HK1032373B - Unit for sterilizing strip material on a packaging machine for packaging pourable food products, and packaging machine comprising such a unit - Google Patents

Description

Device for sterilizing a web on a packaging machine and packaging machine

The present invention relates to an apparatus for sterilizing a web on a packaging machine for packaging a filled food product, and a packaging machine having the apparatus.

Packaging machines for packaging pourable food products, such as fruit juice, wine, tomato sauce, pasteurized or long-storage (UHT) milk, etc., are well known, in which the packages are constituted by a continuous tube of packaging material defined by longitudinal sealing bands.

The packaging material is of a multilayer structure comprising a layer of paper material covered on both sides with layers of heat-seal material, such as polyethylene. For aseptic packages of food products intended for long-term storage, such as UHT milk, the packaging material comprises a layer of barrier material, for example aluminium, which is superimposed on a layer of heat-seal plastic material, and is then covered with another layer of heat-seal plastic material, eventually forming the inner face of the food package.

To produce sterile packages, the strip of packaging material is unwound from a reel and fed through a sterilization unit for sterilization, for example, by immersion in a bath of liquid sterilant, such as a concentrated solution of hydrogen peroxide and water.

In particular, the sterilization device comprises a bath (bath) which is filled with a sterilization agent during use, through which the packaging tape can be passed continuously. The trough typically comprises two parallel vertical sections connected at their bottom and forming a U-shaped channel of a length determined by the speed of conveyance of the belt, so that sufficient time is available for processing the packaging material. In order to perform the treatment efficiently and more quickly in order to reduce the size of the sterilization chamber, the sterilization agent must be kept at a high temperature of about 70 ℃.

The sterilization device also comprises a sterile chamber in which the web of packaging material coming out of the sterilization tank is subjected to mechanical treatment (e.g. by means of drying rollers) and thermal/fluid treatment (e.g. by means of hot air jets) in order to remove any residual sterilization agent. In fact, the amount of residual sterilization agent that can be tolerated in a packaged article has strict limiting criteria (the maximum tolerated amount is about a part per million); and the sterile chamber must be maintained at slightly above ambient pressure in order to ensure that leakage through the seal occurs in an outward direction as opposed to toward the interior of the chamber, thereby preventing the ingress of any contaminating agents.

Before exiting the sterile enclosure, the strip is folded into a cylindrical shape and sealed longitudinally to form a continuous vertical longitudinal sealed tube in a known manner. In practice, the tube of packaging material forms an extension of the aseptic chamber and is continuously filled with the filled food product, which is then fed into a forming and (transverse) sealing device to form the individual packages, and by means of which the tube is clamped between pairs of jaws to seal the tube transversely and form aseptic pillow packs.

The pillow packs are separated by severing the seals between the pillow packs and then sent to a final folding station where they are folded mechanically into finished form.

Packaging machines of the above type are widely used in the food industry and are satisfactory in use; in particular, the performance of the sterilization device is fully in accordance with the control criteria for package sterility and residual sterilant.

In industry, there is a need for further improvements, in particular with regard to the reduction of residual sterilizing agent, since there is a need in the market for packages that: with a reclosable opening feature that is easy to open and easy to fill with food product.

In the case of non-aseptic packaging machines, such components may be applied directly to the strip by injection moulding prior to formation of the package.

In contrast, in the case of aseptic packaging machines, any opening feature is generally applied after the package has been formed, which is disadvantageous from a production point of view, requiring complex and costly equipment to feed and apply the feature. That is, if the opening means is applied to the tape in advance, the opening means will form a break in the geometrically continuous tape, where residual sterilizing agent will accumulate and cannot be completely removed from the tape by known technical means.

On the other hand, the use of additional means for removing the sterilization agent may have a negative effect on the operating parameters of the sterile chamber, in particular on the temperature and pressure, and thus on the performance of the sterilization device.

The object of the present invention is to provide a device for sterilizing strips, particularly for machines for packaging pourable food products, which provides an effective, simple and inexpensive solution to the above-mentioned problems.

