Note: Descriptions are shown in the official language in which they were submitted.
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END STOP FOR RECLOSABLE FASTENER
AND METHOD OF INSTALLATION THEREON
FIELD OF THE INVENTION
The present invention relates to improvements in closure devices for plastic
storage bags, and more particularly, to an end stop for use on a plastic
reclosable
fastener and a method of installation thereon.
BACKGROUND OF THE INVENTION
The use of closure devices for fastening storage containers, including plastic
bags, is generally known. Furthermore, the manufacture of closure devices made
of
plastic materials is generally known to those skilled the in the art, as
demonstrated by
the numerous patents in this area.
A particularly well-known use for closure devices is in connection with
flexible storage containers, such as plastic bags. In some instances, the
closure device
and the associated container are formed from thermoplastic materials, and the
closure
device and the sidewalls of the container are integrally formed by extrusion
as a single
piece. Alternatively, the closure device and sidewall of the container may be
formed
as separate pieces and then connected by heat sealing or any other suitable
connecting
process. In either event, such closure devices are particularly useful in
providing
closure means for retaining matter within the bag.
Conventional closure devices typically utilize mating fastening strips or
closure elements, which are used to selectively seal the bag. In addition,
sliders may
be provided for use in opening and closing the fastening strips. Such
reclosable bags
equipped with sliders are known in the art as "slider bags." The slider may
include a
separator which extends at least partially between the fastening strips. When
the
slider is moved in the opening direction, the separator divides or deoccludes
the
fastening strips and opens the bag. When the slider is moved in the closing
direction,
the slider closes or occludes the fastening strips.
It is well known in the art to provide one or both ends of the reclosable
fastener of a slider bag with an end stop to prevent movement of the slider
past the
ends of the bag. The end stop may be formed from the material of the fastening
strips
such that they protrude transversely from the fastener a distance adequate to
engage
the slider and prevent movement of the slider passed the respective ends of
the bag as
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the slider and prevent movement of the slider passed the respective ends of
the bag as
is known from U.S. Patent No. 5,950,285 to Porchia et al. With this
arrangement the
size of the end stops is limited by the amount of material in the ends of the
fastener.
Another prior art end stop arrangement is disclosed in U.S. Patent No.
5,161,286 to Herrington et al. In this patent the end stops are located at the
opposite
ends of tlie reclosable fastener and each end stops is fashioned as a pair of
clamp
members connected together by a flexible strap which extends over the top of
the
zipper and which are also secured together by a plastic rivet that pierces the
film
material of the bag below the reclosable fastener. A drawback with this
approach is
the potential for leakage that may occur anytime the bag is pierced.
U.S. Patent No. 5,448,807 to Herrington discloses another prior art end stop
arrangement in which the end stop is formed as a separate plastic clip that is
fused
with the ends of the fastening strips of a zipper type reclosable fastener
during
manufacture of the bag. In accordance with the manufacturing method aspect of
the
invention, this patent document teaches to position the clip at opposite ends
of the
reclosable fastener, the clip comprising a strap member that is wrapped over
the top of
the zipper, and then sealing in place along with the profile elements of the
fastening
strips to form a fused mass. This patent document further teaches to use an
insertion
device to hold the clips in place while they are being sealed to the zipper.
In order to
hold the clips in place by themselves, the clips may be provided with an
integral pin
that penetrates the zipper film. Thus, in the line production of thermoplastic
bags, the
multiple steps of positioning the end stop on the bag, holding the end stop in
place
prior to fusing, and fusing the end stop to the bag are done in a lengthy
sequence at a
single station on the line. The lengthy sequence of steps at a single station
in a line
production results in slow line speed and low throughput.
It would be desirable to position and secure end stops on a reclosable
fastener
of a thermoplastic bag in the line production of thermoplastic bags in a
manner in
which increased line speed and greater throughput are achieved.
