WO2007080451A2

WO2007080451A2 - Machine for packaging products with single fold heat shrinkable film

Info

Publication number: WO2007080451A2
Application number: PCT/IB2006/003949
Authority: WO
Inventors: Pietro Di Bernardo
Original assignee: Interdibipack S.P.A.
Priority date: 2005-10-14
Filing date: 2006-09-12
Publication date: 2007-07-19
Also published as: WO2007080451A9; ITMI20051935A1; WO2007080451A3

Abstract

The present invention refers to an improved machine for packagi ng products with so called ' single fold heat shrinkable film where the product is inserted between the two opposite sides of the folded film, the film is sealed by the way of L shaped welding frame inside a chamber (13) closed at the top by a mobile bell (14) and thermally treated by forced circulation of hot air to shrink the film around the product. This improved model consists of additional heating means (R), which are resistors, which are 'L' shaped and are situated in the zone corresponding to the the sealing frame and the means (20) of circulation of hot air are situated in a central position in respect to the additional heating means (R).

Description

MACHINE FOR PACKAGING PRODUCTS WITH SINGLE FOLD HEAT

SHRINKABLE FILM

The present invention refers to a machine for packaging products with so called single fold heat shrinkable film. The invention refers to an improved machine to pack products of various sizes, specifically_/ .but not exclusively of small dimensions with single folded heat shrinkable film. According to this technique the product is inserted between the two opposite sides of the folded film, the film is sealed by the way of L shaped sealing bars and thermally treated by forced 0 circulation of hot air to shrink the film around the product.

Machines of this kind are for example disclosed and illustrated in the United States patent US-4.104.848, in the international patent PCT/EP 97/06946, in the 5 European patent EP-535747 and in the European patent EP1077177. These patents have to be considered if any further clarification is required and has to be considered integrative part of this text in order to understand the state of the art prior of the present invention.

Briefly , the packaging machine referred to in the above-mentioned patents is structurally formed by a packaging room (bottom chamber) which is closed at the top by a mobile bell, generally transparent, on top of a welding frame. Inside said room the over-wrapping process as well as the heat-shrinking process (when necessary) of the single-fold plastic film containing the product to be packaged, are carried out at the same time, thanks to the forced circulation of hot air (obtained from one or more fans), which is heated and kept at a substantially constant high ^' temperature (120⁰C- 15O⁰C), through the use of suitable heating means, placed within the packaging room. More precisely, said heating means (opportunely controlled) are positioned within a "lung" where the heat is accumulated and released.

Any time the bell is closed, the cover of the "lung" is automatically open, the welding blade are activated and forced circulation of hot air is also obtained through activation of electric fans. Generally in all the bell type packaging machines the heating means are positioned in the bottom chamber inside the so called

"lung" or heating storage. Usually the "lung" and the bottom chamber are made with metal (painted steel/stainless steel, aluminium etc.)or plastic.

It is well known that metals are good conductors of heat. For this reason, on the state of the art, to avoid thermal dispersion, unnecessary consume of energy and overheating of the external body of the machine, the interior parts of the bottom chamber (when in metal), is protected or coated with thermal insulating material of wool felt / fibreglass etc, Such protections make difficult or impossible a good cleaning of dirt and make possible that particles of wool, fibreglass, dirt etc. flow away when ventilation for shrink is activated.

Another very important consequence of this system is that the bottom chamber of the machine, where the shrink operation is obtained, remains absolutely "neuter" on regard of the heat necessary for shrinking and the heating of the air is obtained only in the "lung" positioned on the opposite part of the sealing means where the product to be packed is positioned (as much as possible near the L shaped sealing bars) for sealing the centrefoided film around the product himself.

For this reason the temperature of the hot aιr( warmed up in the "lung" only) will substantially decrease when arriving on the opposite part (L shaped sealing bar) of the heat exchanger Clung"), because obviously the hot air gets previously in touch with part of the product that meets before and because all the inside surface of the bottom chamber is "neuter" as regard warm being specifically made of thermal insulating material.

