Note: Descriptions are shown in the official language in which they were submitted.
CA 02369815 2002-01-31
PATCH HANDLE BOTTOM VALVE BAG
The present invention relates in general to bottom valve bags for transporting
or carrying bulk material and in particular to such a bag having a reinforced
handle
portion.
Background of the Invention
Plastic bags for carrying or transporting bulk material, including
particulates,
powders and the like are well known in the art. Such bags typically are
provided with
a bottom fill valve and a closed upper end. The material is injected into the
bag
through the fill valve when the bag is in an inverted condition, the weight of
the
material closing the valve when the bag is reoriented with its upper end
elevated
relative to its bottom end. The bag must be cut open to release the contents.
Such bags typically will have a handle at the top or upper end for carrying
the
filled bag. The handle might be a simple oblong hole cut through the bag
material at
the upper end; it might be formed from a separate piece of plastic or other
material
adhered or otherwise attached to the bag; or, as is illustrated in US Patent
No. 4,610,
029 of September 2, 1986 it might involve a reinforcing patch adhered to the
upper
end of the bag with a handle opening piercing the patch and the underlying bag
material.
While the reinforcing patch concept of the aforementioned US patent can be
effective in creating a strong handle, the concept is somewhat wasteful of
material and
requires the use of an adhesive for securing the patch to the bag material. In
the US
patent strength is achieved by folding part of the upper bag end over on
itself prior to
adhering the patch to the bag. The patch extends across most if not all of the
width
of the bag and extends over and below the transverse heat seal which defines
the
upper closure for the bag. The result is an upper reinforced bag section that
will
exhibit at least five layers of material, four from the bag material and one
from the
patch material. For additional strength the US patent suggests that another
patch can
be adhered to the opposite face of the upper end, creating a six layer
section.
While adhesives will provide a strong bond for the patch, they are aromatic
and
may involve controlled substance catalysts, thereby creating an unhealthy
environment
for workers in a bag assembly plant.
1
CA 02369815 2002-01-31
Summary of the Invention
The present invention on the other hand represents an improvement over the
bag construction of the aforementioned US patent. The invention utilizes a
small
patch of plastic material which is heat sealed to the bag material in the
center thereof
adjacent the upper edge of the bag. By heat sealing the patch to the bag
instead of
using adhesive a stronger bond between the patch and the bag is achieved.
Furthermore, it has been ascertained that, unlike the patch used in the above-
identified US patent, it is not necessary to extend the patch the full width
of the bag.
In fact, a patch which is less than one-half the width of the bag will be more
than
adequate, with a lower limit being about 20% of the bag width. Also, the patch
need
not be much wider than the distance from the upper edge of the bag to the heat
seal
which extends completely across the bag material to establish the upper end of
the
fillable bag body. That heat seal will also extend across the patch adjacent
the lower
edge thereof. In comparison to the patch of the aforementioned US patent the
present
invention represents a considerable saving in patch material.
By using a heat seal to attach the patch to the bag material there is less
likelihood of workers being adversely affected by the attachment process. With
the
prior art adhesively-attached patches there are aromatic solvents associated
with the
adhesive which can be damaging to the environment as well as to the health of
the
workers. As mentioned above, the heat seal attachment for the patch results in
a
stronger attachment than adhesive. Once the patch is heat sealed to the bag
material
a handle opening is cut through the patch and bag material layers, between
upper and
lower lines of heat sealing used to secure the patch to the bag material.
At the opposite end of the bag a flat bottom is formed and a fill sleeve is
inserted in a conventional manner. The sleeve is used to fill the bag in an
inverted
state with bulk material to be carried in the bag.
The present invention also contemplates a fast, efficient production method,
starting with a roll of tubular, plastic bag material which is fed into a
forming machine
in a flattened state. A patch for each bag is brought into contact with the
bag
material, centrally thereof, at a location adjacent to what will be the upper
edge of the
finished bag. The patch is heat sealed to the bag material while in contact
with the
2
CA 02369815 2006-05-05
bag material and, essentially simultaneously, the bag handle opening is cut
through
the layers of patch and bag material. At the next station the bag material is
heat
sealed along a line extending transversely of the bag material to define the
upper limit
of the bag body, this heat seal also extending across the patch adjacent the
lower edge
thereof. Essentially simultaneously, adjacent the opposite or upper edge of
the patch
the bag material is cut transversely thereof to define the upper edge of the
finished
bag. This process severs the bag from the roll of bag material and the severed
blank
or unfinished bag is then fed to a bottom forming station for completion. At
the
bottom forming station a flat or block bottom is created by folding the
material to
create appropriate flaps which in turn are adhered together. Before completion
a valve
sleeve is inserted between selected flaps and adhered in place. The valve
sleeve
provides access to the interior of the bag so that bulk material can be forced
into the
bag until it is full. Once the bag is full it is inverted so that the bag can
sit on the flat
bottom, with the handle at the top for convenient usage. The weight of the
bulk
material in the bag closes the valve sleeve and prevents any leakage of
material from
the bag. If desired a rectangular reinforcing patch of plastic material can be
adhered
to the bottom of the bag.
