Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1081428
.
Sterile Packages of the one-way type are known and are
used, inter alia, for the packing of liquid foods, e.~. milk.
The contents packed in sterile packages have an appreciably
longer keeping period than contents packed in non-sterile packages.
The sterile packages for e.g. liquid dairy products, which are ~-
known are of various types. Common to them all is, however, the
procedure required for the manufacture of sterile packages, in
that the contents as well as the packing material or the package
blanks partly formed from the packing material are sterilized,
whereupon the contents are filled in and the packages are closed
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under aseptic conditions.
A consumer package of the one-way type for beverages,
e.g. milk, frequently encountered is manufactured in that
packing material, which e.g. may consist of a laminate comprising
a carrier layer of fibrous material which is covered on either
side with thin plastic layers, is fed into a packing machine
in the form of a web. During the passage of the web through the
packing machine the material web is folded to tube-shape, in
that both of its longitudinal edges are made to overlap each
other a little and are sealed to one another. This transformation
of the packing material web takes place continuously during the
advance of the material web mainly vertically downwards through
the machine. After the transformation to tube-shape, the contents
are fed to the tube continuously through a filler pipe which
extends into the tube through the upper open end of the same.
,`During the advance downwards of the tube the same is pressed flat
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and sealed by sealing jaws arranged on either side of the tube
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along narrow transverse zones situated at a distance from one
another. The supply of contents is controlled automatically
-~ 30 during the whole time in such a manner that the level of contents
is well above the point where the pressing flat and sealing of
the tube take place. After the sealing of the tube the same is
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cut by transverse cuttiny in the sealing zones, and after a
possible reshaping of the individual packages, the manufacturing
process is complete.
When the type of machine described is used for the
manufacture of sterile packages, the filling takes place under
aseptic conditions, which means that the atmosphere in the
material tube as well as the material tube itself (or in any
case its inside) have to be kept sterile. To achieve the former
a certain pressure of sterile air is maintained in the packing
10 material tube so that non-sterilie air cannot penetrate from
the surrounding atmosphere.
The sterilization of the packing material web takes
place in a known realization of the machine described in that
' the packaging material web, before forming into tube-shape, is
made to run through a bath of chemical sterilizing agent, usually
a solution of hydrogen peroxide, which is made to moisten the
packing materlal, whereupon the excess liquid is stripped off
the material web by means of mangle rollers. The portion of
; sterilizing agent which remains on the packing material web is
~ 20 removed after the formation of the web to a tube from the inside
of the tube by means of a heating arrangement, usually a heating
coil arranged around the filler pipe, a so-called tube heater,
which heats the inside of the packing material tube and the
residues of sterilizing agent remaining thereon to such an
extent that the agent is evaporated and escapes from the upper,
open end of the packing material tube.
This method of sterilization has been found to be
subject to certain disadvantages. Thus it has been found, inter
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alia, to be difficult under certain conditions to control the
quantity of sterilizing agent on the material web with a sufficient
accuracy, since the mangle rollers used for the purpose give a
metering that is difficult to check. To ensure an even application
of sterilizing agent on the web and hence an effective
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sterilization, the sterilizing acJent has to contain moreover
stabilizers and wetting agents, which substances are difficult
to remove completely and which are moreover undesirable for
reasons of cost.
Another method for achieving sterilization of the packing
material web in the type of machine described is also known.
According to this method a liquid sterilizing agent, preferably
a mixture of hydrogen peroxide and water is introduced into a
dishlike container present in the material tube. The container
is situated around the filler pipe and is heated to such a temper- ,
ature that the sterilizing agent when it is delivered dropwise
to the dish, will evaporate immediately. The vapour rises upwards
through the tube and is deposited at the upper end of the inside
wall of the tube. During the continuous movement downwards of
the tube, the vapour condensed at a certain moment at the upper
end of the tube will pass the heating element arranged in the tube,
which heats the inside wall of the tube as well as the sterilizing
agent condensed on the same so vigorously that the agent is
evaporated and rises upwards to the region of the upper end of -
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the tube where it is recondensed on the colder material wall.
This process is repeated as long as the packing machine is in
s - operation and the-whole time a dropwise delivery of mixture of
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sterilizing agent to the heated dish takes place so as to replace
the loss which arises through part of the evaporated sterilizing
agent rising upwards through the upper end of the tube without
; being condensed on the tube wall.
