JP2010259648A - Ozone sterilization method and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for sterilizing an article with ozone-containing gas. <P>SOLUTION: The sterilization method comprises as follows. A sterilization chamber is provided; the article is placed in the sterilization chamber, and the sterilization chamber is sealed hermetically; while the sterilization chamber is sealed hermetically, the temperature of the article and that of an atmosphere within the sterilization chamber are made equal; the vacuum of vacuum pressure, which is beforehand chosen, is applied to the sterilization chamber; steam is supplied to the sterilization chamber under vacuum; the ozone-containing gas is supplied to the sterilization chamber; during preselected processing time, the sealing of the sterilization chamber is maintained; and the vacuum of the sterilization chamber is disengaged; whereby, vacuum pressure is employed so that the boiling point of the water of the sterilization chamber may be lowered at temperature below that within the sterilization chamber. The method includes the following steps. A temperature equalizing step is performed, during the following step in which steam is supplied to the sterilization chamber, the sterilization chamber is sealed hermetically, and the local condensation of water is prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sterilization (disinfection, sterilization) apparatus, and more particularly to an ozone sterilization method and apparatus.

  Sterilization (disinfection, sterilization) is the absolute destruction of viruses, bacteria, fungi, or other microorganisms, whether plant or dormant spores. Conventional sterilization procedures for medical instruments (equipment) include high temperatures (such as steam and dry heat sterilization) or toxic chemicals (such as ethylene oxide, EtO). High pressure steam sterilization was a traditional sterilization method. It is fast and cost effective. However, autoclaves (autoclaves) destroy equipment that is sensitive to heat. As a result, increasingly heat-sensitive devices, such as arthroscopes and endoscopes, are used in therapy, and other types of sterilization need to be used.

Ethylene oxide sterilization is used to pasteurize heat-sensitive equipment. Until recently, ethylene oxide sterilization was the latest technology of pasteurization. Ethylene oxide disinfects those that are sensitive to heat and moisture, and penetrates very much. However, it has been considered carcinogenic and neurotoxic by the national health and safety organization.

A more efficient, safe and cheap sterilization was discovered in the form of ozone O ₃ . Ozone is easily generated from oxygen and is readily available in hospital environments, usually from a wall or ceiling oxygen source, or from a portable "J" cylinder of oxygen if movement is required Is possible.

Ozone generally acts on chemical compounds. It reacts directly or acts via hydroxyl radical species formed during the decomposition of ozone. (Encyclopedia of Chemical Technology, Volume 17, Ozone pages 953-964). Ozone sterilization activity increases rapidly with increasing relative humidity. Spore resistance to ozone varies from strain to strain, but the difference is relatively small at high relative humidity (Ishizaki, 1986, inactivation of Silas spores by gaseous ozone, applied bacteriology Magazine, 60: 67-72). The presence of water often accelerates the reaction of ozone with organic substances (Out Langley, (EDS), 1991, Ozone Water Treatment Applications and Engineering, Lewis Publishers: Chelsea, Michigan, p. 569).

The use of a mixture of ozone gas with fine water mist in a sealed plastic bag container containing the article to be sterilized (article) is described in US Pat. No. 3,719,017. US Pat. No. 5,069,880 describes an apparatus that can generate high relative humidity by bubbling ozone gas in a water bath to increase the water content of ozone gas. However, the use of such high humidity may lead to water condensation on what is to be sterilized. However, condensation is not only undesirable, but must be avoided as it prevents direct ozone access to the organisms (microorganisms) on the surface to be sterilized. PCT CA 2002/01720 describes an ozone sterilization method that includes a temperature equalization step that brings the material to be sterilized to substantially the same temperature as the sterilization environment. As a result, condensation is avoided as much as possible, and this document is incorporated herein in its entirety. This is accomplished by multiple cycles of degassing the sterilization chamber and reintroducing outside air. Such a method would be time consuming due to repeated degassing and replenishment of the sterilization chamber.

(Summary of the Invention)
The present invention seeks to provide a method and apparatus for sterilizing an article with an ozone-containing gas, which substantially prevents condensation of water from the sterilizing atmosphere during the sterilization process.
A preferred sterilization method according to the present invention for sterilization of articles comprises the following steps:
a) has a sterilization chamber;
b) Place the article (object to be sterilized) in the sterilization chamber,
c) sealing the sterilization chamber,
d) equalize the temperature of the article and the atmosphere in the sterilization chamber;
e) applying a vacuum of a preselected vacuum pressure to the sterilization chamber;
f) supplying water vapor to the sterilization chamber under vacuum;
g) supplying ozone-containing gas to the sterilization chamber;
h) maintaining the sterilization chamber sealed for a preselected treatment time; and
i) Release the vacuum in the sterilization chamber, where the sterilization chamber is sealed during the whole process.

