WO1998037797A1

WO1998037797A1 - Device for the cold preservation of meal service trays with in-built heating

Info

Publication number: WO1998037797A1
Application number: PCT/FR1998/000365
Authority: WO
Inventors: René Grandi
Original assignee: Italinnova S.A.S. Di Grandi Rene Vincent & C.
Priority date: 1997-02-26
Filing date: 1998-02-25
Publication date: 1998-09-03
Also published as: FR2759890B1; FR2759890A1; CA2252540A1; EP0914054A1

Abstract

The invention concerns a device in which the refrigerating means comprise: an accumulator of frigories (18), the bottom of which reservoir has a substantially semi-cylindrical deformation (22); resting against said deformation, a control element (23) consisting of a pivoting horizontal cylinder, comprising an insulating top part (23a) and a conducting bottom part (23b) in which are fitted heat pipes (24) projecting in the return loop (16) of the cooling circuit; and in one of the elements (6, 7) of each tray, an exchange plate comprising a first heat pipe network (26) whereof the heat exchangers (26a) are arranged in the zone of the containers to be cooled, said network being provided with end-pieces (26b) for collecting frigories arranged in the descending vertical branch of the cooling circuit.

Description

Device for cold storage of meal trays with localized heating.

The invention relates to devices for cold storage of meal trays with localized heating. It more specifically relates to devices comprising a chassis on a wheel carrying a lower box and an upper box, these two boxes being separated by a space which can contain several meal trays made of thermally insulating material, stacked and removable, and in which each box, made of thermally insulating material, comprises two return loops for the vertical branches of two parallel and independent circuits, formed in the meal trays, namely a cooling circuit and a heating circuit or cooling and heating, one of the boxes being provided with means for producing refrigerants communicating with one of the two circuits. Each of the meal trays, for this type of device, is composed of an upper element and a lower element comprising complementary thermal barriers which interpenetrate each other to divide each tray into two zones, isolated from each other and the outside, each zone of each plate element being traversed by at least two vertical channels, one of which partially surrounds the containers supported by the lower element, while each upper element of each plate has, in its reheating zone, means of calorie production.

In the cabinet described in FR-A-90 07060, the means for producing frigories include an on-board refrigeration unit arranged in the lower box and the evaporator of which is placed either in the upper box or in the lower box. When the cabinet is moved to distribute the meal trays, the power supply to the compressor must be interrupted, which excludes any application of this type of cabinet to the distribution of meals from a remote catering center since, very quickly, the evaporator is no longer able to supply frigories.

Another disadvantage of these means of producing refrigerants is the overweight which, resulting from the refrigeration unit, excludes the use of this type of cabinet for catering in aircraft.

Finally, maintaining the cold temperature of the containers arranged in the trays is carried out by means of the flow of cold air circulating in the two branches of the circuit, either by natural convection or by forced circulation. As a result, even if transverse connecting channels can be provided in the plates to communicate the descending branch of the cold circuit with the ascending branch, the storage temperatures are not uniform on all the trays, this difference can be significant between the trays close to the evaporator and those which are furthest from it.

The object of the present invention is to provide a device which overcomes these drawbacks.

To this end, in the device according to the invention, the means for producing cold comprise:

- in the upper box:

- an accumulator of frigories constituted by a sealed tank, isolated and connectable to a source of fluid at negative temperature, at least the bottom of this tank being thermally conductive and having, at least in the zone of the return loop of the cooling circuit , a substantially semi-cylindrical deformation,

a regulating member constituted by a horizontal cylinder of the same diameter as the aforementioned deformation against which it is in contact and mounted free in rotation, under the control of a command, this cylinder comprising an upper part made of insulating material and a lower part in thermally conductive material in which one of the ends of heat pipe rods is fitted, the free ends of which are in the return loop of the cooling circuit,

- And, in one of the elements of each tray, an exchange plate comprising a first internal heat pipe network whose heat exchangers are arranged in the areas of the containers to be cooled, these exchangers being provided with frigory collection tips arranged in the vertical downward branch of the cooling circuit.

