EP1445197A1 - Apparatus and method for applying a packaging hood of heat-shrinkable foil on a palettised load - Google Patents

Abstract

The process involves placing a control unit under the lower side (29) of a cover (18) to moderately tighten the cover by holding the side by four angles at a preset distance of a load (CH) to maintain an interval open on the periphery during one phase of thermo-retraction. The control unit is removed just before a phase of thermal sealing of the side on a groundsheet (14). The cover is tightened to allow air to escape through the interval and to prevent vertical retreat of the lower side during a portion of the former thermo-retraction phase. An independent claim is also included for a device for packing a palletized load by means of a thermo-retractable plastic cover.

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, durant la thermorétraction, l'air emprisonné entre la housse et la charge en le chassant à travers un intervalle latéral d'échappement vers l'extérieur,
• et à thermosceller le bord inférieur de la housse sur les bords tombants du tapis de sol pour rendre l'emballage étanche.

The invention relates to a device and method for packaging a palletized load using a 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 in order to heat shrink it on the lateral faces of said load,
• to evacuate, during the heat shrinkage, the air trapped between the cover and the load by driving it through a lateral exhaust gap towards the outside,
• and heat seal the bottom edge of the cover over the drooping edges of the floor mat to seal the packaging.

The packaging consists of a multilayer stack of objects or hollow glass or plastic containers, for example bottles. The invention also applies to any other type of object using packaging waterproof and stable heat shrink.

• 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 stability and tightness of such packaging require the following criteria:

• perfect shrinkage without folds of the cover to ensure good cohesion of the load, and avoid weakening the areas adjacent to these folds,
• continuous heat sealing of the lower edge of the cover to the floor mat to guarantee watertightness and tie the load to the wooden support of the pallet.

State of the art

We already know packaging methods and installations consisting of make a cover from a shrink wrap, by example in polyethylene, to open it by orienting the lower edge downwards, cover the palletized load with the cover, and heat the side faces of the cover by a heating frame to ensure its heat shrinkage on the load. The heat shrinking generally requires a special support table of handling, with a suction device to control the conformation of the film during this stage.

The document FR-A-2816587 describes an installation for covering and shrinking, in which the lower edge of the cover is held by the fingers of covering during the whole covering and heat sealing phase.

The document EP-A-376028 relates to a packaging device equipped pressing elements with pivoting levers working outside the moving grippers. During heat shrinkage, the bottom 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 external faces beams from the pallet. The pivoting levers are rotatably mounted in below the positioning plane, and around horizontal axes integral with Table.

The two above-mentioned documents relating to film packaging machines heat shrink, in which the shrinking and shrinking operations are carried out successively on the same workstation.

Other packaging machines have also proposed to improve the phase of shrinkage of the film on a separate station located downstream of the covering station.

According to documents EP-A-249534 and EP-A-205135, to avoid formation air pockets between the palletized load and the cover, a cannula is introduced suction between the bottom edge of the cover and the drooping edges of the format constituting the floor mat, so as to suck the air trapped during the retraction phase. Such a device does not maintain the cover during the retraction.

EP 697337 relates to a method and a device for overpacking of a palletized load, comprising a preliminary step of covering the loaded with a shrink film cover, followed by a shrinking step thermal film, implementing the shrinkage of a film return under the face lower of the lateral sliding supports, and a conformation of the cover along the transverse sides to bring the lower edge of the cover substantially on the underside of the load floor palletized. The lower edge of the cover is not separated from the load by mechanical means. Such a device is intended to clear the passage of handling forks in automatic storage stores.

Document DE 4426369 mentions a packaging device, in which the film is removed from the load by air, not by spacing means mechanical. We first blow inside to distribute the film around the charge, then internal air is drawn in during retraction. The film is then pressed by the effect of depression against the load, which complicates the evacuation air.

Other known installations offer handling tables allowing an elevation of the pallet at the end of retraction, and the suction of the film under the plane deposit. Such an arrangement is not suitable for container loads in glass, since the film tends to come off the bottom of the pallet when handling. Heat sealing is not guaranteed.

