FR2851227A1 - Plastic bottle forming, filling and sealing process and plant uses plastic strip shaped round blowing/filling tube, molded into bottles and sealed after filling - Google Patents

Abstract

During the process a band of plastic film (1) from a roll (2) is cut into strips (B1, B2) and passed through heaters (CH1, CH2) before being formed into cylinders (T) and welded round blowing/filling tubes (CS). During the process a band of plastic film (1) from a roll (2) is cut into strips (B1, B2) and passed through heaters (CH1, CH2) before being formed into cylinders (T) and welded round blowing/filling tubes (CS). The cylinders are blow-molded into bottles (RE1 - RE4) in moulds (8) formed from two halves (M1, M2). Then they are filled, after cooling while inside the moulds and before being sealed at the top by the action of the lower ends of the moulds, and then separated. The sealing process includes the formation of a neck and stopper which is pre-cut for easy opening.

Description

- 1 -

  The present invention relates to a thermoforming process for the production, filling and sealing of plastic bottles.

  It more particularly, but not exclusively, aims to solve the problems of production, filling and sealing of plastic bottles on the same site, to allow the integration of these three stages in an aseptic environment and to meet the needs of the market in terms of packaging of various liquids and in particular of food liquids intended for their consumption.

  In general, we know that there are essentially three types of technology allowing the production of plastic bags, bottles or containers for food liquids: - the extrusion / blowing of high density polyethylene (HDPE) bottles, - blowing polyethylene terephthalate (PET) preforms, - forming bricks from a material made of a cardboard / polyethylene / aluminum complex.

  The HDPE bottle extrusion / blowing technology is the most commonly used for fermented milk drinks and desserts; however, this technology does not allow containers to be filled near the production lines, given the nature and extent of the resources dedicated to the extrusion and blowing of the HDPE material; consequently, it is necessary to provide transport, storage and cleaning logistics before filling the containers.

  The blowing technology of PET bottle preforms is used to produce high-end products; it allows in particular the packaging of carbonated drinks; however, it requires an industrial structure involving three types of trade: the injection of preforms, the blowing of bottles and packaging.

  The importance of the means used to exploit this technology inevitably leads to high costs of achievement. 15 The technology for forming bricks of cardboard / PE / Al composite material is very widespread for non-carbonated drinks; it allows aseptic filling, near the means for forming the composite material; this is made of sheet, then shaped into a tube welded longitudinally 20 then welded transversely after filling, then finally folded into a brick shape. The inherent limitations of cardboard material and folding forming greatly reduce the possibilities in terms of packaging shapes.

  Furthermore, it is known that many types of thermoplastic materials can be used for thermoforming: PS (polystyrene), PET (polyethylene terephthalate), PP (polypropylene), and various multilayer plastic materials such as, for example, PSPE (Polystyrene / polyethylene) which consists of a bilayer plastic sheet used to obtain a more effective oxygen barrier (widely used for compotes which tend to turn brown with oxygen) and PSEVOH which is a multilayer plastic sheet which constitutes a vapor and gas barrier.

  This technology allows the integration of the means of production of containers and packaging of food products.

  It consists in making, by hot stretching, a container from a flat plastic sheet by punching and blowing air under pressure.

  The limitations of this technology are as follows: - the need to produce a slight draft to allow the pot to be removed from the mold by vertical extraction, thus preventing bottles from being produced, - the need to produce an upper, outward-facing collar intended for closing the jar, the latter being ill-suited to the consumption of the food product in the mouth, - the need for a relatively low stretch coefficient limiting the height / section ratio of the container.

  In order to make shapes with undercuts, one solution is to use molds opening in two parts. This technology makes it possible to extract the pot from the mold despite this undercut. In general, this solution causes significant plastic losses because the pots must be sufficiently spaced apart to allow the opening of the molds.

  We know that a solution to these limitations consists in thermoforming two half-25 shells which are then welded together along a median plane defined by flanges situated on the periphery of said half-shells. This solution does not allow the container to stand vertically on its base, since it has part of the overlap joint of the two half-shells.

  The invention therefore more particularly aims to eliminate these drawbacks.

  To this end, it proposes a process for tubular thermoforming of a film of plastic material in a mold, for filling in situ the container thus produced and for sealing said container.

  According to the invention, this process essentially involves the following steps: - the hot shaping of a strip of plastic material around a blowing and filling rod so as to produce a cylindrical film, - the longitudinal welding of the cylindrical film thus produced around said blowing and filling rod, - blow molding of a container from said cylindrical film in a mold produced in two parts, - filling of said container thus produced in said mold, - the sealing of the upper part of said filled container, - separation of said filled container.