In this device, the cold source is constituted by a cold store, the supply of which, carried out in a known manner by connections connected to a central reserve, is ensured by a fluid which can be super-refrigerant, that is to say be constituted by a eutectic liquid or equivalent, brought to very low temperature of the order of - 21 ° C. Due to its thermal insulation by the insulation of the box, this tank, although made of conductive material, can diffuse its frigories only through the regulating member. This member can occupy a completely closed position opposing any exchange between the bottom of the reserve and the return loop of the circuit with which it communicates, position in which the part made of insulating material comes into contact alone against the semi-cylindrical deformation of the tank. As soon as this regulating member is pivoted, and a circular segment of its part in conductive material comes into contact with the semi-cylindrical deformation of the reservoir, the frigories are transmitted by conduction through the bottom of the deformation to the conductive part of the regulating member and, from there, to the internal ends of the heat pipe bars which, due to their inclination and their nature, immediately transmit this energy to their other end, located in the cooling circuit.

The exchange of frigories is regulated by modifying the angular position of the regulating member with respect to the deformation of the reserve, that is to say by modifying the surface of the conductive part of this member in contact. with the face of this deformation.

The frigories, thus entrained in the cooling circuit, meet, in one of the branches thereof, the collection ends of the heat pipe networks of the exchange plates associated with each tray, which allows part of the frigories conveyed to come, by the heat pipe networks, in the areas of the trays to be cooled, that is to say near the dishes and dishes to be maintained at temperature. All these heat transfer functions are carried out by direct conductivity without any accessories and therefore make it possible, after having loaded the tank with frigories, to ensure that the food is kept at the appropriate temperature, without recourse to an external energy source. In one embodiment of the invention, the cooling and heating circuit comprises, in the return loop of the lower box, a heat exchanger and the exchange plate, integral with one of the elements of each plate, comprises a second internal heat pipe network comprising a heat exchanger disposed in the zone of the containers to be heated, this exchanger being extended, in the upward vertical branch of the heating circuit, by a nozzle for collecting calories or frigories.

Thus, the containers arranged in the reheating zone of the meal trays are maintained at hot temperature by means of the exchange plates. In another application, combining in this zone, cooling then heating, these two successive functions are ensured by the second heat pipe network which takes the frigories then the calories in the same branch of the corresponding circuit. In this case, this circuit is regulated by a regulating body independent of the first and able either to transmit the frigories in the upper return loop of the circuit, or to take a position of isolation of the reserve of frigories, to allow the circulation of hot air in the circuit. Advantageously, the heat production means arranged in the loop of the heating circuit, are constituted by the free ends of several heat pipe bars, the other ends of which are in thermal contact with a thermal oil tank containing electrical resistances for reheating under control. thermostatic.

Under these conditions, when the trolley cabinet goes into the food heating phase, the electrical resistances are supplied so as to bring the oil contained in the tank to a determined temperature, and the heat energy of this oil is transmitted, by the heat pipe bars, in the lower return loop of the heating circuit.

When it is necessary to move the carriage to distribute the meal trays, the oil reserve constitutes a reserve of positive calories which continues to ensure the heating of the trays, by the ascending branch of the heating circuit, branch in which the tips of the individual heating circuits for each of the meal trays, until the last meal tray is removed.

The use of these heating means provides a very important advantage which is to allow cleaning by pressurized water jets of the base structure of the cabinet, without risking damaging the electrical contacts, as was the case. case in the prior devices where each plate included means of heating by electrical resistance, the supply circuit of which engaged on terminals of the chassis.

Other characteristics and advantages will emerge from the description which follows with reference to the appended diagrammatic drawing representing, by way of example, an embodiment of this device.

FIG. 1 is a general perspective view of the device according to the invention,

Figures 2 and 3 are side views in cross section of a meal tray, respectively, when in the open position and in the closed position, Figures 4 and 5 are plan views from above, respectively, of the element upper and lower element of an embodiment of a meal tray,

FIG. 6 is a side view in cross section of the device when it is loaded with meal trays, Figures 7 and 8 are partial views, in cross section showing, on an enlarged scale, the dispensing member when it is in the closed position and in the dispensing position.