Although equalization of the temperature of the sterilization chamber and the article is accomplished simply by waiting long enough, this results in an undesirable delay in the sterilization process. The use of multiple pulses of deaeration and flushing of the outside air is time consuming and may cause temperature fluctuations. As a result, temperature equalization is achieved according to the invention by sealing the sterilization chamber and by equalizing the temperature while the sterilization chamber is sealed. Preferably, the equalization is accomplished by continuously recirculating air into the sterilization chamber after the sterilization chamber is sealed. For a more reliable equalization of the temperature of the sterilization chamber and its contents, the sterilization chamber is sealed during the entire process.

A preferred sterilization apparatus according to the present invention includes: That is,
-Sterilization chamber,
Means for equalizing the temperatures of the sterilization chamber, any material placed in the sterilization chamber, and the atmosphere in the sterilization chamber by recirculating the atmosphere in the sterilization chamber;
-Means for supplying ozone-containing gas into the sterilization chamber;
-Means for supplying water vapor to the sterilization chamber; and
Means for applying a sufficient vacuum in the sterilization chamber to lower the boiling point of water below the temperature in the sterilization chamber;

1 is a schematic illustration of an apparatus according to the present invention. 2 is a flowchart of a preferred method according to the present invention. 2 is a flowchart of a preferred electrical control system used in the apparatus of FIG. 2 is a flowchart of a preferred electrical control system used in the apparatus of FIG. 2 is a flowchart of a preferred electrical control system used in the apparatus of FIG. 4 is a pressure graph of a preferred sterilization process according to the present invention.

The invention is explained in more detail by means of the following examples with reference to the accompanying drawings.
The ozone sterilizer (sterilizer) according to the present invention, shown schematically in FIG. 1, is operated in a relatively simple manner. Medical quality oxygen receives an electric field in the ozone generator 22 and converts the oxygen to an ozone-containing gas. This ozone-containing gas is introduced into a humidified sterilization chamber 10 that sterilizes the medical device. The ozone is subsequently converted to ozone using an ozone catalyst 52. The only residue left at the end of the sterilization cycle is oxygen and clean water.

  The ozone sterilization method of the present invention does not substantially require aeration or cooling of the sterilized equipment so that the equipment can be used immediately after the sterilization cycle. This reduces the cost of hospitals that maintain expensive medical equipment. The ozone sterilization method of the present invention further provides several advantages. It does not produce hazardous waste, does not handle dangerous gas cylinders, and does not pose a threat to the environment or user health. Stainless steel equipment and heat-sensitive equipment can be handled at the same time, eliminating the need for some users to separate the sterilization product in two.

This sterilizing atmosphere is humidified to increase the efficiency of the ozone sterilization process. However, sterilization at a predetermined relative humidity close to 100% creates additional challenges associated with undesirable condensation on what is sterilized. The temperature difference between the atmosphere in the sterilization chamber and the one to be sterilized should be avoided as much as possible in order to avoid as much as possible undesired condensation on the one sterilized prior to the ozone injection. PCT CA2002 / 01720 addresses this problem by flushing the outside air between the sterilization chamber exhaust and ambient temperature to equalize the temperature of all materials exposed to the sterilization chamber atmosphere. This is time consuming. This problem is currently achieved by the method according to the invention in which temperature equalization is achieved by recirculation of the atmosphere in a sealed sterilization chamber without introducing outside air.

A preferred sterilization device according to the present invention, depicted schematically in FIG. 1, includes a sterilization chamber 10 whose interior can be sealed to a vacuum. This is accomplished at the inspection port 12, which can be selectively opened to enter the sterilization chamber, and the sterilization chamber can be sealed hermetically. The apparatus includes an ozone generator 22 for supplying ozone-containing gas to the sterilization chamber, a humidifier arrangement 30 for supplying water vapor to the sterilization chamber, and a vacuum pump 40 (ISP500-B, manufactured by Anest Iwata). The vacuum pump 40 is used to increase the entry of the sterilization gas into the sterilization chamber 10 and to make the sterilization chamber 10 sufficiently vacuum so that water vapor can be generated at a temperature below the temperature in the sterilization chamber. The The vacuum pump 40 in the preferred embodiment can provide a sufficient vacuum in the sterilization chamber to lower the boiling point of the indoor water below the actual temperature of the atmosphere in the sterilization chamber. In a preferred embodiment, the vacuum pump can be at a vacuum of 0.1 millibar (mbar).

