GB2326469A - Storage containers for use in refrigerators - Google Patents

Abstract

The invention provides a freezer container, parts of the walls 4, 7 of which comprise inner and outer layers 12, 13 of plastics material. The provision of inner and outer layers permits a rigid container to be made that is both cheaper than the wire mesh-type container and stronger than an injection-moulded plastic drawer made from an equivalent amount of plastics material. A liquid 14 may be provided between the layers which can be frozen in the freezer in which the container is placed. The provision of a freezable liquid improves the energy efficiency of the freezer. The inner and outer layers 12, 13 may contact to create reinforcing dimples.

Description

FREEZER CONTAINER This invention relates to freezer containers.

Typically, freezer containers take the form of wire mesh baskets or injection-moulded plastic drawers. A problem which may be encountered with such containers is that distortion of the base and walls can occur by large and heavy loads being put into the container. It has been proposed to increase the strength of freezer containers by manufacturing wire mesh baskets from thicker steel wire, and to use more plastics material in the manufacture of plastic drawers to increase the thickness of the base and walls. However, these proposals prohibitively increase both the cost and the weight of such freezer containers.

The invention provides a freezer container, parts of the walls of which comprise inner and outer layers of plastics material.

The provision of inner and outer layers permits a rigid container to be made that is both cheaper and lighter than the wire mesh-type container, and stronger than a plastic drawer made from an equivalent amount of plastics material.

Advantageously, the base also comprises inner and outer layers of plastics material.

Preferably, parts of layers which comprise the walls are brought together to further reinforce the walls. Parts of the layers which comprise the base can be brought together to reinforce the base.

It has been proposed to put vessels containing freezable liquid in conventional freezer containers, in order to improve the energy efficiency of the freezer. However, the inclusion of such vessels reduces the available storage capacity of the containers.

A second embodiment of the invention provides a freezer container, parts of the walls of which comprise inner and outer layers of plastics material, between which layers liquid is provided, the liquid being capable of being frozen in use.

This embodiment of the invention permits the energy-saving advantages of the freezable liquid to be retained, without the forfeiture of storage space.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a freezer, the door of which is open; Figure 2 is a perspective view, from above, of a freezer container constructed according the invention; Figure 3a shows a section along A-A of Figure 2; and Figure 3b shows a section along B-B of Figure 2, part of which is shown magnified.

Like reference numerals have been given to like parts throughout each of the figures.

Referring to Figure 1, a freezer, indicated generally by the reference numeral 1, is shown. The freezer 1 comprises a refrigeration cabinet 2a and a door 2b, which is shown open in this drawing. The cabinet 2a has a plurality of freezer containers constructed according to the invention, which are in the form of drawers 3a, 3b, 3c and 3d. The drawers 3a to 3d are slidable to positions partly outside the cabinet, to permit food to be placed in the drawers for cold storage or removed for thawing. The drawers 3a to 3d may be completely removed from the freezer for cleaning.

One of the drawers 3 is shown, removed from the freezer, in Figure 2. The freezer drawer comprises walls 4, 5, 6 and 7 and a base 8. Walls 5 and 6 are the side walls of the container and have respective flanges 9, 10 projecting outwardly from their uppermost edges. The flanges 9 and 10 can be located by guides within the freezer, so that the drawer is slidably movable along the guides. Wall 4 comprises the front wall of the container. The uppermost edge of front wall 4 has a recessed region 11, which can be employed as a handle for moving the drawer along the aforementioned guides.

The freezer container may be manufactured by heating an envelope of plastics material and pressurising it to force it into contact with mould pieces. This method is known as blow moulding. Alternatively, a process known as twin sheet thermoforming may be employed. In this method, reduced pressure is applied to pair of sheets of warmed plastics material, to draw the sheets against tools. The tools are brought together such that the sheets are welded together along a peripheral seam. Application of either method produces a freezer container having an inner layer 12 and an outer layer 13, which layers are spaced. The layers can be seen in the sectional drawings, Figures 3a and 3b.

