GB1590612A

GB1590612A - Method and apparatus for the production by blow-moulding of hollow plastics articles which are closed and sterile

Info

Publication number: GB1590612A
Application number: GB17004/78A
Authority: GB
Original assignee: Compagnie Francaise de Raffinage SA
Current assignee: Compagnie Francaise de Raffinage SA
Priority date: 1977-05-02
Filing date: 1978-04-28
Publication date: 1981-06-03
Also published as: IT7822480A0; BE866524A; NL7804719A; IT1094421B; FR2389477A1; ES469343A1; FR2389477B1; DE2818349A1

Description

(54) METHOD AND APPARATUS FOR THE PRODUCTION BY BLOW MOULDING OF HOLLOW PLASTICS ARTICLES WHICH ARE CLOSED AND STERILE (71) We, COMPAGNIE FRANCAISE DE RAFFINAGE, a French Body Corporate, of 5 rue Michel Ange 75781, Paris Cedex 16, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to the production at a high rate by extrusion-blowing of hollow plastics articles which are closed and sterile.

It is known for the packaging of many products that it is necessary to use hollow bodies, such as bottles, whose interior has been kept or made sterile prior to their filling.

This is especially the case for pharmaceutical products or foodstuffs, such as milk, which must be packaged under aseptic conditions so as to ensure their preservation for long periods.

For this purpose hollow bodies made of plastics materials are frequently used, which are produced by blow-moulding, whose interior is sterile at the termination of manufacture and which are sealed fluid-tightly during the moulding stage. These closed hollow bodies can thus be kept sterile during storage for long periods and it is only necessary to open them in 9 sterile chamber so that they can be filled, under aseptic conditions, with the products which have to be packaged therein.

For producing these hollow bodies a known method lies in using an extruder head to extrude a tube of thermoplastic material, the interior of which is supplied with sterile gas at a low pressure and the end of which is sealed hermetically, the sealing generally taking place during the production cycle of the preceding hollow body. This closed tube is then inserted between the two halves of a mould which is then closed so as to grip therein a portion of the tube forming a parison, the closure of the mould generally being enough to sever this parison, while the lips at the end of the remaining tube, which lips are nipped by the mould, are welded fluid-tightly to one another for the next cycle.

Inside the mould a sterile hollow needle, which is connected up to a supply of sterile gas under pressure, then pierces the parison and the blowing of this latter is subsequently effected by insufflation of sterile gas through this needle. The partial decompression of the hollow body thus produced is then effected by withdrawing the needle and two portions of the hollow body lying opposite one another are then nipped inside the mould, these portions being located between the point where the parison is pierced by the needle and the hollow body proper, so as to weld these portions hermetically. It only remains to open the mould to obtain a moulded hollow body which is closed fluidtightly and whose interior is sterile; it may be stored without difficulty for long periods, before being filled.

There are other processes which enable sterile hollow bodies to be produced. However, these processes have the disadvantage of not being suitable for high rates of mass production, firstly because the operation of blowing the hollow body is a relatively long operation and, secondly because it is necessary to await the termination of a blowmoulding cycle in order to be able to proceed with the production of another hollow body using the same equipment.

It is therefore one object of the invention to reduce the time taken to blow sterile hollow plastics bodies in blow-moulding production methods.

Another object of the invention is to increase the rate of production by blowmoulding of such hollow bodies, by feeding from the same extrusion apparatus a plurality of moulds used simultaneously to carry out the method.

For this purpose the invention provides a method of producing hollow plastics bodies which are closed and sterile, of the type in which extrusion of a tube of thermoplastic material is performed, whose interior is supplied with low-pressure sterile gas and the end of which is sealed fluid-tightly; which method comprises inserting the closed tube between the two halves of a mould which is then closed so as to enclose therein a portion of the tube thus forming a parison; piercing the parison within the closed mould by means of a sterile hollow needle which is connected to a supply of high-pressure sterile gas; blowing the parison with the highpressure sterile gas so as to obtain the hollow body; removing the hollow body after it has been partially decompressed; nipping two portions of the hollow body lying opposite one another inside the mould and maintaining the portions at a high enough temperature to weld them together in a fluid-tight manner; and ejecting the hollow body thus produced from the mould, wherein a plurality of moulds are moved along so as to be successively disposed open at regular intervals at right angles to the same extruder head, the parting plane of each mould being substantially parallel to the axis of the head when the mould is disposed in front of the head, wherein the period during which each mould is disposed at right angles to the head is longer than the production cycle of one hollow body in this mould, wherein in each mould the blowing of the parison is effected by means of at least one needle which is sterilised after each blowing operation, the said needle being directed substantially perpendicularly to the axis of the mould cavity, and wherein in each mould, at least during the blowing phase, a reduction in pressure is brought about between the mould wall and the outer surface of the parison, and therefore of the hollow body.

