JP3730850B2 - Particle transport mechanism in electron beam irradiation equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an industrial electron beam irradiation apparatus, a test electron beam irradiation apparatus, and the like. The electron beam irradiation apparatus is an apparatus that generates thermoelectrons from a filament in a vacuum, accelerates them with an accelerating electrode, emits them into the atmosphere through a window foil, and irradiates the workpiece with an electron beam. Used for cross-linking of polymers such as wire coating. It is also used for curing printed and paint films. It is also used to sterilize medical equipment. The acceleration energy ranges from several MeV to several hundred keV. The appropriate acceleration energy is determined by the object to be processed and the purpose. The system of the device changes depending on the energy.
[0002]
An apparatus that gives higher energy is called a scanning electron beam irradiation apparatus, and scans a thin beam in the left-right direction, that is, two-dimensionally. There is an electromagnetic coil for scanning, and the beam is moved left and right by a magnetic field. It may be swung not only from side to side but also back and forth. Since the beam swings to the left and right, the space for maintaining the vacuum is also formed by a triangular tube that extends downward. A triangular tube is called a scanning tube. The opening at the lower end of the scanning tube is called an irradiation window. The irradiation window is covered with a window foil that separates vacuum and air.
[0003]
The window foil is a thin foil of Ti and Al. Above the window foil is vacuum and below is atmospheric pressure. In the case where the energy boundary is about 300 keV and the acceleration energy is less than that, a non-scanning (area type) electron beam irradiation apparatus is often used. Thermal electrons are generated from a wide area filament over a wide area and accelerated between the filament and the anode. Since a beam with a large area is generated from the beginning, it is not necessary to scan. Since scanning is not performed, the distance from the filament to the irradiation window can be made short and compact.
[0004]
A closed space for irradiating an object to be processed with an electron beam is provided under the irradiation window in both the scanning type and the non-scanning type. Why is it a closed space? When an electron beam hits an object to be treated, it performs useful actions such as a crosslinking reaction, a bactericidal action, and a curing action. However, since a high-energy electron beam hits a substance, a large amount of X-rays are generated. It is necessary to block X-rays, which are harmful radiation, from leaking outside. For this purpose, a closed space is required. The irradiation chamber is made of thick concrete or a thick lead plate. Since the electron beam irradiation is performed in the space, it is not possible to carry the workpiece by hand.
[0005]
An automatic transport mechanism is required to bring the workpiece under the irradiation window and to carry it away. A transport mechanism such as a circular conveyor is provided inside the irradiation chamber. This is a transfer device that connects the entrance and exit of the irradiation chamber and passes directly under the irradiation window. The transport mechanism is bent up and down so as to pass through several metal plate openings. It is a device for preventing X-rays from leaking outside. X-rays should not go straight outside. Of course. Furthermore, the structure of the transfer mechanism and the irradiation chamber is devised so that it does not reach the outside unless it is reflected at least three times.
[0006]
[Prior art]
A transport device used to transport an object to be processed in the electron beam irradiation device is strongly affected by ozone and X-rays generated by the electron beam. Therefore, there are restrictions on the material and structure. As the material, stainless steel is often used which is not easily affected by ozone rust. Heated by the energy of the electron beam. It must be cooled to suppress the temperature rise. For this reason, stainless steel mesh conveyors and steel conveyors have been used to transport rubber and plate materials. And cooling air was blown in the vicinity of the irradiation window to cool the conveyor.
[0007]
In the above-mentioned items, electric wires, plate materials, rubber products, and tangible solids are to be processed. However, in recent years, attempts have been made to sterilize irregular shaped foods such as grains and spices with an electron beam. Foods and foods are usually not sterilized, but some imported foods, raw foods, foods that are stored for a long time, etc. need to be sterilized. Conventionally, sterilizing gases such as methyl bromide and ethylene oxide have been used for sterilizing granular foods such as grains and spices. Sterilize by sucking granular food with these gases. Food ingredients need only be sterilized on the surface. The surface can be sterilized by contact of these toxic gases with the surface. Gas sterilization, however, is toxic in itself and residual gases can adhere to food. Therefore, a safer sterilization method using an electron beam is attempted. This is still a trial and error situation. E-beam sterilization of food has not yet been put into practical use.
