SYSTEM ALLOWING AUTOMATIC EXTRACTION OF COLD GASES IN A FREEZER CABINET OPERATING WITH A CRYOGENIC FLUID

Abstract

The invention relates to a cabinet used for freezing or storing food, medical or biological products, using a cryogenic fluid as cooling fluid, said cabinet being of the type that is: provided with one or more convection fans located in the enclosure of the cabinet and capable of moving the air inside the cabinet and thus of contributing to the thermal exchange that occurs therein; and provided with a system for extracting the gases formed in the enclosure of the cabinet due to the vaporization of said cryogenic fluid, said extraction system including an extraction tube connecting to one wall of the cabinet and linking the enclosure to the outside; characterized in that it includes a flap, located on said wall, at the point where the extraction tube enters the cabinet, and extending into the cabinet, the shape, position and direction of said flap making it possible to divert all or part of the turbulence created by the or said convection fans towards the extraction tube.

Description

BACKGROUND

Field of the Invention

The present invention relates to the field of cabinets used for deep-freezing or storing food, medical or biological products, using a cryogenic fluid as cooling liquid, and relates more particularly to the gas extraction system which is fitted to such cabinets and which is an important element.

Related Art

Indeed, when the cabinet is in operation, it is cooled by injection of a cryogenic fluid such as liquid nitrogen or liquid CO₂ into the closed enclosure of the device, and this fluid is the cold source and its transition from the liquid state to the gaseous state is associated with expansion of the gas. This liquefied gas vaporizes in the enclosure and must subsequently be evacuated from the machine to outside the production facility.

To that end, use is frequently made of an extraction tube (in the manner of a chimney) which connects the enclosure to the outside of the building. The gas then escapes naturally from the enclosure to the outside. The slight overpressure created in the enclosure is sufficient to cause the gas to flow to the outside of the enclosure.

In other cases, the gases are made to flow actively. In such cases, active extraction (fan, turbine, etc.) is installed on the tube and serves to draw the gases to the outside.

When the cabinet is new and functions correctly, the above-mentioned system operates very well.

However, after a certain time, the operating conditions deviate slightly from ideal operation. Indeed, it has been noted that, over time, the seals of the door(s) of the cryogenic cabinets become less effective since no material can withstand the very low temperatures of cryogenic deep-freezers without ultimately becoming rigid or brittle. They therefore allow a greater or lesser quantity of gas to pass through, which can in extreme cases lead to anoxia (lack of oxygen) or intoxication (carbon dioxide) in the personnel present in the production facility.

In order to avoid this, sites are obliged to change the seals very frequently which, in practice, does not always happen, and cryogenic deep-freezer cabinets therefore operate with imperfect seals.

When production facilities are adequately ventilated, this small leakage of gas due to imperfect seals can be regarded as not presenting a critical problem since the gas leaks are ventilated by the ventilation of the facility, and the installation can operate without risk.

However, when the ventilation of the production facility is not adequate for evacuating this gas leak to the outside, two solutions are frequently used:

• • The first solution involves installing a system for permanent heating of the seals so as to avoid their temperature dropping too low such that they lose their elastic properties. Thus, the seals remain flexible and leak-tight for longer than when they are subjected to low temperatures. The problem of leaks is then delayed without being eliminated, which is sometimes satisfactory. However, the cost of this technique is considerable.
  • The second solution involves installing active extraction (a fan in the extraction tube, see above), which serves to create a reduced pressure inside the cryogenic enclosure. Thus, the leaks occurring at the door seals will no longer translate into an escape of gas into the production facility, but rather an ingress of air into the deep-freezing enclosure. Thus, the deep-freezer no longer allows gas to escape into the production facility, and the small ingress of air into the apparatus in no way disrupts the deep-freezing process, provided that this ingress of air remains at a limited level.

Thus, in order to compensate for the imperfect seal of the door seals, and to eliminate the associated problem of gas leakage, active extraction is installed. This extraction consists of a fan installed in the extraction tube, an electricity supply and a control system which triggers operation when necessary. This whole assembly has a considerable cost in the total cost of the deep-freezing installation and, where possible, an installation without active extraction will always be preferred by the production site.

SUMMARY OF THE INVENTION

As will be seen in greater detail below, the present invention has the object of proposing a technical solution which aims to dispense with the problem of the door seals of cryogenic cabinets, at negligible cost.

To that end, the invention proposes using the fans that are in any case present in deep-freezing cabinets (the primary function of these fans is to agitate the air in the cabinet and thus contribute to the thermal exchange that occurs therein) such that they continue to perform this primary function but such that they also perform a function of active extraction of the gases to the outside.

The proposed solution comprises a flap (the cost of this flap being negligible) which is located at the inlet of the extraction tube in the deep-freezing cabinet, this flap extending toward the interior of the cabinet and the shape, position and orientation of the flap making it possible to take advantage of the turbulence created by the fans. When the fans are running, the turbulence created is redirected in part by the flap toward the extraction tube, thus pushing the gases toward the outside of the enclosure and thus creating a reduced pressure inside the deep-freezing enclosure.

The shape and orientation of this flap will be chosen depending on the type of fan used in the cabinet and their direction (clockwise or counterclockwise) of operation.

