WO2000057929A1

WO2000057929A1 - A microwave based device for sterilisation/disinfection of surgical and dental equipment

Info

Publication number: WO2000057929A1
Application number: PCT/DK2000/000146
Authority: WO
Inventors: Peter Michael Nielsen
Original assignee: Medimage Holding Aps
Priority date: 1999-03-25
Filing date: 2000-03-27
Publication date: 2000-10-05
Also published as: EP1191950A1; AU3419100A

Abstract

The present invention relates to an antimicrobial apparatus useful for sterilisation and/or disinfection of articles, said apparatus comprises an accessible volume being able to be confined in a manner such that it constitutes a Faraday cage, at least on microwave source directing microwaves into the accessible volume, at least one microwave field sensor for sensing the intensity of the microwave field in the accessible volume, said sensor provides input to a control unit for controlling the supply of microwaves to the accessible volume. In particular embodiments of the invention the antimicrobial apparatus further comprises a fluid tight container unit for sterilisation and/or disinfection hollow articles, and/or comprises at least one autoclave. Furthermore, the invention also relates to a method of controlling the antimicrobial apparatus.

Description

A MICROWAVE BASED DEVICE FOR STERILISATION/DISINFECTION OF SURGICAL AND DENTAL EQUIPMENT

FIELD OF THE INVENTION

The present invention relates to an antimicrobial apparatus used for sterilisation and/or disinfection of articles such as surgical instrument by use of microwaves.

BACKGROUND OF THE INVENTION

Today, sterilisation and/or disinfection of for instance surgical instrument is typically carried out by use of time consuming and at the same time expensive autoclaves, in * which the instruments to be treated is exposed to high pressure and high temperature for a period of time in order to destroy bacteria and/or virus present at or in these instruments.

As these conventional autoclaves often require special trained personnel in order to treat the instrument correctly, there exists a need for an antimicrobial apparatus which is relatively inexpensive, easy to handle and at the same time does not require the skills of a specially trained person to use.

Accordingly, it is an aim of the present invention to provide an antimicrobial apparatus fulfilling such requirements.

In one aspect, the present invention relates to an antimicrobial apparatus used for sterilisation and/or disinfection of articles, the apparatus comprises an accessible volume being able to be confined in a manner such that it constitute a Faraday cage, at least one microwave source directing microwaves into the accessible volume at least one microwave field sensor for sensing the intensity of the microwave field in the accessible volume, said sensor provides input to a control unit for controlling the supply of microwaves to the accessible volume. Thus, the present invention provides an antimicrobial apparatus wherein the articles such as surgical instruments are sterilised and/or disinfected by placing the articles to be treated inside an accessible volume and exposing them to microwaves. The at least one volume should be accessible in the sense that access should be available when the articles to be treated is to be placed inside the volume

The microwave source can be any conventional magnetron or the like and the output from the microwave source can be intermittent or constant. In the case where a microwave source generating microwaves intermittent the intensity of the microwave field can be controlled by prescribing the duration of the active period i.e. the period where the source generated microwaves. In the case where the source generates microwaves constantly, the intensity can be controlled for instance by controlling the effect applied to the source.

Furthermore, in order to provide homogeneous microwave field inside the accessible volume the apparatus may also comprise microwave distribution means, such as a rotating metal object placed inside the accessible volume, for distributing microwaves inside the accessible volume.

One great advantage of the antimicrobial apparatus according to the present invention is that the sterilisation and/or disinfection process can be monitored and controlled in response to the monitoring. By this kind of feed back control of the process carried out during sterilisation and/or disinfection of the articles, an apparatus is provided which may be able to determine whether the process has been carried out successfully.

This is a major advantage when comparing the present invention with the state of the art, which in general do not include any direct determination possibility relating to the quality of the process. Furthermore, this feed back control makes it possible for an un-trained personal to apply the apparatus with equally good result at each use.

As the apparatus according to the present invention uses microwaves for the sterilisation and/or disinfection process, it is crucial that the user of the apparatus is not exposed to the microwaves. This is achieved according to the broad aspect of the invention by letting the process takes place inside a so-called Faraday cage. The Faraday cage is provided by a metal structure, which can be made up by the walls of the accessible volume or it can be made up by a metal wire frame encircling the accessible volume.

In a preferred embodiment of the present invention, the antimicrobial apparatus may further comprise at least one container situating inside the accessible volume and holding liquid, such as water. This fluid may take up superfluous microwaves and may help to generate an atmosphere participating in the disinfection/sterilisation process.

The antimicrobial apparatus according to the present invention may further comprise least one tray having at least one cavity for housing an article to sterilised and/or disinfected. This tray may support the articles when situated inside the accessible volume.

In a preferred embodiment the at least one tray may preferably be made of a microwave transparent material, such as plastic or the like, so as to provides trays which will not shield the articles from the microwaves exposed to them.

In a specific preferred embodiment of the invention the at least one cavity of the at least one tray match the shape of the article to be sterilised such that substantially only the article intended to be housed by the cavity can be placed properly therein.

Furthermore, a tray according to the present invention may comprise sensor means for sensing the type(s) of instrument(s) when said instrument(s) is(are) placed in said cavity(cavities). Preferably such sensor means is(are) arranged in said cavity(cavities)

A tray according to the invention may further comprise identification means containing information for identifying article(s) housed by the cavity/cavities of the tray. Such information may be static information such as a bar code or the like, or it may be a dynamic information being updated when the articles are placed in the cavities. In the latter case, this is in a preferred embodiment of the invention provided by connecting one or more sensors situated in the cavities to a controlling circuitry.

The controlling of the microwave source is in an important aspect of the present invention made dependent of the articles actually situated in the tray, when these are placed inside the accessible volume. In order to be able to provide input to the control unit of the antimicrobial apparatus, the apparatus may further comprise accessing means for accessing the information contained by the identification means of the tray(s) when the tray(s) is(are) situated in the accessible volume. The accessing means is/are thereby able to provide information to the control unit relating to the articles present in the antimicrobial apparatus.

