Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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STRAPPING TRACK ASSEMBLY AND METHOD OF USING THE SAME
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit under 35 U.S.C. 119(e) of U.S.
Provisional Patent Application No. 60/921,022 filed March 30, 2007, which is
incorporated herein by reference in its entirety.
BACKGROUND
Technical Field
The present invention relates to strapping apparatuses and methods
for applying straps around bundles of objects. More particularly, the
invention
relates to strapping track assemblies for strapping apparatuses and methods of
using the same.
Description of the Related Art
Strapping machines for applying flexible straps around bundles of
objects have been developed in recent years and are disclosed in U.S. Patent
No.
5,560,180; U.S. Patent No. 6,363,689; and U.S. Patent Application Publication
No.
2002/0116900 Al. A conveyor often conveys a bundle of objects to a strapping
station where straps are automatically applied before the conveyor moves the
strapped bundle away from the strapping station.
Figure 1 is a front isometric view of a conventional strapping machine
10. The strapping machine 10 has several major assemblies, including a feed
and
tension assembly 15, an accumulator 14, a strap dispenser 30, a sealing
assembly
40, a track assembly 50, and a control system 60 having an operator interface
region
65. The strapping machine 10 may also include a frame 70 that structurally
supports
and/or encloses the major subassemblies. The assembly and purposes of the
conventional major assemblies are described in detail in U.S. Patent No.
6,363,689.
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During operation, a strap is moved through the track assembly 50 in
the direction indicated by the arrows 20 before applying the strap to the
bundle.
Unfortunately, the track assembly 50 includes features, such as exposed edges
of
strap guides, which interfere with the advancement of the strap. For example,
an
end of the strap can catch on any one of the exposed leading edges of the
strap
guides during a feed sequence. This may cause the strap to become damaged or
stuck and may require user intervention to continue the feed sequence.
Misfeeds
occur when the end of the strap unintentionally passes through gaps along the
track
assembly 50. The section of the strap that escapes from the track assembly 50
is
snaked back into the track assembly 50 so that the strap can be further
advanced
through the track assembly 50. Once the strap is fed through the track
assembly 50,
the strap can be drawn from the track assembly 50 about the bundle adjacent to
the
sealing assembly 40.
BRIEF SUMMARY
Apparatuses disclosed herein can be used to apply one or more straps
around a bundle of objects. A variable or constant force can be applied to
tension
the strap about the bundle of objects while the strap is sealed around the
bundle of
objects. The apparatus may include a strapping track assembly extending about
a
strapping station. The track assembly is adapted to receive a strap during a
feed
sequence and to release the strap during a tensioning sequence. The track
assembly, in some embodiments, is adapted to reduce or prevent the occurrence
of
misfeeds, such as misfeeds attributable to the end of the strap escaping
through
gaps next to an intended strap path within the track assembly. This ensures
that the
strap is properly routed through the track assembly.
In some embodiments, a strapping apparatus for bundling objects
comprises a strapping station and a track assembly. The track assembly is
adapted
to receive a strap and to bundle objects at a strapping station using the
strap. The
track assembly, in some embodiments, comprises a stationary frame, a first
strap
guide, a second strap guide, and a corner strap guide interposed between the
first
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and second strap guides. The stationary frame can keep its configuration
during
operation. The first and second strap guides can be linear strap guides that
extend
along a substantially straight axis. A strap path may be defined between the
first
strap guide and the frame, the second guide and the frame, and the corner
strap
guide and the frame. The strap path can have a generally rectangular shape,
elliptical shape, or any other suitable shape. In some embodiments, the strap
path is
a closed loop path.
The corner strap guide can include a leading end and a trailing end. A
trailing end of the first strap guide can be positioned between the leading
end of the
corner strap guide and a first adjacent section of the strap path. The
trailing end of
the corner strap guide can be between a leading end of the second strap guide
and
a second adjacent section of the strap path. As such, the strap can slide
along the
first strap guide, corner strap guide, and second strap guide without striking
the
upstream end or edges of the strap guides.
The strap guides can be received by one another. In some
embodiments, the trailing end of the first strap guide extends into the corner
strap
guide. The trailing end of the corner strap guide extends into the second
strap
guide. The trailing ends may keep the strap away from the leading edges of the
downstream strap guides.
