WO2015169903A1

WO2015169903A1 - System for folding and rolling out a metal plate for producing a strake

Info

Publication number: WO2015169903A1
Application number: PCT/EP2015/060078
Authority: WO
Inventors: Georges MENARD; Nicolas LAURAIN; Philippe Moreau
Original assignee: Gaztransport Et Technigaz
Priority date: 2014-05-07
Filing date: 2015-05-07
Publication date: 2015-11-12
Also published as: FR3020773B1; CN106457333B; CN106457333A; KR20170003595A; FR3020773A1; KR102324473B1

Abstract

The invention relates to a system (38) intended for folding and rolling out a metal plate (45) for producing a strake (8), the system (3) comprising a frame (39) and a series of shaping units (40, 41, 42) positioned consecutively in the direction of advancement of the metal plate (45) and arranged such that the folding angle of the shaping rollers increases from one shaping unit to the next, such as to gradually fold the lateral edges of the metal plate (45); the last shaping unit (42) being attached to the frame (39) while the first shaping unit (40) projects beyond the frame (39) such that the longitudinal size of the system is reduced by removing the first shaping unit (40) by releasing the attachment member (73) from the following shaping unit (41).

Description

SYSTEM FOR BENDING AND DISINLING A METAL PLATE FOR CARRYING OUT A VIRTUE

Technical area

The invention relates to the field of sealed and thermally insulating tanks, with membranes, for storing and / or transporting fluid, such as a cryogenic fluid.

It relates more particularly to a folding and unwinding system of a metal plate for the production of a strake, intended for the construction of a sealed membrane of a storage tank of a fluid. Technological background

The document FR2968284 describes a storage tank integrated in the hull of a ship, whose sealed barrier, in particular a primary sealed barrier in contact with the fluid contained in the tank, consists of metal strakes which are interconnected, so as to waterproof, with raised edges defining deformable bellows on both sides of a welding wing. These strakes are connected at their ends to a connecting ring via furring sheets both welded to the connecting ring and on the strakes.

It is also known a folding and unwinding machine for unrolling a metal plate inside the tank and fold at the same time its edges to shape a strake with raised edges. Such a machine comprises drive rollers for unwinding the metal plate, forming rollers for folding the lateral edges and support rollers for pressing the metal plate against the forming surface of the rollers of forming. The forming rollers have, in the longitudinal direction of the machine, increasing bending angles so as to gradually fold the lateral edges of the metal plate.

Such folding machines have a relatively large longitudinal dimension. However, it is not possible to unroll and fold strakes when the longitudinal encumberemenii folding machines is substantially greater than the remaining space between the end of the strake and the tank wall adjacent when the strake has been fully unwound. Also, the folding machines of the prior art do not allow unrolling and folding strakes having a length close to the longitudinal dimension of the tank wall to be covered by said strakes.

summary

An idea underlying the invention is to propose a system for folding and unrolling a metal plate which makes it possible to unroll and fold strakes having a length close to the longitudinal dimension of the tank wall to be covered by said strakes.

According to one embodiment, the invention provides a system for folding and unrolling a metal plate for the production of a strake, for the construction of a sealed membrane of a storage tank for a fluid, the strake having, in the width direction, a flat central band and folded lateral edges, the system comprising a frame and a series of forming units carried by the frame and extending along a longitudinal axis of the system each forming unit comprising:

- A frame comprising a releasable fastener adapted to ensure the attachment of the forming unit to an adjacent forming unit;

- Two drive rollers, each drive roller being rotatably mounted on the frame about a horizontal axis to ensure the advance of the metal plate in a direction of advance;

- Two forming rollers rotatably mounted, each of the two forming rollers having a forming surface shaped to fold a side edge of the metal plate at a predetermined angle relative to the horizontal axes of the drive rollers;

- Two support rollers mounted to rotate on the frame about a horizontal axis, each support roller extending vis-à-vis one of the two drive rollers and being arranged to hold the plate metal bearing against the drive roller and against the forming surface of one of the two forming rollers;

the forming units being arranged successively in the direction of advance of the metal plate, and being arranged so that the determined angle of the forming rolls increases from one forming unit to the next to gradually fold the lateral edges of the the metal plate, of a first unit of forming to a last forming unit, the determined angle of the forming rollers of the last forming unit being an angle of 90 ° so that the lateral edges are perpendicular to the flat central band at the outlet of the last forming unit ;

the last forming unit being fixed to the frame while the first forming unit protrudes cantilevered from the frame in a recoil direction opposite the direction of advance of the metal plate so that by removing the first forming unit by releasing its fastener to the next forming unit, the longitudinal dimension of the system is reduced.

Thus, such a system makes it possible to fold and unroll strakes having a length substantially close to the longitudinal dimension of the tank wall to be covered by said strakes since, at the end of the folding and unwinding operation, when the first unit of forming has folded the side edges of a strake along its length, the first forming unit can be removed to reduce the size of the system.

According to embodiments, such a system may include one or more of the following features:

the system comprises a motor equipped with a motor shaft and each forming unit comprises a transmission shaft, extending along the longitudinal axis of the system, rotatably coupled to a drive roller of said forming unit, the transmission shaft of the last forming unit being rotatably coupled to the drive shaft and the transmission shafts each having, at one and / or the other of their ends, a coupling member cooperating with a drive member. complementary coupling carried by one end facing a transmission shaft of an adjacent forming unit so as to allow rotation drive of the drive rollers of the forming units.

each forming unit comprises two lateral blocks connected by spacers, fixed or adjustable, each lateral block comprising a drive roller, a support roller, a forming roller and a transmission shaft rotatably coupled to the drive roller and comprising at one and / or the other of its ends, a coupling member cooperating with a complementary coupling member carried by an end opposite a transmission shaft of an adjacent lateral block of an adjacent forming unit.

the system comprises means for transmitting the movement which, on the one hand, cooperate with the drive shaft and, on the other hand, cooperate with the transmission shafts of the two lateral blocks of the last forming unit so as to allow a transmission of the movement of the motor shaft to the two side blocks of each forming unit.

the system comprises two motors equipped with a motor shaft cooperating respectively with one and the other of the lateral blocks of the last forming unit and the electronic synchronization means of the two motors. the system further comprises a device for guiding the metal plate adapted to ensure that the radius of curvature of the metal plate is greater than a threshold radius of curvature at the entrance of the first forming unit, said guide device of the metal plate being removably attached to the first forming unit.

the guide device is an element having a curvilinear guide surface.

