WO1998030849A1 - Quick freezer for food products in bulk with fluidisation and transfer system - Google Patents

Abstract

The invention concerns a quick freezer for food products in bulk by transfer through it, comprising an elongated table for receiving and transferring (2) the products, open-worked and permeable to air, and means for blowing chilled air provided beneath said table (2) and diffusing air through this table (2) for quick freezing the products and gradually moving them towards the downstream end of said table. The invention is characterised in that at least part of the blowing means or supplementary means (3) diffuse air jets (J) directed towards the table (2) and periodically moved with an oscillating motion, along a generally longitudinal direction relative to the table (2).

Description

 FREEZER FOR BULK FOOD PRODUCTS WITH FLUIDIZATION AND TRANSFER SYSTEM

The present invention relates to a deep freezer for bulk food products equipped with a fluidization and transfer system for said products. More specifically, it relates to a deep freezer which does not have an air permeable conveyor belt under which a series of fans supply cold air. Freezers with breathable conveyor belts are well known. Thus, for example, a document of this type describes in document FR-B-2 699 793 in the name of the applicant.

If, in terms of freezing, this type of installation is generally satisfactory, it nevertheless has drawbacks. Thus, the mechanical means for transferring food (conveyors) consist, for example, of a single perforated belt, with stainless steel or plastic mesh, or even double belts of stainless steel or polyvinyl chloride. Vibrating perforated troughs, vibrating troughs associated with one or more carpets or even single-use plastic strips / films deposited on conventional supports are also used.

All these systems require the use of mechanical components that are all the more reliable as they have to withstand significant temperature variation constraints (from - 40 ° C to + 30 ° C generally).

In addition, all materials and coatings used must be food grade. The construction techniques which it is necessary to employ, namely welding under argon, sealed tight chassis, cleanable open pipes, are restrictive.

Furthermore, the application of new safety standards, notably European and American, are difficult to comply with due to the multiple technical incompatibilities linked to the very principle of the mechanics used: belts, chains, sprockets, etc.

All these components (chassis, supports, slides, belts, shafts, sprockets, chains, vibrators, defrosting / drying belts, motors, reducers, etc.) justify the overall cost of the "installation drive mechanics" which represents about 30 to 50% of the cost of conventional freezers.

These bodies require significant maintenance and represent sources of malfunctions, breakdowns and overconsumption of sensitive energy. Their more or less significant complexity and inaccessibility pose cleaning problems. In addition, they generate overconsumption of water for defrosting and washing.

Most freezers have an outdoor station for defrosting, washing and drying their entrance mat. In addition to the drawbacks of maintenance, cleaning, water consumption and energy, these installations occupy a large space, therefore costly and not used for the effective freezing of products.

It will also be noted that the more or less significant bonding and the infiltration of the particles of products cause progressive fouling of the carpets after a certain operating time. This drawback necessitates constant cleaning.

To ensure proper cleaning, first defrost the carpets. This is done with cold water or, increasingly, with hot water.

After washing the chains or the carpet, they must be dried thoroughly before being reintroduced into the freezer, under penalty of freezing which would cause their wear or even their break in the short term. The effective conventional drying means are provided by centrifugal fans which generate a breath of air at medium pressure and high flow or, high pressure and low flow. In all cases, these drying means drive an energy consumption (about 5 kW per carpet) and a significant noise nuisance.

In addition, in existing freezers, the transfer functions in the freezing process are important. Their implementation, operation and maintenance generate areas and volumes not directly used for the effective freezing of products: - product entry station for defrosting, washing and drying

(Up to 2 meters long).

- length lost for technical access to the inlet and outlet inside the freezer.

- access spaces for maintenance and cleaning. Finally, the internal cleaning of freezers is one of the major problems and concerns of operators because they require a significant internal manual washing time which is painful for the operators, even dangerous. In addition, despite significant water consumption and all the care provided by "washer-defrosters", there are often areas of accumulation of products which very quickly become "bacterial nests". Furthermore, a freezing system has been proposed which does not have a movable conveyor belt which, of course, does not have the abovementioned drawbacks of the prior art.