In preferred embodiments, the identification means may comprise a bar code and the assessing means comprises an optical bar code reader adapted to read the bar code. Alternatively, the identification means may comprise dynamic identification means and the assessing means is then adapted to assess the identification of the identification means. The term "dynamic identification means" denotes means in which information may be altered.

By this way of having matching articles and trays and by controlling the sterilisation and/or disinfection process based on a determination of the number and types of instrument present in the antimicrobial apparatus, the possibility of unintended use of the antimicrobial apparatus is minimised. Such situations where for instance the orientation and/or the relative position of the articles relative to the position of the microwave source plays a role in the process may be avoided. Furthermore, the risk of personel placing the articles too close to each other (which could produce sparks) is similar avoided or at least minimised.

In very important embodiment of the present invention the antimicrobial apparatus may further comprise a fluid tight container unit for sterilisation and/or disinfection of hollow articles, the fluid tight container unit comprises a confined chamber holding means situated in the confined chamber for holding at least one hollow article in a predetermined orientation relative to a bottom plane of the container, liquid holding means situated in fluid communication connection with the confined chamber for holding a liquid, means for distributing vaporised liquid from the liquid holding means to the inside of the hollow articles, and a communication passage which enables a fluid communication at least out of the confined chamber if the pressure inside the confined chamber exceed a predetermined value, such as 3 atm., preferably 3,5 atm., alternatively 4 atm and more preferably 4,5 atm.

Preferably, the means for distributing vaporised liquid from the liquid holding means to the inside of the hollow articles is/are flow channel(s) leading vaporised fluid from the liquid holding means through the article holding means and into the interior of the hollow article(s).

A problem occurring when applying microwaves to sterilise and/or disinfect hollow articles is that these hollow articles constitute a Faraday cage themselves whereby no microwave field is present inside the instruments. In a very important aspect of the present invention, this problem is solved by a fluid tight container wherein the articles to be treated is placed inside a confined chamber of the container unit. The fluid tight container unit is then placed inside the accessible volume of the antimicrobial apparatus according to the present invention and microwave radiation is exposed to the unit. The fluid tight container or at least the liquid holding means is(are), of course, made of the microwave penetrable material.

Preferably, the fluid tight container unit may be releasable assembled by a top part and a bottom part in such a manner that the confined chamber is accessible

The container unit is preferably ttiade of a material letting the microwaves pass through and the microwaves starts to heat up water situated in a liquid holding means. In a preferred embodiment of the fluid tight container unit according to the invention the articles are preferably kept in a vertical orientation and the liquid holding means is situated below the articles such that the pressure increase in the liquid holding means due to the heating of the liquid will force the vaporised liquid, such as steam, up through the hollow part of the articles.

In another preferred aspect of the present invention the fluid tight container unit according to the present invention, may further comprise a temperature sensor and/or a pressure sensor for sensing respectively the temperature and the pressure inside the confined chamber, whereby the temperature and the pressure may be monitored for security or quality purposes and/or the temperature and pressure sensor may provide input to the controlling unit.

In another very important aspect of the present invention the antimicrobial apparatus may further comprise at least one autoclave, said at least one autoclave comprising a container device having an accessible chamber, said accessible chamber is situated inside the accessible volume of the antimicrobial apparatus, said container device comprises a fluid entry passage and a fluid outlet passage both being in fluid communication with the accessible chamber, a condenser device for condensing fluid being in gas phase, said condenser device has an outlet connected to the fluid entry passage and having an inlet connected to the fluid outlet passage, said condenser being situated outside the accessible volume of the antimicrobial apparatus.

Preferably the container device is made of a material being penetrable by microwaves.

In this embodiment article(s) to be sterilised/disinfected is(are) placed inside the accessible chamber and as this chamber is situated inside the accessible volume of the antimicrobial apparatus, microwaves penetrates into the chamber and act on the articles. Furthermore, the microwaves generates steam by heating the fluid entering the container device through the fluid entry passages whereby the article(s) is(are exposed to steam also, which will if not performing the sterilisation/disinfection alone then at least participate thereto. In preferred embodiments, the accessible chamber of the autoclave is defined by a open ended container part and a lid part adapted close the open end of the open ended the container, which lid part preferably is engaged with the container part by a lock means, preferably by bayonet socket, such as a thread.

In order to be able to seal accessible chamber, preferably in order to be able to raise the pressure inside said chamber, the container device of the autoclave may comprise a sealing, such as an o-ring, arranged such that at least a part of the lid part and at least a part of the container part abut the sealing.

Preferably, the autoclave may further comprise a fluid reservoir being in fluid communication with the fluid entry passage and being placed inside the accessible volume of the antimicrobial apparatus. Such a fluid reservoir may preferably be situated below the accessible chamber, which reservoir in this case typically could be embodied by providing a depression in the fluid entry passage. In this and other situations - for instance in combination with the fluid tight container unit - the microwave source(s) (the magnetron(s)) may advantageously be placed below said reservoir (below said liquid holding means when using the fluid tight container unit).

In embodiments where the autoclave comprises more than one accessible chamber the autoclave may comprise only one fluid reservoir being shared by the accessible chambers so that steam is distributed from this reservoir to all the accessible chambers.

In a specific embodiment of the antimicrobial apparatus according to the present invention, the autoclave may further comprise fluid controlling/restriction means, such as valve means, pumping means, Venturi tube means or the like, for controlling/restricting fluid flow to/through the fluid entry passage. Such restriction/controlling of the fluid flow may be used to guarantee that no liquid fluid enters the accessible chamber.

Preferably the condenser device may be a passive device, i.e. a device not requiring active cooling provided for instance by Peltier elements or the like, but alternatively the condenser device may be an active device, where cooling is provided by Peltier elements or a heat pumping device in general. Also preferably the autoclave may be an integral part of said apparatus.

In yet another preferred embodiment of the antimicrobial apparatus the fluid entry passage of the container device may preferably be connected to the outlet of the condenser device by a pipe being inclined relative to horizontal, said inclination being so that the connection between the condenser device and the pipe is situating at a higher vertical position than the connection between the pipe and the fluid entry passage. This inclination may provide a fluid flow from the condenser device to the container device without using pumping means or the like.