the guide device comprises two drive roll trains, a first drive roll train being disposed at the output of a metal plate coil and a second drive roll train being disposed at the input of the first forming unit, the second driving roller train being coupled to a transmission shaft of the first forming unit and the first driving roller train being driven by a motor controlled by a servo device.

each forming unit comprises a support of the support roller which is slidably mounted relative to the frame along a vertical axis and is constrained towards the drive roller by a return member so that the distance between the roll of support and the drive roller of a forming unit dynamically adapts to the thickness of the metal plate.

the support roller support comprises an upper element, a lower element and a removable intermediate element that can be fixed between the upper element and the lower element in order to maintain a fixed spacing between these elements; ci, said support of the support roller being slidably mounted relative to the frame by means of an upper carriage and a lower carriage slidably mounted on a guide rail, the upper element being fixed to the upper carriage and the element lower being attached to the lower carriage, the upper carriage being constrained to the drive roller by the resilient biasing member of the backing roll support, the forming rollers of the last forming unit have a cylindrical forming surface comprising a vertical central axis and are each movable in rotation on a respective forming roller support about said vertical central axis of the cylindrical forming surface, said forming roller support being slidably mounted horizontally with respect to the frame and being constrained by a member elastic strain exerting a constraint directed from the outside to the inside of the system.

the forming rollers of the first forming unit and / or the second forming unit have a cone-shaped or conical-shaped forming surface having a vertical central axis and are rotatable about said vertical central axis, said forming rollers being further slidably mounted relative to the frame along said vertical central axis and each being constrained by an elastic stress member exerting a constraint directed from bottom to top.

the resilient members of the backing roll supports, the resilient members of the forming roller supports of the last forming unit and / or the resilient members of the forming rollers of the first forming unit comprise a stack of Belleville washers.

the series of forming units comprises three forming units, the first and second forming units protruding cantilevered, with respect to the frame, in a direction of recoil opposite the direction of advance of the plate in such a way that, by removing the first and second forming units, the longitudinal dimension of the system is reduced.

According to one embodiment, the invention also provides a method of folding the unwinding of a metal plate for the production of a strake by means of of a aforementioned system comprising a series of n forming units, n being an integer greater than or equal to 2, the method comprising:

n-1 times the succession of the following steps:

a folding and unwinding step of the metal plate during which the metal plate is unrolled and folded to a state in which the lateral edges of the metal plate have been folded over their entire length by a previous forming unit and a portion of the side edges of the metal plate has not been folded by the next forming unit;

- A step of removing the previous forming unit by releasing its fastener to the next forming unit; and

- A recoil step of the frame in the direction of recoil opposite to the direction of advance of the metal plate;

the method further comprising a final step of folding and unrolling the metal plate in which the metal plate is unrolled and folded to a state in which the side edges of the metal plate have been folded over their entire length by the last forming unit.

Some aspects of the invention start from the idea of proposing a particularly compact folding and unwinding system which makes it possible to unroll and fold strakes having a length close to the longitudinal dimension of the tank wall to be covered by said strakes. Some aspects of the invention start from the idea of proposing a folding and unwinding system of a metal plate that is adapted to dynamically adapt to thickness variations of the metal plate. Certain aspects of the invention start from the idea of proposing a folding and unwinding system making it possible to produce strakes extending in one piece between two stop structures, and having a variable thickness so as to be able to be connected directly to the stop structures at their ends while having a smaller thickness between these ends. Such strakes make it possible to provide a sealed and thermally insulated tank which comprises a sealed barrier having a good resistance to fatigue while limiting the amount of material necessary for producing such a sealed barrier. Such strakes also reduce the welding time necessary for the realization of the sealed barrier and reduce the control times of the welds in the tank. Brief description of the figures

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the accompanying drawings.

FIG. 1 is a fragmentary cutaway perspective view of a sealed and thermally insulating tank wall comprising strand-tight membranes for the construction of which a folding and unwinding system of a metal plate is used;

"Figure 2 is a partial perspective view of the zone II of Figure 1 showing the primary waterproof membrane.

• Figure 3 is a sectional view of a detail of a sealed membrane of the vessel wall of Figure 1 along the line III-III.

FIGS. 4a to 4f illustrate the various stages of transformation of a folding and unwinding system of a metal plate, at the end of the folding and unwinding operation of the metal plate.

FIG. 5 is a schematic view of a folding and unwinding system equipped with an electromechanical device for guiding the metal plate capable of ensuring that the radius of curvature of the metal plate is greater than a threshold radius of curvature between the metal plate coil and the first forming unit.

Figure 6 schematically illustrates a side block of the first forming unit.

• Figure 7 schematically illustrates a side block of the last forming unit.

• Figure 8 is a perspective view of a series of forming units coupled to a motor, according to a first embodiment.

FIG. 9 is a schematic view of the means for transmitting motion between the motor and the series of forming units, in the first embodiment of FIG. 8. • Figure 10 is a perspective view of a series of forming units coupled to a motor, according to a second embodiment.

FIG. 11 is a schematic view of the means for transmitting motion between the motor and the series of forming units, in the second embodiment of FIG. 10.

Fig. 12 is a perspective view of a series of two-motor coupled forming units according to a third embodiment.

• Figure 13 is a perspective view, partially exploded, of the first forming unit.

FIG. 14 is a perspective view of a side block of the first forming unit.

FIG. 15 is a detailed perspective view of the backing roll, the backing roll support, the forming roll and the guide support of the forming roll of the side block of FIG.

FIG. 16 is a side view of the forming roll and the guide support of the forming roll of the first forming unit.

• Figure 17 is a side view of a drive roller and a drive shaft of a side block.

• Figure 18 is a front view of a drive roller and a drive shaft of a side block.

• Figure 19 is a schematic view, from above, of a strake.

Detailed description of embodiments

Figure 1 shows sealed and insulating walls of a vessel integrated in a carrying structure of a ship.

The bearing structure of the tank is here constituted by the inner hull of a double-hulled vessel, of which the bottom wall has been referenced with the number 1, and by transverse partitions 2, which define compartments in the inner hull of the ship. The walls of the supporting structure are adjacent two by two at edges. On each wall of the supporting structure, a corresponding wall of the vessel has, in the thickness direction of the tank, from the outside to the inside, a secondary insulation layer 3, a secondary watertight barrier 4, a primary insulation layer 5 and a primary sealed barrier 6. At the angle between the two walls 1 and 2, the secondary watertight barriers 4 of the two walls 1 and 2 and the primary watertight barriers 6 of the two walls are connected by a connecting ring 10 in the form of a square tube. The connecting ring 10 forms a structure which makes it possible to take up the tension forces resulting from the thermal contraction of the metal elements forming the impervious barriers, the deformation of the hull at sea and the movements of the cargo. A possible structure of the connecting ring 10 is described in more detail in FR-A-2549575.

