HK1017870B - Packaging unit for continuously producing sealed packages, containing pourable food products, from a tube of packaging material - Google Patents

Description

Packaging device for continuously producing sealed packages from a tube of packaging material

The present invention relates to a packaging unit for continuously producing aseptic sealed packages containing pourable food products from a tube of packaging material.

More specifically, the packaging unit according to the invention is intended to produce aseptic sealed packages of substantially parallelepiped shape.

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

A typical example of such a package is a parallelepiped-shaped packaging container known by the name Tetra Brik Aseptic (registered trade mark) for liquid or pourable food products, which is formed by folding and sealing a web of packaging material in web form. The web packaging material comprises layers of fibrous material, for example paper, covered on both sides with thermoplastic material, for example polyethylene; and also a barrier layer, for example of aluminium foil, which is also covered with a layer of thermoplastic material, on the side of the packaging material eventually contacting the food product in the package.

As is known, packages of the above type are produced in fully automatic packaging machines in which a packaging material fed in strip form is formed into a continuous tube. The web packaging material is sterilized on the packaging machine, for example by applying a chemical sterilizing agent, such as hydrogen peroxide; after sterilization, the sterilizing agent is removed from the surface of the packaging material, for example by evaporation by heating; and the thus sterilized web packaging material is maintained in a closed, sterile environment and is folded and sealed longitudinally to form a tube.

The tube is filled with the sterilized or sterile-processed food product and sealed at equally spaced transverse portions, where it is then cut into pillow packs, and finally they are folded mechanically into parallelepiped packages.

Packaging machines of the above type are known in which the transverse portions of the tube are sealed by two sealing jaw devices moved by respective arms so as to grip the tube at intervals at successive transverse portions for sealing. One of the sealing jaws includes an induction heating device for locally melting the thermoplastic material when the sealing jaw device is gripping the pipe, thereby welding the thermoplastic material skin and thereby sealing a transverse portion of the pipe.

Each sealing jaw device completes a relatively complex operating cycle in which the respective sealing jaw is brought into contact with the tube at an upper station of the packaging machine; the closing jaw device, which firmly grips the tube, is lowered together with the tube along the feed axis of the tube in order to seal the transverse portion and is then opened at a lower station of the packaging machine. The second closing jaw arrangement also completes the same cycle, but with a time interval corresponding to the production speed of the packaging machine, so that the portion of the tube extending between the first seal formed by one closing jaw arrangement and the second seal subsequently formed by the other closing jaw arrangement forms the packages.

Although widely used and fairly reliable, the production speed of known machines of the above type is limited because of the periodic reciprocating movement of the large-mass parts involved (arms, clamps and corresponding actuators), the inertia of which limits the production speed to thousands of cycles per hour, beyond which dynamic problems are encountered, impairing the functioning of the machine.

In order to increase the production speed of such machines, continuous packaging units have been proposed which comprise two chain conveyors defining respective endless paths and equipped with a set of sealing jaws and counter-sealing jaws, respectively. These two paths comprise opposite and mutually parallel branch paths and feed the tube of packaging material between them; and the sealing jaws on one conveyor cooperate with corresponding counter-sealing jaws on the other conveyor along said branch paths of the respective paths to grip the tube and seal the package at a set of sequential transverse portions. Continuous chain conveyor systems overcome the dynamics problems to some extent and increase the maximum production speeds not achievable with reciprocating systems.

Such a machine is described, for example, in US-re33,467.

Despite the trial for a certain time, the machine, to the applicant's knowledge, has not been put into practical use.

A problem with the above-described machine is that it is difficult to accurately and reliably control the contact pressure exerted by the sealing jaws and the counter-jaws on the packaging material to form the seal, and this contact pressure is generated by the contact between a control cam fixed to the machine structure and a corresponding cam follower which runs along and is connected to the corresponding sealing jaws and counter-jaws. Since the contact pressure is highly dependent on manufacturing and assembly tolerances, considerable difficulties are encountered in setting the machine and maintaining optimum operating conditions once the cam and corresponding cam follower wear, and operating temperature changes.

In order to achieve a reliable production process it is important to control the sealing temperature to ensure that the packaging is not damaged and that the sterility of the enclosed objects is maintained.

The object of the present invention is to provide a packaging unit for continuously producing aseptic sealed packages containing a pourable food product, which overcomes the above-mentioned drawbacks associated with known machines.