The result of such situation is that the parts of product to be packed adjacent to the L shaped sealing bar are usually not well shrinked unless long shrinking time is given. As well when some difficult, very thin or thermaily critic film is used, often the film melt or break in the surface adjacent to the source of hot air, if a reasonable good shrinking and finishing is required in the other surfaces as well (adjacent to L shaped bar sealing)

As mentioned, this machine uses a so-called single- fold film, between the folds of which the product to be package is positioned using a loading area positioned at the side of the packaging room. The product, partially wrapped in the single-fold film, is dragged manually from said loading area onto a net, or grill support, placed inside the room (above the heating means ^nd the fan) and the bell is lowered in order to activate the welding blades that close the open sides of thejϊlm and in order to open the door that close the "lung"

At the same time, when the heat-shrinking process is expected, electric fan/s moves hot air, giving rise to the shrinking of the film itself around the product. In order to pick-up the package made, the operator lifts the bell to have access to the support grill upon which the packaged product lies.

Automatic machines of this kind are also well-known, in which the product is fed to the packaging room by a continual netlike conveyor belt, and in which the lowering and raising of the bell are carried out mechanically, by one or more pneumatic cylinders. In product packaging machines with heat-shrinking of the type mentioned above, the possibility of excluding heat-shrinking of the film on the product is available, therefore creating a package which is similar to a bag, but made from a plastic film.

This method of operation of the machine is achieved by excluding both the forced circulation of hot air from the operative cycle, that is to say deactivating the automatic activation of the fan/s when the bell is lowered, (i.e. at the moment that welding blades are activated) and the heating means. In other words, in _. such a case, the machine simply operates like a common welding frame.

Considering the above, we must point out that, in the so called well-known "bell" type packaging machines, in the method of operation with heat-shrinking of the plastic film onto the product, in each operative cycle, automatic opening of the heat lung is always provided for and at the same time the activation of the fan that provoke the forced circulation of hot air within the packaging room and, consequently, the heat-shrinking of the plastic film on the product to be packaged.

Bell type machines, like the one described above, are used to package numerous products of different kinds, of- the most varied dimensions, maybe so large that they cover most of the support grill or so small that they cover just a tiny part, or in the middle.

In particular, in the packaging of small-sized products or in any case products that on their own cover a small part of the support grill within the packaging room, those skilled in the art know very well that the product must be placed as close as possible to the corner of the grill,, in order to avoid an excessive use and surplus of the material that make more difficult and long the operation of shrinking. This means that, using the bell type machine known, any product (even small) must be packaged one at a time, and the following step corresponding to each operative cycle (packaging) are necessary: lowering of the bell, opening of the door of the "lung", activation of the welding blades, activation of the fan/s that implement the forced circulation of hot air, lifting of the bell and extraction of the packaged product,

Above operation involve generally high energy consumption, even bigger when products are small sized. Since they must be placed in the corner of the support grill (adjacent to L shaped sealing bar) they are not so easily reached by _. the flow of hot air, therefore a longer shrinking time and more energy consume is required. Any time the transparent bell opens, the full volume of hot air contained in the packaging room flow away. A compulsory consequence of above operations is a decrease of temperature of the air and the impossibility to maintain such temperature homogeneous and constant having the generator of warm only in the "lung" situated in the backside of the packaging room.

The main scope of this invention is to obviate the above-mentioned problems providing a packaging machine in which the hot air can maintain as much as possible the same temperature in all part of the bottom chamber, specially in the critics parts far from the main source of warm and where less space is available for circulation of air being the products very near to the L shaped sealing bars. A further . scope of the invention is to provide a machine that can obtain a good shrinking quaiity in all parts of the product with a substantial saving of time per each shrinking operation with a consequent saving of energy.

These scopes are achieved with machine having the features indicated in the attached claims The innovative principles of this invention and its advantages with respect to known technique will be more clearly evident from the following description of a possible exemplificative embodiment applying such principle and referring to the enclosed drawing In the drawings: figure 1 illustrate a "bell" type packaging machine in an operative position (bell lowered); and figure 2 illustrates the packaging room (bottom chamber) without the "bell" figure 3 illustrates the bottom chamber with fan 20, additional resistor-R and the exterior insulating system.

With reference to the drawings the machine according to the invention is generally indicated by 10 and is structurally made up of a fairing 11 including : working plate 12, a packaging room 13 (bottom chamber), a transparent bell 14 for closure of said room 13 and a heating system and forced circulation of air into space identified by said room 13 and bell 14, Furthermore, the fairing 11 brings at least one cradle support 15 of a coil 16 of single-fold heat-shrinking film, idle rolls of film return, and control panels. The above-mentioned heating system and forced air circulation in the space identified by the room 13 and of the bell 14 include thermostated heating means, for example at least one resistor 19, and at least one fan 20. The resistor 19, may be contained within a side "lung" P closed at the top by a flap S which opens when the bell 14 is lowered to the position of figure 1, in a way that is well-known to men skilled in the art, as for example described and illustrated in

US-4.104.484.

