GB1569134A

GB1569134A - Res in a heat-insulated container method and apparatus for storing goods at stable temperatu

Info

Publication number: GB1569134A
Application number: GB4214076A
Authority: GB
Original assignee: Astra Sjuco AB
Current assignee: Astra Sjuco AB
Priority date: 1976-10-11
Filing date: 1976-10-11
Publication date: 1980-06-11

Description

(54) METHOD AND APPARATUS FOR STORING GOODS AT STABLE TEMPERATURES IN A HEAT-INSULATED CONTAINER (71) We, AS1RA-SJUCO AKTIEBOLAG, a Swedish Body Corporate, of Box 1144, 453600, 172 04 Askim, Sweden, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method and apparatus for storing goods which are highly sensitive to deviations from a specific given temperature. It is previously known to store goods which are sensitive to changes of temperature in thermally insulated containers in which socalled cooling blocks are housed. One simple example of such a container is that used by housewives to store food.In this case, the interior of the thermal container need only be kept cool for a relatively short peroid of time. Because of this, and because direct contact of the food with the cooling block is not normally harmful, it suffices to freeze the block to the necessary temperature prior to using the same. The block can be chilled to the required temperature in a domestic refrigerator for example.

In their simplest form, the cooling blocks are filled solely with water, which, when frozen, has a high heat of fusion and consequently is able to maintain the food in a cool environment for a considerable period of time. Such an apparatus is effective to keep food wholesome or to keep beverages cool for a certain period of time at ambient temperatures which lie above the desired storage temperatures.

In the case, however, of the storage or transportation of blood, blood components including serum, or living or dead bacteriological or biological substances including vaccines, or enzymes, or pharmacological substances (hereinafter called "the goods" in this Specification), measures must be taken to ensure that the goods to be stored can be constantly kept within a predetermined specific temperature range, often at extremely close tolerances. Blood, by which is meant predominantly transfusion blood, must be maintained within the temperature range +1 to +6"C during its passage between donor and receiver.The aforementioned apparatus using cooling blocks filled with water is not suitable for the storage of blood within the above-mentioned temperature range, particularly when the ambient temperature falls below the committed storage temperature, since the latent heat of fusion of water to form ice is not released until the temperature falls below 0 C, moreover super-cooling phenomena readily occur.

A further temperature-stable apparatus for storing and transporting goods which are sensitive to temperature change is described in U.S. Patent No. 2,9089,856.

This apparatus comprises a heat-insulated container in which space is provided for the goods to be stored and for heat-absorbing and heat-emitting substances enclosed in containers which are placed in layers against two mutually opposing walls. According to the U.S. Patent Specification, a temperature of 4 4 C (40"F) can be achieved using a eutectic mixture of sodium chloride and potassium chloride and hydrated sodium sulphate (Na2SO4, low20) in the containers.

In practice, however, it has been found that such an apparatus and the eutectic mixtures are not capable of effectively storing temperature-sensitive goods for long periods, nor of maintaining the stored goods at the necessary temperature. It has been found, in practice, that considerable temperature gradients occur within the stored goods after some time has elapsed, and that the stabilising control medium does not prevent the temperature of the stored goods from passing beyond the given tolerance limits within an acceptable period of time.

Blood banks have been established to ensure that blood given to a patient is of a reliably high grade. Blood banks and similar establishments normally have unlimited access to electrical energy, highly efficient temperature-control storage spaces and control equipment thereby enabling blood to be stored quite safely. Great difficulties are encounted, however, in transferring blood from blood banks to remote places since the blood is no longer usable if its temperature falls below + 1 C or rises above +6 C.

The problems encountered when transporting blood in individual containers which lack any form of energy source to remote hospitals, field hospitals and other locations where blood transfusions may be necessary, presents considerable difficulty, particularly as the ambient temperature may vary radically during transport of the blood. These problems cannot be solved with the above-mentioned cooling blocks containing water, the freezing point of which is 0 C. Neither can the problem be solved with the apparatus disclosed in the above-mentioned U.S. Patent Specification, since this apparatus will not ensure that the temperature of the blood stored therein remains stable within the desired 1 -6 C range and will not enable the blood to be stored unimpaired for the requisite period of time.

To reduce the risk of blood being destroyed by excessive chilling and to enable it to be stored within the necessary temperature range, it has been proposed to fill cooling blocks with salt solutions whose solidification points are suitable with respect to the 1 -6 C temperature range in question. In this case, the heat of fusion has been utilised to prevent overheating of the blood. Although such methods have been found satisfactory under certain conditions, they have not been efficient in the long-term storage of blood in widely varying climatic conditions. Moreover, they are incapable of maintaining an environment of constant temnerature within sDecific limits.Eutectic mixtures will not always melt and solidify at an exact solidification temnerature, but will, in practice, melt and solidify at temperatures outside those at which blood can safely be stored.

