EP1445197B1 - Apparatus and method for applying a packaging hood of heat-shrinkable foil on a palettised load - Google Patents

Description

Technical field of the invention

• à placer la charge sur une table support avec interposition d'un tapis de sol recouvrant la face supérieure de la palette,

• à chauffer la housse préalablement déposée sur la charge pour assurer sa thermorétraction sur les faces latérales de ladite charge,
• à évacuer l'air emprisonné entre la housse et la charge en le chassant vers l'extérieur à travers un intervalle latéral d'échappement créé par des moyens de retenue mis en place sous le bord inférieur de la housse, et agencés pour empêcher tout retrait vertical de la housse pendant la thermorétraction,
• et à enlever les moyens de retenue pour thermosceller le bord inférieur de la housse sur les bords tombants du tapis de sol en rendant l'emballage étanche.

The invention relates to a device and method for packaging a palletised load by means of a heat-shrinkable plastic cover, consisting of:

• placing the load on a support table with the interposition of a floor mat covering the upper face of the pallet,

• heating the cover previously deposited on the load to ensure its heat-shrinking on the lateral faces of said load,
• venting air trapped between the cover and the load by forcing it out through a lateral escape gap created by retaining means in place under the bottom edge of the cover, and arranged to prevent withdrawal vertical cover during heat shrink,
• and removing the retaining means for heat sealing the lower edge of the cover on the falling edges of the floor mat by making the package waterproof.

• une rétraction parfaite et sans plis de la housse pour assurer une bonne cohésion de la charge, et éviter de fragiliser les zones contiguës à ces plis,
• un thermoscellage continu du bord inférieur de la housse au tapis de sol pour garantir l'étanchéité et lier la charge au support bois de la palette.

The package is constituted by a multi-layer stack of objects or hollow containers of glass or plastic, for example bottles. The invention also applies to any other type of objects making use of a tight and stable heat-shrinkable packaging.
The stability and tightness of such packaging require the following criteria:

• a perfect retraction and without folds of the cover to ensure a good cohesion of the load, and avoid weakening the areas contiguous to these folds,
• continuous heat sealing of the bottom edge of the cover to the floor mat to ensure watertightness and bind the load to the wood support of the pallet.

State of the art

Packaging processes and installations are already known which consist in making a cover from a sheath of heat-shrinkable film, for example in polyethylene, open it with the lower edge facing downwards, comb the palletised load with the cover, and heat the sides of the cover with a heating frame to heat shrink the load. Heat shrinkage generally requires a particular support table-handling, with a suction device to control the conformation of the film during this step.
The document FR-A-2816587 describes a rigging and retraction installation, in which the lower edge of the cover is held by the stuffing fingers during the entire phase of foaming and heat sealing.
The document EP-A-376028 relates to a packaging device equipped with pivoting lever pressing elements operating outside the gripper moving area. During heat-shrinking, the lower edge of the cover is held by the four pivoting levers, on the one hand against stops integral with the support table, and on the other hand on the outer faces of the beams of the pallet. The pivoting levers are rotatably mounted below the positioning plane, and around horizontal axes integral with the table.
The two aforementioned documents relate to heat-shrinkable film packaging machines, in which the foaming and retraction operations are carried out successively on the same workstation.

Other packaging machines have also proposed to improve the retraction phase of the film on a separate post located downstream of the foaming station.
According to the documents EP-A-249534 and EP-A-205135 , the stuffing of the load intervenes by means of gripping fingers, which release the bottom edge of the cover at the end of the race. The heat-shrinking then takes place on the same station, and during a large part of the heat-shrinking stroke, air is blown inside the cover to inflate it, This blow is operated by cannulas which have a rough part of restraint of the cover. The introduction of these cannulas between the load and the cover must intervene before the houssage, and is possible only in the central part on two opposite faces.

The document EP 697337 relates to a method and a device for overpacking a palletised load, comprising a preliminary step of covering the load with a cover of heat-shrinkable film, followed by a step of thermal shrinkage of the film, implementing the retraction of a return of film under the face lower lateral sliding supports, and a conformation of the cover along the transverse sides to bring the lower edge of the cover substantially at the lower face of the floor of the pallet load. The lower edge of the cover is not removed from the load by mechanical means. Such a device is intended to clear the passage of the handling forks in automatic storage magazines.

