DK178194B1 - Apparatus and method for cooling products in a fluidized bed - Google Patents

Abstract

The invention relates to an apparatus (1) for freezing products in a fluidized bed. The apparatus (1) comprises an air-permeable conveyor belt (6, 61) which forms over a portion of its length a bottom surface (4) of a trough (2, 21) adapted to accommodate the products to be frozen. An air-conducting means (10 ', 10' ') is arranged over said part of the conveyor belt (6, 61) to direct a flow of air (F', F '') which is supplied through the trough via the bottom surface (4). . The air-conducting means (10 ', 10' ') is arranged to direct the flow of air (F', F '') so that a bed formed by the products in the trough (2, 21) is exposed to a first fluidization in one cold zone (A ', A' ') of the trough (2, 21) and another fluidization in a freezing zone (B', B '') of the trough (2, 21) downstream of the cold zone (A ', A' '). The second fluidisation is more powerful than the first and so powerful that the freezing of adjacent products is counteracted. The invention also relates to a method for performing said freezing.

Description

FIELD OF THE INVENTION

The present invention relates to an apparatus for cooling or freezing products in a fluidized bed and comprising an air-permeable conveyor belt which forms over a portion of its length a bottom surface of a trough adapted to accommodate the products to be frozen and an air-conducting means arranged over said part of the conveyor belt to direct a flow of air supplied through the trough via the bottom surface, said air-conducting means arranged to direct the flow of air so that a bed formed of the products in the trough is subjected to a first fluidization in a cold zone of the trough and a second fluidization in a freezing zone of the trough downstream of the cold zone. The invention also relates to a method for freezing products in a fluidized bed.

Prior art

In the food industry, products such as vegetables, fruits, berries and seafood are usually frozen in an individually separated state. This can be done, for example, by supplying the product with a trough which is supplied from its bottom with a flow of cooled air. As a result, the products will form a fluidized bed while freezing. This technique is described, for example, in US 3,169,381, SE 204,095, SE 217,470, SE 216,963, SE 336,362, US 4,281,521 and US 3,886,762. The primary purpose of this technique is to provide very rapid freezing to a temperature just below 0 ° C, for example -2 to -3 ° C, after which the frozen products can be passed to another deep freezing apparatus for a temperature below, for example - 18 ° C.

Such a trough has an inlet end and an outlet end. Fresh products are supplied at the inlet end and discharged in a frozen state at the outlet end. The trough further comprises a lower surface in the form of an endless air-permeable conveyor belt. Under the conveyor belt there is an air-conducting means for directing a flow of air up through the conveyor belt and into the trough. In order to provide a necessary flow of air, but also a necessary velocity of air in the trough to form a fluidized bed, the air-conducting means comprises some type of throttle.

Traditionally, the throttle has always been arranged so that the flow of air will be at its maximum in connection with the inlet end of the trough where the products are fed, so as to gradually fall towards the outlet end of the trough, see, for example, US 3,169,381. This was considered and is still considered in the field as necessary, as products supplied to the trough are assumed at the inlet end to require a higher flow of air initially. A high flow of air is believed to lead to an efficient breaking of the insulating layer of air surrounding the product, and thus rapid cooling. A high initial flow of air is also needed for transporting products if the apparatus has no conveyor belt like some of the prior art apparatus.

However, this distribution of air flow is less advantageous for products having a surface structure and texture that is susceptible to shock or high air flows. For example, freezing of fresh raspberries can be mentioned. Raspberries in a fresh state are very soft and easily damaged while at the same time having a high juice content and an irregular surface. When these berries are applied to the trough and meet the high flow of air and fluidized, they will initially collide with each other before debris freezing and can deform and thereby discharge the juice. This juice is collected in the irregular surface structure where it freezes and can be said to glaze the berry. The juice also tends to clog the conveyor belt and cause undesired throttling of the flow of air to the trough. The juice can also cause freezing of products on the sidewalls of the trough, which requires frequent and expensive production stops for cleaning.

