U.S. patent application number 12/295946 was filed with the patent office on 2009-10-29 for device and method for packaging dry ice in a plastic film.
Invention is credited to Herve Flamant, Jacques Fouche, Philippe Gibert.
Application Number | 20090266031 12/295946 |
Document ID | / |
Family ID | 37498685 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266031 |
Kind Code |
A1 |
Flamant; Herve ; et
al. |
October 29, 2009 |
Device and Method for Packaging Dry Ice in a Plastic Film
Abstract
The present invention relates to a method and device for
packaging dry ice in a plastic film, the said device comprising:
--means for dispensing and shaping a plastic film comprising a
shaping sleeve over the exterior wall of which the plastic film is
paid out, --a dry ice generator connected to a source of liquid
carbon dioxide, the dry ice generator being positioned inside the
shaping sleeve so as to leave a gap between the generator and the
shaping sleeve and allow the plastic film shaped to become filled
with dry ice, --and means for sealing the shaped plastic film,
characterized in that the shaping sleeve is equipped with thermal
insulating means and/or with heating means.
Inventors: |
Flamant; Herve; (Libourne,
FR) ; Fouche; Jacques; (Verrieres-Le-Buisson, FR)
; Gibert; Philippe; (Villepinte, FR) |
Correspondence
Address: |
AIR LIQUIDE;Intellectual Property
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Family ID: |
37498685 |
Appl. No.: |
12/295946 |
Filed: |
March 12, 2007 |
PCT Filed: |
March 12, 2007 |
PCT NO: |
PCT/FR2007/050913 |
371 Date: |
March 20, 2009 |
Current U.S.
Class: |
53/436 ; 53/456;
53/469; 62/530; 62/603 |
Current CPC
Class: |
C01B 32/55 20170801;
F25D 3/12 20130101; F25D 2303/082 20130101 |
Class at
Publication: |
53/436 ; 62/530;
62/603; 53/469; 53/456 |
International
Class: |
B65B 1/24 20060101
B65B001/24; F25D 3/08 20060101 F25D003/08; F25J 1/00 20060101
F25J001/00; B65B 1/04 20060101 B65B001/04; B65B 43/08 20060101
B65B043/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2006 |
FR |
0651164 |
Claims
1-14. (canceled)
15. A device for packaging carbon dioxide snow in a plastic film,
said device comprising an element adapted to dispense and shape a
plastic film that comprises a shaping sleeve along whose outer wall
the plastic film is unwound, a carbon dioxide snow generator
connected to a source of liquid carbon dioxide, the carbon dioxide
snow generator being placed inside the shaping sleeve so as to
leave a free space between the generator and the shaping sleeve and
allow the shaped plastic film to be filled with carbon dioxide
snow, and an element adapted for sealing the shaped plastic film,
characterized in that the shaping sleeve is equipped with a layer
of thermal insulating material and/or a layer of heating
material.
16. The device for packaging carbon dioxide snow of claim 15,
wherein the layer of thermal insulating material and/or layer of
heating material are such that they allow the surface of the wall
of the shaping sleeve along which the plastic film is unwound to be
maintained at a temperature of at least -10.degree. C., preferably
at least 0.degree. C., and more preferably still at least
10.degree. C.
17. The device of claim 15, wherein the layer of thermal insulating
material is made of a material selected from the group consisting
of cork, polystyrene and glass wool.
18. The device of claim 17, wherein a free or empty space is formed
between the layer of thermal insulating material and the inner
surface of the shaping sleeve.
19. The device of claim 17, wherein the inner surface of the
shaping sleeve comprises, instead of the layer of insulating
material or juxtaposed with the layer of insulating material, at
least one layer of heating material.
20. The device of claim 15, wherein said layer of thermal
insulating material and/or layer of heating material comprises a
superposed arrangement of a protective skin, the layer of thermal
insulating material, the layer of heating material and an empty
space adapted to be provided with a heat sensor, the empty space
being situated closest to the inner wall of the shaping sleeve.
