Apparatus for continuously deep-freezing food products

Abstract: An apparatus for continuously deep-freezing food products comprising a rotary drum (1) the axis of which is slanted toward the outlet (22); a cooling system (26); suction means (28) for creating a cooling air stream (G) rising up the drum in countercurrent with respect to the product feeding direction (P) and for discharging said cooling stream; an elongated bridge structure (33) supporting fans (38) for causing the cooling stream (G) to circulate in contact with the product (42) to be deep-frozen and a plurality of fins (40) for continuously mixing the product during the deep-freezing process. The cooling stream can be generated by cryogenic gases or by a refrigerating coil e.g. a freon cooling system.

Description: The present invention relates to an apparatus for continuously deep-freezing food products, apt to hold in a mutually loose condition the separate components of the products in order to yield be it homogeneous products to be admixed after the deep-freezing process, be it assorted products which are already mixed from the start of the deep-freezing process, as well as special mixed products, of a different nature. Already since several years there have been made available on the market deep-frozen food products, such as specific types of vegetable food products, both of an homogeneous and a mixed type, due to the great advantages consisting of a very good preservability, the maintenance of the products organoleptic properties, the great practicality of selling and using metered portions of said products. Of late has also undergone expansion the sale of mixed products, such as seasoned risotto and alimentary pasta products, ready-for-use. Prior systems for deep-freezing large amounts of food products provide for conveying the latter at a low speed through a cooled tunnel or bringing said food products to refrigerating rooms where they are statically deep-frozen. The features of the preamble of claim 1 are known from document WO-A-91 05 212. The document discloses a freezing tunnel, which is used for freezing scrap in recycling scrap operations. The tunnel has a scrap inlet and a scrap outlet, is rotated about its central longitudinal axis and is inclined downwardly towards the tunnel outlet. Through the tunnel gaseous cryogenic material (e.g. liquid nitrogen) is discharged and a plurality of fin is provided in the interior of the tunnel to drop the scrap. This apparatus is mainly provided for freezing scrap (e.g. polyvinylchloride or rubber products) and not suitable for food products, which require rapid and efficient freezing. These prior systems, however, do not allow the product particles or grains to be kept in a mutually loose condition and, even less so, to deep-freeze already seasoned and pasta and risotto food products possibly including vegetable, the use of which is now widely expanding as already stated. Accordingly, the object of the present invention is to provide a deep-freezing apparatus having the following features: a high hourly output and a low labour requirement, of comparatively small' dimensions and low cost so as to be readily suitable also for small to medium users; a continuous faster deep-freezing operation; maintaining in a loose or separated condition the single particles or grains of the starting food product, when in the final deep-frozen condition; a possibility of continuously adding seasoning substances (for example with pasta and risotto food products) during the deep-freezing step; a highly efficient thermal exchange between the deep-freezing gas and the food products to be deep-frozen. According to the invention, the deep-freezing apparatus comprises the features as defined in claim 1. The deep-freezing process is carried out by using a cryogenic gas such as, for example, liquid nitrogen or carbon dioxide, which are supplied through a nozzle diffuser arranged at the outlet of the apparatus in order to create a very low temperature gaseous stream which is conveyed upwardly in countercurrent toward the inlet of the food product, as a result of the action by the fan conveying the gas stream toward an outlet stack. Decisive for achieving the above mentioned objects of providing a rapid deep-freezing process, of keeping the food product in a loose-grain form and of providing a very efficient thermal exchange with a comparatively low use of a cryogenic liquid gas, have been found two measures, both intended for improve the thermal exchange between the food product and super-cooled stream. A first measure comprises providing on the inner surface of the drum a plurality of adjustably sloped fins continuously driving the food product from the periphery of the drum, in particular in an area where an accumulation of the food product occurs, by causing it to fall again toward the central part of the rotary drum. To that end, said food product mixing fins can be arranged either on planes substantially perpendicular to the rotary axis of the drum, or helically on the inner surface of the drum, wherein the screw pitch arrangement of the blades is opposite to the food product feeding direction in order to achieve a more efficient and more even mixing effect of the product, distributed along the overall length of the drum as well as a reduction of the food product feeding speed toward the oulet, thereby improving the