Note: Descriptions are shown in the official language in which they were submitted.
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ROLL TOP BAG CONSTRUCTIONS
TECHNICAL FIELD
This invention relates generally to the field of bags adapted to be closed by
folding or rolling down their upper ends, such as for the packaging of
granular material
and other consumable items. The invention is particularly related to
reclosable surface
closures for gusseted roll-top bags.
BACKGROUND
A conventional roll top bag closure employs one surface fastener element
(e.g., a
section of loop material) at the top edge of the front external face of the
bag, and a
matable fastener element (e.g., a width of hooking material) spaced
approximately two
widths of the fastener element down the back face of the bag. To secure the
top of the
bag in a rolled state, the top is folded down toward the back bag face, the
width of the
fastener element, and then rolled over again to engage the matable surfaces of
the
fastener elements. Once so mated, the fastener elements are loaded primarily
in peel (i.e.,
~ 5 the separation load is generally normal to the plane of the fastener
elements), due to the
tendency of the rolled top to unroll.
It has been realized that hook and loop closures, as well as some adhesive
closures, are stronger when loaded in shear (i.e., when resisting loads
applied generally
parallel to their engagement plane) than in peel. One improvement in roll top
bag
2o construction was introduced by Rinicker in U.S. Patent No. 3,655,118, in an
attempt to
place the hook and loop engagement under shear by facing the lower surface
fastener
element toward the bag face on a flexible flap. To secure the Rinicker bag
closure, one
would roll the bag top down and, lift the flap, and insert the rolled top
between the bag
face and the flap to engage the hooks and loops.
25 Improved closure constructions are desired, especially ones that are
readily
accommodated by modern bag making and filling equipment, are easy to use, and
are
designed for compatibility with various bag constructions, such as gusseted
roll top bags
for such commodities as coffee and the like.
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SUMMARY
In one aspect the invention relates to a gusseted bag of disposable packaging
material having a roll-top closure defined during use by two releasably
engageable
fastener components, one component being associated with an upper edge of a
rollable
top of the bag, and the other component being carried on a flexible flap
secured to a
lower portion of a face of the bag. Each of the components is in the form of a
plastic
base layer carrying respective hook or loop elements.
In one preferred construction, the flexible flap is secured to the face of the
bag
along the upper edge of the flap, with its fastener component facing away from
the face
~ o of the bag and disposed below the attachment of the flap to the bag face.
The top of the
bag is folded down toward the flap, which is then folded upward to engage the
two
fastener components and secure the folded top between the bag face and the
flap.
In another preferred construction in which the flexible flap is secured to the
face
of the bag along the upper edge of the flap, with its fastener component
facing away from
~ 5 the face of the bag and disposed below the attachment of the flap to the
bag face, the top
of the bag is folded down over the flap to engage the two fastener components.
When the
folded top is released and tends to unfold, the flap is bent upward to follow
the unfolding
top and redirect at least a significant portion of the peel load applied to
the fastener into a
shear load.
2o In certain preferred embodiments the packaging material from which the
gusseted
bag is formed has an outer Layer of thermally weldable plastic, in the form of
a film or
coating, and the plastic base layers of the plastic components are of a
compatible
thermally weldable material. In many of the preferred embodiments the plastic
of each of
the layers is of substantially the same molecular type. In one case each
comprises
2s polyethylene, in another case each comprises polypropylene, in another each
comprises
copolymers of EVA and polyethylene and in another case each comprises
polyester.
According to another group of preferred embodiments, the outer surface of the
gusseted bag is defined by paper, and the fastener components carry upon them
an
adhesive layer, preferably in many embodiments pressure-sensitive adhesive, or
in other
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cases heat-activatable adhesive, and appropriate pressure and/or heat are
applied during
manufacture to secure these components to the bag. In a particular example the
outer
surface ofthe bag is paper and adhesive (e.g., moisture-sensitive or gum
adhesive) is pre-
applied to the base layers of the closure components.
In preferred embodiments of the invention, the loop material is a non-woven
material (e.g., formed of needled fibers), such as is available from Velcro
USA of
Manchester, New Hampshire under the trademark ASPEN. Various detailed features
of
this preferred loop material can be found in co-pending U.S. Serial Number
09/262,159,
the contents of which are incorporated herein by reference as if fully set
forth.