The present invention is based on the discovery that heavy water and certain organic compounds can be used as temperature control agents to maintain the temperature in an enclosed heat insulated storage zone in the range 1"-6"C.

According to one asDect of the present invention, there is provided a method of storing goods as hereinbefore defined within the temperature range 1"-6"C, wherein the goods are stored in heat exchange communication with a single temperature control compound which is deuterium oxide, undecyl cyanide, 4-bromodecanoic acid or 2-bromo-decanoic acid.

According to a further aspect of the present invention there is provided a storage container for storing goods as hereinbefore defined at 10 to 60C comprising at least two detachable sections, each of which is made of a heat-insulating material and each of which is recessed such that when the two sections are brought together a storage zone is formed between the sections inside the container, and a storage box made of a heat-conductive material accommodated in the storage zone, the storage box being in heat-conducting contact with a sealable vessel containing a single temperature control compound which is deuterium oxide, undecyl cyanide, 4bromo-decanoic acid or 2-bromo-decanoic acid.

As before mentioned, blood fractions must be stored at a temperature of 1"C to 6"C. To achieve this the sealable vessel is filled with a heat-absorbing and heatemitting, temperature-stabilising compound which is deuterium oxide, undecyl cyanide, 4-bromo-decanoic acid or 2-bromo-decanoic acid. These compounds are homogenous, chemical substances which have a more clearly defined solidification temperature/ melting temperature than materials previously used for this purpose. The temperature-stabilising substances proposed in the above-mentioned U.S. Patent Specification comprise eutectics, i.e. different types of salt solutions.The temperature-stabilising compounds used in the present invention have solidification and melting points which lie very close to 4"C, which is what is required for storing transfusorial blood within the permitted temperature range of 1"C to 6"C. The substances can also be stored for long periods without decomposing and can be safely handled without requiring particular protective equipment.

The invention will now be described in more detail with reference to the accompanying schematic drawings, in which : Figure 1 is an exploded view of a storage and transport apparatus having a storage box, the various components of the apparatus being separated from one another and shown in perspective; Figure 2 is a vertical sectional view of the apparatus shown in Figure 1 with the components of the apparatus shown in their in-use position; Figure 3 is a view in perspective of a vessel containing the temperature control compound with part of the vessel being cut-away for the purpose of illustration, and Figure 4 shows a seed crystal producing device which can be located inside the vessel containing the temperature control compound.

The illustrated apparatus for storing and transporting temperature-sensitive goods comprises a container made of a heat-insulating material and having two parts 10, 11 which, in the illustrated embodiment, am of identical construction and thus exchangeable. The two parts 10, 1I are so constructed that when placed one on top of the other there is formed therein a closed heat-insulated space 15 in which temperaturesensitive goods can be stored and in which a storage box 20 containing two sealable vessels 16 can be placed for stabilising the temperature in the space 15.

Each vessel 16 contains the selected temperature control compound and is made from material having good thermal conductivity, such as aluminium. Vessel 16 is provided with a filling hole 17 which can sealably closed by plug 18. The stored goods must not in any way be affected by the temperature control compound in vessel 16, and consequently vessel 16 should be so constructed and, subsequent to being filled, carefully sealed, so that no contact can take place between the compound and the stored goods Storage box 20 is preferably manufactured from a heat-conductive material such as aluminium or copper, and is provided with a closable lid 19.Consequently local heat flows from without or within the box will not initially cause any appreciable change in temperature of the box, but heat flow will be distributed throughout the box walls as a result of the high coefficient of thermal conductivity of the box. The vessels 16 have a planar surfaces which extend at right angles to each other and whose dimensions, relative to the dimensions of the storage box 20, are such that the vessels 16 are in heat-conducting contact with box 20 on all sides the of except one, this excepted side being the Dne which faces the stored goods. In this way, any local change in the temperature of box 20 will be primarily taken up and equalised by vessel 16 and the stored goods will not be affected by such temperature changes until the total heat capacity of vessels 16 have been exhausted.

Lid 19 of box 20 sealably closes the opening of box 20, thereby preventing a fall in temperature within box 20 when the air content thereof is saturated with vapours resulting from evaporation of the stored goods.

Conveniently, the outer surfaces of box 20 are polished or provided with heat-reflecting layers so as to reflect heat radiation to the greatest possible extent.