In the case of two separate positions for hooding and retraction, the transfer of the load covered from the hooding station to the shrinking 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 stage for heat shrinking, in particular for a better distribution of the perimeter. There are for this purpose pinching the cover against the pallet.

The current installations do not make it possible to satisfy all of the technical constraints in separate shrinkage of the cover. Mixed machines of cover and retraction are not adapted to rates of production of around 100 pallets / hour, and more.

Subject of the invention

The object of the invention is to develop a packaging process intended for improve shrinkage and heat sealing on a sealing format of a shrink film packaging cover placed on a palletized load requiring a perfect seal.

The method according to the invention is characterized in that means are placed retained under the lower edge to moderately stretch the cover while holding it by the four angles, and at a predetermined distance from the load, so keep the gap open during the first heat shrink phase, and then remove these retaining means just before the phase of heat sealing the lower edge of the cover on the floor mat. The setting tension of the edge of the cover allows the escape of trapped air to across said gap, and prevents vertical withdrawal of the bottom edge during minus part of the heat shrink phase.

Before the retention means are put in place, it is advantageous to blow the air inside the cover to move the bottom edge of the load away from the introduction area. The retaining means are first introduced vertically at from a lower level outside the cover to a level higher than the inside of the cover, and said means are then spread horizontally retained around the four corners of the bottom edge to keep the cover open.

Thereafter, the air is drawn in through the lateral exhaust gap to empty the cover completely during the heat-shrinking phase. Finally, we vertically releases the retaining means from the upper level to the level lower outside the cover when heat sealing the lower edge on the mat of soil

A gas injection stage can also be planned after the phase suction. It is preferable to use a gas injected 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 gas escape or air introduction.

The invention also relates to an installation for packaging a load. palletized using a shrinkable plastic cover, comprising a palletized load support table, means for cover to put the cover open around and on the load, means of heating with retraction frame to heat the cover for its heat shrinkage, and means for retaining the lower edge of the cover during heat shrinkage to allow trapped air to escape between the cover and the load. The retaining means include a mechanism recovery with four movable control fingers intended to move apart for stretch the cover by holding it by the four angles, and at a distance predetermined load during the heat shrinking phase.

According to a preferred embodiment, the control fingers are horizontally and vertically movable, being arranged in two housings secured to the two opposite sides of the support table. Each housing contains a pair of control fingers cooperating with drive means to occupy a close position or a moved position. A device suction and supply air is arranged in the support table and under the palette.

• 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 manceuvre coopérant avec un levier pivotant associé à un ressort de rappel pour chaque doigt.

The movement of the control fingers to the separated position can be operated by various drive means comprising:

• either a transmission device actuated by a gearmotor to move each finger along an inclined or curvilinear ramp, or carried by articulated arms, the end positions of which correspond to the close position, and to the position separated from the fingers ;
• or an actuating cylinder 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 any 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 characteristics will emerge more clearly from the description which follows of an embodiment of the invention given by way of nonlimiting 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 the close position, and in the open position;
• Figure 4 is a sectional view along line 4-4 of Figure 1, with the recovery mechanism for actuation of the control fingers shown in the two positions close and apart;
• Figures 5 and 6 are alternative embodiments of the recovery mechanism of Figure 4, respectively in the close position and away from the control fingers for holding the cover.

Description of the process and two preferred embodiments

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

The upper face 15 of the pallet 12 covered by the floor mat 14 is more as wide as the distance between the two external beams or studs 17 extending parallel to the longitudinal direction. The beams 17 form spacers defining the thickness of the pallet 12. The CH load has a shape parallelepiped comprising a lower horizontal face 19 coming in support on the floor mat 14, an upper horizontal face 27, and four faces lateral verticals 28.

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

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

A fan 21 is placed under the pallet 12 inside the support table 13, and is driven by an electric motor 22 reversing the direction of rotation to constitute a device for extracting or blowing air inside the cover 18.

