DE60302588T2 - Method and apparatus for covering a stretch film hood over a palletized load - Google Patents

Description

Technical area of invention

• – Öffnen der Schutzhülle durch Abspreizen an den vier Kanten/Ecken zur Volumengebung über der Ladung,
• – Fälteln der seitlichen Bereiche der Schutzhülle nach Art eines Akkordeons um Fältel-Finger,
• – Strecken des gefältelten Schutzbezugs in transversaler Horizontalrichtung zum Erhalt einer Öffnung, die größer ist als der Umfang der zu umhüllenden Ladung,
• – und Bewegen der gestreckten Schutzhülle über die Ladung entlang einer vertikalen Richtung, wobei ein progressives Entfalten, gefolgt vom Spannen der Folie auf der Ladung beim Platzieren der Schutzhülle hervorgerufen wird.

The invention relates to a method for applying a flexible packaging protective cover, which is obtained from a stretchable film tube, on a pallet-packed charge, which consists of:

• Opening the protective cover by spreading it apart at the four edges / corners for volume distribution over the load,
• - crimping the lateral areas of the protective cover in the manner of an accordion around pleated fingers,
• Stretching the pleated protective cover in a transverse horizontal direction to obtain an opening which is larger than the circumference of the charge to be enveloped,
• And moving the stretched protective wrap over the load along a vertical direction, causing progressive unfolding, followed by tensioning of the foil on the load upon placement of the wrapper.

State of technology

The Using a stretchable film tube is to secure the stability and the tightness of a cargo packed on pallets. In contrast to thermally retractable film, the use of a stretchable film tube no heat source ahead, since it is sufficient the material of the plastic foil in advance mechanically in horizontal transversal To stretch direction before packing on pallets packed Cargo wrapped becomes. After applying the stretched protective cover on the charge turns the tightening of the foil material into natural Way by means of elasticity a, causing the protective cover is held tightly around the cargo.

Of the Hose is generally rolled up on a winding stored, and in its cross-section so contracted that he four bellows having. After unwinding the winding, the opening of the hose is through a mechanical action of a Abspreizens on the four edges / corners causes.

The packaging machines, which are intended to thread a protective film of stretchable film around the load, for this purpose have a splay device to open the stretchable film tube, and a device to the hose on four fingers Accordion- like to crinkle. According to the document EP 344815 For example, a welding device is placed between the splaying device and the crimping device to weld the hose, forming a weld joint. After welding, the tube is then cut transversely by means of a cutting device to realize an independent of the winding, and closed at its top protective cover. The pleated sheath is then stretched in a horizontal plane parallel to the weld, and located above the palletized load. The protective sheath is then unfolded and applied to and around the load according to a vertical movement from top to bottom.

In the 1 to 3 Each pleated finger extends 12 vertically and includes an empty roll 13 ("galet fou"), which is located near the upper end. Four motorized wheels 14 clamp the protective cover 10 against the inner rollers 13 and are set in rotation in the direction of the arrows F1 and F2 to the folding of the protective cover 10 make sure they are in the lower part of the fingers 12 Accordion-like accumulated.

The step of stretching the protective cover horizontally in the direction of arrows F3 and F4 is in FIG 3 shown. The motorized wheels 14 do not turn anymore, and can do so against the plucked fingers 12 be pressed down that the horizontally upper part of the protective cover 10 is stretched more or less strongly during the stretching.

Such allow known mechanisms it, on a reliable Assuming a maximum transverse stretching rate of the order of magnitude from 10% to 40%. Such a route nevertheless remains for certain Types of palletized cargoes insufficient, to the detriment of stability and the mechanical attitude of the palletized cargo. In the upper part, the badly stretched bellows form a substantial wind intervention, with risks of restraint of water, a tearing when stacking two Cargoes, insufficient tightness and an unaesthetic Aspect.

These Limiting the transverse stretching of the protective cover a relatively low rate has the development of this method slowed down, which is often used for over - surging applications bags limited, with the proviso that the latter are not unstable.