A disadvantage of the method described is that the
;' sterilizing agent used must be mixed with a fairly large proportion
of water, and the actual concentration of pure sterilizing agent
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in the mixture is only between 10-35%. The vapour produced will
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`` thus largely consist of water vapour which is undesirable from a
' point of view of sterilization, since it worsens the bactericidal
~!' effect. It can also be difficult to control the process with
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1~81428
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sufficient accuracy, since it is essential that the quantity of
condensed sterilizing agent is not too great to be completely
evaporated when the tube passes the heating element, since otherwise
sterilizing agent may enter also into the packages.
In a further known type of packing machine for liquid
contents, the packages are not manufactured of web-shaped material
but of prefabricated blanks which are provided with an outer
contour and a creaseline-pattern which is adapted for the forming
to finished containers. The blanks are also folded to tubular
bodies which are laid flat and are placed in stacks into the
magazine of the actual packing machine. From here the tubular
bodies a~e intorduced into the machine so as to be provided,~by
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;` folding in of the one end, with a base. The packing containers
, open at the top that have been formed are placed subsequently
onto a belt on which they are conveyed past a number of processing
stations, namely a station for the application of sterilizing liquid
to the inside of the packing containers, a station for the removal
of the sterilizing liquid, a station for the introduction of the
desired contents into the packing container and finally a station
`` 20 for the sealing of the upper end of the packing container. The
station for the sterilization of the packing containers comprises
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a spray nozzle which is located above the packing container and
` so to speak "spray paints" the inside of the packing container
1 with sterilizing liquid. The sterilizing liquid has to act
:~ during the time the packing container is moved to the next station
at which hot air is blown down into the packing container over
such a period that the sterilizing liquid can evaporate completely
~ and escape from the upper end of the packing container.
`~ This method of sterilization is subject first and
foremost to two disadvantages, namely firstly that certain
recesses and corners at the bottom end of the packing container
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cannot easily be reached by sterilizing liquid, and that a
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108142~
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relatively large quantity of ste~ilizing liquid has to be used,
so that the excess is liable to accumulate at the base of the
packing container where possibly residues can remain.
As can be seen from what has been said above, all the
steriliziny systems described are subject to more or less serious
disadvantages.
The present invention provides a method and an arrangement
for the sterilization of objects, especially packing material
webs and packing machines, which method and which arrangement are
designed so that they can be used in hitherto known packing
machines and yet are free from the disadvantages which the
corresponding ones known hitherto possess. ?
The present invention also provides a method and an
arrangement which give an effective sterilization whilst using
, a minimum of sterilizing agent, that is to say an arrangement which
makes possible the application of a thin and continuous layer of
sterilizing agent over the total inner surface of the package.
According to the present invention there is provided
a method for the sterilization of objects by means of liquid
sterilizing agent in which the sterilizing agent is atomized to
form a mist which is mixed with a hot air stream, the temperature
~;~ of the air and the ratio between thequantity of sterilizing
agent and the quantity of air being controlled so that the
sterilizing agent is vaporized and the dew point of the air
molstened with sterilizing agent will be higher than the-temperature
of the surface which is to be sterilized, whereupon the air mixture
is guided towards the said surface which cools the air so that the
sterilizing agent is precipitated in a uniform layer onto the
,j surface where it is allowed to react during a certain period of
time, whereupon it is removed again.
The present invention also provides an arrangement for
the sterilizing of objects by means of liquid sterilizing agent
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814Z8
elements for the supply and heating of air, elements for the
supply and atomization of sterilizing agent, elements for the
mixing of the atomized sterilizing agent and the heated air,
elements for bringing the mixture into contact with the surface
which is to be sterilized and elements for the eventual remova`l
of the sterilizing agent from the said surface.
The invention will be further described with reference
to the accompanying drawing which sho~Ts schematically an
arrangement for the realization ofthe method in accordance with
the invention of a packing machine of the type which manufactures
packages from acontinuously moving conveyor belt.
The basic idea behind the present invention will first
be explained so as to facilitate understanding of the invention.
