Moulding device for moulding a container starting with a parison in plastic material and moulding machine comprising this device

Abstract

Molding device (1) for molding a container starting with a parison (3) in plastic material, comprising: two half-molds (4a, 4b), which may be joined to define at least one housing cavity (5) for the parison (3); a blowing nozzle (6) applicable on the neck (3b) of the parison (3); a plasma generator (8) receiving a blowing fluid at a pressure higher than the atmospheric pressure and supplying plasma at a pressure higher than the atmospheric pressure to the blowing nozzle (6), so that the plasma is blown into the parison (3) placed in the housing cavity (5) to mold it and to decontaminate it.

Claims

1. Moulding device (1) of a container (2) starting with a parison (3) in plastic material, comprising: two half-moulds (4a, 4b) which may be joined to define at least one housing cavity (5) of the parison (3); supply means (7) of a blowing fluid having a pressure higher than the atmospheric pressure; a blowing nozzle (6) applicable on the neck (3b) of said parison (3); and a plasma generator (8) having an inlet (9) receiving the blowing fluid from said supply means (7) and an outlet (10) enabled to supply plasma at pressure higher than the atmospheric pressure to said blowing nozzle (6), so that said plasma is blown into the parison (3) placed in said housing cavity (5) to mould it at least partially and to decontaminate it; wherein said supply means (7) of the fluid comprises: at least one compression stage (16) of the fluid enabled to generate said blowing fluid, said at least one compression stage (16) being placed upstream of the plasma generator (8); a plasma distribution circuit which receives the plasma from the outlet (10) of the plasma generator (8), said distribution circuit including a primary line enabled to transport plasma at a maximum pressure of around 16 bar and a secondary line enabled to transport plasma at a maximum pressure of around 40 bar; and a valve unit configured to place in selective communication said primary line and said secondary line with the blowing nozzle (6).

2. Moulding device (1) according to claim 1, wherein said at least one compression stage (16) generates a blowing fluid with a maximum pressure of around 40 bar.

3. Moulding device (1) according to claim 1, wherein said plasma generator (8) is a plasma torch provided with a mobile plug to allow generation of the plasma independently of the pressure value of the blowing fluid at the inlet (9).

4. Moulding device (1) according to claim 1, wherein said at least one compression stage (16) generates blowing fluid having a maximum pressure of around 8 bar, said moulding device (1) further comprising one or more compression stages (21, 22) of the plasma enabled to compress the plasma coming from said outlet (10) of the plasma generator (8) up to a maximum pressure of around 40 bar.

5. Moulding machine of containers (2) starting from parisons (3) in plastic material, comprising a plurality of moulding devices (1) according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of a moulding device for moulding a container starting with a parison in plastic material, and a moulding machine comprising this device, as illustrated in the accompanying drawings, of which:

(2) FIG. 1 is a block diagram of a moulding device for moulding a container starting with a parison in plastic material, according to the present invention;

(3) FIG. 2 is a block diagram of a first embodiment of the moulding device of FIG. 1, with a detail of the circuit of the supply means supplying the blowing fluid;

(4) FIG. 3 is a partial block diagram of a second embodiment of the moulding device of FIG. 1;

(5) FIG. 4 is a sectional view of a detail of the device of FIG. 1, that is, the area of the blowing nozzle that is applied on the neck of a parison.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(6) With reference to the figures, a moulding device for moulding a container starting with a parison 3 in plastic material, for example PET, is indicated by the number 1.

(7) The parison 3 has a tubular body 3a and a neck 3b that does not undergo the moulding process.

(8) The moulding device 1 comprises two half-moulds 4a, 4b that can be joined to define at least one housing cavity 5 for the parison 3.

(9) A blowing nozzle 6 or seal can be applied on the neck 3b of the parison 3. The moulding device 1 comprises supply means 7 for supplying a blowing fluid having a pressure higher than the atmospheric pressure. For example, the fluid can consist of air.

