Method and device for refrigerating and/or freezing articles

Abstract

A method and a device for refrigerating and/or freezing articles, in particular foodstuffs. The articles are conveyed by a conveyor belt through a treatment zone, where they are sprayed with a refrigerant from above through spray equipment. To prevent refrigerant from flowing down, a reflector level for collecting refrigerant is mounted beneath the conveyor belt. The conveyor belt and the articles on it are therefore additionally cooled from beneath.

Description

This application claims the priority of German Application No. 102004020180.3, filed Apr. 22, 2004, the disclosure of which is expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a method for refrigerating and/or freezing articles, the articles being conveyed by means of a conveyor belt through a treatment zone in which a refrigerant is sprayed on them from above.

Furthermore, this invention relates to a device for refrigerating and/or freezing articles, having a conveyor belt arranged in a treatment zone for conveying the articles through said treatment zone and having spray equipment mounted above the conveyor belt for spraying refrigerant onto the articles.

For refrigerating and/or freezing articles, e.g., for maintaining the stability of foodstuffs or for hardening steel or for other structural changes, equipment is generally used for this purpose in which the articles are conveyed by a conveyor belt through a treatment zone in which they are sprayed with a refrigerant. The refrigerant is usually a liquid gas, in particular liquid nitrogen or liquid carbon dioxide or liquid oxygen. For example, continuous freezing of foodstuffs is often performed in tunnel freezers in which the foodstuffs are conveyed through the freezer on a conveyor belt and are refrigerated and/or frozen in the process. If liquid nitrogen is used as the refrigerant, it is sprayed through spray nozzles from above onto the foods to be frozen in the rear area of the tunnel freezer, for example. Liquid nitrogen evaporates mainly directly on the foodstuffs. However, some of the sprayed liquid nitrogen does not strike the foodstuffs directly or it drips off of the foodstuffs. This lost nitrogen then passes through the conveyor belt, usually made of a mesh belt, into the bottom part of the tunnel freezer, where it makes little contribution to the refrigeration capacity.

The object of the present invention is therefore to provide a method of refrigerating and/or freezing articles, and a device for implementing the method, so that the refrigerant is better utilized.

This object is achieved according to this invention in terms of the process by the fact that the refrigerant dripping off of the articles and/or the refrigerant sprayed onto the conveyor belt is collected beneath the conveyor belt so that the refrigerant cools the bottom side of the conveyor belt and the articles.

In terms of the device, the object of this invention is achieved by the fact that a reflector level for collecting refrigerant is mounted beneath the conveyor belt.

This invention is based on the finding that the efficacy of refrigeration or freezing equipment may be increased if the liquid gas losses are reduced. To do so, a reflector is installed beneath the conveyor belt conveying the articles, preferably in the area of the liquid gas injection. This reflector level keeps the refrigerant that goes below the conveyor belt in contact with the conveyor belt from beneath and in this way cools the articles lying on the conveyor belt from beneath. When using liquid gas as the refrigerant, the liquid gas evaporates, cooling the conveyor belt and the articles. Therefore, as much heat as possible is removed from the articles to be refrigerated and/or frozen. Furthermore, the articles are cooled as uniformly as possible from all sides. Refrigerant dripping down without being used is thus used to improve the refrigeration process according to the invention.

This invention is particularly interesting for refrigeration and/or freezing equipment having a conveyor belt, e.g., a mesh belt, that is permeable for the refrigerant. The refrigerant which is sprayed from above and does not come in contact with the articles to be refrigerated and/or frozen but instead would pass through the conveyor belt is now captured by the reflector level and collected. The refrigerant collected here makes a specific contribution toward cooling the articles from beneath the articles. With traditional refrigeration or freezing equipment, however, the refrigerant passes through the conveyor belt into the bottom part of the equipment, where it evaporates more or less without being used.

The reflector level is preferably designed as a plate. Depending on the design of the refrigeration or freezing equipment, other forms of the reflector level are also conceivable.

To ensure effective cooling of the conveyor belt from beneath, the reflector level is expediently arranged at a distance of 0 mm to 40 mm beneath the conveyor belt. If the conveyor belt is deflected at both ends of the refrigeration or freezing equipment, resulting in an upper conveyor belt conveying articles to be refrigerated or frozen and a lower return conveyor belt, then the reflector level is mounted directly beneath the upper conveyor belt.

