HK1167844A - Sealing element for heat sealing packaging material for producing sealed packages of food products pourable within a tube of packaging material - Google Patents

Description

Sealing element for heat-sealing packaging material to produce sealed packages of food products pourable within a tube of packaging material

Technical Field

The present invention relates to a sealing element for heat sealing packaging material to produce sealed packages of food products pourable within a tube of packaging material.

Background

Many food products, such as fruit juice, pasteurized or UHT (ultra high temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.

A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing a laminated strip of packaging material.

The packaging material has a multilayer structure mainly comprising: a base layer for providing stiffness and strength, which may be defined by a layer of fibrous material (e.g. paper) or a layer of mineral-filled polypropylene material; and a plurality of heat-seal plastic material layers, such as polyethylene films, covering both sides of the base layer.

In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas-and light-barrier material, for example aluminium foil or ethylene/ethylene ethyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.

Such packages are known to be produced on fully automatic packaging units, on which a continuous tube is formed from a web supply of packaging material; the web of packaging material is sterilized, for example by applying a chemical sterilizing agent, for example a hydrogen peroxide solution, in the packaging unit, whereafter the sterilizing agent is removed from the surface of the packaging material, for example by heating and evaporation.

The sterilized web is maintained in a closed, sterile environment, and is folded longitudinally into a cylinder and sealed to form a tube.

The tube is fed along a first vertical direction parallel to its axis, filled continuously with the sterilized or sterile-processed food product, and heat-sealed at equally spaced cross sections by two pairs of jaws to form pillow packs, each having top and bottom transverse sealing bands, i.e. bands extending along a second direction orthogonal to the first direction.

The portion of the tube clamped between each pair of jaws is heat-sealed by a heating element carried by one of the jaws (called sealing jaw), and the heating element locally melts the two layers of heat-seal plastic material clamped between the jaws.

For example, packaging materials in which the barrier material layer comprises a sheet of electrically conductive material (e.g. aluminium) are typically heat sealed by a so-called induction heat sealing process, in which when a tube is clamped by two jaws, a loss of current is generated and the sheet of aluminium is locally heated, thereby locally melting the heat-seal plastic material.

In particular, in induction heat sealing, the heating means mainly comprise an inductor powered by a high-frequency current generator, and the inductor in turn mainly comprises one or more inductor bars made of electrically conductive material and extending parallel to the second direction, and which interact with the tube material to induce a loss current therein and heat it to the required sealing temperature.

The heating member is fitted to a sealing element carried by the sealing jaw.

The other jaw (called counter-jaw) comprises a counter-sealing element fitted with a pressure pad made of elastomeric material and cooperating with the inductor bars to heat-seal the tube along a counter-transversal sealing band.

And, the opposing jaws slidingly receive the cutting element. In particular, the cutting element may be slidable toward and away from the sealing element of the sealing jaw in a third direction orthogonal to the first and second directions.

More precisely, the cutting element is normally maintained in a retracted rest position within the counter-sealing element and is moved to a forward cutting position projecting forward from the counter-jaw and engages the blind groove of the sealing element and cuts along the centre line of the top sealing band of the formed package. This separates the formed package from the tube.

There is a need in the industry to avoid accumulation of residue within the groove of the sealing element. In fact, the cutting element, when received in the groove, exerts a force on these residues, causing the sealing element of the sealing jaw to deform. As a result, the life of the sealing element of the sealing jaw may be significantly reduced, and there may be some risk of damaging the cutting element and/or the sealing element, particularly if the sealing element is metal.

The residue may typically comprise part of the packaging material, especially paper mixed with polyethylene.

The aforementioned need is particularly felt when a plurality of opening devices are pre-applied to the tube of packaging material before the heat-sealing of the packages, and the relative opening devices are accommodated within recesses provided in the sealing element of the sealing jaw during the heat-sealing of each package.

In fact, during the start cycle of the packaging unit, when the section of the tube is heat-sealed, the packaging material may be in an incorrect position with respect to the jaws.

In this case, the opening device is not housed in a groove of the sealing element, but can be maintained at least partially between a retracted rest position and a forward cutting position along the trajectory of the cutting element.

In this way, some plastic residues of the opening device may be cut off by the cutting element and accumulate in the groove.

As a result, even when the packaging material has been automatically set in the correct position with respect to the jaws, the presence of plastic residues in the groove may create a risk of deformation and/or damage of the sealing element and/or the cutting element of the sealing jaws.

