EP1182137A1

EP1182137A1 - Improvements to machines wrapping products with a stretch film

Info

Publication number: EP1182137A1
Application number: EP99962280A
Authority: EP
Inventors: Josu Errasti Iriarte
Original assignee: Ulma CyE S Coop
Current assignee: Ulma CyE S Coop
Priority date: 1999-12-31
Filing date: 1999-12-31
Publication date: 2002-02-27
Also published as: CA2362397A1; MXPA01008792A; WO2001049567A1

Abstract

Applicable to machines in which the film (7-7') is fed by means of two reels (8-8') of different width, consisting in providing independent feeding mechanisms for each of the reels (8-8') mounted on a common support (2) which is capable of changing its height with the assistance of two end pneumatic cylinders (10), so that their respective feeding combs (1-1') are selectively placed facing the extraction pin (9) which pushes the film (7-7') towards the wrapping section in question, where lateral pins (15) are located in order to stretch the film transversally, and the position of these pins may also be adjusted, provided with lateral folding devices (24) which push the film downwards thus wrapping the under section of the tray (25) or article, whose position may also be regulated.

Description

FIELD OF THE INVENTION

The improvements which are the object of this invention refer to the incorporation of certain devices and mechanisms to a machine used for wrapping articles with extensible film as that described under PCT ES98/00198 filed by the same applicant.
These improvements intend to increase the range of products which may be wrapped using in each case precisely the necessary amount of film to that end, thus introducing savings with respect to the film used in each wrap.
More specifically, the purpose of this invention consists in introducing the necessary devices and mechanisms in the wrapping machine to provide an automatic wrapping of trays with articles whose maximum and minimum dimensions comprise all the range of products generally used in the market and likewise obtain a greater use of the film, or in other words, achieve the wrap-up of an ample range of trays with the narrowest film reel.
The abovementioned devices allow for the automatic use of two film reels of equal or different width, both cross-wise and in a longitudinal manner, according to the type of reel used and the positioning and operation of the folding devices according to the dimensions of the product to be wrapped.
The system is controlled by a programmable microprocessor within the machine which decides automatically which of the two reels is to be used, as well as the position of the lateral fastening pins which stretch the film, and the position of the lateral folding devices according to the dimensions of the product required.

BACKGROUND OF THE INVENTION

Extensible film wrap machines used for wrapping trays with products have been known in the art for some time, in these, the trays access the system by means of a loading station which places them on an elevator, which conveys the trays vertically until the film sheet intended for wrapping said product is reached, said sheet having been supplied by a film reel which pays out the same by means of an extraction pin. These machines are provided with a central folding device which transfers the movement to the respective lateral folding devices in order to fold the film under the tray, and with a conveyer system in order to drive the tray to the end section of the machine where the final folding of the tray takes place. Finally, the wrapped tray is moved to a heated tunnel to shrink the film.
Under Patent PCT ES98/00198 owned by the applicant, a description is provided of a machine for wrapping products with extensible film in which all the movements of its devices and its different operational phases are programmed according to the dimensions of the product to be wrapped up, whereby the position of the article to be wrapped and the portion of film used are monitored, as well as the movements of the extraction pin, of the folding plates and the cutting blade, so that this assembly will operate according to the dimensions of the article and the film used. The dimensions of the product are detected by a photoelectrical barrier placed at the entry of the tray feeding conveyer.
In this machine, the extraction pin supplying the film is provided with a variable movement in order to dispense an amount of film in proportion to the length of the product for wrapping, and in each case only the required amount will be dispensed, thus ensuring an optimal folding. This pin likewise conducts a stretching of the film proportionate to the degree of flexibility and tension of the blade required. The extraction pin of the film is capable of pinching the central and lateral areas of the film allowing for a gradual release of the film, first in the lateral sections to facilitate lateral folding, that is, to release the outer surface of the film and allow the folding devices to operate under the product while the central area remains gripped until the final or exit folding is carried out.
The wrapping machine described in this Patent also includes lateral pins which may travel in order to carry out a cross-wise pre-stretching of the film which improves the film's elasticity when the wrapping takes place. This pre-stretching is set at a specific value in order to achieve the same degree of stretching, regardless of the width of the film used.
The wrapping process itself commences with the introduction of the lateral folding blades and a rear folding blade synchronized with the extraction pin, so that the film fastening system will be released the moment in which the lateral folding blade exerts pressure on the film and the folding process starts. The lateral pins are synchronized in order to operate simultaneously with the lateral blades and their relaxation is programmed according to length of the product to be wrapped.
Notwithstanding, this machine has the following setbacks:

