FR3043344A1 - FOLDING MACHINE FOR FORMING A CORRUGATION IN A METAL SHEET AND METHOD OF USING SUCH A FOLDING MACHINE - Google Patents

Abstract

The invention relates to a folding machine (9) of a metal sheet (1) having a first preformed corrugation (3) for forming a second corrugation (2) perpendicular to the first preformed corrugation (3); the folding machine (9) comprising; an upper punch (12); - a lower frame (11) equipped with a matrix (17) fixed relative to said lower frame (11); two knives (22, 23) for deforming the first preformed corrugation (3); and - a device for actuating the knives comprising a mechanism for transmitting the movement, the transmission mechanism including at least one bearing surface (31, 32), positioned inside the cavity (18) and being arranged for transmitting movement between said bearing surface (31, 32) and the knives (22, 23) so that the knives (22, 23) are moved to a high folding position upon movement of the upper punch ( 12) from a rest position to a folding position.

Description

TECHNICAL FIELD The invention relates to a folding machine for forming, in a metal sheet having a preformed corrugation, a corrugation perpendicular to said preformed corrugation.

A metal sheet obtained by means of such a folding machine is particularly intended for the construction of a sealed membrane of a fluid storage tank. Also, the invention also relates to the field of tanks, waterproof and thermally insulating, with membranes, for the storage and / or transport of fluid, such as a cryogenic fluid.

Technological background

Document KR1 00762083 discloses a folding machine for folding a metal sheet in which a high corrugation has previously been formed to form a low corrugation perpendicular to the high corrugation and a node at the intersection of the corrugations. The folding machine comprises an upper frame comprising a punch having a shape complementary to that of the low corrugation to be formed and a matrix having two lateral elements movable laterally and vertically with respect to a lower frame. The lateral elements of the matrix comprise two concave half-imprints together defining an imprint corresponding to the shape of the corrugation to be formed and carry two knives capable of shaping concave corrugations in the ridge of the high corrugation. The folding machine has guide surfaces arranged such that when the upper frame moves down towards the lower die, the side members and knives move laterally toward one another while moving vertically towards the lower die. high compared to the lower frame.

Given the complex movement of the lateral dies, the aforementioned folding machine is particularly complex. In addition, in order not to degrade the mechanical properties of the corrugated metal sheet, it is essential that it has after bending a thickness as constant as possible. Also, for a machine of the aforementioned type, this constraint implies a perfect synchronization of the movements of the punch and the lateral elements.

Moreover, such folding machines require the use of a press capable of exerting relatively large pressures. Finally, such folding machines are relatively bulky.

Also, such a folding machine is not fully satisfactory. summary

An idea underlying the invention is to provide a folding machine for forming a corrugation in a metal sheet having a preformed corrugation which is simple and compact. Another idea underlying the invention is to reduce the power of the presses necessary for forming the undulation and the node area.

According to one embodiment, the invention provides a machine for folding a metal sheet having a first preformed corrugation, to form a second corrugation perpendicular to the first preformed corrugation; the folding machine comprising a lower frame and an upper punch vertically movable relative to the lower frame between a rest position and a folding position; - The upper punch having a head extending in a longitudinal direction and having a V-shaped convex portion of complementary shape to the shape of the second corrugation to form and two flanges straightening towards the horizontal bordering the convex portion; the lower frame being equipped with a fixed matrix with respect to said lower frame, disposed below the head of the upper punch, the die having a concave imprint having a shape complementary to that of the convex portion and intended to receive said portion convex when the upper punch is in its folding position; the folding machine further comprising: - two knives, intended for the deformation of the first preformed corrugation, on either side of the crossing zone between the first preformed corrugation and the second undulation to be formed, the two knives being arranged on either side of the die cavity and being movably mounted on the lower frame between a low position and a high folding position of the first preformed corrugation; and a device for actuating the knives comprising a mechanism for transmitting the movement, the transmission mechanism comprising at least one bearing surface, arranged opposite the head of the upper punch and positioned inside the the impression of the matrix so that, in operation, during the movement of the upper punch from its rest position to its folding position, the metal sheet is clamped between the bearing surface and the upper punch; said motion transmitting mechanism being arranged to transmit movement between said bearing surface and the knives so that the knives are moved to their upper folding position upon movement of the upper punch from its rest position to its position folding.

Thus, during bending operations, the metal sheet is initially clamped between the punch and the bearing surface in order to hold it in place. Therefore, it is possible to do without dedicated clamps for holding the metal sheet against the matrix to ensure that it remains in position, during its folding and ensure the flatness of the sheet. This allows in particular to reduce the size of the folding machine and reduce its tonnage.

