EP1520790A1

EP1520790A1 - Combined apparatus for sealed overwrapping, with tip-up flap shields

Info

Publication number: EP1520790A1
Application number: EP04104825A
Authority: EP
Inventors: Luciano Calzavara
Original assignee: Officina Meccanica Sestese SpA
Current assignee: Officina Meccanica Sestese SpA
Priority date: 2003-10-02
Filing date: 2004-10-01
Publication date: 2005-04-06
Also published as: ITMI20031892A1

Abstract

Combined overwrapping apparatus, of the type comprising a support frame, onto which a system is mounted forming an overwrapping hood made of thermo-shrinking plastic material, and force-fitting said hood onto a load to be overwrapped, as well as a ring structure (1) carrying hot-air generators (2), vertically mobile along the load to cause heat-shrinking of said overwrapping hood. According to the invention, said quadrangular ring structure (1) is provided with a plurality of deflector shields (7), in the shape of plates, rotatably mounted about respective horizontal rotation axes, parallel to the sides of said ring structure (1) and located immediately above the outlet nozzles (5) of said hot-air generators (2). The deflector shields (7) can thus be tipped down from a vertical non-operational position, wherein they leave the inner headroom of the ring structure completely free, to a horizontal or sub-horizontal operational position wherein they intercept a peripheral area of said inner headroom of the ring structure.

Description

The present invention relates to an apparatus for the overwrapping of a load for the packaging industry, in particular a combined apparatus for the overwrapping of a load, i.e. wherein there are provided both means for picking up, opening and force-fitting an upturned bag or hood of heat-shrinkable plastic material on a load placed on a pallet, and also heating means to cause the heat-shrinking of said hood of plastic material.
Such heating means are essentially hot-air generators (such as gas burners, or electric heaters installed along the perimeter of a quadrilateral ring structure, sized so as to encircle the load to be overwrapped and so as to be able to slide vertically therealong, thus evenly applying the heat sufficient to cause shrinking of the hood.
Usually, once the hood has been force-fitted on, the ring of burners moves down to the bottom of the load, where the open edge of the hood is arranged, and it begins to heat (blowing out air as hot as 300°C) while slowly rising back up to the top of the hood. This procedure allows to achieve the best results: in fact, at the beginning, the free edge of the hood is heated which, shrinking, strongly adheres to the pallet lying underneath the load, thereby creating a fastening point for the hood itself; successively, also the upper portion of the hood progressively shrinks around the load and evenly stiffens it.
In traditional technology, the size of the combined overwrapping apparatus is suitably adjusted to the size of the largest load to be handled; this implies, in particular, that the ring structure carrying the hot-air generators be sized so that the outlet of such generators is at a distance, from the surface of the largest load to be overwrapped, which is sufficient to avoid the heat-shrinkable film of the wrapping hood being damaged by the hot air; on the other hand, such distance is to be fairly short in order to ensure correct heat-shrinking of the film even when a small-sized load is handled, the surface of which is at a certain distance from the generators.
A compromise between these two opposite requirements is not always possible and one hence ends up correctly sizing the ring structure for the largest load, forfeiting using the apparatus thus sized for loads too much smaller.
It must also be borne in mind that, should the hot-air generator be of the excess-air gas type, the perimeter size of the load may be subject to sensible variations. Should free flame burners be installed instead, only modest changes of the load perimeter size may be acceptable; the same can be said in case electric hot-air heaters are employed.
It is further necessary to bear in mind that, in order to complete the heat-shrinking process, it is in any case often necessary - even when lifting of the load in order to anchor the film underneath it during the heat-shrinking process is not required - to lift the load, for the purpose of being able to suitable heat-shrink the film around the bottom of the load itself, since it is not possible (for various considerations of bulk) to bring the jet nozzles of the hot-air generators flush with the pallet transport system. Lifting hence implies cost increase and (for applications encompassing wide size variations of the bottom of the load) even the impossibility of automatically carrying out the lifting thereof, unless adopting particularly onerous plant solutions.
It is hence an object of the present invention to provide a combined overwrapping apparatus, of the general type mentioned above, wherein it is possible to solve the problem of a correct heat treatment of the heat-shrinkable wrapping film, both on loads of the maximum size accepted by the apparatus, and on decidedly smaller loads. This result is achieved through the features mentioned in claim 1.
The solution identified by the invention hence provides the use of deflector shields, which are capable of taking up at least two positions:

