Extrusion head for extruding tubular blanks for the production of liquid containers with zones with different properties and characteristics

Abstract

The present invention relates to an extrusion head (1) for extruding thermoplastic material within a blow-molding system (10) for blow molding containers, characterized in that it comprises a distribution channel (3) with areas (31, 32, 13) fed by distinct inlet channels (2, 11), allowing the formation of containers equipped with zones with different properties and characteristics.

Description

[0001] EXTRUSION HEAD FOR EXTRUDING A TUBULAR PARISON FOR PRODUCING LIQUID CONTAINERS EQUIPPED WITH ZONES WITH DIFFERENT PROPERTIES AND CHARACTERISTICS

[0002] The present invention falls within the field of methods for producing liquid- filled containers in parison form, wherein, in a step defined as the “blowing” step (BLOW), the plastic is extruded in a tubular form which, through a pressure difference exerted on its wall, adheres to the walls of a mold to form the container. In the subsequent “sealing” step (SEAL), the container is closed by sealing specific sections of the container, and, before performing the final seal, which closes the opening through which the container can be filled, a filling step (FILL) may be provided, wherein the container can also be filled with a liquid via a movable nozzle.

[0003] In particular, the invention concerns an extrusion head for producing a tube for carrying out the aforementioned method, which comprises at least two internal flow channels for supplying a fluid thermoplastic plastic, which are configured to produce containers with zones having different characteristics.

[0004] Extrusion heads of this type are described in patents EP0361123 and WQ201 9057499, which depict an extrusion head based on the same principle, i.e. extruding material in a tubular form, which presents multiple holes inside, each allowing a respective nozzle and sterile air to pass through.

[0005] A particular requirement of these extrusion heads is to distribute the plastic material uniformly along the entire surface of the tubular form, so as to guarantee the correct thickness and the correct exiting speed of the tubular form as it leaves the extrusion head.

[0006] Such solutions are not optimal from several points of view.

[0007] A commonly existing problem in the BFS process or just in the blow-forming process is that when the parison is formed from the mold, a part of the parison (usually the sides) is discarded because it is not properly formed.

[0008] This is necessary to properly form the central vials, however, a lot of material is wasted, which, in the case of medical products, must be of a very pure and therefore expensive grade.

[0009] The plastic material that comes into contact with the solution must, in fact, be pure, to reduce interactions with the pharmaceutical product.

[0010] Furthermore, the containers to be produced may have different requirements of consistency and mechanical resistance, depending on their areas.

[0011] In the context of the above-mentioned requirements, the main aim of the invention is therefore to propose an extrusion head for extruding thermoplastic plastic to produce containers, which overcomes the drawbacks of the prior art.

[0012] In particular, an aim of the invention is to make the system for producing containers in thermoplastic plastic more versatile, resulting in significant savings in terms of space and warehouse management.

[0013] These and other aims, that will become more apparent below, are achieved by a container produced using an extrusion head for a system for forming containers, as will be more evident hereafter in this description.

[0014] An object of the invention is a first plate of an extrusion head for extruding thermoplastic material within a blow-molding system for blow molding containers, comprising a distribution channel equipped with different areas, each fed by a respective distinct inlet channel, so as to allow the formation of containers equipped with zones having different properties and characteristics.

[0015] In particular, it is possible to provide a first area intended for creating a first wall of the containers, and a second area intended for creating a second wall of the containers. In this way it is possible to produce containers with a more rigid wall and a completely collapsible one, to allow the complete ejection of the contained liquid.

[0016] Another possibility, either in addition to or as an alternative to the previous one, is to provide a third area intended for creating the container sealing edges intended to be discarded. This advantageously allows the use of a third material, for example a non-pure or recycled one, for the parts intended to be discarded, such as those outermost to the matrix of the containers.

[0017] Furthermore, according to the invention, the distribution channel can have a first section adjacent to the material inlet channel, a second section for the material outlet and a third section located between the first section and the second section, inclined to increase the thickness of the internal part of the extrusion head and enhance the uniformity of the tubular form to be extruded.

[0018] In this case, according to the invention, the inclination of the third section can be between 25° and 65°, preferably 45°.

[0019] Moreover, according to the invention, the distribution channel can have an elongated cross-section in its second segment, so as to form a parison tube with an elongated cross-section. In this way, it is advantageously possible to save space and reduce plastic waste.