Thus, the document EP-A-0224289 (GRASSO'S LONINKLIJKE) relates to an apparatus for freezing pieces of solid food such as fragments of cauliflowers, onions, leeks, etc. This apparatus comprises an elongated box provided at one end with a cooled gas inlet. The upper wall of the box is perforated and permeable to cold gas. The bottom wall of the box is oblique and has a freely rotating valve. Depending on the position of this valve, the flow of cold gas is deflected, so that there is a kind of pulsation of the gas above the wall which freezes and gradually displaces the pieces of food.

However, the pieces of food are moved randomly, depending on the position at a given time of the valve. Furthermore, the air flow generated is not sufficient to deagglomerate food and ice aggregates which, inevitably, tend to form during the freezing process. The present invention aims in particular to overcome these drawbacks. More specifically, it aims to provide a deep freezer without a conveyor belt which not only ensures the freezing of food, but also their fluidization and their transfer, that is to say their movement along the deep freezer, this is particularly regular and without creating undesirable agglomerates.

Consequently, the invention also aims to propose a freezer having fewer wasted spaces than the freezers of the state of the art, the internal cleaning of which is reduced and facilitated and which makes it possible to adapt without problems. to new safety standards.

It is therefore a freezer for bulk food products by transfer through it, which comprises an elongated plate for receiving and transferring products, perforated and breathable, as well as means refrigerated air blowing provided below said plate and diffusing air through this plate to freeze the products and move them gradually towards the downstream end of said plate.

This freezer is remarkable in that at least part of said blowing means or additional means diffuses air jets directed towards the plate and driven in a periodic oscillating movement, in a generally longitudinal direction relative to said plate . This means that part of the blowing means diffuse jets of refrigerated air, which are driven by a periodic oscillating movement, or that additional means diffuse such jets. In the latter case, the air can be refrigerated to assist in freezing. However, it may not be refrigerated or not refrigerated enough to help.

Furthermore, according to other characteristics and advantages of the invention:

- Said blowing means consist of ramps pierced with air diffusion orifices;

- Said ramps extend parallel to each other, generally transversely to the general direction of the plate;

- each of said ramps is connected to a blower;

- The freezer includes means for driving all of the ramps according to said oscillating movement;

- These means consist on the one hand of a pinion provided at one end of said ramps, which cooperates with a rack driven by an alternating translational movement;

- the amplitude of oscillation (β) of said jets is of the order of 90 ° ± 30 °;

- said amplitude and the oscillation cadence are adjustable;

- Said plate is formed of a series of juxtaposed rods of isosceles triangular section, the base of which forms a bearing face for food products.

Other features and advantages of the invention will become apparent from the description and the appended drawings which present certain preferred embodiments thereof.

In these drawings: - Figure 1 is a very schematic view in longitudinal section of the freezer of the invention;

- Figure 2 is also a schematic view of the freezer of Figure 1, along a transverse section plane;

- Figure 3 is a perspective diagram showing the arrangement of the cold air projection ramps arranged below the perforated support plate of the food to be frozen;

- Figure 4 is a perspective view of two ramp sections, pierced with openings according to two different embodiments;

- Figure 5 is a cross-sectional view of a ramp and the support plate, as well as means for imparting to the latter an oscillatory movement; - Figures 6 and 7 are cross-sectional views of a portion of the support plate used in the context of the invention, respectively without and with air blowing;

- Figure 8 is a diagram showing a ramp in cross section and intended to explain the effect of the movement of the ramp on the movement of food;

- Figure 9 is a diagram showing the impact of the adjustment of the oscillatory movement of the ramps on the direction of the air jets.

The device 1 shown in Figures 1 and 2 is a deep freezer for bulk food products. It includes an insulated thermal enclosure delimited by longitudinal walls 18 and 19, transverse walls 10 and 11, a ceiling 12 and a sloping floor 13.