The primary insulating layer and the secondary insulating layer consist of heat-insulating element and more particularly parallelepiped heat insulating boxes 20 and 21 juxtaposed in a regular pattern. Each insulating casing 20 and 21 has a bottom panel and a cover panel 23. Side panels 24 and internal webs 25 extend between the bottom panel and the cover panel 23. The panels delimit a space in which is placing a heat insulating insert which may, for example, be expanded perlite. Each box 20 and 21 is held on the support structure by means of anchoring members 26. The boxes 20 and 21 of the primary insulating layer 5 and the secondary insulating layer 3 respectively bear the primary watertight barrier 6 and the secondary watertight barrier 4.

The secondary 4 and primary 6 watertight barriers each consist of a series of parallel Invar® 8 strakes with folded edges, which are alternately arranged with elongate welding supports 9, also in Invar®. The strakes 8 comprise, in the width direction, a flat central strip resting against the cover panels 23 of the caissons 20, 21 and folded lateral edges 13. The folded edges 13 extend substantially perpendicularly to the flat central strip. The strakes 8 extend from a first square tube at a first transverse partition 2 to a second square tube of a second transverse partition, not shown, located on an opposite side of the vessel. The folded edges 13 of the strakes are welded to the welding supports 9 in a sealed manner. Welding supports 9 are retained each time to the underlying insulating layer 3 or 5, for example by being housed in the inverted T-shaped grooves 7 formed in the cover panels 23 of the boxes 20 and 21.

This alternating structure is formed over the entire surface of the walls, which may involve very long lengths of strakes 8. On these long lengths, the sealed welds between the folded edges 13 of the strakes 8 and the soldering supports 9 interposed between them can be made in the form of weld beads 17 rectilinear and parallel to the wall.

The folded edge strakes 8 are connected directly to the connecting ring 10. The folded edge strakes 8 are therefore not connected to the connection ring 10 via the furring sheets as in the document F 2968284. For this purpose, the straightened edge strakes 8 have an end edge 11 welded continuously to the Invar® fins 27, 28 of the connecting ring 10 to take up the tensioning forces. The primary watertight barrier 5 and the secondary watertight barrier 3 are thus welded respectively to a primary fin 27 and a secondary fin 28. Primary heat insulating caissons 20 are positioned between the primary fin 27 and the secondary fin 28. The primary fin 27 is attached to the primary heat insulated casings 20 by screws 30. The secondary vane 28 is fixed in the same way on the secondary heat insulating elements.

The square tube is connected to the walls 1 and 2 by means of plates 31 which extend in the continuity of the sealed membranes 4 and 6 and fins 27, 28. These plates 31 are welded to plates 32 welded perpendicular to the walls 1 and 2 of the supporting structure.

FIG. 2 shows in more detail the connection zone of two strakes 8 of the primary watertight barrier 6 on the welding fin 27. It should be noted that the zone for connecting the strakes 8 of the secondary watertight barrier 4 to the welding wing 28 is made in the same way. The folded edges 13 of the folded edge strake 8 have a profile comprising an inclined portion 14 which rises progressively from the edge 11 in the direction of the strakes 8, then a horizontal portion 15. The strakes 8 are welded edge to edge continuous and sealed at their upper edge along a first Portion 29 using an automatic CMT process or a manual TIG process, with filler wire.

The welding support 9 interposed between two strakes 8 ends slightly before the fin 27. Throughout the central portion of the vessel wall, and to the vicinity of the end edge zone 11, the tight connection between the folded edges 13 of the strakes 8 and the weld supports 9 is formed by the straight weld seams 17, which extend approximately halfway up the folded edges 13 on either side of the weld support 9 and parallel to the support surface. The welding beads 17 are made by a welding machine with wheels.

The rectilinear weld bead 17 extends to near the first portion 29, the weld bead then has an upward curvature to join the edge weld edge to edge on the first portion 29. In another mode not shown, we use a guillochure.

Figure 3 illustrates in more detail the arrangement of the vessel wall at the weld between the fin 27 of the connecting ring 10 and the folded edge strake 8 shown in Figure 2. The fin 27 is attached to the heat-insulating elements 20 by means of screws 30 passing through the fin 27 and screwed into the upper panels 23 of the heat-insulating elements 20. The screw fastening makes it possible in particular to stabilize the fin 27.

The strake 8 extends in one piece between its two end edges 1 1. Between these two end edges the strake 8 is, on a first part of its length, resting on the fins 27 and on a second part of its length, resting on the primary insulating layer 5.

The strake 8 has a folded segment 34, to ensure the support of the strake 8 on both the fin 27 and the primary insulating layer 5, for most of its lower surface. The folded section extends near the edge of the fin 27 parallel to the fin 27 and compensates for the thickness thereof.

The strake 8 further has a variable thickness along its length. Thus, the strake 8 has at its end edges 11 a thick portion 33 fixed to the fins 27. A thin portion 35 extends between the thick portions 33 and has a constant thickness. The thin portion 35 is connected to the thick portions 33 by transition portions 36 in which the thickness decreases gradually from each thick portion 33 to the thin portion 35.

More particularly, according to one embodiment, the thick portion 33 has a thickness of 0.9mm and extends over a length of 400mm and comprises the folded segment 34. The transition portion 36 then extends over a distance of 500mm and has a thickness decreasing from 0.9mm to 0.7mm. Thus, most of the tank wall is covered by the thin portion 35 of the strake 8 which has a thickness of 0.7mm.

The thick portion 33 is connected to the fin 27 by a weld bead 37 made between the edge 11 of the strake 8 and the upper surface of the fin 27, the fin 27 having a thickness of 1.5 mm. Thus, the weld bead making the junction between the strake 8 and the fin 27, namely the welding of a 0.9mm thick strip on a 1.5 mm thick strip, has good fatigue resistance.