According to the present invention, there is provided an apparatus for sterilizing a web packaging material on a machine for packaging pourable food products, said apparatus comprising a tank for containing a sterilizing agent, an aseptic chamber and a main air handling circuit; packaging material may be continuously fed into the bath, the aseptic chamber having an inlet connected to the outlet of the bath, the main air handling circuit comprising first suction means for sucking air from the aseptic chamber, air handling and purification means, and a blower (blowing means) for blowing treated air into the aseptic chamber; comprising an auxiliary circulation circuit comprising second suction means for sucking air out of said aseptic chamber, and nozzle means connected to said second suction means and adjacent to the inlet of said aseptic chamber for directing a jet of air onto at least one predetermined portion of said packaging material.

The extraction of sterile air from the sterile chamber and its return to the chamber makes it possible to effectively remove other residual sterilizing agent with as little influence as possible on the operating parameters of the chamber and to form a sterile package with an opening feature pre-applied to the web material, while at the same time eliminating any residual sterilizing agent. Furthermore, with sterile air already present in the sterilization means of the apparatus, the system is particularly straightforward and inexpensive since no dedicated sterile air production and treatment system is required.

The invention also relates to a packaging machine for producing aseptic packages of a pourable food product from a web packaging material, the apparatus comprising a sterilization device having a primary air-handling circuit comprising first suction means for sucking air from said aseptic chamber, air-handling and purification means, and a compressor for blowing treated air into said aseptic chamber; further comprising an auxiliary circulation circuit comprising second suction means for sucking air from said aseptic chamber, and nozzle means connected to said second suction means and adjacent to the inlet of said aseptic chamber for directing a jet of air onto at least one predetermined portion of said packaging material.

According to a preferred embodiment of the invention, the apparatus preferably comprises a device for applying the opening means upstream of the sterilization device.

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to the embodiment.

FIG. 1 is a diagram of an apparatus for packaging a pourable food product and featuring a sterilization device according to the invention;

FIGS. 2 and 3 are a partial perspective view and a partial front view, respectively, of a sterilization device of the present invention;

FIG. 4 is a diagram of an auxiliary gas circulation loop of the apparatus of FIG. 2;

FIG. 5 is a front view of the nozzle of the apparatus of FIG. 2;

fig. 6 is a cross-sectional view taken along VI-VI of fig. 5.

Number 1 in fig. 1 indicates as a whole an apparatus for packaging pourable food products and for continuously forming web packaging material 2 (hereinafter referred to simply as "web 2" for simplicity) into aseptic packages of pourable food products.

The apparatus 1 comprises a sterilizing device 3 for sterilizing the strip 2, the strip 2 being fed to the sterilizing device 3 by a winch (not shown) along a substantially horizontal path P1.

When producing packages with reclosable opening features 5 made of plastic material, the strip is conveniently fed through a known injection moulding device 4, at the outlet of which device 4 the strip comprises a series of opening features 5 (only schematically shown in fig. 1 along a limited portion of the strip 2) equally spaced along the intermediate longitudinal portion 2a of the strip. At the outlet of the injection-moulding device 4 and upstream of the sterilization device 3, a belt storage zone 6 is conveniently provided to compensate for the different feeding amounts of the belts of the two devices (step-feed and continuous feed, respectively).

The sterilization device 3 essentially comprises a U-shaped sterilization chamber 8 containing a quantity of liquid sterilant, for example: 30% of hydrogen peroxide (H)₂O₂) And an aqueous solution. The tank 8 is formed by a vertical inlet portion 9 and a vertical outlet portion 10, the inlet portion 9 and the outlet portion 10 having top openings 11 and 12, respectively, the top openings 11 and 12 being able to act as an inlet and an outlet, respectively, for the strip 2 into and out of the tank 8; and the input and output sections are connected together at their bottoms by a bottom section 13 of the tank 8, the bottom section 13 being provided with a guide roller 14 having a horizontal axis.

In the tank 8, the belt 2 follows a U-shaped path P2, the length of which is determined by the speed of conveyance of the belt and ensures that the packaging material remains in the sterilization agent for a sufficiently long time (e.g. 7 seconds).

Tank 8 forms part of a known peroxide control system (not shown) and is used at a controlled temperature, for example about 70 c.

The apparatus 1 further comprises a sterile chamber 15, the inlet 12 of the sterile chamber 15 coinciding with the outlet of the tank 8. Sterile chamber 15 comprises a top portion 16 and a bottom portion or column 18, top portion 16 being provided with drying means, generally indicated by the reference numeral 17, for removing residual sterilizing agent from belt 2; the bottom 18 extends in a vertical direction and parallel to the grooves 8, and in the bottom 18, the belt 2 is folded longitudinally into a cylindrical shape and sealed longitudinally to form a continuous cylindrical tube 19.

