Note: Descriptions are shown in the official language in which they were submitted.
1222-7
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A Procedure and an Apparatus for Manufacturing
a Sack or Bag of Thermoplastic Material
_havinq a Carrying Handle
The present invention relates to a procedure for manufacturing
a sack or bag of thermoplastic from a semi-tubular web provided
with a ~ [sigma]-shaped fold joining the overlying web layers in
which a handle strip also of thermoplastic is inserted into the
fold that is open to the outside and welded to the fold by flat
welds that are made at a spacing that equals the subsequent bag
width. The bag is then cut off from the semi-tubular web by
transverse weld seams that pass through the flat welds. The
present invention also relates to an apparatus for carrying out
this procedure.
Bags that are manufactured by this process are preferably used
as diaper bags. In order to fill the bag, the package of diapers
is slid into the open bottom end of the bag, and then the bottom
end is closed by means of a welded cross seam or a transverse
weld seam. When the bag is full, the handle strip, which is
welded by its ends to the bag, is at the top of the bag, so that
it can be grasped conveniently.
In order that bags with handles, such as diaper bags, can be
stacked, transported and filled without difficulty, it is
desirable that they lie flat once they have been cut off from the
semi-tubular web. This assists in stacking. For bags
manufactured by known procedures, the problem arises that the
handle strip enters the fold with too much tension so that it
causes the fold in the bag to contract, and the fold bends. If
the handle strip is too long, it causes the fold to undulate.
In either case, it is no longer possible to stack the bags one
on top of the other without difficulty.
For this reason, the present invention seeks to provide a
procedure by which the handle strip can be installed in the fold
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of the semi-tubular web, under such tension that the sections of
handle strip no longer bend the fold areas of the bag that has
been cut off, or cause it to undulate.
According to the present invention, this problem has been solved
by a procedure enabling the tension of the handle strip that is
inserted into the fold to be controlled. -~
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During the manufacture of the bag, the operator of the machine
observes the bags that are being manufactured, and he varies the
tension of the handle strip that is inserted into the fold if he ~-
identifies bends or undulations in the fold area of the bags
caused by the sections of the handle strip. -~ -
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In addition, the tension of the semi-tubular web can also be
controlled, so that tension-free and buckle-free welding of the
handle-strip sections into the fold of the semi-tubular web can
be achieved by controlling the tension of the handle strip and/or
the semi-tubular web.
:
According to the present invention, this task has been solved by
an apparatus having the following: a pair of pre-tensioning
rollers that pull the semi-tubular web with the ~-shaped fold
into the apparatus continuously; a web storage unit from which
a pair of pre-tensioning rollers, mounted at the start of the
processing section, draws off the web intermittently, one bag
width at a time; a transverse welding device, in combination with
a second pair of pre-tensioning rollers that is driven
intermittently and synchronized with the first pair of
intermittently driven rollers; a feed system for the handle
strip, from which the first pair of intermittently driven rollers
draws this handle strip into the processing section; a device
that places the handle strip into the fold; a welding system that ~ ;
is arranged between the two pairs of intermittently driven ~-
rollers, which makes the flat welds; and a device to discharge ;~
and stack the bags that have been cut off. According to the ` -
present invention, this is done such that the supply system for
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the handle strip comprises a web storage unit with guide rollers
that are mounted on the frame and with a roller that is mounted
on a swinging arm, over which the perforated handle strip is
guided in a zig-zag shape. A pair of pre-tensioning rollers draw
the handle strip continuously into the web storage unit; and a
controllable drive system for the swinging arm is also
incorporated, to provide the handle strip tension that is
required. The particular tension that is required in each
instance can be set very simply with the device according to the
present invention. This ensures that the section handle strip
can be welded into the folds of the semi-tubular web without
excess tension and without buckling.
It is most expedient if the drive system comprise a pressure-
medium piston-cylinder unit that is articulated onto the swinging
arm. The pressure of the pressure medium is controllable by a
pressure-regulating valve.
In a further configuration of the present invention, provision
is made such that the web storage device for the semi-tubular web
comprises guide rollers that are fixed to the frame, and a roller
that is mounted on a swinging arm, the swinging arm being
pivotable by a controllable drive system, for example, a pressure
medium piston-cylinder unit, depending on the web tension that
is desired.