The use of such a strake 8 of variable thickness makes it possible to avoid or limit the use, in the length of the strake 8, of a set of metal sheets having different thicknesses, interconnected by strings of which would have insufficient fatigue strength. Indeed, a weld made between a sheet of 1.5 mm and a sheet of 0.7 mm has a lower fatigue resistance than a weld between a sheet of 0.9 mm and a sheet of 1.5 mm. However, the lower the fatigue resistance of the sealed barrier, the more necessary hull criteria for the vessel in which the tank is integrated are binding, which requires stiffening of the hull important. This stiffening of the hull is reflected in particular by a large amount of steel necessary for the realization of the hull. The use of a strake 8 whose thickness varies along its length allows for a waterproof membrane 6 having good fatigue resistance, while avoiding the use of thick strakes along their entire length. Fatigue resistance being more important, the hull criteria are less restrictive and allow in particular a saving of steel for the realization of the hull. The use of a strake 8 made in one piece over the entire length of the wall also makes it possible to reduce the welding time required for the production of the primary watertight barrier 6 and to reduce the control times of the welds in tank. Figures 4a to 4f, there is shown a folding and unwinding system 38 of a metal plate 45 for producing a strake 8, as described above. FIGS. 4a to 4f more particularly illustrate the various processing steps of the system 38 during the folding and unwinding of the final end of the metal plate 45, as it approaches a transverse partition 2 of the tank.

In FIG. 4a, the folding and unwinding system 38 comprises a frame 39 and a series of forming units 40, 41, 42 carried by the frame 39.

The forming units 40, 41, 42 extend in the longitudinal direction of the system 38. The forming units 40, 41, 42 simultaneously enable the metal plate 45 to be unwound in a direction of advance (arrow f1) and to shape the folded edges 13 of the strakes 8. The forming units 40, 41, 42 gradually fold, in successive steps, the lateral edges of the metal plate 45 until they are brought into their desired final configuration, in which they extend perpendicularly to the plane central strip at the outlet of the last forming unit 42.

In the embodiment shown, the folding and unwinding system 38 is equipped with three forming units 40, 41, 42. Also, by way of example, the first forming unit 40 folds the lateral edges of the metal plate 45 with respect to the central plane band at an angle of 30 °, the second forming unit 41 folds them by an angle of 60 ° while the third and last forming unit 42 folds the lateral edges into their final configuration, in which they extend substantially perpendicularly to the flat central band. Note that, given the allowable tolerances for the welding dial, the angle formed between the side edges and the flat central band may vary a few degrees around 90 °.

The chassis 39 is equipped with wheels to allow a movement of the system 38. Indeed, during the unwinding of the metal plate 45, the system 38 must in particular be movable in a direction of recoil (arrow f2 of Figures 4c, 4d and 4e opposed to the feed direction f1 of the metal plate 45.

The metal plate 45 is provided in the form of a coil which is carried on the folding and unwinding system 38 by means of a coil support member, not shown. The folding and unwinding system 38 comprises also a device for guiding the metal plate capable of ensuring that the metal plate 45 has, between the metal plate coil and the first forming unit 40, a minimum radius of curvature so that the metal plate 45 is not damaged during his peeling. In the embodiment of Figure 4a, the guiding device of the metal plate is an element 43 having a curvilinear guide surface. The curvilinear guide surface may in particular be equipped with a plurality of rollers 44 rotatably mounted to minimize friction between the curvilinear guide surface and the metal plate 45.

The last forming unit 42 is fixed to the frame 39 and extends plumb with it. On the other hand, the other forming units 40, 41 project cantilevered with respect to the frame 39, in a direction opposite to the direction of advance f1 of the metal plate. The forming units 40, 41, 42 are releasably secured to each other by means of releasable fasteners, which will be described in more detail later. Thus, when the metal plate 45 has been folded, unrolled and placed in the tank over a major part of its length and thus the system approaches a transverse wall 2 of the tank, the forming units can be successively removed so that the longitudinal dimension of the system 38 is reduced. Similarly, the element 43 having a curvilinear guide surface is mounted on the first forming unit 40 removably.

With reference to FIG. 4b, it can be observed that, as soon as the metal plate coil 45 is completely unwound, the element 43 having a curvilinear guide surface is disassembled, in order to allow the chassis to recoil in the direction recoil f2, opposite to the feed direction f1 of the metal plate 45.

Subsequently, as shown in FIGS. 4c and 4d, as soon as the lateral edges of the metal plate 45 have been shaped along their entire length by the first forming unit 40, the first forming unit 40 is removed in order to allow further retreat of the system 38. Similarly, as shown in Figures 4d and 4e, as soon as the lateral edges of the metal plate 45 have been shaped along their entire length by the second forming unit 41, the second forming unit 41 is disassembled and removed. The system 48 can thus be further moved back. As illustrated in FIG. 4f, when the metal plate 45 has been completely folded and unrolled, the edge of the strake 8 thus produced is raised or lowered in order to allow the withdrawal of the system 38. It is observed that, in its final configuration , in which the first and second forming units 40, 41 have been removed, the system has a particularly small longitudinal size allowing the metal plate 45 to unwind over its entire length. Such a system 38 is therefore particularly suitable for unwinding and folding strakes 8 which extend from one end to the other of the wall 1 of the tank, between two connecting rings 10 arranged at the two opposite ends of the wall 1.

Figure 8 illustrates a series of forming units 40, 41, 42 coupled to a motor 46, according to a first embodiment. The series of forming units comprises three forming units 40, 41, 42. Each forming unit 40, 41, 42 comprises two lateral blocks 40a, 40b, 41a, 41b, 42a, 42b which are respectively arranged to fold back. both side edges of the metal plate 45. Each side block 40a, 40b, 41a, 41b, 42a, 42b has a body 47 which is attached to the symmetrical body 47 of the other side block of the metal plate. forming unit, by two spacers 48. The body 47 of each lateral block is here formed in the form of two half-shells inside which are housed means for driving the metal plate 45 and forming means lateral edges of the metal plate 45.

The two spacers 48 are fixed to the bodies of the lateral blocks 40a, 40b, 41a, 41b, 42a, 42b by screws 49. The frame of each forming unit 40, 41, 42 is constituted by two symmetrical bodies 47 of the lateral blocks. and the two spacers 48. The frame thus has a frame of rectangular shape, which ensures a significant rigidity. According to one embodiment, the length of the spacers 48 is adjustable so as to allow an adjustment of the spacing between the lateral blocks 40a, 40b, 41a, 41b, 42a, 42b as a function of the width of the strakes 8 that one wish to achieve.

FIGS. 6 and 7 respectively illustrate a lateral block 40a of the first forming unit 40 and a lateral block 42a of the last forming unit 42. Note that the lateral blocks 41a, 41b of the second forming unit 41 have a structure substantially identical to that of a lateral block 40a of the first forming unit 40, only the angle of inclination of the forming surface being different.

