[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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).
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
1. 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.
2. 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.
3. 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.
4. 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.