The present invention relates to a refrigeration system described in the preamble of claim 1.

An essential problem in the refrigeration systems which are used today in refrigerators, refrigerators/freezers, open show-case refrigerators or freezers and the like is to control the temperature in the refrigerated compart¬ ment in a simple, inexpensive and reliable way. This is especially a problem when the goods which are stored in the refrigerated compartment should be stored as close to a predetermined temperature as possible. This problem is even worse when the thermal "load" on the refrigerated compartment shows great variations which is the case in open show-case refrigerators or freezers in shops and which can also be the case in refrigerators and freezers when a big volume of goods at room temperature is put into a refrigerated or freezer compartment.

The object of the present invention is therefore to provide a simple, inexpensive and, with respect to both temperature control and energy consumption, efficient refrigeration system for a compartment, the temperature of which should be kept as close to a predetermined temperature as possible.

The characterizing features of the refrigeration system according to the invention are disclosed in the accompanying claims.

The invention is partly based on the condition that a substance, such as water for example, which has an essentially eutectic phase transformation and which is partly in a solid or frozen state and partly in a liquidated or melted state, has an essentially constant

temperature during freezing or melting and therefore can absorb or emit great amounts of thermal energy, and partly based on the condition that specific substances, such as water for example, solidify or freeze during considerable simultaneous volume change. In the invention the first phenomenon is used to keep the temperature of the refrigerated compartment essentially steady, inde¬ pendent of existing variations in the thermal "load" of the compartment, while the second condition is used to control the supplied refrigerating capacity to the com¬ partment.

The invention will be described in more detail below with reference to the accompanying drawings, which by way of examples show some embodiments of the invention, wherein:

Figs. 1 and 2 schematically and in two perpendicular sectional views illustrate a first embodiment of the invention in an open show-case refrigerator or freezer;

Figs. 3 and 4 schematically and in two perpendicular sectional views illustrate another embodiment of the temperature controlling and refrigeration controlling element in a refrigeration system according to the inven- tion;

Figs. 5, 6, 6A, 7, 7A schematically and by way of example illustrate still another embodiment of the temperature controlling and refrigeration controlling element in a refrigeration system according to the invention;

Fig. 8 schematically and in a sectional view illustrates the invention applied in a refrigerator with a static refrigeration system;

Fig. 9 schematically and in a sectional view illustrates the invention applied in a refrigerator/freezer with a

dynamic refrigeration system;

Fig. 10 schematically and in a sectional view illustrates by way of example temperature controlled sections, according to figs. 5-7, arranged in a refrigerator;

Figs. 11 and 12 schematically and by way of example show an additional embodiment of the temperature controlling and refrigeration controlling element according to the invention; and

Figs. 13 and 14 schematically and by way of example illustrate an application of the invention in a refriger¬ ated compartment, with no refrigerated air flow passing through.

Figs. 1 and 2 show schematically and by way of example an open show-case refrigerator, generally denoted 10, of the kind which is commonly used in shops and which in this embodiment is intended for goods, which shall be kept at a temperature as close to, for example, 0'C as possible and which must not be refrigerated below this tempera¬ ture. The show-case refrigerator is provided with a refrigerant cycle system of a conventional type and comprises a compressor K and an evaporator or refrig¬ erating element 1. A fan 2 with an associated motor M drives an air flow to pass the evaporator, so that a cooled air flow with a temperature essentially below 0'C is obtained downstream of the evaporator 1. The bottom of the compartment in the show-case refrigerator, where the cooled goods, not shown in the drawing, are kept, is formed, according to the shown embodiment of the inven¬ tion, by a number of flat and comparatively thin boxes or containers 3 arranged side by side. The containers are filled with a liquid, preferably water, which has a freezing/melting temperature essentially equivalent to the temperature, which shall be kept in the refrigerated