[0008]
There are various problems waiting to be solved for electron beam irradiation of granular foods. Here, the transport mechanism is a problem. The mesh conveyor cannot be used when the workpiece is granular. This is because the particles leak from the mesh. A steel conveyor or an electromagnetic feeder (vibration feeder) can be considered for conveying the particles. A steel conveyor is a circular conveyor of steel sheets with a smooth and flat surface. Since it is a thin plate, it can be easily folded and wrapped around the roller in the same way as a belt. The electromagnetic feeder advances the object to be processed by asymmetrically vibrating an oblique plate or a horizontal plate up and down. This is called an electromagnetic feeder because the substrate is vibrated by a motor or electromagnetic vibrator to carry the workpiece. It is also called a vibrating conveyor because it vibrates and sends.
[0009]
[Problems to be solved by the invention]
In order to irradiate the particles with an electron beam, the particles need only be transported when irradiated with high acceleration energy that completely penetrates the particles. However, in the case of food sterilization, it is inappropriate for the electron beam to penetrate the granules. This is because when an electron beam passes through the inside, a chemical reaction is induced and the flavor may be lowered or altered. In the case of food ingredients, it is necessary to apply an electron beam thinly only to the particle surface. When irradiating with a low acceleration energy that does not completely pass through the grains, a portion that becomes a shadow of irradiation remains. The shadow part is not irradiated with an electron beam. However, it is not sterilized unless an electron beam is applied to the entire surface. The entire surface of the particles must be irradiated with an electron beam. It is necessary to perform irradiation while rotating the particles so that the entire surface is irradiated.
[0010]
However, none of such a transport mechanism has been realized yet. Several proposals have been made, but the situation is such as a sink that is short to the belt. Although it has not been realized, it also has the meaning of clarifying the problem of transporting food granules, so the prior art will be reviewed next.
[0011]
(1) Japanese Patent Laid-Open No. 10-215765 “Crystal sterilization method and grain rotation device used therefor” is a grain sterilization method in which a tray mounting table is placed on a vibrator and a shaker, and an electron beam irradiation device is provided thereon. Propose the device. Thinly put grains such as brown rice, wheat, red beans, and soybeans in the tray. The vibrator vibrates longitudinally and the shaker vibrates laterally. Wheat jumps, jumps, dances and plays. So the electron beam hits the whole surface. Electron beam energy is low. It is an electron beam with a low acceleration voltage of 160 kV to 230 kV. The process is completed in about 1 hour. Dozens of grams of grain can be sterilized by one treatment.
[0012]
(2) Japanese Patent Application No. 10-142873 “Electron Beam Irradiation Device” proposes an electron beam irradiation device in which grains are placed on a water-cooled flat-surface vibration conveyor and a weak electron beam is applied while being carried by vibration. ing. Vibratory conveyors have the ability to carry workpieces but also roll workpieces. Grain rolls by vibration, jumps up, falls down and moves in one direction. Because it jumps up, it rolls and rolls so that all surfaces hit the electron beam. The weak electron beam is used to hit only the grain surface. Sometimes called soft electrons.
[0013]
(3) Japanese Patent Application Laid-Open No. 1-192362 “Powder Radiation Processing Device” proposes a device for sterilizing granular foods such as wheat flour and spices by radiation. Radiation means three types of radiation: γ-rays, X-rays, and electron beams. The object is exposed to radiation while carrying the object to be treated by gas. “Powder radiation chamber that is installed in a room surrounded by a shielding wall and blows gas from below to float the powder, and radiation irradiation device is provided opposite to the powder suspension chamber. Processing device. "
The powder is blown up by a strong wind and exposed to radiation in a floating state, so that all the grains are exposed to radiation.