The idea is based on the capacity of air to absorb, carry and give
off moisture as a function of the temperature. The capacity of
air to carry moisture increases with increasing temperature and
decreases with decreasing temperature. If a certain amount of
atomized liquid or vapour is injected into heated air, the same
is absorbed and carried by the air as long as the temperature is
sufficlently high, that is to say higher than the condensation
- or dew point of the mixture. When for one reason or another the
temperature of the air thus moistened drops below the condensation
or dew point, it can no longer carry such a large amount of liquid,
but part of the liquid precipitates. This can be made use of
for coating a certain surface with a uniform layer of the liquid
that has been carried by the air, which takes place if a body of
;1 a lower temperature than the condensation temperature of air is
introduced into the moistened air. That part of the air which
comes into contact with the body is cooled thereby and the
, 30 moisture precipitates and condenses on the surface of the body.
During the condensation, heat is llberated which warms the cooler
body and the condensation continues therefore only as long as the
surface is of a sufficiently low temperature. The quantity of
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condensed liquid is a direct function of the temperature of the
surface, that is to say the enthalpy and the thermal conductivity
of the body. If it is assumed that these factors are identical
for the whole surface, the process will be exactly the same on
each part of the surface and in this manner a completely
identical condensation can be obtained over the whole surface
which is thus coated with a uniform layer of the actual liquid.
The abovementioned principle can in accordance with
the invention also be made use of for coating for the purpose
of sterilization a certain surface with a uniform layer of a
liquid sterilizing agent. This may be done by utilizing a
suitable liquid sterilizing agent for moistening the air. Sinae
the air normally contains a certain amount of water it is
desirable, in order to avoid dilution of the sterilizing agent,
to remove as much water as possible from the air, that is to say
:-:
the air must be as dry as possible. To this dry air is supplied
~, such a quantity of energy or heat that it can evaporate the
;j sterilizing agent and thereafter be of a sufficient temperature
for carrying the desired quantity of sterilizing agent. Owing
to the temperature of the airand the ratio between the quantity
~; of sterilizing agent and the quantity of air being controlled, ~
the condensation-or dew point of the air moistened with sterilizing
agent can be controlled to a temperature, which by a certain
amount exceeds the temperature of the surface which is to be coated
with sterilizing agent. When the desired mixture of air and
sterilizing agent has been obtained, the mixture is guided to
the surface which is to be sterilized, whereby the air is cooled
and its capacity for carrying sterilizing agent is diminished so
that a large portion of the sterilizing agent condenses on the
.13 surface. After a suitable reaction time, which will depend on~ the type of sterilizingagent and the concentration of the same`~ as well as the bactericidal effect required, the sterilizing
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~0814~8
agent is removed again. This may be done in different manners,
e.g. by means of hot air or by means of irradiation with any
heating element, e.g. an infrared lamp.
In the following, the method in accordance with the
invention will be described in more detail, such as it is used
in a packing machine of known type. On the enclosed schematic
drawing the packing machine is shown on the righthand side of
the drawing. The machine operates with a packing material web l
which is rolled up on a roll 2. From the roll the web 1 passes
through two chambers 3, 4 arranged in sequence which are described
in detail in the following. The web l is passed over two guide
; rollers 5 and then passes vertically downwards through the
packing machine. During the downwards movement through the machine
the web is transformed to a tube 6 in that its two longitudinal
edges are joined and sealed together in a longitudinal joint.
After transformation and sealing to tubular form the tube is
, filled with the required contents, e.g. milk, via filler pipe 7
which extends through the upper open ~nd of the tube and down to
its lower end, where it finishes. At some distance below the
` 20 lower end of the filler pipe the sealing jaws 8 are arranged, which
at equal distances provide the filled tube 6 moving vertically
- downwards with transverse seals within which the tube is also
divided by means of likewise transverse cuts. The completely
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filled packages 9 so formed are conveyed to a processing or
~' final folding station 10 where they are given a parallelepipedic
form.
~ The sterilizing system in accordance with the invention
.'' '
i which co-operates with the packing machine comprises an air
.
compressor 11, a cooler 12 for the compressed air connected to
the same and a water separator 13 wherein the moisture precipitated
` from the air is removed. The so dehydrated air is guided via a
pipe system to two regulating valves 15, 16 which determine the
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^` 1081428
continued flow. The bulk of the air is passed via the règulating
valve 15 to a heating arrangement or an element 17 which supplies
the air with the desired amount of energy or heat. From the
heating element 17 the air subsequently flows into a chamber 18.
