Sterilization of objects using low-energy electron beams

Abstract

A sterilization device (102) is disclosed. The sterilization device (102) comprises an annular housing (104) having an outer wall (106), an inner wall (108) and a central cavity (302) for receiving an object (306) to be sterilized. The annular housing (104) comprises a thermionic cathode (110) for releasing primary electrons, an anode grid (112) for attracting and accelerating the primary electrons to obtain accelerated primary electrons, and an anode wire (114) for attracting additional electrons released from a gas plasma discharge within the annular housing (104). The anode wire 114 accelerates the additional electrons and the accelerated primary electrons to form a spray of accelerated electrons 308 that is released through the interior wall 108. The spray of accelerated electrons 308 impacts the object 306 and sterilizes the object 306.

Description

[Technical field]

[0001] The subject matter described herein relates generally to radiation-based systems for continuously sterilizing objects in open-to-air conditions, and more specifically to sterilization devices and systems for sterilizing objects using a low-energy electron beam having accelerated electrons. [Background technology]

[0002] The term "sterilization" generally refers to the removal or inactivation of biological contaminants on a particular surface from an object or within a fluid. Sterilization devices and methods are used in a wide range of applications and in multiple industries. For example, bottles may be sterilized before filling the bottles with liquids, machinery and / or devices may be sterilized before sale and use, and food products such as seeds, fruits and vegetables may be sterilized before further processing. Additionally, many industries may perform sterilization of bulk goods or products as well. For example, sterilization may be done for bulk medical products such as containers containing multiple test tubes. Summary of the Invention

[0003] The detailed description is given with reference to the accompanying drawings, in which it should be noted that the description and drawings are merely examples of the present subject matter and are not meant to be representative of the subject matter itself. [Brief description of the drawings]

[0004] [Figure 1] 1 is a block diagram illustrating a sterilization device according to an exemplary embodiment of the present subject matter. [Diagram 2] 1 is a block diagram illustrating a sterilization device in accordance with another exemplary embodiment of the present subject matter. [Figure 3A] FIG. 1 illustrates a sterilization device according to an exemplary embodiment of the present subject matter. [Figure 3B] 1 is a cross-sectional view of an annular housing according to an exemplary embodiment of the present subject matter. [Figure 3C]1 illustrates the emission of an electron spray onto an object in accordance with an exemplary embodiment of the present subject matter. [Figure 4A] FIG. 1 illustrates a system for sterilizing an object according to an exemplary embodiment of the present subject matter. [Figure 4B] FIG. 1 illustrates a system for sterilizing an object according to an exemplary embodiment of the present subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Throughout the drawings, the same reference numbers indicate similar, but not necessarily identical, elements. The drawings are not necessarily to scale, and the size of some parts may be exaggerated to more clearly show the illustrated examples. Moreover, the drawings provide examples and / or embodiments that are consistent with the description, but the description is not limited to the examples and / or embodiments provided in the drawings.

[0006] As technology advances, various methods of performing sterilization have evolved. Examples of such methods may include, but are not limited to, steam, ethylene oxide (EtO), x-rays, gamma radiation (γ-rays), and high-energy electron beams. However, traditional sterilization methods have faced several challenges. For example, steam may be used to sterilize objects in steam-based sterilization. Steam-based sterilization may be beneficial in limited industrial applications and may be an effective method for sterilizing certain device types and objects that are resistant to high temperatures and high humidity. Steam-based sterilization processes allow for effective penetration of the steam sterilant due to the potential transfer of heat to all parts of the medical device and to certain objects. Furthermore, steam-based sterilization is used to sterilize heat-stable liquids and certain polymeric materials such as polypropylene, polycarbonate, polyurethane, Tyvek®, and other materials that are thermally stable and can be sterilized using steam-based sterilization methods. However, steam-based sterilization is only found in a small percentage of industries because materials used in food, drug packaging, and medical devices may be heat-sensitive and are incompatible with high temperatures of steam. High temperatures (typically 121°C to 134°C) can damage electronic devices, polymers, metal oxides, causing corrosion or burning of lubricants within the device. Furthermore, steam-based sterilization may have limited applications and may not be suitable for sterilizing certain types of objects. In one example, steam-based sterilization may not be suitable for sterilizing electronic devices, such as implants with electronic chips and ophthalmic implants, because the steam may damage the device or cause failure of the electronic device. Similarly, the effectiveness of sterilization with ethylene oxide (EtO) is similarly limited to the surface of the object, and mass sterilization is similarly not feasible. Similarly, the emission of EtO and its toxic decomposition products, such as ethylene chlorohydrin and ethylene glycol, from the chamber is highly lethal and susceptible. Ethylene chlorohydrin and ethylene glycol are by-products formed during and after EtO sterilization. They arise as a result of the decomposition of EtO in the sterilization chamber and the sterilization load over a long period of time.A vacuum is generated to remove the sterilant. In addition, nitrogen is used to "flush" the EtO from the device, ensuring that the residual EtO gas concentration is below the flammable limit (approximately 3%). EtO release during the sterilization process of medical devices is of greater concern due to several factors, such as reactivity, flammability, toxicity, and release of materials limiting its use for sterilization of liquids, pharmaceuticals, and biologicals.

[0007] Furthermore, sterilization methods based on high energy electron beams, X-rays, and gamma radiation (γ-rays) have high penetration, and therefore heavy barrier protection needs to be installed to confine the emitted radiation within a closed area. Due to the high radioactivity and penetration, such sterilization methods may not be performed in an open environment and without heavy barrier protection. Similarly, multiple safety equipment may need to be installed to deal with unwanted emergency or accidental situations, such as leakage of radiation from the radiation source being used. Furthermore, such sterilization methods may require special materials that may not be readily available without special permission from the authorities. For example, gamma radiation (γ-rays) based sterilization methods may require radioactive materials such as cobalt-60 (Co(60)), which may not be readily available without special permission. Similarly, the radioactivity of cobalt-60 decreases by up to 1% per month. Thus, consistency of the dose rate is a concern and regular calibration is necessary. Similarly, a certain amount of the isotope is needed every year to compensate for the decay. Obtaining a new cobalt-60 source is a long and costly process. As a result, such sterilization methods may not be cost effective, easy to handle, or rapidly scalable, and involve high hazards.

