Note: Descriptions are shown in the official language in which they were submitted.
CA 02226903 1998-O1-14
769.-197 CIP
Zipper Strip and Method of Positioning
the Strit~ Transverse Lonciitudinal Axis
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to Canadian patent file
# 2,204,712 filed May 7, 1997.
Background of the Invention
- - 1. Field of the Invention _ -
The present invention relates to reclosable
plastic bags of the type in which perishable food
products and other goods are packaged for sale to
consumers in retail outlets. More specifically, the
present invention relates to reclosable plastic bags
manufactured and concurrently filled on horizontal or
vertical form-fill-and-seal (FFS) machines, wherein a
plastic interlocking.zipper for each bag is disposed
transversely relative to the direction of motion of
the thermoplastic sheet material used to form the
reclosable bags -on the FFS machine.
2. Description of the Prior Art
The present invention relates to improvements in
the package-making art and may be practiced in the
manufacture of thermoplastic bags and packages of the
kind that may be used for various consumer products,
but which are particularly useful for food products
which must be kept in moisture- and air-tight
packages, free from leakage until initially opened for
access to the product contents, which packages are
then reclosable by zipper means to protect any
remainder of. the product therein.
CA 02226903 1998-O1-14
The indicated art is fairly well-developed, but
nevertheless remains susceptible to improvement
contributing to increased efficiency and cost
effectiveness.
S One problem that still hampers the production of
packages from continuous zipper-equipped sheet
material is the difficulty in attaining a satisfactory
sealing of the bag or package against leakage, where
the zipper and area of film engaged by the zipper
10 extends through the side (cross? seal areas separating
one bag or package from the next. This problem occurs
where the zipper is longitudinal with respect to the
direction of motion of the thermoplastic sheet
material used to form the reclosable bags on the FFS
1.5 machine, in which case the transverse, or side,
sealing bars must~flatten and seal the zipper at the
same time as they are sealing the thermoplastic sheet
material from which the packages are being made. The
difficulty with which this is consistently and
20 successfully achieved is reflected by the high
occurrence of leaking packages.
Numerous attempts have been made to solve this
problem. Among the approaches that have been taken is
the substitution of a transverse zipper for the
25 longitudinal zipper. Where such a zipper is provided
the transverse sealing bars associated with the FFS
machine do not flatten the zipper as they are making
a side seal, although they may seal the zipper to the
thermoplastic sheet material transversely thereacross
30 without flattening it.
The present invention relates to the provision of
a transverse zipper for reclosable plastic bags or
packages being manufactured on either a horizontal or
vertical FFS machine. More specifically, the present
.35 invention is both a zipper strip and a method for
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CA 02226903 1998-O1-14
.. \
securing the zipper strip transversely across the
thermoplastic sheet material from which reclosable
bags are being produced on a FFS macrine.
Summary of the Invention
Accordingly, the present invention is a zipper
strip for a reclosable bag or package manufactured and
filled using a form-fill-and-seal machine. In
particular, the zipper strip is designed to be
disposed transversely with respect to the movement
through the machine of the thermoplastic sheet
material used to fashion the packages.
The zipper strip comprises a male interlocking
-profile, having a male interlocking member and a male
web coextruded therewith; and a female interlocking
profile, having a female interlocking member and a
female web coextruded therewith. The male
interlocking member is snappingly engagable within the
female interlocking member to join the male and female
interlocking profiles together.
One of the male and female webs i s wider than the
other of the male and female webs in at least one of
two directions from the male and female interlocking
members in the closed zipper strip. The greater width
of the wider of the male and female webs means that it
has a flange extending beyond the other web on one and
possibly both sides. The zipper strip, as a
consequence, may be attached transversely upon
thermoplastic sheet material by sealing the flange of
the male or female web or flanges thereto without
?.0 sealing the male and female webs to each other.
