The present invention relates to a storage container for cooling items or keeping items cool, particularly but not exclusively for storing food items for use in passenger vehicles such as passenger aircraft, and a cooling block suitable for use in such a storage container.

Many airlines offer food to passengers during flights, particularly on medium haul and long haul flights; and may offer 'buy-on-board' food on short haul flights. Such food may for example include sandwiches, wraps, or other food items which must be kept cold until they are to be served in order to comply with food safety regulations, but should not be so cold that they become frozen. In addition they must be stored in a way that is convenient for flight attendants, and enables the flight attendants to dispense the food without difficulty. For example containers should preferably be of a convenient size to carry, and be easy to open to gain access to the food items; in addition the containers must be of a size and shape compatible with storage space on the planes. The use of blow-moulded plastic shells that contain a freezable liquid as a cooling block in such a context is known, but such blow- moulded shells are of non-uniform thickness and have been found to be susceptible to cracking particularly at their corners, for example if they are accidentally dropped. Similar issues arise in the context of railways.

According to the present invention there is provided a storage container with a base, walls and a top which comprise thermal insulation, and with an internal compartment defined in part by a divider sheet, and a cooling block insertable into the internal compartment, wherein the cooling block is of generally rectangular shape with rounded corners, and comprising at least one generally rectangular shell containing a freezable liquid, the shell comprising two injection-moulded half-shells of substantially uniform thickness that are welded together around their periphery.

In another aspect the present invention provides a cooling block for use in such a storage container.

The half-shells may be formed of a plastic which changes colour when cooled to below a threshold temperature below the freezing temperature of the liquid. For example they may be of polypropylene, and may include a dye which changes colour below -10°C assuming that the liquid freezes at 0°C, so that in this case the threshold temperature for the plastic would be below -10°C. The threshold temperature may for example be -20°C. There may be a gradual change of colour with decreasing temperature, for example the plastic being white at temperatures above a first threshold such as -10°C, and changing to pale blue below that first threshold, and becoming gradually darker as the temperature becomes lower, and changing to dark blue below a second threshold such as -20°C.

The rounded corners of the cooling block may additionally be provided with a resilient bumper element; for example these bumper elements may be projecting leaf-spring elements integral with a shell at each end of the leaf-spring. The resilient bumpers protect the corners from damage during use, for example if the cooling block were to be dropped.

The liquid within the cooling block may for example be water, but this may be combined with a mould inhibitor (for example propanoic acid, sodium propionate or calcium propionate), and may be combined with a thickener or viscosity-increasing component which may be a cellulose derivative, for example carboxymethyl-cellulose (CMC), optionally as the sodium salt, i.e. sodium CMC, as this compound is not toxic and is safe in contact with food,, and in addition the CMC forms a eutectic mixture with water that results in a lower freezing point.

The internal compartment may be adjacent to the top, or to a side wall, or to the base of the storage container. The storage container may have rigid walls, or flexible walls, to suit its application.

In one example the storage container is a rectangular box-shaped structure comprising a base, two side walls and two end walls that are connected together, and a top; the top being connected to one wall, and being joined by readily-disconnectable fastening means to the other three walls; the base, the walls and the top each comprising an outer sheet of flexible waterproof plastic and an inner sheet of flexible waterproof plastic, between which is a layer of thermal insulation material. The walls, base and top are not perforated, and are impermeable. Hence when the storage container is closed, with the fastening means closed to secure the top to the walls, there is no free flow or circulation of air between the inside and the outside of the storage container. So the air within the storage container is cooled by the cooling block and remains cold.

Where components of the storage container are said to be "connected" together, and are of the same type of material, they may be integral with each other, or may be fixed together by any convenient assembly method such as gluing, welding or sewing.