SUMMARY OF THE INVENTION
The present invention is directed to an end stop for a thermoplastic bag
having
a reclosable fastener at the open top end of the bag. The reclosable fastener
comprises
a pair of interlocking fastening strips. The end stop is configured to
facilitate snap fit
insertion onto the fastener strips and includes a top portion and a pair of
depending
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side portions that straddle the fastener. The side portions further include
inwardly
directed tab and shoulder structure that engage the reclosable fastener and
prevent the
end stop from being inadvertently pulled off in a transverse direction in
order to hold the
end stop in place prior to being bonded to the bag. The bonding step is
preferably
accomplished by ultrasonic welding.
In the case of the line production of thermoplastic bags wherein a continuous
web
of plastic material is moved from one station to the next, the invention
allows for the
positioning of the end stop onto the reclosable fastener at a first station
and the bonding
of the end stop to the bag at a second station. The positioning and bonding
steps may be
performed simultaneously since the tab and shoulder structure hold the end
stop in place
on the reclosable fastener as the web of plastic material is moved from the
first station to
the second station. The ability to perform the simultaneous sequence of steps
described
above advantageously provides for increased line speed production and
throughput.
The bags may include a slider for use in opening and closing the reclosable
fastener. The slider is slidably disposed on the interlocking fastening strips
for
facilitating the occlusion and deocclusion of the fastening strips when moved
towards
first and second ends of the fastening strips. The first and second ends of
the fastening
strips are secured together and the end stop is provided to the first, closing
end of the
fastening strips. The end stop may be provided with quick release latching
structure
engagable with cooperating latch-receiving structure provided to the mating or
opening
end of the slider to secure the slider when it is moved into engagement with
the end stop
at the closing end of the bag. In accordance with an alternate embodiment, a
second end
stop may be provided at the other end of the bag.
In one aspect, the invention resides in a method of installing an end stop
onto a
reclosable fastener of a thermoplastic bag which includes front and rear side
panels
joined together along three sides to define an open mouth, wherein the
reclosable
fastener extends along the mouth of the bag and a slider straddles the
fastener, the
fastener comprising first and second interlocking fastening strips attached to
respective
ones of said front and rear side panels and arranged to be interlocked over a
predetermined longitudinal x-axis between a first end and second end of the
bag, the
fastening strips being fused together at the first and second ends, the slider
adapted to
occlude the fastening strips when moved toward the first end and deocclude the
fastening
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strips when moved toward the second end, the method comprising: positioning a
generally inverted u-shaped end stop onto said first end of the fastening
strips, said end
stop including a top portion and first and second side portions depending from
said top
portion, said first and second side portions adapted to be positioned adjacent
said first
and second interlocking fastening strips, each of said first and second side
portions
having a lower inwardly directed tab portion with a shoulder adapted to engage
a
lowermost portion of the respective adjacent fastening strip to restrain
transverse
movement of the end stop once positioned onto the fastening strips; and
bonding the
corresponding tab portion of each side portions to the adjacent front and rear
side panels
of the bag.
In another aspect, the present invention resides in a method of installing an
end
stop onto a thermoplastic bag having a reclosable fastener extending along the
mouth of
the bag, the fastener comprising first and second interlocking fastening
strips attached to
respective front and rear side panels of the bag and arranged to be
interlocked over a
predetermined longitudinal x-axis between a first end and second end of the
bag, the
fastening strips being fused together at the first and second ends the method
comprising:
positioning a generally inverted u-shaped end stop onto one of said first and
second ends
of the fastening strips, said end stop including a top portion and first and
second side
portions depending from said top portion, said first and second side portions
adapted to
be positioned adjacent said first and second interlocking fastening strips,
each of said
first and second side portions having a lower inwardly directed tab portion
with a
shoulder adapted to engage a lowermost portion of the respective adjacent
fastening strip
to restrain transverse movement of the end stop once positioned onto the
fastening strips;
and bonding the corresponding tab portion of each side portions to the
adjacent front and
rear side panels of the bag.