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

The installation can include either a single station allowing the combination of covering and shrinking phases, i.e. two separate separate positions, the first upstream for the fitting 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 spread the open bottom edge 29 of the cover 18 with respect to the load CH and the pallet 18 while allowing to remain an interval 24 (Figure 2). The air trapped inside the cover 18 can thus naturally escape through this interval 24 during the phase of retraction as the lowering movement of the heating frame 20 proceeds. The natural peripheral air exhaust can be supplemented by a additional flow generated by a suction effect during commissioning of fan 21. This power-up at the four corners prevents any vertical withdrawal of the lower edge during at least part of the shrinking.

According to the invention, the retaining means comprise a recovery mechanism 23 intended to ensure the conformation and the 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 horizontally movable control fingers 26 and vertically, so as to reposition and moderately tension the cover 18 holding the lower edge 29 by the four angles, and at a distance predetermined sides of the CH load and the pallet 12. The mechanism recovery 23 is arranged in two housings 30 integral on both sides opposite of the support table 13. Each casing 30 contains a pair of fingers 26 capable of occupying a close position (half view on the left, figures 3 and 4), or a spread position (half-view on the right, figures 3 and 4).

When the palletized and upholstered CH load is positioned on the support table 13 for the retraction phase, the control fingers 26 of each pair are initially found in a close position (see half-view on the left, Figure 1), but at a lower level located under the pallet 12. The frame 20 of heating is placed in the high position, at the top of the load CH, but is not yet activated to ensure retraction. Fan 21 can be actuated to cause an air supply intended to draw the lower edge away 29 of the pallet 12 in the insertion zone 31 of the control fingers 26.

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

Drive means 32 of the recovery mechanism 23 move by the following the control fingers 26 horizontally towards the separated position (half-view on the right, Figures 2 and 3 and 4) maintaining the lower edge 29 of the cover at the four corners 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 any creases during the next phase of retraction.

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

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

When the film is shrunk on the load CH, the retraction frame 20 heats the side faces of the cover 18 after moving up and down bottom (arrow F1, figure 2). The air trapped between the load CH and the cover 18 is sucked in by fan 21 rotating in the opposite direction, and is driven towards outside through gap 24. Air is drawn in throughout lowering stroke of the retraction frame 20, so as to completely empty the cover 18.

Positioning the heating frame 20 in the low position (half view left, Figure 2), causes the lower edge 29 of the cover to heat up. The control fingers 26 are released towards the lower level. The result a heat sealing effect of the lower edge 29 on the floor mat 14 making the completely waterproof cover 18. The suction carried out by the fan 21 during of this step promotes this heat sealing, and limits the vertical shrinkage of the cover.

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

In a particular application, the pierced control fingers 26 can be connected to a gas injection device (not shown) to ensure asepticization or any other treatment inside the cover 18. During this gas injection step, the suction by the fan 21 remains maintained, so as to press the cover against the floor mat 14, and make it waterproof the interval 24 between the load CH and the edge of the cover 18.

In the alternative embodiment of Figures 5 and 6, each of the two mechanisms 123 lateral recovery is equipped with a pair of levers 36 for actuating the 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 spread position (see position C in figure 6). Each lever 36 is associated with a tension spring 38 urging the fingers 26 in the close position (see position A in figure 5).

An actuating jack 39 actuates each lever 36 to move it horizontally to an angle of the load CH when the fingers are apart 26. From the close position A of FIG. 5, the fingers 26 are first moved in translation to the intermediate position B of Figure 6 without deviate from the CH load. In this intermediate position, the springs 38 of the levers 36 remain relaxed as in FIG. 5. The continued stroke of the jacks 39 then causes opposite tilting movements of the levers 36 to the position separated from the fingers 26 (see position C, Figure 6). Springs 38 of traction are then tensioned, and automatically return to position close at the end of the retraction phase when the cylinders are recalled 39. The fingers 26 are then released downwards by a vertical displacement of the recovery mechanism 123 or by pivoting around the controlled axis 39 by a pneumatic cylinder 40.