In addition, raspberries have "hair" on their surface that breaks when a raspberry, especially in a frozen state, collides with other raspberries. Another factor that can contribute to the hair being broken is a high air velocity. It is not unusual for raspberries to lose their hair after such a freeze. Berries that have lost their original appearance and quality in this way offer a lower price when sold and, for example, cannot be used for decoration of pastry.

In the case of freezing products using such an apparatus, a considerable amount of "snow", i.e. ice crystals, is formed in and around the evaporators used to cool the air. This is especially a problem in products that discharge a large amount of liquid. As a result of the snow, the effect of the evaporators is gradually reduced and thus necessitates the removal of the snow at regular intervals from the evaporators and the area in which the evaporators are absorbed. This must be done during expensive production stops. In continuous production this may be necessary once or several times a day.

Objects of the present invention

It is thus the object of the present invention to provide an apparatus and method for performing smoother individual freezing of products by which the discharge of liquid and surface deformations of the products is reduced and by which the products are not ground.

It is a further object of the invention to provide an apparatus and method in which the amount of snow formation is reduced.

It is thus an object to provide an improvement of an apparatus and method of the prior art for individual freezing of products.

Summary of the Invention

In order to achieve at least one of the aforementioned objects and also other objects which will become apparent from the following description, there is provided an apparatus and method having the features set forth in claims 1 and 13 of the present invention. Preferred embodiments are set forth in claims 2-12 and 14-17, respectively.

More specifically, the invention relates to an apparatus for freezing products in a fluidized bed and comprising an air-permeable conveyor belt which forms over a portion of its length a bottom surface of a trough adapted to accommodate the products to be frozen and an air-conductive means arranged over said part of the conveyor belt to direct a flow of air supplied through the trough through the bottom surface, which air-conducting means is arranged to direct the flow of air so that a bed formed by the products in the trough, a first fluidization in a cold zone is subjected to the trough and a second fluidization in a freezing zone of the trough downstream of the cold zone. The apparatus is characterized in that the air-conducting means comprises a throttled first part disposed in connection with the cold zone and a throttled second part arranged in connection with the freezing zone, which second part has a smaller throttle than the throttled first part. and that the second fluidization is more powerful than the first and so powerful that antifreeze of adjacent products is counteracted.

By changing the flow of air through the trough in the cold zone and the freezing zone, respectively, and providing a stronger fluidization of the products in the freezing zone than in the cold zone, the very surprising effect is obtained that even the most sensitive products can be frozen individually in a very even manner. Experiments have shown that raspberries can be frozen by the apparatus of the invention with a result in which the carriers are virtually unaffected by the collisions that are inevitable in fluidization.

By ensuring stronger fluidization in the freezing zone, any tendency for adjacent products to freeze to each other, which may occur in and. around the transition between the two zones will be eliminated as the stronger fluidization and thus the mixture is able to separate products that may have begun to freeze the same. Of course, it will be understood that the fluidization and design of the trough means that there is no distinct transition between said zones.

Despite the changing airflow, the required holding time of the products in the appliance and its trough are not significantly affected.

By reducing the damage to the products, so will the discharge of juice and thus the amount of liquid which on the one hand can cause clogging of the conveyor belt and may get stuck by freezing on the walls of the trough, which on the other hand can be converted into snow, be reduced. This leads to fewer production interruptions, which on a large scale produces economic benefits. In addition, the quality of the products will be improved.

The difference in throttling between the two parts means that the flow of air and thus the fluidization in the trough will be stronger in the freezing zone. Thus, by using different throttles for the distribution of the flow of air, a fan or a plurality of fans can be used with the same control in the apparatus, which makes the apparatus simple and inexpensive.

The air-conducting means may comprise a non-sprung second portion arranged in connection with the freezing zone.

