Pull bead and guide rails for easy open flexible containers

An easy-open container having a membrane forming the top edge of the container and hermetically sealing the contents thereof. The membrane is disposed inward from the mouth of the bag, leaving portions of the bag walls extending upward beyond the container top edge to form guide rails which facilitate opening of the container to gain access to the bag contents. A membrane for sealing the mouth opening of a bag-like structure. A method for making a membrane as aforesaid and a method for making an easy-open container having the structure aforesaid are also provided.

The present invention relates to a method for making improved means for 
opening flexible containers. In particular it relates to a method for 
incorporating a separate film or membrane having interlocking zipper 
elements into a bag-like structure to form an easy-open reclosable 
flexible container. The present invention further relates both to the 
membrane and flexible containers produced by the method. 
Because reclosable flexible containers are by their very nature accessible, 
accidental or intentional contamination of contents has long been an 
object of concern. One approach has been to hermetically seal reclosable 
flexible containers to protect the contents thereof. Use of hermetic 
seals, however, has required the further development of easy-open 
features, such as tear strips and perforated or weakened lines for tearing 
to disrupt the seal and gain access to the bag contents. Many easy-open 
features desirably evidence any tampering with the container seals. 
Among the approaches to hermetically sealing flexible containers is the 
attachment of separate films or membranes over the mouth opening of a 
bag-like structure so that the membrane serves as the top edge of a 
container. See, for example, Inagaki U.S. Pat. No. 4,874,257. Thereafter, 
the membrane which forms the hermetic seal may be ruptured to gain entry 
to the bag contents, irreversibly evidencing such entry. In Inagaki 
cutting is evidently the means of rupturing since no other opening means 
are disclosed. 
However, other opening means for rupturing hermetically sealed containers 
are known. Thus, Siegel, U.S. Pat. No. 4,615,045 discloses a bag structure 
having a separable bag top closure including interlocking profiles. One 
flange of the top closure has an upward extension for hanging the bag. 
Opposing flanges form a tongue which seals the bag mouth and may be 
removed by tearing across serrations, perforations, or weakened lines 
therein, to gain access to the bag contents. Unless the tongue on the bag 
is intact, there would be an indication that access to the bag was 
attained or attempted. 
Ausnit, U.S. Pat. No. 4,894,975 (the '975 patent), discloses a membrane 
having interlocking zipper elements. The membrane is folded and sealed to 
opposing bag walls to form a tamper-evident security seal across the mouth 
of the bag which also serves as the top edge of the container. The top of 
the seal may be torn off along parallel lines of weakened tear resistance 
to open the bag. 
Of further relevance is Ausnit et al, U.S. Pat. No. 4,812,074 (the '074 
patent), wherein a film containing interlocking zipper elements is sealed 
to a web of thermoplastic material forming a two-layered area of film and 
web. Folding the web brings the zipper elements into opposing relationship 
with the film layer inside and the web layer outside the top edge of the 
container which results. The film, thus, does not serve alone to seal the 
edge of the container. The '074 patent further discloses a tear strip 
located in the film by which both the film and web may be torn to gain 
access to the bag contents. 
Problems have arisen in the use of various means to open hermetically 
sealed containers. Because of concerns with contamination and freshness, 
use of perforations or serrations to define a weakened line for tearing, 
as disclosed by Siegel, are not practical in many applications, 
particularly in packaging foodstuffs. They provide a series of small 
openings to the bag contents through which bacteria may migrate or 
contaminants may be introduced undetected. Problems have also arisen with 
containers having narrowed regions for tear lines as disclosed in the '975 
patent. For example, consumers have been unable to actually tear the 
thermoplastic material. Further, once weakened regions are initially torn, 
irregular tearing may deviate off-line down the bag lips. Irregular 
tearing is a problem which also accompanies the use of tear strips, such 
as used in the '074 patent, as the tear lines may deviate down the bag 
lips and propagate into the zipper elements, compromising the strength, 
shape and operation of the zipper elements. 
Accordingly, further developments are needed to facilitate easy-opening of 
reclosable containers, while maintaining a tamper-evident barrier to 
contamination. 