21. The device of claim 15, further comprising: a gas feed nozzle
arranged at the inlet of the carbon dioxide generator adapted to
inject inerting gas into the carbon dioxide snow generator, and/or
an injection rod disposed in the free space having a free end
oriented toward the plastic film released by the shaper, said
injection rod being adapted to inject a fluid having a temperature
below a dew point temperature of air into contact with and inside
the plastic film container; and/or at least one tamper for
compacting the carbon dioxide snow in the plastic film
container.
22. A method for packaging carbon dioxide snow in a plastic film
container, comprising the steps of: generating carbon dioxide snow
injecting liquid carbon dioxide into a carbon dioxide snow
generator; introducing the carbon dioxide snow into a plastic film
container, and closing the plastic film container, wherein a gas is
continuously injected into the carbon dioxide snow generator.
23. The method of packaging carbon dioxide snow of claim 22,
further comprising: forming the plastic film container using a
packaging device comprising a shaping sleeve.
24. The method of claim 23, further comprising: maintaining a
temperature of the shaping sleeve, preferably at a temperature of
at least -10.degree. C.
25. The method of claim 22, further comprising: continuously
removing gaseous carbon dioxide from the plastic film container
that is formed during said steps of generating and introducing.
26. The method of claim 22, further comprising: injecting a fluid
having a temperature below a dew point temperature of air into
contact with and inside the plastic film container prior to the
injection of liquid carbon dioxide.
27. The method of claim 22, further comprising: compacting the
introduced carbon dioxide snow.
28. The method of claim 22, wherein said method is continuously
performed.
29. The method of claim 15, further comprising an element adapted
to remove the gaseous carbon dioxide connected, on one hand, to an
adjustable hot air inlet for heating the carbon dioxide gas, and on
the other hand to a line which is itself connected to a vacuum
system.
30. The method of claim 21, further comprising an element adapted
to remove the gaseous carbon dioxide connected, on one hand, to an
adjustable hot air inlet for heating the carbon dioxide gas, and on
the other hand to a line which is itself connected to a vacuum
system.
31. The method of claim 22, wherein the continuously injected gas
is carbon dioxide.
32. The method of claim 23, further comprising: maintaining a
temperature of the shaping sleeve, preferably at a temperature of
at least 0.degree. C.
33. The method of claim 23, further comprising: maintaining a
temperature of the shaping sleeve, preferably at a temperature of
at least 10.degree. C.
Description
[0001] The present invention relates to a device for packaging dry
ice in the form of carbon dioxide snow in a plastic film. The
invention also relates to a method of packaging carbon dioxide snow
in plastic bags in a continuous and automatic manner, using said
device.
[0002] It is known that frozen, deep-frozen or else fresh products,
in particular food products, which have to be maintained at a
controlled temperature of +6.degree. C. to -20.degree. C. or less,
without interruption of their cold chain from the time they are
cooled, frozen or deep-frozen until the time of their use, require
warehouses, means of transport and shops provided with
refrigeration equipment, which at the present time is generally
electrical. However, in many situations, for example in the case of
non-motorized transportation, it is impossible to transport the
products without taking them out of the refrigeration equipment in
which they are stored, since the risks of a rise in temperature are
considerable, particularly if the climate conditions are
unfavorable. In order to avoid such a rise in temperature during
their transportation, it is common practice to place the fresh,
frozen or deep-frozen products in an environment maintained at a
controlled temperature in an isothermal enclosure. The temperature
is regulated, for example, by the slow sublimation of carbon
dioxide snow packed into perforated plastic film bags. Carbon
dioxide snow is a relatively inexpensive product and has a cooling
capacity. Its temperature of approximately -80.degree. C. allows
the products to be kept cold for a relatively long time.
