EP1719591A1 - Method of shaping web or sheet materials and press for carrying out the method - Google Patents

Abstract

The procedure for shaping a strip or sheet material (2) in a curve between upper (10) and lower (20) beams connected to supporting structures (11, 21) and working together on either side of the strip or sheet includes a deliberate and unidirectional elastic deformation phase of one of the supporting structures during compression, in a direction perpendicular to the plane of the material's movement. The supporting structure of one of the beams has variable rigidity mechanism, e.g. formed by cams and rollers (22, 26) to provide the required elastic deformation.

Description

The subject of the present invention is a process for forming a strip or plate material by compression between an upper bed base and a lower bed base, as well as a forming press for carrying out said method.

Such presses are known in particular in the field of converting paper or cardboard for the manufacture of eg folding boxes.

A first type of press, well known to those skilled in the art, works the material of paper or cardboard by flat forming between two plates, one fixed and the other mobile as described for example in the document EP0681892 . The fixed plate is constituted by an upper bed base secured to the frame of the machine. For cutting presses, the cutting tool mounted on this fixed plate consists of a board provided with a multitude of knives for cutting and pressing the material into a desired shape. This board is generally known as a form to be cut by a person skilled in the art. Equipped with counterparts playing the role of an anvil and negative impressions for the knives or push-back nets, the movable turntable is constituted by a lower bed base secured to a supporting structure. In the version described by the document EP0681892 the lower bed is animated by a vertical rhythmic movement. In other known versions, the lower bed base is fixed while the upper bed base is movable and animated with a vertical clocked movement. This periodic movement compresses the material worked between the two plates and thus cut and / or repress in a brief operation on its entire surface.

To be able to perform flat cutting of a surface equivalent to that of a cutting plate, it is necessary to involve considerable compressive forces. In order not to obtain the rapid destruction of the sharpening of the knives of the form to be cut, it is also necessary to ensure that these knives do not come more than necessary to abut against the anvil to cut the material sandwiched between the two turntables. Depending on the thickness and type of material to be shaped, it will be necessary to make various adjustments, one of which is to refine the quality of the cutting by acting on the height of the knives in places where this material has not been sufficiently well cut. To do this, the driver of the machine will have a sheet, called betting sheet, placed on the back of the knives of the form to be cut. This betting sheet is intended to receive small pieces of adhesive tape at the aforementioned places. Thus, during the compression of the material between the two bed bases, the shaping of the latter will be improved by varying the height of the sharp edge of the knives relative to the base of the upper bed.

One of the drawbacks of this practice lies in the fact that this so-called wagering operation is relatively long and requires several successive tests until a satisfactory result is obtained. The time devoted to this operation currently corresponds to the longest preparation of the machine for a new job. For small series, this significant time therefore contributes to higher production costs.

A second type of presses known today refers to the rotary shaping of the material worked between two rolls pressurized against each other. The upper cylinder generally comprises a circular cutting tool whose development corresponds to the shape that is wants to cut. The lower cylinder is a smooth cylinder acting as a cylindrical anvil. Such a machine is illustrated for example in the document EP1331054 .

A third type of presses implements an upper plane bed and a movable lower bed base of curvilinear shape. Thanks to the rounded surface of the mobile bed, the cutting of the material is carried out gradually by the movement of the lower bed base which, in its movement, rolls against the cutting plane of the fixed upper bed. Such a curvilinear cutting press is described in more detail in the document GB914637 .

While the latter method of cutting advantageously reduces the force required for the shaping of the material, on the other hand it has been found that the knives of the form to be cut, integral with the upper plate, wear out quickly and this in a non uniform. Indeed, it has been noted that the sharpening of the knives located in the middle part of the form to be cut deteriorated much more rapidly than that of the knives arranged in the upstream and downstream ends of this tool. This anomaly stems essentially from the curvilinear cutting mode in which the forces involved are twice as large in the middle part of the plate as at its ends supported by the movable structure of the lower bed. These disadvantages lead to the frequent replacement of knives, encourages the production of lower quality articles and require many machine stops for the restoration of the shape to be cut. From the point of view of the specialists in this field, it is these main reasons which prevented the development of the curvilinear molding presses, which finally never worked to satisfaction, unlike the presses of the other two types using flat cutting and cutting. rotary.

