IMPROVED CUTTING DEVICE AND METHOD FOR THE SEPARATION OF BAGS FOR FLEXIBLE PACKAGING MADE FROM LAMINATED FILMS

Abstract

 Device for the transversal cutting of laminated films (1) at V-shaped die-cuts (2) provided on this film at distances corresponding to the length of bags to be produced, wherein said device (10) comprises at least two blades (11, 13) and (12), offset and spaced apart one in relation to the other, such as to be placed astride an apex (3) of said die-cuts (2) during said transversal cutting, one (12) of said blades acting against a side abutment to perform a scissors cut of the film (1).

Description

[0001] The subject of the present invention is a device and a relative cutting method for the separation of bags for flexible packaging obtained from laminated films, for the containment of food for humans, animal feed, etc.

[0002] The laminated films used for the formation of these bags also comprise at least one layer of aluminium or in any case of materials that have a certain rigidity.

[0003] These laminated films are adequately shaped by folding and longitudinal sealing to form a tubular shape, forming any side gussets, seals and transversal cuts to separate the bags one from the other, or to cut the tubular shape to the length of the bag to be formed.

[0004] In order to avoid that, once the bag has been shaped and then filled with the product, the sharp corners of the bag itself during storage and transport will cut into the bags close to it, piercing them, or worse, hurt the end user, during the shaping of the bags the corners are rounded by means of a cutting die.

[0005] In practice, with reference to the accompanying Figure 1, which represents a consolidated prior art, whereof the Applicant is not aware of any patents describing it, before the operation of transversal cutting of the tubular shape to a length corresponding to that of the bag to be obtained, cuts 2 are made on the tubular shape 1 in the shape of a V with rounded edges.

[0006] Due to small inaccuracies during the film feed, it is extremely difficult to match the transversal cut with the apex 3 of the previously performed V-shaped die-cutting 2. This means that a corner of the bag, upper or lower, is not perfectly rounded but has a protuberance 6 (Figure 2) called "beak" which is dangerous because it is sharp and therefore not acceptable for the above.

[0007] To avoid this inconvenience, the state of the art provides for a double cut with a removal of about 2 mm of product as shown in Figure 3, in order to avoid the formation of the beak 6.

[0008] This operation is normally carried out by making a first cut at the theoretical distance of one millimetre from the apex 3 of the V-shaped die-cut 2. The film is advanced by 2 mm from right to left with reference to Figures 1 to 3, and a second cut is made by removing a portion of product 4 of 2 mm.

[0009] For obvious reasons, this double cutting operation leads to a slowdown in production speed.

[0010] Incidentally, it should be noted that in the production of these bags, the film is continuously advanced for the execution of certain operations, such as longitudinal folding, and intermittently for the execution of other operations, such as precisely the die-cutting and transversal cutting.

[0011] It is therefore clear that the advancement of the film between the two consecutive cuts is down time in the production process, as it is not possible in the second cutting operation to perform any other operation on the stationary film.

[0012] The Applicant has sought to solve this problem with European patent application EP18172308.1, not yet published and the content of which is incorporated here as a reference, which provides for a pair of blades placed side by side, distanced one from the other, such as to be placed astride the apex of said V-shaped die-cuts during said transversal cutting of laminated film.

[0013] The pair of blades is carried by a carriage that moves along a linear guide transversally to the film in one direction and in the other, cutting the film at each single stroke. The strip of material that is cut by the two blades is expelled by a blow of air.

[0014] This device, having two blades perfectly side by side, has highlighted two important problems:

• If one of the two blades cuts the material a few tenths of a millimetre before the other, in proximity of the final edge of the bag that is formed, the trimmed part tends to bend and the second blade fails to cut. The waste remains therefore attached to the bag for a few tenths of a millimetre of uncut material 4', as shown schematically in Fig. 4.
• Even if the cut is made correctly, it can happen that the trimmed part is jammed between the two blades, making it difficult to cut the next bags.

[0015] The object of the invention is to eliminate the drawbacks of the prior art illustrated above, in particular those found in the device that is the subject of document EP 18172308.1.

[0016] Therefore, the object of the invention is to improve the device and the method described in document EP 18172308.1, preventing the material waste from staying attached to the bag being formed, or from getting caught between the cutting blades.

[0017] Another object of the invention is to provide a cutting device that is highly reliable and avoids down time in the process of manufacturing flexible packaging bags.

