U.S. patent application number 12/008214 was filed with the patent office on 2008-05-08 for methods for sensing features on moving fastener tape during automated production.
Invention is credited to Victor Delisle, Clifton Ronald Howell, Kevin Owen.
Application Number | 20080108488 12/008214 |
Document ID | / |
Family ID | 36942212 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080108488 |
Kind Code |
A1 |
Delisle; Victor ; et
al. |
May 8, 2008 |
Methods for sensing features on moving fastener tape during
automated production
Abstract
A method of manufacture comprising the following steps: (a)
during a respective indexing portion of a respective work cycle,
advancing a fastener tape made of flexible thermoplastic material
along a process pathway, the fastener tape not advancing during a
respective dwell time of the respective work cycle; (b) during each
dwell time, forming or attaching a respective structural feature of
a type on the portion of the fastener tape that is resident at a
first fixed station situated along the process pathway, the
structural features of that type being spaced at intervals along
the portion of the fastener tape that is downstream of the first
fixed station; (c) while the fastener tape is advancing along the
process pathway during the indexing portion of each work cycle,
transmitting light toward a volume of space at a second fixed
station, the process pathway intersecting and passing through the
volume of space; and (d) photodetecting at least portions of the
transmitted light after some or all of the transmitted light has
entered and then exited the volume of space at the second fixed
station, the photodetected portions of the transmitted light being
converted into electrical signals.
Inventors: |
Delisle; Victor; (Roswell,
GA) ; Howell; Clifton Ronald; (Buford, GA) ;
Owen; Kevin; (Flowery Branch, GA) |
Correspondence
Address: |
OSTRAGER CHONG FLAHERTY & BROITMAN, P.C.
570 LEXINGTON AVENUE
FLOOR 17
NEW YORK
NY
10022-6894
US
|
Family ID: |
36942212 |
Appl. No.: |
12/008214 |
Filed: |
January 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11125755 |
May 9, 2005 |
7311647 |
|
|
12008214 |
Jan 10, 2008 |
|
|
|
Current U.S.
Class: |
493/10 |
Current CPC
Class: |
B31B 70/8131 20170801;
B29C 66/71 20130101; B29C 66/8322 20130101; B29C 66/73921 20130101;
B29C 66/71 20130101; B29C 66/71 20130101; Y10S 493/927 20130101;
B29K 2023/12 20130101; B29C 66/98 20130101; B29K 2077/00 20130101;
B29K 2067/006 20130101; B29K 2069/00 20130101; B29K 2059/00
20130101; B29K 2023/065 20130101; B29K 2055/02 20130101; B29K
2025/06 20130101; B29K 2061/00 20130101; B29C 66/71 20130101; B29C
66/1122 20130101; B29C 66/71 20130101; B29C 66/306 20130101; B29C
65/7891 20130101; B29C 66/71 20130101; B29C 66/474 20130101; B29L
2005/00 20130101; B29C 66/71 20130101; B29C 66/431 20130101; B29D
5/00 20130101; B29C 65/08 20130101; B29C 66/43 20130101; B29C 66/71
20130101; B29C 66/96 20130101; B29C 66/71 20130101; B29C 66/71
20130101; B29C 66/80 20130101 |
Class at
Publication: |
493/010 |
International
Class: |
B31B 49/00 20060101
B31B049/00 |
Claims
1-20. (canceled)
21: A system comprising a fastener processing machine, a fastener
tape comprising mutually interlocked first and second zipper strips
made of flexible material that follow a process pathway through
said fastener processing machine, and a controller for controlling
the operation of said fastener processing machine, wherein: said
fastener processing machine comprises a supply reel having a
portion of said fastener tape wound thereon with a paid-out portion
of said fastener tape connected thereto, a device for attaching or
forming a respective structural feature of a type on the section of
the paid-out portion of said fastener tape that is resident in a
fixed zone along said process pathway, means for advancing the
section that is resident in said fixed zone along said process
pathway, and an optical sensor that detects a boundary of each
passing structural feature of said type as said fastener tape is
advanced along said process pathway; and said controller is
programmed to control the operation of said device and said
fastener tape advancing means so that during an advancement phase
of each work cycle, said fastener tape advancing means advances
said fastener tape; and during a dwell time of each work cycle,
said device is activated, and is further programmed to adjust the
distance that said fastener tape advancing means advances said
fastener tape during a particular work cycle in accordance with an
algorithm that takes into account characteristics of electrical
signals output by said optical sensor during work cycles preceding
said particular work cycle.
22: The system as recited in claim 21, wherein said device
comprises a slider inserter.
23: The system as recited in claim 21, wherein said device
comprises an ultrasonic welding assembly.
24: The system as recited in claim 21, wherein said optical sensor
comprises a light-emitting diode and a photodetector.
25: The system as recited in claim 24, further comprising a first
optical fiber optically coupled to said light-emitting diode and a
second optical fiber optically coupled to said photodetector.
26: The system as recited in claim 21, wherein said optical sensor
comprises a laser scanning transmitter and a laser scanning
receiver.
27: The system as recited in claim 26, wherein said controller is
programmed to compute a change in the heights of respective gaps in
a curtain of laser beams transmitted by said laser scanning
transmitter and received by said laser scanning receiver at
respective times.
28: The system as recited in claim 21, wherein said optical sensor
comprises a laser and a multi-element detector array.
29: The system as recited in claim 28, wherein said optical sensor
further comprises a transmitter lens and a receiver lens.
30: A system comprising: means for advancing a fastener tape made
of flexible thermoplastic material along a process pathway during a
respective indexing portion of a respective work cycle, said
fastener tape not advancing during a respective dwell time of said
respective work cycle; means for deforming said fastener tape in a
respective zone that is resident at a first fixed station situated
along said process pathway during each dwell time, said deformed
zones being spaced at intervals along the portion of said fastener
tape that is downstream of said first fixed station; means for
transmitting light toward a volume of space at a second fixed
station while said fastener tape is advancing along said process
pathway during the indexing portion of each work cycle, said
process pathway being arranged such that said deformed zones
intersect and pass through said volume of space during advancement
of said fastener tape; means for photodetecting at least portions
of said transmitted light after some or all of said transmitted
light has entered and then exited said volume of space at said
second fixed station, said photodetected portions of said
transmitted light being converted into electrical signals that
indicate a time when transmitted light impinges on an edge of a
deformed zone as said deformed zone passes through said volume of
space; and a controller for controlling said advancing means as a
function of electrical signals from said photodetecting means, said
controller being programmed so that the distance that said fastener
tape is advanced during an indexing portion of a particular work
cycle is determined in accordance with an algorithm that takes into
account characteristics of electrical signals from said
photodetecting means acquired in during earlier work cycles.
31: A system comprising: means for advancing a fastener tape made
of flexible transparent or translucent thermoplastic material along
a process pathway during a respective indexing portion of a
respective work cycle, said fastener tape not advancing during a
respective dwell time of said respective work cycle; a slider
insertion device for inserting a respective slider on the portion
of said fastener tape that is resident at a first fixed station
situated along said process pathway during each dwell time, said
sliders being spaced at intervals along the portion of said
fastener tape that is downstream of said first fixed station, each
slider being substantially opaque; means for transmitting light
toward a portion of said fastener tape in a volume of space at a
second fixed station while said fastener tape is advancing along
said process pathway during the indexing portion of each work
cycle, respective portions of said sliders also passing through
said volume of space; means for photodetecting those portions of
said transmitted light that pass through the portion of said
fastener tape resident in said volume of space and that are not
blocked by a slider, said photodetected portions of said
transmitted light being converted into electrical signals that
undergo a change in amplitude in response to a leading edge of said
slider moving into the path of said transmitted light; and a
controller for controlling said advancing means as a function of
electrical signals from said photodetecting means, said controller
being programmed so that the distance that said fastener tape is
advanced during an indexing portion of a particular work cycle is
determined in accordance with an algorithm that takes into account
characteristics of electrical signals from said photodetecting
means acquired in during earlier work cycles.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to methods for
sensing structural features on a moving fastener tape during the
automated manufacture of reclosable packaging. In particular, the
invention relates to methods for sensing deformations or attached
articles on a plastic fastener tape of the type comprising a pair
of mutually interlocked zipper strips, the latter having a length
sufficient to form multiple package-length zippers when processed
on a bag making machine, thermoformed packaging machine,
form-fill-seal machine or other machine for making reclosable
packaging.