The main folding device of the machine relays the movement to the two lateral folding devices so that the lateral or fixed folding obtained has always the same dimensions, wherefore the available film width for the final or exit folding is always the same regardless of the size of the tray, which bears on the distribution of film used under the tray, being exceedingly wide for small-sized trays and exceedingly narrow for large-sized trays thus generating lateral film folds which protrude from the tray in the case of small-sized trays and an insufficient width for the final folding process when wrapping large-sized trays. As the available film for the final folding is insufficient in the case of large trays it becomes necessary to use a wider film reel which increases the amount of film used in each wrapping process.
The abovementioned machine has two lateral pins which grip the film in order to carry out a cross stretching of the same, but the gripping position is exactly the same for both reels whereby the film stretched in the case of the wide reel is identical to the narrow reel, which entails that for the wide reel this pre-stretching action may be insufficient, and when wrapping products of considerable height the film may break as the elastic capacity of the film is exceeded.

DESCRIPTION OF THE INVENTION

The improvements suggested by this invention have been designed to provide a satisfactory solution to all these problems, based on switching the classical fixed position of the folding devices and the lateral pins to a variable one, in both cases controlled by the processor of the machine according to the article to be wrapped and the reel used.
In particular, and pursuant to one of the improvements of this invention, the movement of the central folding device is separated from the lateral folding devices, so that each movement may be controlled according to the article wrapped.
In particular, concerning the feeding system, and with the two reels as the starting point, -preferably of different width - , which are selected automatically according to the dimensions of the article wrapped, one of the improvements of this invention consists in providing each of these reels with an independent feeding system, so that within the same support two combs are assembled, one for each reel, with their corresponding rollers securing the film and their tilting mechanisms; this support is capable of traveling vertically, driven by pneumatic cylinders, between two end positions, so that in each case the comb matching the film reel selected by the microprocessor is placed conveniently facing the film extraction pin in order to convey the same to the wrapping area of the machine.
The abovementioned extraction pin for the film is aided by lateral pins -as is customary - whose purpose is to perform a lateral stretching of the film in question, but with the difference in this case that the position of those lateral pins is now variable depending of the different width intended for the film reel to be used. Wherefore, these lateral pins are mounted on crosswise slides which are operated by means of a swinging motion provided by a cog fitted in a connecting rod which acts on the first stretcher that tilts a side lever to which the respective pins are linked to by means of their corresponding stretchers, with the specialty that the first stretcher is coupled to a pneumatic cylinder which permits the adjustment of its effective length at will and therefore controls the minimum distance between the pins allowing for the lateral pull action on the film.
By means of this pneumatic cylinder not only two different distance points may be determined for the lateral pints but these may also be varied in order to adjust them to reels with different widths.
Pursuant to another of the characteristics of this invention, the lateral folding devices, which are responsible for placing the film under the tray or article in question, may be positioned at a greater distance between them as required if a greater or lesser penetration under the tray is desired, according to the size of the same, varying the size of the lateral folds of the film and thus the width obtained in the final section of the same which provides the final folding, and to that end, the folders are likewise driven by a cog, which by means of a first arm, a stretcher operated by a pneumatic cylinder, a second arm and a pneumatic cylinder, drive the folding devices in question, so that depending on whether these cylinders are active or inactive, the opening position of the lateral folding devices will be modified pursuant to the operating program provided by the microprocessor of the machine.

DESCRIPTION OF THE DRAWINGS

In order to complete the description herein provided and for a further understanding of the characteristics of the invention, a preferred embodiment of the same is provided with its accompanying drawings as part of said description, to be considered as non-limiting examples, in which:
FIG.1 offers a perspective view of the double feeding device for the film which is provided in a wrapping machine built according to the improvements of this invention.
FIG. 2 provides a diagram representing a lateral elevation and a section of the above assembly shown in FIG 1 above.
FIG. 3 provides a similar view to that provided by FIG. 2, with the same assembly as the previous Figure but with one of the combs in a folded position.
FIG. 4 provides a cross-wise diagrammatic view of the device used for adjusting the position of the lateral pins in the operating position for the widest film reel available among those available in the feed station of the machine.
FIG. 5 shows a similar view to that of Figure 4, with the same elements as in the previous Figure with the lateral pins in their appropriate position for the narrowest film reel available.
FIG. 6 provides a similar view to that of Figures 4 and 5, and shows the mechanism that actions and regulates the lateral folding devices to which one of the main improvements of this invention refers.
FIG. 7 provides a detailed view of the cross section of the machine at the level of the abovementioned lateral folding devices in which the multiple positions adopted by said folding devices are shown with a dotted and a continuous line.
FIG 8 finally, provides in it its different sequences - A, B, C and D - a similar depiction to Figure 7 concerning the position of the lateral folding devices considering different types of trays which are likewise shown in those sequences.

