WO2016114108A1

WO2016114108A1 - Electron beam sterilization system having non-stationary external sterilization emitters moving relative to sterilization objects

Info

Publication number: WO2016114108A1
Application number: PCT/JP2016/000037
Authority: WO
Inventors: Kaveh Bakhtari
Original assignee: Hitachi Zosen Corporation
Priority date: 2015-01-14
Filing date: 2016-01-06
Publication date: 2016-07-21
Also published as: JP2018503565A; JP2018502020A; JP2018508933A; WO2016113807A1; WO2016114107A1

Abstract

To efficiently sterilize an outer surface of a sterilization object such as a container of beverage, foods, and pharmaceutical. An electron beam sterilization system of the present invention is an electron beam sterilization system that sterilizes a sterilization object (C) during transport thereof along a transport passage (R). The electron beam sterilization system includes an external sterilization emitter that performs sterilization by irradiating an outer surface of the sterilization object (C) with electron beams and a relative movement device that relatively moves the sterilization object (C) and the external sterilization emitter in a direction different from a direction along the transport passage (R) when the outer surface of the sterilization object (C) is sterilized.

Description

ELECTRON BEAM STERILIZATION SYSTEM HAVING NON-STATIONARY EXTERNAL STERILIZATION EMITTERS MOVING RELATIVE TO STERILIZATION OBJECTS

The present invention relates to a sterilization system that sterilizes a sterilization object such as containers used for packaging of foods, beverage, and pharmaceutical.

The sterilization here refers to a method of disinfection, rendering aseptic or bacteria elimination. In packaging of foods, beverage and pharmaceutical, sterilization is performed for destroying bioburden in order to extend storage lives of the products and to ensure safe and easy distribution of the products. Thus, safe sterilization is required for containers of beverage and foods or containers for pharmaceutical.

In recent years, a sterilization method using electron beams is considered to be extremely advantageous as compared with the other sterilization methods. The sterilization method using an electron beam emitter capable of irradiation of electron beams is quick and highly reliable. In the sterilization method using chemicals, the chemical after use might give a negative influence on the environment and thus, treatment of liquid wastes and discharge air is needed, and the treatment is difficult and expensive. Since the electron beam sterilization system provided with such an electron beam emitter does not use chemicals, the chemical does not remain in a sterilized container, therefore higher consumer safety levels are achieved.

The electron beam sterilization system that sterilizes containers for foods, beverage, and pharmaceutical is described in

Patent Literatures

1 and 2, for example. An electron beam sterilization system 5 described in

Patent Literatures

1 and 2 includes, as illustrated in FIGS. 14 to 16, a first external sterilization emitter E3, a second external sterilization emitter E4, an internal sterilization emitter having a nozzle 24a, transport devices M0 to M3, and a radiation shield S. Black circle portions in FIG. 14 indicate the nozzles 24a of the internal sterilization emitters. In FIG. 16, in the internal sterilization emitter, only the nozzle 24a portions are illustrated, while the other portions are omitted.

The transport devices M0 to M3 have, as illustrated in FIG. 14, holding arms A and continuously transport containers C along a transport passage R while the holding arm A holds the container C. The external sterilization emitters E3 and E4 are, as illustrated in FIG. 15, flat emitters capable of irradiation of the electron beams to a wide range and perform sterilization by irradiating the outer surface of the container C with the electron beams while the holding arms A of the transport devices M0 to M3 hold the containers C. The first external sterilization emitter E3 sterilizes one half of the entire outer surface of the container C, while the second external sterilization emitter E4 sterilizes the remaining half of the entire outer surface of the container C. The internal sterilization emitter sterilizes an inner surface of the container C by the electron beams irradiated from the nozzle 24a while the nozzle 24a is inserted into the container C as illustrated in FIG. 16.

[Patent Literature 1] Japanese Patent Publication No. 2011-201600
[Patent Literature 2] International Publication No. WO 2014/095842

However, in the related art electron beam sterilization system 5, the entire outer surface of the container C is sterilized by the fixed external sterilization emitters E3 and E4. That is, when the outer surface of the container C is sterilized, the sterilization object C and the external sterilization emitters E3 and E4 relatively move only in a direction in which the container C is transported. Thus, distances between the container C and the external sterilization emitters E3 and E4 are different in each portion of the container C.
For example, if the container C has a neck part and a body part, the neck part of the container C has larger distances from the external sterilization emitters E3 and E4, while the body part of the container C has smaller distances from the external sterilization emitters E3 and E4. In order to reliably sterilize the neck part having the large distance, irradiation intensities of the external sterilization emitters E3 and E4 are to be increased or a transport speed of the container C is to be lowered. But then, the body part is excessively irradiated with the electron beams, and undesirably, sterilization of the outer surface of the container C becomes non-uniform.
The present invention has an object to uniformly sterilize the outer surface of the sterilization object such as a container.

