U.S. patent application number 13/504093 was filed with the patent office on 2012-10-18 for packaging container with overpressure relief, packing method and system.
Invention is credited to Jozsef Mandzsu, JR., Jozsef Mandzsu, SR., Zoltan Mandzsu.
Application Number | 20120261278 13/504093 |
Document ID | / |
Family ID | 41459992 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120261278 |
Kind Code |
A1 |
Mandzsu; Zoltan ; et
al. |
October 18, 2012 |
PACKAGING CONTAINER WITH OVERPRESSURE RELIEF, PACKING METHOD AND
SYSTEM
Abstract
The invention relates to packaging container, packaging method
and system. The packaging container, comprises a flexible plastic
wall (2) comprising one or more vents (5), the one or more vents
(5) adapted to conduct gas (29) from an inside of the container
into an air-channel (6) and from the air-channel (6) to an outside
(7) of the container, having air-channel-walls defining the
air-channel (6), comprising internal venting means (10) for
conducting gas (29) from inside the container into the air-channel
(6), at least partly defined by means of at least one sealed or
glued seam (9) having in at least a partial region a reduced degree
of bonding sufficient to allow gas (29) to escape in response to a
suitable pressure. In one or more of the vents (5), if the vent (5)
is formed to comprise a region of the flexible plastic wall (2)
having an interior wall (11) and an exterior wall (12) then the
vent (5) is free of openings penetrating through an interior wall
(11) for conducting gas (29) from inside the container into a
region between interior (11) and exterior walls (12), and otherwise
either the air-channel-walls of the vent (5) are free of openings
constituting internal venting means (10) or at least one
air-channel-wall of the vent (5) comprises one or more openings
constituting internal venting means (10).
Inventors: |
Mandzsu; Zoltan; (Budapest,
HU) ; Mandzsu, SR.; Jozsef; (Budapest, HU) ;
Mandzsu, JR.; Jozsef; (Fot, HU) |
Family ID: |
41459992 |
Appl. No.: |
13/504093 |
Filed: |
October 12, 2010 |
PCT Filed: |
October 12, 2010 |
PCT NO: |
PCT/HU2010/000112 |
371 Date: |
July 2, 2012 |
Current U.S.
Class: |
206/213.1 ;
220/745; 53/434 |
Current CPC
Class: |
B65B 1/24 20130101; B65D
33/01 20130101; B65B 1/22 20130101 |
Class at
Publication: |
206/213.1 ;
220/745; 53/434 |
International
Class: |
B65D 81/18 20060101
B65D081/18; B65B 31/04 20060101 B65B031/04; B65D 25/02 20060101
B65D025/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2009 |
HU |
P0900669 |
Claims
1. A packaging container, comprising a flexible plastic wall (2)
which comprises one or more vents (5), the one or more vents (5)
adapted to conduct gas (29) from an inside of the container into an
air-channel (6) and from the air-channel (6) to an outside (7) of
the container, having air-channel-walls defining the air-channel
(6), formed to comprise a region of the flexible plastic wall (2)
having an interior wall (11) and an exterior wall (12) constituting
air-channel-walls defining the air-channel (6) therebetween,
comprising internal venting means (10) for conducting gas (29) from
inside the container into the air-channel (6), at least partly
defined by means of at least one sealed or glued seam (9) having in
at least a partial region a reduced degree of bonding sufficient to
allow gas (29) to escape in response to a suitable pressure,
wherein in one or more of the vents (5), the vent (5) is free of
openings penetrating through an interior wall (11) for conducting
gas (29) from an inner filling-space of the container into a region
between interior (11) and exterior walls (12).
2. The packaging container according to claim 1, wherein each of
the one or more vents (5) are improved.
3. The packaging container according to claim 1, wherein the
internal venting means (10) comprise one or more openings in a seam
(9) defining a vent (5).
4. The packaging container according to claim 3, wherein the
internal venting means (10) comprise at least one opening selected
from a perforation in a folded seam (9), an interruption of a
welding in a welded seam (9) and an interruption of a gluing in a
glued seam (9).
5. The packaging container according to claim 1, further comprising
a fibrous filter (13) in at least a part or parts of an air-channel
(6).
6. The packaging container according to claim 5, wherein at least a
part or parts of the fibrous filter (13) is contained in a sealed
or glued seam (9) having in at least a partial region the reduced
degree of bonding.
7. The packaging container according to claim 6, wherein the at
least one sealed or glued seam (9), of the reduced degree of
bonding, is a welded seam (9) comprising the fibrous filter (13)
and flexible walls (2) fixed to each other at least partly, and a
material of at least one of the flexible walls (2) fixed in the
welded seam (9) is incompatible for welding, with a material of the
fibrous filter (13) fixed in the welded seam (9), to an extent
sufficient to provide a reduced degree of bonding.
8. The packaging container according to claim 1, further comprising
an air-channel-wall having at least partly a thickness of at least
70 microns.
9. The packaging container according to claim 3, further comprising
spacer means provided in at least one of the one or more openings
in a seam (9) defining a vent (5).
10. The packaging container according to claim 9, wherein the
spacer means comprise one or both of a nonwoven and at least one
projection (21) of a projection height (22) of at least 50
microns.
11. A packing method comprising: a granular product is provided,
and a package is produced, the package comprising a packaging bag
and the package further comprising a quantity of the granular
product mixed with a gas, packed into the packaging bag, the
packaging bag comprising a flexible plastic wall which comprises a
vent for venting the bag in a suitable venting orientation of the
bag by conducting gas from an inside of the bag into an air-channel
and from the air-channel to an outside of the bag, the vent having
air-channel-walls defining the air-channel, and the vent formed to
comprise a region of the flexible plastic wall having an interior
wall and an exterior wall constituting air-channel-walls defining
the air-channel therebetween, and the vent having internal venting
means for conducting gas from inside the container into the
air-channel and the vent being at least partly defined by means of
one or more sealed or glued seams having in at least a partial
region a reduced degree of bonding sufficient to allow gas to
escape in response to a suitable pressure, and the package is
reshaped by at least partially rearranging its contents, for
providing the bag in venting orientation and for providing an
overpressure in the package at least partly adjacently to internal
venting means, wherein the packaging bag is used in which the vent
is free of openings penetrating through an interior wall for
conducting gas from an inner filling-space of the bag into a region
between interior and exterior walls, and the packaging bag is used
in which at least one of the one or more sealed or glued seams is
adapted to open after a pressure-keeping time of at least 1 second,
in order to allow gas to escape from the reshaped package only in
response to an external squeezing of the package.
12. The method according to claim 11, wherein the at least one seam
is opened by means of an external squeezing of the package after a
pressure-keeping time of at least 1 second in order to allow gas to
escape from the reshaped package.
13. The method according to claim 12, wherein the pressure-keeping
time is a period of time of at least 1.5 seconds.
14. The method according to claim 11, wherein in the produced
package, prior to its reshaping, in at least a portion of an inner
filling-space of the packaging bag at least temporarily a pressure,
lower than or essentially equivalent to an ambient atmospheric
pressure, is provided.
15. The method according to claim 11, wherein at least 1 mass
percent of the provided granular product has a granule size below
150 microns.
16. The method according to claim 11, wherein the provided granular
product is suitable to be mixed with air and thereby to be rendered
into, and to remain, at rest, at least for 30 seconds, in an
aerated state in which its apparent density is at most 98% of an
apparent density belonging to the granular product in a fully
compacted state thereof.
17. The method according to claim 11, wherein the provided granular
product contains any one or more of cement, calcium oxide, calcium
carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and
glass.
18. The method according to claim 17, wherein the provided granular
product contains any one or more of cement, calcium oxide, calcium
carbonate and calcium hydroxide.
19. The method according to claim 18, wherein at least 1 mass
percent of the granular product is cement.
20. The method according to claim 12, wherein the package is
externally squeezed by pressing and abutting at least a part or
parts, of a top bag wall panel at least partly comprising the vent,
to a top surface of the granular product contents.
21. The method according to claim 12, wherein the pressure-keeping
time is a period of time of at least 2 seconds.
22. The method according to claim 12, wherein during the
pressure-keeping time the at least one sealed or glued seam is
prevented from allowing gas to essentially escape from the
package.
23. The method according to claim 22, wherein during the
pressure-keeping time the at least one sealed or glued seam is
prevented from allowing gas to escape from the package.
24. The method according to claim 23, wherein during the
pressure-keeping time gas is prevented from escaping from the
package.
25. The method according to claim 20, wherein the external
squeezing also includes compressing of opposed package sides.
26. The method according to claim 11, wherein the packaging bag is
a packaging container according to claim 1.
27. A system comprising a packaging bag (1) containing a quantity
of a granular product (27) mixed with a gas (29), the packaging bag
(1) comprising a flexible plastic wall (2) which comprises a vent
(5), the vent (5) adapted to conduct the gas (29) from an inside of
the packaging bag (1) into an air-channel (6) and from the
air-channel (6) to an outside (7) of the packaging bag (1), having
air-channel-walls defining the air-channel (6), and formed to
comprise a region of the flexible plastic wall having an interior
wall and an exterior wall constituting air-channel-walls defining
the air-channel therebetween, and at least partly defined by a
sealed or glued seam (9) having in at least a partial region a
reduced degree of bonding sufficient to allow gas (29) to escape
only in response to an overpressure in the packaging bag (1)
exceeding a predetermined limit, wherein the vent is free of
openings penetrating through an interior wall for conducting gas
from an inner filling-space of the bag into a region between
interior and exterior walls, and the predetermined limit is
selected from an interval between 0.0001 bars and 10 bars.
28. The system according to claim 27, wherein the predetermined
limit is selected from an interval between 0.001 bars and 10
bars.
29. The system according to claim 27, wherein the predetermined
limit is selected from an interval between 0.01 bars and 10
bars.
30. The system according to claim 27, wherein the predetermined
limit is selected from an interval between 0.1 bars and 10
bars.
31. The system according to claim 27, wherein the upper limit of
the interval is 1 bar.
32. The system according to claim 27, wherein at least 1 mass
percent of the granular product (27) has a granule size below 150
microns.
33. The system according to claim 27, wherein at least some of the
granular product (27), mixed with the gas (29), is in an aerated
state in which an apparent density of the granular product (27) is
at most 98% of an apparent density belonging to the granular
product (27) in a fully compacted state thereof.
34. The system according to claim 27, wherein the granular product
(27) contains any one or more of cement, calcium oxide, calcium
carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and
glass.
35. The system according to claim 34, wherein the granular product
(27) contains any one or more of cement, calcium oxide, calcium
carbonate and calcium hydroxide.
36. The system according to claim 35, wherein at least 1 mass
percent of the granular product (27) is cement.
37. The system according to claim 27, wherein a filling mouth of
the packaging bag is closed.
38. The system according to claim 27, wherein the packaging bag (1)
is a packaging container according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to the packaging of granular
bulk solids, containing fine powder, into plastic bags, and
particularly to methods and plastic packaging containers such as
bags useful for such packaging, preferably in the industrial
packaging of pulverulent bulk solids, like cement, into heavy duty
shipping bags.
BACKGROUND OF THE INVENTION
[0002] Products containing fine powder components, such as cement,
tile adhesives, dry concrete mix, lime powder, dry milk, cocoa
etc., are known to be bagged mixed with air, i.e., in a form of an
air-solid mixture. As it is known, at the moment the filled bag is
closed, the bag contains more air than the granular solid material,
therein, would store in its finally compacted state. Therefore such
packages must be compacted so that they can then be safely
palletized. That makes it necessary to conduct air out of the bags
after they are filled and closed. Bags made of polymer film have
several advantages (e.g. strength, water-resistance, good
printability, light weight, low price, possible compatibility with
automatic low cost and fast form-fill-seal/"FFS"/packaging, good
recyclability etc.) over paper but their problem is that their
walls are impermeable to air, therefore they are well known to need
to be provided with some venting means for letting the entrapped
air out of the bag on the one hand and simultaneously retaining
powder contents in the bag, at least partly, on the other hand. The
typically used venting means comprise a venting air-channel
provided between two film plies, both the inner and outer film
plies being perforated for breathing on the one hand, and the
perforations preferably being provided in an offset or staggered
manner to force the air to be conducted along a winding path in the
air-channel, for dust retaining, on the other hand. The vent is
always used in the top bag wall panel of the package so that it can
conduct out the air which is always collected in the top region of
the package. It means that in practical use the package must be
suitably oriented for venting, with its vent being on top. Good
examples are provided in patent documents U.S. Pat. No. 3,628,720
and EP 1600 399. It is popular to use spacer means (e.g.
projections, embossing, indentations, crimping, fibrous filter
sheet etc.) in the vent's air-channel in order to better maintain a
free path for the airflow therein. It is known that small
perforations, that are needed for effective dust retaining, can
unfortunately be plugged by the dust thereafter not allowing the
air to evacuate, as is discussed for example in document US
20070248291A1 which provides, as a solution, a filter sheet between
the powdery product and the exit perforations to accumulate the
dust and retain it from the exit perforations in order to maintain
the air permeability of the exit perforations. The skilled person
will primarily want to fill and palletize as fast as possible. Fine
powder products are traditionally known to be time-efficiently
packed in valve bags, mainly of porous paper but partly also in
vented plastic valve bags. Every prior art document we know of,
dealing with the filling of aerated fine powdery products into
polymer film bags provided with vent means, teaches to do the
filling as fast as possible and, in order thereof, to use, as much
as possible, the dust-retaining vent means of the polymer bag for
conducting the excess air out of the bag already during the filling
operation, as for example in German utility patent G8133295.5U1, US
2007/0248291A1, U.S. Pat. No. 3,937,395, EP 0444261B1, U.S. Pat.
No. 5,493,844, U.S. Pat. No. 4,441,209, U.S. Pat. No. 4,930,904,
U.S. Pat. No. 4,672,684, German utility patent G9110645.1U1,
DE4033499A1, WO 88/08816, WO 2005/092724A1 and U.S. Pat. No.
4,759,641.
[0003] Patent application US 20050281493A1 deals with the packaging
of fine-dusty and moisture-sensitive granular products, and sets
the goal of fulfilling the demand for a low-cost packaging
container, for building materials, cement and similar aerated
materials, which container can reliably protect these products from
contamination and moisture and relieves the overpressure, typical
of these products, during and/or after said products are filled in.
