Field of the invention
[0001] The present invention relates to an extensible plastic film wrapping apparatus, in
particular a wrapping apparatus and related gripping device for holding such a film.
Background art
[0002] The use of carrying out wrapping of items with a wrapping of thin plastic material
film is known.
[0003] A first major distinction in this technological field is that relating to the used
films, which may be of heat-shrinkable or extensible type.
[0004] The systems that use plastic heat-shrinkable material are relatively expensive, both
for the cost of the plastic film itself, and for the cost of the system, which uses
a shrink oven and therefore involves significant energy consumption.
[0005] Systems that use a thin film of extensible plastic material have greater savings
both for the outlay cost of the film and because they do not involve an energy consumption
comparable to those of use of an oven. In the following we will deal with the latter
technology.
[0006] In particular, the application of a wrapping with extensible film is achieved with
machines which wrap the items to be packaged with one or more spirals of a preferably
prestretched extensible film. Wrapping takes place by defining a relative rotation
of a plastic film spool around the item to be packaged, optionally moving the spool
along a movement axis to determine wrapping turns distributed over a certain length.
Wrapping can take place according to a vertical axis (for example in the traditional
pallet-wrapping machines), along which the item to be packaged is upright, or according
to a horizontal axis, along which the items to be packaged are fed. In the latter
case, each item is fed to the wrapping station along a conveyor belt or a roller conveyor,
which is stopped at this station, then is wrapped with the film and then delivered
onto the conveyor belt of the packaging line.
[0007] According to the prior art, performing the wrapping with horizontal axis involves
the use of a spool supporting carriage, which is moved along a circular guide, arranged
in the wrapping station according to a vertical plane oriented perpendicular to the
feeding line of the items and which encircles the conveyor belt. In the wrapping station,
the item is supported only on cantilevered guide means (typically a shelf and any
lateral containment rails) which connect the feed portion of the conveyor with a delivery
portion. Thus, upon rotation of said spool supporting carriage, the film which unwinds
from the relative spool, performs a wrapping which encircles the item and also said
cantilevered guide means. Once the wrapping has been completed, the items is pushed
towards the delivery line, pulling out the turns of extensible film longitudinally
from the cantilevered guide means: to this end, these guide means are shaped and designed
in such a way as to favour the sliding and pulling out of the packaged item.
[0008] Critical stages of this packaging process are the initial and final ones, respectively,
in which the film must be attached to the item and must then be cut to re-present
it to the next item. For this purpose, a holding and cutting gripper is used, conventionally
placed below the cantilevered guide means, mounted movable longitudinally to the rotation
axis of the supporting carriage.
[0009] Wrapping systems provided with holding grippers are described for example in
WO2015/121334 and
WO2016/193875 - according to which the preamble of the appended main claim has been constructed
- and also in
US 4587796.
[0010] An example of a traditional gripper is shown in Fig. 1, which represents a perspective
view of a gripper of the prior art. A straight gripper, with a holding axis arranged
horizontally and aligned with the rotation axis of the film spool, has a fixed upper
jaw 1 and a movable (pivoting) lower jaw 2 which has a scissor closure on the fixed
jaw 1. The two jaws are arranged to cooperate in retaining a flap end of film and
also to perform, in a position slightly downstream of the retaining line, a cut of
the film (with a cutting blade which is not visible in Fig. 1). To this end, the straight
gripper has a length equal to a substantial part of the width of the film and grasps
the film from a side edge thereof.
[0011] Operationally, the initial flap end of the spool is held by the gripper - stationary
in a fixed position - until at least a part of a first turn of film is formed around
the item to be packaged, as the spool is displaced in rotation on the spool supporting
carriage. In this movement, the film is partially wrapped around the item and tends
to adhere to it naturally, stretched and closely fitted to the corners. When the spool
supporting carriage reaches a position prior to possible interference with the gripper,
the latter is retracted longitudinally to withdraw from underneath the carriage. Given
the considerable size, in fact, the gripper must be moved away from its position before
completing the first film turn, because afterwards it would no longer be possible
to pull it out without compromising the packaging.