The male fastener elements (e.g., hooks) are preferably formed integrally
(e.g.,
molded) with the plastic base layer of the fastener component.
In certain preferred embodiments packaging material, prior to being formed
into
gusseted bags, has pre-applied to it one or both of the two fastener
components.
In some preferred embodiments the two fastener components are introduced to
the
15 bag making process as a single unit (e.g., as parallel portions of a wide
closure strip),
which is then split into the two components and applied to the packaging
material.
In another preferred embodiment, a closure strip that defines both of the
components has a dividing tear strip between them, the components being
secured to the
bag as a unit, the tear strip adapted to be removed by the purchaser to divide
the unit into
2o the two separate components.
In some embodiments, the flexible flap is secured to the face of the bag along
a
lower edge of the flap, with its fastener component facing toward the face of
the bag,
such that the fastener components are engageable by moving the flap away from
the face
of the bag, folding the top of the bag down between the flap and the face of
the bag, and
2s then moving the flap back toward the face of the bag to engage the fastener
components
and secure the folded top between the face of the bag and the flap.
According to another aspect of the invention, a bag of disposable packaging
material has a closure comprising two releasably engageable fastener
components,
wherein each fastener component comprises a plastic base layer carrying either
hook or
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loop elements. One fastener component extends in a strip from an upper edge of
a
foldable top of the bag down one face of the bag, and the other fastener
component
extends in a strip from an upper edge of the foldable top of the bag down an
opposite face
of the bag, such that when the top of the bag is folded downward, one fastener
component
s will engage the other fastener component to hold the top closed.
Preferably, one or both of the fastener components extends from the top of the
bag to a gusseted bottom of the bag. One of the fastener components covers a
fin seal of
the bag in some cases.
In some embodiments, the bag has gusseted sides formed between the faces along
which the fastener components extend.
Various embodiments may also contain features described in U. S. Patent No.
6,202,260, and PCT Serial Number US99/26261, published May 18, 2000 as WO
00/27721, the entire contents of both of which are hereby incorporated by
reference as if
fully set forth.
15 According to another aspect of the invention, a method is provided for
forming a
bag of packaging material having a roll-top closure comprising two releasably
engageable fastener components, each fastener component comprising a plastic
base
layer carrying either hook or loop elements. The method includes forming a
roll-top bag
of the packaging material, with the first fastener component disposed on one
face of a
2o foldable top of the bag, and a flap extending from a lower portion of an
opposite face of
the bag and carrying the second fastener component positioned to be engageable
with the
first component when the top of the bag is rolled downward.
In some embodiments the method includes, before forming the roll-top bag, pre
applying the first fastener component to the packaging material, and securing
the flap to
25 the packaging material, the flap carrying the second fastener component.
In some cases, the method includes introducing the two fastener components to
a
bag making process as parallel portions of a unitary closure strip, splitting
the closure
strip into the two fastener components, and then applying the fastener
components to the
packaging material.
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The details of one or more embodiments of the invention are set forth in the
accompanying drawings and the description below. Other features, objects, and
advantages of the invention will be apparent from the description and
drawings, and from
the claims.
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DESCRIPTION OF DRAWINGS
Fig. 1 is a perspective view of a roll top bag.
Fig. 2A is an end view of the roll top bag of Fig. 1, with the top rolled and
held
down to engage the surface fastener components.
Fig. 2B shows the bag of Fig. 2A after the rolled top has been released.
Fig. 3 is a cross-sectional view, taken along line 3-3 in Fig. 2B.
Fig. 4 is an enlarged~side view of the top portion of the bag, showing the
placement of the surface fastener components.
Fig. 5 is a perspective view of a second roll top bag.
Fig. 6 is a perspective view of the bag of Fig. 5, in its unfilled state.
Figs. 7A and 7B are alternate cross-sectional views, taken along line 7-7 in
Fig. 6.
Figs. 8A-8C sequentially illustrate the opening and reclosing of a third roll
top
bag construction.
Fig. 9 is a transverse cross-sectional view of a first, one-piece closure
strip, and
~5 Fig. 9A shows such a closure strip as installed on a bag.
