MXPA99009917A - A cooling apparatus - Google Patents

Abstract

A cooling apparatus, such as a consumer display unit (400), comprises a covered tray (403) or other compartment for accommodating consumer product to be kept cool, and a housing (420) for accommodating a replaceable charge of dry ice out of contact with the product. A tubular element (421) communicates between the covered tray and the housing (420) to allow cold air and carbon dioxide to flow from the dry ice to the product.

Description

DESCRIPTION OF THE INVENTION This invention relates to a refrigerating apparatus, in particular, but not limited to, a display device. For a long time it has been recognized that the marketing of products through self-sustaining exhibition units leads to a much greater turnover in the products. This has proven to be impractical with products that need to be kept cold, such as butter or other dairy products, since they must be displayed in electrically-activated refrigerators and the cables and power points needed to supply energy for these refrigerators present in stores or in the supermarkets presents logistical problems. An objective of the present invention is to solve these problems. The invention therefore provides a cooling apparatus comprising a first means for accommodating at least one product for the consumer which must be kept cold, a second means for accommodating a replaceable charge of solid refrigerant without contact with the product, and a means of communication between the first and second accommodation means for allowing cold gas to flow from the solid refrigerant to the product. The embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded view of a first housing for the solid refrigerant; Figure 2 is an exploded view of a second housing for the solid refrigerant; Figure 3 is a perspective view of a first embodiment of a display unit according to the invention; Figure 4 is a perspective view of a second embodiment of a display unit according to the invention; Figure 5 is a perspective view of a third embodiment of a display unit according to the invention; Figure 6 is a perspective view of a fourth embodiment of a display unit according to the invention; Figure 7 is a perspective view of a fifth embodiment of a display unit according to the invention; Figure 8 is a perspective view of a sixth embodiment of a display unit according to the invention; Figure 9 is a front elevational view of the unit of Figure 8 of the drawings; Figure 10 is an exploded view of the unit of Figure 8 of the drawings showing the cover detached therefrom; Figure 11 is a plan view of the unit of Figure 8 of the drawings; Figure 12 is a perspective and detailed view of part of the unit of Figure 8 of the drawings; Figure 13 is an exploded and detailed view of part of the unit of Figure 8 of the drawings; Figure 14 is a perspective view of a seventh embodiment of the display unit according to the invention; Figure 15 is a front elevation of the unit of Figure 14 of the drawings; Figure 16 is a cut-away view of the unit of Figure 14 of the drawings showing the cover detached therefrom; Fig. 17 is a plan view of the unit of Fig. 14 of the drawings; Figure 18 is a perspective and detailed view of the unit of Figure 14 of the drawings; Figure 19 is an exploded and detailed view of part of the unit of Figure 14 of the drawings; Figure 20 is a perspective view of an eighth embodiment of a display unit according to the invention; Figure 21 is a front elevation of the unit of Figure 20 of the drawings; Figure 22 is an exploded and side elevation of the cabinet of Figure 20 of the drawings; Figure 23 is a plan view of the cabinet of Figure 20 of the drawings; Figure 24 is a detailed and exploded view of part of the unit of Figure 20 of the drawings; Figure 25 is a cross-sectional view of a ninth embodiment of the invention; and Figure 26 is an exploded view of the embodiment of Figure 25. Referring now to the drawings and in particular to Figure 1, a housing 100 for a solid refrigerant, for use in the embodiments of the invention shown in Figures 3 and 4, comprises a tray 13 open at the bottom of polystyrene, thermally insulated, substantially rectangular in shape and having a rung or flange 14. A grid-like element 15 of a plastic material and having a plurality of openings 150 therein abuts the flange 14 and forms the base of the housing 100. A polystyrene insulating cover 17 is also provided, which forms an upper part of the housing 100 which, when in its place, is housed inside the tray 13, on the upper part of the solid refrigerant which is placed on the element 15. Now with reference to Figure 2 of the drawings, an alternative housing 200 for a solid refrigerant is shown. Device 200, similar to device 100, has the same type of tray 13 with flange 14 and cover 17. Without However, instead of using a grid-like element 15, a plate-like element 115 is provided which rests on the flange 14. The element 115 has a single circular opening 155 located substantially centrally to the Element 115. Opening 115 has a diameter de between 5 mm and 40 mm with a preferred diameter de between 10 mm and 30 mm, and more preferably between 10 mm and mm. When one or more flat packages 16 of a solid refrigerant such as dry ice are used, they are placed in the tray of the housing 100 or 200. The package or packages 16 rest on the element 15 or 115 as the case may be. More specifically, in the case of a housing 200 which has an opening 155 having a diameter? of, for example 15 mm, one or more packages 16 having a weight may be used combined initial of approximately 2 kg. In the case of a housing 200 having an opening 155 with a diameter? of 40 mm, the initial weight of the pack or packages 16 is approximately 4.5 kg. In the case of a housing 200 with an opening 155 having a diameter? of 30 mm, the initial weight of 5 packages is approximately 3.5 kg. Suitable packages of dry ice 16 are manufactured by Hydrogas Limited of South Humberside, United Kingdom, under the trade name HYDROGAS. Each pack 16 is drilled to allow the C02 gas to evaporate as the dry ice is sublimated.