The ozone produced by the ozone generator 22 is invalidated by the ozone catalyst 52 supplied with ozone-containing gas directly from the ozone generator after passing through the sterilization chamber 10 or through a valve 29b (which can be selected). The ozone catalyst 52 (DEST 25, manufacturer TSO3) is connected in series via the vacuum pump 40 so that ozone gas does not leak into the outside air. For economic and practical reasons, it is desirable to use a catalyst for the decomposition of ozone in the sterilizing gas discharged from the sterilizing chamber 10. The catalyst deactivates in contact with ozone and reconverts ozone into oxygen with some of the heat generated. This type of catalyst and its manufacture are well known in the art of ozone generators and need not be described in detail here. A preferred ozonolysis material for catalyst 52 is CARULITE®. Moreover, other means for depleting ozone contained within the sterilizing gas will be readily apparent to those skilled in the art. For example, ozonolysis is accelerated, for example, heated to a temperature of 300 ° C. for a predetermined time.

The humidifier arrangement 30 includes a humidification chamber 32 (HUM 0.5, manufacturer TSO3), which is sealed to the outside air and connected to the sterilization chamber 10 via a conduit and a steam intake valve 34. The humidification chamber 32 includes a level control (not shown) in order to always ensure a sufficiently high water level. Water is supplied from the drinking water or pure water supply connector to the humidification chamber 32. Water is supplied to the humidification chamber 32 by a filter 33, a pressure reducing valve 35, an orifice 31, and an input valve 36. The steam produced in the humidification chamber 32 enters the sterilizer 10 by the steam intake valve 34. The humidification chamber is also preferably equipped with a heating device (not shown), which maintains the water at a high temperature to achieve a higher water evaporation rate.

The preferred ozone generator 22 used in the apparatus of the present invention is of the corona discharge type (OZ, model 14a, manufacturer TSO3), but other ozone generators are known and will be readily apparent to those skilled in the art. Will. In a preferred embodiment of the apparatus of the present invention, the ozone generator is anything known in the art and is cooled to reduce the rate of ozonolysis. In order to achieve a good sterilization rate (lethal rate) in the ozone sterilization process, it is sufficient to obtain a concentration of 48 to 96 milligrams of ozone supplied to the sterilization chamber, preferably 60 to 85 milligrams per liter. It is. At these concentrations, ozone production is accompanied by a relatively high thermal energy loss in the form of heat. Generally, about 95% of the supplied electrical energy is converted to heat and only 5% is used for ozone generation. Since heat accelerates the reverse conversion of ozone to oxygen, it must be removed as soon as possible by cooling the ozone generator 22.

The ozone generator of the device is maintained at a relatively low temperature between 4 ° C. and 6 ° C. by a cooling system 60 (shown schematically). There are many cooling systems, and those skilled in the art will be able to select an appropriate cooling system for use in the apparatus of the present invention without any further description. The cooling system is preferably kept between 4 ° C and 6 ° C. In a preferred embodiment, the cooling system is kept at 4 ° C. so that the ozone-containing gas generated by the ozone generator 22 is at an ambient temperature of approximately 20 ° C. to 35 ° C. Therefore, the ozone-containing gas that enters the sterilization chamber for humidification and sterilization is kept at an outside air temperature of 20 ° C to 35 ° C. This means that ozone decomposition is minimal and the sterilization process is more efficient.

The ozone generator is preferably supplied with medical oxygen from a normal oxygen supply port on the hospital wall, an oxygen cylinder, or other source that can be supplied in the required quality or flow. Oxygen is supplied to the ozone generator 22 through a filter 23 and an electrical oxygen pressure controller. The electrical oxygen pressure controller includes a proportional valve 26, a pressure sensor 26 a and a flow meter 25, a pressure controller 24, a flow meter 25 and an oxygen shut-off valve 26.

The generator is protected against excessive oxygen pressure by an electrical oxygen pressure controller. The ozone-oxygen mixture generated by the ozone generator 22 is directed to the sterilization chamber 10 by the control valve 28 and the mixing supply solenoid valve 29a. The mixture is supplied to the ozone catalyst 52 by a bypass solenoid valve 29b (optional). In a preferred embodiment, in a 125 liter sterilization chamber, pressure controller 24 and orifice 28 preferably control the oxygen input at a flow rate of about 1.5 liters at 2.2 psig per minute. . However, it will be readily apparent to those skilled in the art that other flow rates may be used depending on the model, type of ozone generator 22 and the size of the sterilization chamber.

Temperature equalization is performed via the vacuum pump 40, the sterilization chamber drainage valve 44, and the recirculation valve 46. The vacuum in the sterilization chamber 10 is created by the vacuum pump 40 and the sterilization chamber drain valve 44.
The valve 26 is preferably 013 A 5/32 FPM (manufacturer Burquett Burkert).
The valves 29a and 29b are Teflon solenoid valves (model: M442C1AFS-HT-1mic, manufacturer Techcom Teqcom). Valve 34 (CV25-K2K2-ECNSS-24DC) is preferably a solenoid valve and is the same model as sterilization chamber drainage valve 44 and recirculation valve 46 (manufacturer Varian Varian).