The document DE 4426369 mentions a packaging device, wherein the film is removed from the load by air, and not by mechanical spacing means. We blow first inside to distribute the film around the load, then we suck the internal air during retraction. The film is then plated by the effect of depression against the load, which complicates the evacuation of air.
Other known installations propose handling tables allowing an elevation of the pallet at the end of retraction, and the suction of the film under the laying plane. Such an arrangement is not suitable for loads with glass containers, since the film tends to come off the foot of the pallet during handling. Heat sealing is not guaranteed.

In the case of two separate positions for shrouding and shrinking, the transfer of the hulled load of the hulling station to the retraction station causes a displacement of the lower part of the cover following its friction on the conveyor. It is therefore essential to reposition the cover before the heating step for heat shrink, in particular for a better distribution of the surperimeter. There are for this purpose devices for pinching the cover against the pallet.
The current facilities do not meet all the technical constraints in separate retraction of the houssage. Mixed machines of foaming and retraction are not suitable for production rates of the order of 100 pallets / hour, and more.

Object of the invention

The object of the invention is to develop a packaging method for improving the retraction and heat sealing on a sealing format of a cover Shrink wrap packaging on a palletized load requiring perfect sealing.

• après houssage de la charge, on place les moyens de retenue sous le bord inférieur pour tendre modérément la housse par le bas en tenant le bord inférieur par les quatre angles, et à une distance prédéterminée autour de la charge, de manière à maintenir l'intervalle ouvert sur toute la périphérie pendant toute la phase de thermorétraction,
• et on aspire l'air emprisonné à travers ledit intervalle latéral d'échappement pour vider complètement la housse pendant la phase de thermorétraction.

The method according to the invention is characterized in that:

• after shading the load, the retaining means is placed below the lower edge to moderately tension the cover from below by holding the lower edge by the four corners, and at a predetermined distance around the load, so as to maintain the gap open on the whole periphery during the whole phase of heat-shrinking,
• and entrained air is sucked through said lateral exhaust gap to completely empty the cover during the heat shrink phase.

Energizing the edge of the cover allows escape of air trapped through the gap, and prevents vertical shrinkage of the lower edge during the heat shrink phase.

Before the introduction of the retaining means, it is advantageous to blow air inside the cover to move the lower edge of the load in the introduction zone. The retaining means is first introduced vertically from a lower level outside the cover to a higher level inside the cover, and then said retaining means are horizontally spread towards the four corners of the lower edge for keep the cover open.

Subsequently, air is drawn through the exhaust side gap to completely empty the cover during the heat shrink phase. Finally, the upper level retaining means is vertically disengaged towards the lower level outside the cover when the lower edge is heat-sealed to the floor mat.

A gas injection step can also be provided after the suction phase. An injected gas is preferably used inside the space between the cover and the load, so as to sanitize or treat the internal volume of the cover. The final sealing of the cover by heat sealing takes place immediately after this gas injection, so as to prevent any escape of gas or introduction of air.

The invention also relates to a packaging installation of a palletized load by means of a heat-shrinkable plastic cover, comprising a palletized load support table, covering means for threading the cover open around and on the load, retracting frame heating means for heating the heat-shrinkable plastic cover for heat-shrinking on the load, retaining means in place under the lower edge of the cover to create an air exhaust gap and arranged to prevent vertical shrinkage of the cover during heat shrinkage, and an air suction and blowing device disposed in the support table and under the pallet, characterized in that the retaining means includes a take-back mechanism with four movable control fingers intended to move apart to stretch the cover downwards by holding it by the four angles, and at a predefined distance complete load throughout the shrinking phase.

According to a preferred embodiment, the control fingers are movable horizontally and vertically, being arranged in two casings integral with the two opposite sides of the support table. Each housing encloses a pair of control fingers cooperating with drive means to occupy a close position or a remote position.
An air suction and blowing device is arranged in the support table and under the pallet.

• soit un dispositif de transmission actionné par un motoréducteur pour déplacer chaque doigt le long d'une rampe inclinée ou curviligne, ou portés par des bras articulés, dont les positions de fin de course correspondent à la position rapprochée, et à la position écartée des doigts ;
• soit un vérin de manoeuvre coopérant avec un levier pivotant associé à un ressort de rappel pour chaque doigt.

The movement of the control fingers towards the remote position can be effected by various drive means comprising:

• either a transmission device actuated by a geared motor to move each finger along an inclined or curvilinear ramp, or carried by articulated arms, whose end positions correspond to the close position, and to the position of the fingers ;
• either a maneuvering jack cooperating with a pivoting lever associated with a return spring for each finger.

In a particular application, the control fingers can be drilled and connected to a gas injection device to ensure sanitization or other treatment inside the cover.