[0012] However, since the film is not attached well yet to the item to be packaged, the
gripper moves away holding the initial flap with it, so as not to lose film tension,
which film otherwise would tend to become loose, thus losing adherence to the item
even before completion of a consolidation turn. In this process, as it can be imagined,
the gripper pulls the film with it, which film collapses into a plastic material cord
that remains tucked between the first turn and the item to be wrapped.
[0013] Though, on the one hand, this film cord portion is essential to ensure that the initial
end of film is not released prematurely, on the other hand, however, it constitutes
a side appendix of the packaging, which compromises the aesthetics and functionality
of the packaging itself.
[0014] To avoid this problem, the Applicant has already proposed alternative solutions,
for example by using a temporary retaining device or an air suction retaining element
which is easily removable from the packaging.
[0015] Although these alternative solutions have some advantages, the Applicant has found
that the gripper system is still the most reliable.
[0016] US5027581 discloses a wrapping apparatus and method, where two gripping units are provided
at the opposite edges of the wrapping film. The gripping units are reciprocally moved,
transversally to the longitudinal path of the film, by a cam/follower drive unit;
a cutting blade is also provided, moving vertically up and down below the film path.
Problem and summary of the invention
[0017] The underlying problem of the invention is therefore that of providing an apparatus
and a wrapping method as above, which allows to achieve an efficient extensible film
wrapping, still using a gripper retaining mechanism, but without the drawbacks described
above.
[0018] This problem is solved through the features set out in essential terms in the appended
main claim. The dependent claims describe preferred features of the invention.
[0019] In particular, according to a first aspect of the invention, a wrapping arrangement
for an item, to be wrapped with extensible plastic film is provided, comprising a
driving ring which drives into rotation a support carriage of a spool of extensible
plastic film, on a circular path which wraps an item to be packaged, at least a holding
unit of the film being furthermore provided, equipped with a gripping device and a
cutting device, and further comprising, on two opposite sides of a plane on which
said circular path develops, a pair of holding units arranged on a same operating
line transversal to the longitudinal development of the film, each holding unit being
provided with gripping devices and with cutting devices which can be brought mutually
closer along said operating line.
[0020] In particular, said gripping devices and cutting devices are mounted longitudinally
movable in opposite directions. Preferably, said gripping devices and cutting devices
are mounted on guides and are moved backward and forward by respective first movement
actuators.
[0021] According to a further aspect, second gripping actuators are also provided for mutually
opening and closing pairs of jaws of said gripping devices.
[0022] Preferably, the first and second actuators are mounted so that said gripping devices
may mutually move forward and backward both with said jaws closed and with said jaws
open.
[0023] According to another aspect, said cutting devices are designated as complementary
and have respective cutting means arranged on two parallel but offset planes.
[0024] According to a different aspect, a holding device is provided for a wrapping arrangement
as described above, comprising a pair of holding units, opposite and arranged on a
same operating line transverse to the longitudinal development of a wrapping film,
each holding unit being provided with gripping devices and cutting devices which can
be brought mutually closer along said operating line.
[0025] According to yet another aspect, a method for wrapping an itema is provided by using
an arrangement as above, in which the following steps are provided:
providing a driving ring apt to drive into rotation a support carriage of a spool
of extensible plastic film, on a circular path that wraps an item to be wrapped,
arranging, from two opposite parts of a plane on which said circular path develops,
a pair of holding units arranged on a same operating line transversal to the longitudinal
development of the film, each holding unit being provided with gripping devices and
cutting devices which can be brought mutually closer along said operating line,
bringing said holding units closer together to grasp and retain respective flaps of
opposite side edges of said extensible plastic film,
performing at least one complete turn of said spool around the item on said circular
path,
opening said gripping devices and moving said holding units apart from each other.
[0026] Preferably, the method involves subsequently bringing said holding units closer together
to grasp and retain respective flaps of opposite side edges of said extensible plastic
film,
bringing said cutting devices mutually closer to bring respective cutting means to
cut said film along a cutting line placed between said gripping devices and said item.
