ES2446387T3 - Wrapping apparatus with vertical curtain with multiformat feeder - Google Patents

Abstract

Procedure for wrapping loads loaded on pallets with a film of plastic material, the method providing a wrapping of the load (C) when passing through a curtain of film (P) that comes from at least one storage coil (8- 83) arranged on a first side with respect to a transport line (1) of the load (C), and temporary winding means (19, 20) that can move transversely (XX) with respect to said transport line ( 1), rotating said temporary winding means (19, 20) in a first direction to initially accumulate a film length (P) equivalent to a perimeter part of said load (C), detected and calculated in a preliminary packing phase, and then, turning in a second direction to supply the same length of film (P) during the dragging of said film curtain (P) by means of the load (C), characterized in that at least some transfer means are also provided (12), capable of presenting a final edge of said film from said at least one storage coil (8-83) to the gripping means (21) of said temporary winding means (19, 20) by means of support means and presentation (17) both said temporary winding means (19, 29) and said transfer means (12) are subsequently transferred transversely (XX) with respect to said transport line (1) to arrange said plastic film curtain (P ), first, said transfer means (12) are connected to a movable coupling bar (18) provided with an independent drive control with respect to a motion control of said temporary winding means (19, 20), finally, said means of transfer (12) connected to said mobile coupling bar (18) and said means of temporary winding (19, 20) converge with each other in a central line work zone, where welding and c operations take place film film to define said load wrapping (C).

Description

Wrapping device with vertical curtain with multiformat feeder.

5 Field of the invention

The present invention relates to an improved apparatus for the packaging of products stacked on pallets, hereinafter referred to as the term "cargo", by a film of plastic material. In greater detail, it refers to an apparatus that allows to wrap loads that arrive sequentially, along a line of

10 transport, to a wrapping station in which a plastic film curtain is arranged.

Prior art

As is known, there are several techniques for wrapping pallet mounted loads. When you want to wrap a

15 loading with a plastic film during the movement of the same in a transport line, normally a curtain wrapping equipment is used. In particular, said equipment extends a curtain of plastic film, held in a vertical plane, transversely with respect to the route of the transport line: when the load reaches the plastic film, it pushes it in its same movement, until it starts of the film is guided and stretched properly also on the sides of the film and then on the back surface. In

In relation to the rear surface of the load (with respect to the direction of advance), the film is then welded behind the load and thus cut to begin the cycle with a subsequent load.

Because under these conditions the loads typically have different heights, it is necessary to provide an adjustment of the height of the film curtain, the operation of which is carried out using coils

25 film with different heights.

For this purpose, a conventional multiformat wrapping machine has a plurality of curtains with different heights, successively together with the transport line. Depending on the height of the film to be used, the desired curtain is maintained in proximity to the transport line and the others rise from

30 so that they are well above the transit route of the cargo.

This construction procedure is convenient and effective, also in terms of speed of format change, but has a cost proportional to the amount of different curtain heights that must be provided, which makes it extremely expensive when two or more must be managed. three heights

35 different.

Alternatively, rotating multiformat wrapping machines have proven extremely effective.

A significant example, which represents the prior art closest to the present invention, is the one disclosed in the patents IT 1 356 529 and EP 2 452 881, both in the name of the same applicant, whose content is comprised in its whole in the present application, for a better understanding of the invention.

The wrapping machine described in these documents uses a pair of clamping carts, which move

45 transversely to the transport line and capable of transferring two opposite edges of films of equal heights to the center of the line, edges removed from respective coils belonging to storage stations arranged on both sides of the transport line.

Each side station supports an equal plurality of wrapping film reels, mounted so that

50 can turn. The rotating movement is synchronized with that of the mobile carriages, so that the coils (of desired height) are moved to the extraction positions of the carriages in a synchronized way on both sides.

This equipment has implied an improvement of the market with respect to the prior art solutions, due to

55 which has a cost that is not affected in its entirety by the amount of coils used and, thus, is economically preferable when there is a large number of different heights (for example, 6 coils).

However, the present applicant has noted that other improvements can be made.

60 In fact, an extremely important, if not essential, factor in carrying out the new lines for wrapping, but especially for reconstructing the existing lines in limited spaces, is the containment of the wingspan. Currently, the equipment according to the two documents mentioned above implies, especially due to the presence of two coil loading platforms on the two sides of the transport line, a considerable general transverse span which, often, cannot find a suitable place not even in buildings

65 industrial buildings of recent construction.

In addition, the simultaneous use of two coils, despite providing an important length of film and, thus, reducing downtimes (necessary for the replacement of worn coils), inevitably produces waste. In fact, the two opposite coils are not worn at an identical speed (some consumption asymmetry always takes place, if the position of the load is not always perfectly aligned in the center line between two rotating supports) and when a coil is spent, the other could still have a few meters of film, however, it is replaced so as not to have twice the downtime: this implies a waste of material.