The document does not mention any respects in which relieving the
pressure during the filling would be better or worse than relieving
the pressure after the filling and as concerning "after the
filling" it does not mention any waiting after the filling before
pressure is started to be relieved. The document solves the problem
with a packaging container, comprising: a flexible plastic wall
which comprises a region having an interior wall and an exterior
wall, said region being defined by means of at least one sealed or
glued seam, wherein the interior wall comprises one or more
openings having a size sufficient to allow gas to escape from an
interior portion of the container and to enter into the region
between the interior and exterior walls, wherein said at least one
sealed or glued seam defining said region has in at least a partial
region a reduced degree of bonding sufficient to allow gas to
escape in response to a predetermined pressure. The document does
not mention any particular value as for the said predetermined
pressure, but the solutions, taught therein, of weakening the seam
(such as Corona pre-treating, applying a partial release layer of
lacquer etc.) make it possible for the skilled person to
technically freely select any desired seam strength level from zero
to hundred percent closing strength. The document teaches that
there are adhesive forces in the weakened seam and only if the
adhesive forces in the weakened seam are overcome by a difference
in pressure, such as the overpressure developing during or after
filling, will the seam open and release said overpressure, thus
venting the bag in a controlled manner. The document teaches to
prefer form-fill-seal (hereinafter referred to as "FFS") packaging
for its low cost. According to the document, its plastic bag
reliably protects packed products from contamination and/or
moisture getting into the bag because the venting seam (unlike
earlier vent exit opening solutions, always being uniformly open)
only opens due to a certain overpressure which can only arise from
inside the bag (during as well as after filling) but evidently
never, in practice, from outside the bag. The document says that
contaminants can not enter the interior region since, after the
overpressure has been relieved, the interior and exterior films are
arranged tightly on top of each other, being fixed in this position
by adhesive forces. Also, the document teaches that even the escape
of very fine particles from the bag is practically impossible
through the weakened seam, which can be attributed to the fact that
the adhesive forces acting between the films, which are only in
part firmly connected to each other, produce a certain degree of
adhesion even without a securely sealed or glued connection and
thus the venting seam is partially gas permeable. In summary, the
vented bag of US 20050281493A1 is taught to prevent dust from
leaving the bag and moisture from entering the bag, apparently at
selecting any predetermined, positive limit-value of overpressure
at which the vent seams are designed to open in a controlled
manner.
[0004] Patent application US 20080257450 A1 provides an "FFS"
packaging apparatus that appears to satisfy a long-felt market
demand making the throughput of "FFS" packing of fine powders into
open top bags competitive with that of the known porous paper valve
bag technology. The objective of the document is a form-fill-seal
packaging apparatus for filling aerated fluidized powder products
into open top bags fast. It is clear from the document that with
using a sufficient number, for example 10 or more, of rotating
filling sub-units, the overall output of the packaging can be very
high (probably as high as with FFS packaging of non-dusty solids)
and can be estimated by a skilled person to possibly reach a cycle
time as short as about 3 to 4 seconds per package. In the solution
of the document, during the filling the open-top bag is not
pressurized (i.e. the top surface of the contents is only exposed
to normal atmospheric air pressure) up to the moment at which the
top of the suspended bag is closed with welding.
THE OBJECTIVE OF THE INVENTION
[0005] We believe that our present invention is largely based on
the formulation of a new problem to be solved, whose solution then
needs measures contrary to the technical prejudice. The following
has lead us to elaborating the objectives of our invention.
[0006] Technical prejudice concerning packing methods, based on the
prior art, will prompt the skilled person, faced with the problem
of using plastic bags for the packaging of aerated, pulverulent,
fine bulk solids, to: [0007] endeavor to fill and palletize as fast
as possible, possibly as fast as with full-porous paper valve bags,
[0008] use plastic bags with dust retaining venting means, e.g.
multiwall air-channels, capable of letting out as much air as
possible and capable of retaining and holding as much fine dust as
possible without getting blocked, [0009] in order of an earliest
starting of compacting the powder contents, conduct, as soon as
possible (possibly continuously during as well as after the
filling) as much air as possible from the bag to the environment
through the aforementioned venting means, [0010] exploit, as much
as possible, the dust-filtering capability of the aforementioned
venting means during and after filling, in order of a clean work
environment and package, [0011] close the filled bags and stack
them as soon as possible, and use the aforementioned venting means
to remove (e.g. by squeezing), as soon and as fast as possible,
enough of the residual surplus air from the closed bag in order of
a sufficiently compacted bag that can already be stacked safely,
[0012] make it possible for all residual surplus air to perfectly
be removed from the packages in the long run (practically: let the
stacked packages of the finished pallet load slowly, essentially
perfectly, deflate by themselves in response for example to the
weight of the bags' loose walls pressing the last quantities of air
out of the bags through the ever-open vent means) because even
small amounts of entrapped air can later (typically during
transportation causing vibration in the pallet load) potentially
cause a re-fluidization of the bag contents and thereby a sudden
destabilization of the pallet load as well as a possible later
precipitation of moisture from the entrapped air that could be
harmful to the contents (e.g. to cement).
[0013] Multiwall venting air-channels, as described hereinabove,
have been used in order that fine powder product components be
prevented at least partly from getting, together with the air, out
to the environment. These venting channels capture and retain dust
and therefore they will necessarily accumulate and contain more or
less dust in the end. That fact is confirmed, for example, in
patent document U.S. Pat. No. 3,628,720. As we also illustrated
hereinabove, the fact that venting air-channels accumulate in
themselves dust, only appears as a problem in the prior art either
with respect to a potential blocking thereof (which stops venting)
or because dust can potentially get out to the environment. In
response, prior art solutions endeavor, on the one hand, to
increase the dust holding capacity of the venting channels (e.g. by
using the possible longest vent channels as in US 20050281493A1)
and, on the other hand, to prevent dust in the venting channel from
getting out therefrom to the environment (e.g. by adhesive forces,
acting between the films attached with the partially gas permeable
exit venting-seam, producing a certain degree of adhesion and
retaining even the finest particles, as taught in US
20050281493A1). For example, US 20050281493A1 explicitly says that
any penetration of powdery product contents into the venting
channel region is harmless, since such product can hardly exit
through the partially gas permeable sealed seam. Otherwise the
skilled person who follows the technical prejudice will not be
worried about the quantity of dust captured and held within the
double-wall venting channel of a bag.
[0014] We, however, consider the quantity of the said captured
dust, typical of the prior art practice, unacceptable. We have
recognized several drawbacks of the prior art caused by the too
much captured dust. The quantity of fine powder product finally
contained in the dust retaining venting means of the bag
(hereinafter referred to as the residual powder), is lost for the
customer. Though its proportion in the filling weight is not too
high, it is still a part of the filling weight, and it costs money,
but the end user is unable to pour it out of the bag because it is
stuck into the venting channel. Therefore the residual powder
remains in the emptied bags, and is disposed of, anyway
contaminating the environment with many tons of solid waste. It
also makes recycling of the used bags difficult. Used thermoplastic
packaging bags can simply be re-extruded into pellets. Prior to
re-extrusion, re-collected plastic bags are chopped into pieces or
flakes which are then washed in water in order that any heavier
dirt, attached inside and outside the pieces of bag wall, be
gravity-sorted from the polymer (i.e. sink in the water). The
thermoplastic film pieces are then dried and fed into an extruder
where the plastic is melted and pressed through a metal mesh
filter, positioned at the exit of the extruder, in order of
removing any foreign material from the thermoplastic before its
re-pelletizing. In case of the currently discussed prior-art bags,
however, among the chopped film pieces there are many pieces from
the double-layer venting channels, containing dust contamination
embedded between the two abutting film plies, which is not washed
out of the polymer material. Therefore the residual powder also
enters and travels along the extruder and is finally retained in
the mesh filter which is a drawback because it necessitates
frequent filter changes in spite of a careful pre-washing. An even
much bigger problem, however, is caused if the residual powder is
of a hard, abrasive material (e.g. cement, minerals, stone, ores,
metals, glass etc.) because it (passing along the extruder before
getting caught in the filter) wears out the extruder (both barrel
and screw) extremely fast. The costs thereof are even much higher
than those of frequent filter changes. In case of the most popular
bulk solid products, like building materials, the price of the
packaging bag makes up a surprisingly considerable part of the
price of the relatively inexpensive packed product. If the emptied,
used plastic bags were essentially free of hidden stuck-in dust,
they would be a more valuable re-collectable raw material for
recycling companies, which would add much market value to the
original packed product, too. We believe that a packaging of an
improved quality, i.e. that resulting in decreased quantities of
accumulated residual powder stuck in the bags' walls, is desirable
even though it can cause a somewhat lower packaging throughput due
to somewhat lengthened cycle times of filling, bag closing and/or
palletizing. These latter drawbacks are merely quantity, rather
than quality, issues and can, for example, be eliminated with
installing further packaging apparatuses.
[0015] It is our objective to provide a method for packing
pulverulent bulk solids into vented plastic bags, including
conducting air through dust retaining venting means out of the bags
after they are closed, which method helps to pack with reduced
quantity of residual powder contained in the venting air-channels
of the bags and thereby helps to eliminate the drawbacks caused
thereby (i.e., loss of material for the user, pollution of the
environment, increased costs of filtering in the recycling,
accelerated wear of the recycling extruder). We believe that the
setting of such an objective, based on our formulating a new
problem to be solved, is in itself novel and non-obvious.
[0016] It is also our objective to provide a plastic packaging
container that is especially suitable for use with our invented
method, especially with preferred embodiments thereof, and which,
in particular, has improved dust retaining venting means suitable
to help to vent the bag with a reduced quantity of accumulated
residual powder. It is also our objective to provide systems
comprising novel plastic packaging bag and granular contents packed
therein.
DESCRIPTION OF THE INVENTION
[0017] We consider the aforementioned document US 20050281493A1 as
closest prior art. We intend to improve its solution in a manner
contrary to the technical prejudice. The general technical
prejudice, discussed hereinabove, prompts the skilled person,
intending to implement the teachings of US 20050281493A1, to
select, at forming the plastic bag, a positive but otherwise
definitely low predetermined limit-value of overpressure at which
the vent seams are designed to open. Namely, on the one hand, any
positive value is taught/suggested in the document US 20050281493A1
to be equally useful to keep external moisture and contamination
out of the bag and retain even the smallest dust particles in the
bag, keeping the work environment clean. On the other hand, the
skilled person will realize, that selecting a lower limit-value of
seams-opening overpressure will make venting the bag faster and
easier which is enough to prompt the skilled person to select a
limit-value of overpressure as low as possible. The skilled person,
taught by US 20050281493A1 to prefer FFS packaging for its low
costs, intending, for example, to use the state-of-the-art
apparatus of US 20080257450A1 for FFS-packing powdery goods into
the plastic bags of US 20050281493A1 will try to deflate the bags
as fast as possible in order to minimize the cycle times and
maximize the palletizing speed, all in order to keep up with the
very high output of the apparatus. In addition, the skilled person
will also realize, at least by trial and error, that the higher the
limit-value of overpressure necessary for opening the seams is, the
more entrapped air may remain in the package in the long run. As we
said, palletized packages must, according to the technical
prejudice, be able to vent also after the stacking, which means
that they must be able to reach their full compactness already in
the pallet load. Since the packages are typically individually
compacted, squeezed, to an almost full compactness prior to their
stacking, only a small amount of surplus air remains in the
packages at the time they are palletized, but even that small
quantity of air is known to be necessary to be removed for full
security of the product and of the transportation as we said
hereinabove. Therefore, according to the prior-art prejudice as
well as according to paragraph [0030] of US 20050281493A1, a
venting of the stacked packages is necessary. Such a venting
necessarily means a venting of definitely small quantities of air,
which can only build an extremely low overpressure. (N.B.: In a
palletized stack the weight of the load is held by the compacted
solid granular product thus the load weight does not directly
develop an overpressure in the bags, unless the packages are
re-fluidized by, for example, a vibration from transportation. That
is why the residual air should utterly be removed from the stacked
bags before such a re-fluidization could take place.) Therefore in
this important final (i.e. in-the-stack) phase of the venting the
venting must inevitably happen in response to very low overpressure
values. Namely, vented plastic bags prior to US 20050281493A1,
those with vents venting without any pressure limit-value, would
essentially surely and fully deflate, after the stacking, by
themselves in the long run in response to the weight of the upper
packages and mainly because even a mere weight of the loose top bag
wall could expel essentially all surplus air from the package in
the long run. The special feature, taught in US 20050281493A1, of
an only partially weakened venting seam, taught to have a certain
degree of adhesion, resulting in a predetermined necessary pressure
limit-value, however, can make a spontaneous self-venting of the
package stop too early, i.e. at a certain residual
limit-air-content. The lower the pressure limit-value is, the lower
the potential residual limit-air-content is, i.e. the safer the
packaging is. A nearly zero pressure limit-value provides packages
nearly as compact as those with bags without a venting pressure
limit. A similar or analogous phenomenon can be observed: if we
leave an inflated plastics toy, like a plastic boat, with a fully
open air valve, the toy will be able to completely deflate and
collapse by itself by time, but if we put something in the air
valve that closes it below a certain pressure level, the toy will
remain inflated to a certain degree and it will be rather difficult
to deflate it (e.g. by squeezing) perfectly. To sum it up: nothing
in the prior art would prompt the skilled person to select a
relatively high pressure value for the predetermined overpressure
at which the vent seams are designed to open.