In the subject-matter of this invention and in the rest of this description: - low-pressure sterile gas' means a sterile gas maintained at a pressure very slightly above atmospheric pressure, it being possible for the relative pressure to be close to 1 millibar, for example. This low-pressure sterile gas is supplied to the extruded tube so as to prevent the ingress of unsterile air into this tube.

- high-pressure sterile gas' means a sterile gas kept at a pressure which is high enough to allow blowing of the parison, the relative pressure can be between 1 and 5 bars, for example 3 bars.

By carrying out the blow-moulding method concurrently in a plurality of moulds which are moved along in synchronism so as to be successively disposed open in front of the extrusion device which feeds them, it follows that the rate of production of sterile hollow bodies is considerably increased, especially as during the blowing phase the suction effect applied simultaneous to the outside the parison makes it possible to save considerable time during this phase. Morever, the Applicants have found that by thus combining the blowing and suction, the outer surface of the articles obtained is distinctly superior in quality to that of articles which are merely blown.

The invention also relates to an apparatus for carrying out this method, comprising, in combination, an extruder designed to supply continuously a tube of thermoplastic material, the interior of which is fed with lowpressure sterile gas, a device carrying a number of moulds for the blow-moulding of hollow bodies, means for moving the device so as to bring the moulds successively at right angles to the extrusion head, each mould consisting of mould halves which can move relative to one another and whose parting plane is such that it is substantially parallel to the axis of the extruder head when the mould is disposed at right angles to this latter, each mould including one or more blowing needles coupled to a supply of high-pressure sterile gas, such that the parison formed in the mould from the extruded tube can be transformed into a hollow body, and means for nipping two portions of the hollow body lying opposite one another so as to weld them fluid-tightly together, means being provided to effect in a preset sequence the opening and closing of the moulds and the blowing of the parison contained therein, so that the duration of one moulding cycle is less than the period during which each mould is disposed in front of the extruder head, wherein the blowing needles are connected up to a common supply of sterile gas, each needle being directed substantially perpendicularly to the axis of the mould cavity of the associated mould, wherein each mould is provided with at least one means for sterilising the needle or needles, and wherein each mould has on the internal surfaces of the mould halves one or more orifices which are connected to a suction source common to the different moulds, means being provided to control in a substantially simultaneous manner, after closure of a mould, the injection of sterile gas through the associated needle and the creation of a partial vacuum at the inner walls of the mould halves of this mould.

The device carrying a number of moulds may comprise, for example, a carousel rotating about an axis, or a chain or other endless device, this type of device being well known to the expert.

The means which enable, on the other hand, the blowing needles to be connected to a common supply of high-pressure sterile gas, and on the other hand, the moulds to be connected to a suction source, may comprise a multiple rotary joint or coupling. This coupling also makes it possible to distribute to the moulds the cooling liquid necessary for cooling the hollow body blown.

The nipping of the parison by the mould halves is generally enough to separate the gripped parison from the remainder of the extruded material. However, optionally, it is possible to provide at right angles to the extrusion head and between this head and the mould-carrying device a nipping system designed to sever the parison enclosed within a mould and to seal fluid-tightly the end of the tube.

Of course, the needle used in each mould to effect the blowing of a preform must be sterile. For this purpose each mould will include at least one means for sterilising the associated needle or needles between each blowing operation. Thus, for example, each mould could be provided with a chamber pierced by an aperture lying on the axis of the needle to be sterilised and allowing the needle to pass, this chamber being intended to receive the needle and its support after each blowing operation and being provided with members such as electric resistances for producing a temperature therein which is at least equal to the sterilisation temperature.

Furthermore, a flow of low-pressure sterile gas can be maintained without interruption through the needle between the blowing sequences, this low-pressure sterile gas being supplied by means of the multiple rotary coupling.

It is to be noted that the hollow bodies manufactured according to the invention are sealed hermetically at the level at which the two opposite surfaces have been nipped inside the mould and thus welded to one another. Between this portion and the outside of the mould the hollow body will thus have an appendage which, in certain cases, has to be removed. Consequently, the production moulds could include between the means for nipping the hollow body and the exterior of the mould a cutting system, such as a blade, which enables this appendage to be separated from the remainder of the hollow body actually inside the mould.

However, this arrangement of the moulds merely constitutes an alternative, since the severing of the appendage can take place outside the mould, in a subsequent stage of the production process.

