System comprising a display unit for storing and displaying food products, and multiple shelves, and method for storing and displaying food products in a display unit

Abstract

A system comprises a display unit and shelves. The display unit has an open front chamber for storing food products, a lower air duct with a lower front inlet, an upper air duct with an upper front outlet, a fan and an air refrigerator. The upper front outlet is directed at the lower front inlet for creating an air curtain in front of the open front. At least one of the shelves is a hollow shelf with an inner space, a shelf air outlet at a front side, a shelf air inlet at a back side, a fan, and a shelf heater. The fan is in fluid connection with the shelf air inlet and the shelf air outlet for moving air from the shelf air inlet through the hollow shelf to the shelf air outlet.

Claims

1. A system for storing and displaying food products, comprising: a display unit for storing and displaying food products, and multiple shelves, wherein the display unit has a front side and a back side, and comprises multiple walls, including a top wall, a left side wall, a right side wall, a bottom wall, and a back wall, and the display unit further comprises an air circulation system, and a first air refrigerator, in which the top, left side, right side, bottom, and back walls delimit an open front chamber for the food products, such that the open front chamber is accessible from the open front, the multiple shelves each comprise a placing side, the multiple shelves are placeable in the display unit to each extend in the open front chamber in a vertical spaced relationship and to define an individual corresponding storage space above the respective placing side, the air circulation system comprises a lower air duct with a lower front inlet, an upper air duct with an upper front outlet, and a first air forcing apparatus, the first air forcing apparatus is provided for moving air through the lower and upper air ducts, from the lower front inlet towards the upper front outlet, the first air refrigerator is provided for cooling the air which is moved from the lower front inlet towards the upper front outlet, the upper front outlet is directed at the lower front inlet for creating a front air curtain in front of the open front, wherein at least one of the multiple shelves is a hollow shelf with an inner space, a front side and a back side, which front side and back side in use correspond to the front side and the back side of the display unit, wherein the hollow shelf comprises at least one shelf air outlet at the front side of the hollow shelf, at least one shelf air inlet at the back side of the hollow shelf, a shelf air forcing apparatus, and a shelf heater, and wherein the shelf air forcing apparatus is in fluid connection with the shelf air inlet and the shelf air outlet for moving air from the shelf air inlet through the hollow shelf to the shelf air outlet.

2. The system according to claim 1, wherein the shelf heater is provided in the inner space for heating the air in the inner space of the hollow shelf.

3. The system according to claim 1, wherein the shelf heater is positioned so as to provide heat to the placing side.

4. The system according to claim 1, wherein the shelf heater is a flat heating element extending in the inner space of the hollow shelf.

5. The system according to claim 1, wherein the inner space of the hollow shelf fluidly connects the at least one shelf air inlet with the at least one shelf air outlet.

6. The system according to claim 1, wherein the at least one shelf air outlet defines a flow direction for air flowing out of the outlet, and the flow direction points away upwards from the placing side and backwards towards the back side of the hollow shelf, such that in use the air flowing out of the outlet is directed substantially entirely into the corresponding storage space.

7. The system according to claim 1, wherein the shelf air forcing apparatus is provided inside the inner space.

8. The system according to claim 1, wherein the display unit comprises multiple shelf support means at different heights for supporting the at least one of the shelves at different vertical positions in the display unit.

9. The system according to claim 1, wherein the air circulation system further comprises a lower back outlet at the lower air duct, and an upper back inlet at the upper air duct, and the lower back outlet is directed at the upper back inlet for creating a back air curtain in front of the back wall.

10. The system according to claim 9, wherein a back edge of the hollow shelf is spaced horizontally from the back wall, when positioned in the display unit, for providing sufficient space for the back air curtain between the back edge of the hollow shelf and the back wall.

11. The system according to claim 10, wherein the hollow shelf comprises a replaceable back portion for extending the hollow shelf to the back wall of the display unit.

12. The system according to claim 10, wherein the hollow shelf comprises a replaceable back portion comprising a joint configured to move the replaceable back portion from a retracted position, wherein the back edge of the hollow shelf is spaced horizontally from the back wall, to an extended position, wherein a back side of the replaceable back portion is positioned at the back wall.

13. The system according to claim 12, wherein the joint is a pivot.

14. The system according to claim 1, wherein the back wall comprises a back door, so that the open front chamber is accessible by opening the back door.