  Thus, the method according to the invention can meet the requirements defined above, namely: - the production on the same site of the plastic container and packaging of the food products contained, - the possibility of meeting the standards defined for packaging in aseptic environment, - the possibility of meeting specific needs in terms of container shape, height / section ratio of said container, type of decoration and type of opening in the upper part, - the possibility of using composite materials, comprising in particular a barrier layer, suitable for particular applications.

  Of course, the invention also relates to an installation for implementing the method described above.

  An embodiment of the invention will be described below, by way of nonlimiting example, with reference to the appended drawings, in which: FIG. 1 is a schematic representation of a production line for containers by tubular thermoforming . FIGS. 2 to 13 are partial schematic views of the chain forming station shown in FIG. 1, during the various stages of forming the containers.

  Figure 14 is a partial elevational view of the neck and the container cap.

  Figure 15 is a schematic elevational view of a production line in which the plastic sheet is divided into six strips.

  In this example, the method according to the invention uses an original plastic material in the form of a sheet 1 of plastic material rolled up to form a roll 2.

  This roller 2 is rotatably mounted in the supply station of the chain and is unwound. Leaving the roller 2, the sheet 1 is guided by rollers RI and passes successively through a possible preheating station CH ,, then through a cutting station 4 in which the softened sheet is cut into strips 30 BI, B2 (here two strips) by sectioning rollers R2.

  In the preheating station CH ,, the sheet is heated flat by means of a heating device which can, for example, consist of a heating system by infrared radiation, by a heating system, by convection, for example air hot, or even by a contact heating system, for example with a heating electrode.

  At the exit from the cutting-off station 4, each of the bands BI and B2 is guided by means of deflection rollers R3 in a shaping station in which each of the two bands B1 and B2 is shaped into a T tube. conformation comprises a heating and / or temperature-maintaining tunnel CH2 and a tubular former 6 arranged around a blowing cane for air evacuation and metering CS which extends coaxially inside the former 6 and therefore of the tube T which is shaped, this cane CS being connected to air intake, air evacuation and product intake ducts intended for filling the containers, in its part located upstream of the shaper 6.

  The tube T obtained at the outlet of the shaper 6 passes through a welding station 7 which performs a longitudinal welding of the two longitudinal edges of the strip BI, B2 which overlap or which are simply juxtaposed. This weld can be either continuous or cyclic. Of course, the welding technologies (ultrasound, high frequencies, thermal ...) can vary depending on the nature of the plastic used and the applications.

  Optionally, a second heating station CH3 may be provided so as to carry out a second heating step after conformation of the tube T, prior to forming, in order to ensure a good temperature of the plastic during forming.

  Once welded and possibly heated in this second heating station, the tube T passes through a forming station inside which the hot plastic tube is enclosed in a mold 8 in two parts MI, M2 which open in a axial median plane (in principle vertical).

  In the closed state, this mold 8 comprises in its upper part a cylindrical orifice O in which the tube T and the cane CS pass, the mold / tube / cane sealing, at this passage, being ensured by the plastic material tube T hot. This orifice O has in an axial plane a profile complementary to that of the neck G of the containers RE, to RE4 to be produced. In this example, it comprises, between two cylindrical portions, an annular cavity CA of substantially L-shaped section so as to obtain a stepped rim at the head of the neck G. This mold 8 comprises, opposite the orifice O, a bottom produced by the juxtaposition of two semi-cylindrical half-bottoms FI, F2, respectively integral with the two parts MI, M2 of the mold 8. The face of this bottom situated outside the mold comprises a cavity CB intended to produce a plug 9 with, at the junction between the plug 9 and the neck G, a precut PR allowing easy opening of the plug 9.

  As illustrated in FIG. 14, the plug 9 comprises a cylindrical portion 25 extending the upper end of the neck G and connected to the latter by a precut area PR, this cylindrical portion being extended by a tongue L which extends over all or part of a diameter of this portion.

  The opening of the container is then obtained by exerting a torque on the tongue L so as to cause the pre-cut area PR to rupture.

  However, the use of an opening tab is not a general rule. Indeed, some applications require a screw cap. The thread will then be thermoformed. An additional step will open the bottle. A blade will cut the upper end of the bottle to allow the establishment of the cap. Of course other solutions can be envisaged.

  The CS rod comprises two concentric nozzles, namely: - a central nozzle BC connected to a product supply line 10 intended to fill the container made in the mold (dosing of the product) and - an external nozzle BE which delimits with the central nozzle BC an annular space into which compressed air can be injected so as to obtain a blow molding of the portion of tube T contained in the mold 8; the outer nozzle is shorter than the central nozzle BC; 15 the entire CS rod is coated with a non-stick coating which serves to prevent the hot plastic of the tube from sticking to the rod.

  The external nozzle BE which is used for blowing pressurized air is also used for venting before filling. 20 At the outlet of the mold 8, the containers RE ", RE4 which are initially connected to each other by a bottom / plug connection 9 are guided and driven by a pilgrim's conveyor TR with square movement to a cutting station DC which detaches the bottom / cap connections, then to a container evacuation station EX 25 in which the containers separated from one another are driven one by one.