In FIGS. 6 and 7, each lateral block 40a, 42a comprises a lower drive roller 50 rotatably mounted on the body 47. The drive roller 50 is rotated by the motor 46 via means of rotation. transmission, which will be described in more detail later. The drive roller 50 thus ensures the advance of the metal plate 45 in its direction of advance.

Each lateral block 40a, 42a further comprises an upper support roller 51 mounted rotatably on the body 47 along a horizontal axis. The support roller 51 extends opposite the driving roller 50 and makes it possible to hold the metal plate 45 against the drive roller 50. Moreover, each lateral block 40a, 42a comprises a roller of forming 52, 53, rotatably mounted on the body 47, and for folding a lateral edge of the metal plate 45. To do this, the forming roller 52, 53 has a forming surface which is inclined relative to the horizontal axis so as to fold a lateral edge of the metal plate 45 at a determined angle. The forming surface of the roller 52, 53, plates the lateral edges of the metal plate 45 against the support roller 51, to shape them.

With the exception of the roller 53 of the lateral blocks 42a, 42b of the last forming unit 42, the roller 52 of the other lateral blocks 40a, 40b, 41a, 41b has a cone or truncated cone shape, of revolution As shown in Figure 6. The roller 52 is rotatable about the central axis of the cone. The angle of folding of the roller 52 thus corresponds to the angle formed at the intersection between the generatrices of the conical surface and a horizontal plane. By way of example, the conical forming surface of the rollers 52 of the first forming unit 40 has an inclination of 30 ° with respect to a horizontal plane while the conical forming surface of the rollers 52 of the second forming unit 41 has an inclination of 60 ° with respect to a horizontal plane.

The rollers 53 of the last forming unit 42 have a cylindrical forming surface, as shown in FIG. 7. The roller 53 is rotatably mounted around the central axis of the cylinder. The guidelines of the cylindrical forming surface are vertical. The roller 53 thus makes it possible to fold the lateral edges of the metal plate 45 perpendicular to the flat central band.

The strake 8, shown in FIG. 19, comprises, in the longitudinal direction, an intermediate portion 35, an end portion 33 having a thickness greater than that of the intermediate portion 35 and transition portions 36 extending between the end portion 33 and the intermediate portion 35. Therefore, since the thickness of the metal plate 45 varies along its length, the forming units 40, 41, 42 must be arranged to adapt dynamically to such changes in shape. 'thickness. In particular, the forming units 40, 41, 42 are arranged in such a way that the width W of the flat central strip is kept constant when the thickness of the strake 8 varies (see FIG. 9). It will therefore be observed that, conversely, the total width l _ext of the strake 8 varies with the thickness of the strake 8. The strake 8 thus has a width l _ex t which is greater at the two end portions. 33 having greater thicknesses than at the intermediate portion 35 having a lower thickness. This choice of design of the strakes 8 is particularly advantageous since the increase in width 1 _ext of the strake 8 at the end portions 33 makes it possible to compensate for the disappearance of the soldering supports 9 at the level of said end portions 33.

Returning to FIGS. 6 and 7, it is observed that, in order to allow such dynamic adaptation of the forming units to changes in thickness, the support roll 51 is carried by a support of the support roll 54 which is slidably mounted on the body 47 of the side block. A resilient biasing member 55 acts between the body 47 and the support of the backing roll 54 and exerts on the support of the backing roll 54 a constraint directed from top to bottom, in order to constrain the backing roll 51 to direction of the driving roller 50. Thus, the distance between the backing roll 51 and the driving roller 50 dynamically adapts to the thickness of the metal plate 45. In the illustrated embodiment, the member resilient elastic 55 comprises a stack of spring washers, commonly referred to as Belleville washer, acting between the support of the support roller 54 and the body 47 of the side block. The stack of Belleville washers is designed so that the force it exerts is adapted to a deformation range corresponding to the range of thickness variation of the metal plate 45. Thus, the support force and of forming exerted by the roller 51 on the side edge of the metal plate 45 is adapted to the thickness variation of the metal plate 45.

Moreover, as shown in FIG. 6, the rollers 52 with a conical forming surface are each slidably mounted vertically relative to the body 47 of their respective lateral block 40a. The rollers 52 are guided in translation and in rotation relative to the body 47 by a guide support 68. An elastic stress member 56 exerts on the roller 52 a constraint directed from the bottom upwards so as to press the roller 52 against the edge Lateral of the metal plate 45. The elastic stress member 56 is also constituted by a stack of Belleville washers designed such that the stress force it exerts is substantially constant over a deformation range corresponding to the range. thickness variation of the metal plate 45. It is observed that the rollers 52 having a conical forming surface, their translation along a vertical axis allows to adapt the width l _ext of the strake 8 while maintaining the angle deformation of the lateral edges when the thickness of the metal plate 45 varies.

As shown in FIG. 7, each roller 53 of the last forming unit 42 is rotatably mounted on a roller support 57. The roller support 57 is slidably mounted on the support roller support 54 in a horizontal direction . Furthermore, a constraining member 58 exerts on the support of the roller 57 a stress, directed from the outside towards the inside of the forming unit, so as to press the roller 53 against the lateral edge of the metal plate 45.

In the embodiment detailed in FIGS. 14 and 15, the support of the support roller 54 is slidably mounted with respect to the body 47 of the lateral block 40a by means of two carriages 59, 60 slidably mounted on a guide rail 61. attached to the body 47 of the lateral block 40a. In order to reduce the friction and pre-constrain the adjustment between the carriages 59, 60 and the guide rail 61, the carriages 59, 60 are advantageously bearing carriages which comprise a plurality of rolling bodies capable of cooperating with travel paths. bearings carried by the guide rail 61.

The support roller 51 is connected to the support of the support roller 54 by a pivot connection so that it can rotate freely with the advance of the metal plate 45. To do this, a fixed axis 62 is supported at its two ends. ends by the support of the support roller 54. The support roller 51 is guided in rotation on the axis 62 by 63, 64. According to the embodiment shown, the support roller 51 is guided, on the one hand, by a two-row angular contact ball bearing 63 to take up the radial and axial forces s' exerting on the support roller 51 and, on the other hand, by a single-row rigid bearing 64. In order to limit their bulk, the bearings 63, 64 are housed inside an internal bore of the roller of support 51.

Furthermore, a screw 65 is fixed on the body 47 of the lateral block 40a and has a free end sliding inside a bore formed in the support of the support roller 54. The screw 65 carries a thrust washer 66 , secured to the screw 65 and a stack of Belleville washers 55 which cooperates, on the one hand, with the thrust washer 66 and, on the other hand, with the support of the support roller 54 via a support washer 67 mounted movably in translation on the screw 65. The stack of Belleville washers 55 thus makes it possible to exert, on the support of the support roll 54, a constraint directed from the top to the bottom, in the direction of the metal plate 45.