[0018] These and other objects are achieved by the cutting device according to the invention, which has the features of the appended independent claim 1.

[0019] Advantageous embodiments of the invention are disclosed in the dependent claims.

[0020] Substantially, the device according to the invention for the transversal cutting of laminated films, at V-shaped die-cuts provided on that film at distances corresponding to the length of bags to be produced, comprises at least two blades offset and spaced apart one in relation to the other, such as to be placed astride an apex of said die-cuts during said transversal cut, one of said blades acting against a side abutment to make a scissors cut of the film.

[0021] According to an advantageous embodiment, the device for the transversal cutting of laminated films according to the invention comprises three blades, two of these blades being aligned one with the other, while the third blade is offset and spaced apart with respect to them, such that the blades aligned on one side and the blade offset on the other are placed astride an apex of said die-cuts during said transversal cut, the blade offset and spaced apart being placed in an intermediate position with respect to the aligned blades and acting against a side abutment to make a scissors cut of the film.

[0022] Said blades are carried by a carriage moving along a linear guide placed transversally to the film.

[0023] Said blades are mounted on respective supports that run along a channel determined by two opposed fixed bars placed transversally to the film, and protrude below these bars through a narrow opening of said channel.

[0024] Further features of the invention will be made clearer by the detailed description that follows, referred to a purely illustrative and therefore non-limiting embodiment of the invention, illustrated in the accompanying drawings, in which:

Figures 1, 2 and 3 are schematic plan views showing the successive phases during the transversal cutting of a tubular film for the separation of bags with elimination of the "beak" according to the prior art;

Figure 4 is a plan view substantially similar to the previous figures, showing a film with advancement from right to left that is subjected to transversal cutting with the device according to EP 18172308.1, highlighting a possible drawback illustrated above.

Figures 5 and 6 are schematic views in section taken in the direction of advancement of the film, of the cutting device according to the invention, shown respectively in rest and working position;

Figure 6a is an enlargement of the detail enclosed in circle A of Figure 6;

Figure 7 is a schematic partial view, with parts removed, taken from the right with respect to Figure 5;

Figure 8 is a section taken along line A-A of Figure 7;

Figure 9 is a perspective view of the blade assembly.

[0025] Figure 4 shows schematically in plan view a film 1 in an intermediate stage of the bag production process.

[0026] The film is unwound from a reel and initially fed continuously through a series of stations, where it undergoes in particular a longitudinal folding to form a tubular shape, and then intermittently to be subjected to operations that require the film to be at a standstill.

[0027] In the plant or machine for the production of bags, which will not be described in detail as not the subject of the invention, a device is provided for transforming the advancement of the film from continuous to intermittent.

[0028] The film 1 shown in Figure 4 is downstream of such a device, and therefore undergoes stops during the advancement in order to be subjected to the various operations to be carried out on the stationary film, such as sealing, engraving, die-cutting, transversal cutting and so on.

[0029] In the position of Figure 4, film 1, which is a laminate comprising at least one layer of aluminium or in any case of a material with a certain rigidity, has been folded longitudinally to form a tubular shape, and on it V-shaped die-cuts have been made with rounded edges, at transversal lines 5 placed at a distance corresponding to the length of the bag to be obtained.

[0030] As mentioned above, these die-cuts 2 are made to avoid that the bags produced have sharp corners.

[0031] To avoid the formation of sharp corners, i.e. of the "beak" 6 (Figure 2), unlike what occurred in the preceding prior art, which provided for two successive cuts to remove a strip of material 4, as shown in Figures 1 to 3, EP 18172308.1 proposed to remove this strip of material 4 in a single pass, by means of a pair of blades side by side, which, however, in the case of a slight advance of one blade with respect to the other during cutting, could determine the inconvenience shown in Figure 4, i.e. the remainder of a small section of uncut material 4' with which the strip 4 remained attached to the bag to be formed.

[0032] To solve the problems found in EP 18172308.1, the invention proposes the cutting device shown in Figures 5 to 9, denoted overall by reference numeral 10.

[0033] The device 10 comprises three blades 11, 12, 13, mounted on respective supports 41, 42, 43 (see in particular Figures 7 and 9), carried by a plate 20 in the shape of an overturned L tilted through 180°, fixed to a second plate 21 in the shape of an overturned L, in turn fixed to a carriage 22 sliding transversally on a linear guide 23 arranged transversally to the machine.