Broadly speaking therefore the present invention may be considered as
providing a plastic bag for carrying bulk material comprising: a body portion
defined
by a length of tubular plastic material and exhibiting opposed rectilinear
panels; a
reinforcing patch of a plastic material, having a width less than one half the
width of
the panels, heat sealed to an outer face of one of the panels adjacent a
transverse
upper edge of the panels; a heat seal extending transversely across the full
width of
the panels to seal the panels together, the heat seal being spaced from the
transverse
upper edge of the panels and extending across the patch adjacent a lower edge
thereof; a handle opening pierced through the patch and the panels underlying
the
patch; and a closed bottom portion including a filling valve therein.
The invention may also be considered as providing a method of forming a
plastic
bag having a reinforced handle area comprising the steps of: providing an
indefinite
length of tubular bag material in a flattened state on a roll for dispensing
such material
therefrom; feeding such material into forming apparatus from the roll and,
within such
3
CA 02369815 2006-05-05
apparatus: providing a plurality of patches of plastic material of a width
less than one
half the width of the length of bag material; for each bag to be formed,
positioning
one of the patches centrally of the width of the bag material; heat sealing
the patch
to the bag material; piercing the patch and underlying opposing panels of the
length
of bag material along a line to define a handle opening; effecting a heat seal
transverse
to the length of material, and extending across the patch, to seal together
the
opposing panels of the bag material; simultaneously severing the bag material
along
a line of severance spaced from the transverse heat seal to create an
unfinished bag
section having an upper portion between the transverse heat seal and an upper
edge
created at the line of severance, a body portion below the transverse heat
seal, and
an open bottom portion at the end opposite the upper portion, the patch being
located
in the upper portion; and forming the open bottom portion into a closed bottom
portion
having a filling valve therein.
The present invention will now be described in greater detail and with
reference
to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a carrying bag in accordance with this
invention.
Figure 2 is a front view of the bag of this invention.
Figure 3 is a partial perspective view of the bag bottom.
Figure 4 is a schematic representation of the process for manufacturing the
bag
of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figures 1 and 2 illustrate an industrial carrying bag 10 for bulk material in
accordance with this invention. The bag is generally rectilinear in overall
configuration
and is typically made from a plastics material such as low density
polyethylene (LDPE),
linear low density polyethylene (LLDPE) or high density polyethylene (HDPE)
which will
not be degraded by the material being carried in the bag. The bag 10 has an
upper
transverse edge 12 which is open, defined by opposing panels 14, 16 of the bag
material which are joined along side edges 18, 18. A transverse heat seal 20
extends
the width of the bag material close to the upper edge, defining an upper
portion 22
4
CA 02369815 2002-01-31
between itself and the upper edge 12. Below the heat seal 20 is the main body
portion
24 of the bag, the main body portion terminating at a closed bottom portion
26. The
closed bottom portion 26 is created from a plurality of flaps formed from the
bag
material as will hereinafter be described, and it is provided with a
reinforcing patch 28
which covers most of the bottom surface. A valve sleeve 30 is fixed in the
closed
bottom to provide access to the interior of the bag for filling purposes as is
conventional in the art.
The upper portion 22 of the bag is provided with a reinforcing patch 32 which
is heat sealed to one of the bag panels 14, 16 along a pair of heat seal lines
34, 36
which are generally parallel to each other as well as to the upper edge 12 and
the
transverse heat seal 20. The patch is formed from a material compatible with
the bag
material, either an LDPE, an LLDPE or an HDPE and has a width of between about
20%
and 50% of that of the bag itself. The height of the patch is about the same
as that
of the upper portion 22, with the uppermost edge of the patch being closely
adjacent
the upper edge 12 of the bag. The lower edge of the patch extends below the
transverse heat seal 20. The patch 32 is heat sealed to the bag material
before the
transverse heat seal 20 is effected so that the heat seal 20 can actually
extend across
the patch 32 to provide an additional securement of the patch to the bag. A
flattened
C-shape line 38 is pierced through the patch and the underlying bag material
to create
a handle opening which will be used for carrying the filled bag.
