EP1419966A1 - Method and apparatus for applying a packaging hood of stretch foil on a palettized load - Google Patents

Abstract

The procedure consists of opening the sleeve (10) above the palleted load and folding its sides in accordion pleats on inclined fingers with the aid of rollers (14) turning in a first direction. The sleeve is then stretched horizontally to make an opening larger than the load and drawn over the load from the top, unfolding it as it descends. The fingers are inclined at 0 - 25 degrees to the vertical to achieve an accumulated sleeve portion with evenly-spaced pleats at the lower ends (12A) of the fingers before the sleeve is stretched horizontally. As the load is covered the process is halted at a predetermined level and the direction of the rollers reversed to create a coil before continuing.

Description

Technical field of the invention

• 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,
• 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 a flexible packaging cover obtained from a sheath of stretchable plastic material on a palletized load, comprising:

• open the sheath for volume setting above the load,
• pleating the lateral parts of the accordion sheath on pleating fingers, using motorized rollers rotating in a first direction of rotation,
• then stretch the pleated sheath in the horizontal transverse direction to obtain an opening larger than the perimeter of the load to be packed,
• and moving the stretched sheath over the load in a vertical direction, causing the gradual unfolding of the plies during the covering stroke.

State of the art

The use of a stretch film sheath is well known for ensuring the stability and tightness of a palletized load. Contrary to shrink film, the installation of a stretchy sheath does not no heat source required, as it suffices to stretch mechanically beforehand the plastic film material in the direction transverse horizontal before wrapping the palletized load at wrap. After removing the stretched sheath on the load, the tightening of the stretch film material occurs naturally by elasticity, which firmly holds the sheath around the charge. The sheath can be made of polyethylene, or any other material stretchable plastic.

The sheath is generally stored by winding on a reel, and folded over its section with four bellows. After unwinding of the reel, the opening of the sheath is effected by an action mechanical separation at the four angles.

Packing machines for threading a film cover stretchable on the load, have a device for this purpose spacer to open the stretch film sheath, and a device for pleating to pleat the accordion sheath on four integral fingers of a support frame.

According to document EP 344815, a welding device is arranged between the spacer and the pleating device for weld the sheath by 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 part higher. The pleated cover is then stretched in a plane horizontal parallel to the weld, and is positioned above of the palletized load. The cover is unfolded during the hooding, and deposited on and around the load following a vertical displacement of top to bottom of the frame. Before being pulled over the load, the cover undergoes in the transverse stretched state, a longitudinal stretching in the vertical direction from 5% to 15% of its initial vertical length.

The mechanism of the COVERPAL packaging machine (registered trademark from the company Thimon), is described in detail in the document EP 1060988. Welding and sheath cutting operations for form the cover, are carried out before removal on the fingers of pleating, unlike the mechanism described previously in the document EP 344815. The weld is then perfectly cooled when it is stressed by transverse stretching, and is more resistant to elongation stresses. There are no specific means planned to perform a vertical lengthening of the sheath during the covering following the transverse stretching phase.

In Figures 1 to 3 showing the pleating and stretching phases transverse of a packaging machine of the prior art, the part upper 12B of each finger 12 has a drawing shoe 22 having a curved shape advantageously adapted to the friction of the film during the pleating and unfolding stages. The vertical side of the finger 12 can be fitted with one or two crazy rollers 13, or be fitted with a fixed friction coating with low friction, so as to pinch the sheath and drag it down during pleating by the motorized roller 14. The latter is rotated by a geared motor 24, and cooperates with tilting with an actuator 20 between a spread apart position (not shown), and a position working (Figures 1 to 3) in contact with finger 12.

The four motorized rollers 14 are rotated in the direction of arrows F1 and F2 to ensure the pleating of the cover 10 in accumulating it in an accordion in the lower part 12A of the fingers 12. The top of cover 10 has been previously closed 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 kept pressed against the pleating fingers 12 of so as to tighten more or less strongly the horizontal part upper cover 10 during transverse stretching. It is also possible to control the actuators 20 to spread the rollers 14 motorized during this stretching step in order to allow the film to partially slide on the fingers 12, avoiding any possibility of tearing the film. Such known mechanisms allow to obtain a transverse stretching rate higher than 10%. The quality of the stretch sheaths makes it possible to obtain stretching from 50% to 100%.