[0034] The plates 20, 21 and the carriage 22 form a whole so that here below these elements will be identified also with the carriage 22 alone.

[0035] The carriage 22 is moved by a toothed belt 24 fixed to the upper plate 21 by means of counter plates 25.

[0036] The toothed belt 24 is driven in reciprocal motion by means of a motor and corresponding pinion not shown.

[0037] Naturally, carriage 22 can also be moved in another way, for example by means of worm gears and screw nuts, pneumatic actuators, and the like.

[0038] The supports 41, 42, 43 of the blades 11, 12, 13 run along a channel 27 determined by two opposed bars 30, 30 integral to the structure of the machine (Figures 5 and 6).

[0039] Channel 27 is open above to allow the insertion therein of the blade supports 41, 42, 43, and opens at the bottom as a funnel to allow the exit of the blades 11, 12, 13 that protrude slightly beyond the lower plane 31 of the bars 30.

[0040] In Figures 5 and 6, film 1 has been schematised with a dotted line and is moved intermittently from left to right as indicated by the arrows F.

[0041] Below the bars 30 there are two pressers 32, movable from the bottom upwards and vice versa as indicated by the double arrow F1 to move from a position distanced from the bars 30, as shown in Figure 5, to allow the advancement of the film 1, to a position of blocking of the film 1 against abutment stops 33 provided in the bars 30 during the stop phase of the film, as shown in Figure 6.

[0042] In the embodiment shown in Figures 5 and 6, the pressers 32 are carried by an arm (or rather two side arms) 50, oscillating around a fulcrum 51, which makes the pressers perform a movement along an arc of circle, for the purposes that will be mentioned here below.

[0043] According to the invention, the three blades 11, 12, 13 are arranged so that the blades 11, 13 are perfectly aligned in the transversal direction of the machine, while the blade 12 is slightly offset with respect thereto by a quota corresponding to the width d of the strip 4 of material to be trimmed (normally 2-2.5 mm but could vary by changing the distance between the blades), and spaced apart transversally, so as to result in an intermediate position between the blades 11 and 13.

[0044] In this way, according to the direction of movement of carriage 22, the front blade of the two aligned blades 11, 13 performs the cut, and the other one that follows it remains inactive, while the offset intermediate blade 12 cuts the trimmed part or strip of material 4 in both directions of movement of carriage 22.

[0045] In order to prevent the edge of the bag that is formed by the tubular film from bending after the first cut made by blade 11 or 13 and thus preventing blade 12 from cutting, blade 12 is made to slide in contact with a side abutment, thus cutting like scissors.

[0046] This side abutment is provided by one of the two 32 pressers (the one on the left in Figures 5 and 6) which, during the cutting stroke of the blades, slightly touches the blade 12 to allow the "scissors" trimming cut (see in particular the enlargement of Figure 6a). The movement of pressers 32 around the fulcrum 51 of the arms 50 along an arc of circle allows the corresponding stop 32 to approach blade 2 without interfering with the tip of the blade itself.

[0047] This solution is optimal because it does not force the blades to perform the whole stroke corresponding to the length of the bars 32 to come out from the same at each transversal cut to allow the rise of the pressers 32 after the advancement of the film, but it is possible to optimise the stroke of the blades, varying it according to the width of the bag to be cut, being able to achieve higher production speeds.

[0048] If these advantages are to be relinquished, it would obviously be possible, in an alternative solution, to have the assembly of blades coming out laterally with respect to the mobile locking bars 32. In this case, the bars 32 could also move perfectly vertically.

[0049] During cutting, the material waste 4 is evacuated between the two pressers 32 by means of air nozzles 35 placed at the two sides of the blade assembly (Figure 7), which blow downwards the trimmed part 4, which is collected by an underlying suction hood (not shown).

[0050] After each transversal stroke of carriage 22, the blades 11, 12, 13 remain outside the trajectory of the film 1, which can therefore be moved forward, as shown in Figure 5, then blocked by the pressers 32 in the next stop phase, as shown in Figure 6, and be cut again transversally in the return stroke of carriage 22.

[0051] The fact that the blades 11, 13 and 12 are spaced apart also avoids the problem of the jamming of the trimmed part 4 between the blades.

[0052] The supports 41, 43 of the side blades 11, 13 are fixed, while the support 42 of the central blade 12 can be adjusted forwards and backwards by means of an adjustment screw 45 (Figure 8). In this way, it is easy to adjust the interference between the trimming blade 12 and the abutment plane of the corresponding mobile presser 32.