In an important embodiment of the present invention the antimicrobial apparatus may further comprise a temperature sensor for sensing the temperature inside the accessible chamber of the autoclave and/or a pressure sensor for sensing the pressure inside the accessible chamber of the autoclave. Said sensor(s) may preferably be connected to the controlling unit of the apparatus according to the invention and provide(s) input to said unit so that the disinfection/sterilisation process may be controlled on the pressure and/or temperature inside the chamber, which controlling may be performed based on the pressure and/or temperature alone or in combination with the sensed microwave field.

In preferred embodiments of the apparatus according to the present invention the autoclave may further comprise a detachable basket adapted to hold article(s) to be sterilised/disinfected, said detachable basket being situated inside the accessible chamber of the container device.

A very important aspect of the present invention relates to a method for controlling an antimicrobial apparatus according to any of the preceding claims, wherein the method comprises the steps of - storing in a memory a prescribed spatial and/or time variation of a characteristic microwave field variable inside the accessible volume,

- determining a spatial distribution of an actual characteristic microwave field variable in the accessible volume at prescribed first time intervals, - at each determination of the spatial distribution of the actual characteristic microwave field variable at the prescribed first time intervals

comparing the spatial distribution of the actual characteristic microwave field variable with the corresponding prescribed characteristic microwave field variable variation, and

increasing the output from the microwave source, if the determined characteristic microwave field variable is smaller than the corresponding prescribed characteristic microwave field variable, and

decreasing the output from the microwave source, if the determined characteristic microwave field variable is larger than the corresponding prescribed characteristic microwave field.

Storing of the prescribed spatial and/or time variation of a characteristic microwave field inside the accessible volume may preferably be done in advance of use of the antimicrobial apparatus for instance when the apparatus is produced or when a new variation is needed.

The terms "microwave source" is intended to cover also the case where more than one, for instance, magnetron is used. In this case increase/decrease may be performed by controlling all magnetrons equal but increase/decrease may also be performed by turning off/turning on one or more magnetron.

The characteristic microwave field variable is preferably a variable stating most precisely the effect of the microwave field on the instruments being treated. In a situation where the articles need to be exposed to a prescribed microwave field effect the prescribed spatial and/or time variation of the characteristic microwave field variable is the total effect excerted in the accessible volume, i.e. the accumulated effect during the treatment. -

10

In a preferred embodiment of the method according to the present invention the total effect is determined based upon the measurement from at least one microwave field sensor.

In the situation where the antimicrobial apparatus is used in conjunction with the fluid tight container unit the control method according to the present invention may further comprise the steps of

- storing in a memory a prescribed spatial and/or time variation of a characteristic temperature in the confined chamber(s), - determining a characteristic temperature in the confined chamber(s) at prescribed second time intervals,

at each determination of the characteristic temperature at the prescribed second time intervals,

comparing the characteristic temperature with the corresponding prescribed characteristic temperature, and

increasing the output from the microwave source, if the determined characteristic temperature is smaller than the corresponding prescribed characteristic temperature, and

decreasing the output from the microwave source, if the determined characteristic temperature is greater than the corresponding prescribed characteristic temperature.

The characteristic temperature determined may, both in the case where more than one container unit is utilised and where only one is used, be the smallest measured inside the confined chamber(s) of the at least one fluid tight container unit(s).

In yet another aspect of the present invention an antimicrobial apparatus useful for sterilisation and/or disinfection articles is provided. Said apparatus comprises an accessible volume being able to be confined in a manner such that it constitute a 1 1

Faraday cage, a microwave source directing microwaves into the accessible volume and a control unit for controlling the supply of microwaves to the accessible volume, said apparatus further comprises at least one autoclave, said at least one autoclave comprising - a container device having an accessible chamber, said accessible chamber is situated inside the accessible volume of the antimicrobial apparatus, said container device comprises a fluid entry passage and a fluid outlet passage both being in fluid communication with the accessible chamber, a condenser device for condensing fluid being in gas phase, said condenser device has an outlet connected to the fluid entry passage and having an inlet connected to the fluid outlet passage, said condenser being situated outside the accessible volume of the antimicrobial apparatus, and/or a fluid tight container unit for sterilisation and/or disinfection of hollow articles, the fluid tight container unit comprises a confined chamber holding means situated in the confined chamber for holding at least one hollow article in a predetermined orientation relative to a bottom plane of the container, - liquid holding means situated in fluid communication connection with the confined chamber for holding a liquid, means for distributing vaporised liquid from the liquid holding means to the inside of the hollow articles, and a communication passage which enables a fluid communication at least out of the confined chamber if the pressure inside the confined chamber exceed a predetermined value, such as 3 atm, preferably 3,5 atm. alternatively 4 atm. and more preferably 4,5 atm.

The antimicrobial apparatus according to this aspect may, of course, comprise the features, such as the trays, according to the other aspects of the invention and the autoclave and the fluid tight container unit may, of course, comprise the specific features described herein in connection with the first aspect of the present invention. Furthermore, the methods described herein may, of course, also be utilised for controlling the antimicrobial apparatus according to this aspect. To summarise, this aspect may be regarded as being equal to the other aspects of the present invention except from the absence of a microwave sensor.

In the following the invention will be described in greater details, and in particular preferred embodiments thereof, by way of examples and in connection with the accompanying figures wherein

Fig. 1 is a schematic view of an antimicrobial apparatus according to the present invention,

Fig. 2 is a schematic view of an embodiment of a tray used for holding the articles to be sterilised,

Fig. 3 is a schematic view of another embodiment of a tray used for holding fluid tight containers according to the present invention,

Fig. 4 is a schematic view of a top part of a fluid tight container unit according to the present invention,

- Fig. 5 is a schematic view of a bottom part of a fluid tight container unit according to the present invention,

Fig. 6 is a schematic view of a fluid tight container unit comprises by the bottom and top parts of Fig. 4 and 5,

Fig.7 is a cross sectional view of a fluid tight container unit according to the present invention,

Fig. 8 is a cross sectional view of an autoclave according to the present invention.