The object of the present invention is to remedy, at least in part, the above-mentioned drawbacks so that on the one hand it is no longer necessary to resort to the so-called putting operation, and on the other hand that the force required for shaping tools to be as constant as possible to prevent premature deterioration of these tools.

For this purpose, the subject of the present invention is a process for forming a strip or plate material, in accordance with claim 1, as well as a press for carrying out this method, in accordance with what is stated in claim 4.

• La figure 1 est une vue schématique en élévation d'un mode de réalisation d'une presse conforme à l'invention.
• La figure 2 est une vue schématique en perspective d'un sommier supérieur d'une presse, vu depuis le dessus.
• La figure 3 est une vue schématique en perspective d'un sommier inférieur d'une presse, vu depuis le dessous.
• La figure 4 est une vue schématique en coupe longitudinale d'un sommier formé d'une structure selon un second mode de réalisation.
• La figure 5 est une représentation schématique sous forme de trois diagrammes illustrant respectivement les raideurs dans la structure portante d'un sommier indéformable, la raideur dans un sommier intentionnellement déformable et la combinaison de ces raideurs telle qu'elles apparaissent dans la presse de la présente invention.

The invention will be better understood from the study of a preferred embodiment, taken in a non-limiting manner and illustrated by the appended figures in which:

• Figure 1 is a schematic elevational view of an embodiment of a press according to the invention.
• Figure 2 is a schematic perspective view of an upper bed base of a press, seen from above.
• Figure 3 is a schematic perspective view of a lower bed base of a press, seen from below.
• Figure 4 is a schematic longitudinal sectional view of a bed base formed of a structure according to a second embodiment.
• FIG. 5 is a diagrammatic representation in the form of three diagrams respectively illustrating the stiffness in the supporting structure of a non-deformable bed base, the stiffness in an intentionally deformable bed base and the combination of these stiffness as they appear in the press of the present invention.

From a terminological point of view, and to avoid any confusion in the description that follows, the terms upstream and downstream will be defined with reference to the direction of movement of the material in a strip or plate, as illustrated by an arrow D in the figures. This material moves from upstream to downstream, following the main axis of the machine in a movement clocked by periodic stops. Also, we define the terms longitudinal and transverse to the main axis of the machine. In the same way, we will call the upper and lower bedspreads the set of elements that are on both sides of the material and allow to shape it, so as not to weigh down the description by mentioning construction details without direct relationship with invention and well known to those skilled in the art.

In FIG. 1 is illustrated a press 1 for the work of a material 2, in strip or plate, moving in accordance with the direction of movement illustrated by the arrow D. On either side of the axis scrolling plane. longitudinal X, are an upper bed base 10 and a lower bed base 20. Each of these bed bases being connected to a bearing structure 11 and 21, respectively. The supporting structure of the upper bed base 10 will consist of the frame of the press 1, while that of the lower bed base 20 will be composed of bodies that support and allow the movement of this bed base with respect to a cross member 30. The latter serving as base or base for the press.

The fixed upper bed base is disposed slightly above the material passage plane 2. It is equipped with a forming tool 3, which is called the form to be cut in the case of a press intended for cutting and pressing the worked material. On this form to be cut are arranged a plurality of shaping members 5 of the material 2, thus secured to the upper beam, plus generally from one of the bedsteads 10, 20 or at least one of them. Typically, such forming members 5 consist for example of cutting knives and / or pressers arranged between rubbers or other strips of resilient material 4. These strips are both intended to protect the knives and provide a surface of support and maintenance of the material when it is pressurized by the two sommiers. The transverse line located at the height of the knife furthest downstream with respect to the direction of travel D of the material is called the first thread f1. Conversely, the transverse line located at the height of the last knife upstream is called last f2 net.

Thanks to the supporting structure 21, formed for example of cams 22 and rollers 26, the lower bed base 20 acquires a relatively complex vertical and cutting movement, part of which allows its working surface 25 to roll against the upper bed base 10. The material and the shape to be cut are sandwiched between these two bases, the material being traversed by the cutting nets on which rolls the work surface. The direction of rolling of the movable bed is indicated in FIG. 1 by the arrow R which, during the compression of the material 2, pivots preferably downstream upstream and vice versa when the mobile bed is lowered to allow the scrolling again. momentary of the material worked.

