EP1419966B1 - Method and apparatus for applying a packaging hood of stretch foil on a palettized load - Google Patents

Description

• ouvrir la gaine pour la mise en volume au-dessus de la charge,
• plisser les parties latérales de la gaine en accordéon sur des doigts de plissage, en faisant intervenir des galets motorisés tournant dans un premier sens de rotation, chaque doigt ayant une inclinaison par rapport à la direction verticale,
• étirer ensuite la gaine plissée dans la direction transversale horizontale pour obtenir une ouverture plus grande que le périmètre de la charge à emballer,
• et déplacer la gaine étirée par-dessus la charge selon une direction verticale en provoquant le déplissage progressif des plis lors de la course de houssage.

The invention relates to a method of placing on a palletised load a flexible wrapping cover obtained from a stretchable plastic sheath, consisting of:

• open the sheath for the volume setting above the load,
• pleating the lateral parts of the sheath accordion on pleating fingers, involving motorized rollers rotating in a first direction of rotation, each finger having an inclination relative to the vertical direction,
• then stretch the pleated sheath in the transverse horizontal direction to obtain an opening greater than the perimeter of the load to be packaged,
• and moving the stretched sheath over the load in a vertical direction causing the folds to be progressively unfolded during the foaming stroke.

State of the art

The use of a stretchable film sheath is well known for providing stability and sealing of a palletized load. In contrast to the heat-shrinkable film, the installation of a stretchable sheath does not require a source of heat, because it suffices to mechanically stretch the material of the plastic film beforehand in the horizontal transverse direction before enveloping the palletised load to be wrapped. . After removing the stretched sheath from the load, the squeezing of the stretch film material naturally takes place by elasticity, which firmly holds the sheath around the load. The sheath may be of polyethylene, or any other plastic stretchable material.

The sheath is generally stored by winding in a coil, and folded on its section by having four bellows. After unwinding of the coil, the opening of the sheath is operated by a mechanical action of spacing at the four corners.

The packaging machines for threading a cover of stretch film on the load, have for this purpose a spacing device to open the stretch film sheath, and a pleating device for folding the sheath accordion on four fingers integral with the load. a support frame.

According to EP 344815, a welding device is arranged between the spacer device and the pleating device for welding the sheath forming a welded joint. After welding, the sheath is then cut transversely by a cutting device to make a cover independent of the coil, and closed at its upper part. The pleated cover is then stretched in a horizontal plane parallel to the weld, and is positioned above the palletized load. The cover is unfolded during the houssage, and deposited on and around the load following a vertical movement up and down the frame. Before being pulled over the load, the cover is stretched in the transverse stretched state longitudinally in the vertical direction by 5% to 15% of its initial vertical length.

The mechanism of the packaging machine COVERPAL (registered trademark of the company Thimon), is described in detail in the document EP 1060988. The operations of welding and cutting of the sheath to form the cover, are performed before removal on the pleating fingers, unlike the mechanism described previously in EP 344815. The weld is then perfectly cooled when it is stressed by the transverse drawing, and better withstands the stresses of elongation. There are no specific means provided for effecting vertical elongation of the sheath during the foaming phase following the transverse stretching phase.

In FIGS. 1 to 3 showing the pleating and transverse stretching phases of a prior art packaging machine, the upper part 12B of each finger 12 is provided with a drawing shoe 22 having a shape bent advantageously adapted to the friction of the film during the pleating and unfolding steps. The vertical flank of the finger 12 may be equipped with one or two idle rollers 13, or be equipped with a fixed low friction sliding coating, so as to pinch the sheath and drag down when pleated by the motorized roller 14. The latter is rotated by a geared motor 24, and cooperates with a tilting actuator 20 between a remote position of rest (not shown), and a working position (FIGS. 1 to 3) in contact with the finger 12.

The four motorized rollers 14 are rotated in the direction of the arrows F1 and F2 to ensure the pleating of the cover 10 by accumulating accordion in the lower part 12A of the fingers 12. The top of the cover 10 has been closed beforehand by a welded joint 16.