Such a storage container is lightweight, but provides satisfactory thermal insulation. In one such type of storage container three of the walls are connected to the base, and the divider sheet is a flexible sheet connected to each wall so as to lie just above the base. In this case the cooling block can be inserted into the bottom of the storage container, fitting between the base and the sheet, through a gap between the edge of the base and the wall to which it is not connected.

The outer sheet and the inner sheet of flexible waterproof plastic may each be of waterproof polyvinylchloride (PVC), as this is reasonably hard wearing and waterproof, and is safe in contact with food items. The thermal insulation is preferably a layer or fabric of hollow fibre wadding, for example polyester wadding fabric, and may be between 2 oz and 8 oz wadding (70 g/m and 270 g/m ), for example 4 oz wadding (135 g/m ), consisting of polyester fibres that are bonded together to form a highly porous fabric. Alternative types of thermal insulation would include wadding or batting made of fibres of cotton or wool, that may be resin bonded.

The fastening means may comprise hook-and-loop fasteners such as Velcro™, or poppers, or may use a zip fastener.

The divider sheet may for example be a polyester dipped mesh netting, and may be between 50 and 300 g/m ² ; for example this may be 220 g/m ² or 100 g/m ² . The mesh may for example define apertures no larger than 5 mm across, and may be less than 3 mm across.

Where the storage container is itself flexible, it may be of such a size as to fit into a rigid tray of a standard size. For example the storage container may be of length 360 mm, width 240 mm and height 100 mm.

In a third aspect the invention provides a storage system comprising a plurality of rigid open-topped trays, and a plurality of flexible-walled storage containers as specified above that are of such dimensions as to fit into the open-topped trays, each storage container comprising a cooling block. Such rigid trays may fit into a fixed storage cabinet, for example being supported by rails within the storage cabinet; and the rigid trays may also be transferred into a wheeled trolley to rest on rails within the wheeled trolley.

Thus in the context of an aircraft there may be a fixed storage cabinet for example in a staff-accessible part of the aircraft, in which the food items can therefore be stored during an initial part of a flight. When flight attendants wish to dispense the food items, the trays may be placed into the attendant's wheeled trolley without opening the storage containers. Hence the contents of each storage container may be kept cool until the attendant opens the lid and dispenses the items. This would be equally applicable on a railway, if catering staff are dispensing food items from a trolley.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a storage container of the invention, when closed; Figure 2 shows a sectional view on the line 2-2 of figure 1;

Figure 3 shows a sectional view on the line 3-3 of figure 1, along the middle of the storage container from front to back, but with the container in the opened state;

Figure 4 shows a perspective view of a tray in which the storage container of figure 1 fits, the storage container being indicated in broken lines;

Figure 5 shows a plan view of a cooling block of the storage container of figure 1;

Figure 6 shows a sectional view of the cooling block on the line 6-6 of figure 5;

Figure 7 shows one corner of an alternative cooling block for use in the storage container of figure 1;

Figure 8 shows a sectional view on the line 8-8 of figure 7;

Figure 9 shows a plan view of another alternative cooling block for use in the storage container of figure 1;

Figure 10 shows a perspective view of the cooling block of figure 9, with the base part and top parts separated; and

Figure 10a shows a view to a larger scale of one corner of the base part of the cooling block as shown in figure 10.

Referring to figures 1, 2 and 3, a storage container 10 is of generally rectangular box like shape with a top 11, bottom 12, front wall 13, back wall 14, left wall 15 and right wall 16 (the left wall 15, back wall 14 and bottom 12 are not shown in figure 1), each of which is of sandwich construction, consisting of an inner lining 20 of light duty PVC sheet (for example 210 g/m ), a layer 21 of hollow fibre fabric wadding (for example 115 g/m ) to provide thermal insulation, and an outer sheet 22 of heavy duty waterproof PVC (for example 610 g/m ² ). In the example shown, the back wall 14 is integral with the top 11 and the bottom 12, as shown in figure 3; the left wall 15, the front wall 13 and the right wall 16 are integral with each other. The left wall 15 and the right wall 16 are connected to the back wall 14 along the edges where they meet, for example by sewing; and the left wall 15 and the front wall 13 are connected to the bottom 12 along the edges where they meet, for example by sewing.

