U.S. patent application number 12/075499 was filed with the patent office on 2008-07-03 for leakproof zipper end crush for reclosable bag.
Invention is credited to Donald L. Crevier, David J. Matthews, Lawrence Share.
Application Number | 20080159664 12/075499 |
Document ID | / |
Family ID | 35285576 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080159664 |
Kind Code |
A1 |
Share; Lawrence ; et
al. |
July 3, 2008 |
Leakproof zipper end crush for reclosable bag
Abstract
A reclosable bag that can be hermetically sealed. The bag
comprises a pair of zipper strips that are joined in respective
zones without substantial deformation of the longitudinal profiled
closure elements. These zones of zipper strip joinder assist in
providing a leakproof transition from the openable section of the
zipper to the corner seals, where the longitudinal profiled closure
elements are either substantially deformed (e.g., crushed) or
absent. The method of manufacture involves the steps of
ultrasonically welding a wide area and then thermally crushing a
narrower area overlapping the wide welded area to form leakproof
zipper joints. This method can be applied to string (flangeless)
zippers as well as flanged zippers.
Inventors: |
Share; Lawrence; (Skokie,
IL) ; Matthews; David J.; (Gilman, IL) ;
Crevier; Donald L.; (Essex, IL) |
Correspondence
Address: |
Dennis M. Flaherty, Esq.;Ostrager Chong Flaherty & Broitman P. C.
570 Lexington Avenue
New York
NY
10022-6894
US
|
Family ID: |
35285576 |
Appl. No.: |
12/075499 |
Filed: |
March 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10895769 |
Jul 21, 2004 |
7347908 |
|
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12075499 |
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Current U.S.
Class: |
383/64 |
Current CPC
Class: |
B29C 66/1122 20130101;
B29C 66/71 20130101; B29C 66/71 20130101; B29C 66/71 20130101; B29K
2069/00 20130101; B31B 70/8131 20170801; B29C 66/348 20130101; B29K
2023/12 20130101; B29C 66/71 20130101; Y10T 156/1084 20150115; B65D
81/2038 20130101; B29C 66/47421 20130101; B29C 66/72341 20130101;
B29C 66/71 20130101; B29C 66/71 20130101; B29C 66/71 20130101; A44B
19/60 20130101; B29C 66/81431 20130101; B29K 2025/00 20130101; B29K
2077/00 20130101; B29C 66/71 20130101; B29K 2069/00 20130101; B29C
66/71 20130101; B29K 2067/006 20130101; B29K 2077/00 20130101; B29K
2061/00 20130101; B29K 2059/00 20130101; B29K 2023/12 20130101;
B29K 2027/06 20130101; B29K 2055/02 20130101; B29K 2067/00
20130101; B29K 2025/06 20130101; B29K 2023/086 20130101; B29L
2031/7128 20130101; A44B 19/36 20130101; B29K 2023/06 20130101;
B29C 66/80 20130101; B29K 2055/02 20130101; B65D 33/2541 20130101;
B65D 33/2591 20130101; B29C 66/71 20130101; B29K 2023/065 20130101;
B29C 66/3452 20130101; B29K 2067/006 20130101; B29C 66/71 20130101;
B29K 2059/00 20130101; B29C 65/18 20130101; B29C 66/43 20130101;
B29C 65/08 20130101; B29K 2023/086 20130101; B29K 2995/0067
20130101; B29L 2009/00 20130101; B29C 66/71 20130101; B29C 66/71
20130101; B29C 66/72343 20130101; B29C 66/73921 20130101; B29K
2023/06 20130101; B29K 2023/065 20130101; B29C 66/474 20130101;
B29C 66/71 20130101; B29L 2005/00 20130101; B29C 2793/009 20130101;
B29K 2101/12 20130101; B65D 33/2508 20130101 |
Class at
Publication: |
383/64 |
International
Class: |
B65D 33/16 20060101
B65D033/16 |
Claims
1-17. (canceled)
18: A reclosable bag comprising: a receptacle having an interior
volume and a mouth, said receptacle comprising first and second
panels; and a flexible zipper comprising first and second zipper
strips respectively joined to said first and second panels in the
area of said mouth, said first zipper strip comprising a first base
and a first longitudinal closure element projecting from said first
base, and said second zipper strip comprising a second base and
second and third longitudinal closure elements projecting from said
second base, said first longitudinal closure element being profiled
to project between and interlock with the profiles of said second
and third longitudinal closure elements, wherein said first and
second zipper strips are joined to each other with substantial
deformation of said first through third longitudinal closure
elements in first and second zones of joinder that are respectively
located at opposite ends of said zipper, and are joined to each
other with relatively less deformation of said first through third
longitudinal closure elements in third and fourth zones of joinder
that are respectively located contiguous with and between said
first and second zones of joinder, said first and second zipper
strips being not joined together in a section lying between said
third and fourth zones of joinder.