The horizontal stretching of the cover in the direction of the arrows F3 and F4 is shown in FIG. 3. The motorized rollers 14 no longer rotate, and can be held in abutment against the pleating fingers 12 so as to tend more or less strongly the upper horizontal part of the cover 10 during transverse stretching. It is also possible to control the actuators 20 to move the motorized rollers 14 during this stretching step in order to allow the film to slide partially on the fingers 12, avoiding any possibility of tearing the film. Such known mechanisms make it possible to obtain a transverse stretching ratio of greater than 10%. The quality of the stretchable ducts makes it possible to obtain transverse stretches of 50% to 100%.

The next phase of shading is done by a vertical movement of the frame over the load, so as to cause the progressive unfolding of the cover on the load. After removal of the cover, the tightening of the stretch film material naturally takes place elasticity, which ensures the stable maintenance of the load. The relaxation of the material and the friction of the film on the fingers also create a vertical tension of the film on the load which also contributes to enhancing the stability. This vertical tension is generated without any particular vertical drawing device, since transverse stretching of 50% to 100% reduces the sheath height, and transmits to the load sufficient cohesive forces to ensure stability, as long as this vertical tension is maintained during removal on the load.

The angle of inclination A of the fingers 12 with the vertical direction facilitates the accumulation of folds during pleating by the motorized rollers 14. For a predetermined inclination, the clearance between the cover 10 and the fingers 12 increases progressively as one approaches the lower part, with the consequence of a possibility of disorganization of the folds, which are no longer properly guided during of their sliding towards the base of the fingers.

A lower angle of inclination A of the fingers 12 would have the main disadvantage of hindering the effect of accumulation of the folds, since the sliding of the film down could no longer occur naturally. The motorized rollers 14, in addition to their pleating function, will also have to perform a second function of pushing downwards, which causes friction on the upper folds, with the risk of forming points or vertical lines of weakness of the sheath before the transverse stretching phase.

In EP 633186, the stretchable film is temporarily clamped laterally into the lower area of the load or pallet, against a stop which is placed above the fingers.

Object of the invention

The object of the invention is to develop a method of stretching a packaging cover to obtain a free and regular accumulation without disorganization of the folds during the pleating phase before the transverse stretching, and avoid any risk of tearing the film during the next stage of foaming.

One development of the invention is to create a regular and precise pleat strand during the foaming stage, and to deposit it on the load at any height, or on the pallet.
Another development of the invention relates to a drawing method for obtaining a controlled tension of the film during the foaming.

The drawing method according to the invention is characterized in that the reduction of perimeter around the fingers is limited by a braking and compensating element in the lower part of each inclined finger in order to regularly distribute the folds before the phase of horizontal transverse stretching.

The friction of the sheath that descends along the inclined fingers is performed on both edges of the fingers. Any angle or part protruding on these edges could disrupt the folds.

A disorganization of the folds after the stretching step may indeed disturb the unfolding during the foaming, creating nips of the folds between them may cause a tear of the sheath.

The inclination of the fingers facilitates the accumulation of folds, and limiting the pleating perimeter in the lower part where play is the most important, prevents the disorganization of the folds. The presence of the braking element in the middle of the two edges limits the reduction of the perimeter at the bottom of the fingers, without hindering the descent of the sheath along the fingers. Any formation of successive pinched folds is thus excluded during transverse stretching, which makes it possible to reliably avoid tears during the next step of shading.

According to a development of the invention, a regular pleated strand can be created in the film during the foaming phase, by interrupting the downward movement of the cover at a predetermined level, and by rotating the rollers in a second direction of rotation opposite to the first. By double movement of the fingers, the stranded film can be accurately deposited at any height level of the palletized load. It is thus possible to create either a mini cover at any level of the load or the pallet, or the sealing and maintenance of the upper part of the load, or the removal of the strand on the top of the pallet support allowing a precise clearance the entrance of an automatic palletizer fork.

According to another development of the invention, during the formation of the strand, it blocks the lower portion of the cover portion deposited against the drawing shoe, which is at the top of the fingers. This results in a controlled mechanical tension in the film, with a possibility of vertical stretching of the cover whose value is between 5% to 50% vertical elongation.
The formation of the strand according to these developments, is possible only if previously, the organization of the folds is perfect.

