Note: Descriptions are shown in the official language in which they were submitted.
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Method and apparatus for closing a packing tube
The present invention relates to a method and an apparatus for
closing a packing tube wrapped around an essentially cylindrical
packaged product, in particular a tampon for feminine hygiene.
Such packing tubes are made of a flexible, typically heat-
sealable film which is first arranged in tube shape around the
packaged product in a way such that a forward packing tube
portion, still open, projects beyond the free forward end of the
packaged product.
There are various products which have to be packed to preserve
them before they are used for the intended purpose, in order to
protect them against moisture or other harmful influences. Such
products include for example tampons for feminine hygiene, which
are packed individually in cylindrical packing tubes.
A method and an apparatus for producing such cylindrical packing
tube are for example described in US Patent No. 4 583 964. In
the described method the packing tube is made of a flexible,
heat-sealable film which is wrapped around a winding spindle and
heat-sealed to form a tube with an open end. Thus, at a first
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stage the packing tube projects with an open forward end portion
beyond the winding spindle. For closing this still open end of
the packing tube, US patent No. 4 583 964 describes a gripping
mechanism which clamps the forward end portion of the packing
tube around a shaft introduced into the open forward end. The
gripping mechanism has clamping jaws which are closed against
the shaft with the projecting forward end of the packaging tube
gripped inbetween. The gripped forward end portion of the
packing tube is then rotated with respect to the winding spindle
and the packing tube held thereon, in order to form a twist with
a twist rosette and a twist neck . After the formation of the
twist the clamping mechanism is opened and withdrawn, and a
pressing head having a recess complementary to the forward end
of the winding spindle is advanced against the twist and the
winding spindle. The cylindrical outer edge of the twist rosette
is thereby folded and finally pressed against the outer surface
of the packing tube when the pressing head with its recess has
completely received the forward end of the packing tube on the
winding spindle. Then, the inner walls surrounding the recess of
the pressing head are heated in order to melt the twist and to
join the film material of the twist rosette with the film of the
packing tube.
In other current methods, which are described in German Patent
No. 1 995 600, a packaged product, for example the tampon, is
already placed within the packing tube when the forwardly
projecting, still open end of the packing tube has to be closed.
Also in this method, a gripping mechanism is used to grip a
forward end portion of the packing tube beyond the forward tip
of the tampon. The gripping mechanism holding the forward end
portion of the packing tube is then rotated with respect to the
tampon and the packing tube surrounding it so that a twist is
formed. In a similar way as described above, a pressing head is
then used in order to fold the twist and the twist rosette onto
the forward end portion of the packing tube around the tampon
and to heat-seal the film material in order to form a dome-
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shaped packing closure over the tampon tip.
While this was recognized advance in the art, there remain some
disadvantageous. First, a complicated movement of the machine
components is required in order to grip the forward end portion
of the packing tube and to rotate it with respect to the rest of
the packing tube. This combination of gripping and rotation
movements requires rather complicated machine components in
order to be carried out on an automatic apparatus suitable for
mass-production. This makes the known apparatus rather compli-
cated and costly with respect.to manufacture, maintenance and
operation.
Second, a rather long portion of the packing tube has to project
beyond the forward end of the inserted tampon in order to allow
that a front end of this projecting portion is gripped and that
a twist is formed between the gripped portion and the tip of the
tampon. Thus, a rather high amount of packing film in the open,
forward projecting end portion is needed for the sole purpose of
closing the packing tube, and thus the packing film consumption
of the known method is rather high. Another disadvantage
associated with this rather large amount of packing film
projecting beyond the forward end of the tampon is that by
melting and heat-sealing the twist and the twist rosette this
rather high amount of film material is left on the dome-shaped
tip portion of the packing tube which can create hard balls of
plastic at the front portion of the packing which in turn can
lead to deformation of the packaged product, in particular to
deformation and damage of the tampon.
