BACKGROUND Using containers for air transportation of temperature- sensitive goods has been known for a long time. These known containers have inter alia been provided with thermally insulating walls and with cooling units or other coolants in order to keep the goods in the container at or below a desired temperature in the event of too high an ambient temperature.

An example of known containers is those in which dry ice is used in order to keep the goods at or below a predetermined temperature. Using dry ice affords a number of advantages; it is relatively inexpensive and makes possible very simple construction of the receptacle which is used with the dry ice. Moreover, the use of dry ice requires no electric supply from a battery or external power source. The use of dry ice nevertheless suffers from a number of serious disadvantages. In the case of large quantities of goods (volumes), a large quantity of ice is required, which increases the cost and furthermore makes handling impractical. Dry ice also provides a passive cold which cannot be regulated. The quantity of dry ice has to be dimensioned depending on the ambient temperature prevailing during transport relative to the desired temperature for the goods and also the quantity of goods transported. When the ice has melted, the

temperature of the goods begins to rise, if the ambient temperature is higher than the desired temperature of the goods, which is entirely unacceptable in the case of temperature-sensitive goods. Moreover, there is also : a risk that the use of dry ice will lead to temperatures of the goods which are too low because this principle is sensitive to the ambient temperature.

An alternative method of regulating the temperature in a receptacle for the transport of goods is to use what are known as Peltier elements. This is described in, for example, American patent specifications US 5,603, 220 A and US 6,260, 360 B1. The use of Peltier elements is based on the principle that a temperature difference can be brought about as a consequence of a voltage across a transition between different materials. Although this provides good temperature control of transported goods, this technique is, for practical reasons and reasons of cost, limited to relatively small volumes. Using Peltier elements in a transport container for air transportation which has an internal volume of 2 m3 or more is therefore not practically or commercially possible. The receptacles described in the abovementioned US specifications are smaller receptacles intended for the transport of, for example, medicines or donated organs. They are portable and are usually moved by one person and are therefore not intended, for example, to be left at an airport waiting for reloading onto another plane for onward transport.

SUMMARY OF THE INVENTION One object of the present invention is therefore to produce a transport container for air transportation of the kind indicated in the introduction, with which the abovementioned disadvantages of the known art are eliminated. One object is therefore to bring about good temperature regulation in a container for air transportation with a volume of at least 2 m3.

The invention is based on the identification of the problem that modern air transportation involves transport between many different temperature ranges and that there is a risk of damage to temperature-sensitive goods at an ambient temperature which is too low.

According to the invention, a transport container for air transportation as defined by patent claim 1 is provided.

Further preferred embodiments are defined in the dependent patent claims.

With the transport container according to the invention, reliable temperature regulation of goods transported by air in the transport container is ensured. By virtue of the fact that the unit for temperature regulation not only has a cooling function, as in the known art, but also has a heating function which is made use of when the ambient temperature falls, the need to place the transport container in places which maintain a minimum temperature is avoided.

This is of vital importance particularly in the case of air transportation where it is not possible to predict the ambient temperatures to which the container will be exposed. With the transport container according to the invention, it is moreover ensured that an uninterrupted transport chain from door to door can be maintained without the risk of the goods being damaged or ruined.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail with reference to the accompanying drawings, in which : fig. 1 shows diagrammatically a perspective view of a container according to the present invention; fig. 2 shows a longitudinal, partial section through the container shown in fig. 1;

fig. 3 shows a view from the front of a temperature regulator included in the container with the front plate mounted; fig. 4 shows the regulator shown in fig. 3 with the front plate removed; fig. 5 shows a partial sectional view from the rear of the regulator shown in fig. 3, from which the positioning of an evaporator can be seen; fig. 6 shows a side view partly in cross section of the regulator shown in fig. 5 along the line VI-VI in fig. 5; fig. 7 corresponds to fig. 5 but shows the positioning of a heating element, and fig. 8 shows an alternative embodiment in which phase change material is used.

DETAILED DESCRIPTION OF THE INVENTION A detailed description of the invention will be given below, initially with reference to fig. 1. The figure shows a container 1, which has a bottom 2 and four walls 3,4, 5, 6 rising vertically from this. The container 1 also has a top 7 which holds the walls together. All these elements comprise a framework 8 which is covered with aluminum plates 9 (see fig. 2).

