Note: Descriptions are shown in the official language in which they were submitted.
' CA 02337624 2001-02-21
SEAM CONFIGURATION FOR A FLEXIBLE CONTAINER
TECHNICAL FIELD
A seam configuration for a flexible container and a method for forming
the seam configuration.
BACKGROUND OF THE INVENTION
Flexible containers are commonly used for the handling, storage and
transportation of flowable materials such as particulate substances in
granular or
powder form. Flexible containers are also referred to as "bulk containers",
"flexible
intermediate bulk containers" or "FIBCs". A flexible container may hold up to
a tonne
or more of a flowable material.
A flexible container typically consists of at least a continuous side wall
and a bottom end wall. It may also include a top end wall. One or both of the
end
walls may also be fitted with a spout to facilitate either filling or emptying
of the
flexible container. The side wall of a flexible container may be formed from a
tubular
blank of material or may be formed from one or more panels of material which
are
joined together to create the continuous side wall.
A flexible container is typically made from a synthetic material such as
polyethylene, polypropylene or some other polymer. The synthetic material may
be in
the form of a film material or may consist of a woven material formed by
weaving
together individual strands of synthetic material.
Typically the synthetic material is a woven material which is formed into
panels or sheets which are joined together to create the flexible container.
Usually these
panels of synthetic woven material are joined together by stitching.
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Woven material is generally preferred as a material for constructing
flexible containers because it has relatively high strength in comparison with
film
materials and is relatively economical to produce and use. Stitching is
generally
preferred for use in creating seams in flexible containers because stitching
provides a
relatively strong connection between panels in comparison with techniques such
as
fusing (i.e., gluing, melting, soldering or welding).
Stitching is also preferred for use in creating seams in woven materials
because it has been found that the use of fusing techniques with woven
materials may
result in the seam exhibiting a "zippering" effect in which the seam fails
catastrophically in response to stresses exerted on the seam. A similar
"zippering"
effect can result where seams in film materials are created by stitching, thus
making
stitched seams generally unsuitable for use with film materials.
Flexible containers consisting of stitched panels are generally satisfactory
for transporting and storing relatively coarse grained flowable materials.
Such
containers are, however, less suitable for transporting and storing more fine
grained
materials which are able to pass either through the stitch holes or through
the woven
material itself. The presence of stitch holes and the woven material itself
may also
facilitate the entry of contaminants such as insects, water and other liquids
into the
flexible container.
Where leakage out of or into a flexible container is a concern, a more
"hygienic" design of flexible container may be called for. A challenge in
fabricating
flexible containers is to achieve a design which is both suitably hygienic and
strong
enough to contain large amounts of flowable material. This challenge is made
more
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difficult because of the inherent limitations in the techniques used for
creating seams in
woven material and film material, as discussed above.
One option for preventing leakage from or into a stitched flexible
container is to line the interior of the stitched flexible container with a
liner.
A liner is usually constructed of a film which is made from a synthetic
material such as polyethylene, polypropylene or some other polymer. The liner
may be
made from a continuous tubular blank of film or may be made from panels or
sheets
which are joined together. Panels of synthetic liner material are usually
joined by
fusing the panels together with heat or by some other method which does not
require
stitching, since stitching will introduce holes into the liner material and
may also make
the liner prone to a "zippering" effect.
The primary advantage of a lined flexible container is that the strength
and durability of the flexible container is derived from the stitched woven
material
which forms the flexible container itself, while the hygienic properties of
the flexible
container are derived from the liner, which itself does not need to exhibit
significant
strength. In fact, although a flexible container is typically reusable, a
liner is often used
only once, with the result that typically the liner need only be strong and
durable
enough to withstand a single use of the flexible container.
One disadvantage of a lined flexible container is that although the
presence of a liner may render a stitched flexible container more hygienic
without
compromising its strength and durability, it may also add considerable cost to
the
flexible container, particularly if the liner is replaced following each use
of the flexible
container.
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A second option for at least minimizing leakage from or into a stitched
flexible container is to coat the interior surfaces of a woven material with a
sealant
material in order to close off the interstices inherent in the woven material.
The sealant
material may be comprised of a film coating, a liquid coating, or any other
material
which will close off the interstices.
The primary advantage of using a coated woven material in a flexible
container is that it can provide a relatively hygienic flexible container
without the
expense of a liner and the fabrication costs associated therewith.