For the purpose of reducing heat flow from and to the stored goods and to and from the walls of box 20, the inner walls of box 20 and the inner surface of lid 19 are provided with strips of material having a low coefficient of heat-conductivity, such as cork or foam plastics, thereby to prevent direct heat-conducting contact of said walls and lid with the stored goods. The strips are either continuous or in the form of axially spaced sections, and the strips on the vertically extending sides of the box extend parallel to one another to form air gaps therebetween, the air in the gaps forming an insulating layer. The strips also permit limited convection, which assists in equalising local temperature gradients between different parts of the box walls.In a corresponding manner, the sides of vessels 16 facing the stored goods are provided with strips 21, which define air gaps therebetween. The occurrence of temperature gradients can be further reduced by giving box 20 a slightly smaller dimension than space 15 in the heat-insulated container so as to form a gap 22 around the box on all sides thereof. The width of this air gap is preferably 5 to 15 mm, to bring heat transfer to or from box 20 to a minimum. Box 20 is held in a predetermined position in container 10, 11 by means of a multiplicity of spacers 23 arranged on the lid, base and sides of container 10, 11. In the illustrated embodiment, spacers 23 are formed in the heatinsulated container. Spacers 23 between box 20 and container 10, 11 are made of such a material and have such form that heat transmission by conduction is effectively reduced.Preferably, spacers 23 are in point contact with box 20, so as to occupy as little as possible of air gap 22 around box 20.

The heat insulated container 10, 11 is suitably made of foamed polyurethane, conveniently containing in the pores a gas, or other material having a very low coefficient of thermal conductivity. In Figure 2, box 20 is constructed to receive two vessels 16 such that a parallelepipidic space is defined between opposing walls of vessels 16 and box 20. Alternatively, box 20 may be constructed to accommodate only the goods to be stored, in which case vessels 16 are arranged externally of box 20 in heat-conducting contact with two opposing sides thereof.

Conveniently the outer and inner surfaces of the container 20, 11 are resistant to wear and impact. This can be achieved, for example, by integrally foaming the material forming the insulation. Further, the container should be constructed in a manner such that the parts 10 and 11 are diffusion free.

Despite the fact that the temperature control compounds used in the present invention exhibit good properties, they have a relatively low heat conductivity. Consequently, temperature gradients may occur within the stored goods, so rendering heat exchange between the goods and the temperature control compound difficult. The risk of such temperature gradients can be reduced by placing within vessel 16 a heatconducting, suitably metallic member in the form of corrugated plates 24. Alternatively vessels 16 may be provided with flanges, metal wire net or inserts in the form of lattice structures for the same purpose. These inserts or members can be freestanding or may be connected either wholly or partially to the walls of vessel 16 in intimate heat conducting contact therewith.

It has been found in practice that with vessel 16 filled with one of the temperature control compounds used in this invention, a super-cooling phenomenon occurs in cold environments, that is to say, the temperature of the compound can fall below its normal freezing point without solidification.

The release of the latent heat of solidification is delayed by such super cooling, so that the temperature of some parts of the stored goods can fall below the permitted storage temperature. To avoid this problem, vessel 16 is provided with a solidificationinitiating means 25. Sub-microscopic crystals occur randomly during the supercooling process and the solidification-initiating means provides a focal point so that the crystals approach each other in a manner such that a sufficiently large crystal forms and initiates further crystal growth.

One example of a suitable solidificationinitiating means is a temperature-control bimetal element having a stirrup spring or double bent plate spring which at a predetermined temperature causes a tongue-like element to strike a contact surface, the impart causing the substance to solidify before the super-cooling process has proceeded too far. Such a temperature-controlled element operates in the manner of a microswitch. It is also possible, with certain stored goods, to use an enclosed radioactive sample, e.g. of polonium.

To avoid any disadvantage associated with the use of a radio active substance or a device relying upon mechanical movement, vessel 16 is preferably provided with a device utilising the transportation of heat to form what can be termed a seed crystal, which seed crystal then instigates further crystallisation of the temperature control compound. The advantage afforded by such a seed crystal is that it can be formed before the temperature of vessel 16 or the stored goods has dropped to an unsuitably low level before stabilisation of the temperature to magnitudes within the desired temperature range is obtained.

A seed-crystal producing device is shown in Figure 4 of the accompanying drawings.

