Note: Descriptions are shown in the official language in which they were submitted.
CA 02457657 2006-07-10
RECLOSABLE BAG HAVING WICKET FLAP AND
SLIDER-ACTUATED STRING ZIPPER
BACKGROUND OF THE INVENTION
This invention generally relates to reclosable bags having slider-
actuated plastic zippers. In particular, the invention relates to slider-
actuated
reclosable bags having a header or flap with holes or slits for mounting a
stack
of bags on a wicket.
Reclosable bags are finding ever-growing acceptance as primary
packaging, particularly as packaging for foodstuffs such as cereal, fresh
fruit and
vegetables, snacks and the like. Such bags provide the consumer with the
ability
to readily store, in a closed, if not sealed, package any unused portion of
the
packaged product even after the package is initially opened.
Reclosable bags comprise a receptacle having a mouth with a
plastic zipper for opening and closing. In recent years, many zippers have
been
designed to operate with a slider mounted thereon. As the slider is moved in
an
opening direction, the slider causes the zipper sections it passes over to
open.
Conversely, as the slider is moved in a closing direction, the slider causes
the
zipper sections it passes over to close. Typically, a zipper for a reclosable
bag
includes a pair of interlockable profiled closure strips that are joined at
opposite
ends of the bag mouth. The profiles of interlockable plastic zipper parts can
take
on various configurations, e.g. interlocking rib and groove elements having so-
called male and female profiles, interlocking alternating hook-shaped closure
elements, etc. Reclosable bags having slider-operated zippers are generally
more
desirable to consumers than bags having zippers without sliders
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because the slider eliminates the need for the consumer to align the
intertockable zipper profiles before causing those profiles to engage.
Reciosable bags are commonly used by deti clerks in grocery
stores to package cheese and deli meats sold to consumers. To facilitate
handling of the reclosable bags by the deli clerks, ttie bags often include a
header having one or more holes for munting a stack of bags to one or more
dispensing posts. The reclosable bags are typically mounted to the dispensing
posts in bag packs consisting of a predetermined number of bags. The
dispensing posts may, e.g., take the fonr of a U-shaped wicket wherein the
legs of the U-shaped wicket penetrate respective holes formed in the header of
each bag. The header may take the form of a top header extending upward
from the zippered mouth of the bag or a bottom header extending downward
from the bottom of the bag.
U.S. Patent No. 5,682,730 discloses a plurality of plastic bags
formed into unitary packs for shipping and loading onto dispensing posts. This
is done by stacking the bags and then assembling them into a unitary pack by
penetrating the stack with a heated or ultrasonic pin or punch element to
for'm
apertures. The bags in the pack are heat-welded or ultrasonically welded
together along the periphery of the apertures. To maintain the integr~ty of
the
bag pack during shipping, the bag is mounted to dispensing posts in the form
of
a wicket prior to shipment.
More specifically, U.S. Patent No. 5,682,730 discloses a
reclosable bag. having a bottom header wiEh two holes for mounting the plastic
bag to a pair of dispensing posts. The holes are spaced apart along a lateral
line running generally parallel to the zipper. The bottom header includes a
line
of perforations that allows the bag to be torn away from the header after the
bag has been filled with product. The embodiment illustrated in U.S. Patent
No.
5,682,730 has a bottom header that includes a pair of opposing header panels
connected by a fold. The fold forms a primary bottom, while a seal line of
thermal fusion forms a secondary bottom at the junction of the receptacle and
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the header. This patent further states that one of the header panels can be
eiiminated. The top of the bag U.S. Patent No. 5,682,730 has a slider-actuated
zipper. The zipper comprises two profiled zipper parts that have respective
fins
or flanges thermally fused to the inner surfaces of the receptacle panels.
An altemative to the aforementioned flanged zipper design is the
so-called flangeiess or string zipper, which has substanbaHy no flange
portions
above orbeiow the interiockabie zipper strips. In the case of a string zipper,
the
bag making film Is joined to the backs of the bases of the zipper strips.
String
zippers can be produced at much greater speeds, allow much greater footage
to be wound on a spool, thereby requiring less set-up time, and use less
material than flanged zippers, enabling a substantial reduction in the cost of
manufacture and processirig.
Canadian Patent file No. 2,457,593 discloses a reclosable bag in
which respective marginal portions of the bag film are sealed to the backs of
respective flangeless zipper strips and in which the resulting string zipper
is
actuated by means of a slider.
There is a continuing need for new designs of wicketed
reclosable bags that can be manufactured at low cost.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is directed to a reclosable bag having a
bottom flap with holes configured to allow a stack of bags to be mounted on a
wicket, a slider-actuated string zipper instai)ed in a mouth at the top of the
bag
and a string zipper, not actuated by a slider, installed at the bottom of the
bag.
The invention is further directed to a method of manufacturing such bags. The
string zipper at the bottom of the bag is not intended to be opened once it
has
been closed.