At the top of the fairing 11 two welding and film cutting blades 21, and 22, are provided for, these blades are placed respectively in the transversal and longitudinal directions and their objective is to weld- seai together the- two open sides of the single-fold film and to separate the finished packaged from the film. As those skilled in the art know, said blades 21, and 22, distinguish a so-called welding frame and they cooperate with counter-blades mounted onto the bell 14.

25 indicates a net supporting grill upon which the products to- be packaged are brought and positioned, arranged between the open folds of the film . According with the invention, with the first heating means (resistor 19 being in "lung" P) are associated additional heating means being for example a second resistor R (called Booster) positioned outside on the bottom of the packaging room 13 (such bottom chamber preferably in stainless steel). Preferably resistor is L shaped and is fixed outside the bottom chamber in the correspondent area where on the top are the sealing blade (opposite position from the first "lung" P), In such a way the fan 20 will be located at the centre of a wider and aimed heating system.

The flow of the air moved by fan 20 will reach, as before the "lung" P, but as well the other part of the chamber where the new resistor is keeping hot the L shaped area over the L shaped resistor. Therefore, the air going in this part will receive additional warm to reach, with the necessary and requested hot temperature, the critic parts adjacent to the L shaped sealing bar where the quality of the shrink was insufficient. The resistor R can be connected according to the needs, fore instance only when the fan 20 is stopped (during the over-wrapping operations, transport on the grill and welding) or, if necessary, during the time that the machine is switched on, Can be as well disconnected when is no needed or the machine used purely as sealer.

The resistor R in combination with the "lung" P is granting a uniform temperature of the hot air and a continuity constancy of such conditions in any part of the packaging room. The result of this embodiment will be a quick and perfect shrinking operation with many different films, together with a constant working capacity. The packaging room (bottom chamber) will be covered

(fig.3, 31) or coated outside with thermal insulation materials (wool felt, fibreglass etc) in order to avoid that the heat accumulated in the strategic part of the bottom chamber will waste. The resistor R that- already is in touch with the outside part of the bottom chamber will be as well covered by the .same insulation to avoid unnecessary warm dispersion. In this configuration the inner part of the bottom chamber (usually insulated) will remain naked, therefore will be possible to clean and wash : no more particles of felt, dirt etc. will flow away, The present invention can be used with advantage in all the well-known "bell" type shrink packaging machine and specifically, for the machine described in the European patent EP-1077177, when a plurality of product, only over-wrapped, is made before the Multiple shrink, In this situation the ventilation doesn't work any time that bell and seal frame goes down, consequently, the chamber 13, the supporting grill 25 or a possible metal conveyor, will loose temperature making more difficult to get a quick uniform and homogenous shrink operation. The scope of the invention is therefore defined by the following claim,

Claims

1. A packaging machine so-called "bell" type to be use with shrinkable folded film including : a packaging chamber (13) which is closed at the top by a mobile bell (14) over a welding frame (21, 22), in said chamber (13) are provided means (19) for warming air and means (20) for forced circulation of said hot air. Characterized by having additional heating means (R) positioned on the outside part of the bottom chamber (13).

2. A machine according to claim 1, characterised by the fact that the additional heating means (R) is situated in the zone corresponding to the sealing bars (21,22)

3. A machine according to claim 1, characterised by the fact that the additional heating means R is L shaped and is positioned in the area corresponding to the L shaped welding bars (21,22).

4. Machine, according to claim 1, characterised by the fact that the additional heating means is a resistor (R)

5. Machine , according to claim 1, characterised by the fact that the means for forced circulation of hot air are situated substantially in a central position respect to the first and second heating means (19, R )

6. Machine , according to claim 1, characterised by the fact that the additional heating elements are in contact, outside and on the bottom position of the packaging room

7. Machine , according to claim 1, characterised by the fact that the additional heating element can be totally activated or totally deactivated or activated according to the needs.

8. Machine , according to claim 1, characterised by the fact that the packaging room 13 is made in metals or other heat conductive material 9. Machine , according to claim 1, characterised by the fact that packaging room 13 and additional heating means situated outside the packaging room are insulated in the external side with fibreglass or^'similar warm insulating material.