JPS6058665B2 - Electron beam sterilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sterilizing device for paper, plastic sheets, etc. used as packaging materials for foods and the like.

In many cases, it is difficult to sterilize packaging materials for food products and other items that require hygiene precautions and the packaging does not want the flavor to be spoiled. Sterilization methods using irradiation with radiation are attracting attention. In other words, it has the excellent feature that by irradiating a material to be sterilized, such as packaging material, with a high-energy electron beam, it is possible to sterilize the material by simply irradiating it with no pre-treatment or post-treatment. This is because they are doing so. On the other hand, however, this method requires a high-energy electron beam generator, which results in large and expensive equipment investment, including high-voltage power supply equipment, shielding equipment, and the like.

For this reason, electron beam sterilization systems that operate in-line and are included in automatic packaging systems and automatic filling systems for food and other items to be packaged are impractical due to cost and other reasons, and they are not practical due to cost considerations. It has become common to receive supplies of materials and use them. 1 Therefore, it became necessary to produce and supply the above-mentioned sterile packaging materials, cleaning packaging materials, etc. by sterilizing packaging materials such as paper sheets and plastic sheets in continuous strips with electron beams. Electron beam sterilization equipment for materials to be sterilized has come to be required.

Even in this case, conventionally the strip-shaped material to be sterilized 1
Since one electron beam irradiation device was used per row, the electron beam current was increased as much as possible to increase the transfer speed of the strip-shaped material to be sterilized to increase processing capacity and prevent product costs from rising. . An example of such a conventional sterilization device using electron beam irradiation is shown in FIGS. 1 and 2.

In the figure, 1 is an electron beam generator (hereinafter referred to as E-device), 2 is an electron gun, 3 is a scanning device, and 4 is a thin film for electron beam transmission, for example, made of titanium with a thickness of 30 pm. The titanium window 5 is a strip-shaped material to be sterilized (hereinafter referred to as packaging material). Note that EB represents an electron beam, and A
is an arrow representing the scanning direction of the electron beam EB, and B is the packaging material 5.
There is an arrow indicating the direction of transport. The EB device 1 consists of an electron gun, a scanning device 3, and a titanium window 4. An electron beam accelerated by the electron gun 2 at a predetermined accelerating voltage, for example, 550 kV, is swung in the direction of arrow A by the scanning device 3, and titanium The electron beam is transmitted through the window 4 and radiated into the air as an electron beam EB. Note that the inside of the electron gun 2 and the scanning device 3 are kept in a predetermined vacuum state so that the electron beam is efficiently generated.
It goes without saying that, for example, an electromagnetic deflection device is used to cause the electron beam EB to reciprocate in the direction of the arrow A using a deflection current having a predetermined waveform, such as a triangular wave. Furthermore, although not shown, it is well known that various power supplies necessary for operation, such as accelerating voltage, are provided. So, E-cutting? Operate station 1 and emit electron beam EB.
If the packaging material 5 is transported at a predetermined speed in the direction of arrow B while scanning one-dimensionally in the direction of arrow A, will the packaging material 5 be uniformly irradiated with the electron beam EB? , electron beam E
If the strength of B and the transport speed of the packaging material 5 are set in a predetermined relationship, the radiation dose necessary for sterilization will be sufficiently applied to all parts of the packaging material 5, sterilization will be performed, and the packaging material will be sterile and clean. Packaging materials can be obtained.

By the way, as mentioned above, in this conventional example, only one strip of packaging material 5 can be processed at the same time by one EB device 1, and therefore, as mentioned above, the electron beam current is increased. Even if the moving speed of the packaging material 5 is increased to ensure that the necessary irradiation dose is applied to the packaging material 5, thereby increasing the processing capacity, there is still a drawback that it is not possible to achieve a sufficient cost reduction. It was hot.

Therefore, in order to eliminate this drawback, a method as shown in FIG. 3, for example, has been proposed.

