EP3278969B1

EP3278969B1 - Device for die cutting bags with handles of the shopper type wound in a roll

Info

Publication number: EP3278969B1
Application number: EP17184309.7A
Authority: EP
Inventors: Roberto Trezzi; Maurizio Toniato
Original assignee: Mobert Srl
Current assignee: Mobert Srl
Priority date: 2016-08-05
Filing date: 2017-08-01
Publication date: 2020-10-07
Anticipated expiration: 2037-08-01
Also published as: DK3278969T3; IT201600082865A1; EP3278969A1

Description

The object of the present invention is a die-cutting device, particularly for an automatic heat-sealing machine, apt to produce die-cut handles of shopper-type bags, also known by the term "T-shirt bag", said machine being fed, also continuously, with one or more flattened tubular films, in plastic material, or with one or more strips of heat-sealed and pre-cut bags.
Rolls of pre-cut bags and with die-cut handles of the shopper type (or handles of T-shirt bags) have been known for some time and are normally used, for example, in the fruit and vegetables departments of supermarkets for inserting the goods to be weighed. The handles of the bag are used to close the bag before weighing.
Obviously, the rolls of shopper bags can also have different uses.
Many methods are known for die-cutting a strip of bags (or a tubular film from which to obtain the bags subsequently): one of the known methods is alternative die-cutting with toothed blade, which has the disadvantage of requiring the film to be at a standstill during the die-cutting. Moreover, the die-cutting with toothed blade creates a jagged cutting edge, making the bag unsightly and having points of breakage of the bag itself during the traction of the handles.
Another method for die-cutting continuously a strip of flattened tubular films is described in Italian patent no. 1.394.527 (= EP-A- 2 230 067 ) in the name of the Applicant, which provides a die-cutting station suitable for die-cutting the tubular film or the strip of heat-sealed and pre-cut bags produced by the heat-sealing and pre-cutting station which works on a portion of tubular film whose sliding is stopped momentarily in the working zone of the die, maintaining a continuous feeding of the film.
Said die-cutting assembly, which performs a cut on the fly of the film, that is without counter plate for the cutting means, provides a system of pre-blocking of the film formed by two movable pressers and two respective rubber abutments, intended to block the film, and by a soft central buffer which pushes the central art of the film lightly so as to tension it in order to allow the blade to perform a more uniform die-cutting and, consequently, obtain a product of greater quality.
However, the rubber buffer, forming a tension linked to the consistency of the rubber, is very affected by the thickness and the quality of the film to be cut. This is particularly disadvantageous in the case of film or strips of bags with side gussets such as those of shopper bags made with biodegradable film as laid down by recent regulations adopted by some European countries.
GB 2 168 640 A describes a device for die-cutting handles with bean shape in webs of plastic sheet material, wherein two webs of material are made to move forwards respectively above and below a wedge-shaped punch. In the upper web along the boundary of the hole incisions are formed so that small bridges remain which retain the die-cut material, while in the lower web a hole is made with removal of the die-cut material.
The object of the present invention is to make a device for the die-cutting of one or more flattened tubular films or of one or more strips of heat-sealed and pre-cut bags to make a plurality of bags with handles of the shopper type or T-shirt bag which overcomes the disadvantages of the prior art, allowing efficient die-cutting without being affected by the thickness and/or quality of the film.
A further object is that of having available such a die-cutting device which is easy to make and to manage as well as usable in heat-sealing machines known in the art.
This object is achieved by means of a die-cutting device which has the characteristic features indicated in the independent claim 1.
Further advantageous features of the invention form the object of the dependent claims. The invention will now be described with reference to a purely exemplifying embodiment (and therefore non-limiting) illustrated in the accompanying drawings, wherein:

Figure 1 is a side sectioned view of the die-cutting device, according to the invention, in free film position;
Figure 2 is an enlarged view of the detail enclosed in the square in Figure 1;
Figure 3 is another side sectioned view of the die-cutting device, according to the invention, in free film position, taken along a different plane with respect to that of Fig. 1;
Figure 4 is a front sectioned view of the die-cutting device, according to the invention, in blocked film position, taken along a plane orthogonal to that of Figures 1 and 3;
Figure 5 is a partial and plan view of a sheet or strip of shopper bags die-cut in T-shirt bag form;
Figure 6 shows very schematically a partial side view of a known heat-sealing machine, in which the die-cutting device according to the present invention is installed.