Brief description of the drawings

• les figures 1 et 2 sont des vues schématiques en élévation représentant les étapes successives du procédé selon l'invention ;
• la figure 3 montre une vue en plan de la charge entourée par la housse, laquelle est maintenue par des doigts de commande lors de la phase de rétraction, les, demi-vues de gauche et de droite illustrant respectivement les doigts en position rapprochée, et en position écartée ;
• la figure 4 est une vue en coupe selon la ligne 4-4 de la figure 1, avec le mécanisme de reprise pour l'actionnement des doigts de commande représentés dans les deux positions rapprochée et écartée;
• les figures 5 et 6 sont des variantes de réalisation du mécanisme de reprise de la figure 4, respectivement en position rapprochée et écartée des doigts de commande pour le maintien de la housse.

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 appended drawings in which:

• Figures 1 and 2 are schematic elevational views showing the successive steps of the method according to the invention;
• FIG. 3 shows a plan view of the load surrounded by the cover, which is held by control fingers during the retraction phase, the left and right half-views respectively illustrating the fingers in close position, and in the separated position;
• Figure 4 is a sectional view along the line 4-4 of Figure 1, with the recovery mechanism for actuating the control fingers shown in the two positions close together and spaced apart;
• Figures 5 and 6 are alternative embodiments of the recovery mechanism of Figure 4, respectively in the close position and spaced apart from the control fingers for the maintenance of the cover.

Description of the method and two preferred embodiments

According to the packaging machine schematically illustrated in FIGS. 1 to 4, a load CH consisting of a stack of bottles 10 made of glass or plastic is placed on a rectangular pallet 12 with the interposition of a floor mat 14 projecting beyond the edges of the container. the pallet 12. The pallet assembly 12 and CH load is fed to a support table 13 by means of a conveyor or a chain conveyor 16, which moves in a longitudinal direction perpendicular to the plane of FIGS. 1 and 2.

The upper face 15 of the pallet 12 covered by the floor mat 14 is wider than the distance between the two external beams or studs extending parallel to the longitudinal direction. The beams 17 form spacers defining the thickness of the pallet 12. The load CH has a parallelepipedal shape comprising a lower horizontal face 19 bearing on the floor mat 14, an upper horizontal face 27, and four lateral vertical faces 28 .

A cover 18 is made from a tubular sheath of heat-shrinkable plastic film, especially polyethylene, said sheath being cut before and then welded transversely to form a roof. The cover 18 is then opened by its lower end pointing downwards, and then is threaded on the palletized CH load during a first shading step. The upper face 27 of the load CH is thus completely capped by the cover 18. For example, the device for shaping the cover 18 and covering the load CH is described in detail in the document EP 1060988 .

The floor mat 14 is formed by a format made from a heat-shrinkable plastic film, whose outer edges fall on the lateral faces of the pallet 12. The material constituting the floor mat 14 may be the same as that of the cover 18. In the position of covering, the lower edge 29 of the cover 18 is arranged around the falling edges of the floor mat 14.

A fan 21 is disposed under the pallet 12 inside the support table 13, and is driven by a motor 22 electric reversal direction of rotation to form a device for suction or air blowing inside. of the cover 18.

A heater constituted for example by a retraction frame 20, is arranged with clearance around the load CH coated with its cover 18. The retraction frame 20 is movable vertically (arrow F1) by drive means (not shown) for heating the side surface of the cover 18 from top to bottom during the retraction phase of the film on the load CH.

The installation may comprise either a single station for combining the shading and retraction phases, or two separate separate stations, the first upstream for the implementation of the cover 18, and the second downstream for heating.

Retaining means located under the upper face 15 of the pallet 12, are made active during the retraction phase to move the open bottom edge 29 of the cover 18 relative to the load CH and the pallet 18 leaving an interval 24 (Figure 2). The air trapped inside the cover 18 can thus escape naturally through this gap 24 during the retraction phase as the heating frame descends. The natural peripheral escape of the air can be completed by an additional flow generated by a suction effect when the fan 21 is put into operation. This energization at the four angles prevents any vertical withdrawal of the lower edge during at least part of the heat shrink phase.