(10) Originally, the moulding device 1 comprises a plasma generator 8 that has an inlet 9 receiving the blowing fluid from the supply means 7 and an outlet 10 enabled to supply plasma at a pressure higher than the atmospheric pressure to the blowing nozzle 6, so that the plasma is blown into the parison 3 that is found in the housing cavity 5. Subjected to blowing with the plasma, the parison 3 is thus moulded and decontaminated.

(11) The plasma moulding can take place partially, that is, by sending plasma at a maximum pressure of about 16 bar (pre-blowing phase) or by sending plasma until the moulding is completed (pre-blowing phase and the actual blowing phase).

(12) The two half-moulds 4a, 4b are preferably part of a mould 4 that also comprises a bottom plate (unillustrated) positioned on one of the bases of the mould 4.

(13) In a first embodiment, which is illustrated in FIG. 2, the fluid supply means 7 comprise: a primary line 11 enabled to transport blowing fluid at a maximum pressure of around 16 bar; a secondary line 12 enabled to transport blowing fluid at a maximum pressure of around 40 bar; a valve unit 13 configured to place the primary line 11 and the secondary line 12 in selective communication with the inlet 9 of the plasma generator 8.

(14) In the first embodiment, the plasma generator 8 is interposed between the valve unit 13 and the blowing nozzle 6.

(15) The plasma generator 8 is preferably positioned near the blowing nozzle 6.

(16) Alternatively, the plasma generator 8 is integrated in the valve unit 13.

(17) A discharge line 14 also shown in FIG. 2 is enabled to set the valve unit 13 in communication with the housing cavity 5. This discharge line 14 is provided with a non-return valve 15 and it is placed in parallel with the plasma generator 8 to evacuate residual gas quickly from the inside of the container once the moulding of the latter is completed.

(18) The plasma generator 8 does not in itself represent the object of the present invention. However, it should be noted that in the first embodiment, the structural design chosen for the plasma generator 8 must be capable of operation with inlet pressures of up to 40 bar (in fact, the blowing fluid coming from the secondary line 12 reaches these pressure levels).

(19) It is a known fact that an increase in the pressure of the incoming fluid makes it more difficult to activate the plasma because it increases the resistance of the fluid (which functions as a dielectric) to the discharge. Therefore, the voltage to be applied between the electrodes to activate high inlet pressures would even be in the range of about 20-30 kV.

(20) To meet the need for operation with pressures of about 40 bar, a plasma torch (or gun) can be employed as a plasma generator 8; the torch supplies as output a direct flow of plasma from a nozzle. In particular, the plasma generator 8 consists in the plasma torch described in document DE 10115241.

(21) In this torch, the plasma is activated at a pressure lower than the initial inlet pressure, owing to the presence of a convergent element. Subsequently, the pressure is brought back to its initial level by means of a divergent element. Through the use of this torch in the first embodiment, the plasma can be activated at pressures within the range of 6-8 bar even in the presence of an inlet blowing fluid in the range of about 30-40 bar.

(22) An automatic system of the mobile plug type can the integrated in the plasma torch of document DE 10115241 with the aim of adapting it to the pressure level of the incoming fluid. This system changes the geometry of the elements from convergent to divergent and vice versa. In this manner, the plasma is generated independently of the inlet fluid pressure level. Moreover, the torch disclosed in document DE 10115241 has an added inlet for an additional fluid (for example water vapour or nitrogen) for the purpose of modifying the characteristics of the plasma to make it suitable for use in blowing the parison 3.

(23) In a second embodiment, which is illustrated in FIG. 3, the fluid supply means 7 comprise: at least one compression stage 16 for the fluid, enabled to generate the blowing fluid; a plasma distribution circuit, which receives the plasma (directly or indirectly) from the outlet 10 of the plasma generator 8, and which, in turn, comprises a primary line to transport plasma having a maximum pressure of around 16 bar and a secondary line to transport plasma having a maximum pressure of around 40 bar; a valve unit configured to place the primary line and the secondary line in selective communication with the blowing nozzle 6.