In addition, the metal sheet not being tight against the matrix during the initial phase of deformation of the metal sheet, at least a portion of the matrix can be stationary relative to the lower frame during folding, without generating changes in the thickness of the metal sheet. This also contributes to the simplicity and compactness of the folding machine.

In addition, the bearing surface has a second function since it also contributes to transmitting the movement of the upper punch to the knives that shape the preformed corrugation. Thus, the vertical movement of the knives is synchronized with that of the upper punch and does not require a dedicated actuator.

According to embodiments, such a folding machine may comprise one or more of the following features. - The knives are each slidably mounted in a transverse direction perpendicular to the longitudinal direction of the head, on a support member between a spaced apart position and a close position. Thus, the knives are able to move in a direction transverse to the undulation to be formed, which is necessary so that the thickness of the metal sheet can remain substantially constant at the zones of the preformed corrugation which are shaped by knives. Each of the knives is carried by a carriage slidably mounted on a guide rail which is fixed to the support member and extends in the transverse direction. Each carriage or guide rail comprises a plurality of rolling bodies capable of cooperating with raceways carried by the guide rail or the associated carriage, which makes it possible to limit the friction. - The folding machine comprises one or more resilient members arranged to return each of the knives to their spaced apart position. Thus, the transverse displacement of the knives to their close position can be achieved by means of tensile forces exerted by the metal sheet during its deformation by the upper punch while the elastic members are responsible for recalling the knives to their spaced apart position. The transverse displacement of the knives therefore does not require a dedicated actuator and is synchronized with the movement of the upper punch, which makes it possible to guarantee that the thickness of the metal sheet remains substantially constant at the zones of the preformed corrugation which are shaped. by the knives. - The support member is mounted vertically movable on the lower frame and the movement of the transmission mechanism cooperates with the support member and is arranged so that the support member is moved vertically upwards relative to the lower frame for moving the cutters from their low position to their upper folding position when the upper punch moves from its rest position to its folding position. In one embodiment, the mechanism for transmitting the movement comprises: two bearing surfaces disposed opposite the head of the upper punch and positioned inside the imprint of the die; and two levers which are each mounted articulated on the lower frame and each comprise a first end bearing one of the bearing surfaces so as to cause pivoting of the levers during the movement of the upper punch from its rest position to its position folding and a second end; the second ends of the levers being arranged to transmit a movement to the knives so as to move them from their low position to their upper folding position during the pivoting of the levers driven by a movement of the upper punch from its rest position to its folding position . However, it is possible to realize the mechanism of transmission of the movement by any means other than levers, for example by means of cables, gears or racks for example. - The second end of each of the levers cooperates with the support member so as to move vertically when pivoting the levers. - The first end of each of the levers carries a contact piece which is, on the one hand, articulated on the first end of said lever about an axis of articulation perpendicular to the longitudinal direction of the head and, on the other hand part, comprises a flat sole forming one of the bearing surfaces intended to cooperate with the metal sheet during the movement of the upper punch from its rest position to its folding position. Thus, such a contact piece makes it possible to maintain contact surfaces between the levers and the metal sheet that remain identical during the pivoting of the levers. The levers are symmetrical with respect to a transverse median plane perpendicular to the longitudinal direction of the head of the upper punch. Thus, the levers pivot in opposite directions of rotation which ensures a balancing of efforts. The upper punch comprises a finger protruding from a median zone of the head in the direction of the lower frame and intended to deform the zone of intersection between the first preformed corrugation and the second corrugation to be formed so as to form a protruding vertex in the metal sheet. - The finger has a lamellar shape. - The matrix is interrupted in a median zone to allow the passage of the preformed corrugation. According to one embodiment, the folding machine further comprises: two lateral matrix elements arranged on either side of the cavity and each having a V-shaped groove, intended to receive the first preformed corrugation ; the two lateral die members being each slidably mounted on the lower frame, in a transverse direction perpendicular to the longitudinal direction of the upper punch head between a spaced apart position and a close position; two upper counter-matrices disposed on either side of the upper punch respectively above the one and the other of the two lateral matrix elements, the two upper flanks each having a male element capable of coming to enter the V-shaped groove of one of the lateral matrix elements; the upper counter-matrices being, on the one hand, slidably mounted on an upper frame carrying the upper punch in a transverse direction perpendicular to the longitudinal direction of the head of the upper punch, between a spaced position and a close position and, d on the other hand, moving vertically in relation to the upper frame. Thus, the lateral matrix elements and counter-matrices make it possible to guarantee the flatness of the sheet. In operation, the movement of the upper punch from its rest position to its folding position results in a folding of the metal sheet during which the metal sheet transmits a tensile force in the direction transverse to the lateral die elements and to the flanks and thus moves the lateral matrix elements and the flanks to their close position. According to one embodiment, the two lateral matrix elements are returned to their position separated by a return member.