The accompanying drawings illustrate one form of embodiment of the method according to the invention, in which: Figures 1 to 4 are sectional views showing successive phases in the production of a sterile hollow body in the interior of the same mould of an apparatus used for carrying out the method according to the invention; Figure 5 illustrates diagrammatically an apparatus for carrying out the method of the invention.

As evident from Figure 1, each mould consists of two mould halves, 21 and 22 respectively, which can move relative to one another under the action of drive means (not shown). In the mould half 21 there is provided a duct 23 directed perpendicularly to the axis X X' of the mould cavity and in which a hollow needle 24, which is firmly attached to a base plate 25, is able to move so as to pierce a parison, as will be described below, in order to carry out the blowing of the parison. For this purpose the hollow needle 24 is connected through a line 26, which is couplied to the multiple rotary joint or coupling of a carousel, to a supply of highpressure sterile air, and the base plate 25 forms the piston of an actuator 27 designed to actuate the needle 24. A chamber 28 provided with a means such as an electrical heating element 28', or else a source of infrared radiation, is provided for the sterilisation of the needle 24, when the needle is retracted after each blowing operation.

The chamber 28 may form an integral part of a mould half, as shown in the Figure, or may be fitted on to the mould. Each mould may likewise be provided with two or more chambers each containing at least one needle, in which case the sterilisation time for each needle can be increased and the production rate improved accordingly.

The needle 24 is only supplied with highpressure sterile gas during the blowing operation. Between these operations the needle 24 can be connected up to a supply of lowpressure sterile gas through the line 26' coupled to multiple rotary coupling.

Each mould half 21, 22 has a hollow portion or mould-cavity half 29, 30 respectively, the profile of which corresponds to that of one half of the hollow body which it is desired to mould. In the vicinity of the walls defining the hollow portions 29 and 30 there are provided depressions 31, which are connected through ducts 32 to a vacuum line, so that it is possible to apply a suction effect between the parison and the mould wall during the blowing operation. The depressions 31 communicate with the interior of the mould through vents (not shown).

Each mould half also comprises nippers, 33 and 34 respectively, which can move in recesses 35 36 perpendicularly to the axis XX' under the action of drive means (not shown).

Finally, between the recesses 23 of the needle 24 and recesses 35, 36 of the nippers 33, 34, a movable blade 37 accommodated in a slot 38 in the mould half 22 perpendicular to the axis X-X' can be displaced towards and away from this axis under the action of suitable drive means (not shown).

The mode of operation of the various members of these moulds will now be described with reference to Figures 1 to 4.

Figure 1 illustrates the position of a mould which has been reclosed at 40 on to the tube of thermoplastic material 41 extruded by the extruder head 42. The latter comprises, as is conventional, a die 43 and a mandrel 44. A duct 45, connected to a supply of lowpressure sterile gas, discharges at the centre of the mandrel 44 so as to inject the sterile gas into the tube in order that the latter maintains its shape. Upon closing, the mould halves 21 and 22 enclose inside the mould a parison 46 and at the same time fluid-tightly seal the lower end of the tube 41. The closure of the mould may be enough to separate the parison 46 from the tube 41. It is also possible to provide at the end of the mould a separate system for nipping and cutting the parison depicted at 47.

Figure 2 illustrates the blowing phase. The needle 24 has perforated the parison and has injected into it the high-pressure sterile gas, while at the same time the depressions 31 have been connected up to the vacuum line so as to apply a suction effect on the outer surface of the parison. Under the combined action of this suction and of the blowing, the parison has flattened itself against the hollow portions 29 and 30 of the mould halves 21 and 22, so as to form the sterile hollow body 48.

In Figure 3 the needle has regained its initial position in the chamber 28 where it can be sterilised again, this withdrawal causing simultaneously the partial decompression of the hollow body 48 by means of the aperture 48' communicating with the exterior, the nippers 33 and 34 not having yet been shifted towards one another so as to close the hollow body. However, complete decompression is not carried out so that a slight overpressure is allowed to prevail inside the hollow body 48 with a view to maintaining the shape thereof during subsequent handling or storage operations. When the desired pressure is reached, the two nippers 33, 34 are shifted towards the axis X-X' so as to bring into mutual contact the portions of the hollow body lying opposite one another. This operation takes place before the hollow body has completely cooled, so that the portions in mutual contact are welded hermetically to one another.

In the next phase (Figure 4) the blade 37 cuts off the appendage which separates the hollow body 48 proper from the portion 40.

As already stated, this phase is optional and the appendage may be removed after the mould is opened, the hollow body being ejected during the opening operation.