The reciprocating movement of the tilting of the working surface 25 is illustrated in this same figure by mixed lines 25 '. With this movement, the material 2 is cut gradually while avoiding any possible curl of the latter. The curvilinear cutting technique makes it possible to use forces that are much less important than those required to obtain the same result from a machine intended for flat cutting. Moreover the pressure exerted is generally less important. Indeed, in a machine using the flat cutting technique, a minimum pressure must be ensured at any point of cutting or crushing on the entire surface of the material to be worked. A greater average pressure is then exerted in order to be certain that the minimum pressure is applied in all points which increases the forces involved. The curvilinear cutting technique of rolling the work surface on the cutting nets, the cutting surface at a given moment is lower and the forces involved are thus considerably reduced.

A forming press using the method according to the invention can therefore be substantially lighter than existing machines using a cutting and flattening process flat. The driving device and the frame can then be redefined and undersized with respect to those of a flatbed forming machine. A press according to the invention is therefore less expensive to produce, transport and install.

The curvilinear cutting and curving forming presses according to the state of the art are all based on the same principle as flat-forming presses. Thus, in these presses, the frame and the bed bases are designed as being the most rigid possible, so as to undergo the least deformation possible during shaping.

FIG. 5 gives an illustration, in the form of diagrams, of the notions of forces, stiffness and deformations involved in the supporting structure 11 and in the upper bed base 10, as a function of the position of the force F generated by the compression lower bed base 20 against the upper bed base. This figure will help to better understand the reasons why curvilinear cutting machines known to the state of the technicians saw their shaping tools wear out abnormally.

The schematic representation of this figure derives from a modeling of the elastic resistances calculated in a curvilinear cutting press such as that described with reference to FIG. 1. Due to the curvilinear movement of the movable bed, the force F exerted by this The mattress thus moves downstream upstream along the longitudinal axis X during the time required for shaping the material.

The diagram shown on the left-hand part of FIG. 5 represents an upper bed base of the prior art in the form of a rigid beam connected at these ends to its supporting structure, namely to the frame of the press. Although a priori not flexible, this frame still has a certain intrinsic elasticity when it is subjected to a strong constraint. Behaving like a spring, it therefore has a certain intrinsic rigidity K _built . This stiffness is quite similar to the constant of a spring K _m which is determined by the ratio between the increase of the applied force F and the resulting elongation ΔL. In our case, the elongation ΔL ₁ , ΔL _{2 will} correspond to the deformation of the frame, under the action of the force F ₁ , F ₂ applied to it, with respect to its state at rest corresponding to the withdrawal of the lower bed.

Referring always to the graph on the left which illustrates the variation of the stiffness K _constructed as a function of the position of the force F on the longitudinal axis X, it will be noted that this stiffness increases gradually as soon as the lower bed base enters into position. action to cut the material. This progression continues to a maximum that is halfway to its curvilinear course along the upper bed. Then this stiffness gradually decreases in the same way that it has increased, until returning to the initial value. Because the resultant of two stiffnesses placed in parallel correspond to the sum of these stiffnesses, the maximum value is thus equivalent to twice the initial value. The corresponding force applied to the knives situated midway between the first threader f1 and the last thread f2 is thus also twice that applied to the ends of the form to be cut. This is the reason why the knives of the tools associated with the machines of the prior art were being used both too quickly and non-uniformly.

In order to solve this problem, the shaping method according to the present invention comprises a phase of intentional and essentially unidirectional elastic deformation, of a structure of at least one of the sommiers, during the compression phase of the material between the sommiers. Advantageously, these deformations are oriented substantially perpendicularly to the work surface. It will be noted that the intentional nature of these deformations clearly aims at differentiating them from involuntary deformations, as it exists within this same structure in the transverse or longitudinal directions in particular. Also, the mention of the adverb essentially aims to clarify that the deformations undergone are very largely unidirectional.

In terms of forces, deformations and stiffness, the shaping method according to the invention is illustrated in the following two diagrams of FIG. 5. The central diagram illustrates the reaction of an upper bed base of a shaping press according to the invention. the present invention, connected at both ends to a rigid supporting structure.