A typical packing film material used in the known methods is
cellulose hydrate or regenerated cellulose (known under the
trade mark CELLOPHAN). It would be desirable to use other film
materials, as for example polypropylene. Unfortunately, most, if
not all, forms of polypropylene film are not suitable to be
closed by the above described twisting methods.
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Accordingly, it is an object of the present invention to provide
a method and an apparatus for closing an open forward end of a
packing tube projecting beyond the packaged product which requi-
res less complicated movements of the packing apparatus compo-
nents. In particular, it is an object of the present invention
to avoid a rotating movement between packing tube and gripping
mechanisms in order to form a twist.
It is a further object of the present invention to provide a
method and an apparatus for closing the open end of a packing
tube which requires a shorter projecting length of packing tube
extending beyond the tip of the packaged product, and which
therefore reduces the packing film consumption.
It is a further object of the present invention to provide a
method and an apparatus for closing the open end of a packing
tube which permit the use of a wider range of packaging films.
According to the present invention a front portion of the open,
forward projecting packing tube portion is pressed together and
joined by clamping jaws to form a film sheet. This joining or
closing to a film sheet can be done by heat-sealing, if a heat-
sealable film material is used, or by pressing, if the film
material used has, at least in the area of the forward
projecting end, a coating of a pressure sensitive adhesive. The
film sheet is then folded over and laid onto the outer surface
of the packing tube around the free forward end of the packaged
product. This folded film sheet is then joined with the packing
tube film, either by heat-sealing, or by pressing it onto the
packing tube film, wherein in the latter case the film has to be
coated with pressure sensitive adhesive.
With the method of the present invention the required movements
of the tools for closing the forward end of the packing tube are
considerably simplified since no twist needs to be formed and
therefore no rotation between a gripping mechanism and the
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remaining packing tube is needed. Instead a simple clamping
operation and joining, either by heat-sealing or pressing in
case of using an adhesive coated film, is performed in order to
form a closed film sheet at the forward end of the packing tube.
Subsequently, this film sheet is folded over and laid onto the
outer surface of the packing tube surrounding the tip portion of
the packaged product and joined therewith (again by heat-sealing
or pressing).
Furthermore, the method and apparatus of the present invention
need less packing tube length, extending beyond the tip of the
packaged product since no twist needs to be formed. Therefore,
less packing film is needed in order to form the packaged
product. It was found that with the present invention the
overall amount of packing film needed to form the package can be
reduced by about 10~.
It is a further advantage of the present invention that due to
the reduced amount of packing film needed to form the closed
package tip there is less danger that packing material
accumulations are formed after closing, a . g . by heat-sealing, at
the tip of the package, and therefore there is less danger that
the packaged product, for example the tampon, is deformed or
damaged by such material accumulations at the tip portion.
Another advantage of the present invention is that with the
method and apparatus of the present invention also packing film
materials such as polypropylene which could not be employed with
the known twisting methods, can be used as packing film
materials.
In a preferred embodiment the film sheet formed in a front
portion of the forward projecting end of the packing tube is
formed such that at least one essentially planar first sheet
portion is created which is inclined against the longitudinal
axis of the package tube. Due to this inclination the pressing
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head, when advancing over the forward end of the packaged
product, can easily fold the film sheet onto the packing tube
around the forward end of the packaged product. It is
particularly preferred to form two first film sheet portions
which are symmetrical with respect to a plane including the
longitudinal axis of the package tube and which are inclined in
opposite directions against the longitudinal axis of the package
tube. By this arrangement the pressing head when advancing over
the free forward end of the packaged products folds the two
first film sheet portions onto opposite hemispheres of the
package tube. For example, if,one first film sheet portion is
inclined upwardly and the other downwardly, one film sheet
portion will be folded onto the upper half and the other onto
the lower half of the packing tube around the forward end of the
packaged product. By this means a more uniform distribution of
the film material folded and heat-sealed on the dome-shaped
forward tip of the package is achieved.