Moreover, in the embodiment shown, the carriages 59, 60 are spaced from one another along the guide rail 61 and the support of the support roller comprises an upper element 54a fixed to the upper carriage 59, a lower member 54b fixed to the lower carriage 60 and carrying the support roller 51 and an intermediate element 54c, removable. The removable intermediate element 54c is able to be fixed between the lower element 54b and the upper element 54a in order to maintain a fixed spacing therebetween. The intermediate element 54c can in particular be fixed to the elements, lower 54b and upper 54a by interlocking. By removing the intermediate member 54c, the stroke of the lower carriage 60 and, therefore, the backing roll 51 is much larger. It is thus possible to lift the support roller 51 vertically upwards in order to facilitate the release of the metal plate 45 during a removal operation of the forming unit 40.

We note that, if the backing roll holder 54 is shown in relation to a side block 40a of the first forming unit 40, a similar backing roll holder 54 can be used in all the side blocks 40a, 40b 41a, 41b, 42a, 42b of the system 38.

Furthermore, each roller 52 with conical forming surface is guided in translation and in rotation relative to the body 47 by a guide support 68. In the embodiment shown, the guide support 68 of each roller 52 is attached to the support of the support roller 54. Such an embodiment is advantageous in that it has a simpler design and easier assembly. However, in an alternative embodiment, the guide support 68 of each roller 52 is directly secured to the body 47 of the lateral block 40a.

A support for guiding the roller 68 is shown in detail in FIG. 16. The guide support for the roller 68 has a bore through which a shaft 69 for supporting the roller 52 extends. The shaft 69 cooperates with the support roller guide 68 by guide means arranged to guide the shaft 69 about a vertical axis while allowing its vertical translation. To do this, the guide means comprise a pair of needle bearings without inner ring 70a, 70b. Such bearings 70a, 70b comprise an outer ring which is fixed inside the bore of the guide support of the roller 68, by force or by gluing, for example, and cylindrical rollers of reduced diameter, received in a cage extending inside the outer ring. The absence of inner ring saves space while maintaining a shaft diameter 69 accordingly.

The shaft 69 carries, at its end opposite the roller 52, an axial bearing stop 71 and a stack of Belleville washers 56 which extends between, on the one hand, said axial bearing stop 71, and, on the other hand, on the other hand, a bearing washer 72 slidably mounted on the shaft and held against the guide support of the roller 68. Thus, the stack of Belleville washers 56 exerts on the roller 52 a constraint, directed from the bottom upwards, so as to to press the roller 52 against the lateral edge of the metal plate. The axial thrust bearing 71 makes it possible to provide axial support on the shaft 69, to the stack of Belleville washers 56 while limiting the friction forces opposing the rotational movement of the shaft 69.

The roller 52 and the shaft 69 are here formed in one piece. The roller 52 and the shaft 69 must have an excellent surface state, a high hardness and good resistance to bending. Also, according to one embodiment, the roller 52 and the shaft 69 are formed of hardened steel and rectified.

With reference to FIGS. 8 and 13, it can be observed that the releasable fastening members capable of providing removable fastening of the forming units 40, 41, 42 to one another consist of screws 73. According to one embodiment, a first set of screws 73 allows an assembly of three forming units 40, 41, 42 while the second set allows an assembly of the second and the last forming unit 41, 42. The screws 73 of the first set are introduced via the last forming unit 42, pass through bores formed in the lateral blocks the last and second forming units 41, 42 and cooperate with a threaded bore formed in a side block of the first forming unit. The screws of the second set are also introduced via the last forming unit 42, pass through a bore formed in a lateral block of the last forming unit 42 and cooperate with a threaded bore formed in a lateral block of the second unit 41. The unscrewing of the first set of screws 73 allows the removal of the first forming unit 40, and then, the unscrewing of the second set of screws 73 allows the withdrawal of the second forming unit 41. Note that other types of releasable fasteners may also be used. By way of example, fasteners with grasshoppers that make it possible, by simply tilting a lever to secure a fastening, can also be used.

The body 47 of each of the lateral blocks 40a, 40b is equipped with positioning members, not shown, which are each intended to cooperate with a complementary positioning member carried by the body of an adjacent lateral block. Thus, such positioning members provide precise positioning of the forming units 40, 41, 42 relative to each other. Such positioning members may, for example, include positioning pins which are each intended to cooperate with an orifice carried by a forming unit 40, 41, 42 vis-à-vis.

Furthermore, each of the lateral blocks 40a, 40b, 41a, 41b, 42a, 42b is equipped with a transmission shaft 74, shown in FIGS. 13, 17 and 18, making it possible to couple in rotation its drive roller. 50 to the engine 46.

Each transmission shaft 74 has an endless threaded portion 75 cooperating with a gear 76 rotationally integral with the driving roller 50. The transmission shaft 74 is guided in rotation on the body 47 of a lateral block via a set of two bearings 77, 78 extending on either side of the threaded portion 75. In the embodiment shown, the set of two bearings 77, 78 comprises, on the one hand, a bearing two-row angular contact balls 77 making it possible to take up the axial forces exerted on the transmission shaft 74 by the gear 76 and, on the other hand, a rigid one-row bearing 78. The transmission shafts 74 extend along the longitudinal axis of the system 38. The transmission shafts 74 of the lateral blocks 42a, 42b of the last forming unit 42 are coupled to the drive shaft 46 and the transmission shafts 74 of the lateral blocks 40a, 41a, 42a, on the one hand, and the transmission shafts 74 of the lateral blocks 40b, 41b, 42b, on the other hand, are coupled to each other in order to allow rotation of the drive rollers 50 , synchronously. The transmission shafts 74 are coupled to each other by claws consisting of a male element 79 and a female element 80, complementary in shape to the male element 79, attached to the ends opposite two adjacent transmission shafts 74. The elements, male 79 and female 80, of the clutch can be fixed to the ends of the transmission shafts 74 by means of keys and set screws.

