Device cold plasma sterilization

A device cold plasma sterilization includes a housing, a base, a conveying assembly, a plurality of core modules, a transformer, a control cabinet, a distribution box, a shielding door, and a controller. The housing is disposed on the base. The plurality of core modules is disposed in the housing along a moving direction of the conveying assembly and are spaced apart from each other. The plurality of core modules each include a plurality of electrode assemblies spaced from one another by equal distance and arranged in a row. The transformer, the control cabinet, and the distribution box are disposed in a lower part of the base and are connected to the plurality of electrode assemblies. The conveying assembly is disposed in a middle part of the base. The base includes an inlet for entry and an outlet for exit of a package to be sterilized.

BACKGROUND

The disclosure relates to a device cold plasma sterilization.

Conventionally, the sterilization of food is carried out at high temperatures. For heat sensitive food such as fresh fish and meat products and fresh fruits and vegetables, high temperature sterilization makes them lose original nutrition and taste.

SUMMARY

The disclosure provides a device cold plasma sterilization comprising a housing, a base, a conveying assembly, a plurality of core modules, a transformer, a control cabinet, a distribution box, a shielding door, and a controller. The housing is disposed on the base; the plurality of core modules is disposed in the housing along a moving direction of the conveying assembly and are spaced apart from each other; each of the plurality of core modules comprises a plurality of electrode assemblies spaced from one another by equal distance and arranged in a row; the transformer, the control cabinet, and the distribution box are disposed in a lower part of the base and are connected to the plurality of electrode assemblies; the conveying assembly is disposed in a middle part of the base; the base comprises an inlet for entry and an outlet for exit of a package to be sterilized; the shielding door is disposed next to the inlet and the outlet and configured to open and close the inlet and the outlet; the controller is disposed outside the housing, and comprises a control box and a touch control panel disposed on a front face of the control box; the control box comprises a programmable logic controller (PLC) connected to the touch control panel; the PLC is configured to control operations of the conveying assembly, the plurality of core modules, the transformer, the control cabinet, the distribution box, the shielding door, and the touch control panel; each of the plurality of electrode assemblies comprises an electrode pair and a transmission mechanism connected to the electrode pair; and the electrode pair comprises one or more groups of upper electrodes and lower electrodes oppositely disposed with respect to the upper electrodes; a distance between the upper electrode(s) and the lower electrode(s) is adjustable by the transmission mechanism; the lower electrode(s) is disposed below the conveying assembly and fixed on the housing, and the upper electrode(s) is movable with respect to the lower electrode(s) to press the package to be sterilized.

In a class of this embodiment, the plurality of core modules is 2-5 in number.

In a class of this embodiment, each of the plurality of core modules comprises 2-6 electrode assemblies.

In a class of this embodiment, the distance between centers of two adjacent core modules is 300-500 mm.

In a class of this embodiment, the conveying assembly comprises an active linear slide, a driven linear slide, a conveyor belt, a beam, and a servo motor; the active linear slide and the driven linear slide are vertically disposed oppositely to each other; two synchronous pulleys are respectively disposed on an inner side of the active linear slide and an inner side of the driven linear slide; the conveyor belt is movably wound on the two synchronous pulleys; the beam is movably disposed between the active linear slide and the driven linear slide; the servo motor is disposed on a lower end of the active linear slide to drive the beam to move up and down along with the active linear slide and the driven linear slide.

In a class of this embodiment, the upper electrode(s) comprises a high-voltage electrode, a fixed frame, a first insulating plate, a mounting plate, and a binding post; the first insulating plate is embedded in the fixed frame; the first insulating plate comprises an upper surface, and the upper surface comprises a first central depression; the high-voltage electrode is disposed in the first central depression; the mounting plate is disposed on the fixed frame and the first insulating plate; the mounting plate comprises a central through hole and the binding post is disposed in the through hole; the binding post comprises a first end extending to connect to the high-voltage electrode, and a second end extending through the beam; the first insulating plate comprises polymethylmethacrylate, phenolic resin or epoxy resin and has a dielectric constant of 3.5-5.0; and a thickness of the first insulating plate is 1.8-3.0 mm.

In a class of this embodiment, the distance between two ends of the upper electrode(s) and the transmission mechanism is no less than 150-180 mm.