According to the present invention, there is provided a packaging unit for continuously producing aseptic sealed packages from a tube of heat-seal packaging material containing a pourable food product, the heat-seal material being in the form of sheets and being fed along a vertical feed path; the tube is filled with the food product; and the apparatus comprises:

a first chain conveyor having a set of sealing jaws and defining an endless first path along which said sealing jaws travel;

a second chain conveyor having a set of reverse blocking tongs and defining a second path of circulation along which the reverse blocking tongs travel;

said first and said second path comprise respective operative portions of said feed path adjacent to a tube of packaging material and extend symmetrically on opposite sides of said feed path, so that said sealing jaws and respective counter-sealing jaws cooperate to grip said tube at equally spaced transverse portions;

said device further comprising, at least along said respective working portion, first cam guide means for guiding said sealing jaws and second cam guide means for guiding said counter-sealing jaws; and said sealing jaws and said counter-sealing jaws comprise cam follower means cooperating with said respective first and second cam guide means;

and said sealing jaw and said counter-sealing jaw further comprise heating means for heat-sealing said packaging material and pushing means for applying a clamping pressure for clamping said packaging material towards said heating means, respectively.

Characterized in that said reverse blocking tongs each comprise a main body comprising said cam follower means and defining a link of said second chain conveyor; the urging means includes a pressing member mounted on the main body and movable relative to the main body in the direction of the clamping pressure force, and elastic means interposed between the main body and the pressing member and defining the clamping pressure force.

A non-limiting preferred embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a packaging device according to the teachings of the present invention with parts removed for clarity;

FIG. 2 is a schematic partial side view of the apparatus of FIG. 1;

FIG. 3 is a perspective view of a sealing jaw and a corresponding reverse sealing jaw of the apparatus of FIG. 1;

FIG. 4 is a front view of the reverse sealing jaw of FIG. 3;

FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4;

FIG. 6 is an enlarged detail of FIG. 5;

FIG. 7 is a half cross-sectional view of the sealing jaw and reverse sealing jaw of FIG. 3 in a clamped position with parts removed for clarity.

With reference to fig. 1 and 2, numeral 1 indicates a packaging unit for producing aseptic sealed packages 2 from a continuous tubular packaging material 14, said tubular packaging material 14 containing a pourable food product such as pasteurized or UHT milk, fruit juice, wine or the like.

The tube 14 is formed upstream of the packaging unit 1 in a known manner by folding and sealing a strip of heat-seal material in a longitudinal direction and is filled upstream with the sterilized or sterile-processed food product to be packaged.

The device 1 comprises a frame 3 (fig. 1) defined by two side walls 4, 5 and two parallel transverse walls 6, 7, the transverse walls 6, 7 being rigidly fitted between the side walls 4, 5 and defining, with the side walls 4, 5, an opening 8; and two chain conveyors 10, 11 mounted on the frame 3 and respectively comprising mutually cooperating sealing jaws 12 (only one shown in figure 1) and counter-sealing jaws 13 (only one shown in figure 1) for interacting with a tube 14 of packaging material fed along a vertical path a through the opening 8.

The conveyors 10 and 11 define respective endless paths P and Q along which the sealing jaw 12 and the counter-sealing jaw 13 run and which extend around the walls 6 and 7 of the frame 3, respectively.

Conveyor 10 includes an articulated chain 15 extending along path P; and two drive wheels 16 engaged on either side of chain 15 at the bottom end of path P. The sealing jaw 12 is an integral part of the chain 15 and constitutes spaced links of the chain 15, and the sealing jaw 12 is interconnected in an articulated manner by pairs of links 17.

More specifically, each closing jaw 12 (fig. 3) comprises an elongated body 20 extending in a direction perpendicular to path a and parallel to wall 6 and having respective end projections 21 and 22, each provided with a projecting first and second pin 23, 24, spaced apart from each other and having respective axes 25, 26 parallel to the main dimension of body 20. The links 17 are hinged to the pins 23, 24 of the closing jaws 12, so as to connect the pin 23 of one closing jaw 12 to the pin 24 of the adjacent closing jaw.

Similarly, conveyor 11 comprises an articulated chain 27 extending along path Q; and two drive wheels 28 are engaged with the chain 27 at the bottom end of the path Q. The chain 27 is constituted by a set of mutually articulated opposite sealing jaws 13, and only the differences with respect to the sealing jaws 12 will be described in detail hereinafter, and the same numbering will be used for parts similar or corresponding to those described in connection with the sealing jaws 12. In short, each counter-jaw 13 comprises a body 20 with a pair of end pins 23, 24, around which end pins 23, 24 a link 17 is hinged to connect adjacent counter-jaws 13.