In some embodiments, at least one of the first strap guide, the second
strap guide, and the corner strap guide tapers inwardly (e.g., towards the
strap path)
in the downstream direction. The tapered strap guides can position (e.g.,
center) the
strap with respect to downstream strap guides.
Biasing mechanisms can move the strap guides from open positions to
closed positions. In some embodiments, a plurality of biasing mechanisms can
cooperate to push the strap guides against the frame. The biasing mechanisms
can
include one or more springs that cooperate to apply desired forces to the
strap
guides. If sufficient forces are applied to the strap, the biasing mechanisms
can
allow the strap guides to open.
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In other embodiments, a track assembly for receiving a strap and
bundling objects at a strapping station using the strap is provided. The track
assembly comprises an outer frame and a plurality of strap guides. The
plurality of
strap guides is coupled to the outer frame so as to define a strap path. In
some
embodiments, the strap guides are mounted to the inner periphery of the frame.
The
strap path, in some embodiments, can extend along the length of the track
assembly. Each strap guide has a trailing end that is disposed between the
strap
path and a leading edge of one of the downstream strap guides.
The plurality of strap guides can include a first corner strap guide that
defines a first curved section of the strap path, a second corner strap guide
that
defines a second curved section of the strap path, and an elongate strap guide
(e.g.,
a linear strap guide or an array of linear strap guides) extending between the
first
and second corner strap guides. The elongate strap guide can define a
substantially
linear section of the strap path. If the outer frame has a substantially
rectangular
shape, the elongate strap guide can extend along one side of the frame. In
some
embodiments, the elongate strap guide is a longitudinally-extending, U-shaped
member.
At least one of the strap guides can taper inwardly towards the strap
path. In some embodiments, all or most of the strap guides taper inwardly
towards
the strap path in the downstream direction. Each of the strap guides can
extend
partially through an adjacent pair of the strap guides.
In some embodiments, the strap guides may include respective strap
retainers. The strap retainers together may extend along nearly all of the
longitudinal length of the strap path such that a strap moving along the strap
path is
captured between the strap retainers and the outer frame. The strap retainers
can
cooperate to define a substantially continuous surface along substantially the
entire
strap path, if needed or desired.
In some embodiments, a strap guide can have a narrowed leading end
with respect to a strap path and a widened trailing end with respect to the
strap path.
In some embodiments, for example, a distance between opposing sides at the
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leading end can be less than a distance between the opposing sides at the
trailing
end.
In some embodiments, a method for passing a strap through a track
assembly is provided. The method comprises moving an end of a strap along a
strap path. The path is positioned between a plurality of interconnected strap
guides
and an outer frame.
In some embodiments, each strap guide has a trailing end that is
disposed between the strap path and a leading edge of one of the downstream
strap
guides such that the end of the strap is spaced from the leading end of the
downstream strap guide. In some embodiments, the strap guides are interleaved
and surround the inner periphery of the frame.
In some embodiments, the end of the strap is passed out of
downstream ends of the strap guides disposed within corresponding downstream
strap guides. The strap is subsequently used to bundle objects located at a
strapping station after moving the end of the strap through the track
assembly. The
strap can be tensioned to move the strap guides from a first position (e.g., a
closed
position) for retaining the strap to a second position (e.g., an open
position, spread
apart configuration, etc.) to allow removal of the strap.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
In the drawings, identical reference numbers identify similar elements
or acts. The sizes and relative positions of elements in the drawings are not
necessarily drawn to scale. The shapes of various elements and angles may not
be
drawn to scale, and some of these elements may be arbitrarily enlarged and
positioned to improve drawing legibility.
Figure 1 is an isometric view of a conventional strapping machine.
Figure 2 is a front, top view of a strapping apparatus, in accordance
with one embodiment.
Figure 3 is a front, top view of a strapping track assembly, in
accordance with one embodiment.
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Figure 4 is a front, top view of a strapping track assembly with guard
panels shown removed, in accordance with one embodiment.
Figure 5 is an isometric view of a portion of the strapping track
assembly of Figure 4, in accordance with one embodiment.
Figure 6A is an enlarged pictorial view of a portion of a strapping track
assembly, in accordance with one embodiment.
Figure 6B is a side elevational view of the interface between two guide
members, in accordance with one embodiment.
