EP1932658A1 - Method and machine for folding blanks - Google Patents

Abstract

The folding method involves folding a panel (1a-1d) at 180 degrees around the longitudinal grooves (2a-2d) into a first folding device (30), and forms a longitudinal fold along the groove. A blank (1) is conveyed by a conveyor (11) from a feeder (10) and aligned along the longitudinal fold into a main aligning device (40), and folding blank at 180 degrees around the groove into a second folding device (50). An independent claim is also included for a folder-gluer.

Description

Technical area

The present invention relates to a method of folding a blank of paper, cardboard, plastic, corrugated cardboard or similar material to form a folded box.

The invention also relates to a machine for carrying out the method according to the invention.

State of the prior art

To make a folded box of a given material, it is known to fashion a laying (or cutting) of said material, in a machine called "folder-gluer". For example, to make a parallelepiped box, that is to say a box with a rectangular base, the laying used has the general shape of a rectangle with two lateral sides and two transverse sides.

In relation to the direction of advance of the poses, the front edge of the pose is the transverse side of the pose which enters first in the machine, and the back edge the one which enters last. Similarly, the left edge of the pose is the lateral side of the pose located to the left of the longitudinal axis of the folder-gluer and the right edge is the lateral side of the pose located to the right of the longitudinal axis of the folder-gluer. In a box with rectangular base (otherwise called conventional box), to be folded in the right places, the pose comprises from left to right, four longitudinal grooves (or ups and downs) which divide the pose into five parts: four adjacent flanks and one leg lift-off. In the example of a biconvex box or pouch, the installation comprises two longitudinal grooves that divide the pose into three parts: two adjacent flanks and a glue tab.

To make a box folded, the flanks at the right and left ends of the pose are folded 180 ° to the inside of the pose. In this last position, the distance between the right and left edges of the pose is called the gap. If necessary, the gap at the front of the folded box and the gap at the back of the folded box can be distinguished.

To make a good folded box, it is necessary that the gap of the folded box is equal to a reference gap Gref, fixed by specifications. In the practice, it is observed that it is very difficult to ensure this equality for all the boxes of a production, also, it is tolerated that the gap of a folded box can be equal to Gref + Δ, provided that Δ is the smallest possible. Δ represents the gap deviation with respect to the reference gap, it can be positive or negative.

A good folded box is also a box where the gap at the front is equal to the gap at the back because otherwise the box folded to the shape of a trapeze. This problem is known as "fishtailing".

A first known folding method is to fold simultaneously at 180 ° the end flanks. This folding method does not make it possible to minimize the difference in gap Δ or to prevent fishtailing.

Another known method (see Figures 5a and 5b ) consists of folding successively 180 ° flanks located at the right and left ends of the pose. This folding method does not better minimize the gap gap Δ, nor prevent the fishtailing.

In the state of the art mentioned above, it is also known to align the left or right edge of the laying along an axis parallel to the longitudinal axis of the folder-gluer before folding the end flanks.

Presentation of the invention

A first object of the present invention is to minimize the gap gap Δ. For this purpose, the subject of the present invention is a folding method according to claim 1.

Another object of the invention is to suppress or, at the very least, to reduce fishtailing. Other objects and advantages of the invention will appear more clearly in the description of embodiments, which description will be made with reference to the accompanying drawings.

Brief description of the figures

• The figure 1 is a schematic elevational view of a first embodiment of a folder-gluer for carrying out the method according to the invention;
• The figure 2 is a schematic elevational view of a second embodiment of a folder-gluer for carrying out the method according to the invention;
• The figure 3 is a view of a box being manufactured;
• The figure 4 is a view of a folded box;
• The Figures 5a and 5b show folding steps according to the state of the art;
• The Figures 6a to 6c show folding steps according to the invention;
• The Figures 5c and 6d are a view of a folded reference box.

Best way to realize the invention

The figure 1 schematically illustrates a first embodiment of a folder-gluer for implementing the method according to the invention, the figure 1 also illustrates different steps of the method of folding a pose 1. In the example, the pose 1 is intended to form a conventional box. The arrow 8 indicates the direction of advance of the poses in the folder-gluer, this direction is parallel to the longitudinal axis 9 of the folder-gluer. In the following, the plan of the folder-gluer is defined as the horizontal plane passing through the longitudinal axis of the folder-gluer.