In the illustrated embodiment, the sealing plug 18 is provided with a through-passing bore through which a tubular sleeve 26 of a material of relatively low heat conductivity extends. Extending through the sleeve 26 is a pin 27, pin 27 being arranged in the sleeve such that only the tip 29 thereof is in direct contact with the temperature control compound 28. In the illustrated embodiment, pin 27 is extended upwardly through the wall of vessel 16 housing plug 18 and beyond plug 18 into a recess formed in the container wall adjacent pin 27 in the closed position of the container. Although the pin is shown to have a head 30 and a collar 32, which sealingly abuts said wall, here referenced 31, it will be understood that the provision of said head and collar is an optional feature. Pin 27 comprises a material of high thermal conductivity, such as aluminium.Assuming a drop in ambient temperature to -250C, the temperature within the recess will fall to about --8"C, and consequently the temperature prevailing at the tip 29 will change accordingly, thereby causing the growth of a seed crystal at said tip. Alternatively the end of the pin remote from said tip can be extended into contact with a surface of said wall. The heat-insulating casing 31 causes in the case of a cold environment, the front of the temperature gradient to migrate slowly inwardly through the casing, whereafter a marked gradient remains.

Consequently, in the part located in the insulated casing 31, pin 27 is subjected to a substantially lower temperature than that prevailing in temperature control compound 28, whereupon, as a result of the termal conductivity of pin 27 and the low thermal conductiviey of sleeve 26 and compound 28, a seed crystal is formed at the point 29 of pin 27 in good time.

WHAT WE CLAIM IS: - 1. A method of storing goods as hereinbefore defined within the temperature range 1 060C, wherein the goods are stored in heat exchange communication with a single temperature control compound which is deuterium oxide, undecyl cyanide, 4bromo-decanoic acid or 2-bromo-decanoic acid.

2. A method according to claim 1 wherein the goods are stored inside a storage box which is not in direct physical contact with the temperature control compound.

3. A method according to claim 2 wherein the temperature control compound is contained inside a sealable vessel and the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. control compounds used in the present invention exhibit good properties, they have a relatively low heat conductivity. Consequently, temperature gradients may occur within the stored goods, so rendering heat exchange between the goods and the temperature control compound difficult. The risk of such temperature gradients can be reduced by placing within vessel 16 a heatconducting, suitably metallic member in the form of corrugated plates 24. Alternatively vessels 16 may be provided with flanges, metal wire net or inserts in the form of lattice structures for the same purpose. These inserts or members can be freestanding or may be connected either wholly or partially to the walls of vessel 16 in intimate heat conducting contact therewith. It has been found in practice that with vessel 16 filled with one of the temperature control compounds used in this invention, a super-cooling phenomenon occurs in cold environments, that is to say, the temperature of the compound can fall below its normal freezing point without solidification. The release of the latent heat of solidification is delayed by such super cooling, so that the temperature of some parts of the stored goods can fall below the permitted storage temperature. To avoid this problem, vessel 16 is provided with a solidificationinitiating means 25. Sub-microscopic crystals occur randomly during the supercooling process and the solidification-initiating means provides a focal point so that the crystals approach each other in a manner such that a sufficiently large crystal forms and initiates further crystal growth. One example of a suitable solidificationinitiating means is a temperature-control bimetal element having a stirrup spring or double bent plate spring which at a predetermined temperature causes a tongue-like element to strike a contact surface, the impart causing the substance to solidify before the super-cooling process has proceeded too far. Such a temperature-controlled element operates in the manner of a microswitch. It is also possible, with certain stored goods, to use an enclosed radioactive sample, e.g. of polonium. To avoid any disadvantage associated with the use of a radio active substance or a device relying upon mechanical movement, vessel 16 is preferably provided with a device utilising the transportation of heat to form what can be termed a seed crystal, which seed crystal then instigates further crystallisation of the temperature control compound. The advantage afforded by such a seed crystal is that it can be formed before the temperature of vessel 16 or the stored goods has dropped to an unsuitably low level before stabilisation of the temperature to magnitudes within the desired temperature range is obtained. A seed-crystal producing device is shown in Figure 4 of the accompanying drawings. In the illustrated embodiment, the sealing plug 18 is provided with a through-passing bore through which a tubular sleeve 26 of a material of relatively low heat conductivity extends. Extending through the sleeve 26 is a pin 27, pin 27 being arranged in the sleeve such that only the tip 29 thereof is in direct contact with the temperature control compound 28. In the illustrated embodiment, pin 27 is extended upwardly through the wall of vessel 16 housing plug 18 and beyond plug 18 into a recess formed in the container wall adjacent pin 27 in the closed position of the container. Although the pin is shown to have a head 30 and a collar 32, which sealingly abuts said wall, here referenced 31, it will be understood that the provision of said head and collar is an optional feature. Pin 27 comprises a material of high thermal conductivity, such as aluminium.Assuming a drop in ambient temperature to -250C, the temperature within the recess will fall to about --8"C, and consequently the temperature prevailing at the tip 29 will change accordingly, thereby causing the growth of a seed crystal at said tip. Alternatively the end of the pin remote from said tip can be extended into contact with a surface of said wall. The heat-insulating casing 31 causes in the case of a cold environment, the front of the temperature gradient to migrate slowly inwardly through the casing, whereafter a marked gradient remains. Consequently, in the part located in the insulated casing 31, pin 27 is subjected to a substantially lower temperature than that prevailing in temperature control compound 28, whereupon, as a result of the termal conductivity of pin 27 and the low thermal conductiviey of sleeve 26 and compound 28, a seed crystal is formed at the point 29 of pin 27 in good time. WHAT WE CLAIM IS: -

