3 proceeds of a d istance predetermined according to the length of the tract of the tridimensional stirrup being formed. The oscillation of the first fold pin 9 has the effect, for an initial angular stroke, of carrying into contact with the rod 3 all the working members of the first fold unit 5, and for a further angular stroke, of permanently deforming the rod so as to produce the desired folding.

[51 ] In suitable phase relationship and depending on the structure of the stirrup being formed, the arm 1 1 is operated from the inactive position to the active folding position, so as to make, for example, the folding of the above mentioned tract 32 (see respectively figures 2 and figure 8).

[52] The handling, feeding, backing and folding operations by means of the first and/or the second fold unit follow one another in suitable phase relationship until the complete construction of the tridimensional structure being worked, in particular by making following folded tracts of the rods, on reciprocally inclined planes, as the tracts 33, 34 and 35 illustrated in figures.

[53] The production cycle of the stirrup being formed ends with the separation by means of the cutting members 17 of the finished piece from the row material, that is from the metal rod 3, bar-shaped or unrolled from a roll.

[54] Obviously it is possible to make bidimensional and tridimensional stirrups of any shape, by simply suitably operating the feeding, backing and folding of the rod 3 by means of the first fold unit 5 and the second fold unit 6.

[55] The apparatus object of the invention attains the scope of automatically making tridimensional and bidimensional stirrups in an easy and fast manner. Such a result is obtained in particular thanks to the inventive idea of arranging a first fold unit and a second fold unit substantially overlapped on the same work plane 2. In practice while the first fold unit 5 is arranged in a fixed manner on the work plane 2, the second fold unit 6 is mobile to hide at least partially with respect to the work plane 2, operating the folding of the metal rod 3 around a second mandrel 10 placed between the guide means 4 of the same rod 3 and the first fold unit 5.

[56] A characteristic of the apparatus consists in the extreme compactness of the different working fold units, which in particular allows the construction of tridimensional stirrups of reduced size.

[57] Moreover it is to be observed that the structural compactness of the apparatus comes out as well from the fact that certain working elements perform double functions. As in particular for the guide means 4, which performs the important function of stopping the folding stress issued by the operation of the first fold unit 5 and which can perform as well, according to the invention, the function of central mandrel for the second fold unit 6. Therefore such functional overlapping has the advantageous effect of unburdening the overall structure, reducing the num ber of the mechanical parts necessary for the functioning of the apparatus.

[58] In practice, the embodiment of the invention, the materials used, as well as the shape and dimensions, may vary depending on the requirements.

[59] Should the technical characteristics mentioned in each claim be followed by reference signs, such reference signs were included strictly with the aim of enhancing the understanding the claims and hence they shall not be deemed restrictive in any manner whatsoever on the scope of each element identified for exemplifying purposes by such reference signs.

Claims

1 ) Apparatus for making stirrups, bidimensional and tridimensional, comprising guide means (4) to feed a metal rod (3) along a feed direction (A), a first fold unit (5) comprising a first central fold mandrel (8) and a first eccentric fold pin (9) rotatable about said first central mandrel (8) for folding said metal rod (3) on a work plane (2) orthogonal to said first central mandrel (8), a second fold unit (6) comprising a second central mandrel (10, 18) and a second fold pin (1 1 , 1 10) mobile about said second central mandrel (10, 18) for folding said metal rod (3) on a folding plane inclined with respect to said work plane (2), characterized in that said second fold pin (1 1 , 1 10) is mobile at least partially hidden with respect 10 to said work plane (2) between an inactive configuration and an active configuration for folding, wherein said second fold pin (1 1 , 1 10) is operated in rotation to cooperate with said second central mandrel (10, 18) in the folding of said rod (3) on said inclined folding plane, said second central mandrel (10, 18) of said second fold unit (6) being positioned between said guide means (4) and 15 said first central mandrel (8) of said first fold unit (5) according to said feed direction (A), to perform the folding of said rod (3).