Drying means 17 comprise two idle drying rollers 20, which drying rollers 20 are covered with a relatively soft material and have their respective horizontal axes parallel to each other and are arranged near the entrance of aseptic chamber 15 on opposite sides of belt 2, drying rollers 20 being pressed against opposite surfaces of belt 2 so as to remove any drops of sterilizing agent and to drop them back into tank 8.

The drying roller 20 (fig. 2 and 3) advantageously comprises respective intermediate recesses 20, i.e. respective intermediate portions of small diameter, in order to pass the opening member 5 and prevent interference with the opening member 5 (fig. 3).

The drying device 17 also comprises two air knives 22 located on opposite sides of the belt 2, the air knives 22 being located downstream (in the direction of conveyance of the belt) of the rollers 20 and thus above the rollers 20. The known air knives 22, which are only shown in fig. 4, each comprise a nozzle 23 for spraying air downwardly onto the belt 2, and a corresponding wall 24 for directing a jet of air in a direction substantially parallel to the belt but opposite to the direction of transport of the belt, in use.

The nozzle 23 forms part of a known primary air circuit 21 (not described in detail) comprising an inlet pipe 24 a; a treatment unit 25 having suction means, means for removing residual sterilizing agent and heating means; and a tube 26 for feeding the nozzle 23.

The sterile chamber 15 is kept slightly above ambient pressure so that leakage through the seal occurs in an outward direction opposite to the interior of the sterile chamber. However, the overpressure must be limited to a few millibars in order to prevent excess air contaminated with sterilant from leaking and contaminating the working environment.

According to the invention, the drying device 17 also comprises two nozzles 27 located at the entrance of the aseptic chamber 15 on opposite sides of the belt 2, immediately upstream of the roller 20 and at the notch 20a of the roller 20.

Nozzle 27 is used to direct an air stream onto portion 2a of belt 2 at opening member 5 to remove any residual sterilant from the opening member. The nozzles 27 form part of an auxiliary sterile gas circulation circuit 28, the circuit 28 being shown in fig. 4 and also partially in fig. 2 and 3.

The circuit 28 generally comprises an inlet duct 29 for drawing sterile air from the sterile chamber 15, an air compressor 30 (fig. 4) having an inlet connected to the inlet duct 29, and an outlet duct 31 connected to an outlet of the air compressor 30. The output pipe 31 is divided into two supply pipes 31a, 31b, which are connected to the respective nozzles 27 and each include a variable resistor 32 for adjusting the flow rate of the respective nozzle 27.

The air compressor 30 is of the so-called "side-channel" or "air-ring" type, for example: the Flux-Jet model sold by ESAM s.p.a., which runs completely dry (i.e., does not require a lubricant) to avoid contamination of the sterile air. The above type of air compressor also creates a slight low pressure zone on the suction inlet side and increases the pressure gradually up to its delivery side, so that, due to the suction created at the sterile chamber pressure (slightly above ambient), the air in the air compressor 30 is only slightly below ambient pressure on the suction inlet side, where it is easy to provide a static seal, and elsewhere where it is higher than ambient pressure along its way to ensure that any contamination is avoided.

Fig. 2 and 3 show the inlet pipe 29, the outlet pipe 31 and the supply pipes 31a, 31b for supplying gas to the nozzle 27, which draw sterile air from the sterile chamber 15. Air compressor 30 (not shown) may be conveniently fitted to side wall 35 of sterile chamber 15.

Fig. 5 and 6 show one of the nozzles 27, and since both nozzles are identical, the following description applies to both nozzles.

The nozzle 27 substantially comprises a hollow box-shaped body 36, the box-shaped body 36 having a rear opening 37a which can receive a line fitting (not shown) of the supply pipe 31a or 31 b; the box-shaped body 36 is closed at the front end by a template 37, the template 37 having a plurality (e.g. three) parallel horizontal bosses 38, 39, 40; and each boss 38, 39, 40 has a longitudinal internal cavity 42 (figure 6) communicating with the cavity of the box-shaped body 36, and a row of ejection orifices 43a, 43b, 43c, respectively, constituted by equally spaced ejection orifices 43, each communicating with a respective cavity 42.