Wrapping machines have also been suggested in which the curtain is formed using, on the one hand, a coil that acts as a film storage and, on the other hand, a temporary storage device. Equipment of this type is generally known from US Patent No. 3 910 005 and EP 516 602. These documents set forth the general principles of use of a single storage coil in cooperation with a temporary reserve cylinder, but no operation details are provided in the best configuration. In fact, these systems have remained at the presentation sample level, but they have never been developed industrially with practical solutions that are economical and viable enough for industrialization.

Summary of the invention

The objective of the present invention is to propose an apparatus for multiformat and curtain wrapping, which continues to use a plurality of storage coils and a temporary reserve cylinder, which solves the problems encountered in the prior art.

This objective is achieved thanks to the features described in the appended claims. In particular, according to a first aspect of the invention, there is provided a method for wrapping palletized loads with a plastic film, said method comprising the steps of wrapping a load after passing through a curtain of film from at least one storage coil arranged on a first side with respect to the load transport line, and temporary winding means that can be displaced transversely in said transport line, where at least some transfer means are also provided, suitable for presenting a final edge of said film from said at least one storage coil in the gripping means of said temporary winding means by support and presentation means, then said temporary winding means and said transfer means transverse in said transport line to arrange said plastic curtain, connecting di The transfer means firstly to a mobile coupling bar with an independent drive control with respect to a motion control of said temporary winding means, and wherein said temporary winding means rotate in a first direction to initially accumulate a film length equivalent to a perimeter part of said load, detected and calculated in a preliminary packing phase and then rotated in a second direction to supply the same film length during the drag of said film curtain

(P) by the load and, finally, said transfer means connected to said mobile coupling bar and said temporary winding means converge with each other in a work zone in the center of the line, where welding and welding operations take place. film cutting to define said load wrapping.

According to a preferred aspect, the motion control of said mobile coupling bar depends on the movement of said temporary winding means along said transverse direction to said transport line, whose end of travel is reached when said gripping means face the welding means at the end of said phase of supply of the film curtain.

Additionally, a rotation control of said temporary winding means is preferably coordinated with a translation control of the same temporary winding means and said mobile coupling bar, so that the complete unwinding of the film temporarily accumulated in said means of Temporary winding takes place when said temporary winding means and said transfer means meet together.

According to another aspect, said support and presentation means are mounted floatingly on said transfer means, so that they recede, after having presented said final edge of the film to the gripping means, until they expose a pair of sliding elements in contact with said film.

According to a different aspect of the invention, a curtain wrapping apparatus using a plastic film is provided, said apparatus comprising at least one input frame defining a transport line of the loads to be wrapped, at least one support that holds a series of film reels to select a feed reel based on the characteristics of the load to be wrapped, as well as transfer means that can be moved along a transverse transfer path to said transport line and capable of extracting a film edge from a coil selected between said coils, so that a film curtain is defined for application around the load to be wrapped during its advance, also providing first means welding and cutting mounted on said transfer means, which are also provided

temporary winding means, opposed to said support with respect to said transfer means, capable of temporarily accumulating a certain length of film from said transfer means, said temporary winding means being also able to move along said travel path.

5 transfer, so that they move away and approach with respect to said transfer means and define a film curtain having an extension at least equal to the moving front part of said load to be wrapped, and where

said temporary winding means comprise a tubular winding / unwinding element actuated in

10 rotation, provided with gripping means capable of retaining a final edge of film from said transfer means, as well as second welding means suitable for cooperating with said first welding means in a working position in which said transfer means and said temporary winding means are close and cooperate,

15 said transfer means are arranged so that they alternately engage with a fixed post of the apparatus, in a starting position, and with a controlled mobile coupling bar transverse to said transport line, in a working phase for wrapping,

said mobile coupling bar is controlled so that it can be moved approaching / moving away with respect to said temporary winding means and independently of them, and

a plurality of support and presentation elements are provided capable of presenting a final film edge to said gripping means, mounted so that they are projected and can be retracted at different heights along said transfer means.

According to another aspect, said support and presentation means are mounted floatingly on said transfer means, so that they can be moved back and allow a pair of sliding elements to come into contact with said film. Preferably, said sliding elements are crazy rollers that provide a substantially vertical axis, mounted on said transfer means.

30 According to an additional aspect, said floating support and presentation elements are kept retracted by elastic means and advance to the presentation position when they come into contact with end-of-travel stop means, while exceeding the tension of said elastic means when said transfer means are brought to said resting position. Preferably, the floating support and the

35 presentation elements are in the form of a plurality of sheet-shaped forks, adapted to support as a flag a film-free end edge, said gripping means of the tubular winding / unwinding element being suitable for arrangement between the pins. of said forks.

According to another aspect, the tubular winding / unwinding element is actuated in its rotation so that

40 wind a film length substantially equivalent to half the perimeter in plan of the load to be wrapped, said perimeter being detected upstream of said transfer path axis. Preferably, the tubular winding / unwinding element is rotated in a coordinated manner with a translation control of said temporary winding means and said transfer means, so that substantially the complete unwinding of the temporarily wound film in the themselves takes place when

Said temporary winding means and said transfer means are close to each other in said working position and said gripping means (21) face said welding means.