The present invention also comprises a method for
attaching this zipper strip transversely on a sheet of
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CA 02226903 1998-O1-14
thermoplastic sheet material during the production of
plastic bags or packages on an FFS machine. In this
situation, a length of the zipper strip is attached to
the thermoplastic sheet material, each time it is
5 brought to rest as it advances (incrementa.lly or
continuously) on or to the FFS machine.
This method includes the step of providing a
zipper strip of the above-described variety. The
length of zipper strip is then disposed transversely
l0 upon the sheet of thermoplastic sheet material, with
' the wi3er of the male and female webs in contact with
the sheet and with a flange, or the flange if there is
only one, oriented in the direction of the motion of
the sheet. The flange or flanges are then sealed to
15 the sheet without sealing the male and female webs to
each other. Several specific ways of disposing the
length of zipper strip onto the sheet of thermoplastic
sheet material will be described below.
Finally, the present invention comprises a method
20 for manufacturing reclosable packages on a horizontal
form-fill-and-seal machine. The method includes the
step of providing a sheet of thermoplastic sheet
material having a length of zipper strip attached
thereto at regularly spaced intervals as described
25 above. A product conveyor then deposits a product to
be packaged at regular intervals onto the sheet of
thermoplastic sheet material. The two lateral edges
of the sheet are then folded toward one another and
around the product, and sealed to one another to form
30 a tube therefrom enclosing the product.
The tube is then sealed transversely to each
length of zipper strip without the webs of the male
and female interlocking profiles being sealed to each
other. The tube is then cut transversely adjacent to
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CA 02226903 1998-O1-14
each length of zipper strip to separate each completed
package from the next.
The present inventions will now be described in
more complete detail with frequent reference being
made to the figures identified below.
Brief Description of the Drawings
Figure 1 is a cross-sectional view of a first
embodiment of the zipper strip of the present
invention;
Figure 2 is a cross-sectional view of a second
embodiment of the zipper strip;
Figure 3 is a perspective view of an apparatus
used to attach the zipper strip to thermoplastic sheet
material;
Figure 4 is a perspective view of an alternate
apparatus used for this purpose; .
Figure 5 is a perspective view of still another
apparatus used for this purpose;
Figure 6 is a schematic view of a horizontal FFS
machine;
Figure 7 is a plan view of the thermoplastic
sheet material, with lengths of zipper strip attached
thereto, used to produce packages on the horizontal
FFS machine; and
Figure 8 is a simplified cross-sectional view of
a package formed in a horizontal FFS machine in
accordance with the present invention.
Detailed Description of the Preferred Embodiments
Referring specifically to the figures identified
above, Figure 1 is a cross-sectional view of a first
embodiment of the zipper strip 10 of the present
ir_vention. The zipper strip 10 comprises a male
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CA 02226903 1998-O1-14
interlocking profile 12 and a female interlocking
profile 14. The male interlocking profile 12 includes
a male interlocking member 16 which may have an
arrowhead-shaped cross section or, as is shown in
S Figure 1, an asymmetrical arrowhead-shaped cross
section, designed to make the zipper strip 10 easier
to open from one side than from the other. The female
interlocking profile 14 includes a female interlocking
member 18 comprising two inwardly cunning members
10 forming a receptacle or channel into which male
interlocking member 16 may be snappingly engaged.
Both the male and female interlocking profiles
12, 14 include webs coextruded with the male and
female interlocking members 16, 18. Web 20 of male
15 interlocking profile 12, it may be observed, is wider
than web 22 0~ female interlocking profile 14. As a
consequence, web 20 has a leading flange 24 and a
trailing flange 26, which together make up the amount
by which web 20 is wider than web 22. As will become
20 clear below, the leading and trailing flanges 24, 26
are so called because, when zipper strip 10 is
attached to a thermoplastic sheet material being fed
into an FFS machine, the leading flange 24 "leads" the
transversely attached zipper strip 10 toward the
25 machine, and the trailing flange 26 "trails" or is
last. Ultimately, the leading flange 24 resides
inward of the mouths of the plastic bags or packages
being manufactured and concurrently filled with a
consumer product on an FFS machine. While the male
30 interlocking profile 12 is shown to have both the
leading and trailing flanges 24, 26, both flanges 24,
26 could alternatively be part of the female
interlocking profile 14 instead.
