Note: Descriptions are shown in the official language in which they were submitted.
SPECIFIC~TION
The present invention relates to a method of forming
a plastic fastener and plastic accessory strips and uniting
the same with a film having a single layer or a plurality of
layers, which film is then converted into reclosable bags.
Such bags or pouches are known as having a body made
of a single or a plurality of layers and an opening which
can be opened or closed by means of a plastic fastener. In
such bags or pouches, the opening/closing function can be
assisted by providing ribs in the vicinity of the plastic
fastener so as to prevent the adherence of the film to
itself at the upper edges of the opening and to facilitate
the grasping of the opening lip and by bonding fillets for
reinforcing the bag or pouch to the portion between the ribs
and the plastic fastener.
The p~esent invention is a method of producing a
plastic film having a plastic fastener and accessory strips,
such as ribs and fillets, for making a reclosable bag. The
method includes use of a first forming die which extrudes
~0 the accessory strips, a second forming die which extrudes
the fastener having male and female profiles, a pair of nip
rolls for press-bonding the accessory strips onto the
surface of film being fed thereto, a bonding guide roll for
receiving the film with press-bonded accessory strips and
the fastener from the second forming die placed onto the
film in parallel to the accessory strips such that the
fastener is bonded to the film at the bonding guide roll by
virtue of the heat imparted to the fastener during formation
of the fastener.
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The invention also concerns apparatus for bonding a
plastic fastener, having male and female interlockable
profiles, and a plastic accessory strips means to a plastic
film for preparation of a reclosable plastic bag, comprising
a first forming die for solely extruding said accessory
strip means, a second forming die for solely extruding
therefrom said fastener, a first bonding role adjacent said
first forming die, a second bonding roll adjacent said
second forming die, first and second heating means
respectively associated with said first and second forming
dies for respectively heat welding said accessory strip
means and fastener to said film, and means for conducting
film and accessory strip means against said first bonding
roll and then for conducting said film with accessory strip
means bonded thereto and said fastener against said second
bonding roll.
Fig. 1 is a cross-sectional view of a film to which
a plastic fastener and accessory strips have been bonded.
Fig. 2 is a side elevational view showing a
~0 conventional method for bonding a fastener and accessory
strips to a plastic film.
Fig. 3 is a side elevational view showing a method
of the invention for bonding a fastener and accessory strips
to plastic film.
Fig. 4 is a partial front view of Fig. 3 in the
direction of arrow IV of Fig. 3.
As shown in Fig. 1, reclosable bag film can be
produced by extruding accessory strips, such as ribs 2 and
fillets 3, and the like, as well as a fastener having the
male profile 4 and female profile 5, onto a flat film 1 and
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bonding them to the latter by the heat which has been
imparted to them during forming by extrusion.
A conventional forming and uniting method, as shown
in Fig. 2, employs a single die 6 which simultaneously
extrudes and forms accessory strips 7, such as the ribs 2
and the fillets 3, and a plastic fastener 8, including male
and female profiles 4, 5. The extruded accessory strips 7
and the fastener 8 are bonded by the possessed heat to the
film 1 which runs along a bonding roll 9 disposed in the
vicinity of the die 6. The accessory strips 7 is are then
pressed by means of a press roll 10 onto the film 1 which is
then forwarded to a cooling area 11.
This conventional method, however, has encountered
various problems because of the fact that while the
accessory strips 7 and the fastener 8 had different forms
and material composition weight ratios they were
nevertheless extruded and formed by a single die 6 under the
same temperature condition.
In fact, the fastener and the accessory strips,
~0 which have different shapes and weights should be formed at
~i~erent optimum temperatures. As long as the extrusion is
made with a single die, however, it is not possible to use
different temperatures, so that actually the extrusion is
made at a temperature which is optimum only for either the
~5 fastener or the accessory strips. Assuming for e~ample that
the die temperature is set at an optimum level for the
extrusion of the fastener, the accessory strips may fail to
be united with the film 1, since the bonding thereof is made
under the same conditions as those of the fastener 8. This
is because the accessory strips 7 exhibit greater heat loss
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radiation than the fastener 8 due to their specific weight
being smaller than that of the fastener 8 and due to their
thin-walled flat form presenting a greater heat radiation
surface area. To the contrary, if the extrusion is made at
a die temperature suitable for the bonding of the accessory
strips, such a die temperature is too high for the extrusion
of the fastener so that the fastener is in an undesirably
molten state.