Fig. 9 shows a three dimensional view of an embodiment of container unit of an autoclave according to the present invention, and

Fig. 10 shows schematically a controlling unit according to the present invention.

In Fig. 1 a schematic view of a first embodiment of an antimicrobial apparatus according to the present invention is shown. The antimicrobial apparatus 2 comprises an accessible volume 4, which can be accessed by opening the door 6 as indicated in Fig. 1 . Furthermore, inside the accessible volume a water reservoir containing water (not shown) may be present. The purpose of the reservoir is to diminish the risk of arcing inside the accessible volume.

According to the aim of the present invention, the article(s) to be sterilised is(are) to be sterilised by use of microwaves. Therefore, the antimicrobial apparatus comprises a microwave source 8 which is shown by dotted lines in Fig. 1 . The microwave source can in general be any kind of magnetron and a proper choice will be discussed in greater details below. Furthermore, as it is a crucial objective of the present invention to guarantee a pre-determined spatial distribution of the microwave field and the intensity thereof, at least on sensor 10 - a microwave field intensity sensor - for sensing the intensity of the microwave field is provided inside the accessible volume.

In order to provide a microwave tight volume, the accessible volume 4, when closed by the door 6, constitutes a Faraday cage. In order to provide this Faraday cage, the extremities of the volume 4 and the door must be made of a material being able to conduct electricity, for instance iron. The material may be arranged in many different ways such as a grid of wires encircling the volume 4 or the walls of the volume may be covered by a metal plate or the walls may be made themselves of metal.

In the preferred embodiment the volume 4 is defined at the top, bottom and back by an iron plate and the door 6 is made of a glass plate covered inside by a punched iron plate. All parts defining the volume 4 are in electrical contact with each other, which electrical contact is provided by welding the top, bottom and back parts together and 14

the electrical contact between the punched door's iron plate and the other parts is provided by iron hinges hinging the door to the other parts.

In the preferred embodiment, guiding rails 1 2 for guiding a tray 14 (one such tray is 5 shown in Fig. 2) upon insertion in the volume 4 are provided on the walls of the accessible volume 4. When the tray 14 is situated inside the volume 4, the rails 12 furthermore support the tray 14.

In order to avoid interaction between the microwaves and the tray 14, the tray 14 is 10 made of a microwave transparent material. In the preferred embodiment the tray 14 is made of plastic. Also, in order to avoid interaction between microwaves and the guiding rails 1 2 these rails are made of the same material as the tray 14.

The tray 14 comprises in the preferred embodiment of the present invention cavities 15 1 8 for holding the articles to be sterilised, and it is also preferred that the shape of these cavities match the shape of the articles. The purpose of these cavities 1 8 is to provide a sterilisation apparatus where on the one hand the risk of producing sparks inside the volume is minimised (spark can occur if metal surfaces contacts during radiation with microwaves) and on the other hand a high security is achieved by 20 forming the tray 14 such that unintended articles does not fit into the cavities 1 8.

In a particular important aspect of the invention, the supply of the microwaves is controlled by the type and/or amount of articles present in the volume. In order to automatize the supply of microwaves to the volume 4, accessing means 1 6 being

25 able to access information relating to the contents of the trays 14 is situated inside the volume for reading information relating the contents of the tray 14. Corresponding Identification means 20 corresponding to the accessing means 1 6 is placed on the rear side of the tray 14 such that the information is accessed when the tray 14 is placed inside the volume 4.

30

In one embodiment of the invention, the identification means 20 is static information such a bar code or the like and the accessing means 1 6 is an optical reader being able to read the bar code. Other examples are magnetic strips and electrical circuitry having corresponding readers. 15

In another embodiment of the invention, the identification means 20 is dynamic in the sense that it detects the contents of the tray 14 and the information kept by such dynamically identifications means contains the information relating to the number and type of instruments present in the tray. Such a dynamic identification means comprises sensors present in the cavities 18 of the tray 14. Each sensor is able access a "code" relating to that particular instrument being sensed by the sensor. In this case the instruments are provided a code, such as an id-number, which are read by the sensors 18 and these codes are provided to the instrument by engraving.

Different other choices are possible, the sensor may be shaped so that a major and characteristic part of the instrument must interact with the sensor in order to detect that the instrument and cavity match or the instruments it self may contain a code accessible for the sensor.

As the invention relates to a disinfection and/or sterilisation process of for instance surgical instruments, one has to be certain to a very high degree about the effect of the process. Therefore, the spatial and time variation of the microwave field intensity inside the accessible volume 4 plays a crucial role in the invention.

In order to gain knowledge about the most efficient spatial and time distribution of the microwave field intensity test is typically carried out for a number of different instruments and combinations thereof. Typically, these test is performed by adding e.g. live bacteria to the instruments and then exposing the instruments inside the accessible volume 4 to microwave until the live bacteria is no longer able to reproduce it self.

The results of these tests will be build into a memory of a controlling apparatus 22 (shown schematically only in Fig. 1 by use of dotted lines) for controlling the microwave source, and the results normally comprise a numerical representation of a characteristic microwave field variable, such as the microwave field intensity or the microwave field effect i.e. the accumulated intensity during processing. -

16

Many different choices of such a characteristic microwave field variable may be appropriate, and in the preferred embodiment of the invention, the characteristic field variable is the smallest sensed field intensity found among the field intensity sensed at different spatial positions at substantially the same instant.

This characteristic field intensity is then compared with a corresponding prescribed field intensity and the output of the microwave source is controlled in relation to this comparison.

During operation of the antimicrobial apparatus it is preferred to sense the field intensity at prescribed first time intervals, i.e. the field intensity is measured by use of the sensor(s) 10 periodically for instance every 0.1 msec. Then, in the case where more than one sensor is applied the characteristic field intensity is determined as for instance the smallest measured, and this characteristic field intensity is then compared with the corresponding prescribed field intensity at that particular instant. If the characteristic field intensity is found to be smaller than the corresponding prescribed characteristic field intensity the output of the microwave source is increased, and in the case where the characteristic field intensity is found to be larger than the corresponding prescribed characteristic field intensity the output of the microwave source is decreased.