2) Apparatus according to claim 1 , characterized in that said second mobile fold pin (1 1 , 1 10) comprises an arm handled tilting by a shaft (14), said shaft (14) being oriented according to a direction inclined with respect to the axis of said first fold central mandrel (8).

3) Apparatus according to claim 2, characterized in that said second central mandrel (10) is shaped in a fixed manner by an end edge of said guide means (4).

4) Apparatus according to claim 2, characterized in that said second central mandrel (18) is mobile hidden between said guide means (4) and said first central mandrel (8) of said first fold unit (5) in order to cooperate with said second mobile fold pin (1 1 ) in the folding of said metal rod (3) on said inclined folding plane.

5) Apparatus according to claim 2, characterized in that said second central mandrel (10) is shaped by cut means (17) provided downstream of said guide means (4).

6) Apparatus according to claim 2, characterized in that said second central mandrel (10) of said second fold unit (6) is shaped by an appendix profiled on said first central mandrel (8), directed towards a zone for collecting said shaped stirrups, so as to make the discharge thereof easier.

7) Apparatus according to one of the previous claims, characterized in that in said inactive configuration said second mobile fold pin (1 1 ) is arranged downstream of said first central mandrel (8) according to said feed direction (A).

8) Apparatus accord i ng to claim 3 , 4 or 5, characterized in that in said inactive configuration said second mobile fold pin (1 10) is placed in between said second central mandrel (10) of said second fold unit (6) and said first central mandrel (8) of said first fold unit (5) according to said feed direction (A).

9) Apparatus according to claim 8, characterized in that said second mobile fold pin (1 10) is associated with auxiliary guide means (20) for the metal rod (3) which in said inactive configuration of said second mobile fold pin (1 10) are arranged on said work plane (2) to guide said rod (3) in alignment with said main guide means (4), said second mobile fold pin (1 10) resulting partially hidden with respect to said work plane (2).

10) Method for making tridimensional stirrups, comprising the steps of

(a) , prearranging guide means (4) for a metal rod (3) fed according to a feed direction (A), a first fold unit (5) provided with a first central fold mandrel (8) and with a first eccentric fold pin (9) rotatable about said first central mandrel (8) to fold said metal rod (3) on a work plane (2) orthogonal to said first central mandrel (8), a second fold unit (6) comprising a second central mandrel (10, 18) and a second fold pin (1 1 , 1 10) mobile about said second central mandrel (10, 18) on a folding plane inclined with respect to said work plane (2) between an inactive configuration and an active configuration for folding, wherein said second fold pin (1 1 , 1 10) cooperates with said second central mandrel (10, 18) in the folding of said rod (3) on said inclined folding plane;

(b) . feeding said metal rod (3) along said feed direction (A) through said guide means (4);

(c) . performing through said first fold unit (5) the folding of said metal rod (3) on said work plane (2), by operating in rotation said first eccentric fold pin (9) about said first central mandrel (8);

(d) . optionally handling the controlled advancing or moving back of said metal rod (3) according to said feed direction (A) to position a determined portion of said metal rod (3) at said second central mandrel (10, 18);

(e) . operating in rotation said second eccentric fold pin (1 1 , 1 1 0) from said inactive configuration to said active configuration in order to fold said metal rod (3) on said inclined folding plane about said second central mandrel (10, 18) of said second fold unit (6), said second central mandrel (10, 18) being positioned between said guide means (4) and said first central mandrel (8) of said first fold unit (5) according to said feed direction (A);

(f) . performing the coming back of said second fold pin (1 1 , 1 1 0) into said inactive configuration at least partially hidden with respect to said work plane (2);

(g) . optionally handling the controlled advancing or moving back of said metal rod (3) according to said feed direction (A);

(h) repeating the steps from (c) to (g) in suitable step relation to complete said stirrup to be shaped, making successive folded tracts of said stirrup being shaped on said work plane (2) and/or on said inclined folding plane; (i) separating by means of cut means (17) said shaped stirrup from said metal rod (3) fed through said guide means (4).