Operation A preferred sterilization method according to the present invention includes the following general steps illustrated in the flow chart of FIG. Medical devices to be sterilized are typically sealed in medical packaging containers or bags, such as those used in hospital environments and placed in sterilization rooms. The sterilization chamber door is closed and locked, and the temperature equalization phase begins. This phase involves recirculation of the atmosphere in the sterilization chamber as described in more detail below. At that time, the sterilization chamber is evacuated. Water vapor is introduced into the sterilization chamber to humidify the contents of the sterilization chamber. A mixture of ozone and oxygen is supplied to the sterilization chamber, which is sealed for a predetermined processing time. The steps of applying vacuum and supplying ozone are preferably repeated at least once after the ventilation step, as shown in FIG. After the sterilization process is complete, a ventilation phase is started to remove all residual ozone in the sterilization chamber 10. After the ventilation phase, the door is opened and the sterilized equipment can be removed from the sterilization chamber. The temperature of the bottom of the sterilization chamber, door, steam pipe, humidifier is preferably controlled during the sterilization process.

When an object is placed in the sterilization chamber, the object (cart, equipment, container, bag) is not the same as the temperature of the sterilization chamber wall. What is put in is always lower than the above wall temperature. At some step in the sterilization cycle, the relative humidity in the sterilization chamber is very high (about 90%). The temperature difference between the material being inserted (insert) and the walls in the sterilization chamber will cause water condensation on the insert, which should be avoided as much as possible. Temperature equalization can be achieved by cooling the sterilization chamber walls or warming the insert. In the course of the present invention, the temperature difference is made equal by recirculating the atmosphere (air) in the sterilization chamber, which means the start of the sterilization process (FIG. 1). A vacuum pump 40 is used to recirculate the air in the sterilization chamber.

When the sterilization process is started, the door is closed, the vacuum pump is started, and the sterilization chamber drainage valve 44 and the recirculation valve 46 are opened (step 3 in FIG. 2). Air trapped in the sterilization chamber is drawn by the vacuum pump through the sterilization chamber drainage valve 44. By pumping air from outside the sterilization chamber, the pressure in the sterilization chamber is reduced. Since the recirculation valve 46 is opened, most of the air in the vacuum pump is sucked back through the recirculation valve 46 into the sterilization chamber. The remaining portion to be exhausted is passed through the catalyst 52 for discharge (outside).

When operated at or near atmospheric pressure, the vacuum pump 40 circulates air in the sterilization chamber at a high flow rate (according to the manufacturer's specifications, about 475 liters / minute). This results in a high flow of air through the sterilization chamber 10 and a temperature equalization between the insert, the sterilization chamber and the air. As a side effect of recirculation through the vacuum pump, the air is heated by operation of the pump (in the exemplary embodiment, the air exhausted from the pump is between 55 ° C. and 65 ° C.).

In order to increase the reliability of the recirculation step, the recirculation step is preferably divided into two parts (FIG. 4). In the first part, the air is recirculated for 10 minutes. In the second part, preferably lasts 20 minutes, but there is no recirculation since the sterilization chamber drainage valve 44 and the recirculation valve 46 are both closed at the end of the first part. The total duration of the recirculation process is thus 30 minutes.

During the recirculation process, only the continuation of the first and second parts is controlled, and all other parameters (air flow, air temperature, sterilization chamber pressure) need not be monitored or controlled. Although the displayed throughput of the vacuum pump 40, valves 44 and 46, and other elements of the recirculation circuit is constant, the actual air flow through the pump and sterilization chamber is caused by the load (insert) in the sterilization chamber. Depends on pressure drop. Furthermore, although the heat of the air from the exhaust is generated by any vacuum pump, the degree of the heat depends on the air flow rate and the friction in the vacuum pump, which varies from pump to pump. During the first part of the recirculation step, the pressure in the sterilization chamber first decreases and then stabilizes when maximum air flow is achieved. By evacuating air through the sterilization chamber drainage valve 44, the pressure in the sterilization chamber is reduced, but this lower pressure also draws air in the vacuum pump through the recirculation valve 46 back to the sterilization chamber.