Claims (16)

Method for packaging a palletized load (CH) by means of a cover (18) made of heat-shrinkable plastic, consisting of: placing the load (CH) on a support table (13) with the interposition of a floor mat (14) covering the upper face (15) of the pallet (12), heating the cover (18) previously deposited on the load (CH) to heat shrink it on the lateral faces of said load (CH), to evacuate, during the heat shrinkage, the air trapped between the cover (18) and the load (CH) by expelling it through a lateral exhaust gap (24) towards the outside, and heat sealing the lower edge (29) of the cover (18) on the falling edges of the floor mat (14) to seal the packaging, characterized in that retaining means are placed under the lower edge (29) to moderately tension the cover (18) while holding the lower edge (29) by the four angles, and at a predetermined distance from the load (CH), so as to maintain the interval (24) open over the entire periphery during the first heat-shrinking phase, by allowing the escape of the trapped air through said interval, and by preventing any vertical withdrawal of said lower edge during at least part of the phase heat shrink, and these retaining means are removed just before the second heat sealing phase of the lower edge (29) of the cover (18) on the floor mat (14). Packaging method according to claim 1, characterized in that before the installation of the retaining means, air is blown inside the cover (18) to move the lower edge (29) away from the charge (CH) in the introduction zone (31). Packaging method according to claim 1 or 2, characterized in that the retaining means are first introduced vertically from a lower level outside the cover (18) to a higher level inside the cover, and then spreading said retaining means horizontally towards the four corners of the lower edge (29) to keep the cover (18) open. Packaging method according to one of Claims 1 to 3, characterized in that the air is drawn in through the lateral exhaust gap (24) in order to completely empty the cover (18) during the heat-shrinking phase. Packaging method according to claim 4, characterized in that after the air suction phase, a gas is injected to sanitize or treat the internal volume of the cover. Packaging method according to claim 3 or 4, characterized in that the retaining means are released vertically from the upper level to the lower level outside the cover during the heat sealing of the lower edge (29) on the floor mat (14 ). Device for packaging a palletized load (CH) by means of a cover (18) made of heat-shrinkable plastic, comprising: a palletized load support table (13), cover means for threading the cover (18) open around and on the load (CH), heating means with a retraction frame (20) for heating the cover (18) in order to heat shrink it on the load (CH), and means for retaining the lower edge (29) of the cover (18) during the heat shrinkage to allow the escape of the air trapped between the cover (18) and the load (CH), characterized in that the retaining means comprise a recovery mechanism (23, 123) with four movable control fingers (26) intended to move apart in order to tension the cover (18) while holding it by the four angles, and at a predetermined distance from the load (CH) during the heat shrinking phase. Packaging device according to claim 7, characterized in that the control fingers (26) are movable horizontally and vertically, being arranged in two housings (30) integral with the two opposite sides of the support table (13). Packaging device according to claim 8, characterized in that each casing (30) contains a pair of control fingers (26) cooperating with drive means (32) to occupy a close position or a separated position. Packaging device according to claim 9, characterized in that the drive means (32) of the recovery mechanism (23) comprise a transmission device (33) actuated by a geared motor (34) to move each finger (26) either along an inclined or curvilinear ramp (35), or by articulated arms, the end positions of which correspond to the close position, and to the position separated from the fingers (26). Packaging device according to claim 9, characterized in that the drive means (32) of the recovery mechanism (123) comprise an actuating cylinder (39) cooperating with a lever (36) pivoting to move each finger (26 ) between the close position and the separated position. Packaging device according to claim 11, characterized in that a return spring (38) is associated with each lever (36) to bring it back from the separated position to the close position. Packaging device according to one of Claims 7 to 12, characterized in that an air suction and blowing device is arranged in the support table (13) and under the pallet (12). Packaging device according to claim 13, characterized in that the suction and blowing device consists of a fan (21) coupled to an electric motor (22) reversing the direction of rotation. Packaging device according to claim 7 or 8, characterized in that the control fingers (26) are hollow, and have suction orifices intended to suppress the sliding of the film on said fingers during the retraction phase. Packaging device according to claim 7 or 15, characterized in that the control fingers (26) are hollow, and connected to a gas injection device making it possible to provide sanitization or other treatment inside the cover (18), said gas injection taking place just before heat sealing.

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