JPH11248900A - Electron beam irradiation method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a desired purpose such as sterilization even for a three- dimensionally complex thickness or shape such as a cap and drink bottle. SOLUTION: On a scanning electron beam incidence position, a magnetic field impressing means impressing alternating magnetic field from at least two sides in a plane nearly orthogonally crossing the electron beam incidence direction is arranged so as to constitute capable of scanning the electron beam in circumferential direction. Arranged are a plurality of sets of NS magnets 60 for deflecting the electron beam enclosing the scanning electron beam 8 in a specific position until the electron beam after scanning form the scanning position in the circumferential direction. magnetic line of force is added to the scanning electron beam in the direction deflecting the electron beam by the magnet body 60 and so a part of the electron beam radiated to the object is deflected by the magnetic line of force.

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 has not been known yet, an apparatus as shown in FIG. 6 has been studied. In FIG. 6, reference numeral 1 denotes an electron beam generator / accelerator for generating an electron beam (electron beam) 2. For example, an electron gun for emitting an electron gun and an electron beam emitted from the electron gun have predetermined energy. And a klystron for supplying microwave energy to the accelerator for accelerating the electron beam. The accelerated electron beam 2 passes through a cylindrical beam guide tube 3 through a converging electromagnet 4
(A beam stop lens) to converge the electron beam 2 in the diameter direction, in other words, to narrow the beam by narrowing the beam to 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 is provided with a scanning electromagnet 5 on the entrance side and a slit-shaped irradiation window 7 on the front surface (see FIG. 1B).
Is sealed with an electron beam transmitting film such as a titanium film, and the inside is maintained in a vacuum space. 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 taken in from the scanning electromagnet controller 10, and the scanning electron beam 8 that has been deflected and scanned while controlling the angular velocity. A predetermined sterilization operation is performed by irradiating the entire length of the container 30 while scanning in the base line direction of the container 20 through the scanning horn 6 in the shape of a flat truncated cone and the irradiation window 7.

[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. The voltage is controlled so that the scanning waveform becomes a triangular wave or a sine wave (AC waveform) as shown in FIG. 6C irrespective of the thickness of the irradiation object because of its easy voltage control.

However, when scanning is performed by the triangular wave or the sine wave irrespective of the thickness of the object to be irradiated, the entire inner and outer surfaces of the three-dimensionally complicated beverage container 20 such as a PET bottle, for example, are removed. Sterilization by electron beam irradiation is quite difficult. In particular, since the cap of the beverage container 20 or the like is small, it is very difficult to sterilize the entire inner and outer surfaces by electron beam irradiation.

As shown in FIGS. 5 (B) and 5 (C), the cap has a small diameter of about φ30 mm, a non-slip groove 31 on the outer periphery, and a screw thread 3 on the inner periphery.
It has a complicated structure such as 2 and a projection 33 for sealing. In view of the above, the present applicant has proposed a device for sterilizing a cap 30 such as a food / beverage container by electron beam irradiation in a patent application filed at the same time.

[0008] Such an apparatus, as shown in FIG.
The scanning horn 6 is installed above the cap 30 located at an irradiation position where the cap 30 can be conveyed by a mesh conveyor (not shown) with the opening of the cap 30 facing upward, and the scanning horn 6 irradiates the inner and outer surfaces of the cap 30. Further, deflection magnet plates 19A and 19B for bending an electron beam are provided, and a reflection plate 11 is provided below the cap 30 to irradiate an outer surface such as a bottom surface of the cap 30.

In this case, a pair of deflecting magnet plates 19A and 19B 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. As the distance from the scanning axis increases, the deflection angle increases toward the center. Thereby, the electron beam 8 emitted from the irradiation window 7 is focused on the cap 30 side.

Then, the focused electron beam 8 is applied 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 11.
Is irradiated.

Therefore, according to the present embodiment, unlike an agent, an electron beam can penetrate into a small gap, but since it has a straight traveling property, it is difficult to penetrate a place behind a convex portion. However, according to the present embodiment, it is possible to perform high-level sterilization, which was difficult with conventional chemical sterilization, by bending and irradiating the electron beam so that the electron beam can proceed straight to the screw thread and the seal protrusion. Become. Further, by irradiating the bottom and the outer periphery of the cap 30 with the reflected electron beam 18 by the reflection plate 11 under the cap 30, it is possible to completely sterilize the entire inner and outer surfaces of the cap 30.