The next phase of hooding is carried out by a vertical displacement of the frame over the load, so as to cause the unfolding progressive of the cover on the load. After removing the cover, the tightening of the stretch film material occurs naturally by elasticity, which ensures the stable maintenance of the load. The relaxation of the material and the friction of the film on the fingers create in addition a vertical tension of the film on the load which contributes also to enhance stability. This vertical tension is generated without any particular vertical stretching device, given that a transverse stretch from 50% to 100% reduces the sheath height, and transmits to the load cohesive forces sufficient to ensure stability, since this vertical tension is maintained during deposit it on the load.

The angle of inclination A of the fingers 12 with the vertical direction allows to facilitate the accumulation of folds during pleating by the rollers 14 motorized. For a predetermined inclination, the clearance between the cover 10 and fingers 12 gradually increases as we approaches the lower part, with the consequence of a possibility of disorganization of the folds, which are no longer correctly guided when they slide towards the base of the fingers.

A lower angle of inclination A of the fingers 12 would have as main drawback of hampering the effect of fold accumulation, being since the film sliding down could no longer take place naturally. The motorized rollers 14, in addition to their pleating function, must also exercise a second function pushing down, which causes friction on the folds higher, with risks of dots or lines forming vertical fragility of the sheath before the transverse stretching phase.

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

Subject of the invention

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

A development of the invention consists in creating a regular and precise pleated strand during the covering step, and in depositing it on the load at any height, or on the pallet.
Another development of the invention relates to a stretching process making it possible to obtain a controlled tension of the film during the hooding.

The drawing process according to the invention is characterized in that the inclination of the fingers is between 0 and 25 ° relative to the vertical direction, and we limit the reduction of the pleating perimeter around the fingers to obtain before the transverse stretching phase horizontal, an accumulation without discomfort and a regular distribution folds in the lower part of said fingers. The friction of the sheath which descends along the inclined fingers is effected on both finger edges. Any angle or protruding part on these edges may disrupt the folds.

Disorganization of the folds after the stretching step may indeed disturb the unfolding during hooding, creating pinching of the folds between them which may cause the sheath to tear.

The inclination of the fingers facilitates the accumulation of folds, and the fact of limiting the perimeter of pleating in the lower part where the play is greatest, 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 hampering the descent of the sheath along the fingers. Any formation of successive pinched folds is thus excluded during the transverse stretching, which makes it possible to reliably avoid tearing during the following stage of hooding.
According to a development of the invention, a regular pleated strand can be created in the film during the covering phase, by interrupting the lowering movement of the cover to a predetermined level, and by rotating the rollers in a second direction of rotation. opposite the first. By a double movement of the fingers, the stranded film can be precisely deposited at any level of height 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 the maintenance of the upper part of the load, or the removal of the strand on the top of the support pallet allowing precise clearance from the entrance to an automatic palletizer fork.

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

The invention also relates to a device for packaging a load. palletized using a cover made of plastic film stretchable, and comprising an operating frame equipped with pleating and stretching, each finger having a stretching shoe, and being associated with a motorized roller driven in rotation by a gear motor, means for tilting each motorized roller between a spread position of rest, and a working position in contact with the finger, and means for actuating the frame to cover the load. The inclined lower part of each finger is endowed with means avoiding too much reduction large pleating perimeter around the fingers, and comprising a braking element arranged in the low zone of accumulation of folds where the play between the pleated cover before the stretching phase transverse is the most important.

According to a preferred embodiment, the braking element is straight, and extends vertically projecting from the area center of the inclined lower part of the finger. The braking 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 of the element braking system is arranged under a roller on which the motorized roller during pleating.