According to the invention, the retaining means comprise a recovery mechanism 23 intended to ensure the shaping and holding of the lower edge 29 of the cover 18 during the entire retraction phase. The recovery mechanism 23 is equipped for this purpose with four movable control fingers 26 horizontally and vertically, so as to reposition and moderately tension the cover 18 by holding the lower edge 29 by the four corners, and at a predetermined distance from the faces of the load CH and the pallet 12. The recovery mechanism 23 is disposed in two housings 30 integral with the two opposite sides of the support table 13. Each housing 30 contains a pair of control fingers 26 may occupy a close position (half view left, FIGS. 3 and 4), or a separated position (half-view on the right, FIGS. 3 and 4).

When the palletized and hung CH is positioned on the support table 13 for the retraction phase, the control fingers 26 of each pair are initially in a close position (see half-view on the left, FIG. lower level located below the pallet 12. The heating frame 20 is placed in the upper position, at the upper part of the load CH, but is not yet activated to ensure the retraction. The fan 21 can be actuated to cause an air blast to move the lower edge 29 of the pallet 12 into the insertion zone 31 of the control fingers 26.

The control fingers 26 are then moved vertically towards the upper level (half-view on the right, FIG. 1), so as to insert them into the zone 31 between the pallet 12 and the lower edge 29 of the cover 18. in place, the control fingers 26 remain in close position.

Drive means 32 of the take-up mechanism 23 subsequently move the control fingers 26 horizontally towards the separated position (half-view on the right, FIGS. 2 and 3 and 4) while keeping the lower edge 29 of the cover at the four positions. angles with formation of the gap 24 open to the outside. A blowing of air can then cause a slight inflation of the cover 18 to avoid possible wrinkling during the next phase of retraction.

In the example of FIG. 4, the drive means 32 of the fingers 26 of the recovery mechanism 23 comprise, by way of example, a belt transmission device 33 actuated by a geared motor 34, and driving each finger support 26 along an inclined or curvilinear ramp. The end positions of each ramp 35 correspond to the positions close to and apart from the fingers 26.

It is clear that the inclined or curvilinear ramps can be replaced by articulated arms.

During heat-shrinking of the film on the load CH, the retraction frame 20 heats the lateral faces of the cover 18 following a movement from top to bottom (arrow F1, Figure 2). The air trapped between the load CH and the cover 18 is sucked by the fan 21 rotating in the opposite direction, and is driven out through the gap 24. The suction air is carried out throughout the downward movement of the retraction frame 20, so as to completely empty the cover 18.

Positioning the heating frame 20 in the low position (left half-view, FIG. 2) causes heating of the lower edge 29 of the cover. The control fingers 26 are disengaged towards the lower level. This results in a heat sealing effect of the lower edge 29 on the floor mat 14 making the cover 18 completely watertight. The suction made by the fan 21 during this step promotes this heat sealing, and limits the vertical shrinkage of the cover.

To prevent sliding of the film on the fingers 26 during the retraction phase on the lateral faces of the load CH, it is advantageous to use hollow control fingers 26, laterally drilled with orifices in the portion in contact with the film. Maintaining suction inside the control fingers 26 during the retraction phase overcomes this disadvantage. At the end of retraction, the suction is removed so as to facilitate the release of the cover 18.

In a particular application, the pierced control fingers 26 may be connected to a gas injection device (not shown) to ensure sanitization or other treatment inside the cover 18. During this step of injection of gas, the suction by the fan 21 is maintained, so as to press the cover against the floor mat 14, and seal the gap 24 between the load CH and the edge of the cover 18.

In the variant embodiment of FIGS. 5 and 6, each of the two lateral recovery mechanisms 123 is equipped with a pair of levers 36 for actuating fingers 26. Each lever 36 is pivotally mounted on an axis 37 between two angular positions. , one of which allows the cover 18 to be held in the position removed (see position C in Figure 6). Each lever 36 is associated with a tension spring 38 urging the fingers 26 in a close position (see position A in FIG. 5).

A actuating jack 39 actuates each lever 36 to move it horizontally to an angle of the load CH when the fingers 26 are moved away. From the close position A of FIG. 5, the fingers 26 are first displaced by translation to the intermediate position B of Figure 6 without departing from the load CH. In this intermediate position, the springs 38 of the levers 36 remain relaxed as in FIG. 5. The continued travel of the jacks 39 then causes opposing tilting movements of the levers 36 towards the position spaced from the fingers 26 (see position C, FIG. 6) . The traction springs 38 are then stretched, and automatically return to the close position at the end of the retraction phase during the return of the jacks 39. The fingers 26 are then disengaged downwards by a vertical movement of the recovery mechanism 123 or by a pivoting about the axis 39 controlled by a pneumatic jack 40.