According to one embodiment, the two upper counter-matrices are returned to their position separated by a return member. According to one embodiment, the folding machine comprises return members reminding the counter-matrices vertically at a distance from the upper frame. Such return members consist of gas springs or helical springs, for example.

According to one embodiment, the invention also provides a method of using a said folding machine to form, in a metal sheet having a first preformed corrugation, a second corrugation perpendicular to the first preformed corrugation; said method comprising: positioning a metal sheet bearing against the matrix; the movement of the upper punch towards its folding position in which the head of the upper punch presses the metal sheet inside the cavity of the die to form the corrugation and deform the preformed corrugation on both sides of the crossing zone between the two undulations.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent from the following description of several particular embodiments of the invention, given solely for the purposes of the invention. illustrative and not limiting, with reference to the accompanying drawings. - Figure 1 is a view of a corrugated metal sheet for the construction of a sealed membrane of a liquefied natural gas storage tank. - Figure 2 is a perspective view of a folding machine for forming a corrugation in a metal sheet having a preformed corrugation. FIG. 3 is a perspective view, partially exploded, of the folding machine of FIG. 2. FIG. 4 is a sectional view along a transverse median plane of the folding machine of FIG. a rest position. - Figure 5 is a view similar to Figure 4, the folding machine of Figure 2, in a folding position. - Figure 6 is a sectional view along a longitudinal median plane of the folding machine of Figure 2, in a rest position. - Figure 7 is a view similar to Figure 6 of the folding machine of Figure 2, in a folding position. - Figure 8 is a perspective view of a folding machine according to an alternative embodiment. - Figure 9 is a perspective view of a folding machine according to another embodiment wherein the upper punch is in an intermediate position between its rest position and its folding position. - Figure 10 is a perspective view of the folding machine of Figure 9 in which the upper punch is at the end of stroke, in its folding position.

Detailed description of embodiments

FIG. 1 illustrates a corrugated metal sheet 1 intended for the formation of a sealed membrane of a tank for storing a cryogenic fluid, such as liquefied natural gas.

The metal sheet 1 of rectangular shape comprises a first series of parallel corrugations 2, said low, extending in a direction y from one edge to the other of the sheet and a second series of corrugations 3 parallel, so-called high extending in a direction x from one edge to the other of the sheet. The x and y directions of the series of undulations are perpendicular. The corrugations 2, 3 are, for example, protruding from the side of the inner face of the metal sheet 1, intended to be placed in contact with the fluid contained in the tank. The edges of the metal sheet 1 are here parallel to the corrugations 2, 3. Note that the terms "high" and "low" have a relative meaning and mean that the undulations 2, said low, have a height lower than the undulations 3, say high. In a variant not shown, the corrugations 2, 3 can have the same height.

The metal sheet 1 comprises between the corrugations 2, 3, a plurality of flat surfaces 4. At each crossing between a low corrugation 2 and a high corrugation 3, the metal sheet 1 comprises a node zone 5. The node zone 5 comprises a central portion 6 having an apex projecting inwardly or outwardly of the vessel. Moreover, the central portion 6 is bordered, on the one hand, by a pair of concave corrugations 7 formed in the crest of the high corrugation 3 and, on the other hand, by a pair of recesses 8 into which the low ripple 2.

The corrugations 2, 3 of the metal sheet 1 allow the waterproofing membrane to be flexible in order to be deformed under the effect of thermal and mechanical stresses generated by the liquefied natural gas stored in the tank.

The metal sheet 1 can in particular be made of stainless steel, aluminum, Invar ®: that is to say an alloy of iron and nickel whose expansion coefficient is typically between 1.2.10 6 and 2.10'6 K "1, or in an iron alloy with a high manganese content whose expansion coefficient is typically of the order of 7 × 10 -6 K -1. However, the use of other metals or alloys is also possible. For example, the metal sheet 1 has a thickness of about 1.2 mm. Other thicknesses are also conceivable, knowing that a thickening of the metal sheet 1 causes an increase in its cost and generally increases the rigidity of the corrugations 2, 3. For example, the metal sheet has a width of 1 m and a length of 3 m.