The deflecting means provided by the deflecting magnet plates 19A and 19B have a system in which the distance through which the magnetic field passes is varied within a magnetic field having a uniform magnetic flux density, and the distance through which the electron beam passes through the magnetic field is made constant. There are a system in which the magnetic flux density differs in the state, and a system in which both are combined.

[0013]

However, the above apparatus still has the following problems. That is, the apparatus scans an electron beam in a fan shape by a scanning magnet, and further deflects the scanning electron beam expanded in a two-dimensional direction to the center side by a deflecting magnet plate to irradiate the cap 30 with the electron beam. Since the surface is two-dimensional, the thickness of the cap differs greatly in the three-dimensional direction and the shape is so large that accurate electron beam irradiation is difficult unless the cap is rotated on the irradiation position. However, while it is possible to sterilize a small object such as the cap while rotating it at the irradiation position at the laboratory stage, it is substantially difficult at the manufacturing site. In particular, at a manufacturing site, it is productive to carry out sterilization while transporting the cap in a direction orthogonal to the electron beam irradiation surface by a conveyor or the like, and it has been desired to provide an electron beam irradiation apparatus that can withstand such a request.

The present invention has been made in view of the above technical problem, and is intended to provide a method for achieving the intended purpose of sterilization or the like even when the cap or beverage container has a three-dimensionally complicated thickness or shape. An electron beam irradiation method and apparatus capable of equalizing the amount of electron beam absorption in each part of the irradiation direction of an object, thereby preventing, for example, sterilization unevenness in the container and preventing deterioration in quality due to electron beam irradiation. The purpose is to provide.

[0015]

According to the present invention, in order to solve the above-mentioned problem, in the invention according to the first aspect, an electron beam is emitted from an irradiation window portion of a scanning body for scanning an electron beam in a negative pressure (vacuum) space. In an electron beam irradiation method for achieving an intended purpose such as sterilization while repeatedly irradiating a scanning electron beam to a three-dimensional object to be irradiated such as a food or beverage container, the electron beam irradiation position on an entrance side of the scanning body. An electron beam irradiation method is proposed wherein an alternating magnetic field is applied from at least two sides in a plane substantially orthogonal to the electron beam incident direction to scan the electron beam in the circumferential direction.

According to this invention, since the three-dimensional object to be irradiated, for example, the electron beam irradiated in conformity with the shape of the cap is irradiated while rotating in a three-dimensional shape, specifically, in a conical shape, Even if it has a three-dimensionally complicated thickness or shape, such as a container or a beverage container, even if it is transported in a direction perpendicular to the electron beam irradiation surface by a conveyor or the like, the electron beam irradiation pattern is Since it has a corresponding three-dimensional shape, it is possible to smoothly irradiate the upper side of the object to be irradiated, and it is possible to provide sterilization means capable of preventing uneven sterilization and preventing deterioration in quality due to electron beam irradiation. Becomes

When a small object such as a cap is irradiated with an electron beam by such means, the outer diameter of the container is smaller than the scanning angle at which the electron beam is conically scanned. Illuminates the container, but the outer scanning beam is illuminated outside the cap, most of which is wasted.

In view of the above, the invention according to claim 2 provides
A magnetic field line is applied to the scanning electron beam in a direction to deflect the scanning electron beam (to the center side) after the scanning in the circumferential direction, and the scanning electron beam is irradiated to the outside of the cap (object to be irradiated). The scanning beam is deflected toward the center so that an electron beam can be efficiently irradiated even if the irradiation object has a small shape. In this case, the deflection position of the electron beam by the magnetic force lines may be in the air space on the exit side of the electron beam irradiation window 7 of the scanning horn. However, in the air, the electron beam diverges and cannot be accurately deflected. In other words, when the deflection magnet is installed outside the scanning horn (atmosphere side), when the electron beam exits from the vacuum to the atmosphere, it acts on air molecules and is scattered to enlarge the cross-sectional shape of the electron beam, thereby increasing the deflection efficiency. It has a problem that worsens. Therefore, it is preferable that the deflection position of the electron beam by the magnetic force line is a negative pressure (including vacuum) space formed for scanning the electron beam.

According to a third aspect of the present invention, there is provided an invention relating to an electron beam irradiating apparatus for effectively implementing the first aspect of the present invention. Magnetic field applying means for applying an alternating magnetic field from at least two sides in a plane substantially orthogonal to the incident direction is provided so that the electron beam can be scanned in the circumferential direction.