One aspect of the invention is a reclosable bag comprising: a
receptacle comprising first and second walls joined at their sides, the first
and
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seoond walls comprising respective upper marginal portions that forrn a mouth
at a top of the receptacle and respective lower portions at a bottom of the
receptacle; a first string zipper comprising a first pair of mutualfiy
interiockable
zipper parts respectnrely joined to the upper marginal portions of the first
and
second walls; a second string zipper comprising a second pair of mutually
interfockabfe zipper parts respectively joined to the lower portions of the
first
and second walls; the zipper parts of the second pair being interlocked with
each other; a slider mounted on the first string zipper for opening and
closing
the first string zipper; and a flap extending downward from the bottom of the
receptacle.
Another aspect of the invention is a method of manufacturing a
reclosable bag, comprising the following steps: (a) folding a web of bag
making
film so that a first portion of the web on one side of the fold has an
extension
portion that extends beyond an edge of a second por#ion of the folded web; (b)
joining the backs of first and second flangeless zipper strips to one of the
first
and second web porfions before or after the folding step; (c) joining the
backs
of third and fourth flangeless zipper strips to the other of the first and
second
web portions before or after the folding step, the first and third zipper
strips
being mutually confronting to form a first string zipper, and the second and
fourth zipper strips being mutually confronting to form a second string zipper
that is further away from the folded edge of the web than the first string
zipper
is; (d) cutting respective portions of the first and second web portions
adjacent
the first string zipper to remove the folded edge of the web; and (e)
inserting a
slider on the first string zipper.
A further aspect of the invention is a method of manufacturing a
reclosable bag, comprising the following steps: (a) folding a web of bag
making
film so that a first portion of the web on one side of the fold has an
extension
portion that extends beyond an edge of a second portion of the folded web; (b)
joining the back of a first flangeiess zipper strip to the second web portion
in a
zone proximat to where the fold will or has been formed; (c) joiriing the back
of
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a second flangeless zipper strip to the first web po.dion in a zone that will
confront the first fiangeless zipper strip when the web is in the folded
state; (d)
joining the back of a third flangeless zipper strip to the second web portion
in a
zone proximal to the edge of the second web portion; (e) joining the back of a
fourth flangeless zipper strip to the first web portion in a zone that will
confront
the third flangeless zipper strip when the web is in the folded state; (f)
cutting
respective portions of the first and second web portions adjacent the first
and
second flangeless zipper strips to remove the folded edge of the web; and (g)
inserting a slider on the first and second flangeless zipper strips.
Yet another aspect of the invention is a reclosable bag
comprising: a receptacle having a top and a bottom; a first string zipper
attached to the top of the receptacle for providing access to an interior
volume
of the receptacle; a second string zipper attached to the bottom of the
receptacle; a slider mounted on the first string zipper for opening and
closing
the first string zipper; and a flap extending downward from the bottom of the
receptacle, the flap comprising a discontinuity and a line of weakened tear
resistance that traverses an area disposed between the second string zipper
and the discontinuity.
A further aspect of the invention is a method of manufacturing a
reclosable bag, comprising the following steps: (a) arranging film material to
form opposing walls and a flap connected to one of the walls; (b) joining a
ftrst
portion of the film materiat to a back of a first flangeless zipper strip
before or
after the arranging step; (c) joining a second portion of the film material to
a
back of a second flangeless zipper strip before or after the arranging step;
(d)
joining a third portion of the film material to a back of a third flangeless
zipper
strip before or after the arranging step; (e) joining a fourth portion of the
film
material to a back of a fourth flangeless zipper strip before or after the
arranging step; (f) aligning the first and second flangeless zipper strips
with
each other; (g) aligning the third and fourth flangeiess zipper strips with
each
other; (h) after steps (b), (c) and (f) have been performed, mounting a slider
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onto the atigned first and second flangeless zipper strips, with the first
portion of
the film material being disposed between a first side wall of the slider and a
back of the first flangeless zapper strip, and the second portion of the film
material being disposed between a second side wall of the stider and a back of
the second flangeless zipper strip; and (1) joining fifth and sixth portions
of the
film materia0 to each other and joining seventh and eighth portions of the
film
materiai to each other for forming a receptacle in concert with the first and
second opposing walls and the first and second string zippers, the flap being
connected to the receptacle.
Other aspects of the invention are disclosed and claimed below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. I is a drawing showing a front view of a reclosable bag in
accordance with one embodiment of the present invention. For the purpose of
this illustration, lt has been assumed that the bag fiim is optically
transparent,
so that the string zippers are visible behind a layer of film.
FIG. 2 is a drawing showing a sectional view of a string zipper
lncorporated in the bottom of the bag shown in FIG. 1.
FIG. 3 is a drawing showing a sectlonal view of a sfider string
zipper assembly [previously disclosed in U.S. patent application Ser. No.
10/367,450] incorporated in the bag depicted in FIG. 1. The zipper is shown
sectioned in a plane in front of the closing end of the slider.
FIG. 4 is a drawing showing, on an enlarged scale, a sectlonal
view of the string zipper incorporated in the assembly of FIG. 3.
FIG. 5 is a drawing showing a top view of a continuous-
movement section of an automated production line in accordance with one
embodiment of the present invention. The zipper-film assembly is advanced
from left to right, as indicated by arrow A.