In parallel, the mechanism of the COVERPAL serving machine (registered trademark of the company Thimon) is described in detail in the document EP 1060988 described. In contrast to the previous in the document EP 344815 mechanism described are the operations for welding and cutting the hose to the protective cover 10 are formed during the covering of the previous charge, well before the application to the Fältel-fingers. The weld is then perfectly cooled because it undergoes transversal stretching and better resists the constraints of elongation when using the stretch tubing method.

According to the document DE 4307287 the enveloped charge has a transverse cross-section which is variable in the height direction. During vertical shifting, the plucking and stretching fingers are shifted horizontally to accommodate the profile of the load. Depending on the variation of the transverse cross section of the charge, the opening of the protective cover stretched by the fingers is reduced or enlarged.

According to the document DE 4235409 a first, diagonally opposite finger pair is placed to a first penetration length prior to the withdrawal of the protective cover, and after a predetermined time a second pair of fingers is displaced to a second penetration length which is shorter than the first one. After receiving the protective cover, the second pair of fingers are shifted horizontally outwards, followed ("suivi par la suite") by the first pair of fingers.

According to the document EP 1013549 For example, the protective sheath is formed by an elastic film which is applied against the charge with a longitudinal extension of at least 50% with respect to the protective sheath in the unstretched state.

Object of the invention

The The aim of the invention is to provide the method for stretching improve, and increase the stretch rate, taking the active and reactive Behavior of the hose and products packed on pallets at the steps of stretching the hose and applying it on the charge, as well as the later Behavior taken into account during transport and storage of the wrapped cargo becomes.

This The aim is achieved by the method according to claim 1.

Of the adaptable part of the hose can by means of motor-driven rollers, which when unrolling with the plucked and stretched fingers stay in contact, be unrolled, with the motorization of the rollers when rolling down the thickness reduction of the hose near the fingers limited. The motorization of the rollers when unrolling the hose takes place with a direction of rotation opposite to that is that when Akkordenfälteln is used, wherein the rolling during at least one part of the stretch path, and towards the end of the transverse stretch path preferably at a slow speed, plays.

The Releasing the adjustable part of the hose may further by Removing the motorized rollers during the stretching step, to remove them from the film and to allow the latter partly to slide on the fingers, the tearing of the Foil is avoided.

According to one Feature of the invention allows a step of crossing furthermore, the unfolding force of the tube in the transversal direction to limit by taking into account the relaxation of matter becomes. The effect of overstretching avoids tearing the hose during its application, and the pressing of angular products, especially on the upper layer of the cargo.

Of the Degree of transverse stretching of the tube can exceed 50%, preferably between 70% and 150%. The value of the transverse stretching path the finger can by means of a machine depending on different stored parameters, in particular the scope of enveloping Charge, the nature of the film, its thickness, and a correction factor, which depends on the nature of the palletized cargo become.

Around the protective cover the hose is welded in advance, then cut transversely, before being placed on the fingers, with the weld then when transversal stretching is cooled down perfectly. The stretching of the Protective cover collected on the fingers is in the pleated part the hose is relatively regular. Of the horizontal part, which includes the welding of the protective cover, consists of zones of different thicknesses. The stretching of this horizontal Part is irregular, and more pronounced especially in the zones near the extension fingers. From this results in a reduction in thickness in these zones.

• – man sammelt die Schutzhülle auf den Fingern, um über einen horizontal gespannten Teil zu verfügen,
• – man streckt die Schutzhülle transversal, wobei ein Teil der Folie regelmäßig entfaltet wird, um ihn gleiten zu lassen, um die Oberfläche dieser stark beanspruchten Zone zu verstärken.

To remedy this, proceed as follows:

• - you collect the protective cover on your fingers in order to have a horizontally tensioned part,
• The protective cover is stretched transversely, with part of the film being unfolded regularly to allow it to slide in order to reinforce the surface of this highly stressed zone.

