Refrigeration – Processes – Treating an article
Utility Patent
1999-08-06
2001-01-02
Capossela, Ronald (Department: 3744)
Refrigeration
Processes
Treating an article
C062S374000
Utility Patent
active
06167708
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a process and to an apparatus for the in-line partial or complete freezing of products (which partial freezing may be termed “crust freezing”), of the type comprising an enclosure, a conveyor for introducing the products into the enclosure and for extracting them and a refrigeration system for freezing the products, this system comprising at least a sprayer for impregnating the conveyor with a cryogenic liquid.
(ii) Description of the Related Art
The “crust freezing” of a product is an operation consisting in freezing the surface of at least one of the faces of the product in order to facilitate its preparation or subsequent handling.
The technique of crust freezing is used in particular in the food industry so as to facilitate the preparation and subsequent handling of the products (slicing, weighing, etc.)—mention may be made here, by way of illustration, of the slicing of blocks of ham and loins of pork—but it is known that these crust freezing techniques are also applicable to other food products that have to undergo a preparation step, such as salami, sausage, cheese, fish, etc.
The impregnation of the conveyor allows that face of the products in contact with it to be frozen, this having the result inter alia of eliminating any phenomenon of adhesion between the products and the conveyor. The cryogenic liquid used is generally liquid nitrogen. Reference may be made, for example, to document EP-A-576 665 which describes such food crust freezing techniques.
The crust-freezing apparatuses, and more particularly the conveyor impregnation systems, that are known at the present time usually operate in one of the following ways: either the conveyor is immersed in a bath containing the cryogenic liquid or the conveyor is sprayed with cryogenic liquid on the upper face of its upper run. The amount of cryogenic liquid which impregnates the conveyor is chosen depending on the degree to which it is desired to refrigerate the products and depending on the thickness of the latter. The conveyor may therefore be partially or completely saturated with the cryogenic liquid.
The impregnation system using a bath is complicated to implement since the conveyor has to be immersed in a bath, before or after the products have been introduced.
Spray impregnation systems also have drawbacks, since it is difficult to completely control the impregnation of the belt. This is because the amount of cryogenic liquid, pressurized or unpressurized, discharged onto the upper face of the conveyor must be sufficient for the entire run of the conveyor to be impregnated, despite the presence of the products to be crust-frozen on this same face. Moreover, it is known that a certain amount of liquid tends to percolate through the upper and lower runs of the conveyor. In addition, in all cases, with the known systems a draining phenomenon appears at the drive rollers, because of the tension being exerted at this point. There is therefore excess cryogenic liquid that it is desired in general to recover using a receptacle and by means of a pumping set, in order to be reused or removed. However, it should be noted that this recovered liquid contains fines coming from the products to be crust frozen. These fines cause the pipework of the cryogenic liquid recovery and recycling system to be fouled.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the invention is especially to propose a process and an apparatus for in-line partial or complete freezing not having the abovementioned drawbacks, and in particular allowing controlled impregnation of the conveyors and making it possible to dispense with any system for recovery and recycling excess cryogenic liquid.
For this purpose, the subject of the invention is a process for the in-line partial or complete freezing of products of the aforementioned type, this process being characterized by the combined implementation of the following steps:
a) the conveyor is impregnated by spraying the cryogenic liquid onto the lower face of the upper run of the conveyor;
b) a check is made of the impregnation of the conveyor;
c) the spraying of the cryogenic liquid is regulated depending on the result of the impregnation of the conveyor;
Depending on the particular embodiments, the process according to the invention may have one or more of the following characteristics:
the cryogenic liquid is sprayed onto the lower face of the upper run of the conveyor with at least one spray nozzle located between the two runs of the conveyor and the opening of which spray nozzle is oriented toward the upper run of the conveyor;
the impregnation check makes it possible to determine the extent to which the upper run of the conveyor is not impregnated at the point where the products are extracted;
the check includes a measure of the temperature near the upper run of the conveyor;
the process furthermore includes the action of spraying the cryogenic liquid directly onto the products in a jet arranged so as to be almost perpendicular to the direction in which the products are conveyed.
The invention also relates to an apparatus for the in-line partial or complete freezing of products, of the type comprising an enclosure, a conveyor for introducing the products into the closure and for extracting them, and a refrigeration system for freezing the products, this system comprising a sprayer for impregnating the conveyor with a cryogenic liquid, the apparatus being characterized in that the sprayer for impregnating the conveyor is suitable for spraying the cryogenic liquid onto the lower face of the upper run of the conveyor and in that it includes a sensor for checking the impregnation of the conveyor and a regulator for regulating the operation of the sprayer depending on the result of the impregnation check.
The apparatus according to the invention may also include one or more of the following characteristics:
the sprayer comprises at least one spray nozzle located between the two runs of the conveyor and the opening of which spray nozzle is oriented toward the upper run of the conveyor;
the outlet of the nozzle is inclined toward the downstream end with respect to the direction of travel of the conveyor, for example at an angle close to 45° with respect to the plane of the upper run of the conveyor;
the sensor is suitable for checking the extent to which the upper run of the conveyor is not impregnated at the point where the products are extracted;
the sensor includes a temperature probe close to the upper run of the conveyor;
the refrigeration system furthermore includes a direct sprayer which comprises a nozzle spraying a jet of cryogenic liquid almost perpendicularly to the direction in which the products are conveyed;
the refrigeration system includes a mixer for mixing the atmosphere contained in the enclosure, the mixer being preferably located downstream of the sprayer.
REFERENCES:
patent: 5299426 (1994-04-01), Lermuzeaux
patent: 5454232 (1995-10-01), Lermuzeaux
patent: 5460015 (1995-10-01), Venetucci
patent: 5467612 (1995-11-01), Venetucci
patent: 1 537 431 (1968-07-01), None
patent: 2 708422 (1995-02-01), None
patent: 1 241 061 (1971-07-01), None
patent: 1 482 484 (1977-08-01), None
patent: WO 93/14358 (1993-07-01), None
Capossela Ronald
L'Aire Liquide, Societe Anonyme pour l'Etude et l&apos
Nixon & Peabody LLP
Schulman Robert M.
LandOfFree
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