The transverse walls 10 and 11 are each pierced with an opening 14, respectively 15, for the entry and exit of the food P. To facilitate these operations, the openings 14 and 15 each have a ramp inclined relative to the horizontal .

Along one of the longitudinal walls, in this case the wall 19, is provided an elongated plate 2 for supporting and transferring the products P. This plate has, seen from above, a rectangular shape and extends from the wall 10 to the wall 11. The total length of the enclosure has been designated by the reference 1 and the thickness of the walls 10 and 11 by e. The length of the plate 2 is equal to 1 - 2e, which means that the entire useful length of the enclosure is used to freeze food products.

Plate 2 is openwork and breathable. We will return more precisely to a preferred structure of this plate, later in the description.

Fans 4 are provided in the lower part of the enclosure, six in number in FIG. 1. These are, for example, Woods type fans of 9 kilowatts each delivering 33,333 m ³ / h. They can be fitted with a frequency converter, for example of the DANFOSS brand, which allows a variation in flow rate of around 5 to 110% of their nominal capacity to be obtained.

They are preferably of the helical type to allow the maintenance of good yields at low speed.

These fans produce a flow of air which passes through an evaporator (not shown) and which cools it to a temperature of approximately -30 ° C. The evaporator has for example a power of 360,000 Watt for an air inlet / outlet temperature of

-28 ° C to -32.2 ° C, with an evaporation temperature of -38 ° C. Battery surface is 1,905 m 2 and the supply of this battery, which operates with ammonia, is provided by a pump.

Below the plate 2, but above the fans 4, are provided pulsating turbines 3, preferably with variable flow rate (not shown in FIG. 1) which have the function of ensuring ventilation for fluidization and transfer of P products during deep freezing. They also contribute, to a certain extent, to the freezing of products P. In a way, they complement the freezing action of the fans 4.

These turbines are for example of the brand AIR PROCESS INDUSTRIE, reference EU.502, of power equal to 9kW and delivering a maximum air flow of

Each turbine 3 communicates with a ramp 30 for diffusing air jets, the structure of which we describe precisely.

There is shown in Figure 2 by arrows g the closed circuit that undergoes the refrigerated air inside the enclosure.

In the angles of the latter are mounted washing ramps 5 at very high flow rate connected by pipes not shown to a source of water supply. These ramps are intended to allow cleaning of the deep-freezing equipment between two deep-freezing campaigns. As shown in FIG. 5, the pulsating turbines 3 are arranged transversely with respect to the plate 2. Each of them is connected to a ramp 30 in the form of a pipe of circular section. A tip 31 of the turbine 3 is fitted into the open end of the ramp, with the possibility of pivoting of the ramp relative to the tip. In the embodiment of FIG. 3, the ramps 30 are provided with nozzles 31 for diffusing air jets J. In that of FIG. 5, the ramps are simply pierced with openings 32 for diffusing jets of air. air. Whatever the variant, the jets are directed towards the plate 2. The jets preferably have a diameter of between 6 and 10 mm. In Figure 4 are shown two possible embodiments of the openings 32, namely elongated slots and holes of circular outline. These openings are respectively capable of diffusing jets in the form of bands and nets.

The plate 2 is equipped on its upper face with lateral guides 20, while its lower face receives fixing parts 22 for rings 33 for guiding rotation of the ramp 3, in which it is fitted. These rings are for example made of a synthetic material such as that known under the name TECHNYL.

For the sake of simplification, we have dispensed from showing in FIG. 3 the means for driving the ramps in an oscillating movement. On the other hand, these means are shown in section in FIG. 5.

Thus, the end of the ramps opposite the turbines 3 is closed by a plug 60 which is made in one piece with a notched pinion 6 made of plastic. The set of pinions cooperates with a rack 7 which extends horizontally and perpendicular to the ramps 3. In other words, it extends parallel to the longitudinal axis of the plate 2. It is moved in translation by means not shown such as a gear motor. A part 70 acts as a rail and provides translational guidance for the rack.