One embodiment of the present invention will be described below
on the basis of the drawings appended hereto. These drawings
show the following:
Figure 1: A diagrammatic side view of the apparatus used to
manufacture the bag;
Figure 2: A plan view of the semi-tubular web with the handle
strip, with the steps of the process completed by the
apparatus that is shown in Figure 1.
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The supply roll 1, from which the semi-tubular web 2 is drawn ~ ~-
off, is supported ln a winding apparatus that is conventional and
for this reason not shown herein. The semi-tubular web 2 passes
over a deflector roller and is then drawn into a web storage unit
4 by a pair of pre-tensioning rollers 3. The web storage unit
4 consists of a plurality of guide rollers 5 that are secured to
the frame, and a plurality of guide rollers 8 that are mounted
on the swinging arm 7 that can pivot about the shaft 6; the web -
is guided in a zig-zag path over the rollers 8, after which it
passes over a plurality of fixed guide rollers. The swinging arm
7 is hinged onto the piston rod of a pneumatic cylinder 9 that
is articulated onto the frame. The pneumatic cylinder 9 is
supplied with compressed air through a line 10 and a pressure
regulating valve 11 from a source that is not shown herein. A
pressure gauge 12 is arranged in the compressed-air line 10. A
pair of pre-tensioning rollers 13 intermittently draws the web
2 from the web storage unit 4 into the processing section one bag
width at a time. At the end of the processing section there is
a transverse welding device 14; preceded by a pair of pre-
tensioning rollers 15 that is driven intermittently,
synchronously with the pair of pre-tensioning rollers 13.
Within the processing section, after the intermittently driven
pair of pre-tensioning rollers 13, there is a perforating device
16, which makes a transverse perforation 18 in the web, in the
area of its sigma-shaped fold 17. This transverse perforation
is used to tear open the bag in order to remove its contents.
To one side of, or above the frame, a handle strip roll 19 is
supported in a winding system, and within this, a handle strip
20 is drawn off by a pair of pre-tensioning rollers 21. Ahead
of the pair of pre-tensioning rollers 21 there is a folding
device 22, which folds the handle strip 20 securely onto itself,
so that it enters the web storage unit 23 folded lengthwise. The
web storage device 23 consists of guide rollers 24 that are fixed
to the frame, and of guide rollers 25 that are supported on a
swlnging arm 26 that is supported so as to pivot in the frame.
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213~;320
The swinging arm 26 is articulated onto the piston rod of a
pneumatic cylinder 27 that is hinged onto the frame. The
pneumatic cylinder 27 is supplied with compressed air by a
compressed air line 28, through a pressure regulating valve 29.
A pressure gauge is incorporated in the compressed air line 28.
The handle strip web that has been folded onto itself is
similarly drawn into the processing section through the pair of
pre-tensioning rollers 13. After the perforating device 16, as
viewed in the direction of movement A of the web 2, the folded
handle strip web 20 is inserted into the fold 17 of the semi-
tubular web 2 with its fold on the inside. This insertion can
be effected by a rotating disk [not shown herein].
.,
On both sides of the line of perforation 18, the web 2 is
provided with flat welds 33 in a triangular shape, and these
include the fold 17 and the folded handle strip 20 that has been
inserted therein. The web 2 is then provided with transverse
weld seams 34, which pass through the triangular welds 33 in the
manner shown, so that the triangular weld 33 form corner welds
of the bags 35, and join the sections 36 of the handle strip with
the fold 17 at the end.
The semi-tubular web 2 has a longer web section 37 in which pairs
of stacking holes 38 are made in a punching station (not shown
herein).
The bags 35 that have been cut off in the welding station 14 are
picked up by the arms 40 of a so-called "wicketer" 41, and
transported across the top of this to a stack conveyor belt 42,
where they are threaded onto stacking pins 43 that pass through
the holes 38. As soon as a stack containing a specific number
of bags has been threaded onto the stacking pins 43, the stacking
conveyor belt is moved ahead by one increment.
:;~
If the operator of the machine sees that the bags 35 that are
threaded onto the stacking pins 43 are showing curves or
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undulations in the area of their folds 17, he activates one or
both of the pressure regulating valves 11, 29 so as to change the
tension of the web(s) entering the web storage unit, so that the -:
sections of handle strip can be welded into the folds 17 in such ~ :~
a way that the handle strips can cause no tension or deformation,
which could cause the fold area to curve or undulate in the fold ::
area 17 of the bags 3S.
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