HOME REFRIGERATOR

TECHNICAL FIELD

The present invention relates to a home refrigerator .

More specifically, the present invention relates to a home refrigerator with two independent refrigeration compartments, to which the following description refers purely by way of example.

BACKGROUND ART

As is known, some home refrigerators have two completely separate, independent refrigeration compartments; and one heat-pump cooling circuit designed to regulate the temperature in each refrigeration compartment independently of the other.

More specifically, one of the refrigeration compartments is normally only used to produce ice cubes and similar, and the other for preserving perishable foodstuffs .

In refrigerators of this sort, the heat-pump cooling circuit is therefore designed to keep the first compartment at an operating temperature of a few degrees

below 0 ⁰ C to optimize production of ice cubes or similar, and to keep the second compartment at a temperature of - 2°C to -20 ⁰ C for freezing perishable foodstuffs.

Alternatively, the heat-pump cooling circuit may also be designed to keep the second compartment at a temperature slightly above 0 ⁰ C, and normally ranging between 0 ⁰ C and +6°C, to preserve non-freezable perishable foodstuffs.

More specifically, the heat-pump cooling circuit comprises one refrigerant condenser, normally fixed to and projecting from the rear wall of the refrigerator; and two separate refrigerant evaporators, each housed inside a respective compartment of the refrigerator. The condenser is fed with high-pressure refrigerant from the compressor, and is designed to allow the refrigerant to cool rapidly by releasing heat to the outside and passing partly to the liquid state. Each evaporator, on the other hand, is connected to the condenser outlet via an expansion valve, for rapidly expanding and so rapidly cooling the refrigerant flowing through it, and is designed to allow the refrigerant from the expansion valve to heat rapidly by drawing heat from the contents of the compartment in which the evaporator is installed, and returning to the gaseous state before reaching the compressor inlet.

The cooling circuit of refrigerators of the above type also comprises two electrically controlled on-off valves, each located immediately upstream from a

respective expansion valve; and a low-pressure refrigerant storage tank located immediately upstream from the compressor inlet.

The two electrically controlled on-off valves regulate refrigerant flow to the respective evaporators, and are controlled by an electronic central control unit to connect the condenser selectively to either one of the evaporators; while the storage tank compensates for fluctuations in refrigerant flow to the compressor, and at the same time retains any traces of liquid refrigerant not evaporated completely inside either one of the evaporators, and which, being non-compressible, could irreparably damage the compressor.

Though highly efficient when both refrigeration compartments are more or less at the corresponding operating temperatures, the cooling circuit described above operates poorly when the ice compartment greatly exceeds the set temperature, and so calls for massive heat absorption from inside the compartment. In which case, the electronic central control unit of the refrigerator is forced to keep the ice compartment evaporator running for a prolonged period of time, thus seriously impairing the cooling efficiency of the second compartment, with all the drawbacks this entails. Moreover, when the second compartment also strays excessively from the set temperature, the electronic central control unit of the refrigerator is forced to alter the configuration of the cooling circuit at

regular, fairly close intervals, to supply the two evaporators alternately, thus drastically impairing the overall efficiency of the cooling circuit.

In such conditions, which are far from rare, the refrigerator obviously consumes much more electric energy than in normal operating conditions, with all the drawbacks this entails.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a home refrigerator designed to eliminate the aforementioned drawbacks.

According to the present invention, there is provided a home refrigerator as claimed in Claim 1 and preferably, though not necessarily, in any one of the Claims depending directly or indirectly on Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a side view, with parts in section and parts removed for clarity, of a home refrigerator in accordance with the teachings of the present invention;

Figure 2 shows a schematic of the cooling circuit of the home refrigerator in Figure 1 ; BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, number 1 indicates as a whole a home refrigerator particularly suitable for preserving perishable foodstuffs and producing small

amounts of ice, and which comprises at least two independent refrigeration compartments, each maintained at a predetermined reference temperature preferably, though not necessarily, differing from that of the other compartment .

More specifically, in the example shown, refrigerator 1 comprises a rigid, self-supporting, substantially parallelepiped-shaped casing 2 housing, one over the other, two refrigeration compartments 3 and 4, each of which is lined with thermally insulating material and communicates with the outside through a respective access opening formed in the vertical front wall of casing 2.

Refrigerator 1 also comprises two doors 5 and 6 hinged, one over the other, to the vertical front wall of casing 2 to rotate, about a preferably, though not necessarily, common vertical axis, to and from a closed position, in which each of the two doors rests against the vertical front wall of casing 2 to close the access opening to, and hermetically seal from the outside, a respective refrigeration compartment 3, 4.