According to another characteristic, a clamping element is mounted on the support of each finger extending substantially at the level of the drawing shoe above the corresponding motorized roller. The element clamp is associated with an actuator to be moved between a blocking position in abutment against the shoe, and a position of unlocking discarded from said shoe. The clamping element can be formed by a flexible end stop intended to wedge part of the cover against said shoe in the locked 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 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:

• 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 to Figure 1 showing the transverse stretching phase of the pleated 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 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;
• FIGS. 8 to 11 show the different stages of the covering process, respectively during the normal downward travel 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 load;
• Figure 12 shows a partial perspective view of the covering with removal of the pleated strand on the top of the pallet, leaving free the entry 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 Figures 4 and 5, the lower portion 12A inclined each finger 12 is provided with a rectilinear braking element 26, extending vertically projecting from the central area, and having a width L1 less than that L2 of finger 12. The base of the braking element 26 is secured to the movable support 28 of the finger 12, and its opposite end is located below the roller 13 lower without touching it. The value of angle A can be understood between 0 and 25 °.

The braking element 26 constitutes a compensation means arranged in the low accumulation zone where the play between the pleated cover 10 and the inclined lower part 12A of the finger 12 is the most important. The presence of the braking elements 26 on the four fingers 1 2 inclined limits the reduction of perimeter around the fingers 12, in allowing both an unobtrusive accumulation of folds in the lower part 12A, and a uniform and regular distribution of the pleats along the neighboring vertical edges A1 and A2. Transverse stretching cover 10 can then be operated as in figure 3 (arrows F3 and F4), by spacing the supports 28 in a horizontal plane at the four corners of the frame, and avoiding any creases irregular or pinched risk of tearing during the hooding.

In FIG. 6, a clamping element 30 is mounted on the support 28 of each finger 12, extending substantially at the level of the shoe drawing 22 above the motorized roller 14. Clamping element 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 stopper with a flexible end piece rubber, coming to bear in blocking position against the shoe drawing 22 to pinch the lower part of the cover 10 aux four corners.

The actuator 32 can be constituted by a control cylinder pneumatic, hydraulic or electric. The 24 geared motors four 14 rotating rollers are controlled by variable speed drives adjustable according to various parameters, and the direction of rotation can be reversed during the pleating and hooding.

It is thus possible to produce a terminal pleated strand 34 at the end of cover 10 during or at the end of the covering phase. It is enough to stop the lowering movement of the stretching frame at a predetermined location, and to switch the rollers 14 in the pleating pressing against the rollers 13, but 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 roller 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 palletized CH load following a double displacement of the four fingers 12 according to the arrows F6 and F7. From the figure 7A corresponding to the formation of the strand 34 according to FIG. 6, spread fingers 12 in a first translational movement indicated by arrow F6 (Figure 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 a precise removal of the strand 34 at any height level of the palletized load. Just stop the frame lowering stroke to a predetermined height, and to start the pleating phase for the formation of the strand 34 at by means of rollers 14 rotating in the direction of arrow F5. This process allows you to create either a mini cover at any level of the load or pallet, either sealing and maintaining the part of the CH load, i.e. the removal of the strand 34 on the top of the pallet allowing a precise clearance from the entry of a fork automatic palletizer, as shown in figure 12.

The presence of the clamping elements 30 also makes it more reliable the previous function, thanks to the wedging of the cover 10 in actuator locking position 32. A mechanical tension effect is thus generated in the upper vertical part of the sheath deposited while keeping the film stretched.

The different stages of implementation of the method are illustrated in Figures 8-11:

FIG. 8 shows the step of covering the load CH, following the transverse stretching phase of figure 3. During the race lowering of the finger support frame 12, the clamping element 30 is in a separated position, as is the roller 14 of pleating. The film of the cover 10 slides freely along the shoe 22 curved, and the unfolding of the folds is carried out gradually and without discomfort during the downhill race indicated by arrow F8.

In FIG. 9, the downward movement of the frame is stopped for the formation of a strand. The clamping element 30 of each finger 12 is actuated in the locking position by wedging the film against the shoe 22 in the four angles. After tilting the motorized roller 14 against the rollers 13, the strand is formed following the rotation of the roller in the direction of arrow F5.

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

In FIG. 11, the fingers 12 are brought together horizontally for the removing the strand 34 at a specific location of the CH load or of the pallet 36, followed by a movement to release the support 28 from the fingers 12 down according to arrow F7. The clamping element 30 is then actuated towards the unlocking position to release the strand 34 during its removal. The vertical part of the cover 10 remains taut when the pleated strand 34 is formed, and can even be stretched with a value of up to 5% to 50% of vertical elongation.