19: The bag as recited in claim 18, wherein said first longitudinal
closure element is fused to said second and third longitudinal
closure elements in each of said third and fourth zones of joinder,
and central portions of said first and second zipper strips are
substantially flattened in each of said first and second zones of
joinder.
20: The bag as recited in claim 18, wherein said first and second
panels are joined to each other at first and second side seals
extending generally transverse to an axis of said first and second
zipper strips when the latter are straight and interlocked, and
said first and second panels are joined or connected to each other
along a bottom region.
21: The bag as recited in claim 20, wherein said first side seal
and said first zone of joinder have the same width and are
contiguous.
22: A reclosable bag comprising: a receptacle having an interior
volume and a mouth, said receptacle comprising first and second
panels; and a flexible zipper comprising first and second zipper
strips respectively joined to said first and second panels in the
area of said mouth, said zipper having a length less than a width
of said first and second panels, said first zipper strip comprising
a first base and a first longitudinal closure element projecting
from said first base, and said second zipper strip comprising a
second base and second and third longitudinal closure elements
projecting from said second base, said first longitudinal closure
element being profiled to project between and interlock with the
profiles of said second and third longitudinal closure elements,
wherein said first and second panels are joined to each other in
first and second zones of joinder that are respectively located at
opposite ends of said mouth, said zipper extending across a region
between and contiguous with said first and second zones of joinder,
and said first and second zipper strips being joined to each other
with relatively little deformation of said first through third
longitudinal closure elements in third and fourth zones of joinder
that are respectively located contiguous with said first and second
zones of joinder respectively, said first and second zipper strips
being not joined together in a section lying between said third and
fourth zones of joinder.
23: The bag as recited in claim 22, wherein said first longitudinal
closure element is fused to said second and third longitudinal
closure elements in each of said third and fourth zones of
joinder.
24: The bag as recited in claim 22, wherein said first and second
panels are joined to each other at first and second side seals
extending generally transverse to an axis of said first and second
zipper strips when the latter are straight and interlocked, and
said first and second panels are joined or connected to each other
along a bottom region.
25: A reclosable bag comprising: a receptacle having an interior
volume and a mouth, said receptacle comprising first and second
panels; and a flexible zipper comprising first and second zipper
strips respectively joined to said first and second panels in the
area of said mouth, said first zipper strip comprising a first base
and a first longitudinal closure element projecting from said first
base, and said second zipper strip comprising a second base and
second and third longitudinal closure elements projecting from said
second base, said first longitudinal closure element being profiled
to project between and interlock with the profiles of said second
and third longitudinal closure elements, wherein respective first
portions of said first and second zipper strips are joined to each
other with relatively little deformation of respective first
portions of said first through third longitudinal closure elements
disposed in a first zone of joinder that is leakproof, and
respective second portions of said first and second zipper strips
are joined to each other with relatively little deformation of
respective second portions of said first through third longitudinal
closure elements disposed in a second zone of joinder that is
leakproof, the portions of said first and second zipper strips
lying between said first and second zones of joinder being not
joined together and mutually interlockable.
26: The bag as recited in claim 25, wherein said first zone of
joinder is contiguous with a third zone of joinder in which
respective first portions of said first and second panels are
joined to each other, and said second zone of joinder is contiguous
with a fourth zone of joinder in which respective second portions
of said first and second panels are joined to each other.
27: The bag as recited in claim 26, wherein said first and second
panels are also joined to each other at first and second side seals
extending generally transverse to an axis of said first and second
zipper strips when the latter are straight and interlocked, and
said first and second panels are joined or connected to each other
along a bottom region, said third zone of joinder being contiguous
with said first side seal and said fourth zone of joinder being
contiguous with said second side seal.
28: The bag as recited in claim 25, wherein respective third
portions of said first and second zipper strips are joined to each
other with substantial deformation of respective third portions of
said first through third longitudinal closure elements disposed in
a third zone of joinder, and respective fourth portions of said
first and second zipper strips are joined to each other with
substantial deformation of respective fourth portions of said first
through third longitudinal closure elements disposed in a fourth
zone of joinder, said first and second zones of joinder being
respectively located contiguous with and between said third and
fourth zones of joinder.
29: The bag as recited in claim 28, wherein said first and second
panels are joined to each other at first and second side seals
extending generally transverse to an axis of said first and second
zipper strips when the latter are straight and interlocked, and
said first and second panels are joined or connected to each other
along a bottom region, said third zone of joinder being contiguous
with said first side seal and said fourth zone of joinder being
contiguous with said second side seal.