SUMMARY OF THE INVENTION 
The present invention meets the continuing need for new and improved 
easy-open reclosable containers having hermetic, tamper-evident seals 
which are easily opened without damage to the interlocking zipper 
elements. In the present invention, an easy-open reclosable container 
results from folding and then sealing a membrane across the opening of a 
bag-like structure. A bag-like structure may include, without limitation, 
diverse structures such as balloons, envelopes, socks and sleeves, as well 
as more traditional sacks, pouches and bags, and hereafter for simplicity 
is referred to as a bag. The bag opening is defined by two generally 
opposing bag walls to which the membrane is sealed. So folded and sealed, 
the membrane forms an edge of the container along the fold. 
The membrane, having first and second surfaces, includes interlocking first 
and second zipper elements on the first surface thereof. Means for 
tearing, such as a first bead of thermoplastic material, are preferably 
disposed generally centrally between the zipper elements, and either 
immersed in the membrane material, or on the first or second surfaces 
thereof. Thus, when the membrane is folded and sealed to opposing bag 
walls the zipper elements are brought into opposing relationship, with the 
means for tearing generally located along the edge of the container formed 
by the film. The presence of the membrane eliminates the need for a peel 
seal to protect the contents of the bag. Moreover, disruption of the 
membrane to gain access to the bag, whether by means for tearing or 
otherwise, may be detected, making the bag tamper-evident. 
Of particular significance in the present invention is the sealing of the 
membrane at locations along the inside of opposing bag walls disposed 
inward from the mouth of the bag, leaving portions of the bag walls 
extending upward beyond the container edge to form guide rails. Several 
advantages are provided by this structure. The guide rails thus formed, 
promote upward tearing of the membrane by the means for tearing. As the 
membrane and the bag are separately produced, they may be made from 
different materials making possible the use of different material 
properties and thicknesses. And, while the membrane is preferably made of 
thin thermoplastic material which may be easily ruptured by means for 
tearing, attachment of the membrane inward from the bag opening further 
permits the bag walls to serve as reinforcement against the propagation of 
tear lines down the membrane, protecting the integrity of the zipper 
elements thereon. As well, the guide rails serve as protection against 
accidental damage or puncture of the membrane by shielding contact between 
the second surface thereof and the external environment. Once the 
container has been opened, the guide rails provide additional gripping 
area for opening the bag, and the bag side walls remain of equal length, 
unaffected by opening the bag. Additional means for gripping, such as 
second beads of thermoplastic material, may be added to the membrane 
anywhere on the first surface, preferably between the means for tearing 
and the zipper elements. So located, means for gripping such as second 
beads of thermoplastic material would also serve to resist deviation of 
the tear line down the membrane. 
In sealing the membrane to the inside of the bag walls, the portion of the 
membrane carrying the first and second zipper elements may be left 
unattached to the bag walls. This structure has the advantage of allowing 
the bag to expand somewhat without producing stress which would tend to 
open interlocked zipper elements. This is of particular interest in 
practicing one embodiment of the present invention wherein the bag is 
formed with a cavity or pocket to receive products, such as foodstuffs, 
and in other embodiments where a simple bag is filled with product. 
More efficient bag side seals are made possible by the present invention as 
the zipper elements, disposed on a membrane of thin thermoplastic 
material, present a thinner cross-section which requires less time and 
temperature to seal than traditional thicker, single extrusion low density 
zipper elements. Further, the second surface of the membrane may be 
comprised of high heat melt material, as in the preferred multi-layer 
embodiment below, which facilitates rapid low temperature sealing of the 
membrane to the bag walls. 
In the present invention the preferred means for tearing is an oval-shaped 
bead of thermoplastic material, such as low density polyethylene (LDPE), 
disposed on the first surface of the membrane along with the zipper 
elements which may also be LDPE. It has been found that the oval shape of 
the bead enhances the tearing action of the bead when one of the narrow 
faces of the oval bead is disposed against the first surface. So disposed, 
the narrow face serves as the leading edge for tearing the membrane, and 
its cross-section has a knife-like effect on the membrane. Notches or 
slits along one or more of the bag side seals may be included to help 
initiate tearing. 