[0020] In this case, the distribution channel can consist of two halves that mirror each other relative to the main development plane of the second segment, which advantageously allow for a better distribution of the material during the creation of the parison tube.

[0021] A further object of the invention is a second plate of an extrusion head for extruding thermoplastic material within a blow-molding system for blow molding containers, comprising a slotted opening for the passage of a dispensing group equipped with at least two dispensing holes.

[0022] Preferably, the second plate can have multiple slots, each traversed by one or more dispensing groups equipped with at least two dispensing holes. This allows the blow-molding system to be highly versatile and adaptable to any container mold, even when replacing molds having containers with differing interaxial distances.

[0023] Furthermore, an object of the invention is also an extrusion head comprising such first and second plates, or an extrusion head where the first and second plates are the same plate.

[0024] Further features and advantages of the invention will become more apparent from the description of a preferred, but not exclusive, embodiment of the extrusion head, according to the invention, illustrated for indicative and non-limiting purposes with the aid of the accompanying drawings, wherein:

[0025] - Figure 1 shows a top view of the extrusion head of the invention, in a first variant with a single material inlet channel;

[0026] - Figure 2 shows a sectional view of the extrusion head of Figure 1 , with the dispensing group inserted;

[0027] - Figure 3 shows a top view of the extrusion head of the invention, in a second variant with a double material inlet channel;

[0028] - Figure 4 shows a top view of the distribution channels of the extrusion head of the invention, in a third variant with a double material inlet channel;

[0029] - Figure 5 shows a front view of the parison tube and the containers produced therefrom, not yet detached;

[0030] - Figure 6 shows a perspective view of the parison tube of Figure 5, with welding lines as obtained using the variant of Figure 4;

[0031] - Figure 7a shows the dispensing group with respective support and extension of the invention; - Figure 7b shows the dispensing group with respective support, extension and nozzles of the invention;

[0032] - Figure 8 shows a top view of the parison tube of Figure 5;

[0033] - Figure 9 shows a top view of the parison tube of Figure 5, with areas as obtained using the variant of Figure 3.

[0034] Figure 1 shows a top view of the extrusion head of the invention, generically indicated by 1 , equipped with a slotted opening 6, for the passage of a group 20 of nozzles 8, fixed to a support 15, so as to fill a band of containers 10 formed within a mold to be positioned below the extrusion head 1 .

[0035] In the following, reference will be made to the embodiment shown in the figures, which provides a single slot 6 traversed by a single support 15 to which all the nozzles 8 are fixed, but it is natural that in preferred variants of the invention multiple slots are provided in the same extrusion head, each traversed by a single support with multiple nozzles fixed thereto, or multiple supports are provided that traverse a single slot.

[0036] In this way, advantageously, it is not necessary, as in the prior art, to have very long individual nozzles, but the single support 15, which supports at least one group 20 of nozzles 8 via an extension 7, allows these nozzles 8 to be shorter, and therefore easier to replace and manufacture, as shown in Figure 7b.

[0037] Figure 7a shows a particular variant of the invention wherein an extension 7, directly equipped with dispensing holes 8a and without requiring actual nozzles, is fixed to the support 15.

[0038] In a preferred variant of the invention, the extensions 7 and / or the nozzles 8 may be covered with a coating or layer of insulating material, or they may be made of an insulating material, for example PTFE or PEEK, to reduce heat dispersion and, consequently, the need for cooling inside them.

[0039] Furthermore, if it becomes necessary to change the arrangement of the nozzles 8 to adapt it to a new shape and size of containers 10 to be formed, it is sufficient to replace the support 15, without having to change the entire extrusion head 1 .

[0040] This support 15, the extensions 7 and / or the nozzles 8 can be made with internal cooling channels, to also facilitate their production by 3D printing.

[0041] Such cooling, in particular, can be carried out using:

[0042] - channels for cooling liquid - heat pipes

[0043] - vacuum chambers

[0044] - Peltier modules or

[0045] - combinations of these techniques.

[0046] Thanks to the single opening 6 for multiple nozzles, the airflow is therefore more uniform.

[0047] Finally, cleaning such extrusion head 1 of any pieces of plastic material that have remained stuck is easier because the spaces are larger.