30: The bag as recited in claim 25, wherein said first portion of
said first longitudinal closure element is fused to said first
portions of said second and third longitudinal closure elements in
said first zone of joinder, and said second portion of said first
longitudinal closure element is fused to said second portions of
said second and third longitudinal closure elements in said second
zone of joinder.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to reclosable bags whose
interior volume is hermetically sealed when the bag is closed. In
particular, the invention relates to, but is not limited to,
evacuable reclosable storage containers or other evacuable
reclosable containers.
[0002] Collapsible, evacuable storage containers typically include
a flexible, airtight bag, an opening through which an article is
inserted inside the bag, a zipper for closing the opening and
hermetically sealing the bag, and a fixture through which excess
air is evacuated from the bag. A user places an article into the
bag through the opening, seals the opening, and then evacuates the
air in the bag through the fixture. With the bag thus evacuated, a
compressible article contained therein may be significantly
compressed so that it is easier to transport and requires
substantially less storage space.
[0003] Collapsible, evacuable storage containers are beneficial for
reasons in addition to those associated with compression of the
stored article. For example, removal of the air from the storage
container inhibits the growth of destructive organisms, such as
moths, silverfish, and bacteria, which require oxygen to survive
and propagate. Moreover, such containers, being impervious to
moisture, inhibit the growth of mildew.
[0004] Not only large, compressible items such as clothing may be
stored in a collapsible, evacuable storage container. For example,
it may be desirable to store bulk items made of small particles,
such as powders or granulated resins, in an evacuated container.
One situation that commonly occurs is that a particular bulk item
is shipped in a large, rigid container such as a drum. Bulk items
may be moisture sensitive and are sealed against moisture during
shipment. But many times a user does not need to use the entire
contents of the large container, and so once exposed to air the
remaining bulk contents quickly become unusable and are thus
wasted.
[0005] One collapsible, reusable, evacuable storage container is
shown in U.S. Pat. No. 5,480,030. This patent discloses a bag that
is reclosable by means of a plastic zipper and that is evacuable
via a one-way air valve assembly having a flexible diaphragm that
seals against a valve seat. The valve assembly also has vanes
positioned to prevent the bag material or bag contents from
obstructing air holes or the diaphragm while air is being evacuated
through the valve assembly.
[0006] In many reclosable bags, the zipper comprises a pair of
mutually interlockable zipper strips, each zipper strip having a
respective generally constant profile along the interlockable
portion of the zipper. The ends of the zipper strips are joined
together at the sides of the bag. For example, it is known to fuse
the ends of the zipper strips together, at the same time that the
bag side seals are formed, by the application of heat and pressure.
This "thermal crushing" of the plastic zipper creates a transition
between "as is" zipper and crushed zipper that is susceptible to
the presence of leaks through which air can enter an evacuated
bag.
[0007] Another known problem afflicting evacuable storage
containers is that consumers can inadvertently open an evacuable
storage container too wide, so that the open zippered "mouth" of
the bag is subjected to much stress where the zipper strips meet
and are joined together. If the storage container is opened too
wide (over-opened), the zipper joint (where the zipper strips come
together) can be stressed and damaged, leading to leaks when the
bag is later closed and evacuated.
[0008] There is a continuing need for improvements in the
construction of storage containers that need to be hermetically
sealed. In particular, there is a need for an improved evacuable
storage container wherein leakage is eliminated in the areas where
the bag side seals overlap the ends of the zipper. There is also a
need for a construction that distributes stresses and loads away
from the zipper profiles when the mouth of the bag is over-opened,
thereby preventing leaks induced by over-opening.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The invention relates to a reclosable bag that can be
hermetically sealed. The bag comprises a pair of zipper strips that
are joined in respective zones without substantial deformation of
the longitudinal profiled closure elements. These zones of zipper
strip joinder assist in providing a leakproof transition from the
openable section of the zipper to the corner seals, where the
longitudinal profiled closure elements are either substantially
deformed (e.g., crushed) or absent. The invention is directed to
reclosable bags having certain features and to related methods of
manufacture.
[0010] One aspect of the invention is a method of forming a zipper
joint joining first and second zipper strips made of thermoplastic
material, wherein the first zipper strip comprises a first base and
a first longitudinal closure element projecting from the first
base, and the second zipper strip comprises a second base and
second and third longitudinal closure elements projecting from the
second base, the first longitudinal closure element being profiled
to project between and interlock with the profiles of the second
and third longitudinal closure elements. The method comprises the
following steps: (a) arranging the first and second zipper strips
so that the first longitudinal closure element projects between and
is interlocked with the second and third longitudinal closure
elements; (b) supplying sufficient ultrasonic wave energy into a
first volume having a first width to cause the material of the
interlocked first and second zipper strips in the volume of first
width to fuse together, including at least the first longitudinal
closure element being fused to the second and third longitudinal
closure elements in the first volume; and (c) applying an amount of
pressure in the first volume during step (b), the amount of
pressure applied causing relatively little deformation of the first
through third longitudinal closure elements.