Figure 7 is a cross-sectional view of the strapping track assembly of
Figure 5 taken along line 7-7.
Figure 8 is a pictorial view of a strap guide member, in accordance with
one embodiment.
Figure 9 is a front elevational view of the strap guide member of Figure
8.
Figure 10 is a back elevational view of the strap guide member of
Figure 8.
Figure 11 is a top plan view of the strap guide member of Figure 8.
Figures 12 and 13 are side elevational views of the strap guide
member of Figure 8.
Figures 14 and 15 are pictorial views of a strap guide member of a
corner strap guide, in accordance with one embodiment.
Figure 16 is a front elevational view of a strap guide member of a
corner strap guide, in accordance with one embodiment.
Figure 17 is a side elevational view of a strap guide member of a
corner strap guide, in accordance with one embodiment.
Figure 18 is an isometric view of a frame of a strapping track assembly,
in accordance with one embodiment.
Figure 19 is a front elevational view of the frame of Figure 18.
Figure 20 is a front elevational view of a control system, in accordance
with one embodiment.
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Figure 21 is a side view of operator controls of the control system of
Figure 20.
DETAILED DESCRIPTION
The present disclosure is directed to, among other things, strapping
apparatuses, components and subassemblies of strapping apparatuses (e.g.,
strapping track assemblies), and methods for strapping bundles of objects.
Specific
details of certain embodiments are set forth in the following description, and
in
Figures 2-21, to provide a thorough understanding of such embodiments. A
person
of ordinary skill in the art, however, will understand that the disclosed
embodiments
may have additional components and features, and that the embodiments may be
practiced without several of the details described in the following
description.
Throughout the following discussion and in the accompanying figures,
the strap material is shown and referred to as a particular type of material,
namely, a
flat, two-sided, tape-shaped strip of material solely for the purpose of
simplifying the
description of various embodiments. It should be understood, however, that
several
of the methods and embodiments disclosed herein may be equally applicable to
various types of strap material, and not just to the flat, two-sided, tape-
shaped
material shown in the figures. Thus, as used herein, the terms "strap" and
"strap
material" should be understood to include, without limitation, all types of
materials
used to bundle objects, for example, synthetic materials, natural materials,
metallic
materials, or some other more rigid strap material. One type of strap that may
be
used with all or some of the embodiments described herein is a paper cord-type
strap comprised of individual round cords laterally bonded together to form a
continuous strap. The strap may be rigid, semi-flexible, or flexible depending
on the
application.
Figure 2 illustrates a strapping apparatus 100 that includes a plurality
of conveyors 110 for moving bundles into and out of a strapping station 120,
which is
surrounded by a strapping track assembly 118. Various types of strapping
stations
can be employed based on the dimensions of the bundles to be strapped.
Different
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types of components (e.g., tensioning units, sealing head assemblies, etc.)
can be
located at or proximate to the strapping station 120. Strap employed during
bundling
operations is fed about the strapping track assembly 118 in a strap-feed
direction
119, illustrated in the counter-clockwise direction, along a strap path (e.g.,
a
substantially rectangular or elliptical strap path) within the strapping track
assembly
118. A frame 139 for supporting the strapping apparatus 100 can be temporary
or
permanently affixed to the floor. The independently powered conveyors 110 are
independently supported by conveyor frames 145.
Some of the other major assemblies of the strapping apparatus 100
include, without limitation, a control system for programming and controlling
various
functions of the apparatus, an accumulator 96, and a feed and tension unit for
receiving and feeding the strap around one or more bundles on the conveyors
110.
The strapping apparatus 100 can be further configured with a sealing head
assembly
98 for sealing the strap around the bundle (not shown). At least some of the
major
assemblies can be of modular construction, which allows them to be used in
multiple
frame configurations or attached as add-on components to existing strapping
machines. The illustrated strapping track assembly 118 has a modular
construction
for use with a wide range of strapping machines. Various assemblies and
components of the strapping apparatus 100 are discussed in detail below.