That is, in this method, another packaging material 6 is superimposed on the underside of the packaging material 5 and transported, and the packaging material 6 is simultaneously sterilized by the electron beam EB transmitted through the packaging material 5. be. Note that at this time, the number of packaging materials to be overlapped and transported is not limited to two, but may be increased. Therefore, according to this method, electron beam sterilization can be performed simultaneously for the number of stacked packaging materials, and the processing capacity increases accordingly, making it possible to significantly reduce costs. However, in the method shown in FIG. 3, the electron beam is absorbed by the upper packaging material 5, and the irradiation dose to the lower packaging material 6 is small. The drawback was that it was not possible to arbitrarily provide the required absorbed dose due to differences in the absorbed dose.

An object of the present invention is to eliminate the drawbacks of the prior art described above, to simultaneously irradiate a plurality of packaging materials with electron beams using one EB device, and to irradiate electron beams to each packaging material at the same time. It is an object of the present invention to provide an electron beam sterilizer that can arbitrarily and independently control absorbed doses.

In order to achieve this object, the present invention provides a plurality of rollers parallel to each other and having rotational axes parallel to the scanning direction of the electron beam on the surface irradiated with the electron beam by the EB apparatus, and Multiple strips of packaging material are wrapped around each other and transported by folding.
It is characterized in that a plurality of strips of packaging material are simultaneously irradiated with the electron beam by spreading the electron beam in a direction perpendicular to the scanning direction due to E-shaping.

First, before explaining the present invention, the spread of the above-mentioned electron beam by the EB device will be explained.

In FIG. 4, the electron beam EB that has passed through the titanium window 4 of the EB device 1 is irradiated onto a packaging material 5 located at a close distance, but after passing through the packaging material 5, the electron beam EB passes through the titanium window 4 of the EB device 1, and after that, the electron beam EB passes through the titanium window 4 of the EB device 1. This causes a spread in the direction perpendicular to the scanning direction.

Under normal irradiation conditions, the distance from the titanium window 4 to the packaging material 5 is selected as an appropriate value of 50Wf1&,
The size of the electron beam irradiation surface P1 at this time is 20 to 30
It is relatively small as φ, and the energy is quite concentrated.
After the electron beam EB passes through the packaging material 5, it spreads with energy dispersion depending on the distance from the titanium window 4. By the way, when sterilizing packaging materials, the absorbed dose of the packaging material is in a high energy concentration state at a close distance directly under the window 4, and in a low energy dispersion state at a relatively large distance from the window 4. The absorbed dose is determined by the time integral value of the irradiated electron beam, so there is not much difference apart from some loss.

In other words, in electron beam sterilization, the total amount of absorbed radiation in the packaging material is effective, and energy concentration of the electron beam is not a particularly necessary requirement. Therefore, for example, as shown in FIG.
It can be seen that almost the same sterilization effect can be obtained even if a considerably wide electron beam irradiation surface P2 is formed. Next, the spread of the electron beam EB mentioned above will be explained using experimental data.

FIG. 6 shows the electron beam current density versus the distance in the central axis Z direction passing through the center of the titanium window 4 of the EB device 1, and shows the acceleration voltage E.

550kV1 beam current 1. It is a characteristic diagram when it is set to 17TLA. FIG. 7 is a characteristic diagram showing the irradiation distribution along a line parallel to the scanning direction X passing through the center of the titanium window 4 of the EB device 1, using the z direction as a parameter.

Furthermore, FIG. 8 is a characteristic diagram showing the irradiation distribution along a line parallel to the transport direction Y of the packaging material 5, indicated by arrow B in FIG. 1, with the Z direction as a parameter. be.

Figures 9 and 10 show these characteristic diagrams three-dimensionally and in an easy-to-understand manner.
A diagram created from Figures 7 and 8 to show the distribution of m in the X and Y directions on the plane. FIG. 10 is a diagram showing FIG. 8 extended in the z direction.

Therefore, it can be seen from these figures that if the distance in the Z direction is appropriately selected, it is sufficiently practical even if a fairly wide area is provided as the irradiation surface P2 in FIG.

As is clear from Fig. 7, increasing the distance in the Z direction causes a considerable decrease in the electron beam current density, but as shown in Fig. 11, the electron beam received by the surface at the distance Z Looking at the beam integral value, it is not a very large decrease.