[0011] Another aspect of the invention is a method of manufacture
comprising the following steps: (a) joining a base of a first
zipper strip to a corresponding band-shaped zone of a first panel
made of web material, the first zipper strip comprising a first
longitudinal closure element; (b) joining a base of a second zipper
strip to a corresponding band-shaped zone of a second panel made of
web material, the second zipper strip comprising second and third
longitudinal closure elements, the first longitudinal closure
element being profiled to project between and interlock with the
profiles of the second and third longitudinal closure elements; (c)
arranging the first and second zipper strips so that the first
longitudinal closure element projects between and is interlocked
with the second and third longitudinal closure elements; (d)
supplying sufficient ultrasonic wave energy into a first volume
having a first width to cause the material of the interlocked first
and second zipper strips in the first volume to fuse together,
including at least the first longitudinal closure element being
fused to the second and third longitudinal closure elements in the
first volume; and (e) applying an amount of pressure in the volume
of first width during step (d), the amount of pressure applied
causing relatively little deformation of the first through third
longitudinal closure elements.
[0012] A further aspect of the invention is a method of manufacture
comprising the following steps: (a) joining a base of a first
zipper strip to a corresponding band-shaped zone of a first panel
made of web material, the first zipper strip comprising a first
longitudinal closure element; (b) joining a base of a second zipper
strip to a corresponding band-shaped zone of a second panel made of
web material, the second zipper strip comprising second and third
longitudinal closure elements, the first longitudinal closure
element of the first zipper strip being profiled to project between
and interlock with the profiles of the second and third
longitudinal closure elements of the second zipper strip; (c)
arranging the first and second zipper strips so that the first
longitudinal closure element of the first zipper strip projects
between and is interlocked with the second and third longitudinal
closure elements of the second zipper strip; (d) joining a base of
a third zipper strip to a corresponding band-shaped zone of the
first panel, the third zipper strip comprising a first longitudinal
closure element having the same profile as the first longitudinal
closure element of the first zipper strip, and the first and third
zipper strips being collinear and separated by a gap having a first
width; (e) joining a base of a fourth zipper strip to a
corresponding band-shaped zone of the second panel, the fourth
zipper strip comprising second and third longitudinal closure
elements respectively having the same profiles as the second and
third longitudinal closure elements of the second zipper strip, and
the second and fourth zipper strips being collinear and separated
by the gap of first width; (f) arranging the third and fourth
zipper strips so that the first longitudinal closure element of the
third zipper strip projects between and is interlocked with the
second and third longitudinal closure elements of the fourth zipper
strip; (g) supplying sufficient ultrasonic wave energy to cause the
material of the interlocked first and second zipper strips in a
first volume adjacent one end of the gap to fuse together and to
cause the material of the interlocked third and fourth zipper
strips in a second volume adjacent the other end of the gap to fuse
together, including at least the respective first longitudinal
closure elements being fused to the respective second and third
longitudinal closure elements in each of the first and second
volumes; and (h) applying an amount of pressure in each of the
first and second volumes during step (g), the amount of pressure
applied causing relatively little deformation of the first through
third longitudinal closure elements.
[0013] Yet another aspect of the invention is a reclosable bag
comprising: a receptacle having an interior volume and a mouth, the
receptacle comprising first and second panels; and a flexible
zipper comprising first and second zipper strips respectively
joined to the first and second panels in the area of the mouth, the
first zipper strip comprising a first base and a first longitudinal
closure element projecting from the first base, and the second
zipper strip comprising a second base and second and third
longitudinal closure elements projecting from the second base, the
first longitudinal closure element being profiled to project
between and interlock with the profiles of the second and third
longitudinal closure elements, wherein the first and second zipper
strips are joined to each other with substantial deformation of the
first through third longitudinal closure elements in first and
second zones of joinder that are respectively located at opposite
ends of the zipper, and are joined to each other with relatively
less deformation of the first through third longitudinal closure
elements in third and fourths zones of joinder that are
respectively located contiguous with and between the first and
second zones of joinder, the first and second zipper strips being
not joined together in a section lying between the third and fourth
zones of joinder.