Another problem involved by the conventional method
is the result of the fact that the fastener and the
accessory strips are bonded to the film on the same roll
9. Thus, when the accessory strips 7 is pressed by the
press roll 10, the portion of the roll adjacent to the
fastener 8 is also pressed on causing an elastic deformation
of the rubber with which the roll 9 is covered thereby
forming indentations in that portion of the rubber. Such
indentation causes various problems such as bonding of the
fastener at a slant, deformation of the fastener itself, and
so forth.
Thus, as bonding roll 9 is continuously pressed by
the press roll 10, the pressed portion of the roll is
locally degraded and plastically deformed and loses the
elasticity of the rubber thereby allowing the formation of
indentations in the bonding surface of the roll. This in
turn results in the bonding of the fastener 8 at a slant or
in deformation of the fastener 8 itself.
To eliminate this problem, the present invention
proposes a method in which a die for extruding the accessory
strips and a die for extruding the fastener are arranged on
one or more separate extruders in a side-by-side Eashion, so
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as to allow the forming temperature of the die for extruding
the accessory strips to be higher than the forming
temperature of the die for extruding the fastener. In this
fashion the fastener and the accessory strips are extruded
separately and then welded and bonded -to the film running
around respective sets of bonding rolls.
A preferred embodiment of the invention is described
hereinunder with reference to Figs. 3 and 4. Referring to
these Figures, a first forming die 12 for extruding the
accessory strips 7 and a second forming die 13 for extruding
the fastener 8 having the male and female profiles 4, 5 are
disposed independently of one another and in a side-by-side
fashion to each other and connected to an alongside plastic
extruder 18. The film 1 is unrolled from a reel. The
accessory strips 7 extruded from the first die 12 are
adapted to be joined to the film 1 on a roll 14 which is
disposed in the vicinity of the first forming die 12. A
press roll 16 and opposing embossing roll 17 forming a
rollnip for pressing the accessory strips 7 onto the film 1
are disposed in the vicinity of the roll 14.
A roll 15 disposed in the vicinity of the second die
13 is adapted to bond the fastener 8 to the film having the
accessory strips and to guide this film with the fastener 8
to the next step of process. As shown in Fig. 4, the roll
~S 15 has a groove 19 adapted to guide both sides of the
fastener 8 as it is bonded to the film 1. A reference
numeral 11 designates a downstream cooling step.
In operation, the accessory strips 7 such as ribs 2
and fillets 3 extruded from the first die 12 are welded by
the heat retained from their extrusion to the film 1 running
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on the roll 14. Then, the film together with the accessory
strips 7 is moved through the nip between the press roller
16 and the embossing roller 17, so that the accessory strips
7 are pressed and bonded onto -the film 1.
Subsequently, the film 1 with the accessory strips 7
is transferred onto the roll 15 adjacent to the second die
13, and the fastener 8 consisting of male and female
profiles 41 5, is extruded from the second die 13 and welded
to the film 1 running on the roll 15 by the heat retained
from the extrusion formation of the fastener.
The method of the invention offers a number of
advantages because the first die for extruding the accessory
strips and the second die for extruding the fasteners are
disposed in a side-by-side fashion to each other, and
therefore can operate at the optimum temperatures for the
bond to the film of the accessory strips and the fastener,
respectively~
Since the fastener and the accessory strips are
extruded at optimum temperatures, it is now possible to
optimize the heat possessed by the fastener and the
accessory strips respectively and thus to obtain the precise
shapes required of each, when each is bonded to the film.
~lso, the undesirable damaging of the bonding roll 15 can
now be avoided because the pressing of the accessory strips
to the film for bonding the former to the latter is
conducted in advance to the bonding of -the fastener.
Consequently, it is possible to correctly and smoothly unite
the fastener with the film without the fastener being
subjected to any slanting and/or deformation. Thirdly, the
invention provides an additional advantage in that, since
the accessory strips are bonded to the film before the
bonding of the fastener, the film portion adjacent to the
accessory strips can be advantageously heated, so that the
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fastener can be bonded to the film even when the extrusion
heat of the fastener is low (which may be desirable to
obtain a better fastener shape), i.e. even when the
extrusion is made at a temperature which is less than that
which would be required for the bonding of the fastener.
Although various minor modifications may be
suggested by those versed in the art, it should be
understood that I wish to embody within the scope of the
patent warranted hereon all such modifications as reasonably
and properly come within the scope of my contribution to the
art.
