IL46126A - Process and apparatus for packaging and irradiating articles - Google Patents

Description

qnmpnVl D*san nt»usV \pmi «|» Vnn PROCESS AND APPARATUS FOR PACKAGING AND IRRADIATING ARTICLES The invention has as its subject a process and apparatus for simultaneous packaging and irradiation of £ articles.

It is known that it is very common to irradiate objects by means of a powerful radioactive source such as a cobalt source either in order to sterilise them, as is the case with articles for medical use, or to ensure conservation for example for food products of animal or vegetable origin, for example in the case when microorganism may cause physicochemical modifications (polymerisation, reticulation or grafting or macromolecules) .

For this purpose, there is generally used an irradiation chamber which contains the radioactive source and in which there is circulated according to a predetermined path, the objects to be irradiated. The latter are conveyed by an appropriate transporter and follow in the irradiation chamber a sinuous path causing several passages of the same object in the neighbourhood of the radioactive source, in order to obtain adequate irradiation.

The means o transport generally utilised comprise rigid containers, drawn by a chain or pushed by screws, chambers which at the outlet of the irradiation chamber become discharged and return to the entry of the same enclosure in order to be charged again for a new cycle. As it is important that they provide a minimum of screening between the source of radiation and the objects to be irradiated and consequently the containers used and the transporting means are normally made of light alloys which have a small thickness.

Such systems however have the disadvantage that deformations in the containers appear rapidly during use so that the cost of replacement of these components is high.

Further when the same apparatus has to be used for irradiation of objects of different shape for example in the case where irradiation of food commodities is applied to seasonal products, it is necessary to provide in reserve several different types of metal container resulting in an excessive increase in investment necessary for each installation.

According to one aspect of the invention, there is provided a method of packaging articles to be irradiated, in which the articles are enveloped in bags formed in a train from a continuous sheet of a heat-shrinkable plastics material, the bags containing the articles are formed into parallelepipeds, the parallelepipedal bags are shrunk by heat and thus fixed in their parallelepiped shape, and the train of bags is suspended vertically so that the whole of each bag is exposed to radiation when passed adjacent a radioactive source.

It is believed that such a method allows elimination of undesired obstacles between the objects to be irradiated and the source of radiation while using a desirable form of packaging.

It is also believed that such a method is applicable as a continuous method at a high rate of input and without the necessity for complex or expensive surveillance.

It is further believed, that this method may be applied to irradiation of objects of different dimensions and that the same installation may easily be used for treating articles of different sizes without the necessity for large or costly modifications. The plastics material may be of a type which is not affected by irradiation. £τ Heat-shrinking of the plastics material allows the material to surround the articles tightly and thus renders the packages "indeforinable" , that is the packages retain their size and shape during subsequent handling operations. The packages may be formed to a pre-determined shape before heat-shrinking to ensure that the shrunk packages are formed in a suitable shape to be passed through the irradiation chamber.

The invention is applicable to packaging of individual articles and also to bulk packaging, for example of foodstuffs such as potatoes.

According to another aspect of the invention, there is provided apparatus for packaging and irradiating articles, which comprises means for enveloping the articles in a heat-shrinkable plastics material to form packages, at least one heat source arranged to cause shrinkage of said material after enveloping, an enclosure containing at least one radioactive source and means for transporting the packages through the chamber continuously after heat-shrinking.

In a preferred embodiment of the invention, the packages are suspended from transport means, in such a manner as to expose the whole of the package to irradiation emitted by the irradiation source.

The shaping of the packages may be carried out either after formation thereof for example by passage before the shrinking step between devices capable of flattening them or by means of moulds in which the packages are formed and in which they remain during shrinking.

Preferred embodiments of the invention will be described below by way of example with reference to the accompanying drawings, in which Figure 1 is a diagram showing a first embodiment of the invention without the use of moulds for forming of the packages, Figure 2 is a view in lateral elevation showing a method of storing in small boats, Figure 5 is a transverse view of storing of Figure 2 after shrinking, Figure is a view in lateral elevation showing a storing in bulk, Figure 5 is a transverse view of storage of Figure 4-, after shrinking, Figure 6 is a partial diagram showing a method of storing with the utilisation of a mould, Figure 7 is a diagram of another embodiment of the method of storing of Figure 6, and Figure 8 is a detailed view of a mould.