[0008] The conventional sterilization method may further include performing sterilization using a low-energy electron beam, which is safer, has limited penetration, and negligible photon / X-ray emission encourages safe operation. In such a method, an electron beam or a spray of electron beams with low energy may be emitted by a beam emitter. The emitted beam may strike particles against the object to be sterilized. The electron beam striking particles against the object may break the deoxyribonucleic acid (DNA) chain of living organisms such as bacteria, resulting in the death of the microorganisms and providing sterilization of the object. To perform sterilization, the object may be passed through a beam emitter, sterilizing the object from one side. The object may be further passed through another beam emitter, which may be oriented differently compared to the previous beam emitter, sterilizing the object from another side. Similarly, the object may be passed through multiple beam emitters, which may be oriented differently, completely sterilizing the object from all sides, externally and internally. In another implementation, multiple beam emitters oriented at various angles can be arranged together to sterilize an object from all sides. In yet another example, after sterilizing one side of an object, the object can be rotated and the object can be passed through the beam emitter again to sterilize the other side of the object. This process can be repeated until all sides of the object can be sterilized. Thus, such a sterilization method is time-consuming, requires a lot of effort, and is not economical, since multiple beam emitters need to be installed and maintained. Furthermore, the arrangement and installation of multiple beam emitters can require a lot of space, and the loading pattern should be well defined each time to cover all the surfaces of the object being sterilized.

[0009] The present invention relates to a sterilization device for sterilizing objects in a continuous manner under open air conditions and by a moving conveyor / mechanism. In one example of the present subject matter, the sterilization device can be a radiation sterilization device. The sterilization device can have an annular housing having an outer wall, an inner wall, and a central cavity formed by the inner wall to receive the object to be sterilized. In one exemplary implementation, the annular housing can be in the shape of a circular ring with a circular gap in the center of the circular ring, which represents the central cavity of the annular housing. In another exemplary implementation, the annular housing can be in the shape of a square or a rectangle with a square or a rectangular shaped gap in the center of the annular housing.

[0010] In one exemplary implementation, the annular housing may include a thermionic cathode, an anode grid, and an anode wire. In one example, the thermionic cathode may be a thermal cathode that may release electrons due to thermal emission when heated. The thermionic cathode may be capacitively coupled to a low voltage power supply unit to heat the thermionic cathode. Electrons in the thermionic cathode may receive sufficient energy to overcome the forces holding the electrons in the thermionic cathode, thus resulting in the emission of electrons, hereafter referred to as primary electrons.

[0011] In one exemplary implementation, the thermionic cathode may be coated with a work function emitter to emit additional electrons, increasing the number of primary electrons. In one example, the work function may indicate the minimum energy required to remove electrons from the ground Fermi level to infinity. Thus, the work function emitter may be a material that can emit electrons when it receives a minimum energy, for example in the form of heat. The electrons emitted by the thermionic cathode and the work function emitter may collectively be referred to as primary electrons. The primary electrons may be free electrons that have escaped from the thermionic cathode and the work function. These electrons may not be emitted at a high velocity and may have low energy, which is why they are referred to as low energy free electrons. Thus, these electrons do not form a beam, and may require an electric or magnetic field to pull and accelerate the primary electrons to form an accelerated beam. The anode grid may attract the primary electrons from the thermionic cathode and accelerate the primary electrons to obtain accelerated primary electrons. For example, the anode grid may be supplied with a positive potential from a low voltage power unit, causing the anode grid to have a positive charge. Thus, the anode grid can attract the primary electrons towards the anode grid, accelerating the primary electrons.

[0012] Furthermore, the annular enclosure may have a gas plasma discharge. In one exemplary operation, a vacuum condition may be formed inside the annular enclosure before supplying a voltage to the thermionic cathode, as described below. Furthermore, gas may be injected into the annular enclosure from a gas supply unit connected to the annular enclosure. For example, gas may be injected between the anode grid and the anode wire. And a low voltage supply may be provided to the anode grid and the anode wire. As known to those skilled in the art, by passing a voltage through the gas, some of the components of the gas may be ionized due to their decomposition into ion-electron pairs, forming a plasma. That is, after ionization of the gas atoms, a glow discharge, referred to as gas plasma, hereinafter referred to as gas plasma discharge, may be formed. That is, a large amount of gas may contain a small number of randomly generated electrons. When a voltage is applied between two electrodes (anode wire and anode grid) in the gas, these electrons are accelerated in the electric field between the electrodes. Various collisions between the electrons, ions and neutral gas molecules result in their collapse. Thus, a plasma, or gas plasma discharge, may be formed between the anode grid and the anode wire and may be a mixture of electrons, positive ions and neutral gas molecules.

[0013] Supplying a voltage to the thermionic cathode may accelerate the primary electrons as described above. The accelerated primary electrons may collide with electrons and ions of the gas plasma discharge, liberating and / or exciting further electrons present in the gas plasma discharge, hereafter referred to as additional electrons. For example, when the accelerated primary electrons collide with ions, the accelerated electrons may throw electrons off the ions, bringing the ions to their next highest charge state (charge increased by +1). Similarly, the accelerated electrons may collide with electrons present in the gas plasma discharge, exciting the electrons. Thus, additional electrons may be liberated from the ions and electrons of the gas plasma discharge due to the collision with the accelerated primary electrons. The additional electrons and the primary electrons may again collide with the remaining ions and electrons of the gas plasma discharge, liberating further additional electrons. The anode wire may pull the additional electrons liberated from the gas plasma discharge, thus accelerating the additional electrons. Thus, the anode wire may accelerate the additional electrons and the accelerated primary electrons, forming a spray of accelerated electrons.

