Note: Descriptions are shown in the official language in which they were submitted.
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OPEN BAG OR BAG CLOSED ON TWO SIDES HAVING AN END REGION CLOSED
BY MEANS OF A MATERIAL STRIP, METHOD AND APPARATUS FOR CLOSING
A BAG
FIELD OF THE INVENTION
The present invention relates to a method for closing on one
side a tubular starting material comprising coated or uncoated
polyolefin fabric, in particular polypropylene or HDPE fabric,
to produce an open bag.
The invention further relates to a method for closing a filled
open bag, closed on one side, comprising coated or uncoated
polyolefin fabric, in particular polypropylene or HDPE fabric,
having a substantially tubular base body, to produce a bag
closed on two sides.
The present invention additionally relates to an apparatus for
closing on one side a tubular starting material comprising
coated or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric, to produce an open bag.
The present invention further relates to an apparatus for
closing a filled open bag, closed on one side, comprising
coated or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric, having a substantially tubular
base body, to produce a bag closed on two sides.
PRIOR ART
In packaging technology open bags are very popular as a result
of the flexible type of filling when it is a question of the
packing of free-flowing bulk goods of all kinds (fine-grained,
coarse-grained, powder, granules, pellets etc.). In this
context open bag generally and without restriction to a special
material designates a bag having a substantially tubular base
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body which is only closed in a first end region and open in a
second region. The closure of filled open bags made of coated
or uncoated polypropylene fabric, where polypropylene like
polyethylene belongs to the polyolefins, is principally
accomplished by sewing at the present time. A distinction is
made here primarily between a simple straight sewing and sewing
with overfolding of the open bag. Furthermore, sealing cords or
sealing strips can be used. In the sewing machines used a
distinction is principally made between single-needle and
double-needle sewing machines. The fundamental operating mode
is the same in all systems whereby the filled open bag is fed
to the sewing machine via an insertion system which typically
operates via chains or belts and a conveyor belt located
thereunder and is sewn by the interlinking of at least one
thread.
A disadvantage of this type of closure consists in the
weakening or damaging of the open bag material by needle
piercings. An absolute tightness of the closure can therefore
barely be ensured which, for example, in the case of very fine-
grained filling material has a particularly disadvantageous
effect. There is also the risk that the filling material will
be contaminated by sewing threads, sealing cords or sealing
strips. Sewing with overfolding of the open bag is additionally
economically disadvantageous since an increased expenditure of
open bag material is required for this purpose as a result of
the required greater open bag lengths. Possible thread breaks
additionally cause relatively long production standstills. In
addition, sewing installations are generally relatively
maintenance-intensive and cause a high noise level.
Alternatively to sewing, there is also the possibility of heat
sealing the open bag. In this case, the open end region of the
filled open bag is usually pressed between jaws which are
provided with heating elements whereby a thermal input is
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accomplished - through the entire open bag material - which
results in the heat sealing.
It is problematical to use this method when the region to be
heat-sealed is contaminated by filling material. This is
frequently the case with powdery filling material with the
result that a secure, tight closure is thwarted. Primarily
however the polypropylene bag fabric is weakened or damaged by
the type of heat sealing described, as is necessarily the case
according to the method disclosed in GB 937011 A. In this case
plastic bags are sealed by pulling heat-sealable tape over the
open end of the bag and pressing against the open end,
whereupon the heat sealing then takes place in a heat sealing
machine, where the tape is exposed to thermal energy from
outside from opposite sides. Quite similarly according to US
4278488 A, the lower side edge of a tubular starting material
was closed with a thermoplastic tape, where in this case also
the thermal energy was input from outside through the entire
material.
The methods described above are also used in the manufacture of
open bags, with the associated advantages, where a
substantially tubular starting material is closed in an end
region.
In this context mention should be made of AT 400831 B which
discloses a method for manufacturing a bag having a box-shaped
or rectangular end, in which a flat cover sheet is heat-sealed
onto a folded, flat base surface of a bag comprising a fabric
coated at least on one side of monoaxially stretched polymer
tapes. Here the cover sheet also consists of a coated tape
fabric. The hot air brings about a heating of the mutually
facing coatings as far as plasticizing. The flat cover sheet
and the flat bag bottom surface are then drawn through a cooled
pair of rollers, whereby the heated coatings are pressed
together.