The top 11 is connected by two heavy duty nylon zips 25 to the tops of the side walls 15 and 16 and two the top of the front wall 13. Within the storage container 10, as shown in figures 2 and 3, a sheet 26 of polyester dipped mesh netting is connected to the walls 13-16 adjacent to the bottom of each wall 13-16, so it is a short distance, for example less than 10 mm, above the bottom 12. As shown particularly in figure 2, the right wall 16 is not connected to the bottom 12, so there is a narrow slot 28 below the bottom of the right wall 16, through which a cooling block 30 can be inserted to fit between the bottom 12 and the sheet 26. This may for example be a plastic-walled chamber containing water that has been cooled well below freezing point so that it is ice, which may for example be at -20°C when first inserted into this position. The sheet 26 may define square holes of width 4 mm or 3 mm, so air can circulate through the sheet 26.

As shown in figure 4, the dimensions of the storage container 10 may such as to fit into a rigid tray 32. For example the storage container 10 may be of length 360 mm, width 240 mm and height 100 mm, in order to fit into a rigid tray 32 with corresponding internal dimensions. In the context of an aircraft, there may be a food storage cabinet with multiple rails or shelves to support such rigid trays 32, so that food can be kept cool within storage containers 10 that are placed in these rigid trays 32 and stored in the cabinet. The trays 32 are of such a size that they can be easily handled. When foodstuffs are to be dispensed to passengers, a number of these trays 32 can be placed into corresponding shelves or locations on a serving trolley. A flight attendant can then readily open one storage container 10 at a time to dispense items from it, ensuring that the items in the unopened storage containers 10 remain cold.

The storage container 10 is described by way of example only. It will be appreciated that it can be modified in various ways while remaining with the scope of the invention as defined by the claims. It may for example have different dimensions, although it is desirable that the storage container 10 packed with food items should not be so heavy as to be inconvenient for a crew member to handle. The top 11, the bottom 12, and the walls 13-16 of the storage container 10 as described above are flexible and lightweight, and it will be appreciated that in a modification at least some of these components may be rigid, for example comprising sheets of a rigid thermal insulation, such as expanded polystyrene.

Referring now to figure 5, this shows a plan view of the cooling block 30, partly broken away. The cooling block 30 consists of a hollow plastic shell 33 generally of rectangular shape, with rounded corners. At one point along the periphery there is a recess 34 in which is an inlet port 35 through which the cooling block 30 can be filled with a suitable liquid, the inlet port 35 then being sealed closed.

Referring also to figure 6, the hollow plastic shell 33 comprises two injection- moulded half-shells 36 and 37, which over the top and bottom surfaces of the shell 33 are of substantially uniform thickness. There are a number of grooves or linear depressions 38 (two of which are shown in figure 5) along which the half-shells 36 and 37 are depressed towards each other so that along those lines the top and bottom walls of the shell 33 are in contact with each other, as shown in figure 6. These grooves or linear recesses 38 enhance the stiffness of the top and bottom surfaces of the shell 33. Around the periphery of the shell 33 the half-shells 36 and 37 curve to meet each other at opposed mating surfaces, so as to form a peripheral wall 39 of the hollow plastic shell 33. At each corner 40 of the plastic shell 33, the peripheral wall 39 is rounded, as shown in figure 5; and a plastic leaf spring 42 surrounds the corner 40, the leaf spring 42 being connected to and integral with the shell 33 at each end of the leaf spring 42, but being spaced away from the peripheral wall 39 along the rest of its length. The top half of the leaf spring 42 is initially integral with the top half-shell 36 while the bottom half of the leaf spring 42 is initially integral with the bottom half-shell 37.