In the end, the pressure is naturally stable and the actual pressure level depends on the amount of load and its placement with respect to the inlet or outlet port in the sterilization chamber. In an exemplary sterilizer according to the invention, the pressure is generally stable between 766 and 886 mbar. In the pressure graph of FIG. 4, the sterilization chamber pressure decreases again at the transition from the first part to the second part of the recirculation cycle. This occurs in the exemplary apparatus by closing the recirculation valve 46 for approximately 0.5 seconds before the sterilization chamber drainage valve 44. The pressure between the second part was about 25 torr low. At the end of the temperature equalization step, the sterilization chamber drainage valve 44 was reopened and the vacuum pump 40 was operated until the desired sterilized vacuum was reached (FIG. 4).

Before the sterilization cycle begins, the humidification chamber 32 is filled with water to an appropriate level. This is done by temporarily opening the water input valve 36. The water level control valve 36 also preferably opens automatically during the sterilization cycle if the water level falls below a predetermined limit.

At the beginning of the sterilization cycle, a vacuum is applied to the sterilization chamber (see step 4 in FIG. 2). The sterilization chamber 10 is evacuated to a vacuum pressure of about 1.0 mbar. When the absolute pressure in the sterilization chamber drops below 60 mbar, the steam intake valve 34 is closed. Once a pressure of about 1.0 millibar is achieved, the sterilization chamber drainage valve 44 is closed and the steam intake valve 34 is opened to reduce the pressure in the humidification chamber 32 to the vapor pressure in the sterilization chamber. This is because the water in the humidification chamber is forced to evaporate into the sterilization chamber 10 as a result of the automatically entering vapor pressure due to the increase in volume associated with the transfer of water from the liquid phase to the gas phase. . Preferably, during the humidification period, the valve 34 opens and closes many times during a preset time to control the rate of increase in relative humidity within the sterilization chamber. Instead of using a humidification chamber, the introduction of moisture into the sterilization chamber can be accomplished with one or more spray nozzles connected to the water supply line, or pulse water injection (the amount of water introduced is small each time) ). When the valve 34 opens, the water pressure flowing through the nozzle creates a water mist that evaporates into its volume under vacuum. Before the end of the humidification period (usually 2 to 6 minutes), the ozone generator is started.

The flow of oxygen / ozone mixture in the ozone generator is always controlled by a control valve 28 that can withstand vacuum and can regulate a flow rate of 1-3 liters per minute. As an optional feature, the ozone generator can be started as soon as the humidification period begins. This is realized by the supply valve 26 and the mixture bypass valve 29b. Supply valve 26 opens to introduce oxygen into the ozone generator. The ozone-oxygen mixture produced by the ozone generator is then led directly to the ozone catalyst 52 via the mixture bypass valve 29b. After a 30-90 minute humidification period, the oxygen-ozone mixture is directed into the sterilization chamber by opening the mixture supply valve 29a and closing the mixture bypass valve 29b. The oxygen-ozone mixture is introduced into the sterilization chamber 10 until an ozone concentration of 85 milligrams / liter is achieved in the sterilization chamber. The time required for this step depends on the flow rate and concentration of ozone gas in the mixture (preferably 150 to 190 mg / l NTP), and the ozone concentration can be monitored with known equipment. Once the desired concentration is reached, the mixture bypass valve 29a is closed to seal the sterilization chamber and maintain a humidified ozone / oxygen gas mixture in the sterilization chamber under vacuum.

Once the sterilization chamber is filled with the sterilization gas (mixed gas of oxygen and ozone), the ozone generator is stopped, the oxygen supply valve 26 is closed, and the ozone is sterilized with a volume of 125 liters (4 cubic feet). In contact with what is to be sterilized for about 20 minutes. The length of the sterilization period varies with the volume of the sterilization chamber. At this stage, the sterilization chamber is under the influence of a partial vacuum of about 610 millibar (mb). In an optional second step, the pressure level is raised to about 900 mbar using oxygen as the fill gas.

This pressure level is maintained for about 20 minutes. After the sterilization period, the vacuum is preferably reapplied to about 1.0 mbar. Once the vacuum reaches 1.0 mbar, humidification is started again by re-injection of oxygen / ozone sterilization gas mixture and sterilization period. The sterilization gas injection, humidification and sterilization period, the cycle of about 1.0 millibar vacuum can be repeated, and the number of repeated cycles (minicycles) is selected to achieve complete sterilization of the instrument. The number of repetitive cycles required in the experimental setup of the method and apparatus according to the invention involving 125 liters (4 cubic feet) was 2. This setup met FDA (SAL10-6) Security Assurance Level standards.

After complete sterilization, a ventilation phase is performed to remove all ozone and humidity in the sterilization chamber 10. The ventilation phase begins after the last sterilization period. The sterilization chamber drainage valve 44 is opened and the vacuum is lowered to about 6.5 mbar. When the pressure reaches 60 mbar to exhaust residual ozone in the sterilization chamber, the steam intake valve 34 is closed. Once a vacuum pressure of 6.5 mbar is obtained, the drainage valve 44 is closed, the oxygen supply valve 21 is opened, and oxygen enters the sterilization chamber 10.