[0014] The spray of accelerated electrons can then be released through the inner wall toward the object received by the central cavity. In one example, the inner wall includes a perforated surface, which may have one or more windows, and releases the spray of accelerated electrons toward the object received in the central cavity. Thus, the spray of accelerated electrons can strike particles on the surface of the object received in the central cavity and inactivate pathogens that may be located on the surface of the object. Because the object is located in the central cavity and the annular housing surrounds the object, the spray of accelerated electrons can collide with all surfaces of the object. Thus, the object can be sterilized from all directions or all sides using a single device, i.e., the annular housing. Thus, there is no need to place multiple beam emitters oriented in different directions to sterilize the object from all sides.

[0015] Furthermore, by using a thermionic cathode and a gas plasma discharge, the total number of accelerated electrons that can strike the object with particles can be increased. Thus, the electrons released with low energy by the thermionic cathode can be released with high acceleration, leading to the generation of a spray of more powerful or high energy electrons. Furthermore, due to increasing the number of accelerated electrons that strike the surface of the object with particles, the spray of accelerated electrons can strike the particles completely and effectively on all surfaces of the object. Similarly, the spray of accelerated electrons can have sufficient energy, or acceleration, to penetrate the object sufficiently to sterilize the object from the inside. For example, the object can be a package or container that can have one or more items to be sterilized. The object can be received in a central cavity, and the spray of accelerated electrons can sterilize all surfaces of the object, as well as penetrate the object to sterilize one or more items stored inside the object. Thus, mass sterilization of a group of objects and items located inside the object can be performed. The sterilization device can also be used to sterilize, for example, liquids flowing through tubes or pipes, gases transported through pipes, and irregularly shaped objects.

[0016] Thus, the present invention provides a solution for effectively and completely sterilizing an object from all sides without using multiple beam emitters. Furthermore, the present invention provides a solution to the problems associated with conventional sterilization techniques using steam, ethylene oxide (EtO), X-rays, gamma radiation (γ-rays) and high-energy electron beams. For example, the sterilization device, as disclosed, can sterilize an object from all sides with sufficient penetration, sterilizing the object from the inside without using steam or chemicals. Similarly, unlike gamma radiation (γ-ray) sterilization methods that use radioactive sources, the sterilization device can work with electrons, which are much safer, readily available, less expensive and easier to handle. Furthermore, the penetration is less but sufficient to sterilize an object compared to high-energy electron beam, X-ray and gamma radiation (γ-ray) based sterilization methods. Since the penetration is less and no radioactive source is used, there is no need to introduce heavy protective barriers or shielding facilities for personnel. Furthermore, while conventional sterilization methods require more time, e.g., hours to days, to sterilize a batch of objects, the sterilization device can perform faster batch sterilization, e.g., seconds to minutes. Generally, most of the electron beams are very narrow (less than 10 mm), while objects are larger and irregularly shaped. The spray of accelerated electrons emitted by the sterilization device disclosed herein can provide electron avalanches and wider scattering into the air, thereby reducing the irradiation time and increasing productivity, thus sterilizing objects in a shorter time.

[0017] Additionally, traditional gamma radiation (γ-ray) sterilization methods may not be environmentally friendly due to the use of radioactive or nuclear elements, whereas the sterilization device as disclosed herein is environmentally friendly with no waste, nuclear remnants or chemicals involved in the sterilization process.

[0018] The present subject matter is further described with reference to Figures 1 to 4B. It should be noted that the description and drawings merely illustrate the principles of the present subject matter. Although not explicitly described or shown herein, various arrangements can be devised that incorporate the principles of the present subject matter. Moreover, all references herein that describe principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass their equivalents.

[0019] 1 shows a block diagram of a sterilization device 102 according to an exemplary implementation of the present subject matter. In one exemplary implementation, the sterilization device 102 may include an annular housing 104 having an outer wall 106, an inner wall 108, and a central cavity (not shown in this figure) formed by the inner wall 108 for receiving an object to be sterilized. The annular housing 104 may further include a thermionic cathode 110, an anode grid 112, and an anode wire 114.

[0020] In one exemplary implementation, a vacuum may be formed inside the annular enclosure 104 and a gas may be injected. For example, the gas may be injected between the anode grid 112 and the anode wire 114. A low voltage source may then be provided to the anode grid and the anode wire. By passing a current through the gas, the components of the gas may be ionized due to their decay into ion-electron pairs and form a plasma. That is, after ionization of the gas atoms, a glow discharge may be formed, referred to as a gas plasma, hereinafter referred to as a gas plasma discharge.

[0021] Further, the thermionic cathode 110 may be electrically coupled to a low-voltage power supply unit (not shown in this figure) and may be provided with a negative potential. The low-voltage power supply may heat the thermionic cathode 110, and the electrons in the thermionic cathode may receive sufficient energy to overcome the forces holding the electrons in the thermionic cathode 110, thereby leading to the emission of one or more primary electrons. The anode grid 112 may then attract the one or more primary electrons, thereby accelerating the primary electrons to obtain accelerated primary electrons. In one example, the anode grid 112 may be electrically coupled to a low-voltage power supply unit and may be provided with a positive potential. The positive potential may cause the anode grid 112 to have a positive charge. Thus, the anode grid 112 may attract and accelerate one or more primary electrons emitted from the thermionic cathode 110 to obtain accelerated primary electrons.

[0022] Furthermore, the accelerated primary electrons may collide with ions and / or electrons of the gas plasma discharge. The collision may liberate one or more additional electrons, hereinafter also referred to as additional electrons, synonymously. For example, when the accelerated primary electrons collide with ions of the gas plasma discharge, the accelerated electrons may dislodge electrons from the ions, bringing the ions to their next highest charge state (charge increased by +1). Similarly, when the accelerated primary electrons collide with electrons of the gas plasma discharge, the electrons of the gas plasma discharge may reach an excited state. Thus, when colliding with the accelerated primary electrons, the ions and electrons of the gas plasma discharge may liberate additional electrons.