In a further aspect, the present invention resides in a thermoplastic bag
having
front and rear side panels and a reclosable fastener extending along the mouth
of the bag,
the fastener comprising first and second interlocking fastening strips
attached to
respective ones of said front and rear side panels and arranged to be
interlocked over a
predetermined longitudinal x-axis between a first end and second end of the
bag, the
fastening strips being fused together at the first and second ends, wherein
the
improvement comprises: an end stop located adjacent at least one of said first
and
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second ends of said fastening strips; said end stop being of a generally
inverted u-shaped
configuration and including a top portion and first and second side portions
depending
from said top portion, said first and second side portions adapted to be
positioned
adjacent said first and second interlocking fastening strips, each of said
first and second
side portions having a lower inwardly directed tab portion with a shoulder
adapted to
engage a lowermost portion of the respective adjacent fastening strip to
restrain
transverse movement of the end stop once positioned onto the secured end of
the
fastening strips; and each of said first and second side portions including a
bottom
portion extending a distance downwardly from said reclosable fastener and
bonded to
respective front and rear panels of said bag.
Methods and apparatus which incorporate the features described above and which
are effective to function as described above constitute further, specific
objects of the
invention. Other objects and advantages of the invention will become apparent
upon
reading the following description and upon reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of this invention reference should now be
had
to the embodiments illustrated in greater detail in the accompanying drawings
and
described below by ways of examples of the invention. In the drawings:
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Fig. 1 is a perspective view of a container in the form of a plastic bag
having a
slider and an end stop provided with means for quick release latching
engagement of
the slider in accordance with one embodiment of the present invention;
Fig. 2 is an enlarged perspective view of the slider of Fig. 1;
Fig. 3 is an enlarged perspective view of the end stop of Fig. 1;
Fig. 4 is an enlarged fragmentary side elevation view of the container of Fig.
1;
Fig. 5 is a partial cross-sectional view through the end stop and slider taken
along the line and in the direction of arrows 5-5 of Fig. 4 (note the
reclosable fastener
has been omitted for clarity);
Fig. 6 is a partial cross-sectional view similar to Fig. 5 showing the slider
disengaged from the end stop;
Fig. 7 is an elevational view of a line production assembly of thermoplastic
bags manufactured in accordance with the present invention;
Figs. 8 is a perspective view which illustrates the step of positioning the
end
stop onto the reclosable fastener of a thennoplastic bag;
Fig. 9 is a perspective view similar to Fig. 8 wherein the end stop is shown
in
position on the reclosable fastener; and
Fig. 10 is a perspective view which illustrates the step of bonding the end
stop
to the sides of the thermoplastic bag.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A container constructed in accordance with a preferred embodiment of the
present invention is generally designated by reference numeral 100 in Fig. 1.
The
container 100 is in the form of a plastic food bag 120 having a reclosable
fastener
device 121 at the open top of the bag 120. The bag 120 includes a first
sidewall 122
and a second sidewall 123 joined at seams 125, 126 to define a compartment
accessible through the open top but sealable by means of the closure device
121. The
closure device 121 includes first and second fastening strips 130, 131 and a
slider 132.
The fastening strips 130, 131 are adapted to be interlocked between a first
end 127
and a second end 128. The fastening strips 130, 131 are secured together at
the first
and second ends 127, 128 to form end seals. As shown in the figures, the first
and
second ends 127, 128 include melted portions 135, 137, in which the fastening
strips
130, 131 are melted together by heat sealing, ultrasonic sealing or other
operation to
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form the end seals. In other embodiments, the first and second ends 127 and
128 may
be secured together by plastic clamps, or by other means. The closure device
121
further includes an end stop 134 disposed proximate the first end 127.
The fastening strips 130, 131, slider 132 and end stop 134 have a longitudinal
X-axis 102, a transverse Y-axis 104 and a vertical Z-axis 106. The transverse
Y axis
104, the longitudinal X axis 102 and the vertical Z axis 106 are mutually
perpendicular to one another and define a three axis coordinate system. The
fastening
strips 130, 131 each have a bottom edge 115 and a top edge 117. The closure
device
121 may include a tape portion 118 that extends downward a distance from the
bottom edge 115 of the fastening strips 130, 131 for attachment to the
respective first
and second sidewalls 122, 123. Alternately, tape portion may be omitted and
the
sidewalls 122, 123 may be attached directly to the respective first and second
fastening strips 130, 131.