[0014] A further aspect of the invention is a reclosable bag
comprising: a receptacle having an interior volume and a mouth, the
receptacle comprising first and second panels; and a flexible
zipper comprising first and second zipper strips respectively
joined to the first and second panels in the area of the mouth, the
zipper having a length less than a width of the first and second
side panels, the first zipper strip comprising a first base and a
first longitudinal closure element projecting from the first base,
and the second zipper strip comprising a second base and second and
third longitudinal closure elements projecting from the second
base, the first longitudinal closure element being profiled to
project between and interlock with the profiles of the second and
third longitudinal closure elements, wherein the first and second
panels zipper are joined to each other in first and second zones of
joinder that are respectively located at opposite ends of the
mouth, the zipper extending across a region between and contiguous
with the first and second zones of joinder, and the first and
second zipper strips being joined to each other with relatively
little deformation of the first through third longitudinal closure
elements in third and fourths zones of joinder that are
respectively located contiguous with the first and second zones of
joinder respectively, the first and second zipper strips being not
joined together in a section lying between the third and fourth
zones of joinder.
[0015] Other aspects of the invention are disclosed and claimed
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a drawing showing an isometric view of one
conventional type of collapsible, evacuable storage container.
[0017] FIG. 2 is a drawing showing a portion of a conventional
reclosable storage container having thermal side seals.
[0018] FIG. 3 is a drawing showing a stage in the manufacture of
the reclosable storage container depicted in FIG. 2.
[0019] FIG. 4 is a drawing showing a cross-sectional view of a
known zipper (undeformed) suitable for use with a bag of the type
depicted in FIG. 1.
[0020] FIGS. 5 and 6 are drawings showing respective stages in a
method of manufacture in accordance with one embodiment of the
invention.
[0021] FIG. 7 is a drawing showing a cross-sectional view of a
zipper of the type depicted in FIG. 4, in which the zipper halves
have been fused together, but without significant deformation.
[0022] FIG. 8 is a drawing showing steps of a method of manufacture
in accordance with another embodiment of the invention.
[0023] 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
[0024] FIG. 1 shows a conventional collapsible, evacuable storage
container 2 comprising a bag 4, a valve assembly 6, and a zipper 8
comprising a pair of mutually interlockable extruded zipper strips
that are joined to each other at opposing ends thereof. Although
not shown in FIG. 1, the conventional valve assembly 6 also
typically comprises a cap that can be snapped onto a portion of the
valve assembly that is disposed on the exterior of the bag 4. The
cap must be removed before the bag can be evacuated, and then is
replaced after the bag has been evacuated. The cap is intended to
seal the valve assembly to prevent air from entering the evacuated
bag.
[0025] The bag 4 typically comprises front and rear walls or panels
(made of thermoplastic film material) that are joined together at
the bottom and two sides by conduction heat sealing to form a
receptacle having an interior volume and a mouth in which the
zipper 8 is installed. One wall of bag 4 has a hole (not shown in
FIG. 1) in which to install the valve assembly 6. The bag may be
constructed of a blended extrusion layer of polyethylene sandwiched
between a nylon layer and a layer of polyethylene sheeting.
However, the materials comprising the bag may be altered so as to
prevent interaction with the bag contents. Alternatively, the bag 4
may be made from a web of film that is folded, the fold forming the
bottom of the bag.
[0026] During use, one or more discrete articles or a bulk material
(not shown) may be placed inside the bag 4 while the zipper 8 is
open, i.e., while the closure profiles of the interlockable zipper
strips are disengaged from each other. After the article or
material to be stored has been placed inside the bag, the mouth of
the bag 4 can be sealed by pressing the zipper strips together to
cause their respective closure profiles to interlock with each
other. Although the zipper closure profiles may have many different
designs, the design must be one that ensures that an airtight seal
can be formed at the mouth of the bag.
[0027] The zipper strips can be pressed together using a device
(not shown in FIG. 1) commonly referred to as a "slider" or "clip",
which straddles the zipper. The typical slider has a generally
U-shaped profile, with respective legs disposed on opposing sides
of the zipper. The gap between the slider legs is small enough that
the zipper can pass through the slider gap only if the zipper is in
a closed state. Thus when the slider is moved along an open zipper,
this has the effect of pressing the incoming sections of the zipper
strips together. The zipper is opened by pulling apart the zipper
upper flanges, as explained in more detail below. 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.
[0028] The zipper 8 is designed to form a hermetic seal at the
mouth of the bag 4 when zipper 8 is closed. After the zipper has
been closed, the interior volume of the bag can be evacuated by
sucking air out via the one-way valve assembly 6. Air can be drawn
out of bag 4 through valve assembly 6 using a conventional vacuum
source, such as a household or industrial vacuum cleaner. The valve
assembly 6 and the zipper 8 maintain the vacuum inside bag 4 after
the vacuum source is removed.
