U.S. patent application number 10/090972 was filed with the patent office on 2003-09-11 for reclosable packaging having hermetic zipper and related method of manufacture.
Invention is credited to Fenzl, Eric J., Linton, Basil C..
Application Number | 20030169948 10/090972 |
Document ID | / |
Family ID | 27787647 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030169948 |
Kind Code |
A1 |
Fenzl, Eric J. ; et
al. |
September 11, 2003 |
Reclosable packaging having hermetic zipper and related method of
manufacture
Abstract
A reclosable package or bag having a mouth with a hermetic
plastic zipper installed therein. The hermetic zipper has first and
second interlockable profiled structures connected by a frangible
connection and having no flanges. The package or bag is constructed
such that the frangible connection resides on the product side of
the zipper, i.e., the frangible connection extends inside the
receptacle of the package or bag, when the package is in an
unopened state, i.e., when the zipper is closed. Preferably, the
first interlockable profiled structure has at least one male member
with an expanded head and the second interlockable profiled
structure has at least one female member with a groove for
receiving the expanded head of a male member.
Inventors: |
Fenzl, Eric J.; (Loganville,
GA) ; Linton, Basil C.; (Loganville, GA) |
Correspondence
Address: |
OSTRAGER CHONG & FLAHERTY LLP
825 THIRD AVE
30TH FLOOR
NEW YORK
NY
10022-7519
US
|
Family ID: |
27787647 |
Appl. No.: |
10/090972 |
Filed: |
March 5, 2002 |
Current U.S.
Class: |
383/61.2 ;
383/203; 383/63; 493/213 |
Current CPC
Class: |
B65D 33/2533 20130101;
B65D 33/2541 20130101; B65D 33/2525 20130101 |
Class at
Publication: |
383/61.2 ;
383/63; 383/203; 493/213 |
International
Class: |
B65D 033/16 |
Claims
1. A package comprising a receptacle having a mouth at an upper
end, and a plastic hermetic zipper attached to said mouth, wherein
said hermetic zipper comprises first and second interlockable
profiled structures without flanges and a frangible connection
connecting said first interlockable profiled structure to said
second interlockable profiled structure, wherein said frangible
connection extends inside said receptacle on a product side of said
zipper when said zipper is closed.
2. The package as recited in claim 1, wherein each of said first
and second interlockable profiled structures comprises a respective
base surface, said base surfaces being on opposing sides of said
zipper when said first and second interlockable profiled structures
are interlocked with each other, and wherein said receptacle
comprises first and second walls, said first wall being heat sealed
to at least a portion of said base surface of said first
interlockable profiled structure and said second wall being heat
sealed to at least a portion of said base surface of said second
interlockable profiled structure.
3. The package as recited in claim 1, wherein said first
interlockable profiled structure comprises a male member having an
expanded head and said second interlockable profiled structure
comprises a female member having a groove for receiving said
expanded head of said male member.
4. The package as recited in claim 1, wherein said frangible
connection comprises first and second edges, and said receptacle
comprises first and second walls and first and second side seals,
wherein said first side seal seals said first wall to said second
wall with said first edge of said frangible connection blended into
said first side seal, and said second side seal seals said first
wall to said second wall with said second edge of said frangible
connection blended into said second side seal.
5. The package as recited in claim 1, further comprising an
enclosed header that encloses said zipper, wherein a line of
perforations is formed in said header.
6. A method of manufacturing a plastic zipper comprising the steps
of: continuously extruding a layer of plastic material;
continuously extruding plastic material in the form of first and
second interlockable profiled structures without flanges; joining
said first interlockable profiled structure to a first lateral
portion of said layer; and joining said second interlockable
profiled structure to a second lateral portion of said layer,
wherein said first and second lateral portions of said layer are
separated by an intermediate lateral portion of said layer.
7. The method as recited in claim 6, wherein said extruding steps
are performed concurrently.
8. The method as recited in claim 6, wherein said layer has a
thickness such that said intermediate lateral portion of said layer
is easily breakable by a consumer.
