Note: Descriptions are shown in the official language in which they were submitted.
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"Double-door vertical freezer"
DESCRIPTION
The present invention relates to a double-door vertical freezer, in particular
a very low
temperature freezer.
It is known, for example in the sector of scientific laboratories, to use very
low
temperature freezers, i.e. freezers which are suitable for maintaining
internally
temperatures of between -40 C and -$0 C.
These freezers may have different configurations, for example may have a
substantially
horizontal or substantially vertical extension. This latter configuration
offers the
advantage that, for the same useful internal volume, its occupies a smaller
floor area.
There exist furthermore some configurations which envisage a single
refrigerated
compartment closed by a single door, while other configurations envisage two
separate
compartments which are closed by two independent doors. This latter
configuration is
able to limit the problems associated with the variations in temperature which
are
recorded inside the refrigerated compartments upon opening the door. The
double door
and the double internal compartment allow, for example, separation of the
samples
which must be stored for a long period of time from those which must be stored
for a
shorter period of time. In this case, the latter samples may be placed in the
compartment where the door is opened more frequently, while the other samples
may be
kept in an environment which comes into contact with the exterior less
frequently and
therefore is less exposed to variations in temperature.
Moreover, the double door allows, by means of the use of keys or other means
for
controlling access, two different users to have a specific dedicated space,
without the
activity of one interfering with the activity of the other one.
The configuration described above of the double-compartment and double-door
vertical
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freezer is at present achieved by means of two different constructional
designs. These
constructional designs, although widely used, are however not without
drawbacks.
A first constructional design envisages the substantial arrangement on top of
one another,
within a single cabinet, of two different freezers which are independent of
each other. In
this design, therefore, there is a clear duplication of the plants and
apparatus associated
with cooling of the internal compartments. This obviously results in a
substantial
increase in the freezer production and operating costs.
A second constructional design envisages instead the division, into two, of
the internal
compartment and of the door of a conventional vertical freezer. This design
envisages
that, in order to ensure a temperature of the two compartments which is as
uniform as
possible, a communication channel between the two compartments is maintained
so that
it is possible to establish an airflow between one compartment and the other
one. This
communication channel between the two compartments constitutes a potential
path via
which the samples stored in the upper compartment and the samples stored in
the lower
compartment may contaminate each other.
An object of the present invention is therefore to overcome at least partly
the drawbacks
mentioned above with reference to the prior art.
In particular, one task of the present invention is to provide a double-door
freezer which
ensures complete isolation between the upper compartment and the lower
compartment
and which at the same time ensures temperatures which are substantially the
same in both
compartments.
Another task of the present invention is to provide a double-door freezer
which is able to
ensure lower production and operating costs.
The present invention provides a very low temperature vertical freezer,
comprising:
a thermally insulating cabinet comprising two side walls, an upper wall, a
lower wall
and a rear wall;
a thermally conducting shelf suitable for defining, inside said cabinet, an
upper
compartment and a lower compartment;
an upper door for closing the upper compartment;
a lower door for closing the lower compartment;
wherein:
the freezer comprises a single cooling plant designed to cool the upper
compartment and the lower compartment;
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the thermally conducting shelf forms an air-tight closure between the upper
compartment and the lower compartment; and
the cooling plant comprises a coil circuit running through the upper wall, the
side walls and the rear wall of the cabinet, said coils being distributed with
variable density along the height of the cabinet.
The volume of the upper compartment can be smaller than or equal to the volume
of the
lower compartment and the extension of the coils around the upper compartment
can be
greater than or equal to the extension of the coils around the lower
compartment. The
cooling plant can be designed to cool the compartments to a temperature of
between -
40 C and -80 C. The coils can be distributed in the walls bounding the upper
compartment with a greater average density than in those bounding the lower.
compartment. The upper wall can have a density of coils greater than that in
the side
walls and in the rear wall.