FIGS. 2 to 7 show a folding machine 9 making it possible to form a low corrugation 2, as well as the node zone 5 between this low corrugation 2 and a high corrugation 3, in a metal sheet 1 in which the high corrugation 3 a previously formed.

By convention, the "longitudinal" orientation of the picking machine 9 is directed parallel to the y axis, that is to say parallel to the direction of the corrugation 2 to be formed and the "transverse" orientation is directed parallel to the axis x, that is to say transversely to the direction of the corrugation 2 to form.

The folding machine 9 comprises an upper frame 10 and a lower frame 11, shown schematically in dashed lines in FIG. 2. The upper frame 10 and the lower frame 11 are vertically movable relative to each other between a position rest and a folding position.

The upper frame 10 is equipped with an upper punch 12 and is thus able to exert on the metal sheet a pressure allowing its folding and the formation of the corrugation 2. The upper punch 12 is illustrated, in its rest position, on FIGS. 2, 3, 4 and 6 and in its folding position, at the end of the stroke, in FIGS. 5 and 7. The upper punch 12 has, at its lower end, a head which extends along the longitudinal direction on a length substantially equal to the longitudinal dimension of the metal sheet 1 to be folded. The head has a convex portion 13 whose section has a shape of V corresponding to the shape of the corrugation 2 to be shaped.

The V-shaped section may either consist of two plane lateral faces joining at a ridge zone having a fillet or substantially correspond to a semi-elliptical shape and therefore consist of two arcuate side faces. In the first case, the metal sheet 1 made by means of the folding machine 1 will advantageously be shaped in a second time by another device to give the corrugation 2 thus formed a final semi-elliptical shape. On the contrary, in the second case, the folding machine 1 makes it possible to give the corrugation 2 thus shaped its final shape.

The head also has two flanges 14, 15 laterally bordering the convex portion 13 V-shaped and straightening towards the horizontal.

The upper punch 12 further comprises a finger 16 projecting from the median zone of the head towards the lower frame 11. The finger 16 has a slat shape which is able to deform the intersection zone between the preformed corrugation 3 and the corrugation to be formed so as to form a protruding vertex in the node region.

Furthermore, the folding machine 9 comprises a die 17 which is fixed on the lower frame 11 and has a recessed footprint 18 of complementary shape to that of the convex portion 13 of the head of the upper punch 12. The die 17 is arranged in below the head of the upper punch 12 so that the convex portion 13 engages inside the cavity 18 to shape the corrugation 2 when the upper punch 12 moves from its rest position to its folding position. The matrix 17 has on either side of the footprint 18 upper support edges 21 which are straightened towards the horizontal and are intended to contribute to the support of the metal sheet 1 prior to the movement of the upper punch 12 in the direction from its folding position.

In FIGS. 2 to 7, the matrix 17 is formed of two elements 19, 20 disposed respectively on either side of a median transverse plane and thus providing between them a free space intended to receive the preformed corrugation 3. shown in Figure 3, each of the two elements 19, 20 is formed of two half-shells 19a, 19b, 20a, 20b which each carry a half-cavity portion. It should be noted, however, that the structure of the matrix 17 is described above by way of example and that the matrix may consist of a different number of elements. The matrix 17 may in particular be formed in one piece or two half-shells attached to each other and each carrying a half-cavity. In all cases, the matrix 17 must have, in a medial portion, a free space, that is to say a slot or a gap, allowing passage of the preformed corrugation 3.

Furthermore, the folding machine 9 also comprises two knives 22, 23, carried by the lower frame 11 and a device for actuating the knives, in particular shown in FIGS. 6 and 7. The knives 22, 23 are respectively disposed from and else of the imprint 18 of the matrix 17, in its median zone, that is to say in the zone at which the free space allowing the passage of the preformed corrugation 3 is formed.

The knives 22, 23 each have an upwardly directed blade extending parallel to the longitudinal direction of the cavity 18. The knives 22, 23 are intended for the deformation of the preformed corrugation 3 on either side crossing the preformed corrugation 3 and the corrugation to be formed 2 so as to form concave corrugations in the crest of the preformed corrugation 3.