Disclosure of Invention

The object of the present invention is to provide a sealing element for heat sealing packaging material to produce sealed packages of food products pourable within a tube of packaging material, designed to meet the above-mentioned need in a simple and cost-effective manner.

According to the present invention, there is provided a sealing element for heat sealing packaging material to produce sealed packages of food products pourable within a tube of packaging material, as claimed in claim 1.

Drawings

Preferred, non-limiting embodiments of the present invention will be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 shows a side view of a packaging unit for producing aseptic sealed packages of pourable food products from a tube of packaging material fed along a vertical forming path, with some parts removed for clarity;

figures 2 and 3 show perspective views from different perspectives of respective sides of a sealing element, opposite to each other, according to the invention and fitted to respective sealing jaws of the unit of figure 1, with some parts removed for clarity;

FIG. 4 is a top view of the sealing element of FIGS. 2 and 3 with some parts removed for clarity; and

fig. 5 is a cross section along the line V-V of fig. 4.

Detailed Description

Number 1 in fig. 1 indicates as a whole a packaging unit for producing sealed packages 3 (fig. 1) of a food product from a tube 2 of sheet packaging material.

Unit 1 preferably produces sealed packages 3 of pourable food products, such as pasteurized or UHT milk, fruit juice, wine, etc.

Unit 1 may also produce sealed packages 3 of a food product that can be filled into tube 2 when producing packages 3 and solidified after sealing packages 3. An example of such a food product is a portion of cheese, which melts when producing package 3 and solidifies after sealing package 3.

The packaging material has a multilayer structure (not shown) and comprises a layer of fibrous material, usually paper, covered on both sides with layers of heat-seal plastic material, for example polyethylene. In the case of aseptic packages of long-storage products, such as UHT milk, the packaging material also comprises a layer of gas-and light-barrier material, such as aluminum foil or ethylene/ethylene ethyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered by another layer of heat-seal plastic material forming the inner surface of package 3 eventually contacting the food product.

The packaging material is further provided with a plurality of equally spaced opening devices 11 (fig. 1) for allowing the pourable food product to be filled from the formed package 3.

The tube 2 is formed in a known manner by longitudinally folding and sealing a web (not shown) of heat-seal sheet material, filled with a filling tube (not shown) of sterilized or sterile-processed food products for packaging, and fed in a known manner not shown along a vertical path indicated by axis a in fig. 1.

The unit 1 comprises two forming assemblies 4 which move vertically along respective rails (not shown) and interact periodically and continuously with the tube 2 to clamp it at equally spaced profiles and to perform induction heat sealing and cutting operations on the tube 2.

Each forming assembly 4 essentially comprises a slider (not shown) extending along a respective track, and two jaws 5, 6 (only shown for the sake of clarity of understanding the invention) hinged to said slider about respective horizontal axes and movable between a closed position and a fully open position.

In the example shown, the jaws 5, 6 of each forming assembly 4 have respective arms 7, 8. The jaws 5, 6 extend parallel to a direction B perpendicular to the direction a (fig. 1) and are arranged on opposite sides of the tube 2.

Each forming assembly 4 also comprises two facing forming shells 9, 10 hinged to the respective jaws 5, 6 and movable between an open position (shown in figure 1 with reference to the top forming assembly 4) and a closed position (shown in figure 1 with reference to the bottom forming assembly 4), which are pushed into the open position by elastic means and which match in the closed position to form a space between them defining the shape and volume of the packages 3 to be formed.

Jaws 5, 6 of each forming assembly 4 also comprise an induction sealing element 15 and an opposite sealing element 16, respectively, to perform, on each section of tube 2 of packaging material gripped between opposite jaws 5, 6, an induction heat-sealing operation and a cutting operation, respectively, along the centre line of the section.

Referring to fig. 2 to 5, each sealing member 15 includes:

a support 19 connected by conventional fastening means to the arm 7 of the jaw 5 of the opposite forming assembly 4;

two pairs of inductive elements 20, 21 (shown in fig. 5) housed in respective seats in the supporting body 19; and

two inserts 31 (shown in fig. 5) made of flux-concentrating material and fitted inside the supporting body 19.

Alternatively, the support 19 may be integrally formed with the arm 7 of the jaw 5 of the opposite forming assembly 4.