The zipper strip 10 is disposed transversely
35 across thermoplastic sheet material during the
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CA 02226903 1998-O1-14
manufacture of plastic bags or packages on an FFS
machine. The zipper strip 10 is dispensed with male
and female interlocking profiles 12, 14 joined as
shown in Figure 1 onto thermoplastic sheet material
5 with the male interlocking profile 12 resting
thereupon. Heat seal bars 28 or the like, applied
against the leading and trailing flanges 24, 26 as
suggested by the arrows in Figure 1, seal the male
interlocking profile 12 to the thermoplastic sheet
10 material (not shown) without sealing web 22 of the
female interlocking profile 14 to web 20 of the male
interlocking profile 12.
Heat seal materials 30 may be applied to the
outside of web 20 of male interlocking profile 12,
15 including the outsides of the leading and trailing
flanges 24, 26, as well as to. the inside of the
trailing flange 26 and to the outside of web 22 of the
female interlocking profile 14, to facilitate their
being sealed to thermoplastic sheet material. The
20 trailing flange 26 may also be separable from the rest
of web 20 by perforations.
The outsides of the leading and trailing flanges
24, 26 are attached to thermoplastic sheet material
before the sheet material reaches the shoulder on a
25 vertical FFS machine, or before the sheet material
enters the FFS machine. Later, when the sheet
material is folded over to form a tube with lateral
edges sealed in a fin or overlap seal, the sheet
material is sealed to the inside of trailing flange
30 26, as well as to the outsides of both webs 20, 22,
without sealing the facing portions of webs 20, 22 to
one another.
Figure 2 is a cross-sectional view of a second
embodiment of the zipper strip 40 of the present
35 invention. Elements common to both zipper strip 40
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CA 02226903 1998-O1-14
and zipper strip 10 described above are identified in
Figure 2 using the same reference numbers. A
comparison between Figures 1 and 2 indicates that
zipper strip 40 lacks a trailing flange 26, but is
5 identical to zipper strip 10 in all other respects.
As was the case with zipper strip 10, zipper strip 40
is disposed transversely across thermoplastic sheet
material during the manufacture of plastic bags or
packages on an FFS machine. Male interlocking profile
10 42 rests upon the thermoplastic sheet material. Heat
seal bars 28 or the like, applied against the leading
flange 24, as suggested by the arrows in Figure 2,
seal the male interlocking profile 42 to the
thermoplastic sheet material (not shown) without
15 sealing web 22 of the female interlocking profile 14
to web 44 of the.male interlocking profile 42. As
before, while the male interlocking profile 42 is
shown to have the leading flange 24 , leading flange 24
could alternatively be part of the female interlocking
20 profile 14 instead.
Both zipper strips 10, 40 shown in Figures 1 and
2, respectively, may be extruded from a polymeric
resin material, such as a low-density polyethylene
(LDPE). Heat seal materials 30 may be applied as
25 shown by coextrusion or by coating following the
extrusion of zipper strips 10, 40. Ethylene vinyl
acetate (EVA) copolymers may be used as the heat seal
materials 30.
Figure 3 is a perspective view of an apparatus
30 used to attach zipper strip 10 to thermoplastic sheet
material 50, which is conveyed in the direction of the
arrows thereon toward an FFS machine. Thermoplastic
sheet material 50 is moved intermittently in
increments equal in length to the length of the
35 packages being produced.