a non-operational position in which they are tipped-up, which leaves the headroom of the ring of hot-air generators completely free; this position is used when the wrapping of loads of the maximum size or close-to-maximum size is to be carried out, such that the free headroom between ring and load is small enough to allow perfect heat-shrinking of the corresponding wrapping.
an operational position in which they are tipped down, horizontally or sub-horizontally, which obstructs a peripheral portion of the headroom of the ring of hot-air generators; this position is used when the loading of minimum-size loads or close-to-minimum size loads is to be carried out, such that the free headroom between ring and load would end up becoming too wide to allow perfect heat-shrinking of the corresponding wrapping. In this operational position, in fact, it is obtained that the deflector shields on the one hand block the air flow, open upwards, between the outlet nozzles of the hot-air generators and the wall of the load, hence preventing upward heat loss, and on the other hand they channel the hot-air flow directly onto the wrapping film, once again carrying out perfect heat-shrinking of the corresponding wrapping.

The solution proposed by the invention may be used indifferently both when the ring structure is equipped with electric air heaters, and in the case that gas burners are provided; for this reason, reference is always made in the following of the description to hot-air generators, meaning by this term either one of the types indicated above.
Further features and advantages of the present invention are in any case more evident from the following detailed description of a preferred embodiment, given merely by way of a non-limiting example and illustrated in the accompanying drawings, wherein:
fig. 1 is a diagrammatical, perspective view of a ring structure of hot-air generators according to the invention;
fig. 2a is a vertical cross-section, according to the line II-II of fig. 1, of said ring structure, with deflector shields in an operational position;
fig. 2b is an enlarged cross-section of the detail encircled in oval P2 of fig. 2a;
figs. 3a and 3b are views completely similar to those of figures 2a and 2b, but with deflector shields in a non-operational position;
figs. 4a and 4b are again views completely similar to those of figures 2a and 2b, but with deflector shields in an intermediate operational position.
As can be diagrammatically seen in fig. 1, the ring structure consists of a quadrangular frame 1 and, on each of the four sides thereof, of a hot-air generator assembly 2. Each of these assemblies 2 comprises, in the illustrated case, a gas burner 3 fitted to one end and a blower 4 fitted to the other end to generate mixing air and to push said air towards the outlet nozzles 5 (see figures 2 to 4).
The distance between the opposite inner walls 2A of generator assemblies 2 is shown by (a) in figures 2a, 3a, and 4a. Such distance is just above (as better explained in the following) the maximum admitted size of the load to be wrapped. In an apparatus having a square-shaped ring structure, such maximum size is the same for the two pairs of opposite sides, while it is of course different in the case of rectangular structures.
According to the present invention, immediately above the outlet 5 of the nozzles of the hot-air generators, deflector shields 7 are hinged onto shafts 6 running parallel to walls 2A of assemblies 2. Such shields 7 may be tipped from a non-operational position, visible in figures 3a and 3b, wherein they are arranged vertically, parallel to the vertical walls of the corresponding assemblies 2 (see better in fig. 3b), to a normal operational position, visible in figures 2a and 2b, wherein they are tipped down, in a sub-horizontal position, for example by about 105° to the vertical position, for the function better illustrated in the following. Figures 4a and 4b illustrate an intermediate operational position, wherein the shields are oriented horizontally, i.e. at 90° to the position of figures 2a and 2b.
The tipping down movement of deflector shields 7 is preferably positively controlled by motor means (not shown in detail in the drawings) generally controlled by the apparatus; by this system it is possible to control tipping down of the deflector shields 7 in relation to the size of each load arriving at the wrapping station. However, when it is expected that the loads to be overwrapped arrive in sequences of multiple same-sized loads, such motor drive - which would increase costs - may be avoided by manually providing to tip down the deflector shields at the beginning of each sequence.
When the deflector shields 7 are tipped into an operational position (see figures 2 and 4), they intercept a peripheral area of the inner headroom of the ring structure, i.e. they resize such inner headroom proportionally to the minimum size of the loads to be overwrapped. More specifically, the distance between the opposite inner ends of the shields, in an operational position, is shown by (b) in figures 2 and 4, which is remarkably shorter than the distance (a), but in any case still greater than the plan size of minimum loads or loads slightly larger than minimum loads.
The results are hence the following operational conditions:
I) in case ample size variations of the load to be overwrapped are expected and anchoring of the film under the base of the load itself is required, it is possible, in a single apparatus: a) not to activate the deflector shields when the load size ranges from maximum to standard, hence to overwrap the load after having lifted it, and to proceed with heat-shrinking following the conventional cycle; b) to activate instead the deflector shields when the load size ranges from standard to minimum, hence to overwrap the load after having lifted it, and to proceed with heat-shrinking following the conventional cycle. In these second conditions, the hot-air flow is then suitably channelled towards the load, significantly limiting upward heat dispersion in the circumferential strip which separates the wall of the overwrapped load from the outlet nozzles 5 of the respective hot-air generators.
II) Should ample size variations of the load to be overwrapped be expected and should instead no anchoring of the film under the base of the same be required, it is possible, in a single apparatus and for all the sizes of the load to be overwrapped, to overwrap the load, then to activate the mobile deflector shield and to proceed with heat-shrinking without lifting the load and following the conventional cycle. When minimum-to-standard-sized loads are encountered, the hot-air flow is then suitably channelled towards the load, as already said, significantly limiting upward heat dispersion in the circumferential strip separating the wall of the load from the outlet nozzles of the respective hot-air generators. In the case instead of standard-to-maximum-sized loads, the deflector shields, ending up finding themselves under the load for a short distance, allow to push the wrapping film under the load itself, achieving heat-shrinking at the bottom with no need for lifting. Where necessary, the launch angle can be suitably varied to adjust it to the size requirements of the load to be subject to thermo-retraction. It must here be appreciated that in this case deflector shields are brought back into the vertical non-operational position before driving the ring structure up along the load, so as not to interfere with the walls of load itself.
The advantages achieved by the arrangement according to the invention may be summarised in the following:

it is possible to carry out heat-shrinking of the packing film with no need to lift the load above the level of transport, in that the deflector shields may push the film under the load;
it is possible to carry out the heat-shrinking of a wide range of load sizes, despite keeping the nozzles always in the same position, in that it is possible to overcome the greater distance of the nozzles from the walls of the smaller-sized loads through the channelling action of the deflector shields;
it is possible to achieve more effective heat-shrinking, also of the upper horizontal surface of the load, thanks to the control of hot-air channelling through the deflector shields;
it is possible to contain fuel consumption thanks to the closure, on the part of the deflector shields, of the air compartment surrounding the load, optimising the effectiveness of the hot-air flow;
it is possible to use the deflector-shield arrangement according to the invention both with electric hot-air generators, and with generators equipped with a gas burner.

In any case, it is understood that the invention is not limited to the specific embodiments illustrated above, which represent only non-limiting examples of the scope of the invention, but that a number of changes are possible, all within the reach of an expert in the field, without departing from the scope of the invention as detailed in the following claims.

Claims

Combined overwrapping apparatus, of the type comprising a support frame, onto which a system is mounted forming a wrapping bag or hood made of thermo-shrinking plastic material, and force-fitting said hood onto a load to be overwrapped, as well as a ring structure carrying hot-air generators, vertically mobile along the load to supply hot air towards the surface of said wrapping hood and to cause thermo-shrinking thereof, characterised in that said ring structure is provided, along the inner perimeter thereof, with a plurality of deflector shields, which can be tipped down from a non-operational position, wherein they leave the inner headroom of the ring structure completely free, to an operational position wherein they intercept a peripheral area of said inner overhead of the ring structure.
Overwrapping apparatus as in claim 1), wherein said deflector shields, in said operational position, reduce the inner headroom of said ring structure to a measure greater than the minimum size or close-to-minimum size of the load to be overwrapped.
Overwrapping apparatus as in claim 1) or 2), wherein said ring structure has a quadrangular shape and said deflector shields are in the shape of plates, rotatably mounted about respective horizontal rotation axes, parallel to the sides of said ring structure, between a vertical position, corresponding to said non-operational position, and a horizontal or sub-horizontal position, corresponding to said operational position.
Overwrapping apparatus as in claim 3), wherein said rotation axes of the deflector shields are located immediately above the hot-air outlet nozzles of said hot-air generators and can be tipped up.