  The operation of the production chain previously described is carried out in accordance with the following cycle which includes the steps illustrated in FIGS. 2 to 15.

  During a first step, the forming mold 8 is opened. The preheated strip BI in the heating station 5 continuously undergoes in the forming station 6 a shaping process to cause it to take a tubular shape, then undergoes a welding process of its two longitudinal edges.

  The tube T thus formed descends into the cold thermostated mold 8.

  In this example, the lower end of the tube T is integral with the neck G of the container RE, which has just been produced, which is itself attached to a set of containers RE, with RE4 previously produced and integral with each other 10 by bottom / plug connections, these containers RE1 to RE4 being supported by the transporter TR (FIG. 2).

  During a second step, the forming mold 8 closes around the plastic tube T through which the metering and blowing rod CS 15 passes (FIG. 3).

  Once the mold 8 is closed, the sealing at the top between the mold 8 and the blowing / dosing rod CS is produced by the hot plastic of the tube T. Simultaneously, the stopper 9 of the container RE, previously produced, is obtained by at the bottom recess CB (figure 4).

  During the next step, the compressed forming air is blown into the mold 8 by the blowing / dosing rod CS. The tube T contained in the mold is then deformed and comes to conform to the internal shape of the mold 8 (FIG. 5).

  On contact with the mold 8, the plastic material cools and freezes. The body and the neck of the REo container are permanently conformed. The air overpressure is then evacuated (Figure 6). 30 - 10 Once the plastic has been frozen and the enclosure of the mold 8 has been placed in the atmosphere of the product, the mold 8 can then be opened (FIGS. 7 and 8), while the metering of the product takes place, in synchronism with this opening process and throughout the evacuation of the REo container outside the mold (Figure 9). 5 The REO container leaves the mold 8 from below, always connected to the plastic tube T. The dosing continues throughout the descent of the REo container (Figure 10).

  At the end of evacuation, the neck G of the container REo which is still attached to the tube 10 is positioned relative to the bottom of the mold 8 for sealing and forming the cap 9 by vacuum (FIG. 11).

  At the end of this step, the full REo container is ready to be sealed (Figure 12).

  The forming mold 8 can then be closed in order to seal the container and initiate a new molding cycle (Figure 13). At the same time, the transporter TR engages the container REo while the cutting operation is carried out to separate the first container RE4, carried by the transporter TR, then the evacuation of this container RE4. 20 This manufacturing process by tubular thermoforming has many advantages: It makes it possible to produce pots or bottles deeper than those currently produced in integrated thermoforming while working a thin plastic sheet (<1 mm) thanks to a coefficient of stretching. limit. Indeed, we thermoform a plastic tube and not a pellet. We therefore have a larger original surface area and therefore a lower stretch coefficient. - he

  - It reduces the losses induced by a mold opening with current technologies. The plastic strips are pre-cut before forming.

  - It allows you to make pots or bottles without a collar or with a collar facing the inside of the pot.

  - Thanks to a three-stage thermoforming: 1. forming the body of the bottle, 2. filling the bottle, 3. forming the neck and sealing the bottle.

  - It allows for certain applications to fill the bottle before closing the bottle and therefore to overcome the removal of the lid. A pre-cut plastic material at the neck allows easy opening of the bottle (bottle corresponding to consumption in one go, no resealable cap).

  - It allows ultra-clean filling since the plastic sheet is fully heated on its inner face (around 1500) before forming and the filling is done in a closed enclosure.

  - It can easily evolve towards an aseptic filling (with suitable plastic materials) since the area to be protected will be very small: 20 very short distance between the outlet of the heating box and the sealing of the bottle.

  - It is perfectly suited to the integration of a decorative device by "sleevage", ie using a retractable plastic sleeve.

  - Furthermore, the low stretch coefficient facilitates the use of multilayer plastic sheets. Indeed, there is no risk of tearing the barrier layers.

  - It allows for very varied and original shapes specific to each product or customer, which allows a strong differentiation in the shelves.

  The shape has no constraint linked to a preform or to the drawing coefficient. - 12

  In the example described above, the production line provides three heating zones making it possible to successively preheat the sheet before cutting, heating the strips flat after cutting and heating the plastic tube before forming.

  The invention is not limited to this heating process: In fact, the number and arrangement of the heating and / or preheating stations may vary depending on the nature of the plastic used, it being understood that in certain cases , the conformation of the strips or tubes can be carried out cold. Furthermore, it turns out that the overlap zone at the weld of the tube generates an additional thickness, which results in non-homogeneous forming. It is therefore desirable to flatten the lateral edges of the hot strips before welding.