compartment and which has the characteristics of freezing or solidifying during simultaneous increase in volume. The containers or boxes 3 have rigid, i.e. undeformable, walls with the exception of the bottom side or the lower wall 3a, which is elastic and deformable. When the liquid in a container 3 solidifies to a solid state, the bottom side 3a of the container will consequently belly down to an extent which is depending on how much of the liquid in container 3 has become solid. The boxes or containers 3 which are filled with liquid are arranged above a fixed bottom 4 in the show-case refrigerator, such that there is an elongated, slot-like duct 5 between the bottom side 3a of the boxes 3 and the fixed bottom 4 of the show-case refrigerator. The width of the duct 5 depends on the degree of cooling and consequently the proportion of solid state in the boxes 3. When the freezing of the liquid in a box 3 has reached its maximum, i.e. when all or essentially all liquid is in a solid state, the elon¬ gated duct 5 below the box 3 is considerably reduced, by the fact that the bottom side 3a of the box 3 is close to or partly in direct contact with the fixed bottom 4 of the show-case refrigerator. The cooled air from the evaporator 1, driven by the fan 2, is led through a distribution passage 6 into the elongated duct 5 below the boxes 3. After the passage through the elongated duct 5 the cooled air, which has now reached a temperature essentially equal to the freezing/melting temperature of the liquid in the boxes 3, is led through the open com¬ partment of the show-case refrigerator, above and past the goods in the refrigerator, and is led back to the evaporator 1 via a collecting passage 7.

As the boxes or containers 3 contain a mixture of solid and liquid state, one can realize that the boxes 3 and consequently the compartment above the boxes intended for the storage of goods will keep an essentially steady temperature which is equal to the freezing/melting tern-

perature of the liquid and will not fall below this temperature. Due to the comparatively great amount of thermal energy required for melting the solid phase in the boxes 3, the temperature control in the refrigerated compartment is guaranteed, also when there are great variations in the thermal "load" of the compartment, e.g. as a consequence of variations in the temperature of the surroundings or as a consequence of that additional, warm goods are being put down into the compartment. As the flow area of the elongated duct below the boxes varies as described above, depending on the proportion of solid state in the boxes 3, the refrigeration capacity gene¬ rated by the cooled air flow through the duct is decreas¬ ing also depending upon the proportion of solid phase in the boxes 3, i.e. the generated refrigeration capacity increases if the proportion of solid phase in the boxes 3 is small and decreases if the proportion of solid phase in the boxes increases. When the liquid in a box 3 is maximally frozen to a solid state and no more refrige- ration of the box 3 is required, the elongated duct 5 below the box is at that point essentially closed, such that essentially no or only a small amount of cooled air can circulate through the elongated duct 5 below said box 3. In this way it is automatically achieved that the part of the show-case refrigerator, which has a small thermal "load", is supplied with a small refrigeration capacity. When the air flow through the elongated duct 5 below all the boxes 3 is falling below a specific value, this is detected by a pressure transmitter 8, which detects the pressure drop along the duct 5. When this pressure diffe¬ rence exceeds a specific value, as a result of the fact that the average width of the duct 5 below all the boxes 3 is falling below a predetermined value, the pressure transmitter 8 stops the compressor K. The fan 2 is kept running to transport cold air from the boxes 3 to the storage compartment of the show-case refrigerator not only by heat conduit and convection but also by means of

the air flow generated by the fan 2. While the contents of the boxes 3 are melting, the air flow through the elongated duct 5 is increasing. When the pressure differ¬ ence, mentioned above, drops to a predetermined value, the compressor K is again started.

From the above it is obvious that the liquid in the boxes or containers 3 is chosen with the characteristics of a freezing/melting temperature which is essentially equal to the temperature which shall be kept in the refriger¬ ated compartment. Further, the liquid must have the characteristics of freezing to a solid phase during simultaneous volume increase. Water is preferably being used for temperatures close to 0"C, and the freez- ing/melting temperature can, if necessary, be adjusted to different needs by adding suitable substances. The liquid which is used further preferably can have the character¬ istics of not solidifying to a continuous mass of solids in a liquid phase.

The system for controlling the quantity of the cooled gas or air flow passing the boxes filled with partly frozen liquid, shown in figs. 1 and 2 and described above, can in practice be unreliable and not sufficiently accurate and efficient.