The knives 22, 23 are slidably mounted, relative to the lower frame 11, in a direction transverse between a spaced position and a close position. To do this, the knives 22, 23 are each fixed on a carriage 24 slidably mounted on a guide rail 25. In order to limit the friction between the carriages 24 and the guide rails 25, the carriages 24 are advantageously roller carriages which comprise a plurality of rolling bodies able to cooperate with bearing paths carried by the respective guide rail 25. The guide rails 25 are carried by a support member 26. The support member 26 is mounted vertically movable relative to the lower frame 11 between a low position and a high folding position of the preformed corrugation in which the knives 22 , 23 are able to cooperate with the preformed corrugation to shape it. To guide the translation of the support member 26 relative to the lower frame 11, the support member 26 has in a central portion 27 disposed opposite the finger 16, a cylindrical bore 28 which slides around the a complementary shaped guide tube, not shown, which is fixed on the lower frame 11 and projects towards the upper frame 11.

Elastic members 29, illustrated in Figures 4 and 5 provide automatic return of the knives 22, 23 to their spaced apart position. To do this, the elastic members 29 act between the central portion 27 of the support member 26 and the knives 22, 23. In the embodiment shown, the elastic members 29 are helical springs which each have a first end inserted. in a housing 30 formed in one of the knives 22, 23 and a second end bearing against the central portion 27 of the support member 26.

Figures 6 and 7 show the knife actuating device which is able to move the support member 26 upwards so that the knives 22, 23 are moved from their low position to their upper folding position, when the punch upper 12 moves downwards, that is to say from its rest position to its folding position. To do this, the actuating device comprises a movement transmission mechanism which has two bearing surfaces 31, 32 positioned inside the cavity 18 of the matrix 17. The two bearing surfaces 31 are flush with the level of the upper bearing edges 21 bordering the cavity 18 of the die 17, when the upper punch 12 is in its rest position (see Figure 6).

Thus, during the movement of the upper punch 12 from its rest position to its folding position, the head of the upper punch 12 comes, in a first step, to clamp the metal sheet 1 against said bearing surfaces 31, 32 when the punch upper 12 arrives in an intermediate position of contact with the metal sheet 1. In a second step, the movement of the upper punch 12 from its aforementioned intermediate contact position to its folding position, illustrated in FIG. 7, causes these surfaces to move. bearing 31, 32 downwards towards the bottom of the cavity 18.

The motion transmission mechanism is further arranged to transmit the movement of the bearing surfaces 31, 32 to the support member 26 so that the knives 22, 23 are moved to their upper folding position when the surfaces support 31, 32 are moved down.

In the embodiment shown, the movement transmission mechanism comprises two levers 33, 34. The levers 33, 34 are each articulated mounted on the lower frame 11 about a transverse horizontal axis of rotation 35, 36. The levers 33 , 34 each comprise a first end 37 passing through an opening in the die 17 and opening into the cavity 17 of the die 18. The first end 37 of each of the levers 33, 34 carries a part contact 38 which is mounted articulated on the first end 37 of said lever 33, 34 about a horizontal axis of transverse rotation. The articulation of each contact piece 38 on the first end 37 of one of the levers 33, 34 is here carried out via a semicylindrical portion of the contact piece 38 which is housed in a cradle of complementary shape formed in the first end 37 of one of the levers 33, 34. Furthermore, each contact piece 38 comprises a flat bearing sole forming one of the bearing surfaces 31, 32 positioned inside the cavity 18 of the matrix 17.

Furthermore, the levers 33, 34 have a second end 39 cooperating with the support member 26 in order to move it vertically during the pivoting of the levers 33, 34. The second end 39 of each lever 33, 34 cooperates with a horizontal flange 40 carried by the central portion 27 of the support member 26.

It is observed that the levers 33, 34 are symmetrical with respect to a transverse median plane. The levers 33, 34 therefore pivot in opposite directions of rotation which ensures a balancing of the forces.

In operation, when the upper punch 12 comes into contact with the portion of the metal sheet 1 to be bent, the upper punch 12 exerts on the first end 37 of each of the levers 33, 34 a force tending to pivot said lever 33, 34 so that the second end 39 of said lever 33, 34 acts 33, 34 on the horizontal flange 40 of the support member 26 and the knives 22, 23 move to their upper folding position in which they deform the ridge 3. When the folding operation is completed and the upper punch 12 is raised to its rest position, the support member 26 returns to its lower position of rest under the effect of gravity. causing the levers 33, 34 to pivot in an opposite direction of rotation until they return to their initial rest position, shown in FIG.

The method of using the folding machine 9 is described below.

In a first step, a metal sheet 1 in which a corrugation has been previously formed is placed in abutment on the die 17. The metal sheet 1 then rests on the upper bearing edges 21 and on the flat soles of the contact pieces 38 carried by the first ends 37 of the levers 33, 34.

