FR2710736A1 - Refrigeration appliance with improved freezing device - Google Patents

Abstract

The invention relates to a refrigeration appliance with improved freezing device. This refrigeration appliance, in particular for domestic use, comprising one or more freezing cells which are provided with at least one cooling element and an auxiliary fast freeze device consisting of an eutectic mass (1) contained in a first plate (2) having at least one plane surface (3), is characterised in that a second plate (4) is associated with the said first plate (2), the second plate being similar to the said first plate and also filled with an eutectic mass and capable of being positioned removably on the said first plate, in such a way that the two plane surfaces (3, 5) are contiguous. The said plates are preferably connected together by means of a hinge (6) fixed to the two corresponding edges of the said plates. Main application: household electrical appliances.

Description

 The invention relates to a freezer apparatus, with an improved device, for carrying out rapid freezing of food, a device arranged inside the freezing cell. The invention particularly relates to all types of refrigeration appliances, in particular domestic appliances, provided with at least one food freezing cell; said cell being able to be cooled, either by a forced jet of cold air blown inside said cell (of the no-frost type), or in the traditional way, that is to say at least with an evaporator contained in the cell and which cools the air, under the effect of natural convection.

 For the sake of simplicity, the present description relates to a freezer appliance having only one cell, produced according to the invention, and relates to the method of freezing a slice of meat, chosen by way of example, both for the great delicacy and the value of this type of food, only for its shape, which favors its deposition on a flat surface, thus minimizing the contact surface, but it being understood that the invention can be freely extended also to other types food and other types of refrigerators and / or freezers made up of several freezer cells.

 It should be noted that the results of a process for freezing fresh food strongly depend on the freezing technique used, in addition to the nature of the food; these aspects of freezing techniques have been studied in depth and analyzed in all their aspects and are perfectly known to those skilled in the art and, therefore, will not be recalled.

 All the efforts of the freezing technique, intended for domestic use, are thus oriented to carry out, in the easiest, safe and economical way, freezing processes which aim to approach even more the ideal process, but which are also applicable to household appliances. The fundamental factor which determines the quality of a freezing process is the speed of change of state of the element to be frozen, i.e. the passage of the water contained in the state food liquid in solid state.

 Indeed, it is known that the faster the change in state of the food, the better the subsequent conservation, since the faster will be the transition from the state for which the less damage will be to the cells of the food, damage caused by the formation of ice crystals which can rupture these cells.

 One of the methods for accelerating the passage of the state of food is, as we know, the use of an empty space, having been previously conditioned at a very low temperature and into which the food is carefully introduced to freeze.

 In this case, the cooling of the food will depend, naturally apart from the temperature difference between the empty space and the food, also on the heat exchange capacity and conversely cold, between the ambient atmosphere and the food to be frozen.

 Since the said heat transfer capacity between the atmosphere and a generic food is quite low, attempts have been made to increase the cooling rate by increasing the temperature difference between the food and the empty space and this is for do this so that the freezer cabinets can reach, as we know, very low temperatures of up to -30 OC; however, this technique has inherent limitations, in that the temperature inside the void space cannot be lowered below a certain limit due to technical difficulty and economic costs.

 It is therefore sought to improve the heat transfer capacity between the two elements, using at least in part, not the surrounding atmosphere at low temperature, but a solid surface, preferably metallic, thus able to increase notably the heat exchange between its faces. This is obtained with the use of plates containing eutectic masses, on which the slice of meat to be frozen is placed.

 The use of eutectic masses, as intermediate cooling elements, is known in the state of the art and will not be the subject of a further explanation; it should only be remembered that the property of these substances is to freeze at temperatures significantly below 0 ° C. and, therefore, when they are cooled to a very low temperature, below the freezing temperature, they take up the heat which corresponds to their change of state at this temperature which is significantly lower than 0 OC.