With reference to Figures 1 and 2, refrigerator 1 also comprises a closed-circuit cooling circuit 7, which operates on the heat-pump principle of transferring heat from one fluid to another by exploiting the changes in state of an intermediate refrigerant subjected to a closed thermodynamic cycle, and which is designed to bring each refrigeration compartment 3, 4 to, and keep it

at, a respective predetermined reference temperature normally lower than the outside temperature.

The reference temperature may be user-selected from a predetermined range. More specifically, in the example shown, cooling circuit 7 is designed to keep refrigeration compartment 3 (i.e. the top compartment of the refrigerator) at a reference temperature of below 0 ⁰ C and preferably, though not necessary, ranging between -2°C and -20 ⁰ C, so refrigeration compartment 3 is suitable for producing ice and/or freezing perishable foodstuffs; and to keep refrigeration compartment 4 (i.e. the bottom compartment of the refrigerator) at a higher reference temperature than refrigeration compartment 3 (i.e. above 0 ⁰ C) and preferably, though not necessarily, ranging between 0 ⁰ C and +6°C, so refrigeration compartment 4 is suitable for preserving non-freezable perishable foodstuffs.

With particular reference to Figure 2, cooling circuit 7 comprises an electrically operated refrigerant compressing device or so-called compressor 8, which is supplied at the inlet with gaseous-state refrigerant, and supplies at the outlet gaseous-state refrigerant at a much higher pressure (normally 8-bar) and temperature than at the inlet; and a first heat exchanger or so- called condenser 9, which is connected to the outlet of compressor 8, to receive the high-pressure refrigerant produced by compressor 8, and is designed to allow the refrigerant flowing through it to cool rapidly by

releasing heat to the outside environment and possibly passing to the liquid state.

In the example shown, condenser 9 is defined by a coil 9 fixed to and projecting from the vertical rear wall of casing 2, i.e. outside of refrigeration compartments 3 and 4, and cooling circuit 7 also comprises a second and third heat exchanger or so-called evaporator 10 and 11, which are located inside respective refrigeration compartments 3 and 4, and are designed to allow the refrigerant flowing them to heat rapidly by drawing heat from the contents of respective refrigeration compartments 3, 4 and returning to the gaseous state.

More specifically, with reference to Figure 2, the inlet of evaporator 11 is connected to the outlet of condenser 9 by a connecting pipe 12. And cooling circuit 7 comprises, along connecting pipe 12, a refrigerant expansion valve or similar expansion member 13 for rapidly expanding, and so rapidly reducing the temperature and pressure of, the high-pressure refrigerant from condenser 9; an electrically controlled on-off valve 14 for regulating refrigerant flow from condenser 9 to evaporator 10; and a dehydration filter 15 for eliminating any condensation formed at the outlet of condenser 9.

In the example shown, refrigerant expansion member 13 is defined by a capillary tube 13 connecting connecting pipe 12 to the inlet of evaporator 11, and on-

off valve 14 is located immediately upstream from capillary tube 13.

With reference to Figure 2, the inlet of evaporator 10 is connected to the outlet of condenser 9 by a connecting pipe 18. And cooling circuit 7 comprises, along connecting pipe 18, a refrigerant expansion valve or similar expansion member 19 for rapidly expanding, and so rapidly reducing the temperature and pressure of, the high-pressure refrigerant from condenser 9; an electrically controlled on-off valve 20 for regulating refrigerant flow from condenser 9 to evaporator 10; and a dehydration filter 21 for also eliminating any condensation formed at the outlet of condenser 9.

In this case too, refrigerant expansion member 19 is defined by a capillary tube 19 connecting connecting pipe 18 to the inlet of evaporator 10, and on-off valve 20 is located immediately upstream from capillary tube 19.

Capillary tubes 13, 19, on-off valves 14, 20, and dehydration filters 15, 21 are all parts commonly used in the industry and therefore not described in detail.

With reference to Figure 2, unlike known solutions, compressor 8 is defined by a known constant-flow compressor which, when activated, is designed to supply refrigerant at a constant flow rate sufficient to only continuously supply one of evaporators 10 and 11; and cooling circuit 7 of refrigerator 1 comprises a high- pressure refrigerant storage tank 22, which is located along connecting pipe 18 connecting the outlet of

condenser 9 to the inlet of evaporator 10 housed inside refrigeration compartment 3, and is located upstream from on-off valve 20 and possibly dehydration filter 21.

Preferably, though not necessarily, cooling circuit 7 of refrigerator 1 also comprises a non-return valve 23 or similar, located along connecting pipe 18, immediately upstream from high-pressure refrigerant storage tank 22.

High-pressure refrigerant storage tank 22 temporarily stores a predetermined amount of high- pressure refrigerant from condenser 9, and non-return valve 23 is oriented to permit refrigerant flow along connecting pipe 18 from the outlet of condenser 9 to tank 22, but not vice versa.