[0029] The front and rear wall panels of the bag 4 are respectively
sealed to the zipper strip by lengthwise conduction heat sealing in
conventional manner. Alternatively, the interlockable zipper strips
can be attached to the wall panels by adhesive or bonding strips or
the zipper profiles can be extruded integrally with the bag
material. The walls of the bag may be formed of various types of
gas-impermeable thermoplastic material. The preferred
gas-impermeable thermoplastics are nylon, polyester, polyvinyl
dichloride and ethylene vinyl alcohol. The bag material may be
either transparent or opaque.
[0030] In many reclosable bags, the zipper comprises a pair of
mutually interlockable zipper strips, each zipper strip having a
respective generally constant profile along the interlockable
portion of the zipper. The ends of the zipper strips are joined
together at the sides of the bag, e.g., by the application of heat
and pressure. A representative zipper joint is shown in FIG. 2,
which depicts one corner of such a reclosable bag. The dashed lines
denote a central portion 10 of the zipper 8, comprising the
interlockable profiled closure elements. The ends of the zipper
strips are fused together in area 12 at the same time that the bag
side seals 14 are formed. This "thermal crushing" of the
interlockable profiled closure elements in region 10 of the zipper
8 creates a transition 15 between uncrushed zipper and crushed
zipper that is susceptible to the presence of leaks through which
air can enter an evacuated bag. Such air leakage is indicated by
the dashed arrow in FIG. 2. [For the sake of simplicity, the
transition 15 between uncrushed zipper and crushed zipper has been
represented as a straight line in FIG. 2. However, a person skilled
in the art will recognize that thermoplastic material, when melted
or rendered molten, is unlikely to fuse in a manner that forms a
perfectly straight line.]
[0031] During manufacture, the cross seals are made wide enough so
that respective halves of the sealed area 14 can be incorporated
into two bags, as seen in FIG. 3. The cross-sealed area 14 is
bisected by cutting along a line 16 transverse to the zipper 8. The
area to the right of the cut line 16 forms the trailing cross seal
of the leading bag 4 (assuming advancement of the chain of bags
from left to right in FIG. 3), while the area to the left of the
cut line 16 forms the leading cross seal of the trailing bag
4'.
[0032] The evacuable storage bag may be constructed from two panels
of film joined together (e.g., by conduction heat sealing) along
three sides of a rectangle. To maintain a vacuum inside the storage
bag, the zipper in a closed state must provide a hermetic seal at
the mouth (i.e., fourth side) of the bag. Many different types of
zippers can be used. The present invention is not directed to any
particular zipper construction. For the sake of illustration,
however, a suitable zipper for use with the present invention will
now be described with reference to FIG. 4.
[0033] FIG. 4 shows a conventional zipper 8 that comprises a pair
of mutually interlockable extruded zipper strips 34 and 36. The
zipper strip 34 comprises a pair of projections 38 and 40 having
ball-shaped closure profiles, an upper flange 48, and a lower
flange 50. The zipper strip 36 comprises a trio of projections 42,
44 and 46 having ball-shaped closure profiles, a upper flange 52,
and a lower flange 54. For each zipper strip, the portions
exclusive of the projections will be referred to herein as a
"base". The bag walls may be joined to the respective bases of the
zipper strips by conduction heat sealing across their entire height
or across only portions thereof. For example, the bag walls could
be joined to the zipper lower flanges and to the upper flanges by
means of conduction heat sealing, as shown in FIG. 4.
[0034] Still referring to FIG. 4, the projections 38 and 40
interlock with projections 42, 44 and 46 by fitting inside the
respective spaces therebetween. The upper flanges 48 and 52 can be
gripped by the user and pulled apart to open the closed zipper. The
opened zipper can be reclosed by pressing the zipper strips
together (either manually or using a slider) along the entire
length of the zipper with sufficient force to cause the projections
38 and 40 to enter the respective spaces between the projections
42, 44 and 46. Alternatively, a slider (not shown) can be used to
close the zipper. Typically, such a slider takes the form of a
U-shaped clip that fits over the zipper with clearance for the
upper flanges, while the legs of the clip cam the zipper profiles
of the incoming zipper section into engagement when the slider is
moved along the zipper in either direction. The opposing ends of
the zipper strips 34 and 36 are typically fused together in the
regions of the bag side seals, as previously described.