Brief description of the drawings

Other features and advantages of the invention are apparent from the following detailed description of a preferred embodiment, given only by way of non-limiting example and illustrated in the accompanying drawings, in which:

Figure 1 is a schematic top plan view of a wrapping station according to the present invention, during the closing stage of a wrapper;

Figure 2 is a view, similar to that of Figure 1, showing only the detail of the load at an intermediate stage of the wrapping process;

60 Figures 3 and 4 are top plan views in greater detail of the film transfer means, in the initial film clamping stage, from the storage station and subsequent extraction, respectively;

Figure 5 is a front elevational view of a wrapping station according to the present invention, showing the transfer carriage in the rest position;

Figure 6 is an elevation view, on an enlarged scale with respect to Figure 5, of the transfer carriage in the rest position; Y

Figure 7 is an enlarged view of Figure 1 of the single detail in the welding and cutting work area.

Detailed description of the invention

As shown by the top plan view of Figure 1, the wrapping apparatus according to the present invention provides, in a known manner, a transport line 1 for the progression of loads C, which moves in the direction indicated with the arrow F. This transport line 1 is schematized in Figure 1 by a pair of rails parallel to the longitudinal axis YY of the transport line 1 or, in Figure 5, by a single roller unit 1A with perpendicular cylinder axes to the YY axis.

The transport line 1 runs through an input frame consisting of a pair of posts, one inside 2 and one outside 3, and two transverse elements, one lower 4 and one upper 5, the details of which will be described below.

The entrance defines a pair of rails for the displacement, arranged transverse with respect to the direction of advance F of the transport line, and defining a transverse transfer axis XX, where two transfer carriages can be moved which will be illustrated with more detail below.

Also, a support is provided for holding the coil 6 on the side of the line 1, that is, beyond the inner post 2 with respect to the transport line 1. In said support 6 the plastic film coils are installed which make up the device storage coils. The drawings show, as an example, a support of the rotating type, that is to say essentially consisting of a disk-shaped platform 61 that rotates on a central bolt 6 and a plurality of rotating shaft support spindles 7, 71, 72, 73 where the individual coils are mounted; In the embodiment shown, only four support spindles are provided, for greater clarity of the drawing, but it is obvious that this quantity can be selected as desired depending on the type of intended use.

Each of the spindles 7-73 supports in free rotation mode a shaft with a final T-shape, where a respective coil 8, 81, 82 83 is interlocked for wrapping film P. The different coils mounted on the support 6 typically they have different heights (or other differentiated characteristics that are useful for wrapping the different loads C that pass in the transport line).

Next to the rotating support 6, in a fixed position on the ground, a drive assembly 9 is provided, which determines the brake rewind or the controlled rewind of the coil with which it cooperates. In particular, the drive assembly 9 is arranged so as to cooperate with the coil which, in turn, is selected each time to interact with the transfer carriages and to form the film curtain for wrapping P.

To that end, the assembly 9 comprises a support frame 91 mounted so that it can rotate in the horizontal plane in a vertical bolt 92 under the action of a pneumatic cylinder 93. In the frame 91 a pair of wheels 10 are also mounted, of rubber or other material capable of cooperating with the surface of the coil, which rotate in a respective vertical bolt under the control of a respective motor 11.

The wheels 10 preferably have a large size, for example a radius and a thickness of 80 mm, so that they have a large bearing surface against the lateral surface of the respective coil; in this way, the driven rotation of the coil with which they come into contact is guaranteed, under the thrust of the cylinder 93, but without excessive specific pressure, so that the film is protected.

The film P from each coil is guided along a path to the first respective carriages or transfer means (one for each coil) mentioned in general with references 12, 121, 122, 123, respectively. In this step, the film runs on respective rocker rollers 13, 131, 132, 133, supported by an equal number of rocker arms 14, 141, 142, 143, as schematically explained in Figure 1, which have the function, already known, to transfer the tension changes of the film in angular displacement of the arms 14-143: providing this displacement, detected by a suitable detector or encoder 15, a retroactive signal to proportionally drive the motor 11 and, thus, impart a faster or slower turn to the coil, in the correct direction (winding / unwinding) to maintain the tension of the film at the desired level.

In fact, during the realization of the wrapping of the load C, the film P can undergo tension peaks or loosening phases, which must be secondary by the rewind speed of the coil to prevent said film from breaking or becoming excessively loose. (which could lead to a malfunction). In addition, at the stage of rewinding the film, between one load and the next, as will be seen later, it is necessary to rewind the coil in a controlled manner, so that there is no over-tensioning or tensioning in the film.

In a position opposite to the storage coils 8-83, the apparatus comprises a winding / temporary storage assembly, generally mentioned with reference 19.