[0002] During the automated manufacture of reclosable packages,
typically a thermoplastic fastener tape unwound from a supply reel
or spool is joined (e.g., by conductive heat sealing) to a web of
thermoplastic packaging material. The web-to-fastener tape sealing
operation can be performed either intermittently (i.e., during
dwell times interspersed between intermittent advancements) or
continuously (i.e., while the fastener tape and web are advancing
continuously).
[0003] In cases where a fastener tape without pre-sealing and
without sliders must be joined with a web of packaging material,
there is a need for the fastener tape to be properly aligned with
the web of film (i.e., straightness and cross-machine alignment),
but there is no need to register the fastener tape relative to the
web in a machine direction. This is due to the fact that the
fastener tape has a constant profile along its length and thus has
no structural features that need to be registered relative to
respective package-length sections of the web of packaging
material.
[0004] The fastener tape typically comprises a pair of continuous
zipper strips, each zipper strip having a respective constant
profile produced by extrusion. Typically, the respective zipper
strip profiles have complementary shapes that allow the zipper
strips to be interlocked. These closure profiles may be of the
rib-and-groove variety, the interlocking-hook variety or any other
suitable fastenable structures. Pre-sealing of the fastener tape
involves crushing and fusing the closure profiles and, if the
zipper strips are flanged, the zipper flanges as well at spaced
intervals along the fastener tape at locations where the fastener
tape will be ultimately cut when each finished package is severed
from the work in process. Pre-sealing may be accomplished by
ultrasonic stomping or thermal crushing. In cases where the
fastener tape is pre-sealed before entering the packaging machine,
it is desirable that the midplane of each pre-seal be registered
within a maximum allowable deviation relative to a corresponding
cut line.
[0005] In cases where sliders are inserted at spaced intervals
along the fastener tape before the latter enters the packaging
machine, it is common to combine the joinder of the closure
profiles at spaced intervals with the formation of slider end stop
structures on the fastener tape. Although slider end stops can be
attached to or inserted on the fastener tape, it is common practice
to simply deform and fuse the thermoplastic material of the closure
profiles strips wherever slider end stops are needed. Typically,
the zipper material is softened by applying ultrasonic wave energy
and the thus-softened zipper material is shaped to form a slider
end stop structure. If the zipper has flanges, the zipper flanges
can be fused during the same ultrasonic stomping operation or
during a separate thermal crushing operation. The slider end stop
structure, when bisected by a cut line, will form back-to-back
slider end stops for adjacent packages. The slider end stop
structure is formed at a location such that its midplane will be
generally coplanar with the plane of cutting when the finished
package is severed from the work in process. Thus, it is important
that the midplane of each slider end stop formation on the fastener
tape be registered within a maximum allowable deviation relative to
a corresponding cut line.
[0006] During the initial setup of a machine that joins a fastener
tape to a web or webs of packaging material, the midplane of a
leading pre-seal or slider end stop structure may be manually
aligned with the cutting blade that severs the completed package
from the work in process. There is a need for means to ensure that
each subsequently formed pre-seal or slider end stop structure will
ultimately arrive at a position whereat its midplane will also be
generally aligned with the cutting blade. One method of
accomplishing the foregoing involves the step of sensing or
detecting the passage of each pre-seal or slider end stop structure
(or each slider) at a fixed location during fastener tape
advancement. This information is then used to adjust the distance
by which the fastener tape is advanced in the interval between
successive pre-sealing or slider end stop formation (with
concurrent slider insertion) operations.
[0007] Thus, there is a need for an accurate and reliable method
for sensing or detecting a repeating structural feature formed on
or attached to a moving fastener tape as it passes a fixed location
in a packaging machine.
BRIEF DESCRIPTION OF THE INVENTION
[0008] The present invention is directed to methods for sensing
reoccurring structural features on a moving fastener tape during
automated production of reclosable packages. The invention is also
directed to apparatus for implementing such methods. The invention
takes advantage of the fact that the structural features of
interest, when exposed to impinging beams of light (e.g., LED
beams), will produce changes in those light beams that can be
optically detected, thereby allowing the arrival of the structural
feature or a boundary thereof at a fixed location to be
detected.
[0009] One aspect of the invention is a method of manufacture
comprising the following steps: (a) during a respective indexing
portion of a respective work cycle, advancing a fastener tape made
of flexible thermoplastic material along a process pathway, the
fastener tape not advancing during a respective dwell time of the
respective work cycle; (b) during each dwell time, forming or
attaching a respective structural feature of a type on the portion
of the fastener tape that is resident at a first fixed station
situated along the process pathway, the structural features of the
type being spaced at intervals along the portion of the fastener
tape that is downstream of the first fixed station; (c) while the
fastener tape is advancing along the process pathway during the
indexing portion of each work cycle, transmitting light toward a
volume of space at a second fixed station, the process pathway
intersecting and passing through the volume of space; and (d)
photodetecting at least portions of the transmitted light after
some or all of the transmitted light has entered and then exited
the volume of space at the second fixed station, the photodetected
portions of the transmitted light being converted into electrical
signals.
[0010] Another aspect of the invention is a method of manufacture
comprising the following steps: (a) during a respective indexing
portion of a respective work cycle, advancing a fastener tape made
of transparent or translucent flexible thermoplastic material along
a process pathway, the fastener tape not advancing during a
respective dwell time of the respective work cycle; (b) during each
dwell time, inserting a respective slider on the portion of the
fastener tape that is resident at a first fixed station situated
along the process pathway, the sliders being spaced at intervals
along the portion of the fastener tape that is downstream of the
first fixed station, each slider being substantially opaque; (c)
while the fastener tape is advancing along the process pathway
during the indexing portion of each work cycle, transmitting light
toward a portion of the fastener tape in a volume of space at a
second fixed station, respective portions of the sliders also
passing through the volume of space; and (d) photodetecting those
portions of the transmitted light that pass through the portion of
the fastener tape resident in the volume of space and that are not
blocked by a slider; the photodetected portions of the transmitted
light being converted into electrical signals that undergo a change
in amplitude in response to a leading edge of the slider moving
into the path of the transmitted light.
[0011] A further aspect of the invention is a method of manufacture
comprising the following steps: (a) during a respective indexing
portion of a respective work cycle, advancing a fastener tape along
a process pathway, the fastener tape not advancing during a
respective dwell time of the respective work cycle, and the
fastener tape comprising first and second zipper strips made of
flexible thermoplastic material; (b) during each dwell time,
deforming and fusing respective portions of the first and second
zipper strips that are resident at a first fixed station situated
along the process pathway to form a respective zone of fusion, the
zones of fusion being spaced at intervals along the portion of the
fastener tape that is downstream of the first fixed station; (c)
while the fastener tape is advancing along the process pathway
during the indexing portion of each work cycle, transmitting light
toward a volume of space at a second fixed station, the process
pathway intersecting and passing through the volume of space; and
(d) photodetecting at least portions of the transmitted light after
some or all of the transmitted light has entered and then exited
the volume of space at the second fixed station, the photodetected
portions of the transmitted light being converted into electrical
signals.