And the insert 31 and the inductive elements 20, 21 are assembled to the support body 19 by means of two pairs of injected plastic elements 90, 91.

With particular reference to fig. 5, the inductive elements 20, 21 are defined by respective conductive bars extending along the direction B and arranged in pairs parallel to the direction B on opposite sides of the median plane R. Each plane R is orthogonal to direction a when the respective jaws 5, 6 are in the closed position.

More specifically, the inductive elements 20 are symmetrical about the plane R and are interposed between the inductive elements 21, the inductive elements 21 also being symmetrically disposed on opposite sides of the plane R.

The inductive elements 20, 21 interact with the tube 2 of packaging material by means of respective active surfaces 25, 26, preferably rectangular, which are elongated along direction B, extend in the same plane perpendicular to plane R, and have a width along direction D and a length along direction B. The same active surfaces 25 are obviously interposed between the active surfaces 26 along the direction D, the active surfaces 26 also being identical and having the same length as the active surfaces 25.

More precisely, when the jaws 5, 6 are in the closed position, the direction D is orthogonal to the direction B and coincides with the direction a.

As shown in fig. 5, respective projections 28, which are elongated along direction B, project from active surface 25 towards tube 2 of packaging material. The projections 28 may be continuous or segmented, extend along substantially the entire length of the respective active surface 25, and serve to increase the clamping pressure on the tube 2 when heat sealed.

The support 19 extends symmetrically about the plane R and mainly comprises:

two outer lateral parallel walls 53, 54 lying in respective planes parallel to plane R;

an outer wall 55 connected to jaw 6 and extending between walls 53 perpendicular to walls 53;

an outer wall 56 opposite wall 55 and delimiting cavity 52 housing inductive elements 20, 21 and insert 31.

In particular, the inductive elements 20, 21 cooperate with the wall 56 on opposite sides of the active surfaces 25, 26. Further, the wall 56 cooperates with the insert 31.

Each wall 53, 54 has opposite recesses 57 (fig. 2, 3 and 5) adapted to be engaged by respective opening devices 11 pre-applied on the packaging material. In the illustrated embodiment, the recess 57 is semi-circular.

In particular, on the basis of the side of the sealing element 15 with respect to the direction a and in normal operation of the unit 1, one of the recesses 57 is engaged by the respective opening device 11.

More specifically, the recesses 57 are offset with respect to each other.

Each sealing element 15 includes a groove 60 (fig. 1, 4, and 5) and each opposing sealing element 16 includes a cutting element 62 (fig. 1).

More precisely, the grooves 60 extend parallel to the direction B and symmetrically with respect to the plane R.

Further, the groove 60 is defined by the wall 56 and delimited on one side of the direction a by an opening 61.

The cutting member 62 is flat, is housed in sliding manner inside a front seat on the opposite sealing element 16 of the opposite forming assembly 4, is movable along the plane R, and is actuated in a known manner, not shown, by a hydraulic cylinder housed in the jaw 5.

The cutting member 62 is normally kept in a retracted rest position by known elastic means (not shown), is completely housed inside the relative sealing element 16, and is moved by the relative hydraulic cylinder to a forward cutting position projecting forward from the jaw 5, engages the groove 60 in the sealing element 15 of the relative jaw 6, and cuts along the centre line of the relative section of the pipe 2.

Preferably, the cutting member 62 comprises a plate-like base integral with the output member of the actuating hydraulic cylinder; and a cutter having a smaller thickness than the base in direction a to ensure a high cutting pressure and avoid damaging the packaging material.

The sealing element 15 also comprises two pressure pads 65 (fig. 1) made of heat-resistant elastomeric material, preferably nitrile rubber, and housed in respective front cavities of identical shape formed in the jaws 5 of the opposite forming assemblies 4, symmetrically arranged on opposite sides of the plane R. The pressure pads 65 of each counter-sealing element 16 cooperate with the active surfaces 25, 26 of the inductive elements 20, 21 of the counter-sealing element 15 to grip and heat seal the tube 2 on opposite sides of the plane R.

Advantageously, each sealing element 15 comprises a pair of slots 70 (fig. 5) extending between the groove 60 and the opposite walls 53, 54.

In more detail, each slot 70 extends between an end 80 of the opposite groove 60 opposite the opening 61 and the opposite recess 57. And the slot 70 tapers toward the opening 61.