[0023] In one exemplary implementation, the anode wire 114 can attract additional electrons released from the gas plasma discharge. In one example, the anode wire 114 can be electrically coupled to a power supply unit (not shown in this figure) and can be supplied with a positive potential. Thus, the anode wire 114 can have a positive charge and can attract additional electrons and accelerated primary electrons toward the anode wire 114, forming a spray of accelerated electrons. The spray of accelerated electrons can then be released toward an object received in the central cavity through the inner wall 108. In one example, the inner wall 108 can have a perforated surface, releasing the spray of accelerated electrons toward an object received in the central cavity. Thus, the spray of accelerated electrons can strike particles on at least one surface of the object, sterilizing the object by inactivating one or more microorganisms that may be located on the surface of the object.

[0024] 2 shows a block diagram of a sterilization device 102 according to another exemplary embodiment of the present subject matter. In one example, the sterilization device 102 can be used to sterilize one or more objects. Examples of objects can include, but are not limited to, bottles, seeds, fruits, vegetables, medical implants, electronic devices, medical instruments, fabrics, surgical instruments, adhesives, plastics, cellulose, glass and ceramics, laboratory equipment, disposable medical and pharmaceutical packages, and other temperature-responsive sterilization products. The sterilization device 102 can also be used to sterilize, for example, packages that contain one or more objects, liquids flowing through tubes or pipes or stored in bottles or containers, gases transported through pipes, or other objects of irregular shapes and sizes.

[0025] In one exemplary implementation, the sterilization device 102 may have an annular housing 104 formed by an outer wall 106 and an inner wall 108. In one example, the outer wall 106 and the inner wall 108 may be positioned such that a hollow space is formed between the outer wall 106 and the inner wall 108 making the annular housing 104 hollow from the inside. Furthermore, the inner wall 108 may be joined end to end to form a central cavity of the annular housing 104. The annular housing 104 may be of any shape. In one example, the annular housing 104 may be a three-dimensional parallelepiped with a parallelepiped-shaped void in the center of the annular housing 104, which void represents the central cavity of the annular housing 104. In another example, the annular housing 104 may be an annular housing that is a three-dimensional circular ring with a circular void in the center of the circular ring, which void represents the central cavity of the annular housing 104. The annular housing 104 may be formed of any material. In one example, the annular housing 104 can be formed of an electrically insulating material. In another example, the annular housing 104 can be formed of a material or combination of materials. For example, the annular housing 104 can be formed of any of carbon steel, stainless steel, aluminum, and combinations thereof.

[0026] Further, the annular housing 104 may be filled with a gas as described in FIG. 1. Examples of gases may include, but are not limited to, nitrogen, argon, helium, pure air, hydrogen, and carbon dioxide. In one example, the annular housing 104 may have a flow control valve 202 that may be in fluid communication with a gas supply unit 204 to receive the gas. The flow control valve 202 may control the injection of the gas from the annular housing 104. In a closed state, the flow control valve 202 may restrict the passage of the gas from the gas supply unit 204 to the annular housing 104. Meanwhile, in an open state, the flow control valve 202 may allow the passage of the gas from the gas supply unit 204 to the annular housing 104. The gas may then be injected into the annular housing 104. In one example, the gas supply unit 204 may have a pump 206 that may be in fluid communication with a gas source 208. The gas source 208 may be a source that can supply the gas. For example, the gas source 208 may be a pressurized cylinder filled with gas or a pipeline connected to a source capable of supplying gas. The pump 206 may supply gas from the gas source 208 at a predetermined pressure. The annular housing 104 may further be connected to a pressure measurement unit 210 to measure the pressure of the gas within the annular housing 104. In one example, the pressure measurement unit 210 may be a Pirani gauge.

[0027] Further, in one example, the annular housing 104 may be fluidly connected to a shutoff valve 212. The shutoff valve 212 may be fluidly connected to a vacuum pump 214 to create a vacuum inside the annular housing 104. In a closed state, the shutoff valve 212 may keep the annular housing 104 airtight by preventing any leakage of gas during operation. The outlet of the shutoff valve 212 may be connected to the vacuum pump 214 to shut off the suction of the vacuum pump during electron beam generation inside the annular housing 104. Meanwhile, in an open state, the shutoff valve 212 may allow the gas filled inside the annular housing 104 to be exhausted to achieve a desired vacuum level and generate a gas plasma discharge. In one example, when the shutoff valve 212 is in an open state and the vacuum pump 214 is operated, the gas filled inside the annular housing 104 may be drawn out, thus creating a vacuum inside the annular housing 104. In one example, the shutoff valve 212 may also function as a safety valve, which may release the gas filled inside the annular housing 104 to maintain the required pressure inside the annular housing 104. When the pressure of the gas increases beyond a predetermined pressure level, the shutoff valve 212 may open and release the gas to avoid the occurrence of undesirable situations, such as the bursting of the annular housing 104 due to high pressure created inside the annular housing 104.

[0028] In one example, the annular housing 104 may further include a vacuum vent valve 216 for breaking the vacuum inside the annular housing 104 to introduce normal atmospheric conditions. For example, in an open state, the vacuum vent valve 216 may draw free air from the atmosphere and break the vacuum inside the annular housing 104. In a closed state, the vacuum vent valve 216 may act as a seal that may prevent leakage of the gas filled inside the annular housing 104. Examples of the flow control valve 202, the shutoff valve 212, and the vacuum pump 214 may include, but are not limited to, ball valves, butterfly valves, globe valves, gate valves, plug valves, diaphragm valves, bellows angle valves, pressure reducing valves, and needle valves. The flow control valve 202, the shutoff valve 212, and the vacuum vent valve 216 may be electrically, pneumatically, or electro-pneumatically operated.