Furthermore, the characteristic field variable may also comprise the total field effect excerted during the process in the accessible volume or the total effect excerted may be used alone as a characteristic field variable.

In the latter situation, information from the sensor(s) 1 0 is directed towards the controlling unit 22 at first time intervals and the characteristic field intensity is determined together with the total field effect excerted, i.e. the accumulated effect, until the present instant. If this accumulated effect is smaller than the prescribed, two strategies can be followed in order to achieve the required field effect excerted at the termination of the process: a new process time can be calculated and/or the output from the microwave source may be increased. -

17

A situation where the new process time is calculated to be more than twice as long as the initial prescribed process time could occur for instance if the actual configuration of articles in the accessible volume 4 is such that a "dead-area" has been established. This situation is in the preferred embodiment treated by logging in a memory of the controlling unit 22 which of the sensors 10 measuring the "dead- area" i.e. the sensor which measures the lowest field intensity, and then using the second smallest field effect measured as the characteristic field effect on which the success criteria should be based.

When the process is terminated in such a situation the controlling unit 22 scans the memory for which of the sensors 10 have been measured dead-areas and in the case where only a limited number sensors 10 have been logged, the controlling unit determines trays 14 for which the process has been carried out successfully (i.e. the trays 14 which were exposed to the pre-determined microwave effect) and all the other trays 14 are considered as non-processed. Furthermore, the controlling unit output this information on a screen or similar outputting device.

When the total field effect excerted is used in combination with the minimum field effect measured as controlling parameters, the total field effect is typically used as a fall back position used for checking whether enough effect has been excerted to the accessible volume when the prescribed spatial and time variation of the microwave field has successfully been achieved with respect to the minimum principle stated above.

As mentioned above, the prescribed field effect depends on the type and/or the number of instruments to be sterilised and/or disinfected. The type of instruments can indirectly be determined use of the identification means 20 on the tray 14 and the accessing means 1 6 inside the accessible volume 4. When a tray 14 containing instruments is placed inside the accessible volume 4 the accessing 16 means reads the information contained in the identification means 20 and sends a control signal to the controlling unit 22. This controlling unit responds to this control signal by choosing a prescribed spatial and time variation of the microwave field and the sterilisation and/or disinfection process is ready to be carried out. -

18

In the case where more than one tray 14 containing different types of instruments requiring different spatial and time variations of the microwave fields, the control unit selects the most critical variation. Two situations normally occur in such a preselection: one type of instruments requires a long microwave exposure time and 5 another type of instruments requiring a short microwave exposure time. In this case the prescribed microwave field will be one having a long exposure time.

In general, the prescribed microwave field will be chosen such that the longest exposure time and the highest field intensity required for the various instruments to 10 be treated.

A general problem occurring when using microwaves for sterilised and/or disinfected articles is when these articles comprise hollow parts being able to provide a Faraday Cage. In such a situation, the microwave field will have no possibility to penetrate 15 into such a hollow part and the sterilisation and/or disinfection process will not be carried out in these areas of the articles.

In Fig. 5 a fluid tight container 32 unit is shown which helps solving this problem. The fluid tight container comprises a top part 24 and a bottom part 26. The top part 20 26 which is shown in Fig. 4 is tubular shaped with one end being threaded on the outside and on the other end being closed.

The bottom part 26, which is shown in Fig. 6, comprises means for holding the articles to be processed and a thread corresponding to the thread 28 of the top part 25 for constituting a closed container. Both the top and bottom parts are preferably made of a material allowing microwaves to penetrate.

On Fig. 7 a cross sectional view of a fluid tight container unit 32 according to the present invention is shown. The articles 30 to be processed are placed on holding 30 means 34 used for fixing the position of the articles 30 relative to the orientation of the fluid tight container unit 32.

The bottom part 26 comprises a compartment 38 for containing water. During processing of the articles 30, the fluid tight container unit 32, when placed inside the accessible volume 4, is exposed to microwave radiation which heat the water present in the water reservoir 38. As the temperature of the water increases, steam will be produced and this steam will be forced up through the hollow instrument as indicated by the arrow of Fig. 7.

As steam is produced and the fluid tight container unit 32 does not allow steam to escape its interior, the pressure will increase. This increase of pressure and temperature together with the presence of steam will in combination destroy the bacteria and/or virus present both at the inner side of the articles and on the outer side thereof, where also the effect of the microwave radiation will help in destroying the bacteria and/or virus.

The sterilisation and/or disinfection process normally has to fulfil certain requirement stated by different regulatives. One such requirement denoted prEN 1 30 060 section 1 ,2,3,4 states that the articles must be exposed to an atmosphere being 130°C having a pressure of 3 atm. in at least 3 minutes. In order to be certain about the fulfilment of these conditions, the fluid tight container unit 32 comprises a temperature sensor 42. This temperature sensor is connected to the controlling unit 22 of the antimicrobial apparatus and the output of the microwave source is controlled in a manner that the conditions are fulfilled.

The controller 22 normally controls the output of the microwave source such that the temperature inside the fluid tight container unit evolves in time according to a Poisson-distribution having a prescribed maximum value. In the case where more than one fluid tight container unit 32 is in use at the same time, the evolution of the temperature inside each of the fluid tight container units 32 may be different from each other. In this situation, the controlling of the output of the microwave source 8 depends normally on the most critical fluid tight container unit 32 in the sense that the smallest measured temperature will be the one which govern the process.

In order to keep the pressure below a certain value, a pressure relieve valve 40 is provided in the fluid tight container unit 32. This pressure relieve valve 40 will make a connection between the interior of the unit 32 and the exterior when the pressure exceed a predetermined level, whereby steam or in general fluid present in the unit 32 will escape to the exterior.

The fluid tight container unit 32 contains in a preferred embodiment also a pressure sensor in order to monitor the pressure inside the unit 32 and in some situation to use the pressure as a controlling parameter. In some situations it is found that even though the temperature has reached the desired level the pressure is still to low in order to fulfil for instance the above stated requirement. In this situation one must increase the pressure, which in turn of course increase the temperature, in order to fulfil the requirement.