[0012] Yet another aspect of the invention is a system comprising a
fastener processing machine, a fastener tape comprising mutually
interlocked first and second zipper strips made of flexible
material that follow a process pathway through the fastener
processing machine, and a controller for controlling the operation
of the fastener processing machine, wherein: the fastener
processing machine comprises a supply reel having a portion of the
fastener tape wound thereon with a paid-out portion of the fastener
tape connected thereto, a device for attaching or forming a
respective structural feature of a type on the section of the
paid-out portion of the fastener tape that is resident in a fixed
zone along the process pathway, means for advancing the section
that is resident in the fixed zone along the process pathway, and
an optical sensor that detects a boundary of each passing
structural feature of the type as the fastener tape is advanced
along the process pathway; and the controller is programmed to
control the operation of the device and the fastener tape advancing
means so that during an advancement phase of each work cycle, the
fastener tape advancing means advances the fastener tape; and
during a dwell time of each work cycle, the device is activated,
and is further programmed to adjust the distance that the fastener
tape advancing means advances the fastener tape during a particular
work cycle in accordance with an algorithm that takes into account
characteristics of electrical signals output by the optical sensor
during work cycles preceding the particular work cycle.
[0013] Other aspects of the invention are disclosed and claimed
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a drawing showing a front view of portions of one
known type of a slider-zipper assembly having structural features,
such as sliders and ultrasonically stomped slider end stop
formations and zipper flange joints, which are detectable using the
present invention.
[0015] FIG. 2 is a cross-sectional view (taken along section line
2-2 indicated ion FIG. 1) of the slider-operated plastic zipper
depicted in FIG. 1, except that the zipper flanges have been
abbreviated in length.
[0016] FIG. 3 is an isometric view of a fiber optic sensor being
used to detect a zone where the zipper flanges are fused together
in accordance with one embodiment of the present invention.
[0017] FIG. 4 is an isometric view of a laser scan micrometer being
used to detect a change in thickness in a zone where the closure
profiles are flattened and fused together in accordance with
another embodiment of the present invention.
[0018] FIG. 5 is an isometric view of a laser displacement sensor
being used to detect a zone where the closure profiles are
flattened and fused together in accordance with a further
embodiment of the present invention.
[0019] FIG. 6 is a block diagram representing automated equipment
for inserting sliders and forming slider end stop structures on a
fastener tape and then joining the fastener tape to packaging
material. The automated equipment also incorporates a sensor for
detecting reoccurring structural features on the fastener tape,
which sensor may be one of the types depicted in FIGS. 3-5.
[0020] FIG. 7 is a drawing showing the automated equipment of FIG.
6 wherein the sealing station is incorporated in a
thermoform-fill-seal (TFFS) machine.
[0021] FIG. 8 is a block diagram showing a subsystem for providing
a programmed logic controller with counting signals during
advancement of the packaging material in a TFFS machine, which
signals are used in conjunction with feedback from the sensor that
detects reoccurring structural features on the advancing fastener
tape.
[0022] 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
[0023] For the purpose of describing various methods of optically
detecting reoccurring structural features on an advancing fastener
tape during automated production, an exemplary fastener tape having
sliders inserted at spaced intervals therealong will be described
with reference to FIGS. 1 and 2. Several methods of optical
detection will then be described with reference to this exemplary
slider/fastener tape assembly. However, it should be understood
that the invention is not limited in its application to the
particular slider/fastener tape assembly depicted in FIGS. 1 and 2.
The broad scope of the invention will be apparent from the claims
that follow this detailed description.
[0024] The slider/fastener tape assembly depicted in FIGS. 1 and 2
may be manufactured using a process involving concurrent formation
of slider end stop structures and sealing of zipper flanges at
spaced intervals along a pair of interlocked flanged zipper strips
unwound from a roll or spool. The flanged zipper strips are
typically produced by extrusion so that initially they have a
constant profile along their length. The zipper strips have
complementary closure profiles and respective zipper flanges formed
during the extrusion process. In the embodiments disclosed herein,
the forming/sealing operation is carried out by applying ultrasonic
wave energy to the zipper material. However, instead of ultrasonic
wave energy, thermal or conduction heat sealing methods may be
used. Sufficient energy (ultrasonic or thermal) is applied to the
zipper or closure profiles in a first zone and to the zipper
flanges in a second zone to soften and merge the plastic material
in both zones, the merged material forming a zone of fusion upon
cooling. Each zone of fusion has a plane of symmetry, the planes of
symmetry being spaced, for a typical application, along the zipper
at intervals approximately equal to one package length. Each zone
of fusion is also shaped to form a pair of slider end stops that
are joined at their backs, until when the zipper is cut along the
plane of symmetry in the bag making or packaging machine, as
described in detail below.
[0025] The operations described in the preceding paragraph can also
be employed for sliderless flanged zippers. In this case the
closure profiles are deformed and fused to form zipper pre-seals
instead of slider end stops. As previously described, "pre-sealing"
involves flattening the zipper prior to merging with the packaging
material at a position that will ultimately correspond to the
package edge. The pre-sealing operation facilitates sealing the
sides of the package in the area of the zipper.
[0026] In accordance with one method of manufacturing the
slider/fastener tape assembly seen in FIGS. 1 and 2, the
interlocked zipper strips are advanced intermittently and then the
forming/sealing operation is repeated during each dwell time
between successive advancements. Typically, sliders are inserted at
a station downstream from the ultrasonic stomping station. The
resulting slider/fastener tape assembly comprises a chain of
connected zipper lengths, each zipper length having a respective
slider. This chain can be wound on a spool for storage or
transport, or the chain can be fed directly to a packaging
machine.
[0027] In the embodiments of the invention disclosed herein, slider
end stops are formed and the zipper flanges are sealed before the
fastener tape is joined to film in a packaging machine. A section
of a slider/fastener tape assembly 2 is depicted in FIG. 1. The
assembly 2 comprises a fastener tape 4 having a multiplicity of
sliders 6 (only one of which is shown in FIG. 1) mounted thereon.
Each slider 6 is of the straddling type, i.e., the slider has no
separating finger and thus requires that slider end stops be
provided at the ends of each zipper section.
[0028] The fastener tape 4 comprises a pair of interlockable zipper
strips 26 and 32 (see FIG. 2) having respective flanges 30 and 36
extending from respective closure profiles 28 and 34. In the view
of FIG. 1, only the zipper strip 26 is visible. The closure
profiles of the two zipper strips have complementary (i.e.,
interlocking) shapes. Although FIG. 2 shows a rib and groove
arrangement, the closure profiles of the zipper strips may take any
form. For example, the zipper may comprise interlocking rib and
groove elements or alternating hook-shaped closure elements. The
zipper strips 26 and 32 are made of translucent or transparent
thermoplastic material. The preferred zipper material is
polyethylene or polypropylene.
[0029] To facilitate opening and closing of each zipper after it
has been installed in the mouth of a package or bag, each
package-length section of the fastener tape is provided with a
respective straddling slider 6, as shown in FIGS. 1 and 2. The
slider 6 can be top-loaded onto the zipper without having to
disengage the profiled structures at the loading point since the
slider does not make use of a separating finger. The closure
profiles 28 and 34 are engaged, i.e., interlocked, with each other
as the slider travels in the closing direction. Conversely, the
closure profiles 28 and 34 are disengaged from each other as the
slider travels in the opening direction. The slider 6 may be made
in multiple parts and welded together or the parts may be
constructed to be snapped together. The slider may also be of
one-piece construction. The slider can be made using any desired
method, such as injection molding. The slider can be molded from
any suitable plastic, such as nylon, polypropylene, polystyrene,
acetal, polyketone, polybutylene terephthalate, high-density
polyethylene, polycarbonate, or ABS. Typically, the slider is made
of opaque material, in contrast to the zipper, which is translucent
or transparent.