Each slot 70 includes a portion 71 in direct communication with groove 60 and a portion 72 disposed between portion 71 and the opposing recess 57.

In the example shown in fig. 5, the portion 71 of each slot 70 has a length along direction B and a width along direction D, which is orthogonal to direction B and coincides with direction a when the jaws 5, 6 are in the closed position.

Portion 72 of each slot 70 has a length along direction B and a width along direction E that is oblique to direction D.

The thickness of the portions 71, 72 measured along each direction D, E is constant.

Also, the thickness of each portion 72 measured along direction E is greater than the thickness of the opposing portion 71 measured along direction D and less than the maximum width of the opposing groove 60 measured along direction D.

Portion 72 also comprises, on the opposite side to portion 71, an end opening 75, this end opening 75 being defined by recess 57 and lying in a plane parallel to plane R.

More precisely, the opening 75 is rectangular, with two long sides 76 parallel to the direction B and two short sides 77 orthogonal to the direction B.

In actual use, tube 2 filled with pourable food product and provided with opening devices 11 is fed along direction a, and forming assemblies 4, working out of phase by half a cycle, move up and down on respective tracks.

More specifically, as the forming assembly 4 moves up and down, the jaws 5, 6 move between a closed position (fig. 1) in which they heat seal the section of the tube 2 and an open position disengaged from the tube 2.

When the forming assembly 4 is in operation, the shells 9, 10 perform their work cycle. More precisely, the shells 9, 10 move between an open position (shown in fig. 1 with reference to the top forming assembly 4) and a closed position (shown in fig. 1 with reference to the bottom forming assembly 4).

Once jaws 5, 6 are in the closed position and half-shells 9, 10 are closed around tube 2, the packaging material disposed between sensing elements 20, 21 of sealing element 15 and pad 65 of counter-sealing element 16 is heat-sealed to form a transverse sealing band of counter-package 3.

In normal operation of unit 1, the movement of the packaging material along direction a is preferably perfectly synchronized with the movement of jaws 5, 6 between the respective closed and open positions.

Thus, once jaws 5, 6 of each forming assembly 4 are in the closed position and half-shells 9, 10 are closed around tube 2, the relative opening devices 11 are arranged with their axes parallel to direction a and housed in respective recesses 57 of sealing element 15 of jaws 5.

During heat sealing of the section of tube 2, cutting element 62 remains in a retracted rest position within the seat of the opposite counter-sealing element 16.

Once each sealing element 15 has sealed the section of tube 2 and formed the transversal sealing band of relative pack 3, cutting element 62 is moved towards the forward cutting position.

As a result, cutting elements 62 cut along the centre line of the opposite cross section of tube 2, thereby separating the formed packages 3 from tube 2.

Cutting elements 62 engage opposing grooves 60 when the forward cutting position is reached.

During the start-up cycle of the unit 1, the packaging material may be in an incorrect position relative to the jaws 5, 6 when the cross-section of the tube is heat sealed.

In other words, when each sealing element 15 heat-seals opposite sections of tube 2, the corresponding opening device 11 can be housed outside recess 57.

Instead, the opening device 11 may remain along the trajectory of the cutting element 62.

In this case, the cutting element 62 cuts away some residues of the plastic material of the opening device 11.

These plastic residues are pushed out of the support body 19 through the slots 70 when the cutting elements 62 engage the grooves 60. In particular, the aforementioned plastic residues accumulate on the outer surface of the recess 57, which can be easily removed.

Thus, during the heat-sealing of the section of tube 2, groove 60 is substantially free of plastic residues when the packaging material is completely synchronized for the second time with the movement of jaws 5, 6 and opening devices 11 are successively housed in opposite recesses 57.

Any other possible residue of packaging material (for example paper mixed with polyethylene) that may remain in the groove 60 is pushed outside the supporting body 19 through one or two slots 70 and accumulates on the outer surface of one or two recesses 57 that can be easily removed.

The advantages of the sealing element 15 according to the invention will be clear from the foregoing description.

In particular, due to the presence of the slots 70, residues, such as paper mixed with polyethylene, which may remain in the grooves 60, are easily pushed by the cutting elements 62 towards the outer wall 53 of the sealing element 15, where they can be easily removed.

Thus, cutting element 62 may freely slide within groove 60 without deforming sealing element 15.

As a result, the risk of damaging the sealing element 15 and/or the cutting element 62 is greatly reduced and the service life of the sealing element 15 is increased with respect to the solution described in the introductory part of the description.

