EP0745816B1 - Arrangement for upholding a low temperature in a movable enclosure - Google Patents

Description

The present invention relates to maintaining low temperature of a moving enclosure.

The invention was developed to solve problems with the carts used to transport food, and in particular prepared meal trays, between a preparation and storage room located in a airport and an airplane and then to be taken aboard this plane, so as not to interrupt the cold chain. Of course, the invention is applicable to the solution of analogous problems which may be encountered in others fields, for example in the hospital field.

The carriages we just talked about are made up by an enclosure with insulated wall and watertight door, provided with casters. Inside this enclosure, there is a loading volume equipped with means to contain the objects you want to keep cold. These means are usually consisting of a dry ice drawer, located in the upper part of the enclosure. Usually we go out partially this drawer of the trolley, to deposit a number suitable bread or dry ice packs, prepackaged to facilitate handling. It's about of unit plates usually weighing 750 grams. The handling these ice cold loaves, which are very cold, would be an unpleasant task for the staff. It is therefore necessary to pack them, which increases their cost. In furthermore, this operating mode does not allow adapting with accuracy the amount of dry ice, hence a waste which further increases the cost of the operation.

The Applicant has proposed, see FR-A-2,706,990, to provide a dry ice bin provided with a lateral opening making it possible to inject liquid CO ₂ therein using a distribution means provided with a solenoid valve comprising timing means making it possible to select the duration of injection of liquid CO ₂ into the drawer, and consequently the desired quantity of dry ice.

This solution avoids the drawbacks indicated above. In addition, the drawer no longer has to be taken out each time it is loaded, as it suffices to connect the liquid CO ₂ pipe to an appropriate nozzle.

However, this solution has the disadvantage that it is difficult to obtain a uniform filling of the tank, which replaces the drawer of the prior art, over the entire surface of it. Dry ice tends to accumulate in some points, and to deposit insufficiently in certain areas. In addition, like snow formation carbonic is done inside the enclosure, we cannot control it effectively. In addition, the density of the dry ice thus created is relatively low, if although, for equal weight, it occupies a volume substantially more important than the dry ice wafers of previous use.

The object of the present invention is to remedy these drawbacks, and to provide means for creating and introducing carbon dioxide snow which are further improved. To obtain this result, the invention provides an installation for maintaining a mobile enclosure at low temperature, this enclosure comprising a loading volume capable of containing objects which it is desired to carry or maintain at said low temperature and at least one container which may contain dry ice,
the installation further comprising a stationary source of liquid CO ₂ under pressure and a carbon dioxide snow generator connected to said stationary source by a pipe and capable of spraying the liquid CO ₂ into said container in such a way that this liquid CO ₂ can be transform into carbon dioxide snow in said container,
characterized in that it comprises a fixed loading chamber, which is equipped with said generator, in which the container previously removed from the mobile enclosure can be placed,
and that the stationary loading chamber is further equipped with means capable of packing into the container dry ice formed by said generator and which has fallen into this container.

The invention combines the advantages of the two techniques previous: the fact that we use a container that is not not fixed relative to the enclosure allows, as for the technique using ice blocks, effective control the quantity of refrigerants introduced into the enclosure. On the other hand, the advantages of the technique including carbon dioxide snow formation, know a possibility of precise dosage of the quantity refrigerated refrigerants, and handling relatively easy for the staff.

Because the dry ice has been packed, it occupies, for an equal cooling capacity, a volume more small than if it weren't, which can allow a increase in the useful volume of the enclosure, or, at volume equal useful, an increase in the shelf life of products contained in this enclosure.

For an additional improvement in the duration of conservation of the products, it is planned, according to a complementary mode of the invention, that a second dry ice container is determined by the face internal of the enclosure door and by a sheet, at least partially perforated, parallel to said internal face, and moved away from it a distance small enough not to prevent the door from closing. In practice, it is to use a free space with a thickness of the order a few millimeters. This container is closed on the sides and bottom, and it's open at the top.

A device comprising snow generators carbon dioxide of small dimensions can be introduced less partially in the upper region of the container to form in it an additional amount of dry ice.