Fig. 10 is a transverse cross-sectional view of a first, one-piece closure
strip, and
Fig. 10A shows such a closure strip as installed on a bag.
Figs. 11A-11C show bags with three different top fold multiples.
Like reference symbols in the various drawings indicate like elements.
2o DETAILED DESCRIPTION
Referring to Fig. 1, gusseted bag 10 is formed to have a generally flat bottom
12
to stand up on a horizontal support surface (not shown), as is common in the
packaging
of coffees, for example. The body 14 of the bag is formed of plastic film,
such as a
laminate of polyethylene (on the inner surface of the bag, to promote
freshness) and
25 polyester (on the outer surface of the bag for durability). A transverse
end seal 16 and a
vertical fin seal 18 help to form the film into a pouch as shown, having an
inner cavity as
shown in cross-section in Fig. 3.
6
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Still referring to Fig. 1, bag 10 has two surface fastener components for
releasably
retaining the top of the bag in a closed, rolled condition for storage. A male
surface
fastener 20 is attached to the rear face 22 of the bag along the upper edge of
fastener 20,
with the lower majority of the area of fastener 20 extending freely from the
bag. Fastener
20 is preferably in the form of a width of plastic resin molded to have an
array of
integrally-formed male, loop-engageable fastener elements extending from its
broad outer
surface. Such fasteners may be formed by the process described in Fisher in U.
S.
4,794,028, hereby incorporated by reference. In this embodiment, the faster is
applied
with its longitudinal forming direction extending across the bag face, with
hook-shaped
fastener elements that are directed across the width of the bag. However,
other shapes of
male fastener elements may be employed, or hook shapes that face upward and/or
downward as applied to the bag. Preferably, fastener 20 is of a resin
compatible with the
outer surface of bag 10, such that the upper edge ofthe fastener may be
permanently
attached by heat-staking, for example. Other suitable attachment means include
pressure-
~5 sensitive adhesive (PSA) or moisture-sensitive adhesive (MSA), such as gum
coatings.
A female surface fastener 24 is applied across the front face 26 of bag 10,
toward
the top of the bag. Fastener 24 carries a field of engageable loops or fibers
for mating
with the fastener elements of fastener 20, and is permanently secured to the
bag film at
least along its two long edges (e.g., by heat-sealing), preferably across its
entire back face
20 (e.g., by heat-sealing or adhesives). The field of fibers exposed on the
outer surface of
fastener 24 may be, for example, the ASPEN material referred to above. As
shown,
fasteners 20 and 24 extend across substantially the full width of bag 10.
To close bag 10, the top of the bag is first folded above the upper edge of
loop
fastener 24, as indicated by arrow A. The bag top is folded over again, this
time below
25 the lower edge of fastener 24, as indicated by arrow B. The bag top is then
folded a third
time, this time just above the upper, attached edge of hook fastener 20, to
engage the
exposed, mating surface of fasteners 20 and 24 (as shown in Fig. 2A). Were the
lower
edge of fastener 20 attached to the bag face, releasing the rolled bag top in
this position
would place a normal (i.e., peel) separation load upon the surface fasteners
due to the
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resiliency of the rolled bag top and its associated tendency to unroll.
However, because
the lower portion of fastener 20 is unattached, the resiliency of the rolled
bag top pulls
fastener 20 upward, bending it about its attached upper edge, until it is
directed upward,
on the outer surface of the rolled bag top as shown in Fig. 2B. T have round
that with
thin, flexible hook substrates, fastener 20 can be pulled up to an orientation
of 10 to 30
degrees from vertical. Further tendency of the rolled bag top to unwind places
a load
between the surface fasteners that is predominantly in shear (i. e., parallel
to their
engagement plane), a loading mode known to be more readily resisted by surface
fasteners than peel. As Figs. 2A and 2B illustrate, the lowest fold of the
rolled top almost
completely unfolds after the rolled top is released and allowed to deflect the
lower
fastener 20 up into a shear loading orientation. Tt should be understood that
other folding
multiples are envisioned for this general bag closure construction, with the
last fold of
any such multiple at least partially sacrificed to pull the closure into a
shear loading
orientation. Figs. 1 lA-11C, for example, show various folding multiples. The
more
~ 5 folds, the more sealed the closure.
