Note: Descriptions are shown in the official language in which they were submitted.
Method and Contrivance for Sterilizing,
Disinfecting and/or Drying
The invention concerns a method for sterilizing, disinfecting and/or
drying of pourable, pasty or liquid materials in loose form using
microwave energy in a closed vessel, along with a contrivance for
carrying out the method.
Already known per se is how to disinfect hospital waste by microwave
heating. A system of this kind is described in a promotional
brochure of the firm Vetco Sanitec GmbH. The hospital waste in a
system of this type is first mechanically comminuted, next moistened
and then run past microwave units by means of a worm conveyor in
order to disinfect the waste by rapid, targeted heating to the
boiling point of water, and to push it out to the depository in this
comminuted form. It is clear that the material to be disinfected
does not have to be carefully handled here since it actually next
lands in a refuse depository or the like, so that the desired disin-
fection can always be achieved by strong comminuting and high tem-
peratures.
However, if pourable, pasty or liquid materials are to be carefully
made germ-free or if pourable or pasty materials are to be dried
without the properties and the quality of these materials being im-
paired, then the known method is often not usable because of the
J required comminuting and high temperatures.
.
Known from DE-OS 3,612,606 is a method for sterilizing and/or disin-
fecting pharmaceutical preparations wherewith treatment is carried
out in closed ampoules with the aid of microwaves at a temperature
that is required for sterilization. However, because of this
raising of the temperature, there occurs in the ampoule an overpres-
sure, so that there exists here the danger of destruction. For this
reason, proposed in the case of this known method is to undertake
the microwave treatment of materials found in ampoules in a pressure
vessel under an overpressure, so that the ampoules can not burst.
Known from DE-OS 2,446,471 is a method for drying and sterilizing by
means of microwaves, with the product to be treated likewise being
accommodated in ampoules. To increase the drying action' treatment
is done in a closed vessel using continuous change in pressure, and
indeed beginning with atmospheric pressure, then vacuum, then
overpressure, etc. By doing this, the vapors contained in the
product to be treated are removed in a closed housing without the
effectiveness of the microwaves utilized being impaired thereby.
The object of the present invention is to propose a method - along
with an appropriate contrivance - wherewith is guaranteed a particu-
larly careful but nevertheless effective treatment of materials in
loose form.
In accordance with the invention, the method of the initially-men-
tioned type is characterized by using pressure or vacuum together
with microwave eneryy, whereby the materials in the vessel are
simultaneously rolled around.
Sterilizing or disinfecting of materials can be accomplished either
under pressure or under vacuum. In the case of utilization of pres-
sure, steam can advantageously be introduced into the closed vessel.
If the method in accordance with the invention is used for drying
pourable or pasty materials, vacuum is used so that, in particular
in connection with the rolling around of the materials inside the
~J vessel, the moisture is effectively extracted.
,
One advantageous contrivance for carrying out the method in accord-
ance with the invention is characterized by the fact that the vessel
is constructed pressure- and/or vacuum-tight as well as microwave-
tight and that one or several microwave units are disposed outside
the vessel, and that their microwave energy can be fed into the ves-
sel from the outside via injection openings. This injection of
microwave energy from the outside has the essential advantage that
the microwave units can be disposed outside the vessel and therewith
,are not exposed to the pressure or vacuum prevailing inside the ves-
~,~ sel, as well as to the possibly disadvantageous influence of the
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materials to be treated; furthermore, it is possible to maintain theinside space of the vessel free of projections and dead corners in
which the materials to be treated could otherwise clog. The injec-
tion openings for the microwave units can be closed off in simple
fashion by closure pieces made of dielectric material in order to
also close off the vessel at these places in a pressure- and/or
vacuum-tight fashion.
In order to expose the materials to be treated in the vessel to the
microwave energy as uniformly as possible, preferably arranged in-
~J side the vessel is a mixing mechanism. Additionally achieved bymeans of a mixing mechanism of this type is that the materials to be
treated can be conveyed, in a desired manner, from the region of a
filling opening into the region of an emptying shaft.
According to an advantageous form of embodiment, the vessel is con-
structed as a horizontal, cylindrical container. This method of
construction enables not only the use of a double-worm counterflow
mixing mechanism for the very effective rolling about of the materi-
als to be treated inside the vessel, the vessel along with the
entire contrivance rather being capable of being clamped in the
region of the face walls of the vessel in a simple manner by means
of brac~ets.
