METHOD FOR MOULDING AND STERILIZING A CONTAINER MADE OF PLASTIC MATERIAL, DEVICE FOR MOULDING AND STERILIZING A CONTAINER MADE OF PLASTIC MATERIAL AND MOULDING AND STERILIZING MACHINE

Abstract

Method for moulding and sterilizing a container made of plastic material, comprising the steps of: opening a mould (4) made of metal material; inserting a parison (3) into the mould (4); closing the mould (4); inserting a stretching rod (23) made of metal material into the parison (3); blowing and stretching the parison (3) in such a manner as to obtain the container; keeping the stretching rod (23) inside the moulded container; evacuating the blowing fluid; applying a voltage difference between the stretching rod (23) and the closed mould (4) in such a manner as to transform the fluid at atmospheric pressure remaining inside the moulded container into plasma.

Claims

1. Method for moulding and sterilizing a container made of plastic material, comprising the steps of: preparing a mould (4), at least partially made of metal material, in an open configuration; inserting a parison (3) of plastic material into said mould (4); bringing said mould (4) into a closed configuration; inserting a stretching rod (23) at least partially made of metal material into said parison (3); blowing a blowing fluid into said parison (3) placed in the mould (4) and simultaneously stretching said parison (3) by means of the stretching rod (23) in such a way as to obtain the container, characterized in that it comprises the steps of: evacuating the fluid at the end of the blowing and stretching step; applying a voltage difference between said stretching rod (23) and said mould (4) in the closed configuration in such a way as to transform the fluid at atmospheric pressure remained inside the moulded container into plasma.

2. Method according to claim 2, wherein the step of applying a voltage difference is performed after the completion of the step of evacuating the fluid.

3. Method according to claim 1, wherein the step of blowing the blowing fluid into said parison (3) comprises the substeps of: pre-blowing the fluid having a maximum pressure of around 16 bar; blowing the fluid having a maximum pressure of around 40 bar in such a way as to obtain the container.

4. Device (1) for moulding and sterilizing a container made of plastic material, comprising: a mould (4), at least partially made of metal material, configurable in at least an open configuration to receive a parison (3) of plastic material, and in a closed configuration wherein it defines at least a housing cavity (5) of the parison (3) or the moulded container; a blowing nozzle (6) applicable to the neck (3b) of the moulded parison (3) in order to blow a blowing fluid into it; a stretching rod (23) at least partially made of metal material, insertable inside said parison (3) or said container; a circuit for evacuating the blowing fluid from the moulded container, characterized in that it comprises means for applying a voltage difference between said stretching rod (23) and said mould (4) in such a way as to transform the fluid at atmospheric pressure remained inside the moulded container into plasma.

5. Moulding and sterilizing device (1) according to claim 4, wherein said mould (4) comprises two half-moulds (4a, 4b) suitable for defining the shaping of the body of the container and a bottom plate suitable for defining the bottom of the container.

6. Moulding and sterilizing device (1) according to claim 4, wherein the voltage difference applied between said stretching rod (23) and said mould (4) has a value of about 30 kV.

7. Machine for moulding and sterilizing containers made of plastic material, comprising a plurality of moulding and sterilizing devices (1) according to any one of claim 4.

8. Method according to claim 2, wherein the step of blowing the blowing fluid into said parison (3) comprises the substeps of: pre-blowing the fluid having a maximum pressure of around 16 bar; blowing the fluid having a maximum pressure of around 40 bar in such a way as to obtain the container.

9. Moulding and sterilizing device (1) according to claim 5, wherein the voltage difference applied between said stretching rod (23) and said mould (4) has a value of about 30 kV.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] 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 method for moulding and sterilizing a container made of plastic material, a device for moulding and sterilizing a container made of plastic material, and a moulding and sterilizing machine, as illustrated in FIG. 1, which is a sectional view of a device for moulding and sterilizing a container made of plastic material according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0033] With reference to the figures, a device for moulding and sterilizing a container starting with a parison 3 in plastic material, for example PET, is indicated by the number 1.

[0034] The parison 3 has a tubular body 3a and a neck 3b that does not undergo the moulding process.

[0035] The moulding and sterilizing device 1 comprises a mould 4, partially or entirely made of metal material. The mould 4 is configurable in at least: [0036] an open configuration, in which the mould 4 receives the parison 3 subjected to subsequent operations; [0037] a closed configuration, in which the mould 4 defines [0038] at least a housing cavity 5 for the parison 3 or the moulded container.

[0039] The mould 4 preferably comprises two half-moulds 4a, 4b suitable for defining the shaping of the body of the container and a bottom plate (not illustrated) suitable for defining the bottom of the container.

[0040] The two half-moulds 4a, 4b are relatively mobile with respect to each other in such a manner that: [0041] when the mould 4 is in the closed configuration, the two half-moulds 4a, 4b are brought closer and define the housing cavity 5; [0042] when the mould 4 is in the open configuration, the two half-moulds 4a, 4b are moved away from each other to enable insertion of the parison 3 or to disengage the moulded container.

[0043] The moulding and sterilizing device 1 further comprises a blowing nozzle 6 (or seal) and a stretching rod 23.