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OBJECT OF THE INVENTION
It is therefore the object of the present invention to ensure a
one-sided closure of a tubular starting material comprising
coated or uncoated polyolefin fabric to produce an open bag and
a closure for open bags made of coated or uncoated polyolefin
fabric, without the aforesaid disadvantages occurring, in
particular without the starting material or open bag material
being damaged or weakened.
DESCRIPTION OF THE INVENTION
According to the invention, this is achieved whereby a tubular
starting material made of coated or uncoated polyolefin fabric,
in particular of polypropylene or HDPE ("high density
polyethylene", i.e. polyethylene having a high density), or a
filled open bag made of coated or uncoated polyolefin fabric,
in particular of polypropylene or HDPE fabric, is thermally
heat-sealed at an open end to a coated material strip. A tight
closure is thereby achieved and possible contamination by
thread material, sealing cords or sealing strips is thereby
avoided. It is also economically advantageous that a saving of
open bag or bag material is achieved compared with the closure
by sewing with folding over of the open end region.
In order to achieve an optimal thermal heat sealing, a
thermally activatable sealing layer is advantageous. This can
be provided, for example, by a coating of the material tape,
where the coating can be provided on the most diverse support
materials.
Thus, in an open bag made of coated or uncoated polyolefin
fabric forming a substantially tubular base body, in particular
polypropylene or HDPE ("high density polyethylene") fabric,
having a closed first end region and an open second end region
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or in a bag closed on two sides, made from a coated or
uncoated, filled open bag closed on one side, made from
polyolefin fabric, in particular polypropylene or HDPE fabric,
comprising a substantially tubular base body, it is provided
5 that the closed first end region of the open bag or at least
one end region of the bag closed on two sides is formed by a
strip-shaped coated material strip, which is folded in a V or U
shape in cross-section and whose leg is thermally heat-sealed
to the tubular base body, where the strip-shaped coated
material tape consists of a support material, preferably of
polyolefin fabric, in particular polypropylene or HDPE fabric,
paper or card and is executed with a coating at least on its
side facing the tubular base body.
Thermoplastic materials such as polyolefins are suitable as
sealing layer for the thermal heat-sealing. These are easy to
process and chemically resistant. Polyethylene is such a
plastic. According to a further embodiment it is therefore
provided that on the side of the material strip facing the
tubular base body, the coating of the support material consists
of polyethylene.
According to the invention, a closure method is used which
avoids damage to or weakening of the polypropylene or HDPE
fabric whereby the energy required for the thermal heat sealing
is applied between the layers to be welded and therefore
directly to the surfaces to be welded. Specifically in a method
for the one-sided closure of a tubular starting material made
of coated or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric to produce an open bag it is
provided that a strip-shaped coated or uncoated material strip
is folded in a V or U shape in cross-section and drawn over an
open first end region of the tubular starting material, where
in particular the side of the material strip facing the
starting material can be provided with a coating and as a
result of the drawing over, an overlap region is formed in
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which the V- or U-shaped material strip receives the first end
region of the tubular starting material between itself and
thermal energy, preferably in the form of a hot gas,
particularly preferably in the form of hot air, is introduced,
preferably blown, directly into the overlap region, onto the
side of the material strip facing the starting material and/or
onto the surface of the starting material facing this side of
the material strip, and then material strip as well as starting
material is pressed together in the overlap region.
Similarly in a method for closing a filled open bag closed on
one side made of coated or uncoated polyolefin fabric, in
particular polypropylene or HDPE fabric having a substantially
tubular base body to produce a bag closed on two sides, it is
provided that a strip-shaped coated or uncoated material strip
is folded in a V or U shape in cross-section and drawn over an
open first end region of the tubular base body, where in
particular the side of the material strip facing the starting
material can be provided with a coating and as a result of the
drawing over, an overlap region is formed in which the V- or U-
shaped material strip receives the first end region of the
tubular starting material between itself and thermal energy,
preferably in the form of a hot gas, particularly preferably in
the form of hot air, is introduced, preferably blown, directly
into the overlap region, onto the side of the material strip
facing the starting material and/or onto the surface of the
starting material facing this side of the material strip, and
then material strip as well as base body are pressed together
in the overlap region. Since the strip-shaped material strip is
only folded before drawing over, among other things, the
handling of the material strip is substantially simplified
since it can be unrolled conveniently as a strip from a roll.