9. The method as recited in claim 6, wherein said first
interlockable profiled structure comprises a base and a male member
having an expanded head and said second interlockable profiled
structure comprises a base and a female member having a groove for
receiving said expanded head of said male member, said first and
second lateral portions of said layer being respectively joined to
said bases of said first and second interlockable profiled
structures on a side of said bases which is respectively opposite
to said male and female members.
10. A method of manufacturing a plastic zipper comprising the step
of concurrently continuously extruding first and second
interlockable profiled structures and a web out respective die
orifices arranged so that said continuously extruded first
interlockable profiled structure lands on a first lateral portion
of said web, and said continuously extruded second interlockable
profiled structure lands on a second lateral portion of said web,
said first and second lateral portions of said web being separated
by an intermediate lateral portion of said web.
11. The method as recited in claim 10, wherein said first and
second interlockable profiled structures and said web are made of
the same plastic material.
12. The method as recited in claim 10, wherein said first and
second interlockable profiled structures are made of the same
plastic material and said web is made of a different plastic
material.
13. The method as recited in claim 10, wherein said web has a
thickness such that said intermediate lateral portion of said web
is easily breakable by a consumer.
14. The method as recited in claim 10, wherein said first
interlockable profiled structure comprises a male member having an
expanded head and said second interlockable profiled structure
comprises a female member having a groove for receiving said
expanded head of said male member.
15. A plastic zipper comprising first and second interlockable
profiled structures without flanges and a frangible connection
which connects said first interlockable profiled structure to said
second interlockable profiled structure, said frangible connection
being disposed on one side of said first and second interlockable
profiled structures when said zipper is closed.
16. The zipper as recited in claim 15, wherein each of said first
and second interlockable profiled structures comprises a respective
base having first and second sides, and said frangible connection
connects said first sides of said bases of said first and second
interlockable profiled structures.
17. The zipper as recited in claim 14, wherein said first
interlockable profiled structure comprises a male member having an
expanded head and said second interlockable profiled structure
comprises a female member having a groove for receiving said
expanded head of said male member.
18. A package comprising a receptacle having a mouth at an upper
end, first and second interlockable profiled structures
respectively attached to opposing sides of said mouth and
interlocked with each other, and a frangible connection connected
to said first interlockable profiled structure along a first
juncture, connected to said second interlockable profiled structure
along a second juncture, and connected to said receptacle along
third and fourth junctures, wherein said frangible connection
hermetically seals an inner volume of said receptacle and said
first and second interlockable profiled structures do not have
flanges.
19. The package as recited in claim 18, wherein said first
interlockable profiled structure comprises a male member having an
expanded head and said second interlockable profiled structure
comprises a female member having a groove for receiving said
expanded head of said male member.
20. The package as recited in claim 18, wherein said frangible
connection comprises first and second edges, and said receptacle
comprises first and second walls and first and second side seals,
wherein said first side seal seals said first wall to said second
wall with said first edge of said frangible connection blended into
said first side seal, and said second side seal seals said first
wall to said second wall with said second edge of said frangible
connection blended into said second side seal.
21. The package as recited in claim 18, further comprising an
enclosed header enclosing said first and second interlockable
profiled structures, wherein a line of perforations is formed in
said header.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to bags or packages such as
may be formed from plastic film and having an openable mouth with a
reclosable extruded plastic fastener or zipper situated inside the
mouth. The zipper has complementary profiles that are interlocked
when the zipper is closed and can be separated to open the zipper.
Bags or packages of this kind are well known and in widespread
use.
BACKGROUND OF THE INVENTION
[0002] In the use of plastic bags and packages, particularly for
foodstuffs, it is important that the bag be hermetically sealed and
tamper evident until the purchaser acquires the bag and its
contents, takes them home, and opens the bag or package for the
first time. It is then commercially attractive and useful for the
consumer that the bag or package be reclosable so that its contents
may be protected. Flexible plastic zippers have proven to be
excellent for reclosable bags, because they may be manufactured
with high-speed equipment and are reliable for repeated reuse.