Figure 3 shows the strapping track assembly 118 partially enclosed by
spaced apart guard panels 140a, 140b (collectively 140) and opposing spaced
apart
guard panels 142a, 142b (collectively 142). Each of the guard panels 140, 142
has
cutouts 150, 152 that provide access to components of the strapping track
assembly
118. In some embodiments, the guard panels 140, 142 can be easily removed to
perform maintenance on the track assembly 118. A handle 153 may be used to
move the entire strapping apparatus 100, the track assembly 118 with respect
to the
frame 139, and the like
Referring to Figure 4, the strapping track assembly 118 (shown with
the guard panels 140, 142 removed) may provide the reliability of a fully
enclosed
track configuration while reducing, limiting, or substantially eliminating
problems
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associated with misfeeds, straps catching on edges (e.g., leading edges) of
strap
guides, and the like. The illustrated strapping track assembly 118 includes
five linear
track sections 201 a-e (collectively 201) and four corner sections 202a-d
(collectively
202). Each of the corner sections 202 is interposed between one pair of the
linear
track sections 201 and can be similar to one another.
A plurality of strap guides 220a-e, 222a-d is coupled to a rigid frame
240 to define a strap path of travel. The strap guides 220a-e (collectively
220) are
elongate strap guides (illustrated as substantially linear guides) at
corresponding
track sections 201 a-e, and the strap guides 222a-d (collectively 222) are
corner strap
guides at corresponding corner sections 202a-d. The strap guides 220, 222 are
interleaved in the feed direction such that the leading edges of the strap
guides 220,
222 do not contact the strap so as to reduce, limit, or substantially
eliminate the
occurrence of misfeeds, damage to the strap attributable to the leading edges,
and
the like. Each of the strap guides 220, 222 can have a trailing end (e.g., a
downstream end) that keeps the strap from contacting a leading end (e.g., an
upstream end) of one of the adjacent downstream strap guides, as discussed in
detail below.
As shown in Figure 5, the corner strap guide 222d is interposed
between the strap guides 220d, 220e. A central section 225 of the corner strap
guide 222d extends from the upstream strap guide 220d to the downstream strap
guide 220e. In the illustrated embodiment, a substantial portion of the corner
strap
guide 222d extends between the adjacent strap guides 220d, 220e.
The corner strap guide 222d includes a leading end 260 for
surrounding the upstream strap guide 220d and a trailing end 262 for extending
into
the downstream strap guide 220e. A trailing end 270 of the upstream strap
guide
220d is between the leading end 260 of the strap guide 222d and a strap path
(discussed in connection with Figures 6A, 6B, and 7), and the trailing end 262
of the
corner guide 222d is between a leading end 272 of the downstream strap guide
220e
and the strap path. The trailing ends 270, 262 thus physically separate and
protect
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the strap from the respective leading edges 261, 273. This ensures that the
edges
261, 273 do not cause misfeeds.
Each of the strap guides 220d, 220e, 222d can taper with respect to
the strap path, for example, in the downstream direction. In some embodiments,
including the illustrated embodiment of Figure 5, the narrowed trailing end
270 of the
strap guide 220d extends into the widened leading end 260 of the corner strap
guide
222d, and the narrowed trailing end 262 of the corner strap guide 222d extends
into
the widened leading end 272 of the strap guide 220e. The narrowed trailing
ends
270, 262 can closely surround and help center the strap with respect to the
downstream strap guides 222d, 220e, respectively.
Referring to Figure 6A, a transverse width W of the leading end 260 is
greater than a length L of the portion of the trailing end 270 within the
strap guide
222d. The length L can be measured in the direction of a strap path 302
aligned with
a longitudinal gap 303 extending along the inner periphery of the track
assembly
118. The leading end 260 can closely surround the trailing end 270 while
allowing
slight relative movement between the strap guides 220d, 222d. The length L of
the
portion of the leading end 270 within the strap guide 222d can be selected
based on,
for example, the desired amount of guide overlap, flexibility of the strap,
and ease of
assembly. As such, the end of the strap can move along the strap path 302 past
the
intersection of the strap guides 220d, 222d (see Figure 6B) without the strap
end
passing through any gaps between the strap guides 220d, 222d. In this manner,
strap misfeeds can be avoided.
