Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 2779897 2017-05-30
DEMAND BASED WRAPPING
DESCRIPTION
[001] This application claims priority to United States Application No.
61/258,740, filed November 6, 2009.
Technical Field
[002] The present disclosure relates to an apparatus and a method for
wrapping a load with packaging material, and more particularly, to dispensing
packaging material for wrapping a load based on demand.
Background
[003] Various packaging techniques have been used to build a load of unit
products and subsequently wrap them for transportation, storage, containment
and
stabilization, protection and waterproofing. One system uses wrapping machines
to
stretch, dispense, and wrap packaging material around a load. The packaging
material may be pre-stretched before it is applied to the load. Wrapping can
be
performed as an inline, automated packaging technique that dispenses and wraps
packaging material in a stretch condition around a load on a pallet to cover
and
contain the load. Stretch wrapping, whether accomplished by a turntable,
rotating
arm, vertical rotating ring, or horizontal rotating ring, typically covers the
four
vertical sides of the load with a stretchable packaging material such as
polyethylene packaging material. In each of these arrangements, relative
rotation
is provided between the load and the packaging material dispenser to wrap
packaging material about the sides of the load.
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[004] Historically, wrappers have suffered from packaging material breaks
and limitations on the amount of wrap force applied to the load (as determined
in
part by the amount of pre-stretch used) due to erratic speed changes required
to
wrap "non-square" loads, such as narrow, tall loads, short, wide loads, and
short,
narrow loads. The non-square shape of such loads often results in the supply
of
excess packaging material during the wrapping cycle, during time periods in
which
the demand rate for packaging material by the load is exceeded by the supply
rate
of the packaging material by the packaging material dispenser. This leads to
loosely wrapped loads. In addition, when the demand rate for packaging
material
by the load is greater than the supply rate of the packaging material by the
packaging material dispenser, breakage of the packaging material may occur.
[005] When wrapping a typical rectangular load, the demand for packaging
material varies, decreasing as the packaging material approaches contact with
a
corner of the load and increasing after contact with the corner of the load.
When
wrapping a tall, narrow load or a short load, the variation in the demand rate
is even
greater than in a typical rectangular load. In vertical rotating rings, high
speed
rotating arms, and turntable apparatuses, the variation is caused by a
difference
between the length and the width of the load. In a horizontal rotating ring
apparatus, the variation is caused by a difference between the height of the
load
(distance above the conveyor) and the width of the load. Variations in demand
may
make it difficult to properly wrap the load. The problem with variations is
exacerbated when wrapping a load having one or more dimensions that may differ
from one or more corresponding dimensions of a preceding load. The problem may
also be exacerbated when wrapping a load having one or more dimensions that
vary at one or more locations of the load itself.
[006] The amount of force, or pull, that the packaging material exhibits on
the load determines how tightly and securely the load is wrapped.
Conventionally,
this wrap force is controlled by controlling the feed or supply rate of the
packaging
material dispensed by the packaging material dispenser. For example, the wrap
force of many known commercially available stretch wrapping machines is
controlled by attempting to alter the supply of packaging material such that a
relatively constant packaging material wrap force is maintained. With powered
pre-
stretching devices, changes in the force or tension of the dispensed packaging
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material were monitored. This has been accomplished using feedback
mechanisms typically linked to spring loaded dancer bars, electronic load
cells, or
torque control devices. The changing force or tension of the packaging
material
caused by rotating a rectangular shaped load is transmitted back through the
packaging material to some type of sensing device which attempts to vary the
speed of the motor driven dispenser to minimize the change. The passage of the
corner causes the force or tension of the packaging material to increase. This
increase is typically transmitted back to an electronic load cell, spring-
loaded
dancer interconnected with a sensing means, or to a torque control device.
After
the corner is passed, the force or tension of the packaging material reduces.
This
reduction is transmitted back to some device that in turn reduces the
packaging
material supply to attempt to maintain a relatively constant wrap force or
tension.
[007] With the ever faster wrapping rates demanded by the industry, the
rotation speeds have increased significantly to a point where the concept of
sensing changes in force and altering supply speed in response loses
effectiveness. The delay of response has been observed to begin to move out of
phase with rotation at approximately 20 RPM. The actual response time for the
rotating mass of packaging material roll and rollers approximating 100 lbs
must shift
from accelerate to decelerate eight times per revolution that at 20 RPM is a
shift
more than every one half of a second.
[008] Also significant is the need to minimize the acceleration and
deceleration times for these faster cycles. Initial acceleration must pull
against
clamped packaging material, which typically cannot stand a high force
especially
the high force of rapid acceleration that cannot be maintained by the feedback
mechanisms described above. Use of high speed wrapping has therefore been
limited to relatively lower wrap forces and pre-stretch levels where the loss
of
control at high speeds does not produce undesirable packaging material breaks.
[009] The present disclosure is directed to overcoming one or more of the
above-noted problems, as well as other problems in the art.
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SUMMARY OF THE DISCLOSURE
[010] According to an aspect of the present disclosure, a control system for
a wrapping apparatus may include a packaging material dispenser configured to
dispense packaging material for wrapping a load. The control system may also
include at least one sensor assembly configured to generate a signal based on
instantaneous demand for packaging material at the load. The control system
may
further include a controller configured to control operation of the packaging
material
dispenser based at least in part on the signal.
[011] According to another aspect of the present disclosure, an apparatus
for wrapping a load may include a packaging material dispenser. The packaging
material dispenser may include a dispensing drive configured to drive the
packaging material dispenser to dispense packaging material. The apparatus may
also include a relative rotation assembly configured to provide relative
rotation
between the packaging material dispenser and the load. The apparatus may
further include a first sensor assembly configured to sense a characteristic
indicative of instantaneous demand for packaging material at the load. The
apparatus may also include a controller configured to control operation of the
dispensing drive based at least in part on the instantaneous demand.
[012] According to yet another aspect of the present disclosure, a method
for wrapping a load may include driving a packaging material dispenser to
dispense
packaging material with a dispensing drive. The method may also include
providing
relative rotation between the packaging material dispenser and the load. The
method may also include sensing a characteristic indicative of instantaneous
demand for packaging material at the load. The method may further include
controlling operation of the dispensing drive based at least in part on the
instantaneous demand.
[013] Additional objects and advantages of the disclosure will be set forth in
part in the description which follows, and in part will be obvious from the
description, or may be learned by practice of the disclosure. The objects and
advantages of the disclosure will be realized and attained by means of the
elements and combinations particularly pointed out in the appended claims.
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[014] It is to be understood that both the foregoing general description and
the following detailed description are exemplary and explanatory only and are
not
restrictive of the disclosure, as claimed.
[015] The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate embodiments of the disclosure and
together
with the description, serve to explain the principles of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[016] FIG. 1 shows a top view of a first exemplary wrapping apparatus
according to one aspect of the present disclosure;
[017] FIG. 2 is a schematic showing an exemplary control system according
to one aspect of the present disclosure;
[018] FIG. 3 shows a top view of a second exemplary wrapping apparatus
according to another aspect of the present disclosure;
[019] FIG. 4 shows a top view of a third exemplary wrapping apparatus
according to yet another aspect of the present disclosure;
[020] FIG. 5 is a top view of a packaging material dispenser and a load,
according to one aspect of the present disclosure;
[021] FIG. 6 is a side view of the load of FIG. 5, according to the present
disclosure;
[022] FIG. 7 is a top view of a packaging material dispenser and a load,
according to another aspect of the present disclosure.
[023] FIG. 8 is a top view of a packaging material dispenser and a load,
according to another aspect of the present disclosure.
[024] FIG. 9 is a top view of a packaging material dispenser and a load,
according to another aspect of the present disclosure.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[025] Reference will now be made in detail to present embodiments of the
disclosure, examples of which is illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the
drawings to refer to the same or like parts. The disclosures of each of U.S.