When atmospheric pressure is reached, the oxygen supply valve 21 is closed and the sterilization chamber drainage valve 44 is opened and evacuated again until a pressure of 1.3 mbar is reached. This last 1.3 mbar ventilation cycle is repeated once for a total of 3 ventilation cycles. When atmospheric pressure is reached after the last cycle, the sterilization chamber door mechanism is driven so that the contents of the sterilization chamber can be removed. The ventilation phase has two functions. One is to remove all ozone residues in the sterilization chamber before opening the door, and the second is to dry the material to be sterilized by evaporation when vacuum pressure is applied. Of course, different vacuum pressures, cycle times, and repetition rates can be used as long as the desired ozone removal and drying is achieved.

The ozone-containing gas discharged from the sterilization chamber 10 passes through the ozone catalyst 52 before releasing the gas into the atmosphere to ensure complete decomposition of the ozone in the sterilization gas. The ozone catalyst 52 is used only in the sterilization chamber exhaust during operation of the ozone generator 22 (valves 26 and 29b selected) during the two parts of the sterilization cycle. During the start-up phase of the ozone generator 22, the mixture bypass valve 29b is opened and ozone traverses (passes) the catalyst 52. When the start-up phase of the ozone generator is completed, the bypass valve 296 is closed. During the exhaust of the sterilization chamber 10, the sterilization chamber drainage valve 44 is opened, and the ozone-containing sterilization waste gas is guided to the catalyst 52. When the exhaust of the sterilization chamber 10 is completed, the drainage valve 44 is closed. The circulation of ozone is ensured by the vacuum pump 40. The ozone catalyst 52 is placed upstream or downstream of the vacuum pump 40.

Control system The sterilizer is preferably controlled by the mechanism shown in the electrical block diagram (Fig. 3) and the process flowchart (Fig. 2). The control system is built around a PLC (programmable logic controller) shelf. This shelf consists of a power supply device (107), a CPU unit (108), a transceiver network device (109), a 32 × 24 volt DC discrete input module (110), a 16 × 120 VAC discrete output module (111) and an 8 × 120 VAC. Includes a TRIAC control output module (112). All these modules are located on a physical shelf that contains data and address buses.

Device Net is an industrial serial communication protocol widely used in the instrumentation and control industries. In this sterilizer, the device net transceiver (109) communicates data between the CPU (109), the 15-bit A / D converter (106), and both digital temperature interfaces (120) (121) in full duplex. Used for.

The PLC CPU has three RS232 ports. One is used to send and receive data to the touch screen terminal (118), the second is used to send and receive data to the thermal printer (119), and the third is a PC (personal computer). Used as a service port that can be connected to communicate with the PLC CPU (108) to load up the control protocol program. (Control protocol programs are not within the scope of this document.)

The touch screen terminal (118) is placed in front of the sterilization chamber by the thermal printer (119). The touch screen terminal and the thermal printer constitute a user interface terminal.
The power required for “Thermal Printer (119), Device Net Link (109), (106), (120), (121), Sterilization Chamber Pressure Sensor (104) and PLC Discrete Input (111)” is , Provided by a DC power supply (103).

The sterilization chamber pressure sensor (104) and ozone monitor (105) are standard 0 to 10 VDC output signals. Both signals are sent to a 15-bit A / D converter. Then, both converted signals are sent to the CPU by the digital link processing network device.
The sterilization chamber power input (100) is a three-phase four-wire 208VAC (with neutral terminal) in a star configuration. This three-phase power input is filtered to prevent RFI (101) being routed. The power is then distributed by the output distribution bus (102) to the various electrical systems of many sterilizers.

A cooling system (60) is used to cool the ozone generator. The system includes a cooling unit (114) and a coolant circulation pump (113). The temperature of the cooling liquid in the ozone generator is detected by an RTD arranged in the ozone generator. The temperature is transmitted to the CPU (108) by the network system (109) (120) (121) of the apparatus. The coolant circulator (113) and the cooling unit (114) are controlled by a contactor driven by a PLC output (111) controlled in sequence by a software protocol. All inputs and outputs required to achieve cooling system control are listed in the electrical block diagram: circulation pump contactor, cooling system contactor, circulator overload sensor, cooling system overload system, operation Non-sensor coolant system, non-operating sensor circulation pump, coolant low pressure and coolant flow switch.