According to a particularly preferred embodiment, the spray equipment for supplying the refrigerant is connected to a liquid gas source which is designed in particular as a liquid nitrogen tank, a liquid carbon dioxide tank or a liquid oxygen tank. Especially in combination with use of liquid nitrogen, this invention manifests its advantages in particular. More enthalpy of evaporation is utilized for cooling the product per kilogram of nitrogen sprayed into the system. The efficiency of the refrigeration or freezing equipment is thus improved significantly. Furthermore, the specific refrigerant consumption (kg N₂/kg product) is also reduced.

Another positive effect that should be pointed out is that the reflector level closes part of the flow cross section of the refrigeration or freezing equipment for cold gas circulation. This reduces the cold gas circulation in the area of the nitrogen spraying. Less nitrogen evaporates on the path between the spray nozzles and the articles to be frozen, which increases the amount of liquid available and thus additionally increases the cooling capacity on the articles. In addition, the product is cooled intensely not only from above (through direct spraying of liquid nitrogen) but now is also cooled from beneath through the evaporation on the reflector level beneath the articles to be frozen. The refrigeration and/or freezing take(s) place much more uniformly, more rapidly and results in a better product appearance after refrigeration/freezing.

This invention may be used with all conceivable refrigeration or freezing equipment in which the articles to be refrigerated or frozen are conveyed on a conveyor belt through a treatment zone and a refrigerant is sprayed from above onto the articles. This invention may be used to particular advantage for refrigerating or freezing foodstuffs in refrigerating tunnels.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a tunnel refrigerator in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The figure illustrates a tunnel refrigerator for freezing foods. The tunnel freezer has a housing 1 in which is arranged a conveyor belt 2 for conveying the foodstuffs. The foodstuffs 3 lie on the conveyor belt 2 as they are conveyed through the cooling tunnel. On the path through the refrigerating tunnel, they are sprayed with liquid nitrogen from above through liquid nitrogen spray nozzles 4. The nitrogen gas atmosphere formed due to the evaporation of liquid nitrogen within the housing 1 is circulated by a fan 5. The conveyor belt 2 is deflected downward at the rear end of the cooling tunnel over a deflector roller 6 and returns as the bottom return conveyor belt 7. The conveyor belt 2 consists of a mesh belt that is permeable for the liquid nitrogen. Therefore, liquid nitrogen dripping off of the foodstuffs 3 and liquid nitrogen sprayed directly onto the conveyor belt 2 next to the foodstuffs will pass through the conveyor belt to the underside of the conveyor belt 2. In order for the liquid nitrogen not to run off into the bottom part 8 of the refrigeration tunnel and evaporate there without being utilized, a reflector level 9 is mounted directly beneath the upper belt 2. The liquid nitrogen passing through the conveyor belt 2 is captured by the reflector level 9, which may be designed as a simple reflector plate, for example, and is collected so that the underside of the conveyor belt 2 remains in contact with liquid nitrogen. This ensures that the conveyor belt 2 and thus the foodstuffs 3 are additionally cooled from beneath.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

1. Device for refrigerating and/or freezing articles having a conveyor belt situated in a treatment zone for conveying the articles through the treatment zone and having spray equipment mounted above the conveyor belt for spraying refrigerant onto the articles, wherein a reflector level for collecting refrigerant is mounted beneath the conveyor belt.

2. Device as claimed in claim 1, wherein the reflector level is a plate.

3. Device as claimed in claim 1, wherein the reflector level is arranged at a distance of 0 mm to 40 mm beneath the conveyor belt.

4. Device as claimed in claim 1, wherein the conveyor belt is as a mesh belt.

5. Device as claimed in claim 1, wherein the spray equipment is connected to a liquid gas source.

6. Method for refrigerating and/or freezing articles, whereby the articles are conveyed by a conveyor belt through a treatment zone in which they are sprayed with a refrigerant from above, wherein refrigerant dripping down from the articles and/or refrigerant sprayed onto the conveyor belt is collected beneath the conveyor belt in such a way that the refrigerant cools the underside of the conveyor belt and the articles.

7. A device for refrigerating and/or freezing articles, comprising:

a conveyor belt situated in a treatment zone for conveying the articles through the treatment zone;

refrigerant spray equipment located in the treatment zone above the conveyor belt for spraying refrigerant onto the articles; and

a reflector level located beneath the conveyor belt such that sprayed refrigerant passing beneath the conveyer belt is collected to cool the undersides of the conveyer belt and the articles.

8. A method for refrigerating and/or freezing articles, comprising the steps of:

conveying the articles by a conveyor belt into a treatment zone;

spraying the articles in the treatment zone with a refrigerant from refrigerant spraying equipment located above the articles; and

collecting refrigerant passing beneath the conveyor belt beneath the conveyor belt such that the collected refrigerant cools the underside of the conveyor belt and the articles.