15. The system according to claim 1, wherein at least one further one of the multiple shelves is a flat shelf without a shelf air forcing apparatus.

16. The system according to claim 1, wherein at least one of the upper front outlet and the lower back outlet is provided with slats for guiding the air curtain.

17. The system according to claim 1, wherein at least one of the multiple walls is a transparent wall, wherein the display unit further comprises a conduit wall, which is positioned substantially in parallel to, and at the chamber side of, the transparent wall for creating an air conduit between the conduit wall and the transparent wall, and wherein the air conduit comprises a first conduit inlet, a second conduit inlet, and a conduit outlet, the first conduit inlet fluidly connects the at least one air duct with the air conduit for diverting a portion of refrigerated air moving through the at least one air duct into the air conduit, the second conduit inlet fluidly connects ambient air outside of the display unit with the air conduit for letting in ambient air via the second conduit inlet into the air conduit, and wherein the air conduit is configured to jointly guide the portion of refrigerated air and the ambient air from the respective first conduit inlet and second conduit inlet towards the conduit outlet for jointly exiting the air conduit from the conduit outlet.

18. A method for storing and displaying food products in a display unit, the method comprising: providing the display unit, wherein the display unit comprises an air refrigerator, providing at least one hollow shelf with a shelf heater, a shelf air inlet at a back side of the hollow shelf, and a shelf air outlet at a front side of the hollow shelf, providing food products on the hollow shelf, drawing in air through the shelf air inlet by applied suction with a shelf air forcing apparatus, moving the sucked in air from the shelf air inlet through the hollow shelf to the shelf air outlet, heating the moving air with the shelf heater in the hollow shelf, and blowing the heated air out of the shelf air outlet.

19. The method according to claim 18, wherein the heated air which is blown out of the shelf air outlet is blown upwards and backward, substantially entirely into a storage space above the hollow shelf.

Description

DESCRIPTION OF THE DRAWINGS

(1) The invention, its effects, and advantages will be explained in more detail on the basis of the schematic drawing, in which:

(2) FIG. 1 shows a perspective view of a first embodiment of a system according to the invention,

(3) FIG. 2 shows a cross-section view of a second embodiment of the invention,

(4) FIG. 3 shows detail A from FIG. 2,

(5) FIG. 4 shows a cross-section view of a third embodiment of the invention,

(6) FIG. 5 shows a fourth embodiment, with heated shelves,

(7) FIG. 6 shows the embodiment and configuration of FIG. 5, operating as refrigerated unit, and

(8) FIG. 7 shows in detail a cross-section view of a heated shelf.

DETAILED DESCRIPTION

(9) FIG. 1 shows a system, which is denoted in its entirety by reference number 1, with a display unit 2 and multiple shelves 4, according to the invention. In this embodiment, the multiple shelves 4 are flat shelves 5, i.e. shelves without an inner space. While the different embodiments which are shown in the figures differ in detail, the same or similar elements will be denoted with the same name and reference number and will not be described in detail in relation to each embodiment, in order to prevent unnecessary repetition.

(10) The display unit 2 is designed for storing and displaying refrigerated or hot food products. The display unit 2 has a front side 6 and a back side 8, and comprises multiple walls 10, including a top wall 12, a left side wall 14, a right side wall 16, a bottom wall 18, a back wall 20, and a lower (partial) front wall 22. The back wall 20 comprises back doors, in this embodiment a first slidable back door 23 and a second slidable back door 24. The first slidable back door 23 and the second slidable back door 24 are slidable in a horizontal direction. The display unit 2 of the first embodiment is supported on a support frame 26, in this case a closed frame. It is noted that no support frames are shown for the other embodiments, and that the presence or absence of such support frame is not relevant for the claimed invention.

(11) Referring to FIG. 2, a system 1001 with a display unit 1002 is shown with the same or similar elements as in the previous embodiment. The display unit 1002 comprises an air circulation system 30 with a lower air duct 32, an upper air duct 34, a first air forcing apparatus 36, in this embodiment a first axial-flow fan 38, a second air forcing apparatus 40, in this embodiment a second axial-flow fan 42, and a first air refrigerator 44. The display unit 2 further comprises an upper air treatment system 48, which in this embodiment comprises the second axial-flow fan 42. The first axial-flow fan 38 and the first air refrigerator 44 are provided at the lower air duct 32, and the second axial-flow fan 42 is provided at the upper air duct 34.