Brief description of the drawings
[0027] Further features and advantages of the invention will anyhow be more evident from
the following detailed description of a preferred embodiment, given by mere way of
nonlimiting example and illustrated in the accompanying drawings, wherein:
Fig. 1, as already seen, is a perspective view of a gripper holding device of the
prior art;
Fig. 2A is a perspective view of the film holding device according to the invention;
Fig. 2B is a perspective view opposed to that of Fig. 2A, including an item to be
packaged;
Fig. 2C is a front elevation view of the system of Fig. 2B, including a plastic film
spool;
Figs. 3A-3C are side and perspective elevational views of the system of Fig. 2 in
three different operational steps; and
Figs. 4A-4F are schematic side elevation views showing the system according to the
invention in a sequence of different operational steps.
Detailed description of a preferred embodiment
[0028] An extensible film wrapping apparatus, with a horizontal wrapping axis, is described
by way of example in
WO2015/121334, which is hereby incorporated as a reference.
[0029] A sequence of items to be wrapped runs along a horizontal conveyor line and travels
to a wrapping station, stopping on a support shelf.
[0030] In the wrapping station, in a manner known per se, a driving ring is provided, which
drives into rotation a carriage on which a support shaft of a spool B of extensible
plastic film is installed. The driving ring is traditionally arranged on a vertical
plane arranged substantially perpendicular to the conveying line for items.
[0031] The item or load C to be wrapped, when stationary on the support shelf S, is inside
the circular path of that carriage, so that a plurality of film P turns can be wrapped
around it.
[0032] Further details on this configuration will not be provided below, since it is widely
known and, in itself, it is not the subject of the present application.
[0033] In order to overcome the drawbacks of the prior art, according to the invention,
from the two parts of the plane on which the circular path of the spool B of plastic
film P develops, a pair of holding units 10 and 20 are arranged opposite to one another
on a same operating line transversal to the longitudinal development of the film.
[0034] Typically, the operating line is arranged at a height that is easily accessible to
an operator, but in itself is not relevant to the operation of the system. Preferably,
the two holding units 10 and 20 are located at a height immediately below the support
shelf S of the item C to be wrapped, as shown in Figs. 2B and 2C.
[0035] Each holding unit 10 and 20 provides a gripping device 11 and 21 and a cutting device
12 and 22, both mounted movable longitudinally in opposite directions, so as to be
mutually approached and moved away from each other.
[0036] Both the gripping devices 11, 21 and the cutting devices 12, 22 are mounted on guides
and are moved backward and forward by respective actuators, for example, pneumatic
actuators 14, 15, 24, 25.
[0037] Additional gripping actuators 16 and 26 are provided for mutually opening and closing
pairs of jaws of the gripping devices 11 and 21.
[0038] The latter have a configuration similar to the traditional one, with a fixed jaw
arranged on the horizontal plane and a movable jaw underneath, which abuts against
the fixed jaw pivoting from below. The foot print of these clamping devices is however
very small compared to the prior art, because they are provided for grasping a short
flap of the side edge of the film, as shown in Fig. 4C.
[0039] The operation of the gripping devices 11 and 21 provides that they can move forward
and backward reciprocally both with the jaws closed (tightened) and with the jaws
open (released), by the intervention of the gripper feed actuators 15 and 25.
[0040] The cutting devices 12 and 22 of the two units 10 and 20 are designed as complementary,
so as to obtain a more effective cutting of the film P. In particular, as shown in
the figures, they preferably have respective cutting means 17 and 27 with a cutting
blade oriented respectively with an equal and opposite angle, for example 45° for
the blade of the left unit and -45° for the blade of the right unit. In this way,
the cutting action produced on one side has a component facing upwards which is balanced
by a component of the opposing blade directed downwards.
[0041] The two cutting means 17 and 27 are preferably arranged on two parallel but slightly
offset planes, so that the two blades can cross each other along their movement with
a scissor effect (see Fig. 3C). The crossing between the blades takes place in the
intermediate zone between the two holding units 10 and 20, in an end-of-stroke position
of the actuators 14 and 24 of the cutting devices 12 and 22.
[0042] The operation of the system is described below with reference to Figs. 4A-4F.
[0043] At the end of a wrapping cycle of an item, a film P is laid (Fig. 4A) between a spool
B and the item C, with the holding devices 10 and 20 completely spaced apart from
each other so as not to interfere with the path of the spool B.
[0044] At this point, the gripping devices 11 and 21 with the open jaws are brought mutually
closer until they intercept the area where the two lateral edges of the film are located.