Figs. 3 and 4 show schematically and by way of example an improved design of a box-like element 3 filled with liquid of the kind mentioned above. This box 3 has rigid, undeformable walls all around, and on the bottom side 3a, for example, longitudinal flanges or ribs 3b can be arranged, to obtain flow canals 9 for the cooled gas or air flow on this side of the box. A bellows shaped elastical section 11 is arranged at one end of this box 3, which elastical section 11 will thus catch up the whole increase in volume, when an increasing part of the liquid in box 3 is freezing to a solid state. Owing to

that the length of the bellows shaped section 11 will increase and will effect an element 12 which is connected to or interacting with the free end of the bellows shaped section 11, which element in a suitable way can be used as a sliding throttle or valve element in order to con¬ trol the cooled gas flow in the canals 9. Since the volume of the bellows shaped section 11 of the box 3 is small in comparison with the total volume of the box 3, the variation in volume of the section 11 and thus the movement of the control element 12 can be big. The box or element 3 preferably is arranged in such a way, that the part of the box 3 which is closest to the bellows shaped section 11 is the last part which will freeze to a solid state, i.e. the cooled air flow in the canals 9 is flow- ing from right to left in fig. 4. Preferably it is arranged, such that the liquid in the bellows shaped section 11 never will get enough time to solidify, until the valve element 12 completely will cut off the cooled air flow passing the element or box 3. Damages on the movable, bellows shaped section 11 are prevented by this arrangement.

Fig. 8 shows schematically and in a sectional view a refrigerator, in which an element 3 according to figs. 3, 4 is used to keep the temperature of a compartment 13, which is separated from the refrigerator, as close as possible to a predetermined value. The refrigerator, shown by way of example, has a so called static cooling system, i.e. it has no fan and the air flow is passing the evaporator or the refrigeration element 1 as well as the element 3 by self circulation.

Figs. 9a and 9b show schematically and in a sectional view an alternative embodiment of the refrigerator accor- ding to fig. 8. In this embodiment a pivoting valve 19 is arranged in the vicinity of the refrigeration element 1 and is connected to the end of the elastic bellows shaped

chamber 18 via a connecting link 24. This embodiment has the advantage of a "reversed chimney effect", which can be used behind the refrigeration element to achieve a more efficient air flow above the liquid container 3. When the refrigerator is started and when no part of the liquid in the liquid container 3 is frozen, the control valve 19 will have a position which is shown in fig. 9a. In this position, all the air flow which is passing the back side of the refrigeration element 1 will also be passing the liquid container 3. When the liquid starts to freeze in the liquid container 3, the control valve 19 is pivoted into a position which is shown in fig. 9b, the position of which will throttle the air flow passing the liquid container 3 and an increasingly part of the cooled air flow is passing the valve and not the liquid con¬ tainer 3.

Fig. 10 shows schematically and by way of example a sectional view of a refrigerator/freezer with a dynamic cooling system, i.e. a system in which a fan 2 is used to drive the air flow past the evaporator 1. The refrigerator/freezer comprises a freezer section 14 and a refrigerator section 15 and a separated compartment 16, which is kept very close to a predetermined temperature by means of an element 3 of the kind showed in figs. 2 and 3.

Figs. 5, 6 and 7 illustrate schematically and by way of example another advantageous embodiment of the invention. In the showed example this embodiment is used for cooling box-like storage containers 17, each of which comprises a liquid filled element 3 according to the invention. As best can be seen in fig. 5, this element 3 has on the side which is opposite to the refrigerated container 17, a number of parallel flanges or ribs, in the same way as on the element according to figs. 3, 4. The areas between these flanges constitute flow canals 9 for the cooled gas

or air flow. The liquid filled element 3 has rigid, undefor able walls, and the element is further connected to an elastic, bellows shaped chamber 18 in one of its corners. The chamber 18 is catching up the whole vari- ation in volume of the liquid in the element 3 by its longitudinal variations, when the liquid to a varying degree is transformed to a frozen solid state. Since the volume of the chamber 18 is considerably smaller than the volume of the element 3, the longitudinal variation in the bellows shaped elastic chamber 18 is considerable when the part of the liquid in element 3 transformed to a frozen solid phase varies. The movable free end of the elastic bellows shaped chamber 18 effects a pivotingly mounted valve 19, which is shown most clearly in the enlarged partial views in figs. 6A and 7A, which increasingly throttles and finally completely closes the outlet for the cooled gas or air flow from the canals 9, when the proportion of solid phase in the element 3 increases and consequently also the length of the bellows shaped chamber 18 increases. The chamber 18 may well be located such that the liquid part in the chamber never freezes to a solid state. Damages on the chamber are prevented by this and its secure operation is ensured. The bellows shaped chamber 18 may well be removably connected with the element 3, in order to be easily renewed.

