JPH11248894A - Electron beam irradiation method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam irradiation method and its device capable of unifying the electron beam absorption dose at each part in radiation direction in the case attaining intended purposes such as sterilizing by repeatedly scanning an electron beam for irradiating an object such as foods and drink contains even with objects different in thickness. SOLUTION: By aprlying a dose of radiation to an object by an electron beam reflected from one or a plurality of reflection plates 11 and 12 placed in the vicinity of the object facing in the electron beam irradiation direction, the uniformity of absorbed dose is raised. In this case, the fixing positions of the electron beam reflection plates 11 and 12 desired to be positions where the electron beam can reflect to a specific portion of the object with the least electron beam absorption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intended object such as sterilization by irradiating an object to be irradiated such as a food or beverage container, in particular, a beverage container having a three-dimensional and complicated shape, while repeatedly beam-scanning an electron beam. The present invention relates to an electron beam irradiation method and an apparatus for achieving the above.

[0002]

As a means for sterilizing food and beverage containers, an electron beam (electron beam) is used instead of the conventional sterilizing means using chemicals (ozone water or peracetic acid) or heat sterilizing means.
In recent years, a method of irradiating the container with a beam at a predetermined deflection angle while irradiating the container to sterilize the container has been researched and developed. Such electron beam sterilizing means is effective for sterilizing resin containers with low heat resistance such as PET bottles.

Although a beam scanning type electron beam irradiation apparatus for sterilizing such a container is not yet known, an apparatus as shown in FIG. 10 has been studied. In FIG. 10, reference numeral 1 denotes an electron beam generator / accelerator for generating an electron beam 2, for example, an electron gun for emitting an electron gun, and an acceleration for accelerating the electron beam emitted from the electron gun so as to have a predetermined energy. A klystron for supplying microwave energy to the accelerating tube for accelerating the electron beam. Then, the accelerated electron beam (electron beam) 2 is guided to a converging electromagnet (beam stop lens) 4 via a cylindrical beam guide tube 3, and converges the electron beam 2 in the diameter direction. The aperture is narrowed to reduce the diameter and increase the energy density.

The converging electron beam, which has been densified by the converging electromagnet 4, is introduced into a flat-cone-shaped frustum-shaped scanning horn 6 which expands in the beam scanning direction as it advances toward the front surface.
The scanning horn 6 has a scanning electromagnet 5 on the entrance side, a slit-shaped irradiation window 7 on the front surface, the irradiation window 7 is sealed with an electron beam transmitting film such as a titanium film, and the inside is maintained in a vacuum space. I have. The convergent beam introduced into the scanning horn 6 is deflected and scanned by the scanning electromagnet 5 at a predetermined deflection angle and a predetermined deflection frequency (reciprocating deflection frequency). In other words, in order to control the angular velocity, a control signal for controlling the voltage applied to the scanning electromagnet 5 is fetched from the scanning electromagnet controller 10, and the scanning electron beam 8 that has been deflected and scanned while controlling the angular velocity. While scanning in the base line direction of the container 20 through the scanning horn 6 having a flat truncated cone shape and the irradiation window 7,
Irradiation is performed over the entire length to perform a predetermined sterilization operation.

[0005] The scanning waveform formed by the scanning angular velocity of the electron beam in such an apparatus depends on a change in the magnetic field strength of the scanning electromagnet 5, in other words, a change in the voltage applied to the scanning electromagnet 5, and in a normal beam scanning apparatus. Is controlled so that the scanning waveform becomes a triangular wave or a sine wave (AC waveform) irrespective of the thickness of the irradiation object because of its easy voltage control.

[0006]

However, when the scanning is performed by the triangular wave or the sine wave regardless of the thickness of the irradiation object, the inside of the beverage container 20 such as a plastic bottle having a three-dimensional and complicated shape is obtained. It is very difficult to sterilize the entire outer and outer surfaces by electron beam irradiation, and there is no practical example of a device realizing this, regardless of inside or outside the country.

