FR2846943A1 - Palleted load wrapping procedure using sleeve of stretch plastic film consists of pleating sleeve over fingers inclined at a specified angle - 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

1 2846943

  Palletized process and packaging.

  Technical field of the invention The invention relates to a process for placing a flexible packaging cover obtained from a load on a palletized load. '' a sheath of stretchable plastic, consisting of: - opening the sheath for the volume setting above the load, - pleating the lateral parts of the accordion sheath on pleating fingers, using motorized rollers turning 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 move the stretched sheath over the load in a vertical direction causing the progressive unfolding of the folds during the covering stroke.

  STATE OF THE ART The use of a stretch film sheath is well known for ensuring the stability and sealing of a palletized load. Unlike the heat-shrinkable film, the establishment of a stretchable sheath does not require a heat source, since it suffices to mechanically stretch the plastic film material beforehand in the horizontal transverse direction before wrapping the palletized load in wrap. After depositing the stretched sheath on the load, the stretching of the stretch film material occurs naturally by elasticity, which firmly holds the sheath around the load. 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 the reel, the opening of the sheath is effected by an action

  mechanical separation at the four angles.

  The packaging machines intended to thread a stretch film cover onto the load, have for this purpose a spacer device for opening the stretch film sheath, and a pleating device for pleating the accordion sheath on four integral fingers

of a support frame.

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

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

  covering following the transverse stretching phase.

  In FIGS. 1 to 3 representing the pleating and transverse stretching phases of a packaging machine of the prior art, the upper part 12B of each finger 12 is provided with a stretching shoe 22 having a curved shape advantageously adapted to the friction of the film during the pleating and unfolding steps. The vertical flank of the finger 12 can be equipped with one or two idle rollers 13, or be equipped with a fixed sliding coating with low friction, so as to pinch the sheath and to 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 separated position of rest (not shown), and a position

  working (Figures 1 to 3) in contact with finger 12.

  The four motorized rollers 14 are rotated in the 10 directions of the arrows F1 and F2 to ensure the pleating of the cover 10 by accumulating it in an accordion in the lower part 12A of the fingers 12. The top of the cover 10 has been closed beforehand by a welded joint 1 6. 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 held in abutment against the pleating fingers 12 so as to tension more or less strongly the upper horizontal part of the cover 10 during the transverse stretching. It is also possible to control the actuators 20 to separate the motorized rollers 14 during this stretching step so as to allow the film to slide partially on the fingers 12 while avoiding any possibility of tearing of the film. Such known mechanisms make it possible to obtain a transverse stretching rate greater than 10%. 25 The quality of the stretch sheaths makes it possible to obtain stretching

from 50% to 100%.

  The next covering phase is carried out by a vertical displacement of the frame over the load, so as to cause the progressive unfolding of the cover on the load. After removing the cover, the stretching of the stretch film material takes place 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 also create a vertical tension of the film on the load which also contributes to reinforcing the stability. This vertical tension is generated without any particular vertical stretching device, since a transverse stretch from 50% to 100% reduces the sheath height, and transmits to the load sufficient cohesive forces to ensure stability, therefore that this vertical tension is kept during

deposit it on the load.

  The angle of inclination A of the fingers 12 with the vertical direction makes it possible to facilitate the accumulation of folds during pleating by the motorized rollers 1 4. For a predetermined inclination, the clearance between the cover 10 and the fingers 12 gradually increases as one 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 smaller angle of inclination A of the fingers 12 would have the main disadvantage of interfering with the effect of accumulation of the folds, since the sliding of the film downwards could no longer take place naturally. The motorized rollers 14, in addition to their pleating function, must in addition exercise a second function

  of pushing down, which generates friction on the upper folds, with the risk of the formation of points or vertical lines of brittleness of the sheath before the transverse stretching phase.

  In document EP 633186, the stretch film is provisionally tightened laterally in the lower region of the load or of the

  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 stretching a packaging cover making it possible to obtain a free and regular accumulation without disorganization of the folds during the pleating phase before the transverse stretching, and avoid any risk of tearing of the film during the following stage of covering.

  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 stretching method according to the invention is characterized in that the inclination of the fingers is between 0 and 250 relative to the vertical direction, and the reduction of the pleating perimeter around the fingers is limited to obtain before the phase horizontal transverse stretching, an accumulation without discomfort and a regular distribution of the folds in the lower part of said fingers. The friction of the sheath which descends along the inclined fingers takes place on the two edges of the fingers. Any angle or protruding part on these edges could disrupt the folds. Disorganization of the folds after the stretching step may indeed disturb the unfolding during the 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 most important, prevents 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 avoid in a

  reliable tears during the next stage of covering.