[0003] Thus, application EP 1 186 842 describes a device for
packaging carbon dioxide snow in a plastic film, comprising means
for dispensing and shaping the plastic film, a carbon dioxide snow
generator in the form of a tube connected to a source of liquid
carbon dioxide and placed in such a way as to fill the shaped
plastic film. The means for dispensing and shaping the plastic film
comprise a shaping sleeve for the plastic film that is placed
concentrically around the carbon dioxide snow generator while
leaving a free space between the shaping sleeve and the carbon
dioxide snow generator. When the pressurized liquid carbon dioxide
is released at the upper part of the carbon dioxide snow generator,
it expands to atmospheric pressure and strikes the walls of the
carbon dioxide snow generator, thus leading not only to the
formation of a solid in powdery form, known by the name of carbon
dioxide snow, at a temperature greatly below 0.degree. C., of
around -80.degree. C., but also to the formation of carbon dioxide
in the gaseous state, likewise at a temperature greatly below
0.degree. C., of around -80.degree. C. The carbon dioxide snow thus
obtained drops under gravity into the shaped plastic film, while
the gaseous carbon dioxide escapes through the space formed between
the shaping sleeve and the carbon dioxide snow generator.
[0004] However, this device has a major disadvantage which prevents
it from being used continuously on an industrial scale. This is
because the gaseous carbon dioxide which escapes into the space
formed between the carbon dioxide snow generator and the shaping
sleeve significantly cools the walls of the shaping sleeve, causing
a sudden cooling of the water vapor present in the ambient air,
with the resultant formation of ice crystals on the walls,
particularly the outer walls, of the shaping sleeve. The formation
of ice crystals prevents the plastic film from advancing along the
shaping sleeve. As the moisture level in the ambient air increases,
this phenomenon becomes more pronounced.
[0005] The objective of the present invention is therefore to
overcome all or some of the disadvantages of the prior art
device.
[0006] Accordingly, the invention relates to a device for packaging
carbon dioxide snow in a plastic film, comprising: [0007] means for
dispensing and shaping a plastic film that comprise a shaping
sleeve along whose outer wall the plastic film is unwound, [0008] a
carbon dioxide snow generator connected to a source of liquid
carbon dioxide, the carbon dioxide snow generator being placed
inside the shaping sleeve so as to leave a free space between the
generator and the shaping sleeve and allow the shaped plastic film
to be filled with carbon dioxide snow, and [0009] means for sealing
the shaped plastic film, characterized in that the shaping sleeve
is equipped with thermal insulating means and/or heating means.
[0010] By equipping the shaping sleeve with thermal insulating
means and/or heating means, the gaseous carbon dioxide, which is
formed during the generation of carbon dioxide snow, is prevented
from suddenly cooling the walls of the shaping sleeve. It is thus
possible to avoid the formation of ice crystals on the walls,
particularly the outer walls, of the shaping sleeve. Consequently,
the plastic film no longer sticks to the shaping sleeve and there
are no longer any problems with advancing the plastic film due to
the cooling of the walls of the shaping sleeve by the gaseous
carbon dioxide formed during the generation of carbon dioxide
snow.
[0011] Other features and advantages of the invention will become
apparent on reading the description which follows. Forms and
embodiments of the invention are given by way of non-limiting
examples illustrated by the appended drawings, in which:
[0012] FIG. 1 is a schematic view of a device according to the
invention;
[0013] FIG. 2 is a schematic view of a bagging device;
[0014] FIG. 3 is a detail of the device shown in FIG. 1;
[0015] FIG. 4 is a detail of one particular embodiment of the
invention;
[0016] FIG. 5 is a cross section taken on AA' in FIG. 4.
[0017] The insulating and/or heating means with which the shaping
sleeve is equipped are such that they allow the surface of the wall
of the shaping sleeve along which the plastic film is unwound to be
maintained at a sufficiently high temperature to avoid any
crystallization of the water vapor on this wall. Advantageously,
this temperature is at least -10.degree. C., preferably at least
0.degree. C., and more preferably still at least 10.degree. C.
[0018] In one particular embodiment, the thermal insulating means
can consist of at least one layer of insulating material selected
from the group consisting of cork, polystyrene, glass wool, etc.
