Package making – Apparatus for contraction of cover by stretching or shrinking – By heat shrinking
Patent
1999-05-28
2000-11-28
Johnson, Linda
Package making
Apparatus for contraction of cover by stretching or shrinking
By heat shrinking
B65B 5302
Patent
active
061518719
DESCRIPTION:
BRIEF SUMMARY
This invention refers to a machine for packaging products with film made of heat-shrinkable material. According to this technique, the product to be packaged is wrapped in a film of heat-shrinkable material and placed inside a packaging machine, where the film is sealed and heat-shrunk to enclose the product. The heat required to thermally treat the film is generated by electric heating units disposed in a suitable position inside the compartment receiving the product. An example of these machines is shown in FR-A-2,397,329.
There are known packaging machines in which special fans are disposed on the bottom of the compartment (see FR-A-2,342,894) below the heating unit and the surface supporting the product to be packaged, to create a circulation of air in the compartment in order to distribute the heat over the entire surface of the film.
Despite endeavours made to improve the circulation of the hot air in the compartment, the positioning of the fans according to the known technique does not allow the air to flow evenly enough over the entire surface of the film wrapped around the product. In particular, the lower part of the compartment tends to remain colder than the upper part, due to the tendency of the heat produced by the heating element to migrate upwards by convection. This can result in packaging of an unsatisfactory quality. Unevenness in the distribution of the heat also means that, in order to reach, in the lower part of the compartment, at least the minimum temperature required to shrink the film, the temperature in the upper part is considerably higher, resulting in an evident waste of energy.
A further drawback of the known machines is that, when the operator opens the cover to remove the packaged product, he is inundated by a large quantity of hot air escaping from the compartment. Moreover, since the fan is located in the lower part of the compartment, where dust and other particles of dirt easily accumulate, it inevitably whips up said dust which ends up by blowing onto the operator when he opens the cover. For example, parts of the product to be packaged may fall to the bottom of the compartment and be crushed by the rotating fan and be hurled dangerously at the operator.
The general scope of this invention is to obviate the aforementioned problems by providing a packaging machine in which the heat-shrinkable film wrapped around the product to be packaged is evenly bathed by the hot air circulating inside the compartment, thereby saving a considerable quantity of energy.
A further scope of the invention is to provide a machine in which there is no considerable emission of hot air when the compartment is opened.
These scopes are achieved according to the invention by providing a machine for packaging products with film made of heat shrinkale material.
The innovative principles of this invention and its advantages with respect to the known technique will be more clearly evident from the following description of a possible exemplificative embodiment applying such principles, with reference to the accompanying drawings, in which:
FIG. 1 shows a cutaway side view of a packaging machine according to the invention.
FIG. 2 shows a view similar to that of FIG. 1, but in the operating condition, with the cover closed.
FIG. 3 shows a view similar to that of FIG. 1, referring to a different embodiment of the machine according to the invention.
With reference to FIG. 1, a machine for packaging products 11 by means of film 12 made of heat-shrinkable material is generically indicated by reference 10.
The machine comprises a body 13 containing a lower portion 14 of a shrinkage chamber which houses, inserted between two layers of the film 12, a packet 11 to be packaged. Disposed in this portion of the chamber is a perforated support 15, advantageously a grille to support the packet 11 while at the same time allowing the air to flow towards the surface of the film covering the lower face of the packet.
Hinged onto the body 13 is a cover 16, which defines an upper portion 17 of the shrinkage chamber. The
REFERENCES:
patent: 3357153 (1967-12-01), Shaffer
patent: 4667456 (1987-05-01), Raffault
Johnson Linda
Minipack-Torre S.p.A.
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