The metal sheet 1 is positioned so that its preformed high corrugation 3 is in the median transverse plane in which the matrix 17 has a free space allowing the passage of said preformed corrugation 3.

According to one embodiment, the preformed corrugation 3 has along its length a V-shaped section consisting of two flat lateral faces joining at a ridge zone having a fillet. According to another embodiment, the preformed corrugation 3 has, alternately, semi-elliptic V-shaped sections in each of the zones interposed between two adjacent node-forming zones and V-shaped sections consisting of two faces. lateral planes joining at a crest zone with a fillet in the areas to be deformed by the folding machine. Thus, the preformed corrugation has its definitive shape in the areas that are not intended to be folded by the folding machine 1 and has, on the contrary, in the other areas to be folded a geometry allowing them to be easily folded .

Subsequently, the upper punch 12 is moved down towards the lower frame 11. When the upper punch 12 reaches an intermediate contact position, the metal sheet 1 is clamped between said upper punch 12 and the flat sole of the pieces of contact 38.

Subsequently, when the head of the upper punch 12 engages inside the cavity 18, the metal sheet 1 exerts a force on the levers 33, 34 tending to rotate them which causes a movement of the knives 22 , 23 to their upper folding position. In parallel, the metal sheet 1 deforming exerts on the knives 22, 23 a tensile force that tends to slide them to their close position.

Thus, during the movement of the upper punch 12 from its intermediate contact position to its folding position, a corrugation 2 is formed between the head of the upper punch 12 and the die 17, concave corrugations 7 are formed by the knives 22. , 23 in the crest of the preformed corrugation 3 on either side of the intersection between the two corrugations 2, 3 and a protruding crown area is shaped by the finger 16 in the node zone between the corrugations 2 , 3.

The upper punch 12 can then be brought upwards, away from the lower frame 11, to its rest position. Once the metal sheet 1 thus folded is removed, the knives 22, 23 are automatically recalled by their respective elastic members 29 to their spaced apart position. In addition, the support member 26 returns to its low rest position under the effect of gravity by driving the levers 33, 34 to their rest position.

Figure 8 shows a folding machine 1 according to another embodiment. The folding machine 1 of FIG. 8 differs from the folding machine shown and described in relation with FIGS. 2 to 7 only by the shape of the two flanges 14, 15 laterally bordering the convex portion 13 in the shape of a V of the upper punch. 12 and that of the upper bearing edges 21 of the matrix 17. In fact, compared to the folding machine of Figures 2 and 7, the portions 41 of the flanges 14, 15, shown in dashed lines were added while the portions 42 of the upper support edges 21 have been removed.

It is thus observed that the flanges 14, 15 are inclined in the longitudinal direction relative to the horizontal. The inclination of the flanges 14, 15 is such that they move away from the upper frame 10 as they approach the central zone of the head 16. In a complementary manner, the upper support edges 21 of the matrix are inclined relative to the horizontal, in the longitudinal direction, by an identical angle. The inclination of the upper support edges 21 is such that when they approach a middle zone of the die 17, they are closer to the lower frame 11. The angle of inclination of the flanges 14, 15 and the upper support borders 21 is, for example, of the order of 1 to 4 °. As in the previous embodiment, the flanges 14, 15 and the upper support edges 21 extend horizontally in the transverse direction. According to another embodiment not shown, the flanges 14, 15 and the upper support edges 21 are inclined in the transverse direction, parallel to the preformed wave of an angle of the same order, their inclination being such that they move towards the lower frame as they approach the convex portion 13 V-shaped or the footprint 18.

Such inclinations of the flanges 14, 15 and the upper support edges 21 are intended to compensate for the springback of the sheet occurring when no load is no longer applied to it. These inclinations thus aim to obtain after folding that all the flat areas 4 of the metal sheet extend in the same plane.

In connection with Figures 9 and 10, there is a folding machine according to another embodiment. The folding machine of FIGS. 9 and 10 differs from the folding machine of FIGS. 2 to 7 in that it further comprises two lateral matrix elements 43 and two upper counter-matrices 44. In FIGS. 9 and 10, a only one of the two lateral matrix elements 43 and only one of the two upper counter-matrices 44 are shown.

The two lateral matrix elements 43 are respectively disposed on either side of the cavity 18 of the matrix 17 and are slidably mounted on the lower frame in a transverse direction, between a spaced apart position, shown in FIG. close position shown in Figure 10. Advantageously, the folding machine 1 is equipped with return members, not shown, such as coil springs, for reminding the lateral die elements 43 to their spaced apart position. Both die side members 43 each have a V-shaped groove 45 for receiving the preformed corrugation 3.

