Cooled and frozen goods are conventionally stored in large cold storages and distributed therefrom to retailers and other customers by means of small refrigerator vans. Each of these vans conventionally contains a refrigerating system comprising an electric motor and a compressor, which is connected to a refrigerant conduit system including a condenser and an evaporator. The refrigerator vans in question each comprises a driver's cab and a thermally insulated box containing the cooled or frozen goods to be distributed.

Doors are provided at one or more sides of the insulated box to give access to the goods therein, and each time a customer is visited one or more of the doors has to be opened.

The rather frequent opening of doors causes a substantial loss of cold air, and this loss has to be compensated for by the built in refrigerating system. Because such refrigerator vans should be able to visit customers in city centres, where the streets may be narrow and where severe traffic restrictions are often met, they are subject to certain restrictions as to maximum weight (usually a maximum total weight of 3,500 kg) and maximum dimensions. On the other hand, for economical reasons it is important to maximise the volume and weight of the cooled or frozen goods, which may be transported by each van.

The use of a central refrigerating system for cooling a plurality of compartments containing goods is generally known, e. g. from EP 0 018 661, DE 27 57 891, GB 2 022 230, and US 4,434,623. However, none of these publications teaches how a vehicle without a built in refrigeration system may be used for distributing frozen goods, which must be kept at a low temperature, to a large number of customers at different locations.

The international application WO 98/35193 discloses a temperature storage device for use in a controlled distribution system, which is removable from a load space, e. g. a vehicle interior, for recharging. The storage device is cooled from an external refrigeration plant, and the weight of each storage device is approximately 800 kg, which means that the devices have to be loaded onto the vehicle by use of a forklift truck.

The present invention provides a method of the above type, which allows for a more economical distribution of cooled or frozen goods than the conventional method described above e. g. because the need for a separate refrigerating system in each vehicle may be dispensed with.

Thus, the present invention provides a method of distributing cooled or frozen goods to customers by means of a plurality of vehicles, each vehicle including a thermally insulated compartment for receiving the cooled or frozen goods to be distributed, said compartment containing a plurality of interchangeable coldness accumulators or refrigerating units, said method comprising connecting the insulated compartment to a separate central refrigerating system and cooling the insulated compartment and its contents to a predetermined low temperature well below the freezing point, loading cooled or frozen goods into the compartment, driving the vehicle and distributing a first amount of cooled or frozen goods from the vehicle compartment to customers, subsequently interchanging at least some of the cold accumulators or refrigerating units with similar accumulators or units having a substantially lower temperature, driving the vehicle and distributing a second amount of cooled or frozen goods from the vehicle compartment to further customers, and subsequently reconnecting the insulated compartment to the central refrigerating system so as to cool the compartment and its contents to said predetermined temperature.

By using the method according to the present invention the previously necessary separate refrigerating system in each individual of the vehicles may be dispensed with and be replaced by one larger central refrigerating system. This means a substantial saving in costs and also a substantial reduction of the net weight of each vehicle or van. Therefore, each vehicle may be built to carry more goods without exceeding a predetermined maximum total weight. It has been found that the loss of coldness from the insulated compartment due to opening of doors may be compensated for by interchanging at least some of the coldness accumulators or refrigerating units, which are sufficiently small to be portable and to allow manual replacement.

When the insulated compartments of the vehicles are connected to the central refrigerating system a cooling medium is circulated from the central system to the compartments connected thereto. This cooling medium may be of any suitable kind. As an example, cooled gas or air may be passed into or circulated within the insulated

compartment connected to the central refrigerating system. Alternatively or additionally, cold liquid, such as brine, may be circulated through a cooling conduit arranged within the compartment.

The central refrigerating system for cooling the vehicle compartments and the store for the frozen goods to be distributed may be positioned at different locations. However, the central refrigeration system is preferably located at or within a refrigeration storage for storing the frozen goods to be distributed and possibly also the coldness accumulators at the desired low temperature.

The method according to the invention may be used not only for distributing frozen goods, but also for distributing goods, which have to be kept at a temperature around or slightly above 0°C. However, when used in connection with distribution of frozen goods the temperature should at all times be kept below minus 18°C and preferably below minus 21°C. In such case the insulated compartments with their contents are preferably cooled to a temperature below minus 30°C, preferably about minus 33°C, when connected to the central refrigerating system.

The present invention further provides a vehicle, which may be used in connection with the method described above, for transporting and distributing cooled or frozen goods to customers, said vehicle comprising a thermally insulated compartment for receiving the cooled or frozen goods to be distributed, a plurality of interchangeable coldness accumulators or refrigerating units mounted within the insulated compartment, conduit means for passing cooling medium into or for circulating cooling medium within the insulated compartment, and connecting means for connecting said conduit means to a separate, central refrigerating system, so as to cool the insulated compartment and its contents to a predetermined low temperature well below the freezing point.