In the case where both articles are processed in the container unit 32 and where articles are processed by the general aspect of the invention, the controlling of the output of the microwave source 8 may be performed according to both the requirements for instance by securing the most critical conditions to be matched during the processing.

Eventhough, the fluid tight container 32 is described above as special being adapted to treat hollow articles it should be mentioned, as already stated, that the high pressure/high temperature atmosphere generated will, of course, participate in the sterilisation and/or disinfection process of the outer surfaces of said articles. This aspect has been sophisticated by the embodiment shown in Fig. 8.

In Fig. 8 a second preferred embodiment of a container 32 device is shown. In this embodiment the container device 32, being a cylinder, comprises a chamber 50 in which the article(s) to be sterilised/disinfected is(are) placed. A detachable basket 52 for holding the articles to be treated is placed inside the camber 50. The detachable basket is divided into horizontal sections such that the articles may be contained in the basket 52 without touching, or substantially touching, each other. The walls and bottom of the basket 52 is, of course, penetrable with respect to steam which in the preferred embodiment of Fig. 8 is provided by making the walls and the bottom by a net. The basket 52 is detachable in the sense that the basket 52 can be taken out of the chamber 50 which provides the possibility of lifting out the articles from the chamber 50 after treatment with out touching the articles.

The chamber 50 is defined by container part 56 and a lid part 54 comprising a skirt part 54A extending inside and to the bottom of the chamber 50. At the bottom of the chamber a sealing in form of an o-ring 55 is placed. Also at the bottom of the chamber 50 a Bayonet socket 57 is provided for easy and fast assembling/disassembling of the lid part 54 and the container part 56, whereby the chamber 50 is made ease accessible.

The container device 32 further comprises a fluid entry passage 58 opening into the chamber 50 and a fluid outlet passage 60 also in fluid communication with the chamber 50. The entry and outlet passages 58,60 are connected to a condenser device 62 as shown on Fig. 8. The arrangement of the container device 32 and the condenser device 62 is referred to as an autoclave 80.

The container device 32 is when used placed inside the accessible volume 4 of the antimicrobial apparatus and the condenser device 62 is placed outside the accessible volume 4 of the antimicrobial apparatus. This is indicated on Fig. 8 by a wall section 64 of the accessible volume 4.

The condenser device 62 may optionally comprise fluid controlling/restriction means, such as valve means, pumping means, Venturi tube means or the like, for controlling/restricting fluid flow to/trough the fluid entry. Such means 66 is/are indicated by the dotted line in Fig. 8.

Furthermore, the container device 32 may preferably comprise a fluid reservoir 59.

The autoclave 80 is used in the following manner (in the following it is assumed that the autoclave is an integral part of the antimicrobial apparatus). Articles to be sterilised are placed in the basket 52 which in turn is placed in the accessible chamber 50. The lid part 54 is assembled with the container part 56 which are engaged with each other by the Bayonet socket 57. The o-ring 55 provides a sealing of the chamber. Water - if lacking - is added to the autoclave 80 by such an amount (preferably) that the reservoir 59 is filled. Now microwaves are exposed to the autoclave 80 which will cause at least the water present in the reservoir 59 to evaporate and to flow into the chamber 50.

As the condenser device 62, the chamber 50 and the connections between the container device 32 and the condenser device 62 all are fluid tights, the autoclave 80 has been made fluid tight. When energy is added to this system the pressure will increase inside the autoclave 80 which in turn provides a high temperature steam present inside the chamber 50. This high temperature steam will now act upon the articles and as there exist a flow of steam through the chamber 50 high temperature and high pressure steam will always be present in the chamber 50 which will provide the sterilisation/disinfection of the articles.

When the steam leaves the chamber 50 through the outlet passage 60 it shortly after leaves the volume 4 in which microwaves may act on it. Finally, the steam goes into the condenser device 62 in which a cooling of the steam takes place.

In the preferred embodiment shown in Fig. 8 the condensing device comprises a spiral condenser 68 in which the steam gradually is cooled and finally condensed so that the fluid when leaving the spiral condenser 68 is liquid. The liquid is now led towards the fluid reservoir 59. This fluid circuit is indicated by arrows in Fig. 8.

Optionally, the container device 32 may comprise articles holding means similar to the holding means 34, not shown of Fig. 7 leading steam to the interior of hollow articles.

In a slightly different embodiment of the autoclave 80 the connection pipe 70 connecting the spiral condenser 68 with the inlet 58 has been inclined so that the highest position of that connection pipe 70 is at the outlet of the spiral condenser and the lower point is at the fluid entry passage 58. This will cause the condensed water to flow naturally, i.e. under the effect of gravity, from the spiral condenser to the water reservoir 59. Also in this embodiment of the container device 32 a temperature sensor 42 for measuring the temperature of the steam inside the container device 32 may be provided. Again, the sensor provides input to the controlling unit 22 such that the field effect of the microwaves can be controlled at least partly by said temperature in the manner described above.

Further more the container device 32 may also be provided a pressure sensor 43 such as a pressure transducer so that the controlling of the microwave field may be based on the pressure also - or alone.

Such a sensors will, when present, preferably be placed inside the compartment 50 of the container device 32, but in general they may be placed in any position of the autoclave80. Furthermore, the pressure transducer may be used to guarantee that the pressure inside the compartment 50 of the container unit 32 does not exceed a predetermined level so as to avoid damaging of the container device 32, the condenser 62 or the autoclave.

In Fig. 9 a presently most preferred embodiment of a container device 32 being used as a part of an autoclave 80 is shown. The container device 32 comprises three compartments 50, behind the container part 56, all closed by lid parts 54 engaged with the container part 56 by a Bayonet socket as described in the description of Fig. 8. The fluid entry passages are indicated by reference numeral 58 and the outlet passages are indicated by reference numeral 60.

In the preferred embodiments of the autoclave described above the fluid was considered to be water, but as the autoclave is made fully fluid tight other fluid and even fluids being harmful to people may be used as these can not escape the autoclave. Such fluids include hydrogen peroxide, H₂0₂.