One major disadvantage of a flexible container constructed of a coated
woven material is that such containers are typically fabricated by stitching
in order to
provide the necessary strength for the container and the coating will not
eliminate
leakage at the stitch holes. As a result, flexible containers constructed of a
coated
woven material are not fully effective for eliminating leakage from or into
the flexible
container.
The best option currently available for creating a fully effective hygienic
flexible container is therefore to combine a woven outer flexible container
having
stitched seams with an inner liner having fused seams.
The prior art includes numerous examples of technologies which are
directed at optimizing the fabrication of either a flexible container or a
liner. Some of
these technologies are directed at minimizing fabrication costs by minimizing
the
number of panels which must be joined together to form either the flexible
container or
the liner. Some of these technologies describe seam configurations for
flexible
containers which are directed at ensuring the strength of a seam or ensuring
the sealing
of a seam.
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France Patent Publication No. 2,634,468 A1 (Dafour) describes a flexible
container which is formed from four identical panels of material and which is
lined with
a liner which is formed from a tubular blank of film material. Stitched seams
at each of
the four corners of the flexible container both join the panels of the
flexible container
and hold the liner in place within the flexible container. Welds are also
provided in the
liner adjacent to the locations where the liner is stitched to the flexible
container, thus
isolating the interior of the liner from the stitching which might otherwise
cause leakage
of the liner.
U.K. Patent Application No. 2,103,576 A (Nattrass) describes a seam
configuration for a flexible container which is directed at accommodating a
lifting loop.
The seam configuration is formed by folding back and stitching a "terminal
strip" in
each of two panels to be joined such that the terminal strip forms an open
ended edge
pocket on each panel. The fold edges of the two panels are then stitched
together in
overlapping fashion.
U.S. Patent No. 5,139,346 (Watanabe et al) and U.S. Patent No. 5,181,900
(Watanabe et al) both describe a flexible container which is fabricated from
four
identical assembly sheets. Each of the four assembly sheets is constructed of
a main
sheet, an inlet sheet and an outlet sheet. A stitched hem is formed along the
longitudinal edges of each assembly sheet. The assembly sheets are then
stitched
together along the stitched hem.
U.S. Patent No. 5,618,254 (Derby), U.S. Patent No. 5,746,862 (Derby), U.S.
Patent No. 5,759,144 (Derby) and U.S. Patent No. 5,984,850 (Derby) each
describe a liner
for a flexible container which is fabricated using an automated process. In
the
automated process, a continuous web of gusseted liner material consisting of a
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polymeric film is advanced along a predetermined path where it is
simultaneously cut
and resealed by heated air using a fusing technique. The apparent purpose of
the
invention in Derby is to provide a relatively efficient process for
fabricating liners for
flexible containers.
U.S. Patent No. 4,790,029 (LaFleur et al) and U.S. Patent No. 4,798,572
(LaFleur et al) both describe a flexible container which is fabricated in an
automated
process which is similar in some respects to the process described in Derby.
In LaFleur,
an elongate web of flexible material is severed along a zig zag line having
substantially
straight segments defining the sides of an isosceles triangle. The triangle
portions of the
flexible material are then joined together to form seams either by stitching
(in the case of
a woven material) or by heat sealing (in the case of a film material).
None of these prior art references are directed at the potential for utilizing
fusing techniques to create a seam in a woven material. Furthermore, none of
these
prior art references are directed at a hygienic flexible container which is
constructed
from a woven material but does not include an inner liner.
SUMMARY OF THE INVENTION
The present invention is directed at a seam configuration for a flexible
container, which seam configuration comprises a first hem, a second hem and a
fused
primary seam. The present invention is also directed at a method for forming
the seam
configuration.
The seam configuration of the present invention utilizes the fused primary
seam to eliminate one source of leakage from or into the flexible container.
In a
preferred embodiment, the flexible container can be constructed from a coated
woven
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material in order to seal the interstices in the woven material and thus
eliminate a
second source of leakage from or into the flexible container.
In one method aspect, the invention is a method of forming a seam
configuration in a flexible container, the seam configuration comprising a
primary seam
adjacent to a first peripheral edge and a second peripheral edge in a flexible
material
comprising the flexible container, the method comprising the following steps:
(a) forming a first fold in the flexible material adjacent to the first edge
in
order to create a first hem, wherein the first hem is comprised of a first
hem outer surface and a first hem inner surface;
(b) forming a second fold in the flexible material adjacent to the second edge
in order to create a second hem, wherein the second hem is comprised of a
second hem outer surface and a second hem inner surface;
(c) positioning the first hem outer surface and the second hem outer surface
so that they are contiguous; and
(d) fusing together the first hem outer surface and the second hem outer
surface to form the primary seam.
