Machine for packaging with single-folded heat-shrinkable film, provided with a device for automatically opening the film

Abstract: A machine for packaging with single-folded heat-shrinkable film (12), ie film folded longitudinally to define two opposing faces (13, 14) between which a work table (21) is interposed, comprises, for automatically opening the film (12), a device provided with means for directing between the film faces (13, 14) slightly spaced from the work table (21) a quantity of air able to inflate said film so as to force said faces (13, 14) apart and create a free space (23) into which the article (19) to be packaged can be inserted. Said means are substantially coplanar with said work table (21).

Description: This invention relates to a machine for packaging an article with single-folded heat-shrinkable film which is characteristically provided with an air device able to force apart those opposing sides of the film between which the product to be packaged is to be inserted. The expert of the art is familiar with packaging machines which use single-folded heat-shrinkable film, ie film folded longitudinally to define two opposing faces which when forced apart define a space into which the product to be packaged is inserted. The product is fed, inserted between the film faces, to a welding machine which welds the open sides of the film to form a closed envelope. This envelope is then fed into a hot air circulation oven which shrinks the film onto the product, to form the finished package. A packaging machine of this type is described and illustrated for example in Italian patent No 1,024,614, to which reference should be made for further details. The packaging machine of the cited patent welds and heat-shrinks the film in a single chamber, through which hot air is circulated. The chamber is closed upperly by a preferably transparent movable hood, and the product to be packaged is inserted between the faces of the single-folded film sideways to the hood where a work table is positioned between said film faces. To place the product to be packaged onto the work table the upper face of the single-folded film has to be raised manually, resulting in a time wastage which can be considerable in that these manual packaging machines are inherently rather slow compared with automatic tunnel machines. To overcome this drawback, US-A 3429100 describes a packaging machine in which the film is opened by a quantity of air directed perpendicularly to the work table. The preamble of claim 1 is based on this prior art. A further drawback of machines of known type is that the film has to be perforated so that the air which was incorporated on inserting the article to be packaged between the two film faces can escape during the heat-shrinkage operation. Consequently a package is obtained comprising holes which besides detracting from its appearance allow air to enter, this being undesirable particularly in the food field. An object of the present invention is to obviate the aforesaid drawbacks of the known art by providing a machine for packaging with single-folded heat-shrinkable film which comprises a simple and low-cost device able to automatically raise the upper surface of the film so as to create an open space through which the article to be packaged can be rested comfortably on the work table without having to manually handle the film in any way. A further object of the invention is to provide a machine comprising a device able to eliminate the air present in the film envelope containing the article, so making it unnecessary to perforate the film. Said objects are attained according to the present invention by a machine for packaging with single-folded heat-shrinkable film, ie film folded longitudinally to define two opposing faces between which a work table is interposed, having the features exposed in the annexed claim. The structural and operational characteristics of the invention and its advantages over the known art will be more apparent from an examination of the following description, given with reference to the accompanying schematic drawings, which show one embodiment of a packaging machine incorporating the principles of the invention. In the drawings: Figure 1 is a partly cut-away and partly sectional front elevational view showing one embodiment of a packaging machine provided with the device according to the invention; Figure 2 is a plan view; Figure 3 is a side elevational view; Figure 4 is a section on the line IV-IV of Figure 8; Figure 5 is a section on the line V-V of Figure 8; Figure 6 is a sectional view of a detail taken on the line VI-VI of Figure 4; Figure 7 is a section on the line VII-VII of Figure 8; and Figure 8 is a sectional plan view. On the drawings, which are provided by way of non-limiting example only, the device of the invention is shown applied to a machine for packaging with heat-shrinkable film, of the type described and illustrated in Italian patent No. 1,024,614, however the invention can obviously be applied to machines of a different type. With initial reference to Figures 1 to 3 of the drawings, the machine of the invention is indicated overall by 10 and comprises a chamber 11 in which a single-folded film 12 comprising a lower face 13 and an upper face 14 is welded and heat-shrunk. The chamber 11 is closed upperly by a movable hood 15, preferably of transparent material. Lowering said hood 15 activates welding blades (not shown) positioned on the upper edges 16, 17 of the chamber 11 and one or more blowers 18 which generate air circulation within the chamber 11, the air being heated by electrical resistance elements (not shown) This achieves the welding and heat-shrinkage of the single-folded film 12 wrapping the article 19 to be packaged, which for this purpose is placed on a support grid 20 in the chamber 11. The machine structure or its method of operation will not be described or illustrated in greater detail herein as these are well known to the expert of the art. Reference can however be made to the aforestated Italian patent No. 1,024,614. The article 19 to be packaged must be placed by the operator on a work table 21, which is mounted to the side of the chamber 11 and during machine operation is positioned between the lower face 13 and upper face 14 of the single-folded film 12, which is unwound from an underlying reel 22. In known machines this is done by the operator manually raising the upper face 14 of the film from the work table 21 to define a free space 23 into which the article 19 is inserted. This operation represents a substantial time wastage considering that manual machines of this type are considered intrinsically rather slow. According to the invention, the upper face 14 of the film 12 is raised from the work table 21 by blowing between the faces 13 and 14 of the film a quantity of air sufficient to inflate the film in such a manner as to automatically create the free space 23 for receiving the product 19. In this manner the operator not only does not waste time in manually lifting the upper face 14 of the film, but can handle the article to be packaged with both hands, both for positioning it correctly on the work table 21, and by necessity in the case of articles of a certain weight. The drawings show by way of non-limiting example a device able to feed air between the faces 13, 14 of the single-folded film, however devices of different structure, but falling within the principles of the invention, could be used for feeding air between the faces 13, 14 of the film in order to withdraw the upper face 14 from the work table 21. The device shown by way of non-limiting example comprises a blower 24 and an exhaust fan 25, which are positioned below the machine and, via suitable ducts, deliver and withdraw air in the directions of the arrows 26 and 27 respectively, so that the air fed between the faces 13, 14 of the single-folded film to inflate it is then extracted in order not to disturb the subsquent welding and heat-shrinkage. The ducts and air paths are clearly shown on the drawings. Specifically, Figures 2 and 4-8 clearly show that the air fed by the blower 24 through a duct 28 controlled by a dryer 29 is fed to a manifold 30 which expels it laminarly through a slot 31 to direct it between the work table 21 and the upper face 14 of the single-folded film 12, which is inflated as shown in Figure 1 to allow easy insertion of the article 19 to be packaged into the space 23 above the work table 21. The article 19 inserted in this manner between the film faces 13 and 14 is transferred onto the grid 20 in the chamber 11, the air inside the inflated space 23 then being extracted by the exhaust fan 25 via a duct 32 (Figures 5, 7 and 8). This therefore avoids the need to perforate the film, with all the advantages which this implies. The object stated in the introduction to the description is hence attained. The scope of the invention is defined by the following claims.