Preferably, the outer surface of each of the packages 16 is silver. With particular reference to Figure 3 of the drawings, a first embodiment of the refrigerating apparatus according to the invention is shown, in the form of a unit 10 of exhibition. The unit 10 comprises a container in rectangular shape having side walls 20, 21, an upper wall 22, a lower wall 23 and a rear wall 24. A flange 25 is provided around the walls 20, 21 and the rear wall 24, and a support 11 provides a continuation of the flange through the front of the container. The flange 25 and the support 11 are located in relation to the upper wall 22 so as to provide an opening Ia into which the housing 100 is inserted (or 200). Beneath the opening there is provided a large compartment 28 within which is temporarily accommodated suitable product to be maintained at a temperature in the region from 1 ° C to 7 ° C, preferably to about 5 ° C. Such a product includes, but is not limited to, dairy products, such as butter, cheese, milk and the like; chocolates and other confectionery products; and drinks in bottles or lacquers that include water, carbonated drinks, beer, vintage beer, wine and the like. If desired, a transparent Perspex wall 29 of approximately 50 mm height can be provided at the front lower end of the compartment 28 to prevent the product from accidentally falling out of the unit 10. Articulated to the upper wall 22 is a fin 18 which serves to close the opening Ia when the housing 100 or 200 is in place. With particular reference to Figure 4 of the drawings, a second embodiment of a display unit 30 according to the invention is shown which enjoys all the characteristics of the unit 10 and functions in a similar manner. However, unlike the unit 10, the unit 30 is provided with a plurality of dependent transparent plastic strips 31 which are attached to the support 11 and which, as is well known, provide an insulating curtain for the compartment 28.

It will be understood that, in the embodiments of Figures 3 and 4, the openings 150 in the grid 15, or the single opening 155 in the element 115, provide communication between the housing 100 or 200, and the compartment 28 to allow gas to flow cold (i.e., air and / or carbon dioxide) from the solid refrigerant in the housing 100 or 200 to the product in the compartment 28. Based on the volume of the compartment 28, the opening 155 may vary in size. An example of the relationship between the weight of the ice, the dimensions and the volume of the compartment 28 and the size of the opening 155 of the element 115 is provided below.