In addition to an increase in the cooling capacity of overall, this arrangement allows the distribution of frigories in a more homogeneous way by interesting more especially the bottom of the enclosure, which is not the case with the refrigerant stored in the upper part of this one.

The invention will now be described in more detail. detailed using a practical example illustrated with drawings, among which:

Figure 1 is a schematic perspective view of installation and how to use it.

Figure 2 is a vertical section of the post filling.

Figure 3 is a vertical section of one of the generators of dry ice from the loading station.

Figure 4 is a perspective view illustrating a additional element of the installation of FIG. 1, and how to use it.

Figure 5 is a section along line V-V of the figure 4 of the dry ice generator shown on this figure.

Figures 1 and 4 show a carriage for refrigerated transport of meal trays prepared in advance. Such a cart, known to tradespeople as "trolley", includes a rectangular box provided with casters and which has walls, a bottom and a wall superior in insulating material. Trolley 1 is also fitted with a door 2, also made of insulating material, mounted on a vertical hinge and extending practically over full height of the cart. Inside the cart, are provided with superimposed housings 3 intended to receive all prepared meal trays, not shown. Housing 3 are designed to allow the free movement of the air from top to bottom of the interior space of the carriage 1. The upper housing 4 is somewhat different from the others, because it includes a container 5 for dry ice.

The carbon dioxide snow tank 5 is completely removable from its housing 4, as shown in Figure 1. It is provided a handle 6 of insulating material intended to facilitate its gripping.

Figure 1 also shows a carbon dioxide snow loading station, consisting of a box 7, with an insulating wall. The interior space of this box is divided, as shown in FIG. 2, into an upper compartment 8 and a lower compartment 10. The upper compartment 8 comprises at its base means 9 which constitute a separation allowing the passage of gases to the lower compartment 10. The separation means 9 are also designed to receive a dry ice bin 5, introduced into the box 7 through a slot 11, visible in FIG. 1. As shown in FIG. 2, the insulating handle 6 closes the slot 11 when a dry ice bin is in place in the compartment 8 of the box 7. At the top of the box 7, dry ice generators 12 are provided, distributed evenly above the surface of the tank 5. Three of them are visible in Figure 2 and Figure 3 shows a section through one of them. Each generator consists of a vertical tube 13 open at the bottom and closed at its upper part by a partition 14 traversed by a nozzle 15 capable of spraying liquid CO ₂ inside the tube 13. The nozzle 15 is connected by the '' through an individual stop valve 16 to a manifold 17, itself connected to a pipe 18 for supplying liquid CO ₂ via a thermally insulated pipe 19 provided with a stop valve 20 Line 18 supplies liquid CO ₂ at -20 ° C, under a pressure of 20 bars.

When the valves 16 and 20 are open, the generator 12 produces carbon dioxide snow which falls into the tank 5. The individual valves 16 make it possible to obtain a substantially uniform distribution of the amount of snow on the bottom surface of the tank 5. The shut-off valve 20 can be controlled by computer according to the data of the problem: number of meal trays, duration of the flight, ambient temperature, etc. The lower compartment 10 of the carbon dioxide snow filling station is used only for collecting the cold gases produced during the formation of carbon dioxide snow. A pump 21 is used for the evacuation of these gases formed mainly of gaseous CO ₂ .

Compartment 8, in addition to the snow generators and the location of bin 5, contains a panel of tamping 22 mounted on a horizontal articulation 23 located along one of the walls of the box 7, which can be actuated by a jack 24 so as to pass from a position vertical, shown in solid lines in Figure 2, where it does not prevent the carbon dioxide snow produced by generators 12 to reach the tank 5, and a horizontal position, where it covers substantially the entire surface of bin 5 and cup the snow it can contain, under the effect of the force of the jack 24. It is understood that, each time that the jack 24 is actuated, the snow is packed. It is possible, depending on the circumstances, to operate multiple cylinder 24 until the desired settlement is obtained. Of anyway, the force of the jack is calculated so that the tamping panel 22 does not allow the surface carbon dioxide snow, when compacted, exceeds the level of the edges of the tank 5. This would make the extraction of the tray 5 filled difficult, and some of the dry ice would be retained by slot 11 and would remain in pure loss in box 7. To obtain regular packing, the panel 22 has a thick plate of material such that a foam having an elasticity suitable for low temperature where it is used.