 It follows that, if a piece of meat is placed on a plate whose eutectic mass is already frozen, the heat transfer between the plate and the piece of meat will not be modified during the entire freezing phase of the meat. , since the temperature rise that this food should induce on the plate, since this rise should occur by crossing the thawing temperature and, thus, of change of state of the eutectic mass, and as we know it absorbs a significant amount of heat for the change of state; therefore if the heat capacity and the temperature are chosen appropriately, the eutectic mass remains at a very low temperature for the entire time necessary for the freezing of the piece of meat, or provides the cold necessary for the freezing of the meat at a temperature sufficiently low, thereby correspondingly shortening the freezing time of the meat, given that it freezes at an optimum temperature, just below -1 OC and, ideally, between -1 and -5 OC.

 However, this solution has a drawback: indeed, the rapid freezing of a mass of meat, resting on a eutectic plate at low temperature, causes rapid freezing of the area located in immediate contact with the plate, but also produces freezing non-homogeneous of the rest of the mass, since it is cooled in much larger times, which are close to the freezing times obtained under free atmosphere, and this non-homogeneous freezing is, in turn, cause a subsequent storage uncertain.

 Besides this problem, we also lose the possibility of having a better and faster freezing, since we neglect the possibility of using the upper free surface exposed to the air of the slice of meat to accelerate the later freezing.

 It would thus be desirable and, it is the aim of the present invention, to produce a domestic refrigerator, provided with an improved device, which avoids the disadvantages described, without incurring the complications of construction of a new technology and presenting costs. low production.

 This object, as well as others, are achieved by a refrigerating apparatus with rapid freezing device, in particular for domestic use, comprising one or more freezer cells provided with at least one cooling element and an auxiliary rapid freezing device. , consisting of a eutectic mass contained in a first plate having at least one flat surface, characterized in that said first plate is associated with a second plate similar to said first plate, also filled with a eutectic mass and which can be removably positioned on said first plate, so that the two respective flat surfaces adjust.

 The distance between said plates is adjustable, so that said respective flat surfaces facing one another remain substantially parallel when said plates are closed on each other said plates being provided with an element elastic keeping them in the normally closed position.

 At least one of the flat surfaces placed opposite one another, desdistes plates, is made or covered with non-stick material. Said first and said second plate are reciprocally connected by a hinge fixed on the two corresponding edges of said plates.

 The movable sides of said plates are forcedly locked in the closed position.

 One of said first and second plates is arranged at least partially in contact with said cooling element.

The invention will be better understood on reading the following description, given solely by way of non-limiting example and with regard to the appended drawings in which FIG. 1 schematically represents the composition of a
freezing cell, according to the invention, Figure 2 shows a detail of Figure 1, Figure 3 shows diagrams showing the shape of
the temperature evolution in the food
during freezing.

 The imagined solution basically consists in producing a second eutectic plate, analogous to a first eutectic plate, already existing inside the freezing cell, and in positioning said eutectic plate on the slice of meat already supported on said first plate.

 Referring to the figures, we see a eutectic mass 1, contained in a first horizontal plate 2 provided with a planar upper surface 3, a second plate 4, similar to the first plate, said second plate being in turn provided with a flat lower surface 5.

 Said plates are contained in a freezing cell which also contains a cooling element 10, which can be a traditional evaporator as found in a "no-frost" type freezer, an evaporation battery external to the cell associated with a 10A fan.

 The upper plate is movable and, in particular, it is spread over a slice of meat having been previously placed on the lower plate.

 In this way the slice of meat, or in general the portion of food interposed between said parallel plates containing the respective eutectic masses, is reached by the cold on its two faces, which considerably reduces the duration of freezing and practically cancels the lack of homogeneity of freezing inside the mass to be frozen, in particular if said mass is a slice of meat as in the ideal case.

 In fact, in FIG. 3, we observe the temperature downward curve as a function of time, recorded inside a slice of meat in three cases of conventional freezing, in air (A), of freezing using a single eutectic plate (B) on which the same mass of meat is placed, and freezing the same mass of meat interposed between two similar eutectic masses (C), all the other conditions being equal.

 It should be noted that before starting freezing (above the line of + 1 OC), the line of the temperature drop (D) is equal in the three aforementioned cases, since the cooling of the mass meat has not yet reached freezing temperature and therefore there has been no change in condition.