(12) The top wall 12, left side wall 14, right side wall 16, bottom wall 18, and lower front wall 22 and the back doors 23, 24 delimit an open front chamber 50 for the food products (not shown). The open front chamber 50 is accessible from the open front 52 and by opening one of the back doors 23, 24.

(13) The lower air duct 32 comprises a lower front inlet 60 and lower back outlet 62, and extends from the lower front inlet 60 to the lower back outlet 62. The upper air duct 34 comprises an upper back inlet 64 and an upper front outlet 65, and extends from the upper back inlet 64 to the upper front outlet 65. It is noted that some inlets and outlets are merely openings in the relevant duct wall, while the upper front outlet 65 is formed by a curved duct part in the second and third embodiment, and by a straight duct part which is connected under an obtuse angle with the upper air duct 34 in the first embodiment.

(14) The lower back outlet 62 is directed at the upper back inlet 64 for creating a back air curtain 66 in front of the back doors 23, 24, and the upper front outlet 65 is directed at the lower front inlet 60 for creating a front air curtain 67 in front of the open front 52.

(15) Referring to FIG. 4, a system 2001 with a display unit 2002 is shown with the same or similar elements as in the previous embodiments. In this embodiment, both the upper front outlet 65 is provided with upper front slats 68 for creating a laminar flow air curtain and directing the air curtain, and the lower back outlet 62 is provided with lower back slats 70 for creating a laminar flow air curtain and directing the air curtain. The lower front inlet 60 is provided with lower front slats 72. The lower front slats 72 prevent objects falling into the front inlet 60. The slats 68, 70, 72 are arranged in parallel. The slats have a length which is larger than its width, while the width is larger than the thickness. In particular, the slat width/slat thickness ratio is at least 4:1. Furthermore, the width of the slats is larger than the distance between the slats (also called slot width). In particular, the slat width/slot width ratio is at least 2:1. The slats preferably have a aerofoil profile as seen in cross-section.

(16) The upper air duct 34 is formed by an upper duct upper wall 80, an upper duct lower wall 82, an upper duct left side wall 84, and an upper right side duct wall 86 (see FIG. 1 for side walls 84, 86). Referring to FIGS. 2 and 3, the upper duct upper wall 80 acts as conduit wall 88, which is positioned substantially in parallel to, and at the chamber side of, the top wall 12 for creating an air conduit 90 between the conduit wall 88 and the top wall 12. The air conduit 90 comprises a first conduit inlet 92, which is positioned adjacent of the conduit wall 88, a second conduit inlet 94, which is positioned adjacent of the top wall 12, and a conduit outlet 96, which is positioned at a front edge 98 of the conduit wall 88. The upper air duct 34 further comprises an upper fan housing 100 for the upper axial-flow fan 42, which upper fan housing 100 comprises an upper fan housing top wall 102, and an upper fan housing back wall 104. Moreover, the upper fan housing 100 comprises the upper back inlet 64.

(17) The upper fan housing top wall 102 is vertically spaced above the conduit wall 88 for forming the first conduit inlet 92, which in this embodiment is slit-shaped (see FIG. 3). The first conduit inlet 92 is in fluid connection with the upper air duct 34 for diverting approximately 2% of the air which is moved through the upper air duct 34 by the upper axial-flow fan 42 into the air conduit 90. The upper fan housing top wall 102 is further vertically spaced below the top wall 12 for forming a slit 106. This slit 106 provides a fluid connection between the second conduit inlet 94 and the ambient air outside of the display unit 2.

(18) The top wall 12, the conduit wall 88, and the upper duct lower wall 82 are transparent walls. This enables a user, schematically indicated with eye 110, to better view the content of the open front chamber 50. In particular, the view from a relative high positioned user is improved. Such a position occurs when the display unit 2 is placed relatively low and/or in a congested space so that the user cannot take a step back to view the content. The left and right side walls 14, 16 are transparent walls too. This improves the visibility from the side.