An electron beam sterilization system of the present invention is to solve the problem and is an electron beam sterilization system that sterilizes a sterilization object during transport thereof along a transport passage and including an external sterilization emitter that performs sterilization by irradiating an outer surface of the sterilization object with electron beams and a relative movement device that relatively moves the sterilization object and the external sterilization emitter in a direction different from a transport direction along the transport passage when the outer surface of the sterilization object is sterilized.

According to the electron beam sterilization system of the present invention, the entire outer surface of the sterilization object is sterilized by the external sterilization emitter capable of relative movement with respect to the sterilization object. Thus, in accordance with relative positions of the sterilization object and the external sterilization emitter, irradiation intensity or a transport speed of the external sterilization emitter can be controlled. As a result, uniform sterilization on the entire outer surface of the sterilization object is made possible.

FIG. 1 is a plan view of an electron beam sterilization system according to embodiments of the present invention.

FIG. 2 is a view for explaining structures and operations of an external sterilization emitter and an internal sterilization emitter of the electron beam sterilization system.

FIG. 3 is a view illustrating a part of the electron beam sterilization system and is a B-BB sectional view in FIG. 1.

FIG. 4 is a sectional schematic view of the external sterilization emitter and the internal sterilization emitter of the electron beam sterilization system.

FIG. 5 is a view for explaining structures and operations of an external sterilization emitter and an internal sterilization emitter in another aspect of the present invention.

FIG. 6 is a view for explaining structures and operations of an external sterilization emitter and an internal sterilization emitter in another aspect of the present invention.

FIG. 7 is a view for explaining structures and operations of an external sterilization emitter and an internal sterilization emitter in another aspect of the present invention.

FIG. 8A is a view illustrating another aspect of a nozzle of an external sterilization emitter of the present invention.

FIG. 8B is a view for explaining a state in which electron beams are irradiated from a window portion in the external sterilization emitter illustrated in FIG. 8A.

FIG. 9A is a view illustrating another aspect of a nozzle of an external sterilization emitter of the present invention.

FIG. 9B is a view for explaining a state in which electron beams are irradiated from a window portion in the external sterilization emitter illustrated in FIG. 9A.

FIG. 10 is a view illustrating a distance between the window portion and a sterilization object in different irradiation intensities of an electron beam emitter and a relative dosage to the sterilization object of the electron beam emitter.

FIG. 11 is a plan schematic view illustrating another aspect of an electron beam sterilization system of the present invention.

FIG. 12 is a plan schematic view illustrating another aspect of an electron beam sterilization system of the present invention.

FIG. 13 is a plan schematic view illustrating another aspect of an electron beam sterilization system of the present invention.

FIG. 14 is a plan view of a related art electron beam sterilization system.

FIG. 15 is a view for explaining an external sterilization emitter of the related art electron beam sterilization system.

FIG. 16 is a view for explaining an internal sterilization emitter of the related art electron beam sterilization system.

Embodiment 1
First, an electron beam sterilization system and an electron beam sterilization method according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings. The electron beam sterilization system 1 according to the embodiment of the present invention includes an external sterilization emitter E1 (see FIG. 4) having a nozzle 14a, an internal sterilization emitter E2 (see FIGS. 3 and 4) having a nozzle 24a, a radiation shield S (see FIG. 1), and first to third transport devices M1 to M3 (see FIG. 1) as illustrated in FIGS. 1 to 4. Black circle portions in FIG. 1 indicate the nozzles 14a of the external sterilization emitters or the nozzles 24a of the internal sterilization emitters. In FIGS. 1 and 2, in the external sterilization emitter and the internal sterilization emitter, only the nozzle portions are illustrated, while the other portions are omitted.

The external sterilization emitter E1 is a device that performs sterilization by irradiating an outer surface of a sterilization object C with electron beams. The internal sterilization emitter E2 is a device that performs sterilization by irradiating an inner surface of the sterilization object C with the electron beams. The sterilization object C is a container for packaging beverage, foods, and pharmaceutical, for example, or a preform thereof or the like. The first to third transport devices M1 to M3 transport the sterilization object C while holding it. Specifically, the transport devices M1 to M3 have, as illustrated in FIG. 1, circular first to third turning tables T1 to T3 and holding arms A connected to outer peripheries of the turning tables T1 to T3. While the holding arm A grips and holds a neck part of the sterilization object C, the turning tables T1 to T3 turn so that the sterilization object C is transported.

An arrow R in FIG. 1 indicates a transport passage of the sterilization object C. As indicated by the transport passage R, when the holding arms A connected to the different turning tables T1 to T3 are brought close to each other, the sterilization object C is transferred from the holding arm A of one of the turning tables to the holding arm A of the other turning table, whereby the sterilization object C is transported so as to follow a circular passage.

