FR2850949A1 - DEVICE AND METHOD FOR PACKAGING A PALLETIZED LOAD USING A HEAT SHRINKABLE PLASTIC FILM COVER - Google Patents

Abstract

A method of wrapping a palletized CH load by means of a cover 18 made of heat-shrinkable plastic, consisting of: placing retaining means under the lower edge 29 to moderately tension the cover 18 by holding it by the four angles, and at a predetermined distance from the load CH, so as to keep the gap 24 open during the first heat-shrinking phase, - and to remove these retaining means just before the second heat-sealing phase of the lower edge 29 of the cover 18 on the ground sheet 14. This results in perfect retraction without folds of the cover to ensure good cohesion of the load, and to avoid weakening the areas adjacent to these folds. The continuous heat-sealing of the lower edge of the cover to the groundsheet also guarantees the sealing of the packaging.

Description

Device and method for packaging a palletized load using

  a shrink-wrap plastic film cover.

  TECHNICAL FIELD OF THE INVENTION The invention relates to a device and method for packaging a palletized load using a shrinkable plastic cover, consisting of: 1 5 - placing the load on a support table with interposition a floor mat covering the upper face of the pallet, - heating the cover previously deposited on the load to heat shrink it on the side faces of said load, - evacuating, during heat shrinking, the air trapped between the cover and load by driving it through a lateral exhaust gap to the outside, and heat-sealing the bottom edge of the cover to the drooping edges of the floor mat to seal the package.

  The packaging consists of a multilayer stack of hollow glass or plastic objects or containers, for example bottles. The invention also applies to any other type of object making use of a sealed and stable heat-shrinkable packaging.

  The stability and the tightness of such a packaging require the following criteria: - a perfect shrinkage without folds of the cover to ensure good cohesion of the load, and to avoid weakening the areas contiguous to these folds, - continuous heat sealing from 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 making a cover from a sheath of heat-shrinkable film, for example made of polyethylene, of opening it by orienting the lower edge downwards, of styling the load palletized with the cover, and to heat the side faces of the cover by a heating frame to ensure its heat shrinkage on the load. Heat shrinking generally requires a special support table for handling, with a suction device to control the conformation of the film during this step.

  Document FR-A-2816587 describes a shrinking and shrinking installation, in which the lower edge of the cover is held by the shroud fingers during the entire shrinking and heat sealing phase.

  The document EP-A-376028 relates to a packaging device equipped with pressing elements with pivoting levers working outside the displacement zone of the grippers. During the 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 external faces of the beams of the pallet. The pivoting levers are mounted for rotation below the positioning plane, and around horizontal axes integral with

Table.

  The two aforementioned documents relate to packaging machines with heat-shrinkable film, in which the shrinking and shrinking operations are carried out successively on the same work station.

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

  According to document EP-A-249534, to avoid the formation of air pockets between the palletized load and the cover, a suction cannula is introduced between the lower edge of the cover and the drooping edges of the format constituting the mat. ground, so as to suck the air trapped during the shrinking phase.

  Other known installations offer handling tables allowing an elevation of the pallet at the end of retraction, and the aspiration of the film under the laying plane. Such an arrangement is not suitable for loads with glass containers, since the film tends to take off from the base of the pallet during handling. Heat sealing is not guaranteed.

  1 0 In the case of two separate stations for covering and shrinking, the transfer of the covered load from the covering station to the shrinking station causes a displacement of the lower part of the cover due to its friction on the conveyor. It is then essential to reposition the cover before the heating step for heat shrinking, in particular for a better distribution of the perimeter. There are devices for pinching the cover against the pallet.

  Current installations do not make it possible to satisfy all of the technical constraints in separate shrinkage of the cover. The mixed hooding and shrinking machines 20 are not adapted to production rates of the order of 100 pallets / hour, and more.

  OBJECT OF THE INVENTION The object of the invention consists in developing a packaging method intended to improve shrinkage and heat-sealing on a sealing format of a packaging bag with shrink film placed on a palletized load requiring a perfect seal.

  The method according to the invention is characterized in that retaining means are placed under the lower edge for moderately stretching the cover while holding it by the four angles, and at a predetermined distance from the load, so as to maintain the open interval during the first heat-shrinking phase, and these retaining means are then removed just before the heat-sealing phase from the lower edge of the cover on the floor mat.

  Before the retention means are put in place, air is advantageously blown into the interior of the cover to move the lower edge of the load away from the introduction zone. First the retaining means are introduced vertically from a lower level outside the cover to a higher level inside the cover, and then said horizontal means spread said retaining means towards the four corners of the lower edge to keep the cover open. 1 0

  Thereafter, the air is sucked in through the lateral exhaust gap to completely empty the cover during the heat-shrinking phase. Finally, 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 on the floor mat. A gas injection step can also be provided after the suction phase. . Use is preferably made of 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 escape of gas or introduction of air.