Level with the bottom of the hollow body there is also obtained an appendage similar to the portion designated 40 in Figure 1. This appendage may be removed before the mould is opened by nipping it between two surfaces provided with flutes which extend in opposite directions to one another on either surface, and by displacing one of these surfaces in relation to the other so as to cause a shearing movement parallel to the direction of the flutes on the fixed surface.

Furthermore, the systems for cooling the moulds are of a type well known in the art and they have not been illustrated in the drawings.

With reference to Figure 5, the apparatus comprises an extruder 50 whose fixed extruder head 42 successively feeds a plurality of moulds 51, 52 and 53 with a tube of thermoplastic material 41, into which lowpressure sterile air is introduced through the line 45. The moulds are brought at right angles to the extruder head 42 by a carousel (not shown) rotating about the axis AA', the moulds rotating in the direction indicated by the arrow. Although in Figure 5 only three moulds have been shown, there could be more of them or simply two. The moulds are shown to be rotating in a horizontal plane, but they may also rotate in a vertical plane.

Each mould comprises two mould halves 21 and 22 which can move relative to one another under the action of means which are not shown.

The apparatus also comprises a multiple revolving joint or coupling 54. This coupling is connected: -by the line 55 to a supply of highpressure sterile air, -by the line 56 to a supply of lowpressure sterile air, -by the line 57 to a supply of liquid coolant, -by the line 58 to a suction source.

This coupling is connected to the different moulds through ducts which may be flexible or rigid. If they are connected to a part of the mould which is fixed in relation to the mould support they may either be rigid or flexible.

If this part of the mould is movable they have to be flexible. Likewise they may be arranged at least partly in the actual support for the moulds, when the support comprises, for example, a turntable. These ducts are represented in Figure 5 by the lines 26, 26', 59 and 60. The line 26 supplies the needle 24 contained in the sterilisation chamber 28 with high-pressure sterile air, the line 26' supplies the needle 24 with low-pressure sterile air. The line 59 feeds the cooling circuit of the mould halves 21 and 22. The line 60 enables the inner walls of the mould halves to be placed under a partial vacuum.

Whilst one hollow body is being blown in the mould 53, another is cooling in the mould 52. The blown hollow body 61 is ejected from the mould 52 before this latter is brought in front of the extruder head 42.

The sterile hollow bodies thus produced have an excellent surface quality, particularly at the level of the parting plane.

The above-described method has the additional advantage of considerably increasing the production rates of sterile hollow articles in relation to conventional series-production methods.

The various hollow articles produced by applying the invention may be made from any extrudable material, particularly the polyolefins. Polyethylene gives excellent results.

WHAT WE CLAIM IS: 1. A method for the production of hollow plastics bodies which are closed and sterile, of the type in which extrusion of a tube of thermoplastic material is performed, whose interior is supplied with low-pressure sterile gas and the end of which is sealed fluidtightly; which method comprises inserting the closed tube between the two halves of a mould which is then closed so as to enclose therein a portion of the tube thus forming a parison, piercing the parison within the closed mould by means of a sterile hollow needle which is connected to a supply of high-pressure sterile gas, blowing the parison with the high-pressure sterile gas so as to obtain the hollow body; removing the hollow body after it has been partially decompressed; nipping two portions of the hollow body lying opposite one another inside the mould and maintaining the portions at a high enough temperature to weld them together in a fluid-tight manner, and ejecting the hollow body thus produced from the mould, wherein a plurality of moulds are moved along so as to be successively disposed open at regular intervals at right angles to the same extruder head, the parting plane of each mould being substantially parallel to the axis of the head when the mould is disposed in front of the head, wherein the period during which each mould is disposed at right angles to the head is longer than the production cycle of one hollow body in a mould, wherein in each mould the blowing of the parison is effected by means of at least one needle which is sterilised after each blowing operation, the said needle being directed substantially perpendicularly to the axis of the mould cavity, and wherein in each mould, at least during the blowing phase, a partial vacuum is created between the mould wall and the outer surface of the parison, and therefore of the hollow body.

2. A method as claimed in claim I wherein after closing the mould, the parison enclosed therein is separated from the remainder of the extruded tube, and the end of the tube is sealed by means of an auxiliary member independent of the mould.

3. A method as claimed in any one of claims I or 2, wherein before opening the mould, any appendage formed adjoining the hollow body, at the location where two portions of the parison situated opposite one another have been nipped and welded to one another inside the mould, is separated from the hollow body by being cut off inside the mould.

4. A method as claimed in any one of claims 1 to 3, wherein before opening the mould, any appendage formed at the bottom of the hollow body is separated from the mould by nipping this appendage between two conversely fluted surfaces and by relative displacement of one surface in relation to the other.