TABLE 1 When the housing 100 or 200 of solid refrigerant is to be used, fresh packages 16 of dry ice are placed on the grid 15 or 115 and the cover 17 is placed on them. Then, the housing 100 or 200 is placed in the opening of the unit 10 or 30 and the cover 18 is closed. The product placed in the compartment 28 and housed in the unit 10 or 30 has been found to remain at a temperature of about 5 ° C for a period of 18 hours. With particular reference to figure 1, it will be noted that in the case of the use of the unit 30 having the data provided in table 1 above, and in particular type A, compartment 28 has a temperature of 5 ° C during a period of eighteen hours. Graph 1 represents the test conditions that have the following criteria, that is: i. the ambient temperature is maintained at 21 ° C during the period of the test; ii. unit 10 contains about 7.5 kg of product (comprising varying amounts of margarine, edible oil, yoghurt and water iii) before loading, 5 kg of the product have been stored at a temperature of about 8 ° C and 2.5 kg were stored at approximately 5 ° C. The temperatures were recorded at intervals of minutes and it was considered that the initial temperature of the unit was close to the environment, and a temperature of 5 ° C is obtained in about forty-five minutes after placing the dry ice. The air temperature inside the unit 30 is found to be that shown in graph 1, over the relevant time period. At the end of the eighteen hour period, the product remains below 5 ° C for about 3 hours. It will be appreciated that at the end of the eighteen hour period if a fresh load of dry ice is placed, the temperature will remain at or below 5 ° C. At the end of the eighteen hour period, if it is desired to continue using the unit 30 (or 10), the housing 100 (or 200) is removed, the lid 17 is lifted and fresh ice packs 16 are placed in it. The replenished housing 200 (or 100) is placed in the opening Ia as in the above. With particular reference to Figure 5 of the drawings, a third of a display unit according to the invention is shown, in the form of a display cabinet 301. The display cabinet 301 effectively comprises three display units 10, 10a, 10b. The units 10a and 10b are of construction similar to unit 10. Therefore, the cabinet 301 comprises three separate units 10, 10a, 10b, one above the other, and are housed in support frame 310 which includes a base 22 of cabinet (to elevate units 10, 10a and 10b above the floor for optimal display purposes) and a header unit 23 which may present advertising material pertaining to the product products on display. Each unit 10, 10a, 10b is served by a respective solid coolant housing 100 (or 200) located behind the respective fins 18, 18a and 18b. Alternatively, the display cabinet 301 may be constructed so that the side walls 20, 21, and the rear wall 24 are common to all three units 10, and that the roof 22 of a unit is common with the base 23. of one above the same, with appropriate openings for the three housings 100 (or 200) and three compartments 28 for products. With particular reference to Figure 6 of the drawings, a fourth display mode 302 according to the invention is shown which enjoys all the features of the cabinet 301 (and variations thereof) and which has plastic strips 31 as shown in FIG. show and describe with respect to unit 30 (or 30a, 30b). However, in order to provide better insulation for the lowermost opening 28, a thermally insulated base 35 is provided. With particular reference to Figure 7 of the drawings, there is shown a fifth embodiment of a display unit 303 according to the invention which enjoys all the characteristics of the cabinet 301 (and of variations thereof) and the base 35 of the cabinet 302, but with strips of plastic material 37 similar to the strips 31, except that each strip extends a height of all of the units 10, 10a, 10b (or 30, 30a, 30b).

Unit 10 or 30 of cabinet 301, 302 or 303 is preferably manufactured from a collapsible preform (not shown) of semi-rigid material such as cardboard or other paper-based material. With reference to Figures 8-13 of the drawings, a sixth embodiment of a display unit 400 according to the invention is shown. The display unit 400 comprises a unit 401 with a six-sided base made of cardboard, folded cardboard or plastic, for example Corriplast (trade name) which has a height of approximately 1500 mm. Base unit 401 does not necessarily need to be six sides; It may have a greater or lesser number of sides, or be circular. A tray 402 having substantially the same external shape as the base unit 401 is placed within the open cavity of the base unit 401 so that it is firmly placed therein. The tray 401 has a base 402 and side walls 403. The internal volume of the tray 402 may comprise a single compartment or, as in the case of Figs. 8-13, it may be divided into three subunits 404, 405, 406. A dome 410 of acrylic serves as a cover for the tray 401, the dome and the tray together form a container for consumer products that are placed in the tray, as will be described. The dome 410 has a plurality (preferably three) of openings 411 which provide access to the contents of the tray 401 when the dome 410 is in place. The dome 410 has a housing 420 of dry, insulated ice, which, in the case of Figs. 8-13, is seen in a circular plan. However, the housing 420 may be of any desired shape or configuration. With particular reference to Figure 13, it will be noted that the housing 420 is integral with the dome 410, which is attached thereto by an integral tubular member 421 that provides a conduit for cold gas (i.e., air and / or dioxide). carbon) to flow down from the housing 420 into the interior of the dome 410. As will be seen from Figure 13 of the drawings, the housing 420 has a flange 422 positioned circumferentially internally. Leaning on the rim is a floor 423, which forms the base of the housing 420, having a single circular opening 424 located substantially centrally to the floor 423. The opening has a diameter de of between 5 mm and 40 mm with a diameter of preferred between about 20 10 mm and 15 mm. A layer 425 is provided for the housing 420. As an alternative, the dome 410 may have an opening (not shown) at the apex thereof. A housing 430 is provided (figure 12) which enjoys all the features that have been described with respect to the housing 420 in addition to an integral tubular element 431 of which may coincide with the opening at the apex of the dome 410. When used, the dome 410 is removed from the tray 401 and the tray 401 is stacks with merchandise such as chocolate bars, candies, etc., usually indicated with the number 412. If the tray 401 is divided, as in the case shown here, three types of products can be placed therein. The dome 410 is replaced. Within the compartment 420 one or more packages 16 of dry ice are placed. The packages 16 are preferably of circular cross section. Because the housing 420 is integral with the dome 410, some users may find it unprofitable to place (or replace) the packages 16 due to the need for relatively thick insulating gloves for use by a person responsible for ensuring that there is sufficient dry ice, that must be present. This is avoided by using the housing 430, which can be removed together with the tubular element 431 as a dome unit and which can be supplied easily packed with dry ice packs 16. Thus, for purposes of recharging the 400 cabinet with a fresh change of ice packets 16, the housing 430 of the dome 410 is removed and replaced with another similar housing 430 having a recent charge of a pack 16. As will be seen in figure 13 of the drawings, as the ice sublimes, the cold air and the dioxide of carbon exit through the opening 421, move down the tubular element 421 and below the dome 410, where it bathes the products 412 in a cold environment. The access of the customers to the products 412 is by means of the openings 411. It will be appreciated that the housing 420 or 430 in principle is the same as the housing 200 of figure 2. With reference to figures 14-19 of the drawings , a seventh embodiment of a display unit 500 is shown, according to the invention. The unit 500 has a base unit 501 which has the same characteristics as the base unit 401. A tray 502 is provided which also enjoys the same characteristics as the tray 402, except that in the case of the divided tray 502, the walls 503 end in recesses 504 formed circularly, centrally positioned. A dome 510 is also provided which has the same characteristics as the dome 410, except that the dome 510 does not have a tubular element similar to the element 421 nor does it have an opening placed at the apex thereof. A cooling device 520 is provided which comprises a tubular body 521 having a circumferentially disposed flange 522. A plate-like element 523 abuts the flange 522 to divide the internal volume of the element 521 into a housing 524 of upper dry ice, of which the element 523 forms a base, and a lower conduit 525.