Patent
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No. 4,418,510, entitled "STRETCH WRAPPING APPARATUS AND PROCESS,"
and filed April 17, 1981; U.S. Patent No. 4,953,336, entitled "HIGH TENSILE
WRAPPING APPARATUS," and filed August 17, 1989; U.S. Patent No. 4,503,658,
entitled "FEEDBACK CONTROLLED STRETCH WRAPPING APPARATUS AND
PROCESS," and filed March 28, 1983; U.S. Patent No. 4,676,048, entitled
"SUPPLY CONTROL ROTATING STRETCH WRAPPING APPARATUS AND
PROCESS," and filed May 20, 1986; U.S. Patent No. 4,514,955, entitled
"FEEDBACK CONTROLLED STRETCH WRAPPING APPARATUS AND
PROCESS," and filed April 6, 1981; U.S. Patent No. 6,748,718, entitled "METHOD
AND APPARATUS FOR WRAPPING A LOAD," and filed October 31, 2002; U.S.
Patent Application Publication No. 2006/0248858, entitled "METHOD AND
APPARATUS FOR DISPENSING A PREDETERMINED FIXED AMOUNT OF PRE-
STRETCHED FILM RELATIVE TO LOAD GIRTH," filed April 6, 2006; U.S. Patent
Application Publication No. 2007/0209324, entitled "METHOD AND APPARATUS
FOR SECURING A LOAD TO A PALLET WITH A ROPED FILM WEB," and filed
February 23, 2007; U.S. Patent Application Publication No. 2007/0204565,
entitled
"METHOD AND APPARATUS FOR METERED PRE-STRETCH FILM DELIVERY,"
and filed September 6, 2007; U.S. Patent Application Publication No.
2007/0204564, entitled "RING WRAPPING APPARATUS INCLUDING METERED
PRE-STRETCH FILM DELIVERY ASSEMBLY," and filed February 23, 2007; and
U.S. Patent Application Publication No. 2009/0178374, entitled "ELECTRONIC
CONTROL OF METERED FILM DISPENSING IN A WRAPPING APPARATUS,"
and filed January 7, 2009, are incorporated herein by reference in their
entirety.
[026] According to one aspect of the present disclosure, a wrapping
apparatus 100, shown in FIG. 1, may include a roll carriage 132 mounted on a
rotating arm 112. Roll carriage 132 may include a packaging material dispenser
116. Packaging material dispenser 116 may be configured to dispense packaging
material 118 as rotating arm 112 rotates relative to a load 104 to be wrapped.
In an
exemplary embodiment, packaging material dispenser 116 may be configured to
dispense stretch wrap packaging material. As used herein, stretch wrap
packaging
material is defined as material having a high yield coefficient to allow the
material a
large amount of stretch during wrapping. However, it is possible that the
apparatuses and methods disclosed herein may be practiced with packaging
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material that will not be pre-stretched prior to application to the load.
Examples of
such packaging material include netting, strapping, banding, or tape.
[027] Packaging material dispenser 116 may include a pre-stretch
assembly 120 configured to pre-stretch packaging material before it is applied
to
load 104 if pre-stretching is desired, or to dispense packaging material to
load 104
without pre-stretching. Pre-stretch assembly 120 may include at least one
packaging material dispensing roller, including, for example, an upstream
dispensing roller 121 and a downstream dispensing roller 122. It is
contemplated
that pre-stretch assembly 120 may include an assembly of pre-stretch rollers
and
idle rollers, similar to those described in U.S. Patent Application
Publication Nos.
2006/0248858, 2007/0204565, 2007/0204564, and 2009/0178374, the disclosures
of which are incorporated herein by reference in their entirety. Additional or
fewer
rollers may be used as desired.
[028] The terms "upstream" and "downstream," as used in this application,
are intended to define positions and movement relative to the direction of
flow of
packaging material 118 as it moves from packaging material dispenser 116 to
load
104. Movement of an object toward packaging material dispenser 116, away from
load 104, and thus, against the direction of flow of packaging material 118,
may be
defined as "upstream." Similarly, movement of an object away from packaging
material dispenser 116, toward load 104, and thus, with the flow of packaging
material 118, may be defined as "downstream." Also, positions relative to load
104
(or a load support surface 102) and packaging material dispenser 116 may be
described relative to the direction of packaging material flow. For example,
when
two pre-stretch rollers are present, the pre-stretch roller closer to
packaging
material dispenser 116 may be characterized as the "upstream" roller and the
pre-
stretch roller closer to load 104 (or load support surface 102) and further
from
packaging material dispenser 116 may be characterized as the "downstream"
roller.
[029] A packaging material drive system 124, including, for example, an
electric motor 126, may be used to drive dispensing rollers 121 and 122. For
example, electric motor 126 may rotate downstream dispensing roller 122.
Downstream dispensing roller 122 may be operatively coupled to upstream
dispensing roller 121 by a chain and sprocket assembly, such that upstream
dispensing roller 121 may be driven in rotation by downstream dispensing
roller
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122. Other connections may be used to drive upstream roller 121 or,
alternatively,
a separate drive (not shown) may be provided to drive upstream roller 121.
[030] Downstream dispensing roller 122, and/or packaging material 118
dispensed thereby, may be monitored for the purposes of determining the
rotational
speed of downstream dispensing roller 122, the number of rotations undergone
by
downstream dispensing roller 122, the amount and/or speed of packaging
material
dispensed by downstream dispensing roller 122, and/or one or more performance
parameters indicative of the operating state of packaging material drive
system
124, including, for example, a speed of packaging material drive system 124.
The
monitored characteristics may also provide an indication of the amount of
packaging material 118 being dispensed and wrapped onto load 104.
[031] One way of monitoring is via use of a sensor assembly 128. In one
embodiment, sensor assembly 128 may be configured to sense rotation of
downstream dispensing roller 122. Sensor assembly 128, as shown in FIG. 2, may
include one or more magnetic transducers 138 mounted on downstream dispensing
roller 122, and a sensing device 140 configured to generate a pulse when the
one
or more magnetic transducers 138 are brought into proximity of sensing device
140.
Alternatively, sensor assembly 128 may include an encoder configured to
monitor
rotational movement. The encoder may be capable of producing 720 signals per
revolution of downstream dispensing roller 122 to provide an indication of the
speed or other characteristic of rotation of downstream dispensing roller 122.
The
encoder may be mounted on a shaft of downstream dispensing roller 122, on
electric motor 126, and/or any other suitable area. One example of a sensor
assembly that may be used is a Sick 7900266 Magnetic Sensor and Encoder.
Other suitable sensors and/or encoders known in the art may be used for
monitoring, such as, for example, magnetic encoders, electrical sensors,
mechanical sensors, photodetectors, and/or motion sensors. Sensor assembly 128
may generate a drive signal based at least in part on the monitored
characteristics.
[032] Instantaneous demand for packaging material 118 at the load 104
may be determined and/or approximated for control purposes, such as for
controlling packaging material dispensing. As used herein, the term "demand"
may
be defined as the quantity of packaging material needed to wrap at least a
portion
of the load to achieve a desired wrap force and/or containment force. As used
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herein, wrap force is defined as the force exerted on the load by an
individual web
of packaging material applied to the load. As used herein, containment force
is
defined as the force exerted on the load by cumulative layers of packaging
material. The containment force may be generated by the wrap forces exerted on
the load by multiple layers of packaging material. The term "instantaneous
demand" may be defined as the demand for packaging material at a load at a
particular instant. There are many ways to determine values indicative of
instantaneous demand. The instantaneous demand may be characterized as the
speed an unstretchable material (e.g., a wire) would be dispensed from the
packaging material dispenser onto the load if the unstretchable material was
drawn
from the packaging material dispenser by relative rotation between the
packaging
material dispenser and the load, with a speed of the relative rotation
remaining
substantially constant.