The spray holes 43 on the bottom bosses 38 have an axis which is inclined downwards and in this direction spray a stream of air onto the belt 2 in order to blow off any residual sterilizing agent on the belt 2, in particular on the opening member 5 and return it to the tank 8; the spray holes 43 on the intermediate boss 39 and the top boss 40 have a horizontal axis and spray the gas flow onto the belt 2 in a direction substantially perpendicular to the belt.

The nozzles 27 have narrow crests 44, and therefore the narrower crest bosses 40 have fewer spray holes 43 than the other bosses, so that the nozzles 27 can be brought closer to the respective rollers 20 by positioning the crests 44 substantially within the recesses 20a of the respective rollers.

Tests have shown that the above-described arrangement of the injection openings 43 is particularly effective in removing residual sterilizing agent from the opening member 5. In particular, this arrangement of the ejection apertures 43 on the bosses 38, 39, 40 allows air ejected from the apertures to be removed laterally through the gap between the bosses and the belt 2, thus avoiding stagnation or turbulence which would normally impair effective removal of residual sterilant.

In actual use, the tape 2 is fed stepwise through the injection moulding device 4 and successively through the slot 8 and the sterile chamber 15, the opening means 5 being formed in the injection moulding device 4.

On entering the sterile chamber 15, the portion 2a of the belt 2 with the opening means 5 is flushed on both its surfaces by the air flow emitted by the nozzle 27. The first row of spray holes 43 can blow a certain amount of residue back into the tank 8; two further rows of spray apertures 43 can break the sterilant droplets into small particles to facilitate their removal and evaporation. It should be noted that: the temperature of the air flow from the nozzles 27 is slightly higher than the temperature of the sterile chamber 15, by about 80 ℃, because the temperature drop of the air sucked in by the compressor 30 and conveyed through the inlet and outlet pipes 29 and 31 is compensated by a greater temperature increase of the air compressed in the compressor 30.

The belt 2 is then fed between the rollers 20 and substantially removes the large macroscopic traces of liquid on the lateral side portions of the belt 2 that the nozzles 27 are unable to act on. In this step, the removed sterilant droplet will fall back into the tank 8.

Downstream of the roller 20, the belt 2 without droplets is washed by the jets produced by the air-knife 22 in a direction opposite to its own movement direction; in this way, the remaining liquid is completely removed, the strip 2 is completely dried and folded into a tube, which is then sealed longitudinally, filled and formed/sealed into packages in the transverse direction.

Clearly, changes may be made to apparatus 1, and in particular to sterilization device 3, without, however, departing from the scope of the accompanying claims. In particular, each nozzle 27 can be formed in a different way and direct an air jet onto a more elongated portion of the belt 2; the roller 20 can be omitted if the nozzle 27, for example, ensures complete removal of the residual sterilization agent.

Finally, although it is possible to produce aseptic packages with opening features pre-applied thereto and therefore very advantageous for this purpose, the invention can also be used to produce packages without opening features.

Claims (19)

1. A device (3) for sterilizing a web-shaped packaging material (2) on a packaging machine (1) for packaging pourable food products, said device (3) comprising a tank (8) for receiving a sterilizing agent, an aseptic chamber (15) and a main air-handling circuit (21); packaging material is continuously fed into the tank, the aseptic chamber having an inlet (12) connected to the outlet of the tank (8), the air-handling circuit comprising first suction means (24) for sucking air from the aseptic chamber (15), air-handling means (25), and a compressor (22) for blowing treated air into the aseptic chamber (15); characterized in that it comprises an auxiliary circulation circuit (28) comprising second suction means (29, 30) for sucking air from said aseptic chamber (15), and nozzle means (27) associated with said second suction means (30) and adjacent to the inlet (12) of said aseptic chamber (15) for directing a jet of air onto at least one predetermined portion of said packaging material (2).

2. The apparatus of claim 1, wherein: said nozzle means comprise two nozzles (27) facing opposite surfaces of said packaging material (2) and having respective supply ducts (31a, 31b) associated with said second suction means (30).

3. The apparatus of claim 2, wherein: said tank (8) forming a U-shaped channel (P2) of said packaging material (2) and having a top outlet coinciding with said inlet (12) of said aseptic chamber (15); each of said nozzles (27) comprises a jet device (43) capable of directing a flow of air in an inclined direction towards said tank (8).