[0018] We, however, recognized that in a packaging process it is,
(just contrarily to technical prejudice), beneficial with respect
to our objective if the controlled venting of the plastic container
taught in US 20050281493A1 is exploited in a novel manner, which
means that the bag is formed to have vent seams that allow gas to
first escape only at a relatively high internal pressure. We
recognized that this feature can be used in order of suitably
delaying the starting of the venting of the aerated package after
the bag is filled and closed, which is beneficial based on the
following. While a product, containing fine powder (e.g. lime
powder, cement, tile adhesive, dry concrete mix, milk powder etc.),
is being filled into a bag mixed with surplus air, the filled-in
contents of the bag typically comprise an essentially homogeneous
fluid even if the filling is done without the aid of transportation
air. In the practice of valve bag filling as well as of FFS
filling, essentially immediately after the closing, the package is
placed on a surface in a lying position, i.e. it is typically laid
down, with a relatively large impulse, on a table, a conveyor or
any similar surface, which can be horizontal or inclined. After the
moment of this laying of the package the solid contents are
inevitably mixed with the air contents both together forming a
homogeneous fluidized mass behaving like water, or a very thin
paste, and filling up the inner filling-space of the bag. Also, the
laying down of the package usually generates therein an internal
pressure higher than before, i.e. higher than when the bag was
suspended and/or supported and being filled. This is usually due to
the shape of the bag being changed, i.e. due to the surface/volume
ratio of the bag being higher at its brick-like shape in the
laid-down position than at its more sphere-like or more
cylinder-like shape in a (usually suspended and/or propped-up)
filling position. Namely the size of the outer surface of the bag
is essentially constant and its available volume gets smaller. In
fact its available volume in its said brick-like form is usually
designed to only be sufficient for the compacted solid contents
rather than for the aerated contents and that pressurizes the
aerated package when it is laid down. At the moment the package is
laid down, earlier traditional (i.e. prior-to-US 20050281493A1)
venting means (i.e. those always releasing any gas available for
escaping thus venting in an uncontrolled manner as compared to the
controlled manner of US 20050281493A1) immediately start to vent
the bag and vent it fast, due to the relatively high initial
internal overpressure. Such a venting is relatively intensive at
its beginning, later losing intensity as the pressure drops as the
bag gets deflated. All this is quite common in the prior art and is
very good for an early and fast compacting of the package, but it
also means that the most volume is removed from the bag by venting
just when the contents are the most fluidized, which results in
much of the fluidized air-solid mixture (which is actually
extremely dusty air) flowing through the venting air-channel of the
bag which filters out, and unnoticedly accumulates, the powder
contents of the fluid flown through it. The result is an inevitable
and invisible contamination of the bag. The same is the case with a
plastic bag having a pressure-selective vent as taught in US
20050281493A1 if a low seam-opening limit-pressure value is
selected in it as in accordance with the technical prejudice: the
vent starts to conduct air essentially as soon, or almost as soon,
as the overpressure starts to build up in response to the bag being
reshaped and its contents being rearranged. We recognized that it
is beneficial in the packaging process if we form a bag, for
example a bag of US 20050281493A1, selecting a seam-opening
limit-pressure value higher than the pressure which is generated in
the aforementioned laid-down package. For example: the FFS
apparatus of US 20080257450A1 provides essentially zero
overpressure above the level of the fluid contents of the bag at
the moment it is closed in a suspending orientation. A moment
later, the package is released from the suspending and supporting
and is suddenly turned to lie down which, on the one hand,
horizontally equalizes and stirs up the contents and causes the
whole internal space of the bag to essentially be full of
homogeneous fluid (air-solid mixture) and which, on the other hand,
creates a definite overpressure in the bag which is then maintained
in the absence of any essential venting, in accordance with our
recognition. As the vents resist the internal overpressure, not any
air leaves the bag, not any air enters the air-channel. As the
package lies at rest, or, even better, is suitably, subtly vibrated
e.g. at its part on which it lies (i.e. its momentary bottom), the
solid material immediately starts to separate from the air-solid
mixture. By time, powdery contents settle in the said bottom of the
package and air rises into the top region thereof. During this
(spontaneous or vibration-enhanced) separation process a (generally
horizontal) phase border appears in the bag between the two (gas
and solid) phases and gets more and more definite. The air, above
it, gets clearer and clearer and the granular product, under it,
gets more and more compacted by time. At the end of such a
separation process there is a bubble of definitely pure air above
the definitely compacted granular product in the bag. The speed of
the separation in an unvented package, according to our
observations, depends on several factors like the kind of the
granular material, e.g. how much and how fine powder it contains
and its general mixability with air, the air content at start, the
presence and quality of separation-enhancing vibration etc. The
separation appears to be relatively fast at, and right after, the
start of the separation-process, i.e. the moment the bag is left
lying after it has been closed, dropped and laid down. By every
second's time, spent without venting, the air in the top region of
the package (from which it is then to be conducted out) gets
clearer. During this separation process, the later we conduct a
quantity of air out of the top region of the package, the purer the
said conducted quantity of air will be. The more we wait before we
essentially vent, the less the residual powder in the bag's venting
air-channel in the end will be. When the air bubble in the bag is
already clear enough, we can, for example, compress (for example
both vertically and horizontally) the package to create in it an
internal pressure high enough to open the vent seams and expel an
essential quantity of air out of the package.
[0019] The essence of our method invention is a packing method in
which [0020] a granular product is provided, and [0021] a package
is produced, the package comprising a packaging bag and the package
further comprising a quantity of the granular product mixed with a
gas, packed into the packaging bag, [0022] the packaging bag
comprising a flexible plastic wall which comprises a vent for
venting the bag in a suitable venting orientation of the bag by
conducting gas from an inside of the bag into an air-channel and
from the air-channel to an outside of the bag, [0023] the vent
having air-channel-walls defining the air-channel, and [0024] the
vent having internal venting means for conducting gas from inside
the container into the air-channel, and [0025] the vent being at
least partly defined by means of one or more sealed or glued seams
having in at least a partial region a reduced degree of bonding
sufficient to allow gas to escape in response to a suitable
pressure, and [0026] the package is reshaped by at least partially
rearranging its contents, for providing the bag in venting
orientation and for providing an overpressure in the package at
least partly adjacently to internal venting means, the method being
novel in that [0027] such a packaging bag is used in which at least
one of the one or more sealed or glued seams is adapted to, at
least for a pressure-keeping time of 1 second, only allow gas to
essentially escape from the reshaped package at most in response to
an external squeezing of the package.
[0028] The packing method can for example be implemented manually
or with a mechanized packaging line. The provided granular product
is necessarily suitable to be mixed with gas. Many such product
types are known, generally known to have fine particle sizes, e.g.
flour, cocoa powder, cement etc. The package can for example be
produced by packing the quantity of the granular product mixed with
gas into a packaging bag in any suitable known way, e.g. manually
or automatically, preferably in an FFS process (FFS is preferred to
the traditional individual-valve-bag approach not only on a cost
basis but also because state-of-the-art FFS is more adapted to
provide low or zero overpressure in the bag at the closing
thereof). The packing generally includes a suitable closing of the
bag after it is filled in order of preventing an essential loss of
filling material, which closing can for example be closing a
filling valve of a valve bag or, preferably, closing the open mouth
of the bag with welding or adhering or sewing or with other
methods. In the method the packaging bag comprises a flexible
plastic (i.e. one or both of suitable synthetic and natural
polymer) wall which comprises a vent for conducting gas from an
inside of the bag into an air-channel and from the air-channel to
an outside of the bag, which in itself is generally known to the
skilled person familiar with plastic packaging bags provided with
dust retaining, pocket-like, double-wall or multiwall vents. As it
is also common, the vent is adapted to vent the bag if the bag is
suitably oriented, i.e. if the bag is in a suitable venting
orientation. Namely, as the skilled person knows, a vent
incorporated in a bag wall will typically be adapted to suitably
vent the bag if the bag is oriented in a manner in which the said
bag wall is atop the bag, or is at least partly above the rest of
the bag. The skilled person knows that the bag of the package is in
a suitable venting orientation if the gas in it is adapted to be at
least partly adjacent to an internal venting means of the vent. The
air-channel is defined by air-channel-walls of the vent and is
typically adapted to provide a path for gas, at least partly in and
along the air-channel between the air-channel-walls. The vent
comprises suitable internal venting means for conducting gas from
inside the bag into the air-channel, the internal venting means
possibly constituted for example, as taught in the prior art, by
aperture(s) or perforation(s) in an air-channel-wall, for
conducting air from the inner filling-space of the bag into the
air-channel. The internal venting means can, alternatively, be
constituted for example by suitably formed sealed or glued seam(s)
having reduced degree of bonding sufficient to allow gas to enter
from the inner filling-space of the bag into the air-channel, and
thereby for example to escape from the package, in response to a
suitable internal pressure. The vent is at least partly defined by
means of one or more sealed or glued seams having in at least a
partial region a reduced degree of bonding sufficient to allow gas
to escape in response to a suitable pressure, which is known, for
example, from the aforementioned prior-art document US
20050281493A1. Such seam(s) can, as we said, constitute for example
internal venting means and/or means for conducting gas from the air
channel further towards the outside of the package. Preferably,
this releasing of gas in response to a predetermined pressure can
be achieved by reducing the bonding strength of the surface of the
film, for example by means of a separation medium or Corona
treatment. This is possible on one or more sides, over the entire
surface or over a part of the surface only. Suitable separation
media are all media preventing the plastic film from completely
sealing or gluing, such as oils, greases, paints, lacquers, powdery
solids, or coatings of other agents that produce the desired
effect. A sealed seam includes for example a seam made with heat
fusing or heat welding, e.g. hot-bar, high-frequency or ultrasonic
welding. The term "the vent being at least partly defined" means
that the vent can thus either be purely defined by sealed or glued
seams or edges bordering, for example, the air-channel-walls, or
the vent can, for example, be partly also defined by other means
such as folded edges where adjacent air-channel-walls meet, or any
other suitable means can be provided. When the package is being
closed, it is known to for example be in a generally more or less
vertical, suspended and/or propped-up position whether made by FFS
or individual-bags processes. After the package is produced (in
practice, for example, an open mouth bag is formed from a plastic
FFS film-tube or -halftube, the mixture is filled into the bag and
the top mouth of the bag is closed with a cross-welding), in the
method the package is reshaped by at least partially rearranging
its contents, which is a generally known step and usually means in
practice, for example, that the package is dropped on a horizontal
or somewhat inclined surface and is tossed to lie down towards a
generally more horizontal position of the package, i.e. is laid
down, its contents are horizontally more evenly rearranged and
thereby the package is generally flattened. Due to the contents of
the bag most often being at this time in a generally fluid state,
the package is most often generally relatively easily reshapable. A
turning of the package, for example from a more or less vertical
into a more horizontal orientation, is known to generally stir up
the contents usually rendering it even more fluidized, flowable, if
possible. The term "the package is reshaped" means that the shape
of the package is changed at least to some extent. The at least
partial rearranging of the contents may include redistributing at
least a portion of the contents by, for example, moving, within the
bag, the granular product and the gas horizontally and vertically
as well as separating or mixing the gas and solid materials. The
reshaping of the package by an at least partial rearranging of its
inner contents may for example involve moving the center of mass of
the contents closer to a supporting surface supporting the package,
which may, for example, also result in a reducing of a potential
energy of the package. The reshaping is suitable to provide the bag
in a suitable venting orientation, which means that the package is
reshaped and thereby the bag is either maintained in or rendered
into such an orientation as is suitable for a venting thereof. It
typically means, for example, that the reshaping is suitable to
provide the bag in an orientation at which the gas or fluid in the
package is adapted to be at least partly adjacent to the entirety
or a part of the internal venting means. Most commonly, for
example, the bag wall panel, in which the vent is incorporated, is
provided on the top of the package. The reshaping is suitable to
provide an overpressure in the package at least partly adjacently
to internal venting means, i.e. at least partly adjacently to the
entirety or one or more parts of the internal venting means, which
means that the package is reshaped and thereby such overpressure is
either maintained or created. Suitably changing the shape of the
package (in practice usually rendering it closer to a brick-like
shape), can be used to increase a pressure in the bag. The extent
of this increase, in the absence of an essential loss of gas from
the package, can depend for example on the extent to which the
volume of the inner filling-space of the bag, available for the
compressible gas contents of the bag, is reduced during the
reshaping. Generally speaking, the more the bag is flattened by the
reshaping, the more the reshaping is suitable for increasing the
internal pressure. Thereafter an overpressure (as relative to an
ambient air pressure) is maintained in the gas or fluid inside the
bag at least partly adjacently to the internal venting means, whose
actual pressure value will depend on several factors including, for
example, the pressure originally provided in the package before the
reshaping, the quantity and specific weight of the material of the
granular product, the compacted apparent density value as a
parameter of the provided granular product, the relative air
content of the contained air-solid mixture, the size and shape
(e.g. the proportions of the three dimensions) of the reshaped bag
as well as of the bag before its reshaping, the surface weight of
the flexible plastic wall, especially of the top bag wall panel, of
the packaging bag etc.
[0029] According to the invention, in the reshaped package at least
one of the said one or more sealed or glued seams has the said
(reduced) degree of bonding sufficiently high and thereby the seam
is adapted to at least partly withstand the said provided
overpressure, at least for a pressure-keeping time of 1 second, by
only allowing gas to essentially escape from the package at most in
response to a suitable external squeezing of the package,
notwithstanding that the bag of the package is provided in a
venting orientation. It means that the built-in pressure-selective
venting seam is formed in a manner that its bonding strength is
relatively high, more exactly, is high enough to make the seam at
least partly resist, for a certain period of time, the overpressure
of the bag. In general, the minimal time interval of the at least
partial resisting, here called pressure-keeping time, is usually
implemented as a continuous uninterrupted time interval but it
means accumulated time if the overpressure is, in the meantime,
temporarily suspended for some reason, the reason possibly being
for example a transient in the reshaping procedure or some effect
originating from a separation-enhancing vibration etc. The
pressure-keeping time is a time interval which starts earliest when
the package has been suitably reshaped to at least some extent,
i.e., earliest when its contents have been rearranged to some
extent and the bag of the package is in a venting orientation and
there is suitable overpressure in the package. The term "at least
partly resist" means that the said seam of the reduced strength is
adapted to, at least for as long as corresponds to the
aforementioned uninterrupted or accumulated time parameter value,
only allow gas to essentially escape from the reshaped package at
most in response to a suitable external squeezing of the package
which means that it is adapted to either essentially retain the gas
(if the package is kept free from an external squeezing, for
example, is left lying on a table or conveyor, or the package is
only exposed to a suitably weak external squeezing), or allow gas
to essentially escape only if there is an external squeezing of a
suitable extent exerted on the package. In other words, the seam of
reduced strength is, at least during the specified time interval,
strong enough to prevent any gas from essentially escaping from the
reshaped and overpressurized package unless the package is suitably
externally squeezed. In practice, as we observed, the resistance of
the seam, to the overpressure, being a function of time is
realistic. For example glued seams based on an (especially pressure
sensitive) adhesive closing potentially get (under overpressure
stress) weaker by time. As another example, cross-welded seams,
created at the moment when the bag is closed i.e. immediately
before the reshaping, potentially get stronger (due to a cooling
and solidification) by time, especially in a fast FFS operation.
This time-dependent sealing strength gains a special significance
in our invention, as the settling of the dust in the bag and also
possibly the providing of the overpressure in the bag are
time-dependent processes. As we said we recognized, the best result
can be achieved if the pressure-selective seam prevents any gas
from escaping during the pressure-keeping time unless the package
is compressed, squeezed from outside, which specification can
practically be simply implemented, but which specification,
however, could in practice be formally bypassed without essentially
lessening its technical merits. Not withstanding our aforementioned
recognition; if the seam allows gas to escape, within the
pressure-keeping time without a suitable external squeezing, to
such a small, unessential extent as does not result in essential
quantities of dust being conducted into the air-channel then our
advantage can still be provided. A greater, essential gas
conduction, however, must be prevented according to our invention.
Therefore the definition of the term "to essentially escape" is as
follows: gas is allowed, at a moment, by one seam to essentially
escape from the package if the momentary escaping rate, expressed
for example in cm.sup.3/sec, of the gas through that one seam
would, if sustained, be sufficient to completely compact the
package, as given at the moment, within 5 seconds counted from the
moment. (In accordance with our recognition, in more preferred
embodiments the latter definition value could be selected to be 8
seconds, more preferably 10 seconds, more preferably 15 seconds, 20
seconds, 25 seconds, even better 30 seconds.) The best solution,
however, is, as we said, if the seam is practically impermeable to
the overpressurized gas during the pressure-keeping time unless the
package is externally suitably squeezed. The present invention
provides the advantage that it makes the skilled person capable of
selecting a time at which the gas is first conducted (or at least
first essentially conducted) from the bag, by selecting a time when
a suitable external squeezing is first applied to the bag. (The
skilled person, depending on the given circumstances, should select
effective ways of squeezing, for example a combination of both
vertical and horizontal compression, in order of sufficiently
compacting the packages with respect to a possible lack of a later
spontaneous venting in a later, stacked phase.) As we said, the
more the skilled person decides to wait, the purer the released gas
is. Since, as we said, the gas-solid separation, especially a
vibration-enhanced separation, is fast during the aforementioned,
early time period (pressure-keeping time) during which the gas is
possibly retained, the air can become effectively purer during the
pressure-keeping time. The resulting advantage of our method
invention is that it helps to pack with a reduced quantity of
residual powder contained in the vent of the bag and thereby helps
to eliminate the drawbacks caused by the residual powder.