Moreover, with reference to FIGS. 17 and 18, it can be seen that the drive roller 50 is integral with a shaft 81. The shaft 81 is guided in rotation on the body 47 of the lateral block via Bearings 82, 83. In the exemplary embodiment shown, the shaft 81 is guided, on the one hand, by a two-row angular contact ball bearing 82 making it possible to take up the radial and axial forces exerted on the drive roller 50 and, secondly, by a rigid bearing one row 83. The gear 76 is secured in rotation to the shaft 81, for example by keying. The gear 76 is disposed between the two bearings 82, 83. In addition, two spacer rings 84, 85 extend on either side of the gear 76. The spacer rings 84, 85 are in contact with each other. bearing against the bearings 82, 83 and allow to ensure precise positioning of the gear 76 relative to the threaded portion 75 of the transmission shaft 74.

In the embodiment of FIGS. 8 and 9, the folding and unwinding system 38 has only one motor 46. The motor shaft is oriented transversely to the longitudinal direction of the system and cooperates with a transverse shaft 86. transverse shaft 86 carries two bevel gear wheels 87, 88 which mesh respectively with a conical gear wheel 89, 90 integral in rotation with the drive shaft 74 of the one and the other of the lateral blocks 42a, 42b . Thus, the driving torque is transmitted to the lateral blocks 40a, 40b, 41a, 41b, 42a, 42b extending on each side of the system 38. The transverse shaft 86, as well as the bevel gear wheels 87, 88, 89, 90 are housed in a housing 91, shown in Figure 8. According to one embodiment, the wheel Conical gear 88 is slidably mounted axially on the transverse shaft 86 to allow adjustment of the spacing between the side blocks 40a, 40b, 41a, 41b, 42a, 42b when the length of the struts 48 can be adjusted.

In another embodiment not illustrated, the transverse shaft 86 comprises one or more threaded portions engaged with gear wheels integral in rotation with the transmission shafts 74 of the lateral blocks 42a, 42b. In yet another embodiment, the transmission between the transverse shaft 86 and the drive shafts 74 is provided by cross-axis helical gears each having an inclined toothing gear wheel carried by the transverse shaft and a wheel. gear with inclined toothing rotatably connected to a transmission shaft 74.

In the embodiment of FIGS. 10 and 11, the folding and unwinding system 38 also comprises only one motor 46. In this embodiment, the means for transmitting the movement between the motor 46 and the lateral blocks 42a , 42b comprise a chain or a toothed belt 92 housed inside a housing 91. Each of the transmission shafts 74 of the lateral blocks 42a, 42b is integral in rotation with a toothed wheel 93a, 93b which cooperates with the chain or the toothed belt 92. In order to transmit the movement of the drive shaft 46 to the side blocks 42a, 42b, the motor shaft 46 can either cooperate directly with the chain or toothed belt 92, or be coupled in rotation to the adjacent toothed wheel 93a, for example by a gear transmission mechanism. It is furthermore observed that the transmission means comprise, in addition, a tension adjusting device which is arranged to maintain a constant tension of the chain or toothed belt 92 regardless of the spacing between the lateral blocks 42a, 42b. . In the embodiment shown, the tension adjusting device comprises a pair of pulleys 94, 95 co-operating with the chain or toothed belt 92, one of which 95 is fixed while the other 94 is immobilized in the position assuring the ideal tension of the chain or timing belt 92.

In the embodiment of FIG. 12, the folding and unwinding system 38 comprises two motors 96, 97 cooperating respectively with the transmission shaft 74 of the one and the other of the lateral blocks 42a, 42b of the last forming unit 42. Each of the output shafts of the motors 96, 97 cooperate with a transmission shaft 74 of a lateral block 42a, 42b of the first forming unit 42 via transmission means. The transmission means may in particular comprise a chain or a toothed belt cooperating with gear wheels or gear trains. In such an embodiment, the folding and unwinding system 38 comprises electronic means for synchronizing the motors. Although more expensive in that it requires the presence of two motors 97, 98, this embodiment makes it possible to release the space extending between the lateral blocks, at the exit of the last forming unit 42 which allows to facilitate the release of the metal plate at the end of forming.

FIG. 5 illustrates an embodiment in which the device for guiding the metal plate capable of ensuring that the radius of curvature of the metal plate is greater than a threshold radius of curvature comprises two trains of drive rollers 99, 100 of which one 99 is placed at the exit of the metal plate coil 45 and the other 100 is placed at the entrance of the first forming unit 40. Advantageously, the drive roll train 100 placed at the The inlet of the first forming unit is coupled to one and / or the other of the drive shafts 74 of the first forming unit 40 so that it does not require independent drive. In one embodiment, the drive roll train 100 may have side rollers, not shown, for laterally guiding the introduction of the metal plate 45 into the first forming unit 40. Furthermore, the roll train drive 99 placed at the output of the metal plate coil 45 is driven by a motor controlled by a servo device to ensure a driving speed of the metal plate 45 substantially equal to that of the forming units 40 , 41, 42 so as to maintain the radius of curvature of the metal plate 45 constant.

It will be noted that the design of the forming units described above makes it possible to obtain an extremely compact system. Indeed, by way of example, each forming unit has a dimension less than 100 mm, of the order of 85 mm, in the longitudinal direction of the system 38.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. Furthermore, it is noted that if the invention is described above in connection with a system 38 having three forming units, the system may also include two or more forming units.

The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

1. System (38) for folding and peeling a metal plate (45) for producing a strake (8) for the construction of a sealed membrane (4, 6) of a storage tank of a fluid, the strake having, in the width direction, a flat central band and folded lateral edges (13), the system (38) comprising a frame (39) and a series of forming units (40). , 41, 42), carried by the frame (39), and extending along a longitudinal axis of the system (38), each forming unit (40, 41, 42) including:

a frame comprising a releasable fixing member (73) capable of ensuring the fixing of the forming unit to an adjacent forming unit;

- two drive rollers (50), each drive roller (50) being rotatably mounted on the frame about a horizontal axis to ensure the advance of the metal plate (45) in a direction d 'advance;

- two forming rollers (52, 53) rotatably mounted, each of the two forming rollers (52, 53) having a shaped forming surface for folding a lateral edge of the metal plate (45) at a predetermined angle relative to horizontal axes of the drive rollers (50);

- two support rollers (51), each support roller being rotatably mounted on the frame about a horizontal axis extending opposite one of the two drive rollers (50) and being arranged to hold the metal plate (45) abutting against said drive roller (50) and against the forming surface of one of the two forming rollers (52, 53);

the forming units (40, 41, 42) being arranged successively in the direction of advance of the metal plate (45), and being arranged so that the determined angle of the forming rollers (52, 53) is increased by from one forming unit to the next for gradually folding the lateral edges of the metal plate (45) from a first forming unit (40) to a last forming unit (42), the determined angle of the forming rollers (53) of the last forming unit being an angle of 90 ° so that the side edges are perpendicular to the flat central band at the outlet of the last forming unit (42);

the last forming unit (42) being fixed to the frame (39) while the first forming unit (40) projects cantilevered relative to the frame (39) in a recoil direction opposite to the advance direction of the metal plate (45) such that, by removing the first forming unit (40) by releasing its fastener (73) to the next forming unit (41), the longitudinal dimension of the system is reduced.