The element 523 has a single centrally located, circular opening 526 having a diameter T of between 5 mm and 40 mm, preferably between 10 mm and 15 mm. The conduit 525 is provided with a plurality of openings 527, each 5 having a diameter of approximately 15 mm in the side wall thereof. The device 520 is provided with a cover 528. It will be noted that the construction of the housing 524 for dry ice is in principle the same as for the device 200, and that similarly, the flange accommodates the use, one or more dry ice packets 16 having a circular cross section. The display unit 500 operates in a manner similar to that of the display unit 400, except for the following. With the dome 510 removed, the cooling device 520 has one or more packages 16 of dry ice thereon and is placed in the tray 502, the lower edge of the duct 525 engages the recess 504. The openings 527 are placed in a manner that as will be seen in Figures 15 and 16 of 20 the drawings, are within the space joined by the tray 502 and therefore, the cold air and the CO 2 gas can permeate the merchandise 412 therein. With particular reference to Figures 20-24 of the drawings, there is shown an eighth embodiment of a 600 unit of display according to the invention. The unit 600 has a base unit 601 which has the same characteristics as the base unit 401. A tray 602 is provided which also enjoys the same features as the tray 402. 5 Projecting upwards from the rear of the base unit 601 and preferably integral therewith is a cooling device 620. In order to provide support for the cooling device 620, side-mounted fin elements 630 are provided. The refrigerant device 620 has two main walls, that is, a wall 621 placed rearwardly and a wall 622 placed forwardly. The walls 621, 622 are in a separate substantially parallel relationship and together with the narrow side walls (not shown) define a compartment that is generally shown with the number 623. Reference should be made to Figure 22 or Figure 24 of the drawings. While the wall 621 is without holes, the wall 622 has two holes 624, 625. The hole 624 is circular in cross section and is located below the hole 625. Preferably integral with the orifice 624, a tubular member 626 is provided which projects away from and down relative to the wall 622. The orifice 625 is substantially rectangular in a plan view and is closed by a door or cover 627, which, in the present embodiment, is hinged along the lower edge of the cover 627 in relation to the wall 622. The compartment 623 is divided into four subcompartments 631, 632, 633 and 634. both, the subcompartment 631 is joined by the walls 621, 622, the dome 610 and a first floor 641 placed horizontally. The subcompartment 632 is joined by the wall 621, the floor 641 and a floor 642. The subcompartment 632 is in fluid communication with the tubular member 626. Subcompartment 633 is joined by wall 621, cover 627, floor 642 and floor 643. Subcompartment 644 is joined by walls 621, 622, floor 643 and top 645 of cooling device 620. The floor 641 is located such that the base of the subcompartment 632 and the tubular member 626 provide a uniform conduit for a gas flowing from the subcompartment 632 into the interior of the tubular member 626. The subcompartment 633 constitutes a housing for dry ice 16, the floor 642 forms the base of the housing and is equivalent to the floor 115 of the housing 200. Similar to the floor 115, a centrally disposed circular hole 644 is provided, the diameter? which is between 5 mm and 40 mm, preferably between 10 mm and 15 mm.