[0030] For practical reasons it is preferable if a reshaping of the
package includes flattening and vibrating. Flattening here means
making the package more flat-shaped than before.
[0031] For even purer gas to be provided in the top region of the
filling-space of the bag, it is preferable, if the pressure-keeping
time is a period of time of 1.5 seconds, more preferably 2 seconds,
more preferably 2.5 seconds, more preferably 3 seconds, more
preferably 3.5 seconds, more preferably 4 seconds, more preferably
4.5 seconds, more preferably 5 seconds, more preferably 10 seconds,
more preferably 20 seconds, more preferably 30 seconds. The
advantage thereof is that it helps to keep the air-channel even
cleaner in the end. (The seam could of course keep the pressure
also for a much longer time, but keeping the pressure without
squeezing/deflating longer than for example 24 hours, as a
theoretical optional upper limit in the definition of the
pressure-keeping time, would not add much further practical
advantage in our method.)
[0032] In order of possibly minimizing the overpressure in the
reshaped package, and thereby possibly also keeping the limit
pressure value, at which the weakened seam is meant to open up,
relatively low, it is preferable if, in our method, in the produced
package, prior to its reshaping, in at least a portion of an inner
filling-space of the packaging bag at least temporarily a pressure,
essentially equivalent to, or lower than, an ambient atmospheric
pressure, is provided. This, as we said, is probably simpler to
achieve with an FFS apparatus than with, for example, an
air-assisted valve bag filler. The term "essentially equivalent"
means that for example a pressure difference merely caused by a
weight of loose bag walls or other bag parts, or any similar minor
pressure difference, is to be neglected and in such cases the
pressures are to be considered equivalent.
[0033] We arrived at an insight into the nature of why our basic
problem, i.e., the particles being stuck within the air-channel, is
more serious if the granular product contains markedly fine powder.
Namely, within a particle size interval zero to 150 microns, the
smaller the particles are, definitely the more significant the
attracting effect of surface energies of the particles, and of
adjacent solid surfaces, is. Therefore the really small particles
are much more prone to stubbornly adhering to the inner surfaces of
the air-channels making it more difficult to remove them before a
recycling. In addition, the adhering effect of electrostatic
attraction, very frequent with plastic film bags, also gets more
significant with particles getting smaller. This is based on the
fact that both the surface tension attraction force and the
electrostatic attraction are essentially proportional to surface
area and that the "surface area/weight" ratio of a particle
directly depends on how small the particle is, and is a quite large
value with tiny particles. Therefore our method provides a more
significant advantage over prior art, if at least 1 mass percent,
preferably at least 2, more preferably at least 3, even more
preferably at least 5 mass percent of the granular product has a
granule size below 150 microns, preferably 100 microns, more
preferably 50 microns, even more preferably 25 microns, even more
preferably 10 microns, even more preferably 5 microns. The granule
size should preferably be greater than 0.05 microns, under which it
is more difficult to suitably retain the dust.
[0034] As we said, our newly identified problem originates from
stirred-up, airborne powder particles contents flowing into the
air-channels during venting. After a mixing with air, some powder
types settle from air quickly while others do not. Prior-art
solutions did not set an objective to wait until the dust suitably
settles, nor did they give good solutions for the waiting. Our said
problem, and therewith also providing a good solution therefor, is
especially difficult if the granular product is a slowly-settling
material. We recognized that our problem to be solved, and
therefore also the advantage of our solution, is especially
significant with such granular products as are able to take up
relatively much additional air and are also able to remain, for a
time relatively long with respect to the duration of the filling
process, in an aerated state, at rest. The more air is contained,
and for the longer time, the higher the significance is. It is
therefore preferable if the provided granular product is suitable
to be mixed with air and thereby to be rendered into, and to
remain, at rest, at least for 30 seconds, preferably at least for
45 seconds, more preferably at least 60 seconds, more preferably at
least 90 seconds, more preferably at least 120 seconds,
(preferably, however, at most 168 hours) in an aerated state in
which an apparent density of the granular product is at most 98%
(preferably at most 95%, more preferably at most 90%, more
preferably at most 87%), (preferably, however, at least 15%) of an
apparent density belonging to the granular product in a fully
compacted state thereof, the latter meaning the apparent density
that the granular product has when the granular product is in a
fully compacted state. This specification means that during the
specified time interval (e.g. 30 seconds), which the product (about
1 kg of the product) spends at rest, in an open-top, e.g.
cube-shaped, vessel in normal atmospheric pressure (i.e. free of
artificial over- and underpressure, squeezing etc.), the apparent
density thereof is allowed to increase but at the end of the
specified time interval the apparent density must be at most the
specified value (e.g. 98% of the compacted apparent density).
Apparent density is known to be the density of a loose or compacted
granular material determined by dividing actual mass by volume
occupied by the material including the voids which are in the
material. A granular product is considered by a skilled person to
be in a fully compacted state if it, left at rest in normal
atmospheric pressure, is not losing any air any longer, i.e., if
its apparent density is already constant in time.
[0035] As we said, our problem to be solved (namely to also lessen
the wear of the recycling extruder in a recycling of the material
of the used bag), and thereby also our solution, is more
significant if the granular product contains any one or more of
cement, calcium oxide, calcium carbonate, calcium hydroxide, sand,
mineral, stone, ore, metal and glass. Due to their very hard
material combined with their usually very fine dust structure, the
advantage of our method is especially significant if the granular
product contains any one or more of cement, calcium oxide, calcium
carbonate and calcium hydroxide. Cement is a very abrasive
material. It is manufactured to be applied in hydraulic reactions
therefore it necessarily has very fine granules. A product having
very small granules makes, as we explained earlier, the advantage
of our invention more significant, because of the increased surface
tension effects. Due to a special combination of small particle
size and an extremely abrasive character, cement and other granular
products containing cement make the advantage provided by our
method especially significant. Therefore it is preferable if at
least 1 mass percent, preferably at least 2 mass percent, more
preferably at least 3 mass percent of the granular product is
cement. It can, for example, be Portland cement or any other kind
of cement.
[0036] As we said, the technical prejudice prompts the skilled
person to stack the packages as early as possible in order of
reducing required time. As it is known, if the package spends a
longer time, from reshaping to stacking, on a conveyor which is
usually used for forwarding the packages in a pipeline from the
filling/reshaping station to the stacking station, a longer
conveyor and therewith more room will be needed. For an avoiding
thereof, the technical prejudice will prompt the skilled person to
stack, i.e. palletize, the packages as soon as they are deflated to
such an extent at which they are already acceptably safely
palletized. The said extent of deflation does not mean a final full
extent of deflation in the prior art. Namely, in the case of
packages prior to US 20050281493A1, the packages were typically
stacked with a certain, minor, momentary air content therein which
air later was spontaneously released from the bags through the
(non-pressure-selective) vents at least in response to the weight
of the loose bag walls, similarly to the example mentioned earlier,
of the toy plastic boat deflating if provided with a fully open
valve. With such bags, prior to US 20050281493A1, therefore it was
not necessary to deflate, by direct squeezing, the packages more
than that necessary for a palletizing. In our method, however, the
pressure-selective weakened seam potentially stops a spontaneous
deflation generated by, for example, a weight of loose bag wall
parts, as soon as the internal pressure drops to a limit-pressure
at which the vent potentially closes. That can make it necessary in
our method, after providing a certain settling time free of
essentially releasing gas in accordance with the invention, to
suitably squeeze the package in order of expelling as much
(possibly already relatively purified) gas as possible. This can
mean that in our method, during an external squeezing, a top bag
wall panel of the package must actually be pressed to and, along an
essential area, abutted with, a top surface of the (preferably
already relatively compacted) granular product contents, otherwise
too much gas may finally remain in the package. This kind of full
compression/contacting is not necessarily a must when packages
prior to US 20050281493A1 are squeezed before stacking. On the
other hand, with packages prior to US 20050281493A1 the spontaneous
deflation, starting immediately when the package is first reshaped
and pressurized, may conduct out much gas and early, and thereby
the top bag wall panel may drop (spontaneously or by a little
squeezing) onto the top surface of the granular matter at such an
early time at which the latter is still essentially fluidized which
causes fluidized matter (i.e. dusty air) to enter the air-channel.
If, as with prior-art bags, the top bag wall panel, and therein
some internal venting means (e.g. perforations) for conducting gas
from inside the bag into the air-channel, is firmly pressed against
a top surface of a relatively un-compacted, fluidized granular
material, a risk of dust getting from the fluidized top surface of
the granular material into the air-channel arises, which is bad in
respect of our objective. Our method, however, makes the skilled
person capable of waiting and selecting a time, for this
compression, at which the granular contents are already
sufficiently compacted to prevent too much of the granular contents
from getting into the air-channel. Therefore the advantage provided
by our invention is especially significant if, in the method, after
a reshaping of the package a settling time, which is a period of
time of at least 1 second, is provided and after an end of the
settling time the package is externally squeezed by pressing and
abutting at least a part or parts, of a top bag wall panel at least
partly comprising the vent, to a top surface of the granular
product contents. The settling time is a time interval which starts
earliest when the produced package has been suitably reshaped to at
least some extent, i.e., earliest when its contents have been
rearranged to some extent and the bag of the package is in a
suitable venting orientation and there is suitable overpressure in
the package. After the settling time the top bag wall panel is
either entirely contacted with the level, the top, of the granular
matter or only one or more parts of the top bag wall panel are
pressed thereto. The top bag wall panel is specified to at least
partly comprise the vent. This is realistic since the skilled
person will typically select, as the place of the vent, the bag
wall panel designed to finally become a top bag wall panel under
which the gas, separated from the solids, is collected in a form of
a bubble. The advantage of this method embodiment is, that due to
the feature of possibly waiting for a period of time before we
start to vent, internal venting means for conducting gas from
inside the bag into the air-channel (e.g. perforations), possibly
integrated into the top bag wall panel, can be pressed to and
abutted on the top surface of the granular product contents with
lower risks of polluting the air-channel because at the time of
them being first abutted the said surface can already be relatively
compacted. For even purer gas to be provided in the top region of
the filling-space of the bag, it is preferable, if the settling
time is a period of time of at least 1.5 seconds, more preferably
at least 2 seconds, more preferably at least 2.5 seconds, more
preferably at least 3 seconds, more preferably at least 3.5
seconds, more preferably at least 4 seconds, more preferably at
least 4.5 seconds, more preferably at least seconds, more
preferably at least 10 seconds, more preferably at least 20
seconds, more preferably at least 30 seconds. The advantage thereof
is that it helps to keep the air-channel even cleaner in the end.
(The settling of the powder could of course be waited for (before
essentially squeezing) also for a much longer time, but waiting
without essentially squeezing/deflating longer than for example 24
hours, as a theoretical optional upper limit in the definition of
the settling time, would not add much further practical advantage
in our method.) In respect of our objective it is more preferable
if, in the method, during the settling time the at least one sealed
or glued seam is prevented from allowing gas to essentially escape
from the package. In implementing this preferred embodiment, the
skilled person should use a packaging bag in which the at least one
sealed or glued seam is adapted to sufficiently withstand the
overpressure of the reshaped package for a sufficiently long time
in accordance with the essence of our method invention and, also,
during the settling time the package should be kept free from any
external squeezing of such extent as would cause any gas to be
essentially expelled through the at least one sealed or glued seam.
It means that during the settling time the package is either kept
free from external squeezing or is at most exposed to such external
squeezing as is insufficient to essentially expel gas through the
at least one sealed or glued seam. It is even more preferable if,
in the method, during the settling time the at least one sealed or
glued seam is prevented from allowing gas to escape from the
package. It is even more preferable if, in the method, during the
settling time gas is prevented from escaping from the package. In
order of avoiding the risk of too much of residual surplus air
eventually remaining in the stacked sacks in the absence of an
uncontrolled venting, it is advantageous if as much air is expelled
with the squeezing as possible, therefore it is preferable, if, in
the method, the said external squeezing also includes compressing
of opposed package sides. (In this terminology, the package rests
on its bottom, and it has a top/opposing the bottom/and it further
has package sides.) That can be done, for example, with suitable
pressing conveyors placed on the two sides of a path of the
package. The compressing of the individual package sides and also
that of the top bag wall panel can all take place synchronously or
at different moments.
[0037] It is preferable if, in our method, the packaging bag is any
of the novel packaging containers described below.
[0038] As we said, it is also our objective to provide a plastic
packaging container that has improved dust retaining venting means
suitable to help to vent the bag with a reduced quantity of
accumulated residual powder. The following has lead us to our
product invention. As we said in the previous paragraphs, in a
preferable embodiment of our method, at least a part or parts of a
top bag wall panel at least partly comprising the vent are pressed
to, and abutted upon, a top surface of the granular product
contents, the latter being in a relatively compacted state by the
time of this contacting. As we said our general objective is
preventing dusty air from entering the air-channel. We observed
that in the settled, generally compacted granular product the most
compacted, hardest parts are at the bottom of the package and the
top surface of the granular product, the one to be contacted with
the top bag wall panel comprising the vent, is the least compacted,
in other words the most fluidized, softest or most aerated part of
the bulk of the granular product. At such a state, the gas bubble
filling the top portion of the inner space of the bag, above the
granular product, can be a definitely pure gas, very suitable for
venting. A first phase of a squeezing venting procedure can be
accomplished without problems by conducting much of the
aforementioned pure gas out of the package. Then, in a second phase
of the squeezing venting procedure, if a portion of the top bag
wall panel is pressed to and abutted with the top surface of the
granular product when the latter is still somewhat aerated, the
dust from the top of the granular product can enter into the
perforations of the interior wall of the air-channel, constituting
the internal venting means for conducting gas from inside the bag
into the air-channel as in accordance with the teaching of US
20050281493A1. It causes, for example, the problem, especially with
the most critical granular products discussed hereinabove, that one
may have to wait too long before pressing and abutting with a
desired success. It is our objective to provide a solution by which
it is made possible to even further decrease, especially in the
aforementioned second phase of the squeezing venting procedure, the
quantity of dust entering the air-channel even if a top surface
layer of the granular product is still in a somewhat aerated,
un-compacted state at the time at which the top bag wall panel (at
least partly comprising the vent) is pressed to and abutted with
the top surface of the granular product contents.