In this example, the upper bed base 10 is able to undergo intensional elastic deformations, substantially perpendicular to the work surface, thanks to the flexibility of its structure. Thus, its intrinsic stiffness K will vary between its ends along the longitudinal axis X. The stiffness, or elastic resistance of the upper bed base 10, will be higher at its ends in an intermediate position between them. By correctly dimensioning the structure 12 of the upper bed base 10, the variation of its stiffness best compensates for the increase in stiffness illustrated in the diagram on the left, we obtain a final stiffness almost constant as illustrated by the last diagram to the right of Thus, the force applied to the forming members 5 of such a press 1 no longer undergoes large fluctuations, but is on the contrary as constant as possible during shaping of the material.

Computer modeling has made it possible to compare the forces involved along a series of knives of a cut-off shape mounted a first time on an ordinary platen press and then again on a press according to the invention. . The results have shown that the ratio between the minimum force and the maximum force recorded on all the measuring points in a curvilinear cutting press, according to the present invention, is at least five times better than in the case of a cutting with an ordinary press. This made it possible to highlight the marked improvement in the regularity of the shaping force over the entire surface of the shape to be cut.

From a practical point of view, it will be noted that the compensation of the stiffness results in providing a force per unit length of the forming members 5, in particular knives, which is almost constant during the rolling of the mobile bed against the fixed bed. . The quasi-constancy of this force is of real interest only in the range between the first thread f1 and the last thread f2. Thus, one could also be satisfied to obtain effective compensation limited to this single range.

FIG. 2 shows an embodiment of the structure 12 of the upper bed base 10 shown in FIG. perspective in a view from above. It will be noted that this structure is elastic and anisotropic so that it allows its deformation only along the longitudinal axis X, in a direction perpendicular to the working surface.

Thus, the transverse deformations will be minimized as much as possible by means of reinforcing members 13 of this structure, and in particular by virtue of their positioning relative to the longitudinal axis X of travel.

Advantageously, these reinforcing members are on the one hand arranged in a substantially transverse orientation relative to this axis, and on the other hand erected on their edge, against a sole 14, and then present in this same orientation the best possible resistance to flexion. Preferably, these reinforcing members consist of ribs connected at their ends to the side walls of the press frame, either directly or indirectly via side plates 15. It should be noted in this connection that this connection can be made of different way and that, for example, it is not necessary that it be established over the entire height of the rib.

Also, it will be noted in FIG. 2 that the thicknesses, the heights, the shapes or the profiles of the reinforcing members 13 can vary so as to influence the bending of the upper bed base 10 as a function of the position, along the longitudinal axis X, the force that is applied by the lower bed base 20. The spacing between these reinforcing members is also a factor of influence, as a possible defect of voluntary perpendicularity with respect to the longitudinal axis of travel of the material. In a similar way, it will be mentioned that the connection or attachment of the edge of the reinforcement member 13 to the sole 14 may also have a particular shape so as to influence the behavior of the upper bed base when it is flexed. As illustrated in Figure 2, this sole is preferably not directly attached to the side plates 15. In order to allow the only bending of the bed base in the longitudinal direction, the structure 12 is advantageously neither closed nor provided with crossed ribs intended to deliberately prevent this flexion.

Referring to Figure 3, the latter illustrates an embodiment of the structure 22 of the lower bed base 20, shown in perspective in a view from below. This embodiment and its characteristics are similar to those described above with reference to the upper bed base 10. Thus, in this structure will be found the same organs as those that make up the structure 21, namely reinforcing members 23, a sole 24 and side plates 25, except that due to the mobility of the lower bed base 20, the latter will of course not be connected to the frame of the press 1.

FIG. 4 shows, in a longitudinal sectional view, a second embodiment of the structure 12 of one of the bed bases, in particular of the upper bed base 10. Unlike that described in the previous embodiment, this structure is not not necessarily open and does not include any reinforcing member of the rib type. In this structure, the desired elastic deformations are obtained by the arrangement, in the bed base, of an elastic sole 6 variable stiffness. This stiffness or variable elastic resistance can be produced by varying the thickness of the elastic sole 6 in a chosen direction, namely essentially in the direction of the longitudinal axis X. The forming tool 3 is preferably arranged either directly against the elastic sole 6 in order to benefit from its intensional deformations, either by means of a support plate 7 which is able to support the aforesaid deformations without ever leaving the elastic domain of the material constituting it.