Each pose that is presented at the entrance E of the folder-gluer has the general shape of a rectangle with two lateral sides 5 and 6, parallel to the longitudinal axis of the folder-gluer and two transverse sides 3 and 4, perpendicular to the longitudinal axis of the folder-gluer, in the plane thereof. With respect to the direction of advance of the poses, the transverse side 3 is defined as being the rear edge of the laying and the transverse side 4 as being the front edge of the laying, likewise the lateral side 5 is defined as being the left edge of the pose and the lateral side 6 as the right edge of the pose. Finally, the length of the pose is defined as the distance separating the front edge of the rear edge of the pose.

To be able to be folded in the chosen places, the laying 1 comprises, from left to right, four longitudinal grooves (or upsets) respectively 2a, 2b, 2c and 2d, parallel to the left edge 5 and which delimit four adjacent flanks respectively 1a, 1 b, 1c and 1d. To allow the subsequent formation of the bottom and the lid of the box, transverse grooves 2f and 2g, parallel to the front and rear edges of the laying, are provided at a distance from said edges. Similarly, slots are provided in the extension of the grooves 2a, 2b and 2c between said transverse grooves 2f and 2g and said front and rear edges of the pose.

Each flank has the general shape of a rectangle with two transverse sides which coincide with the rear edges 3 and front 4 of the pose. The lateral sides of the first flank 1a coincide with the left edge 5 of the laying and the longitudinal groove 2a. The lateral sides of the second sidewall 1b coincide with the longitudinal grooves 2a and 2b. The lateral sides of the third flank 1c coincide with the longitudinal grooves 2b and 2c. While the lateral sides of the fourth sidewall 1d coincide with the longitudinal grooves 2c and 2d. The groove 2d separates the fourth flank 1d from a gluing tab 1e delimited by said groove 2d and the right edge 6. Alternatively, the gluing lug 1e may be adjacent to the first sidewall 1a.

In the first embodiment of the machine illustrated in figure 1 , a pose 1 is driven by a conveyor 11 of a margin station 10. Subsequently, a conveyor 31 causes said laying in a first folding module 30. In the folding module 30, the sidewall 1d is folded over the flank 1c by means of a folding propeller 32, that is, the flank 1d is folded at 180 ° around the groove 2c. At the end of this first folding operation, a first longitudinal fold 2'c appears at the location of the groove 2c. Then, a conveyor 41 causes said laying in a main alignment module 40. In the alignment module 40, the first longitudinal fold 2'c of the laying 1 comes into linear contact with a rule 42 (or guide rail) , along this one. In the plane of the folder-gluer, the longitudinal axis of the ruler 42 forms a zero angle with the longitudinal axis of the folder-gluer, that is, the longitudinal axis of the ruler 42 is parallel to the longitudinal axis of the folder-gluer, so that the groove 2a is parallel to the longitudinal axis of the folder-gluer. Thanks to these provisions, any error during the first folding operation is compensated before the second folding operation so as to minimize the gap gap Δ. See the description of Figures 6a to 6c for a detailed explanation.

Then, a conveyor 51 causes said laying in a second folding module 50. In the folding module 50, the sidewall 1a is folded down on the sidewall 1b by means of a folding propeller 52, in other words the sidewall 1a is folded 180 ° around the groove 2a. At the end of this second folding operation, a second longitudinal fold 2'a appears at the location of the groove 2a. Upstream of the second folding operation, the glue lug 1e is glued so that at the end of the folding operation, the flank 1a is glued to the glue lug 1e, the flanks 1a and 1d are then adjacent. The folded box 1 'thus formed preferably has the form of a rectangle with two lateral sides coinciding with the folds 2'a and 2'c, and two transverse sides 3' and 4 'respectively corresponding to the rear edges 3 and front 4 of the pose. In the example, the respective folding helix 32, 52 is made of a synthetic material in the form of a rod describing a curve whose torsion is proportional to the curvature, the axis of the helix coinciding with the folding axis.

In some cases, the laying 1 coming out of the margin station 10 is not correctly positioned for the folding, it is then advantageous to pass the pose first into an auxiliary alignment module 20 before the first module. For this purpose, the pose coming out of the margin station 10 is driven by a conveyor 21 into the auxiliary alignment module 20. In the auxiliary alignment module 20, the left edge 5 of the laying 1 comes in linear contact with a ruler 22 (or guide rail) along it. In the plane of the folder-gluer, the longitudinal axis of the ruler 22 forms a zero angle with the longitudinal axis of the folder-gluer, that is, the longitudinal axis of the ruler 22 is parallel to the longitudinal axis of the folder-gluer, so that the groove 2c is parallel to the longitudinal axis of the folder-gluer.