More specifically, the problem will be specifically described with reference to FIG. 6. FIG. 6B shows a state in which the scanning horn 6 is disposed above the plastic bottle 20 and the electron beam 8 is directed right and left on the upper surface of the bottle 20. Irradiation method while scanning repeatedly, FIG. 6 (A)
Is a method of arranging the scanning horn 6 on the side of the plastic bottle 20 and irradiating while repeatedly scanning from the upper end to the lower end along the base line of the bottle 20, and not shown, but arranged on both left and right sides of the plastic bottle 20, respectively. There is a method in which the PET bottle 20 is irradiated from both sides by two scanning horns 6.

However, in the upward irradiation shown in FIG. 6B, when a deep beverage container 20 such as a PET bottle is irradiated from above, the absorbed dose in the upper part of the container 20 is large,
The absorbed dose at the bottom of the container 20 is very small, and the absorbed dose at the bottom of the container 20 is almost nil, which is not suitable for practical use. FIG. 6
In the side irradiation shown in (A), the mouth of the container 20 is generally thick so that the cap can be sealed, and the electron beam cannot pass therethrough, so that the absorbed dose inside the mouth 23B is very small. Further, the absorbed dose of the container wall 21B located on the side opposite to the side far from the scanning horn 6 is small.

Further, since the thickness of the body portion 21A is thin, the amount of electron beam transmission in the thick portion is small and the amount of transmission in the thin portion is large, and the amount of electron beam absorption inside the container 20 is not uniform. No. In this case, the amount of electron beam absorption necessary for sterilization is equal to or more than a predetermined value. Therefore, if an attempt is made to secure the necessary amount on the inner surface of the thick portion, the amount of electron beam absorption of the thin portion becomes excessive, and the material of the bottle 20 Adverse effects such as weakening, discoloration, etc. On the other hand, when securing the necessary limit of the amount of electron beam absorption on the inner surface of the thin portion, the amount of absorption of the electron beam in the thick portion becomes insufficient, resulting in an adverse effect of insufficient sterilization.

Further, in the case of the irradiation on both sides, the container 20
Irradiation is performed so as to sandwich the body, but the absorbed dose of the body of the container 20 is improved, but the cost is doubled because two extremely expensive irradiation devices are required, which is not suitable for practical use.

In view of the above-mentioned problems of the prior art, the present invention irradiates an object to be irradiated such as a food or beverage container while repeatedly beam-scanning an electron beam in a predetermined direction to achieve an intended object such as sterilization. An electron beam irradiation method capable of equalizing the amount of electron beam absorption in each part of the irradiation direction of the object to be irradiated, thereby eliminating, for example, sterilization unevenness in the container and preventing occurrence of deterioration in quality due to electron beam irradiation. And an apparatus therefor.

[0012]

According to the present invention, in order to solve the above-mentioned problems, the present invention as defined in claim 1, wherein a three-dimensional object such as a food or beverage container is repeatedly irradiated with an electron beam in a two-dimensional or three-dimensional manner. In an electron beam irradiation method for irradiating while scanning a beam in a direction to achieve an intended purpose such as sterilization, electrons reflected from one or a plurality of reflectors installed near an object to be irradiated facing the electron beam irradiation direction. We propose an electron beam irradiation method characterized by increasing the uniformity of the absorbed dose by adding the absorbed dose to the irradiation object by the radiation. In this case, repeatedly scanning the electron beam in the two-dimensional direction refers to, for example, performing a fan-shaped beam scan while applying an alternating voltage to a pair of facing scanning electromagnets, and scanning in the three-dimensional direction refers to, for example, four scans. This refers to a case in which an electromagnet is arranged in a rectangular frame shape around an electron beam, and beam scanning is performed in a conical shape while applying an alternating voltage while shifting the phase difference to the scanning electromagnet between each pair.

According to a second aspect of the present invention, there is provided an apparatus for effectively implementing the present invention, wherein one or a plurality of electron beam reflectors are disposed so as to face the electron beam irradiation direction, and An electron beam reflected by the reflector can be applied to a predetermined portion of the object to be irradiated, which has not achieved its intended purpose only by scanning the beam emitted from the irradiation unit.

In this case, the electron beam reflecting plate is made of a metal or a metal film having a large atomic number, for example, a tungsten plate, a gold plate or a stainless plate plated with gold, so that the electron beam has a low acceleration energy (600 KeV). In this case, reflection of about 50% of electrons can be expected. The shape of the reflecting surface of the electron beam reflecting plate is a focusing (condensing) surface shape for focusing the electron beam on a predetermined portion of the irradiation object, specifically, a bowl shape, a U shape, and the like.
It is preferable that the electron beam is formed in the shape of a letter. After being deflected, it can also be formed by a flat or convex reflecting plate.