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FIG. 6 is a drawing showing a top view of an intermittent-
movement section of the production line, which section follows the continuous-
movement section shown in FIG. 5. The continuous movement in the section
shown in FIG. 5 is converted to intermittent movement in the section shown in
FIG. 6 by a conventional dancer assembly (not shown).
FIG. 7 is a drawing showing a sectional view of the folded edge of
the web af film with a stting zipper installed in the fold and prtor to
trimming.
Reference will now be made to the drawings in which similar
elements in different drawings bear the same reference numerals.
DETAILED DESCRIPTION OF THE INVENTION -
A reclosable bag in accordance with one embodiment of the
invention is shown in FIG. 1. The bag comprises a receptacle 102 having a top
104, a bottom formed by a string zipper 106, and left and right side seals
108,
110.- The string zipper 106 comprises a pair of interlocked zipper strip
joined at
their ends by respective seals 68. Another string zipper 4 is installed at the
top
104 of the bag. String zipper 4 is actuated by a slider 10. The string zipper
4 is
opened when the slider 10 is moved in the direction of the arrow, 0 and closed
when the slider 10 is moved in the direction of the arrow C. The string zipper
4
comprises a pair of interiocked zipper strip joined at their ends by
respective
slider end stops 66.
The bag depicted in FIG. 1 further comprises a flap or panel 112
that extends from the bottom of the receptacle 102 in a direction away from
the
top of the bag. The flap 112 is a rectangle having a length equal to the width
of
the receptacle 102. The flap has a line 114 of weakened tear resistance that
extends along substantially the entire length of the flap 112 in parallel with
and
spaced apart from the string zipper 106. The line 114 of weakened tear
resistance may comprise a line of spaced perforations, a scoreline, or any
other
functionatly equivalent structure. The flap 112 can be integrally formed with
either the front or rear wall of the receptacle 102. The flap 112 has a pair
of
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circular holes 116 which are spaced apart along a line running generatly
parallel
to the line 114 of weakened tear resistance. These holes are used to mount
each bag on a pair of posts or wicket legs (not shown in FIG. 1,) to form a
stack.
Slits can be used instead of holes.
6 Bags of the type depicted in FIG. I are typically manufactured on =
a machine. At the end of the production line, when each finished bag comes off
the macFiine, each finished bag is carried and placed over a pair of posts. A
predetermined number of bags are placed on the posts to. form a stack. The
filled posts are then moved and replaced by another set of posts having no
bags stacked thereon. The stack of bags is then lifted manually or
automatically
off of the posts and while the holes are stiil aligned, the parallel legs of a
U-
shaped wicket made of wire are passed through the holes. The stack of bags is
secured on the wicket and then placed inside a box for shipment, e.g., to a
grocery store. In use, the bags are filled with product manually, as depicted
in
Figure 3 of U.S. Patent No. 5,682,730. Then the open top of the bag is closed
by manipulation of the slider. Finally, the filled bag is removed from the
stack by
tearing the bag along the line of weakened tear resistance, thereby severing
the
filled receptacle from the flap that remains mounted to the wicket.
Attematively, the bags can be sealed to each other by ultrasonic
pins during the process of forming holes for dispensing posts.
As seen in FIGS. 2 and 3, the receptacle 102 comprises a front
wall 2a arid a rear wall 2b. Referring to FIG. 2, the aforementioned flap 112
is
part of the rear wall 2b and extends beyond the edge of the front wail 2a. The
string zipper 106 is sealed, e.g., by conduction-heat sealing, to opposing
band-
shaped zones on the front and rear walls 2a, 2b of the receptacle. The string
zipper 106 extends across the full width of the receptacle and comprises a
pair
of mutually interlocked, extruded plastic zipper. parts or strips 6' and 8'.
The
zipper strip 6' is placed proximal to the edge of front wal 2a.
8
.~ . , ~.. . .. ., .,
............. _.. .. .:,.. ,... ... ,.r. . ..,. 't%r .w.:a..rbA .
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The string zipper 106 is not intended to be reclosable and thus is
designed to not open during normal usage of the reclosabte bag. Although
string zipper 106 has a construction similar to that of string zipper 4,
string
zipper 106 has smaller dimensions and is made of low-slip material. In
particula;, zipper strip 8' comprises a base and two generally arrow-shaped
rfb-
iike male closure elements or members projecting from the base, while zipper
strip 6' comprises two pairs of hook-shaped gripper jaws connected by a
sealing bridge. The male profiles respectivety intedock with the female
profiles
to maintain the closure of string zipper 106. In the disclosed embodiment, the
profile of each maie member has a stem flanked by shoulders or teeth that
converge at the tip of the profile. Each female profile comprises a pair of
gripper
jaws extending from a base or root of the female profile. Each jaw comprises a
wall and a hook integrally formed at the distal end of the respective wall.
The
hooks are inclined and generally directed toward each other, the distal ends
of
the hooks defining a mouth that communicates with a groove defined by the
walls and root of the female profile. Each pair of jaws receives and
interlocks
with a respective male member, as seen in FIG. 2, the hooks effectively
latching the heads of the male members. Other zipper constructions could be
used that are.designed only for interlocking.