[033] For a wrapping apparatus with a packaging material dispenser that
rotates around a stationary load (e.g., a rotating arm apparatus or a rotating
ring
apparatus), the instantaneous demand may be represented or approximated by a
line extending perpendicularly from the rotational axis of the packaging
material
dispenser to a plane defined by a surface of a length of the packaging
material that
extends between the packaging material dispenser and the load. For a wrapping
apparatus with a rotating load instead of a rotating packaging material
dispenser,
such as a rotating turntable apparatus, the instantaneous demand may be
represented or approximated by a line extending perpendicularly from the
rotational
axis of the rotating turntable to the plane. Additionally or alternatively,
the
instantaneous demand may be represented or approximated by a line extending
radially from the rotational axis of the packaging material dispenser to a
point on
the surface of the load (for a rotating packaging material dispenser), or by a
line
extending radially from the rotational axis of the rotating turntable to a
point on the
surface of the load (for a rotating load). Additionally or alternatively, the
instantaneous demand may be represented or approximated by a line extending
from a point on the packaging material dispenser to a plane defined by a
surface of
a length of the packaging material that extends between the packaging material
dispenser and the load.
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[034] For example, as shown in FIG. 5, when the packaging material
dispenser is in the position shown (relative to the load) while wrapping a
bottom
portion of the load, the instantaneous demand at that instant may be
represented or
approximated by R1. When the packaging material dispenser is in the position
shown (relative to the load) while wrapping a middle portion of the load, the
instantaneous demand at that instant may be represented or approximated by R2.
Further, when the packaging material dispenser is in the position shown
(relative to
the load) while wrapping a top portion of the load 104, the instantaneous
demand at
that instant may be represented or approximated by R3. Thus, it should be .
understood that for wrapping a load like the one shown in FIG. 5, the
instantaneous
demand may change during wrapping as the characteristics of the portion of the
load being wrapped change. The varying profile of the load in FIG. 5 may be
due
to the load being composed of units that have different sizes and/or
dimensions,
that may be stacked together to form the load.
[035] FIG. 7 shows representations or approximations of instantaneous
demand for top, middle, and bottom portions of an irregularly shaped load when
the
packaging material dispenser is in the position shown (relative to the load).
The
instantaneous demand while wrapping the top portion may be represented or
approximated by R4, the instantaneous demand while wrapping the middle portion
may be represented or approximated by R5, and the instantaneous demand while
wrapping the bottom portion may be represented or approximated by R6.
[036] Even during portions of the wrapping cycle where the characteristics
of the portion of the load being wrapped do not change, the instantaneous
demand
may change. For example, in FIG. 5, as the packaging material dispenser is
wrapping the bottom portion of the load, when the packaging material dispenser
is
in the position shown (relative to the load), the instantaneous demand may be
represented or approximated by R1. If the packaging material dispenser rotates
in
the counterclockwise direction, then upon reaching an eight o'clock position
in FIG.
5, the instantaneous demand may be represented or approximated by a line R1'.
R1' is shorter than R1, thus indicating that the instantaneous demand
decreased as
the packaging material dispenser traveled from the position shown to the eight
o'clock position. The instantaneous demand decreased even though the
characteristics of the bottom portion of the load did not change. The change
in
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instantaneous demand is due to the shape of the bottom portion of the load.
The
instantaneous demand will increase when the length of packaging material
between packaging material dispenser and the load contacts a corner of the
load,
and may continue to increase for a period of time thereafter. However, as the
length of the packaging material moves toward a face of load, the
instantaneous
demand will begin to decrease until the next corner is encountered.
[037] Instantaneous demand can also be represented or approximated
using a speed of packaging material dispensed by the packaging material
dispenser at a location between the packaging material dispenser and the load.
Further explanation will be provided in subsequent paragraphs.
[038] Instantaneous demand can also be represented or approximated
using a distance measurement from a rotational axis of the packaging material
dispenser to a point on a surface of the load, taken along a line extending
from the
rotational axis to a point on, for example, the packaging material dispenser
(for a
wrapping apparatus where the packaging material dispenser rotates around the
load). Additionally or alternatively, the instantaneous demand can be
represented
or approximated using a distance measurement from a rotational axis of a
rotating
turntable to a point on a surface of the load, taken along a line extending
from the
rotational axis to a point on the packaging material dispenser. Such distance
measurements are shown in FIG. 8. The measured distance may change during
relative rotation between the packaging material dispenser and the load.
Further
explanation will be provided in subsequent paragraphs.
[039] Instantaneous demand can also be represented or approximated
using a distance measurement from a point on, for example, the packaging
material
dispenser, and a plane defined by a surface of a length of the packaging
material
that extends between the packaging material dispenser and the load. The
measured distance is indicative of an angle between a reference line extending
from the point to a point on a surface of a dispensing roller of the packaging
material dispenser at which packaging material leaves the dispensing roller,
and
the plane defined by the surface of the length of the packaging material
extending
between the packaging material dispenser and the load. Such a distance
measurement is shown in FIG. 9. Further explanation will be provided in
subsequent paragraphs.
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[040] As described above, the instantaneous demand maps characteristics
of the load, including, for example, the shape of the load, one or more
dimensions
of the load, and/or a position of the load relative to the packaging material
dispenser. That is, as one or more characteristics changes, the instantaneous
demand changes accordingly. Thus, by monitoring the instantaneous demand
(e.g., taking periodic or continuous measurements), characteristics of the
load can
be modeled.
[041] By controlling the packaging material drive system based at least in
part on the instantaneous demand, adjustments can be made in response to the
variations described above. Thus, loads may be properly wrapped in a
consistent
manner even though different portions of the load being wrapped have different
features or characteristics, or one load to be wrapped has features or
characteristics that differ from those of another load to be wrapped. By
controlling
wrapping of the load as the instantaneous demand changes it may be possible to
obtain more consistently wrapped loads, reduce costs by decreasing the
likelihood
of packaging material breaks and ensuring that excess packaging material is
not
dispensed, wrap a wide variety of loads regardless of their characteristics,
and
improve throughput by allowing adjustments to settings to be made
automatically.
[042] Three exemplary ways of determining and/or approximating the
instantaneous demand for control purposes will now be described. A first way
that
the instantaneous demand may be determined and/or approximated is by
monitoring one or more characteristics of dispensed packaging material 118D
extending between load 104 and downstream dispensing roller 122. As shown in
FIG. 1, dispensed packaging material 118D can have either of two orientations,
one
shown in solid black line (where packaging material dispenser 116 rotates in a
counterclockwise direction) and the other shown in dashed black line (where
packaging material dispenser 116 rotates in a clockwise direction). The one or
more characteristics of dispensed packaging material 118D may be monitored
using a sensor assembly 136 shown in FIG. 1. As dispensed packaging material
118D moves from downstream dispensing roller 122 to load 104, sensor assembly
136 may be configured to sense, for example, a speed of rotation of an idle
roller
134 engaging dispensed packaging material 118D, a speed of dispensed
packaging material 118D, and/or an amount of dispensed packaging material
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118D. Changes in the monitored characteristics may map changes in the
instantaneous demand for packaging material 118 at load 104, and may stem from
changes in the size, shape, and/or placement of load 104 relative to packaging
material dispenser 116. Thus, as the size, shape, and/or placement of load 104
changes, the instantaneous demand may change in response, and as the
instantaneous demand changes, one or more of the characteristics of dispensed
packaging material 118D monitored by sensor assembly 136 may change in
response.