Of course, other drive means can be used, for example a system of links or cams. It is understood that a translational movement alternately in one direction and then in the opposite direction, that is to say in a direction perpendicular to the plane of the drawing, ensures the drive of the ramps 3 according to a periodic oscillating movement (double arrow h ).

The jets J are therefore distributed longitudinally with respect to the large dimension of the plate and in an alternating movement. If necessary, the drive means (pinions 6 and racks 7) are arranged outside the freezer for easier maintenance.

Preferably, the plate 2 is of the type shown in FIGS. 6 and 7, that is to say formed from a series of longitudinal and juxtaposed metal rods 21, held together for example by welding. Each rod assumes in section the shape of an isosceles triangle, the point 211 of which faces downwards, while the base 210 constitutes a bearing face for food products P. Of course, the spacing between the rods 21 must be chosen so as not to allow food fragments to pass between them. In any event, the space E between these rods is sufficient to ensure the passage of cold air, as shown in FIG. 7 where the air flow is symbolized by the arrows A. As shown in FIG. 8 , it can be seen that if the ramp 3 is alternately tilted in the direction h by about a quarter of a turn, the air flow and correspondingly the products P will move in the direction of the arrow f. On the contrary, if the tilting takes place in the direction h ', the placement will take place in the direction f'.

Reference β is given in FIG. 91 'angle of oscillation of the ramps. This is of the order of 45 ° on either side of a median position, with an adjustable amplitude of the order of 30 °. As this figure shows, the middle position (represented by the arrow k) is not necessarily vertical.

Due to the mobile and pivoting nature of the jets emitted by the ramps, the products P are lifted and moved while being frozen. In addition, the jets also have the function of deagglomerating the "packages" of ice and food that come to form.

The jets can be offset transversely to "treat" the entire surface of the plate 2 as well as possible. The amplitude and the speed of pivoting (or oscillation rate) can be adjusted according to the nature of the products. Each ramp can be rotated separately, which makes it possible to obtain cross-jets in the product layer, thereby improving the decompaction efficiency of these products, especially when it is hardwood (leeks, spinach, etc.).

With regard to cleaning, the removal of the moving belt of the freezers of the prior art and of all their drive mechanics eliminates the risks of development of "bacterial nests" by accumulation of products and allows increased washing efficiency as well as '' reduced water consumption.

Claims

1. Freezer for food products (P) in bulk through it, which comprises an elongated plate for receiving and transferring (2) products (P), perforated and breathable, as well as blowing means (4) of refrigerated air provided below said plate (2) and diffusing air through this plate (2) to freeze the products (P) and gradually move them towards the end downstream of said plate (2), characterized in that at least part of said blowing means (4) or additional means (3) diffuse air jets (J) directed towards the plate (2) and animated of a periodic oscillating movement, in a generally longitudinal direction relative to said plate (2). 2. Freezer according to Claim 1, characterized in that the said blowing means (3) consist of ramps (30) pierced with air diffusion orifices (31, 32). 3. Freezer according to claim 2, characterized in that said ramps (30) extend parallel to each other, generally transversely to the general direction of the plate (2). 4. Freezer according to claim 2 or 3, characterized in that each of said ramps (30) is connected to a blower (3). 5. Freezer according to one of claims 2 to 4, characterized in that it comprises drive means (6, 7) of the set of ramps (30) according to said oscillating movement. 6. Freezer according to claim 5, characterized in that these means consist firstly of a pinion (6) provided at one end of said ramps (30), which cooperates with a rack (7) driven by an alternating translational movement . 7. Freezer according to one of claims 1 to 6, characterized in that the oscillation amplitude (β) of said jets is of the order of 90 ° ± 30 °. 8. Freezer according to Claim 7, characterized in that the said amplitude and the rate of oscillation are adjustable. 9. Freezer according to one of Claims 1 to 8, characterized in that the said plate (2) is formed by a series of juxtaposed rods (21) of isosceles triangular section, the base (210) of which faces support for food products (P).