The air-conducting means can be arranged in one piece. However, it is preferred that the air-conducting means be divided into segments in a direction transverse to the conveying direction of the conveyor belt, which segments comprise for varying degrees of throttling. Due to the division into segments, the air-conducting means will be very easy to handle, for example, in cleaning and maintenance, as compared to a one-piece air-conducting means. In addition, the individual segments can easily be replaced or shifted to control the flow of air through the trough to the type of product and the product quality that is optimal for the purpose.

If desired, the trough may also have a deep freezing zone. This means that the apparatus can be used for complete treatment of the products from cold to deep freezing, thereby enabling the apparatus, for example, to be followed by a device for packaging.

If the trough has a deep freezing zone, the air-conducting means should comprise a throttled third part arranged in connection with the deep freezing zone, which third part has a stronger throttle than said second part. As a result, the flow of air in the freezing zone will be lower than in the freezing zone. Since the products have already been frozen, the additional freezing process is more or less independent of a strong flow of air which can therefore be reduced again. In addition, some products in a frozen state may be more fragile than in a non-frozen state and therefore it may be very advantageous to reduce the flow of air in the freezing zone to be careful with the products. This may, for example, apply to shrimps whose "feelers" are very sensitive when frozen and thus stiff.

It is preferred that the flow of air in the cold zone has a velocity of 2-4 m / s, the flow of air in the freezing zone has a velocity of 5-7 m / s, and the flow of air in the freezing zone has a velocity of 2- 4 m / s. This means that the products will be handled most cautiously when they are most sensitive to external influences, that is, in the cold zone and in a freezing zone, if any. In addition, the mixture is most powerful in the freezing zone, where the products are otherwise at risk of freezing to each other.

For continuous transport of the products through the trough from its inlet end to its outlet end, the air-permeable conveyor belt is advantageously endless.

The apparatus of the invention may comprise a second air-permeable conveyor belt which forms along a portion of its length a bottom surface of a second trough adapted to receive and deep-freeze the products frozen in the first trough. Such a second conveyor belt allows easy control of the holding time of the products in the second trough and thus the time for deep freezing of the products. This also means that the first and second troughs, respectively, have the opportunity to have different depths of the product bed. A small depth of the product bed in the first trough is important as it leads to faster freezing, while the depth is less important or not at all important in the subsequent deep freezing.

The first trough may be accommodated in a first compartment and the second trough may be arranged in a second compartment following the first compartment.

According to a second aspect, the invention relates to a method for freezing products in a fluidized bed which comprises fluidizing a bed of products contained in a trough so that the bed is subjected to a first fluidization in a cold zone of the trough and a second one. fluidization, which is more powerful than the first fluidization, in a freezing zone of the trough, which first and second fluidization are each provided by providing the trough with a stronger flow of air in the freezing zone than in the cold zone, which flow of air is controlled by by means of an air-conducting means provided with throttles, which air-conducting means has a greater throttle in the cold zone than in the freezing zone, which other fluidisation is provided to such an extent as to prevent freezing of adjacent products.

DESCRIPTION OF THE DRAWINGS In the following, the invention for exemplification will be described in more detail with reference to the accompanying drawings which illustrate prior art and presently preferred embodiments of the apparatus and method of the invention.

FIG. 1 is a schematic cross-sectional view of a prior art apparatus seen across the conveyor belt.

FIG. 2 is a schematic cross-sectional view of a prior art apparatus, viewed longitudinally of the conveyor belt.

FIG. 3 is a schematic diagram of an air flow diagram and a temperature diagram of a prior art apparatus, respectively.

FIG. 4 is a schematic cross-section of a first embodiment of an apparatus according to the invention, viewed longitudinally of the conveyor belt.

FIG. 5 is a schematic representation of an air flow diagram and a temperature diagram of an apparatus according to FIG. 4.

FIG. 6 illustrates another embodiment of the apparatus according to the invention in which cooling and freezing takes place in a first trough and deep freezing takes place in a second trough.