[0030] FIG. 2 depicts a closing end of the slider 6, with the
zipper shown in cross section. The closing end is shaped to force
the closure profiles 28 and 34 into engagement when the slider 14
travels in the closing direction. During slider travel in the
closing direction, the closing end is the trailing end of the
slider. As shown in FIG. 2, the slider 6 straddles the zipper and
has a top wall 96 from which a first side wall 98 and a second side
wall 100 depend. The first side wall 98 has an inner surface 102
and the second side wall 100 has an inner surface 104. The slider
inner surfaces 102 and 104 are divergent with respect to each other
in the same manner as the outer surfaces of the closure profiles,
and are spaced to push the closure profiles 28 and 34 into
engagement as the slider 6 is moved along the zipper in the closing
direction. The slider side walls 98 and 100 are respectively
provided with retaining shoulders 106 and 108 having upper surfaces
110 and 112 that mate with the lower surfaces of the rails 52 and
54 of the closure profiles. These mating surfaces may be tapered to
maximize their pull-off resistance.
[0031] Opening of the zipper is achieved when the slider 6 is moved
in the opening direction. Although not shown, at the opening end of
the slider, the slider side walls have inner surfaces that are
substantially parallel, rather than divergent as at the closing end
(shown in FIG. 2). As the slider is moved in the opening direction
and the slider side wall inner surfaces change from the "A"
configuration of surfaces 102 and 104 (see FIG. 2) to a
substantially parallel configuration of surfaces (not shown) at the
opening end of the slider, the rails 52 and 54 are forced towards
each other, thereby forcing the fulcrum members 46 and 48 into a
tighter relationship and causing the rib 38 and groove 40 to pivot
oppositely about the fulcrum 50. Simultaneously, a retaining
shoulder (not shown) on the slider side wall 98 forces the male
profile upwardly, while a shoulder (not shown) forces the female
profile downwardly, causing the convex male fulcrum member 46 (see
FIG. 2) to cam upwardly along the concave female fulcrum member 48.
Thus, the resulting action is a simultaneous pivoting of the
closure profiles 28 and 34 oppositely about the fulcrum 50 and an
upward translation of the closure profile 28 relative to the
closure profile 34, resulting in disengagement of the profiled
structures. A cavity (not shown in FIG. 2) in the slider top 96
accommodates the upward translation of the male closure profile
28.
[0032] During bag or package manufacture, the top marginal portions
of the front and rear walls of the receptacle (not shown in FIGS. 1
and 2) of the bag or package are respectively sealed to the zipper
flanges 30 and 36 by a conventional conduction heat sealing
technique. Alternatively, the front and rear walls may be extended
beyond the zones of wall/zipper flange joinder and joined to each
other at the top marginal portions to form a header that shrouds
the slider/zipper assembly. The receptacle may be made from any
suitable film material, including thermoplastic film materials such
as low-density polyethylene, substantially linear copolymers of
ethylene and a C3-C8 alpha-olefin, polypropylene, polyvinylidene
chloride, mixtures of two or more of these polymers, or mixtures of
one of these polymers with another thermoplastic polymer. The
person skilled in the art will recognize that this list of suitable
materials is not exhaustive. Although not intended in a limitative
sense, it is noted that the thickness of the film is preferably 2
mils or less.
[0033] For the slider/fastener tape assembly partially depicted in
FIG. 1, a multiplicity of zones 8 of fused zipper material are
formed, at spaced intervals along a lengthwise direction, by the
application of heat and pressure to the zipper material. The heat
may be generated by the application of ultrasound wave energy as
the fastener tape is pressed between a horn and an anvil of an
ultrasonic welding assembly, e.g., of the type disclosed in
disclosed in U.S. patent application Ser. No. 10/439,847, entitled
"Method and Apparatus for Sealing Flanges and Deforming Profiles of
Plastic Zipper". Each zone of fusion 8 is generally T-shaped. Each
slider 6 is mounted to a respective unfused section disposed
between successive zones of fusion 8. Each zone of fusion 8
comprises a first area wherein the closure profiles of the
interlocked zipper strips are fused to each other and deformed, and
a second area wherein the zipper flanges of the interlocked zipper
strips are fused to each other and deformed.
[0034] The aforementioned first area of the zone of fusion extends
in the lengthwise direction and forms the top of the T shape.
During the forming/sealing operation, some of the plastic material
of the zipper profiles is deformed and pushed upward to form the
extended hump seen in FIG. 1. Also, some of the plastic material of
the zipper profiles in the zone of fusion is deformed and pushed
downward. In the forming process, a generally flattened surface 24
is formed in each zone of fusion 8. In addition, a row of spaced
indentations is formed on one side of the zone of fusion 8 in the
first area where the profiles are fused. A central indentation 18
is disposed along a plane of symmetry of the zone of fusion 8,
which plane is indicated by the dashed line designated by the
letter "C" in FIG. 1. Other indentations 16 (in this example, three
on each side of the central indentation) are formed along a line
generally perpendicular to line C, as seen in FIG. 1. These
indentations are impressed on only one side of the fastener tape by
respective teeth formed on the ultrasonic horn, as fully disclosed
in U.S. patent application Ser. No. 10/439,847. The teeth act as
vertical energy directors to penetrate the heat into the center of
the zipper directly into the fulcrum area of the profiles.
[0035] When the zipper is later cut along line C, the deformed and
fused zipper profiles form respective slider end stops 12 and 14 on
separate packages. In this sense, the first area of the zone of
fusion comprises back-to-back end stops. These end stops prevent
the slider from sliding off the ends of the zipper when the slider
reaches the closed or fully opened position. Such end stops perform
dual functions, serving as stops to prevent the slider from going
off the end of the zipper and also holding the two zipper profiles
together to prevent the bag from opening in response to stresses
applied to the profiles through normal use of the bag.
[0036] The aforementioned second area of the zone of fusion 8
extends transverse to the lengthwise direction and forms the stem
of the T shape. During the forming/sealing operation, some of the
plastic material of the zipper flanges is deformed and merged to
form a flange seal 10. The flange seal 10 comprises an array of
dimples 20. Alternatively, an array of mutually parallel spaced
grooves extending generally parallel to the line C may be formed.
The dimples (or grooves) 20 are impressed on the same side of the
zipper that the above-described indentations are formed. The
dimples and indentations are formed and the surface 24 is flattened
in one operation. A generally planar transitional surface 22 is
also formed between the flattened surface 24 and the flange seal
10. In a later stage of manufacture, respective webs (or folded
sides of the same web) of the packaging material will be sealed to
the opposite faces of each flange seal and will be sealed to each
other along side seams aligned with the flange seals 10.
[0037] In accordance with the embodiments of the invention
disclosed hereinafter, various structural features (or boundaries
thereof) of the slider/fastener tape assembly 2 shown in FIG. 1 can
be optically detected, such as the zipper flange seals 10, the
slider end stop formations 12 and 14, and the slider 6. It should
be appreciated, however, that the optical detection methods
disclosed hereinafter can be employed with sliders and fastener
tapes constructed differently than the construction shown in FIGS.
1 and 2.
