JPH0117934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam sterilizer for continuously sterilizing thin plate-shaped objects having a relatively small area, such as carton base paper used as packaging materials.

As technology advances in goods distribution, the scope of application of the so-called one-way packaging system continues to expand, and paper cartons have come to be used in large numbers for packaging various beverages such as milk.

By the way, such cartons and other products intended for food and drink require sterilization treatment prior to use, and for this purpose conventionally, sterilization by immersion in hydrogen peroxide (H ₂ O ₂ ) or sterilization with ethylene oxide has been used. Chemical sterilization methods such as sterilization,
Physical sterilization methods such as radiation and ultraviolet rays were used.

However, these methods have various drawbacks, so in recent years, a sterilization method using electron beam irradiation has been proposed as a method to eliminate these drawbacks.
It has been put into practical use. This method sterilizes packaging materials by emitting high-energy electron beams accelerated by high voltage into the atmosphere through an electron beam-transmitting window. Because it does not require the use of electron beams, it is easy to use in-line and handle, and by increasing the energy of the electron beam, considerable penetrating power can be obtained, making it an excellent method for sterilizing packaging materials for food and beverages. Because of this, it has become widely used.

However, from a practical point of view, there is a limit to the increase in accelerating voltage, and therefore there is also a limit to increasing the energy of the electron beam, so the penetrating power of the electron beam is γ.
It cannot be expected to have a large penetrating power comparable to that of an electron beam, and as a result, such electron beam sterilizers have traditionally been limited to those that can be used for long strip-shaped packaging materials. Ta.

In other words, long strips of paper, plastic films, and other packaging materials are usually handled as rolls wrapped around a suitable spool or core material, and the rolls are sequentially rolled during sterilization and other treatments. If you pull out the packaging material while unwinding it, it will become part of the transport mechanism and be transported, so simply pulling the packaging material out of the roll while passing through the electron irradiation section will remove the front and back surfaces of the packaging material. It is now possible to sterilize the inside of the packaging material in-line, and it is now possible to sterilize the stacked packaging materials in-line at the same time by using high-energy electron beams that are practically available. Other than long strip-shaped packaging materials, for example, carton base paper used as the base for various beverage cartons (material paper cut into a specified shape from raw material paper, or which is further pasted onto a body and inflated into a cylindrical shape) In the case of packaging materials that are divided into relatively small shapes, such as those that have been prepared to Conventionally, packaging materials were held with claws or sandwiched between holding frames and conveyed using a chain conveyor, etc., for sterilization. Therefore, in principle, complete sterilization was not possible. However, from a practical point of view, sterilization of the transport mechanism and sterilization of the portion where the packaging material is in contact with the transport mechanism tends to be incomplete, and a sufficient sterilization effect cannot be expected.

Therefore, the conventional electron beam sterilizer has the disadvantage that it is difficult to obtain a device that can be expected to have a sufficient sterilizing effect on divided thin plate-shaped packaging materials.

In addition, equipment that uses a large amount of high-energy electron beams, such as an electron beam sterilizer, generates a large amount of radiation such as X-rays, so in such equipment, the irradiation chamber must be shielded. A widely used method is to irradiate an object with an electron beam, and then create a labyrinth of shielding material at the entrance and exit of the object to prevent X-rays from leaking outside.

However, if such a maze is set up,
When the object to be irradiated is in the form of a sheet, it is extremely easy to carry the object into and out of the irradiation chamber even if there is a maze. If each piece is held one by one using a suitable device as in the prior art, the structure of the labyrinth and the mechanism for transporting it through it become extremely complicated, which inevitably increases the cost considerably, and it is also insufficient. There was a drawback that there was a risk that the desired healing effect would not be achieved.

It is an object of the present invention to eliminate the drawbacks of the prior art described above, to provide a sufficient sterilization effect even to relatively small thin plate-like objects such as cartons, and to have a radiation-resistant effect with a simple structure. It is an object of the present invention to provide an electron beam sterilizer which can be sufficiently obtained.

In order to achieve this object, the present invention arranges a plurality of pairs of conveying rollers each consisting of two rollers in a straight line, moves a thin plate-like object with these pairs of conveying rollers, and has a radiation shielding function. It is characterized by the fact that it can be obtained.

The embodiments of the electron beam sterilizer according to the present invention will be described above with reference to the drawings.