With reference to Figures 1 and 2, cooling circuit 7 also comprises an electronic central control unit (not shown) for controlling the two on-off valves 14, 20, as explained below, to regulate refrigerant flow independently to the two evaporators 10, 11; and a low- pressure refrigerant storage tank 24 located along the two connecting pipes 25, 26 connecting the inlet of compressor 8 to the outlet of evaporator 10 and the outlet of evaporator 11 respectively.

More specifically, tank 24 is located immediately upstream from the inlet of compressor 8, and temporarily stores a variable amount of low-pressure refrigerant to compensate for fluctuations in refrigerant flow to compressor 8, and at the same time retains any traces of liquid refrigerant not evaporated completely inside

either one of evaporators 10 and 11.

Low-pressure refrigerant storage tank 24 is a commonly used part in the industry and therefore not described in detail. In the example shown, each of connecting pipes 25,

26 is designed so that a portion of it rests on, is adjacent to, or at any rate is in thermal contact with the capillary tube 13, 19 supplying refrigerant to the corresponding evaporator 10, 11, so as to form an auxiliary heat exchanger 27, 28 for assisting passage of the refrigerant to the gaseous state and improving efficiency of the thermodynamic cycle.

With reference to Figure 2, cooling circuit 7 preferably, though not necessarily, comprises a bypass pipe 29 connecting the outlet of compressor 8 directly to the inlets of evaporators 10, 11, downstream from respective expansion members 13, 19, and so feeding the high-pressure, high-temperature refrigerant from compressor 8 directly to evaporators 10, 11; and an electrically controlled on-off valve 30 located along bypass pipe 29 to regulate refrigerant flow from compressor 8 to evaporators 10, 11.

On-off valve 30 is obviously controlled by the electronic central control unit (not shown) of cooling circuit 7, and is normally turned on to speed up defrosting of the refrigerator, i.e. removal of ice off evaporators 10, 11.

Operation of refrigerator 1 differs from that of

similar currently marketed refrigerators in that, besides opening on-off valves 14 and 20 alternately to connect evaporators 10 and 11 alternately to condenser 9, the electronic central control unit (not shown) of cooling circuit 7 also provides for opening on-off valves 14 and 20 simultaneously for a predetermined maximum time shorter than the time taken to empty high-pressure refrigerant storage tank 22 completely, so that, for a short period, refrigerant can be supplied to both evaporators 10 and 11 to simultaneously cool both refrigeration compartments 3 and 4. High-pressure refrigerant is supplied to evaporator 11 from condenser 9, and to evaporator 10 from tank 22, which is gradually emptied. Obviously, high-pressure refrigerant storage tank 22 is refilled systematically each time the electronic central control unit closes on-off valve 14 and opens on- off valve 20.

The advantages of the new heat-pump cooling circuit 7 are considerable : refrigerator 1 is able to bring refrigeration compartments 3 and 4 to their respective reference temperatures much faster - even in the event of a major difference between the desired reference temperature and the actual temperature of refrigeration compartment 3 for producing ice and/or freezing perishable foodstuffs - using the high-pressure refrigerant stored in tank 22.

Moreover, cooling circuit 7 is extremely cheap to

produce, by employing low-cost, commercial component parts of simple design and proven reliability.

Clearly, changes may be made to refrigerator 1 as described herein without, however, departing from the scope of the present invention.

For example, refrigeration compartment 3 may be a small compartment, not accessible directly from the outside, for exclusively producing ice cubes or similar. In this case, cooling circuit 7 may be designed to keep refrigeration compartment 4 at a reference temperature below 0 ⁰ C and preferably, though not necessarily, ranging between -2°C and -20 ⁰ C, thus making refrigeration compartment 4 particularly suitable for freezing perishable foodstuffs. According to this variation, refrigerator 1 may also comprise a third refrigeration compartment separate from and independent of refrigeration compartments 3 and 4 ; and an auxiliary heat-pump cooling circuit completely separate from and independent of cooling circuit 7, and designed to keep the third refrigeration compartment at a reference temperature above 0 ⁰ C and preferably, though not necessarily, ranging between 0 ⁰ C and +6°C, thus making the third refrigeration compartment particularly suitable for preserving non-freezable perishable foodstuffs.

In a further embodiment, the non-return valve 23 may be replaced with a further on-off valve which is controlled by the electronic central control unit of

cooling circuit 7 together with on-off valves 14, 20. More in details the electronic central control unit of cooling circuit 7 keeps the on-off valve replacing nonreturn valve 23 closed when on-off valve 14 is opened, so as to avoid refrigerant to flow back from tank 22 to condenser 9 and to connecting pipe 12.