FIG. 7 is a schematic diagram of the air flow diagram and the temperature diagram of the apparatus according to FIG. 6th

Technical description

For a better understanding of the invention, a prior art apparatus 1 will be described initially with reference to FIG. 1 and 2. The apparatus 1 is intended for the individual cold and freezing of products, mainly food products, such as fruits, vegetables, berries or seafood.

The terms cold, freezing and deep freezing are used throughout the text. The term cold refers to cooling of the products from the original temperature to a temperature above 0 ° C. The term freezing refers to cooling the products below the freezing point, that is, from just over 0 ° C to approx. -5 ° C, preferably -2 to -3 ° C. Finally, the term deep freeze refers to the cooling of the products from the final freezer temperature to a temperature which is preferably, but not necessarily, below -18 ° C.

The apparatus 1 comprises an elongated trough 2 accommodated in a space 3. The trough 2 has a bottom surface 4 and side walls 5. As shown, the side walls may consist of separate walls or alternatively consist of the walls of the room 3.

In the embodiment shown, an endless air-permeable conveyor belt 6 forms, along portions of its length, a bottom surface 4 of the trough 2. The conveyor belt 6 can have different extents. In the embodiment shown, the entire conveyor belt 6 is entirely arranged in the space 3 and extends over most of its length. It can also be arranged to extend outside the space and out through the end walls 7 thereof in such a way that the conveyor belt 6 has loading and unloading zones arranged outside the space 3. Regardless of the extent of the conveyor belt, the spaces 3 on its end walls 7 have a an inlet 8 through which the products to be cooled are introduced and taken up in the trough 2, and an outlet 9 through which the finished refrigerated products are discharged.

Preferably, the products must be provided to the space 3 and its trough 2 through the inlet 8 by means of a shaking feeder (not shown). The discharge from the space 3 and the trough 2 is preferably carried out by the products being discharged through the outlet 9 by a combination of the movement of the conveyor belt 6 and the fluidisation.

Below the upper part, i.e. the conveying surface, of the conveyor belt 6, which forms the bottom surface 4 of the trough 2, there is an air-conducting member 10. The air-conducting member 10 consists in its simplest form of a metal plate extending over all or most of the of the width and length of the bottom surface 4. As a result of the length of the trough 2, such an air-conducting member 10 may be too heavy and inconvenient during maintenance and cleaning and may instead be divided into a number of separate segments. Such segments are advantageously placed side by side in a direction across the length of the conveyor belt 6.

The air conduit means 10 comprises a hollow pattern 11 which forms droplets 12 of the air flow F distributed into the trough for cooling the products. The air flow F, the hollow pattern 11 and the throttle 12 will be described below.

Parallel to the space 3 is an area 13 which communicates with said space 3 through openings 14 in a partition 15 between the area 13 and the space 3. The area 13 contains one or more evaporators 16 for cooling the air to be brought. to circulate in the apparatus 1.

The area 13 also contains one or more blowers 17. The blowers 17 are advantageously arranged in the said openings 14 in the partition 15.

The fans 17 and evaporators 16 are arranged in the region 13 over the length of the trough 2. The fans 17 are arranged to cause the cooled air to circulate, see the arrows F, from said area 13 through the openings 14 to the space 3, through the air-conducting means 10, up through the conveyor belt 6 and into the trough 2, where the products which is absorbed therein, fluidized, and finally back to the region 13 where the air is passed through the evaporators 16 to be cooled again.

The air circulating through the apparatus is preferably cooled to a temperature which is in the range of -10 to -75 ° C and most advantageously in the range of -20 to -35 ° C.

Thus, a first driving force to initiate the products from the inlet 8 of the trough 2 to its outlet 9 consists of the products in their fluidized state as they push each other forward. Another driving force consists of advancing the conveyor belt 6 towards the outlet 9, see arrow P in FIG. 2, 4 and 6. All products that come into contact with the conveyor belt 6 are thus pressed forward with the aid of the belt. Which is the greatest driving force depends on the degree of fluidization and may vary from time to time.