The The invention further relates to a device for attaching a protective cover an extensible film according to claim 9th

According to a preferred embodiment, the pleat fingers on the upper part comprise Stre Curved shape wedges, which allow to limit the thickness reduction in the tube strip, which later comes into contact with the edges / corners of the / often aggressive palletized products. The stretch wedge of each finger includes a central zone that is curved in a horn shape with respect to the curved shape.

summary Description of the drawings

Other Advantages and features will become clearer from the following description an embodiment of the invention, which by way of non-limiting example, and under Reference to the accompanying drawings in which:

1 Fig. 2 is a schematic side view of an apparatus for crimping an extendable protective cover with which a packaging machine according to the prior art is supplied;

2 a top view of 1 represents;

3 one too 1 is identical view showing the phase of the transverse stretching of the pleated protective sheath;

4 Figure 3 is a schematic view of a finger driven by a maneuvering unit according to the invention during the phase of transverse stretching;

4-II one to that of 4 is identical view of an embodiment variant;

5 a plan view of the four maneuvering units according to 4 worn protective cover shows;

6 shows a perspective view on an enlarged scale of a plucking and stretching finger;

7 to 12 show different diagrams of the hysteresis cycle of a stretchable protective cover;

13 to 16 show the end of the covering process, with the attack of the end of the protective cover 10 located under the pallet.

description a preferred embodiment

Referring to the 4 to 6 becomes the pre-welded protective film 10 subsequently positioned on four maneuvering units UM, each consisting of a control slide 18 exist, which is intended to the Fältelungs fingers 12 along a direction (arrow F5) which substantially coincides / overlaps with the diagonal of the pallet.

Every tax sled 18 is driven by a (not shown) drive device, which may consist of a geared motor or a winch. The vertical or slightly inclined finger 12 is from the associated carriage 18 carried, and is arranged such that it is the crimping and collecting the tube on the base 12A of the finger 12 allows.

The top part 12B of the finger 12 is with a stretch wedge 22 provided, which has a curved shape, which is preferably adapted to the friction of the film in the pleating and unfolding steps. The vertical side of the top 12B of the finger 12 can with one or more empty roles 13 ("galets fous"), or consist of a fixed low-friction sliding plate to the hose when crimping by means of the motorized roller 14 pinch and move it down. The latter is by means of a geared motor 24 set in rotation, and by means of the drive device 20 against the finger 12 applied. During this crimping process, the roll turns 14 in the direction of the arrow F2 the 1 ,

The protective cover 10 is partially made to volume during the transverse stretching phase, and has five levels, one of which is horizontal 5 and four vertical pairs extend along the parallel sides. The horizontal plane is partially stretched, with the four ZA zones being maximally tensioned.

The gearmotors 24 the four rotating wheels 14 are controlled by speed varying devices, which can be controlled in dependence on various parameters, and whose rotation direction can be inverted during the crimping and stretching phases. In the rotational direction F2 of the rollers 14 the tube is crimped, and accordion-like on the part 12A the plucking finger 12 collected. While moving the sled 18 in the direction of F5 associated stretch phase remain the roles 14 in contact with the fingers 12 (please refer 4 ), and make it possible to stretch the film at an elongation rate of more than 50%. Towards the end of the displacement path of the sledges 18 in the direction F5, the geared motors become 24 operated in opposite rotational direction (arrow F6) to, preferably at a slow speed, a part of between the rollers 14 and the fingers 12 unrolled crimped hose. The thinning of the tube in the four corner zones of the horizontal plane of the protective cover 10 is then more limited, due to stretching stress being exerted on a larger surface due to rolling.

This phase of unrolling the pleated foil at the end of the sliding path of the carriages 18 makes it possible to better distribute the stretch of the upper horizontal part of the protective cover, and to obtain a wrapped load without excess material in the horizontal part of the bellows.