Further, the preferred embodiment of the present invention includes a 
membrane having two or more layers which are made of materials which 
provide desirable sealing or manufacturing properties. In one embodiment, 
the membrane has three layers, an inner heat resistant layer which serves 
as the first surface; a middle barrier layer; and an outer sealing layer 
which serves as the second surface of the membrane. The inner heat 
resistant layer, preferably comprised of high density polyethylene (HDPE), 
prevents fusing together opposing portions of the first surface of the 
membrane when the second surface thereof is sealed to opposing bag walls. 
The middle barrier layer, preferably comprised of saran (polyamylidene 
chloride), polyamide or ethylene vinyl alcohol (EVOH), includes properties 
which enhance hermetic sealing with the membrane. The outer sealing layer, 
is preferably a carboxylic acid ethylene copolymer, such as ethylene 
acrylic acid (EAA) or ethylene vinyl acetate (EVA), having a low heat melt 
temperature which facilitates sealing the membrane to opposing bag walls 
at low temperatures and high speeds. In an alternative embodiment, a two 
layer membrane is provided having inner and outer layers providing first 
and second surfaces, respectively. In this alternative embodiment, the 
inner layer, preferably comprised of HDPE, serves to prevent fusing 
together of opposing portions of the first surface of the membrane. The 
outer layer remains as described above. 
The present invention further provides a method for producing an easy-open 
container. The method, best performed in an intermittent step-wise manner, 
produces individual sealed, easy-open containers from three webs, a form 
web and a top web, from which the bag sides are ultimately formed, and a 
membrane web. More particularly, a form web is directed to a horizontal 
forming station where a pouch, pocket or female cavity is formed. The form 
web then proceeds to a filling station where product is loaded into the 
cavities. The form web then proceeds to a pre-seal station where a folded 
membrane web having interlocking zipper elements is aligned with the form 
web and positioned inward from the top edge of the form web. The membrane 
is then sealed to the form web with a first seal. The first seal extends 
along the second surface of the membrane web between the means for tearing 
and the edge of the membrane web, and is preferably in an area inward from 
the means for tearing and above the first zipper element. This first seal 
is accomplished by first feeding then, during a pause in web movement, by 
raising a pre-seal assembly to compress the form web and membrane web 
together against the back-up plate to form a weld seal bond. The form web 
with membrane web sealed thereto, next advances to a pre-flattening 
station. IN the pre-flattening station the top web is drawn over and 
positioned above the form web and membrane web. The top edge of the top 
web is preferably aligned with the top edge of the form web, but may be 
offset slightly to enhance parting the two bag sides which ultimately 
result to access the means for tearing. As the web movement again pauses, 
a sealing assembly lowers to compress the top web against the membrane web 
and form web. Heat and pressure are applied to two areas by the sealing 
assembly. These areas lie roughly in the region where final bag side seals 
will later be formed. The heat and pressure cause meltdown and flattening 
of the means for tearing and zipper elements in two areas, typically 
substantially 0.25 inches to 1.0 inches wide, forming second side seals. 
Following the pre-flattening station, a web assembly of the form web with 
membrane web and top web sealed thereto, advances into the final seal 
station in a vacuum chamber. The web assembly of form web, membrane web 
and top web are positioned therein under a sealing die assembly. The web 
movement is again stopped while a vacuum is pulled or gas is purged into 
the chamber, and the seal die assembly, preferably simultaneously, lowered 
to form bag side seals and a fourth seal, a bottom edge seal between the 
top web and form web. The seal die assembly further forms a third seal, a 
weld seal bond, between the top web and the membrane web along its second 
surface generally opposite the first seal, preferably between the means 
for tearing and the second zipper element. By virtue of the preferred 
multi-layer membrane material, wherein the first surface is comprised of 
heat resistant material, the third seal may be formed without mechanically 
separating opposing first surfaces of the membrane web to prevent their 
sealing together. Thus, in the final seal station, the top web is sealed 
to the form web with the membrane web sealed therebetween, forming a 
container wherein the product is hermetically sealed in an evacuated or 
gas flushed volume. The sealed webs are then advanced to a severing 
station where the web is severed into individual sealed, evacuated or 
gas-flushed containers, loaded with product. The four-sided containers 
which result are easily opened by means for tearing, and are reclosable 
with interlocking first and second zipper elements. 