As indicated in figure 6, the top half-shell 36 as initially manufactured defines a groove 44 around its entire periphery along the mating surface, and also a groove 46 around the mating surface of the top half of the plastic leaf spring 42. Similarly the bottom half-shell 37 as initially manufactured defines a projecting tongue 45 around its entire periphery along the mating surface, and also a projecting tongue 47 along the mating surface of the bottom half of the leaf spring 42. During manufacture, the half-shells are manufactured separately, by injection moulding, which ensures that the desired thickness is attained in all regions. The half-shells 36 and 37 are then brought together, so the tongue 45 fits into the groove 44 and the tongues 47 fit into the grooves 46; and the half-shells 36 and 37 are then welded together along those engaging portions. This may for example use hot wire welding or sonic welding.

The plastic of which the hollow plastic shell 33 is made is polypropylene which is coloured with a dye which is temperature sensitive. In this example the polypropylene is white at temperatures above -10°C; the polypropylene is dark blue at temperatures below - 20°C; and between -10° and -20°C the colour gradually changes through light blue to dark blue.

During manufacture, after the hollow plastic shell 33 has been made in the manner described above, a liquid would be introduced through the inlet port 35 to fill most of the volume within the hollow plastic shell 33. This may for example be an aqueous solution thickened with sodium CMC, and provided with a mould inhibitor. The inlet port 35 would then be sealed closed. This produces the cooling block 30. When the cooling block 30 is to be used, it is placed in a freezer, and left for sufficient time that it has gone blue, indicating that its temperature is below -20°C. It is then inserted into the storage container 10 through the narrow slot 28 into the space between the bottom 12 and the dividing sheet 26 as described above. It has been found that this arrangement ensures that items (such as sandwiches) placed in the storage container 10 are kept cool for several hours, without being frozen themselves.

Where multiple cooling blocks 30 are to be cooled down for insertion into multiple storage containers 10, the colour change of the plastic below -10°C, and more particularly below -20°C, makes it easy to ensure that all the cooling blocks 30 are at the required cold temperature before they are inserted into the respective storage containers 10. If the cooling block 30 is accidentally dropped, the projecting leaf springs 42, in combination with the consistent thickness of the wall of the shell 33 significantly reduce the risk of cracks being formed. Hence the cooling blocks 30 are considerably more reliable and hard wearing than those known hitherto.

The cooling block 30 described above may be modified in various ways while remaining within the scope of the invention as defined in the claims. Referring now to figures 7 and 8 there is shown an alternative cooling block 50 which in many respects is the same as the cooling block 30 described above, in that it is made of the same type of temperature-sensitive plastic. Figure 7 shows a plan view of the cooling block 50, showing only one corner. The cooling block 50 consists of a hollow plastic shell 53 generally of rectangular shape, with rounded corners. Near one corner the plastic shell 53 defines a recess 52 in which is an inlet port 54 through which the cooling block 50 can be filled with a suitable liquid, the inlet port 54 then being sealed closed with a stopper 55. The stopper 55 does not project above the top surface of the plastic shell 53.

As shown in figure 8, the hollow plastic shell 53 comprises two injection-moulded half-shells 56 and 57, which over the top and bottom surfaces of the shell 53 are of substantially uniform thickness. Around the periphery of the shell 53 the half-shells 56 and 57 curve to meet each other at opposed mating surfaces, so as to form a peripheral wall 59 of the hollow plastic shell 53. At each corner 60 of the plastic shell 53, the peripheral wall 59 is rounded, as shown in figure 7; and a projecting arch or leaf spring 62 surrounds the corner 60, the projecting arch or leaf spring 62 being connected to and integral with the shell 53 at each end of the projecting arch or leaf spring 42, but being spaced away from the peripheral wall 59 along the rest of its length. The top half of the projecting arch or leaf spring 62 is initially integral with the top half-shell 56 while the bottom half of the projecting arch or leaf spring 62 is initially integral with the bottom half-shell 57. During manufacture, the half-shells 56 and 57 are manufactured separately, by injection moulding, which ensures that the desired thickness is attained in all regions. Each half-shell 56 defines mating surfaces that are intended to mate to corresponding mating surfaces of the other half-shell 57. These mating surfaces may include tongues 45 and 47 and grooves 44 and 46 as shown and described in relation to figure 6 above; such features are not shown in figure 8. The half-shells 56 and 57 are then brought together, and are then welded together along those mating surfaces. This may for example use hot wire welding.