A fourth aspect of the present invention relates to an apparatus for effectively implementing the second aspect of the present invention.
A plurality of NS sets of electron beam deflecting magnets are arranged so as to surround the scanning electron beam at a predetermined position until the object to be irradiated with the electron beam after scanning from the circumferential scanning position, A magnetic field line is applied to the scanning electron beam in a direction in which the electron beam is deflected by the magnet body, and a part of the electron beam irradiated on the irradiation object is an electron beam deflected by the magnetic field line.

The magnetic field applying means according to claim 3 is
5. A plurality of sets of NS electromagnets disposed so as to surround a scanning body entrance, wherein alternating currents having the same amplitude and different phases are applied to the electromagnets of each set. It is preferable that alternating currents having the same amplitude and different phases are applied to the electromagnet bodies of each set of the magnet body for electron beam deflection described above, and the magnetic field applying means further comprises a plurality of NS magnet sets for electron beam scanning. In this case, the alternating current applied to the magnet for electron beam deflection and the alternating current applied to the magnet for electron beam scanning have opposite phases.

According to this invention, the scanning electron beam which circulates while being expanded in the conical direction by the electron beam scanning magnet body is deflected in the focusing direction (center side direction) by the opposite phase electron beam deflection magnet body. As a result, even if the cap has a small diameter, the electron beam can be smoothly irradiated.

Even if the above configuration is adopted, it is impossible to directly irradiate the bottom of the container located on the opposite side of the irradiation window. Therefore, according to the present invention, a reflecting plate is provided on the opposite side of the scanning body with the object to be illuminated therebetween, and the reflected electron beam reflected from the reflecting plate causes the outer surface of the bottom of the object to be illuminated. Is preferably applied.

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 steel plate plated with gold, so that an electron beam having a low acceleration energy (600 KeV) can be used. 50% electron reflection can be expected. The reflecting surface shape of the electron beam reflecting plate is preferably formed in a converging (light collecting) surface shape for converging the electron beam on a predetermined portion of the irradiation object, specifically, in a hemispherical or concave curved surface shape. It is also possible to form a flat or U-shaped reflecting plate because it needs to be conveyed by a conveyor.

[0025]

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.

FIG. 1 shows a beam scanning type electron beam irradiation apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of the apparatus as viewed from above. 1 and 2, reference numeral 6 denotes a scanning horn whose diameter is expanded conically from the exit end of the beam guide cylinder 3 and has a ring-shaped irradiation window 70 on the front surface. Reference numeral 50 denotes a scanning magnet body for performing beam scanning, which is enclosed in a square frame shape at the entrance (starting end) of the scanning horn 6 in a plane perpendicular to the beam center line. The scanning magnet body 50 forms the magnetic field shown in FIG.
A power supply for generating a scanning magnetic field for applying an alternating current as shown in FIG.

Numeral 60 denotes a deflection magnet body surrounded by a square frame in a plane perpendicular to the beam center line so as to surround the periphery of the scanning horn 6 slightly above the irradiation window 70 on the scanning horn outlet side. A power supply (not shown) for generating a deflection magnetic field, which applies an alternating current as shown in FIG. 3B to form a magnetic field shown in FIG. 4 in a vacuum space in the scanning horn 6, is connected.

On the opposite side of the irradiation window 70, the reflector 12 is disposed at a position facing the bottom of the cap below the cap 30. The reflector 12 is made of a metal having a large atomic number such as gold (plating) or tungsten, and is set so that about 50% of electrons can be reflected even with an electron beam having a low acceleration energy (600 KeV). The reflecting surface of the reflecting plate 12 has a hemispherical reflecting plate 12 corresponding to the electron beam 8 emitted from the scanning horn 6 which is deflected in the expanding or converging direction. However, when the cap 30 is conveyed by a conveyor or the like, the conveyor passage portion may be cut out or formed in a U-shape. When a conveyor is used, it is necessary to form a mesh and facilitate irradiation of the reflected electron beam 18 from the reflection plate 12 arranged on the lower side.