The layer of insulating material can be applied to the inner
surface of the shaping sleeve, that is to say to that surface of
the shaping sleeve opposed to the surface along which the plastic
film slides. Given that this layer is in contact with the carbon
dioxide gas, it is preferably not porous and can optionally be
covered with a thin layer or protective skin made of a non-porous
material which is preferably insulating as well.
[0019] The skin can consist, for example, of a metal or plastic
film.
[0020] According to another embodiment, a free or empty space is
formed between the layer of insulating material and the inner
surface of the shaping sleeve. The free space is a space devoid of
material and filled with ambient air at atmospheric pressure, or
else placed under a vacuum.
[0021] According to one particular embodiment, the inner surface of
the shaping sleeve comprises, instead of the layer of insulating
material or juxtaposed with the layer of insulating material, at
least one layer of heating material.
[0022] The layer of heating material consists, for example, of an
electrical resistor, or else of a hollow element filled with liquid
whose temperature can be adjusted (for example eutectic).
[0023] In the free space can be placed a temperature sensor so that
the temperature of the layer of heating material can be adjusted to
the desired temperature.
[0024] According to one particularly advantageous embodiment, the
inner wall of the shaping sleeve consists of a superposed
arrangement of layers of heating and insulating materials which can
be juxtaposed or separated by at least one empty region.
[0025] Thus, a particularly appropriate superposed arrangement
consists of the successive arrangement of a protective skin, a
layer of insulating material, a layer of heating material and an
empty space, it being possible for the empty space to be provided
with a heat sensor, the empty space being situated closest to the
inner wall of the shaping sleeve.
[0026] A person skilled in the art will be able to adapt the
number, nature and thickness of the constituent layers to suit the
capacities of the machine and the desired production rate.
[0027] By way of illustration, possible thickness ranges can be as
follows: [0028] protective skin: 0.5 mm to 5 mm, preferably 0.8 mm
to 2 mm; [0029] insulating material: 0.5 cm to 10 cm, preferably 2
cm to 5 cm; [0030] heating material: 2 cm to 15 cm, preferably 3 cm
to 10 cm; [0031] empty space: 1 cm to 5 cm, preferably 2 cm to 4
cm; the wall of the shaping sleeve having a thickness of between
0.5 cm and 3 cm, preferably of around 1 cm.
[0032] Advantageously, the device for packaging carbon dioxide snow
comprises means for injecting inerting gas in the region of the
carbon dioxide generator. This makes it possible to continuously
flush the carbon dioxide snow generator in order to prevent air or
carbon dioxide entraining carbon dioxide snow from being sucked
back into the carbon dioxide snow generator when the supply of
liquid carbon dioxide is interrupted and in order to allow improved
dropping of the carbon dioxide snow into the shaped plastic
film.
[0033] The means for injecting inerting gas comprise, for example,
a gas feed nozzle arranged at the inlet of the carbon dioxide
generator.
[0034] The inerting gas used can be any gas which is not reactive
with respect to the carbon dioxide snow. If the carbon dioxide snow
is intended for preserving food products, this gas will be
compatible with such a use. The preferred gas is carbon dioxide.
However, preference is given above all to using a substantially
anhydrous inerting gas (dew point of around -40.degree. C.) in
order, given the temperature of the carbon dioxide snow, to prevent
any traces of water from icing to form water ice.
[0035] According to one particular embodiment, the device for
packaging carbon dioxide snow can comprise means for injecting a
fluid having a temperature below the dew point temperature of air
into contact with and inside the plastic film container. For
example, such means can consist of an injection rod which is
arranged in the space formed between the carbon dioxide snow
generator and the shaper and whose free end is oriented toward the
plastic film released by the shaper.
[0036] Any food-quality fluid is suitable for this purpose.
However, liquid carbon dioxide is preferred.
[0037] According to one particular embodiment, the means for
injecting liquid carbon dioxide is connected to the source of
liquid carbon dioxide which is used to generate carbon dioxide
snow. A valve, generally a solenoid valve, is inserted between the
injection rod and the source of liquid carbon dioxide so as to
start and stop the supply of liquid carbon dioxide. A valve,
generally a solenoid valve, is also inserted between the carbon
dioxide snow generator and the source of liquid carbon dioxide so
as to start and stop the supply of carbon dioxide snow. When the
device according to the invention is switched on, the solenoid
valve of the capillary injection rod is open, then closed, before
the solenoid valve of the carbon dioxide snow generator is opened.
