JP3648537B2 - Electron beam irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a conveyance portion of an electron beam irradiation apparatus for processing powder. The electron beam irradiation apparatus is an apparatus that passes an electron beam generated in a vacuum through an electron beam irradiation window to the atmosphere and irradiates an object to be processed. Used for various purposes such as cross-linking of electric wire polymer coating, resin curing, coating film curing, and medical instrument sterilization. Conventionally, most of the objects to be processed are of a fixed solid. The solid object to be processed is transported inside the casing by an endless conveyor and receives electron beam irradiation when passing under the electron beam irradiation window. In the case of a small solid workpiece, it may be placed on a conveyor in a tray.
[0002]
There are two types of electron beam irradiation devices with different electron beam distributions. A scanning type that scans an electron beam and a non-scanning type (area type) that does not scan. The scanning type scans an electron beam in a direction (y direction) perpendicular to the transport direction (x direction) by the action of an alternating magnetic field. This is often used when energy is high.
[0003]
In the non-scanning type, an electron beam is generated from a filament having a large effective area, a beam having a wide cross section is obtained and accelerated to irradiate an object to be processed. Irradiates an electron beam with relatively low energy. Since the acceleration energy is low, the distance for acceleration is short, and scanning is not performed, so the apparatus can be miniaturized.
[0004]
The generation of electron beams is accelerated in a vacuum. The object to be processed is conveyed in the atmosphere. There is an irradiation window between them. This is a window with a Ti or Al metal foil. The vacuum of the electron beam generator acceleration part is maintained by the window foil. Since the window foil is thin, it transmits the electron beam. The transmitted electron beam is irradiated to the object to be processed in the atmosphere. Since electron beams have high kinetic energy, they can pass through the foil but have transmission loss. Loss energy becomes heat. The window foil is heated strongly for that purpose. In order to avoid melting breakage of the window foil, it is cooled by wind or water.
[0005]
As the conveying device, a conveyor that moves infinitely around the box is generally used. When an electron beam collides with a conveyor or an object to be processed, ozone and X-rays are generated. Both are harmful substances. Hazardous substances and radiation should not go outside. Then the conveyor is surrounded by a closed box. The endless conveyor is supported by a number of rollers and bends up and down several times. Since the rotational driving force is applied to the rollers, the conveyor advances in a constant direction at a constant speed. The speed can be adjusted freely. The box is partitioned by several metal plates. A number of through holes are made in the metal plate, and the conveyor passes through the through holes. The through holes through which the conveyor passes are not arranged in a straight line. This is because X-rays do not leak outside. Nitrogen gas circulates directly under the irradiation window. This is to remove ozone. Without oxygen, ozone is not generated.
[0006]
[Prior art]
Until now, what has been the object of processing of the electron beam irradiation apparatus is a solid having a dimensional shape. In the case of solids, surface treatment is usually the purpose. Therefore, it is often said that an electron beam only needs to hit a certain surface. In the case of a solid having a considerable size and having a fixed shape, it can be placed directly on the conveyor, proceeded from the entrance to the conveyor path, processed by the irradiation window, and directly conveyed to the exit. If the geometry is not suitable for placing on the conveyor, place it in a suitable tray and transport it on the conveyor.
[0007]
However, in recent years, there has been a demand for sterilizing powder using an electron beam irradiation apparatus. Since the powder is amorphous, it cannot be put on the conveyor as it is. There is a method to squeeze into a plastic bag, hold it thin, place it on a conveyor, and hit an electron beam directly under the irradiation window. In the case of powder, an electron beam must hit all of the powder, but the transmission distance of the electron beam is extremely shallow with a few millimeters to 1 cm. Therefore, it is necessary to pack the bag and hold it down to a thickness of a few millimeters for electron beam processing. The conveyor is used as a transport means, but after the bag is packed and processed with an electron beam, it is taken out of the bag. In the case of powder, it takes time to pack the bag and to take out the powder from the bag. There are also losses associated with bagging. Thus, there is a considerable difference in the transport form between solid and powder.
[0008]
[Problems to be solved by the invention]
In addition, there has been a new demand for electron beam processing of granular objects that are neither shaped solids nor amorphous powders. Since powder and granules are similar, it may be thought that an electron beam could be irradiated in the same way as powder. But that is wrong. The granule is an irregular granule having a diameter of several millimeters. It is much larger than the diameter of the powder. Accordingly, when the electron beam is irradiated in a bag, a granule that is not irradiated with the electron beam at all is formed. Rather, it can be said that there are more particles that are not irradiated. In this case, it is not known why the electron beam is irradiated. We must consider a device that can irradiate the particles more efficiently. For example, if the ridges on both sides of the conveyor are not spilled, it can be transported by an infinite circuit.