This temporary storage assembly 19, in turn, is mounted so that it can be moved along the transverse guides of the input frame, along the same manipulation axis XX of the first transfer means 12. To this end, also the translation of the assembly 19 is controlled through a corresponding drive system (illustrated below), in a part of the path opposite to that of the transfer means 12.

According to the invention, the management of the film and its transfer from the transfer means to the temporary winding assembly 19 takes place in an original and efficient way.

Each of the first transfer carts 12-123, one for each storage coil 8-83, consists of a mobile vertical bar 16 (which can be best seen in Figures 5 and 6), which defines a groove / path to through which the final edge of film P passes, leaving the respective coil. In the resting stage, said final edge of the film leaves the bar 16 and is supported as a flag (in a vertical plane) by a plurality of forks in the form of a sheet 17, distributed in a vertical direction so that they can withstand all film heights provided in use; as an example, in figure 5 five forks 17 are shown and in figure 6 only four are shown, for clarity of the drawing.

Thus, the forks 17 are intended to maintain a free edge of film P perfectly arranged in a vertical plane and a mechanically defined position.

The vertical bar 16 of each first transfer carriage is mounted so that it can slide transversely to the transport line 1 (X-X path) in the slide guides defined in the input frame, as illustrated below. The transverse movement of the bar 16, along the axis XX, is guaranteed by upper and lower guides 16 'suitable for assembly with respective rails in the input frame, whose structure is within the reach of one skilled in the art and , thus, will not be described in detail.

In the resting stage, that is, when the respective coil is inoperative, the bar 16 is held securely attached to a fixed origin post 16a integrated with the support 6 of the rotating storage unit, in proximity to the coil respective. For this, coupling means are provided, for example two ratchet devices 16b, which can be operated to open and close, which hold the adjacent bar 16 and assembled with the origin post 16a.

In this state, the film must be prevented from moving longitudinally, losing the correct positioning with respect to the sheet-shaped forks 17: for this, first padded locking handles 16c (figure 3), integrated with the post, are provided of origin 16a, which keep the film pressed against the bar

16. A number of locking grips 16c, arranged in a vertical direction, is sufficient to maintain the relative position of the fixed film with respect to the sheet-shaped forks 17, until the bar is attached to the origin post 16a by ratchet devices 16b.

The locking handles 16c are preferably operated by springs, while their opening is operated by a pneumatic control, so that retention is also guaranteed when the compressed air supply is lost.

A cutting and welding unit 16s, already known, is also mounted on the transfer rod 16. Said unit 16s is mounted so that it protrudes from the leading edge (that is, the edge at the exit of the film, the left edge in Figure 3) of the bar 16.

At the leading edge of the transfer bar 16, two vertical axis cylinders 17a and 17b are also preferably provided, mounted close to each other on both sides of the sheet-shaped forks 17. In said cylinders the plastic film P must slide during the welding and cutting work stage, which will be illustrated below, replacing at that stage the sheet-shaped fork 17 in the guidance and support of the film. In fact, the forks 17 are effective for supporting the film as a flag and presenting it to the temporary winding assembly 19 during the clamping stage (as will be seen below), but it would end up spoiling the film when it is in an orientation. oblique in the stage of supply in the load, as well as in the final stage of welding and cutting.

For said purpose, according to a preferred embodiment, the sheet-shaped forks 17 are not mounted directly on the transfer bar 16, but are mounted on a floating frame 17c, mounted so that it can be moved perpendicularly to the leading edge of bar 16 in the vertical plane.

In the embodiment shown, the frame 17c is guided in its movement by guide rods 17d and is retained in a final travel return position by elastic means 17e. In summary, frame 17c is

it pushes so that it retracts with respect to the transfer bar 16 by elastic means 17e, so as to cause the leaf-shaped forks 17 to retract with respect to the cylinders 17a and 17b (orientation illustrated in Figure 4).

When the transfer bar 16 is released (ratchet devices 16b open) and is separated from the origin post 16a (working stage for wrapping), the forks 17 are kept retracted with respect to the cylinders 17a and 17b, so that the film P leaving the transfer carriage 12 rests on said cylinders 17a and 17b.

On the contrary, in the rest position, when it is necessary to retain the film P as a flag by means of the sheet-shaped forks 17 (stage of presentation of the film to the assembly 19), the position of the transfer bar 16 is such , that the guide rods 17d stop at the end stop travel 17d ', integrated with the origin post 16a. The position of the end-of-travel stop 17d 'is such that the guide rods 17d, with whose frame 17c are integrated, stop against it before the transfer bar 16 completely recoils (Figure 3); this results in the final recession stage of the bar 16 towards the post of origin thereof, in a relative displacement of the frame 17c with respect to the transfer bar 16, overcoming the elastic reaction of the elastic means 17e, which causes the sheet-shaped forks 17 to exit outward / forward with respect to the cylinders 17b (orientation of Figure 3).