The invention also relates to a device for packaging a palletized load by means of a cover consisting of a plastic stretch film, and comprising an operating frame equipped with pleating and drawing fingers, each finger having a drawing shoe, an inclined lower part, and a motorized roller driven in rotation by a geared motor, means for tilting each motorized roller between a position of spaced apart rest, and a working position in contact with the finger, and means operating the frame to carry out the charging of the load. The inclined lower part of each finger comprises a braking and compensation element arranged in the low zone of accumulation of the folds where the play between the folded cover before the transverse stretching phase, is the most important, said braking element and of compensation being rectilinear, and extending vertically protruding from the central zone of the lower inclined portion of the finger

According to a preferred embodiment, the braking and compensation element has a width less than that of the finger, and is secured by its base to the movable support of the finger. The opposite end the braking element is arranged under a roller on which is applied the motorized roller during pleating.

According to another characteristic, a clamping element is mounted on the support of each finger extending substantially at the drawing shoe above the corresponding motorized roller. The clamping element is associated with an actuator to be moved between a locking position bearing against the shoe, and a release position spaced from said shoe. The clamping element may be formed by a stop with flexible tip for catching a portion of the cover against said shoe in the locking position.

Brief description of the drawings

• la figure 1 est une vue schématique en élévation d'un dispositif de plissage d'une housse étirable équipant une machine d'emballage de l'art antérieur ;
• la figure 2 représente une vue en plan de la figure 1 ;
• la figure 3 est une vue identique de la figure 1 montrant la phase d'étirage transversal de la housse plissée ;
• la figure 4 est une vue en perspective d'un doigt de plissage selon l'invention;
• la figure 5 montre une vue en coupe du doigt selon la ligne 5-5 de la figure 4 ;
• la figure 6 est une vue du doigt équipé d'un dispositif de serrage pendant la formation d'un toron plissé ;
• les figures 7A-7C illustrent schématiquement le déplacement d'un doigt pendant la dépose du toron plissé sur la charge;
• les figures 8 à 11 représentent les différentes étapes du procédé de houssage, respectivement pendant la course normale de descente du cadre, lors de la formation d'un toron plissé, lors de l'écartement transversal des doigts, et lors de la dépose du toron sur la charge ;
• la figure 12 montre une vue partielle en perspective du houssage avec dépose du toron plissé sur le haut de la palette, laissant libre l'entrée des fourches d'un palettiseur ;
• la figure 13 est une variante de la figure 10, sans dispositif de serrage spécial.

Other advantages and features will emerge more clearly from the following description of an embodiment of the invention given by way of non-limiting example, and represented in the accompanying drawings, in which:

• Figure 1 is a schematic elevational view of a pleating device of a stretch cover fitted to a packaging machine of the prior art;
• Figure 2 shows a plan view of Figure 1;
• Figure 3 is an identical view of Figure 1 showing the transverse stretching phase of the folded cover;
• Figure 4 is a perspective view of a pleating finger according to the invention;
• Figure 5 shows a sectional view of the finger along the line 5-5 of Figure 4;
• Figure 6 is a view of the finger equipped with a clamping device during the formation of a pleated strand;
• FIGS. 7A-7C schematically illustrate the movement of a finger during the removal of the pleated strand on the load;
• Figures 8 to 11 show the different steps of the foaming process, respectively during the normal course of descent of the frame, during the formation of a pleated strand, during the transverse spacing of the fingers, and during the removal of the strand on the charge;
• Figure 12 shows a partial perspective view of the foaming with removal of pleated strand on the top of the pallet, leaving free the entrance of the forks of a palletizer;
• Figure 13 is a variant of Figure 10, without special clamping device.

Description of a Preferred Embodiment

Referring to FIGS. 4 and 5, the inclined lower portion 12A of each finger 12 is provided with a straight-line braking element 26 extending vertically protruding from the central zone and having a width L1 smaller than that L2 of finger 12. The basis of the braking element 26 is secured to the movable support 28 of the finger 12, and its opposite end is below the lower roller 13 without touching it. The value of the angle A can be between 0 and 25 °.

The braking element 26 constitutes a compensation means arranged in the low accumulation zone where the clearance between the folded cover and the inclined lower portion 12A of the finger 12 is the most important. The presence of the braking elements 26 on the four inclined fingers 1 2 limits the reduction of perimeter around the fingers 12, allowing both an accumulation without annoyance of the folds in the lower part 12A, and a uniform and even distribution of the folds on the along the vertical edges A1 and A2 neighbors. The transverse stretching of the cover 10 can then be operated as in FIG. 3 (arrows F3 and F4), by spacing the supports 28 at the four corners of the frame in a horizontal plane, and avoiding any formation of irregular or risky pinched folds. tears during the foaming phase.