(24) In the second embodiment, the compression stage 16 for the fluid is placed upstream of the plasma generator 8.

(25) For example, there is a single compression stage 16 and it generates blowing fluid having a maximum pressure of about 40 bar. As an alternative, there may be a number of compression stages in a cascade arrangement that are able to generate blowing fluid having a maximum pressure of about 40 bar. As the production of plasma takes place with the pressures of about 40 bar, the plasma distribution circuit receives the plasma directly from the outlet 10 of the plasma generator 8.

(26) Given the high pressure of the blowing fluid supplied at the inlet 9 of the plasma generator 8, the torch disclosed in document DE 10115241, integrated with a mobile plug, can be employed as the plasma generator 8 in this second embodiment as well.

(27) In a preferred variant, the compression stage 16 generates blowing fluid having a pressure of about 8 bar. In this case, it is sufficient to employ a plasma generator capable of operating with relatively low inlet pressures.

(28) In this preferred variant, one or more plasma compression stages 21, 22 are present downstream of the plasma generator 8 and they receive the plasma from the outlet 10 of the plasma generator 8 and compress it to a maximum pressure of about 40 bar.

(29) For example, two plasma compression stages 21, 22 are illustrated in FIG. 3 in a cascade arrangement: a first stage 21 capable of compressing the plasma up to a maximum pressure of about 20 bar; a second stage 22 capable of compressing the plasma up to a maximum pressure of about 40 bar.

(30) In this preferred variant, the plasma distribution circuit receives the plasma indirectly from the outlet 10 of the plasma generator 8, that is, passing through the first stage 21 and the second stage.

(31) FIG. 4 shows the area of the blowing nozzle 6 applied on the neck 3b of the parison 3. In particular, the blowing nozzle 6 creates a tight seal on a transverse protrusion 3c (known in the field by the technical term bague) of the neck 3b of the parison 3 in such a manner as to close the opening of the parison 3 in a tightly sealed manner during the moulding process.

(32) The moulding machine (unillustrated) proposed herein comprises a plurality of moulding devices 1 described hereinabove. The moulding machine is preferably of the rotary carousel type. Alternatively, the moulding machine may be of the linear type.

(33) The operation of the moulding device for moulding a container starting with a parison in plastic material is explained below.

(34) First of all, the mould 4 must be arranged in an open configuration. This is done by moving the two half-moulds 4a, 4b away from each other so as to enable insertion of the parison 3 in the mould 4.

(35) The mould 4 is subsequently brought into a closed configuration, joining the two half-moulds 4a, 4b in such a manner that they define, together with the bottom plate, the housing cavity 5 for the parison 3.

(36) The moulding of the parison 3 by blowing takes place by blowing a plasma having a pressure higher than the atmospheric pressure into the parison 3. As plasma is used rather than a blowing fluid, the parison 3 is also decontaminated.

(37) In particular, the blow moulding process comprises: pre-blowing, in which the plasma is blown into the parison 3 at a maximum pressure of about 16 bar; actual blowing, following the pre-blowing phase, and in which the plasma is blown into the parison 3 at a maximum pressure of about 40 bar.

(38) In the first embodiment, the generation of plasma takes place near the mould 4 starting with the blowing fluid coming from the valve unit 13.

(39) In particular, during the pre-blowing phase, the valve unit 13 enables communication of the inlet 9 of the plasma generator 8 with the primary line 11 bearing the fluid at the maximum pressure of about 16 bar.

(40) During the actual blowing phase, the valve unit 13 enables communication of the inlet 9 of the plasma generator 8 with the secondary line 12 bearing the fluid at the maximum pressure of about 40 bar.

(41) At the end of the moulding process, the residual gas remaining inside the container is evacuated through the discharge line 14.

(42) In the second embodiment, the generation of plasma takes place downstream of the blowing fluid compression stage 16.

(43) In particular, in the preferred variant of the second embodiment, the compression stage 16 generates the blowing fluid having a maximum pressure of about 8 bar, a fluid that is converted into plasma by the plasma generator 8. This plasma is then further compressed in the two plasma compression stages 21, 22 up to about 40 bar.