According to the variant of 4-II it is also possible to use the motorized wheels 14 to lift off during the stretching step, to remove them from the film, and to allow the latter, partly on the fingers 12 to slide, whereby the tearing of the film is avoided. The conception of the fingers 12 is intended to allow this sliding.

• – das Strecken in den stark gestreckten Außen-Teilen der Horizontal-Ebene der Schutzhülle 10, das heißt das Dünnerwerden und das Schwächen der Folie in dieser Zone, zu begrenzen,
• – die Reibung der Folie beim Abdecken auf dem gesamten Schlauch-Streifen zu reduzieren, welcher an den Eck-Produkten der Ladung zum Andruck gelangt. Diese Produkte weisen häufig einen vertikal vorstehenden Grat auf, wie Kanten/Ecken von Kartons oder Trennblätter, welche Riss-Auslösestellen für den Schlauch bilden können.

In 6 includes the stretch wedge 22 from each finger 12 a middle zone 26 , which is retracted horn-shaped with respect to the curved shape. The presence of this middle zone 26 allows:

• - Stretching in the strongly stretched outer parts of the horizontal plane of the protective cover 10 that is, thinning and weakening of the film in this zone,
• - To reduce the friction of the film when covering on the entire hose strip, which comes to the corner products of the load to the pressure. These products often have a vertically protruding ridge, such as edges / corners of cartons or divider sheets, which can form tear release points for the hose.

The stretching of a polyethylene tube results in a hysteresis cycle predetermined by the material, which is shown in the diagrams of FIGS 7 to 12 can be shown.

In transverse stretching, a piece of polyethylene tubing follows the hysteresis cycle of the 7 , The threshold of plastic flow A is quickly reached at the beginning of the stretch path, whereas the tear threshold B occurs when a limit strain is reached. The slope of the curvature between the thresholds A and B is weaker than that at the beginning of the expansion path. In the stretch zone between A and B is the desired stretch.

After stretching is the rapid loosening of the stretched film by the relaxation cycle of 8th shown. The film in the example remains at about 30% of the maximum elongation reached at the initial stretch of 100%.

When the film is held in the extended position under the action of a force F without loosening at 100%, as in FIG 9 To see, after a certain time a temporally progressive reduction of the force is determined, which is necessary to maintain the extension. The loss of stretch force is due to the relaxation of the elastic material, and is on the order of 50% after 48 hours of use.

The necessary for stretching the hose essential forces, and the friction on the fingers when covering, take risks of a tearing, by pressing of the products and a lowering of the corner products by itself. Of the Effort to sustain the stretch is transferred to the charge via cohesive forces. Unfortunately, the relaxation reduces these cohesive forces, and the essential forces for Stretching and covering can not transmitted by high cohesive forces become.

With reference to 10 , and taking into account the expansion / relaxation cycle of 8th , it is possible to predict the relaxation phenomenon, which reduces the holding forces of the charge.

• – Dehnen;
• – Verminderung der Dehnung beim Aufbringen auf die Ladung während des Abdeckens, wobei das Vermindern von dem zum Durchgang der Finger 12 und der Schutzhülle 10 um die Ladung beim Abdecken notwendigen Über-Umfang herrührt. Dieses Spiel wird entlang eines Intervalls in der Größenordnung von 5 bis 8 cm gleichmäßig auf/um die Ladung verteilt,
• – Relaxation des Materials.

When using an extensible tube on a prior art machine, the steps to stretch the film include three separate phases:

• - stretching;
• - Reduction of stretch when applied to the charge during capping, decreasing from that to the passage of the fingers 12 and the protective cover 10 to the charge when covering necessary over-circumference. This game is evenly distributed on / around the load along an interval of the order of 5 to 8 cm,
• - Relaxation of the material.

11 represents the previously stated hysteresis cycle with three phases. It will be noted that the forces maintaining the stretch between the stretch phase to point B, and at the moment when the film contacts the charge at C, are slightly reduced. The frictional forces of the film on the fingers 12 however, when deployed at point B and the forces of applying the film to the charge at point C, they remain significantly higher than the remaining forces useful for charge stability after 48 hours (item D).