In summary, which is important for the operation to be described below, the sheet-shaped forks 17 are mounted so that they can be retracted, so that they retain the edge of the film only when the first transfer carriage 12 is in the retracted rest position, but in all other positions adopted by the transfer bar 16, along the path in the transverse guides to the transport line 1, the film edge is supported and guided by the cylinders 17b while the forks 17 are retracted.

The transfer bars 16 in the respective transfer carriages 12 are, in all the coils that are inactive, in a rest position, coupled to the origin post 16a integrated with the rotating support 6, with the sole function of keeping in the plane vertical and in the correct clamping position the film coming from the coils.

On the contrary, in the case of the work coil, the transfer bar 16 is arranged carefully aligned with the guides integrated with the input frame, so that it is available for a transfer in the T direction (i.e. along from axis XX transverse to the direction of advance of the load F), for the function described below.

For said purpose, in the transfer guides of the input frame, it is mounted so that a coupling bar 18 can slide. Said coupling bar provides second coupling devices 18a, for example, controlled ratchet and gear coupling means. very similar to the 16b provided in the post of origin 16a. The coupling bar 18 is actuated in its translation, for example, by means of kinematic chain mechanisms driven by an electric motor, and its function is to extract and move the transfer bar 16 of the transfer carriage 12.

In particular, when the desired coil is arranged in the correct delivery position, with the transfer carriage 12 aligned with the transverse direction of travel T, the coupling bar 18 approaches (from left to right in Figure 5) to the transfer bar 16, so that it is coupled thereto, using the coupling devices 18a and a support shelf 18a 'that are coupled with coupling bolts 18b provided in said bar 16. After releasing the assembly with the post of origin 16a (opening the ratchet devices 16b), the coupling bar 18 can drive the displacement with its own transfer bar 16 along the transverse guides. The displacement takes place almost to the center line of the progression line 1, as will be better explained later.

On the opposite side to the storage coil assembly, as mentioned above, the temporary winding / storage assembly, generally mentioned with reference 19, is provided.

This temporary storage assembly 19, in turn, is mounted so that it can be moved along the transverse guides of the input frame, in accordance with the same axis of travel XX of the transfer bar 16. To do this, the movement of the assembly 19 is also driven, for example, by a chain system driven by a second electric motor, in a part of the path opposite to that of the transfer bar 16 with respect to the coupling bar 18. The displacement of said coupling bar 18 and of the temporary storage assembly 19 is operated independently, in order to carry out the entire curtain extension process, the winding of the load, the welding of the wrapper and the subsequent start of a new cycle. On the contrary, the bar 16, which forms the movement component of the transfer means 12, does not provide for an independent displacement along the X-X axis, but passively follows the displacement of the coupling bar 18.

This temporary storage assembly 19 comprises a frame with vertical rod 19a, similar to the transfer bar 16 of the assembly 12. The frame 19a supports (as can be best seen in Figures 3 and 4) column winding means 20 and a corresponding motorization driven and controlled properly.

In particular, the column winding means have the shape of a tubular body or drum 20, in which the plastic film P. is intended to be wound.

In the drum 20, a plurality of gripping means 21 is provided; said gripping means being preferably housed inside the perimeter of said drum 20 and can be accessed from the outside through a longitudinal window / groove made on the surface of the drum 20; for this, said drum 20 is preferably constructed with a profile that substantially has a C-shaped section, the opening of which allows access to the gripping means 21.

The gripping means 21 are designed to hold the free edge of the film supported by the sheet-shaped forks 17 and to retain it adjacent to the tubular body 20. In particular, the position of said gripping means 21 along of the height of the drum 20 is such that it matches the gap between the spikes of the sheet-shaped forks 17, when the temporary winding assembly 19 is adjacent to the transfer assembly 16, as shown in Figure 6 : This helps with the perfect support of the film.

The gripping means 21, as mentioned, are preferably mounted inside the tubular body 20 and are provided to hold the edge of the film presented and inserted into the longitudinal window of the drum 20, by means of the fork in the form of sheet 17. Once the film is secured, the rotation of the tubular body 20 on its longitudinal axis causes winding of the rear layers of plastic film close to the outer surface of the tubular body 20.

To this end, the tubular body 20 is mounted so that it can rotate with the main shaft in a vertical direction and is driven in its turn by means of motorization. Said means have, for example, the shape of a vertical axis motor 22 which, by means of a gear 221 and a transmission chain 222, drives the rotation of the drum 20. The transmission chain 222 preferably also runs in a tensioning cylinder of small vertical axis 223, whose position can be adjusted, and whose function is also described more clearly below.

The rotation of the tubular body 20 of the temporary winding assembly is detected by a detection device, typically an encoder, to obtain a signal proportional to the angular position of the drum of the winder

20. Said signal serves both to control the motorization means 22 during the winding of the film in the body 20, so that the desired amount of film is wound, as well as to determine the stop position of the cylinder 20. In fact, it is important, for the correct fastening of the film P and for an effective welding operation, that the position of the gripping means 21 is correctly determined in the initial clamping stage and in the working operation stage, as will be shown later.

