Microwave sterilization device

Details Microwave sterilization device Microwave sterilization device

2000-10-02

2003-02-25

Mayekar, Kishor (Department: 1741)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

With means applying electromagnetic wave energy or...

C422S302000, C422S295000

Reexamination Certificate

active

06524539

ABSTRACT:

The invention is directed to a n apparatus for the drying, heating , sterilization and/or disinfection of dry, moist or wet materials or materials in a moist environment and of liquids, particularly waste which may be infected, e.g., medical waste, in which the materials to be treated are introduced into a microwave-permeable vessel in a pressure-proof treatment space which can be acted upon by microwaves and sealed in a pressure-tight manner, wherein a plurality of magnetrons are coupled into the resonant space forming the treatment space in such a way that microwave dead spaces are prevented, wherein the physical parameters in the device are monitored and utilized, when appropriate, for controlling the installation, and wherein added units are also provided for influencing the course of the process, as well as to processes for pasteurization, disinfection or sterilization of dry, moist, or wet materials or materials in a moist environment and of liquids.
BACKGROUND OF THE INVENTION
An installation of this kind is known, for example, from WO 86/02842 in which there is provided a cylindrical interior space which can withstand internal pressures of up to 5 atmospheres or a partial vacuum. The top of this cylindrical space can be closed by a cover. The magnetrons are provided at the bottom end face of the cylindrical vessel, this underside being closed by a microwave-permeable pressure-proof wall. In order to achieve the most uniform possible distribution of microwave energy in this known construction, the inner cylindrical chamber is suspended so as to be rotatable in order to achieve control of the irradiation density of the individual particles by way of the movement of this cylindrical chamber. Further, because of this construction, the chamber of the known arrangement can only be loaded or charged from the top, which can quickly lead to difficulties when larger quantities of material packed in a drum must be introduced into the vessel. Further, condensation water can form on the wall in this known construction during cooling and must be removed from the vessel.
Another installation of the type mentioned above which is known from EP 0 476 004 B1 is also provided with a cylindrical treatment chamber which can be closed at the top. This treatment chamber (referred to in this reference as a cavity resonator) is lined with a vessel
1
which can be closed so as to be gastight, and the magnetrons are coupled into the treatment space laterally and from the bottom end face. Due to the lining provided in this known construction, the distance of the interior space from the microwave generators is controlled in such a way that a corresponding energy density is also present in this outer area.
This known construction also has the disadvantage that it is chargeable from the top, which accordingly impedes loading. Further, as can be gathered from this reference, the device must be charged with decalcified water because calcium deposits would otherwise occur in the lining. The construction according to this reference is also capable of operating with overpressure or underpressure.
It is known from EP 0 287 549 B1, whose subject matter also refers back to an invention of the Applicant of the present application as co-inventor, to couple a plurality of magnetrons into a cavity resonator in such a way that microwave dead spaces are prevented, wherein the coupling in is carried out via waveguides. However, this known construction is not provided as an overpressure sterilizer.
EP 0 483 104 B1 also cites the present Applicant as co-inventor, wherein, in an installation according to the above-cited EP 0 287 549, a vessel containing infectious waste is introduced into the cavity resonator, that is, the treatment chamber, and this vessel can be closed by a cover so that it can serve as a collecting vessel for this infectious waste. A carrier with physical measurement sensors can be lowered into the vessel from the top through an opening in the cover of this vessel, and water can also be sprayed in via this carrier when the quantity of water or moisture contained in the infectious material is too small. According to the known construction, the quantity of water or moisture is determined by an appropriate weighing device, and the supply of water is controlled by means of a central control device which controls the microwave generators corresponding to the measured physical data.
It is the object of the present invention to provide an installation of the type mentioned above which has the advantages of the side-charging treatment chamber according to EP 483 104 A2 as well as the advantages of a pressure chamber and which can therefore be used as an autoclave.
SUMMARY OF THE INVENTION
According to the invention, this is accomplished in that the magnetrons are coupled into the treatment space in a pressure-tight manner via waveguides, known per se, this treatment space being provided with a side charging opening for introducing the microwave-permeable vessel while leaving a free space between the vessel and the inner wall of the treatment space, wherein the treatment space has a cylindrical or polygonal prismatic shape with vertically extending longitudinal axis, and wherein the devices for monitoring the physical parameters are arranged at carriers communicating with the interior of the vessel. In this way, the distance between the material to be treated and the microwave generators can be controlled via the waveguides and intermediate space remaining between the vessel and the inner wall of the treatment space in such a way that the entire interior of the vessel receives the full microwave output, so that the irradiated microwave energy is sufficient for generating the necessary steam to achieve the operating overpressure. Further, the side charging opening makes it possible for larger-volume vessels that would no longer be manageable in practice with out auxiliary equipment to be introduced into th e treatment s pace.
The charging opening can be advantageously produced by parts of the treatment chamber along an off-center plane extending parallel to the longitudinal axis of the treatment chamber, wherein the bottom wall and top wall are also divided. Accordingly, a portion of the top wall and also a portion of the bottom of the treatment chamber are divided, which considerably facilitates insertion of the vessel by auxiliary means such as a suitably constructed trolley, lift truck or the like. However, the charging opening can be made by cutting out the casing wall of the treatment chamber along two generatrices and parallel to the bottom wall and top wall, so that the entire bottom surface and top surface remain intact and the charging opening is provided only in the wall, which can be advantageous under certain circumstances for purposes of economizing on space.
For a particularly space-saving construction, a combination of wave trap, known per se, and seal, preferably a hose seal which can be acted upon by internal pressure, can be provided along the charging opening for tightly closing this opening by means of the associated closing part. This offers the possibility of a compact construction of the seal for preventing the escape of microwaves and pressure without impairing the free through-opening.
In order to ensure that the sterilizing/disinfecting process actually occurs at the correct temperature within the material and not only at the temperature of the interior space, a thermal sensor by which carriers communicating with the interior of the vessel can be introduced into the microwave-permeable vessel or a noncontacting thermal sensor connected with a control device having a reference value storage and a comparator for comparing with the determined actual value can be provided for determining the regulating variable for the output of the magnetrons. The temperature in the material can be detected in a much more direct manner in this way because the temperature is measured there and then, and the steam or compressed steam flowing out is measured inside the entire installation in the immedia

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