GB2103535A - Process for the construction of thin crush-resistant synthetic resin containers - Google Patents

Abstract

The process relates to the production of a container by blow- moulding a synthetic resin plastic tubular element against the walls of the hollow mould of a die, the blown container having an external extension which extends from its upper mouth, the extension having an internal channel, which was used for injecting air into the tubular element. The process involves the sealing of this channel by means of welding carried out along a line above the upper mouth of the body of the container before the injection of air has ceased so as to maintain the pressure inside the container at least equal to atmospheric pressure. <IMAGE>

Description

SPECIFICATION Process for the construction of thin crushresistant synthetic resin containers, and container obtained with this process This invention refers to a process for the construction of thin crush-resistant synthetic resin containers, and containers obtained with this process.

I has been known for some time that containers or hollow bodies can be built by using a tubular element is synthetic resin, known to the technicians in this industry as a "PARI SON". This "PARISON", extruded from a forming head, is closed between the chills of a die and transferred to an operational station where, by means of a blowing jet, it is expanded against the surface of the hollow mould of the die which reproduces the shape of the desired container.

Then there are the finishing operations of the container (consisting, for example of trimming and knockdown) which give a perfectly shaped container, open and ready for transfer to later operational stations, such as, for example, filling and closing stations.

Nowadays, this type of container is used widely for soap liquids, detergents and also for drinks. These packaging operations are normally carried out by using machines fitted with container pick-up and transfer devices which exert a considerable mechanical stress on the container especially at high speeds.

Thus by using very thin-walled containers, which are subject to crushing or to permanent deformation of their shape you get crushing and dents or permanent deformations of containers which, apart from causing jammings in the packaging cycles, may mean that the containers are unusable and may have to be replaced.

To avoid this inconvenience it has been decided to intervene on the containers lined up on the feed line towards the conditioning machines which, for example, fill them, subjecting them to air jets which inject pressurized air into them so that, as far as possible, the original shape of the container is restored if it has been deformed.

This type of process requires the use of equipment which works in time with the movement and stops of the containers and therefore it requires equipment which, however simple it may be, has a considerable effect on the cost of production of the packaged goods.

The aim of the procedure in this invention is to obtain, by following the moulding technique explained above, a container or hollow body, which even though it has a very thin wall and is made of low mechanical-resistant material, does have a good resistance to bumps or crushing, thus making it possible to supply containers which even when subject to the stress of mechanical pick-up and transfer organs (such as jaws, grippers, pushers etc.) do not undergo any deformation or at the most only undergo a temporary elastic deformation due to contact with these mechanical organs.

This aim is achieved according to the invention by means of a process for the construction of thin-walled synthetic resin containers with the following phases: - formation, by extrusion, of at least one tubular element or PARISON" in hot plastic material; - holding of one or more pieces of this tubular element between the chills forming a die and internally fitted with hollow moulds which determine the shape of the container or containers to be built; - injection of air into this tubular element still in its plastic state and held within the closed die so as to expand it against the surfaces of the hollow moulds, characterised by the following phases: a) formation of the container or containers, obtaining in the expansion phase of the tubular element or "PARISON" an extension which extends without a gap from the access mouth within the container itself, which is fitted with a channel which connects the inside of the container with the outside of the die and through which the air is passed for expanding the tubular element against the walls of the hollow moulds of the die; b) sealing of the channel by means of welding carried out by welders working in time with the equipment which injects air into the tubular element or "PARISON" so as to close the channel in a part of the extension above the mouth of the container before the injection of air has stopped so as to maintain pressurized air inside the container at a pressure at least equal to atmospheric pressure.

With the process in this invention you obtain a pressurization inside the container which gives it a certain mechanical resistance and stops it from being crushed.

The advantage is that containers built and sealed in this manner can be stored in bulk and thus set out in order along feed lines to automatic machines using high speed devices without any risk of their being damaged.

Furthermore the containers remain perfectly sealed practically up to their filling phase which can only take place after removing the extension with a simple cutting operation which can be carried out with the containers in motion and without the need for special equipment. Thus the containers remain perfectly clean inside and can be used immedi ately even after a long storage period.