In another aspect, the invention is a seam configuration for a flexible
container, comprising:
(a) a first hem associated with a first peripheral edge in a flexible material
comprising the flexible container, wherein the first hem has a first hem
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length and wherein the first hem is comprised of a first hem outer surface
and a first hem inner surface;
(b) a second hem associated with a second peripheral edge in the flexible
material, wherein the second hem has a second hem length and wherein
the second hem is comprised of a second hem outer surface and a second
hem inner surface; and
(c) a primary seam between the first hem outer surface and the second hem
outer surface, wherein the primary seam has a primary seam length and
wherein the primary seam is formed by fusing together the first hem outer
surface and the second hem outer surface.
The term "fusing" as used herein includes any technique which is effective
to provide a chemical or physical bond or connection between the first hem
outer
surface and the second hem outer surface without perforating the flexible
material. For
example, the fusing technique may include the use of an adhesive, the use of
heat, or a
combination of techniques.
The flexible material comprising the flexible container may be comprised
of any material which is suitable for use in a flexible container and which is
compatible
with the fusing technique used for creating the primary seam. The flexible
material
may also be comprised of more than one material, in which case the different
materials
should also be compatible with each other.
For example, the flexible material may be comprised of a natural or
synthetic woven material or film material. If the flexible material is a woven
natural
material derived from such organic materials as hemp (i.e., burlap), the
fusing
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technique used to form the primary seam preferably utilizes a glue which is
suitable for
gluing the organic material, since it may not be possible effectively to fuse
such
materials through the application of heat.
Preferably the flexible material comprising the flexible container is a
synthetic material comprising an organic polymer. Although any such organic
polymer
material which is suitable for use in a flexible container may be used,
preferred organic
polymers include polyethylene and polypropylene, both of which are
conventionally
used in the fabrication of flexible containers and are capable of being fused
through the
application of heat.
The flexible material may be comprised of a woven material or a film
material. Preferably the flexible material is comprised of a woven material
because of
the superior strength characteristics of woven materials. Where leakage from
or into
the flexible container is a concern, the woven flexible material is preferably
coated or
impregnated with a sealant to seal the interstices in the woven material.
Any mechanism or technique for sealing the interstices in the woven
material may be used. Preferably the interstices in the woven flexible
material are
sealed by coating the woven material with at least one layer of a film
material as a
sealant so that the flexible material is comprised of a layer of woven
material and a
layer of film material.
The flexible container may be of any shape and may be constructed from
any number of panels of flexible material. Preferably the flexible container
is
constructed from four identical panels which are joined together along four
seam
configurations to form the flexible container so that it has a generally
rectangular cross
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section. As a result, preferably each seam configuration connects a first
panel of flexible
material with a second panel of flexible material.
The flexible container may or may not be equipped with one or both of a
fill spout and a discharge spout. Preferably the flexible container includes
both a fill
spout and a discharge spout. These spouts are preferably integrally formed
with the
four panels of flexible material making up the flexible container so that each
seam
configuration can be formed in a single plane, thus simplifying the
fabrication process
for the flexible container.
The first hem has a first hem length and the second hem has a second hem
length. The hem lengths may be any length relative to the lengths of the
peripheral
edges, so long as the resulting seam is strong enough to withstand the
stresses exerted
upon it in service. Preferably, however, the first hem length is substantially
equal to the
length of the first peripheral edge and preferably the second hem length is
substantially
equal to the length of the second peripheral edge.
The formation of the first fold in the flexible material results in the first
hem inner surface facing a first adjacent portion of the flexible material.
Similarly, the
formation of the second fold in the flexible material results in the second
hem inner
surface facing a second adjacent portion of the flexible material.
Preferably the first hem inner surface is connected with the first adjacent
portion along the first hem length to form a first hem connection having a
first hem
connection length and preferably the second hem inner surface is connected
with the
second adjacent portion along the second hem length to form a second hem
connection
having a second hem connection length.
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The hem connection lengths may be any length relative to the hem
lengths. Preferably, however, the hem connection lengths are substantially
equal to the
hem lengths in order to maximize the strength of the seam configuration.