Claims: A machine for packaging an article with single-folded heat-shrinkable film (12) which is folded longitudinally to define two opposing faces (13, 14) between which a work table (21) is interposed, the machine comprising a device for automatically opening the film (12), the device being provided with blowing means for directing between the film faces (13, 14), which are slightly spaced from the work table (21), a quantity of air able to inflate said film so as to force said faces (13, 14) apart and create a free space (23) into which the article (19) to be packaged can be inserted, characterised in that the blowing means is designed to produce an air stream which is substantially coplanar with said work table (21). A machine as claimed in claim 1, characterised in that said device comprises a blower (24) able to direct a laminar air stream between said film faces (13, 14) by way of a series of ducts. A machine as claimed in claim 1, characterised in that said device also comprises an exhaust fan (25) able to extract the air from said free space (23) when the article to be packaged is fed, wrapped in film, to the packaging machine. A machine as claimed in claim 2, characterised in that said ducts (28) open into a manifold (30) provided with an air expulsion slot (31) substantially coplanar with said work table (21).

Inventors: DI BERNARDO PIETRO, DI BERNARDO, PIETRO
Applicants: INTERDIBIPACK SPA, INTERDIBIPACK S.P.A.
Application year: 1992
Main classification: B65B9
IPC codes: B65B9, B65B45