The scanning magnet body 50 (50A, 50A,
50B) is set to a quadrupole magnet structure in which two facing sides are an N pole and an S pole, respectively, as shown in FIG. That is, the quadrupole magnets constituting the scanning magnet bodies 50A and 50B are formed by two sets of AC electromagnets whose north and south poles face each other. Then, as shown in FIG. 3 (A), when alternating currents having the same amplitude and a different phase by 90 ° are applied to the N / S quadrupole magnets 50A and 50B, they pass through the center of the scanning magnet body 50. It is possible to apply a magnetic field such that the electron beam is scanned circularly.

As shown in FIG. 4, the rectangular frame-shaped deflection magnet body 60 is also set to a quadrupole magnet structure in which two opposite sides are an N pole and an S pole, respectively. That is, the quadrupole magnet constituting the deflecting magnet body 60 is also formed by two sets of AC electromagnets 60A and 60B whose N pole and S pole face each other. And FIG.
As shown in (B), the deflection magnet body 60 is also the scanning magnet body 5.
When an alternating current having a phase 180 ° different from that of the alternating current applied to 0 is applied, the scanning electron beam that has been concentrically expanded by the scanning magnet body 50 and is orbitally scanned becomes a magnetic field having a phase opposite to that of the scanning magnet body 50. Focuses while drawing a circular orbit as if the light passes through a convex lens. The intensity (wave height) of the alternating current applied to the deflection magnet body 60 is set to be larger than the intensity (wave height) of the alternating current applied to the scanning magnet body 50. Corresponding to the diameter of

As a result, the scanning electron beam that circulates while being expanded in the conical direction by the electron beam scanning magnet body 50 is deflected in the focusing direction (center side direction) by the anti-phase electron beam deflection magnet body 60. Is done.

Next, the operation of this embodiment will be described with reference to FIG. First, 4 at the beginning of the conical scanning horn 6
The scanning magnet body 50 having the polar structure circulates the electron beam in a circular shape, and forms a scanning electron beam that is scanned conically. The electron beam scanned in a conical shape is also a deflection magnet body 6 having a quadrupole structure.
By 0, the beam is deflected in the focusing direction (center-side direction). As a result, even if the cap 30 has a small diameter, the electron beam can be smoothly irradiated.

Further, the electron beam 8 is radiated to the cap bottom 26 where the electron beam 8 is hardly transmitted by the reflected electron beam 18 reflected by the reflection plate 12. This makes the cap 3
The absorbed dose can be made substantially uniform at any part of zero.

While the electron beam is traveling straight in the vacuum space inside the scanning horn 6, since there is no diffusion, the deflection magnet body 6 just before the air irradiation position having the largest swing in the vacuum space.
Although it is preferable to arrange 0, the deflection magnet body 60 may be arranged in front of the irradiation window 70 immediately after the atmospheric irradiation position.

[0035]

As described above, according to the first and third aspects of the present invention, an object to be irradiated having a three-dimensional shape, for example, an electron beam irradiated in accordance with the shape of a cap, is formed into a three-dimensional shape, specifically, a cone. Even in the case of a three-dimensionally complicated thickness or shape such as a cap or a beverage container, it is conveyed in a direction orthogonal to the electron beam irradiation surface by a conveyor or the like, in order to irradiate while circulating in a shape. Even if the electron beam irradiation pattern has a three-dimensional shape corresponding to this, it is possible to irradiate the area above the irradiation object smoothly, and there is no sterilization unevenness and the quality is deteriorated by the electron beam irradiation. It is possible to provide a sterilization means capable of preventing the occurrence of germs.

According to the second and fourth aspects of the present invention, magnetic force lines are applied to the scanning electron beam in a direction of deflecting (to the center side) the scanning electron beam after scanning in the circumferential direction, and the cap (covered) is applied. The outer scanning beam, which is radiated to the outside and is mostly wasted, is deflected toward the center, thereby enabling efficient irradiation of the electron beam even for a small-shaped object to be irradiated. Further, in the case of a magnet body, the alternating current applied to the magnet body for electron beam deflection and the alternating current applied to the magnet body for electron beam scanning have opposite phases.

According to this invention, the scanning electron beam which circulates while being expanded in the conical direction by the electron beam scanning magnet body is deflected in the focusing direction (center side direction) by the opposite phase electron beam deflection magnet body. As a result, even if the cap has a small diameter, the electron beam can be smoothly irradiated.