Although the hem connections may be formed in any manner, techniques
which create perforations in the flexible material are preferably avoided. For
example,
stitching the hem connections will introduce holes into the flexible material
which may
cause leakage from or into the flexible container. As a result, the hem
connections are
preferably formed by fusing together the hem inner surfaces with the adjacent
portions.
Most preferably the hem connections are formed by performing a fusing step
which is
similar or identical to the fusing step which is used to form the primary
seam.
The primary seam is formed by fusing together the first hem outer surface
and the second hem outer surface. The purpose of the primary seam is twofold.
First,
the primary seam connects the panels which make up the flexible container.
Second,
the primary seam provides a sealing function which prevents leakage from or
into the
flexible container.
Where the flexible material is comprised of an organic polymer, the fusing
step is preferably comprised of heating the flexible material so that fusing
is effected
through melting, soldering or welding.
The flexible material may be heated in any manner which will facilitate
the fusing step. Preferably the fusing step is comprised of heating the
flexible material
with a stream of heated gas. More preferably the stream of heated gas is
supplied by a
nozzle. Most preferably the fusing step is comprised of inserting the nozzle
between
the first hem outer surface and the second hem outer surface and passing the
heated gas
through the nozzle.
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The fusing step is preferably comprised of heating the flexible material
along the first hem length and the second hem length to form the primary seam
so that
it has a primary seam length. In the preferred embodiment, the fusing step is
comprised of moving the nozzle along the first hem length and the second hem
length
to form the primary seam so that it has a primary seam length.
The primary seam length may be any length relative to the hem lengths.
Preferably the primary seam length is substantially equal to the hem lengths.
The flexible container defines both an interior container space and an
exterior container space. As used herein, the term "interior container space"
refers to
the inside volume of the flexible container and the term "exterior container
space"
refers to the space outside of the flexible container. .Flowable material will
be contained
within the interior container space.
The seam configuration may be oriented so that the first edge and the
second edge are located either within or outside the interior container space.
Similarly,
the fusing step may be performed either from the interior container space or
from the
exterior container space.
Preferably the first edge and the second edge are located within the
interior container space. Preferably the fusing step is performed from the
exterior
container space in order to simplify the fabrication of the flexible
container.
The seam configuration may optionally be further comprised of a
secondary seam connecting the first hem outer surface and the second hem outer
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surface. The purpose of the secondary seam is to reinforce the primary seam
and thus
enhance the strength of the seam configuration.
The secondary seam may be formed by any technique for creating a seam,
including fusing techniques as well as riveting, stapling and stitching
techniques.
Preferably the secondary seam is formed so that the integrity of the primary
seam is not
compromised. In particular, the secondary seam should preferably not introduce
perforations into the flexible container in locations which will enable
leakage from or
into the flexible container.
The secondary seam has a secondary seam length. Preferably the
secondary seam is substantially parallel to the primary seam. The secondary
seam may
be any length relative to the primary seam. Preferably, however, the secondary
seam
length is substantially equal to the primary seam length so that the secondary
seam can
reinforce the primary seam along substantially the entire length of the
primary seam.
Preferably, the secondary seam is comprised of stitching together the first
adjacent portion, the first hem, the second hem and the second adjacent
portion.
Stitching is preferred for the secondary seam because of the superior strength
characteristics of stitched seams in woven materials.
Stitching will, however, create stitch holes in the flexible material. As a
result, preferably the primary seam extends further toward the interior
container space
than does the secondary seam, so that the fused primary seam will provide a
seal or
barrier between the interior container space and the secondary seam to prevent
leakage
from or into the flexible container through the stitch holes of the secondary
seam.
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In addition, preferably the hem connections are formed by fusing and
extend further toward the interior container space than does the secondary
seam, so
that the fused hem connections also provide a seal or barrier between the
interior
container space and the secondary seam to prevent leakage from or into the
flexible
container through the stitch holes of the secondary seam.
In the preferred embodiment, the first hem connection length, the second
hem connection length, the primary seam length and the secondary seam length
are all
substantially equal. In addition, in the preferred embodiment the first hem
connection,
the second hem connection, the primary seam and the secondary seam are
substantially
parallel to each other. This design provides a seam configuration having
maximum
strength characteristics while minimizing the potential for leakage from or
into the
flexible container through the seam configuration.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the invention will now be described with reference to the
accompanying drawings, in which:
Figure 1 is a plan view of a panel of flexible material according to a
preferred embodiment of the invention.