Therefore, the decrease in the irradiation amount over this distance can be sufficiently compensated for by increasing the beam current L. The present invention utilizes such a spread of the electron beam EB, and an embodiment of the electron beam sterilization apparatus according to the present invention will be described below.

FIG. 12 is a schematic diagram showing the principle of the present invention, in which 5 to 8 are packaging materials, 9 to 12 are folding rollers, 1°3 to 16 are rotating shafts of rollers 9 to 12, and the EB device 1 and the electronic gun 2,
The scanning device 3, titanium window 4, etc. are the same as in FIGS. 1 to 5.

Note that EB represents an electron beam and P3 represents its irradiation surface. The folding rollers 9 to 12 are arranged along the electron beam irradiation surface P3 so as to be substantially parallel to each other, and the respective rotation axes 13 to 16 rotate the electron beam E by the scanning device 3.
It is made to be approximately parallel to the scanning direction of B (arrow A in FIG. 1).

Each of the packaging materials 5 to 8 is wrapped around each of the rollers 9 to 12 and folded back, and then wound from a feeding-side packaging material roll to a winding-side packaging material roll (none of which is shown), thereby forming a predetermined shape. Continuously transported at speed.

At this time, the rollers 9 to 12 are arranged so that the folded portions of the packaging materials 5 to 8 by the rollers 9 to 12 are located near the electron beam irradiation surface P3, which is approximately the same distance from the titanium window 4 of the EB device 1. Determine the installation location.
Therefore, if the packaging materials 5 to 8 are transported at a predetermined speed and the EB device 1 is operated to generate the electron beam EB, each of the packaging materials 5 to 8 will be transferred to the folded portion of each roller 9 to 12. The material is irradiated with an electron beam EB and transported sequentially and continuously while being given the necessary absorbed dose, thereby making it possible to obtain sterile packaging material and clean packaging material on the packaging material roll on the winding side. Therefore, according to this example, four strips of packaging material 5 to 8
5 sterilization operations are performed at the same time, and each packaging material 5
Since the irradiation of the electron beam EB onto the packaging materials 5 to 8 is independent of each other, and the speed movement of the packaging materials 5 to 8 is also independent, the transport speed etc. for each of the packaging materials 5 to 8 can be adjusted arbitrarily. If the required absorbed dose is controlled as desired, operation can always be performed under optimal operating conditions.

Next, FIG. 13 shows a more specific embodiment of the present invention.

In FIG. 13, 20 is an electron beam irradiation chamber, 21 is a guide duct on the feeding side, 22 is a guide duct on the winding side, 23 is a packaging material roll on the feeding side, 24 is a packaging material roll on the winding side, and 25 is the first packaging material roll. 26 is a second bending guide roller, 27 is a guide roller, and 28 is a sterile cover 29, which is a flexible material.

The EB device 1, packaging materials 5-8, rollers 9-12, and electron beam irradiation surface P3 are the same as those in the embodiment shown in FIG. The electron beam irradiation chamber 20 is made of a material 29 that is resistant to X-rays, such as lead, to prevent X-rays generated by the impact of the electron beam EB from the EB device 1 due to high-voltage acceleration from leaking to the outside. Guide duct 2 on the feeding side
1 is a packaging material 5 pulled out from the packaging material roll 23 on the feeding side
~ 8 is folded back by guide rollers 25 ~ 27 to roller 9
It functions to introduce up to each of the 12. Similarly, the guide duct 22 on the winding side carries the packaging materials 5 to 8 folded back by the folding rollers 9 to 12, respectively, to the guide rollers 22.
27 serves to guide the material to the packaging material roll 24 on the winding side.

Each of these guide ducts 21 and 22 is bent at least twice at a right angle or more at the portion where the first and second guide rollers 25 and 26 are provided.
~8, thereby guiding the X-rays generated within the chamber 20 through the guide ducts 21, 220? When leakage is attempted to the outside through either of them, the structure is such that it collides with the inner walls of these ducts 21 and 22 at least twice and is attenuated.

The sterile cover 28 is provided to cover the exit side of the winding-side guide duct 22, and the packaging material 5 that has been sterilized by completing electron beam irradiation and wound up on the winding-side packaging material roll 24.
-8 to prevent contamination by the atmosphere.