The stretching method according to the invention is to overstretch the tube to bring it to a circumference which is greater than that which is necessary for the protective cover. To enable this over-routing, the control sleds point 18 , the finger 12 and the roles 14 For this purpose, a displacement path which is greater than that which is necessary for the protective envelope of the charge. The value of this transverse stretching path can be adjusted depending on various parameters, in particular the extent of the charge to be wrapped, the nature of the foil, and so on. For this purpose, a (not shown) machine is used to supply the geared motors 24 the roles 14 to control, and the displacement of the control slide 18 drive.

• – Strecken: OA, AB, dann BB';
• – Entspannen: Verringern der Streckung B'C';
• – Entfalten bei C'
• – Aufbringen auf die Ladung bei D.

Referring to 12 are fingered immediately after the overstretching has been effected 12 returned to a position which corresponds to the usual extent for the capping phase. The stages of the cycle are the following:

• - Routes: OA, AB, then BB ';
• - Relax: Reducing the stretch B'C ';
• - unfold at C '
• - Applying to the charge at D.

The on the machine established program is dependent from the circumferences of the hose and the charge for calculated a point D, wherein the restoring force (force to maintain the extent at the periphery of the charge) is substantially equal to F / 2, where F is the force of extension at points B or B '.

By means of this special cycle of the invention, the frictional forces of the film on the fingers 12 when unfolding, thereby making it possible to avoid tearing of the film and to facilitate deployment. The power of applying the film to the products is optimized, avoiding any subsequent reduction over time due to the relaxation phenomena. Pressing of the product is avoided and the cohesive force of the charge is kept at the maximum that possible for the film.

The 13 to 16 show the end of the covering process, the attack of the end of the protective cover 10 is under the pallet, which is on the transporter 28 is arranged.

The protective cover 10 gets on the four stretch wedges 22 placed in pairs on a pair of longitudinal longitudinal members 30 . 32 are mounted, which are parallel with respect to the transporter 28 extend. In the last step of covering, the side members are lowered 30 . 32 (Arrow R1, 13 ) on both sides of the transporter 28 off while the wedges 22 be positioned below the placement plane of the palletized cargo. A small part of the film is on the four wedges 22 accumulated and the pincers avoid any anticipated sliding of the film.

The wedges 22 are then translated by a translational movement along each side member 30 . 32 approached each other (arrow R2, 14 ). The film is positioned under the four edges / corners of the plane of the cargo, and completely leaves the stretch wedges 22 , The latter are by a vertical movement of the transporter 28 averted (arrow R3, 15 ).

Such a cycle makes it possible to avoid any lifting movement of the palletized load, to the horizontal displacement of the fingers 12 towards the center of the cargo. It allows the film to be press-fitted against the four edges / corners of the cargo's positioning plane without risking tearing of this stretched film. The good coupling of the stretched protective cover at the corners / edges makes it possible to guarantee the stability of the wrapped cargo.

Claims (12)