(19) Referring to FIGS. 1 and 4, the multiple shelves 4 are placeable in the display unit 2 to each extend in the chamber in a vertical spaced relationship. The display unit 2 comprises a shelf support system 120 which comprises two shelf support frames 122 in the shape of an inverted U. The legs of the inverted U are support on, or at, the bottom wall 18. The top of the inverted U is positioned at the top wall 12. Each of the shelf support frames 122 is positioned at the inside of a respective left or right side wall 14, 16. The shelf support system 120 further comprises multiple shelf support means 124 at different heights for supporting the shelves 4 at different vertical positions in the display unit 2, as indicated by dotted lines. The shelf support means 124 are distributed in a vertical spaced relationship over the legs of both shelf support frames 122. The shelves 4 comprise corresponding front connection means 126 and back connection means 128 for removably attaching the relevant shelf 4 in the open front chamber 50.

(20) A back edge 130 of the shelves 4 is spaced from the back door 23, 24, so that the back air curtain 66 can flow between the shelves 4 and the back door 23, 24, as shown in FIG. 2. Note that FIG. 4 shows in black that the back connection means 128 extend beyond the back edge 130 of the relevant shelf 4, so that it is connectable to a backward one of the shelf support means 124. Seen from a top view, the back connection means 128 and the back edge 130 thus form an open U-shape for the back air curtain 66. The shelf support means 124 are provided such, that the shelves 4 are positioned either in a horizontal orientation, or at a slight angle of less than 20 degrees with the horizontal.

(21) FIGS. 5-6 show a system 3001 with a display unit 3002 according to another embodiment of the invention. The display unit 3002 as shown is the same, or similar, to the ones shown in the previous embodiments, and may have some different elements as described in the final paragraphs of this specification. According to the inventive concept, the display unit 3002 itself is provided with an air refrigerator 44, while at least one of the multiple shelves 4 is a hollow shelf 140 with a shelf air outlet at the front side, a shelf air inlet at the back side, a shelf air forcing apparatus, and a shelf heater (details inside of the hollow shelf 140 not shown).

(22) FIG. 7 shows in detail a similar hollow shelf 141 which has a front side 142 and a back side 144, which in use correspond to the front side 6 and the back side 8 of the display unit 2. The hollow shelf 141 comprises at least at least one shelf air outlet 146 at the front side 142, one shelf air inlet 148 at the back side 144, a shelf air forcing apparatus 150, in this embodiment an axial-flow fan 152, and a shelf heater 154, in this case a flat electrical heating element 156.

(23) The hollow shelf 141 comprises a substantially flat shelf top 158, which functions as placing side 160 on which food items can be positioned in a storage space 161 above the relevant shelf. The hollow shelf 141 further comprises shelf sides (not shown), and a shelf bottom 162. The shelf top 158, shelf sides and shelf bottom 162 define an inner space 164. The inner space 164 of the hollow shelf 141 fluidly connects the shelf air inlet 148 with the shelf air outlet 146.

(24) The shelf bottom has a flat section 166, extending in parallel to the shelf top 158 over a forward and middle part of the shelf 141, and has a down bulking section 168 which extends downwards for defining an enlarged portion of the inner space 164 for housing the axial-flow fan 152. The axial-flow fan 152 is in fluid connection with the shelf air inlet 148 and the shelf air outlet 146 for moving air from the shelf air inlet 148 through the hollow shelf 141 to the shelf air outlet 146.

(25) The flat shelf heater 154 extends inside the inner space 164 for heating the air in the inner space 164 of the hollow shelf 141, and for providing heat to the placing side 160. The shelf air outlet 146 defines a flow direction 170 for air flowing out of the outlet, and the flow direction 170 points away upwards from the placing side 160 and backwards towards the back side 144 of the hollow shelf 141. The air flow is deflected by a shelf bottom 162 of a shelf above the relevant shelf 141, or the top wall 12 of the display unit 2, as well as by the back wall 20 and/or the back doors 23, 24, as shown with dotted lines.

(26) The hollow shelf 140 of FIGS. 5 and 6 differs from the hollow shelf 141 of FIG. 7, in that the back edge 130 of the hollow shelf 140 is spaced horizontally from the back wall 20 and/or back doors 23, 24, when positioned in the display unit 2, for providing sufficient space for a back air curtain 66 between the back edge 130 of the hollow shelf and the back wall 20 and/or back doors 23, 24, as shown in FIG. 6. The hollow shelf 140 of this embodiment comprises a replaceable back portion 172. When put into place at the back side 144 of the hollow shelf 140, the replaceable back portion 172 extends the hollow shelf 140 to the back wall 20 and/or back doors 23, 24 of the display unit 2, as shown in FIG. 5. The replaceable back portion 172 comprises a joint 174, in this embodiment a pivot 176, in order to move the replaceable back portion 172 from a retracted position, wherein the back edge 130 of the hollow shelf 140 is spaced horizontally from the back wall 20 and/or back doors 23, 24 of the display unit 2, to an extended position, wherein a back side 178 of the replaceable back portion 172 is positioned at the back wall 20 and/or back doors 23, 24 of the display unit 2. This position improves the air circulation above the hollow shelf 140 while the display unit 2 is in use as heated display unit, because it decreases the exchange of air between the space above and below the hollow shelf 140. By retracting the replaceable back portion 172, the shelf 140 can remain in the display unit 2 while it is being used as refrigerated display unit 2.