  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 deposited with precision 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 of a

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 palletized load by means of a cover made of a stretchable plastic film, and comprising an operating frame equipped with pleating and stretching fingers, each finger having a drawing shoe, and being associated with a motorized roller driven in rotation by a geared motor, means for tilting each motorized roller 20 between a separated position of rest, and a working position in contact with the finger, and means actuation of the frame to carry the load. The inclined lower part of each finger is provided with means which avoid too great a reduction in the pleating perimeter around the fingers, and comprising a braking element arranged in the low zone of accumulation of folds or the play between the pleated cover before the stretching phase

transverse is the most important.

  According to a preferred embodiment, the braking element is rectilinear, and extends vertically projecting from the central zone 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 braking element 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 clamping element is associated with an actuator to be moved between a locking position in abutment against the shoe, and an unlocking position separated from said shoe. The clamping element can be formed by a flexible end stop intended to wedge a part of the

  cover against said shoe in the locked position.

Brief description of the drawings

  Other advantages and characteristics will emerge more clearly

  of the description which follows of an embodiment of the invention given by way of nonlimiting example, and shown in the drawings

  attached, 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; - Figures 7A-7C schematically illustrate the movement of a finger during the removal of the pleated strand on the load; - Figures 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 cover 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.

  With reference to FIGS. 4 and 5, the inclined lower part 12A of each finger 12 is provided with a straight braking element 26, extending vertically projecting from the central zone, and having a width L1 less than that L2 of the 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 below the lower roller 1 3 without touching it. The value of angle A can be understood

between O and 250.

  The braking element 26 constitutes a compensation means arranged in the low accumulation zone where the play between the pleated cover 1i0 and the inclined lower part 12A of the finger 12 is the most important.

  The presence of the braking elements 26 on the four inclined fingers 1 2 10 limits the reduction in perimeter around the fingers 12, allowing both an unobtrusive accumulation of the pleats in the lower part 12A, and a uniform and regular distribution of the pleats along the neighboring vertical edges Ai and A2. The transverse stretching of the cover 10 can then be carried out as in FIG. 3 (arrows 15 F3 and F4), by spacing the supports 28 at the four corners of the frame in a horizontal plane, and avoiding any formation of irregular or pinched folds risking tears during the hooding phase. In FIG. 6, a clamping element 30 is mounted on the support 28 of each finger 12, extending substantially at the level of the drawing shoe 22 above the motorized roller 14. The clamping member 30 is coupled to an actuator 32 so as to be moved between a locking position and an unlocking position. The clamping element 25 30 is formed by way of example by a stopper with a flexible rubber tip, coming to bear in the locking position against the shoe 1 2 of stretching 22 to pinch the lower part of the cover 10 to the

four corners.

  The actuator 32 may be constituted by a pneumatic, hydraulic or electric control cylinder 5. The gearmotors 24 of the four rotary rollers 14 are controlled by variable speed controllers adjustable as a function of various parameters, and the direction of rotation of which can be reversed during the pleating and hooding phases. It is thus possible to produce a terminal pleated strand 34 at the end of the cover 10 during or at the end of the covering phase. It is sufficient to interrupt the downward movement of the drawing frame at a predetermined location, and to switch the rollers 14 in pleating mode in abutment against the rollers 13, but by reversing the direction of rotation (arrow F5, figure 6) compared 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 FS.

  According to FIGS. 7A-7C, the stranded film of the cover 10 can then be deposited on the palletized load CH following a double displacement of the four fingers 12 according to the arrows F6 and F7. From FIG. 7A corresponding to the formation of the strand 34 according to FIG. 6, the fingers 12 are spread apart according to a first translational movement indicated by the arrow F6 (FIG. 7B), followed by a second orthogonal movement 13 of 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 level of height of the palletized load. It is sufficient to interrupt the downward travel of the frame at a predetermined height, and to start the pleating phase for the formation of the strand 34 by means of the rollers 14 rotating in the direction of the arrow F5. This process makes it possible to create either a mini cover at any level of the load or of the pallet, or the sealing and holding of the upper part of the load CH, or the removal of the strand 34 on the top of the pallet allowing precise clearance from the fork entry

  automatic palletizer, as shown in figure 12.