Further, as described in claim 3, the mounting position of the one or a plurality of electron beam reflectors is a position where the electron beam can be reflected on a predetermined portion of the irradiation object having the smallest electron beam absorption amount. Is preferred.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

The left side of the beverage container 20 such as a PET bottle shown in FIG.
When the scanning horn 6 is arranged on one side from the left side as shown in FIG. 6A and electron beam irradiation is performed, the body part 21A of the bottle 20 near the electron beam irradiation window 7, the shoulder part 22A of the bottle 20,
And the left side 2 of the bottle mouth on the side where the scanning horn 6 is arranged
The absorbed dose of 3A is increased, and the bottle mouth right front side 23 located on the opposite side of the bottle mouth inner peripheral surface 23B and the scanning horn 6
Since the absorbed dose of C is low, a large variation occurs in the absorbed dose at each part of the bottle 20.

The bottle 20 has a body 21A and a shoulder 22.
On the side facing the irradiation window 7 such as A, the electron beam irradiation distance is short, and this leads to a small energy loss of the electron beam in the air. As a result, the absorbed dose is high, and especially the acceleration energy is low. The low (about 600 KeV) electron beam has poor penetration ability, so the inner peripheral surface of the bottle mouth 23B
On the right front side 23C, the absorbed dose is very low because the thickness of the bottle mouth 23 is large. In addition, since the bottle bottom 26 may have a very complicated shape due to the bottle 20, depending on the portion, as shown in FIG. Due to the arrival of line 8, the absorbed dose can be very low.

In the case of a PET bottle, the amount of electron beam absorption necessary for sterilization is equal to or more than a predetermined value. Therefore, when the dose is applied to the bottle inner peripheral surface 23B and the right front side 23C, etc., which have the lowest absorbed dose, The body part 21A and shoulder part 22A of the bottle 20 on the side where the irradiation window 7 is located have an excessively absorbed dose,
Disadvantages such as discoloration and luxury of the bottle 20 occur.

Therefore, according to the embodiment of the present invention, the reflection plate 11 and the reflection plate 11 are provided near the bottle mouth 23 and the bottle bottom 26, respectively, which are located on the side opposite to the electron beam irradiation window 7 and have the smallest electron beam absorption.
12 are arranged. 1 and 2 show a beam scanning type electron beam irradiation apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view, FIG. 2 is a front view (A) and a plan view (B) viewed from above.
It is.

In these figures, 5 is a pair of scanning magnets, 6 is a flat cone-shaped scanning horn having an irradiation window 7 on the front surface, and 20 is a PET bottle, which is located on the mesh conveyor 14 at the irradiation position in an upright state. Conveyed sequentially.

Conveyor guides 15 are arranged on both left and right sides of the mesh conveyor 14, but the conveyor guides 15 are cut off at the irradiation positions of the bottles 20, so that the irradiation of the electron beam by the conveyor guides 15 is not hindered. It has such a structure. The reason why the conveyor 14 is formed in a mesh shape is to facilitate the irradiation of the electron beam.

The first reflector 11 is placed at a position opposite to the right front side 23C of the opening 23 of the bottle 20 having the smallest amount of electron beam absorption, which is located on the side opposite to the electron beam irradiation window 7 below the mesh conveyor 14. The second reflection plate 12 is arranged at a position facing the bottom 26 of the bottle.

The reflectors 11 and 12 are made of a metal having a large atomic number, such as gold (plating) or tungsten, so that about 50% of electrons can be reflected even with an electron beam having a low acceleration energy (600 KeV). You have set. The reflecting surfaces of the respective reflecting plates 11 and 12 are formed in a U-shape or slightly arm-shaped so that the electron beam is focused on the mouth 23 of the plastic bottle 20 and the bottom 26 of the bottle 20 respectively. The plane has been set. (See FIGS. 2A and 2B)

Next, the operation of the embodiment will be described. First, an electron beam is scanned (scanned) by a scanning magnet 5 for generating an alternating (AC) magnetic field at the base of the electron beam scanning horn 6. The alternating (AC) magnetic field is controlled so that the scanning waveform becomes triangular wave scanning as shown in FIG. The scanned electron beam 8 is emitted into the air from the irradiation window 7, irradiates the PET bottle 20 and, at the bottle opening 23 and the bottle bottom 26 where the electron beam 8 is hardly transmitted, the reflection plate 1.
Irradiation is carried out by the electron beam 18 reflected at 1 and 12.