Above the second turning table T2 of the second transport device M2, as illustrated in FIG. 3, a mount plate T21 is provided. The second turning table T2 and the mount plate T21 are mounted on a common rotating shaft T22 so that each one of them is turnable around the rotating shaft T22. At a position above the holding arm A in the mount plate T21, the internal sterilization emitter E2 is provided. Between the second turning table T2 and the holding arms A, an elevating mechanism T23 is provided, respectively. The rotating shaft T22, the elevating mechanism T23, and the internal sterilization emitter E2 are connected to a control unit CU, respectively.

The control unit CU rotates the rotating shaft T22, whereby the internal sterilization emitter E2 turns with the sterilization object C. During this period, the control unit CU causes the elevating mechanism T23 to be moved up/down in a axial direction V so as to also move the sterilization object C held by the holding arm A up/down. As a result, the nozzle 24a of the internal sterilization emitter E2 is inserted into the sterilization object C. In this state, the control unit CU causes the internal sterilization emitter E2 to irradiate electron beams. As a result, as illustrated in FIG. 2, the electrons irradiated from the nozzle 24a are scattered in the air and form electron cloud, and the internal sterilization emitter E2 sterilizes the inner surface of the sterilization object C.

The external sterilization emitter E1 is provided on the mount plate T21 similarly to the internal sterilization emitter E2 but is provided at a position other than the position above the holding arm A. Specifically, the external sterilization emitters E1 are arranged on the transport passage R and between the internal sterilization emitters E2 as illustrated in FIG. 1. That is, the external sterilization emitters E1 and the internal sterilization emitters E2 are aligned alternately on the transport passage R at an equal pitch. The control unit CU causes the rotating shaft T22 to rotate, whereby the external sterilization emitter E1 is turned with the sterilization object C. The external sterilization emitter E1 is connected to the control unit CU, and the control unit CU causes the external sterilization emitter E1 to irradiate electron beams. As a result, as illustrated in FIG. 2, the electrons irradiated from the nozzle 14a are scattered in the air and form electron cloud, and the external sterilization emitter E1 sterilizes the outer surface of the sterilization object C. As a result, when the external sterilization emitter E1 sterilizes the outer surface, too, the sterilization object C can be moved in the axial direction V by the elevating mechanism T23 of the transport device M2.

When the external sterilization emitter E1 and the internal sterilization emitter E2 irradiate electron beams, radiation such as X-rays harmful to human bodies is generated. The radiation shield S illustrated in FIG. 1 is to surround a part of the transport passage R in order to shield such radiation. By surrounding the part of the transport passage R by the radiation shield S, a plurality of sterilization enclosures R1 to R3 are formed. Each of the transport devices M1 to M3 is provided inside of each of the sterilization enclosures R1 to R3, respectively. All the external sterilization emitters E1 and the internal sterilization emitters E2 are provided in the same sterilization enclosures R2.

Subsequently, specific constitutions of the external sterilization emitter and the internal sterilization emitter according to this embodiment will be described with reference to FIG. 4. The external sterilization emitter E1 includes a power supply 11, a cathode 12, a electron lens 13, a flange 14, and a chamber 15. The internal sterilization emitter E2 also includes a power supply 21, a cathode 22, an electron lens 23, a flange 24, and a chamber 25 similar to the external sterilization emitter E1.

The cathode 12 (22) is connected to the power supply 11 (21), and the ‘duality of cathode 12 (22) and electron lens 13’ has a negative potential by a voltage applied from the power supply 11 (21). When an electric current is supplied from the power supply 11 (21) to the cathode 12 (22), heat is given to the cathode 12 (22). Since the heat is given to the cathode 12 (22), electrons inside the cathode 12 (22) are excited.

The flange 14 (24) has the nozzle 14a (24a). The flange 14 (24) is grounded and has a potential higher than that of the ‘duality of cathode 12 (22) and electron lens 13’ which has a negative potential when a voltage is applied. As a result, an electric field is generated in a direction from the flange 14 (24) toward the cathode 12 (22). The electric field may be intensified by increasing acceleration voltage between the ‘duality of cathode 12 (22) and electron lens 13’ and the flange 14 (24).

The chamber 15 (25) surrounds the cathode 12 (22) and the electron lens 13 (23). At the tip end surface of the nozzle 14a (24a) of the flange 14 (24), a window portion 14b (24b) capable of transmitting the electron beams is provided. The flange 14 (24) and the chamber 15 (25) form a closed space. This space is kept in a vacuum state by a vacuum pump 15a (25a) connected to the chamber 15 (25).