As used herein, the term "strap guide" can include, but is not limited to,
one or more components adapted to engage and guide a strap along a desired
strap
path. A strap may slide smoothly between strap guides positioned along a strap
path without damaging the strap. In some embodiments, a strap guide can be a
monolithically formed one-piece component. In other embodiments, a strap guide
can include a plurality of separate components. For example, the strap guide
220e
of Figures 6A, 6B, and 7 includes a pair of spaced apart strap guide members
236a,
236b movable between a closed position 237 and an open position 238 (shown in
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phantom). Each of the strap guide members 236a, 236b includes a respective
sidewall 239a, 239b and a respective strap retainer 243a, 243b. The
illustrated
sidewall 239a is approximately parallel to the sidewall 239b when the strap
guide
220e is closed.
Figures 8-13 show the strap guide member 236a that includes the
retainer 243a extending substantially perpendicularly from the sidewall 239a.
The
retainer 243a includes a lower engagement surface 247 for slidably contacting
the
strap. The sidewall 239a includes a plurality of openings 250 (Figure 8)
through
which elongate rods 251 (Figure 5) or biasing mechanisms 203a, 203b can
extend.
The openings 250 can be holes, slots, and the like.
As shown in Figures 14-17, a strap guide member 238a of the strap
guide 222d includes a sidewall 273 and an arcuate strap retainer 277. The
strap
retainer 277 includes an engagement surface 279 for slidably contacting the
strap.
Because the strap guide 220d is substantially perpendicular to the strap guide
220e
(see Figure 4), the strap retainer 277 subtends an angle of about 90 degrees
such
that the tensioned strap can curve along the strap retainer 277 between the
strap
guides 220d, 220e. Other configurations and curvatures of the strap retainer
277 are
also possible.
With reference again to Figure 5, biasing mechanisms 203a, 203b can
bias the strap guide members 236a, 236b to the illustrated closed position.
The
biasing mechanisms 203a, 203b can be generally similar to each other. The
biasing
mechanism 203a includes a spring retainer 241 and a biasing member 239
captured
between the spring retainer 241 and the guide member 236a. The spring retainer
241 can be a free floating cap screw extending outwardly from both sides of
the track
assembly 118. The biasing members 239 can be interposed between the guide
members 236a, 236b and the caps of the spring retainer 241. In some
embodiments, the retainer 241 is a floating cap screw and an associated hex
nut are
centered about the track 118 by two compression biasing members 239 in the
form
of compression springs applying somewhat equal forces. This has the effect of
providing an equal load on both sides of the strap as the strap is pulled from
the
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track assembly 118. In other embodiments, the stop 241 is fixedly coupled to
the
frame 240 such that the biasing member 239 presses the strap guide member 236a
against the frame 240. The biasing member 239 can be in the form of one or
more
springs (e.g., helical springs, coil springs, etc.), elastically compressible
members,
and the like. Other types of biasing members can also be used.
Referring to Figures 5 and 7, the biasing mechanisms 203a, 203b may
hold the strap guide 220e proximate to or against the outer frame 240 so as to
form
a partially or fully enclosed channel 300. The strap path 302 (shown in
phantom line
in Figures 6A and 7) extends longitudinally along the open channel 300. A
strap
304, shown in phantom line in Figure 7, can move along the strap path 302
through
the track assembly 100. The edges of the strap 304 can slide along the strap
retainers 243a, 234b. As such, the strap path 302 can be defined, at least in
part, by
the strap guides 220, 222 and the frame 240, as well as other components
suitable
for contacting the strap.
With reference to Figures 6A, 6B, and 7, the strap retainers 243a, 243b
are spaced from an engagement surface 283 of the frame 240. The strap 304 can
be captured between lower surfaces of the strap retainers 243a, 243b and the
surface 283. The illustrated strap 304 is spaced from the engagement surface
283.
Each of the plurality of strap guides 220, 222 can include one or more
strap retainers that extend along nearly all of their respective lengths. The
strap
retainers can extend along nearly all, or all, of the length of the strap path
302. In
some embodiments, the strap retainers collectively extend along at least 95%,
90%,
or 80% of the length of the strap path 302 defined by the strapping strap
assemble
118. Such embodiments ensure that the strap is properly guided along a
substantial
portion of the strap path 302.
With respect to Figures 18 and 19, the frame 240 includes a plurality
interlocked elongate frame sections 301 a-e (collectively 301) and corner
frame
sections 302a-d (collectively 302). The assembled track sections 201 are
formed by
the respective frame sections 301 and strap guides 220 movable with respect to
the
frame sections 301. The corner track sections 202 are formed by the respective
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corner frame sections 302 and the strap guides 222 movable with respect to the
corner frame sections 302. In other embodiments, the frame 240 can have a one-
piece construction. Such embodiments may be more rigid than the multi-piece
frame
240 illustrated in Figures 18 and 19.