If low-porosity material is used with aseptic air as the expansion fluid for the tubular element or "PARISON", according to the invention, you can get containers which are perfectly sterilized on the inside.

The operational phases of the process in this invention and the features of the contain ers obtained with this process will now be illustrated better with the following description of the production cycle of a container, with reference to the attached drawings, in which: Figure 1 illustrates in a diagram and purely as an example, the main parts of a possible type of machine for the carrying out of this process; Figure 2 partially illustrates in a diagram a possible type of container obtained with this process and with the upper part seen in perspective including the extension along which a sealing operation is carried out or the channel which allows air to be injected into the tubular element from which the container has been formed;; Figure 3 illustrates the container as seen in Fig. 2 with a partial cross-section and with the welding equipment used for sealing the chan nel shown in a diagram.

From Fig. 1 you can see that the process in the invention can be carried out by using a machine which includes, for example, an extrusor unit 1 fitted with a special loading hopper 2 from whose head 3 a tubular element 4 is continuously extruded, commonly known as a "PARISON" It is in fact a tubular pre-mould for hot plastic material. The machine can include a die-holding unit 5 which can be moved in both directions along guides 6 which allows you to transfer alternately the die-holding unit 5 from the operational station marked A, in which the extrusor unit 1 is situated, to the operational station marked B, in which a pneumatic unit 7 is situated, fitted with a blowing plug or jet 8 through which, as will be explained later, pressurized air is injected into the piece of "PARISON" held in the die.

In the illustrated case the die marked 9 is made up of two chills which can be translated towards each other in relation to the dieholder 5 and connected to equipment providing the movement, not illustrated in the drawings, which determines the closing and opening of the die bringing the chills into reciprocal frontal contact and moving them away from each other.

Each chill has a hollow mould which gives the shape of half the container to be built.

In the case illustrated, with die 9, you can get only one container for each operational cycle.

This die 9 can also be fitted with further moulds for the sinultaneous production of two or more containers: obviously in this case the number of tubular elements or "PARISONS" 4 leaving the extrusor unit 1 must be equal to the number of moulds in the die 9, in the same way that there must be an equal number of injecting plugs or jets 8 in the pneumatic unit 7. 10 marks a knife positioned in station A between the extrusor unit 1 and the die 9. The knife 10 serves for cutting from the tubular element 4, leaving the head 3, a piece of "PARISON" long enough for the desired height of container. This piece will, in any case, always be long enough so that on closing die 9 the lower end of the "PARI SON" is squashed in such a way as to close it on the bottom.

11 marks a welding unit which in the illustrated case is coupled with the die-holder unit 5 and is made up of two welding elements 12, working one opposite the other, held by supports 13 connected to the dieholder unit 5. Each welding element is subject to a moving device 14 which it gives it its alternate movement in relation to the relative support 13 on a horizontal plain and in the direction of the blowing plug or jet 8 of the pneumatic unit 7.

The welding elements 12 are positioned in such a way that when the die 9 is stationary in the operational station B aligned along the axis which intersects the vertical axis of the blowing plug or jet 8.

Obviously in the case where the machine has been set for producing more than one container for each production cycle the number of welding elements 12 must be equal to the number of containers coming from the die 9, or rather the welding elements must be fitted with a number of welding heads equal to the number of containers coming out of the die.

15 marks a receiving table for the formed containers situated downstream from operational station B to receive the containers as they are produced.

The transfer of the containers from operational station B to transporter 15 can be obtained by means of mobile pick-ups 16, synchronized to welders 12, from a position in which they grip the containers in station B, freed from the die 9, to a position in which they release the containers onto the receiving table 15 and they return to their initial position.

In the initial phase of an operational cycle, purely as an example, we can imagine the following situation: - the die-holder unit 5 is in operational station A and the die 9 has the chills open; - the "PARISON" 4 is continually extruded from the extrusor unit and passes through the open chills of the die 9 in a direction to which the chills are symmetrical; - the knife 10 is stationary and in such a position as not to disturb the descent of the "PARISON" from the head of the extrusor unit 1; - the welding elements 12 are stationary near operational station B; - the blowing plug or jet 8 of the pneumatic unit 7 is completely in the upper position; - the pick-up devices 16 are open and stationary in station B.