[0053] The advantages of the device according to the invention appear clear from the above, which allows a safe detachment of the trimmed part 4 from the film 1, also preventing it from getting caught between the blades.

[0054] In the accompanying drawings, the blades 11, 12, 13 have been indicated as double-edged, i.e. with a V-shaped tip, in order to be able to cut in one direction and in the other. However, the side blades 11, 13 could be single cut, as also the central blade 12 could be made up of two perfectly aligned opposed single-cutting blades.

[0055] According to an alternative embodiment of the invention, only one of the two lateral blades 11, 13 can be provided, in which case the cut would only take place in one direction of movement of the carriage, with an empty return stroke. In this case, both blades could be single-cutting, unidirectional.

[0056] Naturally the invention is not limited to the particular embodiment previously described and illustrated in the accompanying drawings, but numerous detailed changes may be made thereto within the reach of the person skilled in the art, without thereby departing from the scope of the invention itself, as defined by the appended claims.

Claims

1. Device for the transversal cutting of laminated films (1) at V-shaped die-cuts (2) provided on said film at distances corresponding to the length of bags to be produced, characterised in that said device (10) comprises at least two blades (11, 13) and (12) spaced apart and offset from each other, such as to be arranged astride an apex (3) of said die-cuts (2) during said transversal cut, one (12) of said blades acting against a side abutment to make a scissors cut of the film (1).

2. Device for the transversal cutting of laminated films (1) according to claim 1, characterised in that it comprises three blades (11, 12, 13), two of said blades (11, 13) being aligned with each other, while the third blade (12) is spaced apart and offset with respect to them, such that the blades (11, 13) on one side and the blade (12) on the other are arranged straddling an apex (3) of said die-cuts (2) during said transversal cutting, the spaced apart and offset blade (12) being arranged in an intermediate position with respect to the blades (11, 13) and acting against a side abutment to perform a scissors cut of the film (1).

3. Cutting device according to claim 1 or 2, characterised in that said blades (11, 12, 13) are carried by a carriage (22) movable along a linear guide (23) arranged transversally to said film (1).

4. Cutting device according to claim 3, characterised in that said blades (11, 12, 13) are mounted on respective supports (41, 42, 43) which run along a channel (27) determined by two opposed fixed bars (30, 30) placed transversally to the film (1), and protrude below these bars through a narrow opening of said channel (27).

5. Cutting device according to claim 4, characterised in that it comprises a pair of pressers (32) placed below the bars (30, 30) and movable from the bottom upwards and vice versa, to abut against rubber stops (31) provided in said bars for locking the film (1) during the cutting step, one of said pressers acting as side abutment for said blade (12).

6. Cutting device according to claim 5, characterised in that said pressers (32) move along an arc of a circle, or along a straight line vertically.

7. Cutting device according to any one of claims 4 to 6, characterised in that air nozzles (35) are arranged at the two sides of the blade assembly (11, 12, 13) which blow on the scrap of material (4) to evacuate it through the lower opening of said channel (27).

8. Cutting device according to any one of claims 4 to 6, characterised in that said supports (41, 43) of the blades (11, 13) are fixed, whereas the support (42) of the blade (12) is adjustable by means of an adjustment screw (45).

9. Method for the transversal cutting of a laminated film (1) for the production of bags, said film (1) having been previously subjected to V-shaped die-cuts (2) at distances corresponding to the length of the bags to be produced, characterised in that a double cut is provided, performed simultaneously with two blades (11, 13) and (12) spaced apart and offset from each other, which are arranged astride the apices (3) of said V-shaped die-cut (2), and slide transversally to the film (1), one (12) of said blades sliding in contact with a side abutment to perform a scissors cut of the film (1).

10. Method according to claim 9, wherein three blades (11, 12, 13) are provided, which run in the two directions transversally to the film (1), two of said blades (11, 13) being aligned with each other, while the third blade (12) is spaced apart and offset with respect to them, being arranged in an intermediate position with respect to the blades (11, 13), such that according to the direction of movement of the blades, the forward one of the two aligned blades (11, 13) makes the cut, and the other one that follows it remains inactive, while the spaced apart intermediate blade (12) cuts the trimmed part or strip of material (4) in both directions of movement of the blades sliding in contact with a side abutment to make a scissors cut of the film (1).

Drawing