Referring to Figure 3b, the magnified section shows a portion of the base 8. The outer layer 13 has been pushed against inner layer 12 to create a reinforcing dimple in the base. In this magnified drawing, it can be seen that the outer layer 13 and inner layer 12 have been squeezed together such that plastics material is displaced away from the region of contact. This has been done for a plurality of parts of the base, as shown in Figures 3a and 3b, to produce an array of regularly spaced dimples. This procedure can be carried out during the aforementioned blow moulding or twin-sheet thermoforming process by the use of appropriately shaped mould pieces or tools being pressed against the base 8. In this manner, the rigidity of the base 8 is increased. The walls 4 to 7 may also be strengthened in this way.

A freezable material 14, in the form of a liquid, is introduced in the space between the inner layer 12 and outer layer 13. The material 14 is introduced via holes in the peripheral seam joining the inner and outer layers 12, 13 of plastics material, which holes are subsequently sealed. In these drawings, the liquid material 14 completely fills the space between the layers 12 and 13. However, an air gap may be provided.

The liquid material 14 is capable of being frozen by the freezer. Suitable materials include water solutions of calcium chloride, sodium chloride or alcohol. When the container is put into the freezer, the liquid 14 undergoes a phase transition so that it is in a solid form. Latent heat is released by the material 14 during the transition from the liquid to the solid phase, this heat energy being absorbed by the refrigerant in the freezer.

Food to be frozen is placed in the container, inside the freezer. The comparatively warm food releases heat energy into the walls 4 to 7 and the base 8 of the box. The material 14 has a high latent heat of fusion. For instance, an aqueous solution of sodium chloride has a specific latent heat of fusion in the order of 175 kJ kg-l. If the heat energy released by the food is sufficient to melt the solid material 14, the phase transition from solid to liquid causes a large amount of heat energy, i.e. the latent heat of fusion, to be absorbed. This property of the material 14 brings about a more rapid cooling of the food than was achievable hitherto with conventional freezer containers.

It is known that, in the first few minutes of a refrigeration cycle, the appliance uses energy at a greater rate than during the rest of the cycle. It is, therefore, desirable to have long refrigeration cycles. The high latent heat of fusion of the material 14 means that excess heat energy within the freezer is absorbed by the container, with only a slight increase in temperature. Thus, the temperature within the freezer is more stable in comparison with freezers incorporating prior art containers, and the time between refrigeration cycles is increased.

In the event of a power failure to the freezer, the material 14 within the container absorbs the consequent surplus heat energy and reduces the increase of temperature inside the freezer, thereby delaying the process of thawing of the food.

The thickness of the walls of the container is in the region of ten millimetres, which is only slightly thicker than conventional prior art freezer containers.

The freezer container of the invention can be fabricated to have smooth inner surfaces which makes it easier to clean than the prior art plastic drawers which incorporate a plurality of reinforcing ribs. The container can support heavier loads than a typical wire mesh type of container.

Variations may be made without departing from the scope of the invention. For instance, the material 14 need not occupy all of the space between the inner layer 12 and outer layer 13; for example, it may be desirable that only parts of the and/or parts of the base walls have the material 14 interposed between the layers. The invention has been described with reference to a drawer. However, the invention can be applied to other types of containers, for example a basket or a tray.

Claims (8)

1. A freezer container, parts of the walls of which comprise inner and outer layers of plastics material.

2. A freezer container, parts of the walls of which cdmprise inner and outer layers of plastics material, between which layers liquid is provided, the liquid being capable of being frozen in use.

3. A freezer container as claimed in claim 1 or claim 2, the base of which comprises inner and outer layers of plastics material.

4. A freezer container as claimed in claim 3, wherein a liquid is provided between the layers, the liquid being capable of being frozen in use.

5. A freezer container as claimed in claim 3 or 4, wherein parts of the layers which comprise the base are brought together such that the base is reinforced.

6. A freezer container as claimed in any one of claims 1 to 5, wherein parts of the layers which comprise the walls are brought together such that the walls are reinforced.

7. A freezer container, substantially as hereinbefore described, with reference to, or as illustrated in, the accompanying drawings.

8. A refrigeration appliance including a container as claimed in any one of claims 1 to 7.