[043] As one example, sensor assembly 136 may be configured to monitor
the rotation of idle roller 134, positioned downstream from dispensing roller
122 and
configured to engage dispensed packaging material 118D. This monitoring may be
for purposes of sensing the rotational speed of idle roller 134. Sensor
assembly
136 may include components similar to those in sensor assembly 128. One
example of a sensor assembly that may be used is a Sick 7900266 Magnetic
Sensor and Encoder. Other suitable sensors and/or encoders known in the art
may
be used for monitoring, such as, for example, magnetic encoders, electrical
sensors, mechanical sensors, photodetectors, and/or motion sensors.The
instantaneous demand and the monitored characteristics of dispensed packaging
material 118D may be linked. For example, an increase in the instantaneous
demand may produce an increase in the speed of dispensed packaging material
118D, the amount of dispensed packaging material 1180, and/or the speed of
rotation of idle roller 134, while a decrease in the instantaneous demand may
produce a decrease in the speed of dispensed packaging material 118D, the
amount of dispensed packaging material 118D, and/or the speed of rotation of
idle
roller 134. One reason for this is that as the instantaneous demand increases,
load
104 tends to draw packaging material 118 more quickly over idle roller 134,
and
when instantaneous demand decreases, load 104 tends to draw packaging
material 118 more slowly over idle roller 134. Thus, sensor assembly 136, by
monitoring the speed of rotation of idle roller 134 during wrapping, monitors
the
instantaneous demand for packaging material 118 at the portion of load 104
being
wrapped. Accordingly, the signal generated by sensor assembly 136, based on
monitoring the speed of rotation of idle roller 134, is indicative of
instantaneous
demand at the portion of load 104 being wrapped. As the instantaneous demand
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increases (producing an increase in the speed of rotation of idle roller 134),
the
instantaneous demand signal from sensor assembly 136 may increase. As the
instantaneous demand decreases (producing a decrease in the speed of rotation
of
idle roller 134), the instantaneous demand signal from upstream sensor
assembly
136 may decrease.
[044] Additionally or alternatively, one or more characteristics of dispensed
packaging material 118D may be monitored with another sensor assembly, similar
to sensor assembly 136, but positioned to engage a different portion of
dispensed
packaging material 1180. This other sensor assembly may include, for example,
a
sensor assembly 114 configured to monitor an idle roller 133. Idle roller 133
may
be similar to idle roller 134. Sensor assembly 114 may also generate an
instantaneous demand signal based on the one or more sensed characteristics.
[045] A second way that the instantaneous demand may be determined
and/or approximated, in addition to or as an alternative to the first way, is
by using a
distance measuring device 137 (see FIG. 8), including, for example, a
photoeye,
proximity detector, laser distance measurer, ultrasonic distance measurer,
electronic rangefinder, and/or any other suitable distance measuring device,
to
provide an signal indicative of instantaneous demand. Exemplary distance
measuring devices may include, for example, an IFM Effector 01D100 and a Sick
UM30-213118 (6036923).
[046] As shown in FIG. 8, distance measuring device 137 may be placed on
or near packaging material dispenser 116. For example, distance measuring
device 137 may be mounted on roll carriage 132 which supports, and therefore
moves vertically and in rotation with, packaging material dispenser 116.
Distance
measuring device 137 measures a distance between itself and a surface point on
load 104, along a line extending radially from a center of rotation 139 of
packaging
material dispenser 116. The measured distance may be subtracted from a known
distance between the distance measuring device 137 and the center of rotation
139
to find a radial distance between the center of rotation 139 and the surface
point on
load 104. The calculated distance may provide an indication of instantaneous
demand.
[047] In FIG. 8, line Li represents the distance measured by distance
measuring device 137 when packaging material dispenser 116 and load 104 are in
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the position shown. Line L1' in FIG. 8 represents the radial distance found by
subtracting the measured distance L1 from the known distance between the
distance measuring device 137 and the center of rotation 139. As relative
movement takes place between the packaging material dispenser 116 and the load
104, packaging material dispenser 116 may occupy positions where the lines L2,
L3, and L4 represent the distance measured by distance measuring device 137,
in
which case lines L2', L3', and L4', respectively, represent the radial
distances found
by subtracting the measured distances from the known distance between the
distance measuring device 137 and the center of rotation 139. It is also
contemplated that distance measuring device 137 may be selectively movable on
a
track or other adjustable mounting such that distance measuring device 137 may
occupy positions corresponding to those shown at lines L2, L3, and L4 while
packaging material dispenser 116 is in the position shown in FIG. 8.
[048] Signals generated by distance measuring device 137 may provide
data on the measured distances and/or the calculated radial distances. These
signals may provide an indication or approximation of instantaneous demand at
the
surface point on load 104 where the measurement is taken. As the instantaneous
demand increases (exemplified by an increase in the radial distance between
the
center of rotation 139 and the surface point on load 104), the instantaneous
demand signal from distance measuring device 137 may increase. As the
instantaneous demand decreases (exemplified by a decrease in the radial
distance
between the center of rotation 139 and the surface point on load 104), the
instantaneous demand signal from distance measuring device 137 may decrease.
The signals from distance measuring device 137 may be sent to controller 170
together with signals indicative of relative rotation speed, allowing
controller 170 to
adjust wrap settings.
[049] Distance measuring device 137 may be positioned on or near
packaging material dispenser 116 such that distance measuring device 137 may
be
used to anticipate changes in the instantaneous demand. For example, distance
measuring device 137 may be positioned at a location on or near a forward end
of
packaging material dispenser 116. This may allow distance measuring device 137
to measure the distance to a portion of load 104 that is not yet being
wrapped. By
determining the instantaneous demand at that portion of load 104, controller
170
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may anticipate the instantaneous demand at that portion. This may provide
controller 170 with additional time to adjust operational settings based on
the
anticipated instantaneous demand. For example, controller 170 may gradually
adjust operational settings over a period of time to prevent spikes in force
on
packaging material 118, and/or to ensure smoother running of packaging
material
dispenser 116. It should be understood that a calculated delay may be required
to
align packaging material dispensing with the instantaneous demand determined
and/or approximated using distance measuring device 137.
[050] A third way that the instantaneous demand may be determined and/or
approximated, in addition to or as an alternative to the first and second
ways, is by
using a distance measuring device 141 (see FIG. 9) , including, for example, a
photoeye, proximity detector, laser distance measurer, ultrasonic distance
measurer, electronic rangefinder, and/or any other suitable distance measuring
device, to provide a signal indicative of instantaneous demand. Exemplary
distance measuring devices may include, for example, an IFM Effector 01D100
and
a Sick UM30-213118 (6036923).
[051] As shown in FIG. 9, distance measuring device 141 may be placed on
or near packaging material dispenser 116. For example, distance measuring
device 141 may be mounted on roll carriage 132, Distance measuring device 137
measures a distance between itself and a point on a surface of dispensed
packaging material 118D. The measured distance, identified with reference
numeral 145 in FIG. 9, corresponds to an angle between a reference line 143
(extending from a tangent point on idle roller 134 and center of rotation 139)
and a
plane defined by the surface of dispensed packaging material 118D. The
measured distance and/or the angle provide an indication or approximation of
the
instantaneous demand for packaging material 118 at the portion of load 104
being
wrapped.
[052] Signals generated by distance measuring device 141 may provide
data on the measured distances and/or angles. Thus, these signals may be
indicative of instantaneous demand at the surface point on load 104 being
wrapped. As the instantaneous demand increases (exemplified by an increase in
the measured distance or angle), the instantaneous demand signal from distance
measuring device 141 may increase. As the instantaneous demand decreases
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(exemplified by a decrease in the measured distance or angle), the
instantaneous
demand signal from distance measuring device 141 may decrease. The signals
from distance measuring device 141 may be sent to controller 170 together with
signals indicative of relative rotation speed, allowing controller 170 to
adjust wrap
settings.