When the "PARISON" 4 has reached the desired length die 9 clos#es and the knife 10 is activated which cuts from the continuous tubular elements a piece of "PARISON" which is then held in the die.

The die-holder unit 5 is activated and is transferred from station A to station B. The die 9 is thus transferred to station B with its upper opening, from which the piece of "PARISON" protrudes, aligned along the axis of the blowing plug or jet 8.

At this point the plug 8 descends towards the die 9 and is inserted into the opening.

The pneumatic unit 7 supplies pressurized air to the plug 8 and thus to the inside of the "PARISON" held in the die 9, which, still in its plastic state, is expanded against the internal surface of the moulds formed by the chills of the die itself.

At the end of the expansion phase of the "PARISON" the die 9 opens and the container thus obtained, marked 20, resets held on to the blowing plug or jet 8.

The die-holder unit 5 returns to station A and when the welding unit 11 is moved to operational station B together with the pickups 16.

The die 9 re-closed while at the same time the welding elements 12 are reciprocally brought together until they reach the position in which they cause the localized crushing of an extension 17 of the container 20 which extends from its mouth 18 (see Figs. 2 and 3). At the same time the pneumatic unit 7 is deactivated and, before the injection of air into the container 20 stops, the welding elements 12 seal channel 19 through which the air from the plug 8 has been injected into the container.

Thus the sealed container remains internally pressurized.

At the same time as the welding elements 12 are activated the jaw of the pick-ups 16 are reciprocally brought together so that at the end of the phase in which air is injected into the body of the container 20 when the plug or jet 8 is raised the container rests in the grip of these jaws.

There then follows a new translation of the die-holder unit 5 from station A to station B and at the same time the welding unit 11 and the pick-ups 16 are translated from station B to a position in which the container 20 is deposited on the receiving table 15.

Then there is the return of the welding elements 12 where they are reciprocally held apart and the pick-ups open and thus the production cycle of a container is finished.

What has been illustrated above is purely an example in that the process can be carried out by using machines which are different from those illustrated.

For example, the welding elements 12 could be incorporated in the die 9 and could be activated when it is in station B before its opening.

The containers which can be obtained with the process in this invention terminate at the top with a neck 22 from whose edge or mouth 18 extends a prolongation 17 which is all part of the container 20. This prolongation 17 thus forms a kind of all-in-one top connected to the body of the container 20 and which keeps the container pressurized thus giving it a good resistance to mechanical bumps.

The container 20 can thus be stored in bulk or even be subjected to highspeed mechanical pick-up or transfer organs without getting crushed or in any case without undergoing permanent deformation, thus making mechanical packaging easier.

At the moment in which the container 20 is filled the extension 17 can be easily removed from the neck 22 by means of shearing or cutting which can be carried out along a fracture line 26 which is obtained in the moulding phase and which marks the upper edge of the neck 22 of the container.

Claims (3)

1. Process for the construction of thin crush-resistant synthetic resin containers, with the following phases: - foramtion, by extrusion, of at least one tubular element or PARISON" in hot plastic material; - holding of one or more pieces of this tubular element between two chills of a die fitted internally with two hollow moulds which determine the shape of the container or containers to be built; - injection of air into this tubular element, or elements held in the die still in their plastic state so as to expand them against the surfaces of the hollow moulds characterised by the following phases; a) formation of the container, or containers, obtaining in the expansion phase of the tubular element or "PARISON" an extension which extends, without a gap, towards the outside of the container starting from the neck of the container itself, fitted with a channel which connects the inside of the container with the outside of the die through which air is passed for the expansion of the tubular element against the walls of the hollow moulds of the die; b) sealing of this channel by means of welding carried out with welders working in time with the equipment which injects air into the tubular element, so as to seal the container before the injection of air ceases so as to maintain pressurised air inside the container at a pressure at least equal to that of atmospheric pressure.

2. Synthetic resin container obtained according to the process in claim 1, characterised by the fact that it has an extension which is an all-in-one part of the container obtained during the moulding phase, and is sealed above the access mouth within the container.

This extension can be removed from the body of the container along a pre-set fracture line which marks the upper edge of the container.

3. Process for the construction of thin crush-resistant synthetic resin containers substantially as hereinbefore described with reference to the accompanying drawings.