[0048] Each of the halves 31 and 32 of the distribution channel is connected to the extruder via a respective supply channel 3 for supplying the parison mass.

[0049] It is possible to adjust the flow in the channels 3 independently of each other, using flow adjustment screws (not shown).

[0050] The distribution channel 31 , 32 leads to the slotted opening 6.

[0051] In its lower segment 5, adjacent to the slotted opening 6, the distribution channel also presents the shape of a slot, which extends without interruptions in the circumferential direction of the slotted opening 6 itself.

[0052] An issue that arises from creating this slotted opening 6 is the weakening of the internal part of the structure of the extrusion head 1 .

[0053] The solution proposed by the present invention is to make the distribution channel inclined in its cross-section 4, possibly only in the terminal part of the distribution channel, for example at an angle between 25° and 65° - for example, at 45°, so as to increase the thickness of the section of the extrusion head 1 , located between the slotted opening 6 and the distribution channel, reinforcing the internal part of the head as much as possible and also reducing the loads, that would otherwise tend to deform the internal part of the structure.

[0054] In this way, in fact, this section is advantageously prevented from undergoing high deformations, due to the high pressures of the extrusion process, which would impact the uniformity of the tubular form.

[0055] An issue that arises when the distribution channels are inclined is that in the curved parts the internal surface of the distribution channels varies greatly.

[0056] To better explain this concept, we can take as an example a truncated cone, with a 45° inclination: the surface of the upper face of the truncated cone is much smaller than the lower surface. This effect is similar within the conical distribution channels. This effect does not occur in the linear parts, and this could lead to instability and a non-uniform distribution of the plastic material in the final flat tube exiting the extrusion head.

[0057] The distribution channels must always be smaller / narrower towards the exit direction of the plastic in order to compress it and make it uniform.

[0058] This reduction in section must result in a consistent extrusion surface at each height along the oval of the parison to prevent some parts from exiting faster than others and thereby avoid a completely crooked parison.

[0059] To solve this problem, the shape of the extrusion head 1 has been designed to ensure that the reduction of the internal surface of the distribution channels remains uniform in both the flat and curved segments.

[0060] In particular, at the end facing the distribution channels 3, each of the halves 31 and 32 of the distribution channel has a linear development parallel to the long sides of the slotted opening 6, without touching each other.

[0061] At the lower end of the extrusion head 1 , however, the halves 31 and 32 join together, forming a development that runs completely parallel to the slotted opening 6.

[0062] The inclination of the two halves 31 and 32 of the distribution channel causes their upper ends to be farther from the slotted opening 6 than their lower ends, so that the opening of the flat parison tube 9 is as close as possible to the slotted opening 6.

[0063] In this way, the material poured into the channel 3 follows a path inclined relative to a vertical axis and converging towards the centre of the extrusion head 1.

[0064] Advantageously, as shown in Figure 3, it is possible to feed the two halves

[0065] 31 and 32, placed side by side and not overlapping, with two distinct materials that have different properties, for example, in the first half 31 there could be a very flexible material entering from the material input channel 2, and in the second half

[0066] 32 there could be a more rigid and / or thicker material, arriving from the second material inlet channel 11 .

[0067] In this way, it is advantageously possible to create the two opposite sides of a vial with two different types of material, the first of which can completely collapse onto the second to eject all the liquid contained within it.

[0068] Moreover, advantageously, as shown in Figure 4, the two halves 31 and 32 can be further subdivided, presenting a further joint area 33 alongside the two halves 31 and 32, to create the parison tube 9 with a further vertical section made from another type of material along its curved part 13.

[0069] In detail, with reference to Figure 6, this latter solution allows the parison flat tube 9 to be produced from two different types of material: a pure material coming from the first inlet channel 2 (Fig. 4), used to create the two parallel segments 12 of the flat tube, which will then generate the body of the vials 10, while another material entering from the second inlet channel 11 (Fig. 4) - which could even consist of waste from the process itself - is conveyed into the joint area 33 and used to create the curved parts 13, which will then be discarded (see Figures 4, 5, 6 and 8), with welding lines 14 between the two materials in correspondence with the outermost weld of the outermost vial, resulting in an obvious economic advantage.