In Figure 6, a clamping member 30 is mounted on the support 28 of each finger 12, extending substantially at the drawing shoe 22 above the motorized roller 14. The clamping member 30 is coupled to an actuator 32 so as to be moved between a locking position and an unlocking position. The clamping element 30 is formed by way of example by a stop with a flexible rubber tip, bearing in the blocking position against the shoe drawing 22 to pinch the lower portion of the cover 10 at the four corners.

The actuator 32 may be constituted by a pneumatic, hydraulic or electric actuating jack. The geared motors 24 of the four rotary rollers 14 are controlled by variable speed drives adjustable according to various parameters, and whose direction of rotation can be reversed during the pleating and foaming phases.

It is thus possible to produce a pleated strand 34 at the end of the cover 10 during or at the end of the shading phase. It suffices to interrupt the descent movement of the drawing frame at a predetermined location, and to tilt the rollers 14 pleating mode bearing against the rollers 13, but by reversing the direction of rotation (arrow F5, Figure 6 ) relative to that (arrow F2, Figure 1) used for pleating before transverse stretching. The folds of the strand 34 accumulate between the upper roll 13 and the drawing shoe 22 during the rotation of the roller 14 in the direction F5.

According to FIGS. 7A-7C, the stranded film of the cover 10 can then be deposited on the palletised load CH following a double movement of the four fingers 12 according to the arrows F6 and F7. From FIG. 7A corresponding to the formation of the strand 34 according to FIG. 6, the fingers 12 are spread apart according to a first translational movement indicated by the arrow F6 (FIG. 7B), followed by a second movement orthogonal vertical clearance (arrow F7, Figure 7C) for the application of the strand 34 on the load CH.

It is thus possible to obtain an accurate removal of the strand 34 at any height level of the palletized load. It suffices to interrupt the descent stroke of the frame to a predetermined height, and to engage the pleating phase for the formation of the strand 34 by means of the rollers 14 rotating in the direction of the arrow F5. This method makes it possible to create either a mini cover at any level of the load or the pallet, or the sealing and maintenance of the upper part of the load CH, or the removal of the strand 34 on the top of the pallet allowing a precise clearance of the input of an automatic palletizer fork, as shown in FIG.

The presence of the clamping elements 30 also makes it possible to make the previous function reliable, thanks to the jamming of the cover 10 in the locked position of the actuators 32. A mechanical tension effect is thus generated in the upper vertical portion of the sheath deposited while maintaining the film stretched.

The different stages of implementation of the process are illustrated in FIGS. 8-11:

FIG. 8 shows the step of covering the load CH, which follows the transverse stretching phase of FIG. 3. During the lowering stroke of the finger support frame 12, the clamping element 30 is located in a remote position, and the roller 14 of pleating. The film of the cover 10 slides freely along the arched shoe 22, and the unfolding of the folds takes place progressively and without hindrance during the downward stroke indicated by the arrow F8.

In Figure 9, it stops the descent movement of the frame for the formation of a strand. The clamping member 30 of each finger 12 is actuated in the locking position by wedging the film against the shoe 22 in the four corners. After tilting the motorized roller 14 against the rollers 13, the strand is formed following the rotation of the roller in the direction of the arrow F5.

In Figure 10, the support 28 of the fingers 12 is then spaced horizontally in the direction of the arrow F9. The clamping element 30 and the motorized roller 14 of each finger 12 remain in contact with the cover during this spacing movement, so as to maintain correct positioning of the strand between the shoe 22 and the upper roller 13, and to keep the tension of the film in the part of the cover already deposited.

In FIG. 11, the fingers 12 are horizontally brought together to remove the strand 34 at a precise location of the load CH or pallet 36, followed by a release movement of the support 28 of the fingers 12 downwards along the arrow F7. The clamping member 30 is then actuated to the unlocking position to release the strand 34 upon removal. The vertical portion of the cover 10 remains stretched during formation of the pleated strand 34, and can even be stretched by up to 5% to 50% vertical elongation.

Indeed, during the handling of the loads, the vertical tension of the duct section which links the first layer of products with the pallet 36, is essential to ensure good holding of the load. At the end of the shading stage, the vertical stretching associated with the strand deposited against the pallet, guarantees the stability of the load

In Figure 12, it is noted that the strand is placed just above the clearance of the pallet 36 to allow the entry of the fork of a palletizer.