[0009]
However, there is no record of doing so. In the first place, the electron beam treatment of the particulate material itself is a new demand, and there is no record of treatment. Because it is a new requirement, a new countermeasure will be required. There is no distinction between the front and back of granular materials. In the case of a granular material, it is necessary to irradiate the entire surface with an electron beam. In other words, it is necessary to irradiate an electron beam not only on a certain surface but also on the back surface and side surface. This presents difficulties for electron beam processing of particulate matter.
[0010]
When the diameter D is smaller than the penetration depth d of the electron beam (D <d), the electron beam can reach the back surface. This could be possible by increasing the electron beam acceleration energy. However, if it does so, an electron beam will enter the inside of the granular material. However, there are times when it is better not to be exposed to an electron beam inside. In that case, the inside of the granular material should not be altered by the electron beam. In the case of a granular object, an electron beam does not enter inside, and an electron beam must be applied to the entire peripheral surface. However, it is not easy. Even if a granular object is simply put into a zaza and a conveyor and carried, the electron beam hits the upper surface but not the back surface. Moreover, even if the particles are dropped from the hopper onto the conveyor little by little, the group of particles is solidified to form a mountain. In the case of a mountain, the electron beam only hits the top grain. However, it is not easy to spread a single layer of granular material on a conveyor. In other words, when an electron beam treatment is performed on a granular material, it is almost impossible that the granular material does not overlap each other and only one layer is placed on a conveyor and the back surface is irradiated with an electron beam.
[0011]
Since this is not possible, there is still no electron beam irradiation apparatus capable of processing particulate matter. It is a first object of the present invention to provide an electron beam irradiation apparatus capable of processing a granular object. It is a second object of the present invention to provide an electron beam irradiation apparatus in which the granular materials do not overlap each other and block the electron beam. It is a third object of the present invention to provide an electron beam irradiation apparatus that can uniformly apply an electron beam to the front surface, side surface, and back surface of a granular material.
[0012]
[Means for Solving the Problems]
The present invention uses an oscillating conveyor to convey particulate matter. In addition, a path for cooling water is provided on the back of the vibrating conveyor to directly cool the vibrating conveyor. When the granular material is dropped from the hopper onto the vibrating conveyor, the vibrating conveyor feeds the granular material in a certain direction by the vibration of the plate surface. Since there is a vibrating conveyor that extends from the entrance to the exit through the irradiation position directly under the irradiation window, the granular material advances in a certain direction along with the vibration.
[0013]
Unlike endless conveyors, they themselves do not travel and carry particulates by vibration. Because it vibrates, the particles rotate and turn upside down, so the electron beam strikes almost evenly on any surface. This is an important advantage. Even if it is a weak electron beam, it can hit an electron beam to the whole surface, and it can be prevented from entering the inside. Even if it temporarily becomes a mountain, the mountain collapses due to vibration and eventually becomes a distribution of one layer, so that all the particles can be equally exposed to the electron beam.
[0014]
Although the conveyor is heated by the electron beam irradiation, the cooling water is allowed to flow directly to the back surface of the plate surface, so that the plate surface is effectively cooled. Unlike the circular conveyor, the same part is always heated by receiving an electron beam, so cooling is particularly important. The present invention provides sufficient cooling by allowing cooling water to flow directly to the back of the plate.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic longitudinal sectional view of an electron beam irradiation apparatus according to an embodiment of the present invention. The horizontally long casing 1 is made of a metal plate such as an iron plate or a lead plate, and the inside is used as a conveyance space for the object to be processed. The electron beam generator 2 is provided in the intermediate part. Although the non-scanning type electron beam generator 2 is shown here, a scanning type device may be used. The electron beam generator 2 includes a vacuum chamber 3, a filament 4 provided inside, and an irradiation window 5 for taking out the electron beam to the outside. A direct current flows through the filament 4 to generate heat. The temperature rises, so thermoelectrons are emitted. Further, since a negative bias is applied to the vacuum chamber 3, the thermoelectrons are drawn in the direction of the irradiation window 5.
[0016]
The irradiation window 5 is a square opening. Here, a window foil 6 of Ti or Al is pasted. Above the window foil is a vacuum and below is the atmospheric pressure. The extremely thin window foil 6 absorbs part of the electron beam 7. Since this generates heat, it is usually cooled by blowing air or the like. However, the window foil cooling device is not shown here.