The space formed between the inner and outer aluminum plates is filled with an insulation material 10, preferably polyurethane foam, such as the material marketed under the brand Divinycell@. On one of or both the longitudinal sides of the container 1, there are lockable doors 11, which can easily be opened and closed for filling or emptying the container 1.

The end wall 6 has a cutout 12 (see fig. 2), which is delimited by a reinforcement in the wall element itself

for easily exchangeable mounting by means of bolts or the like of a separate temperature regulator 14, which is intended to maintain a constant, desired temperature in the goods space 13 of the container 1 irrespective of where in the supplier/customer transport chain it is. This temperature regulator 14 is shown mounted in fig. 1 and has been provided with standardized dimensions in order for it to be possible for it to fit in different container sizes and models, and its mounted position is indicated by dashed lines in fig. 2.

The temperature regulator 14, which will now be described in detail, has a square front side (see fig. 3) and a lateral appearance which is inclined at the upper, inner corner (see figs 2 and 5). It is divided into two mutually separate spaces : an outer space 14a which faces toward the outside of the container and an inner space 14b which faces toward the interior of the container. The extent of the outer space 14a is shown by dashed lines in fig. 6 and during normal use it is covered by a cover plate with a cutout for a regulating panel 15 and cutouts provided with gratings for ventilation of the outer space.

The regulating panel 15 is used for controlling the operation of the temperature regulator. It has a keyset and a display and can in this way provide the functions necessary for operation, such as on/off, timer, defrosting times, indicator and warning lamps etc.

Connections for an external electric supply are also located on the regulating panel.

In addition to the regulating panel 15, the outer space 14a of the temperature regulator 14 comprises (see fig. 4 which shows a front view with the cover plate removed) a thermostat-controlled compressor 22, a condenser 23 connected to the compressor, a motor 24

for operating the compressor 22, fans (not shown), batteries 19, and a battery charger (not shown).

The compressor 22, which is a two-cylinder compressor, is mounted in the space 14a via shock-absorbing and vibration-damping means. The compressor is driven by means of a belt by the motor 24, which is a brushless electric DC motor. This choice of motor affords advantages compared with the conventional motors found in known containers because the functioning of the compressor can be controlled in a more accurate way.

The built-in power source consists of two parallel- connected 24 V maintenance-free lead batteries 19.

These can be charged by means of an external electric source which is connected via the connections on the regulating panel 15. A possible external electric supply is either up to 230 V AC, 50-60 Hz, or 24 V DC.

Regulation of the electric system including battery charging takes place by means of the battery charger.

The battery charger is not in operation while flying.

Separate electric fans (not shown) cause air to circulate around the compressor 22 and the condenser 23. The air flow through the condenser 23 can also ventilate the compressor motor 24 and the battery space.

The condenser is connected via a throttle valve (not shown) to an evaporator 20, which is located in the inner, fan-equipped space 14b (see fig. 5). In this way, by compressor cooling, heat can be taken up from the goods space 13 of the container 1 to the inner space 14b where it is taken up by the evaporator 20 and conveyed to the outer space 14a for onward conveyance to the surrounding environment. In order to strengthen the heat flow between the goods space and the inner space of the temperature regulator, a fan 25 is

arranged in an opening in the plate which covers the inner space (see fig. 6).

Also arranged in the inner space are electric heating elements 21 which, in the preferred embodiment, have a combined power of 400 W. These heating elements are connected to the electric system of the temperature regulator and can therefore, controlled by the functions of the regulating panel 15, heat the air in the inner space 14b. This hot air can be blown into the goods space 13 of the container by means of the fan system of the inner space. Furthermore, the heating elements 21 are positioned against the plate behind, as a result of which this is heated and contributes to heating of the goods space, and this contributes to accurate temperature regulation of this space. By virtue of the heating function, the regulatable temperature range of the transport container is moreover increased and is made essentially independent of the ambient temperature.

In the preferred embodiment, the cooling capacity is dimensioned for 1.0 kW at-10/+40°C. The temperature range for thermostat operation is normally adjustable between approximately +2°C and +20°C using a two-stage neutral zone thermostat but can be adjusted outside this range for special transports. This provides the container according to the invention with an advantage because the temperature can also be maintained above the ambient temperature.

A selected temperature can be maintained in the goods space 13 throughout transport from door to door even at very low ambient temperatures. With continuous connection to an external electric source, a selected temperature can be maintained for an unlimited time.