In a further aspect of the present invention, a separate membrane is 
provided which may be used for sealing the opening of a bag-like 
structure. The membrane has first and second surfaces, and is comprised of 
two or more layers as described above. The membrane includes first and 
second interlocking zipper elements and means for tearing, preferably an 
oval-shaped bead of thermoplastic material, on its first surface. In 
addition, means for gripping may be added to the first surface. The means 
for tearing may, alternately, be disposed on the second surface. 
A method for making a membrane is further provided. A thermoplastic 
membrane web having two or more layers is provided or extruded, having a 
first heat resistant surface, a second sealing surface and a barrier layer 
capable of hermetically sealing a bag therebetween. Next is a step of 
extruding, on the first surface, a means for tearing generally centrally 
down the length of the membrane web; and preferably simultaneously 
extruding base layers with first and second zipper elements along opposite 
sides of the membrane web.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, in accordance with the present invention, a 
reclosable flexible container 10 is shown having a membrane 12 sealing the 
opening of bag 14. As seen more clearly in FIG. 3, membrane 12 is sealed 
to the inside of bag walls 16 and 18 inward from the bag opening 20 along 
seals 22, 24. Portions of bag walls 16, 18 thereby extend above seals 22, 
24 to form guide rails 26, 28. 
Membrane 12 includes on its first surface interlocking first and second 
zipper elements 32, 34 and a means for tearing 30 shown also in FIGS. 4 
and 5. Preferably, means for tearing 30 is an oval-shaped first bead of 
thermoplastic material 30', such as LDPE, which is disposed generally 
centrally between zipper elements 32, 34. The oval-shaped first bead of 
thermoplastic material 30' is preferably attached slightly off-center 
along a wide face of the oval between zipper elements 32, 34 to facilitate 
folding membrane 12. As a result, a narrow face of the first bead 30' is 
oriented to serve as the leading edge for tearing membrane 12 when 
membrane 12 is folded. Guide rails 26, 28 urge and promote upward tearing 
of membrane 12 by means for tearing 30, and serve as reinforcement against 
downward deviation of a tear line on membrane 12. 
An illustrative example of membrane 12 of the present example is set forth 
with reference to FIG. 5. In a typical application involving a 22 
cm.times.30 cm container, dimension B of guide rails 26, 28 may be 2 mm, 
while dimension C extends downward from the top edge 7 mm. The overall 
dimension A from the top edge to the bottom of zipper elements 32, 34 may 
be 21 mm, with the bottom flap dimension F extending as desired, say 1.5 
mm. The area in which seals 22 and 24 are preferably formed (shown in FIG. 
3) is dimension D, which in this example is 11 mm, centered in dimension 
A. Dimension E, the width of zipper elements 32, 34, is given as 3.2 mm in 
this example. 
Referring again to FIG. 1, bag walls 16, 18 are sealed together along bag 
side seals 36, 38 and bottom edge seal 40. As is preferred, slits 42 are 
provided in bag side seals 36, 38 to assist the consumer to initiate 
tearing of membrane 12. By virtue of guide rails 26, 28, the length or bag 
walls 16, 18 will remain unchanged whether container 10 is sealed or open. 
Bag walls 16, 18 may be of different lengths so that one guide rail may 
extend upward further than the other to facilitate their separation. Once 
container 10 is torn open, guide rails 26, 28 assist the consumer in 
gripping bag walls 16, 18 to obtain access to the contents of the bag. 
Further shown in FIG. 3 are additional means for gripping 44. Preferably 
second beads of thermoplastic material 44' such as LDPE, means for 
gripping 44 may be placed in various locations on membrane 12 as shown 
typically in FIG. 3. While FIGS. 1-5 and 7 show an embodiment of container 
10 having a cavity 48, bag walls 16, 18 of container 10 could, as well, 
both be flat or have other forms impressed therein. 