  The invention also relates to an installation for packaging a palletized load by means of a cover made of heat-shrinkable plastic, comprising a table supporting the palletized load, covering means for threading the open cover around and onto the load. , heating means with a retraction frame for heating the cover for its shrinking, and means for retaining the lower edge of the cover 30 during the shrinking to allow the escape of the air trapped between the cover and the load . The retaining means comprise a recovery mechanism with four movable control fingers intended to move apart in order to tension the cover while holding it by the four angles, and at a predetermined distance from the load during the heat-shrinking phase.

  According to a preferred embodiment, the control fingers are movable horizontally and vertically, being arranged in two housings integral with the two opposite sides of the support table. Each casing contains a pair of control fingers cooperating with drive means 5 to occupy a close position or a separated position. An air suction and blowing device is placed in the support table and under the pallet.

  The displacement of the control fingers towards the separated position can be operated 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, 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 pierced and connected to a gas injection device making it possible to provide sanitization or any other treatment inside the cover.

Brief description of the drawings

  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 elevation views representing the successive stages 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. 1 0

  Description of the process and of two preferred embodiments According to the packaging machine illustrated diagrammatically in FIGS. 1 to 4, a load CH composed of a stack of glass or plastic bottles 10 is placed on a rectangular pallet 12 with interposition of a floor mat 14 extending 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 chain conveyor 16, which moves in a direction longitudinal perpendicular to the plane of Figures 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 17 extending parallel to the longitudinal direction. The beams 17 form spacers defining the thickness of the pallet 12. The load CH has a rectangular shape 25 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, 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 oriented downwards, then is threaded onto the palletized load CH during a first stage of covering. The upper face 27 of the load CH is thus entirely covered by the cover 18. By way of example, the device for shaping the cover 18 and for covering the load CH is described in detail in document EP 1060988.

  The floor mat 14 is formed by a format produced from a film of heat-shrinkable plastic, the outer edges of which 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 cover position, the lower edge 29 of the cover 18 is arranged around the falling edges of the floor mat 14. 1 0

  A fan 21 is placed under the pallet 12 inside the support table 13, and is driven by an electric motor 22 with reversal of the direction of rotation to constitute a device for extracting or blowing air inside cover 18. 1 5

  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 can be moved vertically (arrow Fl) by drive means (not shown) for heating the lateral surface of the cover 20 18 from top to bottom during the phase of retraction of the film on the load CH.

  The installation may include either a single station allowing the combination of the covering and shrinking phases, or two separate separate stations, the first upstream for the fitting of the cover 18, and the second downstream 25 for the heating.

  Retaining means located under the upper face 15 of the pallet 12 are made active during the retraction phase to separate the open lower edge 29 of the cover 18 from the load CH and the pallet 18, leaving 30 a interval 24 (Figure 2). The air trapped inside the cover 18 can thus naturally escape through this gap 24 during the shrinking phase as the heating frame 20 moves down.

  The natural peripheral exhaust of the air can be supplemented by an additional flow generated by a suction effect when the fan 21 is put into service.

  According to the invention, the retaining means comprise a recovery mechanism 5 23 intended to ensure the conformation and the holding of the lower edge 29 of the cover 18 throughout the retraction phase. The recovery mechanism 23 is equipped for this purpose with four control fingers 26 movable horizontally and vertically, so as to reposition and moderately stretch the cover 1 8 while holding the lower edge 29 by the four angles, and at a distance 1 0 predetermined faces of the load CH and the pallet 12. The recovery mechanism 23 is arranged in two casings 30 integral with the two opposite sides of the support table 13. Each casing 30 contains a pair of control fingers 26 capable of occupying a close position (half-view on the left, Figures 3 and 4), or a remote position (half-view on the right, Figures 3 1 5 and 4).

  When the palletized and upholstered load 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. 1), but at a lower level located under the pallet 12. The heating frame 20 is placed in the high position, at the upper part of the load CH, but is not yet activated to ensure retraction. The fan 21 can be actuated to cause an air blowing intended 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 level upper (half right view, Figure 1), so as to insert them in the area 31 between the pallet 12 and the lower edge 29 of the cover 18. During this positioning, the control fingers 26 remain in position close. 30 Drive means 32 of the recovery mechanism 23 subsequently move the control fingers 26 horizontally to the separated position (half-view on the right, FIGS. 2 and 3 and 4) while maintaining the lower edge 29 of the cover at four angles with formation of gap 24 open to the outside.

  A blowing of air can then cause a slight inflation of the cover 18 to avoid possible folds 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 transmission device 33 with belt actuated 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 close and apart positions of the fingers 26. 1 0

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

  During the heat-shrinking of the film on the load CH, the retraction frame 20 1 5 heats the lateral faces of the cover 18 following a movement from top to bottom (arrow Fl, FIG. 2). The air trapped between the load CH and the cover 18 is sucked in by the fan 21 rotating in opposite directions, and is expelled towards the outside through the gap 24. The air is sucked in throughout the downward travel of the retraction frame 20, so as to completely empty the cover 18.