Fig. 4 shows a preferred spacing of fasteners 20 and 24 to enable the folding
described above. Loop fastener 24 has a width "w" of about 1/2 inch (12.5
millimeters),
and is spaced down from the upper edge 28 of the bag a distance equal to its
width minus
a fraction "x" of about 1/8 inch (3.2 millimeters). Hook fastener 20 is
attached to the bag
2o face a distance down from loop fastener 24 equal to the width "w" of
fastener 24 plus
fraction "x". These fraction adjustments aid in the rolling of the bag top, by
accounting
for the fold thickness. The array of fastener elements earned upon fastener 20
is also of
about width "w".
Fig. 5 shows a bag 20 with a roll top closure that is functional with the top
folded
25 over any one of several numbers of times. Such a bag construction is
particularly useful,
for example, for applications in which the user desires to incrementally
collapse the bag
as its contents are depleted. Bags for charcoal briquettes, for example, are
one such
application. A strip of loop fastener 24 is carried vertically all the way up
the front face
32 of the bag, and a matable strip of hook fastener (not shown in this view)
extends in
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parallel fashion up the rear face 34 of the bag. then the bag top is folded
over one or
more times, its two opposite faces, and the respective fasteners they carry,
engage to form
a releasable fastening. In this embodiment, the hook and loop strips are both
permanently
attached to the bag film along their entire length, which also corresponds to
the entire
length of the bag. It will be understood that this particular construction
does not obtain
the advantages of predominant shear loading, but does obtain many of the other
advantages noted above.
Fig. 6 shows the same bag 30 empty and open, as before filling, for example.
The
loop component 24 is shown in dashed outline only, to illustrate that the
longitudinal fin
seal 18 of the bag extends up its front face and is covered by the loop
component for an
aesthetically pleasing appearance. The loop component 24 may be attached to
the bag
film on both sides of the longitudinal fin seal with adhesive 36, as shown in
Fig. 7A, or
may have one edge aligned with the free edge of the fin seal, as shown in Fig.
7B. Both
approaches have distinct advantages, as the fasteners as shown in Fig. 7A can
be applied
to the bag after formation of the fin seal, and even after completion of the
form and fill
process, if desired. On the other hand, the fasteners as shown in Fig. 7B,
which are heat-
staked or welded directly to the bag film, may be applied to the sheet-form
bag film in
advance of forming and filling the bags, with the fastener strips introduced
directly to the
bag forming equipment as continuous lengths, or applied to a respective edge
and middle
2o region of the bag film as it is spooled from a roll, to name two preferred
examples.
Figs. 8A-8C illustrate a roll top bag construction that combines the
advantages of
shear loading and variable adjustability. A strip of loop component 24 is
permanently
attached to the front face of bag 40, similar to the arrangement of the loop
strip on the
bag of Fig. 5. On the back face of the bag, however, hook component 20 is
attached only
25 at its upper and lower ends to the bag, with its array of hook elements
facing toward the
bag f lm along its entire length. As shown in Fig. 8A, the upper edge of
filled bag 40 is
sealed to form a pouch suitable for perishable goods, with the upper seal of
the bag
forming a tear strip 42 to be torn from the bag upon its initial opening. Hook
component
20 is attached at its upper end only to tear strip 42, and contains an upper
frangible joint
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(e.g., a transverse score line or tear notch, not shown) adjacent the tear
strip, such that
when the tear strip is torn away, the upper end of hook component 20 is freed
from the
bag as shown in Fig. 8B. To reclose the bag, the top is rolled up as much as
desired, then
the extended hook strip 20 is wrapped over the top of the bag (as shown in
Fig. 8C),
engaging the loop strip 24 over a wide area in predominantly shear loading.
The two fasteners may also be provided as part of a unitary strip. For
example,
Fig. 9 shows a closure strip 50 that has a unitary resin substrate 52 from
which both a tear
rib 54 and an array of integrally molded fastener elements 56 extend in
parallel,
longitudinally continuous form. Loop material 58 is also carried on the
substrate, with
~ o fibers of the loop material embedded in and secured by resin of the
substrate. Methods of
forming such unitary closure strips are described more fully in U. S. Patent
No. 6,202,260.