In order to obtain the dose absorbed by the reflected electron beam 18 at the bottom 26 of the PET bottle, the PET bottle 2
0 is conveyed on the mesh conveyor 14 and the reflection plate 1
The mesh conveyor 14 where the parts 1 and 12 are located is the conveyor 14
The guide 15 supporting both sides has a cut shape.

The effect of the present invention will be described with reference to FIGS. In order to make the absorbed dose uniform by irradiating a PET bottle 20 such as a beverage bottle with an electron beam, generally at least three electron beam irradiation devices are required as shown in FIG. As shown in FIG. 2, in the present embodiment, the same irradiation as the irradiation with these three units can be realized by one irradiation device, so that the electrons emitted from the electron beam irradiation window 7 into the air are emitted. By irradiating a part of the line 8 with the electron beam 18 reflected by the reflectors 11 and 12 to the bottle mouth 23 and the bottle bottom 26 having a low absorption dose, the absorption dose is substantially uniform at any part of the bottle 20. Can be

Further, in this embodiment, the transport conveyor of the PET bottle 20 is the mesh conveyor 14 so that the reflected electron beam 18 is more irradiated to the PET bottle bottom 26,
Further, at a portion where the reflection plate 12 is provided, a conveyor guide 15 that supports the mesh conveyor 14 on both sides is also cut so as not to hinder the conveyance. Further, each of the reflectors 11, 12
Efficiently reflects the reflected electron beam 18 toward the part where the absorbed dose is low.
It is advantageous to form a concave structure so as to irradiate light.

The mouth portion 23 of the plastic bottle 20 needs to be sufficiently sterilized in order for a person to put on the mouth. FIG. 3 shows another embodiment focusing on this point, in which the scanning horn 6 of the electron beam irradiation device is disposed above the plastic bottle mouth 23 and the U-shaped reflector is provided on the lower side of the mesh conveyor 14 below the bottle bottom 26. 13 are arranged. According to this embodiment, since the mouth portion 23 which is thickest and needs to be sufficiently sterilized is close to the electron beam irradiation window 7, a large number of electron beams 8 are required.
The bottle bottom 26, which is the farthest from the electron beam irradiation distance, is provided with an absorbed dose to the irradiated object by the electron beam 18 reflected from the reflecting plate 13, so that the uniformity of the absorbed dose is improved. Can be done.

FIG. 4 shows a cap 30 of the food and beverage container 20 and the like.
1 shows an apparatus for sterilizing by electron beam irradiation. It is very difficult to sterilize the entire inner and outer surfaces of the cap 30 such as the beverage container 20 having a three-dimensional and complicated shape by electron beam irradiation. As shown in FIG. 5, the cap 30 has a diameter of φ3.
It is as small as about 0 mm, and a non-slip groove 31 is provided on the outer peripheral side,
The inner periphery has a complicated structure such as a screw thread 32 for fastening and a projection 33 for sealing. Therefore, as shown in FIG. 4, the scanning horn 6 is installed above the cap 30 located at the irradiation position, which can be transported by the mesh conveyor 14 (not shown) with the opening of the cap 30 facing upward. Is provided with a deflecting magnet 29 for bending the electron beam 8 so as to irradiate the inner and outer surfaces of the cap 30, and a reflector 19 is provided below the cap 30 to irradiate an outer surface such as the bottom surface of the cap 30. .

In this case, a pair of deflecting magnets 29 are arranged on the left and right sides on the exit side of the scanning horn 6, and in order to increase the deflection angle corresponding to the deflection angle of the electron beam in the scanning horn 6, the deflection magnets 29 are arranged with respect to the scanning axis. As the distance increases, the deflection angle increases toward the center. Thereby, the electron beam 8 emitted from the electron beam irradiation window 7 is focused on the cap 30 side.

Then, the focused electron beam 8 is irradiated to the outer peripheral surface from the upper opening of the cap 30. On the other hand, the bottom surface side of the cap 30 is the electron beam 18 reflected by the reflection plate 19.
Is irradiated.