[0039] In order to make our recognition, we arrived at an insight
into the nature of the problem of the dust entering the
perforations (see FIG. 11). Namely, when the top bag wall panel is
abutted, along an essential surface area, on the top surface of the
granular product contents, at least portions of the interior wall
of the air-channel, taught by US 20050281493A1, are pressed into an
essentially full-surface abutment with the top surface of the
granular product contents. It results in that each perforated
opening in those abutted portions of the interior wall are more or
less isolated from the gas bubble being above the said top surface
by which these openings can not any longer conduct gas directly
from the region of the inner filling-space of the bag in which the
(relatively pure) gas is. As the pressing and abutting procedure
proceeds the further squeezing generates an overpressure that will
be released through the said isolated openings into the
air-channel. The result is that contents, comprising a mixture of
granular product and gas, enter the openings from under the top
surface of the granular product. This is possible because the top
layer of the granular product is somewhat aerated, fluidized,
flowable, conductive to gas as we said. As we observed, in this
state of the granular product the granular product is, thanks to an
earlier waiting for a suitably long time, typically compacted and
hard enough to provide a suitable solid and definite abutting
surface which prevents the bag wall portions from being too much
immersed into the granular product, but is still aerated enough to
conduct fluidized mixture (i.e. dusty gas) from the top layer of
the granular product into the openings of the interior wall of the
vent. The flow direction of this conducting is, in the prior art,
generally normal to the top surface of the granular product
(corresponding to the orientation of the openings, e.g.
perforations, penetrating through the interior air-channel-wall).
This special flow direction contributes to the fact that the gas
can not be conducted to the openings, isolated from the gas bubble
of the package, other than through the somewhat aerated layer of
the bulk of the granular product. We recognized that we can solve
this problem if either we eliminate the openings that penetrate
through the interior air-channel-wall and select alternative,
improved internal venting means for conducting gas from inside the
container into the air-channel, or we eliminate the general flat
construction of the vent in which it is arranged in an "interior
wall-exterior wall" combination as taught by US 20050281493A1,
which, as we could see, is inherently available for a problematic
full surface abutment with the top surface of the granular
product.
[0040] We believe that this recognition is non-obvious, as nothing
in the prior art leads the skilled person away, in these respects,
from the definite teachings of US 20050281493A1. Namely, as
concerning our aforementioned second improvement approach to
eliminate the general flat construction of the vent: all prior-art
air-channel-vented plastic heavy duty shipping bags known to have
been successfully implemented in the practice of industrial
packaging of bulk solids are arranged in the usual flat, interior
wall-exterior wall combination, as also taught by US 20050281493A1,
and there is nothing in US 20050281493A1 or in the prior art as a
whole that would make the skilled person arrive at selecting a
different (and probably technically more difficult) approach for
the air-channel structure instead of the usual flat, interior
wall-exterior wall structure. Now as concerning our aforementioned
first improvement approach comprising a vent based on the known
flat, interior wall-exterior wall combination but with alternative
internal venting means, it is known that it is possible to apply,
as internal venting means, interruptions in the welding seams
joining the air-channel-walls together and defining the area of the
air-channel. This approach, however, is known to be used with
air-assisted filling (typically for example: cement-filling with
pneumatic filling systems into valve bags) where the very much
transportation air, used for conveying the filling material, must
simultaneously be vented, through the weld-interruption, during the
filling, in order to prevent the bag from bursting. This approach
provides high venting capacity but is not believed to be attractive
for the skilled person, relying on the technical prejudice, faced
with the problem of packing, preferably FFS-packing, fine powders
into vented plastic bags simultaneously preventing fine powder from
being released from the bag and especially from the internal
filling-space of the bag, because such un-welded interruptions are
known to be practically impossible to be implemented to constitute
such small openings as the fine pin-perforations and as are
necessary for solving this problem successfully in the prior-art
approach simultaneously endeavoring to vent as early as possible.
We are supporting this as follows. Prior art document U.S. Pat. No.
3,937,395 provides a plastic bag whose vent comprises overlapping
panels forming an air-channel having interior and exterior walls.
The openings, for conducting the air into and out of the
air-channel, are taught to possibly be interruptions in the seams
joining the panels together. In the document the purpose of the
vent is to at least allow the escape, from the otherwise
air-impermeable bag, of the air that carries the powder into the
bag, so that filling is not interrupted. The document does not
mention an objective of effectively retaining the dust. On the
other hand, patent document U.S. Pat. No. 4,743,123 states that
plastic bags comprising perforations formed by the action of
needles present the disadvantage that needle perforations are
generally large in diameter, which means that, particularly during
packaging loosely poured, particularly very fine materials such as
cocoa and lime, particles are able to escape through the
perforations. The document provides a plastic bag for packing
loosely poured material comprising venting perforations having a
size of 50 microns to 100 microns in the bag foil wall. Patent
document US20080273820A1 provides a perforated film, comprising
perforations of a size of at most 100 microns in order of an
acceptably low powder leakage. Summing it up, it is known, from the
prior art, to the skilled person that for retaining fine powders in
vented bags, definitely fine perforation is needed, and that it is
very difficult, in fact practically impossible to achieve an
acceptable result by trying to retain fine particles from a fluid
with interrupted seams. In addition, our closest prior-art document
US 20050281493A1 suggests the skilled person to retain, as much as
possible, fine dust from entering through the internal venting
means into the air-channel. Namely, the document says that after
some venting, the interior and exterior films are arranged tightly
on top of each other in the weakened seam, being fixed in this
position by adhesive forces. Also, the document teaches that the
special weakened seam, acting as external venting means for
conducting gas from the air-channel to an outside of the bag, is a
very good filter, and even the escape of very fine particles is
practically impossible through the weakened seam, which can be
attributed to the fact that the adhesive forces acting between the
films, which are only in part firmly connected to each other,
produce a certain degree of adhesion even without a securely sealed
or glued connection and thus the venting seam is partially gas
permeable. The document teaches that in its most preferred
embodiment the width of the weakened seam is very small (see FIG.
3. of US 20050281493A1). The document further says that though it
is possible to provide, as internal venting means, slits or other
openings in the interior wall permitting gas penetration,
preferably the openings in the interior wall are perforations made
by needling. The document further says that particularly where very
fine product is concerned, the internal openings are preferably
arranged such that the distance from the openings to the seam,
allowing the gas to escape, is as long as possible, explicitly
teaching the skilled person to take measures to keep fine dust from
reaching the weakened seam. This also means a (not surprising)
teaching for the skilled person that fine dust can, from the fluid,
enter the air-channel even with fine perforations, like needle
perforations, applied. The skilled person, as we earlier said, is
generally prompted by the technical prejudice to avoid overloading
the dust retaining air-channels with too much dust because that can
clog the vent from breathing. In the US 20050281493A1 document the
weakened exit seam of the air-channel is capable of retaining all
small particles but it, unlike fibrous filters, does not actually
have a filtering volume capable of accumulating the filtered-out
dust in its matrix without harm. It directly stops the dust at its
entrance cross section area, and in addition, it has an extremely
small effective cross section (width as well as height). This
filter seam, taught in US 20050281493A1 to be partially gas
permeable, is apparently easy to clog, and evidently needs
attention from the skilled person in order of preventing too much
dust from entering into the air-channel. It is known from the prior
art, and also the document provides such hints, that if the
internal perforations in the bag of US 20050281493A1 are fine but
not fine enough then much powder enters from the fluid contents
into the air-channel which involves a risk of clogging the exit
seam. The skilled person therefore will be prompted to endeavor to
select internal venting means comprising as fine perforations as
possible. In our present inventive concept, common in this whole
description, however, the preventing of the air-channel from
getting loaded with dust is not based on filtering the fluid at the
internal venting means but is, instead, based on providing, through
the suitable use of suitably formed vents having weakened seams, a
relatively pure (i.e. relatively dust-free) gas for conducting into
the air-channel as a result of a previous separating procedure in
which the solid and gas components are at least partly
separated.
[0041] The essence of our product invention is a packaging
container, comprising a flexible plastic wall which comprises one
or more vents, the one or more vents [0042] adapted to conduct gas
from an inside of the container into an air-channel and from the
air-channel to an outside of the container, [0043] having
air-channel-walls defining the air-channel, [0044] comprising
internal venting means for conducting gas from inside the container
into the air-channel, [0045] at least partly defined by means of at
least one sealed or glued seam having in at least a partial region
a reduced degree of bonding sufficient to allow gas to escape in
response to a suitable pressure, the packaging container being
novel in that in one or more of the vents, [0046] if the vent is
formed to comprise a region of the flexible plastic wall having an
interior wall and an exterior wall then the vent is free of
openings [0047] penetrating through an interior wall [0048] for
conducting gas from inside the container into a region between
interior and exterior walls, and [0049] otherwise [0050] either the
air-channel-walls of the vent are free of openings constituting
internal venting means [0051] or at least one air-channel-wall of
the vent comprises one or more openings constituting internal
venting means.
[0052] The terms used in the invention are interpreted as follows.
Packaging containers according to the invention are, among others,
FFS tubes, center-folded FFS films (so-called half-tubes), block
bags, open-mouth gusseted bags and flat sacks, valve sacks (glued
and heat-sealed), hexagonal bottom sacks, automatic machine (flat)
films, etc. The flexible plastic (i.e. synthetic or natural
polymer) wall can be single-layer or multiple-layer (for example
coextruded or laminated) or a combination of both. The bag wall
comprises a vent or more vents, which can either be the usual flat
vent having a generally flat air-channel (preferably with suitable
spacers therein) defined by interior and exterior walls (most
typically provided by overlapping bag wall panel edges) or any
other, e.g. generally non-flat, structure comprised by the bag wall
and adapted to suitably conduct gas from the inside of the
container into an air-channel and from the air-channel to the
outside of the container according to the invention. Accordingly,
the air-channel-walls can be of a general structure similar to, for
example, that of US 20050281493A1 (without regard now to openings
therein) or can be different, as long as they define an air-channel
adapted to provide a path for gas, at least partly, in and along
the air-channel between the air-channel-walls. The vent comprises
suitable internal venting means for conducting gas from inside the
bag into the air-channel. In general, internal venting means can
possibly be constituted for example, as taught in the prior art, by
aperture(s) or perforation(s) in an air-channel-wall, for
conducting air from the inner filling-space of the bag into the
air-channel. Internal venting means can, for further example, be
constituted by suitably formed sealed or glued seam(s) having in at
least a partial region a reduced degree of bonding sufficient to
allow gas to enter from the inner filling-space of the bag into the
air-channel in response to a suitable internal pressure, thereby
allowing gas to escape. As concerning external venting means for
conducting gas from the air-channel to the outside of the bag, it
is known, for example, from the aforementioned prior-art document
US 20050281493A1, that the vent can be at least partly defined by
means of at least one sealed or glued seam having in at least a
partial region a reduced degree of bonding sufficient to allow gas
to escape in response to a suitable pressure. The skilled person
could form the aforementioned sealed or glued seam (comprising, for
example, one or more of corona treatment, lacquer layer, adhesive
coating etc.) to have a (reduced) degree of bonding corresponding
to any positive value in the range of 0 to 100 percent bonding
strength as compared to the bonding strength achievable without the
said reduction. The prior-art prejudice prompts the skilled person
to select a value definitely close to zero, as we explained earlier
herein. Based on our present general inventive concept, however,
now the skilled person would select relatively higher values, as
depending on the selection of the skilled person in accordance with
his/her practical application objective, thus depending, for
example in a given packing method, for example on the size and
shape of the bag, on the surface weight of the wall of the bag, on
the quantity and specific weight of solid contents packed in the
bag, on initial gas contents provided in the bag during packing
etc. A sealed seam includes for example a seam made with heat
fusing or heat welding, e.g. high frequency or ultrasonic welding.
The vent can thus either be purely defined by sealed or glued seams
or edges bordering the air-channel-walls, or the vent can, for
example, be partly also defined by other means such as folded edges
in which adjacent air-channel-walls meet, or any other suitable
means can be provided. The novelty of the invention, is an
improvement in the vent which is essentially related to the
specification of the internal venting means for conducting gas from
inside the container into the air-channel. Namely, if, on the one
hand, the vent is formed to comprise a region of the flexible
plastic wall having an interior wall and an exterior wall then the
vent is free of such openings which openings penetrate through an
interior wall for conducting gas from inside the container into the
region between interior and exterior walls. In other words, if the
vent is formed to comprise a region of the flexible plastic wall
having an interior wall and an exterior wall then the vent at most
comprises openings other than openings penetrating through an
interior wall for conducting gas from inside the container into the
region between interior and exterior walls. In this case the
internal venting means (for conducting gas from inside the
container into the air-channel) can comprise, for example, one or
more openings being between an interior wall and an exterior wall,
preferably provided in the form of interruptions in the welding (or
glue-) seams joining the interior and exterior walls together. This
can, for example in a packing process, mean that the gas enters
into the flat shaped air-channel through its side edge and in a
direction parallel with the bag wall and with a plane of the flat
region and with the top surface of the granular product, which has
the advantage that air, going through the interruption opening, can
be conducted above the top surface of the granular product and is
not forced to penetrate the granular product. Here the interior
wall can contribute to providing a spacer providing a free space
for the gas-conducting, corresponding to a sum of the wall
thickness of the interior wall and the height of possible spacer
means in the opening, thanks to the top surface of the granular
product possibly rendered, in a suitable packing process, solid
enough to prevent the interior wall from essentially immersing into
it. Another solution can be found among the examples later herein.
And if, on the other hand, the vent is formed otherwise, then the
skilled person is free to select internal venting means comprised
of openings in any of the air-channel-walls of the vent as well as
to select a solution in which any of the air-channel-walls is free
of openings penetrating therethrough and constituting internal
venting means. In this respect, the construction of one
air-channel-wall is independent from that of another
air-channel-wall, thus it is possible to form one or more
air-channel-walls with openings penetrating therethrough and
constituting internal venting means and, at the same time, to form
one or more other air-channel-walls without openings penetrating
therethrough, constituting internal venting means. Here any
suitable vent structure can be selected other than the usual
structure, more exactly other than a vent comprising a region of
the flexible plastic wall having an interior wall and an exterior
wall. A simple solution can be, for example, forming an air-channel
sharply projecting into the inner filling-space of the bag
providing the projecting air-channel with a positive projection
height, in which structure a flat envelope of the air-channel is
essentially perpendicular to the bag wall to which it belongs,
rather than parallel therewith (which is the case with the usual
interior wall/exterior wall approach). A projecting end edge of the
air-channel can serve, during a squeezing in a packing process, as
an abutting point, abutting on the top surface of the granular
product and thus providing spacer means providing a space between
the bag wall and the top surface of the granular product in which
space the air can be conducted to the air-channel. The skilled
person will readily select air-channel-wall parameters (e.g. film
base material and dimensions) suitable for this spacing. The two
air-channel-walls of this possible vent embodiment could be
essentially symmetrical and both could be essentially normal to the
bag wall to which they belong. They are thus neither interior nor
exterior walls but they are side walls instead, which preferably
comprise penetrating perforations to receive the aforementioned gas
flow, arriving, in a packing process, parallel with the top surface
of the granular product. One or both of these air-channel-walls,
however can as well be free of openings, in which case the internal
venting means can comprise openings, for example, in the edge which
borders the air-channel-walls, being formed, for example, as the
aforementioned seam interruptions, as is described in the example
later herein. In accordance with all that has been described
hereinabove in connection with our method inventions, the advantage
of the packaging container invention is that it, during an external
squeezing of the package in a packing process, helps to conduct
purified gas from the upper gas bubble into the air-channel
directly, i.e. without conducting the said gas through a top layer
of the granular product, by which it is suitable to help to vent
the bag with a reduced quantity of accumulated residual powder. The
advantage of the aforedescribed invention is that it achieves our
objective to provide a plastic packaging container that has
improved dust retaining venting means suitable to help to vent the
bag with a reduced quantity of accumulated residual powder.