[0014]
(4) Japanese Patent Application Laid-Open No. 8-52201 “Powder Electron Beam Sterilizer” provides a slightly inclined tube part in a huge processing chamber with a thick concrete wall, and a perforated plate parallel to the axial direction in the middle of the tube part Air is blown from below, the powder workpiece is introduced from above the perforated plate, the workpiece is lifted with air, and the workpiece is carried obliquely downward and exposed to an electron beam from the side. ing. The object to be treated, which is carried along with a large amount of air, is separated from the air by a cyclone and only the powder is recovered. Because it soars with air, an electron beam hits the entire surface of the workpiece.
[0015]
(5) Japanese Patent Application No. 11-61327 “Electron Beam Irradiation Device, Electron Beam Irradiation Method, and Object to be Processed” has a porous plate extending in the horizontal direction at the lower and upper portions of the horizontal transfer space, and a vertical hole at the front end. A plate is provided, gas is blown up from the lower perforated plate, gas is blown down from the upper perforated plate, and gas is transported from the front perforated plate to transport the powder to be processed by gas. It is a skillful object that irradiates an electron beam while transporting gas. The gas from the front perforated plate gives the driving force. The gas blown up from the lower porous plate gives lift. The gas blown down from the upper perforated plate suppresses diffusion. It is a difficult mechanism that requires delicate balance. Since it is a gas transfer and does not use a conveyor, the problem of rotating and irradiating powder particles has been solved.
[0016]
(6) Japanese Patent Application No. 11-114312 “Electron Beam Irradiation Device and Granular Body Sterilization Method” transports grains by a vibrating conveyor having a large number of projections and depressions. The grain particles are flipped over and flipped by protrusions and bumps. There is a probability that all surfaces face upward, and the entire surface is thinly irradiated with an electron beam, so that the surface can be sterilized.
We have glanced at various technologies that have been proposed so far. An object of the present invention is to provide a transport mechanism in which electron beam irradiation is equally performed on the entire surface of a granule. That is, it is an object of the present invention to provide a transport mechanism that turns a granular material so that the entire surface faces the electron beam irradiation direction.
[0017]
[Means for Solving the Problems]
The present invention utilizes a vibrating conveyor (electromagnetic feeder) for conveying the particles. The transport plate has a staircase with a small hole in part or in whole, a blowout gas duct is provided on the back side of the staircase, the gas is blown from the small hole, the staircase is vibrated, and the particles are rotated and jumped in one direction. It is designed to be transported.
[0018]
That is, the transport mechanism of the present invention is
(1) Use an electromagnetic feeder that moves the object to be processed by vibrating the conveying plate;
(2) A staircase was provided in part or all of the transport plate directly under the irradiation window.
(3) The staircase is provided with a duct for blowing gas,
(4) The staircase has a feature that a small hole is formed so that the gas from the blowing gas duct is blown out from the small hole.
[0019]
Since it is a granule, it can be transported by a flat and smooth conveyor, but in that case, the electron beam hits only one side. In order to irradiate an electron beam on the entire surface of the particle, the particle must be rolled and rotated. It is more suitable to use a vibrating conveyor than a circular conveyor that moves quietly for rolling particles. Since it does not rotate easily by itself, an attempt is made to provide an opportunity for rotation by providing a staircase on the transport plate and rolling it down. It is possible that the direction does not change just by falling down the stairs. Therefore, gas is blown out from the staircase so that the particles rise. That is, the present invention uses three different means to rotate the granules. There are three types: wind-up by wind, rolling by stairs, and spring-up by vibrating conveyor. Any shape of particles can be directed once in the direction of the electron beam by soaring, flipping up, or rolling.
[0020]
The position of the stairs on the transport plate should include the area directly under the irradiation window. Since it receives an electron beam directly under the irradiation window, it only needs to rotate here. Of course, there may be stairs on the entire transport plate. The duct is provided directly under the transport plate. From here, the blowing gas is guided to the staircase small hole. Since the vibratory conveyor does not substantially move, a duct can be provided. The depth of one step of the stairs is, for example, about 0.5 to 2 cm (preferably about 1 cm), and the height is about 2 mm to 1 cm. The small holes may be slit-shaped. In the case of a slit shape, the width is about 0.5 mm and the length is about 20 mm to 30 mm.