In fact, when handling loads, the vertical tension of the section of sheath that links the first layer of products with the pallet 36, is essential to ensure good load handling. Finally covering step, the vertical stretch associated with the strand deposited against the pallet, guarantees the stability of the load

In Figure 12, we note that the strand is placed just above the release of the pallet 36 to allow the entry of the fork of a palletizer.

With reference to FIG. 13, the clamping element 30 is deleted, and the end of the drawing shoe 22 is protruding enough to hold the strand at the top 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 sheath, opened by depression effect, and taken at four points by the frame of hooding.

Claims (15)

Method for placing on a palletized load (CM) a flexible packaging sheath obtained from a stretch film sheath, comprising: open the sheath for volume setting above the load, pleating the lateral parts of the concertina sheath on pleating fingers, using motorized rollers (14) rotating in a first direction of rotation (F1, F 2), then stretch the pleated sheath in the horizontal transverse direction to obtain an opening larger than the perimeter of the load (CM) to be packed, and move the stretched sheath over the load (CM) in a vertical direction, causing progressive unfolding during the covering stroke, characterized in that the inclination of the fingers (12) is between 0 and 25 ° relative to the vertical direction, and the reduction in the pleating perimeter around the fingers (12) is limited so as to obtain before the transverse stretching phase horizontal, an accumulation without discomfort and a regular distribution of the folds in the lower part (12A) of said fingers. Method according to claim 1, characterized in that during the covering phase, the lowering movement of the cover (10) is interrupted to a predetermined level, and a strand (34) is formed by rotating the rollers (14) in a second direction of rotation (F5) opposite to the first. Method according to Claim 2, characterized in that the deposited portion of the cover (10) is blocked against the drawing shoe (22) at the upper part (12B) of the fingers during the formation of the strand (34). Method according to claim 2 or 3, characterized in that the strand (34) is retained against a projecting part of the shoe (22) at the upper part of the finger. Method according to one of 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 vertical mechanical tension checked in the movie. Method according to claim 4 or 5, characterized in that the film of the cover (10) is stretched by a value between 5% to 50% of vertical elongation. Device for packaging a palletized load (CH) by means of a cover (10) made of a stretchable plastic film, and comprising: an operating frame equipped with pleating and stretching fingers (12), each finger carrying a stretching shoe (22), and being associated with a motorized roller (14) driven in rotation by a geared motor (24), means for tilting each motorized roller (14) between a spaced apart position, and a working position in contact with the finger (12), means for actuating the frame for carrying the load (CM), characterized in that the inclined lower part (12A) of each finger (12) is provided with means avoiding too great a reduction in the pleating perimeter around the fingers, and comprising a braking element (26) arranged in the lower region of accumulation of folds where the clearance between the pleated cover before the transverse stretching phase is greatest. Packaging device according to claim 6, characterized in that the braking element (26) is rectilinear, and extends vertically projecting from the central zone of the inclined lower part 12A of the finger (12). Packaging device according to claim 7 or 8, characterized in that the braking element (26) has a width (L1) less than that of the finger (12), and is secured by its base to the support (28) movable finger (12). Packaging device according to claim 8, characterized in that the opposite end of the braking element (26) is arranged under a roller (13) on which the motorized roller (14) is applied during pleating. Device according to one of claims 6 to 9, characterized in that a clamping element (30) is mounted on the support (28) of each finger (12) extending substantially at the level of the shoe (22) d drawing above the corresponding motorized roller (14). Device according to claim 10 or 11, characterized in that the clamping element (30) is associated with an actuator (32) to be moved between a locking position in abutment against the shoe (22), and an unlocking position removed from said shoe. Device according to claim 11, characterized in that the clamping element (30) is formed by a stop with flexible tip intended to wedge a part of the cover (10) against said shoe (22) in the locked position. Device according to one of claims 11 or 12, characterized in that the actuator (32) consists of a pneumatic, hydraulic or electric control cylinder. Device according to one of Claims 6 to 13, characterized in that the geared motor (24) of each roller (14) is controlled by a speed variator with reversal of the direction of rotation.

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