When the products are supplied to the trough 2 through the inlet 8, they will initially be cooled, which takes place in a zone referred to as the cold zone A, next to the inlet of the trough 2. As the temperature of the products passes 0 ° C, the products are frozen to a temperature of approx. --2 to -5 ° C, preferably -2 to -3 ° C, which takes place in a zone referred to as the freezing zone B located downstream of the cold zone A. Depending on the length of the trough 2 and the holding time of the products in the trough For example, freezing zone B may enter a deep freezing zone C located downstream of the freezing zone, wherein the products are frozen down to a final temperature preferably below -18 ° C. Of course, it should be understood that it is not possible to specify precise limits for temperature values indicating where one zone ends and the other begins, as the products under fluidisation randomly tumble around the trough 2 with successive advance in the conveying direction of the conveyor belt 6.

The apparatus 1 may merely comprise a cold zone and a freezing zone B, in which case deep freezing is carried out in a separate room. Deep freezing can even be performed in an apparatus of a completely different type.

The air conduit means 10 of the prior art apparatus, as described above, will now be described with reference to FIG. 2 and 3.

As mentioned above, according to the prior art, without exception, the strongest air flow F and thus the strongest fluidisation is used in the cold zone A and especially at the end thereof next to the inlet 8. The reason for this is that, as mentioned above, it is traditionally assumed that that fresh products require a higher air flow F at the inlet end of the trough and thus stronger fluidization to reduce their temperature rapidly.

In order to provide this higher air flow F and thus greater fluidization, the air-conducting means 10 has a hollow pattern 11 having a smaller throttle 12 and thus a higher air flow F next to the inlet of the trough 2 and a throttle 12 which is subsequently gradually increased to provide a lower air flow F in a downstream direction. As a result, the air flow F is highest in the cold zone A and then falls and is practically constant in the freezing zone B and in a deep freezing zone C, if any. This is shown schematically in the diagram of FIG. 3. The same diagram also schematically shows how the product temperature Temp gradually decreases as the products are directed towards the outlet 9 of the trough 2.

However, in connection with the present invention, it has been recognized that this traditional distribution of air flow causes unnecessary vigorous mixing of the products in the cold zone A, that is, at the stage where the products are most sensitive. Furthermore, nothing is gained by having the strongest mixture at the inlet 8 of the trough 2, since the products do not reach the freezing zone temperature until they are in the freezing zone B, which is in fact the place where they must be separated to provide individual freezing. The solution to this problem - and thus the invention, will now be described with reference to FIG. 4 and 5, are cross sections of the apparatus 1 according to the invention and a diagram with an air flow F 'and a product temperature Temp', respectively, seen along the length of the trough.

The apparatus 1 according to the invention has the same design as that described above and will therefore not be described again. The apparatus 1 according to the invention comprises an air-conducting means 10 'arranged as follows. In the cold zone A ', the air flow F' is moderate and practically constant through a strong or even very strong throttle 12 'in the air conduit 10'. The throttle 12 'in the air conduit 10' falls in the transition to the freezing zone ES ', and the air flow F' and thus the fluidisation will become stronger. Thus, the air flow F 'has its maximum, that is, the throttle 12' has its minimum, in the freezing zone ES ', where the products start to freeze and thus risk freezing together. Any tendency to freeze is eliminated by locally stronger fluidization that separates products that are freezing together.

If the trough comprises a deep freezing zone C, it is arranged downstream of the freezing zone ES '. In and in connection with such a deep freezing zone C ', the air-conducting member 10' has a throttle 12 'which is larger than in the freezing zone B', that is, the air flow F 'and the fluidization in the deep freezing zone C' is less than in the freezing zone B '. .