The plastic material used in the extrusion of the zipper strips 6'
and 8' is selected or treated to provide tow-stip surfaces. Because the string
zipper 106 is intended to remain closed during usage, no opening mechanism,
such as a slider or pull flaps, is provided. The bag making film is attached
to the
backs of the zipper strips 6' and 8', so that no peeling action is generated
by the
internal forces exerted when the bag is filled with product. After the bag
making
film has been joined to the backs of the zipper strips of string zipper 106,
the
ends of the zipper strips are fused together by the application of ultrasonic
wave energy.
Referring to FIG. 3, the bag further comprises a string, zipper 4
installed in the mouth at the top of the receptacle and a slider 10 mounted on
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the string zipper 4 for opening and closing the mouth of the bag. The string
zippers 4 and 106 at the top and bo#tom of the receptacle are generally
mutually parallel. The string zipper 4 extends across the full width of the
receptacle and comprises a pair of mutually interiocked, extruded plastic
zpper
parts or strips 6 and 8, the latter, in accordance with one embodiment, being
similar in structure to zipper strips 6' and 8' respectively, with several
distinctions described hereinafter. However, depending on the closing strength
required at the bottom of the bag, the structure of string zipper 4 may be
different. The upper marginal portions of the front and rear bag walls 2a and
2b
(see FIG. 3) are respectively sealed to the backs of the zipper strips 6 and 8
by
a conventional conduction heat sealing technique. The preferred zipper
material is polyethylene or polypropylene.
The string zipper 4 is shown on a larger scale in FIG. 4. Again the
numerals 2a and 2b indicate the opposing walls (made, e.g., of plastic film)
of
the receptacle. Zipper strip 8 comprises a base 14 and two generally arrow-
shaped rib-like male closure elements or members 20 and 28 projecting from
base 14, while zipper strip 6 comprises two pairs of hook-shaped gripper jaws
16, 18 and 22, 24 connected by a sealing bridge 12. The pairs of gripper jaws
16, 18 and 22, 24 form respective complementary female profiles for receiving
the male profiles of closure elements 20 and 28.
Still referring to FIG. 4, the sealing bridge 12 and the base 14 are
resitiently flexible setf-supporting structures having a thickness greater
than the
thickness of the bag film. The male closure eiemertits are integrally formed
with
the base 14, while the female closure elements are integrally formed with the
sealing bridge 12. The upper margins of the walls 2a and 2b of the bag are
joined to the backs of the sealing bridge 12 and the base 14 respectively. The
upper margins of the bag film may have short free ends that extend beyond the
termination points depicted in FIG. 4, provided that the free. ends are not so
long as to interfere with travel of the slider along the zipper or become
entangled with the zipper profiles.
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The end face of upper edge 30 of the base 14 that carries the
male closure elements 20 and 28 is inclined at.about a 45 angle to facilftate
loading of the slider onto the zipper from above without snagging on a corner
of
the upper edge. The bottom edge of the base 14 cooperates with a retaining
ledge on the slider (to be described later) to increase the slider pull-off
resistance. For the same purpose, a rib 26 is formed on zipper part 6, the rib
26 cooperating with a retaining ledge on the other side of the slider_
To open the closed zipper, the zipper parts 6 and 8 are pushed
apart with sufficient force by the slider plow (item 42 in FIG. 3) to pry the
heads
of the male members out of the female profiles. When the shoulders of the
male members clear the hooks of the outwardly flexed gripper jaws, the male
and female members are no longer interlocked and the zipper is open.
Numerous configurafions for the interiockable male and female
members are known in the art. The present invention is not limited to use with
male members having an arrow-shaped head. Male members having expanded
heads with other shapes may be used. For example, instead of an expanded
head having a pointed tip, the front face of the expanded head may be
rounded. In other words, the head could have a semicircular profile instead of
a
triangular profile. Attematively, the expanded head of the male member could
have a trapezoidal profile. In addition, although FIGS. 2 and 4 show rib and
= groove arrangements, the profiles of the zipper strips may take any form.
For
example, either string zipper may comprise altemating hook-shaped closure
elements.
Nor is the invention limited to having two female profiles on one
zipper strip and two male profiles on the other zipper strip. In the first
place, the
string zipper could have one complementary set of male and female profiles, or
it could have more than two complementary sets of male and female profiles.
Furthermore, in the case of two complementary sets of male and female
profiles, one zipper part could have one male profile and one female profile,
while the other zipper part has one female profile and one male profiie. Other
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vadations should be apparent to persons skilled in the art of resealable
packaging.
Referring again to FIG. 1, the string zipper 4 further comprises
end stops 66 for preventing the. slider from sliding off the end of the zipper
when the slider reaches the zipper closed or fully opened posi#ion. Such end
stops perform dual.functions, serving as stops to prevent the slider from
going
off the end of the zipper and also holding the two zipper profiles together to
prevent the bag from opening in response to stresses applied to the profiles
through normal use of the bag. In accordance with one embodiment of the
invention, the end stops comprise stomped areas on the zipper parts
thernseives. The stomped end stops comprise sections of the zipper parts that
have been fused together and flattened at the ends of the zipper. During
deformation, thermoplastic zipper material fiows upward such that the end
stops are raised in height above the peak of the undeformed zipper on which
the slider rides. Such stomping can be carried out using ultrasonic welding
equipment. The horn and anvil of the ultrasonic welding apparatus disclosed
theiein are specifically designed so that the ultrasonic stomping operation
create
a vertical hump on the zipper to stop the slider, while at the same time
preserving
the base of the zipper profile to resist pull-off of the slider. Sufficient
heat
penetrates into the mass of the zipper profile in the end stop areas to fuse
the
zipper parts together, posing an obstacle to the slider plow. Also, a V-shaped
notch can be formed in one end or both ends of the slider top wall for
receiving
the vertical hump of respective formed end stops. This allows the plow to abut
against the fused end of the zipper in the zipper fully closed state.