[0053] If, however, we aim to prevent dusty air from entering the
air-channel and the container has more than one of the
above-specified vents then each of them should preferably be
improved as specified herein. As we could see, in embodiments
advantageous in a manufacturing respect and in respect of operation
in our methods, the packaging container is preferably such as its
internal venting means comprise one or more openings in a seam
defining a vent. In this sense a seam defining a vent means such a
seam as takes part in defining one or more of the said one or more
vents. The packaging container is more preferably such as its
internal venting means comprise at least one opening selected from
a perforation in a folded seam, an interruption of a welding in a
welded seam and an interruption of a gluing in a glued seam. The
said seam interruptions can be relatively short, for example having
a length similar to, or not too much greater than, an
air-channel-wall thickness, but the seam interruptions can
theoretically be rather long as well, even potentially occupying
the majority or even almost the whole of a total seam length. As
the seam interruptions can possibly conduct more dust into the
air-channel than a fine perforation through the interior
air-channel-wall, the packaging container is preferably such as it
has fibrous filter in at least a part or parts of an air-channel.
Further it is preferable if at least a part or parts of the fibrous
filter is contained in a sealed or glued seam having in at least a
partial region the reduced degree of bonding. This has the
advantage that the fibrous filter can take part in forming the
reduced degree of bonding. It is even more preferable if the at
least one sealed or glued seam, of the reduced degree of bonding,
is a welded seam comprising the fibrous filter and flexible walls
fixed to each other at least partly, and a material of at least one
of the flexible walls fixed in the welded seam is incompatible for
welding with a material of the fibrous filter fixed in the welded
seam to an extent sufficient to provide a reduced degree of
bonding. This way a reduced degree of bonding can be provided, for
example with providing different polyolefins for the welding in the
seam. N.B.: the material of the fibrous filter fixed in the seam
can be in a state in which its fibers are partly or completely
fused and distorted. As we could see, in several cases the
air-channel-wall can provide spacer means whose space size depends
on a wall thickness of the air-channel-wall. Therefore (however a
thick air-channel-wall is not necessary for the air-channel to work
well) the packaging container is more preferably such as it has an
air-channel-wall having at least partly a thickness of at least 70
microns (optionally limited to at most be, for example, 5000
microns). Also, as we could see, in any of these cases, any spacer
means provided in the openings also help to keep the top bag wall,
in a packing process, farther from the top of the granular solid,
thus providing a space not only in the opening but also above the
top surface of the granular solid. Therefore the packaging
container is more preferably such as it has spacer means provided
in at least one of the one or more openings in a seam defining a
vent. For a more reliable spacing above the top surface of the
granular product, the said spacer means preferably comprise one or
both of a nonwoven and at least one projection of a projection
height of at least 50 microns (optionally limited to at most be,
for example, 5000 microns).
[0054] As we said, it is also our objective to provide systems
comprising a novel plastic packaging bag, which has improved dust
retaining venting means suitable to help to vent the bag with a
reduced quantity of accumulated residual powder, and granular
contents packed therein. Our system invention is also based on our
present general inventive concept, common in this whole
description, namely the preventing of the air-channel from getting
loaded with dust is not based on filtering the fluid at the
internal venting means but is, instead, based on adapting the
system to provide, through the suitably formed vents having
weakened seams, a relatively dust-free gas, at least partly
separated from the solids, for conducting into the air-channel.
[0055] As we said earlier, at forming the aforementioned sealed or
glued weakened seam (comprising, for example, one or more of corona
treatment, lacquer layer, adhesive coating etc.) to have a
(reduced) degree of bonding corresponding to a positive value in
the range of 0 to 100 percent bonding strength, as compared to the
bonding strength achievable without the said reduction, the skilled
person is prompted by prior-art prejudice to select a value
definitely close to zero. In accordance with our present inventive
concept, however, now the skilled person would select relatively
higher values. As we recognized, a bag containing an air-solid
mixture and provided with a vent having a pressure selective
weakened seam can more easily be handled in a way suitable for our
objectives if the pressure selective weakened seam is strong
enough, i.e. is adapted, to suitably safely withstand such
overpressures (of the package) as may arise in the bag while the
package is handled, before a final squeezing thereof (for a final
venting), in the usual way in the industry, including for example
filling, compacting, then closing, then dropping, tumbling,
tossing, laying down, conveying, flattening and vibrating. The
actually arising overpressures depend on many circumstances,
mentioned earlier hereinabove. In our general recognition, pressure
values possibly defining, in any combination, the two ends of the
interval from which the predetermined limit pressure could possibly
be selected in case of need, depending on the circumstances, like
filling weight, bag dimensions and bag wall thickness, could, for
example, include 0.0000001 bars, 0.000001 bars, 0.00001 bars,
0.0001 bars, 0.001 bars, 0.01 bars, 0.1 bars, 1.0 bar, and 10
bars.
[0056] The essence of our system invention is a system comprising a
packaging bag containing a quantity of a granular product mixed
with a gas, the packaging bag comprising a flexible plastic wall
which comprises a vent, the vent [0057] adapted to conduct the gas
from an inside of the packaging bag into an air-channel and from
the air-channel to an outside of the packaging bag, [0058] having
air-channel-walls defining the air-channel, and [0059] at least
partly defined by a sealed or glued seam having in at least a
partial region a reduced degree of bonding sufficient to allow gas
to escape in response to an overpressure in the packaging bag
exceeding a predetermined limit, the system being novel in that the
predetermined limit is selected from the interval between 0.0001
bars and 10 bars.
[0060] Most of the terms used were already defined. The packaging
bag may be fully filled with the mixture but it is also possible
that the packaging bag also contains other contents than the
mixture, for example separated solids or gas. The advantage of the
system is that it, due to the reduced bonding strength of its
pressure-selective vent being high enough, is easier to be
processed into a compacted, vented package with a reduced degree of
residual powder contamination.
[0061] In respect of our objective it is preferable if the
predetermined limit is selected from the interval between 0.001
bars and 10 bars, more preferably from the interval between 0.01
bars and 10 bars, even more preferably from the interval between
0.1 bars and 10 bars. Mainly in case of filling weights not
exceeding the most common industrial filling weights it is
preferable if in any of the aforementioned intervals the upper
limit of the interval is 1 bar rather than 10 bars.
[0062] Our system provides a more significant advantage over prior
art, if at least 1 mass percent, preferably at least 2, more
preferably at least 3, even more preferably at least 5 mass percent
of the granular product has a granule size below 150 microns,
preferably 100 microns, more preferably 50 microns, even more
preferably 25 microns, even more preferably 10 microns, even more
preferably 5 microns. The granule size should preferably be greater
than 0.05 microns, under which it is more difficult to suitably
retain the dust.
[0063] The more air is mixed with the granular product in the
packaging bag, the higher the significance and benefit of our
invention is. It is therefore preferable if at least some of the
granular product, mixed with the gas, is in an aerated state in
which an apparent density of the granular product is at most 98%
(preferably at most 95%, more preferably at most 90%, more
preferably at most 87%), (preferably, however, at least 15%) of an
apparent density belonging to the granular product in a fully
compacted state thereof, the latter meaning the apparent density
that the granular product has when the granular product is in a
fully compacted state.
[0064] Analogously to our earlier results, our solution is more
significant if the granular product contains any one or more of
cement, calcium oxide, calcium carbonate, calcium hydroxide, sand,
mineral, stone, ore, metal and glass, preferably any one or more of
cement, calcium oxide, calcium carbonate and calcium hydroxide. It
is preferable if at least 1 mass percent, preferably at least 2
mass percent, more preferably at least 3 mass percent of the
granular product is cement. It can, for example, be Portland cement
or any other kind of cement.
[0065] For a better separation of the contents it is preferable if
the filling mouth of the packaging bag is closed. This includes
closed by any possible closing means, generally in order of
preventing an essential loss of filling material, which can for
example be a closed filling valve of a valve bag or, preferably,
the top mouth of the bag being closed by any one or more of
welding, adhering and sewing or with other methods. It is
preferable if the packaging bag is a packaging container according
to any of the embodiments of our product invention.
[0066] All publications, patent applications, patents mentioned
herein are incorporated by reference in their entirety. In case of
conflict, the present specification, including definitions, will
control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] FIG. 1a. is a side view of an open-mouth flat bag with two
vents.
[0068] FIG. 1b. is cross section "B-B" of a vent of the bag of FIG.
1a.
[0069] FIG. 1c. is cross section "C-C" of a vent of the bag of FIG.
1a.
[0070] FIG. 1d. is cross section "D-D" of the bag of FIG. 1a.
[0071] FIG. 1e. is cross section "E-E" of the bag of FIG. 1a. after
a cross-welding of its mouth
[0072] FIG. 2a. is a side view of an endless tube, for FFS
packaging, with a vent.
[0073] FIG. 2b. is cross section "B-B" of the vent of the tube of
FIG. 2a.
[0074] FIG. 2c. is cross section "C-C" of the vent of the tube of
FIG. 2a.
[0075] FIG. 2d. is cross section "D-D" of the vent of the tube of
FIG. 2a.
[0076] FIG. 3a. is a side view of an open-mouth flat bag with two
vents.
[0077] FIG. 3b. is cross section "B-B" of a vent of the bag of FIG.
3a.
[0078] FIG. 3c. is cross section "C-C" of a vent of the bag of FIG.
3a.
[0079] FIG. 3d. is cross section "D-D" of a vent of the bag of FIG.
3a.
[0080] FIG. 3e. is cross section "E-E" of the bag of FIG. 3a.
[0081] FIG. 4a. is a perspective view of a section of an endless
tube, for FFS packaging, with a vent.
[0082] FIG. 4b. is a side view of a section of the endless tube of
FIG. 4a, with the vent.
[0083] FIG. 4c. is cross section "C-C" of the vent of the endless
tube of FIG. 4a.
[0084] FIG. 4d. is cross section "D-D" of the vent of the endless
tube of FIG. 4a.
[0085] FIG. 4e. is cross section "E-E" of the vent of the endless
tube of FIG. 4a.
[0086] FIG. 5a. is a perspective view of a section of an endless
tube, for FFS packaging, with a vent.
[0087] FIG. 5b. is a side view of a section of the endless tube of
FIG. 5a, with the vent.
[0088] FIG. 5c. is cross section "C-C" of the vent of the endless
tube of FIG. 5a.
[0089] FIG. 5d. is cross section "D-D" of the vent of the endless
tube of FIG. 5a.
[0090] FIG. 5e. is cross section "E-E" of the vent of the endless
tube of FIG. 5a., also showing welded seam detail (32, 38) behind
the section plane.
[0091] FIGS. 6a-h. illustrate the phases of a packing process in
vertical section.
[0092] FIG. 7a. is the vertical section of a package being squeezed
by a squeezing-conveyor.
[0093] FIG. 7b. is the magnified portion "B" of FIG. 7a as in
accordance with Example 6.
[0094] FIG. 8. is the magnified portion "B" of FIG. 7a as in
accordance with Example 7.
[0095] FIG. 9. is the magnified portion "B" of FIG. 7a as in
accordance with Example 8, not showing welded seam details behind
the section plane, for easier reading.
[0096] FIG. 10a. is the vertical section of a prior-art package as
in accordance with Comparative Example 9.
[0097] FIG. 10b. is the magnified portion "B" of FIG. 10a.
[0098] FIG. 11a. is the vertical section of a prior-art package as
in accordance with Comparative Example 10.
[0099] FIG. 11b. is the magnified portion "B" of FIG. 11a.
[0100] FIG. 12a. is a side view of a closed flat bag FFS tube
section with one vent.
[0101] FIG. 12b. is cross section "B-B" of the vent of the bag of
FIG. 12a.
[0102] FIG. 12c. is cross section "C-C" of the vent of the bag of
FIG. 12a.
[0103] FIG. 12d. is cross section "D-D" of the bag of FIG. 12a.
EXAMPLES
Example 1
A Packaging Container
[0104] Reference is made to the figures, especially to FIG. 1a to
1e. This example packaging container is an open-mouth flat bag 1.
It comprises two opposed, 150-micron thick coextruded polyethylene
bag walls 2, a top open mouth 3 and a cross welded bottom 4. One of
the bag walls 2 comprises two vents 5, each adapted to conduct air
from inside of the bag 1, from its filling space 15, into an
air-channel 6 and from the air-channel 6 to the outside 7 of the
bag 1. In both vents 5 uniformly, the construction of the vent 5 is
such as the vent 5 has two, generally parallel air-channel-walls
between which the vent 5 has an air-channel 6 adapted to provide a
path for air in and along the air-channel 6 between the
air-channel-walls. One of the air-channel-walls is constituted by
the bag wall 2 and the other air-channel-wall is a 100-micron thick
polyethylene film tape, connecting the bottom 4 edge 14 and the
open mouth 3 and fixed to the inner surface 8 of the bag wall 2
with sealed seams 9. The air-channel 6 is defined by two side seams
9 (being welded seams) parallel with the film tape and generally
connecting the bottom 4 edge 14 and the open mouth 3 and the
air-channel 6 is further defined by a pressure-sensitively adhered
cross-seam 9 in the bottom 4 edge 14 and further by the open mouth
3. (In a later use, the open mouth 3 is adapted to be closed with a
cross welding which will complete the defining of the air-channel 6
by closing the other end thereof.) The pressure sensitively adhered
cross-seam 9 (see FIG. 1d) of the air-channel 6, in the bottom 4
edge 14, constitutes pressure-selective seam portion 16 as it has a
reduced degree of bonding sufficient, in a practical application of
the bag 1, to allow gas 29 to escape in response to a suitable
predetermined pressure provided in the bag 1. The skilled person
can select a bonding strength and durability in accordance with the
given application, for example using the teaching of US
20050281493A1. The cross-seam 9 at the bottom 4 provides in the
vent 5 external venting means for conducting air from the
air-channel 6 to the outside 7 of the bag 1 in response to the
aforementioned pressure provided. On the other hand, in one of the
two welded side seams 9, partly defining the air-channel 6, there
are interruptions provided in the welding of the welded seam 9. The
interruptions provide internal venting means 10, and provide
openings for directly conducting air from inside the bag 1 into the
air-channel 6. Thus the structure of both of the vents 5 is such as
the vent 5 is formed to comprise a region of the flexible plastic
bag 1 wall 2 having a 100-micron thick interior wall 11 and a
150-micron thick exterior wall 12. The vent 5 is free of openings
penetrating through the interior wall 11, because, as we said, the
internal venting means 10 are provided as interruptions in the
welding of the welded seam 9, between the interior wall 11 and
exterior wall 12. There is a fibrous filter 13 provided in the form
of a spunbonded nonwoven sheet, at least partly containing
polypropylene and of about 17 g/m.sup.2 surface weight, placed in
between the air-channel-walls, i.e. between the interior wall 11
and exterior wall 12, simultaneously being spacer means and fibrous
filter 13. As at the manufacturing of the tube 44 from which the
bag 1 was made the nonwoven sheet or tape was endlessly applied
into the tube 44, the fibrous filter 13 is contained in the seam 9
having the reduced degree of bonding, at the bottom 4 of the bag 1.