  The positioning of the heating frame 20 in the low position (half-view on the left, FIG. 2), causes the lower edge 29 of the cover to heat up.

  The control fingers 26 are released 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 waterproof. The suction produced by the fan 21 during this step promotes this heat sealing, and limits the vertical withdrawal of the cover.

  To avoid the film sliding on the fingers 26 during the retraction phase 30 on the lateral faces of the load CH, it is advantageous to use hollow control fingers 26, laterally pierced with orifices in the part in contact with the film. Maintaining suction inside the control fingers 26 during the retraction phase eliminates this drawback. 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 can be connected to a gas injection device (not shown) making it possible to provide sanitization or any other treatment inside the cover 18. During this step d gas injection, the suction by the fan 21 remains 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. 1 0

  In the alternative embodiment of FIGS. 5 and 6, each of the two lateral recovery mechanisms 123 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 separated position (see position C in FIG. 6). Each lever 36 is associated with a tension spring 38 urging the fingers 26 in the close position (see position A in FIG. 5).

  An actuating cylinder 39 actuates each lever 36 to move it horizontally towards an angle of the load CH when the fingers 26 are moved apart. From the close position A in FIG. 5, the fingers 26 are first moved in translation towards the intermediate position B of FIG. 6 without deviating from the load CH. In this intermediate position, the springs 38 of the levers 36 remain relaxed as in FIG. 5. The continued stroke of the jacks 25 39 then causes opposite movements of tilting of the levers 36 towards the position separated from the fingers 26 (see position C, FIG. 6 ). The traction springs 38 are then tensioned, and automatically return to the close position at the end of the retraction phase when the cylinders 39 are returned. The fingers 26 are then released downwards by a vertical movement of the recovery mechanism 123 or by pivoting about the axis 39 controlled by a pneumatic cylinder 40.

Claims (16)

claims   1. Method of packaging a load (CH) palletized by means of a cover (18) 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 10 (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 1 5 (18) and the load (CH) by driving it through a gap (24) lateral exhaust to the outside, - and to heat seal 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 stretch the cover (18) while holding it by the four angles, and at a predetermined distance from the load (CH), so as to keep the gap (24) open during the first heat-shrinking phase, - and these retaining means are removed just before the second heat-sealing phase from the lower edge (29) of the cover (18) on the floor mat ( 14).   2. A packaging method according to claim 1, characterized in that before the positioning of the retaining means, air is blown inside the cover (18) to move the lower edge (29) ) of the charge (CH) in the introduction zone (31).   3. A packaging method according to claim 1 or 2, characterized in that first of all the vertically retaining means are introduced from a lower level outside the cover (18) to a higher level inside of the cover, and then spreading said retaining means 5 horizontally towards the four corners of the lower edge (29) to keep the cover (18) open.   4. Packaging method according to one of claims 1 to 3, characterized in that the air is sucked through the lateral exhaust gap (24) to completely empty the cover (18) during the heat shrink phase.   5. A 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.   6. A 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).   7. Device for packaging a palletized load (CH) by means of a cover (18) made of heat-shrinkable plastic, comprising: - a support table (13) for the palletized load (CH), - means for covering for threading the cover (18) open around and on the load (CH), - heating means with retraction frame (20) for heating the cover (18) with a view to its shrinking 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 30 trapped between the cover (18) and the load (CH), characterized in that the means retaining devices comprise a recovery mechanism (23, 123) with four movable control fingers (26) intended to move apart in order to tension the cover (18) by holding it by the four angles, and at a predetermined distance from the load ( CH) during the heat shrinking phase.   8. Packaging device according to claim 7, characterized in that the 5 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) .   9. Packaging device according to claim 8, characterized in that each 1 0 housing (30) contains a pair of control fingers (26) cooperating with drive means (32) to occupy a close position or a position discounted.   10. Packaging device according to claim 9, characterized in that the 1 5 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 separated position of the fingers (26). 20 11. Packaging device according to claim 9, characterized in that.   drive means (32) of the recovery mechanism (123) comprise an actuating cylinder (39) cooperating with a pivoting lever (36) for moving each finger (26) between the close position and the separated position. 25 12. 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.   13. 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).   14. Packaging device according to claim 13, characterized in that the suction and blowing device is constituted by a fan (21) coupled to an electric motor (22) reversing the direction of rotation.   15. Packaging device according to claim 7 or 8, characterized in that the control fingers (26) are hollow, and include suction orifices intended to suppress the sliding of the film on said fingers during the retraction phase.   1 0 16. 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 with inside the cover (18), said gas injection taking place just before heat sealing.