The floor 643 is located so that a sub-compartment 633 is provided large enough to have one or more packages 16 of dry ice. A dome 610 is provided which is substantially similar to dome 410, except that the hole is not provided at the apex thereof. Instead, a hole 611 is provided which, when the dome 610 is in place, coincides with the tubular member 626 whereby it allows cold air and gas C02 to flow into the space joined by the dome 610 so that it provides a cold environment for the merchandise 412. It will be appreciated that the display unit 400, 500 and 600 function in a manner similar to each other and similar to the display unit 30. In a ninth embodiment of the invention, Figures 25 and 26, the apparatus comprises a cylindrical apparatus 700 for keeping a product such as a bottle or a wine 724 cold. A removable cover 712 for the container comprises a hollow cylindrical body in which an external stage 711 is formed. Step 711 prevents excessive insertion of cap 712 into container 700. An internal stage (not shown) is formed within cap 712 and a cylindrical open mesh grid 715 is located within the cap that rests on the stage . A bag 716 of 250 g of dry ice granules is located on grid 715, and this in turn is covered by thermally insulating polystyrene disk 717. The contents of the lid 712 are held in place with a removable push-on lid 718, while the bottom of the container is also closed with a similar push-on lid 718 '. It will be appreciated that the elements 715, 717 and 718, together with the side walls of the lid 712, form a housing for solid refrigerant with the same principle as the housing 100 described in relation to Figure 1. Of course, instead of the 715, a plate having a single circular hole as described for the housing 200 can be used instead. Although some of the above embodiments have been described as a housing for solid refrigerant having only a single circular opening in the At the base of the housing, such an opening preferably has a diameter of between 5 mm and 50 mm, more preferably between 10 mm and 15 mm, and it will be appreciated that more than one opening may be provided in the base of the housing, in which case the The cumulative area of the holes is preferably equivalent to the area of a circle having a diameter between 5 mm and 50 mm, more preferably between 10 mm and 15 mm. The invention, particularly with respect to Figures 8-24 of the drawings, provides convenient, inexpensive and easy to use examples of display units which allow merchandise to be presented under favorable sales conditions, but also under temperature conditions which They are particularly suitable for the product without the need for an electrical supply. The invention is not limited to the embodiments described herein, which may be modified or varied without departing from the scope of the invention.

Claims (30)

1. A refrigerating apparatus comprising a first means for accommodating at least one product for the consumer, which is to be kept cold, a second means for accommodating a replaceable charge of solid refrigerant without contact with the product, and a means of communication between the first and second accommodating means, to allow gas to flow from the solid refrigerant to the product.

2. The refrigerant apparatus as described in claim 1, wherein the second accommodating means comprises a housing for the solid refrigerant located removably adjacent to the inner ceiling of a container, the first accommodating means being the region of the container below the housing, such a region has at least one opening to allow the consumer access to the product or products, and wherein the communication means comprises at least one opening in the base of the housing.

3. The refrigerant apparatus as described in claim 1, comprising a cabinet having a plurality of compartments vertically placed one above the other, wherein a second respective accommodating means is provided for each compartment in the form of a housing for solid refrigerant located removably adjacent to the interior ceiling of the compartment, each compartment has a first accommodation means which is in the region of the compartment under the respective housing, such region has at least one opening to allow the consumer access to the products, and in wherein each compartment has a communication means which comprises at least one opening in the base of the respective housing.

4. The refrigerant apparatus as described in claim 1, wherein the first accommodation means comprises a container including a transparent cover, the cover has at least one opening to allow the consumer access to the products, wherein the second accommodation means comprises a housing for solid refrigerant, and wherein the communication means comprises a conduit between the housing for solid refrigerant and the container.

5. The refrigerant apparatus as described in claim 4, wherein the container includes a tray which is covered by a transparent cover.