When the bag 1 is later closed by a cross-welding of its mouth 3,
the cross-welding will produce (see FIG. 1e) a welded seam 9,
partly defining the vent 5, in which the fibrous filter 13 will
also be contained, in which, as the skilled person knows, a
partial, predeterminable incompatibility of the materials of the
nonwoven and of the flexible walls 2 (one of them being the
original 100-micron thick air-channel-wall) in the seam 9 can be
utilized in order of creating also in the bag 1 mouth 3 a seam 9 of
a reduced degree of bonding to create a further pressure-selective
seam portion 16 in the bag 1.
Example 2
A Packaging Container
[0105] Reference is made to the figures, especially to FIGS. 2a to
2d. This example packaging container is an endless tube 44 for FFS
packaging. The container is formed from a flexible plastic, for
example polyethylene, film wall 2 that has been folded around a
longitudinal direction, such that a vent 5, in the form of a region
with an interior wall 11 and an exterior wall 12 (acting as
air-channel-walls defining an air-channel 6 therebetween), is
formed between two overlapping outer edges 14 of the film wall 2.
Two seams 9 extending in longitudinal direction fix the outer edges
14 of the film wall 2 to the film wall 2 portion overlapped
therewith, and thereby a tube 44 (a so-called FFS tube 44) is
formed, providing a filling-space 15 in the inside of the
container. The one of the longitudinal seams 9 ("inner seam 9",
being the leftmost one of the two seams 9 in FIGS. 2a and 2b) which
is adjacent to the filling-space 15 of the container is a glued
seam 9 and the other one of the longitudinal seams 9 ("outer seam
9", being the rightmost one of the two seams 9 in FIGS. 2a and 2b),
which is adjacent to the outside 7 of the container, is a welded
seam 9. Before being filled, the packaging container is to be
provided with a welded seam 9 perpendicular to the longitudinal
direction, forming a bottom 4 and, after having been filled, with a
welded seam 9, also perpendicular to the longitudinal direction,
for closing the package 32. The internal venting means 10 comprise
openings formed by interruptions in the gluing of the glued
longitudinal inner seam 9, and pressure-selective external venting
means are constituted by pressure-selective seam portions 16, of
reduced degree of bonding, in the welding of the outer seam 9, the
pressure-selective seam portions 16 being arranged in a staggered,
offset manner in relation to the openings of the inner seam 9. In
the pressure-selective seam portions 16 the surface of the flexible
walls 2 was treated with Corona discharge before welding and
therefore in these pressure-selective seam portions 16 the seam 9
has a reduced degree of bonding sufficient to allow gas 29 to
escape in response to a suitable predetermined pressure. Also, the
surface part of the interior wall 11 adjacent to the air-channel 6
has a Corona-treated surface 17 which was treated with Corona
discharge in an endless stripe in the longitudinal direction and
thereby the aforementioned welded seams 9, later to be formed
perpendicularly to the longitudinal direction to form a bottom 4
and mouth 3 of the container, will also contain, at the
Corona-treated surface 17, pressure-selective seam portions 16
having a reduced degree of bonding sufficient to allow gas 29 to
escape in response to a suitable predetermined pressure. A fibrous
filter 13, and simultaneously spacer means, is constituted by a
weldable polyethylene nonwoven inserted in the air-channel 6
between the interior wall 11 and the exterior wall 12, and also
partly within the inner seam 9, and thus it also provides spacer
means in the openings constituted by the interruptions in the glued
inner seam 9. As it can be seen in this example, the vent 5 is
formed to comprise a region of the flexible plastic wall 2 having
an interior wall 11 and an exterior wall 12 and the vent 5 is free
of openings penetrating through an interior wall 11. (It is also
possible for the skilled person to modify this construction and to
provide in the wall 2 of the container, for a better venting, two
parallel vents 5 of such kind/not shown in figure/but care must be
taken in order that then both of the vents 5 must be free of
openings penetrating through an interior wall 11 for conducting gas
29 from inside the container into a region between interior wall 11
and exterior wall 12.)
Example 3
A Packaging Container
[0106] Reference is made to the figures, especially to FIGS. 3a to
3e. This example packaging container is an open-mouth flat bag 1.
It comprises two opposed bag walls 2 of a thickness of 150 microns,
a top open mouth 3 and a cross welded bottom 4. One of the bag
walls 2 comprises two vents 5, each adapted to conduct air from the
inside of the bag 1 into an air-channel 6 and from the air-channel
6 to the outside 7 of the bag 1. In both vents 5 uniformly, the
construction of the vent 5 is such as the vent 5 has two
air-channel-walls, generally parallel with the said one of the bag
walls 2, of a thickness of 90 microns, between which the vent 5 has
an air-channel 6 adapted to provide a path, for air, in and along
the air-channel 6 between the air-channel-walls. The air-channel 6
runs in a longitudinal direction and connects the bottom 4 and the
open mouth 3. The air-channel-walls form an air-channel 6 of a
generally flat envelope shape. One of the air-channel-walls ("outer
air-channel-wall" 18) is adjacent to, and generally abutting with,
the inner surface 8 of the bag wall 2 to which the vents 5 belong
and the other air-channel-wall ("inner air-channel-wall" 19) is
adjacent to the filling-space 15 of the bag 1. The outer
air-channel-wall 18 and the inner air-channel-wall 19 meet in two
longitudinal seams 9: one of them (the leftmost one in FIG. 3b) is
a folded seam 9 and the other one (the rightmost one in FIG. 3b) is
a welded seam 9. The folded seam 9 is generally loose from the
inner surface 8 of the bag wall 2 while the welded seam 9 is a seam
9 in which also the inner surface 8 of the bag wall 2 is welded to
the outer air-channel-wall 18. The air-channel 6 is thus defined by
the said folded seam 9 and welded seam 9 and it is further defined
by a welded cross seam 9 in the bottom 4 and further by the open
mouth 3. (In a later use, the open mouth 3 is adapted to be closed
with a cross welding which will complete the defining of the
air-channel 6 by closing the other end thereof/not shown/.) The
surface of the outer air-channel-wall 18 adjacent with the
air-channel 6 is a lacquered surface 20, i.e. a surface covered in
a suitably thin layer of a suitable lacquer which causes the
cross-welded ends of the air-channel 6, in the bottom 4 of the bag
1 and, after a closing/not shown/of the mouth 3, in the mouth 3 of
the bag 1, to be pressure-selective seam portions 16, having a
reduced degree of bonding sufficient to allow gas 29 to escape in
response to a suitable predetermined pressure. Internal venting
means 10 are constituted by perforation openings penetrating
through the outer air-channel-wall 18 (FIG. 3d) and through the
folded seam 9 (FIG. 3c). Thus the inner air-channel-wall 19 is, in
both of the vents 5, free of perforations. Embossed projections 21,
of a projection height 22 of about 100 microns, are provided as
spacer means distributed uniformly and with a suitable closeness in
the whole surface, adjacent to the inner surface 8 of the bag wall
2, of the outer air-channel-wall 18 as well as in the whole
surface, adjacent to the air-channel 6, of the inner
air-channel-wall 19.
Example 4
A Packaging Container
[0107] Reference is made to the figures, especially to FIGS. 4a to
4e. This example packaging container is an endless tube 44 for FFS
packaging. The container is formed from an endless flexible plastic
flat film wall 2 with two side edges 14, by folding the film wall 2
around a longitudinal direction, and by adjoining the two
symmetrical side edges 14 and folding them into an inside of the
container FFS tube, as is illustrated in the relevant drawings
(e.g. FIG. 4a, 4c). Both wall 2 edges 14 project sharply,
essentially perpendicularly from the inner surface 8 of the
container wall 2 ("base surface"), into the filling-space 15 of the
container with a positive projection height 22, corresponding to a
projection height 22 of the vent 5. The wall 2 edges 14, projecting
into the filling-space 15, are fastened to each other with a
welded, so-called distal seam 23 which is distal from the inner
surface 8 of the container wall 2, i.e., from the base surface, and
whose plane is generally normal to the base surface. The wall 2
portions folded into the inside of the container are further
adjoined in another welded, so-called proximal seam 24, which is
adjacent to the inner surface 8 of the container wall 2, i.e., to
the base surface, and whose plane is also generally normal to the
base surface. The parts, of the folded-in wall 2 portions, between
the distal seam 23 and the proximal seam 24 constitute air-channel
side-walls 45 and the air-channel 6 is defined by the air-channel
side-walls 45, the distal seam 23 and the proximal seam 24. The
air-channel 6 thus has an envelope shape sharply projecting into
the inner filling-space 15 of the container providing the
projecting air-channel 6 with a positive projection height 22, in
which structure the flat envelope of the air-channel 6 is
essentially perpendicular to the portion of the tube 44 wall 2 to
which it belongs. The two air-channel side-walls 45 are essentially
symmetrical and both are essentially normal to the container wall 2
to which they belong. Surfaces of the air-channel side-walls 45
adjacent to the air-channel 6 are provided with embossed
projections 21 projecting into the air-channel 6, as spacer means.
Before being filled, the packaging container is to be provided with
a welded bottom 4 seam 9 perpendicular to the longitudinal
direction, forming the bottom 4 and, after having been filled, with
a welded mouth 3 seam 9, also perpendicular to the longitudinal
direction, for closing a mouth 3 of the package 32. The internal
venting means 10 and external venting means are located between the
place of the bottom seam 25 and the place of the mouth seam 26 and
preferably as far from both as possible, at least as far from both
where it is assured that the vent 5 is freely projecting into the
filling-space 15 rather than being distorted by any of the bottom 4
seam 9 and mouth 3 seam 9. The external venting means are
constituted by pressure-selective seam portions 16 in the proximal
seam 24 (see FIG. 4c), in which the welded surface parts of the
wall 2 were treated with Corona discharge to an extent suitable for
providing the pressure-selective seam portions 16 with a reduced
degree of bonding sufficient to allow gas 29 to escape in response
to a suitable predetermined pressure. The suitable extent can, for
example, be found with trial and error at any given application.
The internal venting means 10 are constituted by perforation
openings penetrating through the air-channel side-walls 45,
preferably nearer to the proximal seam 24 than to the distal seam
23 (see FIG. 4e). The openings constituting the external venting
means are formed in a staggered, offset manner in relation to the
openings constituting the internal venting means 10.
Example 5
A Packaging Container
[0108] Reference is made to the figures, especially to FIGS. 5a to
5e. This example packaging container is an endless tube 44 for FFS
packaging and differs from the container of Example 4 in that the
internal venting means 10 are constituted by openings penetrating
through the distal seam 23, the openings constituted by
interruptions in the welding of the distal seam 23. In the
interruptions embossed spacer projections 21 are provided for
keeping the openings free for a gas-conducting. The vent 5 is
provided with a relatively lower projection height 22 at the
interruptions and with a relatively larger projection height 22
elsewhere.
Example 6
A Packing Method
[0109] Reference is made to the figures, especially to FIG. 6 to 7.
The granular product 27, provided, is a cement based dry adhesive
powder, containing, among others, quartz sand, and with a total
cement content of about 30 mass percent. At least about 1 mass
percent of the adhesive powder has a granule size below 5 microns.
At least about 10 mass percent of the adhesive powder has a granule
size below 150 microns. In our separate test, such adhesive powder
proved suitable to be mixed with air and thereby to be rendered
into an aerated state in which an apparent density of the adhesive
is about 79% of its apparent density in a fully compacted state
thereof. We found that 120 seconds after the aerated adhesive
powder was put at rest, its apparent density was still far lower
than 87% of its apparent density in its fully compacted state. For
producing the package 32, a packaging bag 1 according to Example 1
is provided. As it is shown in FIG. 6a., the bag 1 is kept
suspended and propped up with its open mouth 3 looking upwards. 25
kg's of the granular product 27 is prepared in a hopper 28 for
filling. It is a solid state material in the hopper 28. As the
granular product 27 is made to drop from the hopper 28, it
immediately is mixed with gas 29 (air) and thereby a fluidized
filling mixture, i.e. a fluid 30 is provided, having an apparent
density which is about 79% of the apparent density of the fully
compacted adhesive powder. The fluid 30 is filled into the
packaging bag 1 through its open mouth 3. Referring now to FIG.
6b., after the filling, the open mouth 3 of the bag 1 is closed
with a cross seam 9 by welding means 31. Under the cross seam 9,
there is a small quantity of gas 29 in the bag 1 whose pressure is
the same as the ambient atmospheric pressure. This could be
performed in an FFS apparatus. Then, as can be seen in FIG. 6c.,
essentially without delay the produced package 32 is released from
the suspended and supported state and placed, in an essentially
vertical orientation, onto a horizontal conveyor 33 on which it is
started to immediately be conveyed in a horizontal
conveyor-direction 34. Then, as illustrated in FIG. 6d., with a
fixed tossing bar 35 positioned above the conveyor 33, the package
32 is tossed, moved in a tossing direction 36, into a horizontal
orientation and is caused to lie on the conveyor 33 in a suitable
venting orientation with its vent 5 being in its top bag wall panel
37 (see FIG. 6e.). Here, and further downstream, the conveyor 33 is
provided with a vibrator 38 underneath, for subtly vibrating the
package 32 for an enhancing of a separation of its gas 29 and solid
contents. This way the homogeneous fluid 30-state contents of the
package 32 are rearranged, i.e. redistributed in the bag 1
approximately uniformly, and thereby the package 32 is reshaped
into a reshaped package 32 of an inflated pillow-like shape (see
FIG. 6e.). This reshaping causes the volume of the package 32 to
somewhat decrease and the inner pressure of the package 32 to
somewhat increase. Thereby in the package 32 overpressure is
provided which can be recognized from its top bag wall panel 37
being taut enough. Now turning to FIG. 6f., at least for 35 seconds
(the pressure-keeping time) from this pressurizing of the package
32, the pressure-selective seam portions 16 of the bag 1 withstand
the overpressure provided in the package 32, by preventing any gas
29 from escaping from the package 32, as in the absence of any
external squeezing of the package 32. During the said 35 seconds
the lying package 32 is kept in motion in the conveyor-direction 34
on the conveyor 33, exposed to subtle vibration from underneath.