The vacuum control system includes a vacuum pump 40 and a pressure sensor 104. The start and stop operation of the vacuum pump is controlled according to the control protocol. All inputs and outputs required for the vacuum system are listed in the figure: vacuum pump contactor, vacuum pump without operating sensor, vacuum pump overload sensor, sterilization chamber pressure reducing valve (44), recirculation valve ( 46) and an oxygen supply valve (21) to the sterilization chamber. The pressure sensor output is converted by a 15-bit A / D converter (106) and sent to the CPU by the digital link network (109) of the device. The pressure sensor also has two discrete outputs that indicate to the CPU (108) the following conditions: a temperature dependent sterilization chamber pressure sensor and a thermal sterilization chamber pressure sensor. These two signals are listed in the electrical block diagram as PLC inputs.

The sterilization chamber door actuator system includes a screw-type electrical drive and has four inductive sensors that allow detection of the presence of the door and the locked or unlocked position of the actuator as part of the control protocol. . The door opening system uses an alarm condition management protocol to ensure user safety. All the inputs and outputs required to accomplish the door actuator system are listed in the electrical block diagram: door lock contactor, door open contactor, door closed lower sensor (S2), door closed upper sensor (S1). ), Door closing sensor (S4), door opening sensor (S3).

The ozone power supply (116) includes a full-wave rectifier, an oscillation circuit, and a high voltage transformer. The output of the high voltage transformer is connected to an ozone generator (22). The power supply (116) is mounted as a resonator that uses the untuned characteristics of a high voltage transformer. The PLC 108 controls ozone production through a feedback control loop, ascertained by the ozone monitor 104, and controls the D / A converter at which the desired concentration for sterilization is achieved and maintained during the sterilization cycle. All inputs and outputs required for the ozone generation system are listed in the figure: Oxygen supply valve (26), ozone supply valve to sterilization chamber (29a), ozone exclusion catalyst valve (29b), output of ozone monitor Zeroization and cycle counter, high voltage control, high voltage current limiter, ozone high voltage overload sensor rectifier high temperature sensor, ozone high voltage sensor not operating sensor, ozone monitor without detection mistake.

The ozone supply valve (29a) and the ozone exclusion catalyst valve (29b) to the sterilization chamber are driven by an electronic solenoid output damper (117). This device prevents overheating of the valve.

The oxygen supply system includes an electronic oxygen pressure regulator comprising a proportional valve 26, a pressure sensor 26 a and a flow meter 25. The oxygen supply system further includes a valve 21 and a maximum 350 millibar (gauge) pressure regulator 24 for supplying oxygen directly to the sterilization chamber 10. The sensor and pressure regulator are an integral part of the alarm status protocol to ensure user protection. The inputs used for alarm conditions are listed in the electrical block diagram: oxygen high pressure sensor and oxygen low pressure sensor.

The control system includes a user interface 118. In a preferred embodiment, this interface includes a liquid crystal (LCD) touch display screen 118, a performance reporting printer 119, and a COM port (series RS232) that allows the user to send and receive as required for use of the device. It will be apparent to those skilled in the art that other types of user interfaces can be used, such as touch sensor pads, keyboards, and other types of communication interfaces. Thermal printer input status appears in the electrical block diagram: printer offline sensor and printer out of paper.

The system according to the invention can produce a relative humidity of 95% or more.
The energy required to evaporate water during the humidification phase is taken from a number of sources. In principle, it is received from the water and structure of the humidification unit. This contributes to further cooling of the humidifier and its contents. In effect, at 20 ° C, water boils to an absolute pressure of 23.3 mbar, and at 35 ° C, water boils to an absolute pressure of 56.3 mbar. The vacuum in the sterilization chamber is preferably adjusted so that the boiling temperature of water is equal to or lower than the temperature in the sterilization chamber. Since the boiling temperature is very low, the temperature of the water in the humidifier will drop rapidly and based on the energy available from the surrounding structure and liquid, the water in the humidifier may freeze before evaporating Absent. The evaporation process may cool the humidifier until the humidity in the room condenses and freeze the outer surface of the humidifier. In other preferred embodiments, this is avoided by sufficiently heating the outer surface of the humidifier to maintain the outside of the humidifier and the water in the humidifier at room temperature. It will be readily apparent to those skilled in the art that this is achieved by a heating arrangement (not shown). Also, due to the high level of relative humidity achieved in the sterilization chamber, there is condensation on the interior and interior water evaporation pipes. In order to reduce water condensation, the bottom of the sterilization chamber, the door and the water evaporation pipe are also heated.

Water vapor generated in the humidifier increases the relative humidity in the sterilization chamber. The humidification phase is continued until the relative humidity of the gas surrounding the medical device contained in the packaging bag or packaging container reaches a minimum of 85%, preferably 100%. For a sterilization chamber with a volume of about 125 liters, permissible water vapor increases the pressure to about 50 mbar in the sterilization chamber. Since this value is temperature dependent, it is an approximate value.