Therefore, also in this embodiment, the winding side packaging material roll 2
4 is rotated at a predetermined speed, these packaging materials 5 to 8 are sequentially and continuously pulled out from the feeding-side packaging material roll 23, and are passed from the feeding-side guide duct 21 to the rollers 25, 26.
The film passes through the folding rollers 9 to 12, wraps around these rollers and is folded back, and is sequentially and continuously irradiated with the electron beam EB from the E-coupling device 1. After being given a predetermined absorbed dose, the film is moved to the winding side. roller 26 in the guide duct 22 of
, 25, and is wound up in a sterile state on the winding-side packaging roll 24 housed in the cover 28, and the sterilization operation is completed.

Also in this embodiment, the four strips of packaging material 5 to 8 can be irradiated with the electron beam at the same time.
Efficient operation of the EB device 1 is possible, and it is easy to reduce the cost of sterile packaging materials and clean packaging materials.
The absorbed dose for each can also be controlled arbitrarily and independently. At this time, the amount of energy of the electron beam EB for each of the packaging materials 5 to 8 is reduced compared to the conventional example shown in FIG. 1, but as already explained, the reduction in absorbed dose is due to the beam energy.

can be sufficiently compensated for by increasing the Four folding rollers 9 on the irradiation surface P3
- 12 are provided, thereby making it possible to sterilize four strip-shaped packaging materials 5 to 8 at the same time, but the number of these folding rollers is arbitrary depending on the number of strips of packaging material to be sterilized at the same time. Needless to say, it can be changed to

As explained above, according to the present invention, a single EB device can sterilize multiple strips of packaging materials at the same time, while controlling the electron beam irradiation conditions for each packaging material arbitrarily and independently. Because you can
It is possible to provide an electron beam sterilizer that eliminates the drawbacks of the prior art, increases the operating efficiency of the EB device, and can supply sterile packaging materials and clean packaging materials at low cost.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a conventional example of an electron beam sterilizer, Fig. 2 is a side view thereof, Fig. 3 is a side view showing another conventional example, and Fig. 4 is a schematic diagram showing a conventional example of an electron beam sterilizer.
5 and 5 are explanatory diagrams showing the spread of the electron beam, and FIG.
11 to 11 are characteristic curve diagrams of an electron beam, FIG. 12 is a schematic diagram showing an embodiment of the basic configuration of an electron beam sterilizer according to the present invention, and FIG. 13 is a specific embodiment of the present invention. FIG. 1... Electron beam generator (E-cutting station), 2...
...electron gun, 3...scanning device, 4...
・Titanium window, 5-8... Strip-shaped material to be sterilized (packaging material), 9-12... Roller for folding, 20... Electron beam irradiation chamber, 21・・・
...Feeding side guide duct, 22... Winding side guide duct, 23... Feeding side packaging material roll, 24... Winding side packaging material roll, 25, 26.
...Bending roller.

Claims (1)

[Claims] 1. An electron beam source that generates an electron beam by scanning in one dimension, and irradiating a strip-shaped material to be sterilized that continuously moves in a direction substantially perpendicular to the scanning direction of the electron beam. In an electron beam sterilizer of the type, a plurality of rollers each having a rotation axis substantially parallel to the scanning direction of the electron beam are moved along a surface irradiated with the electron beam by the electron beam source perpendicular to the scanning direction of the electron beam. The electronic device is characterized in that it is configured such that a simultaneous sterilization operation can be performed on a plurality of strips of material to be sterilized by wrapping the strips of material to be sterilized around each of the plurality of rollers and transporting the material in a folded manner. Line sterilizer. 2. In claim 1, at least two bent portions are provided in each of the supply path and the take-out path of the strip-shaped material to be sterilized to the roller, and these bent portions prevent X-rays caused by electron beam irradiation. An electron beam sterilizer characterized in that it is configured to have a radiation shielding function. 3. In claim 1 or 2, means is provided for independently controlling the transfer speed for each of the strip-shaped materials to be sterilized, so that a predetermined absorbed dose can be arbitrarily set for each strip-shaped material to be sterilized. What is claimed is: 1. An electron beam sterilizer characterized in that the device is configured to give