1. A method of storing goods as hereinbefore defined within the temperature range 1 060C, wherein the goods are stored in heat exchange communication with a single temperature control compound which is deuterium oxide, undecyl cyanide, 4bromo-decanoic acid or 2-bromo-decanoic acid.

box and the vessel are each located inside a storage zone bounded by a heat insulator.

4. A method according to claim 3 wherein the interior of the vessel is provided with heat-conductive means serving to enlarge the effective heat conductivity area of the interior.

5. A method according to claim 4 wherein the heat-conductive means are in direct contact with the walls of the vessel.

6. A method according to any one of claims 3 to 5 wherein the vessel further comprises crystallisation inducing means to inhibit super-cooling of the temperature control compound.

7. A method according to claim 6 wherein the crystallisation inducing means has the form of a pin having a relatively high heat-conductivity extending through a sleeve having a relatively low heat conductivity, said pin and said sleeve extending sealingly through one wall of the vessel, and wherein one end of said pin protrudes from said sleeve so as to be in direct contact with the temperature control compound, and the other end of said pin extends beyond said one wall.

8. A method according to any one of claims 3 to 7, wherein the vessel is provided on one side thereof with spacer elements having a low heat-conductivity.

9. A method according to claim 8, wherein each spacer element has the form of a continuous coherent strip.

10. A method according to claim 8, wherein each spacer element has the form of axially spaced strip sections.

11. A method according to any one of the preceding claims in which the goods stored is whole blood or a blood fraction.

12. A method according to claim 1 substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

13. A storage container for storing goods as herein before defined at 10 to 6"C comprising at least two detachable sections, each of which is made of a heat-insulating material and each of which is recessed such that when the two sections are brought together a storage zone is formed between the sections inside the container, and a storage box made of a heat-conductive material accommodated in the storage zone, the storage box being in heat-conducting contact with a sealable vessel containing a single temperature control compound which is deuterium oxide, undecyl cyanide, 4bromo-decanoic acid or 2-bromo-decanoic acid.

14. A container according to claim 13, wherein the interior of said vessel is provided with heat-conductive means serving to enIarge the effective heat-conductivity area of the interior.

15. A container according to claim 14, wherein said heat-conductive means are in direct contact with the walls of the vessel.

16. A container according to any one of claims 13 to 15, wherein the vessel further comprises crystallisation inducing means to inhibit super-cooling of the temperature control compound.

17. A container according to claim 16, wherein the crystallisation inducing means has the form of a pin having a relatively high heat-conductivity extending through a sleeve having a relatively low heat conductivity, said pin and said sleeve extending sealingly through one wall of the vessel and wherein one end of said pin protrudes from said sleeve so as to be in direct contact with the temperature control compound, and the other end of said pin extends beyond said one wall and into a cavity formed in the wall of the storage-container adjacent thereto in the closed position of said section or into engagement with said wall.

18. A container according to any one of claims 13 to 17, wherein means are provided for holding the box in a determined position in the zone.

19. A container according to any one of claims 13 to 18, wherein the storage box has inwardly facing surfaces on at least two mutually opposite walls and these inwardly facing surfaces are provided with strips of material of low heat-conductivity, the strips defining therebetween insulating air gaps.

20. A container according to claim 19, wherein the strips are made of cork.

21. A container according to claim 19, wherein the strips are made of foamed polyurethane.

22. A container according to any one of claims 19 to 21, wherein the vessel is arranged within the storage box so all sides of said vessel except one are in contact with cooperating sides of the box, wherein said one side is provided with strips of material of low heat-conductivity defining insulating air gaps therebetween.

23. A container according to any one of claims 13 to 22, in which the storage box is smaller than the zone, so that a heat insulating gap is formed around the box.

24. A container according to claim 23, wherein said gap is from 5 to 15 mm in width.

25. A container according to claim 13 substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.