Oxygen / ozone-containing sterilization gas is injected into a sterilization chamber humidified at an adjacent ambient temperature. The ozone-containing gas is not heated as in the prior art. For optimum operation of a sterilizer having a 125 liter sterilization chamber and according to the present invention, the system uses about 85 mg / l (liter) of ozone to obtain at least 10600 mg of ozone for each of the sterilization chamber contents. And can produce an ozone flow of about 1-3 liters per minute.

In another preferred process, humidification of the sterilization chamber is performed by a pair of nebulizers. Water is supplied to each of the sprayers from a water tank connected to a drinking water supply source or a pure water (purified water) source. Ozone is supplied from the ozone accumulation tank to the sprayer. The nebulizer is made of an ozone-resistant material and is installed directly in the sterilization chamber. When a vacuum level is reached in the sterilization chamber, the nebulizer releases water and ozone. Ozone is moistened in the nebulizer. The ozone / spray mixture penetrates into the sterilization chamber. Injection of water into the sterilization chamber under vacuum has the effect of evaporating the water immediately. The operating temperature of the sterilization chamber is 25 ° C. to 40 ° C., which is the temperature at which water evaporates at a pressure of 31.7 mbar to 73.8 mbar. Therefore, water becomes steam by the vacuum created by the vacuum pump. The resulting ozone / water vapor mixture enters the material to be sterilized.

Modifications and changes in the specifically described embodiments may be made without departing from the scope of the invention, which is limited only by the appended claims.

DESCRIPTION OF SYMBOLS 10 Sterilization room 22 Ozone generator 30 Humidifier arrangement 32 Humidification room 40 Vacuum pump 60 Cooling system

Claims (15)

A method of sterilizing an article in a sterilization chamber in a gas atmosphere, comprising the following steps:
a) has a sterilization chamber;
b) Place the article in the sterilization chamber,
c) sealing the sterilization chamber,
d) While the sterilization chamber is sealed, equalize the temperature of the article and the atmosphere in the sterilization chamber,
e) applying a vacuum of a preselected vacuum pressure to the sterilization chamber;
f) supplying water vapor to the sterilization chamber under vacuum;
g) supplying ozone-containing gas to the sterilization chamber;
h) maintain the sterilization chamber sealed for a preselected treatment time;
i) The sterilization chamber is sealed during the whole process and the vacuum of the sterilization chamber is opened. The equalizing step includes
By evacuating the sealed sterilization chamber and recirculating the exhausted air to the sterilization chamber for a preselected time to equalize the temperature of the evacuated air and the temperature of the article 2. The method of claim 1, comprising equalizing the temperature of the article, the atmosphere in the sterilization chamber, and any article and material in contact with the atmosphere. The method according to claim 1, wherein the temperature in the sterilization chamber is operated at 25C to 60C. The method of claim 3, wherein the temperature is operated at 25C to 35C. The method of claim 3, wherein the temperature is operated at 40C to 60C. The method according to claim 1, wherein the vacuum pressure is between 0.1 mbar and 10 mbar. 6. The method according to claim 5, wherein the vacuum pressure is between 0.5 mbar and 2 mbar. The method of claim 1, wherein during step c), the temperature of the evacuated and recirculated air increases and the relative humidity of the evacuated air decreases. The method of claim 1, wherein the amount of water is selected to bring the relative humidity level in the sterilization chamber to between 85% and 100%. The method of claim 7, wherein the amount of water is selected so that the level of relative humidity is at least 95%. The method of claim 1, wherein steps (c) through (g) are repeated at least once. 10. The method of claim 9, wherein steps (c) through (g) are repeated many times to ensure complete sterilization of the article. The method of claim 1, further comprising the step of passing all the gas exhausted from the sterilization chamber through means for passing through the ozone depleting means to prevent release of ozone into the atmosphere. -Sterilization chamber,
-Means for sealing the sterilization chamber against the environment;
-Means for equalizing the temperature of the sterilization chamber, the material placed in the sterilization chamber, and the atmosphere in the sterilization chamber by recirculating the atmosphere;
-Means for supplying ozone-containing gas to the sterilization chamber;
-Means for supplying water vapor into the sterilization chamber;
as well as,
An apparatus for sterilizing an article comprising means for supplying a sufficient vacuum to the sterilization chamber to lower the boiling point of water below the temperature in the sterilization chamber. 15. The apparatus of claim 14, wherein the equalization means includes means for evacuating the atmosphere in the sterilization chamber and a recirculation valve for returning at least a portion of the atmosphere evacuated to the sterilization chamber.

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