The slider 132 straddles the fastening strips 130, 131 and is mounted so that
the slider 132 is restrained from being inadvertently pulled off of the
fastening strips
130, 131 along the vertical Z axis 106 but is free to slide back and forth
along the
longitudinal X axis 102. The slider 132 engages the fastening strips 130, 131
so that
when the slider moves in the occlusion direction 114, the fastening strips
130, 131
interlock and the bag 120 is sealed, and when the slider 132 moves in a
deocclusion
direction 116, the fastening strips 130, 131 separate and the bag is open.
Fig. 2 is a perspective view looking into the opening end of the slider 132.
The slider 132 includes a top portion 140, a first side portion 142 and a
second side
portion 144. The first side portion 142 has an inner side wall 146 and an
outer side
wall 148, and an inwardly directed bottom tab 150. Similarly, the second side
portion
144 has an inner side wall 152 and an outer side wall 154, and an inwardly
directed
bottom tab 156. As best seen in Figs. 4 and 5, the outer side walls 148 and
154 are
bowed outward.
The first and second side portions 142, 144 straddle the respective first and
second fastening strips 130, 131 and the inwardly directed tabs 150, 156 mate
with the
respective bottom edges 115 of the fastening strips 130, 131. The slider 132
is
prevented from being accidentally pulled off of the reclosable fastener 121 by
the
engagement between the upper surfaces of the inwardly directed bottom tabs
150, 156
and the bottom edge 115 of the respective first and second fastening strips
130, 131.
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As best seen in Fig. 2, inner sidewall 152 of the second side portion 144 is
provided with a recess 158, the purpose of which will be described in greater
detail
below. Although not visible in Fig. 2, the inner sidewall 146 of the first
side portion
142 is similarly provided with a recess 159. In accordance with an alternate
embodiment, only one of the first and second side walls is provided with a
recess.
Each of the outer sidewalls 142 and 154 is provided with upraised ridges 160
which
provide gripping areas for the user's fingers when moving the slider 132 back
and
forth along the reclosable fastener 121. As best seen in Figs. 2, 4 and 5, the
ridges
160 sit within a shallow well 162 provided to the respective outer sidewalls
148, 154
of the first and second side portions 142, 144 so as to maintain the bowed
outward
contour of the outer sidewalls 148, 154.
Referring to Figs. 3 and 4, the end stop 134 includes a top portion 170, a
first
side portion 172 and a second side portion 174. The first side portion 172
includes a
latch member 176 having a base end 176a connected to the first side portion
172 and a
free end 176b that extends in the longitudinal x-axis 102. The free end 176b
includes
an end face 178 that is tapered inwardly in the direction of the longitudinal
x-axis 102.
The free end 176b further includes a ridge member or projection 180 that
extends
outwardly in the direction of the transverse y-axis 104. In similar fashion,
the second
side portion 174 includes a latch member 182 having a base end 182a connected
to
the second side portion 174 and a free end 182b that extends in the
longitudinal x-axis
102. The free end 182b includes an end face 184 that is tapered inwardly in
the
direction of the longitudinal x-axis 102. The free end 182b further includes a
ridge
member or projection 186 that extends outwardly in the direction of the
transverse y-
axis 104.
The end stop 134 straddles the fastening strips 130, 131 at the first end 127
of
the bag. End stop side portion 172 includes a bottom portion 188 having an
inwardly
projecting tab 198 adapted to engage against the bottom edge 115 of fastening
strip
130. Similarly, end stop side portion 174 includes a bottom portion 200 having
an
inwardly projecting tab 202 adapted to engage against the bottom edge 115 of
fastening strip 131. The lower inside corners of each tab 198, 202 are
provided with
upwardly and inwardly tapered surfaces 204 and 206, respectively. The tapered
surfaces 204, 206 facilitate snap fit insertion of the end stop 134 onto the
reclosable
fastener 121. The end stop 134 is secured in straddling position over the
reclosable
fastener 121 by heat sealing, ultrasonic sealing or other operation to form
seals
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between the bottom portions 188, 200 and the respective adjacent sides of the
bag
120. The sequence of steps in positioning and securing the end stop 134 to the
fastener 121 is illustrated in Figs. 8-10.