According to one embodiment, the thermal energy is introduced
substantially at the same time as the drawing of the material
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strip over an open first end region of the tubular starting
material or base body.
According to a further embodiment, it is provided that the
starting material or the base body are continuously moved
further during the closing and the material strip is drawn over
the open first end region of the starting material or base body
at controllable, preferably synchronous speed in relation to
the starting material or base body.
According to a further embodiment, the starting material or the
base body is trimmed to a defined length before drawing the
material strip over the first end region thereof, wherein
preferably the accumulating section strips are conveyed into a
collecting container.
According to a further embodiment, it is provided that after
the trimming but before introducing the thermal energy the
starting material or the base body is cleaned by means of
compressed air in the open first end region. In this way, it
should be ensured that the heat sealing of the surfaces to be
heat-sealed is not adversely affected by impurities such as,
for example, bulk material, in particular powdery bulk material
or by the residue of starting material or base body material
caused by the trimming.
In order to carry out the sealing and material-protecting heat-
sealing method according to the invention, an apparatus is
proposed which is characterised by low maintenance and a lower
noise level compared with known sewing systems. For the closure
process according to the invention, in an apparatus for closing
on one side a tubular starting material comprising coated or
uncoated polyolefin fabric, in particular polypropylene or HDPE
fabric, to produce an open bag, it is provided that the
apparatus comprises a material strip unrolling system for a
strip-shaped, material strip and comprises means for folding in
a V or U shape in cross-section and drawing the material strip
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over an open first end region of the starting material and
means for introducing thermal energy directly into an overlap
region in which the V- or U-shaped material strip receives the
first end region of the tubular starting material between
itself, onto the side of the material strip facing the starting
material and/or onto the surface of the starting material
facing this side of the material strip, as well as pressing
means for pressing the material strip onto the starting
material surface.
Similarly in an apparatus for closing a filled open bag closed
on one side comprising coated or uncoated polyolefin fabric, in
particular polypropylene or HDPE fabric, comprising a
substantially tubular base body to produce a bag closed on two
sides, it is provided that the apparatus comprises a material
strip unrolling system for a strip-shaped, material strip,
means for folding in a V or U shape in cross-section and
drawing the material strip over an open first end region of the
base body and means for introducing thermal energy directly
into an overlap region in which the V- or U-shaped material
strip receives the first end region of the tubular base body
between itself, onto the side of the material strip facing the
base body and/or onto the surface of the base body facing this
side of the material strip, as well as pressing means for
pressing the material strip onto the base body surface.
The above apparatus is intended to ensure a continuous closure
of tubular starting material or of filled open bags closed on
one side. This is achieved by conveying the starting materials
or the open bags continuously through the apparatus. According
to one embodiment it is therefore provided that the apparatus
comprises conveying means for conveying the starting material
or base body at constant speed and the material strip unrolling
system can be controlled synchronously to this speed, wherein
the conveying means preferably include a belt system which
fixes the starting material or the base body on the open first
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end region and leads to the means for folding and drawing over
the material strip and away from these.
According to a further embodiment, the conveying means further
comprises a conveyor belt system by means of which the
preferably horizontal starting material or the preferably
vertical base body is conveyed.
The continuous movement of the starting materials or the open
bags through the apparatus means that the material strip must
be applied to moving starting materials or open bags which
necessitates special measures. Therefore a further embodiment
provides that the means for folding and drawing over the
material strip over the first end region of the starting
material or base body comprises a forming shoulder which has a
gap through which the open first end region can be guided in a
conveying direction. The forming shoulder enables the folding
and drawing over of the material strip.
The fact that the starting material or the open bag is moved
continuously through the apparatus and therefore also through
the forming shoulder requires that the thermal energy should be
introduced specifically and at the correct time. Therefore
thermal energy is only introduced into an overlap region when
this is actually present, i.e. when the V- or U-shaped material
strip actually receives the first end region of the starting
material or the base body between itself. According to a
further embodiment, the means for introducing thermal energy
therefore comprise at least one movably disposed air nozzle
which can be moved from a rest position into a working
position, wherein the at least one air nozzle is disposed in
the working position such that substantially parallel to the
conveying direction of the starting material or base body, hot
gases, preferably hot air, can be blown into the overlap
region, onto the side of the material strip facing the starting
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material and/or onto the surface of the starting material
facing this side of the material strip.