[0038] A method of optically detecting structural features formed
on or attached to a fastener tape in accordance with one embodiment
of the invention is shown in FIG. 3. The fastener tape 4 is the
same as that previously described with reference to FIG. 1, except
that no sliders are shown in FIG. 3. This method employs a fiber
optic sensor 122 that has an output port connected to an optical
fiber 124 and an input port connected to an optical fiber 126. The
optical fibers 124 and 126 must be fixed in respective positions on
opposite sides of the zipper flanges of the moving fastener tape 4,
with the respective distal portions of the optical fibers aligned
so that portions of a beam of light exiting the transmitting
optical fiber 124 and passing through the zipper flanges will enter
the receiving optical fiber 126 and be returned to the fiber optic
sensor 122. This may be accomplished, for example, by passing the
slider/fastener tape assembly through a slotted slider guide, to
which a sensor mount (that supports the ends of the optical fibers
in the required relationship) is mounted. The beam of light from
one optical fiber passes through the slots in the slider guide and
through the fastener tape and into the other optical fiber.
[0039] The fiber optic sensor 122 may comprise a light-emitting
diode for outputting an LED beam at the output port to which the
transmitting optical fiber 124 is connected and a photodetector for
detecting the portion of the transmitted LED beam 125 that passes
through the fastener tape and enters the receiving optical fiber
126 (disregarding the ambient light that enters the receiving
optical fiber for purposes of this discussion). The photodetector
inside the fiber optic sensor 122 converts impinging light into an
electrical signal having an amplitude proportional to the intensity
of the impinging light, which electrical signal is then amplified.
The LED beam emitted from the transmitting optical fiber 124 has a
constant intensity, whereas the intensity of the light entering the
receiving optical fiber 126 will depend on the portion of the
transmitted LED beam that passes through the fastener tape, which
in turn will depend on the structure of the fastener tape at the
location where the LED beam passes through.
[0040] In the implementation depicted in FIG. 3, the LED beam is
targeted at the zipper flanges of the fastener tape and is oriented
generally perpendicular to the plane of the zipper flanges.
However, it is preferred that the LED beam be directed at a
non-perpendicular angle (e.g., 30 degrees from the plane of the
zipper flanges). As the fastener tape advances along a process
pathway, the structure of the fastener tape exposed to the LED beam
changes. Over the major portion of each package-length section of
the fastener tape, the LED beam is transmitted through unjoined
sections of two zipper flanges that are separated by an air gap,
the translucence of these unjoined sections of the zipper flanges
being unaltered. In contrast, over a minor portion of each
package-length section of the fastener tape, i.e., across each
flange seal 10, the LED beam is transmitted through a section where
the two zipper flanges are fused together. The fused zipper flanges
have a translucence that is less than the translucence of the
unaltered zipper flanges, resulting in a decrease in the intensity
of the light arriving at the photodetector inside the fiber optic
sensor 122. The fiber optic sensor 122 has a digital display for
indicating the intensity of the received light and also outputs an
electrical signal representing the received light intensity to a
PLC (not shown in FIG. 3). The stream of electrical feedback to the
PLC contains information indicating the instants of time when the
leading and lagging edges respectively of the moving flange seal 10
cross the path of the transmitted LED beam. The PLC receives
similar information for each successive flange seal that crosses
the LED beam.
[0041] Using the foregoing optical detection technique, the PLC is
able to acquire information representing the instants of time when
the leading edges of successive flange seals cross the path of the
transmitted LED beam. However, this information alone does not
indicate the distance separating the leading edges of successive
flange seals. Additional means may be provided for determining the
distance that the section of fastener tape with flange seals has
traveled in the intervals between successive flange seal leading
edge detection events. An example of such means will be disclosed
later herein with reference to FIG. 8.
[0042] In accordance with a variation of the optical detection
technique depicted in FIG. 3, the optical fibers 124 and 126 can be
positioned so that the sliders on the moving fastener tape will
cross the path of the LED beam. In this case, the opaque slider
will completely block the LED beam, so that the stream of
electrical feedback to the PLC contains information indicating the
instants of time when the leading and lagging edges respectively of
the moving slider cross the path of the LED beam. Before and after
the slider is blocking the LED beam, at least a portion of the
transmitted LED beam will reach the receiving optical fiber 126.
For example, the optical fibers could be positioned such that the
LED beam passes through the closure profiles when the slider is
absent. However, since the slider extends above and below the
closure profiles, a person skilled in the art will readily
appreciate that the LED beam could be aimed at a location above or
below the closure profiles while still impinging on each passing
slider.
[0043] Suitable fiber optic sensors are marketed under the product
designation FS-V20 Series by Keyence Corporation.
[0044] A method of optically detecting structural features formed
on or attached to a fastener tape in accordance with another
embodiment of the invention is shown in FIG. 4. Again, the fastener
tape 4 is the same as that previously described with reference to
FIG. 1, except that no sliders are shown in FIG. 4. This method
employs a laser scanning micrometer comprising a laser scanning
transmitter 128 and a laser scanning receiver 130, which are
separated by a scanning gap across which a laser beam is scanned in
a vertical plane. The fastener tape 4 is passed between the laser
scanning transmitter and receiver with the zipper flanges disposed
in a plane which is generally parallel to the scanning laser beams
132. The laser scanning transmitter and receiver must have a fixed
relationship to each other, with the scanned laser beams being
directed into a slit formed on the housing of the laser scanning
receiver 130. Typically, this fixed relationship is maintained by
mounting the transmitter 128 and the receiver 130 on opposite ends
of a rigid platform (not shown in FIG. 4).
[0045] The laser scanning transmitter 128 scans a laser beam in a
vertical plane to create a curtain of laser beams 132 that are
interrupted by any intervening portions of the fastener tape. Over
the majority of each package-length section of the fastener tape,
the closure profiles are not crushed and therefore the full width
of the interfering interlocked closure profiles will create a gap
in the curtain of laser beams received by the laser scanning
receiver 130. The received laser beams are converted into
electrical signals, which are output to the PLC (not shown in FIG.
4). The PLC is programmed to compute the height of the gap in the
curtain of received laser beams, which height is equivalent to the
thickness of the uncrushed closure profiles. In a minor portion 24
of each package-length section of the fastener tape, the closure
profiles are crushed and therefore the reduced width of the
interfering crushed closure profiles will create a gap in the
curtain of laser beams received by the laser scanning receiver 130
that is smaller than the gap produced by the uncrushed closure
profiles. Accordingly, the PLC will compute the thickness of the
crushed closure profiles as well. The instant of time at which the
leading edge of the crushed section 24 of the closure profiles
crosses the path of the curtain of laser beams 132 can thus be
determined by detecting the change in thickness of the closure
profiles (i.e., the change in height of the gap in the curtain of
scanned laser beams), which is measured continuously as the
fastener tape is advanced.
[0046] The structure and operation of different types of laser
scanning micrometers is well known in the art. One such device that
is suitable for the present application is the LS-5000 Series
high-speed laser scan micrometer commercially available from
Keyence Corporation.
[0047] In accordance with a variation of the optical detection
technique depicted in FIG. 4, the PLC can be programmed to detect a
change in the height of the gap in the curtain of scanned laser
beams caused by the intervention of a slider, which has a lateral
dimension much greater than the thickness of the uncrushed closure
profiles.
