JP2009198355A - Electron beam irradiating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To irradiate each portion of an object with an electron beam having uniform intensity. <P>SOLUTION: An electron beam irradiation device for scanning by a scanning part 3 the electron beam emitted toward a commodity box X from an electron beam generation part 1, and irradiating the commodity box X therewith, includes an electron lens 5 for deflecting a traveling direction of the electron beam on each scanning position to a direction approximately orthogonal to an irradiation plane of the commodity box X. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electron beam irradiation apparatus.

Patent Document 1 below discloses an electron beam irradiation apparatus that sterilizes or sterilizes an irradiation object by irradiating the irradiation object conveyed by a belt conveyor with an electron beam from above. This electron beam irradiation apparatus accelerates an electron beam emitted from an electron gun to a predetermined speed by an accelerating tube, and scans the accelerated electron beam in a direction orthogonal to a moving direction (conveying direction), thereby irradiating an object. The whole is irradiated with an electron beam. Further, this electron beam irradiation apparatus is configured to deflect an electron beam in a vacuum-evacuated scan horn and to emit the electron beam into the atmosphere from a titanium (Ti) extraction window provided at the lower part of the scan horn. Is provided.
An apparatus similar to such an electron beam irradiation apparatus is also disclosed in Patent Documents 2 to 10 below.
JP-A-2005-329140 Japanese Patent Laid-Open No. 2002-341098 JP 2005-227024 A JP 2002-181999 A JP-A-11-169438 JP 2002-107500 A JP 2002-277600 A JP 2004-239819 A JP 2005-249671 A Japanese Patent Laid-Open No. 11-044800

  By the way, the conventional electron beam irradiation apparatus scans an electron beam and irradiates the irradiation object, so that the incident angle of the electron beam differs depending on the part of the irradiation object. That is, the incident angle is the maximum incident angle at a portion of the irradiation object corresponding to the electron beam deflection angle of “zero”, that is, a portion of the irradiation object located immediately below the electron beam emission position of the acceleration tube. However, since the incident angle becomes smaller as the distance from the position immediately below the electron beam emission position becomes smaller, the conventional electron beam irradiation apparatus that scans the electron beam and irradiates the irradiation target object Therefore, it is not possible to irradiate each part of the irradiation object with an electron beam having a uniform intensity, and therefore, it is impossible to uniformly sterilize or sterilize each part of the irradiation object.

  The conventional electron beam irradiation apparatus emits the electron beam deflected in the scan horn from the extraction window and irradiates the irradiation object. However, since the expensive extraction window deteriorates due to the transmission of the electron beam, the electron beam irradiation apparatus deteriorates for a certain period of time. When driving, it is necessary to replace the take-out window, which increases the running cost.

The present invention has been made in view of the above-described circumstances, and has the following objects.
(1) Irradiate each part of the object with an electron beam of uniform intensity.
(2) The running cost is reduced as compared with the conventional case.

In order to achieve the above object, in the present invention, as a first solution, an electron beam irradiation apparatus that scans an electron beam emitted from an electron beam generation unit toward an object and irradiates a countermeasure object with the scanning unit In this case, an electron lens that deflects the traveling direction of the electron beam at each scanning position in a direction substantially orthogonal to the irradiation plane of the object is employed.
As a second solution, in the first means described above, the electron beam generator and the scanning unit are evacuated vacuum spaces, and the reduced pressure space and the atmosphere are disposed at the tip of the scanning unit in the traveling direction of the electron beams. A means of providing an electron beam transparent partition plate for partitioning is employed.
As a third solving means, in the first or second means, a means is adopted in which the electron lens is at least a pair of magnets having different polarities facing each other across the scanning line.

According to the present invention, since the electron lens that deflects the traveling direction of the electron beam at each scanning position in a direction substantially orthogonal to the irradiation plane of the object is provided, an electron beam having a uniform intensity is applied to each part of the irradiation object. Irradiation is possible, whereby each part of the irradiation object can be uniformly sterilized or sterilized.
Further, in the case of a type including an electron beam transmissive partition plate that partitions the decompressed space and the atmosphere at the tip of the scanning unit in the traveling direction of the electron beam, the partition plate can be reduced in size by including an electron lens. Therefore, it is possible to make the thickness of the partition plate for satisfying the same mechanical strength thinner than that of the conventional one, and thus the life of the partition plate can be extended, so that the running cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electron beam irradiation apparatus according to the present embodiment. In this figure, reference numeral 1 is an electron gun, 2 is an acceleration tube, 3 is a scanning unit, 4 is a scan horn, 5 is an electronic lens, 6 is a partition plate, 7 is a shielding frame, X is a product box, and Y is a belt conveyor. It is. This electron beam irradiation apparatus has an irradiation apparatus main body constructed by connecting an electron gun 1 → acceleration tube 2 → scanning unit 3 → scan horn 4 → electron lens 5 → partition plate 6 in this order. The product box X, which is fixed upward and transported on the belt conveyor Y, is sterilized or sterilized by irradiating it with an electron beam from above.