According to a further embodiment it is provided that the
movement of the at least one air nozzle from the rest position
5 into the working position is accomplished by a pivoting in a
vertical plane which lies parallel to the conveying direction
of the starting material or base body.
For the heat sealing, in addition to the heating, it is
necessary to produce an intimate connection of the surfaces to
10 be welded by pressing these onto one another. Therefore in a
further embodiment the pressing means comprise pressing rollers
applied directly following the forming shoulder.
A further embodiment provides that the pressing rollers are
frictionally connected to the material strip and pull the
material strip away from the material strip unrolling system.
In order to ensure a successful welding, it is necessary that
the first end region of the tubular starting material or base
body is actually located inside the gap of the forming shoulder
and does not project over the forming shoulder when the
material strip is drawn over the first end region. It is
therefore provided according to a further embodiment that the
apparatus comprises a trimming device in order to trim the
starting material or the base body to a defined, selectable
length at the first end region over which the material strip
is drawn.
Finally it is provided in a further embodiment that the
apparatus comprises a chopping unit in order to cut the
material strip in the conveying direction before and after the
first end region of the starting material or base body which is
drawn over with the material strip. The starting material or
the base body can then be conveyed subsequently from the
apparatus - without residue of the material strip projecting in
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or contrary to the conveying direction in the closed first end
region.
BRIEF DESCRIPTION OF THE FIGURES
The invention is now explained in more detail with reference to
an exemplary embodiment for the closure of a filled open bag
closed on one side comprising coated or uncoated polyolefin
fabric, in particular polypropylene or HDPE fabric, comprising
a substantially tubular base body to produce a bag closed on
two sides. The drawings are exemplary and are intended to
present the inventive idea but in no way restrict or even
definitively reproduce it.
In the figures:
Fig. 1 shows a schematic diagram of the frontal cross-section
and side view of an open bag according to the invention
which has an end region closed with a strip-shaped
material strip folded into a V shape
Fig. 2 shows a schematic diagram of the frontal cross-section
and side view of bag closed on two sides whose end
regions according to the invention are closed with a
strip-shaped material strip folded into a U shape
Fig. 3 shows a schematic front cross-sectional view of an end
region closed according to the invention of an uncoated
and a coated bag or open bag
Fig. 4 shows an axonometric view of an apparatus for closing
open bags according to the invention comprising coated
or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric, where an open bag is
located in the apparatus and the closure process is
approximately half completed
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Fig. 5 shows an enlarged view of Fig. 4 but without support
structure and conveyor belt
Fig. 6 shows an axonometric detailed view of the region A from
Fig. 5
Fig. 7 shows an axonometric view of the forming shoulder
Fig. 8 shows an axonometric view of the forming shoulder with
material strip drawn thereover
Fig. 9 shows a front view of the forming shoulder with
material strip drawn thereover and inserted end region
of the open bag
Fig. 10 shows a section through the forming shoulder along the
gap, where the material strip is pulled over and an
open end region of the open bag is inserted and the air
nozzles are in the working position
Fig. 11 shows a further axonometric view of the apparatus
without support structure and conveyor belt, where the
closure process is completed and the bag now closed on
two sides is located in the apparatus.
WAYS FOR IMPLEMENTING THE INVENTION
Figure 1, left, shows a schematic diagram, not to scale, of the
frontal cross-sectional view of an end region of an open bag 4
closed according to the invention with a strip-shaped material
strip 14 folded into a V shape, having a surface 34. Here the
legs 27 of the material strip 14 are thermally heat-sealed to
the tubular base body 23 of the open bag 4. Figure 1, right,
shows a schematic side view, not to scale, where a closed first
end region 24 and an open second end region 26 are indicated.
Compared to this, Figure 2, left, shows the schematic frontal
cross-sectional view, not to scale, of a bag 25 closed on two
sides 25, having a surface 34, where both end regions according
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to the invention are closed with a strip-shaped material strip
14 folded in a U shape. Here the legs 27 of the material strip
14 are thermally heat-sealed to the tubular base body 23 of the
bag 25. The schematic side view, not to scale, shown on the
right in Fig. 2 again shows the two closed end regions 38, 39
of the bag 25 closed on two sides.