(44) During the pre-blowing phase, the valve unit enables communication of the primary line bearing the plasma at a maximum pressure of about 16 bar with the blowing nozzle 6.

(45) Continuing to blow plasma is also possible during the actual blowing phase, setting the secondary line, which bears the plasma at the maximum pressure of about 40 bar, in communication with the blowing nozzle 6.

(46) The presence of a stretching rod 23 is preferably comprised in all the embodiments described herein. In particular, during the pre-blowing phase, the blowing nozzle 6 creates a tight seal on the bague 3c so as to close the mouth of the parison 3 in a tightly sealed manner. The stretching rod 23 is gradually inserted inside the tubular body 3a of the parison 3 until it reaches the bottom thereof. After touching the bottom, the stretching rod 23 continues its linear course so as to stretch the tubular body 3a of the parison 3 until substantially reaching the desired length of the container to be obtained.

(47) During the actual blowing phase, the stretching rod 23 retracts until it emerges from the moulded container.

(48) All the embodiments described and illustrated herein include the option of completing decontamination of the internal walls of the moulded container by blowing more plasma inside the latter once moulding by blowing and stretching has been completed. Upon completion of the moulding process, the residual gas remaining inside the container passes through the blowing nozzle 6 and is evacuated through a discharge line (unillustrated) controlled by the valve unit.

(49) The characteristics and the advantages of the moulding device for moulding a container starting with a parison in plastic material according to the present invention prove to be clearly indicated in the description provided.

(50) In particular, by generating the plasma at a pressure higher than the atmospheric pressure and using it as a substitution for the blowing fluid, the parison can be moulded and decontaminated at the same time.

(51) The proposed moulding device is compact and structurally simple, in that it requires the sole presence of a plasma generator, in addition to the normal elements already present in a moulding device for moulding by blowing and stretching (compressor, valve unit, mould, stretching rod, blowing nozzle, etc.).

(52) Given that sterilisation and moulding of the parison are inseparable processes, no further measures are required to maintain ambient contamination below the desired level. In fact, the container is moulded under sterile conditions owing to the plasma blown into it. Therefore, the dimensions are limited and the line is simplified in light of the simultaneous execution of the decontamination and moulding processes, which until now had always been performed sequentially.

(53) The structural complexity of the aseptic blower with an isolator can thus be left aside, along with all the members operating at the interface thereof (e.g. sealing systems between the sterile zone and the external environment, confinement of the stretching rod, sterilisation system for the blown air circuit, etc.).

(54) A conventional blower can be employed, given that the sterilisation process is carried out in the blowing cavity, at the same time as the blowing process and/or subsequently on the moulded container (prior to reopening the mould). This conventional blower thus becomes a blower-steriliser.

(55) Sterilisation cycles for sterilising the environment and the blown air prior to production are no longer necessary. The steriliser for sterilising the parisons upstream of the blower can thus be eliminated.

(56) Moreover, the use of plasma makes it possible to reduce sterilisation time, to avoid the use of chemical agents and the accumulation of peroxides in the container and to decontaminate the parison and the container in a substantially uniform manner.

(57) In the first embodiment, by positioning the plasma generator near the blowing nozzle greater efficiency is also achieved due to the reduction of the pathway for radical species (commonly known by the acronym R.O.S. for Reactive Oxygen Species) present in the plasma, which are short-lived.

(58) Again, in the first embodiment, the incorporation of the plasma generator in the valve unit makes for an even more compact solution.

(59) The first embodiment further comprises the discharge line in parallel with the plasma generator so as to prevent drops in pressure due to evacuation of the residual gas to the plasma generator.

(60) In the preferred variant of the second embodiment, the plasma generator operates with relatively low inlet pressures (maximum 8 bar, approximately), which further simplifies the overall structural design.

(61) In conclusion, owing to the fact that the blowing nozzle creates a tight seal on the bague, the plasma also flows over the external surface of the neck of the parison and thus decontaminates it.