Moreover, this flap must be studied so as to present minimum disruption to the deep-freezing process of the cabinet (studied for example by modelling or simply by testing on a real cabinet), in particular in order to verify that the flap provides the desired effect, which is to establish a reduced pressure within the cabinet, that the flap does not excessively disrupt the flow of air in the cell, and that it does not impair the coefficient of thermal transfer in the deep-freezing cabinet.

BRIEF DESCRIPTION OF THE FIGURES

The appended figures show four exemplary embodiments of these flaps, depending on whether the extraction is located at the bottom or at the top of the deep-freezing cabinet, and depending on whether the fans rotate in the clockwise or counterclockwise direction.

appended FIG. 1 shows (in the left-hand view, extraction tube not equipped with a flap) that the turbulence created by the fans passes in front of the inlet to the extraction tube (located in the lower portion of the cabinet) whereas, with the aid of the flap positioned at the inlet to the extraction tube towards the interior of the deep-freezing cabinet (middle view), at least part of the turbulence enters the inlet of the extraction tube (right-hand view). In this case, the flap is in the form of a “folder” or “scoop”.

appended FIG. 2 shows (in the left-hand view, extraction tube not equipped with a flap) that, here too, the turbulence created by the fans passes in front of the inlet to the extraction tube and, with the aid of the flap positioned at the inlet to the extraction tube towards the interior of the deep-freezing cabinet (middle view), at least part of the turbulence enters the inlet of the extraction tube (right-hand view). In this case too, the flap is in the form of a “folder” or “scoop”.

appended FIG. 3 shows a situation of clockwise operation of the fans, and in which the extraction is located at the top of the deep-freezing cabinet. Here too, by virtue of the flap positioned at the inlet to the extraction tube towards the interior of the deep-freezing cabinet (middle view), at least part of the turbulence enters the inlet of the extraction tube (right-hand view). In this case, the flap is in the form of a truncated cylinder.

and appended FIG. 4 shows a situation of counterclockwise operation of the fans, and in which the extraction is again located at the top of the deep-freezing cabinet. Here too, by virtue of the flap positioned at the inlet to the extraction tube towards the interior of the deep-freezing cabinet (middle view), at least part of the turbulence enters the inlet of the extraction tube (right-hand view). In this case, the flap is in the form of an “elbow tube”.

It is clear that the forms of the flaps illustrated here are only illustrative examples of the invention, and it will be possible to use other forms but also to invert the forms in the cases mentioned above (it will for example be possible to use an elbow tube in the configuration of FIG. 1).

DETAILED DESCRIPTION OF THE INVENTION

Thus, the invention relates to a cabinet used for deep-freezing or storing food, medical or biological products, using a cryogenic fluid as cooling liquid, said cabinet being of the type that is:

• • provided with one or more convection fans located in the enclosure of the cabinet and capable of agitating the air inside the cabinet and thus of contributing to the thermal exchange that occurs therein;
  • and provided with a system for extracting the gases formed in the enclosure of the cabinet due to the vaporization of said cryogenic liquid, said extraction system including an extraction tube that is connected to one wall of the cabinet and links the enclosure to the outside;

characterized in that it includes a flap, located on said wall, at the point where the extraction tube enters the cabinet, and extending into the cabinet, the shape, position and orientation of said flap making it possible to divert, toward the extraction tube, all or part of the turbulence created by the or said convection fans.

Tests carried out with a system in accordance with one of the examples mentioned above have demonstrated excellent results:

• • the reduced pressure created in the enclosure can be adjusted by changing the speed of the fans, and can reach 200 Pa (2 mbar).
  • this device acts similar to an active extractor (fan installed in the extraction conduit) such as implemented according to the prior art, but with no active fan and without the associated cost (the cost of the flap implemented here is entirely negligible).
  • in practice, this permits entirely safe operation whatever the situation, with imperfect door seals and with no leakage of gas into the production facility.
  • the deep-freezing process is not disrupted.
  • this system is suitable for deep-freezing cabinets operating with liquid nitrogen or liquid CO₂. It will be particularly useful for applications operating with CO₂ since, in this case, even small gas leaks often have a large impact on the production floor and are rarely tolerable.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

The singular forms “a”, an and “the” include plural referents, unless the context dearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”.

“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

Claims

1. (canceled)

2. A deep-freezing or storage cabinet for food, medical or biological products using a cryogenic fluid as cooling liquid, comprising: a cabinet with an enclosure;one or more convection fans located in the enclosure and capable of agitating air inside the cabinet and thus of contributing to the thermal exchange that occurs therein; anda system for extracting gases formed in the enclosure due to vaporization of said cryogenic liquid, said extraction system including an extraction tube that is connected to one wall of the cabinet and links the enclosure to the outside, the extraction system including a flap that is located on said wall at a point where the extraction tube enters the cabinet and that extend into the cabinet, a shape, position and orientation of said flap making it possible to divert, toward the extraction tube, all or part of turbulence created by the one or more convection fans.

3. The deep-freezing or storage cabinet of claim 1, wherein the flap is in the form of a scoop.

4. The deep-freezing or storage cabinet of claim 1, wherein the flap is in the form of a truncated cylinder.

5. The The deep-freezing or storage cabinet of claim 1, wherein the flap is in the form of an elbow tube.