Referring to Figure 1, there is unwound from a reel 1 a film 2 of a thermo-shrinkable plastics material, that is to say a film folded in such a manner as to have the shape of a U, of which the bottom will form the bottom of an envelope in which will be packaged an article to be irradiated. This film, is welded vertically by means of a welder 4- at regular intervals in such a manner as to form a series 5 of bags 6 (Figure 2) whic are filled at 7 with the articles to be irradiated. The individual bags are closed at their upper part at (Figure 2) by means of a welder 10. The bags 6 are formed to the shape appropriate to the shape and dimensions of the irradiation chamber in which they will eventually be introduced, for example by flattening them by means of plates such as 11 moved by jacks.. The bags thus formed are then introduced into an oven 12. in which they are rendered indeformable by shrinkage by heat of the plastics material of which they are formed. During all these operations the series of bags may be supported by a rectilinear conveyor of alternating type 13 » by means of which the bags pass from the vertical to the horizontal between the soldering point 10 and the shaping positi 11. If filling of the bags involves formation of dust, as is the case when the articles to be irradiated are vegetables, for example potatoes, this operation may be carried out in a dust removal cabinet 1 „ After shrinking of the material forming the bags the latter are suspended vertically from claws 13 (Figures 2 and 3) on a continuous transporting chain 16, which introduces them into the irradiation chamber 17 provided with protective screen 18 inside which the chain 16 describes a sinuous path in such a manner as to maintain for a long time the objects to be irradiated in the proximity of the irradiation source 19 from which they are only shielded by the thickness of the bag, that is to say, by a quantity of material which is practically negligible. At the exit of the chamber 17 the bags are separated one from another at 20 and discharged at 21 from the chain 16, which continues its path of travel so that the new bags are fed to the entry of the chamber 17 , for a new cycle of irradiation.

It will be noted that, to allow the claws 15 to grip the train of bags 6, a flap 22 may advantageously be pro^¾ied in the plastics material, above the closing weld 9. This weld and the flap 22 may be formed simultaneously or separately. It is also possible to fix to the train of bags a prefabricated flap, of paper or other material, which may be fixed by various means such as clips or welding.

Several variations of this first embodiment of the invention may be provided. It is possible for example to use initially a film 1 which is continuous but to separate the filled bags 6 after shrinking of the plastics material, before introducing them into the irradiation chamber 17. Instead of starting with a film it is also possible to use initially distinct bags of a thermo-shrinkable material. It is also possible, as shown in Figures and 5, to carry out the prcces using bulk packaging of products or articles in the film in Ά order to obtain, instead of elementary bags 6, a bulk package 23, of greater dimensions on the condition, naturally, that the dimensions of the package should be compatible with the geometry of the irradiation chamber.

There will now be described with reference to Figure 6, another embodiment of the invention.

In this embodiment, as in the first-described embodiment, a continuous film 30 of thermo-shrinkable plastics material is unrolled from a bobbin 31 and passes through a vertical welder 32, in such a manner as to form a train of bags connected to each other. Each elementary bag is then - - introduced at 33 in a mould such as mould 4-, shown in Figure 8 which comprises two grilles 35 separated by two longitudinal slots 36 to allow passage of the band of pieties material connecting the bags to each other. During filling of the bags in the chamber 3 the mould J gives to the bag the form and dimensions which are suitable for the geometry of the irradiation chamber. Each bag, taken by the transporter 38, is then closed by welding at 39 a d introduced still encased in the mould into the oven 40. When it leaves the oven the plastics material which forms it is shrunk in such a manner as to render the p'ackage indeformable and it is then possible to open the mould at 41, to feed the train of bags to the transporter chain 42 which introduces them into the irradiation chamber (not shown) . The following part of the process is identical to that which has already been described with reference to Figure 1. The variants which have already been described in connection with the first embodiment may also be applied to this embodiment.

The operations from filling to shrinking are generally carried out at a chain of distinct positions, the mould and the bag being fed successively to these positions either by a longitudinal transporter such as that shown by reference 38 in Figure 6 or by a roundabout such as the roundabout 43 of Figure 7» n which the positions already described with reference to Figure 6 have the same reference numerals. In this embodiment using a roundabout all the operations of filling the bag, closing by welding and shrinking are carried out at the same fixed position 44.