Figure 2 is a transverse section view of the panel of flexible material of
Figure 1, taken along line 2-2 of Figure 1.
Figure 3 is a pictorial view of a flexible container constructed according to
a preferred embodiment of the invention.
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Figure 4 is a transverse section view of the flexible container of Figure 3,
taken along line 4-4 of Figure 3.
Figure 5 is a detail section view of a seam configuration from Figure 4,
taken at location 5 of Figure 4.
DETAILED DESCRIPTION
The present invention relates to a seam configuration for a flexible
container and to a method for creating the seam configuration. The invention
also
relates to a flexible container which includes the seam configuration and to a
method
for fabricating the flexible container.
Referring to Figures 3 and 4, the invention is directed broadly at the
construction of a flexible container (20). The flexible container (20) may be
of any shape,
may be constructed of any number of panels of material, and each of the panels
making
up the flexible container (20) may be of any shape as may be dictated by the
specific
design of the flexible container (20).
In the preferred embodiment the flexible material is comprised of woven
polyethylene or woven polypropylene, but other flexible materials or
combinations of
flexible materials may be used. If the flexible container (20) is intended for
use in
circumstances where leakage from or into the flexible container (20) is a
concern, the
flexible material may further comprise a sealant for sealing the interstices
in the woven
material. The sealant is preferably comprised of coating the flexible material
with at
least one layer of film material so that the flexible material is comprised of
a layer of
woven material and a layer of film material.
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Referring to Figure 3, in the preferred embodiment the flexible container
(20) has a generally rectangular cross-section and includes a side wall (22),
a top end
wall (24), a bottom end wall (26), a fill spout (28) and a discharge spout
(30). Referring
to Figures 3 and 4, the flexible container (20) is constructed of four
identical panels
(32,34,36,38) of a flexible material which are connected together using the
seam
configuration (40) of the invention.
Referring to Figures 1 and 2, representative panel (32) is comprised of a
side wall portion (42), a top end wall portion (44), a bottom end wall portion
(46), a fill
spout portion (48) and a discharge spout portion (50).
It can be seen that the general shape of the flexible container (20) will be
determined by the number of panels that are used to construct the flexible
container
(20) and by the relative dimensions of the side wall portion (32) of the
panels. Other
features of the flexible container (20), such as the existence and dimensions
of the fill
spout (28), the discharge spout (30) and the existence of the top end wall
(24) are
determined by the specific configuration of the individual panels
(32,34,36,38).
For example, the fill spout portion (48) of the panel (32) may be omitted if
the fill spout (28) is not required and the discharge spout portion (50) of
the panel (32)
may be omitted if the discharge spout (30) is not required. In addition, the
top end wall
portion (44) of the panel (32) may be omitted if the flexible container (20)
is to be open at
the top.
The panel (32) is defined longitudinally by side edges (52) which extend
along the entire length of the panel (32) from the fill spout portion (48) to
the discharge
spout portion (50). The lengths and orientations of the side edges (52)
through the
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various portions (42,44,46,48,50) of the panel (32) will determine many of the
features of
the flexible container (20).
In the preferred embodiment, the side edges (52) are preferably
substantially parallel to each other through the side wall portion (42) of the
panel (32) so
that the flexible container (20) has a substantially constant cross-section
through the
entire length of the side wall (22).
Through both the top end wall portion (44) of the panel (32) and the
bottom end wall portion (46) of the panel (32) the side edges (52) each
deflect obliquely
so that they converge at an angle of about 90 degrees relative to each other.
This
configuration facilitates the connection of the top end wall portion (44) of
the four
panels (32,34,36,38) to form the top end wall (24) of the flexible container
(20) and
facilitates the connection of the bottom end wall portion (46) of the four
panels
(32,34,36,38) to form the bottom end wall (26) of the flexible container (20).
Through both the fill spout portion (48) of the panel (32) and the discharge
spout portion (50) of the panel (32) the side edges (52) are preferably
substantially
parallel to each other so that the fill spout (28) and the discharge spout
(30) have a
substantially constant cross-section throughout their entire length.
Alternatively, if
either a tapered or flared fill spout (28) or discharge spout (30) is desired,
the side edges
(52) may be configured not to be parallel through either or both of the fill
spout portion
(48) or the discharge spout portion (50), as the case may be.