(27) The hollow shelves 141 are suitable for a heated operation of the display unit 2, while they are further suitable for a refrigerated operation in a display unit with a back air duct instead of a back air curtain. In an embodiment of the system 3001 with a back air curtain, where these hollow shelves 141 are positioned, it is preferably possible to remove one or more of the hollow shelves 141 and replace them by a flat shelf without a shelf air forcing apparatus, e.g. a flat shelf 5 as shown and described in relation to the previous embodiments, by means of shelf support means and connection means, e.g. such as those as shown in, and described in relation to, FIG. 4.

(28) In use, an inventive display unit as defined by the claims, such as one of the display units 2, 1002, 2002, 3003 as described above, is used for either storing refrigerated or heated food products. While in use for refrigerated goods, the slats at the outlets provide for a laminar air flow air curtain and direct the air curtain to the respective inlet. This reduces air movement around the refrigerated food products, which prolongs the time that the food products are consumable.

(29) In use, the same, or similar, display unit is provided with back doors and a back air curtain. This enables the display unit to be used in a crowded and busy environment wherein it is important that the open front chamber is accessible from the back as well, for refilling the display unit without disturbing the customers.

(30) The back and front air curtain, in particular as they have a directed laminar flow, keep the food products inside of the open front chamber in a refrigerated envelope, thus keeping the food products at a desired low temperature compared to the ambient temperature, without the need for directing refrigerated air onto the food products.

(31) A display unit with back and front air curtains, in particular directed laminar air curtains, is also very suitable to be used with exchangeable, height adjustable shelves, as the circulation of refrigerated air is independent of the shelves as long as they do not extend into the air curtains.

(32) In use, the same, or similar, display unit is provided with one or more transparent walls and a conduit wall, as described in relation to FIGS. 2 and 3, although these features are present in all the shown embodiments. The transparent walls improve the visibility of the food products inside the open front chamber. Ambient temperature conditions of the display unit may range from 12° C. to 25° C., while the air temperature of the air which is used to cool the content of the display unit and to create an air curtain may be in the range of −4° C. to +4° C. In prior art display units, this cold air would cause condensation on the outside of the transparent wall and diminish the visibility of the food products. This is solved according to the invention by admitting ambient air between the transparent wall and the conduit wall. This prevents cooling off of the transparent wall, so that the temperature of the transparent wall remains above the dew point of the ambient air. At the same time, refrigerated air is admitted between the transparent wall and the conduit wall to, in order to keep the temperature of the air flowing along the conduit wall at a low level, so that the temperature of the conduit wall itself remains above the dew point of this air, in order to prevent condensation on the conduit wall.

(33) The prevention of condensation is improved by minimising the mixture of ambient air and refrigerated air in the air conduit. This is achieved by a combination of having a relative flat air conduit and by a suitable choice of the dimensions of both air inlets. The optimum flatness of the air conduit and the mutual ratios of the dimensions of the air conduit and the air inlets is different for different sized display units and for display units operating under different conditions, and is therefore to be determined by trial and error. It is noted that a complete separation of the ambient air and the refrigerated air in the air conduit is impossible, and also not necessary. In other words, the ambient air flowing along the inside of the transparent wall will be slightly colder than the ambient air outside of the display unit. Likewise, the refrigerated air in the air conduit will be slightly warmer than the refrigerated air at the other side of the conduit wall. This does not deter from preventing condensation, as long as the temperatures of the relevant walls are above the dew point of the surrounding air.

(34) In use, the same, or similar, display unit is provided with hollow shelves, as described in relation to FIGS. 5-7. Such hollow shelves may be fixed in the display unit, or exchangeable for other shelves. The inventive hollow shelves direct heated air substantially entirely into the storage space above the relevant shelf. This enables the storage of heated products on a display unit which is otherwise designed for refrigerating food products.