In the slider-zipper assembly shown in FIG. 3, the slider 10 for
opening or closing the reclosable zipper is generally shaped so that the
slider
straddles the zipper profiles. The upper margins of the bag walls 2a and 2b,
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which are joined to the backs of the zipper strips 6 and 8, are disposed
between the respective zipper strips and the respective side walls of the
slider.
The slider 10 shown in FIG. 3 is more fully disclosed in Canadian
Patent file No. 2,457,593. The slider 10 comprises a top wall 32,
a pair of side walls 34 and 36 connected to opposing sides of the top wall 32,
the top wall 32 and side walls 34, 36 forming a tunnel for passage of the
string
zipper therethrough. The ends of the slider are open to allow the zipper to
pass
through. The width of the tunnel is substantially constant along the section
that
is divided by the plow and then narrows from a point proximal to the end of
the
plow to the dosing window at one end face of the slider. The narrowing section
of the tunnel is formed by a pair of substantially planar, inclined interior
surfaces
(not visible in FIG. 3), which converge toward the closing window of the
slider.
The inclined surfaces funnel or squeeze the zipper strips toward each other,
causing the zipper profiles to interiock, as the slider is moved in the
closing
direction. The side walls 34 and 36 are formed with concave curved
indentations where the user may place the tips of an index finger and a thumb
for gripping the slider. Aitematively, convexities (e.g., ribs) could be
formed on
the sides of the slider to facilitate grasping.
The slider 10 also comprises a plow or divider 42 that depends
downward from a central portion of the top wall 32 to an elevation below the
lowermost portions of each side wall. The plow partitions the tunnel inside
the
slider and is disposed between opposing sections of the zipper strips that
pass
through the tunnel. The tip of the plow 42 is truncated and has rounded edges
and flattened corners at opposing ends for facilitating insertion of the plow
between the zipper profiles without snagging.
The plow 42 comprises a beam having a cross-sectional shape
that is a rectangle with rounded comers. The axis of the beam is generally
perpendicular,to the top wall of the slider. As the slider is moved in the
opening
direction (i.e., with the closing end leading), the plow 42 pries the
impinging
sections of zipper strips 6 and 8 apart. The plow 42 dividos the opening end
of
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the slider tunnel into respective passages for the separated zipper strips to
pass through.
As partly seen in FIG. 3, the slider 10 further comprises a
retaining projection or ledge 38 that projects inward from the side wall 34
and a
retaining projection or ledge 40 that projects inward from the side wall 36.
The
ledges 38 and 40 project toward each other, forming respective latches for
latching the siider onto the zipper. The ledges 38 and 40 have substantially
coplanar, generally horizontal upper surfaces on whic.ti the bottom edges of
the
zipper profiles can sit, thereby effectively latching the slider under the
bottom
edges of the zipper parts to increase slider pull-off resistance. For improved
gripping, the upper surfaces of the retaining ledges may be angled upward
toward the distal edge.
The ledges 38 and 40 further comprise respective inclined bottom
surfaces 50 and 52 that extend downward and outward from the respecctivve
inner edges of the generally horizontal surfaces. The inclined,surfaces 50 and
52 are each substantially planar, with the respective planes of these inclined
surfaces intersecting at a line inside the tunnel that is generally parallel
to the
longitudinal axis of the slider. The inclined surfaces 50 and 52 serve to
guide
the respective zipper strips 6 and 8 into the slider tunnel during insertion
of the
slider onto the zipper. The sliders are typically inserted at spaced intervals
onto
a zipper-film assembly that is being intermittently advanced in a machine
direction by automated slider insertion equipment.
The generally horizontal surfaces of ft retaining ledges latch
under the zipper profiles and assist in retaining the stider on the zipper,
while
the inclined bottom surfaces of the retaining ledges assist in slider
insertion
onto the zipper by guiding or funneling the respective zipper parts into the
slider
passageway, including the passages on opposing sides of the plow.
The slider may be made in mu#iple parts and welded together or
the parts may be constructed to be snapped together. The slider may also be of
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CA 02457657 2006-07-10
one-piece construction. The slider can be made using any desired method,
such as injection molding. The slider can be molded from any suitable plastic,
such as nylon, polypropylene, polystyrene, acetal, polyketone, polybutylene
terephthalate, high-density polyethylene, polycarbonate, or ABS. To reduce the
cost of manufacture, the slider may be designed to reduce the amount of
material used and to increase the speed with which such siiders _can _be
injection molded.