The gripping devices 11 and 21 are then clamped, lifting the lower jaw against the
upper fixed jaw, so that the two gripping units 11 and 21 firmly grasp the respective
opposite lateral edges of the film P (Fig. 4C). According to a qualifying aspect of
the system of the invention, in this step the gripping devices 11 and 21 move away
from each other, keeping the film tightly clamped in the jaws, so as to cause a slight
stretching which extends the film transversely (Fig. 4D). In this state, the cutting
means 17 and 27 are brought mutually closer, through the respective actuators 14 and
24, which efficiently cut through the stretched film, until they cross in the central
area (Figs. 3C and 4F). The blades run along a line located between the gripping devices
11 and 21 and the wrapped item, so as to separate the film P from the item, but leaving
the end flap of film coming from the respective spool clamped between the gripping
devices 11 and 21 (Fig 2C) .
[0045] At the end of the cut, the two blades 12 and 22 are withdrawn towards the starting
position and the free flap of film remains joined to the item (due to its own elasticity),
while the other end coming from the spool B remains held by the two opposite gripping
devices 11 and 21. In this state, the spool B can be brought into rotation around
a new item to be wrapped, laying at least one film turn, even partially against the
two opposite gripping devices. Since the clamping devices are of small size - since
they are intended to grip only a short flap of film and not the whole film width as
in the prior art - the opening movement of the jaws, at least to the extent sufficient
to release the film, can take place in any case even if an extensible film turn has
been placed on it. Therefore, after laying at least one film turn, which thus remains
well locked on the load, the two grippers can be opened to free the film end, which
thus remains well stretched and captured under the first wrapping turn. Once the jaws
have been opened, the two grippers can be moved away from each other until they return
to the initial condition.
[0046] As can be understood from the above description, the system of the invention perfectly
achieves the purposes stated in the introduction. In fact, the two opposite holding
units allow to effectively manage the gripping and cutting of the film; working from
opposite sides laterally, the film is always kept well stretched and the formation
of the unwanted cord of the prior art is prevented; moreover, since the holding effect
occurs only on a small part of the edge of the film and the cutting operation takes
place with separate, longitudinally movable means, the footprint of the grippers is
minimal and they can hold the film even below the first turn (e.g. between the shelf
and the first turn, as in Fig. 2C), without the wrapping being compromised during
the release step.
[0047] It is understood, however, that the invention is not to be considered as limited
by the particular arrangement illustrated above, which represents an exemplary embodiment,
but different variants are possible, all within the reach of a person skilled in the
art, without departing from the scope of the invention itself, as defined by the following
claims.
1. Wrapping arrangement for an item to be wrapped with extensible plastic film, comprising
a driving ring which drives into rotation a support carriage of a spool (B) of extensible
plastic film (P), on a circular path which wraps an item to be wrapped, a pair of
holding units (10, 20) of the film being furthermore provided, on two opposite sides
of a plane on which said circular path develops, equipped with a gripping device,
said pair of holding units (10, 20) being arranged on a same operating line transversal
to the longitudinal development of the film, characterized in that each holding unit (10, 20) is provided with cutting devices (12, 22) apt to be brought
mutually closer along said operating line, said gripping devices(11, 21) and cutting
devices (12, 22) being mounted longitudinally movable in opposite directions and mounted
on guides, and to be moved backward and forward, by respective first movement actuators
(14, 15, 24, 25), and wherein further second gripping actuators (16, 26) are provided
for mutually opening and closing pairs of jaws of said gripping devices (11, 21) and
wherein said first and second actuators (14, 24, 15, 25, 16, 26) are mounted so that
said gripping devices (11, 21) can mutually move forward and backward both with said
jaws closed and with said jaws open.
2. Wrapping arrangement as in 1, wherein said cutting devices (12, 22) are designed as
complementary and have respective cutting means (17, 27) arranged on two parallel
but offset planes.