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Each time the thermoplastic sheet material 50 is
momentarily brought to rest, a length of zipper strip
10 is sealed transversely across the upwardly facing
side thereof. Zipper tape 10 is dispensed from a roll
5 or other supply not shown in Figure 3 , a.nd '~ ed through
a stationary clamp 52, and through a reciprocating
shuttle 54, which includes a clamp 56 and a guillotine
58, the latter of which is used to cut the zipper
strip 10 when required.
10 Shuttle 54 reciprocates each time the
thermoplastic sheet material 50 is momentarily brought
to rest. When shuttle 54 moves outward over
thermoplastic sheet material 50, clamp 56 is closed
onto zipper tape 10, while stationary clamp 52 is
15 open, so that shuttle 54 pulls a length of the zipper
tape 10 from the roll. The outward end of shuttle 54
is a probe 60, which allows the leading flange 24 and
the trailing flange 26 0~ the zipper tape 10 to
protrude from the sides thereof.
20 As shown in Figure 3, the shuttle 54 is in its
retracted position. When i~ its forward position, not
shown, the probe 60 extends into the space between the
top sealing jaw 62 and its corresponding bottom
sealing jaw 64, the latter of which is on the
25 underside of the thermoplastic sheet material 50. The
leading and trailing flanges 24, 26 extend outward
from between the top and bottom sealing jaws 62, 64.
When the jaws 62, 64 close, heat seal bars 28 seal the
flanges 24, 26 to the thermoplastic sheet material 50.
30 Jaws 62, 64 then are opened; guillotine 58 cuts the
next length of zipper strip 10; clamp 56 is opened;
and clamp 52 is closed. Then shuttle 54 retracts to
the position shown in Figure 3, while thermoplastic
sheet material 50 moves a length equal to the length
35 of a package being manufactured to repeat the process.
CA 02226903 1998-O1-14
Figure 4 is a perspective view of an alternate
apparatus used to attach zipper strip 10 to
thermoplastic sheet material 50. As before,
thermoplastic sheet.material 50 is conveyed in the
5 direction of the arrow thereon toward an FFS machine,
and is moved intermittently in increments equal in
length to the length of the packages being produced.
Again, each time the thermoplastic sheet material
50 is momentarily brought to rest, a length of zipper
10 strip 10 is sealed transversely across the upwardly
facing side thereof. Zipper strip 10 is dispensed
from a roll or other supply not shown in Figure 4,
being pulled therefrom by a first clamp 70, which
reciprocates back and forth along mechanism 74 in step
15 with a second clamp 72. First and second clamps 70,
72 grasp leading flange 24 of zipper strip 10 to pull
the zipper strip 10 transversely across the
thermoplastic sheet material. Second clamp 72 holds
the zipper strip 1C in position while it is being
20 sealed to the upwardly facing side of the
thermoplastic sheet material 50. A stationary
guillotine 76 is used to cut the zipper strip 10 when
required.
Each time the thermoplastic sheet material 50 is
25 momentarily brought to rest, second clamp 72 brings a
length of zipper strip 10 cut by stationary guillotine
76 transversely outward thereover to the position
shown in Figure 4. At the same time, first clamp 70,
moving in step with second clamp 72, moves a length of
30 zipper strip 10 through guillotine 76. Top sealing
. jaw 62 and its corresponding bottom sealing jaw 64,
the latter of which is on the underside of the
thermoplastic sheet material 50, seal the leading
flange 24 and the trailing flange 26 of the zipper
35 strip 10 thereto, while the second clamp 72 holds onto
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the leading flange 24. Then, first clamp 70 and
second clamp 72 retract from the positions shown in
Figure 4, the first clamp 70 retracting to a position
adjacent to guillotine 76, and the second clamp 72
retracting upstream from the guillotine 76 along
zipper strip 10. Thermoplastic sheet material 50 then
moves a length equal to the length of a package being
manufactured to repeat the process.