Therefore, unlike a drug, an electron beam can penetrate into a small gap, but because of its straightness, it may be difficult to penetrate a place behind a convex part. According to the example, a high level of sterilization, which was difficult with conventional chemical sterilization, can be performed by bending and irradiating an electron beam so that the electron beam can travel straight on a screw thread or a seal protrusion. Further, the cap 3 is formed by the reflection plate 19 below the cap 30.
By irradiating the bottom and outer periphery, the cap 30
It is possible to completely sterilize all of the inner and outer surfaces.

[0034]

As described above, according to the present invention, by arranging the reflection plate at a predetermined position corresponding to the different thickness or the amount of electron beam transmission in the irradiation direction of the irradiation object, the entire irradiation object can be obtained. And the required amount of electron beam absorption can be obtained.

Thus, when the object to be irradiated is a food or beverage container, a uniform sterilizing ability can be obtained in each part in the container, and it is possible to prevent the occurrence of sterilization unevenness and a decrease in quality.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a beam scanning electron beam scanning device according to an embodiment of the present invention.

FIG. 2 is a front view (A) and a plan view (B) viewed from above in the embodiment.

FIG. 3 is an overall schematic view of a beam scanning type electron beam scanning apparatus according to another embodiment of the present invention, in which a scanning horn is arranged above a container.

FIG. 4 is an overall schematic view of a beam scanning type electron beam scanning device for sterilizing a cap according to another embodiment of the present invention, and (A).
Is a front view and (B) is a side view.

FIG. 5 shows a cap shape to be sterilized by the device of FIG.

FIG. 6 is a novel comparative technique for explaining the problem of the present invention. FIG. 6 (A) is an explanatory view in which the scanning horn is arranged on the side of a plastic bottle, and FIG. FIG.

FIG. 7 is a diagram illustrating a novel comparative technique for explaining the problem of the present invention, in which the scanning horn is arranged above, below, and on the side of a plastic bottle.

FIG. 8 is a perspective view showing a schematic shape of a PET bottle.

FIG. 9 is an explanatory diagram showing an electron beam transmitting state at the bottom of the plastic bottle in the apparatus of FIG. 6 (A).

10A and 10B show a basic configuration of the beam scanning type electron beam scanning device which is a premise of the present invention, wherein FIG. 10A is a front view, and FIG.
Shows the shape of the window of the scanning horn, and (C) shows the scanning state of the electron beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron beam generation / accelerator 5 Scanning magnet 6 Scanning horn 7 Irradiation window 8 Scanning electron beam 11, 12, 13, 19 Reflector 14 Mesh conveyor 15 Conveyor guide 18 Reflected electron beam 20 Container (pet bottle) 29 Deflection magnet 30 Cap

Claims (4)

[Claims] An electron beam irradiation method for irradiating a three-dimensional object such as a food or beverage container while repeatedly scanning an electron beam in two-dimensional or three-dimensional directions to achieve an intended purpose such as sterilization. In the above, the uniformity of the absorbed dose is increased by adding an absorbed dose to the irradiated object by an electron beam reflected from one or a plurality of reflectors installed near the irradiated object facing the electron beam irradiation direction. An electron beam irradiation method characterized by the above-mentioned. 2. An electron beam irradiation apparatus for irradiating a three-dimensional object to be irradiated such as a food or beverage container while repeatedly scanning an electron beam in two-dimensional or three-dimensional directions to achieve an intended purpose such as sterilization. In the above, one or a plurality of electron beam reflectors are arranged facing the electron beam irradiation direction, and only a beam scan emitted from the electron beam irradiation unit does not achieve the intended purpose. An electron beam irradiation apparatus characterized in that a portion can be irradiated with an electron beam reflected by the reflection plate. 3. The electron beam irradiation apparatus according to claim 2, wherein the reflection surface shape of the one or more electron beam reflection plates is a converging (light-condensing) surface shape for converging an electron beam on a predetermined portion of an irradiation object. . 4. The electron beam irradiation apparatus according to claim 2, wherein the one or more electron beam reflectors are attached at positions where the electron beam can be reflected on a predetermined portion of the irradiation object having the smallest amount of electron beam absorption. .