FIG. 1 is a side view of the entire device showing an embodiment of the present invention partially in perspective, in which 1 is an electron beam irradiation device (hereinafter referred to as EB device), 2 is an electron beam (EB) transmission window, and 3 is a side view of the entire device. EB irradiation chamber, 4 a pair of conveyor rollers, 5 a carton magazine, 6 a carton stripper, 7,
8 is a carton pusher, 9 is a carton lifter, 1
0 is a conveyor, 11 is a packaging film, 12 is a film sealer, and 13 is a conveyor for carrying out.

Note that a ₁ to _{a 5} represent cartons undergoing sterilization treatment, and 4a and 4b represent the holding roller and drive roller of the transport roller pair 4.

EB device 1 is equipped with a high voltage power supply and uses high energy
EB is generated and radiated into an EB irradiation chamber 3 through an EB transmission window 2 made of a thin film such as titanium.

The conveyor roller pair 4 includes a drive roller 4b that is rotationally driven by a drive motor (not shown) or the like;
It consists of a holding roller 4a that is in contact with it from above with a predetermined pressing force, and these rollers 4
It functions to sandwich a carton between a and 4b and transport it in the direction of the arrow in the figure. As is clear from the figure, these plurality of conveyance roller pairs 4 are arranged so that the direction of conveyance of the carton by them passes through the center of the EB irradiation chamber 3 and forms a straight line on both sides thereof.

The carton stripper 6 has a suction device thereon, and moves up and down between the upper position shown by the broken line and sequentially strips the cartons stacked in the carton magazine 1. It works to extract things from the bottom.

Therefore, the cartons in the carton magazine 5 are first removed by the carton stripper 6.
After being taken out as carton a ₁ , the pusher 7 inserts the carton between the leftmost rollers 4a and 4b of the pair of conveyor rollers 4, and then the carton _a2 passes through the pair of conveyor rollers 4 in the direction of the arrow. ~a It is transported as shown in ₄ . And as shown in carton _A3
When passing through the EB irradiation chamber 3, sterilization is performed by receiving high-energy EB irradiation from the EB device 1.

The sterilized carton is placed on the rightmost conveyor roller pair 4.
The cartons are discharged onto the carton lifter 9 (indicated by the broken line), and after rising to the position shown in the figure, they are pushed in the direction of the arrow by the pusher 8, transferred from the conveyor 10 by the sealer 12, and are delivered to a predetermined number of sheets at a time. After wrapping with packaging film 11, conveyor 13
It will be carried out.

Next, FIG. 2 is an enlarged side sectional view showing the main parts of this embodiment, in which 20 is an EB irradiation part, 21
22 is a transport chamber on the supply side; 23 is a wall member made of a radiation-resistant material such as lead and forming the transport chambers 21 and 22;
24 is a sterile air outlet for cooling the EB transmission window 2, 25 is an air discharge passage, 26 is a cooling water pipe, 23a and 23b are inner wall surfaces of the wall member 23, and 23c and 23d are rollers 4a and 4b. This is a recess provided on the inner wall surface of the wall member 23 to accommodate the. Note that the EB device 1, EB transmission window 2, EB irradiation chamber 3, transport roller pair 4, holding roller 4a, drive roller 4b, cartons _a2 to _a4, etc. are the same as in FIG.

Each roller 4a, 4b forming the conveyance roller pair 4
are depressions 23c, 2 formed in the wall member 23.
3d, and among these, the upper holding roller 4a is displaced up and down as shown by the broken line when the cartons A ₂ to A ₄ are sandwiched and when it is not, and the upper holding roller 4a moves up and down as shown by the broken line. When the cartons _A2 to _A4 are sandwiched, the carton is separated from the lower drive roller 4b by the thickness of the carton _A2 to _A4 , as shown in FIG.
When the cartons _A2 to _A4 are not sandwiched, the upper holding roller 4a is in complete contact with the lower driving roller 4b, as shown in FIG. 4, so that there is no gap between them. . Note that these FIGS. 3 and 4 are for the transfer chamber 21 or 22 in FIG.
are views seen from the side, and in these views,
Reference numeral 27 indicates a limit switch provided on the shaft of the upper holding roller 4a, which is turned on and off in response to the vertical movement of the holding roller 4a.