Various types of production cycles can be performed using the
strapping track assembly 118. During the tensioning cycle, a sealing head
assembly
98 grips the free end of the strap and a feed/tension unit begins to tension
the strap
around the product surrounded by the strapping track assembly 118. As the
strap is
drawn back by the feed/tension unit, the forces may overcome the bias of the
biasing
mechanisms 203a,b to cause the closed strap guides 220, 222 to move (e.g.,
pivot)
to the open positions, thereby allowing the strap to escape from the separated
strap
guides 220, 222. As the strap forces the track sections 220, 222 open, each
successive set of strap guides 220, 222 are urged open by the previous set of
strap
guides, thereby providing a controlled release of the strap. The amount of
overlap
between the strap guides 220, 222 can be selected such that the strap guides
open
together. During the tensioning cycle, the interleaved track design also has
the
advantage of having few or no gaps between strap guides to catch the strap
edges
and to reduce the occurrence of the strap escaping from the track assembly
118.
The strapping apparatus 100 can be controlled by a control system 800
illustrated in Figure 20. The control system 800 can be mounted or
incorporated into
the accumulator 96 and may include a programmable logic controller (PLC) 802
which operates in conjunction with various input and output devices and
controls the
major subassemblies of the strapping apparatus 100. Input devices may include,
for
example, momentary and maintained push buttons, selector switches, toggle
switches, limit switches, photoelectric sensors, and inductive proximity
sensors.
Output devices may include, for example, solid state and general purpose
relays,
solenoids, and indicator lights. Input devices are scanned by the controller
802, and
their on/off states are updated in a controller program. The controller 802
executes
the controller program and updates the status of the output devices
accordingly.
Other control functions of the controller 802 are described below in further
detail.
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In some embodiments, the programmable controller 802 and its
associated input and output devices may be powered using a 24 VDC power
supply.
The controller 802, power supply, relays, and fuses may be contained within a
control panel, as illustrated in Figure 21. The momentary and maintained push
buttons, selector switches, and toggle switches 810 may be located on the
control
panel. The limit switches, inductive proximity sensors, photoelectric sensors,
and
solenoids are typically located within the strapping apparatus 100 at their
point of
use. An indicator light stack may be mounted on the top of the arch indicating
a
strap mis-feed, out-of-strap, normal running or machine malfunction condition,
for
example.
One commercially-available PLC 802 suitable for use with the
strapping apparatus 100 is the MICROLOGIX 1500 manufactured by Allen-
Bradley/Rockwell. This device includes PNP digital and relay type outputs. In
addition the PLC utilizes input and output cards to interface to external
production
line equipment control system and to four machine mounted motors (e.g.,
Dunkermotoren BG75 servomotors) which drive the accumulator 96, feed and
primary tension, secondary tension and sealing head functions. One skilled in
the
art will understand that another industry standard PLC may also be used in
place of
the PLC described above.
The MICROLOGIX 1500 PLC 802 has communication ports, including an
RS232C port for program uploads, downloads and monitoring and a RS232C port
for
connection to an EZ-AUTOMATION HMI (Human-Machine-Interface) 812 mounted
to the control panel side. The HMI provides machine diagnostics and
operational
data (e.g., number of straps applied, sensor status, etc.) in addition to
providing
operational parameter selections (e.g., strap position on the bundle, number
of
straps per bundle, etc.).
The operation of the strapping apparatus 100 may involves pulling
strap from a dispenser and feeding a free end of the strap through the
accumulator
96, through the feed and tension unit, up through the sealing head assembly
98, and
then around the strapping track assembly 118. U.S. Application No. 12/072,107
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discloses these components and their functionality. Because the track assembly
118
is adapted to minimize or limit the occurrence of misfeeds and/or damage to
the end
of the strap due to unwanted large gaps between strap guides, strap can be
consistently fed through the track assembly 118. After the strap is fed around
the
strapping track assembly 118, the free end is guided back into the sealing
head
assembly 98. At this point, the strap is in position to start a strapping
cycle where
the strap can be tensioned and secured about a bundle of objects.