4. The apparatus of claim 2 or 3, wherein: the injection device comprises a plurality of injection holes (43) arranged in a plurality of horizontal rows (43a, 43b, 43c) spaced apart in the conveying direction of the packaging material (2).

5. The apparatus of claim 4, wherein: -the holes (43) of at least a first (43a) of said rows (43a, 43b, 43c) are inclined to said slot (8); while the holes (43) of the other rows (43b, 43c) are substantially perpendicular to said packaging material (2).

6. The apparatus of claim 5, wherein: said rows (43a, 43b, 43c) of holes being formed on respective front bosses (38, 39, 40) of each of said nozzles (27); and the first row (43a) is adjacent to the inlet (12) of the aseptic chamber (15).

7. An arrangement according to any one of the preceding claims, characterized in that the auxiliary circulation circuit (28) comprises a dry-operated compressor (30).

8. An arrangement according to claim 7, characterized in that the compressor (30) is of the side channel type.

9. A device as in any one of claims 2 to 8, wherein said nozzle (27) is positioned facing a median longitudinal portion (2a) of said packaging material (2).

10. A device according to any one of the preceding claims, comprising two drying rollers (20) acting on the packaging material from opposite sides, which rollers are located immediately downstream of the nozzle (27).

11. A device as claimed in claim 10 when dependent on claim 9, wherein said drying roller (20) has a respective intermediate recess (20a) located on said intermediate longitudinal portion (2a) of said packaging material (2).

12. A device as claimed in claim 11, wherein said nozzles have respective narrow tops (44) at least partially housed in said respective recesses (20a) of said drying roller (20).

13. An apparatus according to any one of the preceding claims, wherein the compressor of the main air treatment circuit (21) comprises two air knives (22) located on opposite sides of the packaging material (2) downstream of the drying roller (20).

14. A packaging machine (1) for making packages of pourable food products from a web of packaging material (2), which apparatus (1) comprises a sterilizing device (3) for sterilizing said packaging material (2), and which sterilizing device comprises a tub (8) for containing a sterilizing agent, into which the packaging material is continuously feedable, an aseptic chamber (15) which also comprises an inlet (12) connected to an outlet of said tub (8), and a main air-handling circuit (21) which comprises first suction means (24) for sucking air from said aseptic chamber (15), air-handling means (25), and a compressor (22) for blowing treated air into said aseptic chamber (15); characterized in that it comprises an auxiliary circulation circuit (28) comprising second suction means (29, 30) for sucking air from said aseptic chamber (15), and nozzle means (27) associated with said second suction means (30) and adjacent to the inlet (12) of said aseptic chamber (15) for directing a jet of air onto at least one predetermined portion of said packaging material (2).

15. A packaging machine as claimed in claim 14, wherein said nozzle means comprise two nozzles (27) facing opposite faces of said packaging material (2) and having respective feed pipes (31a, 31b) connected to said suction means (30); each of said nozzles (27) having injection orifices (43) arranged in a plurality of horizontal rows (43a, 43b, 43c) formed on respective spaced apart forward bosses (38, 39, 40); the holes (43) of at least one row (43a) of the plurality of rows adjacent to the inlet (12) of the aseptic chamber (15) are inclined towards the tank (8); and the holes (43) of the other rows (43b, 43c) are substantially perpendicular to said packaging material (2).

16. A packaging machine as claimed in claim 14 or 15, characterized by comprising a device (4) for applying opening members (5) to said packaging material (2) upstream of said packaging device (3).

17. A packaging machine as claimed in claim 16, wherein said nozzle (27) is positioned facing an intermediate longitudinal portion (2a) of said packaging material (2) provided with said opening member (5).

18. A packaging machine according to any one of the preceding claims 14 to 17, comprising two drying rollers (20) acting on the packaging material from opposite sides, immediately downstream of the nozzle (27); said drying roller (20) having a respective intermediate recess (20a) located on said intermediate longitudinal portion (2a) of said packaging material (2) to allow the passage of said opening means (5).

19. A machine as claimed in claim 18, wherein said nozzles have respective narrow tops (44) at least partially housed in said respective recesses (20a) of said drying roller (20).