2. System (38) according to claim 1, comprising a motor (46, 96, 97) equipped with a motor shaft and wherein each forming unit (40, 41, 42) comprises a transmission shaft (74), extending along the longitudinal axis of the system, rotatably coupled to a driving roller (50) of said forming unit (40, 41, 42), the transmission shaft (74) of the last forming unit (42) being rotatably coupled to the drive shaft (46, 96, 97) and the drive shafts (74) each having, at one and / or both of their ends, a coupling member ( 79, 80) cooperating with a complementary coupling member (80, 79) carried by one end opposite a transmission shaft (74) of an adjacent forming unit (40, 41, 42). so as to allow a rotational drive of the drive rollers (50) of the forming units (40, 41, 42).

3. System (38) according to claim 2, wherein each forming unit (40, 41, 42) comprises two lateral blocks (40a, 40b, 41a, 41b, 42a, 42b) connected by fixed or adjustable spacers (48). ), each lateral block (40a, 40b, 41a, 41b, 42a, 42b) having a drive roller (50), a support roller (51), a forming roller (52, 53) and a shaft transmission unit (74) rotatably coupled to said drive roller (50) and having at one and / or both of its ends a coupling member (79, 80) cooperating with a complementary coupling member (80, 79) carried at one end facing a transmission shaft (74) of a side block (40a, 40b, 41a, 41b, 42a, 42b) adjacent to a forming unit adjacent (40, 41, 42).

4. System (38) according to claim 3, comprising motion transmission means which, on the one hand, cooperate with the drive shaft and, on the other hand, cooperate with the transmission shafts (74) of the two blocks. laterally (42a, 42b) of the last forming unit (42).

5. System (38) according to claim 3, comprising two motors (96, 97) equipped with a motor shaft cooperating respectively with one and the other side blocks (42a, 42b) of the last forming unit ( 42) and electronic synchronization means of the two motors (96, 97).

6. System (38) according to any one of claims 1 to 5, further comprising a device for guiding the metal plate capable of ensuring that the radius of curvature of the metal plate (45) is greater than a radius of curvature threshold at the entrance of the first forming unit (40), said guide device of the metal plate being removably attached to the first forming unit (40).

The system (38) of claim 6, wherein the guide means is a member (43) having a curvilinear guide surface.

The system (38) of claim 6 when dependent on any one of claims 2 to 5, wherein the guide device comprises two drive roll trains (99, 100), a first set of rollers the drive (99) being disposed at the output of a metal plate coil (45) and a second drive roll train (100) being disposed at the input of the first forming unit (40), the second a drive roll train (100) being coupled to a drive shaft (74) of the first forming unit (40) and the first drive roll train (99) being driven by a motor driven by a drive device servo.

The system (38) according to any one of claims 1 to 8, wherein each forming unit (40, 41, 42) comprises a support of the backing roll (54) which is slidably mounted relative to the frame ( 39) along a vertical axis and is constrained to the drive roller (50) by a resilient biasing member (55) such that the distance between the backing roll (54) and the drive roller (50) ) a forming unit dynamically adapts (40, 41, 42) to the thickness of the metal plate (45).

10. System (38) according to claim 9, the support of the support roller (54) comprises an upper element (54a), a lower element (54b) and a removable intermediate element (54c) adapted to be fixed between the upper member (54a) and lower member (54b) for maintaining a fixed gap therebetween, said support of the backing roll (54) being slidably mounted relative to the frame (39) by means of a carriage upper (59) and a lower carriage (60) slidably mounted on a guide rail (61), the upper member (54a) being secured to the upper carriage (59) and the lower member (54b) attached to the lower carriage (60), the upper carriage being constrained towards the drive roller by the resilient biasing member (55) of the support of the backing roll (54).

The system (38) according to any one of claims 1 to 10, wherein the forming rollers (53) of the last forming unit (42) have a cylindrical forming surface having a vertical central axis and are each movable in rotation on a respective forming roller support (57) about said vertical central axis of the cylindrical forming surface, said forming roller support (57) being slidably mounted horizontally with respect to the frame (39) and being constrained by a resilient biasing member (58) exerting a constraint directed from the outside to the inside of the system (38).

The system (38) according to any one of claims 1 to 11, wherein the series of forming units comprises three forming units (40, 41, 42) and wherein the first and second forming units ( 40, 41) protrude cantilevered from the frame (39) in a recoil direction opposite the direction of advance of the metal plate (45) so that, by removing the first and the second forming unit (40, 41), the longitudinal dimension of the system is reduced.

The system (38) according to any one of claims 1 to 12, wherein the forming rollers (52) of the first forming unit (40) and / or the second forming unit (41) have a surface cone-shaped or truncated-cone shaped forming having a vertical central axis and are rotatable about said vertical central axis, said forming rollers (52) being further slidably mounted relative to the frame (39) along said axis vertical and each being constrained by an elastic stress member (56) exerting a constraint directed from the bottom upwards.

A system (38) according to any one of claims 10, 11 and 13, wherein the resilient biasing members (55) of the backing roll supports (54), the elastic stress members (58) of the supports forming roller (57) of the last forming unit (42) and / or the resilient members (56) of the forming rollers (52) of the first forming unit (40) comprise a stack of Belleville washers.

15. Method for folding and unrolling a metal plate (45) for producing a strake (8) by means of a system (38) according to any one claims 1 to 14 having a series of n forming units (40, 41, 42), n being an integer greater than or equal to 2, the method comprising:

n-1 times the succession of the following steps:

a folding and unrolling step of the metal plate (45) during which the metal plate (45) is unwound and folded to a state in which the lateral edges of the metal plate (45) have been folded over any their length by a previous forming unit (40, 41) and a portion of the lateral edges of the metal plate has not been folded by the next forming unit (41, 42);

- A step of removing the previous forming unit (40, 41) by releasing its fastener to the next forming unit (41, 42); and

- A recoil step of the frame (39) in the direction of recoil opposite the direction of advance of the metal plate (45);

the method further comprising a final step of folding and unrolling the metal plate (45) in which the metal plate (45) is unwound and folded to a state in which the side edges of the metal plate have been folded back along their entire length by the last forming unit (42).