PREFERRED EMBODIMENT OF THE INVENTION

Taking into account the figures described above and in particular, Figures 1 to 3, it may be seen that the machine built according to the improvements introduced by this invention, and in particular in the feeding device for the film, we find two combs (1-1'), assembled on a support (2) by means of their respective end brackets (3-3'), which tilt on a common axis (4), so that each of these combs is capable of adopting an operational position as may be gathered from Figure 1 in the case of comb (1), or the inactive position which adopts comb (1') in the same Figure, clearly visible by means of their respective tilting brackets (3-3'), and each of these combs (1-1') are operated by a set of rollers (5-6) and (5'-6') which secure the film (7-7'), provided by the respective supply reels (8-8'), with different film widths, and in any case each fastening pair of rollers in question must (5-6) or (5'-6'), and in particular their corresponding combs (1-1'), conveniently face the extraction pin (9), as seen in Figure 2. Therefore, the support (2) must be capable of traveling vertically for an equal distance to that existing between the combs(1-1'), wherefore said support (2) is driven by two pneumatic cylinders (10) located at the end-points of the same, and in its turn, a couple of pneumatic cylinders (11) allow the upper comb to open and close (1), while another cylinder (12) opens and closes the lower cylinder (1'), and to achieve this, the rods fitted in the pneumatic cylinders (11), mounted on the support (2), act on rivets (13) coupled to the end tilting brackets (3) of the upper comb (1), whereas the rod of the intermediate cylinder (12) operates a cross bar (14) which in its turn drives the end brackets (3') tilting the lower comb (1').
Pursuant to this operating structure, in order to load the films (7-7') it shall suffice to open the combs operating on the cylinders (11) and (12), and place the films in question on the appropriate comb (1-1'), and subsequently said combs will be closed whereby each film will be locked in position, so that they may not slip backwards from their respective chromed roller (6-6'), as these incorporate at their end points a tripping device that only allows for a forward movement of the film. Once the combs have been closed (1-1'), the films (7-7'), each of a different width, are fastened by rollers (6-6') against rollers (5-5') and any of these may then action the extraction pin (9), provided that it is facing the same, acting on the pneumatic cylinders (10), whereby an automatic selection of the film takes place (7-7') according to the dimensions of the article, and to that end, the machine is equipped with photocell barriers in order to detect the length of the tray and likewise a photoelectrical barrier and an encoder to measure the width of the same. The control point receives information on the dimensions of the tray by means of impulse signaling by the encoder when the tray travels through the photoelectrical systems. The machine control point may be programmed according to the data relayed in order to activate the abovementioned cylinders (10) and change the position of the comb so that the extraction pin (9) pulls the selected film up to a length which has been likewise programmed according to the dimensions of the product to be wrapped.
Once the film has been paid out, the lateral pins (15) must conduct a lateral folding of the same and likewise according to the invention, these pins (11) may vary their position to provide a greater or lesser stretching of the film pursuant to the different reel widths (8-8') foreseen.
To that end, the abovementioned pins (15) are mounted on cross slides (16) whereby they may move inwards or outwards, and these pins (15) are operated by means of their respective stretchers (17-17') by a side lever (18) to which a third stretcher is coupled (19) which in its turn receives the motion from a cog (20) fitted in a connecting rod (21) so that said cog (20) provides a swinging motion to the pins (15), from a position in which there is the least distance between each other, and these close on the marginal borders of the film (7), to the opposite situation of maximum distance, which corresponds to the stretching of the film in question, but with the specialty that these limit positions are adjustable, as the stretcher (19) is powered by pneumatic cylinder (22) provided with an extension (23) whereby the effective length of the stretcher may be regulated and therefore the position of the side lever (18) which gives rise to the distancing motion of the pins (15) as shown in Figures 4 and 5, so that in the position shown in Figure 4, the lateral pins (15) are adjusted to the position of the film (7) which has the greatest width, whereas in Figure 5 said adjustment is made to the film which has the least width.
Once the central pin (9) extracts the selected film and the lateral pins (15) stretch the film, the control panel of the machine actions the main motor in order to transfer the article from the feeding station to the wrapping section on the hoist. When the hoist completes its vertical run with the article, the lateral folding devices (24) commence to wrap the film around the under section of the tray or article (25), and it has been foreseen that the position of the folding devices (24) may be varied automatically according to the dimensions of the article (25) to be wrapped.
So that the lateral folding devices (24) may fold the film in different positions, the control board may be programmed according to the dimensions of the article to be wrapped and the mechanisms of the folding system will then be conveniently operated.
In particular, the lateral folding devices (24) receive the motion from the cam shaft of the machine, which is powered by the main motor and in particular from the cogs (26) which provide a constant and oscillatory movement in each cycle of the machine by means of the arms (27) and (28), linked by means of a stretcher (29) which is driven by a pneumatic cylinder (30), and the arm in its turn (28) ends in another pneumatic cylinder (31) with a different run, so that the combination of action and inaction of these cylinders varies the initial opening position of the lateral folding devices (24). More specifically, the control panel of the machine may be programmed according to the dimensions of the article, in order to action said cylinders (29) and (31), in order to achieve four different opening positions for the lateral pins, as shown in Figure 8, adjusted to the different sizes of the tray (25). The constant movement of the folding devices in order to fold the film laterally in each cycle will be performed equally from any of the opening positions of the abovementioned transversal folding devices (24) shown in the four sequences of Figure 8.
In the narrowest folding position, which is shown in Figure 8 A, achieved when the two cylinders (29) and (31) are inactive, it may be exactly adjusted to the tray or article (25) with smaller dimensions, following an adjustment of the stretcher (29), which generates a position of the lateral stretchers (24) in which the distance between them is exactly that required for the lateral film to fold beneath the tray (25) and create a final fold which does not exceed the dimensions of the tray in question. The widest position of the lateral folding devices (24) is achieved when the two cylinders, (29) and (31), are operated, which allows for the wrapping of large-sized trays (25), as the distance between said folding devices (24) generates a final open fold which fully covers the underside of the tray (25) as shown in figure 8D.
If the control panel is conveniently programmed it may action only a cylinder (31), thus achieving an operating position which is specially apt for middle-sized trays as that shown in Figure 8B, or if only the pneumatic cylinder is operated (30), then an intermediate position for the lateral folding devices is achieved (24), which is wider than in the preceding case due to the different run of the cylinders, and suited for trays (25) shown in Figure 8C.