Each sealing jaw 12 comprises an induction heating element 29 mounted on the body 20 in a direction perpendicular to the path a of the pipe 14, which then comprises a pair of straight and parallel active surfaces 30, and is supplied with power by a pair of contact brushes 34, which in use cooperate with a power supply bar (not shown) mounted on the frame 3 and extending in the region of the path P inside the opening 8.

Opposite a heating element 29, each counter-jaw 13 comprises a pressure bar 35 (fig. 4 and 5), which pressure bar 35 cooperates with the heating element 29 of the respective jaw 12 to grip a transverse portion of the tube 14 (fig. 2). On the front surface 46 of the respective closing jaw 12 in use, the pressure bar 35 comprises two bands 36 made of relatively flexible elastic material, the bands 36 cooperating with the packaging material in a position opposite the active surface 30 of the heating element 29.

The sealing jaw 12 and the counter-sealing jaw 13 each comprise a respective control device 37 for controlling the volume of the package 2 as it is formed. The respective control devices 37 do not form part of the present invention and are not described in detail.

The movement of the sealing jaw 12 and the counter-sealing jaw 13 is controlled by a respective pair of cams 50, 51, which pairs 50, 51 are mounted on the walls 6, 7 of the frame 3 and cooperate with a respective pair of rollers 52, 53 mounted on the sealing jaw 12 and the counter-sealing jaw 13.

More specifically, as shown in fig. 3, each of the sealing jaw 12 and the counter-sealing jaw 13 comprises a first pair of rollers 52, 53 mounted idly in the end bosses 21 of the main body 20, and a second pair of rollers 52, 53 mounted idly in the end bosses 22 of the main body 20; and projections 21, 22 each comprise a pair of parallel and juxtaposed seats 54, 55 machined on the rear side (i.e. the side facing away from heating element 29 or pressure bar 35) and extending in a direction perpendicular to axes 25, 26 of pins 23, 24 and parallel to the plane defined by axes 25, 26.

The rollers 53 of each pair are housed in respective outer seats 54 (i.e. near the end of the body 20) and are mounted on respective pins 23; the rollers 52 of each pair are received in respective inner seats 55 and are mounted on respective pins 24.

Two pairs of cams 50, 51 are provided on the wall 6 (figure 1) with which the respective pairs of rollers 52, 53 of the sealing jaw 12 engage. And similarly, the wall 7 is provided with two pairs of cams 50, 51 with which respective pairs of rollers 52, 53 of the counter-pliers 13 cooperate.

Cams 50, 51 comprise a substantially U-shaped portion 50a, 51a extending around the top edge of respective wall 6, 7 to define a transition zone for respective chains 15, 27 of conveyors 10, 11 opposite respective drive wheels 16 and 28; and respective portions 50b and 51b extending along respective walls 6, 7 within opening 8. The portions 50a, 51a define a path portion P1, Q1 along which the sealing jaw 12 and the counter-sealing jaw 13 approach each other and come into contact with the tube 14 of packaging material; portions 50b, 51b define face-to-face substantially parallel path portions P2, Q2 along which sealing jaw 12 and counter-jaw 13 are held in pressure contact to form a seal defining package 2.

Cams 50, 51 release respective chains 15, 27 downstream of respective drive wheels 16, 28 at respective portions P3 and Q3 of paths P and Q.

Along the portions P3, Q3, the chains 15, 27 cooperate with the respective pairs of tensioners 56 to tension the chains in such a way as to ensure that the rollers 52, 53 of the sealing jaw 12 and of the counter-sealing jaw 13 remain in contact with the respective cams 50, 51.

Each tensioner 56 comprises a movable guide 57 hinged on a support 58 about a horizontal axis, the support 58 being fixed to the wall 6 or 7; and a spring 59 interposed between the guide plate 57 and the wall 6 or 7. On the surface facing away from the wall 6 or 7, the guide plate 57 comprises two juxtaposed rolling tracks 60, 61, which cooperate by means of a spring 59 with the rollers 52 and 53 of the sealing jaw 12 or counter-sealing jaw 13, respectively.

According to the invention, the pressure bar 35 of each counter-clamp is fixed to the body 20 in such a way as to allow limited movement thereof in a direction perpendicular to a plane defined by the axes 25, 26 of the pins 23, 24, the direction indicated by X in figures 5 and 7 defining, in use, the direction in which the pressure is applied by each clamp/counter-clamp to the pipe 14.