[0035] Welding and sealing of thermoplastic material by ultrasonic
vibrations is an established process and has been used for forming
slider end stops on the ends of a slider-operated zipper in a
reclosable bag and for forming zipper joints generally. A typical
ultrasonic welding apparatus in which a workpiece is fed through an
ultrasonic weld station comprises an anvil and an oppositely
disposed resonant horn. The frontal surface of the horn and the
anvil are urged toward mutual engagement, for coupling the
ultrasonic vibrations from the activated horn into the
thermoplastic material of the workpiece, thereby effecting
ultrasonic welding. The horn is energized from a power supply that
provides electrical high-frequency power at a predetermined
ultrasonic frequency to an electro-acoustic transducer, which, in
turn, provides mechanical vibrations at that frequency to a booster
or coupling horn for coupling these vibrations to the horn.
[0036] In accordance with one embodiment of the present invention,
air leakage into an evacuated bag at the zipper joints can be
eliminated by providing zones of joinder where the profiled
interlockable closure elements (e.g., the ball-shaped closure
profiles described in FIG. 4) are fused together with little
deformation. This is accomplished by ultrasonically welding the
zipper strips together in the zones of joinder using a horn 60 and
an anvil 62 having the structure shown in FIG. 7. In this case, the
horn 60 has a groove or recess 64 disposed between two coplanar
flat surfaces 80 and 82, while the anvil 62 has a groove or recess
66 disposed between two coplanar flat surfaces 84 and 86. During
welding, surfaces 80 and 82 of the horn respectively confront
surfaces 84 and 86 of the anvil, while groove 64 of the horn
confronts groove 66 of the anvil. The groove 66 of the anvil is
used to guide the zipper relative to the horn during zipper/film
advancement, and also assists groove 64 of the horn to "contain"
the central portions of the zipper strips during welding. More
specifically, the grooves 64 and 66 are configured to provide
clearance for the central portions of the zipper strips, including
the profiled interlockable closure elements. The surfaces of the
grooves are shaped to contact the central portions of the zipper
strips during welding (i.e., when the horn and anvil are brought
together) with an amount of pressure that is sufficient to ensure
acoustically coupling of the horn to the zipper strips, but not so
great as to cause the profiled interlockable closure elements to
undergo substantial deformation. The confronting flat surfaces 80
and 84 weld the zipper upper flanges together, while the
confronting flat surfaces 82 and 86 weld the zipper lower flanges
together. In addition, webs 56 and 58 of bag making film are sealed
to the backs of the respective zipper strips 34 and 36 from the top
to the bottom of the zipper (or from a point near to the top to a
point near to the bottom) during ultrasonic welding.
[0037] FIG. 6 shows a portion of a zipper sandwiched between and
already joined (e.g., by conduction heat sealing) to marginal
portions of respective webs of film material, only the front web 56
is indicated in this view. [For the sake of illustration, it is
assumed that the film material of web 56 is optically transparent,
so that the zipper is visible in FIG. 6.] The hatched area in FIG.
6 represents the zone where the zipper strips are joined (by
ultrasonic welding) to each other, and where the respective webs of
bag making film are joined to the respective backs of the zipper
strips. The upper flanges of the zipper strips are ultrasonically
welded together in area 18, the lower flanges of the zipper strips
are ultrasonically welded together in area 20, and the profiled
interlockable closure elements are ultrasonically welded together
(with little or no deformation) in area 22. Welded area 22 includes
the material that occupies the aforementioned grooves in the horn
and anvil during the welding operation.
[0038] After the zone of zipper joinder has been formed by
ultrasonically welding areas 18, 20 and 22, the opposing webs of
bag making film and the continuous zipper strips joined thereto are
advanced one package length or multiple package lengths. At the
next work station, the panels are cross sealed by conduction heat
sealing. More specifically, sufficient heat and pressure are
applied in a strip-shaped zone 14 (see FIG. 6), which extends
transverse to the zipper 8, to thermally crush the zipper strips
and join the panels together across the full height of the panels.
The cross seal 14 overlaps with the zone in which the zipper strips
were ultrasonically welded together. As seen in FIG. 6, the width
of the cross seal 14 is less than the width of the zone in which
the zipper strips have been ultrasonically welded together. Within
this zone of overlap (indicated by cross hatching in two directions
in FIG. 6) the central region 10 of the zipper 8 is thermally
crushed, i.e., flattened. As a result, the profiled interlockable
closure elements of each zipper strips undergo substantial
deformation.
[0039] As seen in FIG. 6, the cross seal 14 at the zipper is
inboard of the ultrasonic weld. Preferably a line of symmetry of
the ultrasonically welded regions 18, 20, 22 is generally collinear
with a centerline of the cross seal 14, which are in turn generally
collinear with a line of cutting, indicated by the dashed line 16.
However, precise collinearity is not required. When the zipper 8
and bag making film are cut along line 16, the bag on one side of
line 16 will be separated from the bag on the other side of line
16, and the cross seal 14 will be divided into respective side
seals on the respective bags.