If the fill spout (28) is to be omitted from the flexible container (20), the
side edges (52) may converge to a point through the top end wall portion (44)
of the
panel (32). Similarly, if the discharge spout (30) is to be omitted from the
flexible
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container (20), the side edges (52) may converge to a point through the bottom
end wall
portion (46) of the panel (32).
Referring to Figures 1-5, the seam configuration (40) connects each of the
four panels (32,34,36,38) together along substantially the entire length of
the side edges
(52) to form the flexible container (20). In the preferred embodiment four
separate and
identical seam configurations (40) are utilized to construct the flexible
container. Each
seam configuration (40) in the preferred embodiment is a combination of a hem,
a
primary seam and a secondary seam.
Referring to Figures 1 to 5, each panel (32,34,36,38) is further comprised of
peripheral edges (54). Referring to Figure 1, to prepare the panel (32) for
creation of the
seam configuration (40), a hem (56) is created adjacent to each of the
peripheral edges
(54) by forming a fold in the flexible material adjacent to the peripheral
edge (54) and
coincident with the side edge (52). In order to create a smooth hem (56), it
may be
necessary to cut the flexible material at locations where the side edges (52)
changes
direction in order to avoid gathering up of flexible material at such
locations.
Each hem (56) is comprised of a hem outer surface (58) and a hem inner
surface (60). The hem inner surface (60) faces an adjacent portion (62) of the
flexible
material. Each hem (56) has a hem length which is substantially equal to the
length of
its associated peripheral edge (54).
The hem inner surface (60) is connected with the adjacent portion (62) of
the flexible material to form a hem connection (64). The hem connections (64)
may be
formed using any technique for forming seams, including riveting, stapling,
welding
and fusing techniques.
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In the preferred embodiment, the hem connection (64) is formed by
performing a fusing step to fuse together the hem inner surface (60) and the
adjacent
portion (62) to avoid creating perforations in the flexible material.
In the preferred embodiment this fusing step is performed by heating the
flexible material with a stream of heated gas supplied by a nozzle and moving
the
nozzle along the length of the panel (32) to form each hem connection (64) so
that it has
a hem connection length which is substantially equal to the length of its
associated hem
(56).
Referring to Figures 4 and 5, in the preferred embodiment the next step in
the creation of the seam configuration (40) is the formation of a primary seam
(66)
which is adjacent to a first peripheral edge (68) on one of the panels
(32,34,36,38) and a
second peripheral edge (70) on another of the panels (32,34,36,38) so that two
of the
panels (32,34,36,38) can be connected by the seam configuration (40).
Each primary seam (66) is formed by positioning a first hem outer surface
(72) on one of the panels (32,34,36,38) and a second hem outer surface (74) on
another of
the panels (32,34,36,38) so that they are contiguous, and then fusing together
the first
hem outer surface (72) and the second hem outer surface (74).
In the preferred embodiment, each primary seam (66) is formed by a
fusing step which is performed by heating the flexible material with a stream
of heated
gas supplied by a nozzle and moving the nozzle along the length of the
adjacent panels
(32,34,36,38) to form each primary seam (66) so that it has a primary seam
length which
is substantially equal to the length of its associated hems (56) and hem
connections (64).
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Referring to Figure 4, in the preferred embodiment, each primary seam
(66) is formed so that the peripheral edges (68,70) of the panels
(32,34,36,38) are located
within an interior container space (76) which is defined by the flexible
container (20). It
is believed that this configuration may provide greater strength for the
primary seam
(66) in comparison with a reverse configuration in which the peripheral edges
(68,70)
are located outside of the interior container space (76).
In addition, in the preferred embodiment, the fusing step for forming the
primary seam (66) is performed from an exterior container space (78) which is
defined
by the flexible container (20). Performing the fusing step in this manner may
simplify
the fabrication of the flexible container (20) and may be easier to automate
than if the
fusing step is performed from within the interior container space (76).
If the flexible container (20) is intended for use in circumstances where
leakage from or into the flexible container (20) is not a concern, the hem
connections
(64) and the primary seam (66) may be formed by stitching or by other
techniques
which may perforate the flexible material.
If the flexible container (20) is intended for use in circumstances where
very high stresses are likely to be experienced by the seam configuration
(40), each seam
configuration (40) may optionally include a secondary seam (80) for connecting
the first
hem outer surface (72) and the second hem outer surface (74). The secondary
seam (80)
may be formed using any technique for forming seams, including riveting,
stapling,
stitching and fusing techniques.