Figure 3, left shows in detail a schematic frontal cross-
sectional view, not to scale, of a first end region 24, 38,
closed according to the invention, of an uncoated tubular base
body 23. In particular, the support material 28 of the material
strip 14 folded in a U shape and a coating 29 on the side
facing the base body 23 can be identified. Figure 3, right,
shows the situation for a tubular base body 23 coated on the
surface 34 and a V-shaped folded material strip 14.
The invention is explained in the following with reference to
the closure process of a filled open bag 4 according to the
invention to produce a bag 25 closed on two sides, where the
already-closed second end region 39 is also closed according to
the invention or with another, known method, e.g. by sewing.
Figure 4 shows an axonometric view of an apparatus for closing
open bags according to the invention, comprising coated or
uncoated polyolefin fabric, in particular polypropylene or HDPE
fabric. A filled open bag 4 is conveyed further by a conveyor
belt system in a conveying direction 20 vertically and with the
open side pointing upwards continuously through the closure
apparatus, whose components are held by a support system 1. The
conveyor belt system consists of a conveyor belt 15, a conveyor
belt motor 18 and a height-adjustable guardrail 22. The
conveyor belt 15 is driven by an electric motor which can be
controlled via a frequency inverter. The height-adjustable
guardrail 22 prevents the filled open bag 4 from falling over
and provides coarse guidance of the open bag 4.
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The open first end region 38 is additionally fixed by means of
an electrically driven belt system 2 and guided to those
components of the apparatus where the actual closure process
takes place or where the open first end region 38 is prepared
for the closure, see Fig. 5. Furthermore, the belt system 2
guides the open first end region 38 away from these components
again. The belt system 2 is driven by means of its own motor 17
and can also be controlled by means of frequency inverters. At
the same time, the belt speed is synchronously adapted to the
speed of the conveyor belt 15. The typical working range of the
belt speed which is at the same time the throughput speed of
the open bag 4 lies between 8 and 20 m/min.
The open bag 4 is initially guided through a continuously
running trimming device 3 where it is trimmed by means of two
knife blades to a defined selectable height. The accumulating
section strips are transported, for example, by means of
compressed air nozzles and baffles integrated in the trimming
device 3 or vacuum suction into a collecting container provided
for this purpose. Optionally the open first end region 38 to be
heat-sealed or sealed subsequently is then cleaned by means of
nozzles (not shown).
After exit from the trimming device, the actual closure process
begins, this being started by means of a sensor 10 for
detection of open bags, see Fig. 6. In this case, a coated or
uncoated material strip 14 is used, which can also be
designated as rider cord. In the exemplary embodiment
described, a coated material tape 14 is assumed as an example
in the following, whose support material 28 can be constructed
of polypropylene fabric, card or paper, in particular Kraft
paper. Here a tear-proof paper whose cellulose fibres are
obtained by the so-called Kraft process is designated as Kraft
paper.
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The material strip 14 is placed or drawn over the cut edge 36
of the first end region 38. To this end, the material tape 14,
which is drawn off from a material strip unrolling system 7 is
guided via a forming shoulder 8 downwards in the direction of
5 the open bag 4 so that the material strip 14 surrounds the open
first end region 38 of both sides extending substantially
parallel to the conveying direction 20 of the open bag 4 and a
coated side of the material strip 14 points in the direction of
the open bag surface 34, see Fig. 5 and Fig. 6. Here the
10 coating 29 of the material strip 14 on the side pointing in the
direction of the open bag surface 34 is formed from a material
which is suitable for thermal heat sealing with the open bag
surface, such as for example polyethylene. The material strip
14 can be uncoated on its other outer side, i.e. the outer side
15 of the material strip 14 is formed by the support material 28,
as shown in Fig. 3. Alternatively to this, the material strip
14 can have the same coating 29 on the outside as the side
facing the open bag surface 34. However, it is also feasible
that the material strip 14 has a different coating on its outer
side, in order for example to meet visual or other demands.
Figure 7 shows the forming shoulder 8 in detail in an
axonometric view obliquely from below. The forming shoulder
consists of two parts which are mirror-symmetrical with respect
to a plane spanned by the conveying direction 20 of the open
bag 4 and the direction in which the open side of the open bag
4 is pointing (i.e. vertically upwards). The two parts form a
gap 31 by means of which the material strip 14 is folded and
through which the open first end region 38 is conveyed.