(35) Throughout this specification, the term air duct should be interpreted broadly, in that one air duct, e.g. the lower air duct or the upper air duct, may comprise different physical parts such as pipes, connectors, adapters. Moreover, a part of the air moving apparatus and/or the air refrigerator, or the inside of a double wall may be considered to be part of the air duct too. The air conduit does not comprise physical parts, such as a further wall, in the air conduit between the transparent wall and conduit wall to separate the ambient air and the cooled air in the air conduit, in particular no physical parts, such as a further wall, extend between the transparent wall and conduit wall along the length of the air conduit.

(36) The material of transparent wall is preferably glass or plastic, such as polycarbonate (PC), polymethyl methacrylate (e.g. Perspex, registered trademark of the Lucite International UK Limited), polyethylene terephthalate (PET) or polyvinyl chloride (PVC). The material of non-transparent walls is preferably metal or plastic, such as an insulating type of plastic, e.g. a plastic foam. A wall is considered transparent in the context of this specification if a user can see through a substantial part of the relevant wall, and is able to see at least part of the food products in the open front chamber through the transparent wall.

(37) Several variants are possible within the scope of the attached claims. The features of the above described preferred embodiment(s) may be replaced by any other feature within the scope of the attached claims, such as the features described in other embodiments, and in the following paragraphs.

(38) The inventive slats do not need to be arranged as straight parallel slats. In an embodiment, the slats are short and define an open honeycomb structure. In an embodiment, the slats have a non-rectangular profile as seen in cross-section. In particular, the slats have a thickness in their middle part which is larger than at the edges. This reduces drag. In another embodiment, the slats have a rectangular cross-section. This provides a simple solution which reduces the cost.

(39) In an embodiment, the display unit may be provided with fixed shelves instead of replaceable shelves. Both a fixed shelf which is placed permanently or semi-permanently in the display unit and a replaceable shelf are considered a shelf which is placeable in the display unit in the context of this description. In an embodiment, a lower shelf is integrated with the bottom wall of the open front chamber. In an embodiment, a plurality of shelves, in particular all the shelves, are hollow shelves with an inner space, a shelf air inlet at the back side, a shelf air outlet at the front side, a shelf air forcing apparatus, and a shelf heater. In an embodiment, the shelf air forcing apparatus is provided at the relevant hollow shelf in fluid communication with the shelf air inlet and the shelf air outlet, but not inside of the hollow shelf, or at least not completely inside of the hollow shelf. In an embodiment, the shelf heater is one, or a series of, heating wires, in particular spiral shaped wires.

(40) In an embodiment, the inner space of the hollow shelf is provided with one or more air ducts for connecting the shelf air inlet with the shelf air outlet. In an embodiment, the at least one shelf air outlet is directed downwards for creating an air curtain in front of the storage space below the relevant shelf. In a variant, the at least one shelf air outlet is directed upwards, but substantially not backwards, for creating an air curtain in front of the storage space above the relevant shelf. In an embodiment, one hollow shelf is provided with a plurality of shelf air outlets. In particular, at least part, more in particular all, of the plurality of shelf air outlets are positioned at the front side of the relevant shelf and/or are directed upwards and/or backwards. In particular, at least one of the plurality of shelf air outlets is provided at the front side of the shelf, while a portion of the plurality of shelf air outlets is positioned between the front and the back side of the shelf at the placing side of the relevant hollow shelf and/or at an underside of the relevant hollow shelf.

(41) In an embodiment, the replaceable back portion of the hollow shelf is not connected via a joint and is to be taken out of the display unit, when said unit is used as refrigerated display unit with a back air curtain. In an embodiment, the replaceable back portion is connected to the hollow shelf via a sliding joint. In an embodiment, the hollow shelf completely extends to the back wall without a back portion which is removable. In such an embodiment, the relevant hollow shelf is taken out of the display unit when said unit is used as refrigerated display unit with a back air curtain. In another embodiment, the back side of the hollow shelf is spaced from the back wall in order to provide space for the back air curtain.

(42) In an embodiment, at least one of the walls is double walled for insulation, and in particular provided with insulation material. In an embodiment, the bottom wall is double walled, wherein the space between the bottom walls forms the lower air duct. In another embodiment, the bottom wall is double walled, wherein a pipe or other separate means is provided as lower air duct in the space between the bottom walls. In yet another embodiment, the bottom wall is a single wall and the lower air duct is provided as separate means either inside the display unit, e.g. on the bottom wall, or at the outside of the display unit.