[0003] A typical zipper has a grooved member at one side of the bag
mouth and a ribbed member at the other side, which rib may
interlock into the groove when the sides of the mouth of the bag
are pressed together. Alternatively, a strip having a plurality of
ribs may be on one side of the bag mouth, while a strip having a
plurality of channels may be on the other side, the ribs locking
into the respective channels when the sides of the mouth of the bag
are pressed together. In the latter case, there may be no
difference in appearance between the two fastener strips, as the
ribs may simply be the intervals between channels on a strip that
may lock into another of the same kind. In general, some form of
male/female interengagement is used to join the two sides of the
bag mouth together. The fastener strips are bonded in some manner
to the material from which the bags themselves are manufactured.
Usually, pull flanges extend above the ribbed and grooved fastener
strips, which pull flanges may be pulled apart for access to the
interior of the bag.
[0004] It is known to provide a zipper package construction that is
designed to undergo some permanent change in the package appearance
when the package is opened for the first time. In particular, it is
known to provide a zipper package with a sealed header that extends
over the zipper and encloses the zipper. For example, the header
may comprise extensions of the front and rear package walls, the
extensions being joined by a seal. The seal may be a peel seal,
which may be readily ruptured by a consumer to expose the zipper,
or a "hard" seal, the latter being a seal that is not intended to
be broken. In the case of a header formed using a hard seal, it is
known to provide the package header with one or more lines of
perforations that must be torn open by a consumer to obtain access
to the slider. In place of a line of perforations (or to facilitate
tearing the package along the line of perforations), it is also
known to provide one or more notches at a side edge of the header
for starting a tear across the header. In any event, the header
must be opened before access can be had to the zipper. If a package
evidences a torn header before the package is purchased by a
consumer, this should indicate to the consumer that the package has
been tampered with, e.g., previously opened.
[0005] The perforations in a sealed header allow oxygen to enter
the space between the header and the closed zipper. Since a typical
zipper having no additional gasket or sealing means is not
hermetic, oxygen in the chamber under the sealed header can
penetrate the closed zipper and enter the receptacle that holds the
contents of the package. In the case of many kinds of foodstuff,
e.g., chunk cheese, the presence of oxygen inside the receptacle
will spoil the food product. Thus, it is common in reclosable
packaging of perishable food products such as chunk cheese to
incorporate a colored tear strip, instead of perforations, to allow
the customer to access the package.
[0006] There is a need for a hermetic zipper design that would
allow perishable food products to be packaged in bags having
perforations, instead of the more expensive-to-manufacture tear
strips, in the sealed header. The inventors are currently unaware
of any device for dispensing and sealing tear strips transverse to
the web (film) direction.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a plastic zipper for
hermetically sealing the contents of a reclosable package or bag
and to a method for manufacturing such a zipper. The hermetic
zipper comprises first and second interlockable profiled structures
connected by a frangible connection. The interlockable profiled
structures and the frangible connection are mono-extruded and
fused, the frangible connection acting as a cast flange. Preferably
the first interlockable profiled structure comprises at least one
male member having an expanded head and the second interlockable
profiled structure comprises at least one female member having a
groove for receiving the expanded head of a male member. The
extruded interlockable profiled structures do not have flanges.
[0008] The invention is further directed to a reclosable package or
bag comprising a receptacle having a mouth at its upper end and
having a plastic hermetic zipper installed in the mouth. The zipper
comprises first and second interlockable profiled structures
connected by a frangible connection and not having flanges. The
package or bag is constructed so that the frangible connection
resides on the product side of the zipper, i.e., the frangible
connection extends inside the receptacle of the package or bag,
when the package is in an unopened state, i.e., when the zipper is
closed.
[0009] In accordance with the preferred embodiment of the
invention, each of the first and second interlockable profiled
structures of the zipper comprises a respective base surface. These
base surfaces are on opposing sides of the zipper when the first
and second interlockable profiled structures are interlocked with
each other. The receptacle comprises first and second walls, the
first wall being heat sealed to at least a portion of the base
surface of the first interlockable profiled structure and the
second wall being heat sealed to at least a portion of the base
surface of the second interlockable profiled structure. The
frangible connection comprises first and second edges, and the
receptacle further comprises first and second side seals, wherein
the first side seal seals the first wall to the second wall with
the first edge of the frangible connection blended into the first
side seal, and the second side seal seals the first wall to the
second wall with the second edge of the frangible connection
blended into the second side seal. In accordance with the preferred
embodiment, the package further comprises an enclosed header that
encloses the zipper. A line of perforations for tearing open the
package are preferably formed in the header.