The mould may be enclosed in an enclosure which serve as an oven and it is then necessary to cool it before ^ introduction of another bag, or the shrinking may be carried : out by a blast of hot air without using an oven.

The advantages of packaging in thermo-shrinkable plastics material for irradiation are many.

It is known that to ensure homogeneity of the irradiation dose the thickness of the packages should be quite small and uniform. Shrinking allows obtention of bags of rectangular section which are quite uniform whereas without shrinking there would be required clamping means or a special container for the packages.

Further the packages may serve after irradiation for storage and distribution of the articles to the users.

For packaging certain food commodities the use of micro-porous film may be advantageous. The pores increase in size during the process of the invention and aeration during storage is ensured. In various countries, regulations concerning the sale of potatoes which are irradiated require indication on the packages of the method of conservation but this marking may be carried out easily at the start of the process.

It will be noted that use of an airtight film prevents contamination of the objects between irradiation and use.

It will be apparent from the description above that a process according to the invention is particularly suitable to packaging of a large number of articles. The apparatus may be designed to feed the same irradiation chamber by two or more transporters in parallel simultaneously.

Finally, the apparatus which has been described may be used without major modification for objects and packages of varied ohapoo and "dimensions.

By way of example there will now be described the use of the process for packaging and conservation of potatoes. It is known that the medical requirements impose in this case irradiation dose of 10 ,000 to 15, 000 rads. If there is used radioactive cobalt source of 150 , 000 Ci, it is possible to treat 400 tons of potatoes per day, that is 8, 000 50 kg bags of potatoes in 24 hours. Taking account of stoppages which represent 8% of the total duration, this corresponds to about 6 bags per minute. Each bag may have a height of 75 cm, a width of 25 cm and a thickness in its direction of advance of 50 cm, which corresponds to an apparent density of 0.6. The spacing between bags, in a process of a continuous type illustrated by Figure 1 , may be 16 cm. The advance of the conveyor may be discontinuous : 2 seconds advance, during which it travels 66 cm, followed by 8 seconds stop. The heating required to produce shrinkage will be about one minute and the length of the oven about 4 metres.

Claims (7)

1. WHAT WE CLAIM IS: 1. A method of packaging articles to be irradiated, in which the articles are enveloped in bags formed in a train from a continuous sheet of a heat-shrinkable plastics material, the bags containing the articles are formed into parallelepipeds, the parallelepipedal bags are shrunk by heat and thus fixed in their parallelepiped shape, and the train of bags is suspended vertically so that the whole of each bag is exposed to radiation when passed adjacent a radioactive source.

2. A method according to claim 1, in which the bag s are closed around the articles and pressed to parallelepipedal shape after closing.

3. A method according to claim 1, in which the bags are formed to parallelepipedal shape by moulding as the articles are enveloped in the bags.

4. A method according to any preceding claim in which the train is suspended from gripping members engaging an edge of the sheets.

5. A method according to any preceding claim, in which the bags are formed by welding the folded sheet.

6. A method of irradiating articles, which comprises packaging the articles by a method according to any preceding claim and transporting them past a radioactive source.

7. Apparatus for carrying out a method according to claim 6, which comprises means for enveloping the articles in bags formed in a train from a continuous sheet of a heat-shrinkable plastics material, means for forming the bags into a parallelepipedal shape, at least one source of heat arranged to shrink the plastics material of the bags and the heat source is arranged to shrink the material in the mould. 9. Apparatus according to claim 7 or 8, in which the means for transporting the train of bags comprises a rectilinear or roundabout conveyor arranged to transport the bags during enveloping and heat-shrinking and through a chamber containing a radioactive source. 10. Packaging means comprising a train of bags of heat shrunk plastics material connected by a sheet of the plastics material, the bags being fixed in a parallel-pipedal shape and the train being provided with suspension means for suspending it vertically for transport such that the whole of each bag is exposed to radiation when the train is transported past a radioactive source. 11. Packaging means according to claim 10, in which the suspension means comprises a portion of the sheet extending outside the bags and gripping means for gripping said portion. 12. A method of packaging and irradiating articles, which comprises packaging the articles in packaging means according to claim 10 or 11 and transporting them through a chamber containing a radioactive source.