As best seen in Fig. 4, the slider 132 and the end stop 132 are conformingly
contoured in outer appearance so as to provide an aesthetic blend of the two
parts and
so that they interfacially fit together when the slider 132 is positioned
against the end
stop 134 at the closing end 127 of the bag 120. The respective top portions
140 and
170 of the slider 132 and end stop 134 slope upward to form a common peak at
the
point of interfacial engagement between the respective mutually facing end
faces 155
and 196 of the slider 132 and end stop 134. Each of the end stop side portions
172
and 174 further include upstanding longitudinally oriented ribs 190 having end
faces
192 adapted to conform with and abut against the respective leading edges 194
of the
first and second side portions 142, 144 of the slider 132 when the slider is
moved into
to the fully closed position on the bag 120.
In accordance with the present invention there is provided means for the quick
release latching engagement of the slider 132 to the end stop 134. Referring
now to
Figs. 5 and 6, a positive latching of the slider 132 to the end stop 143 is
effectuated by
the cooperating receiving engagement of the outward projections 180, 186 on
the
latch members 176, 184 of the end stop 134 within the corresponding recesses
158,
159 of the slider 132. The inward tapered faces 178, 184 on the respective
free ends
of latch members 176, 182 help guide the interfacial latching engagement
between the
slider 132 and end stop 134. The latch members 176, 182 of the end stop 134
are
inwardly bendable or deflectable in the direction of the transverse y-axis 104
as
shown in Fig. 6. The inward deflection of the latch members 176, 182 moves the
respective outward projections 180, 186 out of engagement with the recesses
158, 159
thereby permitting the slider 132 to be moved in the opening direction of the
bag.
While, a dual latch member arrangement has been shown and described, it is
understood that a single latch member arrangement may also be used with
equally
good results. In other words, the end stop 134 described herein may have only
one
side portion equipped with a deflectable latch member that is receivingly
engagable
within a recess provided to an inner sidewall of the slider 132.
Fig. 7 illustrates a line production of a series of thermoplastic bags B in
which
end stops 134 embodying the present invention are positioned onto the
reclosable
fastener 121 of the bags B at a first station (Station 1) and then bonded to
the sides of
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the bags B at a second station (Station 2). The bags B are advanced from
Station 1 to
Station 2 to as indicated by directional arrow A. The slider 132 may be
positioned
onto the reclosable fastener 121 either upstream or down stream of Station 1
or
Station 2.
Referring now to Figs. 8-10, there is shown in greater detail the steps of
positioning and bonding the end stop 134 onto the reclosable fastener 121. End
face
196 of the end stop top portion 170 and end faces 203, 205 of the respective
end stop
side portions 172, 174 are straight edges and are all aligned in a common
plane to
facilitate bowl feeding of the end stops for positioning (inserting) onto the
reclosable
fastener 121. The interior surfaces of side portions 172, 174 of the end stop
134 are
configured for snap fit insertion onto the reclosable fastener 121. As noted
above in
connection with the description of Fig. 3, the shoulder structure as defined
by the
inwardly projecting tabs 198, 200 of the respective side portions 172, 174
function to
restrain transverse movement of the end stop 134 relative to the reclosable
fastener
121. Stated in another way, the tabs 198, 200 prevent the end stop from being
in
advertently pulled off of the reclosable fastener 121 prior to welding. The
gap
between the vertical faces of the inwardly projecting tabs 198, 200 is
dimensioned for
a close tolerance snug fit engagement over the fastening strips 130, 131 of
the
reclosable fastener 121. The respective inner bottom surfaces 204 and 206 of
the tabs
198, 200 are inwardly and upwardly tapered to facilitate the downward snap fit
insertion of the end stop 134 onto the reclosable fastener 121 as indicated by
directional arrow C in Fig. 8. The bottom portions 188, 190 are configured to
provide
a sufficient surface area to permit ultrasonic welding to the respective side
panels 122,
123 of the bag. The resultant bond created at Station 2 (Fig. 7) that is
formed between.
the bottom portion 188 and the adjacent side panel 122 is indicated by the
cross-
hatching shown in Figs. 1, 4, and 10.