3. Method for wrapping an item using an arrangement as in any one of claims 1 to 6, wherein
the following steps are provided:
arranging a driving ring apt to drive into rotation a support carriage of a spool
(B) of extensible plastic film (P), on a circular path that wraps an item to be wrapped,
arranging, from two opposite parts of a plane on which said circular path develops,
a pair of holding units (10, 20) arranged on a same operating line transversal to
the longitudinal development of the film, each holding unit (10, 20) being provided
with gripping devices (11, 21) and cutting devices (12, 22) apt to be brought mutually
closer along said operating line,
bringing said holding units (10, 20) closer together to grasp and hold respective
flaps of opposite side edges of said extensible plastic film (P),
performing at least one complete turn of said spool (B) around the item on said circular
path, opening said gripping devices (11, 21) and moving said holding units away from
each other
subsequently bringing said holding units (10, 20) mutually closer so as to grasp and
hold respective flaps of opposite side edges of said extensible plastic film (P),
bringing said cutting devices (12, 22) mutually closer so as to lead respective cutting
means (17, 27) to cut said film (P) along a cutting line located between said gripping
devices (11, 21) and said item.
1. Umhüllungsanordnung für einen mit einer dehnbaren Kunststofffolie zu umhüllenden Gegenstand,
mit einem Antriebsring, der einen Tragschlitten einer Spule (B) von dehnbarer Kunststofffolie
(P) auf einer Kreisbahn, die einen zu umhüllenden Gegenstand umhüllt, in Drehung versetzt,
wobei ferner ein Paar Halteeinheiten (10, 20) der Folie vorgesehen ist, auf zwei gegenüberliegenden
Seiten einer Ebene, auf der sich die Kreisbahn entwickelt, ausgestattet mit einer
Greifvorrichtung, wobei das Paar von Halteeinheiten (10, 20) auf einer gleichen Arbeitslinie
quer zur Längsentwicklung der Folie angeordnet ist, dadurch gekennzeichnet, dass jede Halteeinheit (10, 20) mit Schneidvorrichtungen (12, 22) versehen ist, die geeignet
sind, sich entlang der Bearbeitungslinie einander anzunähern, wobei die Greifvorrichtungen
(11, 21) und die Schneidvorrichtungen (12, 22) in entgegengesetzten Richtungen längsbeweglich
und auf Führungen montiert sind und durch entsprechende erste Bewegungsaktuatoren
(14, 15, 24, 25) vorwärts und rückwärts bewegt werden können, und wobei weiter zweite
Greifaktuatoren (16, 26) für zueinander öffnende und schließende Backenpaare der Greifvorrichtungen
(11, 21) vorgesehen sind, und wobei erste und zweite Aktuatoren (14, 24, 15, 25, 16,
26) so montiert sind, dass sich die Greifvorrichtungen (11, 21) sowohl bei geschlossenen
als auch bei geöffneten Backen gegenseitig vorwärts und rückwärts bewegen können.
2. Umhüllungsanordnung wie in 1, wobei die Schneidvorrichtungen (12, 22) komplementär
gestaltet sind und jeweils Schneidmittel (17, 27) aufweisen, die auf zwei parallelen,
aber versetzten Ebenen angeordnet sind.
3. Verfahren zum Umhüllen eines Gegenstandes unter Verwendung einer Anordnung nach einem
der Ansprüche 1 bis 6 , wobei die folgenden Schritte vorgesehen sind:
Anordnen eines Antriebsrings, der geeignet ist, einen Tragschlitten einer Spule (B)
aus dehnbarer Kunststofffolie (P) auf einer kreisförmigen Bahn, die einen zu umwickelnden
Gegenstand umwickelt, in Drehung zu versetzen,
Anordnen eines Paares von Halteeinheiten (10, 20) von zwei gegenüberliegenden Teilen
einer Ebene aus, auf der die kreisförmige Bahn verläuft, die auf einer gleichen Bearbeitungslinie
quer zur Längsentwicklung der Folie angeordnet sind, wobei jede Halteeinheit (10,
20) mit Greifvorrichtungen (11, 21) und Schneidvorrichtungen (12, 22) versehen ist,
die sich entlang der Bearbeitungslinie gegenseitig annähern können,
Bringen der Halteeinheiten (10, 20) näher zueinander, um jeweilige Klappen von gegenüberliegenden
Seitenkanten der dehnbaren Kunststofffolie (P) zu greifen und zu halten,
Ausführen mindestens einer vollständigen Umdrehung der Spule (B) um den Gegenstand
auf der kreisförmigen Bahn, Öffnen der Greifvorrichtungen (11, 21) und Bewegen der
Halteeinheiten voneinander weg, und
anschließend Bringen der Halteeinheiten (10, 20) gegenseitig näher, um die jeweiligen
Klappen der gegenüberliegenden Seitenkanten der dehnbaren Kunststofffolie (P) zu greifen
und zu halten,
wobei die Schneidvorrichtungen (12, 22) gegenseitig näher gebracht werden, um die
jeweiligen Schneide mittel (17, 27) zum Schneiden der Folie (P) entlang einer zwischen
den Greifvorrichtungen (11 ,21) und dem Gegenstand liegenden Schnittlinie zu führen.