[053] By controlling the relationship between the operation of packaging
material drive 124 and the instantaneous demand, as determined and/or
approximated using one or more of the ways described above, apparatus 100 may
wrap at least a portion of load 104 at a desired and/or predetermined payout
percentage even as conditions change. The word "predetermined," as used
herein,
means "determined and set in advance." Values described herein as
"predetermined" may include values determined through, for example,
experimentation, analysis of historical performance data, use of mathematical
equations and formulas, measurement, and/or any other suitable ways of making
determinations, that are set in advance (e.g., before starting a wrapping
cycle or
during a wrapping cycle as conditions change) to achieve a desired goal. As
used
herein, the phrase "payout percentage" is defined as a ratio of the amount of
packaging material dispensed for at least a portion of a wrapping cycle to the
demand for packaging material at the load for that same portion of the
wrapping
cycle.
[054] The desired and/or predetermined payout percentage may be input
into apparatus 100 by a machine operator. A controller 170 (shown in FIG. 2),
or
any other suitable computing device, may determine, based on the payout
percentage, and signals from sensing assembly 136, distance measuring device
137, and/or distance measuring device 141 (which provide indications or
approximations of instantaneous demand), the length of packaging material 118
that should be dispensed for a period of time or portion of a relative
revolution
= between packaging material dispenser 116 and load 104. For example, if
the
operator enters a payout percentage of 110%, and the instantaneous demand is
111 inches for a period of time, then the output from packaging material
dispenser
116 for that period of time may be approximately 121 inches of packaging
material
118. If the operator enters a payout percentage of 100%, then the output from
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packaging material dispenser 116 for the same instantaneous demand of 111
inches would be approximately 111 inches of packaging material 118.
[055] Wrapping apparatus 100 may include a relative rotation assembly 106
configured to rotate rotating arm 112, and thus, packaging material dispenser
116
mounted thereon, relative to load 104 as load 104 is supported on load support
surface 102. Relative rotation assembly 106 may include a rotational drive
system
108, including, for example, an electric motor 110. It is contemplated that
rotational
drive system 108 and packaging material drive system 124 may run independently
of one another. Thus, rotation of dispensing rollers 121 and 122 may be
independent of the relative rotation of packaging material dispenser 116
relative to
load 104. This independence allows a length of packaging material 118 to be
dispensed per a portion of relative revolution that is neither predetermined
or
constant. Rather, the length may be adjusted periodically or continuously
based on
changing conditions.
[056] Wrapping apparatus 100 may further include a lift assembly 146. Lift
assembly 146 may be powered by a lift drive system 148, including, for
example,
an electric motor 150, that may be configured to move roll carriage 132
vertically
relative to load 104. Lift drive system 148 may drive roll carriage 132, and
thus
packaging material dispenser 116, upwards and downwards vertically on rotating
arm 112 while roll carriage and packaging material dispenser 116 are rotated
about
load 104 by rotational drive system 108, to wrap packaging material spirally
about
load 104.
[057] An exemplary schematic of a control system 160 for wrapping
apparatus 100 is shown in FIG. 2. Rotational drive system 108, packaging
material
drive system 124, and lift drive system 148 may communicate through one or
more
data links 162 with a rotational drive variable frequency drive ("VFD") 164, a
packaging material drive VFD 166, and a lift drive VFD 168, respectively.
Rotational drive VFD 164, packaging material drive VFD 166, and lift drive VFD
168
may communicate with controller 170 through a data link 172. It should be
understood that rotational drive VFD 164, packaging material drive VFD 166,
and
lift drive VFD 168 may produce outputs to controller 170 that controller 170
may
use as indicators of rotational movement. For example, packaging material
drive
VFD 166 may provide controller 170 with signals similar to signals provided by
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sensing assembly 128, and thus, sensing assembly 128 may be omitted to cut
down on manufacturing costs.
[058] Controller 170 may include hardware components and software
programs that allow it to receive, process, and transmit data. It is
contemplated
that controller 170 may operate similar to a processor in a computer system.
Controller 170 may communicate with an operator interface 176 via a data link
178.
Operator interface 176 may include a screen and controls that may provide an
operator with a way to monitor, program, and operate wrapping apparatus 100.
For
example, an operator may use operator interface 176 to enter or change
predetermined and/or desired settings and values, or to start, stop, or pause
the
wrapping cycle. Controller 170 may also communicate with one or more sensor
assemblies (described above) through a data link 174, thus allowing controller
170
to receive performance related data during wrapping. It is contemplated that
data
links 162, 172, 174, and 178 may include any suitable wired communications
medium known in the art. It is also contemplated that data links 162, 172,
174, and
178 may include any suitable wireless communications medium known in the art
that allows the sensor assemblies to transmit data wirelessly to controller
170.
[059] By controlling the operation of packaging material drive 124 based at
least in part on the instantaneous demand with controller 170, apparatus 100
may
wrap at least a portion of load 104 at the predetermined and/or desired payout
percentage for at least a portion of a wrapping cycle. The portion of the
wrapping
cycle may be a portion of a single relative revolution between the dispenser
and the
load, a complete relative revolution, or more than a single relative
revolution.
During that portion of the wrapping cycle, load 104 may be wrapped with a
substantially equal wrap force around its perimeter. This may be achieved even
though the instantaneous demand may change during the portion of the wrapping
cycle. Such changes in instantaneous demand may be caused by, for example, a
change in one or more dimensions of the load, the shape of the portion of the
load
being wrapped, the placement of the load being wrapped relative to packaging
material dispenser 116, and/or the speed of relative rotation of packaging
material
dispenser 116 relative to load 104.
[060] The instantaneous demand, as well as changes in the instantaneous
demand may be determined and/or approximated by or using sensor assembly
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136, distance measuring device 137, and/or distance measuring device 141.
Controller 170 may receive signals from sensor assembly 136, distance
measuring
device 137, and/or distance measuring device 141. Along with the signals from
distance measuring device 137 and/or distance measuring device 141, controller
170 may also receive a relative rotation speed signal from any suitable sensor
(not
shown) monitoring rotational drive system 108. Controller 170 may also receive
the
drive signal from sensor assembly 128, as it monitors dispensing roller 122.
Controller 170 may be programmed to set or adjust operation of packaging
material
drive system 124 by changing the frequency of electrical power supplied to
packaging material drive VFD 166, based on the instantaneous demand signal.
Additionally, controller 170 may be programmed to set or adjust operation of
packaging material drive system 124 based at least in part on the relative
rotation
speed signal when the instantaneous demand signal is from distance measuring
device 137 of distance measuring device 141.
[061] For example, controller 170 may be programmed to use the
instantaneous demand signal from sensor assembly 136, distance measuring
device 137, and/or distance measuring device 141 as a baseline signal, and may
adjust operation of packaging material drive system 124 as the instantaneous
demand signal changes. If the instantaneous demand signal increases,
controller
170 may adjust operation of packaging material drive system 124 to produce a
corresponding increase in the drive signal. If the instantaneous demand signal
decreases, controller 170 may adjust operation of packaging material drive
system
124 to produce a corresponding decrease in the drive signal. Controller 170
may
adjust operation of packaging material drive system 124 until the drive signal
is
equal to the instantaneous demand signal (producing a payout percentage of
100%
and/or equal rotation speeds for dispensing roller 122 and idle roller 134),
and/or
within a predetermined and/or desired range above the instantaneous demand
signal (producing a payout percentage of more than 100% and/or a rotation
speed
for dispensing roller 122 that exceeds the rotation speed of idle roller 134)
or below
the instantaneous demand signal (producing a payout percentage of less than
100% and/or a rotation speed for dispensing roller 122 that is exceeded by the
rotation speed of idle roller 134). The adjusted drive signal may be linked
with the
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speed of downstream dispensing roller 122 required to produce the desired
payout
percentage in light of the instantaneous demand.