 During the state change phase, the three lines have an almost horizontal appearance, since in this phase the heat transfer takes place at constant temperature and, finally, there is a subsequent gradual lowering of temperature due to the gradual transfer. from the cold of the surrounding atmosphere (atmosphere or eutectic mass).

 It can be seen that the times required to complete these phases of change of state, or more briefly of freezing, vary in the following way: in the case of a traditional freezing in air (A), the time requested is designated by Ta and it is longer; in the case of a single plate with a eutectic mass, a notable shortening of the freezing time is obtained, designated by Tb. Finally, if a device according to the invention is used, an additional significant shortening of the freezing time is obtained, then designated by Tc.

 The consequent advantage, which is expressed by the reduction of the time Tb - Tc is the result of the present invention.

 A first improvement of the invention consists in the possibility that the distance between the two plates can vary according to the thickness of the slice of meat, so as to improve the contact between the upper plate and the upper surface of the slice of meat.

 Thus this can be obtained either by means of an appropriate hinge 6 mounted on the corresponding edges of the two plates, on which they are thus articulated, or by means of a device, that is to say a buttonhole 12 , by means of which said plates are connected and which allows a certain degree of reciprocal movement of said plates. A further improvement of the present invention consists in providing the device for connecting said plates with an elastic element, that is to say a spring or a torsion bar, which tends to keep said plates permanently closed; the usefulness of this elastic element comes from the fact that it applies a clamping force which is added to the inherent force of the gravity of the upper plate, thus improving the contact between the plates and the interposed food.

 Since, however, the pressure of the plates on the meat, with the effect of the very low temperature, can cause the meat itself to adhere against these plates, an advantageous improvement of the invention consists in making their internal surfaces with non-stick materials, this being achieved by one of the multiple methods and materials offered by the state of the art.

 In addition, another improvement of the invention is obtained by the fact that, also according to a variant with the elastic element for clamping between the abovementioned plates, an adjustable locking element can be installed between the two plates, so that the slice of meat can be clamped by the action on said blocking element which closes the movable sides 8, 9 of the respective plates 2, 4, depending on the dimensions thereof. This clamping element, that is to say a handle that can deform and rotate, is easily produced by those skilled in the art and, therefore, will not be explained.

 A final improvement of the present invention consists in adhering, at least partially, one of said plates, illustrated above, with the cooling element 10; that is to say by eliminating the insulation formed by the space or air space between said cooling element 10 and the eutectic plate, by making it possible to obtain maximum transfer of cold from said cooling element and, thus , to minimize the freezing time of food.

 Obviously any rapid freezing device, according to the indications given above, can also be produced in a form different from that which has been shown without thereby departing from the protective field of the present invention.

Claims (7)

 1. Refrigerating appliance, in particular for domestic use, comprising one or more freezer cells provided with at least one cooling element (10) and an auxiliary rapid freezing device, consisting of a eutectic mass (1) contained in a first plate (2) having at least one flat surface (3), characterized in that said first plate (2) is associated with a second plate (4) similar to said first plate, also filled with a eutectic mass and can be removably positioned on said first plate, so that the two respective flat surfaces (3, 5) are adjusted.  2. Refrigerating appliance according to claim 1, characterized in that the distance between said plates is adjustable, so that said respective flat surfaces (3, 5) placed opposite one another, remain substantially parallel when said plates are closed one over the other.  3. Refrigerating appliance according to any one of the preceding claims, characterized in that the said plates are provided with an elastic element, maintaining the said plates in the normally closed position.  4. Refrigerating appliance according to any one of the preceding claims, characterized in that at least one of the flat surfaces (3, 5), placed opposite one another, of said plates, is made or covered with non-stick material.  5. Refrigerating apparatus according to any one of the preceding claims, characterized in that said first and said second plate are reciprocally connected by a hinge (6) fixed on the two corresponding edges of said plates.  6. Refrigerating apparatus according to claim 5, characterized in that the movable sides (8, 9) of said plates are forcedly locked in the closed position.  7. Refrigerating appliance according to any one of the preceding claims, characterized in that at least one of said first and second plates is arranged at least partially in contact with said cooling element (10).