[0021]
The transport plate may be horizontal, but can be inclined to facilitate advancement. The inclination angle is about 5 to 10 degrees. Even in the horizontal direction, it is possible to advance the particles with vibration asymmetry.
[0022]
The objects to be processed are granular food ingredients such as wheat, rice, barley, spices and pepper. The electron beam energy is a low energy of 100 keV to 200 keV. This is because only the surface is sterilized and does not enter the interior. Low energy electron beam irradiation devices are cheaper and more convenient.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an electron beam irradiation apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a conveyance plate portion of an electromagnetic feeder (vibrating conveyor). FIG. 2 is a longitudinal sectional view thereof. The conveyance plate 1 has a stepped portion 2 in part. The staircase portion may be the whole or a part of the transport plate, but the staircase portion 2 is always present immediately below the irradiation window 9 of the electron beam irradiation apparatus. The depth of one step of the stairs is about 1 cm and the height is about 2 mm to 10 mm. It is not necessary for the horizontal plate 7 to be always horizontal.
[0024]
A blowout gas duct 3 is provided immediately behind the staircase 2. At the start end of the transport plate 1, a granule input mechanism 4 that inputs the particles 6 onto the transport plate 1 is provided. In this example, only a part of the scanning tube 5 of the scanning electron beam irradiation apparatus is illustrated. Actually, there are a high-voltage power source, an acceleration tube, a filament, a scanning coil, a scanning tube, an irradiation chamber, etc., but they are omitted. The lower end of the scanning tube 5 is an irradiation window 9. The present invention can also be applied to an area type electron beam irradiation apparatus instead of a scanning type. Since it is better to use a low energy electron beam, it can be said that it is more suitable for an area type electron beam irradiation apparatus.
[0025]
A small hole 8 is formed in a part of the horizontal plate 7 of the staircase portion 2 of the conveying plate 1. The small hole 8 may be a slit or a round hole. The duct is provided with a hose for guiding gas here, but the illustration is omitted here. The blowing gas is nitrogen or a rare gas. The gas guided to the duct 3 is blown out from the small hole 8 to above the stepped portion 2. The conveyance plate 1 has frames 10 and 10 on both sides and a frame 11 on the upstream side. Since the particles are transported, they are surrounded by a frame so that they do not spill from the back or side.
[0026]
FIG. 3 shows a staircase having slits 8 formed in a staggered manner. The slit length is about 20 mm to 30 mm, and the width is about 0.5 mm to 1 mm. The particles are soared by the wind blowing from here. Since it is an electromagnetic feeder, there are a motor and a vibration mechanism under the conveying plate 1, and asymmetric vibration having an amplitude in the front oblique direction is given to the conveying plate 1. Even if the conveying plate 1 is horizontal, the particles can be advanced by asymmetric vibration. In order to increase the transport speed, the transport plate 1 may be tilted forward as shown in FIG. The granular material 6 can roll on an inclined surface. The forward tilt angle θ is about 5 to 10 degrees. As described above, it may be 0 degree. Of course, the angle may be 0 to 5 degrees, but if it is such a low inclination, the forward effect by the inclination is small. An appropriate angle of θ can be selected depending on the type of grain.
[0027]
These transport mechanisms are inside X-ray shielding walls and containers, but the walls and containers are not shown. A granule 6 which is an object to be processed such as a food ingredient is guided to a granule input mechanism 4 at one end of an irradiation chamber (not shown). The granule 6 slides down here and falls to the start end of the conveying plate 1 in the irradiation chamber. Since the electromagnetic feeder generates a vibration having an amplitude in the front oblique direction, the granular material (particles) 6 travels leftward on the conveying plate 1. The particles are pushed up on the inclined surface and move while rolling. In the staircase portion 2, the granule 6 rotates as it falls down the step. The particles are swollen by the wind force blown from the small holes 8 in the horizontal plate 7. Rotate by soaring. The gas also has an effect of cooling the conveying plate in addition to the rotation of the particles.