Air that has been sterilized by a pre-filter or the like is introduced into the EB irradiation chamber 3 from the sterile air outlet 24, which cools the EB transmission window 2 and releases the EB.
To prevent the functionality of the device 1 from deteriorating. and,
The sterile air blown into this EB irradiation chamber 3 is
After cooling the EB transmission window 2, the transfer chamber 21,
It flows into the EB irradiation chamber 3 and the transport chambers 21 and 22 to maintain a pressure slightly higher than atmospheric pressure, that is, a so-called positive pressure. Note that control of the positive pressure within the transport chambers 21 and 22 at this time is performed by the air exhaust passage 25.
Also, it goes without saying that the inside of the device needs to be pre-sterilized before use, but in this case, there is no particular need to pre-sterilize the inside of the transport chamber 21 or to maintain its positive pressure. do not have. That is,
This is because unprocessed cartons are carried into the transport chamber 21, so even if a positive pressure is maintained, bacteria and the like will enter together with these cartons.
These bacteria are completely sterilized in the EB irradiation chamber 3, and the transport chamber 22 is completely sterile-shielded from the transport chamber 21 by the EB irradiation in the EB irradiation chamber 3.

The cooling water pipe 26 is for cooling the wall surface on which the EBs collide in the EB irradiation chamber 3, and serves to prevent damage to the carton due to temperature rise.

Therefore, as explained in FIG. 1, if the cartons are fed into the conveyance chamber 21 one after another at predetermined time intervals, the fed cartons _A2 , _A3 , _A4 , and so on are sequentially moved to the right side. The high-energy EB is transported to the
Exposure to irradiation results in a complete sterilization process. At this time, in the EB irradiation chamber 3, the carton _a3 is sent out from the pair of conveyor rollers 4 on the left side, and is sent from its tip to the pair of conveyor rollers on the right side 4 while sequentially receiving EB irradiation on its surface. Therefore, in the area where EB is irradiated, there are no parts such as claws for holding cartons or holding frames that would cast shadows on EB, and therefore, complete sterilization is possible with EB irradiation. .

Furthermore, in such an EB sterilization device, a large amount of radiation such as X-rays is generated in the EB irradiation section 20, particularly in the EB irradiation chamber 3. In other words, the basic property of high-energy charged particle beams such as EB is that they not only cause ionization loss when they interact with matter, but also cause radiation loss due to the particles' own bremsstrahlung radiation, which generates a large amount of radiation. It is. The spectrum of radiation emitted at this time extends from X-rays to γ-rays, and is extremely harmful, so adequate protection is required.

In order to do this, it is possible to install a hardening material such as lead or concrete, but such EB
Sterilizers require a passageway for transporting cartons and other objects to be sterilized into and out of the EB irradiation chamber, which makes it difficult to thoroughly empty and clean this area, and it is also difficult to transport objects to be sterilized. easy to become

However, in the above embodiment, since all the conveying roller pairs 4 are arranged so that the moving direction of the carton is in a straight line, the conveying of the carton is carried out extremely smoothly. etc. are completely unnecessary. On the other hand, the upper and lower sides of each of the rollers 4a and 4b constituting the transport roller pair 4 are located in the recess 2 of the wall member 23.
3c and 23d, and among these, the upper holding roller 4a is in close contact with the lower driving roller 4b when the carton is not sandwiched between these rollers. All radiation such as X-rays that has entered the transport chambers 21 and 22 from the chamber 3 is suppressed by the transport roller pair 4, and there is no risk of leaking into the carton supply and discharge side passages. . That is, as already explained, since the operation of feeding cartons into the transport chamber 21 is performed sequentially at predetermined time intervals, the EB In the transport chambers 21, 22 including the irradiation chamber 3, the cartons are positioned a predetermined distance apart, as indicated by _a2 to _a4 . Therefore, in the conveyance chambers 21 and 22, there is always a plurality of conveyance roller pairs 4 that do not sandwich a carton, and these rollers 4a and 4b
Since they are in close contact with each other, radiation from the EB irradiation chamber 3 can be completely prevented from leaking out from between the rollers 4a and 4b.

In addition, each roller 4a, 4b and depressions 23c, 2
Although there is a considerable gap between 3d and
This gap is not in a straight line with respect to the direction of radiation leakage, but is shaped along the surfaces of the rollers 4a and 4b. For this reason, the X that invaded this part
Radiation such as a line repeats reflection and refraction multiple times between the surfaces of the rollers 4a and 4b and the surface of the wall member 23, and is greatly attenuated and its intensity is significantly reduced, so that practically no leakage occurs. It becomes like this.

Therefore, according to the above embodiment, although the conveyance path of the thin plate-like object such as a carton is made into a straight line so that the conveyance can be carried out sufficiently smoothly and reliably, Radiation protection can be achieved almost completely.