The plastic of which the hollow plastic shell 53 is made is polypropylene which is coloured with a dye which is temperature sensitive. In this example the polypropylene is white at temperatures above -10°C; the polypropylene is dark blue at temperatures below - 20°C; and between -10° and -20°C the colour gradually changes through light blue to dark blue.

During manufacture, after the hollow plastic shell 53 has been made in the manner described above, a liquid would be introduced through the inlet port 54 to fill most of the volume within the hollow plastic shell 53. This may for example be an aqueous solution thickened with sodium CMC, and including a mould inhibitor. The inlet port 35 would then be sealed closed with the stopper 55. This produces the cooling block 50.

Referring now to figure 9, this shows a plan view of an alternative cooling block 70, which may be of the same overall dimensions as the cooling block 30 or the cooling block 50 described above. For example it may be 246 mm x 323 mm in plan, and of thickness 13 mm to fit in the storage container 10 of figure 1. The cooling block 70 defines four hollow plastic shells 73 of generally rectangular shape, with rounded corners. Each plastic shell 73 defines a recess and port 74 on its upper surface, through which the plastic shell 73 can be filled with a suitable liquid as described above, after which the port 74 is sealed with a stopper which may be the same as the stopper 55 shown in figure 8, such that the stopper does not protrude above the top surface of the plastic shell 73.

Referring also to figure 10, the cooling block 70 comprises an injection-moulded base part 75 of substantially uniform thickness, defining four generally rectangular recesses 76 (corresponding to the four hollow shells 73) held together by a web 77, and at each corner of the base part 75 there is a curved projecting leaf spring 80 attached at each end to the wall of the adjacent recess 76 to act as a protective bumper. The cooling block 70 also comprises four substantially flat top plates 82. During assembly each top plate 82 is welded around its rim, for example by sonic welding, to close the top of one of the rectangular recesses 76, so forming the hollow shells 73. By way of example the top of the wall of each recess 76 may define a step all around its periphery, and the top plate 82 may define a corresponding downward-projecting flange around its rim, to mate with the step. This ensures correct alignment of the top plate 82 onto the wall of the recess 76, and assists in ensuring a reliable weld. (The mating step and flange are equivalent to the groove 44 and tongue 45 as shown and described above in relation to figure 6.)

Each top plate 82 defines a circular depression 84 at its centre, and a corresponding circular protrusion is similarly defined at the centre of each of the recesses 76, such that when the top plate 82 is welded to the wall of the recess 76, the circular depression 84 rests on the corresponding circular protrusion at the centre of the recess 76, so that the components defining the top and bottom walls of the shell 73 are in contact in an equivalent way to that in which the grooves 38 contact each other in the cooling block 30 as shown in figure 6.

It will be appreciated that a cooling block of the invention may differ from those described above in a variety of different ways while remaining within the scope of the invention, which is defined by the claims. For example the cooling block may have different overall dimensions, particularly if it is for use in a different application. The plastic used to form the or each shell may differ from that described above, and the thermochromic dye

incorporated in the plastic may be of a different colour to that described above. Where there are a plurality of hollow shells that form a cooling block, as in the cooling block 70, there may be a different number to that described above. Furthermore, the linking element between such a plurality of hollow shells, corresponding to the web 77, may be flexible to allow bending of one part of the cooling block relative to another, which may be

advantageous during insertion into a storage container.