In Fig. 10 a controlling unit 22 special adapted to control the microwave field intensity based on measured temperatures inside a container device 32 is shown schematically. The controlling unit comprises, with reference to Fig. 10, the following components: -

24

A Personal computer: Processor: K6-2 400Mhz, storage: 6Gb HD, memory: 64Mb ram, mouse, keyboard and a spare serial port. Screen: 1 5" SVGA 800x600 with 256 colours. Operating system: Windows 98.

1 ADAM-4520 RS232 to RS485 Converter:

Input / Output half duplex rs232 to rs485 converting

1 ADAM-4018 8 input mv, V, mA, Thermocouple

Ports: 6 differentials + 2 single ended Input ranges: J,K,T,E,R,S and B thermocouple; + /- 1 5mV, + /-50mV, + /-

1 00mV, + /-500mV, + /- 1 V, + /- 2.5V og + /- 20mA

OutputRS485 (2-vires), 1 200-2400-4800-9600-1 9.2K and 38.4K bps Accuracy: 0.1 % or higher Sample rate: 10 / sec

1 ADAM-4050 Digital I/O 7 input 8 output

Digital input: 7 channels; Logic 0 < + 1 V, logic 1 > + 3.5V to + 30V Digital output: 8 channels: open collector to 30V, current sink = 30mA OutputRS485 (2-vires), 1 200-2400-4800-9600-1 9.2K AND 38.4K bps

2 Type K thermocouple encapsulated in stainless steel

Range: -40 to 1 100 degrees Celsius Output : 40uV / grader Celsius

2 Type K thermocouple PTFE isolated

Range: -40 to 350 degrees Celsius Output: 40uV / degrees Celsius

1 SensorTecnics PS20000 0 - 30 psi pressure transducer. Range: 0 - 30 psi

Output : 0 - 1 00 mV

2 Teccor solid state relay 10 A.

Input: 3 - 30 V Output:240 VAC / 10A

3 Teccor solid state relay 2 A.

Input: 3 - 30 V Output: 240 VAC / 2A

1 power supply 12V 2A.

Program: Delphi 4 programming language, ADAM API, controlling system developed by use of Delphi 4 and ADAM API.

The different components are connected in the manner sketched in Fig. 10, i.e.: The serial port (rs232) of the PC is being connected to ADAM-4520. ADAM-4018 and ADAM-4050 are being connected to ADAM-4520 - the temperature sensors, ts1 -ts4, are being coupled to ADAM-4018. tsl is being mounted in the accessible volume of the antimicrobial apparatus (steel encapsulated) ts2 is being mounted in compartment 50 (steel encapsulated) ts3 is being mounted on magnetron 1 (isolated by ptfe) - ts4 is being mounted on magnetron 2 (isolated by ptfe)

Two magnetrons have been used in order to provide high output power, and the locations of these relative to the autoclave, as indicated on fig. 10, are so that interaction between them is avoided.

the solid state relays ssr1 -ssr5 are being coupled to ADAM-4050, ssrl drives magnetron 1 (10A); ssr2 drives magnetron 2 (10A); ssr3 drives the cooling fan (2A) of magnetron 1 ; ssr4 drives the cooling fan (2A) of magnetron 2; ssrδ drives the cooling fan (2A) of chamber.

A 12 volts supply is connected to the ADAM-modules, the solid state relays and the pressure transducers.

Claims

1 . An antimicrobial apparatus useful for sterilisation and/or disinfection of articles, said apparatus comprises - an accessible volume being able to be confined in a manner such that it constitute a Faraday cage, at least one microwave source directing microwaves into the accessible volume at least one microwave field sensor for sensing the intensity of the microwave field in the accessible volume, said sensor provides input to a control unit for controlling the supply of microwaves to the accessible volume.

2. An antimicrobial apparatus according to claim 1 , further comprising at least one container situating in the accessible volume and holding liquid, such as water.

3. An antimicrobial apparatus according to claim 1 or 2, further comprising at least one tray having at least one cavity for housing an article to sterilised and/or disinfected.

4. An antimicrobial apparatus according to claim 3, wherein the at least one tray is made of a microwave transparent material, such as plastic or the like.

5. An antimicrobial apparatus according to claim 3 or 4, wherein the at least one cavity of the at least one tray match the shape of the article to be sterilised such that substantially only the article intended to be housed by the cavity can be placed therein.

6. An antimicrobial apparatus according to any of the claims 3-5, wherein the at least one tray comprises sensor means for sensing the type(s) of instrument(s) when said instrument(s) is(are) placed in said cavity(cavities).

7. An antimicrobial apparatus according to claim 5, wherein said sensor means is(are) arranged in said cavity(cavities).

8. An antimicrobial apparatus according to claim 4 or 7, wherein the at least one tray further comprises identification means containing information for identifying the article(s) housed by the cavity/cavities of the tray.

9. An antimicrobial apparatus according to claim 8, wherein the apparatus further comprises accessing means for accessing the information contained by the identification means of the tray(s) when the tray(s) is(are) situated in the accessible volume.

10. An antimicrobial apparatus according to claim 9, wherein the identification means comprises a bar code and the assessing means comprises an optical bar code reader.

1 1 . An antimicrobial apparatus according to claim 9, wherein the identification means comprises dynamic identification means and the assessing means is adapted to assess the identification of the identification means.

1 2. An antimicrobial apparatus according to claim 9, wherein the accessing means comprises means for generating an input to the controlling means for controlling the microwave source.

1 3. An antimicrobial apparatus according to any of the preceding claims further comprising a fluid tight container unit for sterilisation and/or disinfection of hollow articles, the fluid tight container unit comprises - a confined chamber holding means situated in the confined chamber for holding at least one hollow article in a predetermined orientation relative to a bottom plane of the container, liquid holding means situated in fluid communication connection with the confined chamber for holding a liquid, means for distributing vaporised liquid from the liquid holding means to the inside of the hollow articles, and a communication passage which enables a fluid communication at least out of the confined chamber if the pressure inside the confined chamber exceed a predetermined value, such as 3 atm, preferably 3,5 atm. alternatively 4 atm. and more preferably 4,5 atm.

