A METHOD AND AN APPARATUS FOR SHRINKING OF WRAPPING FILMS

Abstract: With a method shrinking wrapped films (4) around a product, a product is conveyed through a shrinking tunnel (1) where it is subjected to a heating. To obtain a shrinking where the wrapped product (3) appears with pure (dry) and smooth surfaces to facilitate a preceding treatment in form of weighing, labelling, etc., heating is performed by means of water steam (8) which is introduced into the tunnel (1) through steam nozzles (6) adjustably suspended in brackets (7).

Description: A METHOD AND AN APPARATUS FOR SHRINKING OF WRAPPING FILMS BACKGROUND OF THE INVENTION The present invention relates to a method for heat shrinking wrapping films for a product, preferably a food product, by conveying the pre- wrapped product through an essentially closed shrinking zone wherein a steam, preferably a water steam, is introduced which heats the wrap¬ ping film so that it shrinks tightly around the product. In hitherto known methods shrinkage is achieved in heat tunnels by using hot water or hot air. These media are sprayed and injected, re¬ spectively, into the tunnel or the shrinking zone and down onto the pre-wrapped product. Thus a shrinkage of the wrapping film takes place which film thereby contracts around the product. These known methods are associated with several problems. They are ex¬ pensive as relatively much hot water is required which is expensive to heat and use as the water is directly discharged as waste water and in some situations this involve expenses for cleaning, etc. The water may also be deposited on the wrapped product, so that a considerable amount of water is removed from the shrinking zone. This may cause inconveni¬ ence to succeding weighing and labelling units. Thus the water may result in inexact weighing results and reduce the attachability of labels on the wrapped product. Furthermore, the shrinking effect ob¬ tained by use of water is not particularly good and it is almost im- possible to defir.e how and to what extent the shrinkage is desired on different regions of the product. Hot air is rarely used for shrinking since this method is associated with high operating costs and since furthermore the hot air has a ten- dency to "burn" the surface both on the wrapping film and on the pro¬ duct proper. To eliminate the drawbacks associated with the known methods, an appa¬ ratus is proposed in GB patent No. 2,164,911 which uses the method mentioned above for shrinking by means of steam heating. However, the apparatus described in this patent is associated with several draw¬ backs. Thus use of stationary steam nozzles will yield an unsatisfac¬ tory shrink packing of irregularly shaped products. Furthermore, the heating effect of the shrinking film will be concentrated in certain areas according to the location of the steam pipe and the orientation of the steam jets. Especially irregularly shaped products will appear with a non-uniform surface of the shrunk film thus rendering the fol¬ lowing treatment, like e.g. labelling, difficult. It is the object of the present invention to provide a method whereby it becomes possible to eliminate the drawbacks associated with the known method and which makes it possible to obtain a variable shrink¬ age adapted to the shape of the product so that the wrapped product appears with pure and smooth surfaces thus facilitating the succeeding treatment and imparts to the product an aesthetic attractive appear¬ ance. This object is achieved with a method mentioned in the introductory part which is characterized in that the steam is introduced into the shrinking zone through adjustable discharge means which are adjusted to emit a steam mist in a direction extending substantially penpendi- cularly to the conveying direction or at an angle in relation to a plane perpendicularly to the conveying direction and that the inten- sity of the steam mist along the entire circumference of the product is varied in order to provide varying shrinking effect. The steam being introduced through adjustable discharge means, an ad¬ justment of quantity, pressure and temperature may be performed and the discharge means may be adjusted to induce varying amounts of steam onto different parts of the product to provide an adapted shrinking effect. This provides optimum possibility for shrinking the wrapping film in the best possible way in order to obtain the smooth surface and the aesthetic appearance which are important for sales considera- tions. Besides, such optimum shrinking is advantageous for the shelf- life of the product when it comes to foodstuffs as it becomes possible supplant substantially all air from the wrapping film. By using steam jets of a relatively low velocity and providing relati- vely wide dispersion, a direct heating of substantially the entire wrapping film is advantageously obtained as the steam "clings" around the product. It is essential to secure a shrinking of the areas which are not directly exposed to a steam jet, e.g. because of the irregular