The electron lens 13 (23) is a conductor of metal or the like and surrounds the cathode 12 (22) except at an aperture 13a (23a). The electron lens 13 (23) is connected to the power supply 11 (21) similarly to the cathode 12 (22) and has an electric potential substantially the same as that of the cathode 12 (22).

Since the electron lens 13 (23) is a conductor, the electric field from the flange 14 (24) toward the cathode 12 (22) is shielded except a spot where the aperture 13a (23a) is formed. In other words, the electric field from the flange 14 (24) toward the cathode 12 (22) acts only on the portion of the cathode 12 (22) located at the spot where the aperture 13a (23a) is formed. The electrons excited on the cathode 12 (22) are emitted from a portion of the cathode 12 (22) on which the electric field acts, and the electron beams are irradiated to an outer side of the sterilization emitter E1 (E2) through the aperture 13a (23a), the nozzle 14a (24a), and the window portion 14b (24b).

That is, the external sterilization emitter E1 and the internal sterilization emitter E2 are to accelerate the electrons excited by heat by applying the electric field and are so-called thermionic emission type electron beam emitters. Irradiation intensity of the electron beams of this type of electron beam emitter depends on a current value supplied to the cathode 12 (22) or a value of an electric field (acceleration voltage) between the cathode 12 (22) and the flange 14 (24). Such current value or the value of the acceleration voltage is controlled by the control unit CU (see FIG. 3). As a result, the control unit CU can control the irradiation intensity of the electron beams of the external sterilization emitter E1 and the internal sterilization emitter E2.

According to the electron beam sterilization system 1 of this embodiment, when the external sterilization emitter E1 sterilizes the outer surface of the sterilization object C, the sterilization object C is moved up/down in the axial direction V. Thus, in the axial direction V, sterilization on the entire outer surface of the sterilization object C can be made uniform. In the related art electron beam sterilization system illustrated in FIGS. 14 and 15, for example, the entire outer surface of the sterilization object C is sterilized by the fixed external sterilization emitters E3 and E4. That is, when the outer surface of the sterilization object C is sterilized, the sterilization object C and the external sterilization emitters E3 and E4 relatively move only in the direction in which the sterilization object C is transported.

Thus, the distances between the sterilization object C and the external sterilization emitters E3 and E4 are different among portions of the sterilization object C. If the sterilization object C has a neck part and a body part, for example, the neck part of the sterilization object C has larger distances from the external sterilization emitters E3 and E4, while the body part of the sterilization object C has smaller distances from the external sterilization emitters E3 and E4. In order to reliably sterilize the neck part having the large distance, irradiation intensities of the external sterilization emitters E3 and E4 are to be increased or a transport speed of the sterilization object C is to be lowered. Consequently, the body part is excessively irradiated with the electron beam, and unfortunately, sterilization of the outer surface of the sterilization object C becomes non-uniform.

Regarding this point, according to the electron beam sterilization system of this embodiment, when the outer surface of the sterilization object C is sterilized, since the sterilization object C is moved up/down in the axial direction V, the relative heights of the sterilization object C and the external sterilization emitter E1 are also changed in sterilization of the outer surface of the sterilization object C. Thus, the irradiation intensity of the external sterilization emitter E1 or the moving speed of the sterilization object C can be controlled in accordance with the relative heights of the sterilization object C and the external sterilization emitter E1. That is, when the window portion 14b of the external sterilization emitter E1 is located in the vicinity of the neck part, the neck part can be reliably sterilized by increasing the irradiation intensity of the external sterilization emitter E1 or by lowering the moving speed of the sterilization object C. As a result, the sterilization of the entire outer surface of the sterilization object C can be made uniform in the axial direction V. The control unit CU can control the irradiation intensity of the external sterilization emitter E1 or the moving speed of the sterilization object C in accordance with the height of the sterilization object C.

A position where moving up/down of the sterilization object C is started is preferably within a region where the sterilization object C is not affected by the electron beams irradiated from the external sterilization emitter E1. In this case, sterilization of the entire outer surface of the sterilization object C can be made further uniform. Assume that, at a given time when sterilization of the outer surface of the sterilization object C is started, the window portion 14b of the external sterilization emitter E1 is located in the vicinity of the height of the body part of the sterilization object C. At this time, if the moving up/down of the sterilization object C has not been started yet, that is, if the sterilization object C is stationary in the axial direction V, the body part of the sterilization object C is affected by the electron beams for a period of time longer than the other portions. Thus, the electron beams are excessively irradiated to the body part of the sterilization object C, and sterilization of the entire outer surface of the sterilization object C might be non-uniform.