The valves can be controlled by a timer determining how long they
remain open and hence the amount of carbon dioxide snow to be
packaged. The timer can be started by any means, including a
coin-operated system.
[0038] According to one advantageous embodiment, the device for
packaging carbon dioxide snow comprises at least one means for
removing the gaseous carbon dioxide. This means can consist of the
space formed between the outer wall of the carbon dioxide snow
generator and the inner wall of the shaping sleeve. The removal
means is connected at its top to a containment box, which will be
connected, on the one hand, to an adjustable "hot" air inlet for
heating this carbon dioxide gas, which is at a temperature of
around -80.degree. C., and on the other hand to a line which is
itself connected to a vacuum system used to suck in this toxic
mixture.
[0039] The means for dispensing, shaping and moving the plastic
film are those conventionally employed in known packaging devices.
Generally, these means consist in continuously dispensing a strip
of plastic film, in shaping it into a tube by winding it around a
preshaping sleeve, in sealing the two edges of the tube which meet,
and in sliding the tube obtained downstream of the preshaping
sleeve. The means for sealing the plastic film, once said film has
been shaped, make it possible to close the tube by thermal welding
and then to cut it at the welded film stage in order to obtain a
bag. In this case, the carbon dioxide snow generator is placed
inside the shaping sleeve in such a way that the snow produced is
directed into the bag being formed. Preferably, the means for
dispensing and shaping the plastic film are positioned in such a
way as to form a vertical bag whose opening is on the top side, and
the carbon dioxide snow generator is oriented vertically in such a
way that the carbon dioxide snow formed drops under gravity into
the shaped plastic bag and in such a way that, once the latter has
been sealed and cut, the bag containing the carbon dioxide snow
also drops under gravity.
[0040] The plastic film is generally chosen from materials allowing
evacuation of the gaseous carbon dioxide resulting from the
sublimation of the carbon dioxide snow. This property can be
achieved by the porosity of the plastic film. The plastic film used
is then microporous or has microperforations. Thus, the plastic
film can be chosen such that the perforations make it possible for
the significant mass of expansion gas to escape and also for the
fine crystals making up the carbon dioxide snow to be retained and
contained. The microperforations can be produced at the time of
manufacturing the plastic film or during the method according to
the invention, for example in a prior step of preparing the plastic
film such as by passing the plastic film over perforating spikes.
Preferably, the plastic film can be thermally welded. It is also
preferable, on the one hand, for it to be strong enough to
withstand the pressure of the carbon dioxide snow while it is being
filled and handled, and, on the other hand, for it to be
sufficiently thermally insulating to avoid any risk of cold burns
when it is being handled; these two properties can be obtained by
choosing a sufficiently large thickness of material. Furthermore,
if the container is intended for use in the food industry, the
material chosen must of course be suitable for this use. Finally,
it is generally preferable for the plastic film to be biodegradable
in order to respect the environment. According to the preferred
implementation of the invention, the plastic film is
microperforated polypropylene having a thickness of between 25 and
80 microns, preferably between 35 and 70 microns.
[0041] Of course, the thickness of the plastic film will be
tailored to the quantity of carbon dioxide snow contained in a bag.
In the same way, the number of perforations and their diameter will
be tailored to suit the quantity of carbon dioxide snow contained
and the desired rate of sublimation.
[0042] The device can also comprise at least one means for
compacting the carbon dioxide snow in the plastic film container.
Such a means can consist of a tamper arranged on the lower part of
the plastic film container. Said tamper can be actuated by a system
of electromagnets or by an electropneumatic system.