[062] A plot of drive signal values and instantaneous demand signal values
over time may produce a drive signal curve and an instantaneous demand signal
curve that are similar. For example, the drive signal curve and the
instantaneous
demand signal curve may be sinusoidal (due, for example, to the presence of
sides
and corners on rectangular loads), and may be coincident, vertically offset
(i.e.,
parallel) by a predetermined and/or desired magnitude, and/or horizontally
offset by
a predetermined and/or desired magnitude. By performing these steps,
controller
170 may produce the predetermined and/or desired payout percentage for the
portion of the wrapping cycle. Of course, when the instantaneous demand signal
remains substantially constant, controller 170 may operate packaging material
drive
system 124 in a substantially constant manner.
[063] It is also contemplated that controller 170 may be programmed to use
the instantaneous demand signal from sensor assembly 114 as the baseline
signal,
if sensor assembly 114 is provided. It is further contemplated that sensor
assembly
128 may be ignored or omitted, and controller 170 may be programmed to adjust
operation of packaging material drive system 124 as the instantaneous demand
signal changes, without monitoring downstream drive roller 122. In such an
embodiment, controller 170 may increase the speed of packaging material drive
system 124 when the instantaneous demand signal increases, and decrease the
speed of packaging material drive system 124 when the instantaneous demand
signal decreases. The change in the speed of packaging material drive system
124
may be proportional to the magnitude of the change in the instantaneous demand
signal. Moreover, the speed of packaging material drive system 124 may be set
at
a first level relative to the instantaneous demand signal to achieve a first
payout
percentage, at a higher level to achieve a higher payout percentage, and at a
lower
level to achieve a lower payout percentage. A plot of the speed of packaging
material drive system 124 and instantaneous demand signal values over time may
produce a drive speed curve and an instantaneous demand signal curve that are
similar (e.g., sinusoidal, coincident, vertically offset, and/or horizontally
offset).
[064] By using the instantaneous demand signal as a baseline, controller
170 may make adjustments when wrapping loads with varying profiles, including,
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for example, loads composed of units having different dimensions; when
wrapping
loads with irregular shapes, including, for example, non-square loads; or when
wrapping square loads that are positioned off-center of load support surface
102.
When wrapping such loads, it is possible for the instantaneous demand to
change
a plurality of times. For example, when packaging material dispenser 116 moves
from wrapping a top portion 151 to a middle portion 149 of load 104 (see,
e.g.,
FIGS. 5 and 6), or middle portion 149 to a bottom portion 147, or when
packaging
material dispenser 116 wraps a corner of load 104 after having wrapped a flat
surface of load 104, the increase in the instantaneous demand will produce an
increase in the instantaneous demand signal generated by sensor assembly 136.
As another example, when packaging material dispenser 116 moves from wrapping
bottom portion 147 to middle portion 149, or middle portion 149 to top portion
151,
or when packaging material dispenser 116 wraps a flat surface of load 104
after
having wrapped a corner of load 104, the decrease in the instantaneous demand
will produce a decrease in the instantaneous demand signal generated by sensor
assembly 136. Controller 170 may adjust packaging material drive system 124 to
compensate for such variations in the manner described above. Thus, wrapping
may continue uninterrupted in spite of the variations, since input from an
operator is
not required in order to compensate for the variations.
[065] It is also contemplated that if, after load 104 is wrapped, a subsequent
load to be wrapped has one or more dimensions and/or a shape that is different
from that of load 104, the predetermined and/or desired payout percentage may
still
be produced during wrapping of the subsequent load. For example, if the
subsequent load is larger than load 104, there will be a greater instantaneous
demand for packaging material 118 at the subsequent load. The increase in
instantaneous demand will result in an increase in the instantaneous demand
signal, and an increase in the speed of downstream dispensing roller 122 in
response. Thus, the predetermined and/or desired payout percentage may be
achieved as the speed of downstream dispensing roller 122 rises to meet the
increase in the instantaneous demand. If, on the other hand, the subsequent
load
is smaller than load 104, there will be a smaller instantaneous demand for
packaging material 118 at the subsequent load. The decrease in instantaneous
demand will result in a decrease in the instantaneous demand signal, and a
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decrease in the speed of downstream dispensing roller 122. Thus, once again,
the
predetermined and/or desired payout percentage may be achieved as the speed of
downstream dispensing roller 122 falls to meet the decrease in the
instantaneous
demand. As such, wrapping at the predetermined and/or desired payout
percentage may be accomplished although the actual dimensions of the load
being
wrapped are unknown, and/or a series of loads to be wrapped have random
shapes and/or dimensions.
[066] A buffer may be added to dampen or reduce the amplitude of the
speed variation undergone by downstream dispensing roller 122. By doing so,
the
buffer may allow smoother operation to be achieved during wrapping. The buffer
may also reduce stress on packaging material 118, helping to prevent packaging
material breaks from occurring.
[067] The buffer may operate by dampening or delaying the instantaneous
demand signal from sensing assembly 136 in instances where the instantaneous
demand is trending down or decreasing. Dampening and/or delaying the
instantaneous demand signal may weaken, reduce, and/or slow the response of
controller 170 to the decrease in instantaneous demand. While this could
result in
loose wrapping for a portion of the wrapping cycle, such loose wrapping may be
remedied by subsequent wrapped layers of packaging material 118. Moreover, the
dampening or delaying may help prevent packaging material breaks. When
packaging material 118 is torn or otherwise damaged, that portion of packaging
material 118 may cause idle roller 134 to slow as it passes over idle roller
134. If
controller 170 immediately reacts to the slowing of idle roller 134, as if it
was
indicative of a decrease in instantaneous demand, controller 170 will increase
stress on the damaged portion and potentially cause a packaging material
break.
By dampening or delaying the instantaneous demand signal, additional time is
provided for the damaged portion to be wrapped onto load 104, allowing
wrapping
to continue. Thus, the benefits obtained by reducing or slowing the response
of
controller 170 may outweigh any potential drawbacks.
[068] Dampening and/or delaying the instantaneous demand signal from
sensing assembly 136, while desirable when the instantaneous demand decreases,
may be undesirable when the instantaneous demand increases. For example,
when wrapping a corner of load 104 or an enlarged portion of load 104, the
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instantaneous demand may increase, producing an increase in the instantaneous
demand signal. If the instantaneous demand signal is dampened and/or delayed,
controller 170 may not be able to adjust packaging material drive system 124
quickly enough to ensure that enough packaging material 118 is dispensed to
meet
the increased demand. Tension in dispensed packaging material 118D may
increase to a point where a tear, or even a break, may develop. Thus, when the
instantaneous demand signal increases, any dampening and/or delaying of the
instantaneous demand signal may be avoided.
[069] Controller 170 may also be programmed to detect packaging material
breaks during at least a portion of the wrapping cycle. As used herein, the
term
"break" is meant to describe a complete or total severing of packaging
material 118,
that is, a cutting or tearing across the entire width of packaging material
118 that
splits the packaging material 118 into separate pieces. The term "break" is
not
meant to refer to a relatively small puncture, rip, or tear in packaging
material 118
that may be carried through onto load 104 during wrapping. However, if the
relatively small puncture, rip, or tear in packaging material 118 stretches to
the
point that it completely severs packaging material 118 before making its way
onto
load 104, then the relatively small puncture, rip, or tear will have become a
break.
The direction of rotation of idle roller 134 may reverse due to recovery of
the
packaging material after breakage or backlash of the broken packaging
material.
Thus, controller 170 may recognize that a packaging material break has
occurred
when a reversal is sensed. When a packaging material break is detected,
controller 170 may instruct packaging material drive VFD 166 to stop packaging
material drive system 124, thus halting the dispensing of packaging material
118
from packaging material dispenser 116. It is also contemplated that packaging
material breaks may be detected using photodetectors, loads cells, spring-
biased
rollers, and/or any other suitable devices known in the art.