14. An antimicrobial apparatus according claim 13 wherein the fluid tight container unit is releasable assembled by a top part and a bottom part in such a manner that the confined chamber is accessible.

1 5. An antimicrobial apparatus according to claim 1 3 or 14, further comprising a temperature sensor for sensing the temperature inside the confined chamber.

1 6. An antimicrobial apparatus to any of the claims 1 3-1 5, further comprising a a pressure sensor for sensing the pressure inside the confined chamber.

1 7. An antimicrobial apparatus according to claim 1 5 and/or 1 6, wherein the temperature and/or pressure sensor provides input to the controlling unit.

18. An antimicrobial apparatus according to any of the preceding claims further comprising at least one autoclave, said at least one autoclave comprising a container device having an accessible chamber, said accessible chamber is situated inside the accessible volume of the antimicrobial apparatus, said container device comprises a fluid entry passage and a fluid outlet passage both being in fluid communication with the accessible chamber, a condenser device for condensing fluid being in gas phase, said condenser device has an outlet connected to the fluid entry passage and having an inlet connected to the fluid outlet passage, said condenser being situated outside the accessible volume of the antimicrobial apparatus.

1 9. An antimicrobial apparatus according to claim 1 8, wherein the accessible chamber of the autoclave is defined by a open ended container part and a lid part adapted close the open end of the open ended the container.

20 An antimicrobial apparatus according to claim 1 9, wherein the lid part is engaged with the container part by a lock means, preferably by bayonet socket, such as a thread.

21 An antimicrobial apparatus according to any of the claims 18-20, wherein the container device of the autoclave comprises a sealing, such as an o-ring, arranged such that at least a part of the lid part and at least a part of the container part abut 5 the sealing.

22. An antimicrobial apparatus according to any of the claim 18-21 , wherein the autoclave further comprises a fluid reservoir being in fluid communication with the fluid entry passage and being placed inside the accessible volume of the antimicrobial

10 apparatus.

23. An antimicrobial apparatus according to any of the claim 1 8-22, wherein the autoclave further comprises fluid controlling/restriction means, such as valve means, pumping means, Venturi tube means or the like, for controlling/restricting fluid flow

15 to/through the fluid entry passage.

24. An antimicrobial apparatus according to any of the claims 18-23, wherein the condenser device is a passive device,

20 25. An antimicrobial apparatus according to any of the claims 18-24, wherein the condenser device is an active device.

26. An antimicrobial apparatus according to any of the claims 18-25, wherein the autoclave is an integral part of said apparatus.

25

27. An antimicrobial apparatus according to any of the claims 18-26, wherein the fluid entry passage is connected to the outlet of the condenser device by a pipe being inclined relative to horizontal, said inclination being so that the connection between the condenser device and the pipe is situating at a higher vertical position

30 than the connection between the pipe and the fluid entry passage.

28. An antimicrobial apparatus according to any of the claims 18-27, further comprising a temperature sensor for sensing the temperature inside the accessible chamber of the autoclave.

29. An antimicrobial apparatus according to any of the claims 1 8-28, further comprising a pressure sensor for sensing the pressure inside the accessible chamber of the autoclave.

30. An antimicrobial apparatus according to any of the claims 1 8-29, further comprising a detachable basket adapted to hold article(s) to be sterilised/disinfected, said detachable basket situating inside the accessible chamber of the container device.

31 . A method for controlling an antimicrobial apparatus according to any of the preceding claims, wherein the method comprises the steps of

- storing in a memory a prescribed spatial and/or time variation of a characteristic microwave field variable inside the accessible volume, - determining a spatial distribution of an actual characteristic microwave field variable in the accessible volume at prescribed first time intervals,

- at each determination of the spatial distribution of the actual characteristic microwave field variable at the prescribed first time intervals

32. A method according to claim 31 , wherein the prescribed spatial and/or time variation of the characteristic microwave field variable is the total effect excerted in the accessible volume.

33. A method according to claim 32, wherein the total effect is determined based upon the measurement from at least one microwave field sensor.

34. A method of controlling an antimicrobial apparatus according to any of the claims 1 5-1 7 and/or 28-30 utilising the method according to any of the claims 30-33, which method further comprises the steps of

- storing in a memory a prescribed spatial and/or time variation of a characteristic temperature in the confined chamber(s) and/or accessible chamber(s), - determining a characteristic temperature in the confined chamber(s) and/or accessible chamber(s) at prescribed second time intervals,

35. A method according to claim 34, wherein the characteristic temperature determined is the smallest measured inside the confined chamber(s) of the at least one fluid tight container unit(s).

35. A method according to claim 33 or 34, wherein the prescribed characteristic temperature is Poisson distributed in time.

36. An antimicrobial apparatus useful for sterilisation and/or disinfection of articles, said apparatus comprises an accessible volume being able to be confined in a manner such that it constitute a Faraday cage, a microwave source directing microwaves into the accessible volume and a control unit for controlling the supply of microwaves to the accessible volume, said apparatus further comprises at least one autoclave, said at least one autoclave comprising a container device having an accessible chamber, said accessible chamber is situated inside the accessible volume of the antimicrobial apparatus, - said container device comprises a fluid entry passage and a fluid outlet passage both being in fluid communication with the accessible chamber, a condenser device for condensing fluid being in gas phase, said condenser device has an outlet connected to the fluid entry passage and having an inlet connected to the fluid outlet passage, said condenser being situated outside the accessible volume of the antimicrobial apparatus, and/or a fluid tight container unit for sterilisation and/or disinfection of hollow articles, the fluid tight container unit comprises a confined chamber - holding means situated in the confined chamber for holding at least one hollow article in a predetermined orientation relative to a bottom plane of the container, liquid holding means situated in fluid communication connection with the confined chamber for holding a liquid, - means for distributing vaporised liquid from the liquid holding means to the inside of the hollow articles, and a communication passage which enables a fluid communication at least out of the confined chamber if the pressure inside the confined chamber exceed a predetermined value, such as 3 atm, preferably 3,5 atm. alternatively 4 atm. and more preferably 4,5 atm.