(43) In an embodiment, the top wall is double walled, wherein the space between the top walls forms the upper air duct. In another embodiment, the top wall is double walled, wherein a pipe or other separate means is provided as upper air duct in the space between the top walls. In yet another embodiment, the top wall is a single wall and the upper air duct is provided as separate means either inside the display unit, e.g. attached under the top wall, or at the outside of the display unit.

(44) While the display unit has an open front chamber, in an embodiment there are one or more front walls at the lower, side, or upper edge of the open front. In an embodiment, the conduit wall is positioned parallel of a side wall, a back wall, or a front wall. In an embodiment, one wall is a transparent wall. In another embodiment, a plurality of walls are a transparent wall. In particular, one of the plurality of transparent walls is provided with a conduit wall. In a variant, two or more of the plurality of transparent walls are each provided with a conduit wall. In an embodiment, the conduit wall is not part of an air duct, but just a wall provided in parallel to another wall.

(45) In an embodiment, more than two air forcing apparatus are provided. In particular, a plurality of air forcing apparatus is provided in parallel, i.e. next to each other. Such a row of a plurality of air forcing apparatus is provided in the lower air duct and/or in the upper air duct.

(46) In an embodiment, the air forcing apparatus is a fan which is provided in the relevant duct. In an embodiment, a centrifugal fan is used as air forcing apparatus. In another embodiment, a cross-flow fan is used as air forcing apparatus. In yet another embodiment, a fan using the coanda effect is used as air forcing apparatus. In this embodiment, the blades of the actual fan are outside of the relevant air duct, sucking in a relative small amount of air, compressing this air and blowing a thin high-velocity laminar airflow from holes or a continuous slot across the inner surface of the relevant duct. This high-velocity air induces and/or entrains ambient air through viscous shearing, thus multiplying the amount of air which is drawn through the relevant duct. In yet another embodiment, a bellows is used as an air forcing apparatus.

(47) In an embodiment, the air refrigerator surrounds the relevant air duct, e.g. by cooling the wall of the air duct from the outside. In another embodiment, the air refrigerator comprises a heat exchanger, wherein a first side of the heat exchanger is part of the air duct, while a second side of the heat exchanger is in contact with a cooling fluid.

(48) In an embodiment, the back door is a pivotable door, a loose panel which is to be removed from the back of the display unit, or a curtain. In an embodiment, a slidable back door slides in a vertical direction. In an embodiment, the open front may be provided by a curtain or a front door for temporarily closing the front of the display unit.

(49) In an embodiment, the air circulation system comprises a back air duct which fluidly connects the lower air duct with the upper air duct. The position and number of air refrigerators and air moving apparatus are less critical in such an embodiment, than in an embodiment with a back air curtain. The air refrigerator(s) and/or air moving apparatus are provided at the lower air duct, the back air duct, and/or the upper air duct.

(50) In an embodiment, there is a plurality of lower air ducts extending in parallel from the front to the back side of the display unit. In an embodiment, there is a plurality of upper air ducts extending in parallel from the back to the front side of the display unit. In an embodiment, there is a plurality of back air ducts each extending from a lower air duct to an upper air duct.

(51) In an embodiment, there is a plurality of lower front inlets. In particular, the plurality of lower front inlets communicates with one and the same lower air duct. In a variant, each of the plurality of front inlets communicates with an individual lower air duct. In an embodiment, there is a plurality of upper front outlets. In particular, the plurality of front outlets communicates with one and the same upper air duct. In a variant, each of the plurality of front outlets communicates with an individual upper air duct. The same or similar embodiments are possible for the back inlets and back outlets.

(52) In an embodiment, the upper air treatment system comprises only the air refrigerator. By cooling the air in the upper air duct, it becomes heavier than the ambient air and as a result flows downwards from the upper front outlet without the need for an upper air moving apparatus. In an embodiment, the upper air treatment system comprises the first air refrigerator, and there is no second air refrigerator. This means that the air in the upper air duct is cooled sufficiently for cooling the whole display unit. In an embodiment, the first air refrigerator is provided in the lower air duct, and the second air refrigerator is provided in the upper air duct. In an embodiment, the second air forcing apparatus is provided in the upper air duct.