  The electron gun 1 generates an electron beam based on a control signal input from a control device (not shown) and emits the electron beam to the acceleration tube 2, that is, downward. The accelerating tube 2 is formed of a cylindrical member having a predetermined length, accelerates to a predetermined speed by applying an electric field to free electrons incident from one end (upper end), and exits from the other end (lower end) toward the scanning unit 3. To do. The electron gun 1 and the acceleration tube 2 constitute an electron beam generator.

  The scanning unit 3 applies a magnetic force to the electron beam incident from the accelerating tube 2 so that the electron beam is perpendicular to the transfer direction of the product box X, and the upper surface of the rectangular product box X (rectangular irradiation). Scanning across the width of the plane) (width in the direction perpendicular to the transfer direction). That is, the scanning direction (scanning line direction) of the electron beam in the scanning unit 3 is a direction orthogonal to the transfer direction of the product box X, and the scanning range of the electron beam in the scanning unit 3 is the upper surface of the product box X. It is equivalent to the width.

  The scan horn 4 is a horn-like member that forms a space through which the electron beam scanned by the scanning unit 3 passes, and its horizontal cross section has a shape including the scanning direction and scanning range. The electron lens 5 applies a magnetic field to the scanning electron beam incident through the scan horn 4 so that the traveling direction of the electron beam at each scanning position is substantially perpendicular to the irradiation plane of the product box X. To deflect.

  FIG. 2A is a view taken along the line AA in FIG. 1 and shows a detailed configuration of the electron lens 5. As shown in this figure, the electron lens 5 is composed of a pair of bar magnets 5A and 5B having different polarities facing each other across the scanning line. That is, in the electron lens 5, the pair of bar magnets 5A and 5B composed of the N pole and the S pole are opposed to each other with the polarities different from each other with the scanning line interposed therebetween, and are parallel to the scanning line and in a horizontal posture. Is arranged in.

The pair of bar magnets 5A and 5B arranged in this way has a magnetic field strength distribution shown in FIG. 2B with respect to the scanning line. That is, each of the bar magnets 5A and 5B has a magnetic field strength of zero at the division position of the N pole and the S pole, that is, at an intermediate position of the length, but the magnetic field intensity increases as the distance from the intermediate position increases. The magnetic field intensity distribution shown in FIG. The electron beam at each position (scanning position) on the scanning line is deflected in a direction substantially orthogonal to the irradiation plane of the product box X by the electron lens 5 having such a magnetic field intensity distribution.
The pair of bar magnets 5A and 5B are arranged close to and near the lower end of the scan horn 4 having a rectangular cross-sectional shape as shown in FIG. Apply a magnetic field.

The partition plate 6 is an electron beam transmissive material that partitions the internal space (the decompressed space decompressed by being evacuated) and the external space (in the atmosphere) of the accelerating tube 2, the scanning unit 3, and the scan horn 4 connected to each other. It is a thin plate. The partition plate 6 is a thin plate made of titanium (Ti), for example, and is a rectangular plate having a length slightly longer than the length of the scanning line. The partition plate 6 is provided at a position corresponding to the scanning line at the rectangular open end (lower end) of the scan horn 4 having a rectangular cross-sectional shape. Note that, at the rectangular open end of the scan horn 4, the region other than the partition plate 6 is closed by a plate member made of the same material as the scan horn 4.
The shielding frame 7 is a frame provided so as to surround the scan horn 4 and the belt conveyor Y, and is a safety device for preventing leakage of radiation generated from the electron beam to the outside.

  The product box X is a rectangular box in which products are stored, and is placed on the belt conveyor Y at predetermined intervals. The belt conveyor Y is driven by a motor (not shown), and sequentially conveys the product box X in a constant direction at a predetermined constant speed.