In the accompanying drawings, corresponding elements will be identified by means of the same reference numerals.
The die-cutting device according to the present invention, denoted by reference numeral 100, is made up of a lower fixed part carrying a plate 1 (in detail in Fig. 2) and an upper movable part, opposite to the lower fixed part.
Said upper movable part comprises an outer blocking plate 5 attached on a movable beam 6, a cutting blade 7, also supported by the movable beam 6, and an inner blocking plate 10 attached to the beam 6 but placed inside said cutting blade 7.
In the lower fixed plate 1 an incision or recess 2 is formed (Fig. 2) coinciding with the shape of the blade 7 of the die-cutting machine, generally having such a shape as to form an opening 52 (Fig. 5) in the flattened tubular film or in the strip of heat-sealed bags 50 fed to said die-cutting machine 100, whose shape can be, for example, that illustrated in Figure 5.
Adjacent to the recess 2 and above the fixed plate 1, an elastic compensation element is placed, such as for example a rubber profile 3 which serves as abutment to the upper movable blocking plates 5 and 10.
Both the upper plates 5 and 10, which are coaxial one in relation to the other, are shaped so that their profile is adjacent to the cutting blade 7.
The coaxial plates 5, 10 are situated on a same horizontal plane when in position of machine open with film free.
The profile of each of the upper blocking plates 5 and 10, in the area adjacent to the cutting blade 7, has a pointed projection 8 which has the function of blocking tooth.
This tooth 8, on closure of the upper movable plates 5, 10 on the lower fixed plate 1, goes to engrave the rubber 3 of the lower fixed plate 1, before the blade 7 engraves the film 50, thus causing a further secure blocking of the film 50 when this is in contact with the two upper movable plates 5, 10 and the lower fixed plate 1.
The two upper movable plates 5 and 10 are subjected to respective independent elastic means, more particularly springs 12, 12' so that the blocking of the inner and outer parts of the strip of film 50 is independent of the thickness, self-adapting to the thickness of the film 50 to be blocked.
In practice the two coaxial plates 5, 10 are apt to block one of the two surfaces of the film 50 against the counter plate 1 and thanks to the springs 12, 12' said plates 5 and 10 can adapt to the thickness of the film 50 when said coaxial plates 5 and 10 are in contact with said film 50 lying on the lower plate 1.
Inside the cutting blade 7 and at the central part of the upper inner plate 10 there is a nozzle 11 which, at the unblocking of the film 50 after die-cutting, emits a puff of air which facilitates the removal of the scrap, pushing it through an opening 4 formed at the centre of the lower plate 1 towards the underlying system of aspiration of the die-cutting scrap following the cutting.
The blocking system of the present die-cutting device 100 constituted by the upper plates 5, 10, by the respective teeth 8 and by the lower plate 1 and elastic abutment 3, therefore goes to block both the area of the film 50 with gussets 51 which has a thickness equal to four layers of film, and the central area 52 which has a thickness equal to two layers of film: the elastic compensation element, such is the rubber 3, allows secure blocking of the central area 52 of the strip of film 50 which has half the thickness (two layers of film) with respect to the lateral outer zone of the gussets 51 (four layers of film).
The die-cutting device 100 described above could also be made upside down, that is with the fixed plate 1 placed in an upper position with respect to the film 50 and the movable blocking plates 5, 10 placed in a lower position with respect to the film 50, or both the lower plate 1 and the upper plates 5 and 10 could be movable without thereby departing from the scope of the present invention.
It should be noted that said beam 6 can rise and lower in phase with the movement of a trolley 80 (Fig. 6), placed in a heat-sealing machine of known type in which the present die-cutting machine 100 can be installed: said trolley 80 is apt to determine an elongation of the path of the film 50 in input to the die-cutting machine 100 and therefore a momentary stop of the film when it is die-cutting, as will be explained here below by way of example.
Therefore, when the film 50 (Fig. 5) stops, the movable beam 6 lowers, pressing the upper plates 5 and 10 against the lower plate 1. Continuing in the stroke downwards, the blade 7 goes then to engrave the film 50 determining the cutting of the part to be removed.
The present die-cutting device 100, which allows a cut of the film to be performed "on the fly", that is without counter plate for the cutting blade, is particularly advantageous when the cutting blade 7 has to act on a strip of tubular film which does not have a single thickness in its entire extension: as illustrated in Figure 5, to allow the obtaining of handles, the strip of tubular film 50 has generally side gussets 51 at which the thickness of the strip of film 50 is greater with respect to the central area of the strip.
As mentioned, the present die-cutting device 100 is particularly advantageous when installed in an automatic heat-sealing machine such as that described in Italian patent No. 1.394.527 in the name of the Applicant, where the die-cutting machine is placed between two loops in which the film can be accumulated when the trolley 80 stops the sliding of a portion of the tubular film with respect to the die-cutting station.
The automatic heat-sealing machine described in the Italian patent no. 1.394.527 is continuously fed with at least one flattened tubular film 50 in plastic material and is suitable for producing and winding at least one strip of pre-cut bags with die-cut handles.
Said heat-sealing machine comprises a station 40 for winding of the strip of bags and, for each tubular film 50:

a heat-sealing and pre-cutting station 60 for producing a strip of heat-sealed and pre-cut bags from the tubular film; and
a die-cutting station 100, operating on the portion of tubular film whose sliding is stopped by the abovementioned stop means, which die-cuts the tubular film or the strip of heat-sealed and pre-cut bags produced by the heat-sealing and pre-cutting station, if this is placed upstream of the die-cutting machine;
means apt to stop the sliding of a portion of the tubular film 50 with respect to the die-cutting station 100 and to that of heat-sealing and pre-cutting 60.

In Figure 6 the die-cutting station 100 is in accordance with the present invention and is placed upstream of the heat-sealing and pre-cutting station 60 yet, without departing from the scope of the invention, the present die-cutting station 100 can be placed downstream of the heat-sealing and pre-cutting station 60.
A pair of motorised rollers 170, placed between the die-cutting station 100 and that of heat-sealing and pre-cutting 60, maintains the tension of the film 50 constant between the two stations, when the film does not advance on the flat between them. Obviously, the present device can be applied also on machines not provided with said motorised rollers.
The means apt to stop the sliding of a portion of the tubular film 50 with respect to the die-cutting station 100 and to that of heat-sealing and pre-cutting 60 comprise at least one trolley 80 (which carries the motorised rollers 90 and 91) and two rollers 110 and 120 integral with the frame of the machine. The tubular film 50, passing over the rollers 110 and 90, and over the rollers 91 and 120, forms respectively the loops 130 and 140.
The trolley 80 translates along rectilinear guides 190 in an alternate direction with respect to the forward movement of the tubular film 50 which moves from left to right in the example given.
When the trolley 80 translates along the guides 190 in a direction opposite to that of forward movement of the tubular film 50 at a speed equal to half that of forward movement of the tubular film 50, the motorised roller 90, integral with the trolley 80, moves away from the roller 110, making the breadth of the loop 130 increase, while the motorised roller 91, integral with the trolley 80, moves towards the roller 120, integral with the frame of the machine, making the breadth of the loop 140 decrease, and causing a momentary stop of the film.
Consequently, the film 50 entering the heat-sealing machine accumulates in the loop 130, while the winding station 40 (or another apparatus placed downstream of the heat-sealing machine) is fed by the strip of pre-cut and die-cut bags which had previously accumulated in the loop 140.
The operations of die-cutting and of heat-sealing and pre-cutting are therefore carried out in conditions of film 50 practically at a standstill.
Having performed these operations the trolley 80 reverses its motion, allowing the film 50 accumulated in the loop 130 to bring itself at the die-cutting stations 100 and the die-cut film 50 to bring itself at the station of heat sealing and pre-cutting 60, accumulating in the loop 140 the strip of pre-cut and die-cut bags with which to feed subsequently the winding station 40.
Preferably the die-cutting and the heat-sealing of the film 50 are performed simultaneously.
The joining in a single machine body of the die-cutting 100 and heat-sealing and pre-cutting 60 stations allows easy synchronisation of these stations one in relation to the other and with the rollers (not identified in the accompanying drawings with reference numerals for simplicity of graphic representation) which regulate the speed of forward movement of the film 50 and of the strip of die-cut bags obtained therefrom, eliminating the problems of phasing between the heat-sealing and pre-cutting station 60 and that of die-cutting 100, simplifying therefore considerably the operations of format change of the bags.
In order to simplify further the operations of format change of the bags, one of the die-cutting 100 and heat-sealing and pre-cutting 60 stations is fixed while the other is mounted on a slide 150, movable on a support surface 160, which allows the distance between the die-cutting station 100 and that of heat-sealing and pre-cutting 60 to be varied in order to adapt it to the length of the bags to be produced.
In Figure 6 the die-cutting station 100 is fixed while the heat-sealing and pre-cutting station 60 is mounted on the slide 150 yet, without departing from the scope of the invention, the die-cutting station 100 can be mounted on the slide 150 and the heat-sealing and pre-cutting station 60 kept fixed.
Moreover, as mentioned, the die-cutting station 100 can be placed upstream or downstream of the heat-sealing and pre-cutting station without thereby departing from the scope of the present invention.
The winding station 40 is any type of machine for winding film in rolls known in the art, for example the winding station described in the Italian patent no. 1.394.527 incorporated here in full for reference, is particularly suitable for winding strips of bags with gusset which in the area of the handles have folds which, superimposing when a considerable number of bags is rolled, can create rolls of bags with different diameter on a par with the number of bags wound.
Without departing from the scope of the invention, a person skilled in the art can make to the automatic heat-sealing machine described previously all the changes and improvements suggested by normal experience and/or by the natural advance in the art.