[0040] In the final product, each zipper comprises five distinct
sections: respective thermally crushed sections 70, 72 at the ends
of the zipper, in which the zipper strips are fused together and
the interlocked profiled closure elements are substantially
deformed; respective ultrasonically welded sections 74, 76
contiguous with the thermally crushed sections 70, 72, in which the
zipper strips are fused together and the interlocked profiled
closure elements are not substantially deformed; and the remaining
section 78 of the zipper (having one end contiguous with one
ultrasonically welded section and another end contiguous with the
other ultrasonically welded section) in which the zipper strips are
interlockable and disengageable (i.e., the profiled closure
elements are not fused together). The transition from undeformed
("as is") zipper to each ultrasonically welded region of zipper is
very smooth, eliminating or at least reducing leaks.
[0041] The foregoing construction could be used on many other
zipper end stomps (at the bag's cross seal) where leakage is a
problem, by not deforming the zipper and, at the same time, sealing
off the bag making film to the zipper flanges and sealing the
flanges together. Furthermore, the concept of ultrasonically
welding a wide area and then thermally crushing a narrower area
overlapping the wide welded area to form leakproof zipper joints
can be applied to string (flangeless) zippers as well as flanged
zippers.
[0042] Reclosable bags of the type described herein can be
manufactured on an automated production line. In accordance with
one automated method of manufacture, two webs of film are paid off
respective rolls and brought into overlying relationship.
Downstream respective sets of pull rollers are provided for pulling
the webs through the bag making machine. A continuous length of
interlocked zipper strips is paid off a spool and fed between the
advancing film webs. Typically the webs and the zipper are advanced
intermittently, while certain operations are performed during the
dwell times. At a first sealing station, marginal portions of
opposing sections of each web are sealed to the backs of opposing
section of the respective zipper strips by a first pair of
horizontal heated sealing bars. At the same time, marginal portions
of opposing sections of each web are heat sealed together to form a
bottom seal. At an ultrasonic welding station, the zipper is
stomped as shown in FIG. 5. At a second sealing station, the cross
seals are formed by conduction heat sealing as shown in FIG. 6. At
a cutting station, the individual bags are severed from one another
by cutting along a line that bisects the cross seal, thereby
forming respective side seals on the separated bags. A person
skilled in the art will appreciate that the bag could be formed
from a single web that is folded and cross sealed, instead of from
two webs that are bottom sealed and then cross sealed together.
Also the zipper strips could be joined to the respective webs
separately and then interlocked before ultrasonic welding of the
zipper joints.
[0043] In accordance with another embodiment of the invention, the
technique of ultrasonically welding the ends of the zipper strips
together without substantial deformation could be used in
conjunction with segmented zipper to make packages or bags. In this
application, equal-length zipper segments are joined to both webs
of bag making film. The zipper segments are disposed in a line with
respective gaps separating successive zipper segments. This
arrangement allows for no zipper in the cross seal 14, as shown in
FIG. 8. The zone of ultrasonic welding is denoted in FIG. 8 by the
hatching lines that rise from left to right, while the zone of
thermal crushing is denoted by the hatching lines that rise from
right to left. These two zones overlap in the areas 32 and 32',
which are located in the gap between successive zipper segments 8a
and 8b. Zones 30 and 30' in FIG. 8 represent areas where the film
webs are ultrasonically welded together (with no conduction heat
sealing); zones 24 and 24' represent areas where the zipper upper
flanges are ultrasonically welded together and the film webs are
ultrasonically welded to the upper flanges; zones 26 and 26'
represent areas where the zipper lower flanges are ultrasonically
welded together and the film webs are ultrasonically welded to the
lower flanges; and zones 28 and 28' represent areas where the
central portions 10 of the zipper strips are ultrasonically welded
together without substantial deformation and the film webs are
ultrasonically welded to the backs of the central portions. To
accomplish the desired ultrasonic welding in zones 24, 26, 28, 30,
32 and zones 24', 26', 28', 30', 32' without substantial
deformation in zones 28 and 28', a horn can be used that has a flat
surface except for recesses corresponding to zones 28 and 28'.
[0044] While the invention has been described with reference to
various embodiments, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements 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. 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.
[0045] As used in the claims, the verb "joined" means fused,
welded, bonded, sealed, 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, co-extrusion (e.g., of zipper and
bag), etc. In addition, each recitation of a "width" is a
respective dimension measured along the same axis. For example, the
width of an ultrasonically welded area and the width of a thermally
crushed area are both measured along a lengthwise direction of the
zipper. As used in the claims, the term "relatively little
deformation" means an amount of deformation that is substantially
less than the relatively large deformation that occurs when two
profiled closure elements are crushed or flattened.
* * * * *