The coils can be distributed in the side walls and in the rear wall in such a
way as to have
an almost constant average density along the section bounding the upper
compartment
and in such a way as to have a variable density along the selection bounding
the lower
compartment. The density of the coils can increase from the bottom to the top
of the
lower compartment.
In one embodiment, 54% of the total of the coils can extend around the upper
compartment and the remaining 46% can extend around the lower compartment. The
air-
tight closure between the upper compartment and the lower compartment can be
obtained
by means of a silicone bead. The overall inner volume of the freezer can be
divided up
differently between the upper compartment and the lower compartment. The
volume of
the upper compartment can be about the 45% of the total volume cooled by the
freezer,
while the volume of the lower compartment can be about 55% of the total volume
cooled
by the freezer. The upper door and the lower door can be identical to each
other.
In one embodiment, the freezer can further comprise a thermally insulating
band between
the two doors, the shelf having a smaller thickness than the band and being
mounted
above, flush with band, and can further comprise control means for allowing
separate
access to the two compartments.
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The characteristic features and further advantages of the invention will
emerge from the
description provided hereinbelow, of some examples of embodiment, provided by
way
of a non-limiting example, with reference to the accompanying drawings in
which:
- Figure 1 shows a first perspective view of a freezer according to the
invention;
- Figure 2 shows a second perspective view of a freezer according to the
invention;
- Figure 3 shows a third perspective view of a freezer according to the
invention where
the doors have been removed for greater clarity;
- Figure 4 shows a transparent perspective view of a freezer according to the
invention
in which part of the cooling plant is shown.
With reference to the accompanying figures, 10 denotes in its entirety a very
low
temperature vertical freezer according to the invention. The freezer 10
comprises:
- a thermally insulating cabinet 12 comprising in turn two side walls 14 and
16, an
upper wall 18, a lower wall 20 and a rear wall 22;
- a thermally conducting shelf 24 suitable for defining, inside the cabinet
12, an upper
compartment 26 and a lower compartment 28;
an upper door 30 for closing the upper compartment 26; and
- a lower door 32 for closing the lower compartment 28.
The freezer 10 according to the invention comprises a single cooling plant 34
designed
to cool the upper compartment 26 and the lower compartment 28.
Moreover, the thermally conducting shelf 24 defines an air-tight closure
between the
upper compartment 26 and the lower compartment 28. Finally, the cooling plant
34
comprises a coil circuit 36 running through the upper wall 18, the side walls
14 and 16
and the rear wall 18 of the cabinet 12. The coils 36 are distributed with a
variable
density along the height of the cabinet 12.
In connection with the present description the expression "very low
temperature", as
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conventionally used in the sector, is understood as meaning a temperature of
between
-40 C and -80 C.
The density of the coils 36 may be defined in various manners, for example as
the ratio
between the overall length of the linear extension of the coils which travel
along a wall
and the area of the wall itself. As the person skilled in the art may easily
understand,
this definition may be applied also to surfaces smaller than the entire wall,
but cannot be
meaningfully applied if the surfaces in question are very small.
According to one embodiment of the freezer 10, the coils 36 are distributed so
as to
achieve a greater average density in the walls which bound the upper
compartment 26
than in the walls which bound the lower compartment 28. In particular, the
upper wall
18 has preferably a greater density than the side walls 14 and 16 and the rear
wall 22.
According to some embodiments of the freezer 10, the volume of the upper
compartment 26 is smaller than or equal to the volume of the lower compartment
28 and
the extension of the coils around the upper compartment 26 is greater than or
equal to
the extension of the coils 36 around the lower compartment 28.
According to one embodiment of the freezer 10, the coils are distributed in
the side
walls 14 and 16 and in the rear wall 22 so as to have an almost constant
average density
along the section which bounds the upper compartment 26 and so as to have a
variable
density along the section which bounds the lower compartment 28. In
particular, the
density increase preferably from the bottom towards the top of the lower
compartment
28.
According to some embodiments of the freezer 10, more than half of the coils
36 extend
around the upper compartment 26. According to the embodiment of the freezer 10
shown in Figure 4, 54% of the total of the coils extend around the upper
compartment
26 and the remaining 46% extend around the lower compartment 28.