As shown in FIG. 1, the device according to the invention is composed of a chassis 2, carrying a lower box 3 provided with rollers 4, and an upper box 5. The interval between the boxes 3 and 5 is intended to receive meal trays each composed, as shown in more detail in FIGS. 2 to 5, of an upper element 6 and of a lower element 7. Each of these elements is insulating and comprises ribs 8 or grooves 9, complementary forms, capable of forming, when the two elements 6 and 7 are in contact, thermal barriers insulating, from one another and from the outside, two zones of the plate, namely, an zone F intended solely for be cooled and zone C can only be reheated or first cooled and then reheated. In each of these two zones, the elements 6, 7 of the plate include vertical channels, namely vertical and lateral channels 10 and 11 and at least one, and even two vertical and central channels 12. The channels 12, arranged in the lower elements 7 of each meal tray are, as shown in FIG. 5, constituted by grooves interposed between bearing surfaces 13 intended to support the containers 14 containing the food. FIG. 3 clearly shows that each zone F or C of the plate is completely isolated from the other by the thermal barrier 8, 9. For certain applications, at least one of the elements 6, 7 of each plate comprises, as shown for the tray 7 in FIG. 5, grooves 15 communicating the lateral channel 10 with the channel or channels 12. When the device is loaded with these meal trays, as shown in FIG. 6, the superposed channels 10 and 12 form the two branches, respectively ascending and descending, of two independent circuits whose return loops, respectively upper 16 and lower 17, are formed, respectively, in the upper box 5, containing means for producing cold, and in the lower box 3, containing the means for producing heat.

According to the invention, the means for producing cold consist of a reservoir 18 made of heat conducting material and, for example, of steel or aluminum inserted into the insulation of the casing 5 and communicating by two conduits 19 with fittings 20 can be connected to a source of liquid fπgongène. This reservoir has, at its bottom, two semi-cylindrical deformations transverse 22, each arranged in the vicinity of the return loops 16 of the cooling circuits, since the carriage shown in this figure is a carriage of the type in which zone C provides both cooling and heating of food and therefore comprises a circuit providing both cooling and heating separate from the other circuit providing only cooling. Against each of these deformations, a transverse cylinder 23 constituting the regulating member is mounted to rotate freely.

As shown in more detail in Figures 7 and 8, each cylinder 23 is composed of a cylindrical segment 23a of insulating material and a cylindrical segment 23b of heat conductive material. These two segments are linked to each other, for example by bonding, so as to avoid any heat transfer between them. FIG. 7 shows that, the circular arc on which the insulating segment 23a extends, is greater than the circular arc of the cylindrical deformation 22, formed in the bottom of the reservoir 18, so that, when the member regulation is in the isolation position, shown in Figure 7, no heat exchange can take place between the bottom of the tank and its conductive segment 23b. In this conductive segment 23b, the internal ends of heat pipe bars 24 are fixed, projecting substantially radially from the regulating member inside the corresponding return passage 16. The number, the shape, and the angular distribution of the heat pipe bars 24 depend on applications and refrigeration requirements.

When the regulating member is pivoted in the direction of the arrow 25 in FIG. 8, its conductive segment 23b comes into contact with the face of the deformation 22, which allows, by conduction, the thermal transfer of the frigories from the reservoir to this segment 23b, then from the segment to the bars 24 which, in turn, exchange with the air circulating in the return loop 16. By more or less pivoting the member 23, it is thus possible to regulate the quantity of frigories exchanged . This adjustment can be carried out manually by a notched button accessible from outside the box 5 and provided with an index cooperating with a scale, or automatically by a device reacting to a temperature sensor disposed in the upper return loop 16 or in the lower return loop 17.

In this device equipped with two regulating members 23, their adjustment means are distinct and independent.

FIG. 6 shows that, when zone C is in the heating phase, the corresponding regulating member 23 is in the isolation position, which prevents any transfer of the frigories in the corresponding loop 16, but also any transfer of the calories captured by the heat pipe bars 24 in the direction of the reservoir 18.