In fact, at the stage of securing the film, the gripping means must be substantially aligned with the transport axis X-X, so as to hold the edge of the film supported by the sheet-shaped forks 17 (Figure 3). In contrast, in the welding work stage, in order to achieve the minimum loss of film, on the contrary it is appropriate that the gripping means 21 are oriented in a direction parallel to the forward direction F of the transport line, so that the part of the film between the grips 21 and the welding system is minimal (see Figure 7).

As mentioned, the system is finally completed by a welding and cutting assembly. Said assembly comprises, in a known manner, opposite welding blocks 16s (those that are arranged integrated with the transfer bar 16) and 19s (those that are integrated in the temporary winding assembly, that is, integrated with the rod of support 19a), respectively.

Welding blocks 16s and 19s, traditionally heated by the Joule effect, run along the entire height of assemblies 12 and 19 and are suitable for mutual contact, imprisoning the edges of the film between them. It will be welded, during the closing stage of the wrapper, as detailed below. In the vicinity of one of the welding blocks, preferably 16s of the transfer assembly 12, a cutting blade 16t is also provided, on the upstream side (with respect to the unwinding direction of the film P) of said blocks of welding: it is expected that said sheet will cut the wrapper, after welding, of the remaining part of the film P that connects to the coil. These elements and the corresponding operation will not be described in greater detail in this context, since they are already known to those skilled in the art.

During operation, a load to be wrapped along a transport line 1 in the direction F is advanced. Upstream of the wrapping station, the main dimensions of the load C are detected. In particular, the The height reading is used to determine the coil 8-83, which is to be selected and then used, which acts in the control of the rotating support 6 in order to drive the selected coil with the corresponding transfer assembly 12 to the axis of XX transfer. In addition, the other dimensions of

load, to determine the extent of the perimeter in the plant.

Before the load C reaches the line XX, the coupling bar 18 and the temporary winding assembly 19 approach the transfer bar 16, sliding on the guides of the transverse elements 4 and 5. Said coupling bar 18 it is assembled, by coupling means 18a, to the transfer bar 16. At the same time, the sheet-shaped forks 17 present the film to the gripping means 21 and said gripping means are inserted between the pins of the forks, holding the free edge of the film P.

Next, the winding assembly 19 and the bar 16 of the transfer assembly 12 are moved towards the center line of the transport line. The film is unwound from the respective coil, beginning to extend the curtain, and the sheet-shaped forks 17 are retracted with respect to the bar 16 and, thus, to the winding assembly 19. Actually, as best described previously, the removal of the transfer assembly 12 from the origin post 16a causes a recession of the guide forks of the frame 17, so that said forks are caused to retract upstream of the guide cylinders 17a, 17b where it is made to slide the movie P.

At this time, the tubular body 20 is actuated in its rotation and a winding stage of the film P begins: using the signal from the detection device (encoder), the rotation continues until a substantially equal linear film length is wound at the half perimeter of the load C, minus the half width of the front side. In substance, in the drum 20, a sufficient length of film must be wound to cover half (the left in the drawings) of the perimeter of the load C, minus the film that is already extended "in the form of a curtain" in the transport line.

In fact, while the winding drum 20 is driven in its rotation, the entire temporary winding assembly 19 is caused to move away from the transfer means 12, that is, it moves to the left in the figure

1. At the same time, the transfer means 12 also travels in a short path towards the center line of the transport line, without obstructing the load path C.

When the winding assembly 19 has reached the end of travel (figure 2) opposite the transfer bar 16 and the transfer assembly 12 moves forward (the left one in figure 1) in a certain amount, a film curtain It is extended transversely on a transport line 1.

At this point, the load C arrives which, in contact with the film P, determines its own wrapping as it passes. Actually, the film P is loosened both from the left, specifically by means of the winding drum 20 that is released in its rotation (by the controlled friction action), and from the right, specifically by the main coil 8 (also controlled in its rotation through the cylinders 10).

In other words, the advancing load C, when it corresponds to the vertical plane X-X, rests against the curtain formed by the film P extended between the assemblies 12 and 19 and drags it in its forward movement. In this way, the film is gradually arranged in the position shown in Figure 2, that is, immediately leaning on the front side of the load C and relying more and more on the lateral sides of the load C. While on the one hand, the necessary length of film guided by the transfer means 12 is provided directly by the coil 8, on the other hand, the length guided by the assembly 19 is supplied by the winding assembly 20, which returns to the one had previously accumulated in the default extension.

The maintenance of the correct unwind tension of the film outside the assembly 19, according to the embodiment illustrated by way of example, is ensured by a small tensioning cylinder 223 that is suitably equipped with a friction device. On the contrary, the maintenance of the correct winding tension of the film from the respective coil 8 is ensured, at this stage, by the tilting roll 13 which provides the correct control to the motor 11 and, thus, to the wheels 10.

This allows the application of a vertical film layer to the front side and on the two lateral sides of the load C (figure 2) without creating a relative sliding of the film in the load.