Pins 65, whose two axes are respectively parallel to the direction X, are mounted in a projecting manner, in particular by screwing, at the rear of the pressure bar 35, at the opposite ends of the front surface 46 of the pressure bar, and are respectively loosely engaged with positioning holes 66 made in the body 20.

The rod 35 is mounted on the body 20 by interposing two elastic connection assemblies 67 for generating, in use, a reaction pressure in the X direction to abut the rod 35 against the respective closing jaw 12.

The assemblies 67 are located at opposite ends of the rod 35 and lie against the front surface 46, one of the assemblies 67 being shown in section on an enlarged scale in fig. 6, to which reference is made below.

Each module 67 substantially comprises a guide shaft 70 having an axis parallel to direction X, which guide shaft 70 is mounted on body 20 with a substantially cylindrical through cavity 71, with considerable looseness in the radial direction, and each module 76 further comprises an end flange 72 mounted on the rear portion of body 20 around through cavity 71 by means of a set of screws 73.

The through-cavity 71 houses a highly rigid helical spring 75 made of steel wire of quadrangular section and compressed between the flange 72 and a cup-shaped member 76, the cup-shaped member 75 being axially loosely slidable in the through-cavity 71 and connected to the rod 35 in axial and radial directions. More specifically, cup 76 comprises an annular base wall 77 axially cooperating with spring 75, and a cylindrical wall 78 loosely housed in through cavity 71, wall 77 comprising a tapered internal edge 79 cooperating in sliding manner with shaft 70.

Through cavity 71 comprises a circumferential groove 80 housing an annular seal 81 which cooperates in sliding manner with cylindrical wall 78 of cup-shaped member 76; and the through cavity 71 and the cup 76 are conveniently supplied with lubricating oil.

The small diameter end 82 of the shaft 70 is housed inside a cylindrical seat 83 of the pressure rod 35, between which a bush 84 of elastomeric material is interposed.

Bushing 84 is interposed between a shoulder 85 of shaft 70 and a stop washer 86 coaxial with shaft 70, washer 86 being mounted on the end of shaft end 82. The periphery of the washer 86 axially cooperates with an annular shoulder 87 of the seat 83 of the rod 35 to axially press the shoulder 87 against the bushing 84 and fix the rod 35 towards the cup 76 against the spring 75. More specifically, the base wall 77 of the cup 76 defines a retaining ring 90, the retaining ring 90 engaging the seat 83 of the pressure rod 35.

The operation of the device 1 is as follows.

As indicated by the arrows in fig. 2, conveyors 10 and 11 are made to rotate in opposite directions in a known manner, so as to engage tube 14 of packaging material from the end of portion P1, Q1 of respective path P, Q and along respective portions P2, Q2, respective sealing jaw 12 and counter-sealing jaw 13, according to a movement defined by the profile of cams 50, 51.

After the first stage, in which the tube 14 is contacted and progressively compressed and comprises a flat sealing band 88 in which the material is partially folded to form a band extending transversely of the tube 14, the sealing jaws 12 and the counter-sealing jaws 13 reach the respective rectilinear portions 50b, 51b (figure 2) of the cams 50, 51, where the maximum clamping pressure is applied to the tube 14 and the heating element 29 of each sealing jaw 12 is energised to form the heat seal.

The distance between the portions 50b and 51b of the substantially similar respective cams 50, 51 of the sealing jaw 12 and the counter-sealing jaw 13 is constant along a substantial part of said portions and is chosen so as to slightly compress and deform the spring 75 of the counter-sealing jaw 13.

This pressing is made possible by the fact that the elastic stiffness of the bush 84 made of spring material is significantly less than the stiffness of the spring 75, so that when the rod 35 cooperates with the heating element 29 of the respective closing jaw 12 to grip the packaging material, the pressure to which the rod 35 is subjected axially compresses the bush 84 in the gripping direction X and is almost completely transmitted to the spring 75 through the respective cup 76.

Since the spring 75 is only deformed to a small extent, the clamping pressure exerted on the packaging material is substantially determined by the preload of the spring 75.

The advantages of the device 1 according to the invention are evident from the above description.

In particular, the assembly 76 of elastically connecting the pressure bar 35 to the respective counter-clamp 13 allows to precisely and reliably control, in a straight-ahead manner, the clamping pressure exerted on the packaging material.

Moreover, by means of the inner lip 79, which allows the cup 76 to rock on the shaft 70, and the softer elastic bushing 84, the assembly 67 allows, to a certain and limited extent, the positioning of the stem 35, so that the stem 35 is able to exert a uniform pressure along the entire sealing portion, even in the presence of small positioning errors of the stem 35 due to machining and assembly tolerances.