In a class of this embodiment, the lower electrode(s) comprises a ground electrode, a base plate, and a second insulating plate; the base plate comprises an upper surface, and the upper surface comprises a second central depression; a grounding stud is disposed in the central depression; the ground electrode is disposed in the second central depression and is connected to the grounding stud; the second insulating plate is disposed on the ground electrode; the second insulating plate comprises polymethylmethacrylate, phenolic resin or epoxy resin and has a dielectric constant of 3.5-5.0; and a thickness of the second insulating plate is 3.0-4.5 mm.

In a class of this embodiment, the transformer comprises an output interface in parallel connection to the upper electrode(s) and the lower electrode(s) of the electrode assemblies via a high voltage shielding line; in the presence of a 220 V voltage, a 60-90 kV electric field is produced between the upper electrode(s) and the lower electrode(s).

In a class of this embodiment, the housing comprises a metal shell and an observation window, and the observation window comprises glass and a metal mesh shielding layer fastened to the glass.

In a class of this embodiment, the control box comprises an input and output port connected to a master computer of a production line.

In a class of this embodiment, the device further comprises an air blower, an alarm lamp, and a ground connector; the air blower is disposed in the housing; the ground connector is disposed on the housing; the alarm lamp is disposed on the housing and connected to the PLC; when a fault occurs, the PLC controls the alarm lamp to send out a warning signal.

The following advantages are associated with the device cold plasma sterilization of the disclosure: in the presence of a 220 V voltage, a 60-90 kV electric field is produced between the upper electrode(s) and the lower electrode(s) of the device. The packed food is placed between the upper electrode(s) and the lower electrode(s). The high voltage electric filed stimulates the gas in the packed food to produce plasma thus achieving safe and efficient sterilization effect.

DETAILED DESCRIPTION

To further illustrate, embodiments detailing a device cold plasma sterilization are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

As shown inFIGS.1-2, provided is a device comprising a housing1, a base2, a conveying assembly3, 2-5 core modules4, a transformer5, a control cabinet6, a distribution box7, a shielding door8, and a controller9. The housing1is disposed on the base2. The 2-5 core modules4are disposed in the housing along a moving direction of the conveying assembly3and are spaced apart from each other. The 2-5 core modules4each comprise a plurality of electrode assemblies41spaced from one another by equal distance and arranged in a row. The transformer5, the control cabinet6, and the distribution box7are disposed in a lower part of the base2and are connected to the 2-6 electrode assemblies41. The conveying assembly3is disposed in a middle part of the base2. The base2comprises an inlet for entry and an outlet for exit of a package to be sterilized. The shielding door8is disposed next to the inlet and the outlet and configured to open and close the inlet and the outlet. The controller9is disposed outside the housing1, and comprises a control box91and a touch control panel92disposed on a front face of the control box91. The control box91comprises a programmable logic controller (PLC) connected to the touch control panel. The PLC is configured to control operations of the conveying assembly3, the plurality of core modules4, the transformer5, the control cabinet6, the distribution box7, the shielding door8, and the touch control panel92.

A distance between centers of two adjacent core modules4is 300-500 mm.

In certain embodiments, the 2-5 core modules4each comprise a plurality of electrode assemblies41spaced from one another by equal distance and arranged in a row.

Referring toFIG.3, the 2-6 electrode assemblies each comprise an electrode pair42and a transmission mechanism43connected to the electrode pair42. The electrode pair42comprises one or more groups of upper electrodes421and lower electrodes422oppositely disposed with respect to the upper electrodes. A distance between the upper electrode(s)421and the lower electrode(s)422is adjustable by the transmission mechanism43. The lower electrode(s)422is disposed below the conveying assembly3and fixed on the housing2, and the upper electrode(s)421is movable with respect to the lower electrode(s)422to press the package to be sterilized.

The conveying assembly3comprises an active linear slide431, a driven linear slide432, a conveyor belt433, a beam434, and a servo motor435. The active linear slide431and the driven linear slide432are vertically disposed oppositely to each other. Two synchronous pulleys436are respectively disposed on an inner side of the active linear slide431and an inner side of the driven linear slide432. The conveyor belt433is movably wound on the two synchronous pulleys436. The beam434is movably disposed between the active linear slide431and the driven linear slide432. The servo motor435is disposed on a lower end of the active linear slide431to drive the beam434to move up and down along with the active linear slide431and the driven linear slide432.