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With such a.distribution of the coil density, it is possible to exploit in an
optimum
manner the natural convention which tends, as a result of gravity, to displace
the cold
air downwards.
As mentioned above, the shelf 24 defines an air-tight closure between the
upper
5 compartment 26 and the lower compartment 28. This seal may be achieved, for
example, by means of a silicone bead and prevents any mutual contamination of
the
samples stored in the two compartments. In this respect, the fact that the
shelf 24 is
thermally conducting, makes it easier to achieve a uniform temperature inside
the two
compartments even when there is no circulating air flow.
As already mentioned, according to some embodiments of the freezer 10, the
overall
internal volume is divided up differently between the upper compartment 26 and
the
lower compartment 28, preferably so that the lower compartment 28 has a volume
greater than that of the upper compartment 26. For example, in the embodiment
of the
accompanying figures, the volume of the upper compartment 26 constitutes 45%
of the
total cooled volume, while the remaining 55% is destined for the lower
compartment
28. Applying this proportion, a freezer 10 according to the invention with an
overall
cooled volume of 800 litres has preferably an upper compartment 26 with a
volume of
360 litres and a lower compartment 28 with a volume of 440 litres.
In the front view of the freezer 10, the two thermally insulating doors 30 and
32 are
separated by a band 38 which is also thermally insulating.
According to one embodiment, the upper door 30 and the lower door 32 of the
freezer
10 are identical to each other. Considering that the doors 30 and 32 are
identical to each
other, the difference in the volumes of the respective compartments 26 and 28
is due to
the fact that the shelf 24 has a thickness smaller than that of the band 38
and the fact
that the shelf 24 is mounted above, flush with the band 38. For this reason,
the lower
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compartment 28 is internally higher than the upper compartment 26.
Moreover, mounting of the shelf 24 above, flush with the band 38, facilitates
substantially the operations for internal cleaning of the upper compartment
26. This
particular configuration of the freezer 10 is clearly visible from a
comparison of Figure
1 with Figure 2. In Figure 1, in fact, the view from above shows how the
surface 24 is
mounted flush with the band 38, while in Figure 2 the view from below shows
the
difference in thickness between the shelf 24 and the band 38.
This type of distribution of the volumes acts in synergy with the particular
distribution
of the coil density, allowing the natural convection to be exploited.. even
more
effectively.
With the particular configuration described above, where the density of the
coils 36 is
variable along the height of the cabinet 12 and, preferably, where the volumes
of the
two compartments 26 and 28 are different, it is possible to obtain, during
operation, a
temperature which is substantially the same in both compartments 26 and 28.
Specific
tests carried out by the applicant have shown how the temperatures in the two
compartments 26 and 28 differ at the most by 1 C. This difference is the same
as or
less than the differences which commonly occur between the two compartments of
conventional freezers with air circulation.
According to one embodiment, the freezer 10 also comprises control means for
allowing
separate access to the two compartments 26 and 28. For example, each of the
two doors
and 32 may be protected by an independent control system based on
identification of
the user by means of an electronic key. A control system of this type is
already used by
the applicant on other devices with the trade name Bioguard . By means of this
system,
the users may be provided with a programmable electronic key (for example a
card)
25 which allows access to only one compartment or to both compartments.
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In the light of the above description it will be clear to the person skilled
in the art how
the freezer according to the invention is able to overcome the drawbacks
mentioned
above with reference to the prior art.
In particular, in the light of all that described above, it will be clear how
with the freezer
10 according to the invention it is possible to obtain a temperature which is
substantially
the same inside the two compartments 26 and 28, without at the same time the
risk of
mutual contamination and without the need for duplication of the refrigeration
plant.
With regard to the abovementioned embodiments of the double-door freezer, the
person
skilled in the art may, in order to satisfy specific requirements, make
modifications to
and/or replace elements described with equivalent elements, without thereby
departing
from the scope of the accompanying claims.