shape of the product. The present invention also relates to an apparatus for shrinking of a wrapping film by a method according to the invention and comprising a shrinking tunnel comprising a conveyor for conveying pre-wrapped pro¬ ducts through the tunnel and means for discharging steam, preferably water steam, heating the film so that it shrinks, said apparatus being characterized in that the steam discharge means are adjustable in dif¬ ferent positions and are provided with means for individual adjustment of quantity, pressure, dispersion and temperature. Such an apparatus is advantageous as the adjustable steam discharging means permit a differentiated shrinking effect in different areas of the product. Thus the steam discharge means may be adjusted for de¬ livering a greater quantity of steam or a more concentrated steam jet towards areas where strong shrinking is to be performed. The remaining steam discharge means are adjusted for delivering a smaller quantity of steam. Effective utilization of the steam is hereby obtained as the steam concentration is only high in the areas where a large shrinking effect is desired. DESCRIPTION OF THE DRAWINGS The invention will now be further explained with reference to the ac- companyning drawing, wherein Fig. 1 shows a view of an apparatus for use by the method according to the invention as seen in the conveying direction for a product through the shrinking zone, Fig.2 is a side view of the apparatus shown in Fig. 1. Fig. 1 shows a shrinking tunnel 1. A conveyor 2 and a product 3 in the form of a cheese are provided inside the shrinking tunnel 1. The pro¬ duct is conveyed by means of the conveyor 2 through the shrinking tun¬ nel. The product 3 is pre-wrapped in a film 4, and at each end said film is closed with a clip 5. The conveyor 2 may be of an open type which also exposes the underside of the product 3. The tunnel is connected to a water steam generator (not shown) generating steam which is introduced into the tunnel 1 via discharging means in form of steam nozzles 6. The steam nozzles com¬ prise means (not shown) for individual adjustment of quantity, pres- sure, dispersion and temperature. The nozzles 6 are mounted in brack¬ ets 7 which permit an adjustment of the nozzles so that the position of their orifices are set according to the product to be shrink-pack- ed. Thus the steam nozzles emit a steam mist 8 over the product. Through adjustment of the nozzles 6 the intensity of the steam mist may be varied across the circumference of the product so that a vary¬ ing shrinking effect is obtained which makes it possible to obtain a more smooth and aesthetic attractive wrapping of the products 3. This may be obtained even with products having very irregular outer con- tours. Three nozzles are illustrated in Fig. 1 which are in the plane sub¬ stantially perpendicurlar to a conveying direction 9 (see Fig. ) for the product. However, it is obvious that this number is only stated for purpose of illustration and that it is possible to use any number of nozzles in order to obtain optimum steam mist around the product to be shrink-packed. It will also be possible to off-set the nozzles in the tunnel and the individual nozzles may be oblique in relation to the mentioned substantially perpendicular plane. Two successively mounted series of nozzles 6 arranged in this way are illustrated in Fig. 2. However, it is possible to provide any number of successively mounted series which may be practical with a view to the type of products to be packed. The brackets 7 support a sleeve 10 permitting an axial displacement of the nozzles 6 forwards and backwards through the sleeve 10. Further¬ more, the sleeve 10 is arranged for displacement along the bracket 7. Furthermore, the sleeve 10 comprises a ball connection (not shown) permitting an arbitrary angle position of the nozzle 6 in relation to the bracket 7. Thus it is possible to perform a more precise adjust¬ ment of the nozzle. Fig. 2 shows more clearly how a shrinking effect causing the film 4 to fit closely around the product is already imparted to the product 3 with its end being directed forwards in the conveying direction. At the rearwardly facing end of the product, the shrinking effect is not yet completed. By using the apparatus the conveying velocity of the conveyor 2 is so adapted and the quantity and the velocity of the steam mist 8 is so adjusted that the wrapping film 4, when the product 3 leaves the shrinking zone of the tunnel, is shrunk completely so as to closefit the product. The term "shrinking zone" of the tunnel means the area of the tunnel in which the steam nozzles 6 are active. Fig. 1 and 2 illustrate the elements necessary to understand the in¬ vention. It is obvious that a completely functional apparatus demands further details in the form of driving units, connection wires, con¬ trol units, discharge channels, etc. However, it will be possible for a person skilled in the art to provide such further elements on the basis of the above description of the invention.