Claims

Improvements introduced in machines used for wrapping products with extensible film in which the article or the product in question when fed into the machine goes through a barrier which detects its dimensions and submits this information to a microprocessor that controls all the movements of the machine, thus placing the product in the adequate position of the hoist whose run is checked by a traction pin paying out a specific amount of film supplied by two reels, preferably of different width, and controlling the lateral pins which perform a transversal stretch of the film, as well as the movements of the folding blades, characterized in that the feeding station (1-1') of the two film sheets (7-7') which differ in width, operate independently and are capable of facing the extraction pin (9) selectively, according to the instructions received from the control panel of the machine, and in their turn, the position of the lateral pins (15) which perform a crosswise stretching of the film may also be conveniently adjusted, according to the band width of the film (7-7') selected, and it has been foreseen that the position of the lateral folding devices (24) may also be adjusted by the control panel of the machine, in order to regulate their distance according to the different formats or sizes of the trays (25) or articles to be wrapped.
Improvements introduced in machines used for wrapping products with extensible film as per Claim 10, characterized in that each feeding comb (1-1') for the different band widths of the film (7-7') is mounted independently and tilted on a common support (2), by means of two pairs of end brackets (3-3'), driven by their respective rollers (5-6) and (5'-6') which fasten the film (7-7'), the tilt of the combs is achieved by their respective pneumatic cylinders (11-12), and it has been foreseen that the foregoing support (2) is in its turn driven by a pair of end pneumatic cylinders (10) which allow each comb to face (1-1') the extraction pin (9), and all these pneumatic cylinders are monitored by the control panel of the machine.
Improvements introduced in machines used for wrapping products with extensible film as per Claim 10, characterized in that the lateral pins (15) receive a counter motion provided by their respective stretchers (17-17'), from a side lever (18), from a third stretcher (19) and from a connecting rod (22), whereas the cog (20) provides a swinging motion, moving inwards and outwards from said pins, with the special feature that the third stretcher (19) is driven by a pneumatic cylinder (22) whose effective length may be determined at will in order to adjust the distance between the extraction pins (15) to the two different film widths available (7-7').
Improvements introduced in machines used for wrapping products with extensible film as per Claim 10, characterized in that the lateral folding devices (24) are also operated by a connecting rod (26) by means of a first arm (27), a stretcher (29) and a second arm (28), with the special feature that the stretcher (29) is driven by a pneumatic cylinder (30) and that the second arm (28) ends in a second pneumatic cylinder (31), all of which ensures that when the cylinders, (30) and (31), are fully withdrawn, a specific relative position between the lateral folding devices (24) is established, and when one or both of the cylinders are in operation, two other relative positions are obtained, and if both cylinders are in operation, then a fourth relative position between the lateral folding devices is achieved (24) in order to adjust the initial opening of the blades to the different formats or sizes of the trays (25) or articles to be wrapped.
Improvements introduced in machines used for wrapping products with extensible film as per Claim 10, characterized in that the cylinders (30) and (31) have a different run.