Referring to Fig. 13, the clamping member 30 is omitted, and the end of the drawing shoe 22 is sufficiently protruded to retain the strand at the upper part of the finger. This strand is then deposited on the load according to the same cycle described above.

The invention also applies to a flat duct, open by the effect of depression, and taken at four points by the frame of the hood.

Claims (14)

1. Method for fitting a flexible packaging cover obtained from a plastic cling film sleeve on a palletized load (CH), method consisting in:

   - opening the sleeve to achieve the required volume above the load,

   - accordion pleating the lateral parts of the sleeve on pleating fingers (12) by means of motor-driven roller wheels (14) rotating in a first direction of rotation (F1, F2), each finger having an inclination with respect to the vertical direction,

   - then stretching the pleated sleeve in the horizontal transverse direction to obtain a larger opening than the perimeter of the load (CH) to be packaged,

   - and moving the stretched sleeve in a vertical direction above the load (CH) resulting in progressive smoothing of the pleats during the pallet covering travel,

   characterized in that the reduction of the perimeter around the fingers (12) is limited by a slowing-down and compensating means (26) in the bottom part (12A) of each inclined finger to distribute the pleats regularly prior to the horizontal transverse stretching phase.
2. Method according to claim 1, characterized in that, during the covering phase, the downward movement of the cover (10) is interrupted at a preset level and a strand (34) is created by making the roller wheels (14) rotate in a second direction of rotation (F5) opposite to the first direction.
3. Method according to claim 2, characterized in that the fitted portion of cover (10) is blocked against the stretching block (22) at the top part (12B) of the fingers during formation of the strand (34).
4. Method according to claim 2 or 3, characterized in that the strand (34) is retained against a salient part of the block (22) at the top part of the finger.
5. Method according to one of the claims 1 or 2, characterized in that, during or at the end of the covering phase, the cover (10) is blocked against the fingers (12) to obtain a controlled vertical mechanical tension in the film.
6. Method according to one of the claims 4 or 5, characterized in that the film of the sleeve (10) is stretched by a vertical elongation value comprised between 5% and 50%.
7. Device for packaging a palletized load (CH) by means of a cover (10) formed by a plastic cling film, and comprising:

   - an operating frame equipped with pleating and stretching fingers (12), each finger comprising a stretching block (22) and an inclined bottom part,

   - a motor-driven roller wheel (14) driven in rotation by a geared motor (24) to operate in conjunction with each finger (12),

   - means for making each motor-driven roller wheel (14) swivel between a separated rest position and a working position in contact with the finger (12),

   - means for actuating the frame to perform covering of the load (CH),

   characterized in that the inclined bottom part (12A) of each finger (12) comprises slowing-down and compensating means (26) arranged in the bottom accumulation zone of the pleats where the clearance between the pleated cover prior to the transverse stretching phase is the largest, said slowing-down and compensating means (26) being straight and extending vertically and salient from the central zone of the inclined bottom part (12A) of the finger (12).
8. Device for packaging according to claim 7, characterized in that the slowing-down means (26) present a smaller width (L1) than that of the finger (12) and are secured via the base thereof to the mobile support (28) of the finger (12).
9. Device for packaging according to claim 7, characterized in that the opposite end of the slowing-down means (26) is arranged under a roller (13) whereon the motor-driven roller wheel (14) presses when pleating is performed.
10. Device according to claim 8 or 9, characterized in that securing means (30) are fitted on the support (28) of each finger (12) and extend substantially at the level of the stretching block (22) above the corresponding motor-driven roller wheel (14).
11. Device according to claim 9 or 10, characterized in that the securing means (30) are associated with an actuator (32) so as to be moved between a blocking position pressing against the block (22) and a released position away from said block.
12. Device according to claim 10, characterized in that the securing means (30) are formed by a stop with a flexible end-part designed to jam a part of the cover (10) against said block (22) in the blocking position.
13. Device according to claim 11, characterized in that the actuator (32) is formed by a pneumatic, hydraulic or electric jack.
14. Device according to one of the claims 7 to 12, characterized in that the geared motor (24) of each roller wheel (14) is controlled by a variable speed drive the direction of rotation whereof can be reversed.

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