  Next, the operation of the electron beam irradiation apparatus configured as described above will be described in detail with reference to FIG.

  In the present electron beam irradiation apparatus, the electron beam emitted from the electron gun 1 is accelerated by the accelerating tube 2 to be accelerated to energy sufficient to sterilize or sterilize the product box X. Then, the electron beam thus accelerated is scanned by the scanning unit 3 and passes through the scan horn 4, and as shown in FIG. 2B by the electron lens 5 provided in the vicinity of the lower end of the scan horn 4. Affected by magnetic field strength distribution.

  FIG. 3 is a schematic diagram showing the effect of the magnetic field intensity distribution on the electron beam. The electron beam that has entered the center of the electron lens 5, that is, the position where the deflection angle is “zero” and the magnetic field intensity is zero is not affected by the magnetic field intensity distribution and passes through the electron lens 5 without being deflected. Is “non-zero”, that is, an electron beam incident at a position where the magnetic field strength is not zero is deflected at a deflection angle corresponding to the magnitude of the magnetic field strength. The traveling direction is a direction substantially orthogonal to the upper surface (irradiation plane) of the product box X. And such an electron beam is irradiated over the whole upper surface (irradiation plane) of the product box X transferred to a fixed direction at a predetermined speed.

  Therefore, according to the present electron beam irradiation apparatus, each position along the scanning line on the upper surface of the product box X is in a state in which the electron beam is incident substantially vertically, that is, a state in which an electron beam having a uniform intensity is irradiated. Therefore, the product box X can be uniformly sterilized or sterilized.

Further, according to the present electron beam irradiation apparatus, the length of the partition plate 6 in the scanning line direction can be made shorter than before, and thereby the thickness for obtaining the same mechanical strength as before can be increased. Since the deterioration of the partition plate 6 due to the transmission of the electron beam can be suppressed as compared with the conventional one, the life of the partition plate 6 can be extended as compared with the conventional one. Running cost can be reduced.
Further, the configuration of the electron lens 5 is extremely simple as shown in FIG. 2, and thus the present electron beam irradiation apparatus is a product without significantly increasing the cost compared to the conventional electron beam irradiation apparatus. The uniform sterilization or sterilization of the box X can be realized.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) FIG. 4 is an arrow view (corresponding to FIG. 2) showing a detailed configuration of an electronic lens 5 ′ as a modified example. The electron lens 5 ′ is composed of two pairs of square magnets 5C to 5F instead of the pair of bar magnets 5A and 5B described above. Each of the square magnets 5C to 5F is a square magnet having the N pole on the front side and the S pole on the back side, and is arranged so that different polarities face each other across the scanning line as illustrated. Such an electron lens 5 'also has a magnetic field strength distribution substantially similar to that of the above-described electron lens 5.
The bar magnets 5A and 5B and the square magnets 5C to 5F may be configured as permanent magnets or electromagnets.
(2) Further, the countermeasure is not limited to the product box X. Any material may be used as long as it requires sterilization or sterilization.

It is a schematic diagram which shows schematic structure of the electron beam irradiation apparatus concerning one Embodiment of this invention. 1 shows a detailed configuration of an electron lens 5 according to an embodiment of the present invention, and is a view taken along line AA in FIG. It is a schematic diagram which shows the effect | action of the electron lens 5 in one Embodiment of this invention. It is a line arrow figure which shows the modification of the electronic lens 5 in one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Acceleration tube, 3 ... Scanning part, 4 ... Scan horn, 5 ... Electronic lens, 6 ... Partition plate, 7 ... Shielding frame, X ... Product box, Y ... Belt conveyor

Claims (3)

An electron beam irradiation device that irradiates a countermeasure object by scanning an electron beam emitted from an electron beam generator toward an object with a scanning unit,
An electron beam irradiation apparatus comprising: an electron lens that deflects the traveling direction of an electron beam at each scanning position in a direction substantially orthogonal to an irradiation plane of an object. The reduced pressure space where the electron beam generator and the scanning unit are evacuated,
2. The electron beam irradiation apparatus according to claim 1, further comprising an electron beam transmissive partition plate that partitions the decompressed space and the atmosphere at the tip of the scanning unit in the traveling direction of the electron beam.   3. The electron beam irradiation apparatus according to claim 1, wherein the electron lens is at least a pair of magnets having different polarities facing each other across the scanning line.

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