Referring to FIG. 6, the preferred embodiment of the membrane used in the 
present invention is shown. Membrane 12 is comprised of two or more layers 
of thermoplastic material, chosen for their advantageous sealing and 
manufacturing properties. In the embodiment shown, three layers are 
provided, inner layer 54, middle layer 52 and outer layer 50. Inner layer 
54 is a heat resistant layer, preferably of HDPE, which prevents the 
opposing surfaces of membrane 12 and bag walls 16 and 18 from sealing 
together when membrane 12 is sealed to bag walls 16 and 18 to form 
container 10. Middle layer 52 is a barrier layer, preferably of saran, 
polyamide or EVOH, to provide the desired hermetic seal across bag opening 
20. Outer layer 50 is a sealing layer, preferably of a carboxyl acid 
ethylene copolymer such as EVA or EAA, having a low heat melt temperature, 
which facilitates sealing membrane 12 to the inside of bag walls 16, 18. 
Bag walls 16, 18 are preferably made of polyethylene. 
Alternatively, middle layer 52 and inner layer 54 may be combined in one 
material as inner layer 54' as shown in FIG. 6. In this alternative, inner 
layer 54' has properties which provide both heat resistant and hermetic 
sealing properties desired in membrane 12. One such material would be 
surlyn (a carboxylic acid-ethylene copolymer). 
The present invention further provides a method for producing an easy-open 
container 10. Shown schematically in FIG. 7, a form web 58 of 
thermoplastic material having a top edge and a bottom edge advances to 
horizontal forming station 70. Preferably, cavities 48 are formed therein 
at spaced intervals. Form web 58 then proceeds to filling station 72 where 
product 60 is loaded into cavities 48. As form web 58 next proceeds to 
pre-seal station 74, folded membrane web 62, having interlocking first and 
second zipper elements 32, 34 and means for tearing 30 is positioned above 
form web 58, inward from the top edge thereof, for sealing thereto. 
Membrane web 62 further preferably includes perforations 35 located 
between zipper elements 32, 34 and means for tearing 30, preferably midway 
therebetween. Membrane web 62 is first fed into the tracking shoe of a 
back-up plate 76 and then, during a pause in web movement, sealed along 
its second surface to form web 58 by raising pre-seal assembly 78 to 
compress form web 58 and membrane web 62 together against back-up plate 
76. First seal 24 (see FIG. 3), a weld seal bond, preferably extends along 
the second surface of membrane web 62 in an area inward from means for 
tearing 30 and upward from first zipper element 32. Form web 58 with 
membrane web 62 sealed thereto advances to pre-flattening station 80, 
wherein top web 56 is drawn over and positioned above form web 56 and 
membrane web 62. Top web 56 having top and bottom edges, is positioned so 
that membrane web 62 is inward from the top edge of top web 56. As the web 
movement again pauses, sealing assembly 82 lowers to compress top web 56 
against membrane web 62 and form web 58. Heat and pressure are applied to 
two areas of the assembled webs by sealing assembly 82. These areas lie 
roughly in the regions where bag side seals 36, 38 will finally be formed. 
The heat and pressure cause meltdown and flattening of means for tearing 
30, and zipper elements 32, 34, and sealing of top web 56 to both form web 
58 and membrane web 62 to form second seals in the two areas, each 
substantially 0.25 to 1.0 inches wide. Following pre-flattening station 
80, a web assembly of form web 58 with membrane web 62 and top web 56 
sealed thereto, advances into final seal station 84 in vacuum chamber 86. 
The web assembly of form web 56, membrane web 62 and top web 56 are 
positioned therein under sealing die assembly 88. Web movement is again 
paused while chamber 86 is evacuated by vacuum pumping means for pumping 
90. Perforations 35 in membrane 12 also permit evacuation of air trapped 
in membrane 12 between zipper elements 32, 34 and means for tearing 30. 
Gas may also be purged into chamber 86 at this time by means for injecting 
gas 92 to package or preserve product 60. Preferably simultaneously, seal 
die assembly 88 is lowered to finally form bag side seals 36, 38 and a 
fourth seal, bottom edge seal 40. Seal die assembly 88 also forms third 
seal 24 (see FIG. 3) at this time, a weld seal bond, between top web 56 
and membrane web 62, extending along the second surface of membrane web 62 
generally opposite first seal 22, between means for tearing 30 and second 
zipper element 34. In addition, third seal 22 also covers the area of 
membrane web 62 having perforations 35, to seal perforations 35, first 
seal 24 having performed the same additional function, as well. 