6. The refrigerant apparatus as described in claim 5, wherein the transparent cover is in the form of a dome.

7. The refrigerant apparatus as described in claim 5 or 6, wherein the tray is supported on the upper part of the base unit.

8. The refrigerant apparatus as described in any of claims 4 to 7, wherein the housing for solid refrigerant is mounted outside the container and connected to the cover by the conduit which extends downwardly from the bottom of the housing, the The conduit is in communication both with the interior of the housing and with the interior of the container to provide such a path.

9. The refrigerant apparatus as described in claim 8, wherein the housing and the duct are mounted directly on, and are removable as a single unit from the cover.

10. The refrigerant apparatus as described in any of claims 4 to 7, wherein the housing for solid refrigerant is mounted within the compartment above the conduit.

11. The refrigerant apparatus as described in claim 10, wherein the housing and the conduit are removable as a single unit from the interior of the compartment.

12. The refrigerant apparatus as described in any of claims 4 to 11, wherein the housing for the solid refrigerant communicates with the conduit by means of at least one opening in the base of the housing.

13. The refrigerant apparatus as described in claim 1, wherein the first accommodating means is a container for the product, the container has a removable lid, wherein the second accommodating means comprises a housing for the solid refrigerant within the container. cover, and wherein the communication means comprises at least one opening in the base of the housing.

14. The refrigerant apparatus as described in any of claims 2 to 13, wherein the opening area at the base of the housing, or the cumulative area is greater than one, and is equivalent to the area of a circle having a diameter of between 5 mm and 50 mm, and preferably between 10 mm and 15 mm.

15. The refrigerant apparatus as described in claim 14, wherein the solid refrigerant is dry ice and the volume of the replaceable charge is such that initially between 2 kg and 4.5 kg of dry ice, more preferably 3.5 kg, is provided.

16. An display apparatus, as described in claim 1, wherein the first accommodation means comprises a container that includes a floor on which the product or products for the consumer can be placed, and a transparent cover, the cover has at least one opening for allowing the consumer access to the products, wherein the second accommodation means comprises a housing for solid refrigerant having a base, the housing is supported in the container with a space between the base of the housing and the floor of the container, and wherein the communication means comprises at least one opening in the base of the housing.

17. The display apparatus as described in claim 16, wherein the container includes a tray which is covered by a transparent cover.

18. The display apparatus as described in claim 17, wherein the transparent cover is in the form of a dome.

19. The display apparatus as described in claim 17 or 18, wherein the tray is supported on the upper part of the base unit.

20. The display apparatus as described in any of claims 16 to 19, including means for varying the area of the openings in the base of the refrigerant housing.

21. The display apparatus as described in claim 20, wherein the base of the housing for refrigerant comprises two substantially parallel plates, placed immediately adjacent and in alignment with each other, each plate having a plurality of openings, and wherein a plate is rotatable in relation to the other plate so that for different angular positions of a plate there is a different degree of superposition of the openings in the two plates, whereby the sublimation rate of the solid refrigerant in the housing is varied.

22. The display apparatus as described in one of claims 16 to 21, wherein the coolant housing is removably accommodated in a sleeve of insulating material surrounded by an open end tube, the lower ends of the sleeve and the tube are also separate from the floor of the container.

23. A housing for solid, rechargeable refrigerant, for use with a display apparatus, the housing has a base with at least one opening to allow sublimation of solid refrigerant granules contained in the housing.

24. The housing as described in claim 23, wherein the housing has a side wall with a substantially constant external cross section for slidable insertion of the housing into the surrounding thermal insulation sleeve.

25. The housing as described in claim 24, wherein the side wall is cylindrical.

26. The housing as described in claim 24 or 25, wherein the side wall has an upper closure which allows solid refrigerant granules to be introduced into the housing through the closure.

27. The housing as described in claim 26, wherein the top closure comprises a flexible membrane with at least one slot.

28. The housing as described in claim 27, wherein the membrane also includes at least one vent hole.

29. The housing as described in any preceding claim, which includes means for varying the area of the openings in the base of the refrigerant housing.

30. An display apparatus, as described in claim 29, wherein the base of the housing for refrigerant comprises two substantially parallel plates placed immediately adjacent and in alignment with each other, each plate having a plurality of openings, and wherein a plate is rotatable relative to the other plate so that, for different angular positions of a plate, there is a different degree of superposition of the openings in the two plates, whereby the rate of sublimation of the solid refrigerant in the housing is varied.