[070] Controller 170 may also be programmed to give priority to some
signals from sensing assembly 136, distance measuring device 137, and/or
distance measuring device 141, over other signals. For example, rather than
treating all of the signals as equally important, the controller 170 may give
the
signals corresponding to the corners of load 104 (such as those represented by
R3,
R4, and R5 in FIG. 7; L4' in FIG. 8; and any of the lines representing
dispensed
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packaging material 118D in FIG. 9) higher priority. Signals corresponding to
the
corners may be sensed by controller 170 due to the presence of peak values
(e.g.,
packaging material speed, radial distance, and packaging material path angle)
at
the corners. Each corner may be treated as an effective girth of load 104,
such that
the instantaneous demand recognized by controller 170 for all parts of load
104,
including the substantially flat faces between the corners of load 104, is the
instantaneous demand for the corner being sensed by the controller 170. When a
subsequent corner is sensed by controller 170, the instantaneous demand
recognized by controller 170 for all parts of load 104 is the instantaneous
demand
for that corner. This process takes place as each corner is sensed, and
eliminates
or reduces fluctuations associated with adjusting dispensing to meet the needs
of
corners and faces of the load 104. Reducing or eliminating fluctuations by
focusing
on the corners and downplaying or ignoring the flat surfaces of load 104 may
provide smoother machine operation.
[071] FIG. 3 shows a wrapping apparatus 200 of the rotating ring variety.
Wrapping apparatus 200 may include elements similar to those shown in relation
to
wrapping apparatus 200. While each and every element in FIG. 3 is not
described
in detail, it should be understood that elements in FIG. 3 that are similar to
elements in FIG. 1 are represented with similar reference numerals. As shown,
wrapping apparatus 200 includes a rotating ring 212 in place of rotating arm
112 of
wrapping apparatus 100. However, it should be understood that wrapping
apparatus 200 may operate in a manner similar to that described above with
respect to wrapping apparatus 100.
[072] Wrapping apparatus 200 may include an idle roller 234 and a sensing
assembly 236 similar to idle roller 134 and sensing assembly 136. Sensing
assembly 236, like sensing assembly 136, may provide a signal indicative of
instantaneous demand. Additionally or alternatively, a distance measuring
sensor
237, similar to distance measuring sensor 137, may be mounted on or near any
point on packaging material dispenser 216, roll carriage 232, rotating ring
212,
and/or any other suitable location where distance measuring sensor 237 can
measure the distance to load 204 while rotating relative to load 204. It is
contemplated that distance measuring sensor 237 may be mounted such that its
view is not obstructed by dispensed packaging material 218D. Additionally or
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alternatively, a distance measuring sensor 241, similar to distance measuring
sensor 141, may be mounted on or near any point on packaging material
dispenser
216, roll carriage 232, rotating ring 212, and/or any other suitable location
where
distance measuring sensor 241 can measure the distance to dispensed packaging
material 218D while load 204 is wrapped.
[073] Wrapping apparatus 200 may also include a controller (not shown)
similar to controller 170. The controller may receive signals from sensor
assembly
236, distance measuring device 237, and/or distance measuring device 241. The
controller may also receive a drive signal from a sensor assembly 228 (similar
to
sensor assembly 128), as it monitors a dispensing roller 222 (similar to
dispensing
roller 122). The controller may be programmed to set or adjust operation of a
packaging material drive system 224 (similar to packaging material drive
system
124) by, for example, changing the frequency of electrical power supplied to a
packaging material drive (not shown, but similar to packaging material drive
VFD
166) based on the instantaneous demand signals from sensing assembly 236,
distance measuring device 237, and/or distance measuring device 241,
[074] FIG. 4 shows a wrapping apparatus 300 of the rotating turntable
variety. Wrapping apparatus 300 may include elements similar to those shown in
relation to wrapping apparatus 100. While each and every element in FIG. 4 is
not
described in detail, it should be understood that elements in FIG. 4 that are
similar
to elements in FIG. 1 are represented with similar reference numerals. As
shown,
wrapping apparatus 300 includes a rotating turntable 312 for rotating load 304
while
packaging material dispenser 316 remains fixed, in place of rotating arm 112
of
wrapping apparatus 100. However, it should be understood that wrapping
apparatus 300 may operate in a manner similar to that described above with
respect to wrapping apparatus 100.
[075] Wrapping apparatus 300 may include an idle roller 334 and a sensing
assembly 336 similar to idle roller 134 and sensing assembly 136. Sensing
assembly 336, like sensing assembly 136, may provide a signal indicative of
instantaneous demand. Additionally or alternatively, a distance measuring
sensor
337, similar to distance measuring sensor 137, may be mounted on or near any
point on packaging material dispenser 316, roll carriage 332, and/or any other
suitable location where distance measuring sensor 337 can measure the distance
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to load 304 while rotating relative to load 304. It is contemplated that
distance
measuring sensor 337 may be mounted such that its view is not obstructed by
dispensed packaging material 318D. Additionally or alternatively, a distance
measuring sensor 341, similar to distance measuring sensor 141, may be mounted
on or near any point on packaging material dispenser 316, roll carriage 332,
and/or
any other suitable location where distance measuring sensor 341 can measure
the
distance to dispensed packaging material 318D while load 304 is wrapped.
[076] Wrapping apparatus 300 may also include a controller (not shown)
similar to controller 170. The controller may receive signals from sensor
assembly
336, distance measuring device 337, and/or distance measuring device 341. The
controller may also receive a drive signal from a sensor assembly 328 (similar
to
sensor assembly 128), as it monitors a dispensing roller 322 (similar to
dispensing
roller 122). The controller may be programmed to set or adjust operation of a
packaging material drive system 324 (similar to packaging material drive
system
124) by, for example, changing the frequency of electrical power supplied to a
packaging material drive (not shown, but similar to packaging material drive
VFD
166) based on the instantaneous demand signals from sensing assembly 336,
distance measuring device 337, and/or distance measuring device 341.
[077] While pre-stretched packaging material is included in the exemplary
embodiments described above, it should be understood that other types of
packaging material, such as those that do not undergo pre-stretching (e.g.,
netting,
strapping, banding, or tape), may also be used. Such an embodiment would be
similar to the embodiment including pre-stretched packaging material, except
that
the speed of rotation of the upstream dispensing roller, which may be
indicative of
the speed and/or amount of undispensed packaging material coming off the
upstream dispensing roller, may be substantially equal to the speed of
rotation of
the downstream dispensing roller, which may be indicative of the speed and/or
amount of dispensed packaging material coming off the downstream dispensing
roller.
[078] A first exemplary method for wrapping a load will now be described.
Reference will be made to elements in FIGS. 1 and 2. Initially, packaging
material
dispenser 116 may be in its home position, that is, proximate clamping device
180
shown in FIG. 1. Packaging material 118 may extend from packaging material
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dispenser 116 toward clamping device 180. Clamping device 180 may grip a
leading end of packaging material 118. Load 104 may be placed on wrapping
surface 102. Load 104 may be placed on wrapping surface 102 by a pallet truck
(not shown), may be conveyed onto wrapping surface 102 using a conveying
means (i.e., rollers or a conveying belt; not shown), or may be built on
wrapping
surface 102 by stacking or arranging a number of items thereon.
[079] The predetermined and/or desired payout percentage may be
obtained by or entered into controller 170. The predetermined and/or desired
payout percentage may be selected, for example, based on the desired wrap
force.
The desired wrap force may be obtained by, for example, looking at historical
performance data to identify a wrap force that has successfully prevented
shifting of
loads similar to load 104 during shipping.
[080] With load 104 in place, and controller 170 programmed with the
predetermined and/or desired payout percentage, controller 170 may begin
wrapping load 104. Controller 170 may implement operational settings of
wrapping
apparatus 100 so that a sufficient amount of packaging material 118 is
dispensed
initially to prevent pulling the initial end of packaging material 118 out of
or off of
clamping device 180, and so that load 104 may be properly wrapped. For
example,
controller 170 may implement settings to produce the predetermined and/or
desired
payout percentage.