Alternatively, where membrane 12 does not include perforations 35, membrane 
web 62 and contiguous portions of top web 56 and form web 58 are disposed 
outside chamber 86, while cavity 48 in form web 58 and contiguous portions 
of top web 56 are inside chamber 86 for evacuation or gas-flushing. In 
this alternative, a peel seal 37 may preferably be formed in the area 
generally below zipper elements 32, 34 to seal product 60 in vacuum or in 
gas. (See FIG. 5). Finally, the method of the present invention may 
equally be practiced to produce unevacuated or non-gas flushed containers. 
Regardless of the precise manner of sealing, the sealed web assembly 
including webs 56, 58 and 62 is then advanced to severing station 94 where 
the sealed web assembly is severed into individual sealed, evacuated or 
gas-flushed containers 10, loaded with product. While the method of the 
present invention is representatively shown producing a series of single 
containers 10, the method may be practiced to produce multiple containers 
10 side by side or in groups. As well, the position of first and second 
zipper elements 32, 34 on membrane web 62 may be reversed. 
In a further aspect of the present invention, a separate membrane 12 is 
provided. Membrane 12 is shown in FIG. 6, partially folded. Membrane 12 
may be used for sealing the opening of a bag-like structure such as 
opening 20 of bag 14 shown in FIG. 3. Best shown in FIGS. 3-5, membrane 12 
includes first and second interlocking zipper elements 32, 34 and means 
for tearing 30, preferably an oval-shaped first bead of thermoplastic 
material 30'. Preferably, membrane 12 also includes perforations 35 to aid 
in evacuating an assembly including membrane 12. 
Means for tearing 30 is shown, as is preferable, disposed on the first, 
inner surface of membrane 12, but could also be disposed on the second, 
outer surface of membrane 12 or integral in the material itself. 
Preferably, first bead 30' is attached slightly off-center between zipper 
elements 32, 34, to enhance folding of membrane 12. By attaching a wide 
face of first bead 30' to membrane 12, a narrow face of first bead 30' may 
be oriented upward when membrane 12 is folded to serve as the leading edge 
for tearing. 
As further shown in FIG. 6, membrane 12 is comprised of two or more layers 
of thermoplastic material having qualities, characteristics and material 
composition as previously described above. In addition, means for gripping 
44, preferably second beads of thermoplastic material 44' such as LDPE, 
may be added to membrane 10 on the first, inner surface thereof as shown 
FIG. 3. 
Finally, a method for making a membrane for use in sealing the opening of 
an easy-open container 10 is provided. The first step is to provide or 
extrude a thermoplastic membrane web 62 having two or more layers 
including a first heat-resistant surface and a second sealing surface. The 
next step is extruding a means for tearing 30, preferably an oval-shaped 
first bead of thermoplastic material 30' onto the first surface of 
membrane web 62. This step further includes simultaneously extruding base 
layers known in the art with interlocking first and second zipper elements 
32, 34 onto the first surface of membrane web 12. Interlocking zipper 
elements 32, 34 are disposed generally along opposite edges of membrane 
web 62, while first bead 30' is generally centrally disposed therebetween, 
preferably slightly off-center. The method may further comprise folding 
membrane web 12 to bring interlocking first and second zipper elements 32, 
34 into opposing relationship. The method may preferably further include 
perforating opposing portions of membrane 12, along its length between 
zipper elements 32, 34 and means for tearing 30, preferably midway 
therebetween. Further, the step of extruding first bead 30', base layers 
and zipper elements 32, 34 may include also extruding means for gripping 
44, comprising one or more second beads of thermoplastic material 44', 
onto the first surface of membrane web 62. 
While certain representative embodiments and details have been shown for 
purposes of illustrating the invention, it will be apparent to those 
skilled in the art that various changes in the articles and methods 
disclosed herein may be made without departing from the scope of the 
invention, which is defined in the appended claims.