  This operation can be carried out for example with heating knobs which perform the flattening and with cooling guides which ensure that the edges which have just been flattened are frozen.

  In the embodiment illustrated in FIG. 15, the plastic sheet 21 emanating from the roller 20 engages directly in a cutting-off station 22 where it is divided into six bands BAI to BA6.

  Leaving the cutting station 22, the bands BAI to BA6 which extend substantially in the same plane, engage in an edge crushing station using a series of heating knobs MC and cooling guides GF .

  These strips BAI to BA6 are then driven by rollers 23 before passing through a shaping station 24 where they are each formed into a tube in which the thinned edges are overlapped. On leaving this covering station, the covering edges are continuously welded in an ultrasonic welding station 25.

  Once welded, the tubes pass through a heating station 26 in which they are gradually brought to the forming temperature. For this purpose, this heating station may extend over a length equal to a multiple of the advance of the strip.

  Leaving the heating station 26, the tubes engage in a single forming mold 27 comprising two movable parts, one with respect to the other, which each have six indentations.

  The containers RCI to RC6, obtained at the outlet of this molding station 27 are supported by carriers with pilgrim's steps of the type of that previously described. - 14

Claims (14)

claims   1. Thermoforming process intended for the production, filling and sealing of a container made of plastic material, characterized in that it comprises the following stages: - the hot forming of a strip (BI, B2) of material plastic around a blowing and filling rod (CS), so as to produce a cylindrical film (T) - the longitudinal welding of the cylindrical film (T) thus produced around said blowing and filling rod (CS) , - the blow-molding of a container (RE1 to RE4) from said cylindrical film (T) in a mold (8) produced in at least two portions (MI, M2), - the filling of said container (RE, to RE4) thus produced in said mold 15 (8), this filling phase taking place after the forming phase, when the mold (8) is opened and the container is removed (RE1 to RE4), - the sealing of the upper part of the container (RE, to RE4) filled by action of the lower part of the two por of the mold (MI, M2), on the lower end of the tube adjoining the container (REf to RE4), when closing said mold (8) which follows said extraction.   2. Method according to claim 1, characterized in that it comprises, before the aforesaid hot conformation phase, a phase of flattening of the lateral edges of the strip then a phase of freezing by cooling of the edges thus flattened.   3. Method according to claim 1, characterized in that it comprises after the blowing phase a phase of cooling the plastic material after blowing. -   4. Method according to one of the preceding claims, characterized in that the sealing phase comprises a step of shaping a neck (G) and a plug (9) with, between the plug (9) and 5 the neck (G), a precut allowing easy opening of the cap (9).   5. Method according to claim 4, characterized in that the sealing phase is obtained by the action of the two parts of the bottom of the mold (8).   6. Method according to claim 5, characterized in that the plug (9) comprises a cylindrical portion extended by a tongue (L).   7. Method according to one of claims 4 to 6,   characterized in that the above-mentioned sealing and shaping phase of a neck (G) comprises a suction phase.   8. Method according to one of the preceding claims, characterized in that at the end of the mold (8), the bottom of the last container (RE,) is integral with the cap of the penultimate container (RE2) and in that that the above-mentioned separation phase is carried out at the end of a transport phase of a succession of containers (RE, to RE4) integral with each other.   9. Installation for implementing the method according to one of the previous claims,   characterized in that it successively comprises: - a tunnel for heating a plastic band, - a tubular former arranged around a blowing, air evacuation and metering rod which extends coaxially inside the shaper, - 16 - a welding station which welds the two longitudinal edges of the strip, - a forming station in which the hot plastic tube thus formed engages, this forming station comprising a mold or at least two parts which can close around the tube and open to release the shaped container in the mold, - compressed air blowing means, suction means as well as metering means connected to the base, - means of transporting the containers leaving the mold, and - cutting means used to separate the first container carried by the means of transport of the other containers.   10. Installation according to claim 9, characterized in that the said rod comprises two concentric tubes, namely: a central tube connected to a product supply conduit intended to fill the containers and an external tube which delimits with the internal tube an annular space into which compressed air can be injected.   11. Installation according to one of claims 9 and 10, characterized in that, in the closed state, the mold comprises in its upper part a cylindrical orifice in which the aforementioned tube passes, the sealing of the mold / tube / rod being produced by the hot plastic of the tube.   12. Installation according to one of claims 9 to 11, characterized in that the aforementioned strip is obtained by cutting a sheet (21) of plastic material in a cutting station.   13. Installation according to claim 12, characterized in that, in the cutting-off station, the aforesaid sheet (21) is divided into a plurality of strips on which the steps of hot-forming, of longitudinal welding, of forming by blowing, filling and sealing are carried out in parallel.   14. Installation according to claim 13, characterized in that the blow-molding is obtained by means of a single forming mold (27), comprising two parts movable relative to each other which each have a number of 'footprints equal to the number of bands.