As an example, the air velocity through the trough 2 may be 2-4 m / s in the cold zone A ', 5-7 m / s in the freezing zone B and 2-4 m / s in a deep freezing zone C', if any.

In the embodiment described above, the fans (not shown) are arranged in a common area (not shown) parallel to the room. Thus, it is difficult to use the blowers to control the air flow through the trough to obtain the various zones and their different degrees of fluidization of the bed of products. The use of an air-conducting device with varying degrees of throttling is therefore a simple, inexpensive and reliable solution which is also easy to vary according to, for example, the type of product and the individual requirements thereof. The reduced air flow in the freezing zone C, if any, is made possible, since the size of the air flow, in terms of freezing, is less important once the products have started to freeze.

The air conduit means 10 'according to the invention are advantageously divided into segments (not shown) which are directed transversely to the feed direction of the conveyor belt 6. The air conduit means 10 'preferably consists of one or more plates having a hollow pattern 11' which is, for example, punched or cut into a suitable pattern. For example, the hollow pattern 11 'may consist of circular or oval through holes or slits extending longitudinally or transversely of the air-conducting member 10' provided in one piece or in segments. The geometric shape of the hollow pattern 11 'is immaterial. What is important for the invention is that the hollow pattern is designed so that the droplet 12 'is at its minimum in and in connection with the freezing zone B', where the products are most sensitive.

The throttle 12 'may advantageously be reduced or increased in or in connection with the transition between two zones. For example, the throttle 12 'of the air-conducting means 10' may be arranged to gradually fall in the cold zone A 'towards the freezing zone B'. Similarly, the throttle 12 'thereof in the freezing zone may be gradually increased toward a deep freezing zone C, if any.

Advantageously, the air-conducting member 10 'is arranged to be secured by a hinge along the length of the trough 2. As a result, the air-conducting member 10 'can be easily tilted to allow cleaning. In addition, the air-conducting means 10 should be easily removable and replaced to allow the hollow pattern 11 'and thus the air flow F' through the trough 2 to be adjusted to the type of products to be processed in the apparatus 1. For example, a shrimp requires a different air flow. and fluidization than, for example, a pea in the various zones to reach the required temperature and product quality during its holding time in the trough.

Referring now to FIG. 6 and 7, where another embodiment of the apparatus 1 according to the invention will be described. FIG. 6 is a cross-section of the apparatus 1, while FIG. 7 is a diagram with an air flow F '' and a product temperature Temp '', respectively, seen along the length of the apparatus.

The apparatus 1 is divided into two compartments 31, 32 which are constructed in substantially the same manner as the pre-described compartment 3, and therefore only the features unique to this embodiment will be described. The trough 21 in the first compartment 31 comprises a cold zone A '' and a freezing zone B '', while the trough 22 in the second compartment 32 constitutes a deep freezing zone C11.

The first compartment 31 comprises an air conduit means 10 '' which, in a first portion adjacent to the inlet 8, has a strong or even very strong throttle 121 'to create said cold zone A'1. The air flow F '' and thus the fluidization in this cold zone A'1 is moderate or low and practically constant. In the transition to and in the freezing zone B1 ', the throttle 12' 'of the air-conducting member 10' 'decreases, thus making the air flow F'1 and the fluidization in the freezing zone B11 stronger than in the cooling zone A' '. For example, the air flow F '' in the cold zone A '' can have a velocity of 2-4 m / s and the air flow F'1 in the freezing zone B '' a velocity of 5-7 m / s.

The first trough 21 is of such length that the products reach a suitable freezing temperature during their holding time therein. By a suitable freezing temperature is meant as before a temperature in the range of 0 ° C to -5 ° C and more advantageously -2 to -3 ° C.

In the area (not shown) parallel to the first compartment 31 there are one or more fans which create an air flow which is later distributed by the air-conducting means to obtain the desired air flow through the trough 21 and its cold zone A 'and freezing zone. B 1 1.