Reclosable packages of the type depicted in FIG. 1 can be
manufactured on an automatic production line. An exemplary production line is
shown in FIGS. 5 and 6. FIG. 5 shows a section of the production line in which
the zipper strips and bag making film move continuously. FIG. 6 shows a
further section in which the zipper strips and bag making film move
intermittently. The continuous movement in the section shown in FIG. 5 is
converted to intermittent movement in the section shown in FIG. 5 by a
conventional dancer assembly (not shown).
The operations performed continuously during continuous
advancement include: folding a web of film so that one side of the web extends
beyond the edge of other (short) side of the web, the extending portion being
hereinafter referred to as the "flap"; introducing one string zipper at an
angle
and sealing it to the two sides of the web a short distance from the fold;
introducing another string zipper at an angle and sealing it to the two sides
of
the folded web proximal to the edge of the short side of the folded web;
trimming the folded edge of film at a point proximal to the nearest string
zipper,
and forming a line of perforations in the flap (i.e., the extended porlion of
the
.25 long side of the folded web) at a point beyond the edge of the short side
of the
folded web.
The operations performed intermittentiy during dwell times
include: inserting sliders on the string zipper adjacent to which the folded
edge
of the film was trimmed; forming slider end stops at spaced intervals on that
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same string zipper; presealing the other string zipper at spaced intervals;
forming pairs of holes in the flap at spaced intervals; and cutting the zipper-
film
assembly with - a hot knife that both seals and severs to form separate
packages. Other operations are performed during intermittent advancement of
the zipper-film assembly. For example, during each intermittent advancement,
the zipper is pried open by a stationary separator assembly at a point
upstream
of the slider insertion zone. In addition, downstream of the slider insertion
zone,
a previously inserted slider is held stationary while the zipper-film assembly
moves relative thereto, such relative movement of the slider closing a
corresponding section of the upper string zipper. The transition from
continuous
advancement of the film to intermittent advancement of the film is
accomplished by a conventional dancer assembly. The foregoing operations
will now be described in more detail with reference to FIGS. 5 and 6.
FIG. 5 shows a portion of a web 60 of bag making film after the
web has been unwound from a roll (not shown) and then passed over a folding
board or plow (not shown) in conventional fashion. The film web is pulled
through the by conventional guide and drive rollers (not shown). In FIG. 5,
the
numeral 76 designates the fold in the web of film. Although the fold is along
a
line generally parallel to the edges of the web, the fold line is closer to
one edge
73 than to the other edge 71. Because the fold is located off-center in the
web,
one side of the folded web 60 is longer than the other. The shorter side of
the
folded web is designated 2a in FIG. 2; the longer side is designated 2b and
will
uitimately form the wicket flap (item 112 in FIG. 1). The web of film 60
advances continuously in the direction indicated by arrow A.
At the same time, a pair of closed string zippers 70 and 72, each
comprising a respective pair of mutually interiocked flangeless zipper strips,
are
unwound from a respective reel (not shown), fed continuously at an angle and
guided into respective positions between the opposing sides of the folded web
60. The zipper 72 is placed proximal to the fold 76, while the zipper 70 is
placed
adjacent the edge 73 of the web.'At a zipper sealing station, opposing
portions
16
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of the web are joined to the backs of the mutually interlocked zipper strips
of
string zipper 70 by a pair of mutually opposing conventionat heated sealing
bars
75 (only one of which is visible in FIG. 5), while opposing portions of the
web
are joined to the backs of the mutually interlocked zipper strips of string
zipper
72 by a pair of mutually opposing conventionai heated sealing bars 74 (only
one of which is visible in FiG. 5).
The zipper sealing station is conventional apparatus. As the
folded web 60 with closed string zipper 72 advances continuously between the
opposing sets of sealing bars 74, the respective zipper strips have their
backs
sea{ed to the opposing portions of the bag making film, thereby continuously
attaching incoming sections of the moving string zipper to adjoining sections
of
the moving web. The sealing is accomplished by electrically heating the
sealing
bars 74, the heat being conducted through respective 'endless barrier strips
(not
shown) made of Teflon or similar materiai, which circulate on respective sets
of
'i5 rollers (not shown). Each Teflon barrier strips passes between a
respective side
of the folded web and a respective sealing bar In the gaps between the
opposing sealing bars, the web and string zipper are sandwiched between and
held together by the Teflon barrier strips, which move with the web and zipper
and prevent the bag making film from sticking against the stationary heated
sealing bars during conduction heat sealing. The Teflon barrier strips and
intervening web and zipper pass through the nips of a series of guide rollers
(not shown). The apparatus that seals zipper 70 to the opposing sides of the
web may have the same construction.
Immediately downstream from the zipper sealing stations, the
folded edge of the web 60 above the zipper 72 is cut by a pair of stationary
knives 78 (only one of which is visible in FIG. 5). More specifically, each
knife
cuts a substantial portion of the film that extends beyond the zone of film-to-
zipper strip joinder to the fold 76, thereby removing the folded edge of the
web.