Advantageously, the folded box 1 'coming out of the second folding module 50 is driven by a conveyor 61 in a calibration module 60. In the calibration module 60, the folded box 1' passes between two longitudinal bars 62. The distance between the bars 62 is equal to the width of a folded reference box. Thus, when the folded box that enters the calibration module has a width greater than the width of reference, the box is pressed on its lateral sides 2'a and 2'c by the bars 62. The action of the bars 62 has the effect of dimensioning the width of the folded box. A folded reference box is a box that meets the dimensional specifications set. The width of the folded box is the distance separating the lateral side 2'a from the lateral side 2'c. If necessary, the width Lf at the front of the folded box of the width Lr at the back of the folded box (see FIG. figure 4 ). The width Lf is the distance between the lateral side 2'a of the lateral side 2'c, the transverse side 4 ', while the width Lr is the distance between the lateral side 2'a of the lateral side 2'c, the transverse side 3 '. The bars 62 may be constituted by ramps of rollers (not shown).

Advantageously, support means (not shown) are provided in the calibration module 60 to exert a vertical pressure on the sidewall 1a, where the latter is in contact with the gluing tab 2d, this allows to improve the glue taking. Thus, the folded boxes coming out of the calibration module 60 are ready to be conditioned, for example, they can be transferred to a receiving station where they will be recovered to be stored in piles on a pallet or rows in a container.

To the figure 2 there is shown an alternative embodiment of the folder-gluer for the implementation of the method according to the invention. In this variant, we find all the elements of the figure 1 as well as all the steps of the process, only the value of the angles changes. The numbering of the elements of the figure 1 has been kept.

In this second embodiment of the folder-gluer, the longitudinal axis of the rule 22 forms with the longitudinal axis of the folder-gluer an angle α non-zero, so that the pose 1 coming out of the alignment module auxiliary 20 is offset by an angle α relative to the direction of advance of the pose. Similarly, the longitudinal axis of the ruler 42 forms with the longitudinal axis of the folder-gluer a non-zero angle β, so that the laying 1 which leaves the main alignment module 40 is shifted by an angle β relative to the direction of advance of the pose. By these provisions, we intend to solve the problem of fishtailing.

In principle, to avoid completely the fishtailing, the flank 1 d must be folded at 180 ° around the longitudinal groove 2c by a folding force which is exerted simultaneously at least in two points; a first point near the front edge 4 of the pose and a second point near the rear edges 3 of the pose. If the folding force is exerted in only one point, it is still possible to avoid the fishtailing by placing this point somewhere on the median axis of the flank 1d. On the other hand, if the single point of contact is placed elsewhere than on the median axis of the flank 1d, the fishtailing problem is difficult to avoid. The median axis of the sidewall 1d is defined here as being the axis parallel to the front or rear edge of the laying and located equidistant from said front and rear edges.

When the laying 1 arrives at the entrance of the first folding module 30, the sidewall 1d is driven by its front edge 4 in a folding propeller 32. During the advance of the laying, the propeller 32 exerts on the flank 1 of a folding force which is applied on the front edge 4. This folding force tends to angularly shift the axis of folding (or axis of rotation) of the blank with respect to the axis of the longitudinal groove 2c , in the plane of the folder-gluer. Such a shift is a generator of fishtailing.

To overcome this problem, in the second embodiment of the folder-gluer, the laying arrives at the entrance of the first folding module 30 is offset by an angle α relative to the direction of advance of the pose, l angle α is chosen to correspond to the offset of the folding axis. By this arrangement, the axis of the longitudinal groove 2c coincides with the axis of folding of the sidewall 1d, so that the folding 180 ° of the sidewall 1d is well around the longitudinal groove 2c.

The problem with the folding of the sidewall 1 d is also posed with the folding of the sidewall 1a. Indeed, when the laying 1 arrives at the entrance of the second folding module 50, the flank 1a is driven by its front edge 4 in a folding propeller 52. During the advance of the laying, the propeller 52 exerts on the flank 1 a folding force which is applied on the front edge 4. This folding force has a tendency to angularly offset the axis of folding (or axis of rotation) of the blank with respect to the axis of the groove longitudinal 2a, in the plane of the folder-gluer. This offset is fishtailing generator.

To overcome this problem, in the second embodiment of the folder-gluer, the laying arriving at the entrance of the second folding module 50 is shifted by an angle β relative to the direction of advance of the laying, l angle β is chosen to correspond to the offset of the folding axis. By this arrangement, the axis of the longitudinal groove 2a coincides with the fold axis of the sidewall 1a, so that the 180 ° bending of the sidewall 1a is well around the longitudinal groove 2a.