At the upper end of the chamber is located an ultrasonic nozzle
l9 which is operated by means of the part of the air stream from
the water separator 13 controlled by the regulating valve 16. To
the ultrasonic nozzle 19 also leads a supply line for sterilizing '-
agent which is fed from a tank 20 via suitable lines and a pump
21 to the ultrasonic nozzle 19. The ultrasonic nozzle is of a
design known in itself and functions in such a manner that the
air stream from the regulating valve 16 creates a standing wave
of a very high frequency (approx. 30 kHz). Into this,standing
wave is introduced sterilizing agent which atomizes the liquid
to droplets of a size of 5-15 micrometre. This highly atomized
liquid or mist is mixed in the container or mixing chamber 18
with hot air whereby the mist changes into vapour which via a
pipe 22 is passed to the previously mentioned chamber 3, through
which the packing material passes on its way from the roll 2 to
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,' 20 the forming part of the packing machine. In the chamber 3 the
mlxture of sterilizing agent and air comes into contact with the~
' moving material web l which cools the mixture so that the steriliz-
~ ing agent condenses to a uniform layer on the web. Part of the
', sterilizing agent will condense on the wall of the chamber and
~, will be removed through a drain pipe 23.
;~ As mentioned previously, the web l passes through a
further chamber 4 which viewed in the direction of movement of
'j the web is situated at some distance after the chamber 3. When
, the layer of sterilizing medium has been applied to the web l
~, 30 in the chamber 3, the web emerges from the chamber 3 to enter
' after a certain distance into the chamber 4 wherein the sterilizing
' agent is removed again from the web. The distance between the
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1~8~28
two chambers 3 and 4 determines lhe time during which the
sterilizing agent ls permitted to act upon the web and the
distance between the chambers is appropriately adapted so that
the time will be sufficient for obtaining the desired bactericidal
effect. The sterilizing agent is removed in chamber 4 from
the web by means of a stream of hot air which is generated in
a water ring compressor 24. The water ring compressor is of the
known type and the compressed air generated is passed via a
water separator 25 which separates residual sealing water from
the air, and a heating element 26 to the chamber 4. After the
sterilizing agent has been evaporated and removed for a certain
time in the chamber, the air mixed with sterilizing agent is
returned to the water ring compressor 24 where it is stripped
of sterilizing agent which is mixed with the sealing water and
; is separated in the water separator 25.
As is evident from the above, it is important for the
method in accordance with the invention that the air used can
absorb a certain amount of hydrogen peroxide. To make this possible
and so as to avoid the hydrogen peroxide being mixed up with the
` 20 moisture normally present in the air, dehydrated air is used in
` accordance with the invention. This is obtained by comrpessing ~;
the air by means of the compressor 11 to a pressure of 6-7 kg/cm2.
The air heated by the compression is then passed to the cooler 12
in which it is cooled down to a temperature of 15-20C. Hereby
a large portion of the moisture carried by the air is precipitated
which is removed in the following moisture trap 13. The resulting
dehydrated air now has an absolute moisture which has been reduced
~; from approx. 0.01 kg/kg to 0.003 kg/kg.
The dehydrated air, as mentioned earlier, is passed
partly via the heating element 17 to the mixing chamber 18,
partly to the ultrasonic nozzle 19 so as to operate the same
and generate the standing wave which atomizes the sterilizing
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-- 1081428
agent fed to the ultrasonic nozzle. The standing wave has a
frequency of approx. 30 kHz and distributes the sterilizing
agent pumped-in to a mist with a droplet size of approx. 10
micrometre. The mist is sprayed directly into the mixing chamber
18 where it encounters and is mixed with the bulk of the dehydrated
air from the moisture trap 13, to which in the heating arrangement
17 is supplied the desired amount of heat by heating to high
temperature. This high temperature implies that the droplets
~; of sterilizing agent forming the injected mist directly come to
boil and are vaporized. The temperature of the mixture is reduced
thereby to approx. 100C-and the condensation temperature or dew
point at an absolute moisture of approx. 0.150 kg/kg will be
approx. 60C. This dew point has been found to ensure condensation
i
~, on the packing material web 1 even under unfavourable conditions,
e.g. at high temperature ofthe outside air. Naturally the
dew point can be varied upwards or downwards by a variation of
~, the quantity of sterilizing agent and the quantity of air in rela-
tion to one another.
The mixture of sterilizing agent vapour and air which
reaches chamber 3 is guided in such a manner that it flows along
~' the packing material web 1 through the whole length of the chamber.
, .