In FIG. 1, there is also shown, schematically, an external carbon dioxide snow generator 30, connected to the box 7 by a liquid CO ₂ supply duct 31. This external generator is shown in more detail in FIGS. 4 and 5, which correspond to a complementary method of the invention.

In Figure 4, we find the carriage 1 described in figure 1. In figure 4, this carriage presents as peculiarity that its door 2 presents, on its face interior, an additional wall 32, spaced 6 to 7 mm apart from the door itself. This double wall 32 is maintained against the door by irons 33 arranged on these two sides, and at its bottom. Such extra thickness is designed so as not to hinder the closing of the door and occupies a space normally left free to facilitate vertical air circulation inside the carriage when it is closed. Door 2 forms, with double wall 32 and fixing irons 33, a sort of pocket open upwards, that we're going to fill with carbon dioxide snow.

For this, the generator 30 is used. It is formed of a front plate 34 made of insulating material, and a rear plate 35, also made of insulating material. Dry ice generators are mounted on the back plate 35, and held in position in grooves provided in the front and back plates. As shown in FIG. 5, which is a section in the plane separating the front and rear plates, each generator 36 consists of a stainless steel tube of small diameter, for example 4 mm inside diameter, open at the bottom, and in which opens out a capillary 37 connected to a collecting chamber 38, itself connected to the supply line 31, which is flexible, and provided with a solenoid valve 39 and a stop valve 40.
The structure of the dry ice generators 36 is thus quite similar to that of the dry ice generators 12 described above but with much smaller dimensions. To fill the space between the perforated plate 32 and the door 2, the generator 30 is introduced, carrying it by handles 41, 42, of insulating material, in the space between the door 2 and the plate 32. A holding part 43, fixed on the face of the rear plate 35 which is opposite to the generators 36, comes to rest on the upper edge of the door 2, to keep the generator 30 in a suitable position. It then suffices to open the valves 39 and 40 to fill the space between the door 2 and the plate 32 with a quantity of carbon dioxide snow which, despite the small size of the generators, is not negligible, because it can reach, in practice, up to 900 grams of dry ice.

Claims (5)

1. System for maintaining a moveable enclosure at a low temperature, this enclosure (1) having a loading volume capable of containing objects that it is desired to cool down to, or to maintain at, the said low temperature and at least one container (5) which can contain dry ice,
      the system furthermore comprising a stationary source of pressurized liquid CO₂ and a dry-ice generator (12) which is connected to the said stationary source via a pipe (18) and is capable of spraying the liquid (CO₂) into the said container in such a way that it is converted into dry ice in the said container,
      characterized in that it comprises a stationary loading chamber (7) which is equipped with the said generator, in which chamber the container, withdrawn beforehand from the moveable enclosure, may be placed,
      and the stationary loading chamber is furthermore equipped with a means (22) capable of compacting, within the container, dry ice that has been formed by the said generator and has dropped into the container.
2. System according to Claim 1, characterized in that the means capable of compacting the dry ice comprises a pressing plate (22) that can move inside the loading chamber (7) between a first position, in which it does not prevent the dry ice from dropping into the container, and a second position, in which it exerts a downward vertical force on the dry ice that has dropped into the container.
3. System according to Claim 2, characterized in that the pressing plate (22) includes a material that is compressible and elastic at the temperature at which the dry ice is formed.
4. System according to one of Claims 1 to 3, characterized in that a second dry-ice container is also provided, this being defined by the inside surface of a door (2) of the enclosure (1) and by an at least partly perforated metal sheet (32) parallel to the said inside surface and separated from the latter by quite a small distance in order not to prevent the door from being closed, and in that a device (30) having dry-ice generators (36) of such a size that they can be at least partially inserted into the upper region of the container, in order to form an additional amount of dry ice therein, is also present.
5. System according to Claim 4, characterized in that the device (30) having generators consists of two superimposed sheets (34, 35) of insulating material which hold dry-ice generators between them, the assembly having a thickness small enough for it to be able to be at least partly introduced into the said open space.

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