Claims (14)

1. Method for packaging a palletized load (CH) by means of a pallet cover (18) made from heat-shrink plastic material, consisting:

   - in placing the load (CH) on a support table (13) with an interposed groundsheet (14) covering the top surface (15) of the pallet (12),

   - in heating the pallet cover (18) placed beforehand on the load (CH) to achieve heat-shrinking thereof on the side faces of said load (CH),

   - in removing the air trapped between the pallet cover (18) and the load (CH) by expelling it via a lateral outlet gap (24) created by retaining means fitted under the bottom edge (29) of the pallet cover and arranged to prevent any vertical retraction of the pallet cover during heat-shrinking,

   - and in removing the retaining means to heat-seal the bottom edge (29) of the pallet cover (18) onto the overhanging edges of the groundsheet (14) rendering the packaging airtight,

   characterized in that

   - after the pallet cover has been placed on the load (CH), the retaining means are placed under the bottom edge (29) to moderately stretch the pallet cover (18) via the bottom holding the bottom edge (29) by the four corners, and at a predetermined distance around the load (CH), so as to keep the outlet gap (24) open over the whole periphery throughout the heat-shrinking phase,

   - and the trapped air is sucked through said lateral outlet gap (24) to empty the pallet cover (18) completely during the heat-shrinking phase.
2. Method for packaging according to claim 1, characterized in that, before the retaining means have been fitted in place, air is blown into the pallet cover (18) to move the bottom edge (29) of the load (CH) away in the insertion area (31).
3. Method for packaging according to claim 1 or 2, characterized in that the retaining means are first inserted vertically from a lower level outside the pallet cover (18) to an upper level inside the pallet cover, and that said retaining means are then moved away horizontally towards the four corners of the bottom edge (29) to keep the pallet cover (18) open.
4. Method for packaging according to claim 1, characterized in that after the air suction phase, a gas is injected to aseptize or treat the internal volume of the pallet cover.
5. Method for packaging according to claim 3, characterized in that the retaining means are withdrawn vertically from the upper level to the lower level outside the pallet cover when heat-sealing of the bottom edge (29) is performed on the groundsheet (14).
6. Device for packaging a palletized load (CH) by means of a pallet cover (18) made of heat-shrink plastic material, comprising:

   - a support table (13) supporting the palletized load (CH),

   - pallet covering means to fit the open pallet cover (18) around and on the load (CH),

   - heating means with a heat-shrink frame (20) to heat the pallet cover (18) to achieve heat-shrinking of the latter on the load (CH),

   - retaining means fitted under the bottom edge (29) of the pallet cover to create an air outlet gap and arranged to prevent any vertical retraction of the pallet cover during heat-shrinking,

   - and an air suction and blowing device arranged in the support table (13) and under the pallet (12),

   characterized in that the retaining means comprise a take-up mechanism (23, 123) with four movable control fingers (26) designed to move away from one another to stretch the pallet cover (18) downwards holding the latter by its four corners, and at a predetermined distance from the load (CH) throughout the heat-shrink phase.
7. Device for packaging according to claim 6, characterized in that the control fingers (26) are horizontally and vertically movable, being arranged in two housings securedly attached to the two opposite sides of the support table (13).
8. Device for packaging according to claim 7, characterized in that each housing (30) contains a pair of control fingers (26) operating in conjunction with drive means (32) to occupy a near position or a separated position.
9. Device for packaging according to claim 8, characterized in that the drive means (32) of the take-up mechanism (23) comprise a transmission device (33) actuated by a geared motor (34) to move each finger (26) along an inclined or curved ramp (35), or by articulated arms the end-of-travel positions whereof correspond to the near position and to the separated position of the fingers (26).
10. Device for packaging according to claim 8, characterized in that the drive means (32) of the take-up mechanism (123) comprise an operating jack (39) operating in conjunction with a swivelling lever (36) to move each finger (26) between the near position and the separated position.
11. Device for packaging according to claim 10, characterized in that a return spring (38) is associated with each lever (36) to move the latter from the separated position to the near position.
12. Device for packaging according to claim 6, characterized in that the air suction and blowing device is formed by a fan (21) coupled to an electric motor (22) with reversal of the direction of rotation.
13. Device for packaging according to claim 6, characterized in that the control fingers (26) are hollow and comprise suction holes designed to eliminate sliding of the film on said fingers during the heat-shrink phase.
14. Device for packaging according to claim 6, characterized in that the control fingers (26) are hollow and are connected to a gas injection device for performing aseptizing or another treatment inside the pallet cover (18), said gas injection being performed just before heat-sealing.

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