The untrimmed folded edge 2c is depicted in FIG. 7, with the cutting lines
being
indicated by numerals 180 and 162. The cutting lines 160 and 162 should be
17
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placed close enough to the respective zipper strips 6 and 8 so that the
remnants of film projecting above the zipper are not long enough to interfere
with operation of the slider as it moves along the zipper.
Again referring to FIG. 5, a line of spaced perforations 114 is
formed in the flap 112 by a perforator 164. Other means for forming a line of
weakness could also be used. The perforator 164 may be a reciprocating
device mounted at a fixed station. As the zipper-film assembly advances in the
machine direction, the reciprocating device will form spaced perforations in
the
moving flap along a line slightly below the edge of the short side of the
folded
web.
The trimmed and perforated zipper-film assembly then wends its
way through a conventional dancer assembly (not shown in either FIG. 5 or
FIG. 6) on its way to the machinery depicted in FIG. 6. The dancer assembly
converts the upstream continuous advancement of the film into downstream
intermittent advancement of the film. In the intermittent advancement phase,
the zipper-film assembly is moved one package increment and then stopped for
a period of time, i.e., the dwell time. This cycle is repeated.
Referring to FIG. 6, at the first station after the dancer assembly,
the slider 10 is inserted onto the zipper-film assembly. The slider insertion
station comprises three assemblies (namely, a separator assembly, a pusher
assembly and a clamping assembly) that cooperate to insert the slider on the
zipper while the zipper is being held open on both sides of the slider
insertion
zone.
Upstream of the slider inser#on zone, a separator assembly 80
disengages the strips of string zipper 72 while the zipper-film assembly is
advanced one package length. The separator assembiy 80 comprises a central
splitter plate separated by gaps from upper and lower guides disposed above
and below the splitter plate. Only the upper guide 82 of the separator
assembly
is visible in FIG. 6. The upper and lower guides hold the respective strips of
18
CA 02457657 2006-07-10
zipper 72 in respective grooves formed in the splitter plate (not shown).
Thus,
as the zipper-film assembly is pulled through the bag making machine (by
conventional means not shown), the splitter plate will pry open successive
package-length sections of zipper during successive zipper-film advancements.
In the slider Insertion zone, a pusher assembly 81 comprises a
pusher 88 , that pushes a slider 10 onto the zipper 72. The pusher 88 is
extended by actuation of an air cylinder 90. When the pusher 88 is retracted,
the next slider must be automatically fed to a pre-insertion position directty
in
front of the pusher. This is accomplished by a conventional pneumatic slider
feeding system (not shown).
The upper and lower guides of the separator assembly 80 further
comprise respective blades that extend in cantilevered fashion into the
.slider
insertion zone. These blades are disposed to brace the respective zipper
strips against deflection as the slider 10 is pushed onto the zipper.
Downstream of the slider insertion zone, the zipper is clamped by
a clamping assembly 83 comprising a retractable separator plate 84 that is
interposed between the strips of an open section of the zipper 72. The
clamping assembly 83 further comprises upper and lower zipper clamps that
clamp the zipper strips against the extended separator plate 84. Only the
upper
zipper clamp 86 is visible in FIG. 6. The separator plate 84 is extended by
actuation of an air cylinder 92. Following extension of the separator plate
84,
the upper and lower zipper clamps are extended by actuation of respective air
cylinders that are not shown in FIG. 6.
Thus, the upper and lower guides of the separator assembly 80,
and the upper and lower clamps of the clamping assembly 83 serve to stabilize
the zipper during slider insertion. The interposition of the splitter plate
(not
shown) and the separator plate 84 between the Apper strips upstream and
19
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tTW-13971
downstream, respectively, of the slider insertion zone means that the zipper
is
maintained in an open state, with a gap between the zipper strips, in the zone
where the slider is inserted. The zipper strips are held in respective
positions
such that the slider plow 42 (see FIG. 3) enters the gap between the zipper
strips and then the slider side walls respectively pass over the zipper strips
during slider insertion. The slider is pushed onto the zipper until the
retaining
ledges Qn the slider interior latch under the zipper strips to hold the slider
securely on the zipper.
During the same dwell time that a slider is being inserted, a slider
end stop structure 67 is being formed on the zipper at an ultrasonic stomping
station downstream from the slider insertion device. This slider end stop
structure 67 will be bisected later during cutting by a hot knife 100 to form
two
slider end stops 66 (see FIG. 1), i.e., the end stop at the zipper fully
closed
slider park position for one package and the end stop at the zipper fully open
slider park position for the next package. The end stop structure 67 is formed
byan uitrasonic stomping assembly 85 comprising a hom 94 and an anvil (not
shown in FIG. 9). The hom 94 transmits sufficient uttr=asound wave energy into
that plastic zipper material that the plastic is fused into a structure (e.g.,
a
vertically extending hump) defined by the surfaces of the hom and anvil. The
hom and anvil may be of the reciprocating or rotary var-ety.
While the slider end stops 67 are being fonned on the string
zipper 72, the string zipper 70 is being pre-sealed at package length
intervals
by another uttrasonic stomping assembly comprising a hom 61 and an anvil
(not shown in FIG. 6). Preferably, guiding means are provided for maintaining
the zipper strips in alignment while presealing occurs, so that the mafe and
female profiles are pressed together and interlocked by the sealing mechanism.