Parallel, continuous bands of adhesive 60 are provided on the back side of the
closure
strip for securing the strip to a bag, as shown in Fig. 9A, for example. The
narrow band
of adhesive 60 on the hook side of rib 54 attaches the closure strip to the
face of the bag,
and the wider band of adhesive 60 on the loop side of the rib secures the
strip to the
rolled top of the bag after filling. With the closure strip so applied to the
bag, closure
strip 50 provides desirable tamper evidence, as the bag cannot be opened
without
damaging or tearing the closure strip. To open the bag, tear rib 54 is grasped
and pulled
across the face of the bag and discarded, severing the substrate 52 of the
closure into two
2o parallel portions, each carrying an associated one of the mutable
fasteners. Substrate 52
is provided with molded tear channels (not shown) on either side of rib 54 to
assist in
controlled opening. The bag can then be reclosed by rolling the top of the bag
down to
engage the two fasteners, as discussed above. As the lower edge of closure
strip 50
remains unattached to the bug, the lower fastener component is free to be
hinged about its
associated adhesive attachment to the bag face, to orient the fastening plane
in a shear
loading direction.
Fig. 10 shows another illustrative embodiment of a unitary bag closure strip
70
useful for roll top bags. In this example, the molded male fastener elements
56 are
formed on a side opposite the side carrying the tear rib 54 and loop material
58. One
to
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wide band of adhesive 60 extends below the loop material, and a narrow band of
adhesive
60 is disposed under the longitudinal edge adjacent the hook elements. The
narrow band
of adhesive secures the lowermost edge of the bag closure 70 to the face of
the bag, with
hook elements 56 facing the bag film as shown in Fig. 10A. The wide band of
adhesive
60 permanently secures the closure strip to the rolled or folded top of the
filled bag. Tear
rib 54 is grasped and pulled to tear through the substrate of the closure for
initial opening
of the filled bag, and the bag is thereafter reclosed by tucking the rolled
top between the
face of the bag and the flap formed by the severed, lower, hook portion of the
closure.
Although this closure sequence requires both the flap and the rolled top to be
simultaneously manipulated, thereby generally requiring a two-handed
operation, it does
provide the shear loading advantages discussed above. Furthermore, the one-
piece nature
of the closure strip enhances ease of assembly and provides tamper evidence.
Because
the closure is attached to the bag top only after filling, the loop component
can be
positioned according to the actual requirements of each individually filled
bag. Thus, the
upper portion of the closure can be adhered to the filled bag with its top
already rolled
down to an advantageously very tight, space-minimizing position, the closure
thus put
into tension as would a piece of adhesive tape. Such tight packaging is
desirable to
remove air and promote sealing (e.g., for perishable items) and to reduce
shipping and
shelf space for retail goods.
2o The lower band of adhesive 60 in each of the closure strips shown on bags
in
Figs. 9A and 10A could be replaced, for example, with a thermal weld. In such
a case,
the closure strip can be applied to the bag before filling. The closure strip
can be
provided in continuous form, and cut to length as applied, or can be provided
as finite
lengths upon a release liner and applied with typical labeling equipment.
2s It should be realized that the above-described drawings are not to scale,
but do
schematically represent the concepts claimed. The closure components discussed
above,
for example, typically have a substrate thickness of only about 0.003 to 0.007
inch
(preferably, between about 0.004 to 0.005 inch), although as illustrated they
appear much
thicker than the bag film, which is preferably about the same thickness as the
closure
11
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substrates. The thinness and flexibility of the closure substrate, especially
for the bag
construction shown in Fig. 1 and compared to the bag film itself, enables the
lower
closure component to be readily pulled upward into a shear loading
orientation. Thicker
bag films can tend to be more resilient, providing greater roll top restoring
force fox re-
orienting the closure. The thinness ofthe closures also enables the use of
standard
handling and packaging equipment.
A number of embodiments of the invention have been described. Nevertheless, it
will be understood that various modifications may be made without departing
from the
spirit and scope of the invention. Accordingly, other embodiments are within
the scope
of my claims.
12