When said load has almost completely exceeded line XX, both the temporary winding assembly 19 and the coupling bar 18 (and the transfer assembly 12 thereof), simultaneously converge towards the central line of the transport line, transferring the film also on the rear side of the load C. The convergence continues until the two assemblies 19 and 12 approach each other, in particular by contacting the respective welding blocks (Figures 1 and 7).

According to a preferred embodiment, the location of the coupling of the two assemblies, thus, the position of the weld in the wrapper, is not necessarily in the center line of the transport line 1, but is defined by the encoder of the motor 22: in fact, it is desired that the apparatus be as illustrated in Figure 7, that is, with gripping means 21 facing the welding blocks (whose orientation guarantees the least possible loss of film). Therefore, the movement of the transfer assembly 12 depends on and is actuated by the movement of the winding assembly 19, said winding in turn depending on the signal

from the encoder or other drum rotation detector 20.

In order for the process to take place as required, as mentioned, it is appropriate that the length of the film wound in the assembly 19 substantially corresponds to that necessary to cover half the perimeter of the load, less the film that is already extended between the winding assembly 19 and the transfer assembly 12. If the length wound in the assembly 19 were shorter or longer than that required, it would result in the welding and cutting area of the wrapping being finalized. very displaced with respect to the central line of the load, to one side or the other (because the cooperative position of the two assemblies, where welding takes place, is determined by detecting the complete unwinding of the assembly 19). If the length were much longer or shorter than that required, obviously, it would not be possible to complete the wrapping, unless unwanted sliding movements of the film were allowed to take place in the load.

For this, as mentioned above, it is advantageous to provide a control that detects the size of the load and that envelops the correct length of film in the temporary winding drum 20, as well as controlling the supply of film, both from the drum 20 as from the coils (8-83), during the unwinding stage in the load.

At this time, the winding drum 20 has completely unwound the previously stored film and only retains a short edge, between the gripping means 21, which runs in the welding blocks and stretches around the load (Figure 6).

Welding blocks 16s and 19s are carried out in a mutual assembly, so as to carry out the welding of the final edge of the film, now completely removed from the column winding unit 20, against the part of film held by the assembly 12 and still attached to the respective coil 8.

At the end of the welding operation, the wrap around load C has finished and it is necessary to cut it from the rest of the film P that connects to the respective coil. For this, the short edge of the film from the temporary winding assembly 20 is simply released from the grips, while the other part of the film that connects to the coil is cut by means of the blade 16t, after having locked it upstream in the transfer assembly 12 by means of a second padded fastener 12a integrated with the transfer bar 16. This last film edge, which is extended between the cylinders 17a, 17b and the cut-off point in the load C, is the one that is returned to Correctly support by means of the forks 17 when the bar 16 returns resting on the origin post 16a, again causing the forks 17 to move forward with respect to the cylinders 17a and 17b.

In fact, once this welding and cutting stage is over, the temporary winding assembly 20 and the transfer means 12 can return to the rotating support 6, to start a new cycle of clamping and extending the film with the same coil or with a new one.

As can be understood from the description mentioned above, the device according to the invention perfectly achieves the objectives set forth in the premises.

In particular, the curtain wrapping apparatus according to the invention requires a single support station for the plurality of coils, with the advantage of a significant reduction in the size and costs. In addition, the presence of a single coil per type makes management more efficient and reduces downtime, as well as wasted film. The novel cooperation between the temporary reserve stacking assembly 19, the coupling bar 18 and the transfer means 12 allows efficient film management, which leads to the total absence of jamming, high machine productivity, and also in the presence of changes in the reels, and a minimum waste of unused plastic film.

However, it will be understood that the invention should not be considered limited to the specific arrangement illustrated above, which only represents an exemplary embodiment thereof, but that a number of variants are possible, all within the scope of the person skilled in the field, without departing from the scope of protection of the invention, as defined by the following claims.

For example, although reference has always been made to a rotating support in the description, it is not ruled out that it can be replaced in an equivalent manner by a sliding support for a plurality of coils arranged in line.

Claims (11)

1. Procedure for wrapping loads loaded on pallets with a film of plastic material, the procedure providing a wrapping of the load (C) when passing through a curtain of film (P) that comes from at least one storage coil (8-83) arranged on a first side with respect to a transport line (1) of the load (C), and temporary winding means (19, 20) that can move transversely (XX) with respect to said transport line (1), rotating said temporary winding means (19, 20) in a first direction to initially accumulate a film length (P) equivalent to a perimeter part of said load (C), detected and calculated in a preliminary packing phase, and then rotating in a second direction to supply the same length of film (P) during the drag of said film curtain (P) by means of the load (C), characterized in that there are also provided at least transfer means (12), capable of presenting a final edge of said film from said at least one storage coil (8-83) to the gripping means (21) of said means of said temporary winding (19, 20) by means of support and presentation (17) both said temporary winding means (19, 29) and said transfer means (12) are then transferred transversely (X-X) with respect to said transport line (1) to arrange said plastic film curtain (P), first, said transfer means (12) are connected to a mobile coupling bar (18) provided with an independent drive control with respect to a motion control of said temporary winding means (19, 20), finally, said transfer means (12) connected to said mobile coupling bar (18) and said temporary winding means (19, 20) converge with each other in a central line work zone, in which the operations of welding and cutting of film to define said load wrapping (C).