5. An apparatus for the production by blow-moulding of hollow plastics articles which are closed and sterile comprising, in combination, an extruder designed to supply continuously a tube of thermoplastic material, the interior of which is fed with lowpressure sterile gas, a device carrying a number of moulds for the blow-moulding of hollow bodies, means for moving the device so as to bring the moulds successively at right angles to the extrusion head, each mould consisting of mould halves which can move relative to one another and whose parting plane is such that it is substantially parallel to the axis of the extruder head when the mould is disposed at right angles to this latter, each mould including one or more blowing needles coupled to a supply of high-pressure sterile gas, such that the parison formed in the mould from the extruded tube can be transformed into a hollow body, and means for nipping two portions of the hollow body lying opposite one another so as to weld them fluid-tightly together, means being provided to effect in a preset sequence the opening and closing of the moulds and the blowing of the parison contained therein, so that the duration of one moulding cycle is less than the period during which each mould is disposed in front of the extruder head, wherein the blowing needles are connected up to a common supply of, sterile gas, each needle being directed substantially perpendicularly to the axis of the mould cavity of the associated mould, wherein each mould is provided with at least one means for sterilising the needle or needles, and wherein each mould has on the internal surfaces of the mould halves one or more orifices which are connected to a suction source common to the different moulds, means being provided to control in a substantially simultaneous manner, after closure of a mould, the injection of sterile gas through the associated needle and the creation of a partial vacuum at the inner walls of the mould halves of this mould.

6. An apparatus as claimed in claim 5 wherein the means for sterilising the needle comprises at least one sterilisation chamber situated inside one mould half.

7. An apparatus as claimed in claim 5 wherein the means for sterilising the needle

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The above-described method has the additional advantage of considerably increasing the production rates of sterile hollow articles in relation to conventional series-production methods. The various hollow articles produced by applying the invention may be made from any extrudable material, particularly the polyolefins. Polyethylene gives excellent results. WHAT WE CLAIM IS:

1. A method for the production of hollow plastics bodies which are closed and sterile, of the type in which extrusion of a tube of thermoplastic material is performed, whose interior is supplied with low-pressure sterile gas and the end of which is sealed fluidtightly; which method comprises inserting the closed tube between the two halves of a mould which is then closed so as to enclose therein a portion of the tube thus forming a parison, piercing the parison within the closed mould by means of a sterile hollow needle which is connected to a supply of high-pressure sterile gas, blowing the parison with the high-pressure sterile gas so as to obtain the hollow body; removing the hollow body after it has been partially decompressed; nipping two portions of the hollow body lying opposite one another inside the mould and maintaining the portions at a high enough temperature to weld them together in a fluid-tight manner, and ejecting the hollow body thus produced from the mould, wherein a plurality of moulds are moved along so as to be successively disposed open at regular intervals at right angles to the same extruder head, the parting plane of each mould being substantially parallel to the axis of the head when the mould is disposed in front of the head, wherein the period during which each mould is disposed at right angles to the head is longer than the production cycle of one hollow body in a mould, wherein in each mould the blowing of the parison is effected by means of at least one needle which is sterilised after each blowing operation, the said needle being directed substantially perpendicularly to the axis of the mould cavity, and wherein in each mould, at least during the blowing phase, a partial vacuum is created between the mould wall and the outer surface of the parison, and therefore of the hollow body.

comprises at least one sterilisation chamber located outside the mould.

8. An apparatus as claimed in any one of claims 5 to 7 wherein the device carrying a number of moulds is in the form of a carousel.

9. An apparatus as claimed in any one of claims 5 to 8, including a multiple rotary joint or coupling for connecting to the supply of high-pressure sterile gas through a common duct the individual high-pressure sterile gas lines for each of the moulds, and for connecting to the suction source through a common duct the individual suction lines for each of the moulds.

10. An apparatus as claimed in any one of claims 5 to 9 including a member independent of the moulds for separating the parison enclosed in a mould from the remainder of the extruded tube and for sealing the end of this tube.

11. An apparatus as claimed in any one of claims 5 to 10 wherein each mould includes, arranged between the nipping members and the blowing needle, a cutting blade designed to be moved perpendicularly to the axis of the mould cavity.

12. An apparatus as claimed in any one of claims 5 to 11 wherein each mould includes means for severing any appendage formed at the bottom of the hollow body before the mould is opened.

13. A method of producing hollow plastics bodies which are closed and sterile substantially as hereinbefore described with reference to the accompanying drawings.

14. An apparatus for producing hollow plastics bodies which are closed and sterile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

15. Sterile hollow articles when produced by an apparatus or in accordance with a method as claimed in any one of the preceding claims.