[0029] In one example, the annular housing 104 can have a thermionic cathode 110, an anode grid 112, and an anode wire 114. In one example, the thermionic cathode 110, the anode grid 112, and the anode wire 114 can be disposed within a hollow space formed inside the annular housing 104. In one exemplary implementation, as shown in FIG. 3B, the thermionic cathode 110 can be disposed proximate to the outer wall 106, the anode grid 112 can be disposed proximate to the thermionic cathode 110, and the anode wire 114 can be disposed adjacent to the anode grid 112 and proximate to the inner wall 108.

[0030] In one exemplary implementation, before the annular housing 104 is operated or begins to be operated, a vacuum condition may be initially formed inside the annular housing 104. For example, the flow control valve 202 may be operated in an open state, and the vacuum pump 214 may be started to evacuate the annular housing 104. Further, gas may be injected from the gas supply unit 204 through the flow control valve 202 into the annular housing 104. For example, gas may be injected between the anode grid 112 and the anode wire 114. And, a low voltage source may be supplied to the anode grid 112 and the anode wire 114. In one example, the anode grid 112 and the anode wire 114 are electrically coupled to the low voltage power unit 218 and receive a current. Examples of the low voltage power unit 218 may include, but are not limited to, an alternating current (AC) power source and a direct current (DC) power source.

[0031] As can be seen, by passing an electric current through a gas, some of the gas components can be ionized due to decomposition into ion-electron pairs, forming a conductive plasma. That is, after ionization of the gas atoms, a glow discharge can be formed, which is called a gas plasma discharge. That is, a large amount of gas can contain randomly generated electrons. When a voltage is applied across the two electrodes (anode wire 114 and anode grid 112), these electrons are accelerated in the electric field between the electrodes. Various collisions between electrons, ions, and neutral gas molecules result in decomposition. Thus, a plasma, i.e. a gas plasma discharge, can be formed between the anode grid 112 and the anode wire 114, which can be a mixture of electrons, positive ions, and neutral gas molecules.

[0032] After the gas plasma discharge, the thermionic cathode 110 may be operated to initiate the release of one or more primary electrons. In one exemplary implementation, a current may be provided to the thermionic cathode 110 to initiate the release of one or more primary electrons. In one example, the thermionic cathode 110 may be a thermionic cathode electrode that may emit primary electrons due to thermal emission. The thermionic cathode 110 may have a filament formed of a refractory metal, such as tungsten. The thermionic cathode 110 may be electrically coupled to a low voltage power supply unit 218 to receive a current to heat the filament. For example, the thermionic cathode 110 may be electrically coupled to a cathode terminal of the low voltage power supply unit 218 as shown in FIG. 3B to receive a negative potential to heat the thermionic cathode 110. In one example, the thermionic cathode 110 may be provided with a negative potential in the range of −100V to −500V and a current in the range of 1 to 2 amperes. By heating the filament, the electrons in the thermionic cathode 110 may receive energy that overcomes the forces holding them within the thermionic cathode 110, thereby leading to the emission of primary electrons.

[0033] In one example, the thermionic cathode 110 can be a cathode electrode in the shape of a flat plate. In another example, the thermionic cathode 110 can be a conical cathode electrode, as shown in FIG. 3B. In yet another example, the thermionic cathode 110 can be a parabolic cathode electrode. Having a conical or parabolic cathode electrode can increase the charge concentration at the surface area of ​​the nose available for electron emission, as compared to an electrode in the form of a flat plate or other flat geometry. Due to the converging surface area, sufficient additional primary electrons can be emitted from the surface of the thermionic cathode 110. Similarly, due to the conical or parabolic shape, a strong electric field at the nose end can create enough primary electrons that can interact with the gas plasma discharge. As a result, secondary electron production can increase inside the annular housing 104 and spread out over a wider area instead of forming a focused narrow beam of primary electrons.

[0034] In one exemplary implementation, the thermionic cathode 110 may be coated with a work function emitter (not shown) to increase the number of primary electrons emitted from the thermionic cathode 110. In one example, the work function may indicate the minimum energy required to pull an electron from the ground Fermi level to infinity. Thus, the work function emitter may be a material that may emit electrons upon receiving a minimum energy, for example in the form of heat. Thus, the work function emitter may be coated on the thermionic cathode 110 and may emit additional electrons due to heating of the thermionic cathode 110. The electrons emitted from the thermionic cathode 110 and the work function emitter are hereinafter collectively referred to as primary electrons. Examples of work function emitters can include, but are not limited to, lanthanum hexaboride (LaB6), barium hexaboride (BaB6), barium oxide (BaO / BaO2), zirconium diboride (ZrB2), hafnium nitride (HfN), and cerium hexaboride (CeB6).

[0035] In one exemplary implementation, the primary electrons released by the thermionic cathode 110 may be attracted toward an anode grid 112 disposed in close proximity to the thermionic cathode 110. The anode grid 112 may attract and accelerate one or more primary electrons to obtain accelerated primary electrons. In one example, the anode grid 112 may be an anode electrode in the form of a grid or mesh that may be electrically coupled with an anode electrode of a low-voltage power supply unit 218, as shown in FIG. 3B. The anode grid 112 may be formed of, for example, titanium, stainless steel, nickel, and the like. The low-voltage power supply unit 218 may provide a positive potential to the anode grid 112. Due to the positive potential, the anode grid 112 may have a positive charge and attract the primary electrons, thereby accelerating the primary electrons.

[0036] The accelerated primary electrons may collide with ions and / or electrons of the gas plasma discharge filling the annular enclosure 104, as described above. In one example, the primary electrons may collide with ions and / or electrons of the gas plasma discharge, liberating one or more additional electrons from the gas plasma discharge. The additional electrons and the primary electrons may further collide with ions and electrons remaining in the gas plasma discharge after the collision, liberating further additional electrons. Similarly, the additional electrons and the primary electrons may collide multiple times with remaining ions and / or electrons of the gas plasma discharge, liberating still further additional electrons.