For temperature-monitoring of the goods transported in the container, sensors are arranged inside its freight

space, which sensors are connected to a digital temperature regulating unit (not shown) and indicate the temperatures which have applied throughout transport. In this way, confirmation can be obtained that the goods have always been within the correct temperature range.

Transport from door to door can take place in the following way. First, the goods to be transported are cooled down to the correct temperature, before they are loaded for transport. When the container is to be transported by truck to, for example, an airport, the temperature regulator can be driven by the truck batteries (24 V) during transport. At the airport, the temperature regulator can be connected to up to 230 V AC if the container has to wait for loading or departure. When the aircraft is on the ground and in the air, the regulator is driven by its own batteries.

During the flight itself, no charging of these batteries takes place owing to safety regulations.

The defrosting function of the temperature regulator 14 automatically stops the compressor 22 and the condenser fan for approximately twenty minutes at three-hour intervals.

The temperature regulator 14 is protected by relays, which disconnect the regulator when the voltage is too low or the current is too high or a short-circuit occurs.

In an alternative embodiment of a temperature regulator, designated generally by 14'in fig. 8, what is known as a Phase Change Material (PCM) is made use of in order to extend the period of operation in the case of battery operation and also to provide extra back-up in the event of operational disruption. PCM means materials with which use is made of the latent

energy required for converting the material between solid and liquid phase.

The heat from the condenser 23 is usually dumped to the surrounding environment without contributing to any useful work. In the case of ambient temperatures which are lower than the temperature inside the container, heat leaks out of the container. If the goods in the container are to maintain the correct temperature, additional heat is therefore required. In the first embodiment, this heat is generated by means of the electric heating elements 21. If there is a requirement for heat when there is no access to an external voltage source for the container, the power has to be drawn from the battery. As the battery capacity is limited, this is a"costly"way of heating.

Fig. 8 shows how a PCM store 31 with a suitable melting point, such as roughly +20°C to +35°C, is arranged in such a way that it takes up heat from the condenser.

The heat can in this way be stored in what is known as a heat battery.

When the ambient temperature falls, the cooling unit is shut off. The air flow inside the container is redirected by means of a fan 32 from first having passed through the cold evaporator to now passing through the heat battery, as can be seen from the arrows in fig. 8. During passage through the heat battery, the PCM gives off its latent heat to the air.

The process continues for the time it takes for the PCM to solidify.

In the same way, a cold store (PCM battery) 33 is integrated in proximity to the evaporator. The PCM has a melting point of roughly-15°C to 0°C.

This store is made to solidify when there is access to an external voltage source. During the solidification

process, the latent heat from the PCM is supplied to the evaporator. When the solidification process is complete, the PCM battery is charged.

If the cooling system in the container suffers an operational stoppage, the"reserve cold"can start to function. This takes place by a cold air flow being made to pass through the PCM battery (cold store) with the aid of a small free-standing fan 34 which is driven by a small separate battery. The capacity of the cold store is determined by the quantity of PCM and the geometrical construction of the cold battery. When all the PCM has been melted, the cooling capacity is used up.

Preferred embodiments of a transport container according to the invention have been described. It will be understood that these can vary within the scope of the accompanying patent claims. The outer shape of the transport container as well as the shape of the temperature regulator can therefore be varied as required.

An external power source or batteries have been mentioned as an energy source. It will be understood that the top of the container can be provided with solar cells, which provide supplementary charging of the batteries, which takes place if the container is located outside.

In the event of faults on the components present in the container or if the temperature is for some reason not within the range set, there are light/alarm devices, which immediately alert personnel that action must be taken.

Heating elements with a combined maximum power of 400 W have been described. It will be understood that both the heating capacity and the cooling capacity can be

dimensioned according to the volume of the goods space 13 of the transport container and other relevant parameters, such as the degree of insulation. This can be effected simply on a temperature regulator of the type described, for volumes greater than 2 m3 as well.

It is also therefore possible to imagine heating capacities exceeding 400 W, above 600 W as well, or even above 800 W.

The use of PCM batteries has been described. It will be understood that these can be used either in combination with the embodiment shown in figs 1-7 or independently.

In the latter case, the cold and heat stores can be "charged"outside the temperature regulator and put in place immediately before transport. The spaces in which the PCM batteries are positioned are preferably thermally insulated from other spaces, the fans being used when use is made of the PCM batteries.