Figure 5 is a perspective view cf another
10 apparatus used to attach zipper strip 10 to
thermoplastic sheet material 50. Thermoplastic sheet
material 50 is conveyed in the direction of the arrow
thereon toward an FFS machine, and, as before, is
moved intermittently in increments equal in length to
15 the length of the packages being produced.
Again, each time the thermoplastic sheet material
SO is momentarily brought to rest, a length of zipper
strip 10 is sealed transversely across the upwardly
facing side thereof. Zipper strip 10 is dispensed
20 from a roll or other supply not shown in Figure 5,
being pulled therefrom by a perforated belt 80
entrained about chambers 82, 84 attached to a vacuum
or suction. Suction through the perforated belt 80 is
used to transport the zipper strip 10. A stationary
25 guillotine 85, through which the zipper strip 10
passes, is used t:o cut the zipper strip 10 when
required.
Each time the thermoplastic sheet material 50 is
momentarily brought to rest, perforated belt 80 draws
30 a length of zipper strip 10 transversely across
thermoplastic sheet material 50. The leading flange
24 and the trailing flange 26 of the zipper strip 10
extend beyond the t:wo sides of the perforated belt 80
and chamber 82, which extend into the space between
35 the top sealing jaw 62 and its corresponding bottom
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sealing jaw 64, the latter of which is one the
underside of the thermoplastic sheet material 50. The
leading and trailing flanges 24, 26 extend outward
from between the tap and bottom sealing jaws 62, 64.
The vacuum is turned off. When the jaws 62, 64 close,
heat seal bars 28 seal the flanges 24, 26 to the
thermoplastic sheet material. The jaws 62, 64 are
then opened, and the thermoplastic sheet material 50
is moved a length equal to the length of a package
being manufactured. The vacuum is then turned on;
guillotine 86 cuts the zipper strip 10; and the
perforated belt 80 draws the portion of zipper strip
10 transversely across the thermoplastic sheet
material 50 to repeat the process.
Any of these preceding apparatus for attaching a
zipper strip 10 to thermoplastic sheet material 50 may
be used in the manufacture of packages on a horizontal
or vertical FFS machine. In this regard, Figure 6 is
a schematic view of a horizontal apparatus. A roll 90
of thermoplastic sheet material 50 dispenses the sheet
50 intermittently in lengths equal to that of the
packages being manufactured and filled. A length of
zipper strip 10 is applied by the zipper applicator
92, which may include any of the three apparatus
described, to the center of the sheet material SO, as
shown ir. Figure 7, leaving sufficient material along
the two lateral edges 96 of the sheet material 50 to
fold over toward one another for joining in an overlap
or fin seam.
An accumulator 94 is used to convert the
intermittent motion of the thermoplastic sheet
material 50 to a continuous motion.
A product conveyor 98 carries the product 99 to
be packaged toward. the wrapping machine 100, which
comprises a forming area 102, a pealing area 104, and
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CA 02226903 2002-08-22
y
a cross-seal area 106. In the forming area 102, the two lateral
edges 96 of the sheet material 50 are folded upward and around the
product. In the sealing area 104, the two lateral edges 96 are
sealed to ane another with a fin or lap seal to form a continuous
film tube with the product and zipper strips 10 inside. In the
cross-seal area, the webs of the zipper strip 10 are sealed to the
sheet material 50, without sealing the webs to each other and the
packages are separated from one another along lines 112 and
carried onward by the takeaway conveyor 108.
Fig. 8 depicts 110 formed in accordance with the above and
containing therein the product 99. In this package the top twide)
flange 26 of one of.the profiles is sealed to the portions of the
film web forming the package bottom 114 as well as the package top
116. The other wide flange 24 of that profile is secured to the
portions of the film web forming the package bottom 114 while the
narrow flange of the other profile is secured only to the portions
of the film web forming the package top 116.
Modifications to the above would be obvious to those of
ordinary skill in the art, but would not bring the invention so
modified beyond the scope of the appended claims.
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