[0037] In one example, the anode wire 114 may attract one or more additional electrons emitted from collisions of the additional electrons and the primary electrons with ions and / or electrons of the gas plasma discharge. In one example, the anode wire 114 may be in the form of a cylindrical electrode that may be electrically coupled to a high voltage supply unit 220. The anode electrode of the high voltage supply unit 220 may be electrically coupled to the anode wire 114 and provides an output end of an ungrounded power supply having a positive potential and an anode grid 112 as well as a low voltage supply, as shown in FIG. 3B. In one example, the high voltage supply unit 220 may provide a voltage in the range of 150 kV to 300 kV. Thus, the anode wire 114 may carry a positive charge and thus attract the additional electrons. By attracting the additional electrons, the additional electrons may be further accelerated. Furthermore, due to the positive charge, the anode wire 114 may attract the accelerated primary electrons, thereby further accelerating the accelerated primary electrons. Thus, the anode wire 114 can form a spray of accelerated electrons, which includes accelerated additional electrons and further accelerated primary electrons.

[0038] The spray of accelerated electrons may be released through the inner wall 108 toward an object being received by the central cavity. In one example, the inner wall 108 may have a perforated surface 222 to release the spray of accelerated electrons toward the object. The perforated surface 222 may have one or more windows to release the spray of accelerated electrons. In one example, the perforated surface 222 may be formed from stainless steel and the inner wall 108 may be formed from a tungsten window foil that is 15 microns to 20 microns thick. The one or more windows may allow the spray of accelerated electrons to exit the inner wall 108.

[0039] Thus, the spray of accelerated electrons can impinge on at least one surface of the object, sterilizing the object. In one example, since the object is placed inside the central cavity, all sides of the object can be subjected to the spray of accelerated electrons or can be hit by particles of the spray of electrons, as shown in FIG. 3C. Thus, all sides of the object can be sterilized.

[0040] FIG. 3A illustrates a sterilization device 102 according to an exemplary implementation of the present subject matter. FIG. 3B illustrates a cross-section of an annular housing 104 according to an exemplary implementation of the present subject matter. FIG. 3C illustrates the delivery of an electronic spray to an object according to an exemplary implementation of the present subject matter. As described above, the sterilization device 102 may have an annular housing 104 formed by an outer wall 106, an inner wall 108, and a central cavity 302, such as the central cavity described in FIG. 1 and FIG. 2. The annular housing 104 may further have a front wall 304 and a rear wall (not shown) that close a hollow space formed between the outer wall 106 and the inner wall 108. As described above, the annular housing 104 may be of any shape. In one example, the annular housing 104 is a generally square-shaped annular housing, and as shown, has a generally square-shaped central cavity 302. The central cavity 302 may receive an object 306 for sterilization. As described above, the annular housing 104 may further include a thermionic cathode 110 positioned adjacent to the outer wall 106, an anode grid 112 positioned adjacent to the thermionic cathode 110, and an anode wire 114 positioned adjacent to the anode grid 112 and adjacent to the inner wall 108.

[0041] In one exemplary implementation, the vacuum pump 214 may then be operated to create a vacuum inside the annular housing 104. After creating the vacuum, the annular housing 104 may be filled with gas for gas plasma discharge by the gas supply unit 204. In one example, the annular housing 104 may further be coupled to a pressure measurement unit 210 to measure the pressure of the gas filled inside the annular housing 104. When the presence of gas increases above a predetermined pressure level inside the annular housing 104, the shutoff valve 212 may release the gas filled inside the annular housing 104.

[0042] Once the annular enclosure 104 is filled with gas, the low voltage power supply unit 218 and the high voltage power supply unit 220 may be operated. In one example, the low voltage power supply unit may be electrically coupled to the thermionic cathode 110 and the anode grid 112, as well as a floating power supply at the output end of the high voltage power supply unit 220, as shown in FIG. 3B. Furthermore, the thermionic cathode 110 may be a hot cathode electrode, which may release primary electrons due to thermal emission, as described above. In one example, the thermionic cathode 110 may be electrically coupled to the cathode terminal of the low voltage power supply unit 218, and may be supplied with a negative potential of −150 keV (kiloelectron volts), heating the thermionic cathode 110. Due to the heating, electrons in the thermionic cathode 110 may receive energy that overcomes the forces holding the electrons in the thermionic cathode 110, thus causing the thermionic cathode 110 to emit primary electrons. In one exemplary implementation, the thermionic cathode 110 may be coated with a work function emitter (not shown) to increase the number of electrons in the primary electrons emitted from thermionic cathode 110, as described above.

[0043] The primary electrons released by the thermionic cathode 110 may be attracted towards the anode grid 112. In one example, the anode grid 112 may be electrically coupled to an anode terminal of the low voltage power supply unit 218 and may be supplied with a positive potential. Due to the positive potential, the anode grid 112 may have a positive charge and thus may attract the primary electrons, thereby accelerating the primary electrons. The accelerated primary electrons may collide with ions and / or electrons of the gas plasma discharge present in the annular housing 104, as described above. In one example, the primary electrons collide with the ions and / or electrons of the gas plasma discharge to release additional electrons. The additional electrons and the primary electrons may further collide with ions and / or electrons remaining in the gas plasma discharge after the collision, further releasing further electrons. Similarly, a chain of collisions between the additional electrons, the primary electrons and the remaining ions and / or electrons of the gas plasma discharge may cause the release of additional electrons.