Method for applying a flexible packaging protective cover to a pallet-packed load, which protective cover is obtained from a stretchable film tube, which method consists of the following steps: opening the protective cover ( 10 ) by spreading at the four corners to bulk over the charge, - folding the lateral areas of the protective cover in the manner of an accordion around the fingers ( 12 ) for crimping and stretching, - stretching the crimped protective cover ( 10 ) by spreading the fingers ( 12 ) in transverse horizontal direction to obtain an opening which is larger than the circumference of the charge to be enveloped, - and moving the stretched protective cover ( 10 ) over the charge according to a vertical direction, wherein the folds are gradually pulled apart and the film is then wrapped around the charge ( 10 ), characterized in that - the transverse extension stroke of the fingers ( 12 ), depending on parameters relating to the properties of the film and the dimensions and type of products of the cargo, so that the hose is overstretched to bring it to a circumference greater than the opening required for the protective casing , And then the fingers ( 12 ) returns toward the first position so that the tube is pressed onto the palletized load with a lateral cohesive force substantially equal to half the force of transverse extension. A method according to claim 1, characterized gekenn characterized in that an adaptable part of the pleated tube during the process of transversal stretching of the protective cover ( 10 ), whereby this loosening of the adaptable part of the hose by creating a gap between motor-driven rollers ( 14 ) during the stretching process to remove them from the film and to allow this, partially on the fingers ( 12 ) to glide. A method according to claim 1, characterized in that the adaptable part of the hose by means of motor-driven rollers ( 14 ) in contact with the pleats and stretch fingers ( 12 ), whereby the motorisation of the rollers ( 14 ) when rolling the thickness reduction of the hose near the fingers ( 12 ) limited. Method according to claim 3, characterized in that the motorisation of the rollers ( 14 ) when unrolling the hose with a direction of rotation opposite that used in accordion folding, with unrolling occurring during at least part of the stretching operation. Method according to claim 3 or 4, characterized that unrolling a part of the crimped tube to the end the transverse extension path is at slow speed. Method according to claim 1, characterized in that that the initial one Degree of transverse elongation of the hose over 50%, preferably between 70% and 150%. Method according to one of claims 1 to 6, characterized in that the value of the transversal stretching and hyperextension stroke of the fingers ( 12 ) is adjusted by means of a machine depending on different stored parameters, in particular the extent of the charge to be wrapped and the properties of the film. Method according to one of claims 1 to 7, characterized in that the cut-off tube for the production of the protective cover before putting on the fingers ( 12 ) is welded; the weld is optimally cooled during transverse stretching. Device for applying a stretch film protective cover to a pallet-wrapped load, comprising: - means for opening the protective cover ( 10 ) by spreading at the four corners to bulk over the charge, - means for crimping the lateral areas of the protective cover in the manner of an accordion around the pleat and stretch fingers ( 12 ), - means for stretching the plaited protective cover ( 10 ) by spreading the fingers ( 12 ) in transverse horizontal direction to obtain an opening which is larger than the circumference of the charge to be enveloped, and means for moving the stretched protective sheath (US Pat. 10 ) over the charge according to a vertical direction, wherein the folds are gradually pulled apart and the film is then wrapped around the charge ( 10 ), characterized in that it comprises: - a machine with a program created for applying the method according to one of claims 1 to 8, - and a control carriage ( 18 ), which is intended to increase the transverse extension stroke of the fingers ( 12 ), depending on parameters relating to the properties of the film, and on the dimensions and type of products of the cargo, so that the hose is overstretched to bring it to a circumference greater than the opening required for the protective casing lies, and then the fingers ( 12 ) to return to the first position so that the tube is pressed onto the palletized load with a lateral cohesive force substantially equal to half the force of the transverse stretch. Device for attaching a protective film made of a stretchable film according to claim 9, characterized in that it comprises rollers ( 14 ) by means of geared motors ( 24 ) are driven with reversal of the direction of rotation, in each case when the hose is crimped around the fingers ( 12 ) and when unrolling the tube at the end of the transverse extension. Device for attaching a protective cover made of a stretchable film according to claim 9 or 10, characterized in that the pleats and stretch fingers ( 12 ) in the upper part ( 12B ) Stretch wedges ( 22 ) each having a central area recessed with respect to the crescent shape ( 26 ), which allows limiting the reduction in thickness in the strip of tubing which later comes into contact with the corners of palletized products. Device for applying a protective film made of a stretchable film according to claim 11, characterized in that the pleats and stretch fingers ( 12 ) in pairs on a pair of side members ( 30 . 32 ) are mounted parallel to the conveyor ( 28 ), wherein the fingers for positioning the film under the four corners of the plane of the load on each side rail ( 30 . 32 ) approximated and can be removed from each other.