Thanks to these provisions, the gap at the front of the folded box is equal to the gap at the back of the box, in other words, the box folded to the shape of a rectangle, the problem of fishtailing has been solved.

Regarding the value of the offset of the folding axis, it depends on many different parameters, for example, the size of the flanks to bend, the material of the laying, its thickness, the depth and the length of the grooves around which the flanks are bent, the length of the propellers. Because of this, it is very difficult to predict the offset before folding a pose. Consequently, the angles α and β are chosen as a function of the offsets noted. For example, if it is noted for a given pose that the offset of the folding axis in the first and second folding module is + 2 ° and -2 respectively, the angles α and β are chosen equal to + 2 ° and -2 ° respectively.

In the example of figures 1 and 2 the upper parts of the conveyors 11, 21, 31, 41, 51 and 61 have not been shown, only the lower parts are visible. The conveyors may be of the belt or roller type. The conveyors 11 and 21 can be grouped together in the same conveyor, as are the conveyors 51 and 61. Similarly, the second folding module 50 and the calibration module 60 can be grouped together in a single module.

To the figure 3 it shows a pose at the exit of the first folding module 30 (the grooves have not been shown). At this stage of the process according to the invention, the sidewall 1 d is folded down on the sidewall 1c. In this figure we can also see that the left edge 5 of the pose does not extend over the entire length of the pose. The edge 5 has a recess 5 'between the transverse grooves 2f and 2g and the respective front and rear edges of the pose. In the example, the edge 5 'is parallel to the edge 5. Similarly, it can be seen that the right edge 6 of the pose does not extend over the entire length of the pose. The edge 6 has a recess 6 'between the transverse grooves 2f and 2g and the respective front and rear edges of the pose. In the example, the edge 6 'is parallel to the edge 6. With these features, the folded box will appear with a slot in the extension of the groove 2d between the transverse grooves 2f and 2g and the respective front and rear edges of the pose.

To the figure 4 it shows a folded box, that is to say a pose at the exit of the second folding module 50 (the grooves have not been shown). At this stage of the process according to the invention, the flank 1a is folded on the side 1b, on the one hand, and glued to the glue lug 1e, on the other hand, so that the folded box is sealed. In this example, we have chosen to measure the gap between the edges 5 'and 6'. If necessary, the gap Gf at the front of the folded box and the gap Gr at the back of the folded box can be distinguished. The gap Gf is the distance between the left edge 5 'of the right edge 6', the transverse side 4 ', while the gap Gr is the distance between the left edge 5' of the right edge 6 ', the transverse side 3 '.

To the Figures 5a and 5b a folded box is shown after the method of the state of the art. For convenience, the same numbering as used in connection with the folded box resulting from the method according to the invention will be used. The figure 5a shows a pose of the state of the art seen in section along the axis AA of the figure 3 , the figure 5b shows a box of the state of the art seen in section the axis BB of the figure 4 , the figure 5c shows a reference box in a view similar to that of the figure 5b .

If, during the 180 ° bending of the sidewall 1d, the position of the axis of rotation of the sidewall 1d is shifted by e1 relative to that of the reference box, this results in a shift of the position of the right edge 6 ' equal to 2 x e1 (see figure 5a ). Similarly, if during 180 ° bending of the sidewall 1a, the position of the axis of rotation of the sidewall 1a is shifted by e2 relative to that of the box of reference, this results in an offset of the position of the left edge 5 'equal to 2 x e2 (see figure 5b ). Consequently, the gap resulting from the two successive bends is equal to Gref + 2 x e1 + 2 x e2, where Gref is the gap of a folded reference box and 2 x e1 + 2 x e2 is the gap gap Δ (see figure 5c ).

To the Figures 6a to 6c the folding of a box according to the invention is shown. The Figures 6a and 6b show a pose seen in section along the axis AA of the figure 3 , the Figure 6c is a sectional view along the BB axis of the box of the figure 4 , the figure 6d shows a reference box in a view similar to that of the Figure 6c .

If at the end of the folding of the sidewall 1d in the first folding module 30 an error e1 appears, the passage of the laying in the main alignment module 40, before passing into the second folding module 50, makes it possible to compensate this error on the resulting gap. Indeed, because in the main alignment module 40 the longitudinal fold 2'c of the pose comes into linear contact with the rule 42, along it, an offset e1 of the position of the fold 2'c is translated by a shift e1 of the position of the left edge 5 'and 2 x e1 of the position of the right edge 6'. For example, if the position of the axis of rotation of the sidewall 1d is shifted 1 mm to the right relative to that of the reference box, the right edge 6 'is shifted 2 x 1 mm to the right by relative to its reference position (see figure 6a ). Then align the laying along the 2'ca fold to shift the pose 1 mm to the left and thus shift 1 mm to the left the right edge 6 'and the left edge 5' (see figure 6b ).