Claims

Die-cutting device (100) for die cutting at least one tubular film, or a strip of heat-sealed and pre-cut bags (50) with lateral gussets (51), for producing handles of a shopper bag or T-shirt bag, said device consisting of a fixed lower portion and an upper movable portion or vice versa, and comprising:
a cutting blade (7) apt to make an opening (52) on said tubular film (50) or on said strip of bags,

blocking means, located on said lower portion and/or on said upper portion of said die-cutting device (100), for blocking said tubular film (50) or said strip of bags,

an opening (4) in said lower or upper portion for the ejection of the die-cutting scrap following cutting, wherein said blocking means are comprised of a movable outer plate (5) and a movable inner plate (10), coaxial one to the other and which enclose said cutting blade (7), said coaxial plates (5, 10) being situated on a same horizontal plane when in position of machine open with film free,

said two coaxial plates (5, 10) being apt to block said film (50) or said strip of bags against a counter plate (1) integral with said fixed portion and opposed to said two coaxial plates (5, 10), wherein said opening (4) is formed,

an elastic compensating element (3) being placed between said coaxial plates (5, 10) and said counter plate (1) for making a safe blocking on the different thicknesses of said tubular film or of said strip of bags (50),

said elastic element (3) being a rubber profile placed above said counter plate (1), and

wherein said outer blocking plate (5) and said inner blocking plate (10) are subjected to respective independent elastic means (12, 12').
Die-cutting device (100) according to claim 1, wherein a recess (2) is provided on said counter plate (1) apt to receive said blade (7).
Die-cutting device (100) according to any one of the preceding claims, wherein said outer blocking plate (5) and said inner blocking plate (10) are carried by a beam (6) movable vertically for bringing said coaxial plates (5, 10) into contact with said tubular film or strip of bags (50) blocking the latter against the counter plate (1).
Die-cutting device (100) according to claim 3, characterised in that said outer blocking plate (5) and said inner blocking plate (10) are connected to said movable beam (6) through said respective independent elastic means (12, 12').
Die-cutting device (100) according to any one of the preceding claims, wherein the profile of each of said coaxial blocking plates (5, 10) has, in the area adjacent to the cutting blade (7), a pointed projection (8) acting as blocking tooth, engraving said elastic element (3) present on the counter plate (1).
Die-cutting device (100) according to any one of the preceding claims, wherein inside the cutting blade (7) at the central portion of the inner plate (10) there is a nozzle (11) which, after the unblocking of the tubular film or strip of bags (50) following the die-cutting, issues an air blow which facilitates the removal of the scrap, pushing it through the opening (4).
An automatic heat-sealing machine, continuously fed with at least one flattened tubular film (50) in plastic material and suitable for producing and for winding at least one strip of pre-cut bags with die-cut handles, comprising
- a heat-sealing and pre-cutting station (60), suitable for producing a strip of heat-sealed and pre-cut bags from the tubular film (50);
characterised in that it further comprises a die-cutting device (100) as defined in any one of the preceding claims.
Heat-sealing machine according to claim 7, 8 , wherein said die-cutting device (100) is placed upstream or downstream of said heat-sealing and pre-cutting station (60), said die-cutting device being also able to be movable with respect to said heat-sealing and pre-cutting station (60).