During this, the part of the mixture which comes into contact with
the packing material web is cooled down and the sterilizing agent
condenses to a uniform layer on the surface of the web. In
t''' connection with the condensation heat is liberated which passes
; to the material web and warms the same. The condensat~on goes
, ,
on until the temperature difference has evened out (on the
``~ assumption that the packing material 1 has not come to leave the
chamber 3already before this). Since the walls oE chamber 3, at
"i
least to begin with, were at a lower temperature than the air
mixture the sterilizing agent will also condense on them. The
excess sterilizing agent is conducted from the chamber 3 via the
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- 1081428
pipe 23 and may be collected in a vessel. The air escaping from
the chamber 3 continues to contain a certain amount of sterilizin~
agent, and it may therefore be suitable to pass the mixture to
the water ring compressor 24, wherein the sterilizing agent is
mixed with the sealing water and separated in the moisture trap
25.
After a suitable reacting time, the sterilizing agent
is removed again from the packing material web 1, as described
earlier, in the chamber 4, through which hot air is blown contin-
uously at a temperature of approx. 130C. It is appropriate
: to return the used air from this chamber too via a return line
to the water ring compressor 24 for the stripping off of sterilizing
agent.
The sterilizing agent can also be removed from the webin some other suitable manner, e.g. by heating of the web by
means of a heating element of the infrared type.
When the packing material web 1 has been wholly freed
from sterilizing agent the same runs in a manner protected from
bacteria and contaminations through the packing machine where,
in a manner described earlier, it is converted to a tube 6 - -
which is filled with sterile contents, transversely sealed
- and cut so as to form individual, completely filled packing
containers.
The method and the arrangement in accordance with
the invention may be used on any oftheknown types of packaging
machines. When the arrangement is to be used on a packing machine ~-
which operates with preformed blanks, the chambers 3 and 4 must
of course be modified in a suitable manner and be adapted to the
t .
shape ofthe packing material blanks. The functional description
described, however, applies to all types of packing machines.
As a sterilizing agent preferably a mixture of 35%
hydrogen peroxide and 65~ water is used, but other proportions
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and other liquid sterilizing agents are conceivable. The numerical
values specified in the description relate to the case where
: hydrogen peroxide and water are used.
; When a packing machine of the sterile type is to be
started up lt is essential that the parts of the machine which
will come into contact with the contents or the packing material
,- web are presterilized. It is known to carry out this pre-sterili-
zation in a number of different manners. For the method and
arrangement in accordance with the invention it is appropriate
that, as during operation of the machine, the mixture of air
and sterilizing agent generated in the mixing chamber 18 should
.`,f' be made use of. When the machine is to be pre-sterilized, the
, outlet of the mixing chamber 18 is thus connected in such a manner
. to the parts of the packing machine which are to be pre-sterilized
; ., .
(supply pipe for contents arranged in the tubular part of the
packing material, elements for the regulation of the liquid contents
level etc, the chamber in which the packing material web 1 runs
from the chamber 3 to the sealing station etc.), that a closed
system is created through which the mixture can circulate. Since
the walls of the pipes and ducts through which the mixture
circulates have a temperature which is lower than the dew point
of the mixture, a condensation of the sterilizing agent will take
place. The mixture is made to flow through the machine for a
sufficiently long time to ensure that the sterilizing agent is
condensed on all the surfaces which are to be sterilized. When
the feed of sterilizing agent mixture has ceased, the condensed
.:, i .
sterilizing agent is removed again, aftera sultablereacting time,by
~i~ causing hot air to flow through the ducts. By doing this, the
~i~ walls are heated and the sterilizing agent vaporized which then
accompanies the hot air out of the machine. The inflow of hot
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`~ air is achieved by connecting the water ring compressor 24, the
water separator 25 and the heating element 26 via a suitable valve
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1(~814Z8
to the sterilized spaces. In this manner it is possible to
provide a pre-sterilization of the packing machine by making
use of the method and arrangement in accordance with the
invention and without major arrangements. The pre-sterilization
will be especially effective, slnce similarly to what happens
in the sterilization of the packing material web, sterilizing
agent will condense on each component and in each space along
the path followed by the packing material web, provided only
that the said components or spaces are at a sufficiently low
temperature to permit condensation.
Although the method in accordance with the invention
; . is intended primarily to be used in packing machines, and has
been described in connection therewith, the same principle can
be used of course for any object whatever, provided that the same
is introduced into a mixture of peroxide vapour and water vapour
of an appropriate temperature.
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