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In practical fashion, the mixing mechanism is driven from the out-
side at selectable, different speeds, with the bearing shaft of the
mixing mechanism being brought out through pressure- and/or vacuum-
tight stuffing boxes. A simple loading and emptying of the material
to be treated into andtor out from the vessel is then possible if
the vessel is provided at one end with a closable filling opening
and on the underside with a closable emptying shaft. Furthermore,
it is practical to provide, laterally, closable cleaning openings.
The microwave units are preferably arranged on the top side in the
middle region of the vessel.
The method of construction with brackets for supporting the entire
contrivance has the advantage, in accordance with another advanta-
geous form of embodiment, that the brackets can be supported on four
foot points in which are mounted weighing cells. In this manner, it
is possible to determine the quantity of material to be treated.
The invention will be explained in more detail in the following with
the aid of an example of embodiment, while referring to the accom-
panying drawings.
J Fig. 1 shows a side view of the contrivance in accordance with
the invention, and
Fig. 2 shows a cut along the line II-II of Fig. 1.
The contrivance shown in Fig. 1 and 2 contains a cylindrical vessel
1 that is disposed in horizontal fashion. Attached to the front
walls 2 are brackets 3 that rest by means of four weighing cells 4
on a mounting base 5. By means of these weighing cells 4 it is
possible to weigh out the weight of the entire contrivance in the
empty condition and in the filled condition, and therewith to deter-
mine the weight of the poured-in materials. Provided on the top
side of the cylindrical vessel 1 are several microwave units 6, the
J microwave energy of which can be fed into the cylindrical inner
space of the vessel 1 via the injection openings 17. The injection
openings 17 are closed off in pressure- and/or vacuum-tight fashion
by closure pieces 14 made of a dielectric material.
Located at one end of the cylindrical vessel 1 is a filling opening
9 and/or a filling stub to which is connected a filling hopper 11
for easier pouring in of the materials to be treated. Disposed on
the underside of the vessel 1 is an emptying shaft 10 via which the
treated materials can be emptied out. The filling opening 9 as well
as the emptying shaft 10 are both capable of being closed off, in
the case of the emptying shaft 10 by means of an appropriate hinged
cover. The materials to the treated are present in loose form, i.e.
they are not in containers or bundles.
Provided inside the cylindrical vessel 1 is a mixing mechanism 16
which, in the present example, is constructed as a double-worm
counterflow mixing mechanism, in order to enable an effective
rolling about of the materials to be treated inside the container 1.
This leads to a particularly uniform and careful treatment. The
mixing mechanism 16 is supported on the face sides of the vessel 1,
and the bearing shaft 18 is brought out through pressure-tight
~J and/or vacuum-tight stuffing boxes. Connected at the one end of the
bearing shaft 18, via a gear train 13, is a drive motor 12 with
which the mixing mechanism 16 can be driven at a suitable speed.
The rotational speed (rpm) of the mixing mechanism 16 can be varied
by an appropriate adjusting or regulating contrivance.
Since the vessel l is closed on ail sides, but occasionally a clean-
ing or an inspection of the inside, in particular of the mixing
mechanism 16, can be required, provided laterally are two cleaning
openings 7 that are closed via pressure- and/or vacuum-tight covers.
i
Provided at the filler stub of the filling opening 9 is a vacuum/
pressure connection 15 via which the inside of the vessel 1 can be
placed under pressure or be evacuated. AdditionaLly provided, pre-
ferentailly in the lower region, is a steam connection 19, via which
steam can also be introduced selectably when removing germs or
sterilizing for the purpose of wetting and additionally heating the
product to be treated.
The vessel 1 of the contrivance in accordance with the invention is
preferably constructed both pressure-tight and vacuum-tight; this
also applies for the other components such as stuffing boxes,
covers, etc. With a contrivance of this type , the materials to be
treated can then be treated selectably either under pressure
removal of germs and/or sterilizing) or vacuum ~drying as well as
,
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removal of germs or sterilizing also), depending upon effectiveness
and compatibility. However, it is also possible to design the
vessel 1 to be only pressure-tight or only vacuum-tight; in this
case, only the one or the other type of treatment is possible.
Instead of the double-worm counterflow mixing mechanism used in the
example of embodiment, it is also possible to use other types of
mixing mechanisms or roller contrivances, e.g. an impact-beater
mixing mechanism.
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