deep-freezing effect. The second measure, synergically cooperating with the first, is that of causing the cooling stream to recirculate, which is attained thanks to a plurality of fans offset from the vertical median plane of the drum and rotatively driven in opposite directions one from the other, alternatively. The concept is to perform, within one and the same refrigerating environment, while maintaining a continuously operating process, the conveyance of the product through cascade arranged processing chambers in each of which the product comes into contact with the cooling stream, with the highest possible yield. The above has been effectively achieved thanks to the circulation of the deep-freezing stream in every sector within said drum, by means of a plurality of fans, suspended on the uppermost portion of the drum, which cause the supercooled stream to recirculate in the opposite direction from one drum sector to its adjacent one. This provision has been found to be very effective for rapidly cooling the food product resulting in reducing the length of the drum and, accordingly, the cost and overall size of the apparatus. In this connection it is evident that the cooling cycle can be adapted to the specific type of food product being processed, by varying the rotary speed of the drum and/or the slope thereof. An embodiment of the invention shall be disclosed in detail hereinafter, having reference to the accompanying drawings. In the drawings: Figure 1 is a longitudinal vertical-section view illustrating the device according to the invention; Figure 2 is a top plan section view of the subject device taken along the line 2-2 of Figure 1; Figure 3 is a cross-section view of the device taken along the line 3-3 of Figure 1; Figure 4 is a cross-section view of the device taken along the line 4-4 of Figure 1; Figure 5 illustrates a cross-section of the device taken along the line 5-5 of Figure 1; Figure 6 is a schematic view illustrating the mixing of the food product performed by mixing blades fitted inside the drum. As shown in figure 1, the apparatus for continuously deep-freezing food products comprises a drum 1 consisting of a double metal pipe 2 and 3, the space between which is insulated. The drum 1 is supported by a framework 6 provided with supporting elements 7 and 8 the height of which can be adjusted in order to vary the slope of the drum axis as needs be. The drum can turn on flanges 9 and 10 bearing on rollers and it is driven by a motor 12 (see Figure 4) for example by a belt 14. The first and second ends 16 and 18 of said drum are provided with thermally insulating end structures 17 and 19 comprising respective loading and unloading elements 20 and 22 for the food product. A duct 25 extending throughout the thermally insulating structure 19, feeds a cryogenic liquid to be atomized by means of a plurality of atomizing nozzles 26 to provide a minimum temperature inner area of even less than -90°C, at the second end 18 of the rotary drum 1. Within the inner area 5 of said drum, the cryogenic stream, generated by atomizing the liquefied cryogenic gas, rises according to the arrow G, whereas the food product, gradually introduced into the loading hopper 20, will be driven downward along the rotary drum in a countercurrent direction, as indicated by the arrow P. The thermally exhausted gas is sucked off at the first end 16 for the product to be deep-frozen, by a suction device 28 and it is conveyed to an outlet stack 30 through a conveying duct 29. In the inlet structure 17, as well as in the outlet structure 19, supporting elements 32, 32' for supporting a bridge structure 33 are provided, said bridge structure consisting of a pair of tubular rods 34, 34' to which are cantilever-wise coupled a plurality of shelves 36 each supporting a fan 38. Said fans, which are spaced from one another, turn, as shown in Figure 2, in reciprocally opposite directions to effectively distribute and homogenize the cooling gas throughin the several drum sectors. Figures 2 and 4 in particular illustrate the arrangement of the fans 38 and related supporting shelves 36 offset from the median vertical plane M of the drum, such an arrangement being so designed as to cause the cryogenic gas to swirl in said drum. Figures 4 and 6 illustrate the arrangement and operation of the stirring fins 40. Figure 6 schematically illustrates the shifting in the drum rotary direction, of the food product mass 42 undergoing cooling. The fins 40 are coupled to the inner surface of the inner pipe 3 of said drum 1 so as to cause the food product mass 42 to be detached from the bottom in such a manner as to remove layers thereof closest to said inner surface, causing them to fall to the central portion of the drum, thereby providing a good contact between the food product mass and the cryogenic gas. The fins 40 can be arranged on adjoining planes perpendicular to the axis of the drum, but, more effectively, they can be helically arranged, so as to affect the overall longitudinal extension of the drum and provide an evenly distributed and constant mixing effect. The apparatus as disclosed and illustrated relies substantially on the use of cryogenic gases which allow to reach very low temperatures, for achieving the object of the invention of a small sized rapid deep-freezing system, suitable for small concerns, in particular while solving at the same time