In a preferred embodiment not only a front portion of the
packing film is pressed together but also the packing film
around a forward end portion of the packaged product. This can
be achieved by adapting the clamping jaws to form, when closed,
a recess of complementary shape to the forward end portion of
the packaged product. Thus, the clamping jaws can be adapted to
receive the forward end portion of the packaged product within
the recess and to press portions of the packing film surrounding
the forward end portion of the packaged product together. The
film sheet surrounding the forward end portion of the packaged
product can be in the form of a second essentially planar sheet
portion.
In a preferred embodiment the clamping jaws are pivotally
mounted and arranged to be longitudinally movable, against a
biasing force, in the direction towards the axis of the pivotal
movement. By this arrangement the clamping jaws, when closing
around the forward end portion of the packaged product, can
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adapt to the actual position of the forward end of the packaged
product by moving backwardly against the biasing force if
necessary, to thereby accommodate length variations of the
packaged products. Each clamping jaw can for example be attached
to a rod which in turn is slidably received in a guiding
cylinder of a pivot member. A spring force is acting on the rod
to bias it into its extended position. This ability of the
clamping jaw to move in a direction perpendicular to the pivot
axis, I.e. in the longitudinal direction of the packaged product
when the clamping jaws are closed, allows on the one hand that
the clamping jaws can adapt to the position of the forward end
of the packaged product, when the clamping jaws with their
recess close around the forward end and are pressed to move
slightly backward if the position of the forward end of the
packaged product requires that. On the other hand this
arrangement of the clamping jaws to be movable in the direction
towards the pivot axis has the further advantage that the
clamping jaws, when closing with their recess around the forward
end of the packaged product, in most cases ( I . a . whenever the
forward end of the packaged product extends beyond a
predetermined position) perform a slight backward movement,
thereby tightening the packing film around the packaged product
and thus improving the quality of the package.
In a preferred embodiment, which performs heat-sealing, the
clamping surfaces of the clamping jaws are pre-heated already
before they reach the closed position to thereby shorten the
time needed for heat-sealing the pressed film sheets, in order
to allow to increase the speed or processing rate of the
packaged products. The pre-heating of the clamping surfaces is
particularly advantageous if polypropylene is used as packing
film because this material has a rather small temperature
tolerance which means that it must not be overheated over the
temperature needed for heat-sealing, or may be overheated only
by a small fraction of about 10 ~ of the temperature needed for
heat-sealing. For this reason the heat-sealing step cannot be
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accelerated by increasing the heating power of the closed
clamping jaws . Therefore, in principle a longer time would be
needed for heat-sealing the polypropylene film by moderately
heating it up to the heat-sealing temperature; this heat-sealing
time can advantageously be shortened in accordance with the
present invention if the clamping surfaces of the clamping jaws
are already pre-heated before they press the packing film
together.
The present invention can be used with all film materials useful
in the field of packing technology. Among them are the already
mentioned films of cellulose hydrate which can be non-coated or
coated with lacquer. Furthermore, polymer coated cellulose
hydrate films can be used, for example films with a coating of
polyvinyl dichloride. However, also non-cellulose films of all
kinds are suitable, for example polypropylene films. Generally,
also composite films of all kinds can be used, for example
combinations of cellulose hydrate films with co-extruded
polypropylene (PPOS), with oriented polypropylene (PPO) or
unoriented polypropylene (PPN). Furthermore, composite films of
cellulose hydrate films and polyethylene films can be use, or
any combinations of cellulose hydrate films with polyamide,
polyester, polyethylene and/or polypropylene layers. In addition
also plastic films with a metal coating, for example with a
aluminum layer can be used. Furthermore, dry coated films and
shrinking films can be used in connection with the invention.
The packing films to be utilized in connection with the present
invention should have a thickness in the range of 20 to 120 Vim.
In principle all films can be processed which can be sealed
either by heat-sealing or which have a pressure sensitive
coating in the area to be closed.
The invention will be described in the following in connection
with an embodiment shown in the attached drawings, in which:
Figure 1 shows a schematical side view, partly in cross-section,
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of the clamping jaws and their operating mechanism;
Figure 2 shows a front view of the clamping jaws in the closed
position of Figure 1;
Figure 3 shows a side view of the clamping jaws and their
operating mechanism as in Figure 1, but with the clamping jaws
in the open position;
Figure 4 shows a front view of the clamping jaws in the open
position of Figure 3;
Figure 5 shows a schematical front view of the packaged product
with two inclined film sheet portions formed at the forward end.