1. Agencement d'emballage pour un article à emballer avec un film plastique extensible,
comprenant un anneau d'entraînement qui entraîne en rotation un chariot de support
d'une bobine (B) de film plastique extensible (P), sur une trajectoire circulaire
qui emballe un article à emballer, une paire d'unités de support (10, 20) du film
étant en outre prévue, des deux côtés opposés d'un plan sur lequel ladite trajectoire
circulaire se développe, équipée avec un dispositif de préhension, ladite paire d'unités
de support (10, 20) étant agencée sur une même ligne opérationnelle transversale par
rapport au développement longitudinal du film, caractérisé en ce que chaque unité de support (10, 20) est prévue avec des dispositifs de coupe (12, 22)
aptes à être rapprochés mutuellement le long de ladite ligne opérationnelle, lesdits
dispositifs de préhension (11, 21) et les dispositifs de coupe (12, 22) étant montés
de manière longitudinalement mobile dans des directions opposées et montés sur des
guides, et pour être déplacés vers l'arrière et vers l'avant, par des premiers actionneurs
de mouvement (14, 15, 24, 25) respectifs, et dans lequel d'autres seconds actionneurs
de préhension (16, 26) sont prévus pour ouvrir et fermer mutuellement des paires de
mâchoires desdits dispositifs de préhension (11, 21) et dans lequel lesdits premier
et second actionneurs (14, 24, 15, 25, 16, 26) sont montés de sorte que lesdits dispositifs
de préhension (11, 21) peuvent mutuellement se déplacer vers l'avant et vers l'arrière
à la fois avec lesdites mâchoires fermées et avec lesdites mâchoires ouvertes.
2. Agencement d'emballage selon la revendication 1, dans lequel lesdits dispositifs de
coupe (12, 22) sont conçus comme étant complémentaires et ont des moyens de coupe
(17, 27) respectifs agencés sur deux plans parallèles mais décalés.
3. Procédé pour emballer un article à l'aide d'un agencement selon l'une quelconque des
revendications 1 à 6, dans les étapes suivantes sont prévues :
agencer un anneau d'entraînement apte à entraîner en rotation un chariot de support
d'une bobine (B) de film plastique extensible (P), sur une trajectoire circulaire
qui emballe un article à emballer,
agencer, à partir de deux parties opposées d'un plan sur lequel ladite trajectoire
circulaire se développe, une paire d'unités de support (10, 20) agencées sur une même
ligne opérationnelle transversale au développement longitudinal du film, chaque unité
de support (10, 20) étant prévue avec des dispositifs de préhension (11, 21) et des
dispositifs de coupe (12, 22) aptes à être rapprochés mutuellement le long de ladite
ligne opérationnelle,
amener lesdites unité de support (10, 20) plus à proximité les unes des autres afin
de saisir et maintenir les rabats respectifs des bords latéraux opposés dudit film
plastique extensible (P),
réaliser au moins un tour complet de ladite bobine (B) autour de l'article sur ladite
trajectoire circulaire, ouvrir lesdits dispositifs de préhension (11, 21) et déplacer
lesdits unités de support à distance les unes des autres,
amener ensuite lesdits unités de support (10, 20) mutuellement plus à proximité afin
de saisir et maintenir des rabats respectifs des bords latéraux opposés dudit film
plastique extensible (P),
amener lesdits dispositifs de coupe (12, 22) mutuellement plus à proximité afin d'amener
lesdits moyens de coupe (17, 27) respectifs à couper ledit film (P) le long d'une
ligne de coupe positionnée entre lesdits dispositifs de préhension (11, 21) et ledit
article.