[0044] Additionally, the anode wire 114 may attract additional electrons. In one example, the anode wire 114, electrically coupled to the positive terminal of the high voltage power supply unit 220, may receive a positive potential, such as 150 kV (kilovolts). Thus, the anode wire 114 may carry a positive charge and thus attract additional electrons toward the anode wire 114. As such, the additional electrons are accelerated. Similarly, due to the positive charge, the anode wire 114 may attract the accelerated primary electrons, thereby further accelerating the already accelerated primary electrons. Thus, the anode wire 114 may form a spray of accelerated electrons, as shown by arrow 308 in FIG. 3C, which includes the accelerated additional electrons and the further accelerated primary electrons.

[0045] The spray of accelerated electrons may then be released through the inner wall 108 toward the object 306 received by the central cavity 302. In one example, the inner wall 108 may have a perforated surface 222 (illustrated by dashed lines, and openings between the dashed lines may represent the windows 310) with one or more windows 310 to release the spray of accelerated electrons. In one example, the perforated surface 222 may be formed from a heat-resistant, high-strength metal foil. Thus, the spray of accelerated electrons impacts at least one surface of the object 306 and sterilizes the object 306. In one example, as shown in FIG. 3A, since the object 306 is disposed inside the central cavity 302 that may be surrounded by the inner wall 108, all sides of the object 306 may receive the spray of accelerated electrons or may be hit by particles of accelerated electrons, as shown in FIG. 3C.

[0046] 3C illustrates the emission of a spray of accelerated electrons toward an object 306 in accordance with an exemplary implementation of the present subject matter. As described above, the spray of accelerated electrons, indicated by arrows 308, may be released through the inner wall 108 toward the object 306 received in the central cavity 302. The inner wall 108 may surround the object 306 as the object 306 is disposed inside or may pass through the central cavity 302. Thus, the spray of electrons released from the inner wall 108 may impinge on all sides of the object 306, thereby completely sterilizing the object 306 from all sides.

[0047] Additionally, as described above, ions of the gas plasma may release electrons due to collisions with additional electrons and accelerated primary electrons. The release of electrons from an ion may cause the ion to assume its next highest charge state. For example, the release of an electron from an ion may increase the charge of the ion by +1. Similarly, when ions individually release additional electrons, the charge of the ion may increase, thus causing the ion to have a positive charge. In one exemplary implementation, since the thermionic cathode 110 is supplied with a negative potential, the thermionic cathode 110 may tend to have a negative charge. Thus, the thermionic cathode 110 may attract positively charged ions (the movement of the positively charged ions is indicated by dashed arrows 312).

[0048] Once the object 306 has been sterilized, the flow control valve 202 can be operated to an open state, allowing the release of the gas plasma discharge that fills the annular enclosure 104 and creates a vacuum inside the annular enclosure 104.

[0049] 4A and 4B show a system 400 for sterilizing objects according to an exemplary implementation of the present subject matter. The system 400 may be implemented in any industry, such as food packaging or processing industry, medical equipment or device manufacturing industry, beverage industry, textile industry, pharmaceutical industry, etc., to perform sterilization. The system 400 may have a conveying unit 402 for receiving an object, such as the object 306, and a sterilization device, such as the sterilization device 102 described in FIGS. 1 to 3C, for sterilizing the object 306. As shown, the conveying unit 402 may also receive multiple objects 306 for sterilization. The multiple objects 306 may be interchangeably and collectively referred to as the object 306 or multiple objects 306.

[0050] In one exemplary implementation, the transport unit 402 may include a movable conveyor 404 to receive the object 306 to be sterilized. In one example, the movable conveyor 404 may include a conveyor belt that may move in a direction indicated by arrow 406. In another example, the movable conveyor 404 may include a plurality of rollers that may rotate toward the direction indicated by arrow 406. In one example, the transport unit 402 may include one or more motors (not shown) to move the movable conveyor 404 in the direction indicated by arrow 406. In one example, a worker positioned near the movable conveyor 404 may place the object 306 to be sterilized on the movable conveyor 404. In another example, one or more robots, e.g., robotic arms, may be positioned near the movable conveyor 404 to place the object 306 on the movable conveyor 404.

[0051] Further, the movable conveyor 404 may move toward a sterilization section 408 of the transport unit 402 to sterilize the object 306. In one example, the sterilization section 408 may include a sterilization device 102. In one exemplary implementation, the sterilization device 102 may include an annular housing 104 that may sterilize the object 306 as described in FIG. 1 to FIG. 3C. The sterilized object 306 may then move to a final section 410 of the transport unit 402. In one example, the movable conveyor 404 may move toward the final section 410 after sterilizing the object 306 in the sterilization section 408. In the final section 410, a worker or one or more robots may receive the sterilized object 306. Similarly, multiple objects 306 may be received by the transport unit 402 for sterilization, and the objects 306 may be sterilized by the sterilization device 102. Thus, the system 400 may enable sterilization of multiple objects 306 in a serial manner and may be used in multiple industries, as described above, to sterilize multiple objects 306 .

[0052] The system 400 may further include other units 412. In one example, the other units 412 may include a power supply unit 414 to supply power to the transport unit 402 and the sterilization device 102. The other units 412 may further include a control unit 416 to control the operation of the transport unit 402 and the sterilization device 102. For example, the control unit 416 may include one or more switches to turn on and off the transport unit 402 and the sterilization device 102, respectively. The control unit 416 may also include one or more buttons that may be used by an operator to regulate the power supplied to the sterilization device 102. For example, the operator may define a negative potential supplied to the thermionic cathode 110 by the low voltage power supply unit 218, a positive potential supplied to the anode grid 112 by the low voltage power supply unit 218, and a positive potential supplied to the anode wire 114 by the high voltage power supply unit 220. The control unit 416 may similarly have one or more buttons that may be used by an operator to control the gas supply unit 204 to supply ionized gas to the annular housing 104 and to control the vacuum pump 214 to draw the ionized gas from within the annular housing 104.