[0070] Finally, a further innovation (not shown in the figures) would be to design this head to extrude multilayer film. This extrusion head would consist of two linear multilayer extruders, joined at the sides by two segments of an additional plastic material, creating a single closed tubular form with 2 multilayer segments.

[0071] To create a parison tube with an elongated cross-section, so as to save space and avoid excessive plastic waste, the extrusion head 1 has an elongated shape, and presents a distribution channel, consisting of two halves 31 and 32 that mirror each other relative to the plane connecting the two half-shells of the mold.

[0072] The flat parison tube 9, exiting the final segment 5 of the distribution channel, is formed in the mold matrix, which has groups of containers 10 positioned adjacent to each other.

[0073] To allow the simultaneous filling of all the containers 10 formed by the mold matrix, there are filling nozzles 8 that are guided in longitudinal movement within the slotted opening 6 by one or more supports 15.

[0074] In order to create a compact system, these supports 15 extend through the extrusion head 1 along the central separation plane between the two half-shells of the mold and the two halves 31 and 32 of the distribution channel.

[0075] The lower end of the slotted opening 6 is positioned centrally between the two halves 31 and 32 of the distribution channel, so that the free lower ends of the nozzles 8 are positioned exactly equidistant from the long sides of the flat parison tube 9 that surrounds them.

[0076] In Figure 2, the halves 31 and 32 of the distribution channel are shown in section, along with the respective inclined segments 4 and the terminal segments 5.

[0077] The nozzles 8, connected to the support 15 which is in turn equipped with an extension 7, pass through the inside of the slot 6 which is adapted to allow the nozzles 8 to pass through the slot and reach the inside of the containers.

[0078] All details may be replaced by other technically equivalent elements. In practice, the materials used, as well as the specific shapes and dimensions, may be varied according to the contingent needs and the state of the art.

[0079] When the construction features and techniques mentioned in the following claims are accompanied by reference signs or numbers, these reference signs or numbers have been included with the sole purpose of enhancing the intelligibility of the claims themselves and, consequently, they do not in any way limit the interpretation of each element identified, purely by way of example, by these reference signs.

Claims

1. An extrusion head (1) for extruding a tubular thermoplastic material (9) in a blow moulding system for blow moulding containers (10), characterised in that it comprises a distribution channel (3) with two adjacent regions (31, 32, 33) fed by different inlet channels (2, 11), with the possibility of moulding a tubular element (9) having two different sections (12, 13) formed from material emerging from a corresponding inlet channel, wherein said sections (12, 13) have different properties and characteristics.

2. An extrusion head (1) according to claim 1, in which said regions (31, 32, 33), fed by different inlet channels (2, 11), include a first region (31) intended to create a first wall of the containers (10), and a second region (32) intended to create a second wall of the containers (10).

3. An extrusion head (1) according to claim 1 or 2, in which said regions (31, 32, 33), fed by different inlet channels (2, 11), include a first region (31) and a second region (32), intended to create the front and rear walls of the containers (10), and a third region (33), intended to create the sealing edges (13) of the containers (10) intended for disposal.

4. An extrusion head (1) according to one of the preceding claims, in which the distribution channel has a first section (31, 32) adjacent to the inlet channel (2, 11), a second section (5) for discharging the material and a third section (4) located between the first section and the second section and inclined to increase the thickness of the inner part of the extrusion head (1) and to improve the homogeneity of the extruded tubular shape (9).

5. An extrusion head (1) according to claim 4, in which the angle of inclination of the third section (4) is from 25° to 65°, preferably 45°.

6. An extrusion head (1) according to claim 4 or 5, in which the distribution channel (3) has an elongated cross-section in the second portion (5) for forming a tube of thermoplastic material (9) with an elongated cross-section.

7. An extrusion head (1) according to claim 6, in which the distribution channel consists of two halves (31, 32) that are mirror images of each other relative to the main plane of passage of the second section (5).

8. An extrusion head (1) according to one of paragraphs 1-7, characterized in that it has a slit-shaped opening (6) for the passage of a dispensing device (20) having at least two dispensing openings (8; 8a) for dispensing liquid into said containers (10) during the molding process.

9. An extrusion head (1) according to claim 8, characterized in that it has several slit-like openings (6), through each of which one or more of the said dispensing devices (20) pass.