On this matter Fig. 8 also shows the forming shoulder 8 in
detail but with material strip 14 drawn thereover. The surfaces
flanking the inlet opening for the open bag 4 are convex and
designed to slope from top to bottom in the conveying direction
20. This on the one hand enables nestling of the material strip
14 against the forming shoulder 8 and on the other hand a
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problem-free introduction of the open bag 4 into the forming
shoulder 8 so that the material strip 14 is placed or drawn
over the cut edge 36 of the first end region 38.
An overlap region 30 is thus formed in which the material strip
14 receives the open first end region 38 in a V or U shape
between itself. This overlap region 30 can be clearly seen in
Fig. 9 in a frontal view (when viewed in the conveying
direction 20) of the forming shoulder 8 with folded and drawn
over material strip 14 and inserted open bag 4.
At the same time as the drawing of the material strip 14 over
the forming shoulder 8, air nozzles 6 are pivoted by means of a
hydraulic stamp 16 from a rest position 32 (compare Fig. 11)
into a working position 33 (see in particular Fig. 10). In this
position, the air nozzles 6 are disposed such that they have a
defined selectable distance of typically 2 to 8 mm from the
forming shoulder 8. In the illustrated exemplary embodiment, a
total of two air nozzles 6 are provided, where respectively one
air nozzle is located on each side extending substantially
parallel to the conveying direction 20 of the open bag 4. The
outlet openings 37 of the air nozzles 6 point slightly towards
one another and in the pivoted state in the conveying direction
20 of the open bag 4, see Fig. 6 or Fig. 10. The outlet
openings 37 are each located at the end of a substantially
rectangular knee, which adjoins respectively one perpendicular
pipe in the working position 33, through which hot air is
supplied. The outlet openings 37 of the air nozzles 6 are also
bevelled, similarly to the contour of the forming shoulder 8,
see Fig. 6, Fig. 10 and Fig. 11, which favours the pivoting.
Hot compressed air or other suitable hot gases are blown in via
the air nozzles 6 into the overlap region 30 in which the
material strip 14 receives the open first end region 18 in a V
or U shape between itself. By this means thermal energy is
therefore applied without transfer through the support material
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28 of the material strip 14 or through the open bag 4 between
and therefore onto to the surfaces 29, 34 to be joined so that
these start to melt. Depending on whether the surfaces to be
joined are coated or uncoated, the respective coating or the
material of the base body or the support material begins to
melt. The compressed air or suitable gases are heated by means
of a controllable air heater 5. The energy input can in this
case be specifically varied by means of the gas temperature
and/or the pressure - and therefore by means of the blown-in
amount of gas.
The molten surfaces 29, 34 of the open bag 4 and the material
strip 14 are then pressed onto one another by pressing rollers
9 applied directly after the forming shoulder 8 whereby the
sealing or heat-sealing process is ended. That is, the legs of
the material strip 14 are now thermally heat-sealed to the base
body of the open bag 4.
The pressing rollers 9 are frictionally connected to the
material strip 14 and function at the same time as drawing of
the material strip 14 from the material strip unrolling system
7. The pressing rollers 9 are driven by means of an electric
motor 19 which can be controlled by means of frequency
inverters, see Fig. 5 and run at synchronous speed to the belt
system 2.
After the pressing rollers 9, another sensor 12 is attached
which starts the chopping unit 11 comprising two blades, which
is placed thereafter, see Fig. 6. The chopping unit 11
initially cuts the material strip when viewed in the conveying
direction 20 before the already-closed first end region 38, see
Fig. 6. This minimizes or avoids protrusion of the material
strip 14 beyond the closed cutting edge 36 or the first end
region 38 in the conveying direction. After the belt system 2
has conveyed the open bag 4 through the chopping unit 11, the
material strip 14 is cut after the closed first end region 38
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when viewed in the conveying direction 20, see Fig. 11. Thus,
the bag 25 now closed on two sides can be conveyed unhindered
from the closure machine. The accumulating section strips are
transported for example by means of compressed air nozzles and
baffles or vacuum extraction into a collecting container
provided for this purpose.