[0053] 4B shows a covering unit 418 that may be optionally disposed covering the transport unit 402 and the sterilization device 102. In one example, the covering unit 418 may protect the transport unit 402 and the sterilization device 102 from external contamination that may be undesirable for the transport unit 402 and the sterilization device 102 to function. Examples of external contamination may include, but are not limited to, polluted air, dust, moisture, and the like. In one example, the covering unit 418 may act as a shield for the sterilization device 102, which may prevent the electron beam from flying into the surroundings. Additionally, a radiation monitoring system (not shown) may be externally attached to the covering unit 418 to measure and display the beta particle radiation level in the surrounding area.

[0054] Additionally, the coating unit 418 may have one or more windows 420. In one example, the one or more windows 420 may be open to improve air circulation inside the coating unit 418. In another example, the one or more windows 420 may allow an operator to see through the windows 420 that the system 400 is functioning without having to remove the coating unit 418.

[0055] Although examples of the subject matter have been described in language for embodying structural features and / or methods, it is to be understood that the appended claims are not limited to the specific features or methods described. Rather, the specific features and methods have been disclosed and described as examples of the subject matter.

Claims

1. A sterilization device (102) for sterilizing an object (306), comprising: The sterilization device (102) a housing (104) having an outer wall (106), an inner wall (108) and a central cavity (302) defined by the inner wall (108); the object (306) to be sterilized is positionable adjacent to the center of the central cavity (302); The housing (104) a thermionic cathode (110) for releasing one or more primary electrons; an anode grid (112) for attracting and accelerating one or more of the primary electrons to obtain accelerated primary electrons; an anode wire (114) that attracts one or more additional electrons, the one or more additional electrons being released from a gas plasma discharge within the enclosure (104); Equipped with the anode wire (114) accelerates one or more of the additional electrons and the accelerated primary electrons to form a spray of accelerated electrons directed toward a center of the central cavity (302).

2. the thermionic cathode (110), the anode grid (112) and the anode wire (114) are disposed in a hollow space formed between the outer wall (106) and the inner wall (108) of the housing (104); 2. The sterilization device of claim 1, wherein the thermionic cathode (110) is disposed adjacent to the outer wall (106), the anode grid (112) is disposed adjacent to the thermionic cathode (110), and the anode wire (114) is disposed adjacent to the anode grid (112) and adjacent to the inner wall (108).

3. the inner wall (108) includes a perforated surface (222) for releasing the spray of accelerated electrons toward the object (306) received in the central cavity (302); 2. The sterilization device of claim 1, wherein the perforated surface (222) comprises one or more windows through which the spray of accelerated electrons is released.

4. the gas plasma discharge comprises one or more ions; one or more of the primary electrons collide with one or more of the ions to liberate one or more of the additional electrons from the gas plasma discharge; 2. The sterilization device of claim 1, wherein the one or more additional electrons and the one or more primary electrons collide with one or more of the ions to release the one or more additional electrons.

5. 2. The sterilization device of claim 1, wherein the thermionic cathode (110) releases one or more of the primary electrons upon heating.

6. the thermionic cathode (110) being at least one of a conical cathode electrode and a parabolic cathode electrode; 2. The sterilization device of claim 1, wherein the thermionic cathode (110) comprises a coating of a work function emitter to increase the number of electrons in the one or more primary electrons emitted from the thermionic cathode (110).

7. The work function emitter is lanthanum hexaboride (LaB ６ ), barium hexaboride (BaB ６ ), barium oxide (BaO / BaO ２ ), zirconium diboride (ZrB ２ ), hafnium nitride (HfN) and cerium hexaboride (CeB ６ 7. The sterilization device according to claim 6, characterized in that it is at least one of the following:

8. a low voltage power supply unit (218) for supplying a negative potential to the thermionic cathode (110) for heating the thermionic cathode (110) and a positive potential to the anode grid (112) for attracting and accelerating one or more of the primary electrons; a high voltage power supply unit (220) for supplying a positive potential to the anode wire (114) to attract the one or more additional electrons and accelerate the one or more additional electrons and the accelerated primary electrons; a vacuum pump (214) for creating a vacuum inside the housing (104); a gas supply unit (204) for supplying gas for the gas plasma discharge; a flow control valve (202) for receiving the gas from the gas supply unit (204) and allowing the gas to enter the enclosure (104); a pressure measurement unit (210) for measuring the pressure of the gas inside the housing (104); The sterilization device according to claim 5, further comprising:

9. a conveying unit (402) for receiving an object (306) to be sterilized; a sterilization device (102) for sterilizing said object (306); A system (400) comprising: The sterilization device (102) comprises a housing (104) formed by an outer wall (106), an inner wall (108) and a central cavity (302) defined by the inner wall (108); the object (306) to be sterilized is positionable adjacent to the center of the central cavity (302); The housing (104) a thermionic cathode (110) disposed adjacent the outer wall (106) and configured to emit one or more primary electrons; an anode grid (112) disposed adjacent to the thermionic cathode (110) and configured to attract one or more of the primary electrons to obtain accelerated primary electrons; an anode wire (114) disposed proximate to the anode grid (112) and configured to attract one or more additional electrons liberated from the gas plasma discharge within the annular housing (104); Equipped with the anode wire (114) accelerates one or more of the additional electrons and the accelerated primary electrons to form a spray of accelerated electrons directed toward a center of the central cavity (302).

10. The system of claim 9, wherein the transport unit (402) comprises a movable conveyor (404) for receiving the object (306) to be sterilized, a sterilization section (408) for sterilizing the object (306), and a final section (410) for receiving the sterilized object (306).

11. The system of claim 10, wherein the sterilization device (102) is located in the sterilization section (408) of the moving conveyor (404).

12. the movable conveyor (404) moves the object (306) toward the sterilization section (408) for sterilization, and from the sterilization section (408) to the final section (410); The system of claim 11, wherein the object (306) is transported to the final section (410) after being sterilized in the sterilization section.

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