When the products have reached the desired freezing temperature, they leave the first compartment 31 and are led to a second compartment 32 which follows the first compartment. In the second compartment 32, the products are accommodated in a second trough 22 in which the products are frozen. Thus, the second compartment 32 is a freezing zone C1 'where the products are fluidized to reach a temperature of preferably at least -18 ° C. The second compartment 32 does not have air-conducting means.

The second compartment 32 is adjacent to another area (not shown) comprising one or more blowers generating the air flow F '' which is led up through the second trough 22 to the desired degree of fluidization of the products occupied. therein. Since the purpose of the second compartment 32 is to freeze the products, a uniform flow of air F'1 is necessary only through the second trough 22.

The air flow F '' in the second compartment 32 can be kept at a low level and for example have a velocity of 2-4 m / s, that is considerably lower than in the freezing zone B1 'in the first compartment 31. It is in fact that prefer that the products are subjected to less intense fluidization during freezing than during freezing, on the one hand to prevent damage during impact and, on the other hand, that the degree of fluidization does not affect the rate at which the products are frozen when the products have reached a temperature below 0 ° C.

The holding time of the products in the second trough 22 and thus the time for obtaining the desired freezing temperature is controlled by the conveying speed of the conveyor belt 62. Since the time for freezing the products is shorter than the time for deep freezing, the conveyor belt 62 in the second compartment 32 may have a significantly lower feed rate than the conveyor belt 61 in the first compartment 31.

The two compartments 31, 32 are advantageously arranged in immediate extension of each other and with a relative height difference, whereby the products discharged from the first compartment 32 fall directly into the second compartment 32 by gravity.

The two compartments 31, 32 are physically separated from one another, but it is clear from FIG. 6, that their low pressure zones, that is, the zones above the troughs 21, 22, may be interconnected.

The material selected and the surface quality of the compartments 3, 31, 32, the area 13 and the equipment provided therein should be adapted to optimal food hygiene. This means, if possible, that the material should be stainless steel and that unnecessary corners, edges and joints should be eliminated or made available for cleaning. Rooms 3, 31, 32 and area 13 should be easily accessible for cleaning and maintenance. Rooms 3, 31, 32 and area 13 preferably have doors or covers (not shown) through which personnel can enter for maintenance and cleaning. In addition, the air-conducting means 10, 10 'and the conveyor belts 6, 61, 62 should be accessible for cleaning. Conveniently, the air-conducting member 10 ', 10' 'is provided with a hinge mechanism (not shown), whereby it can be tilted from its operating position, preferably directed in the horizontal plane, to a maintenance position where its surface and hollow pattern are easy. to access and easily replace.

The air-conducting means 10 ', 10' 'have been described above as comprising a hollow pattern 11' with throttles 12 ', 12' 'to obtain the desired air flow F', F * '. This hole pattern 11 'has further been described as extensive holes cut or shaped in some way. Of course, it will be appreciated that the hollow pattern 11 'can also be provided in the form of shutters or valves. Such shutters or valves can be controlled to achieve the desired degree of throttling over the length of the air-conducting member 10 ', 10' ', depending on the product currently being treated.

It is to be understood that the present invention is not limited to the embodiments shown. Thus, several modifications and variants may be envisaged within the scope of the invention which, as a result, are defined solely by the appended claims.