The presence of the slot 70 is particularly advantageous in the case of tubes 2 equipped with pre-applied opening devices 11.

In fact, in this case, when heat-sealing the section of tube 2, the packaging material may be in an incorrect position with respect to jaws 5, 6.

Thus, instead of being housed in the recess 57 of the opposite sealing element 15, the opening device 11 can be held between the retracted rest and forward cutting positions along the trajectory of the cutting element 62, and some residues of plastic material can be cut off by the cutting element 62.

Due to the presence of the slots 70, these plastic residues do not remain in the groove 60, but are easily pushed by the cutting element 62 towards the outer wall 53 of the sealing element 15, where they can be easily removed.

As a result, the groove 60 is substantially free of plastic residues even when the packaging material has been automatically set in the correct position for the second time with respect to the jaws 5, 6 and the opening device 11 is accommodated in the opposite recess 57.

In this case, therefore, the risk of damaging the sealing element 15 and/or the cutting element 62 is also greatly reduced, and the service life of the sealing element 15 is improved with respect to the solution described in the introductory part of the description.

Clearly, changes may be made to sealing element 15 as described and illustrated herein without, however, departing from the scope of the present invention as defined in the accompanying claims.

In particular, the sealing element 15 can be equipped with different heating means, such as a sonotrode or a heating rod.

Also, the packaging unit may have no track and slider, but comprises two chain conveyors provided with a respective plurality of jaws 5 and 6, so as to define a cavity into which the tube 2 is fed, and moves along respective closed paths having respective linear portions facing each other.

The portion 71 of the slot 70 may have different thickness values measured along the direction D. In particular, the thickness of portion 71 measured along direction D may be equal to the thickness of groove 60 measured along direction D.

Finally, the support body 19 of the sealing element 15 may comprise only one central slot 70.

Claims (8)

1. A sealing element (15) for heat-sealing packaging material to produce sealed packages (3) of a food product pourable within a tube (2) of packaging material;

the sealing element (15) comprises:

-heating means (20, 21) adapted to heat-seal said packaging material at spaced sections of said tube (2) so as to form a plurality of said sealed packages (3); and

-a groove (60) engageable by a cutting element (62) carried by the counter-sealing element (16) during a cutting operation to separate the sealed package (3) from the tube (2);

-characterized by comprising at least one slot (70) extending between the groove (60) and the first outer wall (53, 54) of the sealing element (15).

2. A sealing element according to claim 1, wherein the first outer wall (53, 54) defines a recess (57) which, during the cutting operation, can be engaged by an opening device (11) located on the packaging material; the slot (70) is disposed between the recess (57) and the groove (60).

3. The sealing element according to claim 2, characterized in that said slot (70) comprises:

-a first portion (71) adjacent to said groove (60) and in direct communication with said groove (60); and

-a second portion (72) arranged between the first portion (71) and the recess (57), adjacent to the first portion (71) and the recess (57) and in direct communication with the first portion (71) and the recess (57).

4. A sealing element according to claim 3, characterized in that the thickness of the second portion (72) is smaller than the thickness of the groove (60) and larger than the thickness of the first portion (71).

5. A sealing element according to claim 3 or 4, wherein the groove (60) and the slot (70) both have a length in a second direction (B) transverse to the first direction (A) along which the tube (2) extends.

6. A sealing element according to claim 5, characterized in that the second portion (72) is inclined with respect to the first portion (71).

7. A sealing element according to any one of the preceding claims, characterized by comprising a second outer wall (56) defining an outer opening (61) of said groove (60) and adjacent and transversal to said first wall (53).

8. A packaging unit (1) for producing sealed packages (3) of a food product from a tube (2) of packaging material fed along a first direction (a) and filled continuously with said food product;

the unit (1) comprises:

-at least two pairs of jaws (5, 6) acting periodically and continuously on the tube (2) to grip the tube (2) at spaced sections;

-a sealing element (15) and an opposite sealing element (16) fitted to the first and second jaws (5, 6) of each said pair, respectively, and adapted to heat seal the packaging material at said spaced sections so as to form a plurality of sealed packages (3);

-said counter-sealing element (16) comprises a cutting element (62) adapted to interact with said packaging material to separate the formed package (3) from said tube (2);

characterized in that the sealing element (15) is a sealing element according to any one of the preceding claims.