In general, it will be mentioned that the structure 12, 22 of the or one of the bed bases 10, 20 of the press 1 is formed of at least one member with variable stiffness and that this member may consist of said elastic sole 6 by example, but also reinforcing members 13, 23 as described above.

Similarly, the same reasoning can be made for the intrinsic stiffnesses involved in the lower bed base 20. In general, it will be mentioned that the structures of the lower and upper bed bases are dimensioned so that the sum intrinsic stiffness in these beds and in their supporting structures 11, 12 is such that it is close to a value that is constant during the rolling of the mobile bed against the fixed bed. According to a particular embodiment, the two mattresses 10, 20 each have an intentionally deformable elastic structure and undergo conjugated intensional deformations.

Preferably, the radius of curvature at any point of the curvilinear working surface is greater than or equal to five times the working distance between the first and the last thread, which makes it possible to smooth the variations of stress on the compressed material by increasing the width of the compressed area.

In a more general way, it will also be mentioned that the tasks performed by these presses are not limited solely to cutting or upset operations, but could be adapted to any other shaping operation such as embossing, metallized striping or printing.

Advantageously, the present invention makes it possible to completely eliminate the needling operation required in ordinary flat-forming presses. This deletion allows on the one hand to reduce the preparation time of the machine, and on the other hand allows the accomplishment of these tasks by less qualified personnel.

Advantageously again, the present invention makes it possible to benefit to the maximum from the advantages of curvilinear shaping by allowing the use of lighter presses, which reduces nuisance and costs, while sparing the tools of premature wear. As a result, not only is the life of these tools prolonged, but also the quality of the cutting and the creasing of the material are improved compared to those obtained in ordinary platen presses.

Claims (10)

A method of curvilinear forming of a strip or plate material (2) by compression between an upper bed base (10) and a lower bed base (20) each connected to a supporting structure (11, 21) and working jointly on both sides other of the plane of travel of the longitudinal axis material (2) (2), characterized in that it comprises, during the compression phase, an essentially unidirectional intentional elastic deformation phase of a structure (12, 22) of one of said bed frames (10, 20). Method according to claim 1, characterized in that said intentional deformations are essentially oriented perpendicular to the plane of travel of the material (2). Method according to claim 1, characterized in that the compression phase also comprises an essentially unidirectional intentional elastic deformation phase of a structure (12, 22) of the second of said bedsteads (10, 20), the two phases of elastic deformation being combining. Press (1) for forming a strip or plate material (2) for carrying out the method according to claim 1, comprising an upper bed base (10) and a lower bed base (20) each connected to a supporting structure (11, 21) and working jointly on both sides of the plane of travel of the material (2) of longitudinal axis (X), one of said bed frames (10, 20) being mobile and the other being fixed , one of the two bedsteads (10, 20) supporting a curvilinear working surface (25), characterized in that the structure (12, 22) of one of said bedsteads (10, 20) comprises at least one member (6) , 13, 23) with variable stiffness intended to elastically deform intentionally during the compression phase. Press (1) according to claim 4, characterized in that said structure (12, 22) comprises an elastic sole (6) variable stiffness. Press (1) according to claim 4, characterized in that said structure (12, 22) comprises reinforcing members (13, 23) opposing the bending of said bed base (10, 20) along the transverse axis the scrolling plane of the material (2). Press (1) according to claim 6, characterized in that said reinforcing members (13, 23) consist of ribs. Press (1) according to claim 4, characterized in that said structure (12, 22) is open. Press (1) according to claim 4, characterized in that the movable bed supports a curvilinear working surface (25) for rolling against the fixed bed base during the shaping operation of the material (2), in a meaning which opposes the scrolling of matter (2). Press (1) according to claim 4, characterized in that at any point on the curvilinear work surface (25), the radius of curvature is greater than or equal to five times the working distance between the first thread and the last thread. .

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