In certain embodiments, the electrode pair42comprises one or more groups of upper electrodes421and lower electrodes422oppositely disposed with respect to the upper electrodes. The length of the conveyor belt433increases with the increase of the distance between the active linear slide431and the driven linear slide432(If the distance is too large, the beam434may get tilted owing to the movement of the conveyor belt433. In this case, an electric sliding table equipped with a double servo motor may be used in combination with the PLC to achieve synchronized operation).

Referring toFIG.4, the upper electrode(s)421comprises a high-voltage electrode4211, a fixed frame4212, a first insulating plate4213, a mounting plate4214, and a binding post4215. The first insulating plate4213is embedded in the fixed frame4212. The first insulating plate4213comprises an upper surface, and the upper surface comprises a first central depression4216.

The high-voltage electrode4211is disposed in the first central depression4216; the mounting plate4214is disposed on the fixed frame4212and the first insulating plate4213; the mounting plate4214comprises a central through hole and the binding post4215is disposed in the through hole. The binding post4215comprises a first end extending to connect to the high-voltage electrode4211, and a second end extending through the beam434. The movement of the beam434leads to the movement of the binding post4215, and so does the upper electrodes421. The first insulating plate4213comprises polymethylmethacrylate, phenolic resin or epoxy resin and has a dielectric constant of 3.5-5.0; and the thickness of the first insulating plate4213is 1.8-3.0 mm. In certain embodiments, the high-voltage electrode4211, the fixed frame4212, the first insulating plate4213, and the mounting plate4214are in sealed connection.

The first insulating plate4213is connected to the mounting plate4214via a guide post4217. A spring (no shown) is disposed around the guide post4217. The spring and the guide post constitute an entire structure. When the high-voltage electrode4211contacts the package to be sterilized, the entire structure is slightly pressed and the package is compacted by the high-voltage electrode4211. The high-voltage electrode4211discharge electrons with a dielectric barrier discharge method.

Referring toFIG.5, the lower electrode(s)422comprises a ground electrode4221, a base plate4222, and a second insulating plate4223. The base plate4222comprises an upper surface, and the upper surface comprises a second central depression4224. A grounding stud4225is disposed in the central depression4224. The ground electrode4221is disposed in the second central depression4224and is connected to the grounding stud4225. The second insulating plate4223is disposed on the ground electrode4221. The second insulating plate4223comprises polymethylmethacrylate, phenolic resin or epoxy resin and has a dielectric constant of 3.5-5.0. The thickness of the second insulating plate4223is 3.0-4.5 mm.

The structural units of the upper electrode(s)421and the lower electrode(s)422are mutually sealed thus preventing the creepage between the upper electrode(s)421and the lower electrode(s)422under high voltage. The high-voltage electrode4211and the ground electrode4221both comprise aluminum because of its light weight and durability.

In certain embodiments, a distance between two ends of the upper electrode(s)421and the transmission mechanism43is no less than 150-180 mm. The active linear slide431and the driven linear slide432both comprise metals. When the distance between the upper electrode(s)421and/or the lower electrode(s)422and the linear slide431and/or the driven linear slide432is too close, a current may be generated, posing hidden risks. In certain embodiments, an optimal distance can be obtained through a number of experiments. The optimal distance ensures that the upper electrode(s)421and the lower electrode(s)422operates under normal condition, almost unaffected by the linear slide431and the driven linear slide432.

EXAMPLE

Sterilization of instant betel nut with the first insulating plate having different dielectric constants.

Experimental Method

The instant betel nut was inoculated with a micro-organism and incubated to allow the micro-organism to grow (400,000 colonies total). 10 g of the inoculated instant betel nut was packed into a packaging bag, and cold sterilized using the first insulating plate having different dielectric constants.

Sterilization Condition

Cold sterilization for 30 s with a 90 s interval for three cycles, at a voltage intensity of 16.5 kV/cm, a current of 0.9 mA, an operating room temperature of 25° C., and a humidity of 55%.