As seen in Figures 1 to 3 the bag bottom 26 is formed from the bag material,
generally as described below, such that a flat bottom surface 40 is created,
the surface
40 having a generally rectangular central section 42 and triangular end
sections 44,
46. One of the end sections 46 is completely sealed whereas the other end
section 44
is not. The unsealed end section 44 is provided with the valve sleeve 30 which
extends
from the outside of the bag to the interior and is used for filling the bag
with the
material to be carried thereby. The sleeve is also made from a plastics
material that
is durable and flexible. The bag will be filled in an inverted orientation,
with the sleeve
uppermost. Once it has been filled the bag is flipped end to end so that the
flat bottom
is lowermost and the bag can rest on its bottom. In this orientation the
weight of the
material in the bag will maintain the valve sleeve in a compressed, closed
condition so
5
CA 02369815 2002-01-31
that there will be no leakage from the filled bag.
The manufacturing process in accordance with this invention is illustrated
schematically in Figure 4. The process starts with the provision of the raw
material
from which the bag will be formed, generally in the form of a roll 50 of
tubular plastic
material which is in a flattened state, defining the opposing panels or bag
sides 14, 16.
The material is drawn from the roll 50 through a set of dancing rollers 52 to
maintain
tension in the material into the forming apparatus generally indicated by
reference
number 54.
At the first station in the apparatus a plurality of rectangular plastic
patches 32
are provided, one for each bag to be made. A patch 32 is brought into contact
with
one panel of the bag material, centrally of the width thereof and at contact
the patch
is heat sealed to the panel using heat sealers 54, 56 along the spaced-apart
heat seal
lines 34, 36 which are parallel to each other and generally normal to the bag
edges 18,
18. Also concurrently with the heat sealing of the patch to the bag material a
flattened
C-shaped cut 38 is pierced through the patch 32 and the bag material using die
cutter
58 so as to define the handle opening.
At the next station a heat seal 20 is applied transversely of the entire bag
width,
using heat sealer 60, the heat seal being positioned such that it extends
across the
patch 32 adjacent the lowermost edge thereof, below the lower one 34 of the
patch
heat seals. Concurrently with the application of the transverse heat seal 20 a
knife 62
is actuated so that the bag section 64 is severed from the length of bag
material along
a line of severance 66 which is located above and closely adjacent to the
uppermost
edge of the patch 32, thereby creating the upper edge 12 of the bag.
The severed bag section 64 is fed to the final station in the forming
apparatus
whereat the closed bottom 26 is formed. At that station adhesive is applied to
both
sides of the bag one to two inches from the bottom end thereof. This end is
then
scored, folded, opened, and folded again to create flaps. This is done in a
conventional
manner using suction cups, duckbills and rollers. The score location is
determined by
the desired width of the closed bottom 26. Pressure rollers are used to
maintain the
creases, and to hold the flaps down. In this way the flaps are presented up,
with
adhesive, ready to receive the valve 30.
6
CA 02369815 2002-01-31
The sleeve 30 is preformed of LDPE/LLDPE/HDPE film tape and is placed on one
end of the bag bottom flaps. Pressure rollers are used to tack it down to the
adhesive
already applied to the flaps. The flaps are then folded over to create the
rectangular
bottom end of the bag. The sleeve 30, as described above, provides access to
the bag
interior.
The bag bottom may be reinforced by a rectangular patch 28 of heavy gauge
LDPE/LLDPE/HDPE adhered to the bottom of the bag after the forming thereof as
described above. After application of the reinforcing patch 28 the bottom of
the bag
is passed though a set of pressure rollers which ensure good sealing of the
adhesive
to the flaps, sleeve and patch.
The resulting bag is strong, light in weight and uses less material than other
plastic carrying bags that are available on the market for the transporting of
bulk
powder or particulate material, including that of US Patent No. 4,610,029.
While particular embodiments of the present invention have been described
herein it is understood that modifications to the invention can be effected
without
departing from the true scope of the invention.
7