The interchangeable coldness accumulators or refrigerating units may in principle be arranged at any suitable position within the thermally insulated compartment, for example along any of the side walls. However, in order to secure a substantially uniform temperature within the compartment based on natural circulation, the accumulators are preferably arranged at the upper part of the insulated compartment. Thus, for example, the coldness accumulators or refrigerating units may be panel-shaped and mounted

below the ceiling of the insulating compartment, so that air cooled by the accumulators may flow downwards and generate a natural circulation of air.

Preferably, the coldness accumulators or refrigeration units contain a liquid having a freezing point within the temperature range within which the frozen goods should be kept.

Thus, the liquid is in a frozen condition when the compartment has been cooled by the central refrigerating unit and also when accumulators are used for replacing other accumulators in the compartment as explained above. This means that heat in air flowing into the compartment when doors are opened may be absorbed by the coldness accumulators and used as melting heat. As an example, the coldness accumulators or refrigeration units may be closed plastic containers containing a liquid having a freezing point in the range of minus 33°C to minus 23°C. An example of such liquid is an eutectic solution of magnesium chloride having an eutectic point of minus 33°C.

Preferably, the weight of each coldness accumulator is between 5 and 20 kg, such as 8 and 17 kg, such as 10 and 15 kg, so that they can be interchanged by hand and so that a truck or other equipment is not needed for that purpose. The coldness accumulators to be inserted in the compartment can be stored at different locations, e. g. along the driver's distribution route, but preferably at the same location as the cold store for the frozen goods. Thus, the driver can, at the same time as a second amount of frozen goods is loaded, interchange the accumulators with accumulators having a lower temperature.

As the insulated compartment comprises a plurality of interchangeable coldness accumulators, the driver usually only has to change some of the accumulators and not the entire compartment, when the temperature within the compartment becomes too high.

Even though natural circulation of air within the compartment may be sufficient, air- circulating means for circulating air within the compartment may be provided. In such case the operation of the circulating means may be stopped when compartment doors are open.

The invention will now be further described with reference to the drawings, wherein Fig. 1 is a diagrammatic perspective view showing a central cold storage and a central refrigerating system for servicing a plurality of vehicles or vans, and

Fig. 2 is a diagrammatic perspective view of a box or compartment of one of the vans shown in Fig. 1 for containing frozen goods, a pair of the walls having been removed.

Fig. 1 shows a plurality of vehicles or vans 10 each comprising a driver's cab 11 and a box or compartment 12 having doors 13 in one or more of its side walls. The vans 10 are arranged around a building 14, which contains a supply of frozen goods (not shown) and a central refrigerating system 15. The refrigerating system 15 produces cold air at a very low temperature, for example about minus 40°C. The inner space of a van compartment 12 can be realisably connected to the cold air supply of the refrigerating system 15 by means of any of a plurality of cold air supply conduits 16.

Fig. 2 diagrammatically illustrates the arrangement of the inner space of one of the boxes or compartments 12. In Fig. 2 a sidewall comprising the doors 13 and a top wall or ceiling have been removed, and only a thermally insulated floor wall 17, a pair of opposite insulated end walls 18, and an insulated sidewall 19 are shown. The inner space is divided into chambers, which are defined by vertical partition walls 20 and horizontal shelves 21.

A plurality of flat, closed containers 22 are replaceably arranged in the upper part of the compartment 12. The containers 22 may be flat plastic containers containing an eutectic solution of magnesium chloride. Each of the containers 22 may be retained by a pair of channel-like rails 23, which receive opposite, parallel edge parts of the containers. A section of the rails 23 next to the doors 13 may be hinge-connected so that they may be pivoted between a horizontal position and a substantially vertical position as shown in Fig.

2.

The plant described above may be used as follows : When the vehicles or vans 10 return to the building 14 containing the central refrigerating system 15 in the evening in a more or less empty condition they may be loaded with additional cooled or frozen goods and connected to the central refrigerating system via the conduits 16. Thereby the thermally insulated compartments 12 of the vehicles 10 and their contents, which may include the goods and the containers or coldness accumulators 22, are cooled down to a low temperature, such as minus 33°C or lower, during the night. In the morning the drivers only need to disconnect the vehicles 10 from the central refrigerating system 15 before

they can start distributing the frozen goods to the customers. During the day the doors 13 of the vehicle compartment 12 will be opened several times. Therefore, the temperature within the insulated compartment eventually rises slowly. Well before the temperature reaches a predetermined maximum value, such as minus 21°C, the driver has to return to the central refrigerating system or central cold store and replace at least some and preferably all of the interchangeable containers 22, which have a substantially lower temperature, such as minus 33°C. At the same time the driver may fill further frozen goods into the insulated compartment of the vehicle or van 10, if necessary. Such replacement of the containers 22 and possible refilling of goods may conveniently take place, for example in connection with the driver's lunch break or any other time when the driver has to return anyhow. Thereafter, the distribution of goods may be continued the rest of the day. When the driver returns to the central refrigerating system at the end of the day, the insulated compartment may be refilled with goods and connected to the central system to make ready for the following day.