Although several interlocking fastening strip embodiments have been
specifically described and illustrated herein, it will be readily appreciated
by those
skilled in the art that other kinds, types, or forms of fastening strips can
alternatively
be used without departing from the scope or spirit of the present invention.
The interlocking fastening strips may be manufactured by extrusion through a
die and may be formed from any suitable thermoplastic material including, for
example, polyethylene, polypropylene, nylon, or the like, or from a
combination
thereof. Thus, resins or mixtures of resins such as high-density polyethylene,
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medium-density polyethylene, and low-density polyethylene may be employed to
prepare the interlocking fastening strips.
When the fastening strips are used in a sealable bag, the fastening strips and
the films that form the body of the bag may be conveniently manufactured from
heat
sealable material. In this way, the bag may be economically formed by using an
aforementioned thermoplastic material and by heat sealing the fastening strips
to the
bag. For example, the bag may be made from a mixture of high pressure, low-
density
polyethylene and linear, low-density polyethylene.
The fastening strips may be manufactured by extrusion or other known
methods. For example, the closure device may be manufactured as individual
fastening strips for later attachment to the bag or may be manufactured
integrally with
the bag. In addition, the fastening strips may be manufactured with or without
flange
portions on one or both of the fastening strips depending upon the intended
use of the
fastening strips or expected additional manufacturing operations.
Generally, the fastening strips can be manufactured in a variety of forms to
suit the intended use. The fastening strips may be integrally formed on the
opposing
sidewalls of the container or bag, or connected to the container by the use of
any of
several known methods. For example, a thermoelectric device may be applied to
a
film in contact with the flange portion of the fastening strips or the base
portion of
fastening strips having no flange portion, to cause a transfer of heat through
the film
to produce melting at the interface of the film and a flange portion or base
portion of
the fastening strips. Suitable thermoelectric devices include heated rotary
discs,
traveling heater bands, resistance-heated slide wires, and the like. The
connection
between the film and the fastening strips may also be established by the use
of hot
melt adhesives, hot jets of air to the interface, ultrasonic heating, or other
known
methods. The bonding of the fastening strips to the film stock may be carried
out
either before or after the fihn is U-folded to form the bag. In any event,
such bonding
may be done prior to side sealing the bag at the edges by conventional thermal
cutting. In addition, the first and second fastening strips may be positioned
on
opposite sides of the film. Such an embodiment would be suited for wrapping an
object or a collection of objects such as wires. The first and second
fastening strips
should usually be positioned on the film in a generally parallel relationship
with
respect to each other, although this will depend on the intended use.
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Both the slider and/or end stop may be multiple parts and snapped together. In
addition, both the slider and/or may be made from multiple parts and fused or
welded
togetlier. The slider and/or end stop may also be a one-piece construction.
They can
be colored, opaque, translucent or transparent as desired. Both pieces may be
injection molded or made by any otlzer method. The slider and/or end stop may
be
molded from any suitable plastic material, such as high-density polyethylene,
polypropylene, nylon, acetal, toughened acetal, polyketone, polybutylene
terrephthalate, polycarbonate or ABS (acrylonitrile-butadiene-styrene)
From the foregoing it will be understood that modifications and variations
may be effectuated to the disclosed structures - particularly in light of the
foregoing
teachings - without departing from the scope or spirit of the present
invention. As
such, no limitation with respect to the specific embodiments described and
illustrated
herein is intended or should be inferred. On the contrary, it is intended to
cover all
alternatives, modifications and equivalents as may be included within the
spirit and
scope of the invention as defined by the appended claims.