Moreover, the two upper counter-matrices 44 are respectively disposed on either side of the upper punch 12 respectively above the one and the other of the lateral matrix elements 43. The two upper counter-matrices 44 are , on the one hand slidably mounted on the upper frame 10 in a transverse direction between a spaced position, shown in Figure 9 and a close position shown in Figure 10 and, secondly, mounted vertically movable on the upper frame. Advantageously, the folding machine 1 is equipped with return members, not shown, such as helical springs, for returning the two upper counter-matrices 44 to their spaced apart position. In addition, the folding machine is also equipped with return members 47 for returning the upper counter-matrices 44 downwards relative to the upper frame, that is to say away from the upper frame. These return members 47 are for example helical springs or gas cylinders. The two upper counter-matrices 44 each comprise a male element 46 which is intended to be introduced into the groove 45 of the lateral die element 43 vis-à-vis.

With such a folding machine 1, when the metal sheet 1 in which a corrugation has been previously formed is placed in abutment on the die 17, the metal sheet 1 also rests on the lateral die elements 43. The preformed corrugation is then housed inside the groove 45 of each of the lateral matrix elements 43.

Subsequently, the upper frame 10 is moved downwards towards the lower frame 11 to an intermediate contact position, illustrated in FIG. 9. In this position, the upper counter-matrices 44 are positioned in a position of in which their male element 46 is inserted inside the groove 45 of one of the lateral matrix elements 43. The upper countermatrices 44 then pinch the metal sheet against the lateral matrix elements 43.

When the upper frame 10 continues to descend towards the lower frame 11, the return members 47 compress while the upper punch 12 deforms the metal sheet 1.

Since the metal sheet 1 is clamped between the upper counter-matrices 44 and the lateral matrix elements 43, the metal sheet, by deforming under the effect of the upper punch 12, exerts a tensile force on the upper counter-matrices 44 and the lateral matrix elements 43, against their return members, in order to move them towards their close position (FIG. 10). Thus, the upper counter-matrices 44 and the matrix side members 43 are moved to their close position synchronously with the movement of the upper punch 12, without the need for dedicated actuation means.

When the upper punch 12 has reached its extreme position, the upper frame 10 can then be brought upward, away from the lower frame 11. Therefore, the upper counter-matrices 44 and the matrix side members 43 are automatically recalled by their respective return members to their discarded position.

We observe that if the folding machines 9 described above can form a corrugation in a metal sheet 1 having a single preformed corrugation 3, the invention is not limited to such embodiments. In particular, it is possible to form a corrugation in a metal sheet having a plurality of parallel preformed corrugations 3 by aligning a plurality of folding machines 9 as described above, one after the other according to their longitudinal direction. .

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. 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 (13)