[0043] The invention also relates to a method of packaging carbon
dioxide snow in a plastic film container, wherein: [0044] carbon
dioxide snow is generated in a carbon dioxide snow generator by
injecting liquid carbon dioxide, [0045] the carbon dioxide snow
formed is introduced into a plastic film container, and [0046] the
plastic film container is closed, characterized in that an inerting
gas is continuously injected into the carbon dioxide snow
generator.
[0047] As mentioned above in relation to the device for packaging
carbon dioxide snow according to the invention, the injection of an
inerting gas into the carbon dioxide snow generator makes it
possible to continuously flush the carbon dioxide snow generator in
order to prevent air or carbon dioxide from being sucked back into
the carbon dioxide snow generator when the vaporization is stopped
and to allow improved dropping of the carbon dioxide snow into the
shaped plastic film.
[0048] Any gas which does not react with the carbon dioxide snow is
suitable for this purpose. Of course, if the carbon dioxide snow is
intended for a food use, the gas used will be of food quality.
Preferably, carbon dioxide is used.
[0049] The injection of carbon dioxide into the carbon dioxide snow
generator takes place in a pulsed manner, that is to say that the
vaporization is stopped as soon as a sufficient quantity of liquid
carbon dioxide has been injected to give the desired quantity of
carbon dioxide snow.
[0050] The method can additionally comprise a step of forming a
plastic film container. This step allows the continuous formation
of an open plastic film container. The carbon dioxide snow formed
is then introduced into said container through its opening and then
the opening is closed, for example, by heat sealing.
[0051] Advantageously, the plastic film container is formed using a
packaging device comprising a preferably cylindrical shaping sleeve
which is arranged vertically and whose operation has been described
above in connection with the device. The carbon dioxide snow formed
fills the container under gravity and then, when the desired
quantity of carbon dioxide snow has been introduced, the upper part
of the container is sealed.
[0052] According to one particularly advantageous embodiment of the
method of the invention, a continuous additional step of
maintaining the temperature of the shaping sleeve is added. In this
step, the temperature of the shaping sleeve is maintained at a
temperature of at least -10.degree. C., preferably at least
0.degree. C., and more preferably still at least 10.degree. C.
[0053] The method according to the invention can also comprise a
step of continuously removing the gaseous carbon dioxide formed
during the step of carbon dioxide snow formation. The gaseous
carbon dioxide removed along the carbon dioxide snow generator is
generally discharged away from the premises in which the carbon
dioxide snow is packaged, for safety reasons.
[0054] Another optional step of the method according to the
invention comprises injecting a fluid having a temperature below
the dew point temperature of air into contact with and inside the
plastic film container prior to injecting liquid carbon
dioxide.
[0055] According to the preferred embodiment of the invention, the
fluid having a temperature below the dew point temperature of air
is liquid carbon dioxide. Thus, during the step of carbon dioxide
snow formation, or prior to this step, it is sufficient to inject a
small quantity of liquid carbon dioxide so as to cool the inner
wall of the plastic film container to a temperature below the dew
point temperature of air. Generally, a few grams of liquid carbon
dioxide at -80.degree. C. or a squirt of the latter from a
capillary is sufficient. This step can be carried out at each new
step of carbon dioxide snow formation or else only when starting up
the device after a prolonged shutdown.
[0056] At the end of the filling step, the method can comprise a
compacting step which makes it possible to compact the carbon
dioxide snow in the container in order to facilitate sealing of the
upper part of the container.
[0057] According to one preferred embodiment of the invention, the
method is a continuous carbon dioxide snow packaging method.
[0058] Generally, the liquid carbon dioxide which is injected
inside and into contact with the plastic film container and that
which is injected into the carbon dioxide snow generator come from
the same source of liquid carbon dioxide. The carbon dioxide source
can be a cylinder of pressurized carbon dioxide in the liquid
state, but it is preferably rather a source of refrigerated
low-pressure liquid carbon dioxide since this type of source leads
to better efficiency in terms of carbon dioxide snow generation. In
this second case, the conditions under which the source of liquid
carbon dioxide is stored can, for example, be a temperature of
-20.degree. C. and a pressure of approximately 20 bar, or even
less.