Regarding this point, if the position in which moving up/down of the sterilization object C is started is within the region where the sterilization object C is not affected by the electron beams irradiated from the external sterilization emitter E1, such a situation that a portion of the sterilization object C is affected by the electron beams for a period of time longer than the other portions can be prevented. As a result, sterilization of the entire outer surface can be made further uniform. For the same reason, a position in which the moving up/down of the sterilization object C is finished is preferably within the region where the sterilization object C is not affected by the electron beams irradiated from the external sterilization emitter E1. Here, an example of the "region not affected by the electron beams" includes a region away from the window portion 14b of the external sterilization emitter E1 to such a degree that it is not affected by the electron beams, a region partitioned by a shielding structure for shielding the electron beams or the like from the window portion 14b of the external sterilization emitter E1.

According to the electron beam sterilization system 1 according to this embodiment, the external sterilization emitter E1 is moved in a direction of transport together with the sterilization object C. As a result, efficiency of sterilization treatment of the sterilization object C can be improved. In a related art electron beam sterilization system 5 illustrated in FIG. 14, for example, since the external sterilization emitters E3 and E4 are fixed, respectively, the distances between the sterilization object C and the external sterilization devices E3 and E4 change as time elapses. Thus, in order to sufficiently sterilize the outer surface of the sterilization object C, it is necessary to increase the electron beam intensities of the external sterilization emitters E3 and E4 or to lower the transport speed of the sterilization object C, which lowers efficiency of the sterilization treatment of the sterilization object. Specifically, in the related art electron beam sterilization system 5, if the transport speed of the sterilization object C is increased, a period of time during which the external sterilization emitters E3 and E4 are located close to the sterilization object C becomes short. Thus, in order to perform sufficient external sterilization of the sterilization object C, the intensities of the electron beams of the external sterilization emitters E3 and E4 need to be increased.

Regarding this point, according to the electron beam sterilization system 1 according to this embodiment, since the external sterilization emitter E1 moves in the transport direction together with the sterilization object C, the distance between the sterilization object C and the external sterilization emitter E1 in the transport direction can be made constant. Thus, the outer surface of the sterilization object C can be sterilized regardless of the transport speed of the sterilization object C. As a result, efficiency of sterilization treatment of the sterilization object C can be improved as compared with the related art electron beam sterilization system 5. By increasing the transport speed of the sterilization object C in the electron beam sterilization system 1 according to this embodiment, too, for example, the external sterilization emitter E1 is also moved in the direction of transport together with the sterilization object C and thus, time during which the external sterilization emitter E1 is located close to the sterilization object C can be sufficiently obtained. Thus, even if the transport speed of the sterilization object C is increased, the intensity of the external sterilization emitter E1 does not have to be increased.

As compared with the related art electron beam sterilization system, since the time during which the external sterilization emitter E1 is located close to the sterilization object C is long, even if the irradiation intensity of the electron beams of the external sterilization emitter E1 is lowered, the outer surface of the sterilization object C can be sufficiently sterilized. As a result, energy required for sterilization of the outer surface can be reduced, and efficiency of external sterilization can be improved.

Here, since the external sterilization emitter E1 and the internal sterilization emitter E2 are both nozzle emitters, they can both have the same structure and specification. For example, in the related art electron beam sterilization system illustrated in FIGS. 14 to 16, the external sterilization emitters E3 and E4 are flat emitters, while the internal sterilization emitter is a nozzle emitter. Thus, the specifications of the external sterilization emitter and the internal sterilization emitter are largely different from each other, which causes the entire system to be complicated. On the other hand, by applying the same specification to the external sterilization emitter E1 and the internal sterilization emitter E2, the system can be simplified. The structure of the nozzle 14a of the external sterilization emitter E1 may be made different from that of the nozzle 24a of the internal sterilization emitter E2.

For example, as illustrated in FIG. 5, a diameter D1 of the nozzle 14a of the external sterilization emitter may be made larger than a diameter D2 of the nozzle 24a of the internal sterilization emitter. The nozzle 24a of the internal sterilization emitter is designed so as to be able to be inserted into the sterilization object C, but the nozzle 14a of the external sterilization emitter is not inserted into the sterilization object C. Thus, there is no such restriction and moreover, if the diameter of the nozzle 14a is made larger, the electron cloud can be scattered farther in the periphery, and it is considered that the outer surface of the sterilization object C can be sterilized more easily.

As illustrated in FIG. 6, a length L1 of the nozzle 14a of the external sterilization emitter may be made smaller (shorter) than a length L2 of the nozzle 24a of the internal sterilization emitter. In this case, an upper part of the sterilization object C is easily sterilized. On the other hand, as illustrated in FIG. 7, the length L1 of the nozzle 14a of the external sterilization emitter may be made larger (longer) than the length L2 of the nozzle 24a of the internal sterilization emitter. In this case, a lower part of the sterilization object C is easily sterilized. Here, the length L1 of the external sterilization emitter E1 and the length L2 of the internal electron beam emitter E2 are assumed to mean the length of the nozzle 14a (24a) protruding from the lower surface of the mount plate T21 (see FIG. 3). Therefore, even if the external sterilization emitter E1 and the internal sterilization emitter E2 have the same nozzle, if the lengths of the nozzles protruding from the lower surface of the mount plate T21 are different, the length L1 of the nozzle 14a of the external sterilization emitter E1 and the length L2 of the nozzle 24a of the internal sterilization emitter E2 are different.