the problem stemming from the new demand of preparing deep-frozen seasoned risotto and pasta food products. Actually, the apparatus allows to continuously add seasoning substances during the deep-freezing stage-step, while preventing the sauces from being polluted because of prolonged handling in the presence of air, since the atmosphere inside the rotary drum substantially consists of inert gases such as nitrogen or carbon dioxide. Moreover, the apparatus has a very high operating flexibility, since it allows to also deep-freeze granular vegetable products while keeping them in a mutually loose condition and to packing them in any desired metered quantity. In effect the deep-frozen product, being in a granular and loose condition, can be suitably stored before being divided into different size sales packages. Moreover, it is possible to meter and distribute the product also in multidose bags since, said granular product having been deep-frozen individually the user can easily remove from a package only the quantity strictly necessary, thus avoiding unnecessary waste; moreover, the single doses of the product can be weighed in a more precise manner. The rapid deep-freezing process achieved through the product being exposed to the effect of a low temperature gas distributed in a more effective manner tanks to the provision of fans and to the efficient mixing effect attained through the fins suitably arranged in said rotary drum, allows to obtain a deep-frozen product presenting completely loose particles and to adapt the deep-freezing cycle to the particular size and mixing ratios of the food product components. While preserving the same basic concept of the invention but not being covered by the scope of the claims, the apparatus can also be employed for cooling cycles different from that based on cryogenic gases, for example by utilizing known cooling systems, by adjusting the size of the rotary drum and suitably arranging cooling coils or closed coil evaporators inside the drum along its overall extension or only at the two ends thereof, yet while continuing to rely on the system of mixing the product and of recirculating the cooled stream, as herein disclosed and illustrated.

Claims: An apparatus for continuously deep-freezing food products, including: a rotary drum (1) having a first end (16) for introducing a product to be deep-frozen and a second end (18) for discharging the deep-frozen food product, said first and second ends being closed by respective end structures (17, 19) which are thermally insulated and not rotatable; the first end (16) being arranged at a higher level than that of said second end (18) in order to provide a slanting of the drum axis suitable for causing an automatic feeding of the food product mass (42) toward the second end (18) along a product feed direction (P); a cooling system (26) that injects cryogenic gases at said second end (18) of said drum (1); means (28) for providing a depression at said first end (16) in order to cause the very low temperature deep-freezing gas stream to flow in a direction (G) opposite to said food product feed direction (P) inside said drum and to suck and convey the cooling gas stream, after having passed through said drum, toward an outlet stack (30); and a plurality of fins (40) for mixing said product (42) to be deep-frozen, said fins being applied on the periphery of the inner surface of said drum (1); characterized in that of further comprising a plurality of fans (38) arranged in the inner area (5) of said drum (1) and supported by a bridge structure (33) extending along the overall length of said drum. An apparatus according to claim 1, characterized in that said bridge structure (33) carrying said fans (38) is connected at its ends to supporting elements (32, 32') respectively connected to said fixed end structures (17, 19) and preferably consisting of a pair of tubular rods (34, 34') arranged near the vertical median plane (M) of the drum (1). An apparatus according to claims 1 and 2, characterized in that said fans (38) are mounted on shelves (36) cantilever-wise connected to a lower tubular rod (34') of said bridge structure (33), said fans (38) being offset from said vertical median plane (M) of said drum (1). An apparatus according to claim 3, characterized in that the fins of said fans (38) are rotatively driven in opposite rotary directions from each other, alternately. An apparatus according to claims 1 to 4, characterized in that said mixing fins (40) arranged inside said drum (1) for mixing the food product during the deep-freezing process are so slanted as to present their attachment side at a forward position with respect to the rotary direction (R) of said drum to facilitate the removal of layers of the food product (42) closest to the inner surface of said drum, causing said layers to fall to the central part of said drum. An apparatus according to claim 5, characterized in that said attachment sides of said fins (40) fitted inside said drum (1) are arranged on several planes which are perpendicular to the axis of said drum. An apparatus according to claim 5, characterized in that said attachment sides of said fins (40) fitted inside said drum (1) are helically arranged.

Inventors: PUGNALE BRUNO, PUGNALE, BRUNO
Applicants: PUGNALE S R L, PUGNALE S.R.L.
Application year: 1997
Main classification: F25D3
IPC codes: A23L3, F25D13, F25D3