Claims (17)

An apparatus (1) for freezing products in a fluidized bed comprising an air-permeable conveyor belt (6, 61) forming over a portion of its length a bottom surface (4) of a trough (2, 21) which is adapted to accommodate the products to be frozen and an air-conducting means (10 ', 10' ') arranged over said portion of the conveyor belt (6, 61) to direct a flow of air (F1, F11), which is supplied through the trough (2, 21), via the bottom surface (4), which air-conducting means (10 ', 10'1) is arranged to direct the flow of air (F *, F' ') so that a bed formed by the products in the trough (2, 21) is subjected to a first fluidization in a cold zone (A ', A1') of the trough {2, 21) and a second fluidization in a freezing zone CB ', B' ' ) of the trough (2, 21) downstream of the cold zone (A ', A'1), characterized in that the air-conducting means (10', 10 '') comprises a sprinkled first portion arranged in connection with the cold zone (A '). , A ''), and a choppy second part arranged in connection with the freezing zone (ES ', ES'1), the second part having a smaller throttle (12', 12 '') than the throttled first part, and the second fluidization being more powerful than the first and so powerful that the freezing of adjacent products is counteracted. Apparatus according to claim 1, in which the air-conducting means (10 ', 10' '} comprises a non-sprung second part arranged in connection with the freezing zone (ES', B ''). Apparatus according to claim 1 or 2, in which the air-conducting means (10 ', 10' ') is arranged in one piece. Apparatus according to claim 1 or 2, in which the air-conducting means (10 ', 10' ') is divided into segments in a direction transverse to the direction (P) of the conveyor belt (6, 61), which segments have different degrees of thrush (12 ', 12' '). Apparatus according to any one of claims 1-4, in which the trough (2, 21) has a freezing zone (C, C1 1). Apparatus according to claim 1 or 2, wherein the air-conducting means (10 ') comprises a throttled third part arranged in connection with the freezing zone (C), which third part has a greater throttle (12') than the second part. . Apparatus according to any one of claims 1-6, in which the flow of air (F'f F '') in the cold zone (A ', A' ') has a velocity of 2-4 m / s. Apparatus according to any one of claims 1-6, in which the flow of air (F ', F'1) in the freezing zone (B Γ, B111) has a velocity of 5-7 m / s. Apparatus according to claim 5, wherein the flow of air (F ', F' ') in the freezing zone (C, C' ') has a velocity of 2-4 m / s. Apparatus according to any one of claims 1-9, in which the air-permeable conveyor belt (6, 61) is endless. Apparatus according to any one of claims 1-9 and comprising a second air-permeable conveyor belt (62) forming along a portion of its length a bottom surface (4) of another trough (22) adapted to receive and deep-freeze the products frozen in the first trough (2, 21). Apparatus according to claim 11, in which the first trough (2, 21) is accommodated in a first compartment (3, 31) and the second trough (22) is arranged in a second compartment (32) which follows the first compartment (32). room. A method of freezing products in a fluidized bed and comprising fluidizing a bed of products contained in a trough (2, 21) so that the bed is subjected to a first fluidization in a cold zone (8, 8 ') by the trough (2, 21) and a second fluidization, which is more powerful than the first fluidization, in a freezing zone (B1, B1 ') of the trough (2, 21), each first and second fluidization being each provided by the trough ( 2, 21) is provided with a stronger flow of air (F ', F'1) in the freezing zone (B', B1 '} than in the cold zone (A', A ''), which flow of air (F1, F11) is controlled by means of an air-conducting means (10 ', 1011) / provided with throttles (12', 12 ''), which air-conducting means has a larger throttle (12 ', 12' ') in the cold zone (A1, A'). 1) than in the freezing zone (B ', B' '), which other fluidization is given to such an extent that counterclockwise mating of adjacent products is counteracted. The method of claim 13, comprising the feature of fluidization taking place in such a way that the bed is subjected to a third fluidization in a deep freezing zone (C, C'1), which third fluidization is less powerful than the second fluidization. The method of claim 14, wherein the freezing zone (C, C '') is arranged in a second trough (22). The method of claim 15, wherein the first trough (21) is arranged in a first compartment (31) and the second trough (22) is arranged in a second compartment (32) following the first compartment. A method according to any one of claims 13-16, wherein the bed during its fluidisation is conveyed through the respective troughs (2, 21, 22) carried on a bottom-forming, air-permeable conveyor belt (6, 61, 62) arranged therein.