Finally, the elastic bushing 84 prevents the sliding connection between each pressure rod 35 and the respective shaft 70, preventing, together with the seal 81, the penetration of external agents, in particular liquids, into the through-cavity 71, which could oxidize the spring and cause the formation of scale, preventing the effective functioning of the elastic connection assembly 67.

It is clear that, as mentioned above, many modifications can be made to the device 1 without going beyond the scope of the claims.

Claims (8)

1. A packaging unit (1) for continuously producing aseptic sealed packages (2) from a tube (14) of heat-seal packaging material, wherein the packages (2) contain a pourable food product, the heat-seal material being in the form of sheets and being fed along a vertical feed path (a); the tube (14) is filled with the food product; and the apparatus comprises:

a first chain conveyor (10) with a set of sealing jaws (12) and defining a first path (P) of circulation along which said sealing jaws (12) travel;

-a second chain conveyor (11) with a set of counter-jaws (13) and defining a second path (Q) of circulation along which said counter-jaws (13) travel;

said first and said second path (P, Q) comprising respective operative portions (P1, P2; Q1, Q2) of said feed path (A) close to a tube (14) of packaging material and extending substantially symmetrically on opposite sides of said feed path (A), so that said pincers (12) cooperate with said respective counter-pincers (13) to grip said tube (14) at equally spaced transverse portions (88);

said device (1) comprising, at least along said respective working portions (P1, P2; Q1, Q2), first cam guide means (50, 51) for guiding said sealing jaws (12) and second cam guide means (50, 51) for guiding said counter-jaws (13); and said sealing jaw (12) and said counter-sealing jaw (13) comprise cam follower means (52, 53) cooperating with said respective first and second cam guide means (50, 51);

and said sealing jaw (12) and said counter-sealing jaw (13) further comprise heating means (29) for heat-sealing said packaging material, and pushing means (35, 67) for applying a clamping pressure so as to clamp said packaging material towards said heating means (29), respectively;

characterized in that said counter-jaws (13) each comprise a main body (20), then the main body (20) comprises said cam follower means (52, 53) and defines a link of said second chain conveyor (11), said pushing means (35, 67) comprising a pressure member (35) mounted on the main body (20) and movable with respect to said main body (20) along said clamping pressure direction X, and spring means (75) interposed between said main body (20) and said pressure member (35) and defining said clamping pressure.

2. A device as claimed in claim 1, characterized in that said pressure member (35) is in the form of an elongated rod extending in a direction perpendicular to said feed path of the tube (14) of packaging material; the pushing means comprise a pair of elastic connection assemblies (67) with respective elastic means (75) and connecting the pressure member (35) to the main body (20) near respective opposite ends of the pressure member (35).

3. The device according to claim 1 or 2, characterized in that said elastic connection assemblies (67) each comprise a substantially closed seat (71) housing said elastic means (75); and sealing means (81, 84) for preventing the penetration of external media into said seat (71).

4. The device according to claim 2, characterized in that said elastic connection assemblies (67) each comprise a guide (70) for said pressure member (35), said guide (70) being mounted on said main body (20) and extending in the direction (X) of said clamping pressure; and positioning means (76, 84) for positioning said pressure member (35) with respect to said guide member (70) and allowing a small amount of misalignment.

5. The device according to claim 4, characterized in that said positioning means comprise a flexible member (84), said flexible member (84) being connected to said pressure member (35) and to said guide member (70) in the direction (X) of said clamping pressure, and said flexible member (84) being deformable so as to allow said pressure member (35) to move with respect to said guide member (70).

6. The device according to claim 4 or 5, characterized in that said guide is a shaft (70) whose axis is parallel to said direction (X) of said clamping pressure and extends through said seat (71) housing said elastic means (75) and is rigidly fixed to said body (20); said elastic means comprise a spring (75) coaxial with said shaft (70); and said positioning means comprise a cup (76), said cup (76) being connected to said pressure member (35) and having a base wall (77) axially cooperating with said spring (75), and a side wall (78) slidingly accommodating said spring (75) in said seat (71).

7. The device according to claim 6, characterized in that said base (77) of said cup (76) comprises a tapered inner edge (79) sliding on said shaft (70).

8. The device according to claim 6, characterized in that said sealing means comprise an annular seal (81) housed in said seat (71) and cooperating in a sliding manner with said side wall (78) of said cup-shaped member (76).