According to another characteristic of the invention, each of the meal trays 6, 7 is equipped with heat transfer means by heat pipes. More precisely and as shown in FIG. 4, corresponding to the upper element of a meal tray for the device shown in FIG. 6, the zone of the tray corresponding to the cooling zone F comprises an exchange plate with a first heat pipe network. 26, while the other zone C comprises an exchange plate with a second heat pipe network 27. Each of these networks can, for example, be constituted by a metal plate bonded to the upper face of the plate element 6 and whose heat exchanger 26a or 27a is disposed above the channels 12 of the corresponding zone. It is obvious that this exchanger has passages allowing the free circulation of the air flow. Each network is connected to a nozzle 26b, 27b coming in the corresponding side channel 10 and 11.

Thus, and as shown in FIG. 6, in zone F when, the flow of air cooled by the passage over the heat pipe bars 24 of the cooling circuit, borrows the vertical descending branch, formed by the vertical channels 10 and 11, it meets the ends 26b which capture the frigories and lead them by the first heat pipe networks 26 to the exchange plates 26a arranged in the ascending branch of the circuit and above the containers 14 to be cooled. The thermal transmission by the heat pipes being very fast, and practically without loss of yield, each of the containers is thus maintained at an identical temperature, whatever the position of its tray in the stack. The action of the heat pipes is supplemented by the supply of calories taking up the ascending branch of the circuit, possibly with the help of a tangential turbine 28.

The cooling of the containers 14 in compartment C is carried out in the same way. It is the same for the reheating of the dishes placed in the compartment C which is carried out by means of a flow of air heated in the lower return loop 17 of the lower compartment 3 by reheating means 30 and which is forced, for example, by a tangential turbine 31. The vertical branch of the circuit formed by the lateral duct 11 is then used in the opposite direction, so that the heat is captured by the nozzles 27b of the second heat pipe networks and leads to the exchange exchangers 27a, above the containers 14 to be heated and provided with a cover 14a. This arrangement makes it possible to obtain a regular and constant temperature in each of the trays and this with a heat transfer means also serving for the transfer of frigories and requiring no connection with the chassis, since each of the heat pipe networks remains adherent to the upper element. 6 of the corresponding meal tray. As a result, the chassis is free of all electrical contact and can be cleaned with a pressure jet, like each of the plates, which makes it possible to comply with food hygiene rules.

In the embodiment shown, the heat producing means 30 consist of the free parts of several heat pipe bars 32 arranged in the lower return loop 17. These bars are in thermal contact with the thermal oil 33 of a tank 34 containing an electrical heating resistor 35. In operation, the resistor carries the thermal oil 33 to its operating temperature, regulated by a thermostat, and the heat of the oil is transmitted, by the heat pipe bars 32, in the return loop 17, where these bars yield their calories to the circulating air flow. Thus, the calories are brought to the ends 27b of the second exchange networks.

When, after reheating and the device moved, after having been electrically disconnected, the heat energy stored in the tank 34 by the thermal oil ensures the temperature maintenance of the dishes, and this for a sufficient time to be able to move the carriage from the place to reheat the place of distribution, and to ensure distribution.

The device, which has been described above, can also be applied to a cabinet comprising a cooling zone and a zone ensuring only the reheating. In this case, the reservoir 18 for the refrigerant extends only over a part of the carriage and does not include a regulating member 23 in its part adjoining the return loop 16 of the heating circuit.

In the case of a "constant level" meal tray distribution cabinet, a jack 36 actuated by a pedal allows the ascent of each tray. In an alternative embodiment, the reservoir 18 contains hollow bodies, such as capsules, filled with a eutectic liquid as described in patent FR-A-96 09991, the cooling of these capsules trapped in the reservoir is ensured by a food eutectic liquid precooled to a temperature below 0 ° c - up to -50 or 80 ° c - and brought to the tank by supply and return conduits leading to the fittings 20. In another variant, the heat exchangers 30 of the plates are heated by electric heating collars surrounding the end pieces 27b.