[0048] A method of optically detecting structural features formed
on or attached to a fastener tape in accordance with a further
embodiment of the invention is shown in FIG. 5. Again, the fastener
tape 4 is the same as that previously described with reference to
FIG. 1, except that no sliders are shown in FIG. 5. This method
employs a laser displacement sensor 134, which transmits a laser
beam 136 onto the fastener tape 4 (e.g., onto the closure profiles
thereof) and then detects a reflected portion 138 of the
transmitted laser beam. In the optical detection technique depicted
in FIG. 5, the transmitted laser beam 136 is directed onto the
closure profiles. As the fastener tape advances along a process
pathway, the structure of the closure profiles exposed to the laser
beam changes. Over the major portion of each package-length section
of the fastener tape, the laser beam is reflected off of an angled
surface of one of the uncrushed closure profiles (the angled outer
surfaces of the uncrushed closure profiles can be seen in FIG. 2).
The angle of the beam reflected from the uncrushed closure profile
may be such that the beam impinges upon the light-receiving element
of the laser displacement sensor at a particular location. In the
area 24 where the closure profiles are crushed and fused, the angle
of the reflected beam will be different than the angle of the beam
reflected from the uncrushed portion. More specifically, the beam
reflected from the crushed portion will impinge upon the
light-receiving element of the laser displacement sensor at a
location different than the location where the beam reflected from
the uncrushed portion impinged. The laser displacement sensor uses
a triangulation measurement system to produce electrical signals
representative of the distance to the detected surface, which
signals are output to the PLC (not shown in FIG. 5), enabling the
latter to determine the respective instants of time when the
leading and lagging edges of the crushed portion of the closure
profiles cross the path of the transmitted laser beam 136.
[0049] The technique of triangulating distance to the surface of an
object using lasers and multi-element detector arrays is well known
in the art. Distance measurement is accomplished when an optical
beam is projected out from a source and strikes the object surface.
The beam is then viewed by a camera that is displaced from the axis
of projection of the beam by some baseline distance. The camera is
angled so that the laser beam crosses the field of view of the
camera. When the beam strikes a surface at a point within the field
of view of the camera, light reflected from that point is typically
imaged by a lens onto the camera's detector. The detector may be
either a continuous device such as a position sensing detector
(PSD), which generates an electrical signal proportional to the
position of the spot image on the PSD, or a linear charge coupled
device (CCD) array, which consists of a single line of photodiode
detector elements, each of which generates an electrical signal in
proportion to the amount of light falling on it. The signal from
the camera is typically processed by a microprocessor or other
electronic logic which determines the location of peak light
intensity on the camera, and a calibration table and/or equation is
used to translate this location among the camera's pixels to a
distance from the sensor. The data is then output in a form that
can be read and used by, for example, a PLC.
[0050] One device suitable for the present application is the LK
Series CCD laser displacement sensor commercially available from
Keyence Corporation. In this device, a laser beam is generated by a
laser diode and passed through a transmitter lens. The light
reflected by the target passes through a receiver lens that focuses
the light on the CCD. The CCD detects the pixel where the peak
value of the light quantity distribution of the beam spot
occurs.
[0051] The optical detection techniques disclosed herein can be
used in any situation wherein the instant of time at which a
structural feature on a moving fastener tape arrives at a fixed
location must be determined during automated production of
reclosable packaging. One application of the optical detection
techniques disclosed herein will now be described with reference to
FIGS. 6-8, which show portions of a thermoform-fill-seal (TFFS)
machine that operates in conjunction with a fastener tape
processing machine.
[0052] Each thermoformed package is manufactured with a
slider-operated zipper. Only one component of the TFFS machine,
namely, a sealing station 78, where the fastener tape is joined to
a bottom web of packaging material, is shown in FIG. 6. Various
known components of the TFFS machine that are disposed upstream of
the sealing station 78 are shown in FIG. 7. Various known
components of the TFFS machine that are disposed downstream of the
sealing station 78 are generally represented in FIG. 8.
[0053] Referring to FIG. 6, a length of thermoplastic fastener tape
4 (the sliders are not shown), comprising, e.g., respective
continuous lengths of a pair of interlocked flanged zipper strips
(e.g., of the type shown in FIG. 2), is unwound from a supply reel
of a powered unwind stand 60 and passed through an unwind dancer
assembly 62. The latter comprises a weighted dancer roller 64 that
is supported on a shaft, which shaft is freely vertically
displaceable (as indicated by the double-headed arrow in FIG. 6)
along a slotted support column (not shown). The weight of the
dancer roller 64 takes up any slack in the portion of the fastener
tape suspended between the supply reel 60 and a guide roll 66. A
sensor (not shown in FIG. 6) may be provided for detecting the
vertical position of the dancer roller 64. The feedback signal from
that sensor is used by a PLC (not shown in FIG. 2) to control the
motor that powers the unwind stand 60, thereby controlling the
payout of fastener tape 4.
[0054] An ultrasonic welding assembly 68 is disposed downstream of
the guide roll 66. During each dwell time, the plastic zipper
strips are softened and/or melted and shaped by the ultrasonic
welding assembly in a respective zone. The ultrasonically welded
plastic material of the respective zipper strips is shaped to form
a respective slider end stop structure in each zone upon cooling.
The deformed portions of the zipper strips are also fused together
in each zone. Each slider end stop structure will form back-to-back
slider end stops when the end stop structure is cut during bag
formation. The ultrasonic welding assembly 68 may comprise an
ultrasonic transducer acoustically coupled to a horn, the horn
being opposed by an anvil (not shown in FIG. 6). Either the horn or
the anvil or both reciprocate between retracted and extended
positions. The ultrasonic transducer is activated and the horn
and/or anvil is extended in response to activation signals from the
PLC (not shown in FIG. 6). While a portion of the fastener tape is
being pressed between the horn and anvil, the horn emits ultrasonic
wave energy at an intensity and frequency designed to soften and/or
melt the thermoplastic fastener tape during each dwell time. The
horn and/or anvil may be provided with recesses designed to form
the softened and/or molten thermoplastic material into a slider end
stop structure. When the softened/melted material cools, the
material of the respective zipper strips fuses together to form a
zipper joint.
[0055] The ultrasonically welded and shaped portion of fastener
tape is then advanced to the next station, comprising a
conventional slider insertion device 70 that inserts a respective
slider (not shown in FIG. 6) onto each package-length section of
fastener tape during each dwell time. Each slider is inserted
adjacent a respective slider end stop structure on the continuous
fastener tape. The slider insertion device comprises a
reciprocating pusher that is alternately extended and retracted by
an air cylinder (not shown in FIG. 6). The pusher of the slider
inserter 70 is extended in response to activation signals from the
PLC. As the pusher extends, it pushes the slider onto the fastener
tape. The other parts of such a slider insertion device, including
a track along which sliders are fed, are well known and will not be
described in detail herein.
[0056] During each dwell time, the fastener tape 4 is gripped by a
clamp 74, so that the unwound length of fastener tape spanning the
distance between guide roller 66 and clamp 74 is stationary during
ultrasonic welding and slider insertion. The clamp 74 may comprise
a clamping gripper assembly of the type disclosed in U.S. patent
application Ser. No. 11/081,369 and entitled "Apparatus for
Repeatedly Advancing Fastener Tape a Predetermined Distance". This
clamping gripper assembly comprises a pair of oppositely moving
gripper arms (not shown). When the clamping gripper assembly is in
a closed state, respective gripper pads on the gripper arms grip a
first section of the length of straight zipper material. The
gripper arms are actuated by a double-acting parallel motion air
cylinder (not shown in FIG. 6), which is controlled by the
aforementioned PLC. The clamping gripper assembly may comprise a
carriage that is slidable along a straight rail to allow adjustment
of its longitudinal position. But once the adjustment has been
made, the clamping gripper assembly is secured relative to the
rail, e.g., by means of a thumbscrew, so that the clamping gripper
assembly is stationary during machine operation.
[0057] At the end of each dwell time, the fastener tape is gripped
by a grip-and-pull mechanism 72 and then released by the clamp 74.