As described above, the window portion 14b that enables transmission of the electron beams is provided on the tip end surface of the nozzle 14a of the external sterilization emitter. Here, as illustrated in FIGS. 8A and 9A, the nozzle 14a of the external sterilization emitter may have another window portion 14c provided on a side surface in the periphery of the tip end surface in addition to the window portion 14b provided on the tip end surface. By providing the window portion 14c on the side surface in the periphery of the tip end surface of the nozzle 14a of the external sterilization emitter, as illustrated in FIGS. 8B and 9B, since the electron cloud irradiated from the external sterilization emitter is emitted to the periphery of the nozzle 14a, it is thought that the outer surface of the sterilization object C can be sterilized easily. Regarding the tip end shape of the nozzle 14a, it may have a tapered shape with a narrowed tip end as illustrated in FIGS. 8A and 8B or may have a cylindrical shape as illustrated in FIGS. 9A and 9B.

Moreover, the irradiation intensity of the external sterilization emitter E1 may be controlled so as to be different from the irradiation intensity of the internal sterilization emitter E2. The irradiation intensity of the external sterilization emitter E1 is controlled by the control unit CU on the basis of a graph illustrated in FIG. 10, for example. A lateral axis of the graph illustrated in FIG. 10 indicates a distance [mm] in the air from the window portion of the nozzle of the electron beam emitter to the sterilization object C. A vertical axis of the graph illustrated in FIG. 10 indicates a relative dosage of the electron beams irradiated from the electron beam emitter to the sterilization object C. This relative dosage indicates an index on whether or not the sterilization object C can obtain sufficient sterilization effects.

As described above, the electrons irradiated from the window portion are scattered in the air so as to form the electron cloud, but as the distance from the window portion becomes larger, energy is lost gradually. The dose is a function of the beam current, electron energy and exposure time. An amount of energy loss of the electrons depends on the electron energy of the electron beams of the electron beam emitter. If the electron energy of the electron beams is 90 keV as illustrated in FIG. 10, for example, when the distance between the window portion of the nozzle and the sterilization object C becomes 50 mm, the relative dosage is approximately 15%, and the sterilization effect cannot be sufficiently obtained. On the other hand, if the electron energy of the electron beams is 175 keV, even when the distance between the window portion of the nozzle and the sterilization object C is 100 mm, the relative dosage becomes approximately 100%, and sufficient sterilization effect is obtained.

Regarding the internal sterilization emitter E2, the distance from the window portion 24b thereof to the sterilization object C is 4 mm, for example. In this case, energy of the electrons lost by scattering is negligible. On the other hand, the external sterilization emitter E1 might be provided at a position where the distance from the window portion 14b thereof to the sterilization object C is 100 mm, for example. In this case, if the electron energy of the external sterilization emitter E1 is 125 keV, the relative dosage is approximately 40%, and a sufficient sterilization effect cannot be obtained. On the other hand, by increasing the electron energy of the external sterilization emitter E1 to 150 keV, the relative dosage is approximately 80% or by increasing it to 175 keV, the relative dosage is approximately 100%, and a sufficient sterilization effect can be obtained.

Moreover, instead of the increase of the electron energy of the external sterilization emitter E1 or at the same time as that, by arranging the window portion 14b so that the distance between the window portion 14b of the external sterilization emitter E1 and the sterilization object C becomes small, too, the sufficient sterilization effect can be obtained. If the distance between the nozzle 14b of the external sterilization emitter E1 and the sterilization object C is 25 mm, for example, when the electron energy of the electron beams of the external sterilization emitter E1 is 110 keV, the relative dosage is 80% or more, and the outer surface of the sterilization object C can be effectively sterilized. In order to effectively sterilize the outer surface of the sterilization object C, it is only necessary that the window portion 14b of the external sterilization emitter E1 is arranged or the electron energy of the external sterilization emitter E1 is controlled so that the relative dosage becomes 60% or more or more preferably 80% or more.

In the electron beam sterilization system 1 according to this embodiment, the aspect in which the external sterilization emitter E1 and the internal sterilization emitter E2 are arranged alternately on the transport passage R is described but that is not limiting. For example, two units of the external sterilization emitters E1 may be continuously provided with respect to one unit of the internal sterilization emitter E2. Moreover, the internal sterilization emitter E2 needs to be provided on the transport passage R since the nozzle 24a thereof is inserted into the sterilization object C, but the external sterilization emitter E1 does not have to be arranged on the transport passage R.