[0028]
That is, in the staircase, the particles rotate by three different triggers.
1. It is picked up and rotated by vibration from a vibrating conveyor,
2. Rotating by spilling down the stairs,
3. It is blown up by gas, soars and rotates.
Thus, the novel device of the present invention exists where the particles are rotated by three means.
[0029]
There is an irradiation window 9 of the electron beam irradiation device immediately above the staircase portion 2. Here, the granular object is subjected to electron beam irradiation. A weak electron beam of about 100 keV to 300 keV hits only the surface, but the particles are soared, rolled, and spilled, so that they are rotated so that they rotate and hit the entire surface. In the case of sterilization of food, only the surface needs to be sterilized. In the case of electron beam sterilization, it is difficult to irradiate only the surface with an electron beam, but here, rotational force is given by three means.
[0030]
As shown in FIG. 4, the particles are blown and rolled up and pass directly under the irradiated part, so that the electron beam hits all surfaces. There is no inconvenience that an electron beam hits only one side of a grain.
The conveying plate is a metal plate such as a stainless steel plate. It is not altered by X-rays or ozone.
[0031]
【The invention's effect】
If you want to sterilize food ingredients with an electron beam, it is impossible to irradiate the entire surface with an electron beam, so even if only the particle surface needs to be irradiated, accelerated electrons will reach the back of the particle. Conventionally, a high energy electron beam was applied to completely pass through the particles.
[0032]
The present invention applies rotational force by spilling down a staircase, which is spun up by a vibrating conveyor to rotate the particles and rolls up and rotates the particles with gas. It is full of opportunities to cause rotational rolling disturbance fluctuation.
[0033]
Since irradiation can be performed while rotating the particles according to the present invention, the surface of the particles may be irradiated with an electron beam with the necessary acceleration energy. Irradiation is possible with a low energy accelerator. Low energy devices are cheaper and smaller than high energy devices. In addition, power consumption is low. Therefore, the irradiation cost can be reduced. In addition, when an electron beam enters inside, many proteins and lipids are altered and the flavor is lowered, resulting in a decrease in commercial value. Since the present invention successfully applies a low energy electron beam only to the surface, there is no risk of flavor deterioration and quality deterioration. It can be applied to any granular food. In other words, it is possible to irradiate an object for which irradiation inside the granule is not desirable. Although not applicable to foods unless the requirement of internal non-irradiation is met, this is possible with the present invention.
[0034]
If nitrogen gas that does not contain oxygen is used as the gas to be blown, the generation of ozone is suppressed and rust is suppressed. Not only that, but there is no possibility of the ozone smell moving into the particles. It is a meaningful invention.
[Brief description of the drawings]
FIG. 1 is a plan view of a conveyance plate of an electromagnetic feeder according to the present invention.
FIG. 2 is a cross-sectional view of the electromagnetic feeder of the present invention.
FIG. 3 is a partial plan view of a staircase portion of a transport plate according to the present invention.
FIG. 4 is a cross-sectional view showing a rolling state of a granular material at a conveying plate staircase according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conveyance plate 2 Staircase 3 Duct 4 Granule throwing mechanism 5 Scanning tube 6 Granule 7 Horizontal plate 8 Small hole 9 Irradiation window 10 Frame 11 Frame

Claims (1)

In an electron beam irradiation apparatus that generates and accelerates thermoelectrons in a vacuum and transports an object to be processed by a transport mechanism while irradiating the object with an electron beam, the object to be processed is a granule, and the transport mechanism is a vibration feeder. A step part having a small hole is formed in a part or the whole of the conveying plate of the vibration feeder, a duct for blowing gas is provided at the lower part of the step part, and the conveying plate is vibrated to advance the particles while rolling the stairs. Electrons characterized in that the particles are rotated by rolling down the particles, the particles are swirled and rotated by the gas blown from the staircase hole, and the rotating particle object is irradiated with an electron beam. Particle transport mechanism in a beam irradiation device.

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