Also, the ultrasonic horn or anvil or both are retracted and the
pusher of the slider inserter is retracted, so that the length of
fastener tape is free to advance. Then the grip-and-pull mechanism
72 is operated to pull the unwound length of fastener tape
(ultrasonically stomped and carrying sliders) forward a desired
distance. As will be explained in detail below, in accordance with
one embodiment, the stroke of the grip-and-pull mechanism 72 is
adjusted to be approximately equal to the distance that the bottom
web of packaging material moves in the TFFS machine during each
advancement. [Alternatively, if means are provided for stretching
the section of fastener tape being sealed to the bottom web in the
packaging machine, the stroke of the grip-and-pull mechanism 72 is
adjusted to be approximately equal to the distance that the bottom
web of package material moves during each advancement less any
increase in the length of the fastener tape caused by the
stretching.] During pulling of the portion of the fastener tape
disposed upstream of the clamp 74, the most recently inserted
slider leaves the slider insertion zone and the most recently
formed slider end stop structure is moved from the ultrasonic
welding station to the slider insertion zone. The clamp 74 is then
closed again, following which the grip-and-pull mechanism 72 is
opened and returned to its home position.
[0058] The grip-and-pull mechanism 72 may comprise an indexing
gripper assembly that is linearly displaced by an indexing drive
mechanism as disclosed in the aforementioned U.S. patent
application Ser. No. 11/081,369. The indexing gripper assembly
comprises a carriage that rides on a straight rail. The indexing
drive mechanism comprises a lead screw driven to rotate by a
servomotor under the control of the PLC. The indexing gripper
assembly further comprises a nut threadably coupled to the lead
screw and rigidly coupled to the carriage. The nut converts the
rotation of the lead screw into linear displacement of the
carriage. The indexing gripper assembly further comprises a pair of
oppositely moving gripper arms. When the indexing gripper assembly
is in a closed state, respective gripper pads on its gripper arms
grip a second section (disposed upstream of the clamped first
section) of the length of fastener tape. The gripper arms of the
indexing gripper assembly are actuated by a double-acting parallel
motion air cylinder, which is again controlled by the PLC.
[0059] Downstream from the clamp 74, the slider/fastener tape
assembly 2 passes in front of a sensor 76 and then through a
sealing station 78. As seen in FIG. 6, the sensor 76 is disposed
between the clamp 74 and the sealing station 78. In this particular
example, the sensor 76 is arranged to detect the leading edge of a
respective slider end stop structure on the fastener tape as the
slider end stop structure passes in front of the sensor during each
intermittent advancement. (Alternatively, the sensor could be
arranged to detect the leading edge of each slider or the leading
edge of each flange seal, as previously disclosed.) During each
dwell time, the section of fastener tape resident at sealing
station 78 is joined by conductive heat sealing to a corresponding
section of the bottom web of packaging material (not shown in FIG.
6, but see FIG. 7).
[0060] Various known components of the TFFS machine that are
disposed upstream of the sealing station 78 are shown in FIG. 7.
The components shown in FIG. 7 that bear reference numerals
previously seen in FIG. 6 have the functionality previously
described.
[0061] Still referring to FIG. 7, the bottom web 84 is unrolled
from a supply roll 82 and pulled through a thermoforming station
86, where a respective trough 88 for product is formed by
deep-drawing using vacuum and heat during each dwell time. One
trough is formed for each package-length section of web 84, but the
trough is surrounded by a perimeter of packaging material that is
not thermoformed, including a lateral margin where a package-length
section of the slider/fastener tape assembly 2 will be attached.
The thermoformed bottom web 84 is advanced to the sealing station
78, where a respective package-length section of fastener tape is
joined to each package-length section of the bottom web.
[0062] More specifically, a respective section of the
slider/fastener tape assembly 2 (comprising a pair of interlocked
zipper strips with a respective slider mounted thereon) is joined
to the bottom web 84 by conventional conduction heat sealing during
each dwell time. This may be accomplished by a reciprocating heated
sealing bar 56 arranged below the bottom web 84. The sealing bar 56
reciprocates between retracted and extended positions under the
control of the PLC 100. In the extended position, the heated (i.e.,
"hot") sealing bar 56 presses against a stationary unheated (i.e.,
"cold") bar 58, with the flanges of the zipper strips and the
non-thermoformed margin of the bottom web sandwiched therebetween.
When sufficient heat and pressure are applied, the bottom web 84 is
joined to the flange of the lower zipper strip by conductive heat
sealing. To prevent seal-through of the zipper flanges, just enough
heat is conducted into the zipper material from the hot sealing
bar. Alternatively, a separating plate may be interposed between
the flanges during sealing, or the zipper flanges may have a
laminated construction comprising sealant layers on the exterior
surfaces or non-sealant layers on the interior surfaces.
[0063] As a result of the joinder of certain sections of the
slider/fastener tape assembly 2 to the bottom web 84 of the
packaging material, the section of the slider/fastener tape
assembly disposed immediately upstream of the sealing station 78
will be pulled forward during each intermittent advancement of the
bottom web 84.
[0064] Preferably, the sensor 76 is fixed at a location that will
lie between successive slider end stop structures (or sliders or
flange seals) upon completion of each intermittent advancement,
i.e., during each dwell time. For example, the sensor 76 may be
located midway between successive slider end stop structures of the
section of the stationary fastener tape disposed in front of the
sensor. During each advancement, the sensor 76 provides feedback
signals to the PLC 100 that contain information indicating the
precise instant of time when the leading edge of the slider end
stop structure (or slider or flange seal) passed a precise location
relative to the sensor. Any suitable optical detecting means can be
used. Several embodiments of suitable optical detecting means are
shown in FIGS. 3-5.
[0065] The PLC 100 then uses that information, with other
information from the TFFS machine (described later with reference
to FIG. 8), to adjust the stroke of the grip-and-pull mechanism 72
in a manner that maintains proper registration of the slider end
stop structures relative to the thermoformed troughs 20 of a bottom
web 16 of packaging material. In response to a sensor feedback
signal indicating the instant when the leading edge of the
attachment or modified structure is detected, the PLC 100
correlates that event with a count signal representing the position
of the concurrently advancing bottom web 84. Each leading edge
detection event is correlated with a respective count, thereby
enabling the PLC to compare the distance between successive leading
edges to the distance by which the bottom web has advanced, which
distance is directly proportional to the count
[0066] A subsystem for providing the count signal (representing the
advancement of the bottom web) to the PLC 100 is generally depicted
in FIG. 8. The bottom web 84 may be intermittently advanced by
conventional means 120. The portion of the bottom web 84 paid out
from the bottom web supply roll (item 82 in FIG. 7) is advanced by
a pair of endless chain belts 114 (only one of which is depicted in
FIG. 8, the other being directly behind) that circulate on
respective sprocket wheels 116 and 118, the latter of which is
driven as explained below. In a known manner, spring-loaded clamps
(not shown in FIG. 8) are mounted to both chain belts 114 for
clamping the lateral margins of the bottom web 84. As the chain
belts 114 circulate, the clamps carried thereon pull the bottom web
through the sealing station (78 in FIG. 7). The structural details
concerning the various components of the web advancing means 120,
such as spring-loaded clamps, respective bearing-mounted sprocket
wheels and respective engagement discs associated with the sprocket
wheels and serving to open the spring-loaded clamps, are disclosed
in full in U.S. Pat. No. 4,826,025 and will not be described in
detail herein. Alternatively, a pair of drive belts that bear
against the lateral margins of the bottom web could be used in
place of the chain belts with spring-loaded clamps.