[0010] In accordance with the preferred embodiment of the
invention, a zipper comprising interlockable profiled structures
with a frangible connection is manufactured by a method comprising
the following steps: continuously extruding a layer of plastic
material; continuously extruding plastic material in the form of
first and second interlockable profiled structures; joining the
first interlockable profiled structure to a first lateral portion
of the layer; and joining the second interlockable profiled
structure to a second lateral portion of the layer. The first and
second lateral portions of the layer are separated by an
intermediate lateral portion of the layer. The extruding steps are
preferably performed concurrently. The layer has a thickness such
that the intermediate lateral portion of the layer is easily
breakable by a consumer, e.g., by pulling apart the interlocked
profiled structures. Alternatively, the extruded layer may have a
central region with a thickness less than the thickness of the
remainder of the extruded layer. When the resulting zipper is
incorporated in a reclosable package or bag, the tear during
opening by the consumer will occur in the thinned region of the
frangible connection.
[0011] Other objects, features and advantages of the invention will
be readily apparent from the following description of certain
preferred embodiments thereof, taken in conjunction with the
accompanying drawings, although variations and modifications may be
effected without departing from the spirit and scope of the novel
concepts of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a sectional view of a reclosable bag having a
plastic hermetic zipper in accordance with one preferred embodiment
of the invention.
[0013] FIG. 2 is a schematic showing a plastic zipper having a
frangible connection in accordance with one preferred embodiment of
the invention. The zipper is shown in a closed state.
[0014] FIGS. 3 and 4 are schematics illustrating respective steps
of a method for manufacturing a plastic zipper having a frangible
connection in accordance with the preferred embodiment shown in
FIG. 2.
[0015] FIG. 5 is a schematic illustrating an automated system for
applying a plastic zipper to folded plastic film.
[0016] FIG. 6 is a schematic illustrating a portion of a station
for heat sealing a plastic zipper to folded thermoplastic film,
which station is incorporated in the system depicted in FIG. 5.
[0017] FIG. 7 is a schematic showing a plastic zipper having a
frangible connection in accordance with another preferred
embodiment of the invention. The zipper is shown in a closed
state.
[0018] FIGS. 8 and 9 are schematics illustrating respective steps
of a method for manufacturing a plastic zipper having a frangible
connection in accordance with the preferred embodiment shown in
FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Reference will now be made to the drawings, in which similar
elements in different drawings bear the same reference numerals.
The structure of a reclosable bag having a flexible plastic zipper
with a frangible connection for hermetically sealing the interior
volume of the bag is shown in FIG. 1. The reclosable bag is
generally indicated by the reference numeral 2, while the zipper is
generally indicated by reference numeral 4. It should be understood
that the zipper shown in FIG. 1 can be installed in a reclosable
bag of the type shown in FIG. 1 or in any other reclosable package
having a mouth which can be opened and closed by a flexible plastic
zipper installed in the mouth.
[0020] Still referring to FIG. 1, a bag 2 may be made from any
suitable sheet material or plastic film and comprises opposite wall
panels 6 and 8, which may be secured together at opposite side
edges of the bag by seams (not shown). The opposing bottoms of the
wall panels 6 and 8 may be joined, for example, by means of a heat
seal 10 made in conventional fashion, e.g., by application of heat
and pressure or ultrasonic energy. Typically, the bottom of the
package is formed by a fold in the original packaging film.
Optionally, the bag may be provided with side gussets having
respective junctures with the front and rear wall panels. In the
latter case, the bag may also be provided with a bottom panel
having respective junctures with the front and rear wall panels and
with the side gussets.