For example, as illustrated in FIG. 11, the nozzles 14a of the external sterilization emitters may be provided so as to surround four sides around the nozzle 24a of the internal sterilization emitter on a plan view, or as illustrated in FIG. 12, the nozzles 14a of the external sterilization emitters may be provided so as to surround three sides around the nozzle 24a of the internal sterilization emitter on a plan view. If the distance between the nozzle 14a of the external sterilization emitter and the sterilization object C is short and the number of external sterilization emitters is larger, the outer surface of the sterilization object C can be sterilized more reliably.

In the electron beam sterilization system according to this embodiment, the aspect in which the transport devices M1 to M3 transport the sterilization object C so that the sterilization object C follows the circular transport passage R is described, but that is not limiting. For example, as illustrated in FIG. 13, instead of the transport devices M1 to M3, a transport device M4 such as a conveyer or the like for transporting the sterilization object C so that the sterilization object C follows a linear transport passage R' may be employed. The nozzles 24a of the internal sterilization emitters are continuously arranged on the linear transport passage R'. The nozzles 14a of the external sterilization emitters may be arranged so that the nozzles 24a of the internal sterilization emitters and the nozzles 14a of the external sterilization emitters form a lattice state or form a staggered state.

In the electron beam sterilization system 1 according to this embodiment, the aspect in which the external sterilization emitter E1 and the internal sterilization emitter E2 are provided in the same sterilization enclosure R2 is described, but that is not limiting. Even if the internal sterilization emitter and the external sterilization emitter are provided in separate sterilization enclosures, as long as the external sterilization emitter E1 and the sterilization object C are moved relatively in the axial direction, the problem of the present invention can be solved. If the external sterilization emitter E1 and the internal sterilization emitter E2 are provided in the same sterilization enclosure, since the inner surface and the outer surface of the sterilization object C can be sterilized simultaneously, possibility of re-contamination is eliminated, efficiency of the sterilization treatment can be improved, and the size of the entire system can be reduced.

In the electron beam sterilization system 1 according to this embodiment, the aspect in which by means of moving up/down of the holding arm A in the axial direction V, the nozzle 24a of the internal sterilization emitter E2 is inserted into the sterilization object C is described, but that is not limiting. The nozzle 24a of the internal sterilization emitter E2 can be inserted into the inner surface of the sterilization object C if the internal sterilization emitter E2 and the sterilization object C can be relatively moved with respect to the axial direction V. For example, instead of the moving of the holding arm A, the nozzle 24a of the internal sterilization emitter E2 may be inserted into the sterilization object C by moving the internal sterilization emitter E2 up/down in the axial direction V. At this time, the external sterilization emitter E1 may be also moved up/down in the axial direction V. The direction is not limited to the axial direction V, but the holding arm A may be moved in a direction in which the nozzle 24a of the internal sterilization emitter E2 comes into/out of the inside of the sterilization object C.

The relative movement between the external sterilization emitter E1 and the sterilization object C is not limited to the axial direction V. If the external sterilization emitter E1 and the sterilization object can be moved in a direction different from the transport direction of the sterilization object C, contribution can be made to uniform sterilization of the entire outer surface of the sterilization object C. The aspect in which the transport device M2 relatively moves the external sterilization emitter E1 and the sterilization object C is described, but that is not limiting. A relative movement device for relative movement of the external sterilization emitter E1 and the sterilization object C in a direction different from the transport direction of the sterilization object C may be separately provided.

The aspect in which the external sterilization emitter E1 and the internal sterilization emitter E2 are so-called thermionic emission type electron beam emitters is described, but that is not limiting. The external sterilization emitter and the internal sterilization emitter of the present invention may be so-called electric-field emission type electron beam emitters by irradiating the electron beams by the electric field without thermionically exciting electrons, for example. The aspect in which the external sterilization emitter E1 and the internal sterilization emitter E2 are both provided is described, but that is not limiting. For example, if the sterilization object C does not have an inner surface or if sterilization of the inner surface of the sterilization object C has been already completed, an aspect not providing the internal sterilization emitter E2 but providing only the external sterilization emitter E1 may be employed.