However, the shapes, dimensions and arrangements of the various elements may vary within the limit of equivalents, as indeed the materials used, without changing the general conception of the invention which has just been described.

Claims

CLAIMS 1. Device for the cold storage of meal trays with localized heating comprising a frame (2) on casters carrying a lower box (3) and an upper box (5), these two boxes being separated by a space which can contain several meal trays (6, 7), made of thermally insulating material, stacked and removable, and in which each box (3, 5), made of thermally insulating material, comprises two return loops (16, 17) for the vertical branches of two parallel circuits and independent housings in the meal trays, namely a cooling circuit and a heating or cooling and heating circuit, one of the boxes being provided with means for producing frigories communicating with at least one of the two circuits, while each of the meal trays is composed of an upper element (6) and a lower element (7) comprising complementary thermal barriers ( 8, 9) interpenetrating to divide each plate into two isolated zones (C and F), one from the other and from the outside, each zone of each element of the plate being crossed by at least two vertical channels ( 10, 11, 12) one of which (12) partially surrounds the containers (14) supported by bearing surfaces (13) of the lower element (7), and which each upper element (6) of each tray comprises, in its part corresponding to the heating zone (C), means for producing heat, characterized in that the means for producing cold comprise:

- in the upper box (5):

- a cold store consisting of a sealed reservoir (18), insulated and connectable to a source of fluid at negative temperature, at least the bottom of this reservoir being thermally conductive and having, at least in the region of the return loop ( 16) of the cooling circuit, a substantially semi-cylindrical deformation (22),

a regulating member (23) consisting of a horizontal cylinder of the same diameter as the above-mentioned deformation (22) against which it is in contact and mounted to rotate freely, under the control of a command, this cylinder comprising an upper part ( 23a) of insulating material and a lower part (23b) of thermally conductive material in which one of the ends of heat pipe rods (24) is fitted, the free ends of which are in the return loop (16) of the cooling circuit,

- And, in one of the elements (6, 7) of each tray, an exchange plate comprising a first heat pipe network (26) whose heat exchangers (26a) are arranged in the areas of the containers to be cooled, this network being provided with ends (26b) for collecting frigories arranged in the vertical downward branch of the cooling circuit.

2. Device according to claim 1, characterized in that the cooling and heating circuit comprises, in the return loop (17) of the lower box, a heat exchanger (30), as well as one of the elements of each plate , comprises a second internal heat pipe network (27) comprising a heat exchanger (27a), disposed in the zone of the containers to be heated, and a nozzle (27b) for collecting calories or frigories coming in the upward vertical branch of the heating circuit.

3. Device according to claim 2, characterized in that the heat exchanger (30) disposed in the loop (17) of the heating circuit consists of several heat pipe bars (32) one of the ends of which is in thermal contact with a thermal oil tank (34) containing electric heating means (35) under thermostatic control.

4. Device according to claim 1, characterized in that the tank

(18) of frigories extends above the two return loops (16) of the two circuits and comprises, in the vicinity of each of these loops, a semi-cylindrical deformation (22) serving as a housing for a regulating member (23 ), each of these members (23) being under the control of a separate command.

5. Device according to claim 1, characterized in that the regulating member (23) is linked in rotation to a manually actuated adjustment button provided with an index cooperating with a fixed graduation.

6. Device according to claim 1, characterized in that the regulating member (23) is linked in rotation (25) to a drive means reacting to at least one temperature sensor disposed in the corresponding circuit.

7. Device according to claim 1, characterized in that the part (23a) of insulating material of the regulating member (23) extends over a circular arc having a value greater than that of the circular arc on which extends the deformation (22) of the reservoir (18) receiving it.

8. Device according to claim 1, characterized in that one of the elements of each tray comprises a second internal heat pipe network (27) comprising a heat exchanger (27a), disposed in the zone of the containers to be heated, and a nozzle ( 27b) surrounded by an electric heating collar.

9. Device according to claim 1, characterized in that the reservoir (18) contains hollow bodies which filled with a eutectic liquid are trapped in this tank and are cooled by the passage by circulation of another food eutectic liquid brought to a temperature between 0 ° c and -50 ° c.