[0021] At its top end, the bag 2 has an openable mouth, on the
inside of which is an extruded plastic zipper 4. The zipper 4
comprises a pair of interlockable profiled structures 20 and 22 and
a frangible connection 24 joined to the interlockable profiled
structures. The wall panels 6 and 8 are respectively sealed to the
base surfaces of the interlockable profiled structures 20 and 22 by
hard seals 12 and 14. Alternatively, the interlockable profiled
structures can be attached to the wall panels by adhesive. The
front and rear wall panels 6 and 8 preferably extend beyond the
heat seals 12 and 14 to form an enclosed header 18. These upward
extensions of wall panels 6 and 8 may be joined at the top by a
heat seal 16. Preferably, however, the top of the enclosed header
is formed by a fold in the original packaging film. Alternatively,
the enclosed header 18 could be formed by folding a separate piece
of plastic material and sealing the ends of the folded piece to the
respective interlockable profiled structures.
[0022] In accordance with the preferred embodiment of the
invention, the frangible connection 24 extends between the
respective interlockable profiled structures 20 and 22. When the
zipper is closed, as depicted in FIG. 1, the frangible connection
24 is folded, with the fold extending into the interior volume 26
of the receptacle, on the so-called "product side" of the zipper.
The frangible connection must extend across the full length of the
mouth in which the zipper is installed, from one side seal of the
receptacle to the other side seal, with the side edges of the
folded frangible connection 24 being blended into the respective
side seals of the package. The side seals (not shown in FIG. 1) may
be formed in a conventional manner, e.g., ultrasonically or by
means of heat sealing. The result is that the edges of the folded
connection 24 are captured in and hermetically sealed by the side
seals. The hard seals 12 and 14, in conjunction with the side seals
that capture the side edges of connection 24, enable the frangible
connection 24 of the zipper 4 to act as a hermetic seal, preventing
the admission of air into the interior volume 26 of the bag until
that hermetic seal is broken. Preferably the connection 24 is thin
enough to provide for easy tearing open by the consumer and easy
blending into the ultrasonically or heat sealed side seals. In the
preferred embodiments shown in the drawings, the entire connection
has a constant thickness, but this is not necessary. The connection
24 could have a central section extending in the machine direction
which is thinner than the remainder of the connection to facilitate
tearing. The placement of the connection 24 on the product side
provides leverage when the consumer attempts to tear open the
connection 24 by pulling apart the interlockable profiled
structures 20 and 22.
[0023] The closed zipper 4 depicted in FIG. 1 can be seen in
greater detail in FIG. 2. The zipper 4 is preferably an extruded
plastic structure comprising a first interlockable profiled
structure 20 having two male members 28 and 28', and a second
interlockable profiled structure 22 having two female members 30
and 30'. Each male member has a generally arrow-shaped rib-like
male profile; each female member has a complementary, generally
groove-shaped female profile. Each interlockable profiled structure
further comprises a respective base 32 and 34. Preferably, each
base 32 and 34 is a resiliently flexible self-supporting structure
having a thickness greater than the thickness of the receptacle
walls of the package or bag in which the zipper will be installed.
FIG. 2 shows male member 28 engaged in female member 30 and male
member 28' engaged in female member 30'.
[0024] In a typical zipper, the profile of each male member has a
stem flanked by shoulders of the main rib portion of the profile,
and a tip of the profile points toward the opposing female member,
the tip 32 being the point of the male member furthest away from
the base of the profiled structure. The profile of each female
member comprises a pair of gripper jaws extending from a base or
root of the female member. 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 member. The
groove of the female member receives the head of the male member
when the zipper is closed, as shown in FIG. 2.
[0025] When the male members 28 and 28' are properly aligned with
and then moved into engagement with the opposing female members 30
and 30', the head of each male member will penetrate the opening in
the opposing female member. As the head of each male member
penetrates, the resilient hooks of the opposing gripper jaws are
pushed toward the groove root of the corresponding female member
and are cammed apart by the inclined surfaces running from the tip
to the shoulders of each male member. The camming force exerted on
the hooks of each female member by the head of the penetrating male
member is transferred to the resilient walls of the gripper jaws,
causing those walls to flex outwardly. The walls are flexed
outward, in opposite directions, until the hooks of the female
member pass by and snap into interlocking relation behind the
shoulders of the male member. The heads of the male members 28 and
28' are received in the grooves of the female members 30 and 30'
respectively and held there by the interlocked hooks, this
situation constituting the closed state of the zipper.