In the following detailed description only the design and
operation of the clamping jaws will be further described,
whereas the design and operation of the pressing head, which is
conventional, will not be further described. For joining the
films, in the following embodiment reference is made to heat-
sealing, in principle, however, also films can be used which
are, at least in the areas to be joined, coated with pressure
sensitive adhesive so that no heat-sealing step is needed.
Figure 1 shows the front part of the mounting and operating
mechanism for the clamping jaws 10, 10' which are in their
closed position. The clamping jaws 10, 10' are mounted on pivot
member 20, 20', respectively, which are pivotally mounted and
which are operated by a rod mechanism for periodically opening
and closing them. The clamping jaws 10, 10' are shown in Figure
3 in their opened position.
Clamping jaw 10 (10') is mounted via a rod 12 (12') on a pivot
member 20 (20') in which the rod 12 (12') is slidably received.
A spring force is acting on the rod 12 (12') to bias it to its
forward, extended position as shown in Figure 1. During the
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movement of the clamping jaws from their open position shown in
Figure 3 to the closed position shown in Figure 1 the clamping
jaw 10 (10') is, at the first part of the movement, guided on a
guiding surface 22 (22'). In the second part of the closing
movement the clamping jaw 10 (10') comes free of the guiding
surface 22 (22') so that the clamping jaw 10 (10'), when
approaching the closed position, is free to move backwardly,
with the rod 12 (12') moving further into the pivot member 20
(20') against a biasing force. By this resilient mounting of the
clamping jaws 10, 10', they are movable towards their respective
pivot axes, i.e. to the right hand side in the representation of
Figure 1, in order to be able to adapt to the actual position of
the forward end of the packaged product which is received in a
recess 14 of the clamping jaws 10, 10'.
The further linkage and rod mechanism shown in Figures 1 and 3
which is utilized to periodically open and close the pivot
members 20, 20', when a new packaged product is moved into
position, is not part of the present invention and will not be
described in more detail here.
The design and operation of the clamping jaws 10, 10' can best
be described in connection with Figures 3 and 4. The clamping
jaws are formed with a recess 14 being located in the center of
the clamping jaws (see Figure 4) and are therefore shown in
dashed or phantom lines in Figure 3. The recess 14 is, when the
clamping jaws 10, 10' are closed, of complementary shape to the
dome-shaped forward end of the packaged product 2 so that the
clamping jaws can be closed around a forward end portion of the
packaged product 2.
Surrounding the recess 14 are second clamping surfaces 11, 11'
which serve to press the packing film around a forward end
portion of the packaged product received in the recess 14 in
order to form an essentially planar second film sheet.
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In the region of the clamping jaws 10, 10' which press the open,
forward projecting tube portion 3 several clamping surfaces are
provided in the clamping jaws in order to form first sheet
portions in the portion 3 of teh packing tube projecting beyond
the forward end of the packaged product. These first clamping
surfaces include opposite clamping surfaces 16, 16' and 18, 18'
which are symmetrically located with respect to a plane
perpendicular to the second clamping surfaces 11, 11', wherein
opposite clamping surface 16, 16' and 18, 18' each form an
essentially planar film sheet portion 6 and 8 (see Figure 3 and
5) which are inclined in opposite direction with respect to the
longitudinal axis of the packaged product. Thus, the open
forward projecting end 3 of the package tube is formed by these
first clamping surfaces 16, 16' , 18, 18' into two essentially
planar first film sheet portions 6, 8, being inclined in
opposite directions with respect to the longitudinal axis of the
packaged product, as schematically shown in the front view of
Figure 5. These two oppositely inclined film sheets or "flaps"
6, 8 are connected by an inclined intermediate film portion.