According to the sixth aspect of the present invention, a reflector is provided on the opposite side of the scanning body with respect to the object to be illuminated, and the outside of the bottom surface of the object is illuminated by the reflected electron beam reflected from the reflector. Additional irradiation can be performed.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a beam scanning type electron beam scanning apparatus according to an embodiment of the present invention, where (A) is a perspective view of a main part and (B)
Is an overall front view.

FIG. 2 is a plan view of the beam scanning electron beam scanning device according to the embodiment of FIG. 1 as viewed from above.

3A is a phase waveform diagram of an AC current applied to a scanning magnet body, and FIG. 3B is a phase waveform diagram of an AC current applied to a deflection magnet body.

FIG. 4 shows 4 used for the scanning magnet body and the deflection magnet body, respectively.
FIGS. 4A and 4B show a polar magnet structure and the relationship between a magnetic field formed by the quadrupole magnet and an electron beam. FIGS.

FIG. 5A is an overall schematic view of a beam scanning type electron beam scanning apparatus according to a comparative technique of the present invention, in which a scanning horn is arranged above a cap. (B) is a perspective view showing a cap shape, and (C) is a sectional view thereof.

6A and 6B show a basic configuration of the beam scanning type electron beam scanning apparatus as a premise of the present invention, wherein FIG. 6A is a front view, FIG. 6B shows a shape of a window of a scanning horn, and FIG. The scanning state of the line is shown.

[Description of Signs] 50 Scanning Magnet Body with 4-Pole Structure 6 Scanning Horn 60 Deflection Magnet Body with 4-Pole Structure 70 Irradiation Window 8 Scanning Electron Beam 12 Reflector 30 Cap

Claims (8)

[Claims] A scanning electron beam emitted from an irradiation window of a scanning body for scanning an electron beam in a negative pressure (vacuum) space while repeatedly irradiating a three-dimensional object such as a food or beverage container. In an electron beam irradiation method for achieving an intended purpose such as sterilization, an alternating magnetic field is applied from at least two sides in a plane substantially orthogonal to the electron beam incident direction on the electron beam incident position on the scanning body entrance side. And scanning the electron beam in the circumferential direction. 2. A magnetic field line is applied to the scanning electron beam in a direction of deflecting the scanning electron beam after scanning in the circumferential direction, and a part of the electron beam irradiated on the irradiation object is deflected by the magnetic field line. The electron beam irradiation method according to claim 1, wherein the electron beam is irradiated. 3. A three-dimensional object such as a food or beverage container is repeatedly irradiated with a scanning electron beam emitted from an irradiation window of a scanning body for scanning an electron beam in a negative pressure (vacuum) space. In an electron beam irradiation apparatus for achieving an intended purpose such as sterilization, an alternating magnetic field is applied from at least two sides in a plane substantially orthogonal to the electron beam incident direction on an electron beam incident position on the scanning body entrance side. An electron beam irradiating apparatus, wherein a magnetic field applying means for irradiating an electron beam is provided so that an electron beam can be scanned in a circumferential direction. 4. A plurality of NS magnet sets for deflecting an electron beam so as to surround a scanning electron beam at a predetermined position until the object is irradiated with an electron beam after scanning from the scanning position in the circumferential direction. Is arranged, in the direction of deflecting the electron beam by the magnet body,
4. The electron beam irradiation apparatus according to claim 3, wherein a magnetic field line is applied to the scanning electron beam, and a part of the electron beam irradiated on the irradiation object is an electron beam deflected by the magnetic field line. 5. The magnetic field applying means according to claim 3, comprising a plurality of sets of NS electromagnets arranged so as to surround the entrance of the scanning body, wherein each set of electromagnets has the same amplitude and phase. 4. The electron beam irradiation apparatus according to claim 3, wherein different AC currents are applied. 6. An electron beam irradiation apparatus, wherein alternating currents having the same amplitude and different phases are applied to the respective sets of electromagnet bodies of the magnet body for electron beam deflection according to claim 4. 7. When the magnetic field applying means is a plurality of NS magnet bodies for scanning an electron beam, the alternating current applied to the magnet body for deflecting the electron beam and the alternating current applied to the magnet body for scanning the electron beam, respectively. 5. The electron beam irradiation apparatus according to claim 4, wherein the electron beam irradiation apparatus has an opposite phase. 8. A reflector is provided on the opposite side of the scanning body with the object to be illuminated therebetween, and the outside of the bottom of the object to be illuminated is additionally illuminated by a reflected electron beam reflected from the reflector. The electron beam irradiation apparatus according to claim 3.