In operation, during a tensioning or bundling operation, the tensioning
of the strap occurs in two stages, a primary tension stage and a secondary
tension
stage. In the primary tensioning stage, the strap is pulled out of the track
assembly
118 and, in some processes, down onto the bundle of objects. The secondary
tensioning sequence involves binding the strap tightly around the bundle of
objects
located in the strapping station 120. After the strap is tensioned to the
point that a
servomotor stalls, a controller permits a predetermined amount of time to pass
so as
to allow the sealing head assembly 98 to rotate to grip the strap. After
securing the
strap, the tension is released just prior to cutting the strap from the supply
to prevent
the strap from fraying. The strap is then cut and sealed. Once the sealing
operation
is complete, the feeding sequence may then be repeated.
The primary tensioning sequence provides enough force on the strap
to pull the strap inwardly away from the frame 240 and through the
longitudinal
openings 303 provided by the strap guides 220, 222. As the strap is tensioned
around the bundle of objects, the straight and corner track guides 220, 222
can be
opened by the strap 102, allowing the strap to pull clear of the channel 300.
The
force applied to the strap can overcome the biasing of the biasing mechanisms
for
convenient opening of the strap guides 220, 222. The strapping track assembly
118
may be configured to permit controlled sequential strap removal from the strap
guides 220, 222, thereby reducing, limiting, or substantially eliminating
damage to
the strap. After the strap clears the channel 300, the strap is pulled around
a bundle
of objects and both the straight and corner track guides 220, 222 close
because of
the biasing mechanisms.
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Once the strap has been sufficiently tensioned around the bundle of
objects, the non-free end of the strap can be cut and then both ends of the
strap can
be sealed together. The sealing operation commences when several sealing head
cams in the sealing head assembly 98 begin to rotate, forcing a gripper to
pinch the
free end of the strap against an anvil. Those skilled in the art will
recognize that the
strapping apparatus 100 can be configured, depending on strap orientation, to
accommodate the same gripper on the opposite side. After gripping the free end
of
the strap in the sealing head assembly 98, the feed and tension unit retracts
the
excess strap from the track assembly 118 (i.e., the tensioning operation
discussed
above).
In one embodiment, the strap used to bundle objects can have a heat-
activated adhesive applied thereon. Preferably, the adhesive on the strap is
applied
to the strap during the manufacturing process of the strap. Heat is applied to
the
strap by inserting a heater blade between the two overlapping ends of the
strap and
lightly pressing the ends against the blade by raising a press platen. Various
types
of further processing can be performed on the strap to ensure that strap is
properly
secured. At this point, the strapping track assembly 118 is ready for the
strap to be
fed again.
Except as described herein, the embodiments, features, systems,
devices, materials, methods and techniques described herein may, in some
embodiments, be similar to any one or more of the embodiments, features,
systems,
devices, materials, straps, methods and techniques described in U.S. Patent
Publication No. 2004/0200191, U.S. Patent Application No. 12/072,107, and U.S.
Provisional Patent Application No. 60/921,022. In addition, the embodiments,
features, systems, devices, materials, methods and techniques described herein
may, in certain embodiments, be applied to or used in connection with any one
or
more of the embodiments, features, systems, devices, materials, methods and
techniques disclosed in the above-mentioned U.S. Patent Publication No.
2004/0200191 and U.S. Provisional Patent Application No. 60/903,230. U.S.
Patent
Publication No. 2004/0200191, U.S. Patent Application No. 12/072,107, and U.S.
16
CA 02682085 2009-09-24
WO 2008/121887 PCT/US2008/058768
Provisional Patent Application No. 60/921,022 are hereby incorporated by
reference
herein in their entireties.
Although specific embodiments of, and examples for, the invention are
described herein for illustrative purposes, various equivalent modifications
are
possible within the scope of the invention, as those skilled in the relevant
art will
recognize. The teachings provided herein of the invention can be applied to
other
methods and apparatus for strapping bundles of objects, and not just to the
methods
and apparatus for strapping bundles of objects described above and shown in
the
figures. In general, in the following claims, the terms used should not be
construed
to limit the invention to the specific embodiments disclosed in the
specification.
Accordingly, the invention is not limited by the foregoing disclosure, but
instead its
scope is to be determined by the following claims.
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