[0017]
There is a transport mechanism inside the housing. This is not a normal endless conveyor. Instead, the vibrating conveyor 8 is a transport mechanism. This is a feature of the present invention. The object to be treated with the electron beam irradiation is a granular material 9. At one end of the housing 1 is an inlet hopper 10 for guiding the granular material 9 to the housing. Particulate matter enters the inlet region 11 of the housing 1 from the inlet hopper 10. The vibration conveyor 8 includes a vibration bottom plate 12, a vibration side plate 13, a support column 14, a vibration generator 15, and the like. The support column 14 supports the vibration bottom plate 12 in the front, rear, left, and right directions so as to vibrate. A part of the column 14 is made of anti-vibration rubber 16 to allow the vibration bottom plate 12 to vibrate up and down. The vibration generator 15 is constituted by, for example, a motor and an eccentric cam. Alternatively, vibration can be applied by an ultrasonic vibrator or the like. As a result, the vibrating bottom plate 12 vibrates but has a slight inclination, so that the granular material advances in a certain direction. Even if there is no inclination, it can be advanced in a certain direction by making the vibration mode asymmetrical in the longitudinal direction. Moreover, it can also be made to convey only to one direction by giving the vibration bottom plate 12 a special surface shape.
[0018]
When moving forward (x direction) on the vibrating bottom plate 12, the granular material eventually reaches directly below the irradiation window 5. Here, the granular material 9 receives electron beam irradiation. Appropriate processing is performed on the granular material by the electron beam. A cooling water pipe 17 is provided directly below the vibration bottom plate 12. The vibration bottom plate 12 generates heat by receiving the electron beam 7. If left as it is, the bottom plate 12 is burned out. It is cooled to avoid this. FIG. 2 shows a cross-sectional plan view of the cooling water pipe 17 portion.
[0019]
In this example, the cooling water pipe 17 has a bottom plate 18, a side wall 19, a front wall 20 and a rear wall 21, and partition walls 22, 22... Are provided in order to form a meandering flow path. There is a cooling water inlet 23 at the beginning of the flow path and a cooling water outlet 24 at the end. A meandering flow path from the inlet 23 to the outlet 24 is formed. The cooling water 25 passes through this while meandering. The cooling water pipe 17 directly cools the vibration bottom plate 12.
[0020]
Heat generated by electron beam irradiation is cooled by the action of cooling water. The cooling water is heated and discharged from the outlet 24.
When the granular material is conveyed by the vibration conveyor, the granular material rolls back and forth and left and right by vibration as shown in FIG. Although it is a minute vibration, it vibrates up, down, front, back, left and right, so that the granular material jumps up and rolls around. Since the granular material is rolling, the surface toward the electron beam always changes. So every surface is equally irradiated with electron beam. The electron beam energy is low so that no electron beam enters the inside of the granular material, but all surfaces are subjected to electron beam processing because they are rolled by a roller and a vibrating conveyor. This is a very advantageous property. This is not the case with ordinary endless conveyors that do not vibrate.
[0021]
The particulates fall from here when it reaches the exit area 26 of the housing at the end of the vibrating conveyor. It passes through the outlet hopper 27 and falls to the next conveyor 28. It is conveyed to the apparatus of the next process by this conveyor.
[0022]
【The invention's effect】
The present invention uses an oscillating conveyor for conveying particulate matter inside the housing. Unlike normal endless conveyors, the granular material rolls around because the vertical and horizontal movements are applied to the granular material. Therefore, the entire surface can receive an electron beam irradiated from above. Since the electron beam is equally applied to the surface of the granular material, an ideal surface treatment is performed.
[0023]
In addition, since a water cooling device is provided on the bottom plate of the vibration conveyor, heat can be released even if heat is generated by the electron beam, and the bottom plate is not damaged by heat. Although the granular material itself may change in quality when it is heated too much, since the present invention cools the bottom plate with cooling water, the temperature of the granular material can be prevented from excessively rising.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an electron beam irradiation apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional plan view of a cooling water pipe provided immediately below a vibration bottom plate.
FIG. 3 is a longitudinal sectional view of a part of a vibration bottom plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing | casing 2 Electron beam generator 3 Vacuum chamber 4 Filament 5 Irradiation window 6 Window foil 7 Electron beam 8 Vibrating conveyor 9 Granular material 10 Inlet hopper 11 Inlet area 12 Vibration bottom plate 13 Vibration side plate 14 Strut 15 Vibration generator 16 Anti-seismic rubber 17 Cooling water pipe 18 Bottom wall 19 Side wall 20 Front wall 21 Rear wall 22 Partition wall 23 Cooling water inlet 24 Cooling water outlet

Claims (1)

  A housing that should contain a mechanism for conveying an object to be processed, an electron beam generator that is provided in a part of the housing and generates an electron beam in a vacuum, and a window at the boundary between the housing and the electron beam generator The irradiation window provided with foil, the vibration conveyor that is placed inside the housing and transports the object to be processed by vibration, and the coolant is provided on the bottom plate of the vibration conveyor that is provided below the site where the electron beam of the vibration conveyor hits. An electron beam irradiation apparatus comprising: a cooling mechanism that is in direct contact.

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