By the way, in such an EB sterilizer, the EB irradiation section and the loading/unloading section of the objects to be sterilized are strictly sealed and sealed, so it is difficult to check the transportation condition of the objects to be sterilized in this section. It is difficult to monitor, and for this purpose, for example, it is necessary to provide a viewing window made of radiation-resistant glass or use an industrial television camera, which tends to increase costs.

However, according to the embodiment described above, the conveyance state of the carton in the conveyance chambers 21 and 22 and the EB irradiation chamber 3 can be easily monitored.
That is, in FIGS. 3 and 4, 27 is a limit switch for detecting the vertical position of the shaft of the upper holding roller 4a, and as shown in FIG. When the carton is inserted and the shaft of the holding roller 4a moves in the direction of the arrow, and as shown in FIG. The contact switching state operates differently depending on the direction of movement.

Therefore, if this limit switch 27 is provided in all the conveyor roller pairs 4 or some of them, the contact switching state of the limit switch 27 can be
The position of the carton in the transport chambers 21 and 22 including the EB irradiation chamber 3 can be known, and the operation can be monitored.

For example, if the contact is turned on when the limit switch 27 is in the state shown in Figure 3, and an indicator lamp is provided that lights up when the limit switch 27 is turned on, the location of the carton can be determined by the lighting of the indicator lamp. Become.

In addition, in such an EB sterilizer, it is necessary to maintain the inside of the transfer chamber including the EB irradiation chamber at a pressure slightly higher than atmospheric pressure, so-called positive pressure, to prevent bacteria from entering the inside. In the above embodiment, the sterile air outlet 24 for this purpose is connected to the EB transmission window 2.
The EB transmitting window 2 is cooled by the air blown in from the EB transmitting window 2.
This prevents a rise in temperature of the EB device 1 and prevents the deterioration of the function of the EB device 1, and also maintains the above-mentioned positive pressure with this sterile air, which simplifies the mechanism and facilitates cost reduction.

Furthermore, according to this embodiment, the transport chamber 2
1 and 22 are in a straight line and there is no maze, etc., so their internal volume is relatively small, which reduces the amount of sterile air inflow required to maintain the positive pressure mentioned above. This has the effect of requiring less energy for operation.

As explained above, according to the present invention, EB sterilization is possible without holding thin plate-like objects such as cartons with claws or holding frames, and there is no need for a labyrinth for radiation shielding. , it is possible to provide at low cost an EB sterilizer that has a complete sterilization effect, has a simple configuration, is easy to monitor its operation, and is useful for energy saving, except for the drawbacks of the conventional technology.

[Brief explanation of drawings]

FIG. 1 is a partially transparent side view of an embodiment of an electron beam sterilizer according to the present invention, FIG. 2 is a partially enlarged side cross-sectional view, and FIGS. 3 and 4 show a pair of conveying rollers. It is an operation explanatory diagram. 1...Electron beam irradiation device (EB device), 2...Electron beam transmission window, 3...Electron beam irradiation chamber, 4...Transport roller pair, 4a...Holding roller, 4b...Drive roller, 21, 22 ...Conveyance chamber, 23...Wall member, 23a, 23b...Inner wall surface, 23c, 23d
... recess, 24 ... sterile air outlet.

Claims (1)

[Scope of Claims] 1. In an electron beam sterilizer that sterilizes a thin plate-like object by sequentially irradiating it with an electron beam one by one while conveying the object, the thin plate-like object is held and moved in a direction parallel to its surface. a radiation-resistant member having a recessed portion for accommodating at least a portion of each roller of the plurality of conveyance roller pairs, and the plurality of conveyance rollers. roller holding means for holding one roller of the pair movably in a direction away from the other roller; pressing means for elastically pressing the one roller against the other roller; Transport chambers are arranged and housed on both sides of the electron beam irradiation unit at predetermined intervals so that the object movement direction is in a straight line, and a thin plate-shaped object is moved onto a pair of transport rollers arranged in a straight line at a predetermined distance. An electron beam sterilizer characterized in that it is configured to perform sterilization treatment by supplying electricity at time intervals. 2. In claim 1, a sterile air blowing section is provided around the electron beam emitting port provided in the electron beam irradiation section, and the method is configured to cool the electron beam emitting port and maintain positive pressure within the sterilizer. An electron beam sterilization device characterized in that it is configured to perform sterilization with an electron beam. 3. The electron beam sterilizer according to claim 2, further comprising means for detecting the movement of one of the rollers to enable monitoring of the sterilization operation.