Furthermore, the withdrawal of material strip with the pressing
rollers 9 is stopped by means of the sensor 12 and the pivoting
process of the air nozzle 6 from the working position 33
(compare Fig. 6) into the rest position 32 (compare Fig. 11) is
started. Figure 11 shows that in the exemplary embodiment the
air nozzles 6 pivot vertically upwards so that the pivoting
process takes place in a vertical plane, which lies parallel to
the conveying direction 20 of the open bag 4.
Depending on the chemical composition and the thermal material
properties of the open bag 4 or the surface thereof 34 and the
material strip 14 or its coating 29, the speed of the belt
system 2, the temperature and the pressure or the amount of
blown-in hot gases and the exact position of the air nozzles 6
in the pivoted state with respect to the forming shoulder 8 are
crucial for the closure process. In addition, external
influences such as ambient temperature, air humidity and
impurities, particularly dust can affect the heat-sealing
process. The closure process can be controlled and adapted in
this respect by means of control elements which are mounted in
the switchgear cabinet 13 shown in Fig. 4.
The closure of a substantially tubular starting material
comprising coated or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric is accomplished in exactly the
same way as for the production of an open bag 4 and is not
shown additionally. In this case, instead of the filled open
bag 4 a tubular starting material comprising coated or uncoated
polyolefin fabric, in particular polypropylene or HDPE fabric
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appears in the exemplary embodiment shown, of which an open
first end region 24 is closed with the material strip 14
according to the invention. In this case, it can possibly be
favourable to convey the starting material horizontally. In
this case, the spatial arrangement of the apparatus must be
adapted. In particular, the positioning of the trimming device
3, the air nozzles 8 in the working position 33, the forming
shoulder 8, the pressing rollers 9 and the chopping unit 11
must be selected so that the horizontally conveyed starting
material is trimmed at an open first end region 24, inserted
into the forming shoulder 8, drawn over with the material strip
14 and heat-sealed and conveyed out from the apparatus again.
In another embodiment also not shown extra, the material strip
14 can be additionally sewn, in order to meet particular
stresses.
With the invention presented, it is also feasible to close an
already-closed end region 24 of an open bag 4 or a bag 25
closed on two sides comprising coated or uncoated polyolefin
fabric, in particular polypropylene or HDPE fabric with a
coated or uncoated material strip 14 according to the invention
a second time. That is, in this case the material strip 14
would be drawn over a closed first end region 24, 38 and
thermally heat-sealed with this. For example, an already-sewn
end region could be reliably sealed or a first end region 24,
38 already closed according to the invention could be
additionally reinforced.
It is understood that during the manufacture of open bags 4
comprising coated or uncoated polyolefin fabric, in particular
polypropylene or HDPE fabric, the one-sided closure according
to the invention can also be applied when the tubular starting
material additionally comprises material for an inner bag.
Likewise filled open bags 4 comprising coated or uncoated
polyolefin fabric, in particular polypropylene or HDPE fabric,
'
CA 02829265 2013-09-06
can be closed according to the invention to produce bags closed
on two sides 25 according to the invention if the substantially
tubular base body 23 comprises an inner bag.
5
CA 02829265 2013-09-06
21
REFERENCE LIST
1 Support structure
2 Belt system for guiding and fixing the open bag
3 Trimming device
4 Filled open bag comprising coated or uncoated polyolefin
fabric, in particular polypropylene or HDPE fabric
5 Air heater
6 Air nozzles
7 Material strip unrolling system
8 Forming shoulder
9 Pressing rollers
10 Sensor
11 Chopping unit
12 Sensor
13 Switchgear cabinet with control elements
14 Material strip
15 Conveyor belt
16 Hydraulic stamp
17 Motor for belt system
18 Motor for conveyor belt
19 Motor for pressing rollers
20 Conveying direction
21 Deflecting roller
CA 02829265 2013-09-06
22
22 Height-adjustable guide rail
23 Tubular base body
24 First end region of open bag
25 Bag closed on two sides
26 Second end region of open bag
27 Leg of material strip
28 Support material
29 Coating
30 Overlap region
31 Gap
32 Rest position
33 Working position
34 Surface of the open bag or the bag closed on two sides
35 Surfaces of the forming shoulder
36 Cutting edge
37 Outlet openings of the air nozzles
38 First end region of the bag closed on two sides
39 Second end region of the bag closed on two sides