A machine for folding (9) a metal sheet (1) having a first preformed corrugation (3) to form a second corrugation (2) perpendicular to the first preformed corrugation (3); the folding machine (9) having a lower frame (11) and an upper punch (12) movable vertically with respect to the lower frame (11) between a resting position and a folding position; the upper punch (12) comprising a head extending in a longitudinal direction and having a V-shaped convex portion (13) of shape complementary to the shape of the second corrugation (2) to be formed and two flanges (14, 15) straightening towards the horizontal bordering the convex portion (13); the lower frame (11) being equipped with a matrix (17) fixed with respect to the said lower frame (11), disposed below the head of the upper punch (12), the die (17) having an imprint (18); concave having a shape complementary to that of the convex portion (13) and intended to receive said convex portion (13) when the upper punch (12) is in its folding position; the folding machine further comprising: - two knives (22, 23) for deforming the first preformed corrugation (3), on either side of the crossing zone between the first preformed corrugation (3) and the second corrugation to be formed (2), the two knives (22, 23) being disposed on either side of the cavity (18) of the matrix (17) and being movably mounted on the lower frame (11) between a low position and a high folding position of the first preformed corrugation (3); and a device for actuating the knives comprising a mechanism for transmitting the movement, the transmission mechanism comprising at least one bearing surface (31, 32) arranged opposite the head of the upper punch (12). ) and positioned inside the cavity (18) of the matrix (17) so that, in operation, during the movement of the upper punch (12) from its rest position to its folding position, the metal sheet (1) is clamped between the bearing surface (31, 32) and the upper punch (12); said motion transmission mechanism being arranged to transmit movement between said bearing surface (31, 32) and the knives (22, 23) so that the knives (22, 23) are moved to their upper position folding during the movement of the upper punch (12) from its rest position to its folding position. 2. folding machine (9) according to claim 1, wherein the knives (22, 23) are each slidably mounted, in a transverse direction perpendicular to the longitudinal direction of the head, on a support member (26) between a spread position and a close position. 3. Folding machine (9) according to claim 2, wherein each of the knives (22, 23) is carried by a carriage (24) slidably mounted on a guide rail (25) which is fixed to the support member (26) and extends in the transverse direction. 4. Folding machine (9) according to claim 2 or 3, comprising one or more resilient members (30) arranged to return each of the knives (22, 23) to their spaced apart position. Folding machine (9) according to any one of claims 2 to 4, wherein the support member (26) is mounted vertically movable on the lower frame (11) and wherein the movement transmission mechanism cooperates with the support member (26) and is arranged in such a way that the support member (26) is moved vertically upwardly relative to the lower frame (11) in order to move the knives (22, 23) of their low position towards their high folding position during the movement of the upper punch (12) from its rest position to its folding position. 6. Folding machine (9) according to any one of claims 1 to 5, wherein the movement transmission mechanism comprises: - two bearing surfaces (31, 32), arranged vis-à-vis the upper punch head (12) and positioned within the cavity (18) of the die (17); and - two levers (33, 34) which are each mounted articulated on the lower frame (11) and each comprise a first end (37) carrying one of the bearing surfaces (31, 32) so as to cause pivoting levers (33,34) upon movement of the upper punch (12) from its rest position to its folding position and a second end (39); the second ends (39) of the levers (33, 34) being arranged to transmit a movement to the knives (33, 34) so as to move them from their low position to their upper folding position when the levers (33, 34 are pivoted). ) driven by a movement of the upper punch (12) from its rest position to its folding position. 7. Folding machine (9) according to claims 5 and 6 taken in combination, wherein the second end (39) of each of the levers (33, 34) cooperates with the support member (26) so as to move it vertically when pivoting the levers (33, 34). 8. Folding machine (9) according to claim 6 or 7, wherein the first end (39) of each of the levers (33, 34) carries a contact piece (38) which is, on the one hand, articulated on the first end (37) of said lever (33, 34) about an axis of articulation perpendicular to the longitudinal direction of the head and, on the other hand, comprises a flat sole forming one of the bearing surfaces (31,32) for cooperating with the metal sheet (1) during the movement of the upper punch (2) from its rest position to its folding position. 9. Folding machine (9) according to any one of claims 6 to 8, wherein the levers (33, 34) are symmetrical with respect to each other, with respect to a transverse median plane perpendicular to the longitudinal direction of the head of the upper punch (12). Folding machine (9) according to any one of claims 1 to 9, wherein the upper punch (12) comprises a finger (16) projecting from a median zone of the head towards the lower frame (11). ) and for deforming the crossing zone between the first preformed corrugation (3) and the second corrugation to be formed (2) so as to form a protruding vertex in the metal sheet (1). Folding machine (9) according to any one of claims 1 to 10, wherein the die (18) is interrupted in a central zone to allow passage of the preformed corrugation (3). 12. Folding machine (9) according to any one of claims 1 to 11, further comprising: - two lateral matrix elements (43) arranged on either side of the footprint (18) and each having a V-shaped groove (45) for receiving the first preformed corrugation (3); the two lateral die members (43) being each slidably mounted on the lower frame (11) in a transverse direction perpendicular to the longitudinal direction of the upper punch head (12) between a spaced apart position and a close position; - two upper counter-matrices (44) disposed on either side of the upper punch (12), respectively above the one and the other of the two lateral matrix elements (43), the two counter-matrices upper members (44) each having a male member (46) adapted to be introduced into the groove (45) of one of the die side members (43); the two upper countermatrices (44) being, on the one hand, slidably mounted on an upper frame (10) carrying the upper punch (12) in a transverse direction perpendicular to the longitudinal direction of the head of the upper punch (12) , between a spaced position and a close position and, secondly, vertically movable relative to the upper frame (10). 13. A method of using a folding machine (9) according to any one of claims 1 to 12, for forming, in a metal sheet (1) having a first preformed corrugation (3), a second corrugation (2). perpendicular to the first preformed corrugation (3); said method comprising: positioning a metal sheet (1) against the die (17); moving the upper punch (12) to its folding position in which the upper punch head (12) presses the metal sheet (1) into the cavity (18) of the die (17) to form the corrugation (2) and deform the preformed corrugation (3) on either side of the crossing zone between the two undulations (2, 3).