[081] During wrapping, the instantaneous demand for packaging material
118 at load 104 may change due to changes in load girth within load 104,
features
associated with the shape of load 104 (e.g., flat surfaces and/or corners),
one or
more dimensions of load 104, and/or placement of load 104 relative to
packaging
material dispenser 116 (e.g., on or off center with respect to the rotational
axis of
packaging material dispenser 116). If the instantaneous demand increases,
producing an increase in the instantaneous demand signal from sensor assembly
136, distance measuring device 137, and/or distance measuring device 141,
controller 170 may increase the speed of dispensing roller 122 in response to
maintain the predetermined and/or desired payout percentage. When the
instantaneous demand signal is supplied by distance measuring device 137 or
distance measuring device 141, controller 170 may also obtain a relative
rotation
speed signal for determining the speed of dispensing roller 122 in response to
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maintain the predetermined and/or desired payout percentage. If the
instantaneous
demand at load 104 decreases, producing a decrease in the instantaneous
demand signal, controller 170 may decrease the speed of dispensing roller 122
in
response to maintain the predetermined and/or desired payout percentage. For
example, the instantaneous demand at load 104 may decrease as packaging
material dispenser 116 moves from wrapping middle portion 149 of load 104 to
wrapping top portion 151 of load 104, since top portion 151 has a smaller
girth than
middle portion 149. This decrease in the portion of load 104 being wrapped may
correspond to a decrease in the instantaneous demand that is sensed by sensor
assembly 136, resulting in a decrease in the instantaneous demand signal to
controller 170, which decreases the speed of dispensing roller 122 in response
to
maintain the predetermined and/or desired payout percentage.
[082] Controller 170 may implement a buffer to ensure that it responds to
decreases in the instantaneous demand signal, as indicated by sensing assembly
136, less severely and/or less quickly than it responds to increases in the
instantaneous demand signal. The buffer may dampen and/or delay the
instantaneous demand signal from sensing assembly 136 when the instantaneous
demand signal decreases. Dampening may reduce fluctuations, thus providing for
smoother machine operations. Dampening may also allow damaged portions (e.g.,
portions with a hole and/or a partial tear) of packaging material 118 to pass
onto
load 104 without causing complete failure of packaging material 118.
[083] Packaging material dispenser 116 may dispense packaging material
118 to form one or more layers around a bottom portion of load 104, a top
portion
of a pallet 153 supporting load 104, the sides of load 104, and a top portion
of load
104. With load 104 substantially wrapped, packaging material dispenser 116 may
proceed back towards its home position proximate clamping device 180 in FIG.
1.
With packaging material dispenser 116 in its home position, the wrapping cycle
ends. Newly wrapped load 104 may be conveyed or otherwise removed from
wrapping surface 102 to make room for a subsequent load. Since the
instantaneous demand is determined and/or approximated during wrapping of a
load, the subsequent load may have a different size, shape, and/or placement
as
compared to the preceding load, and yet the subsequent load can be wrapped at
the desired payout percentage.
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[084] During wrapping, controller 170 may also monitor the rotation of an
idle roller, such as idle roller 134, using downstream sensor assembly 136, to
detect when a break has occurred in packaging material 118. Controller 170 may
determine that a break has occurred if a decrease in the sensed instantaneous
demand is of a magnitude, and/or occurs within a period of time, indicative of
a
break having occurred. Additionally or alternatively, if sensor assembly 136
senses
that at least idle roller 134 has undergone a reversal in rotation, controller
170 may
recognize that a break has occurred. If a break is detected, controller 170
may
instruct packaging material drive VFD 166 to stop packaging material drive
system
124, thus halting the dispensing of packaging material 118 from packaging
material
dispenser 116. It should be understood that idle roller 133 and sensor
assembly
114 may be used in place of, or in combination with, idle roller 134 and
sensor
assembly 136, in the steps described above.
[085] In a second exemplary method for wrapping a load, packaging
material dispenser 116 may be in its home position proximate clamping device
180,
packaging material 118 may extend from packaging material dispenser 116 toward
clamping device 180, and clamping device 180 may grip the leading end of
packaging material 118. Load 104 may be placed on wrapping surface 102 in a
manner similar to that described in the first method. The predetermined and/or
desired payout percentage may be obtained by or entered into controller 170,
after
having been selected in a manner similar to that described in the first
method. With
load 104 in place, and controller 170 programmed with the predetermined and/or
desired payout percentage, controller 170 may begin wrapping load 104.
[086] During wrapping, controller 170 may make adjustments to the
operational settings of wrapping apparatus 100 so that load 104 may be
properly
wrapped. For example, controller 170 may implement settings to produce the
predetermined and/or desired payout percentage. Controller 170 may retain the
instantaneous demand signals from sensor assembly 136, distance measuring
device 137, and/or distance measuring device 141, in a memory location for one
or
more relative revolutions between packaging material dispenser 116 and load
122.
For example, controller 170 may generate a curve indicative of instantaneous
demand versus time for the one or more relative revolutions, and/or a curve
indicative of instantaneous demand versus time for corners of load 104. The
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curves may be used by controller 170 as a model of the size and/or shape of
load
104. Controller 170 may use the curve as a baseline, and may set and adjust
operation of packaging material drive system 124 and its dispensing roller 122
based on the curve, to wrap load 104 at the predetermined and/or desired
payout
percentage.
[087] After load 104 has been modeled during the one or more relative
revolutions, controller 170 may wrap load 104 without referring back to sensor
assembly 136, distance measuring device 137, and/or distance measuring device
141, for additional data. Additionally or alternatively, controller 170 may
replace the
curve with an updated curve if the instantaneous demand signals from sensor
assembly 136 are outside of a predetermined range with respect to the curve.
The
one or more relative revolutions during which controller 170 may model load
104
may include the first relative revolution between packaging material dispenser
116
and load 104 during the start-up period of the wrapping cycle. Additionally or
alternatively, the one or more relative revolutions may include the first
relative
revolution between packaging material dispenser 116 and load 104 during the
intermediate period of the wrapping cycle. It is contemplated, however, that
the
one or more revolutions may include any of the one or more relative
revolutions
between packaging material dispenser 116 and load 104 during the wrapping
cycle.
[088] During wrapping, controller 170 may also monitor the rotation of idle
roller 134, using downstream sensor assembly 136, to detect when a break has
occurred in packaging material 118, in a manner similar to that which was
described in the first method. Controller 170 may also include a buffer to
dampen
and/or delay the instantaneous demand signal when the instantaneous demand
signal decreases. With load 104 substantially wrapped, packaging material
dispenser 116 may proceed back towards its home position. Similar steps may be
performed during wrapping with wrapping apparatuses 200 and 300, where similar
elements have similar reference numerals and perform similar operations.
[089] In a third exemplary method for wrapping a load, any of the methods
or steps described in U.S. Patent Application Publication No. 2009/0178374,
which
is incorporated herein by reference in its entirety, may be performed during
the
wrapping of one or more loads,
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[090] It is also contemplated that any sequence or combination of the
above-described methods may be performed during the wrapping of one or more
loads. For example, while wrapping a load, one method may be performed,
whereas while wrapping another load, another method may be performed.
Additionally or alternatively, while wrapping a single load, two or more of
the three
methods may be performed. One method may be performed during one portion of
the wrapping cycle, and another method may be performed during another portion
of the wrapping cycle. Additionally or alternatively, one load may be wrapped
using
a first combination of methods, while another load may be wrapped using a
second
combination of methods (e.g., a different combination of methods, and/or a
different
sequence of methods).
[091] Each of the elements and methods described in the present
disclosure may be used in any suitable combination with the other described
elements and methods.
[092] Other embodiments will be apparent to those skilled in the art from
consideration of the specification and practice of the present disclosure. It
is
intended that the specification and examples be considered as exemplary only,
with
a true scope and spirit of the disclosure being indicated by the following
claims.
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