  The presence of the clamping elements 30 also makes the previous function more reliable, thanks to the jamming of the cover 10 in the locking position of the actuators 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 FIGS. 8-11: In FIG. 8 is shown the step of covering the load CH, which follows the transverse stretching phase of FIG. 3. During the lowering stroke of the finger support frame 12, the clamping element 30 is in a separated position, as well as the roller 14 of 1 4 pleating. The film of the cover 10 slides freely along the curved shoe 22, 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 corners. After tilting of the motorized roller 14 against the rollers 13, the strand is formed following the rotation of the roller 10 in the direction of arrow F5. In FIG. 10, the support 28 of the fingers 12 is then spread horizontally in the direction of the arrow F9. The clamping element 30 and the motorized roller 14 of each finger 12 remain in contact with the cover 15 during this spacing movement, so as to maintain correct positioning of the strand between the shoe 22 and the upper roller 13, and at keep the film tension in the part of the

cover already removed.

  In FIG. 11, the fingers 12 are brought together horizontally for the removal of the strand 34 at a precise location of the load CH or of the pallet 36, followed by a movement of release of the support 28 from the fingers 12 downwards according to the arrow F7. The clamping element 30 is then actuated towards the unlocking position to release the strand 34 25 during its removal. The vertical part of the cover 10 remains taut during the formation of the pleated strand 34, and can even be stretched

  with a value of up to 5% to 50% of vertical elongation.

  1 5 Indeed, during the handling of the loads, the vertical tension of the sheath section which links the first layer of products with the pallet 36 is essential to ensure good behavior of the load. At the end of the covering step, the vertical stretching 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 clearance of the pallet 36 to allow the entry of the fork of a palletizer.

  Referring to Figure 13, the clamp 30 is removed, and the end of the drawing shoe 22 is sufficiently protruding to retain 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 vacuum effect, and taken at four points by the covering frame. 1 6

Claims (15)

claims   1. Method for placing on a palletized load (CM) a flexible packaging sheath obtained from a stretch film sheath, consisting of: - opening the sheath for volume setting above the load, - pleating the lateral parts of the accordion sheath on pleating fingers, using motorized rollers (14) rotating in a first direction of rotation (F1, F 2), - then stretching the pleated sheath in the direction horizontal transverse to obtain an opening larger than the perimeter 15 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 20 0 and 25 relative to the vertical direction, and the reduction in the pleating perimeter around the fingers (12) is limited to obtain before the transverse stretching phase horizont al, an accumulation without discomfort and a regular distribution of the folds in the lower part (1 2A) of said fingers.   2. 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 the first.   3. Method according to claim 2, characterized in that the   deposited portion of the cover (10) against the shoe (22) stretching at the upper part (12B) of the fingers during the formation of the strand (34).   4. Method according to claim 2 or 3, characterized in that the strand (34) is retained against a protruding part of the shoe (22) at the upper part of the finger.   5. 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 controlled in the film.   6. 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.   7. 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 fingers (12) for pleating and drawing, each finger carrying a drawing shoe (22), and being associated with a motorized roller (14) driven in rotation by a geared motor (24), 1 8 - means for tilting each motorized roller (14) between a position apart from rest, and a working position in contact with the finger (12), - means for actuating the frame to carry the load lifting (CM), characterized in that the lower part (12A) inclined of each finger (12) is provided with means avoiding an excessive reduction of the pleating perimeter around the fingers, and comprising a braking element (26) arranged in the low zone of accumulation of folds o 10 the play between the pleated cover before the transverse stretching phase, is Most important.   8. Packaging device according to claim 6, characterized in that the braking element (26) is straight, and extends vertically 15 projecting from the central zone of the inclined lower part 12A. finger (12).   9. 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) moving finger (12).   10. 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 when pleating. 1 9   11. 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 ) stretching   above the corresponding motorized roller (14).   12. 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 blocking position in abutment against the shoe (22), and   an unlocked position separated from said shoe.   13. Device according to claim 11, characterized in that the clamping element (30) is formed by a flexible tip stop intended to wedge a part of the cover (10) against said shoe (22) in position blocking.   14. Device according to one of claims 11 or 12, characterized in that the actuator (32) consists of a control cylinder   pneumatic, hydraulic or electric.   15. Device according to one of claims 6 to 13, characterized in that   that the gear motor (24) of each roller (14) is controlled by a   speed variator with reverse direction of rotation.