This inclined intermediate film portion is formed by the
intermediate clamping surfaces which connect the first clamping
surfaces 16 and 18, or 16' and 18', respectively.
In this preferred embodiment two first film sheet portions 6, 8
are formed in the region projecting beyond the forward tip of
the packaged product. However, in principle a single essentially
planar first film sheet can be formed which is preferably
inclined against the longitudinal axis of the packaged product.
However, it is preferred to form at least two first film sheet
portions 6, 8 which allows to achive a more uniform distribution
of the film material when the first film sheet portions 6, 8 are
folded onto the packing film 1 around the packaged product 2. In
principle, also more than two first film sheet portions could be
formed.
In an alternative embodiment also shorter forms of clamping jaws
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10, 10' which do not include a recess 14 could be used. In this
case the clamping jaws would only press a front portion of the
forwardly projecting packing tube portion 3 to form a pressed
film sheet in front of the forward end of the packaged product,
without enclosing the forward end of the packaged product and
without pressing the packing film surrounding the forward end of
the packaged product.
When carrying out a method of the present invention the packing
tube 1 around the packaged product 2 has, in the initial phase
as shown in Figure 3 by dashed lines of the packing film 1, an
open forward end portion 3 which projects beyond the forward end
of the packaged product 2. The packaged product 2 with the
surrounding open packing tube 1 is held in the position shown in
Figure 3 by a mechanism which is not shown. Starting at this
position the operating mechanism of the clamping jaws 10, 10'
moves the clamping jaws to a closed position as shown in Figure
1, whereby the forward end portion of the packaged product 2 is
received in the recess 14 and the forward projecting open
packing tube portion 3 is pressed together to form two inclined
first film sheet portions 6, 8 in front of the packaged product
2, and a second film sheet portion around the dome-shaped
forward end of the packaged product.
In a preferred embodiment the clamping surfaces 16, I6', 18,
18', 11, 11' are already pre-heated before the clamping jaws
reach the closed position in order to introduce as much heat as
possible in a short time period in order to achieve sealing of
the first and second film sheet portions in the shortest
possible time period without overheating the film material.
In a next station of the apparatus which is not shown in the
Figures, the packaged product 2 with its closed film sheet end
portions 6, 8 is moved in front of a pressing head which has a
recess of complementary shape to the front end portion of the
packaged product 2. This recess is moved over the front end
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portion of the packaged product 2 to thereby fold the first film
sheet portions 6, 8 onto the packing tube 1 around the forward
end of the packaged product, wherein the film sheet portion 6
will be folded onto the lower half and the film sheet portion 8
will be folded onto the upper half of the packaged product 2.
When the front portion of the packaged product is fully received
within the recess, also the second film film sheet portions are
pressed against the packing tube. The walls surrounding the
recess of the pressing head are pre-heated in order to melt the
packing film material to join the film sheet portions with the
packing film around the packaged product by heat-sealing.
As shown in Figure 3 the clamping jaws 10, 10' abut against
guiding surfaces 22, 22' which guide the clamping jaws 10, 10'
during a first part of their closing movement. The guiding
surfaces 22, 22' are shaped such that at a certain point of the
closing movement the clamping jaws 10, 10' get free of the
guiding surfaces when closing further and are held by the
biasing force against their rods 12, 12' in their extended
position. When reaching the final stage of closing movement the
clamping jaws 10, 10' are thus free to move into the direction
of their pivotal axes (I.e. to the right side in Figure 1)
against the biasing force. This elastically resilient mounting
of the clamping jaws 10, 10' permits that, when their recess 14
closes around the dome-shaped forward end of the packaged
product 2, they adapt to the actual position of the forward end
of the packaged product and thus adapt to length variations of
the packaged product. Furthermore, this elastically resilient
mounting scheme of the clamping jaws 10, 10' has the effect
that, since the clamping jaws will be arranged to slightly move
backwards in case of the average product size, in most cases the
clamping jaws when closing around the packaged product move
slightly backwards thereby tightening the packing film around
the packaged product and thus improving the quality of the
packing.
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