In the sterilization system 1 according to this embodiment, the aspect in which the external sterilization emitter E1 and the internal sterilization emitter E2 are electron beam emitters, each having a nozzle, that is, nozzle emitters is described, but that is not limiting. Particularly, the external sterilization emitter E1 may be a flat emitter as illustrated in FIG. 15. It is not limited that the electron lens 13 includes one aperture 13a. If the external sterilization emitter is a flat emitter, the electron lens 13 includes multiple apertures 13a like a grid structure. Regarding the external sterilization emitter E1 and the internal sterilization emitter E2, the aspect in which the one nozzle 14a (24a) is provided in the one chamber 15 (25), respectively, is described, but that is not limiting. For example, the chamber 15 (25) of the external sterilization emitter E1 and the internal sterilization emitter E2 may be constituted such that a plurality of nozzles 14a (24a) are provided therein. Alternatively, the nozzle 14a of the external sterilization emitter E1 and the nozzle 24a of the internal sterilization emitter E2 may share one chamber. Whatever specifications the external sterilization emitter employs, when the outer surface of the sterilization object C is sterilized, the problem of the present invention can be solved by relatively moving the external sterilization emitter E1 and the sterilization object C in the axial direction. In the electron beam sterilization system according to this embodiment, transport of the sterilization object C may be continuous or intermittent.

Embodiment 2
In the electron beam sterilization system 1 according to Embodiment 1, the aspect in which the external sterilization emitter E1 is moved together with the sterilization object C is described, but in the electron beam sterilization system according to Embodiment 2, the external sterilization emitter is movable in a direction getting closer to or separating away from the sterilization object. Differences from the Embodiment 1 will be described below in detail.

The transport device M4 and the like illustrated in FIG. 13 intermittently transport the sterilization object C. That is, transport is stopped once for sterilization of the sterilization object C and when the sterilization is completed, the transport of the sterilization object is resumed in some cases. In this case, the internal sterilization emitter can be moved up/down so that the nozzle 24a can be inserted into the sterilization object C while transport of the sterilization object C is stopped.

In the electron beam sterilization system according to this embodiment, in the external sterilization emitter, too, its nozzle 14a can be moved up/down for relative movement with the sterilization object C. On the other hand, in order to sterilize the outer surface of the sterilization object C while the sterilization object C is stopped, the external sterilization emitter does not have to be constituted so as to move together with the sterilization object C. Since the external sterilization emitter can be moved up/down, sterilization of the entire outer surface of the sterilization object C can be made uniform in the axial direction V.

Regarding the electron beam sterilization system according to this embodiment, the aspect employing the transport device M4 is described, but that is not limiting, and the transport devices M1 to M3 illustrated in FIG. 1 may be employed. The aspect in which the external sterilization emitter is moved up/down is described, but that is not limiting. By allowing the external sterilization emitter and the sterilization object C to be relatively moved in a direction different from the direction in which the sterilization object C is transported, the problem of the present invention can be solved. The external sterilization emitter is not limited to a nozzle emitter but may be a flat emitter.

Claims

An electron beam sterilization system that sterilizes a sterilization object during transport thereof along a transport passage, comprising:
an external sterilization emitter performing sterilization by irradiating an outer surface of the sterilization object with electron beams; and
a relative movement device relatively moving the sterilization object and the external sterilization emitter in a direction different from a transport direction along the transport passage when the outer surface of the sterilization object is sterilized.
The electron beam sterilization system according to claim 1, wherein
the external sterilization emitter is moved together with the sterilization object to be transported in a direction in which the sterilization object is transported.
The electron beam sterilization system according to claim 1, further comprising:
an internal sterilization emitter performing sterilization by irradiating an inner surface of the sterilization object with electron beams; and
at least one sterilization enclosure surrounding a part of the transport passage, wherein
the external sterilization emitter and the internal sterilization emitter are provided in the same sterilization enclosure.
The electron beam sterilization system according to claim 1, further comprising:
an internal sterilization emitter performing sterilization by irradiating an inner surface of the sterilization object with electron beams, wherein
the relative movement device moves the sterilization object relatively to the external sterilization emitter and the internal sterilization emitter.
The electron beam sterilization system according to claim 1, further comprising:
an internal sterilization emitter performing sterilization by irradiating an inner surface of the sterilization object with electron beams, wherein
the internal sterilization emitter and the external sterilization emitter have nozzles, respectively, and are nozzle emitters sterilizing the sterilization object by irradiating the sterilization object with electron beams from the nozzles.
The electron beam sterilization system according to claim 5, wherein
the nozzle of the external sterilization emitter has a diameter larger and/or longer or shorter than the nozzle of the internal sterilization emitter.
The electron beam sterilization system according to claim 1, wherein
the external sterilization emitter has a nozzle and is a nozzle emitter that sterilizes the sterilization object by irradiating the sterilization object with electron beams from the nozzle; and
the nozzle of the external sterilization emitter has, besides a window portion provided on a tip end surface, another window portion provided on a side surface in a periphery of the tip end surface.
The electron beam sterilization system according to claim 1, further comprising:
an internal sterilization emitter performing sterilization by irradiating an inner surface of the sterilization object with electron beams, wherein
the external sterilization emitter and the internal sterilization emitter are moved together with the sterilization object to be transported in a direction in which the sterilization object is transported.