[0059] FIGS. 1 to 5 illustrate the device and the method according
to the invention. The complete system (1) is represented in FIG. 1.
The device (2) according to the invention is supplied with liquid
carbon dioxide contained in a refrigerated reservoir (3) of liquid
carbon dioxide via a lagged pipe (4) and a lagged hose (5). Filters
(6a and 6b) and shutoff valves (7, 8) can be placed between the
carbon dioxide source (3) and the generator (2), it being possible
in particular for one (8) of these valves to be placed between the
pipe and the hose. The lagged pipe can be provided with an orifice
(9) connected to a shutoff solenoid valve (10) leading to a
degassing pot (11), the lower part of the degassing pot being
connected to the lagged pipe (4) by means of a cross-section
increasing system (12) allowing the separation of the gas and the
liquid. A valve (13) is also present between the stop valve (8) and
the production valve (14). After this production valve (14) is
mounted an injection nozzle (15). The carbon dioxide snow generator
(16) is adjoined by a system (17) for flushing with dry air or
gaseous CO.sub.2 at low pressure (a few millibar) maintained by a
regulator (18), which can be controlled by a solenoid valve
(19).
[0060] The carbon dioxide snow generator (16) is placed inside the
shaping sleeve (20) of a vertical bagging machine (21) represented
in FIG. 2.
[0061] When the method is implemented, the plastic film (22) is
wound around itself to form a tube which is taken up by the shaping
sleeve (20). The film is wound in such a way as to bring the two
vertical edges of the film closer together: these edges are made to
overlap and are then bonded together by thermal welding with
vertical sealing means (23) over their entire length. The tube
formed is moved downward by guide pulleys (24) so as to form a
plastic bag or container (25) into which carbon dioxide snow can be
introduced. In FIG. 2, the arrows indicate the movements of the
shaping and sealing means. Once the bag has been formed into shape,
the solenoid valve (14) opens for a few tenths of a second: the
liquid carbon dioxide comes out and the generator (16) then
produces carbon dioxide snow (26), which drops under gravity into
the plastic bag (25). The solenoid valve (14) is closed. During all
its operations, the carbon dioxide gas is removed from the plastic
bag (25). The solenoid valve (14) is closed. The carbon dioxide gas
is removed through the space (27) formed between the plastic film
shaping sleeve (20) and the carbon dioxide snow generator (16).
Finally, the sealing tools (28) of the bagging machine close the
plastic by thermal welding and cut the welded plastic to form a
closed bag (29).
[0062] The device (2) according to the invention is described in
more detail in FIGS. 3 to 5, which show the carbon dioxide snow
generator (16) arranged inside the shaping sleeve (20) along whose
outer wall is unwound the plastic film (22) which is driven by the
drive rollers (24). The space (27) formed between the generator
(16) and the inner wall of the shaping sleeve, which is covered
with an insulating means (28), makes it possible to remove the
carbon dioxide formed. The carbon dioxide snow (26) which drops
into the plastic film container under gravity is formed by
injecting liquid carbon dioxide through the nozzle (15) into the
upper part of the generator (16). An inerting gas is injected
through the nozzle (17).
[0063] The preferred embodiment of the means for insulating and
heating the shaping sleeve is illustrated in FIGS. 4 and 5. In this
embodiment, the insulating and heating means (28) consist of a
superposed arrangement of layers of different materials in the
following way. Starting from the inner wall (20a) of the shaping
sleeve (20) are situated an empty space (29), a layer (30) of
heating material, a layer of insulating material (31), and a
protective skin (32). In the empty space is arranged a heat sensor
(33). These figures also show the rod (34) for injecting a fluid
whose temperature is below the dew point temperature of air.
[0064] By employing a device as described above, it is possible to
continuously fill bags of carbon dioxide snow at a rate of 1 minute
per bag for bags containing 2 kg of carbon dioxide snow.
[0065] No problem is encountered when closing the plastic bag by
thermal welding or with regards to continuously unwinding the
plastic film, even after a long shutdown of the device.
* * * * *