[0044] The blowing nozzle 6 is applicable to the neck 3b of the parison 3 in order to blow a blowing fluid such as air into it.

[0045] In the embodiment described and illustrated herein, the fluid is provided by supply means of a known type.

[0046] As can be seen in FIG. 1, the blowing nozzle 6 is applied to the neck 3b of the parison 3 in such a manner as to abut and create 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.

[0047] The stretching rod 23, which is at least partially made of metal material, is insertable inside the parison 3 or the moulded container. The stretching rod 23 is preferably entirely made of metal material.

[0048] The moulding and sterilizing device 1 further comprises a circuit for evacuating the blowing fluid from the moulded container.

[0049] Originally, means are provided for applying a voltage difference between the stretching rod 23 and the mould 4 in such a manner as to transform the fluid at atmospheric pressure remaining inside the moulded container into plasma.

[0050] In other words, in the closed configuration, the stretching rod 23 and the mould 4 constitute the electrode and counter electrode of a plasma generator, respectively.

[0051] Given that the seal 6 is at the same potential as the two half-moulds 4a, 4b, the plasma is also generated in the external zone of the neck 3b of the parison 3.

[0052] The voltage difference applied between the stretching rod 23 and the mould 4 in the closed configuration preferably has a value of about 30 kV.

[0053] The moulding and sterilizing machine (not illustrated) proposed herein comprises a plurality of moulding and sterilizing devices 1 described hereinabove.

[0054] The moulding and sterilizing machine is preferably of the rotary carousel type. Alternatively, the machine may be of the linear type.

[0055] The method for moulding and sterilizing a container made of plastic material is explained below.

[0056] First of all, the mould 4 must be arranged in the open configuration.

[0057] For this purpose, the two half-moulds 4a, 4b are moved away from each other to enable insertion of the parison 3.

[0058] Once the parison 3 has been inserted, the two half-moulds 4a, 4b are moved close to each other to define the housing cavity 5 for the parison 3.

[0059] In this manner, the mould 4 is brought into the closed configuration.

[0060] The blowing nozzle 6 is applied to the neck 3b of the parison 3 in such a manner as to create a tight seal on the bague 6c and close the opening of the parison 3 in a tightly sealed manner. The stretching rod 23 is inserted inside the parison 3. In particular, the stretching rod 23 passes through the blowing nozzle 6 and gradually penetrates the parison 3.

[0061] At the same time, the blowing fluid is blown into the parison 3.

[0062] In particular, the blowing step comprises two separate substeps: one for pre-blowing and one for actual blowing.

[0063] During the pre-blowing step, the fluid blown into the parison 3 has a maximum pressure of about 16 bar.

[0064] During the pre-blowing step, the stretching rod 23 gradually penetrates the parison 3 until reaching 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.

[0065] During the pre-blowing step, the fluid blown into the parison 3 has a maximum pressure of about 40 bar.

[0066] Upon completion of the blowing and stretching step, the pressurized fluid remaining inside the container is evacuated to the exterior by means of the evacuation circuit. The evacuation circuit is of a known type and therefore it is not described herein.

[0067] In the meantime, the stretching rod 23 is kept inside the moulded container. The stretching rod 23 is preferably kept in the moulded container for a length of time that can last up to 2 seconds.

[0068] At this point, a voltage difference is applied between the stretching rod 23 and the mould 4 when still in the closed configuration; the voltage difference is such as to transform the fluid at atmospheric pressure remaining inside the container after evacuation into plasma.

[0069] For example, a voltage difference in the range of 20-30 kV is applied so as to bring about an electrical discharge that leads to the generation of plasma.

[0070] The characteristics and the advantages of the method for moulding and sterilizing a container made of plastic material, of the device for moulding and sterilizing a container made of plastic material, and of the moulding and sterilizing machine according to the present invention prove to be clearly indicated in the description provided.

[0071] In particular, the moulding device proposed herein also makes it possible to sterilize the moulded container, owing to the generation of plasma directly inside the container while it is still in the mould at the end of the blowing and stretching step.

[0072] Activation of the plasma does not require special technical measures given that it takes place following evacuation of the blowing fluid, and therefore at atmospheric pressure. In fact, it is a known fact that an increase in the pressure of the 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, activation is decidedly simpler if the fluid is at atmospheric pressure, as in the proposed invention.

[0073] The moulding and sterilizing device is compact and structurally simple in that it only requires the application of a voltage difference between the metal stretching rod and the closed mould.

[0074] Given that sterilization of the parison is carried out in the housing cavity following the moulding process, a conventional blower can be used. This conventional blower thus becomes a blower/sterilizer.

[0075] 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, sterilization system for the blown air circuit, etc.).

[0076] Sterilization cycles for sterilizing the environment and the blown air prior to production are no longer necessary.

[0077] Moreover, the sterilizer for sterilizing the parisons upstream of the blower can thus be eliminated.

[0078] In conclusion, the use of plasma makes it possible to reduce sterilization time, to avoid the use of chemical agents and the accumulation of peroxides in the container, and to sterilize the internal surface and the external neck of the parison and the container in a substantially uniform manner.