[0067] Still referring to FIG. 8, rotation of the sprocket wheel
118 is driven by a servomotor 94, which is controlled by the PLC
100. During operation of the TFFS machine, the PLC 100 is
programmed to activate the servomotor 94 at regular intervals
interspersed with dwell times. During each activation, the
servomotor 94 causes the bottom web 84 to be advanced by a constant
indexing distance equal to one package length. The shaft of
servomotor 94 is coupled to an encoder 92 that encodes shaft
rotation by outputting a number proportional to the angle of
rotation. That number, which is also proportional to the distance
that the bottom web is advanced, is provided as feedback to the PLC
100. Provided that the servomotor 94 is activated in a repeatable
manner, the number output by the encoder 92 will increase by the
same amount for each intermittent advancement of the bottom web.
For example, the encoder count might increase by 1000 for each
package-length advancement of the bottom web. This increasing count
will be provided as feedback from the encoder 92 to the PLC
100.
[0068] The PLC 100 is programmed to adjust the distance between the
leading edges of successive slider end stop structures (or other
modifications) or sliders (or other attachments) to compensate for
any variation from one package length. The PLC accomplishes this by
adjusting the forward stroke of the grip-and-pull mechanism.
[0069] For the exemplary implementation wherein one package
length=1000, assume that the encoder count is 1500 when the n-th
leading edge is detected and 2480 when the (n+1)-th leading edge is
detected. The difference in these counts is 2480-1500=980, meaning
that the distance between the n-th and the (n+1)-th leading edges
deviates by -2% from one package length (=1000). To adjust for this
deviation, PLC 100 controls the grip-and-pull mechanism to increase
its forward stroke by a distance equal to 2% of one package length.
In general, if the count separating leading edge detection events
deviates from the count representing one package length by -x %,
then the forward stroke of the grip-and-pull mechanism will be
increased by a distance equal to x % of one package length.
Conversely, if the count separating leading edge detection events
deviates from the count representing one package length by +x %,
then the forward stroke of the grip-and-pull mechanism will be
decreased by a distance equal to x % of one package length. This is
only one possible algorithm that can be used. A person skilled in
the art will readily appreciate that many different algorithms
could be employed to adjust the distance between successive leading
edges of structural features repeatedly attached or formed on the
fastener tape. For example, the adjustment to the stroke of the
grip-and-pull mechanism could be a function of a moving average
deviation over multiple work cycles.
[0070] In accordance with one implementation, the PLC 100 controls
all of the activatable components depicted in FIGS. 6-8. More
specifically, the PLC is programmed to control various solenoids
that open various strategically placed valves that, when open,
connect a source of compressed air to various air cylinders. These
air cylinders in turn respectively actuate movement of various
components represented in FIG. 6, such as the following: (a) an
indexing gripper assembly of the grip-and-pull mechanism 72; (b) a
stationary gripper assembly of the clamp 74; (c) a horn (or anvil)
of the ultrasonic welding assembly 68; and (d) a pusher of the
slider insertion device 70. The PLC 100 also controls a waveform
generator that supplies an electrical waveform to an ultrasonic
transducer, which transducer in turn outputs acoustic waves that
are delivered to the fastener tape by the aforementioned horn of
the ultrasonic welding assembly 68. In addition, the PLC 100
controls various servomotors including the following: (a) a
servomotor (not shown in FIG. 6) that drives rotation of a lead
screw of the grip-and-pull mechanism 72, which rotation is
converted into linear displacement of the indexing gripper assembly
by means of the type previously described: (b) a servo motor (not
shown in FIG. 6) that drives rotation of the power unwind stand 60;
and (c) the servomotor 94 (shown in FIG. 8) that drives advancement
of the bottom web through the packaging machine. The PLC 100 also
controls the operations of the thermoforming station 86 and the
various sealing stations, the sealing station 78 for joining the
bottom web to the fastener tape being the only sealing station
depicted in FIG. 7.
[0071] Furthermore, as previously explained in detail, the PLC 100
receives feedback from the sensor 76 (see FIG. 7) and the encoder
92 (see FIG. 8), and then controls the servomotor that drives
rotation of the lead screw of the grip-and-pull mechanism 72 (see
FIG. 7). By controlling that the number of revolutions of the
servomotor, the PLC can adjust the forward stroke of the
grip-and-pull mechanism 72 to advance the fastener tape by a
desired distance. As previously explained, the adjustment is a
function of the discrepancy between the distance separating
successive leading edges of the slider end stop structures (or the
sliders), which distance is detected by the sensor 76, and the
distance by which the bottom web is advanced, which is reflected in
the change in the count from the encoder 92 as the result of each
bottom web advancement.
[0072] The PLC 100 is programmed to control the various components
in accordance with a regular work cycle. In particular, the TFFS
machine and the zipper processing machine must be coordinated such
that the bottom web of packaging material and the fastener tape are
both stationary during each dwell time and are both advanced during
the remainder of each work cycle. Accordingly, during the
advancement phase, the PLC 100 activates the servomotor of the
power unwind stand 60 to pay out wound fastener tape; activates the
servomotor of the grip-and-pull mechanism 72 to advance previously
paid-out fastener tape; and activates the servomotor 94 of the web
advancement mechanism to advance the bottom web. During this phase,
the clamp 74 is open. At the end of the forward stroke of the
grip-and-pull mechanism 72, the clamp 74 is closed, thereby
gripping the portion of fastener tape thereat. Once the fastener
tape has been gripped by the clamp, the ultrasonic welding assembly
68 and the slider insertion device 70 are activated in the zipper
processing machine, and the thermoforming station 86 and the
sealing station 78 (and other sealing stations) of the TFFS machine
are activated. While these operations are being performed, the PLC
100 activates the servomotor of the grip-and-pull mechanism 72 to
cause the grip-and-pull mechanism 72 to return to its home position
and await the next advancement phase. During each advancement
phase, the PLC 100 receives feedback from the sensor 76 and the
encoder 92, as previously described in detail. Naturally the PLC
also controls other components such as the evacuation means and the
cutting means of the TFFS machine. The PLC 100 is typically a
computer or processor having associated memory that stores a
program for operating the machine.
[0073] The various components that move between retracted and
extended positions (e.g., slider pusher, ultrasonic horn, clamp,
sealing bar, etc.) may be coupled to respective double-acting
pneumatic cylinders (not shown in FIG. 6). Operation of the
cylinders is controlled by the PLC 100, which selectively activates
the supply of fluid to the double-acting cylinders in accordance
with an algorithm or logical sequence. Hydraulic cylinders can be
employed as actuators in place of air, i.e., pneumatic, cylinders.
A person skilled in the art of machinery design will readily
appreciate that displacing means other than a cylinder can be used
to displace components such as the horn of the ultrasonic welding
assembly and the pusher of the slider inserter. For the sake of
illustration, such mechanical displacement devices include rack and
pinion arrangements or lead screw/coupling nut assemblies, rotation
of the pinion or lead screw being driven by an electric motor.
[0074] While the invention has been described with reference to
preferred embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for members thereof without departing from the scope of
the invention. In addition, many modifications may be made to adapt
a particular situation to the teachings of the invention without
departing from the essential scope thereof. 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.
[0075] As used in the claims, the term "controller" means a
programmed logic controller, an electronic computer, a central
processing unit, a microchip, a microcontroller or other
programmable device or a system of interconnected and synchronized
control units, each control unit comprising a programmed logic
controller, an electronic computer, a central processing unit, a
microchip, a microcontroller or other programmable device. Also, in
the absence of explicit language in any method claim setting forth
the order in which certain steps should be performed, the method
claims should not be construed to require that steps be performed
in the order in which they are recited.
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