Claims: AMENDED CLAIMS [received by the International Bureau on 6 August 1990 (06.08.90); original claims 1-9 replaced by amended claims 1-8 (2 pages)] 1. A method for heat shrinking wrapping films (4) around a product (3), preferably a food product, by conveying the pre-wrapped product through an essentially closed shrinking zone wherein a steam, prefer- ably a water steam, is introduced which heats the wrapping film so that it shrinks tightly around the product, c h a r a c t e r i z e d in that the steam (8) is introduced into the shrinking zone (1) through adjustable discharge means (6) which are adjusted to emit steam mist in a direction extending substantially perpendicularly to the conveying direction (9) or at an angle in relation to a plane per¬ pendicular to the conveying direction (9), that the intensity of the steam mist along the entire circumference of the product (3) is varied in order to provide varying shrinking effect and that the steam (8) is discharged at a very low velocity from the steam discharge means so that the steam clings around the product rather than hitting the pro¬ duct hard and being thrown back. 2. A method according to claim 1, c h a r a c t e r i z e d in that the pre-wrapped product (3) is conveyed continuously through the shrinking zone (1) at a velocity which is adapted so that the intended shrinking effect has been obtained when the product leaves the shrink¬ ing zone. 3. A method according to claim 1, c h a r a c t e r i z e d in that the product is conveyed through several successive series of steam discharge means (6) and that a desired variation of intensity along the circumference of the product is impared to each series of steam discharge means. 4. A method according to anyone of the preceding claims, c h a r a c - t e r i z e d in that the position of the discharge means is adjusted during the passage of the product through the shrinking zone (1) and that the position adjustment is performed in consequence of a preced¬ ing registration of the contours of the product. 5. A method according to claim 1, c h a r a c t e r i z e d in that the temperature and quantity of the steam are adapted to impart to the wrapped product as little heating as possible and that the product is steamed several times to obtain the desired total shrinking effect. 6. An apparatus for shrinking a wrapping film by a method according to the invention and comprising a shrinking tunnel (1) comprising a con¬ veyor (2) for conveying pre-wrapped products (3) through the tunnel and means (6) for discharging the steam (8), preferably water steam, heating the film so that it shrinks, c h a r a c t e r i z e d in that the steam discharge means (6) are provided with means (7) for indivi¬ dual adjustment of quantity, pressure, dispersion and temperature and that the steam discharge means (6) are individually adjustable as each of the steam discharge means are arranged for a sideways displacement in a plane substantially perpendicularly to the conveying direction (9), a translation perpendicular to said plane and for an angle posi¬ tion in relation to said plane. 7. Apparatus according to claim 6, c h a r a c t e r i z e d in that the steam discharge means are provided in a plane substantially per¬ pendicularly to the conveying direction (9) and in a number making it possible to cover substantially the entire circumference of the pro¬ duct and that the tunnel comprises several successively arranged seri¬ es of steam discharge means (6) arranged in this manner. 8. Apparatus according to claim 6, c h a r a c t e r i z e d in that it comprises means for registration of the contours of the product and for controlling of the position of the steam discharge means in conse¬ quence of this registration. O 90/11223 10 STATEMENTUNDERARTICLE19 The new claim 1 has been amended in substance by adding the content of the original claim 4 in order to underline that the steam is introduced into the shrinking zone at a very low velocity (as contrasted to an introduction in the form of a steam jet). In the new claim 6 (corresponding to the old claim 7) features from old claim 8 have been incorporated in order more clearly to state that the discharge means are individually adjustable and that each might by adjusted both by a translatory displacement and by an angle setting. The features incorporated in claims 1 and 6, respectively are clearly ap- pearant from the original disclosure, more specific from claim 4 and claim 8, respectively. As it occurs from the above the amendments effected are within the disclo¬ sure of the international application as filed. The amendments effected will impact the description only in a cosmetic way as the "background of the invention" preferably should be amended in accor¬ dance with the new wording of claims 1 and 6.

Inventors: BRESSENDORF OLE, BRESSENDORF, OLE
Applicants: BRESSENDORF OLE, BRESSENDORF, OLE
Application year: 1990
Main classification: B65B53
IPC codes: B29C35, B65B53