2.

Method for wrapping according to claim 1, wherein the motion control of said mobile coupling bar (18) depends on the movement of said temporary winding means (19, 20) along said direction (XX) transverse to said transport line (1), whose end of travel is reached when said gripping means (21) are facing the welding means (16s, 19s) at the end of said film curtain supply phase (P).

3.

Method for wrapping according to claim 2, wherein a rotation control of said temporary winding means (19, 20) is coordinated with a translation control of the same temporary winding means (19, 20) and of said bar of mobile coupling (18), so that the complete unwinding of the film (P) temporarily accumulated in said temporary winding means (19, 20) occurs when said temporary winding means and said transfer means (12) are carried Turn towards each other.

Four.

Method for wrapping according to claims 1, 2 or 3, wherein said support and presentation means (17) are floatingly mounted on said transfer means (12), so that they move backwards, after having presented said final edge of the film (P) to the gripping means (21), until exposing a pair of sliding elements (17a, 17b) in contact with said film (P).

5.

Apparatus for wrapping a curtain using a plastic film (P), which comprises at least one input frame defining a transport line (1) of loads to be wrapped (C), at least one support ( 6) which carries a series of film reels (8-83) to select a feed reel based on the characteristics of the load to be wrapped, as well as transfer means (12) that can be moved along of a transverse transfer path (XX) with respect to said support line (1) and capable of extracting a film edge from a coil selected from said coils (8-83), so that a film curtain is defined which is to be applied around the load to be wrapped (C) during its advance, the first welding and cutting means (16s, 16t) being mounted on said transfer means (12) additionally provided, in which

temporary winding means (19, 20) are also provided, opposite to said support (6) with respect to said transfer means (12), suitable for temporarily accumulating a certain length of film (P) from said transfer means (12), said temporary winding means (19, 20) being able to also move along said transfer path (XX), so that they move away and approach said means of transfer (12) and define a film curtain (P) having an extension at least equal to the moving front part of said load to be wrapped (C), said temporary winding means (19, 20) comprise a tubular winding / unwinding element (20) actuated in rotation, provided with gripping means (21) capable of retaining a final edge of film (P) coming from said means of transfer (12), as well as second welding means (19s) suitable for cooperating with said first welding means (16s) in a working position, said means being of transfer (12) and said temporary winding means (19, 20) coming and cooperating, said transfer means (12) are arranged, so that they alternately engage with a fixed post (16a) of the apparatus, in a rest position, and with a mobile coupling bar (18) controlled transversely (XX) with respect to to said transport line, in a phase of work to wrap, said mobile coupling bar (18) is controlled, so that it can approach / move away from said temporary winding means (19, 20) and independently of them, and because 10 is provided a plurality of support and presentation elements (17) suitable for presenting a final film edge (P) to said gripping means (21), mounted so that they protrude and can be retracted to different heights along said transfer means (12). 6. Apparatus according to claim 5, wherein said support and presentation means (17) are mounted in 15 floating manner in said transfer means (12), so that they can move backward and allow a pair of sliding elements (17a, 17b) to come into contact with said film (P). 7. Apparatus according to claim 6, wherein said sliding elements are crazy rollers (17a, 17b) having a substantially vertical axis, mounted on said transfer means (12). twenty 8. Apparatus according to claim 6 or 7, wherein said floating support and presentation elements (17) are held retracted by elastic means (17e) and advance in the presentation position when they come into contact with the stop means of end of travel (17d), while exceeding the tension of said elastic means (17e) when said transfer means (12) are brought to said resting position. 9. Apparatus according to claim 8, wherein said floating support and presentation elements are in the form of a plurality of sheet-shaped forks (17) capable of supporting a film-free end edge (P) as a flag , said gripping means (21) of the tubular winding / unwinding element (20) being able to be placed between the pins of the forks (17). 10. Apparatus according to any of the preceding claims 5 to 9, wherein said tubular winding / unwinding element (20) is rotatably driven, so that it coils a film length substantially equivalent to half perimeter in plan of the load that it will be wrapped (C), said perimeter being detected upstream of said transfer path axis (XX). 11. Apparatus according to claim 10, wherein said tubular winding / unwinding element (20) is rotated in a coordinated manner with a translation control of said temporary winding means (19, 20) and said means of transfer (12), so that substantially all of the unwinding of the film (P) temporarily wound therein occurs when said temporary winding means (19, 40 20) and said transfer means (12) are close to each other in said working position and said gripping means (21) face said welding means (16s, 19s).