Figs. 11 illustrates schematically and by way of example a sectional view of a refrigerator, in which temperature controlled boxes or containers of the kind showed in figs. 5-7 can be installed as separate units 22.

Figs. 12 and 13 show schematically and by way of example still another embodiment of the invention. The drawing shows schematically a part of the thin box-like element

3, which is filled with a suitable liquid and is arranged between a flow canal 9 for the cooled air flow and the

compartment, which is not shown in detail, the tempera¬ ture of which shall be controlled. At one of its ends, and preferably at the end which is least cooled by the air flow in the canal 9, the element 3 is provided with a projecting, tube formed element 20, which is bent into a coil and which has elastic deformable walls. A pivoting valve 21 and its axis is attached to the end of this coil formed element 20, in such a way that the valve 21 increasingly throttles the flow canal 9 when the coil formed element 20 expands when the frozen part of the liquid in the container 3 is increasing. One can realize that the element 3 may well be provided with a projecting coil formed element 20 at each of its two ends, so that the pivoting valve 21 is attached to one such coil formed element 20 at each of its two ends.

In the embodiments of the invention described above it has been assumed, that the refrigeration system in question is of a kind in which the cooled air flow, after passage through the flow canal which is controlled by the control system according to the invention, is led into the refrigerated compartment for refrigeration of this compartment and its contents. The invention can also be applied for keeping the temperature invariable in a sealed refrigerated compartment, in which you do not want to have any circulation of air, e.g. in a so called vacuum box. Figs. 13 and 14 show schematically and by way of example and in two relatively perpendicular views such an application of the invention. The drawing shows a sealed compartment 23, e.g. a so called vacuum box, which shall be kept at a predetermined temperature. The com¬ partment 23 is enclosed by walls 24 with good thermal conduction, for example of metal. Outside and in contact with the outside of at least one of these walls there is an element 3 in accordance with the invention, and which for example is designed principally as shown in figs. 3- 7, which defines one or several parallel flow canals 9

for cooled air flow on the side which is opposite to the compartment 23. The air flow through this canal 9 is controlled by a valve 25, for example as shown in either of figs. 5-7 or figs. 11, 12. The thermal conduction from the inner part of the refrigerated compartment 23 to the cooled air flow is thus effected completely via the thermal conducting walls 24 of the compartment and the temperature keeping and controlling element 3 according to the invention.

Different systems for controlling the air flow through the regulated compartment are conceivable within the scope of the invention. In one system no part of the cooled air flow, which is used to regulate the tempera- ture of the compartment in question by passing the liquid elements 3, is led into and through the compartment. One other system comprises a control equipment which is guiding a portion of the cooled air flow into and through the regulated compartment. In another system the cooled air flow is guided and used in such a way that all of the cooled air flow is passing into and through the regulated compartment.

In the above described embodiments it has further been assumed that a liquid is used, which shows an increase in volume at the transformation into a solid state. However, one can realize that there are other embodiments of the invention, where a liquid is used which shows a decrease in volume at the transformation into a solid state.

It is obvious from the above that a refrigeration system according to the invention can be designed in many various ways and can be used for several different purposes. It is further obvious that the liquid in the temperature regulating and refrigeration controlling element should have an essentially well defined freez¬ ing/melting temperature, which is essentially equal to

the temperature which shall be kept in the refrigerated compartment. Furthermore, it is obvious that the mech¬ anism, which uses the variation in volume of the liquid in the element to control the amount of the cooled gas flow, can be designed in a number of different ways.