[0026] To open the closed zipper, the two sides of the zipper are
pulled apart with sufficient force to pull the heads of the male
members out of the female members. 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.
[0027] FIGS. 3 and 4 illustrate first and second steps of a method
for manufacturing a plastic zipper having a frangible connection in
accordance with the preferred embodiment of FIG. 2. The first step,
symbolically represented in FIG. 3, comprises the concurrent
continuous extrusion of plastic material out three orifices of a
die to form a layer 24, a profiled structure 20 having a base 32
and a pair of male members 28 and 28' supported by the base 32, and
a profiled structure 22 having a base 34 and a pair of female
members 30 and 30' supported by the base 34. In the next step
depicted in FIG. 4, the profiled structures 20 and 22 are joined to
respective lateral portions of the extruded layer 24. Preferably,
the layer 24 is continuously extruded concurrently with the
profiled structures 20 and 22. The plastic material exiting the die
orifices is in a sticky or partially molten state. The profiled
structures 20 and 22 are joined to the layer 24 upon contact and
fused thereto by subsequent cooling, e.g., by immersion in water.
In accordance with the preferred embodiment, the intermediate
portion of the layer (between the profiled structures) is
frangible. As used herein, the term "frangible" means that, when
the zipper is installed in the mouth of a plastic package or bag,
the intermediate portion of layer 24 can be readily torn when the
zipper halves are pulled apart by the consumer. FIG. 4 shows the
finished zipper in an unfastened, i.e., open state, while FIG. 2
shows the finished zipper with the profiled structures interlocked,
i.e., in a closed state.
[0028] FIG. 5 is a schematic illustrating an automated system for
applying a plastic zipper tape to folded plastic film. Package film
36 is paid off a roll 38 of the same at an unwind station.
Downstream a pull roller (not shown) is provided for driving the
film 36 through the machine. A V-shaped board or folder plow 40
positioned downstream of the film roll 38 folds the package film 34
about a bottom crease 42 to form opposing package walls 44 and 46.
(Although FIG. 5 depicts the package walls 44 and 46 as having
different heights, the person skilled in the art will recognize
that their heights may be equal.) The folded film assumes a
generally V shape with front and back walls 44 and 46 on either
side of the fold in a substantially vertical plane.
[0029] At the same time, a zipper tape 48, with the zipper halves
interlocked, is paid off a roll 50 of the same and fed between the
advancing package walls. The zipper tape is turned from a
substantially vertical orientation to a substantially horizontal
orientation (shown by dashed lines) by a guide roller 52. The
zipper tape is positioned near the fold in the bottom of the
packaging film, so that the folded bottom region will later become
the enclosed header of the package.
[0030] The zipper tape 48 is sealed to the opposing package walls
44 and 46 at a pair of sealing stations. The first sealing station
comprises a pair of opposing seal bars 54, as seen in FIG. 6. The
second sealing station also comprises a pair of opposing seal bars
56, only one of which is visible in FIG. 5. The sets of opposing
seal bars at the two sealing stations are located at the elevation
of the horizontally continuously moving zipper tape and are in
contact with the continuously moving package walls that sandwich
that zipper tape. The seal bars apply constant heat and pressure
for sealing the thermoplastic film of the package walls to the base
surfaces of the profiled structures of the zipper. Alternatively,
one sealing station or more than two sealing stations could be
used. The intermediate result is a continuous web of folded
thermoplastic film with a zipper tape sealed between the opposing
walls of the film. This zippered folded web of packaging film is
then passed under a second V-shaped board 58 to unfold the film.
The unfolded zippered film is then conveyed to a form-fill-seal
machine, e.g., a horizontal form-fill-seal machine (not shown in
FIG. 5).
[0031] In the case of a cheese packing plant, for example, the
cheese would be placed on the zippered film. A horizontal
form-fill-seal machine would fold panel 44 to form the bottom of
the package, seal panel 44 to the opposing panel 46, stomp the
zipper ultrasonically at locations corresponding to the side seals,
form the side seals by application of heat and pressure, form
perforations in the header, and then cut the package to width. All
of these steps can be performed by well-known techniques. Most
chunk cheese packages use a red tear strip to enable the consumer
to access the contents of a hermetically sealed package or bag. The
hermetic seal provided by the present invention would allow the
cheese packager to use perforations in the header for opening the
package, while still preventing oxygen from entering the unopened
package and spoiling the product, thereby eliminating the need for
a tear strip.