Bactericidal Effect

Total number (CFU/g) of colonies on the sterilized instant betel nut is shown in Table 1:

The transformer5comprises an output interface in parallel connection to the upper electrode(s)421and the lower electrode(s)422of the electrode assemblies41via a high voltage shielding line. In the presence of a 220 V voltage, a 60-90 kV electric field is produced between the upper electrode(s)421and the lower electrode(s)422.

The upper electrode(s)421and the lower electrode(s)422are both high-voltage electrodes and connected respectively to the transformer5. The upper electrode(s)421is disposed on the transmission mechanism43, and moves up and down along with the active linear slide431and the driven linear slide432. The lower electrode(s)422is disposed below the conveying assembly3. A high-voltage electric field is formed in the space above the conveyor belt and ionizes the air inside the package, thereby transferring electron and generating plasma. The plasma is used for the micro-organism surface sterilization of foods using. Each production line may comprise one or more electrode assemblies41in accordance with different technical requirements. In certain embodiments, three electrode assemblies41are used for detailing the disclosure.

Referring toFIG.6, the conveying assembly3comprises a motor31, a conveyor belt32, a transmission mechanism33, a drive roller34, and at least two driven rollers35, and a tension roller36. The conveying assembly3is configured to support and transport the materials to be sterilized.

The drive roller34and the tension roller36are disposed respectively on both sides of the base2. The at least two driven rollers35are disposed respectively beneath the drive roller34and the tension roller36. The conveyor belt32is wound around the drive roller34, the at least two driven rollers35, and the tension roller36, thereby giving the conveying assembly3an inverted trapezoid structure. The motor31is connected to the drive roller34via the transmission mechanism33. The conveyor belt32comprises nylon or rubber without any metallic materials.

In certain embodiments, the motor31is a servo motor that can accurately control the movement and stop of the conveyor belt. The conveyor belt32comprises silica gel thus ensuring the mechanical strength for the transport of workpieces, and in the process of discharge, the conveyor belt functions as a dielectric barrier plate of the lower electrode422. The length of the production line determines the number and position of the driven rollers35and the tension roller36. In certain embodiments, the drive roller34is disposed in the opposite direction of the tension roller36. The two driven rollers35are disposed beneath the drive roller34and the tension roller36. A connection device (not shown) and a metronome (not shown) are disposed respectively on both sides of the conveying assembly3to provide accurate positioning for the materials being transported along the belt.

Referring toFIG.2, the housing1comprises a metal shell and an observation window10disposed on the obverse side of the production line. The observation window10comprises glass and a metal mesh shielding layer fastened to the glass. The conveyor belt32further comprises a vertical-lift shielded door8for the housing1. The shielded door8is lowered to block the high-voltage electrical field when an electrical discharge takes place. The shielded door8comprises an aluminum alloy plate.

The controller9comprises a control box91and a touch control panel92, and can work independently or be controlled by a master computer. The control box91comprises a programmable logic controller (PLC) which is configured to receive all the detection signals from the device and send out all the control signals to the device. The control box91further comprises an input and output port93connected to a master computer of a production line, which allows the device to be controlled by the touch control panel92or the master computer that provides automation in production.

In certain embodiments, the device further comprises an air blower11, an alarm lamp12, and a ground connector. The air blower11is disposed in the housing1. The ground connector is disposed on the housing. The alarm lamp12is disposed on the housing1and connected to the PLC. When a fault occurs, the PLC controls the alarm lamp to send out a warning signal.

Safety protection for the device cold plasma sterilization of the disclosure:1. Protection against high-voltage breakdown. Overcurrent protection is used in the host power supply of a differential power supply. When the current level gets too high, the power is cut off to prevent electrical breakdown due to high voltage.2. Protection for high-voltage insulation. Insulating materials are used to separate electrically the conducting parts such as high-voltage cables, terminals, electrode plates, etc. Each of the conducting parts has a distance through insulation of 150-180 mm.3. Protection for high-voltage electric field. The device is shielded by a metal housing. The metal mesh shielding layer is fastened to the observation window. The conveyor belt comprises a vertical-lift shielded door for the housing. The shielded door is closed to block the high-voltage electrical field when an electrical discharge takes place.4. Power-off protection when opening the door. All the doors that can be opened comprise respectively a proximity sensor. When the device is not being debugged, the device cannot work unless all the doors are closed.