In the case where the folding of the flank 1a is error free, that is to say that the position of the axis of rotation of the sidewall 1a is not offset from that of the reference box, the bending at 180 ° of the flank 1 aa has the effect of reversing the offset resulting from the alignment of the laying along the fold 2'c (see Figure 6c ). On the other hand, if the position of the axis of rotation of the sidewall 1a is shifted, for example by 1 mm to the left relative to that of the reference box, the left edge 5 'is then shifted by -1 + 2 x 1 or 1 mm to the left from its reference position.

With the method according to the invention, the error e1 of position of the axis of rotation of the sidewall 1d is compensated before the folding of the sidewall 1a, so that the gap resulting from the two successive bends is independent of the error e1 . More generally, if at the end of the folding of the sidewall 1a in the second folding module 50 an error e2 appears (see Figure 6c ), the gap resulting from the two successive folds is limited to Gref + 2 x e2, where Gref is the gap of a folded reference box and 2 x e2 is the gap gap Δ (see figure 6d ).

It is clear that the calculation of the gap is done in the same way at the front and the back of the folded box.

Thanks to these provisions, the gap deviation Δ has been minimized by passing from the value 2 x e1 + 2 x e2 in the state of the art to the value 2 x e2 according to the invention.

It is obvious that the invention is not limited to the embodiment described and shown above and from which we can provide other embodiments, without departing from the scope of the invention. The method according to the invention has been described in connection with the folding of a cutout intended to form a conventional box, but it goes without saying that the process in question can be used to fold a cutout intended to form any type of box. when said cutout has at least two flanks to fold in parallel.

Claims (13)

Method of folding a blank (1) of paper, cardboard, plastic, corrugated board or similar material to form a folded box (1 '), cutout comprising a left longitudinal edge (5), a longitudinal edge right (6) and, from left to right, at least two respective longitudinal grooves (2a; 2b; 2c; 2d) delimiting at least two respective adjacent flanks (1a; 1b; 1c; 1d); least the following successive steps: a) Folding 180 ° of the sidewall (1d) around the longitudinal groove (2c) in a first folding module (30) and forming a longitudinal fold (2'c) along the groove (2c); b) aligning the blank (1) along the longitudinal fold (2'c) in a main alignment module (40); c) 180 ° bending of the sidewall (1a) around the groove (2a) in a second folding module (50). A forming method according to claim 1 comprising, prior to step a), a step a ') of aligning the blank (1) along the left edge (5) in an auxiliary alignment module (20). The forming method according to claim 2 wherein the aligning step a ') comprises placing the left edge (5) of the blank (1) in linear contact with a ruler (22), along the ruler Shaping method according to claim 3 wherein the longitudinal axis of the rule (22) forms a non-zero angle α to the longitudinal axis of the folder-gluer, in the plane thereof. Shaping method according to one of claims 1 to 4 wherein the alignment step c) is to put the longitudinal fold (2'c) of the blank (1) in linear contact with a rule (42), the along this one. Shaping method according to claim 5 wherein the longitudinal axis of the rule (42) forms a non-zero angle β with the longitudinal axis of the folder-gluer, in the plane thereof. Shaping method according to one of claims 1 to 6 comprising, following step c), a step d) of calibration of the folded box (1 ') in a calibration module (60). The forming method according to claim 7 wherein the step of calibrating d) is to pass the folded box (1 ') between two longitudinal bars (62), the distance between the bars (62) being predetermined. Folder-gluer machine for carrying out the folding method defined in claim 1 comprising, from the entrance of the machine to the outlet, a first folding module (30), followed by a main alignment module ( 40), followed by a second folding module (50). Folder-gluer machine according to claim 9, characterized in that it further comprises an auxiliary alignment module (20) placed before the first folding module (30). Folder-gluer machine according to claim 9, characterized in that the main alignment module (40) comprises a ruler (42) whose longitudinal axis forms a non-zero angle with the longitudinal axis of the folder-gluer. Folder-gluer machine according to claim 10, characterized in that the auxiliary alignment module (20) comprises a ruler (22) whose longitudinal axis forms a non-zero angle with the longitudinal axis of the folder-gluer. Folder-gluer machine according to one of claims 9 to 12, characterized in that it further comprises a calibration module (60) following the second folding module (50).

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