The pre-sealed regions 69 are bisected dur(ng cutting by the hot knife 100 to
form two pre-seals 68 (see FIG. 1). Upstream of the pre-sealing station, the
zipper strips of string zipper 70 are separated by a separator plate 59, so
that
CA 02457657 2004-02-13
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the zipper sections between the pre-sealed zones will be open when the bags
come off the machine.
During each dwell time, other ultr=asonic apparatus forms a pair of
holes 116 in that portion (i.e., flap 112) of the long side of the web that
extends
beyond the edge of the short side of the web. For example, a pair of
uftrasonic
homs 62 and 62' are designed to form respective pairs of circular holes 116 in
each package length section of the flap 112. The anvils that cooperate with
horns 62 and 62' are not shown in FIG. 6. Altematively, holes or stits could
be
made using suitabiy shaped cutters or punches.
After each dwell time, the zipper film iassembly is advanced.
During each intermittent advancement, a slider stopper assembly 87 restrains a
slider 10 so that a respective section of zipper is closed. The slider stopper
assembly 87 comprises a stopper element 96 coupled to an air cylinder 98. The
stopper element 96 is movable from a retracted position to an extended
position by actuation of the air cylinder 98. The stopper element 96 is in its
extended position when the advancement of the zipper-film assembly begins. In
this extended position, the stopper element 96 interferes with the slider and
blocks it from advancing with the zipper. This causes a displacement of the
slider relative to the zipper in a zipper closing direction, thereby closing a
section of zipper. Before the advancement of one package length is completed,
the stopper element 96 is retracted, which allows the slider to advance past
the
retracted stopperelement.
In addition, during each dwell time, a hot cutting knife 100 (which
may comprise a solitary blade or a pair of opposed blades) cuts and forms side
seals in the film on both sides of the cut, thereby severing a bag (not shown
in
F1G, 8) from the remainder of the web 60 on the bag making machine. Each
bag is then placed so that the holes 116 in the wicket flap 112 align with and
are penetrated by a pair of posts. Each successive bag takes its place atop
the
stack of bags mounted to the posts until a predetermined maximum number of
bags is achieved. Then the stack is removed from the posts and a wicket is
21
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CA 02457657 2004-02-13
ITW-1397'i
inserted into the aligned holes, these steps being typically performed either
manually or automatically.
A stack of wicketed slider bags can be used to package produce,
deli meats, or other products. Because the bottom of the bag is open, the
packer can simply lift the top layer of the bag bottom, insert the product and
then close the bottom of the bag by pressing the zipper strips of the string
zipper 70 closed.
In accordance with an alternative embodiment of the automated
production line disclosed above, the web of film material and the string
zippers
could be moved intermittently through the section depicted in FIG. S. In this
case respective lengths of the string zippers would be sealed to the film
(e.g.,
by reciprocating seaiing bars) during each dwell time, with the string zippers
and film being advanced an equal length during each interval between
successive dwell times. The cutting and perf'orating operations would be
performed during advancement of the film.
A reclosable bag having the structure depicted in FIG. '! can be
manufactured using methods other than those described with reference to
FIGS. 5 and 6: For example, instead of folding the web of film and then
inserting and joining string zipper material between opposing web portions,
one
side of each string zipper material could be joined to the film, the film is
then
folded, and thereafter the other side of each string zipper is joined to a
confronting portion of the folded web. Aftematively, respective flangeless
zipper
strips could be joined in paraliel to an unfolded web, the web is then folded
along a centerline, and the zipper strips are interloclced after folding.
Instead of starting with a single web that is foided; one could
begin with two webs that will be sealed on two sides with respective string
zippers being attached at opposing ends of each receptacle. The use of two
webs would again entail the three variations, for each string zipper, of: (1)
placing the string zipper between the webs and sealing the sides of the zipper
22
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CA 02457657 2004-02-13
1TW-13971
to the respective webs; (2) seafing one side of the string zipper to one web,
placing the other web in opposing relationship, and then seaiing the other
side
of the string zipper to the other web; and (3) sealing one flangeless zipper
strip
to one web, sealing the other flangeless zipper strip to the other web, and
then
interlocking the zipper strips while attached to the respective webs.
The invention does not require that the slider have a plow or
separating finger. The slider-zipper assembly could be designed so that the
side walls of a straddling slider cam or push the zipper open, without the aid
of
a plow or separating finger, when the slider is moved in an opening direction.
White the invention has been described with reference to
preferred embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
members thereof without departing from the scope of t!-ie invention. In
addition,
many modifications may be made to adapt a particular situation to the
teachings of -the invention without departing from the essential scope
thereof.
Therefore it is intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out this
invention, but that the invention will include all. embodiments fatling within
the
scope of the appended claims.
As used in the claims, the verb "joined " means fused, bonded,
seated, adhered, etc., whether by application of heat and/or pressure,
application of ultrasonic energy, application of a layer of adhesive material
or
bonding agent, interposition of an adhesive or bonding strip, etc. As used in
the
claims, the term "string zipper" means a zipper comprising two interiockabie
closure strips that have substantially no flange portions.
23
~._._. ,