During this period of time the granular product 27 contents within
the package 32 largely separate from the gas 29 (air) contents, the
granular product 27 settling and compacting at the lowest part of
the package 32 and the gas 29 gathering, in a form of a flat bubble
of purer and purer air, above the solid-state granular product 27,
the two separated by a phase border 39 getting more and more
definite by time. During the said 35 seconds (as settling time) the
package 32 is kept free from external squeezing. Thereafter, in
order of producing the compacted package 32, essentially full of
solid state granular product 27, as illustrated in FIG. 6h, the
package 32 is (as can be seen in FIG. 6g.) externally squeezed by,
on the one hand, compressing its two opposed sides horizontally
with lateral conveyors (horizontal compressing and lateral
conveyors not shown in the figure) and, on the other hand, by
pressing essentially its whole top bag wall panel 37 downwards,
with an upper squeezing-conveyor 40. Thereby the top bag wall panel
37 comprising the vent 5 is pressed to, and abutted with, the top
surface 41 of the solid bulk of the granular product 27 contents in
the bag 1. The circumstances of the squeezing and venting are
illustrated in more details in FIG. 7, as follows. In the bag 1,
the vent 5 comprises (also see FIG. 1) a region of the flexible
plastic wall 2, which is now in the top bag wall panel 37, having
an interior wall 11 and an exterior wall 12. The interior wall 11
(which separates the air-channel 6 and the inner filling-space 15
of the bag 1) is free of openings penetrating therethrough.
Instead, internal venting means 10, being openings for conducting
gas 29 from the filling-space 15 of the container into the
air-channel 6, i.e. between the interior 11 and exterior walls 12
of the vent 5, are comprised of interruptions of the weld line in
the welded seam 9 separating the inner filling-space 15 of the bag
1 from the air-channel 6. When the top bag wall panel 37 is pressed
down, the interior wall 11 of the vent 5 is abutted on the top
surface 41 of the granular product 27. This top surface 41 is, by
this time of abutting, relatively compact, densified, which
prevents the abutting interior wall 11 from too much immersing in
it. A space 42, between the inner surface 8 of the top bag wall
panel 37 and the top surface 41 of the granular product 27 is
maintained with the help of the interior wall 11 and the fibrous
filter 13 in the air-channel 6 the fibrous filter 13 simultaneously
also acting as spacer means in the opening. In the maintained space
42, purified gas 29 can, in response to the internal pressure of
the package 32 being increased by the external squeezing, flow, in
an air-flow direction 43, staying above the top surface 41 of the
granular product 27, from the air bubble in the top range of the
package 32 directly into the air-channel 6 through the said
openings constituting internal venting means 10.
Example 7
A Packing Method
[0110] Reference is made to the figures, especially to FIG. 6, FIG.
7a and FIG. 8. This example method differs from the method of
Example 6 in that the packaging bag 1 according to Example 4 is
provided for the packing. The circumstances of the squeezing and
venting are illustrated in more details in FIG. 7a and FIG. 8, as
follows. In the bag 1, the vent 5 projects sharply into the
filling-space 15 of the bag 1 and comprises (also see FIG. 4) a
distal seam 23 and a proximal seam 24, the two, together with the
air-channel side-walls 45, defining the air-channel 6. The internal
venting means 10 are constituted by perforation openings
penetrating through the air-channel side-walls 45, nearer to the
proximal seam 24 than to the distal seam 23. When the top bag wall
panel 37 is pressed down, the distal seam 23 of the vent 5 is
abutted on the top surface 41 of the granular product 27. This top
surface 41 is, by this time of abutting, relatively compact,
densified, which prevents the abutting distal seam 23 from too much
immersing in it. A space 42, between the inner surface 8 of the top
bag wall panel 37 and the top surface 41 of the granular product 27
is maintained with the help of the vent 5. In the maintained space
42, purified gas 29 can, in response to the internal pressure of
the package 32 being increased by the external squeezing, flow, in
air-flow directions 43, staying above the top surface 41 of the
granular product 27, from the air bubble in the top range of the
package 32 directly into the air-channel 6 through the said
openings constituting internal venting means 10.
Example 8
A Packing Method
[0111] Reference is made to the figures, especially to FIG. 6, FIG.
7a and FIG. 9. This example method differs from the method of
Example 6 in that the packaging bag 1 according to Example 5 is
provided for the packing. The circumstances of the squeezing and
venting are illustrated in more details in FIG. 7a and FIG. 9, as
follows. In the bag 1, the vent 5 projects sharply into the
filling-space 15 of the bag 1 and comprises (also see FIG. 5) a
distal seam 23 and a proximal seam 24, the two, together with the
air-channel side-walls 45, defining the air-channel 6. The internal
venting means 10 are constituted (also see FIG. 5e) by openings
penetrating through the distal seam 23, the openings constituted by
interruptions in the welding of the distal seam 23. When the top
bag wall panel 37 is pressed down, the distal seam 23 of the vent 5
is abutted on the top surface 41 of the granular product 27. In the
maintained space 42, purified gas 29 can, in response to the
internal pressure of the package 32 being increased by the external
squeezing, flow, in air-flow directions 43, staying above the top
surface 41 of the granular product 27, from the air bubble in the
top range of the package 32 directly into the air-channel 6 through
the said openings constituting internal venting means 10.
Comparative Example 9
A Comparative Example from the Prior Art
[0112] Reference is made to FIG. 10. The circumstances of the
squeezing and venting in typical a prior-art solution are
illustrated in details, for comparison, in FIG. 10, as follows. In
a typical prior-art venting process the package 32 comprises a
typical prior-art vented bag 1, and has the vent 5 in its top bag
wall panel 37. The typical prior-art vent 5 has an interior wall 11
and an exterior wall 12. The interior wall 11 (which separates the
air-channel 6 from the inner filling-space 15 of the bag 1)
comprises, as internal venting means 10, perforation openings
penetrating therethrough. In the typical traditional prior-art
process the venting starts latest immediately after the filling and
reshaping/flattening, as soon as an overpressure is started to be
built up in the bag 1, at which moment the bag 1 is full of
stirred-up fluid 30. In a process, spontaneously driven by the
overpressure in the bag 1 and especially driven, in addition, by an
additional typical immediate aggressive external squeezing by a
squeezing-conveyor 40, the homogeneous fluid 30 is driven, in an
air-flow direction 43, out of the filling-space 15 of the bag 1
into the air-channel 6 through the perforation openings
constituting internal venting means 10, which loads the air-channel
6 with fluid 30 eventually leaving residual pollution in the
air-channel 6, thus illustrating the drawback of the prior art.
Comparative Example 10
A Comparative Example from the Prior Art
[0113] Reference is made to FIG. 11. The circumstances of the
squeezing and venting in another prior-art process are illustrated
in details, for comparison, in FIG. 11, as follows. The package 32
comprises a prior-art vented bag 1, and has the vent 5 in its top
bag wall panel 37. The prior-art vent 5 has an exterior wall 12 and
an interior wall 11, the latter with perforation openings
penetrating therethrough, constituting internal venting means 10.
The figure shows what happens if the contents of the package 32 are
already somewhat separated at the time of the illustrated venting.
In response to an external squeezing by the squeezing-conveyor 40,
the perforated interior wall 11 is abutted on the top surface 41 of
the granular product 27. In response to the overpressure, gas 29
can only flow, from the air bubble in the top range of the package
32 into the air-channel 6, in an air-flow direction 43 through a
fluid 30 layer under the top surface 41 of the granular product 27,
through the said openings constituting internal venting means 10,
which loads the air-channel 6 with fluid 30 eventually leaving
residual pollution in the air-channel 6, thus illustrating the
drawbacks of the prior art.
Example 11
A System (Package)
[0114] Reference is made to the figures and especially to FIG. 6c
and FIG. 12. A polyethylene packaging bag 1 contains 75 kg's of
Portland cement mixed with air. One panel of the flexible
polyethylene wall 2 includes a vent 5. The vent 5 comprises an
air-channel 6 being a lengthwise, overlapped region of the wall 2
having an interior wall 11 and an exterior wall 12. As internal
venting means 10, the vent 5 has perforations in the interior wall
11 for conducting air into the air-channel 6. Internal venting
means 10 can, alternatively, be formed as interruptions in the seam
9 separating the air-channel 6 from the internal filling-space 15
of the bag 1 (see the bag in FIG. 12). The bag 1 is an FFS-made bag
1, and is defined by crosswise (mouth--3 and bottom--4) welding
seams 9. One of the film surfaces welded in both of the sections of
the crosswise welding seams 9 adjacent to the air-channel 6, the
weakened, pressure-selective seam portions 16, have a pretreat
print layer of a separating lacquer which could be, for example, of
the type WP74-076D from Company XSYS Print Solution, Germany. The
layer thickness of the lacquer layer is formed to adapt the
weakened seam 9 to withstand the internal overpressure of the bag 1
up to 1.0 bar pressure. This layer, its shape and thickness, could
be formed by trial and error, for example. Both of the said
weakened, pressure-selective seam portions 16 open up in response
to the inner pressure exceeding the one bar predetermined limit and
conduct air from the air-channel 6 to the outside 7 of the bag 1.
Such a pressure can be formed in the package 32 by external
squeezing, prior to which the closed package 32 can be handled,
including dropping, turning, laying down, vibrating, flattening etc
without losing air, since the form of the package 32 is suitably
selected, with respect to the contents, in order of preventing the
inner pressure of spontaneously reaching the one bar limit without
a definite external squeezing. The cement contents could be in an
aerated state in which its apparent density is about 79% of its
apparent density belonging to the fully compacted state
thereof.
Example 12
A Packaging Container
[0115] Reference is made to FIG. 12. This example packaging
container is a flat bag 1 FFS tube section, closed with cross
welding at its bottom 4 and mouth 3. The bag 1 has been formed from
a polyethylene film wall 2 that has been folded around a
longitudinal direction, such that a vent 5, in the form of a region
with an interior wall 11 and an exterior wall 12 (acting as
air-channel-walls defining an air-channel 6 therebetween), is
formed between two overlapping outer edges 14 of the film wall 2.
Two seams 9 extending in longitudinal direction fix the outer edges
14 of the film wall 2 to the film wall 2 portion overlapped
therewith. The two longitudinal seams 9 are welded seams. The
welding of one of the longitudinal seams 9 ("inner seam 9", being
the leftmost one of the two longitudinal seams 9 in FIGS. 12a and
12b) which is adjacent to the filling-space 15 of the bag 1, has
interruptions, forming the internal venting means 10 (see FIG.
12c). The welding of the other longitudinal seam 9 is
uninterrupted. The surface of the interior wall 11 adjacent the
air-channel 6 is provided with embossed projection 21 spacers.
Also, the one, of the two overlapping edges 14 of the film wall 2,
which is adjacent the inner seam 9 is provided with embossed
projection 21 spacers that keep the internal venting means 10 open.
One (alternatively: both) of the film surfaces welded in both of
the sections of the crosswise welding seams 9 adjacent to the
air-channel 6, the weakened, pressure-selective seam portions 16,
have a pretreat print layer of a separating lacquer which could be,
for example, of the type WP74-076D from Company XSYS Print
Solution, Germany. The layer thickness of the lacquer layer is
formed to adapt the weakened seam 9 to withstand an internal
overpressure of the bag 1 up 1.0 bar pressure. This layer, its
shape and thickness, could be formed by trial and error, for
example. Alternatively, we used a water based lacquer of the WP
series manufactured by Torda Ink AB, Sweden. The lacquer is
available from G.A.C.H. kft, Hungary and is marketed by the
manufacturer, specifically for the beverage packaging industry,
under the trade name "Easy Opening Lacquer" on the public internet
address
"http://www.torda.com/page.asp?Menu=3&SubMenu=9&h=Easy+opening+lacquer"
where it is alleged to be "a smart and user friendly solution that
seals openings that must be opened easily". We made trial-and-error
printings and weldings and found that both parameters, the
thickness of the printed lacquer layer and the welding energy (one
or both of the welding time and welding temperature), can be used
together or alone, to form the reduced bonding strength selected as
desired from a definitely wide range, reduced in relation to the
maximum welding strength achievable without separation efforts. We
experienced that, not surprisingly, with one given print sample the
bonding strength can be reproducibly set to values from very weak
to markedly strong, with using different welding energies while all
of these welding energies proved to produce industrially applicable
bag-closing-strength weldings on film surfaces free of lacquer.
Bonding strength of the lacquered polyethylene surfaces proved to
be much more sensitive to the welding energy than the un-lacquered
polyethylene film. We made the present example bag 1 with different
welding energies applied to the crosswise welding bar and each of
the resulting bags 1 had apparently uniformly strong package
closing at the mouth 3 and bottom 4 and they apparently only
differed in the bonding strengths (and thereby in the predetermined
limit pressures) of their pressure-selective seam portions 16.
Alternatively, the external venting means could also be provided
with additional pressure-selective adhesive layer(s) adjacently to
the welded pressure-selective seam portions 16 in order of further
improving their behavior, for example their re-closure after some
venting.
INDEX OF SIGNS OF REFERENCE
[0116] 1 bag [0117] 2 wall [0118] 3 mouth [0119] 4 bottom [0120] 5
vent [0121] 6 air-channel [0122] 7 outside [0123] 8 inner surface
[0124] 9 seam [0125] 10 internal venting means [0126] 11 interior
wall [0127] 12 exterior wall [0128] 13 fibrous filter [0129] 14
edge [0130] 15 filling-space [0131] 16 pressure-selective seam
portion [0132] 17 Corona-treated surface [0133] 18 outer
air-channel-wall [0134] 19 inner air-channel-wall [0135] 20
lacquered surface [0136] 21 projection [0137] 22 projection height
[0138] 23 distal seam [0139] 24 proximal seam [0140] 25 place of
bottom seam [0141] 26 place of mouth seam [0142] 27 granular
product [0143] 28 hopper [0144] 29 gas [0145] 30 fluid [0146] 31
welding means [0147] 32 package [0148] 33 conveyor [0149] 34
conveyor-direction [0150] 35 tossing bar [0151] 36 tossing
direction [0152] 37 top bag wall panel [0153] 38 vibrator [0154] 39
phase border [0155] 40 squeezing-conveyor [0156] 41 top surface
[0157] 42 space [0158] 43 air-flow direction [0159] 44 tube [0160]
45 air-channel side-wall
* * * * *
References