[0032] In the case of a tortilla packing plant, for example, the
zippered film is not unfolded. Instead, an ultrasonic presealer
crushes (i.e., stomps) the zipper in what will be the sides of the
bag (in this case, the zipper is on top). Then the side seals are
formed by application of heat and pressure in a well-known manner.
Each bag is then cut to width and stacked on a conveyor for final
packaging. In this case the bag bottom would be open to allow a
converter to hand pack tortillas and then run the filled packages
through another sealer to make the bottom seal. This "tortilla"
film being thin lends itself better to a perforated header. Also
polymeric film (nonlaminated) stretches and thus does not tear
well.
[0033] A zipper 4' in accordance with a second preferred embodiment
of the invention is shown in FIG. 7 in a closed state. The zipper
4' is preferably an extruded plastic structure comprising a first
interlockable profiled structure 20' having one male member 28 and
a second interlockable profiled structure 22' having one female
member 30. The male member has a generally arrow-shaped rib-like
male profile of the type previously described; the female member
has a complementary, generally groove-shaped female profile of the
type previously described. Each interlockable profiled structure
further comprises a respective base 32 and 34. Preferably, each
base 32 and 34 is a resiliently flexible self-supporting structure
having a thickness greater than the thickness of the receptacle
walls of the package or bag in which the zipper will be installed.
FIG. 7 shows male member 28 engaged in female member 30.
[0034] When the male member 28 is properly aligned with and then
moved into engagement with the female members 30, the head of the
male member will penetrate the opening in the female member. As the
head of the male member penetrates, the resilient hooks of the
opposing gripper jaws are pushed toward the groove root of the
corresponding female member and are cammed apart in the manner
previously described, causing the resilient walls of the gripper
jaws to flex outwardly, in opposite directions, until the hooks of
the female member pass by and snap into interlocking relation
behind the shoulders of the male member. The head of the male
member 28 is thus held by the interlocked hooks of the female
member 30 to maintain the closed state of the zipper.
[0035] FIGS. 8 and 9 illustrate first and second steps of a method
for manufacturing a plastic zipper having a frangible connection in
accordance with the preferred embodiment of FIG. 7. The first step,
symbolically represented in FIG. 8, comprises the concurrent
continuous extrusion of plastic material out three orifices of a
die to form a layer 24, a profiled structure 20' having a base 32
and a single male member 28 supported by the base 32, and a
profiled structure 22' having a base 34 and a single female member
30 supported by the base 34. In the next step depicted in FIG. 9,
the profiled structures 20' and 22' are joined to respective
lateral portions of the extruded layer 24. Preferably, the layer 24
is continuously extruded concurrently with the profiled structures
20' and 22'. The plastic material exiting the die orifices is in a
sticky or partially molten state. The profiled structures 20' and
22' are joined to the layer 24 upon contact and fused thereto by
subsequent cooling. In accordance with the preferred embodiment,
the intermediate portion of the layer (between the profiled
structures) is frangible. FIG. 9 shows the finished zipper in an
unfastened, i.e., open state, while FIG. 7 shows the finished
zipper with the profiled structures interlocked, i.e., in a closed
state.
[0036] Numerous configurations for the interlockable 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. Alternatively, the expanded head of the male member could
have a trapezoidal profile.
[0037] In addition, although the interlockable profiled structures
can be fused directly to the walls of the packaging material, this
is not necessary to practice of the present invention. For example,
the interlockable profiled structures could be attached to the wall
panels of the package or bag by means of intermediate thermoplastic
bonding strips or by means of adhesive.
[0038] While 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
the 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. For example, the zipper
halves and frangible connection need not be extruded from the same
plastic material. More specifically, the connection could be made
of a material that is more brittle than the material used to form
the zipper halves. 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 falling within the scope of
the appended claims.
[0039] As used in the claims, the term "package" includes bags,
pouches, and any other type of packaging in which a flexible
plastic zipper can be incorporated.
* * * * *