Referring to Figures 4 and 5, in the preferred embodiment the secondary
seam (80) is formed by stitching together the hems (56) and adjacent portions
(62) of
flexible material which are adjacent to the seam configuration (40). One or
more rows
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CA 02337624 2001-02-21
of stitching may be used to form the secondary seam (80). Stitching is
preferred for the
secondary seam (80) because of the superior strength characteristics of
stitched seams in
woven materials.
Since stitching will perforate the flexible material, both the primary seam
(66) and the hem connections (64) should extend further toward the interior
container
space (76) than does the secondary seam (80) if leakage from or into the
flexible
container (20) is a concern. This will ensure that the primary seam (66) and
the hem
connections (64) effectively "seal" the interior container space (76) from the
perforations
in the flexible material which are created by the secondary seam (80). This
will also
make it possible for the secondary seam (80) to be formed from the exterior
container
space (78), which may simplify the fabrication of the flexible container (20)
and readily
facilitate automation of the fabrication process.
In the preferred embodiment, each secondary seam (80) has a secondary
seam length which is substantially equal to the length of its associated hems
(56), hem
connections (64) and primary seam (66). In addition, in the preferred
embodiment the
hem connections (64), the primary seam (66) and the secondary seam (80)
associated
with each seam configuration (40) are substantially parallel to each other.
The seam configuration (40) of the invention is particularly suited for use
in constructing flexible containers which are fabricated from woven synthetic
polymer
materials such as polyethylene and polypropylene.
The seam configuration (40) facilitates the use of fusing techniques to form
the primary seam (66) instead of techniques such as riveting, stapling and
stitching, all
of which introduce perforations into the flexible material. It has been found
that the
seam configuration (40) of the invention has reduced tendency to exhibit the
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CA 02337624 2001-02-21
"zippering" effect which is commonly experienced when fused seams are used
with
woven materials.
The reason for this phenomenon is not completely understood, but it is
theorized that forming the primary seam (66) between the hem outer surfaces
(72,74)
has the effect of isolating the primary seam (66) from some of the stresses
that are
experienced by the flexible material when the flexible container (20) is in
service. It is
believed that this effect may be due to a combination of the configuration of
the hems
(56) and the location of the primary seam (66) relative to the hems (56).
The seam configuration (40) of the invention provides several advantages
over conventional seams for flexible containers (20).
First, the seam configuration (40) of the preferred embodiment does not
introduce perforations into the flexible material in locations where the
perforations can
communicate with the interior container space (76). This advantage is made
possible
through the use of fusing techniques for forming the hem connections (64) and
the
primary seam (66).
When this advantage is combined with the use of woven flexible materials
which comprise a sealant, the result is a flexible container (20) which is
relatively
hygienic and does not permit leakage from or into the flexible container (20).
Second, because the seam configuration (40) utilizes fusing techniques for
formation of the hem connections (64) and the primary seam (66), it offers the
potential
for reduced fabrication costs and increased potential for automation of the
fabrication
process, since fused connections and seams can potentially be formed for lower
cost
than those formed using riveting, stapling or stitching techniques.
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When this advantage is combined with the use of four or fewer identical
panels for the fabrication of the flexible container (20), which panels
include a side wall
portion (42), a top end wall portion (44), a bottom end wall portion (46), a
fill spout
portion (48) and a discharge spout portion (50), further reduced fabrication
costs and
further increased potential for automation of the fabrication process may
result.
In particular, by providing that the flexible container (20) may be
fabricated simply by forming seam configurations (40) between side edges (52)
of
adjacent panels (32,34,36,38), each seam configuration (40) may be formed in a
single
plane. This has the potential for further simplifying automated fabrication
processes by
limiting to two dimensions the motions that must be performed in forming the
seam
configurations (40) in comparison with some conventional fabrication methods
which
require the fill spout (28) and the discharge spout (30) to be fastened to the
flexible
container (20) in a process separate from the fabrication of the flexible
container (20).
Third, the seam configuration of the present invention facilitates the
addition of the optional secondary seam (80) which can be formed by riveting,
stapling
or stitching techniques to enhance the strength of the seam configuration (40)
without
compromising the hygienic properties provided by the fused hem connections
(64) and
fused primary seam (66).
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